Substrate transfer shuttle

RELATED APPLICATIONS

P-0001[0001] The present application is related to co-pending U.S. patent application Ser. No. 08/946,922, entitled “MODULAR CLUSTER PROCESSING SYSTEM,” filed Oct. 8, 1997. The present application is also related to the following U.S. patent applications which are being filed concurrently with this application: (1) “Method and Apparatus for Substrate Transfer and Processing” [attorney docket 2519/US/AKT (05542/235001)]; (2) “Multi-Function Chamber For A Substrate Processing System,” [attorney docket 2712/US/AKT (05542/268001)]; (3) “An Automated Substrate Processing System,” [attorney docket 2429/US/AKT (05542/245001)]; (4) “Substrate Transfer Shuttle Having a Magnetic Drive,” [attorney docket 2638/US/AKT (05542/264001)]; (5) “In-Situ Substrate Transfer Shuttle,” [attorney docket 2703/US/AKT (05542/266001)]; and (6) Modular Substrate Processing System,” [attorney docket 2311/US/AKT (05542/233001)].

P-0002[0002] The foregoing patent applications, which are assigned to the assignee of the present application, are incorporated herein by reference.

BACKGROUND

P-0003[0003] The invention relates to substrate processing, and more particularly to transferring substrates to and from processing chambers.

P-0004[0004] Glass substrates are being used for applications such as active matrix televisions and computer displays, among others. A large glass substrate can form multiple display monitors, each of which may contain more than a million thin film transistors.

P-0005[0005] The processing of large glass substrates often involves the performance of multiple sequential steps, including, for example, the performance of chemical vapor deposition (CVD) processes, physical vapor deposition (PVD) processes, or etch processes. Systems for processing glass substrates can include one or more process chambers for performing those processes.

P-0006[0006] The glass substrates can have dimensions, for example, of 550 mm by 650 mm. The trend is toward even larger substrate sizes, such as 650 mm by 830 mm and larger, to allow more displays to be formed on the substrate or to allow larger displays to be produced. The larger sizes place even greater demands on the capabilities of the processing systems.

P-0007[0007] Some of the basic processing techniques for depositing thin films on the large glass substrates are generally similar to those used, for example, in the processing of semiconductor wafers. Despite some of the similarities, however, a number of difficulties have been encountered in the processing of large glass substrates that cannot be overcome in a practical way and cost effectively by using techniques currently employed for semiconductor wafers and smaller glass substrates.

P-0008[0008] For example, efficient production line processing requires rapid movement of the glass substrates from one work station to another, and between vacuum environments and atmospheric environments. The large size and shape of the glass substrates makes it difficult to transfer them from one position in the processing system to another. As a result, cluster tools suitable for vacuum processing of semiconductor wafers and smaller glass substrates, such as substrates up to 550 mm by 650 mm, are not well suited for the similar processing of larger glass substrates, such as 650 mm by 830 mm and above. Moreover, cluster tools require a relatively large floor space.

P-0009[0009] One way to improve such processing tools is disclosed in U.S. patent application Ser. No. 08/946,922, entitled “MODULAR CLOSTER PROCESSING SYSTEM.” assigned to Applied Komatsu Technologies, Inc. of Santa Clara, Calif., and incorporated above by reference. The use of a modular processing system is disclosed, with substrate movement exterior of processing islands performed by conveyors or robots on tracks. Substrate movement interior of processing islands is performed by a substrate transporter. In this type of system, the transporter may move a substrate into or out of a processing chamber, after which the transporter may stay resident in either load lock.

P-0010[0010] Similarly, chamber configurations designed for the processing of relatively small semiconductor wafers are not particularly suited for the processing of these larger glass substrates. The chambers must include apertures of sufficient size to permit the large substrates to enter or exit the chamber. Moreover, processing substrates in the process chambers typically must be performed in a vacuum or under low pressure. Movement of glass substrates between processing chambers, thus, requires the use of valve mechanisms which are capable of closing the especially wide apertures to provide vacuum-tight seals and which also must minimize contamination.

P-0011[0011] Furthermore, relatively few defects can cause an entire monitor formed on the substrate to be rejected. Therefore, reducing the occurrence of defects in the glass substrate when it is transferred from one position to another is critical. Similarly, misalignment of the substrate as it is transferred and positioned within the processing system can cause the process uniformity to be compromised to the extent that one edge of the glass substrate is electrically non-functional once the glass has been formed into a display. If the misalignment is severe enough, it even may cause the substrate to strike structures and break inside the vacuum chamber.

P-0012[0012] Other problems associated with the processing of large glass substrates arise due to their unique thermal properties. For example, the relatively low thermal conductivity of glass makes it more difficult to heat or cool the substrate uniformly. In particular, thermal losses near the edges of any large-area, thin substrate tend to be greater than near the center of the substrate, resulting in a non-uniform temperature gradient across the substrate. The thermal properties of the glass substrate combined with its size, therefore, makes it more difficult to obtain uniform characteristics for the electronic components formed on different portions of the surface of a processed substrate. Moreover, heating or cooling the substrates quickly and uniformly is more difficult as a consequence of its poor thermal conductivity, thereby reducing the ability of the system to achieve a high throughput.

P-0013[0013] As noted above, efficient production line processing requires rapid movement of the glass substrates from one work station to another. Other requirements include a structure that can firmly support the glass substrate during transfer and that can transport the glass substrate to all areas of a work station or processing island.

