Electrodes for semiconductor electroplating apparatus and their application

Description of equivalent WO 9931299 A1

TITLE OF THE INVENTION

ELECTRODES FOR SEMICONDUCTOR ELECTROPLATING APPARATUS AND THEIR APPLICATION

CROSS-REFERENCE TO RELATED APPLICATIONS

0004This application is a continuation-in-part of United States Patent Applications

000508/ , (Atty. Docket No. SE10-0139, U.S. Postal Express Mail Label No.

0006EM025335115), filed September 30, 1997 which is pending; 08/ , (Atty. Docket

0007No. SE10-0122, U.S. Postal Express Mail Label No. EM025335067), filed Spetember 30,

00081997, which is pending, 08/ , (Atty. Docket No. SE10-0123, U.S. Postal Express

0009Mail Label No. EM025335075), filed September 30, 1997 which is pending; 08/ ,

0010(Atty. Docket No. SE10-0125, U.S. Postal Express Mail Label No. EM025335098), filed

0011September 30, 1997 which is pending, 08/ , (Atty. Docket No. SE10-0127, U.S.

0012Postal Express Mail Label No. EM025335084), filed September 30, 1997 which is pending, each of which is incorporated by reference herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

0015Not Applicable BACKGROUND OF THE INVENTION

0016In the production of semiconductor integrated circuits and other semiconductor articles from semiconductor wafers, it is often necessary to provide multiple metal layers on the wafer to serve as interconnect metallization which electrically connects the various devices on the integrated circuit to one another. Traditionally, aluminum has been used for such interconnects, however, it is now recognized that copper metallization may be preferable.

0017The application of copper onto semiconductor wafers has, in particular, proven to be a great technical challenge. At this time copper metallization has not fully achieved commercial reality due to practical problems of forming copper layers on semiconductor devices in a reliable and cost efficient manner.

0018The industry has sought to plate copper onto a semiconductor wafer by using a damascene electroplating process where holes, more commonly called vias, trenches and other recesses are used in which the pattern of copper is desired. In the damascene process, the wafer is first provided with a metallic seed layer which is used to conduct electrical current during a subsequent metal electroplating step. The seed layer is a very thin layer of metal which can be applied using one or more of several processes. For example, the seed layer of metal can be laid down using physical vapor deposition or chemical vapor deposition processes to produce a layer on the order of 1000 angstroms thick. The seed layer can advantageously be formed of copper, gold, nickel, palladium, and most or all other metals. The seed layer is formed over a surface which is convoluted by the presence of the vias, trenches, or other device features which are recessed. In damascene processes, the copper layer that is electroplated onto the seed layer is in the form of a blanket layer. The blanket layer is plated to an extent which forms an overlying layer, with the goal of completely providing a copper layer that fills the trenches and vias and extends a certain amount above these features. Such a blanket layer will typically be formed in thicknesses on the order of 10,000-15,000 angstroms (1-1.5 microns).

0019After the blanket layer has been electroplated onto the semiconductor wafer, excess metal material present outside of the vias, trenches or other recesses is removed. The metal is removed to provide a resulting patterned metal layer in the semiconductor integrated circuit being formed. The excess plated material can be removed, for example, using chemical mechanical planarization. Chemical mechanical planarization is a processing step which uses the combined action of a chemical removal agent and an abrasive which grind and polish the exposed metal surface to remove undesired parts of the metal layer applied in the electroplating step.

0020In the electroplating of semiconductor wafers, an anode electrode is disposed in a plating bath and the wafer with the seed layer thereon is used as a cathode with the face of the wafer that is to be plated contacting an upper surface of the plating bath. The semiconductor wafer is held by a support system that also provides be requisite cathode potential to the wafer. The support system may comprise conductive fingers that secure the wafer in place and also contact the wafer in order to conduct electrical current for the plating operation.

0021The present inventors have found that the electrode contacts to the semiconductor wafer are important to the uniformity of the deposited metal layer. Improper electrode contacts may result in non-uniformity of the plated layer on a single wafer, and may also cause substantial wafer-to-wafer non-uniformities. The present inventors have recognized various electrode contact problems and have provided solutions to address many above these identified problems.

BRIEF SUMMARY OF THE INVENTION

0023Wafer contact electrode assemblies useful for supporting a wafer surface to be electroplated are disclosed herein. These fingers provide the electrical contact necessary for providing electric power between a wafer and a corresponding anode in order to electroplate the surface all of the wafer. Such conductive fingers are useful in the production of electroplated products having reduced surface irregularities compared to products made by electroplating equipment and methods employing existing conductive fingers. In particular, the electrodes set forth herein are useful in electroplating apparatus and processes for the copper metallization of semiconductor wafers.

0024The various conductive electrode constructions disclosed herein are advangeous in the electroplating of semiconductor wafers for one or more respective characteristics. Such characteristics include one or more all of the following: 1) the construction allows for control of local current density as well as current density across the entire wafer surface to be plated; 2) the construction facilitates the application of uniform plating layers to the wafer; 3) the construction provides a seal around the electrode contact area thereby reducing electrode exposure to the plating bath and thus reducing plating of and deposit build-up on the electrode; 4) the construction reduces the occurrence of localized high current densities at or around the finger and the contact area thereby resulting in more uniform current distribution. Such factors that may contribute to the reduction of plating surface irregularities during the electroplating process. As a result, higher quality metallization layers on semiconductor wafers may be obtained. Additionally, greater wafer to wafer uniformity may be achieved in batch production processes using the conductive fingers described herein.

0025This invention also relates to apparatuses for electroplating comprising the conductive fingers described herein, methods of electroplating using the conductive fingers described herein, and also relates to semiconductor wafers made by the apparatus and processes using the conductive fingers described herein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

0027Fig. 1 is a schematic block diagram of an electroplating system.

0028Fig. 2 is a perspective view of the various components of a current thief assembly that may be used in the electroplating system of Fig. 1.

0029Figs. 3 A and 3B generally illustrate a wafer contact electrode for use in the electroplating system of Fig. 1.

0030Figs. 4-6 illustrate one embodiment of a wafer holder assembly that may be used in the electroplating system of Fig. 1.

0031Figs. 7-10 illustrate one embodiment of the various components used to actuator the wafer contact electrodes to and from contact engagement with a wafer disposed on the wafer holder assembly illustrated in Figs. 4-6.

0032Figs. 11-16 illustrates a further embodiment of a reactor assembly that may be used to electroplate a surface of a semiconductor wafer.

0033Figs. 17-28 illustrate various finger transmission assemblies that may be used in the embodiment of the reactor assembly shown in Figs. 11-16.

0034Figs. 29-48 illustrate various embodiments the wafer finger contacts suitable for use in the foregoing reactor assemblies. DETAILED DESCRIPTION OF THE INVENTION

0035Fig. 1 is a schematic block diagram of a plating system, shown generally at 50, for electroplating a metallization layer, such as a patterned or blanket copper metallization layer, on, for example, a semiconductor wafer 55. The illustrated system generally comprises a vision system 60 that communicates with a main electroplating control system 65. The vision system 60 is used to identify the particular product being formed on the semiconductor wafer 55 before it is placed into an electroplating apparatus 70. With the info.rmation provided by the vision system 60, the main electroplating control system 65 may set the various parameters that are to be used in the electroplating apparatus 70 to electroplate the metallization layer on the wafer 55.

0036In the illustrated system, the electroplating apparatus 70 is generally comprised of an electroplating chamber 75, a rotor assembly 80, and a stator assembly 85. The rotor assembly 80 supports the semiconductor wafer 55, a current control system 90, and a current thief assembly 35. The rotor assembly 80, current control system 90, and current thief assembly 95 are disposed for co-rotation with respect to the stator assembly 85. The chamber 75 houses an anode assembly 100 and contains the solution 105 used to electroplate the semiconductor wafer 55.

0037The stator assembly 85 supports the rotor assembly 80 and its associated components. A stator control system 110 may be disposed in fixed relationship with the stator assembly 85. The stator control system 110 may be in communication with the main electroplating control system 65 and may receive information relating to the identification of the particular type of semiconductor device that is being fabricated on the semiconductor wafer 55. The stator control system 110 further includes an electromagnetic radiation communications link 115 that is preferably used to communicate information to a corresponding electromagnetic radiation communications link 120 of the current control system 90 used by the current control system 90 to control current flow (and thus current density) at individual portions of the current thief assembly 95. A specific construction of the current thief assembly 95, the rotor assembly 80, the stator control system 110, and the current control system 90 is set forth in further detail in U.S.S.N. ( an Attorney

0038Docket Number 11829US01).

