Lipseals and contact elements for semiconductor electroplating apparatuses

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application is a divisional of and claims priority to U.S. patent application Ser. No. 13/584,343, filed Aug. 13, 2012, which claims the benefit of U.S. Provisional Patent Application No. 61/523,800, filed Aug. 15, 2011 and titled “LIPSEALS AND CONTACT ELEMENTS FOR SEMICONDUCTOR ELECTROPLATING APPARATUSES,” all of which are hereby incorporated by reference herein in their entireties for all purposes.

TECHNICAL FIELD

0002This invention relates to the formation of damascene interconnects for integrated circuits, and electroplating apparatuses which are used during integrated circuit fabrication.

BACKGROUND

0003Electroplating is a common technique used in integrated circuit (IC) fabrication to deposit one or more layers of conductive metal. In some fabrication processes it is used to deposit single or multiple levels of copper interconnects between various substrate features. An apparatus for electroplating typically includes an electroplating cell having a pool/bath of electrolyte and a clamshell designed to hold a semiconductor substrate during electroplating.

0004During operation of the electroplating apparatus, a semiconductor substrate is submerged into the electrolyte pool such that one surface of the substrate is exposed to electrolyte. One or more electrical contacts established with the substrate surface are employed to drive an electrical current through the electroplating cell and deposit metal onto the substrate surface from metal ions available in the electrolyte. Typically, the electrical contact elements are used to form an electrical connection between the substrate and a bus bar acting as a current source. However, in some configurations, a conductive seed layer on the substrate contacted by the electrical connections may become thinner towards the edge of the substrate, making it more difficult to establish an optimal electrical connection with the substrate.

0005Another issue arising in electroplating is the potentially corrosive properties of the electroplating solution. Therefore, in many electroplating apparatus a lipseal is used at the interface of the clamshell and substrate for the purpose of preventing leakage of electrolyte and its contact with elements of the electroplating apparatus other than the inside of the electroplating cell and the side of the substrate designated for electroplating.

SUMMARY OF THE INVENTION

0006Disclosed herein are lipseal assemblies for use in an electroplating clamshell for engaging and supplying electrical current to a semiconductor substrate during electroplating. In some embodiments, a lipseal assembly may include an elastomeric lipseal for engaging the semiconductor substrate and one or more contact elements for supplying electrical current to the semiconductor substrate during electroplating. In some embodiments, upon engagement, the elastomeric lipseal substantially excludes plating solution from a peripheral region of the semiconductor substrate.

0007In some embodiments, the one or more contact elements are structurally integrated with the elastomeric lipseal and include a first exposed portion which contacts the peripheral region of the substrate upon engagement of the lipseal with the substrate. In some embodiments, the one or more contact elements may further include a second exposed portion for making an electrical connection with an electrical current source. In certain such embodiments, the current source may be a bus bar of the electroplating clamshell. In some embodiments, the one or more contact elements may further include a third exposed portion connecting the first and second exposed portions. In certain such embodiments, the third exposed portion may be structurally integrated on a surface of the elastomeric lipseal.

0008In some embodiments, the one or more contact elements may include an unexposed portion connecting the first and second exposed portions, and the unexposed portion may be structurally integrated underneath a surface of the elastomeric lipseal. In certain such embodiments, the elastomeric lipseal is molded over the unexposed portion.

0009In some embodiments, the elastomeric lipseal may include a first inner diameter defining a substantially circular perimeter for excluding a plating solution from a peripheral region, and the first exposed portion of the one or more contact elements may define a second inner diameter that is larger than the first inner diameter. In certain such embodiments, the magnitude of the difference between the first inner diameter and the second inner diameter is about or less than 0.5 mm. In certain such embodiments, the magnitude of the difference between the first inner diameter and the second inner diameter is about or less than 0.3 mm.

0010In some embodiments, a lipseal assembly may include one or more flexible contact elements for supplying electrical current to the semiconductor substrate during electroplating. In certain such embodiments, at least a portion of the one or more flexible contact elements may be conformally positioned on an upper surface of the elastomeric lipseal and, upon engagement with the semiconductor substrate, the flexible contact elements may be configured to flex and form a conformal contact surface that interfaces with the semiconductor substrate. In certain such embodiments, the conformal contact surface interfaces with a bevel edge of the semiconductor substrate.

0011In some embodiments, the one or more flexible contact elements may have a portion which is not configured to contact the substrate when the substrate is engaged by the lipseal assembly. In certain such embodiments, the non-contacting portion comprises a non-conformable material. In some embodiments, the conformal contact surface forms a continuous interface with the semiconductor substrate, whereas in some embodiments, the conformal contact surface forms a non-continuous interface with the semiconductor substrate having gaps. In certain such later embodiments, the one or more flexible contact elements may include multiple wire tips or a wire mesh disposed on the surface of the elastomeric lipseal. In some embodiments, the one or more flexible contact elements conformally positioned on the upper surface of the elastomeric lipseal include conductive deposits formed using one or more techniques selected from chemical vapor deposition, physical vapor deposition, and electroplating. In some embodiments, the one or more flexible contact elements conformally positioned on the upper surface of the elastomeric lipseal may include an electrically conductive elastomeric material.