SUMMARY

P-0014[0014] The present invention allows large glass substrates to be moved within a processing station and from one processing station to another. In systems according to the invention, at least a first and second chamber are provided. Typically, the first chamber is a load lock and the second chamber is a processing chamber. The processing chamber may serve as an inspection station, a CVD chamber, a PECVD chamber, a PVD chamber, a post-anneal chamber, a cleaning chamber, a descumming chamber, an etch chamber or a combination of such chambers. The load lock may be employed to heat or cool the substrate. Two load locks may be employed, one to perform heating and the other to perform cooling. The load locks each include a platen for supporting the substrate.

P-0015[0015] A substrate transfer shuttle is used to move substrate along a guide path defined by, e.g., guide rollers.

P-0016[0016] The substrate transfer shuttle is moveable along a linear path defined by guide rollers between one position in the first chamber and another position in the second chamber. In this way, the substrate may be transferred, in both a forward and a reverse direction, between the first chamber and the second chamber. The substrate transfer shuttle is structured so that a substrate may be removed therefrom by moving the platen from a lowered position to an intermediate position, after which the substrate transfer shuttle may be removed from the processing chamber. The substrate transfer shuttle includes first and second longitudinal side rails at respective first and second sides thereof. The shuttle also includes first and second pluralities of substrate support elements extending inwardly from the first longitudinal side rail and positioned to pass below the substrate when the substrate transfer shuttle is removed from the processing chamber. The substrate support elements extend about 15-30% of a dimension of the substrate, and more particularly about 22% of the width of the substrate. Drive mechanisms are employed that engage with at least the first longitudinal side rail to move the substrate transfer shuttle along at least portions of the shuttle path.

P-0017[0017] Implementations of the invention may include one or more of the following. A valve may be employed to selectively seal the first chamber from the second chamber when closed and to permit transfer of the substrate between the first chamber and the second chamber through the valve when open. Multiple shuttles may be employed for convenience in a particular process. Further, multiple intermediate chambers may be located between the first and second chambers.

P-0018[0018] The susceptor in the processing chamber includes a plurality of lift pins which are movable through holes in the susceptor and which support the substrate above the susceptor.

P-0019[0019] Steps of the method include positioning a substrate onto a substrate transfer shuttle in a load lock, and moving the substrate transfer shuttle from the load lock into a processing chamber along a first portion of a path. The substrate is removed from the substrate transfer shuttle and positioned it on a platen in the processing chamber. The substrate transfer shuttle is then removed from the processing chamber and the substrate is processed. Following processing, the substrate transfer shuttle is moved into the processing chamber and the substrate is positioned thereon. The substrate transfer shuttle and the substrate are moved into the load lock, and the substrate is removed from the substrate transfer shuttle.

P-0020[0020] Advantages of the invention include one or more of the following. The invention eliminates unnecessary substrate movement in a semiconductor processing system. For example, the substrate may be transferred horizontally except for loading and unloading on the susceptor. The invention also eliminates more expensive and cumbersome vacuum robots and transfer chamber systems. The invention allows removal of a substrate transfer shuttle during processing, reducing contamination.

P-0021[0021] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

P-0022[0022]FIG. 1 is a top plan schematic view of a processing island of a system according to the present invention.

P-0023[0023]FIG. 1A is a side schematic view of a section of a load lock emplying alcoves.

P-0024[0024] FIGS. <b>2</b>A-<b>2</b>C are top plan views of a shuttle and lifting fork according to the present invention.

P-0025[0025]FIG. 2D is a side view showing a heated bowing glass substrate supported on support fingers.

P-0026[0026]FIG. 3 is a side schematic view of a processing island of a system according to the present invention.

P-0027[0027]FIG. 4 is a perspective view of a substrate transfer shuttle according to the present invention.

P-0028[0028]FIG. 5 is a partial cross-sectional view of a processing chamber and substrate transfer shuttle according to the present invention.

P-0029[0029]FIG. 6A is a transverse cross-sectional view of a processing island and shuttle according to an embodiment of the present invention.

P-0030[0030]FIG. 6B is a transverse cross-sectional view of a processing island and shuttle according to an alternative embodiment of the present invention.

P-0031[0031] FIGS. <b>7</b>A-<b>7</b>C are partial schematic cross-sectional views of a load lock chamber according to the present invention, showing a substrate in various stages of transfer from without to within a load lock chamber.

P-0032[0032]FIGS. 7D and 7E are perspective views of alternative embodiments of a substrate transfer shuttle and a platen as may be located in a load lock chamber.

P-0033[0033] FIGS. <b>8</b>A-<b>8</b>B are schematic cross-sectional views of a chamber according to the present invention, shown in different stages of transfer of a substrate between a shuttle and a susceptor in a processing chamber.

P-0034[0034] Like reference numbers and designations in the various drawings indicate like elements.

DETAILED DESCRIPTION

P-0035[0035]FIG. 1 shows a processing island <b>42</b> of a fabrication system according to an embodiment of the present invention. Arrow <b>101</b> defines a direction pointing from “upstream” to “downstream” in the processing island. The island <b>42</b> includes a substrate heating load lock chamber <b>50</b> at a first end of the island and a substrate cooling load lock chamber <b>52</b> at a second end of the island, longitudinally opposite and downstream of the first end. Of course, the terms “heating” and “cooling” are not intended to be limiting. Rather, they are descriptive of exemplary features such chambers may possess.