0039In operation, probes 122 make electrical contact with the semiconductor wafer 55. The semiconductor wafer 55 is then lowered into the solution 105 in minute steps by, for example, a stepper motor or the like until the lower surface of the semiconductor wafer 55 makes initial contact with the solution 105. Such initial contact may be sensed by, for example, detecting a current flow through the solution 105 as measured through the semiconductor wafer 55. Such detection may be implemented by the stator control system 110, the main electroplating control system 65, or the current control system 90. Preferably, however, the detection is implemented with the stator control system 110.

0040Once initial contact is made between the surface of the solution 105 and the lower surface of the semiconductor wafer 55, the wafer 55 is preferably raised from the solution 105 by a small distance. The surface tension of the solution 105 creates a meniscus that contacts the lower surface of the semiconductor wafer 55 that is to be plated. By using the properties of the meniscus, plating of the side portions of the wafer 55 is inhibited. After the desired meniscus has been formed at the plating surface, electroplating of the wafer may begin.

0041The system illustrated in Fig. 1 may incorporate a current thief assembly. Fig. 2 illustrates one embodiment of such a system including a current thief assembly 95 and a rotor assembly 80. The wafer electrode contacts of the present invention may be used in conjunction with such a system.

0042As shown, the current thief assembly 95 comprises a plurality of conductive segments 130 that extend about the entire peripheral edge of the wafer 55. The current thief assembly 95 is disposed for co-rotation with the rotor assembly 80. With reference to Fig. 2, a printed circuit board 135 is attached on a surface of a hub 210 of the rotor assembly 80. The board 135 is spaced from the hub 210 by an insulating thief spacer 215 and secured to the spacer 215 using a plurality of fasteners 220. The spacer 215, in turn, is

0043secured to the hub 210 of the rotor assembly 80 using fasteners 220 that extend through securement apertures 225 of both the spacer 215 and hub 210.

0044The hub 210 of the rotor assembly 80 is also provided with a plurality of support members for securing the wafer 55 to the rotor assembly 80 during the electroplating process. In the illustrated embodiment, the support members comprise insulating projections 230 that extend from the hub surface and engage a rear side of the wafer 55 and, further, a plurality of conductive wafer electrodes 235. The electrodes 235 of the disclosed embodiments are generally in the form of j-hooks and contact a seed layer on the surface of the wafer that is to be plated. Preferably, each of the segments 130 and electrodes 235 may be respectively associated with individual resistive elements that are preferably disposed on the board 135. Preferably, the resistance value of each resistive element may be individually controlled. The current flow through each of the fingers 235 and its respective section of the wafer 55 may thus also be controlled. Still further, conductive portions of the fingers 235 that contact the electroplating solution during the electroplating process may also perform a current thieving function and, accordingly, control current density in the area of the fingers. To this end, the amount of exposed metal on each of the fingers 235 may vary from system to system depending on the amount of current thieving required, if any, of the individual fingers 235.

0045Each conductive finger 235 may be part of a finger assembly 240 such as the one illustrated in Figs. 3 A and 3B. As shown, the finger assembly 240 is comprised of a transmission actuator 250 including a rod 255. The rod 255 engages the finger 235 at a removable interconnect portion 260 for ease of removal and replacement of the finger 235. Further, the actuator 255 is biased by springs 265 so as to urge the fingers against the wafer 55 as shown in Fig. 3A. The fingers 235 may be urged to release the wafer 55 by directly driving end portion 252 in the direction of arrow 275. Application of the

0046mechanical pressure urges the fingers 235 in the direction shown by arrow 275 of Fig. 3B thereby facilitating removal of the wafer 55 from the rotor assembly 80.

0047The following description delineates representative embodiments of the assemblies, semiconductor wafer holders and supports (as well as drive systems and electronic systems associated with them) that may comprise the conducting electrode fingers and finger

0048assemblies.

0049Fig. 4 is a side elevational view of one embodiment of a semiconductor wafer holder

0050810. As illustrated, wafer holder 810 is used for processing a semiconductor wafer such as a semiconductor wafer shown in phantom at W. One preferred type of processing undertaken with wafer holder 810 is a wafer electroplating process in which a semiconductor wafer is held by wafer holder 810 and an electrical potential is applied to the wafer to enable plating material to be electroplated thereon. Such can be, and preferably is accomplished utilizing a processing enclosure or chamber which includes a bottom half or bowl 811 shown in

0051phantom lines in Fig. 1. Bottom half 811 together with wafer holder 810 fonns a sealed, protected chamber for semiconductor wafer processing. Accordingly, reactants can be introduced into the chamber for processing. Another aspect of wafer holder 810 is that it moves, rotates or otherwise spins the held wafer during processing as will be described in more detail below.

0052In the illustrated embodiment, semiconductor wafer holder 810 includes a wafer

0053support assembly 812. Wafer support assembly 812 includes a processing head or spin head

0054assembly 814 and a a head operator or lift/rotate assembly 816. Spin head assembly 814 is

0055operatively coupled with lift/rotate assembly 816. Spin head assembly 814 enables a semiconductor wafer to be spun or moved about a defined axis during processing. Such spinning may be used to enhance conformal coverage of the plating material, such as copper, over the surface of the semiconductor wafer. Lift/rotate assembly 816 lifts spin head assembly 814 out of engagement with the bottom half 811 of the enclosure in which the preferred processing takes place. Such lifting is preferably along an axis x,. Once so lifted, lift/rotate assembly 816 also rotates the spin head and held wafer about an axis x₂ so that the wafer can be presented face-up and easily removed from wafer support 812. In the illustrated embodiment, such rotation is about 180 degrees from the disposition shown in Fig. 4. A new wafer can be fixed or otherwise provided to the wafer holder 810 for further processing.

0056The wafer can be removed from or fixed to wafer holder 810 automatically by means of a robotically controlled arm. Alternatively, the wafer can be manually removed from or fixed to wafer holder 810. Additionally, more than one wafer holder can be provided to support processing of multiple semiconductor wafers. Other means of removing and fixing a semiconductor wafer are possible.

0057Fig. 5 is a front sectional view of the semiconductor wafer support assembly 812 shown in Fig. 4. As shown, support assembly 812 includes a motor 818 which is operatively

0058coupled with a rotor 820. Rotor 820 is mounted for rotation about a rotor spin axis 822 and

0059serves as a staging platform upon which at least one wafer contact electrode assembly 824 is

0060mounted. Preferably, more than one wafer contact electrode assembly is mounted on rotor 820. More preferably, four or more and, even more preferably, six or more such finger assemblies are mounted thereon. The preferred finger assemblies are used in fixing or otherwise holding a semiconductor wafer on semiconductor wafer holder 810 and for providing

0061an electrical contact during electrochemical deposition processing of the wafer.

0062Each electrode assembly 824 is operatively connected or associated with an actuator

0063825. The actuator is preferably a pneumatic linkage which serves to assist in moving the finger

0064assemblies between a disengaged position in which a wafer may be removed from or added to the wafer holder, and an engaged position in which the wafer is fixed upon the wafer holder for

0065processing. Such is described in more detail below.

0066Fig. 6 is a top or plan view of rotor 820 which is effectively taken along line 6-6 in Fig. 5. As shown, rotor 820 is generally circular and resembles from the top a spoked wheel with a nearly continuous bottom surface. Rotor 820 includes a rotor center piece 826 at the

0067center of which lies rotor axis 822. A plurality of struts or spokes 828 are joined or connected to rotor center 826 and extend outwardly to join with and support a rotor

0068perimeter piece 830. Four of spokes 828 support respective finger assemblies 824. Finger

0069assemblies 824 are positioned to engage a semiconductor wafer, such as a wafer W which is

0070shown in phantom lines in the position such would occupy during processing. When a wafer is so engaged, it is held in place relative to the rotor so that processing can be effected. Such processing can include exposing the wafer to processing conditions which are effective to form a layer of material on one or more surfaces or potions of a wafer or other wafer. Such processing can also include moving the wafer within a processing environment to enhance or improve conformal coverage of a layering material. Such processing can, and preferably does include exposing the wafer to processing conditions which are effective to form an electroplated layer on or over the wafer.

0071Referring now to Figs. 7-9, various views of one embodiment of a finger assembly are illustrated. Fig. 7 is an isolated side sectional view of the finger assembly. Fig. 8 is a side elevational view of the finger assembly turned 90 degrees from the view of Fig. 7. Fig. 9 is a fragmentary cross-sectional enlarged view of a finger assembly and associated rotor structure. The fmger assembly as set forth in Figs. 7 and 8 is shown in the relative position such as it would occupy when processing head or spin head assembly 814 (Figs. 4 and 5) is moved or rotated by head operator or lift/rotate assembly 816 into a position for receiving a semiconductor wafer. The finger assembly is shown in Figs. 7 and 8 in an orientation of about 180 degrees from the position shown in Fig. 9. This typically varies because spin head assembly 814 is rotated 180 degrees from the position shown in Figs. 4 and 5 in order to receive a semiconductor wafer. Accordingly, finger assemblies 824 would be so rotated. Lesser degrees of rotation are possible.