0012Also disclosed herein are elastomeric lipseals for use in an electroplating clamshell for supporting, aligning, and sealing a semiconductor substrate in the electroplating clamshell. In some embodiments, the lipseal includes a flexible elastomeric support edge and a flexible elastomeric upper portion located above the flexible elastomeric support edge. In some embodiments, the flexible elastomeric support edge has a sealing protrusion configured to support and seal the semiconductor substrate. In certain such embodiments, upon sealing the substrate, the sealing protrusion defines a perimeter for excluding plating solution. In some embodiments, the flexible elastomeric upper portion includes a top surface configured to be compressed, and an inner side surface located outward relative to the sealing protrusion. In certain such embodiments, the inner side surface may be configured to move inward and align the semiconductor substrate upon compression of the top surface, and in some embodiments, configured to move inward by about or at least 0.2 mm upon compression of the top surface. In some embodiments, when the top surface is not compressed, the inner side surface is located sufficiently outward to allow the semiconductor substrate to be lowered through the flexible elastomeric upper portion and placed onto the sealing protrusion without contacting the upper portion, but wherein upon placement of the semiconductor substrate on the sealing protrusion and compression of the top surface, the inner side surface contacts and pushes on the semiconductor substrate aligning the semiconductor substrate in the electroplating clamshell.

0013Also disclosed herein are methods of aligning and sealing a semiconductor substrate in an electroplating clamshell having an elastomeric lipseal. In some embodiments, the methods include opening the clamshell, providing a substrate to the clamshell, lowering the substrate through an upper portion of the lipseal and onto a sealing protrusion of the lipseal, compressing a top surface of the upper portion of the lipseal to align the substrate, and pressing on the substrate to form a seal between the sealing protrusion and the substrate. In some embodiments, compressing the top surface of the upper portion of the lipseal causes an inner side surface of the upper portion of the lipseal to push on the substrate aligning it in the clamshell. In some embodiments, compressing the top surface to align the substrate includes pressing on the top surface with a first surface of the cone of the clamshell, and pressing on the substrate to form a seal includes pressing on the substrate with a second surface of the cone of the clamshell.

0014In some embodiments, compressing the top surface to align the substrate includes pushing on the top surface with a first pressing component of the clamshell, and pressing on the substrate to form a seal includes pressing on the substrate with a second pressing component of the clamshell. In certain such embodiments, the second pressing component may be independently movable with respect to the first pressing component. In certain such embodiments, compressing the top surface includes adjusting the pressing force exerted by the first pressing component based upon the diameter of the semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

0015<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of a wafer holding and positioning apparatus for electrochemically treating semiconductor wafers.

0016<figref idref="DRAWINGS">FIG. 2</figref> is a cross-sectional schematic of a clamshell assembly having contact rings made with multiple flexible fingers.

0017<figref idref="DRAWINGS">FIG. 3A</figref> is a cross-sectional schematic of a clamshell assembly having a lipseal assembly with integrated contact elements.

0018<figref idref="DRAWINGS">FIG. 3B</figref> is a cross-sectional schematic of another clamshell assembly having a different lipseal assembly with integrated contact elements.

0019<figref idref="DRAWINGS">FIG. 4A</figref> is a cross-sectional schematic of a lipseal assembly having flexible contact elements.

0020<figref idref="DRAWINGS">FIG. 4B</figref> is a cross-sectional schematic of the lipseal assembly of <figref idref="DRAWINGS">FIG. 4A</figref> shown forming a conformal contact surface interfacing with a semiconductor substrate.

0021<figref idref="DRAWINGS">FIG. 5A</figref> is a cross-sectional schematic of a lipseal assembly configured to align a semiconductor substrate within a clamshell assembly.

0022<figref idref="DRAWINGS">FIG. 5B</figref> is a cross-sectional schematic of the lipseal assembly of <figref idref="DRAWINGS">FIG. 5A</figref> with a surface of the cone of the clamshell assembly pressing on an upper surface of the lipseal assembly.

0023<figref idref="DRAWINGS">FIG. 5C</figref> is a cross-sectional schematic of the lipseal assembly of <figref idref="DRAWINGS">FIG. 5A</figref> and <figref idref="DRAWINGS">FIG. 5B</figref> with a surface of the cone of the clamshell assembly pushing on both an upper surface of the lipseal and on the semiconductor substrate.

0024<figref idref="DRAWINGS">FIG. 6</figref> is a flowchart illustrating a method of electroplating a semiconductor substrate.

DETAILED DESCRIPTION

0025In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented concepts. The presented concepts may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail so as to not unnecessarily obscure the described concepts. While some concepts will be described in conjunction with specific embodiments, it will be understood that these embodiments are not intended to be limiting.

0026An exemplary electroplating apparatus is presented in <figref idref="DRAWINGS">FIG. 1</figref> in order to provide some context for the various lipseal and contact element embodiments disclosed herein. Specifically, <figref idref="DRAWINGS">FIG. 1</figref> presents a perspective view of a wafer holding and positioning apparatus <b>100</b> for electrochemically treating semiconductor wafers. The apparatus <b>100</b> includes wafer-engaging components, which are sometimes referred to as “clamshell components,” or a “clamshell assembly,” or just as a “clamshell.” The clamshell assembly comprises a cup <b>101</b> and a cone <b>103</b>. As will be shown in subsequent figures, the cup <b>101</b> holds a wafer and the cone <b>103</b> clamps the wafer securely in the cup. Other cup and cone designs beyond those specifically depicted here can be used. A common feature is that a cup that has an interior region in which the wafer resides and a cone that presses the wafer against the cup to hold it in place.