P-0036[0036] Between the load lock chambers <b>50</b> and <b>52</b> are a plurality of processing chambers <b>54</b>A-<b>54</b>C, which are connected in series between the load lock chambers. Each processing chamber <b>54</b>A-<b>54</b>C includes first and second gate valves <b>56</b>A-<b>56</b>C and <b>58</b>A-<b>58</b>C, respectively, at the first and second ends of each processing chamber (see also FIG. 3). The valve <b>56</b>A selectively seals the load lock chamber <b>50</b> from the processing chamber <b>54</b>A when closed and permits transfer of substrates through the valve between the load lock chamber <b>50</b> and the processing chamber <b>54</b>A when open. Similarly, the valve <b>58</b>C selectively seals the load lock chamber <b>52</b> from the processing chamber <b>54</b>C in a closed condition and permits the transfer of substrates through the valve in an open condition. The valves <b>58</b>A and <b>56</b>B seal the first processing chamber <b>54</b>A from the second processing chamber <b>54</b>B when closed and permit the transfer of substrates through the valves when open. Likewise, the valves <b>58</b> and <b>56</b>C selectively seal the second processing chamber <b>54</b>B from the third processing chamber <b>54</b>C in closed conditions and permit the transfer of substrates through the valves in open conditions. The pairs of valves <b>58</b>A, <b>56</b>B and <b>58</b>B, <b>56</b>C may be replaced with single valves although the illustrated configuration has advantages described below. An example of the type of valve which may be employed is described in above-mentioned U.S. patent application entitled “Isolation Valves”, [attorney docket number 2157 (226001)] filed on even date herewith, and incorporated by reference above.

P-0037[0037] This detailed description describes an embodiment in which a glass substrate is used. The term “substrate” is intended to broadly cover any object that is being processed in a process chamber, including flat panel displays, glass or ceramic plates, plastic sheets, or disks. The present invention is particularly applicable to large substrates such as glass plates having dimensions of 650 mm by 830 mm or even larger.

P-0038[0038] In this system, the substrate is supported by support fingers. The support fingers may all be parallel, as shown in the embodiment of FIGS. 1, 4 and <b>7</b>D, or some may be angled as shown in the preferred embodiment of FIGS. <b>2</b>B-<b>2</b>C and <b>7</b>E. In the described embodiments, the short dimension of the substrate is generally parallel to the direction of movement within a processing island.

P-0039[0039]FIGS. 1 and 3 show a substrate transfer shuttle in each of the load locks <b>50</b> and <b>52</b>. As shown in FIG. 3, the load lock chambers <b>50</b> and <b>52</b> have respective gate or slit valves <b>60</b> and <b>62</b> positioned along one side of the island. The valves <b>60</b> and <b>62</b> (FIG. 3) selectively seal their associated load lock chambers from atmosphere in closed conditions and allow introduction or removal of substrates to or from the load lock chambers in open conditions. In this figure, valves <b>56</b>A, <b>58</b>A, <b>56</b>B and <b>58</b>B are shown open, and valves <b>56</b>C and <b>58</b>C are shown closed.

P-0040[0040] The substrates may be introduced through the valve <b>60</b> to the load lock chamber <b>50</b> which forms an entrance load lock chamber. With the load lock chamber <b>50</b> in a condition sealed from the atmosphere and process chamber <b>54</b>A, the load lock chamber may be pumped to vacuum and the substrate heated.

P-0041[0041] The load lock system allows a staged vacuum to occur. That is, the process chamber vacuum need not be breached for substrates to be loaded and unloaded. Since the load locks are independently pumped-down prior to the opening of the valves separating them from the process chambers, the process chamber pumps need only evacuate a chamber that is already partially at vacuum. That is, they need only maintain process vacuum conditions. Such a capability is particularly important for, e.g., physical vapor deposition (PVD), which may often require the lowest pressure of any process.

P-0042[0042] Each load lock chamber may be multifunctional. Process steps such as heating, cooling, and descumming may be provided for in each load lock. Heating and cooling may be provided for by heating and cooling plates which may be moved into and out of thermal contact with the substrate. Typically, the load lock <b>50</b> may be used to heat and descum, while the load lock <b>52</b> may be used to cool. Ashing processes may also be provided for in the chambers. The substrate is then passed among the processing chambers <b>54</b>A-<b>54</b>C. In each processing chamber, a specific semiconductor process may be performed on the substrate. Ashing or descumming may also occur in a processing chamber. More details of a multifunctional load lock may be found in above-mentioned U.S. patent application entitled “Multi-Function Chamber for a Substrate Processing System,” [attorney docket number 2712 (268001)] filed on even date herewith, and incorporated by reference above.

P-0043[0043] A processed substrate may be cooled in the cooling load lock chamber <b>52</b>, which forms an exit load lock chamber, and may also be brought up to atmospheric pressure. Thereafter, the substrate may be removed from the system through the valve <b>62</b>. Introduction and removal of substrates to and from the load lock chambers <b>50</b> and <b>52</b> may be performed by robots <b>64</b>A and <b>64</b>B, respectively (see FIG. 1). Alternatively, just one robot may be employed, operating on a track or conveyor, to introduce or remove substrates.

P-0044[0044] Each robot includes an end effector in the form of a lifting fork <b>66</b>A, <b>66</b>B at the distal end of an arm <b>68</b>A, <b>68</b>B. At its proximal end, each arm <b>68</b>A, <b>68</b>B is coupled to an associated vertical linear actuator (not shown) to permit the arm and lifting fork to be raised and lowered. Referring to FIGS. 2A and 2C, the top of the lifting forks <b>66</b>A and <b>66</b>B may have thereon a number of supports <b>154</b> to support a substrate <b>126</b> on top of the fork <b>66</b>A, <b>66</b>B.