0072Finger assembly 824 includes a finger assembly frame 832. Preferably, finger assembly

0073frame 832 is provided in the form of a sealed contact sleeve which includes an angled slot

0074832a, only a portion of which is shown in Fig. 8. .Angled slot 832a advantageously enables the

0075finger assembly to be moved, preferably pneumatically, both longitudinally and rotationally as will be explained below.

0076Finger assembly frame 832 includes a finger assembly frame outer flange 834 which,

0077as shown in Fig. 9, engages an inner drive plate portion 836 of rotor 820. Such engagement

0078advantageously fixes or seats finger assembly frame 832 relative to rotor 820. Such, in turn, enables the finger assembly, or a portion thereof, to be moved relative to the rotor for engaging the semiconductor wafer.

0079Referring to Figs. 5 and 7-9, the finger assembly includes a finger assembly drive system which is utilized to move the finger assembly between engaged and disengaged positions. The finger assembly drive system includes a bearing 838 and a collet 840 operatively adjacent the bearing. Bearing 838 includes a bearing receptacle 839 for receiving

0080a pneumatically driven source, a fragmented portion of which is shown directly above the receptacle in Fig. 9. The pneumatically driven source serves to longitudinally reciprocate and rotate collet 840, and hence a portion of finger assembly 824. Longitudinal reciprocation is affected by a biasing mechanism in the form of a spring 842 which is operatively mounted between finger assembly frame 832 and a spring seat 844. The consttuction develops a bias between finger assembly frame 832 and spring seat 844 to bias the finger into engagement against a wafer. The cooperation between the above mentioned pneumatically driven source as affected by the biasing mechanism of the finger assembly drive system, enables collet 840 to be longitudinally reciprocated in both extending and retracting modes of movement. As such, finger assembly 824 includes a biased portion which is biased toward a first position and which is movable to a second position away from the first position. Other manners of longitudinally reciprocating the finger assembly are possible.

0081Referring to Figs. 5 and 8, the finger assembly preferably includes a finger assembly electrical system which is util.ized to effectuate an electrical bias to a held wafer and supply electrical current relative thereto. The finger assembly electrical system includes a pin connector 846 and a fmger 848. Pin connector 846 provides an electrical connection to a

0082power source (not shown) via wire 585 and associate slip ring mechanism. Pin connector 846 also rides within angled slot 832a thereby mechanically defining the limits to which the finger

0083assembly may be both longitudinally and rotationally moved.

0084Finger 848 is fixed or secured to or within collet 840 by a nut 850 which threadably engages a distal end portion of collet 840 as shown best in Fig. 18. An anti-rotation pin 852

0085secures finger 848 within collet 840 and prevents relative rotation therebetween. Electrical current is conducted from connector 846 through collet 840 to finger 860, all of which are conductive, such as from stainless steel. The finger and collet can be coated with a suitable dielectric coating 856, such as TEFLON or others. The collet 840 and finger member 860 are in one form of the invention made hollow and tubular to conduct a purge gas therethrough. Finger assembly 824 may also optionally include a distal tip or fmger tip 854. Tip

0086854 may have a purge gas passage formed therethrough. Finger tip 854 engages the semiconductor wafer (see Fig. 9) and assists in holding or fixing the position of the wafer relative to wafer holder 810. Finger tip 854 also assists in providing an operative electrical connection between the finger assembly and a wafer to which an electrical bias is to be applied and through which current can move. Finger tip 854 can include an electrode contact 858 for electrically contacting a surface of a semiconductor wafer once such wafer is

0087secured as describe below.

0088A finger assembly drive system interface is operatively coupled with the finger assembly drive system to effectuate movement of the finger assembly between the engaged and disengaged positions. One component of the finger assembly drive system interface is a finger

0089actuator 862. Finger actuator 862 is provided for moving the finger assembly between the

0090engaged and disengaged position. Finger actuator 862 acts by engaging bearing receptacle 839 and moving finger assembly 824 between an engaged position and a disengaged position. In

0091the engaged position, fmger tip 854 is engaged against a semiconductor wafer. In the disengaged position finger tip 854 is moved away from the wafer.

0092The finger assembly drive system interface includes pneumatic actuator 825 (Fig. 5). Pneumatic actuators 825 are operatively connected to an actuation ring 863 and operates

0093thereupon causing the drive plate to move reciprocally in the vertical direction as viewed in Fig. 5. Finger actuator 862 is operatively connected to actuation ring 863 in a manner which, upon pneumatic actuation, moves the finger actuator into engagement with bearing receptacle 839 along the dashed line in Fig. 5. Such allows or enables the finger assembly to be moved longitudinally along a first movement path axis 864.

0094Pneumatic actuator linkage 825 also includes a secondary linkage 865. Secondary

0095linkage 865 is pneumatic as well and includes a link arm 867. Link arm 867 is connected or

0096joined to an actuator torque ring 869. Preferably, torque ring 869 is concentric with rotor 820

0097(Fig. 6) and circuitously links each of the finger actuators together. A pneumatic operator 871

0098is advantageously linked with the secondary linkage 865 for applying force and operating the linkage by angularly displacing torque ring 869. This in turn rotates the finger assemblies into and away from the engaged position.

0099Finger actuator engagement bit 862, under the influence of pneumatic linkage 825, moves the fmger assembly, and more specifically collet 840 and finger 848 along a first axial movement path along axis 864. The finger actuator engagement bits 862, then under the influence of pneumatic operator 871 are turned about the axes of each bit like a screwdriver. This moves collet 840 and finger 848 in a second angular movement. Such second movement turns the fingers sufficiently to produce the angular displacement shown in Fig. 10. Such movement of the finger assemblies between the engaged and disengaged positions takes place when spin head assembly 814 has been moved 180 degrees from its Fig. 4 disposition into a face-up condition.

0100The engagement bits 862 can be provided with a purge gas passage theremrough. Gas is supplied via tube 893 and is passed through the finger assemblies.

0101Fig. 10 is a view of a portion of a finger assembly in the engaged and disengaged positions and movement therebetween relative to a wafer W. In the disengaged position, finger 848 is positioned adjacent the semiconductor wafer and the finger tip and electrode contact do not overlap with wafer W. In the engaged position, the finger tip overlaps with the wafer and the electrode is brought to bear against the wafer. From the disengaged position, finger assembly 824, upon the preferred actuation, is moved in a first direction away from the disengaged position. Preferably, such first direction is longitudinal and along first movement path axis 864. Such longitudinal movement is linear and in the direction of arrow A as shown

0102in Figs. 7 and 8. The movement moves the finger assembly to the position shown in dashed lines in Fig. 7. Such movement is effectuated by pneumatic operator 825 which operates upon actuation ring 863 (Fig. 5). This in turn, causes finger actuator 862 to engage with finger assembly 824. Such linear movement is limited by angled slot 832a. Thereafter, the finger assembly is preferably moved in a second direction which is different from the first direction and preferably rotational about the first movement path axis 864. Such is illustrated in Fig. 10 where the second direction defines a generally arcuate path between the engaged and disengaged positions. Such rotational movement is effectuated by secondary linkage 865 which pneumatically engages the finger actuator to effect rotation thereof. As so moved, the finger assembly swings into a ready position in which a semiconductor wafer is ready to be engaged and held for processing. Once the finger assembly is moved or swung into place overlapping a wafer, the preferred finger actuator is spring biased and released to bear against the wafer. An engaged wafer is shown in Fig. 9 after the wafer has been engaged by fmger tip 854 against a wafer standoff 865, and spin head assembly 814 has been rotated back into the position shown

0103in Fig. 4. Such pneumatically assisted engagement takes place preferably along movement path axis 864 and in a direction which is into the plane of the page upon which Fig. 10 appears.

0104As shown in Fig. 7, finger 848 extends away from collet 840 and preferably includes a bend 866 between collet 840 and finger tip 854. The preferred bend is a reverse bend of

0105around 180 degrees which serves to point finger tip 854 toward wafer W when the finger assembly is moved toward or into the engaged position (Fig. 10). Advantageously, the collet 840 and hence finger 848 are longitudinally reciprocally movable into and out of the engaged

0106position.

0107Fig. 11 shows various components of a further semiconductor processing station 900

0108suitable for electroplating a metal, such as copper, onto a semiconductor wafer. The two principal parts of processing station 900 are a processing head, shown generally at 906, and an

0109electroplating bowl assembly 303.

0110As shown in Fig. 11, the electroplating bowl assembly 303 includes a cup assembly

0111320 which is disposed within a reservoir container 317. Cup assembly 320 includes a fluid cup portion 321 holding the chemistry for the electroplating process. The cup assembly of the

0112illustrated embodiment also has a depending skirt 371 which extends below the cup bottom 323 and may have flutes open therethrough for fluid communication and release of any gas that

0113might collect as the chamber of the reservoir assembly below fills with liquid. The cup is preferably made from polypropylene or other suitable material.