0027In the depicted embodiment, the clamshell assembly (which includes the cup <b>101</b> and the cone <b>103</b>) is supported by struts <b>104</b>, which are connected to a top plate <b>105</b>. This assembly (<b>101</b>, <b>103</b>, <b>104</b>, and <b>105</b>) is driven by a motor <b>107</b> via a spindle <b>106</b> connected to the top plate <b>105</b>. The motor <b>107</b> is attached to a mounting bracket (not shown). The spindle <b>106</b> transmits torque (from the motor <b>107</b>) to the clamshell assembly causing rotation of a wafer (not shown in this figure) held therein during plating. An air cylinder (not shown) within the spindle <b>106</b> also provides a vertical force for engaging the cup <b>101</b> with the cone <b>103</b>. When the clamshell is disengaged (not shown), a robot with an end effector arm can insert a wafer in between the cup <b>101</b> and the cone <b>103</b>. After a wafer is inserted, the cone <b>103</b> is engaged with the cup <b>101</b>, which immobilizes the wafer within apparatus <b>100</b> leaving a working surface on one side of the wafer (but not the other) exposed for contact with the electrolyte solution.

0028In certain embodiments, the clamshell assembly includes a spray skirt <b>109</b> that protects the cone <b>103</b> from splashing electrolyte. In the depicted embodiment, the spray skirt <b>109</b> includes a vertical circumferential sleeve and a circular cap portion. A spacing member <b>110</b> maintains separation between the spray skirt <b>109</b> and the cone <b>103</b>.

0029For the purposes of this discussion, the assembly including components <b>101</b>-<b>110</b> is collectively referred to as a “wafer holder” (or “substrate holder”) <b>111</b>. Note however, that the concept of a “wafer holder”/“substrate holder” extends generally to various combinations and sub-combinations of components that engage a wafer/substrate and allow its movement and positioning.

0030A tilting assembly (not shown) may be connected to the wafer holder to permit angled immersion (as opposed to flat horizontal immersion) of the wafer into a plating solution. A drive mechanism and arrangement of plates and pivot joints are used in some embodiments to move wafer the holder <b>111</b> along an arced path (not shown) and, as a result, tilt the proximal end of wafer holder <b>111</b> (i.e., the cup and cone assembly).

0031Further, the entire wafer holder <b>111</b> is lifted vertically either up or down to immerse the proximal end of wafer holder into a plating solution via an actuator (not shown). Thus, a two-component positioning mechanism provides both vertical movement along a trajectory perpendicular to an electrolyte surface and a tilting movement allowing deviation from a horizontal orientation (i.e., parallel to the electrolyte surface) for the wafer (angled-wafer immersion capability).

0032Note that the wafer holder <b>111</b> is used with a plating cell <b>115</b> having a plating chamber <b>117</b> which houses an anode chamber <b>157</b> and a plating solution. The chamber <b>157</b> holds an anode <b>119</b> (e.g., a copper anode) and may include membranes or other separators designed to maintain different electrolyte chemistries in the anode compartment and a cathode compartment. In the depicted embodiment, a diffuser <b>153</b> is employed for directing electrolyte upward toward the rotating wafer in a uniform front. In certain embodiments, the flow diffuser is a high resistance virtual anode (HRVA) plate, which is made of a solid piece of insulating material (e.g. plastic), having a large number (e.g. 4,000-15,000) of one dimensional small holes (0.01 to 0.050 inch in diameter) and connected to the cathode chamber above the plate. The total cross-section area of the holes is less than about 5 percent of the total projected area, and, therefore, introduces substantial flow resistance in the plating cell helping to improve the plating uniformity of the system. Additional description of a high resistance virtual anode plate and a corresponding apparatus for electrochemically treating semiconductor wafers is provided in U.S. patent application Ser. No. 12/291,356, filed on Nov. 7, 2008, which is hereby incorporated by reference herein in its entirety for all purposes. The plating cell may also include a separate membrane for controlling and creating separate electrolyte flow patterns. In another embodiment, a membrane is employed to define an anode chamber, which contains electrolyte that is substantially free of suppressors, accelerators, or other organic plating additives.

0033The plating cell <b>115</b> may also include plumbing or plumbing contacts for circulating electrolyte through the plating cell—and against the work piece being plated. For example, the plating cell <b>115</b> includes an electrolyte inlet tube <b>131</b> that extends vertically into the center of anode chamber <b>157</b> through a hole in the center of anode <b>119</b>. In other embodiments, the cell includes an electrolyte inlet manifold that introduces fluid into the cathode chamber below the diffuser/HRVA plate at the peripheral wall of the chamber (not shown). In some cases, the inlet tube <b>131</b> includes outlet nozzles on both sides (the anode side and the cathode side) of the membrane <b>153</b>. This arrangement delivers electrolyte to both the anode chamber and the cathode chamber. In other embodiments, the anode and cathode chamber are separated by a flow resistant membrane <b>153</b>, and each chamber has a separate flow cycle of separated electrolyte. As shown in the embodiment of <figref idref="DRAWINGS">FIG. 1</figref>, an inlet nozzle <b>155</b> provides electrolyte to the anode-side of membrane <b>153</b>.

0034In addition, plating cell <b>115</b> includes a rinse drain line <b>159</b> and a plating solution return line <b>161</b>, each connected directly to the plating chamber <b>117</b>. Also, a rinse nozzle <b>163</b> delivers deionized rinse water to clean the wafer and/or cup during normal operation. Plating solution normally fills much of the chamber <b>117</b>. To mitigate splashing and generation of bubbles, the chamber <b>117</b> includes an inner weir <b>165</b> for plating solution return and an outer weir <b>167</b> for rinse water return. In the depicted embodiment, these weirs are circumferential vertical slots in the wall of the plating chamber <b>117</b>.