P-0045[0045] The robot <b>64</b>A, for instance, can retrieve and return substrates to and from substrate holding cassettes. In a first loading position, the robot <b>64</b>A may load a substrate into heating load lock chamber <b>50</b> of the island through the gate or slit valve <b>60</b> (FIG. 3). Robot <b>64</b>B operates in a similar fashion to robot <b>64</b>A. More details of the robots may be found in U.S. patent application entitled “Modular Substrate Processing System,” filed on even date herewith, and incorporated by reference above. In a first or lowered position, the fork <b>66</b>A may be inserted beneath a substrate in a cassette or on a shuttle in a load lock chamber. The fork design is such that the same fork may be used for either, facilitating considerable advantage in incorporating the system into existing product lines. When raised to an intermediate position, the upper surface of the fork <b>66</b>A or, more particularly, supports <b>154</b> (see FIGS. 2A and 2C) along the upper surface of the fork tines, engage the lower surface of the substrate. When further elevated to a second or raised position, the fork <b>66</b>A lifts the substrate out of engagement with the cassette or shuttle.

P-0046[0046] During loading, a z-rotary actuator of the robot <b>64</b>A is caused to rotate the loading end effector <b>66</b>A 180° so that the substrate may be introduced into load lock heating chamber <b>50</b> through the slit valve <b>60</b>. Fine adjustments may be made by the z-linear actuator to adjust the height of the substrate so that the substrate may enter through the slit valve <b>60</b> (FIG. 3) unimpeded. During substrate loading, the slit valve <b>60</b> is opened and the substrate is moved by a y-linear actuator in the y-direction. This movement loads the substrate into load lock heating chamber <b>50</b> where it is lowered onto the shuttle <b>70</b> using the z-linear actuator. The empty end effector <b>66</b>A may then be withdrawn from the chamber. Slit valve <b>60</b> is then closed and the heating and evacuation process begun.

P-0047[0047] Associated with each load lock chamber <b>50</b> and <b>52</b> is a transfer shuttle <b>70</b> and <b>72</b>, respectively, configured for transporting substrates between chambers. The first and second shuttles <b>70</b> and <b>72</b> are positioned in the heating and cooling load lock chambers during introduction of a substrate to the heating load lock chamber <b>50</b> and removal of a substrate from the cooling load lock chamber <b>52</b>, respectively. Transfer shuttles <b>70</b> and <b>72</b> may be made of stainless steel, invar, ceramics or any other similar material. Invar may be preferable as it has a low coefficient of thermal expansion.

P-0048[0048] The load lock chambers <b>50</b> and <b>52</b> may be equipped with maintenance windows or slits <b>152</b> (FIG. 1). These windows <b>152</b> allow the removal of the components from the load locks for maintenance or repair. During such a maintenance situation, both shuttle and chamber components may be repaired.

P-0049[0049] Referring to FIGS. 1, 2B, <b>4</b>, and <b>7</b>D-<b>7</b>E, each shuttle <b>70</b>, <b>72</b> has a first end <b>31</b>A facing from the associated load lock chamber toward the adjacent processing chamber and a second end <b>31</b>B opposite the first end. Each shuttle further has first and second sides <b>32</b>A and <b>32</b>B, respectively. The shuttles may be mirror images of each other and are positioned facing each other.

P-0050[0050] Referring specifically to FIG. 4, each shuttle includes first and second side rails <b>74</b>A and <b>74</b>B along the respective first and second sides of the shuttle. Both side rails extend substantially between the first and second ends of the shuttle. The side rails are parallel to and spaced-apart from each other. Each side rail includes a generally flat horizontal strip <b>75</b>. Along an outboard portion of the underside of each strip, the rail bears a rack <b>76</b>. An outboard portion <b>77</b> of the underside of each rack bears angled teeth <b>33</b> (the shape of the teeth are not shown). An inboard portion <b>78</b> of the underside of each rack is flat for engaging a number of guide rollers as described below. First and second cross-members <b>80</b>A and <b>80</b>B, respectively, proximate the first and second ends of the shuttle, structurally connect the first and second side rails to each other. Each cross-member is slightly recessed from the associated end of the shuttle, and each cross-member includes a flat central horizontally-extending strip <b>82</b>. First (<b>83</b>A and <b>84</b>A) and second (<b>83</b>B and <b>84</b>B) legs depend from first and second ends of the strip and connect such ends to the first and second side rails, respectively.

P-0051[0051] An “X” indicates the location of the center of the substrate. This X location should roughly correspond with the center of the processing chamber, as measured in a horizontal plane, for optimum processing of the substrate.

P-0052[0052] Substrate support fingers <b>86</b>A, <b>88</b>A, <b>86</b>B and <b>88</b>B extend inwardly from the associated first and second side rails, respectively. Referring to FIGS. 4 and 5, each support finger has a proximal portion <b>90</b> extending upwardly from the associated side rail <b>75</b> and a distal portion <b>92</b> extending horizontally inwardly from the proximal portion and ending at a tip. At the tip, the upper surface of each finger bears a pad <b>94</b> for supporting a substrate held by the shuttle. As the shuttle must endure the temperatures used for heating substrates, to temperatures of about 460° C. or even higher, the pads <b>94</b> may advantageously be made of a material such as a <b>30</b> ceramic, stainless steel, quartz, or other such materials. It should be noted, however, that the temperature requirements of the substrate transfer shuttle components may be lower than in prior systems. In many prior systems, such as cluster tools, substrates would be removed from a heating chamber by a vacuum robot which would then transport the substrate to a processing chamber, resulting in cooling of the substrate. A solution was to overheat the substrate, intending for it to cool when transported.