0114A lower opening in the bottom wall of the cup assembly 320 is connected to a polypropylene riser tube 330 wliich is adjustable in height relative thereto by a threaded

0115connection. A first end of the riser tube 330 is secured to the rear portion of an anode shield 393 which supports anode 334. A fluid inlet line 325 is disposed within the riser tube 330. Both the riser tube 330 and the fluid inlet line are secured with the processing bowl assembly 303 by a fitting 362. The fitting 362 can accommodate height adjustment of both the riser tube and line 325. As such, the connection between the fitting 362 and the riser tube 330 facilitates

0116vertical adjustment of the anode position. The inlet line 325 is preferably made from a conductive material, such as titanium, and is used to conduct electrical current to the anode 334, as well as supply fluid to the cup.

0117Process fluid is provided to the cup through fluid inlet line 325 and proceeds therefrom

0118through fluid inlet openings 326. Plating fluid then fills the chamber 321 through opening 324

0119as supplied by a plating fluid pump (not shown) or other suitable supply.

0120The upper edge of the cup side wall 322 forms a weir which limits the level of

0121electroplating solution within the cup. This level is chosen so that only the bottom surface of wafer W is contacted by the electroplating solution. Excess solution pours over this top edge surface into an overflow chamber 345. The level of fluid in the chamber 345 is preferably

0122maintained within a desired range for stability of operation by monitoring the fluid level with appropriate sensors and actuators. This can be done using several different outflow configurations. A preferred configuration is to sense a high level condition using an appropriate sensor and then drain fluid through a drain line as controlled by a control valve. It is also possible to use a standpipe arrangement (not illustrated) as a final overflow protection device. More complex level controls are also possible.

0123The outflow liquid from chamber 345 is preferably returned to a suitable reservoir. The liquid can then be treated with additional plating chemicals or other constituents of the plating or other process liquid and used again.

0124In preferred use of the apparatus for electroplating, the anode 334 is a consumable anode used in connection with the plating of copper or other metals onto semiconductor materials. The specific anode will vary depending upon the metal being plated and other specifics of the plating liquid being used. A number of different consumable anodes which are commercially available may also be used as anode 334.

0125Fig. 11 also shows a diffusion plate 375 provided above the anode 334 for providing a more even distribution of the fluid plating bath across the surface of wafer W. Fluid passages are provided over all or a portion of the diffusion plate 375 to allow fluid communication therethrough. The height of the diffusion plate witliin the cup assembly is adjustable using diffuser height adjustment mechanisms 386.

0126The anode shield 393 is secured to the underside of the consumable anode 334 using anode shield fasteners 394 to prevent direct impingement by the plating solution as the solution passes into the processing chamber 321. The anode shield 393 and anode shield fasteners 394

0127are preferably made from a dielectric material, such as polyvinylidene fluoride or polypropylene. The anode shield is advantageously about 2-5 millimeters thick, more preferably about 3 millimeters thick.

0128The anode shield serves to electrically isolate and physically protect the back side of the anode. It also reduces the consumption of organic plating liquid additives. Although the e.xact mechanism may not be known at this time, the anode shield is believed to prevent disruption of certain materials which develop over time on the back side of the anode. If the anode is left unshielded, the organic chemical plating additives are consumed at a significantly greater rate. With the shield in place, these additives are not consumed as quickly.

0129The processing head 906 holds a wafer W for rotation within the processing chamber 312. The processing head 906 includes a rotor assembly 984 having a plurality of wafer- engaging fingers 979 that hold the wafer against features of the rotor. Fingers 979 are preferably adapted to conduct current between the wafer and a plating electrical power supply and may be constructed in accordance with various configurations disclosed herein to act as current thieves.

0130As Fig. 11 indicates, portions of the processing head 906 mate with the processing bowl assembly 303 to provide a substantially closed processing vessel which encloses a substantially enclosed chamber 904. The processing head 906 holds a wafer W for rotation

0131within the chamber 904. The rotor assembly 984 has a plurality of wafer contact fingers

0132979 that hold the wafer against features of the rotor.

0133The processing head 906 is supported by an head operator 907. Head operator 907

0134includes an upper portion 908 which is adjustable in elevation to allow height adjustment of the

0135processing head. Head operator 907 also has a head connection shaft 909 which is operable to

0136pivot about a horizontal pivot axis 910. Pivotal action of the processing head using operator

0137907 allows the processing head to be placed in an open or face-up position (not shown) for loading and unloading wafer W Fig. 11 illustrates the processing head pivoted into a facedown position in preparation for processing.

0138A variety of suitable head operators which provide both elevational and horizontal pivoting action are possible for use in this system. The preferred operators are also fitted with positional encoders (not shown) which indicate both the elevation of the processing head and its angular position as pivoted about horizontal head pivot axis 910.

0139Figs. 12 and 13 show additional details of one embodiment of processing head 906. The processing head 906 includes a main part which moves with and is relatively stationary with respect to the pivot shaft 909. The main part supports a rotating assembly which will be described in greater detail below.

0140The main part includes a processing head housing 970 and processing head frame 982.

0141The processing head frame 982 includes a door plate 983. A door ring member 984 is joined to

0142plate 983 using suitable fasteners to provide a door assembly which serve as the principal parts covering the upper opening of the processing bowl when the processing head is mated with the

0143bowl.

0144The processing head frame also includes a frame-pivot shaft connection 985 which

0145includes two mounting rings which receive and securely connect with the processing head pivot shaft 909. In the embodiment shown in Fig. 13, the pivot shaft connection mounting rings are made in two parts and secured by fasteners (not shown). The pivot shaft connection base 935 is

0146secured to the door plate 983 using fasteners.

0147Processing head 906 is generally round in shape when viewed in plan view. The processing head main part includes a housing 970 which has a first housing part 971 and a

0148second housing part or housing cap 972. The processing head housing 970 encloses a main part enclosure which surrounds a processing head main part mechanism chamber 973.

0149Chamber 973 is used to house additional processing head components, such as the spin motor, the finger actuators, and related service lines, such as discussed more fully below.

0150The upper surface of the door ring member 984 is provided with a groove which receives the lower edge of the first housing piece 971. The outer periphery of the door ring member also advantageously includes a peripheral groove 986 which mounts an inflatable door seal 987. Seal 987 seals with portions of the processing bowl to form a more fluid-tight processing chamber merewithin.

0151The lower surface of the door ring member 984 is preferably provided with an annular

0152rotor receiving groove 988 which receives top peripheral portions of the rotor therein in close

0153proximity. This construction allows a gas purge (not shown) to be applied between the door and rotor to help prevent processing vapors from migrating behind the rotor and into to the various mechanisms present in the main part of the processing head. The periphery of the door ring member is further provided with a chamfered lower edge to facilitate mating with the processing bowl.

0154The processing head 906 also includes a moving assembly in the form of a wafer holder 978. The wafer holder includes the fingers 979 for holding the semiconductor wafer.

0155The processing head main part also includes a wafer holder drive which moves the wafer holder relative to the main part of the processing head. The preferred action is for the wafer holder drive to be in the form of a rotor drive wliich rotates the wafer holder. The rotor drive can be an electric motor, pneumatic motor or other suitable drive. As shown, the processing head includes an electric wafer spin motor 980.

0156The drive motor 980 has stator armatures 916 wliich drive motor shaft 918 in rotational

0157movement. Drive motor 980 is supported by bottom motor bearing 921 in bottom motor

0158housing 922. Bottom motor housing 922 is secured to the main part of the processing head

0159906 at a central opening in the door plate 983. Motor 980 is also held in place by a top motor

0160housing 923. Drive motor 980 is rotationally isolated from top motor housing 923 by a top motor bearing 927, which is disposed between the spin motor shaft 918 and the top motor

0161housing. Both motor housings are secured to the processing head frame 982 using fasteners 924 which extend down through the motor housings and into the door plate 983. The fasteners 924 also extend upwardly through frame ejctensions 925. Frame extensions 925 support a top

0162frame piece 926. Cap 972 is screwed onto piece 926 at mating threads along the lower interior

0163portion of the cap. The drive motor is preferably an electric motor provided with a supply of electricity via wiring run through pivot shaft 909 or otherwise extending to the processing

0164head.

0165The hollow shaft 918 of the drive motor receives a portion of a rotor assembly therein. The rotor assembly is secured to the motor shaft and is rotated therewith. The rotor assembly

0166930 includes a rotor shaft 931. Rotor shaft 931 has a rotor shaft hub 932 which is held within a shaft hub receptacle 933 fonned in an inner rotor part 934. The inner or first rotor part 934,

0167also called an inner rotor drive plate, has a plurality of spokes which extend from the inner rotor part hub 935 outwardly to connect with a peripheral band 936. The shaft hub 932 is held

0168in the hub receptacle 933 using a snap-ring 937.