0035As stated above, an electroplating clamshell typically includes a lipseal and one or more contact elements to provide sealing and electrical connection functions. A lipseal may be made from an elastomeric material. The lipseal forms a seal with the surface of the semiconductor substrate and excludes the electrolyte from a peripheral region of the substrate. No deposition occurs in this peripheral region and it is not used for forming IC devices, i.e., the peripheral region is not a part of the working surface. Sometimes, this region is also referred to as an edge exclusion area because the electrolyte is excluded from the area. The peripheral region is used for supporting and sealing the substrate during processing, as well as for making electrical connection with the contact elements. Since it is generally desirable to increase the working surface, the peripheral region needs to be as small as possible while maintaining the functions described above. In certain embodiments, the peripheral region is between about 0.5 millimeters and 3 millimeters from the edge of the substrate.

0036During installation, the lipseal and contact elements are assembled together with other components of the clamshell. One having ordinary skilled in the art would appreciated the difficulty of this operation, particularly, when the peripheral region is small. An overall opening provided by this clamshell is comparable to the size of the substrate (e.g., an opening for accommodating 200 mm wafers, 300 mm wafers, 450 mm wafers, etc.). Furthermore, substrates have their own size tolerances (e.g., +/−0.2 millimeters for a typical 300 mm wafer according to the SEMI specification). A particularly difficult task is alignment of the elastomeric lipseal and contact elements, since both are made from relatively flexible materials. These two components need to have very precise relative location. When a sealing edge of the lipseal and contact elements are positioned too far away from each other, insufficient or no electrical connection may be formed between the contacts and substrate during operation of the clamshell. At the same time, when the sealing edge is positioned too close to the contacts, the contacts may interfere with the seal and cause leakage into the peripheral region. For example, conventional contact rings are often made with multiple flexible “fingers” that are pressed in a spring-like action onto the substrate to establish an electrical connection as shown in the clamshell assembly of <figref idref="DRAWINGS">FIG. 2</figref> (note cup <b>201</b>, cone <b>203</b>, and lipseal <b>212</b>). Not only are these flexible fingers <b>208</b> very difficult to align with respect to the lipseal <b>212</b>, they are also easily damaged during installation and difficult to clean if and when electrolyte gets into the periphery region.

Lipseal Assemblies Having Integrated Contact Elements

0037Provided herein are novel lipseal assemblies having contact elements integrated into elastomeric lipseals. Instead of installing and aligning two separate sealing and electrical components (e.g., a lipseal and a contact ring) in the field, the two components are aligned and integrated during fabrication of the assembly. This alignment is maintained during installation as well as during operation of the clamshell. As such, the alignment needs to be set and inspected only once, i.e., during fabrication of the assembly.

0038<figref idref="DRAWINGS">FIG. 3A</figref> is a schematic representation of a portion of an clamshell <b>300</b> having a lipseal assembly <b>302</b>, in accordance with certain embodiments. Lipseal assembly <b>302</b> includes an elastomeric lipseal <b>304</b> for engaging the semiconductor substrate (not shown). Lipseal <b>304</b> forms a seal with the substrate and excludes a plating solution from a peripheral region of the semiconductor substrate as described in other parts of this document. Lipseal <b>304</b> may include protrusion <b>308</b> extending upwards and towards the substrate. The protrusion may be compressed and to certain degree deformed to establish the seal. Lipseal <b>304</b> has an inner diameter defining a perimeter for excluding the plating solution from the peripheral region.

0039Lipseal assembly <b>302</b> also includes one or more contact elements <b>310</b> structurally integrated into lipseal <b>304</b>. As stated above, contact element <b>310</b> is used for supplying an electrical current to the semiconductor substrate during electroplating. Contact element <b>310</b> includes an exposed portion <b>312</b> defining a second inner diameter that is larger than the first inner diameter of lipseal <b>304</b> in order to prevent interference with the sealing properties of lipseal assembly <b>302</b>. Contact element <b>310</b> generally includes another exposed portion <b>313</b> for making an electrical connection with a source of electrical current such as a bus bar <b>316</b> of the electroplating clamshell. However, other connection schemes are also possible. For example, contact element <b>310</b> may be interconnected with distribution bus <b>314</b>, which may be connected to bus bar <b>316</b>.

0040As stated above, integration of one or more contact elements <b>310</b> into lipseal <b>304</b> is performed during fabrication of lipseal assembly <b>302</b> and is preserved during installation and operation of the assembly. This integration may be performed in a variety of ways. For example, an elastomeric material may be molded over contact element <b>310</b>. Other elements, such as current distribution bus <b>314</b>, may be also integrated into the assembly to improve rigidity, conductivity, and other functionalities of assembly <b>302</b>.

0041The lipseal assembly <b>302</b> illustrated in <figref idref="DRAWINGS">FIG. 3A</figref> has a contact element <b>310</b> with a middle unexposed portion located between the two exposed portions <b>312</b> and <b>313</b> and connecting the two exposed portions. This unexposed portion extends through the body of the elastomeric lipseal <b>304</b> and is fully enclosed by the elastomeric lipseal <b>304</b> being structurally integrated underneath a surface of the elastomeric lipseal. This type of lipseal assembly <b>302</b> may be formed, for example, by molding the elastomeric lipseal <b>304</b> over the unexposed portion of contact element <b>310</b>. Such a contact element may be particularly easy to clean since only small portions of contact element <b>310</b> extend to the surface of lipseal assembly <b>302</b> and are exposed.