P-0053[0053] In the present invention, the substrate transfer shuttle <b>70</b> moves the substrate into a processing chamber directly from the heating chamber. Thus, the requirement for overheating the substrate is alleviated if not eliminated.

P-0054[0054]FIG. 5 also shows inner and outer chamber walls <b>38</b>B and <b>38</b>A. respectively. A slot <b>38</b>C is located in inner wall <b>38</b>B to allow the flat rail <b>75</b> of the shuttle to extend into the opening in wall <b>38</b>B to engage rollers <b>98</b>. In this way, contamination caused by guide rollers <b>98</b> may be minimized. Further, the process performed within the chamber is kept separate from the mechanical components causing the shuttle movement.

P-0055[0055] The width of the lifting forks <b>66</b>A, <b>66</b>B may be close to but less than the distance between the two exterior support fingers <b>88</b>A and <b>88</b>B along one side of the shuttle <b>70</b>. The central cut-out section of the fork should be large enough such that it does not interfere with the central support finger <b>86</b>A. In the embodiment of FIGS. <b>2</b>B-<b>2</b>C and <b>7</b>E, where diagonal support fingers are employed, the width of the fork may be larger.

P-0056[0056] In the illustrated preferred embodiment of FIGS. <b>2</b>B-<b>2</b>C and <b>7</b>E, there are three support fingers associated with each side rail: a central support finger <b>86</b>A, <b>86</b>B and two lateral diagonal support fingers <b>88</b>A, <b>88</b>B. Each support finger preferably extends about 15-30% of a dimension such as the length or the diagonal of the substrate in order to adequately support the substrate, and even more preferably about 22% of the length approximately (0.22 l) of the substrate. Referring to FIG. 2D, such placement ensures that when a substrate <b>126</b> is heated, bowing caused by the substrate flexibility results in a minimal volume swept out by the bowing substrate as it moves along the flow path. In particular, by constructing the fingers <b>86</b>A, <b>86</b>B, <b>88</b>A, and <b>88</b>B and pads <b>94</b> in this configuration, where the pads are located at about the 22% point, a minimal volume is swept out by the bowing substrate as it is moved from one processing chamber to another, or between a processing chamber and a load lock. Thus, the chance of such a substrate striking, e.g., a platen or a susceptor, is substantially reduced. This consideration is particularly important for glass substrates on which TFT's are formed for flat panel displays, as these may be only about 0.7-1 mm thick.

P-0057[0057] The height of pads <b>94</b> is also important. The height should be chosen such that when the heated substrate bows, the edges of the substrate do not make contact with the fingers directly. The importance of this aspect to the quality of the resulting substrate depends on the process requirements.

P-0058[0058] Another advantage of such a configuration is that the same support fingers may be used to support several different sizes of substrates. Moreover, the location of the support fingers is adjustable to accommodate various substrate sizes. The location of the pads <b>94</b> is also variable to accommodate different substrate sizes. It should also be noted that while a shuttle servicing the load lock chamber <b>50</b> must be designed to withstand high temperatures, the shuttle servicing load lock chamber <b>52</b> has somewhat more forgiving requirements, as it is less inclined to see the maximum processing temperatures.

P-0059[0059]FIGS. 1, 4, and <b>7</b>D show an alternate embodiment in which lateral support fingers <b>88</b>A and <b>88</b>B are not diagonal but rather are parallel to support fingers <b>86</b>A and <b>86</b>B. Other angled fingers may be used, so long as they adequately support the substrate.

P-0060[0060] The above designs allow each shuttle to accept substrates from two directions, each 90° away from each other. First, the shuttle may accept and release substrates in a direction perpendicular to the side rails. Second, the shuttle may accept and release substrates in a direction parallel to the side rails. In any of the embodiments, a plurality of stoppers <b>201</b> may be provided, as shown in FIGS. <b>2</b>B-<b>2</b>C, <b>4</b>-<b>5</b> and <b>8</b>A-<b>8</b>B, to ensure accurate placement of the substrate on the support fingers and to prevent accidental shifting of the substrate on the shuttle during transport. Substrates may also be centered on the fingers by using the plurality of stoppers <b>201</b>. These stoppers <b>201</b> may have the general shape of an inverted truncated cone, such as an inverted frustum.

P-0061[0061] Along each side of the island (FIGS. 1, 3, <b>5</b>, and <b>7</b>A-<b>7</b>C), each load lock chamber and each processing chamber includes a number of pairs of guide rollers <b>98</b> (e.g., two rollers per side of the processing chambers and three rollers per side of the load locks) positioned so as to provide support and guidance to one or both shuttle(s) as such shuttle(s) pass through the chambers. The guide rollers <b>98</b> may be Teflon®-coated aluminum, Vespel®, or any other such material that is not particulate-generating and is soft for dampening vibrations. Alternatively, suspensions may be employed to provide a smooth movement. The guide rollers are all at substantially even level and define a fixed path along which the shuttles may move back and forth. The guide rollers are configured to engage the flat inboard portion <b>78</b> of the underside of each rack as a shuttle passes over the guide rollers so as to position and orient the shuttle and provide smooth shuttle movement along the predefined path.

P-0062[0062] As shown in FIG. 3, between each of the processing chambers <b>54</b>A-<b>54</b>C and the load lock chambers are chamber isolation valves whose housings may each include a shuttle drive mechanism <b>100</b>. Such a configuration reduces particulate contamination within the processing chambers as is often required, e.g., in TFT formation. Such an island layout also facilitates a high degree of modularity because each chamber has a similar structure and is interchangeable. With one drive mechanism within the housing of each isolation valve, the length of the shuttles used is generally longer, as described in more detail below, than the associated distance between the driving mechanisms. Moreover, the overall length of the shuttles used is generally longer than the length of any process chambers through which they pass.