0169The inner rotor part 934 also includes a plurality of receptacles 937. Receptacles 937 are used to mount a plurality of actuator transmission assemblies 960. The quantity and location of these assemblies are a function of the process application. The transmission

0170receptacles 937 receive lower portions of the transmission assemblies or finger actuators. The

0171receptacles have bottom openings through which the finger assemblies 979 (see Fig. 12) extend and are mounted in the transmission assemblies.

0172In the embodiment illustrated in Figs. 12-16, the rotor assembly 930 includes a second or outer rotor part 940. The inner and outer rotor parts are secured together by fasteners 941 (see Fig. 12). The outer rotor part 940 includes a rotor face panel 943 which extends across the disk-shaped rotor part 940 to form a barrier to processing fluids. Wafer support standoffs 721 are mounted upon the face of the rotor to support the back side of the

0173wafers in opposition to the forces exerted by the fingers 979. The face of the rotor can also advantageously be provided with wafer peripheral guide pins 722 to facilitate proper location of

0174a wafer upon installation upon the face of the rotor.

0175Along the back side of the outer rotor part are reinforcing ribs 942 which align with the

0176spokes of the inner rotor part 934. The reinforcing ribs 942 receive fasteners 941 and connect the two rotor parts together. At the periphery of the outer rotor part is a side wall 944. The

0177upper or back edge of the peripheral side wall 944 is in close fitting relationship with the door ring 984 at annular groove 988 to resist migration of processing fluids to the back side of the rotor assembly.

0178The outer rotor part 940 also has an array of bosses 948 at the peripheral end of the reinforcing ribs 942. Within bosses 948 are finger passageways 949 which allow the finger

0179assemblies 979 to mount in the finger actuator transmission assemblies 960.

0180The rotor shaft 931 fits inside of motor shaft 918 and protrudes from the top of the shaft. It is secured thereto by a rotor shaft mounting nut 888. Also mounted near the top of

0181the rotor shaft is an optical rotary indicator 499. Optical rotary indicator 499 is securely attached to motor shaft 918 and features, such as notches, formed on a sensor wheel of the position sensor 499 are optically detected to provide a verification of rotor angular position. The optical emitter-detector couplet used with optical rotary position sensor 499 are not shown, but are mounted on either sides of the wheel to allow selective passage of light therethrough. In the illustrated embodiment, the rotor assembly is provided with a angular position encoder 498. As shown, encoder 498 is mounted to the top motor housing 923 so as to remain

0182stationary with respect to the main part of the processing head. The angular position encoder 498 and optical rotary position sensor 499 allow the speed, acceleration, and precise rotational position of the motor shaft 918 and rotor assembly to be known and controlled.

0183To accomplish the electroplating, an electric current is provided to the wafer through the fingers 979. To provide electric current to the electrode fmgers 979, conductive wires (not shown) are provided to finger actuators 960 from the hub of the rotor. Current is supplied to the electrode fingers 979 through the hollow rotor shaft using wires (not shown) connected to a rotary electrical connector 687 mounted near the upper end of shafts 918 and 931.

0184Figs. 17 - 19 show one embodiment of the finger actuator transmission 960 in greater detail. The lower end of transmission 960 includes a finger head mounting receptacle 954.

0185Receptacle 954 is advantageously provided with a locking feature included to secure the fingers in the receptacles. As shown, the receptacle includes a convoluted, bayonet-type, locking pin

0186groove 955. Locking pin groove 955 receives a transversely mounted finger mounting pin 956

0187(see Fig. 29) which is a rolled or other suitable pin secured in the head of the finger assembly.

0188The transmission assemblies 960 include a transmission base 961 which is provided

0189with a mounting cutout 962 which is borne upon by retainers 951 when installed in the rotor.

0190The base 961 also includes a central passageway within which is received a transmission shaft

0191963. Shaft 963 can both pivot and move axially within the central passageway. The shaft and

0192base 961 are constructed to interact in a manner which controls the relative motion of the shaft. This is done to provide the compound pivotal and axial movement of the shaft and a finger 979 which is held therein. As shown, the inactive mechanism is provided in the form of a shaft

0193channel or groove 964 which is engaged by a shaft camming control member 965. The

0194camming action of the groove is provide by a helical advance over a pivotal movement range of approximately 60 degrees of rotation. The associate axial travel is in the range of approximately 5-20 millimeters, more preferably about 10-15 millimeters.

0195The camming control member 965 of the disclosed embodiment is in the form of a ball

0196966 held into the groove 964 using a ball support fastener 967. Fastener 967 has a ball socket

0197which receives portions of the ball. Fastener 967 also serves as a convenient electrical contact teπninal when electricity is supplied to the fingers 979.

0198The shaft 963 is provided with an interior shaft passageway 968 which receives a spring

0199retainer 969. Spring retainer 969 has an engagement head which mechanically engages with a

0200finger mounting spring 938. The spring 938 serves to bias the respective finger assembly 979

0201into a locked position using the locking pin 956 held in biased relationship by groove 955. Spring retainer 969 is secured in the passageway by a set screw 939.

0202As shown in Fig. 19, the actuator transmission 960 includes a transmission head 656

0203which is connected to the upper end of shaft 963 using a bearing 657 which allows the shaft to

0204pivot relative to the head pieces 658 and 659. Head pieces 658 and 659 capture the bearing

0205between them, and are joined by head fasteners 660. The head fasteners 660 tliread into a pair

0206of head guide rods 661. Head guide rods 661 are slidably received by two guide passageways

0207662 formed in the transmission base 961. The head assembly is biased upwardly by two head bias springs 664. Engagement between ball 966 and groove 964 limits the upward movement

0208of the head assembly under action by springs 664. The lower end of shaft 963 is sealed to the base 961 using a shaft seal 667 which helps

0209to prevent contamination of the fingers 979. Shaft 963 also has a transverse hole 665 which is used as an electrical connection feature that receives a wire (not shown) run from the rotary electrical contact down the rotor shaft. The wire is secured in hole 665 by a set screw (not shown).

0210The transmissions 960 are activated by a transmission head depression ring 683 (see

0211Fig. 12). Depression ring 683 is connected to an operator output connection ring 684 (see

0212Fig. 13). The operator output connection ring is secured by fasteners to the output shafts of pneumatic actuator engines 691. As shown in Fig. 13, pneumatic manifolds 692 are used to

0213supply air to the actuator engines 691. The prefeired construction shows three actuator engines 691 which have outputs which move upwardly and downwardly to depress the transmission heads 658 and operate the fingers in the compound axial and pivotal motion.

0214In operation, the fmgers 979 are biased by the actuator transmissions 690 to the position illustrated in Fig. 16. In this position, the fingers 979 are biased against the wafer to secure the wafer against members 721. When the actuator engine outputs are extended, they depress rings 683 and 684, and, as a result, drive against transmission heads 658. This causes fingers 979 to move from the inboard retracted positions of Fig. 16 to the outboard extended positions of Fig. 15 to facilitate removal of the wafer from a processing head.

0215Alternate embodiments of the actuator transmissions are illustrated in Figs. 20-26. The embodiments illustrated in these figures differ from the embodiment described above in several respects. First, the actuator transmissions of Figs. 20-26 employ a dual ball, cam style actuator. The dual ball type actuators have a doubly grooved shaft rather than a single groove shaft of the prior embodiment. Second, the particular construction of the actuator transmissions makes them easier to manufacture. Third, the transmissions are provided with mounting assemblies that may be used to adjust the extent of the rotational movement of the finger with respect to the wafer.

0216A first embodiment of the dual ball, cam style actuator is shown generally at 1000 of Figs. 20-24. As illustrated, the actuator 1000 comprises a centrally disposed shaft 1013 including a bore hole disposed through a central portion thereof for accepting a corresponding mating portion of a respective wafer contact electrode. A .Lee spring 1002 is disposed in the bore hole and is secured therein with a retaining spring 1012. The actuator 1000 is disposed through a sleeve 1008 at a lower portion thereof which, in turn, engages a ring mount 1009. A second Lee spring 1003 is disposed in a concentric manner around shaft 1013. Sleeve 1008 includes a channel 1004 into which an O-ring 1016 is placed to seal against outer hub

0217assembly 940.