0042<figref idref="DRAWINGS">FIG. 3B</figref> illustrates another embodiment where contact element <b>322</b> extends on the surface of elastomeric lipseal <b>304</b> and does not have a middle region enclosed by the lipseal assembly. In some embodiments, the middle region could be viewed as a third exposed portion of the contact element which is structurally integrated on a surface of the elastomeric lipseal, and is located between the first two exposed portions of the contact element <b>312</b> and <b>313</b>, connecting these two portions. This embodiment may be assembled, for example, by pressing contact element <b>322</b> into the surface, or by molding it into the surface, or by gluing it to the surface, or by otherwise attaching it to the surface. Regardless of how the contact elements are integrated into the elastomeric lipseal, a point or surface of the contact element making an electrical connection to the substrate will preferentially maintain its alignment with respect to the point or surface of the lipseal making a seal with the substrate. Other portions of the contact element and lipseal may be movable with respect to each other. For example, an exposed portion of the contact element that makes an electrical connection to the bus bar may move with respect to the lipseal.

0043Returning to <figref idref="DRAWINGS">FIG. 3A</figref>, the first inner diameter defines the peripheral region while the second inner diameter defines overlap between the contact element and substrate. In certain embodiments, the magnitude of the difference between the first and second inner diameters is about or less than 0.5 millimeters (mm), which means that exposed portion <b>312</b> of contact element <b>310</b> is separated by about or less than 0.25 mm from the electrolyte solution. This small separation allows having a relatively small peripheral region while maintaining a sufficient electrical connection to the substrate. In certain such embodiments, the magnitude of the difference between the first and second inner diameters is about or less than 0.4 mm, or about or less than 0.3 mm, or about or less than 0.2 mm, or about or less than 0.1 mm. In other embodiments, the magnitude of the difference between these diameters may be about or less than 0.6 mm, or about or less than 0.7 mm, or about or less than 1 mm. In certain embodiments, the contact elements are configured to conduct at least about 30 Amperes or, more specifically, at least about 60 Amperes. A contact element may include multiple fingers such that each contacting tip of these fingers is fixed with respect to the edge of the lipseal. In the same or other embodiments, an exposed portion of the one or more contact elements includes multiple contact points. These contacts points may extend away from the surface of the elastomeric lipseal. In other embodiments, an exposed portion of the one or more contact elements includes a continuous surface.

0000Lipseal Assemblies Having Flexible Contact Elements which Form a Conformal Contact Surface

0044Electrical connection to the substrate may be significantly improved by increasing the contact surface between the contact elements and the substrate during the sealing of the substrate in the clamshell assembly and the subsequent electroplating. Conventional contact elements (e.g., “fingers” shown in <figref idref="DRAWINGS">FIG. 2</figref>) are designed to make only a “point contact” with the substrate that has a relatively small contact area. When a tip of the contact finger touches the substrate, the finger bends to provide a force against the substrate. While this force may help to decrease the contact resistance somewhat, there oftentimes still remains enough contact resistance to create problems during electroplating. Furthermore, the contact fingers may become damaged over time by many repetitions of the bending action.

0045Described herein are lipseal assemblies having one or more flexible contact elements conformally positioned on an upper surface of an elastomeric lipseal. These contact elements are configured to flex upon engagement with semiconductor substrate and form a conformal contact surface that interfaces with the semiconductor substrate when the substrate is supported, engaged, and sealed by the lipseal assembly. The conformal contact surface is created when the substrate is pressed against the lipseal in a manner similar to the manner in which the seal is created between the substrate and the lipseal. However, the sealing interface surfaces should generally be distinguished from the conformal contact surface even though the two surfaces may be formed adjacent to one another.

0046<figref idref="DRAWINGS">FIG. 4A</figref> illustrates a lipseal assembly <b>400</b> having a flexible contact element <b>404</b> positioned on the upper surface of elastomeric lipseal <b>402</b> prior to positioning and sealing the substrate <b>406</b> onto lipseal <b>402</b>, in accordance with certain embodiments. <figref idref="DRAWINGS">FIG. 4B</figref> illustrates the same lipseal assembly <b>400</b> after the substrate <b>406</b> has been positioned and sealed with the lipseal <b>402</b>, in accordance with certain embodiments. Specifically, flexible contact element <b>404</b> is shown to flex and form a conformal contact surface at the interface with the substrate <b>406</b> when the substrate is held/engaged by the lipseal assembly. The electrical interface between flexible contact element <b>404</b> and substrate <b>406</b> may extend over the (flat) front surface of the substrate and/or the beveled edge surface of the substrate. Overall, a larger contact interface area is formed by providing a conformal contact surface of flexible contact element <b>404</b> at the interface with the substrate <b>406</b>.

0047While the conformal nature of the flexible contact element <b>404</b> is important at the interface with the substrate, the remaining portion of flexible contact element <b>404</b> may also be conformal with respect to lipseal <b>402</b>. For example, flexible contact element <b>404</b> may conformally extend along the surface of lipseal. In other embodiments, the remaining portion of the flexible contact element <b>404</b> may be made from other (e.g., non-conformal) materials and/or have a different (e.g., non-conformal) configuration. Therefore, in some embodiments, the one or more flexible contact elements may have a portion which is not configured to contact the substrate when the substrate is engaged by the lipseal assembly, and this non-contacting portion may comprise a conformable material, or it may comprise a non-conformable material.