P-0063[0063] As shown in FIG. 6A, each drive mechanism <b>100</b> includes a motor <b>102</b> external to the interior cavity of the associated chamber and coupled to a drive shaft assembly <b>104</b> extending into and within the interior of the load lock or valve housing. The inner chamber wall <b>38</b>B is not shown for clarity. The drive shaft assembly <b>104</b> may employ vacuum-compatible rotary feedthroughs. The drive shaft assembly carries first and second pinion ears <b>106</b>A and <b>106</b>B adjacent first and second sides of the associated chamber, and first and second guide rollers <b>108</b>A and <b>108</b>B immediately inboard of the first and second pinion ears, respectively. The pinion gears are configured to mesh with the toothed outboard portions <b>33</b> of the racks while the guide rollers are configured to contact the smooth surface of the inboard portion of the racks of a shuttle passing over the drive mechanism (see also FIGS. 4 and 5). Optionally, the drive mechanism <b>100</b> includes an encoder <b>110</b> which provides input to a control system <b>111</b> responsive to rotation of the associated drive shaft assembly. The control system <b>111</b> may be connected to any and each of the various chambers for controlling their operations as well as the operation of any handling or processing equipment external to the island. The control system may comprise a user-programmable computer or other controller incorporating appropriate software or firmware.

P-0064[0064]FIG. 6B shows an alternate configuration in which no drive shaft is employed. In this configuration, the shuttle is driven from one side only, and the motor may drive a pinion gear <b>106</b> without using the drive shaft assembly <b>104</b>. Laterally positioned guide rollers <b>203</b> may be used in addition to guide roller <b>108</b>A and <b>108</b>B to ensure that the shuttle moves in a straight horizontal direction and is not caused to misalign due to its only being driven on one side. Rollers <b>203</b> are positioned on each side of a guide rail <b>112</b> in order to keep the shuttle <b>70</b> moving in a straight and controlled direction.

P-0065[0065] In either of these embodiments, it should be noted that it is not crucial that the guide rollers be inboard of the pinion gears. In fact, in an alternative embodiment, the guide rollers may be outboard of the pinion gears or the relative position may be different on each side of a line of chambers. In yet another embodiment, rollers may be placed on the substrate transfer shuttle and a smooth flat ridge may be located along each side of a line of chambers to support the shuttle guide rollers.

P-0066[0066] In the following discussion, the placement of a substrate into a load lock chamber is described with respect to FIGS. <b>7</b>A-<b>7</b>E. In the discussion of FIGS. <b>7</b>A-<b>7</b>E, the support on which the substrate is placed is referred to as a platen. The platen has slots through which fingers of the shuttle may move when transferring substrates. The placement of a substrate into a process chamber from a load lock chamber is described with respect to FIGS. <b>8</b>A-<b>8</b>B. In the discussion of FIGS. <b>8</b>A-<b>8</b>B, the support on which the substrate is placed is referred to as a susceptor. The susceptor has passages with extendable “T”-shaped pins for use in transferring substrates, as described below. It should be noted that the above definitions for platen and susceptor are used herein for clarity. The susceptor in the processing chamber may be equally well termed a “platen” and the platen in the load lock may be equally well termed a “susceptor.”

P-0067[0067] As shown in FIGS. <b>7</b>A-<b>7</b>C, each load lock chamber <b>50</b>, <b>52</b> (only chamber <b>50</b> is shown) includes a platen <b>120</b> for supporting a substrate during heating or cooling prior to or after processing. A pedestal <b>122</b> supports the platen <b>120</b> and is raisable and lowerable to raise and lower the platen <b>120</b> between a first or retracted position and a second or extended position. The platen <b>120</b> is generally rectangular and slightly larger than the plan area of the substrate and has a plurality of channels <b>124</b> (FIGS. 7D and 7E) extending inwardly from the opposite sides of the platen. The channels are configured so as to accommodate the fingers <b>86</b>A, <b>86</b>B, <b>88</b>A, and <b>88</b>B of a shuttle <b>70</b> when the platen <b>120</b> is raised or lowered through such a shuttle <b>70</b> as described below.

P-0068[0068] Initially, the load lock chamber <b>50</b> is vacant and is shielded from the adjacent chamber <b>54</b>A by the valve <b>56</b>A. The load lock chamber <b>50</b> is vented to atmosphere and its slit valve <b>60</b> is opened to permit introduction of a substrate to the island. As shown in FIG. 7A, a substrate <b>126</b> is loaded into the load lock chamber <b>50</b> by the robot end effector <b>66</b>A. The end effector and substrate are inserted via a horizontal (y-direction) movement into the chamber <b>50</b> at a height at which the underside of the end effector <b>66</b>A is above the fingers <b>88</b>A. <b>88</b>B of the shuttle <b>70</b>. The end effector <b>66</b>A carrying the substrate <b>126</b> is stopped with the substrate <b>126</b> located centrally above the platen and then lowered. Eventually, the end effector <b>66</b>A reaches a second height shown in FIG. 7B. During movement between the first height and the second height, the end effector passes below the fingers of the shuttle, with e.g., one tine of the end effector <b>66</b>A passing on each side of the central fingers <b>86</b>A and <b>86</b>B and just inboard of adjacent lateral support fingers <b>88</b>A, <b>88</b>B. When the upper surface of the end effector <b>66</b>A reaches the height of the pads <b>94</b> at the tip of the fingers, the pads <b>94</b> will engage the underside of the substrate <b>126</b> causing the shuttle <b>70</b> to acquire the substrate <b>126</b> from the end effector <b>66</b>A. When the end effector <b>66</b>A reaches the position shown in FIG. 7B, it may be withdrawn from the load lock chamber <b>50</b> via horizontal translation. Once the end effector <b>66</b>A is withdrawn, the valve <b>60</b> may be closed and the chamber <b>50</b> pumped down.