0218Spring 1003 engages sleeve assembly 1008 at a lower portion thereof and at a flange of retainer assembly 1015 at an upper portion thereof. In the illustrated embodiment, the retainer assembly 1015 includes an upper race 1014 and a lower race 1011 that secure bearings 1018 against an upper channel of shaft 1013. As illustrated, the lower race 1011 includes a flange portion that engages the top of spring 1003. Upper race 1014 and lower race 1011 are held together by a cap 1019 having an upper lip engaging a top surface of the upper race 1014 and a lower lip engaging a bottom surface of lower race 1011. Preferably, cap 1019 is made from a plastic or Teflon material. Lower lip is preferably dimensioned to allow cap 1019 to snap over the upper and lower races during assembly and/or disassembly. Once assembled in the illustrated manner, retainer assembly 1015 bears against spring 1003 to bias a finger electrode connected to shaft 1013 to a position in which the electrode engages the semiconductor wafer. Further, retainer assembly 1015 provides a ready means by which the transmission may be assembled and disassembled.

0219As illustrated in Fig. 22, a dual bearing cam mechanism is employed to provide the rotational movement to the respective finger electrode. To this end, shaft 1013 is provided with two cam grooves at an exterior surface thereof. Each cam groove includes a corresponding bearing 1017 disposed therein. A circular retaining spring 1016 retains bearings 1017 in respective channels of a collar 1020 at an upper portion of sleeve 1008 for bearing against and within respective grooves of the shaft 1013.

0220Preferably, shaft 1013 is made from a conductive material to facilitate an electrical connection of electroplating power to the respective fmger electrode. A connection pin 1010 extends through a corresponding aperture 1021 of shaft 1013. A set pin 1022 may extends through the upper portion of shaft 1013 to engage connection pin 1010 within aperture 1021 to ensure that a proper electrical connection is made.

0221The transmission actuators, and the attached finger electrodes, of the disclosed embodiments may be set at a variety of initial angular positions with respect to the wafer thus allowing for adjustment of the finger electrode contact points with the surface to be plated. This flexibility makes it possible to alter the contact points at which plating power is applied to the surface to be plated.

0222Figs. 21 and 24 are top and perspective views, respectively, of the actuator transmission. As illustrated, the actuator transmission 1000 includes mounting holes 1018 disposed through ring mount 1009 that are continuous along a radial path. As such, actuator transmission 1000 can be mounted to the inner rotor part 934 and outer rotor part 940 to vary the position and extent that the respective finger electrode contacts the wafer. Figs. 27 and 28 illustrate the mounting of such a transmission to the outer rotor part 940 and inner rotor part 934. As illustrated, the actuator transmissions 960 are mounted in their extreme contour clockwise position. The transmissions 960 may be rotated for alignment to a more clockwise position by merely loosening securements 1024 and rotating the transmission 960 in the clockwise direction.

0223An alternate embodiment of a transmission 960 having only two predetermined angular relationships for securement to the inner and outer rotor parts 934 and 940 is illustrated in Figs. 25 and 26. As shown, this alternate embodiment is provided with two mounting holes 1038 on each side of ring mount 1009. Thus, this embodiment only provides for two selectable positions for mounting of the transmission 960 to the rotor and, thus, two positions to which the respective finger may extend onto the wafer. With respect to the remaining components of this embodiment, it is substantially similar to the o embodiment discussed above in connection with Figs. 20 through 25.

0224The grooved shafts have ball bearings contained inside each groove to provide smooth operation of the actuator when alternating between the engaged and disengaged positions and distributes the forces and friction of the actuator shaft during engage/disengage actions. This avoids any concentration of friction forces at isolated areas along the shaft and results in smoother and more consistent operation of the actuator. That, in turn, ultimately results in greater uniformity of positioning of the electrode finger contacts with the electroplated surface and more consistent contact force between the electrode contact and the surface. Improved unifoπnity of electrode contacting gives rise to more uniform electroplating.

0225Fig. 15 shows the front face of the outer rotor part 940 in a face-up orientation with fingers 979 extending therefrom and, together with Fig. 16, illustrates a preferred movement of the wafer contact electrodes. As illustrated, the fingers of the disclosed embodiment are J- shaped and mounted for pivotal action about a finger pivot axes 953. The pivotal action

0226preferably ranges between an outboard position and an inboard position. In the outboard position the J-shaped fmgers are positioned outwardly and clear of the wafer peripheral edge. A preferred outboard position is illustrated in Fig. 15. In the outboard position the hooked portions of the J-shaped fingers are oriented at approximately 15 angular degrees outward from a line drawn tangent to the periphery of the wafer adjacent to the finger. In the inboard

0227position the fingers are positioned inwardly to engage the wafer, as shown in Fig. 16. In the inboard position the hooked portions of the J-shaped fingers are oriented at approximately 45 angular degrees inward from a line drawn tangent to the periphery of the wafer adjacent to the

0228finger.

0229The face of the rotor assembly is provided with wafer standoff supports 721 which are

0230in complementary position to the engagement ends of the fingers when the fingers are in a retracted position to hold the wafer. This construction securely captures the wafer or other wafer between the fingers and the standoffs.

0231In addition to the pivotal action of the engagement fingers, the fingers also move axially toward and away from the face of the rotor. In the inboard position the fmgers are retracted toward the wafer to engage the exposed, front face of the wafer along a marginal band adjacent to the periphery of the wafer. In the outboard position the fingers are extended away from the face of the wafer to prevent rubbing action as the fmgers pivot away from the wafer. This compound action including both a pivot component and an axial component is accomplished using a finger acmator transmission 960 shown in perspective relationship to the rotor in Fig. 14. Transmissions 960 are mounted within the transmission receptacles 937 of the inner rotor part 934. The transmissions are further mounted by transmission retainers 951 which are secured by fasteners to inner rotor part 934.

0232The processing head also preferably includes a wafer detection subsystem. This subsystem allows the processing head to determine whether or not there is a wafer held in the rotor. This is of particular significance if the system experiences a power inteiruption or otherwise is being started in any situation where wafers may be present in the machine.

0233Operational safeguards can then be included in the control system to prevent mishandling of wafers or processing stations which may have a wafer held therein.

0234As shown in Fig. 12, the processing head frame part 983 is provided with a mounting

0235738 which is an appropriately shaped recess used to mount a detector 739. Detector 739 is

0236preferably an optical emitter-detector unit which emits a beam which passes downwardly as oriented in Fig. 12. The emitted beam passes through wafer detector windows 741 formed in

0237the face panel of the outer rotor part. The windows can be discrete inserts, or more preferably, they are thinly dimensioned panel portions of the rotor face panel 943. The rotor face panel is advantageously made of a material which is transmissive of the detector beam being used. For example, the panel can be made from polyvinylidene fluoride polymer which is thinned to a suitably thin dimension, such as in the approximate range from about 1-5 millimeters. A suitable detector 739 is a Sunx brand model RX-LS200, and other commercially available detectors. The preferred detector uses an infrared beam emitter (not individually shown) which is detected by a pair of beam detectors (not individually shown). The beam emitter and beam detectors are preferably part of the same unit which seizes as the wafer detector. The wafer detector preferably operated in a trigonometric mode. In the trigonometric mode, the angle of the reflected beam is an important discriminating parameter. Thus any portion of the beam reflected by the detector window 741 is incident upon the pair of detectors at a reflection angle which is outside of the normal detection angel range. Such portions of the beam reflected by the window 741 are thus minimized and the detector is not triggered by such reflectance. Instead, the pair of beam detectors are adjusted to sense a reflected beam which is incident at a reflected angle associated with the wafer or other wafer surface which is more distant than the window. When there is no wafer held in the wafer holder, then the detector senses the absence and this is used by the control system as an indication that there is no wafer present in the wafer support.

0238In general the emitted infrared beam used in the preferred wafer detector subsystem is sufficient to detect the presence of a wafer or other semiconductor wafer held in a stationary position with the rotor positioned so that one of the windows 741 is in position aligned to allow the emitted beam to pass therethrough and be reflected by the wafer back through the window for detection. The detection system described herein is not sufficient to allow detection during rotation of the rotor and any wafer held thereon. The invention may also be practiced in a situation where sensing can be accomplished while the rotor rotates.

0239The wafer detector arrangement shown has the distinct benefit of being mounted wholly behind the rotor face panel without provision of any openings which might allow processing fluids to enter the space behind the rotor. This reduces maintenance, improves reliability, and simplifies construction costs.

0240Figs. 29-48 show a number of different electrode finger constructions. Fig. 29 shows a finger assembly 631 having intended application for contacting a semiconductor wafer during

0241blanket plating of copper. Finger assembly 631 includes a finger shaft 632 which is formed in

0242a J-shape and made from an electrically conductive material, such as stainless steel , titanium, platinum coated titanium or other noble metals. The finger assembly also includes an integral finger head 633 which is received into the receptacle 954 of the actuator transmission 960.

0243The head has a pin aperture wliich receives the locking pin 956 therein for engagement with the

0244locking groove 955 formed in the receptacle of the actuator transmission 960.

0245Finger assembly 631 also includes dielectric sheathing 634 and 635. Dielectric

0246sheathing 634 and 635 may be made from a polyvinylidene fluoride coating or other non- conductive layer applied to the shaft of the finger. The dielectric sheathing is preferably provided upon only limited portions of the electrode shaft and adjacent the contact head 636.