0048Furthermore, it should be noted that although a conformal contact surface may form a continuous interface between the flexible contact element <b>404</b> and semiconductor substrate <b>406</b>, it is not required to form a continuous interface. For example, in some embodiments, a conformal contact surface has gaps forming a non-continuous interface with the semiconductor substrate. Specifically, a non-continuous conformal contact surface may be formed from a flexible contact element <b>404</b> which comprises many multiple wire tips and/or a wire mesh disposed on the surface of the elastomeric lipseal. Even if non-continuous, the conformal contact surface follows the shape of the lipseal while the lipseal is being deformed during the closing of the clamshell.

0049Flexible contact element <b>404</b> may be attached to the upper surface of the elastomeric lipseal. For example, flexible contact element <b>404</b> may be pressed, glued, molded, or otherwise attached to the surface, as described above with reference to <figref idref="DRAWINGS">FIG. 3A</figref> and <figref idref="DRAWINGS">FIG. 3B</figref> (albeit not in the specific context of flexible contact elements which form a conformal contact surface). In other embodiments, flexible contact element <b>404</b> may be positioned over the upper surface of the elastomeric lipseal without providing any specific bonding features between the two. In either case, conformality of flexible contact element <b>404</b> is ensured by the force exerted by the semiconductor substrate when the clamshell is closed. Furthermore, although the portion of the flexible contact element <b>404</b> which interfaces with the substrate <b>406</b> (forming a conformal contact surface) is an exposed surface, other portions of the flexible contact element <b>404</b> may be unexposed, for example, being integrated underneath a surface of the elastomeric lipseal, in a manner somewhat similar to the integrated, albeit non-conformal, lipseal assembly illustrated in <figref idref="DRAWINGS">FIG. 3B</figref>.

0050In certain embodiments, a flexible contact element <b>404</b> includes a conductive layer of conductive deposits deposited on the upper surface of the elastomeric lipseal. The conductive layer of conductive deposits may be formed/deposited using chemical vapor deposition (CVD), and/or physical vapor deposition (PVD), and/or (electro)plating. In some embodiments, the flexible contact element <b>404</b> may be made of an electrically conductive elastomeric material.

Substrate Aligning Lipseals

0051As previously explained, the peripheral region of the substrate from which plating solution is excluded needs to be small, which requires careful and precise alignment of the semiconductor substrate prior to closing and sealing the clamshell. Misalignment may cause leaking on the one hand, and/or unnecessary covering/blocking of substrate working areas on the other. Tight substrate diameter tolerances may cause additional difficulties during alignment. Some alignment may be provide by the transfer mechanism (e.g., depending on the accuracy of a robot handoff mechanism), and by using alignment features such as snubbers positioned in the side walls of the clamshell cup. However, the transfer mechanism needs to be precisely installed and aligned during installation with respect to the cup (i.e., “taught” about relative position of other components) in order to provide precise and repetitive positioning of the substrates. This robot teaching and alignment process is rather difficult to perform, is labor intensive, and requires highly skilled personnel. Furthermore, the snubber features are difficult to install and tend to have big tolerance stack-ups because there are many parts positioned between the lipseal and snubbers.

0052Accordingly, disclosed herein are lipseals which are not only used for supporting and sealing the substrate in the clamshell but also for aligning the substrate in the clamshell prior to sealing. Various features of such lipseals will now be described with reference to <figref idref="DRAWINGS">FIGS. 5A through 5C</figref>. Specifically, <figref idref="DRAWINGS">FIG. 5A</figref> is a cross-sectional schematic representation of a clamshell portion <b>500</b> having a lipseal <b>502</b> supporting a substrate <b>509</b> prior to compressing a portion of lipseal <b>502</b>, in accordance with certain embodiments. Lipseal <b>502</b> includes a flexible elastomeric support edge <b>503</b> comprising a sealing protrusion <b>504</b>. The sealing protrusion <b>504</b> is configured to engage the semiconductor substrate <b>509</b>, providing support, and forming a seal. Sealing protrusion <b>504</b> defines a perimeter for excluding a plating solution, and may have a first inner diameter (see <figref idref="DRAWINGS">FIG. 5A</figref>) defining the exclusion perimeter. It should be noted that the perimeter and/or first inner diameter may slightly change while sealing the substrate against the elastomeric lipseal due to deformation of the sealing protrusion <b>504</b>.

0053Lipseal <b>502</b> also includes a flexible elastomeric upper portion <b>505</b> located above the flexible elastomeric support edge <b>503</b>. The flexible elastomeric upper portion <b>505</b> may include a top surface <b>507</b> configured to be compressed, and also an inner side surface <b>506</b>. The inner side surface <b>506</b> may be located outward relative to the sealing protrusion <b>504</b> (meaning that the inner side surface <b>506</b> is located further from the center of a semiconductor substrate being held by the elastomeric lipseal than the sealing protrusion <b>504</b>), and be configured to move inward (towards the center of a semiconductor substrate being held) when the top surface <b>507</b> is compressed by another component of the electroplating clamshell. In some embodiments, at least a portion of the inner side surface is configured to move inward by at least about 0.1 mm, or at least about 0.2 mm, or at least about 0.3 mm, or at least about 0.4 mm, or at least about 0.5 mm. This inward motion may cause the inner side surface <b>506</b> of the lipseal to contact the edge of a semiconductor substrate resting on the sealing protrusion <b>504</b>, pushing the substrate towards the center of the lipseal and thus aligning it within the electroplating clamshell. In some embodiments, the flexible elastomeric upper portion <b>505</b> defines a second inner diameter (see <figref idref="DRAWINGS">FIG. 5A</figref>) which is greater than the first inner diameter (described above). When top surface <b>507</b> is not compressed, the second inner diameter is greater than the diameter of the semiconductor substrate <b>509</b>, so that the semiconductor substrate <b>509</b> may be loaded into the clamshell assembly by lowering it through the flexible elastomeric upper portion <b>505</b> and placing it onto the sealing protrusion <b>504</b> of flexible elastomeric support edge <b>503</b>.