P-0069[0069] The platen <b>120</b> may then be raised from its initial height in FIG. 7A to a raised height shown in FIG. 7C. During movement between the initial height and the raised height, the platen <b>120</b> passes around the fingers of the shuttle, each finger being accommodated by an associated one of the channels <b>124</b> (see FIGS. 7D and 7E). When the upper surface of the platen <b>120</b> contacts the underside of the substrate <b>126</b>, it raises the substrate <b>126</b> off of the fingers (more particularly, pads <b>94</b>) to acquire the substrate <b>126</b> from the shuttle <b>70</b>. With the substrate <b>126</b> held by the platen <b>120</b> as shown in FIG. 7C, the substrate <b>126</b> may be heated or otherwise prepared to ready it for processing.

P-0070[0070] A multiple substrate cassette (not shown) may also be employed in the load lock chambers <b>50</b> or <b>52</b>. By repeating the above procedure for each substrate in a multiple substrate cassette, the load lock chamber <b>50</b> may be used as a buffer for storage of substrates prior to processing. More details of a multiple substrate cassette are provided in above-mentioned U.S. patent application for an “In-Situ Substrate Transfer Shuttle,” [attorney docket number 2703(266001)], filed on even date herewith, and incorporated by reference above.

P-0071[0071] Once the substrate <b>126</b> is heated, the platen <b>120</b> may be lowered and returned to the position of FIG. 7B, with the shuttle <b>70</b> reacquiring the substrate <b>126</b> from the platen <b>120</b> in the process.

P-0072[0072] With a substrate <b>126</b> supported on the shuttle <b>70</b> in the load lock chamber <b>50</b>, after any heating of the substrate <b>126</b> and pump down of the load lock chamber <b>50</b> and of the first processing chamber <b>54</b>A, the valve <b>56</b>A may be opened to establish communication between the load lock chamber <b>50</b> and the processing chamber <b>54</b>A. With the shuttle in this initial position, the pinion gears of the drive mechanism <b>100</b> of the load lock <b>50</b> are engaged to the racks of the shuttle <b>70</b> adjacent the downstream ends of the shuttle's rails. To move the substrate into the processing chamber, the motor of the drive mechanism may be powered so as to move the shuttle downstream through the valve <b>56</b>A and into the first processing chamber. When the shuttle reaches a target position in the first processing chamber <b>54</b>A, its <b>15</b>. movement is stopped, leaving the shuttle and substrate in the target position.

P-0073[0073] As shown in FIGS. <b>8</b>A-<b>8</b>B, each processing chamber includes a susceptor <b>130</b> for supporting a substrate <b>126</b> during processing. The plan area of the susceptor <b>130</b> is slightly larger than that of the substrate <b>126</b> and the susceptor <b>130</b> has an upper surface <b>132</b> configured to contact substantially the entire underside of the substrate <b>126</b> during processing. The upper surface <b>132</b> of the susceptor <b>130</b> is continuous except for interruptions caused by the presence of passages for the lift pins <b>134</b> which may extend through the susceptor <b>130</b> from below. As illustrated, the susceptor <b>130</b> has a central pedestal <b>136</b> which may be raised and lowered to raise and lower the susceptor <b>130</b>. The lift pins <b>134</b> are secured at their lower ends to a pin plate <b>138</b>. The pins and pin plate are generally raised and lowered by an outer shaft <b>139</b> which surrounds the central pedestal <b>136</b>. In one embodiment, lift pins <b>134</b> and pin plate <b>138</b> move independently from susceptor <b>130</b>. Lift pins <b>134</b> support a substrate when they are in an extended position. As the lift pins are retracted, the substrate is lowered onto the susceptor <b>130</b>. When susceptor <b>130</b> is caused to rise, the lift pins are caused to retract to a position below the surface <b>132</b> of the susceptor <b>130</b>. The pins may pass below surface <b>132</b> by virtue of a counterbore located within surface <b>132</b>.

P-0074[0074] This embodiment allows a convenient way of transferring support of the substrate from the pins <b>134</b> to the susceptor <b>130</b> as the susceptor <b>130</b> is raised. More details of this pin system may be found in U.S. patent application Ser. No. 08/950,277, entitled “A Vacuum Processing System Having Improved Substrate Heating and Cooling”, filed Oct. 14, 1997, assigned to the assignee of the present invention and incorporated herein by reference.

P-0075[0075] In the illustrated embodiment, each chamber includes six lift pins <b>134</b> arranged in pairs extending from upstream to downstream in the chamber. Like the support fingers and for the same reasons, the lift pins <b>134</b> may also be advantageously located at about 15-30% of the dimension of the substrate <b>126</b> and more preferably about 22% of the width of the substrate <b>126</b>. They may even more preferably be located just inside of the distal end of the pad <b>94</b> location. While it would be preferable to have both the pins <b>134</b> and the pads <b>94</b> at the 22% point, such placement would not allow the same to pass around each other. Thus, it may be advantageous to have the pins and pads close to each other, but to have the pins just nearer to the centerline of the substrate that the pads. In this way, relative movement can be accomplished without contact.