0247The contact head has a contact face 637 which directly bears upon the wafer to pass electrical

0248current between the electrode and, for example, a seed layer on the wafer. The contact face 637 is disposed at a level that is approximately equal to a fluid submersion boundary 639. The submersion boundary indicates the approximate level of the plating liquid during processing.

0249The limited coverage of the dielectric sheathing assists in improving the uniformity of plating performed upon semiconductor wafers held in the wafer support. It is believed that the submersible surfaces of the electrode finger are best provided with dielectric sheathing segments which comprise between approximately 25 percent and 75 percent of the submersible area of the electrode. These amounts do not consider the contact face as part of the areas.

0250The embodiment of Fig. 29 includes two segments 634 and 635 which cover about 50 percent of the electrode finger shaft exterior surfaces from the submersion line 639 downward,

0251as positioned in a plating liquid bath during processing. The first dielectric segment 634 is adjacent to the contact face 637. a first electrically conductive segment 642 exists between the

0252dielectric segment 634 and the contact face 637. A second electrically conductive segment 643 exists between first and second dielectric segments 634 and 635. A third electrically

0253conductive segment 644 exists between the second dielectric segment 635 and submersion line

0254639. The electrically conductive segments 642-644 provide current transfer areas which cause plating current that is supplied through the finger head 633 to be directly passed to the plating liquid contained in a plating bath. This is believed to provide a more uniform current density and more unifoπn voltage profile across the surface of a wafer which is being blanket plated with copper or other plating metals.

0255Fig. 30 shows another plating system wafer support electrode 651 having many of the same features as electrode 631 described immediately above. The same reference numerals have been used to designate similar parts. Electrode 651, however, has three current transfer areas 642-644. The size and shape of areas 642-644 are somewhat different from the corresponding areas of electrode 631. More specifically, the second and third current transfer areas 643 and 644 are elongated along the shaft. The second dielectric sheath segment 635 is shortened. A third dielectric segment 653 has been included. The third dielectric sheath 654

0256forms the submerged dielectric segment 653 and also extends above the submersion line 639 to head 633. The area of the submerged current transfer segments is between 25 and 75 percent of the submerged surface area, more particularly, about 50 percent.

0257Electrode 651 is also provided with a distal contact insert part 655. Insert part 655 is

0258received within an insert receptacle 616 formed in the distal end of the electrode shaft. The insert contact tip 655 defines a contact face 617 wliich bears upon a wafer being held. The

0259insert contact part is made from a conductive material which is preferably non-corrosive material, such as platinum or stainless steel.

0260Fig. 31 shows a further electrode finger construction in the form of electrode finger

0261979. Similar parts to electrode fingers 631 and 651 are similarly numbered in this figure. The

0262electrode shaft is covered by a dielectric sheath 621 which largely covers the electrode shaft and

0263leaves only a first current conductive area 642 which is immediately adjacent to the contact face 637. Tliis construction is contrasted to the electrodes 631 and 651 because electrode finger 979 does not have current transfer areas which comprise 25 percent of the submerged portion of the electrode. It also does not have current transfer areas which are exposed in a manner which is separated by a dielectric segment interpositioned between the contact face 637 and the removed or remote current conductive segment.

0264Fig. 32 shows a further electrode finger 601 which has submerged current transfer areas 642-644. It also has dielectric segments 634 and 635. Dielectric segment 635 of this figure has a differing shape and coverage area as compared to the other electrodes discussed above. In this constraction the dielectric sheath extends along the outer curvature of the electrode J-bend. Curved upper edges extend so as to provide an overlying web portion 603 which covers the inner curvature of the J-bend. Performance in terms of plating uniformity has been found to be superior in some processes which employ the electrode of this figure.

0265The electrodes 631, 651 and 601 are preferably used in novel processes according to this invention. These processes include contacting a surface of the semiconductor article or wafer with an electrode at a contact face thereof. The methods also include submersing a portion or portions of the electrode into a plating bath containing a plating liquid which is typically a solution and mixture have various components known in the art. The methods also preferably include wetting a processed surface of the semiconductor article with the plating bath. Further included is the step of moving or conducting electrical current through the electrode and plating bath to perform an electroplating action to occur upon at least the processed surface of the wafer or other article. The methods further advantageously include diverting a portion of the electrical current directly between the electrode and the plating bath along at least one electrically conductive segment of the electrode. The electrically conductive segment is preferably spaced from the contact face a substantial distance, such as greater than 5 millimeters, and preferably is spaced therefrom by an intervening dielectric sheath.

0266Fig. 33 shows another electrode finger 681 which is similar to electrode finger 651

0267except that it includes a full dielectric sheath 682 which extends from above submersion line

0268639 to contact insert side walls 619. This construction preferably uses a coating layer 682,

0269such as from polyvinylidene fluoride, which can be applied by dipping or otherwise forming the layer over the shaft of the electrode. This construction includes the dielectric layer over the distal end of the electrode shaft and into sealing relationship with the side walls of the insert

0270contact part or tip 655. The dielectric coating or other layer 682 excludes corrosive processing fluids. Since the contact tip is preferably made from a non-corrosive material, such as platinum, the only material of the electrode wliich is exposed to direct corrosive action is the non-corrosive tip which is able to maintain good service despite the difficult operating environment.

0271Additionally, the construction of electrode 681 is particularly advantageous because the joint formed between the inserted contact tip 655 and receptacle 616 is covered and protected from direct exposure to the corrosive plating liquid and fumes present in the processing chamber.

0272The methods for using the foregoing wafer contact include contacting a surface of the wafer with an electrode assembly using a contact face, such as face 617, on a contact part, such as contact insert part 655. The contact insert is mounted on the distal end of the electrode shaft. It is further preferably provided with a dielectric layer formed about the distal end in sealing relationship against the contact part. The methods further preferably include submersing or otherwise wetting a processed surface of the wafer, such as in a plating bath liquid used to plate the wafer with a plating material. The methods also preferably include excluding the plating bath liquified from the contact part joint, such as the joint formed between the contact part 655 and receptacle 616. The methods further include electroplating the wafer with plating material by passing electrical current through the contact part and between the semiconductor wafer and electrode assembly. The contact face plating layer is more preferably formed from the plating material as is described below in additional detail. The method is most preferably used to plate copper onto the surface of semiconductor materials, such as silicon or oxides thereof. Figs. 34 and 35 illustrate a fuither embodiment of a electrode contact finger 2026. Finger 2026 comprises a shaft 2027 made from a conductive metal, such as stainless steel, titanium, platinum-plated titanium or other noble metals plated with platinum, that is suitable for forging into the desired shape. The embodiment shown is again a J-shape. Finger 2026 also comprises a contact tip 2028, which is comprised of a an alternate conducting metal, such as platinum, copper, tantalum, platinum plated tungsten, or other metal plated with platinum. The tip 2028 is is attached to the finger shaft 2027 by pressing it into the shaft, also known as a pressed interference fit. It may also be attached by a diffusion bond process. The shaft may be coated with a dielectric material. This electrode constructionmakes it possible to use a contact tip comprising a different metal from the one used in the finger shaft. This finger is also useful in that smaller amounts of conducting metals, particularly expensive metals, may be utilized in the contact tip while using a suitable but less expensive material for the shaft. The contact tip is more robust to plating processes and conditions than a solid metal. Problems such as flaking off of the plated metal layer, product or wafer contamination and inconsistent current

0273conductance (i.e., caused when a plated metal tip, e.g., Pt/Ti, begins to lose some of its Pt plating, the exposed undermetal may become oxidized and form a non-conductive coating), that are associated with plated contacts are avoided. Also, this results in an electrode that may be more robust, particularly if the tip is a solid single metal tip and suitable for more aggressive cleaning schedules and processes. This finger may also optionally be coated with a dielectric material, such as polyvinylidene fluoride. This coating may be over a portion of the electrode, from about 10% to about 90%, or alternatively from about 25% to about 75% of the surface area. Figs. 36 - 39 illustrate another wafer contact 2030, comprising a finger shaft 2031 and a pin 2032. The finger has an aperture 2033, to receive a locking pin for attachment to the finger assembly of a plating apparatus. In this embodiment, no platinum coating is used on the finger, which thereby increases the useful life of the electrode finger. The finger is made of titanium or other suitable metal, and then coated with a dielectric material. Additionally, because lesser amounts of platinum, a relatively expensive metal, are used, the finger assembly 2030 can be manufactured at a lower cost than certain other fmger electrodes. Press in pin 2032 acts as a contact and may further act as a current thief. As the metal pin is solid, it is a more robust finger those made with coated metal layers. The pin 2032 may be attached by a diffusion bond in order to provide greater corrosion protection and electrical contact integrity. In this embodiment, the pin is referred to as an "on-axis" current thief. It may also optionally be partially coated with a dielectric material, such as polyvinylidene fluoride. This coating may be over a portion of the electrode, from about 10% to about 90%, or alternatively from about 25% to about 75% of the surface area.