0054Elastomeric lipseal <b>502</b> may also have an integrated or otherwise attached contact element <b>508</b>. In other embodiments, contact element <b>508</b> may be a separate component. In any event, whether or not it is a separate component, if contact element <b>508</b> is provided on inner side surface <b>506</b> of lipseal <b>502</b>, then contact element <b>508</b> may also be involved in the aligning of the substrate. Thus, in these examples, if present, contact element <b>508</b> is considered to be a part of inner side surface <b>506</b>.

0055Compression of the top surface <b>507</b> of the elastomeric upper portion <b>505</b> (in order to align and seal the semiconductor substrate within the electroplating clamshell) may be accomplished in a variety of ways. For instance, top surface <b>507</b> may be compressed by a portion of the cone or some other component of the clamshell. <figref idref="DRAWINGS">FIG. 5B</figref> is a schematic representation of the same clamshell portion shown in <figref idref="DRAWINGS">FIG. 5A</figref> immediately prior to being compressed with cone <b>510</b>, in accordance with certain embodiments. If cone <b>510</b> is used to press on top surface <b>507</b> of upper portion <b>505</b> in order to deform upper portion as well as to press on substrate <b>509</b> in order to seal substrate <b>509</b> against sealing protrusion <b>504</b>, then cone may have two surfaces <b>511</b> and <b>512</b> offset with respect to each other in a particular way. Specifically, first surface <b>511</b> is configured to press top surface <b>507</b> of upper portion <b>505</b>, while second surface <b>512</b> is configured to press on substrate <b>509</b>. Substrate <b>509</b> is generally aligned prior to sealing substrate <b>509</b> against sealing protrusion <b>504</b>. Therefore, first surface <b>511</b> may need to press on top surface <b>507</b> prior to second surface <b>512</b> pressing on substrate <b>509</b>. As such, a gap may exist between second surface <b>512</b> and substrate <b>509</b> when first surface <b>511</b> contacts top surface <b>507</b>, as shown in <figref idref="DRAWINGS">FIG. 5B</figref>. This gap may depend on necessary deformation of upper portion <b>505</b> to provide alignment.

0056In other embodiments, top surface <b>507</b> and substrate <b>509</b> are pressed by different components of the clamshell that may have independently controlled vertical positioning. This configuration may allow for independently controlling the deformation of upper portion <b>505</b> prior to pressing onto the substrate <b>509</b>. For example, some substrates may have larger diameters than others. Alignment of such larger substrates may need and even require, in certain embodiments, less deformation than smaller substrates because there is a less initial gap between the larger substrates and inner side surface <b>506</b>.

0057<figref idref="DRAWINGS">FIG. 5C</figref> is a schematic representation of the same clamshell portion shown in <figref idref="DRAWINGS">FIG. 5A</figref> and <figref idref="DRAWINGS">FIG. 5B</figref> after the clamshell is sealed, in accordance with certain embodiments. Compression of top surface <b>507</b> of upper portion <b>505</b> by first surface <b>511</b> of cone <b>510</b> (or some other compressing components) causes deformation of upper portion <b>505</b> such that inner side surface <b>506</b> moves inwards, contacting and pushing on semiconductor substrate <b>509</b>, in order to align semiconductor substrate <b>509</b> in the clamshell. While <figref idref="DRAWINGS">FIG. 5C</figref> illustrates a cross-section of a small portion of the clamshell, one of ordinary skill in the art would appreciate that this alignment process occurs simultaneously around the entire perimeter of substrate <b>509</b>. In certain embodiments, a portion of the inner side surface <b>506</b> is configured to move by at least about 0.1 mm, or at least about 0.2 mm, or at least about 0.3 mm, or at least about 0.4 mm, or at least about 0.5 mm towards a center of the lipseal when the top surface <b>507</b> is compressed.

Methods of Aligning and Sealing a Substrate in a Clamshell

0058Also disclosed herein are methods of aligning and sealing a semiconductor substrate in an electroplating clamshell having an elastomeric lipseal. The flowchart of <figref idref="DRAWINGS">FIG. 6</figref> is illustrative of some of these methods. For instance, some embodiment methods involve opening the clamshell (block <b>602</b>), providing a substrate to the electroplating clamshell (block <b>604</b>), lowering the substrate through an upper portion of the lipseal and onto a sealing protrusion of the lipseal (block <b>606</b>), and compressing a top surface of the upper portion of the lipseal to align the substrate (block <b>608</b>). In some embodiments, compressing the top surface of the upper portion of the elastomeric lipseal during operation <b>608</b> causes an inner side surface of the upper portion to contact the semiconductor substrate and push on the substrate aligning it in the clamshell.

0059After aligning the semiconductor substrate during operation <b>608</b>, in some embodiments, the method proceeds by pressing on the semiconductor substrate in operation <b>610</b> to form a seal between the sealing protrusion and the semiconductor substrate. In certain embodiments, compressing the top surface continues during pressing on the semiconductor substrate. For example, in certain such embodiments, compressing the top surface and pressing on the semiconductor substrate may be performed by two different surfaces of the cone of the clamshell. Thus, a first surface of the cone may press on the top surface to compress it, and a second surface of the cone may press on the substrate to form a seal with the elastomeric lipseal. In other embodiments, compressing the top surface and pressing on the semiconductor substrate are performed independently by two different components of the clamshell. These two pressing components of the clamshell are typically independently movable with respect to one another, thus allowing compression of the top surface to be halted once the substrate is pressed upon and sealed against the lipseal by the other pressing component. Furthermore, the compression level of the top surface may be adjusted based upon the diameter of the semiconductor substrate by independently altering the pressing force exerted upon it by its associated pressing component.

0060These operations may be part of a larger electroplating process, which is also depicted in the flowchart of <figref idref="DRAWINGS">FIG. 6</figref> and briefly described below.

0061Initially, the lipseal and contact area of the clamshell may be clean and dry. The clamshell is opened (block <b>602</b>) and the substrate is loaded into the clamshell. In certain embodiments, the contact tips sit slightly above the plane of the sealing lip and the substrate is supported, in this case, by the array of contact tips around the substrate periphery. The clamshell is then closed and sealed by moving the cone downward. During this closure operation, the electrical contacts and seals are established according to various embodiments described above. Further, the bottom corners of the contacts may be force down against the elastic lipseal base, which results in additional force between the tips and the front side of the wafer. The sealing lip may be slightly compressed to ensure the seal around the entire perimeter. In some embodiments, when the substrate is initially positioned into the cup only the sealing lip is contact with the front surface. In this example, the electrical contact between the tips and the front surface is established during compression of the sealing lip.

0062Once the seal and the electrical contact is established, the clamshell carrying the substrate is immersed into the plating bath and is plated in the bath while being held in the clamshell (block <b>612</b>). A typical composition of a copper plating solution used in this operation includes copper ions at a concentration range of about 0.5-80 g/L, more specifically at about 5-60 g/L, and even more specifically at about 18-55 g/L and sulfuric acid at a concentration of about 0.1-400 g/L. Low-acid copper plating solutions typically contain about 5-10 g/L of sulfuric acid. Medium and high-acid solutions contain about 50-90 g/L and 150-180 g/L sulfuric acid, respectively. The concentration of chloride ions may be about 1-100 mg/L. A number of copper plating organic additives such as Enthone Viaform, Viaform NexT, Viaform Extreme (available from Enthone Corporation in West Haven, Conn.), or other accelerators, suppressors, and levelers known to those of skill in the art can be used. Examples of plating operations are described in more detail in U.S. patent application Ser. No. 11/564,222 filed on Nov. 28, 2006, which is hereby incorporated by reference in its entirety herein for all purposes, but in particular for the purpose of the describing plating operations. Once the plating is completed and an appropriate amount of material has been deposited on the front surface of the substrate, the substrate is then removed from the plating bath. The substrate and clamshell are then spun to remove most of the residual electrolyte on the clamshell surfaces which has remained there due to surface tension and adhesive forces. The clamshell is then rinsed while continued to be spun to dilute and flush as much of the entrained electrolytic fluid as possible from clamshell and substrate surfaces. The substrate is then spun with rinsing liquid turned off for some time, usually at least about 2 seconds to remove some remaining rinsate. The process may proceed by opening the clamshell (block <b>614</b>) and removing the processed substrate (block <b>616</b>). Operational blocks <b>604</b> through <b>616</b> may be repeated multiple times for new wafer substrates, as indicated in <figref idref="DRAWINGS">FIG. 6</figref>.

0063In certain embodiments, a system controller is used to control process conditions during sealing the clamshell and/or during processing of the substrate. The system controller will typically include one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc. Instructions for implementing appropriate control operations are executed on the processor. These instructions may be stored on the memory devices associated with the controller or they may be provided over a network.

0064In certain embodiments, the system controller controls all of the activities of the processing system. The system controller executes system control software including sets of instructions for controlling the timing of the processing steps listed above and other parameters of a particular process. Other computer programs, scripts or routines stored on memory devices associated with the controller may be employed in some embodiments.

0065Typically, there is a user interface associated with the system controller. The user interface may include a display screen, graphical software to display process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc.

0066The computer program code for controlling the above operations can be written in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program.

0067Signals for monitoring the processes may be provided by analog and/or digital input connections of the system controller. The signals for controlling the processes are output on the analog and digital output connections of the processing system.

0068The apparatuses/processes described hereinabove may be used in conjunction with lithographic patterning tools or processes, for example, for the fabrication or manufacture of semiconductor devices, displays, LEDs, photovoltaic panels and the like. Typically, though not necessarily, such tools/processes will be used or conducted together in a common fabrication facility. Lithographic patterning of a film typically comprises some or all of the following steps, each step enabled with a number of possible tools: (1) application of photoresist on a workpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curing of photoresist using a hot plate or furnace or UV curing tool; (3) exposing the photoresist to visible or UV or x-ray light with a tool such as a wafer stepper; (4) developing the resist so as to selectively remove resist and thereby pattern it using a tool such as a wet bench; (5) transferring the resist pattern into an underlying film or workpiece by using a dry or plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF or microwave plasma resist stripper.

Other Embodiments

0069Although illustrative embodiments and applications of this invention are shown and described herein, many variations and modifications are possible which remain within the concept, scope, and spirit of the invention, and these variations would become clear to those of ordinary skill in the art after perusal of this application. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.