0274Figs. 40 and 41 illustrate another finger assembly 2040, comprising finger 2041 and spring pin 2042. In this embodiment, the finger tip contact has a radius tip. The radius tip helps reduce occurrence of high current density locahzation when the tip first contacts the surface to be plated, which can lead to variability and inconsistencies in plating uniformity during electroplating. Such a configuration also alleviates the diversion of current density from the wafer back to the finger itself that may occur with tips with 90 degree edges during the plating process. Tliis assembly may comprise a dielectric coating, such as polyvinylidene fluoride, over a portion of the surface area of the electrode, from about 10% to about 90%, or alternatively from about 25% to about 75% of the surface area.

0275The example in Figs. 41 - 43 show an embodiment of the radius tip electrode fmger having a finger 2051, bayonet mount boot 2052 and spring pin 2053. The bayonet boot comprises a fluoroelastomer, such as for example, AFLAS or KAL-REZ, which must be inert to the plating solution used in electroplating. The boot protects the spring pin 2053 from exposure to plating solution. This is particularly useful when the finger is turned upside down as part of the plating process, and the solution drips down the finger shaft where it may lead to problems such as disturbing mechanical and electrical connections, and plating of metal at undesired areas of the finger or apparatus. This embodiment is otherwise similar to fingers in FIGS. 39-40.

0276Fig. 44 shows a further electrode finger 583 which has features similar to 651 and such

0277similar features are identified with the same reference numbers. Electrode finger 583 differs from finger 651 in that the electrode shaft 584 is covered between the head 633 to the distal end of the electrode shaft with a cover or boot 585. Boot 585 is preferably made in a manner

0278which provides a continuous cover from near the electrode head 633 to a distal contact lip 586.

0279The boot includes additional features adjacent the contact insert part 655. More specifically,

0280the boot includes a sl irt portion 587 which extends above the electrode shaft distal end surface

0281588. The contact face 617 of the insert part 655 is preferably about even with the distal contact

0282lip 586 which is formed upon the end of the skirt portion 587. The skirt portion serves as a defoπnable seal wliich comes into contact with a surface of a wafer or other semiconductor wafer being contacted. .Alternatively, the contact 617 may extend beyond the slάrt by a distance corresponding to the depth of a photoresist layer or the like. This electrode configuration may be used in patterned plating operations in which the contact extends into contact with a seed layer or of the like beyond the depth of a photoresist layer or the like while the skirt assists in preventing direct deposition in the region of the contact. Figs. 45 and 46 illustrate such use. The methods involve plating metals onto the surface of semiconductor wafers, specifically onto a semiconductor wafer W which has a substrate or other subjacent layer 561 which has been previously provided with a thin metallic

0283seed layer 562 which is shown by a heavy black line in that figure. A via or other opening 563 exists in a photoresist layer 564 which overlies the substrate and seed layers.

0284Fig. 45 shows the electrode 583 poised in a disengaged position in preparation for contact with the surface while Fig. 41 shows the electrode 583 retracted against the surface of the wafer in contact with the seed layer. In the engaged position the contact face 617 is extended through the opening 563 and into direct electrical contact with exposed areas of the seed layer 562 which are not covered by the layer of photoresist or other covering layer. A seal is formed by depressing the skirt 587 and attached lip 586 against the outer surface of the photoresist layer 564.

0285The novel methods of using such an electrode construction include selecting an electrode assembly having desired features, such the features of electrode finger 583. More specifically, the selecting step preferably includes selecting an electrode assembly having an electrode contact which is surrounded by an electrode boot or other sealing member. The methods also include engaging coated surface portions, such as photoresist layer 564, with the sealing member or boot. The sealing can occur about a continuous peripheral sealing line, such as defined by the engagement of lip 586 against the photoresist surface. It is important to engage the lip against the photoresist surface and not against the seed layer 562 because sealing against the seed layer can cause erosive or corrosive effects to occur at or near the line or area of engagement of the boot with the seed layer. Such erosive or corrosive actions can cause the seed layer to become discontinuous or even totally isolated. A discontinuous or isolated contact region will lead to electroplating failure because the needed current will not be communicated in an even manner to the areas adjacent to the electrode which need current to accomplish plating. The engagement of the seal against the coating causes a sealed space to be enclosed within the seal by the electrode boot and the processed surface of the wafer.

0286The novel methods further include enclosing a via or other opening within the seal. The via is present on the processed surface and has associated exposed seed layer portions therein for allowing electrical contact to be made. The via is needed to allow direct contact between the contact face of the electrode finger assembly and the seed layer which is used to communicate electrical current across the wafer for electroplating a metal thereonto. Thus, the methods further include contacting the seed layer through the via with the electrode contact to

0287form an electrically conductive connection between the electrode assembly and the seed layer. This contacting step is advantageously performed using a contact face which bears upon the seed layer and is enclosed with the sealed space. Other desirable attributes explained hereinabove in connection with other electrodes can also be utilized to advantage in perforaiing this process.

0288The methods still further include wetting the processed surface of the wafer with a plating or other processing liquid. This is typically done by lowering the wafer holder into position to bring the outer, processed surface of the wafer into direct contact with a plating liquid held in a plating bath, such as described elsewhere herein in additional detail.

0289The methods also preferably include passing electrical current through the electrode and plating bath to cause electroplating to occur upon exposed seed layer areas of the processed surface. Such exposed seed layer areas may be trenches, vias or other features where the photoresist layer 564 is not present to cover the seed layer 562. The electrical current causes electroplating to occur on such exposed seed layer areas.

0290Still further, the methods preferably include excluding plating or other processing liquid from the sealed space to substantially reduce or eliminate plating or other action in the area

0291immediate adjacent to the contact with the electrode.

0292Figs. 46 and 47 illustrate pre-conditioning of a wafer contact electrode in accordance with further features of the disclosed plating system. Fig. 46 shows distal end portions of an electrode 614. Electrode 614 is otherwise similar to electrode 681 described above. At the distal end of electrode finger 614 is a distal exposed surface 615 that is made from a material,

0293such as stainless steel or tungsten. A dielectric sheath 616 is provided along the exterior

0294portions of the electrode adjacent to the distal exposed surface 615.

0295Fig. 47 shows the electrode 614 with a deposited contact face plating layer 618 formed thereon. The layer 618 is preferably a layer made from the same or a very similar material as is being plated onto the semiconductor wafers with wliich electrode 614 is to be used. For example, if copper is being plated onto the semiconductor device, then the layer 618 is a layer plated from the same plating bath or from a plating bath which will provide a layer 618 which is the same or very similar to the constituency of the copper deposited onto the semiconductor device being plated. Preferably, the exposed distal surfaces 615 are placed into a plating bath and electrical current is conducted through the bath and distal end of the electrode 614. This causes a plating action to occur which deposits the layer 618. The resulting layer is preferably at least 1 micron in thickness, more preferably in the approximate range of 1-100 microns thick. Alternatively, the resulting layer may be at least 0.01 microns in thickness, more preferably from about OJ to about 100 microns thick.

0296This method and resulting construction results in a pre-conditioned electrode contact surface wliich is of the same or very similar material as plated onto the semiconductor device during the later plating operation. The use of the same or similar materials prevents galvanic or other types of chemical reactions from developing due to dissimilarity of the metals involved.

0297The pre-conditioned wafer contact electrodes may be used in methods for plating metals onto the surface of a semiconductor wafer that include contacting a surface of the semiconductor wafer with an electrode at a contact face forming a part of the electrode. The contact face is covered or substantially covered by a contact face plating layer. The contact face plating layer is formed from a contact face plating material which is the same or chemically similar to thee plating material which is to be plated onto the semiconductor wafer during processing. The methods also preferably include submersing or otherwise wetting a processed surface of the wafer into a plating bath or using a plating liquid or fluid. Other means for depositing the plating material as a contact face layer may alternatively be used. The methods further include electroplating wafer plating material onto the semiconductor wafer by passing electrical current between the wafer and the electrode having such contact face plating layer. The methods are of particular advantage in the plating of copper onto semiconductors using a copper contact face plating layer.

0298This method and resulting construction results in a pre-conditioned electrode contact surface which is of the same or very similar material as plated onto the semiconductor device during the later plating operation. The use of the same or similar materials prevents galvanic or other types of chemical reactions from developing due to dissimilarity of the metals involved.

0299Numerous modifications may be made to the foregoing system without departing from the basic teachings thereof. Although the present invention has been described in substantial detail with reference to various specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the scope and spirit of the invention as set forth in the appended claims.