P-0076[0076] The lift pins <b>134</b> may have the general cross-sectional shape of a “T”. A corresponding counterbore, as mentioned above, may be placed in the susceptor <b>130</b> around the lift pin holes so that the lift pins, when fully retracted, are below the level of the top surface <b>132</b> of the susceptor <b>130</b>. The substrate then does not contact the lift pins in their retracted positions. In this way, the lift pins have a minimal thermal signature. In other words, the lift pins <b>134</b>, and their passages through the susceptor <b>130</b>, do not significantly affect the even distribution of temperature across the susceptor <b>130</b> and thus across the substrate <b>126</b>. Thus, the high process requirements with regard to uniformity of temperature for, e.g., TFT formation may be advantageously achieved.

P-0077[0077] When the shuttle <b>70</b> carrying the substrate <b>126</b> enters the processing chamber <b>54</b>A, the substrate <b>126</b> and shuttle fingers <b>86</b>A, <b>86</b>B, <b>88</b>A, and <b>88</b>B pass over the susceptor <b>130</b> which is at a first height as shown in FIG. 8A. The lift pins <b>134</b> may be in an extended position relative to the susceptor <b>130</b> (as shown in FIGS. 8A and 8B) or may be in a retracted position. When the substrate <b>126</b> and shuttle <b>70</b> are stopped in a target position immediately above the susceptor <b>130</b>, the susceptor <b>130</b> and/or lift pins <b>134</b> are raised. As lift pin plate <b>138</b>, lift pins <b>134</b>, and/or the susceptor <b>130</b> are raised, the pins (stationary and in the extended position) contact the underside of the substrate <b>126</b> (FIG. 8A) and raise the substrate <b>126</b> out of the engagement with the shuttle <b>70</b> (FIG. 8B). With the substrate <b>126</b> in this intermediate position, the shuttle <b>70</b> may be withdrawn from the processing chamber <b>54</b>A, with the fingers <b>86</b>A, <b>86</b>B, <b>88</b>A, and <b>88</b>B passing around the lift pins <b>134</b> and between the substrate <b>126</b> and the susceptor <b>130</b>, at least one of the cross members <b>80</b>A, <b>80</b>B of the shuttle <b>70</b> passing over the substrate <b>126</b>. The shuttle <b>70</b> may be withdrawn to the load lock chamber <b>50</b> or may be driven into the second processing chamber <b>54</b>B or therebeyond, e.g., to service other substrates by transporting the same to other chambers, etc. Once, however, the shuttle <b>70</b> is out of the chamber <b>54</b>A, the chamber <b>54</b>A may be sealed by shutting the valve <b>56</b>A (and valves <b>58</b>A and <b>56</b>B if these have been opened). The pins <b>134</b> may then be lowered relative to the susceptor <b>130</b> to place the substrate atop the susceptor <b>130</b>.

P-0078[0078] At this point, processing may begin. When processing is complete and any process gases evacuated (if necessary), the valve <b>56</b>A may be opened, establishing communication between the load lock chamber <b>50</b> and the processing chamber <b>54</b>A. Of course, valves <b>58</b>A and <b>56</b>B may also be opened if the shuttle has been sent downstream. The lift pins <b>134</b> and pin plate <b>138</b> may then be raised, thus raising the substrate above the susceptor <b>130</b> such that the substrate is supported on the lift pins. The shuttle <b>70</b> is returned to the processing chamber <b>54</b>A in a similar fashion as when delivering the substrate <b>126</b> to the processing chamber <b>54</b>A. As the shuttle approaches a target position, the fingers <b>86</b>A, <b>86</b>B, <b>88</b>A, and <b>88</b>B pass between the substrate <b>126</b> and the susceptor <b>130</b>, passing around the lift pins <b>134</b>. The cross-member <b>80</b>A passes over the substrate <b>126</b>. When the shuttle <b>70</b> reaches the target position, the susceptor <b>130</b> and/or pins <b>134</b> may be lowered to the position of FIG. 8A, during which the fingers <b>86</b>A, <b>86</b>B, <b>88</b>A, and <b>88</b>B acquire the substrate <b>126</b> from the pins <b>134</b>.

P-0079[0079] Next, the substrate <b>126</b> may be delivered to the second processing chamber <b>54</b>B through valves <b>58</b>A and <b>56</b>B. The steps of this transfer may be similar to the steps involved in the transfer from the load lock chamber <b>50</b> to the first processing chamber <b>54</b>A. Via a similar process, the substrate <b>126</b> may be transferred to the third processing chamber <b>54</b>C. This may be done with either of the shuttles <b>70</b> and <b>72</b>. Finally, the substrate may be withdrawn from the third processing chamber <b>54</b>C into the load lock chamber <b>52</b> by the shuttle <b>72</b> via a reverse of steps similar to those performed with the shuttle <b>70</b> in transferring the substrate from the load lock chamber <b>50</b> to the first processing chamber <b>54</b>A. Similarly, the extraction of the substrate <b>126</b> from the cooling load lock chamber <b>52</b> by the robot end effector <b>68</b>B may be performed by substantially reversing the steps used with the robot end effector <b>66</b>A in introducing the substrate <b>126</b> to the heating load lock chamber <b>50</b>.

P-0080[0080] The use of such lift pins <b>134</b> provides another advantage. In any of the chambers, lift pins <b>134</b> may be used to elevate the substrate <b>126</b> above the heated or cooled susceptor <b>130</b>. Such elevation may be maintained for as long as necessary to bring the substrate temperature to a desired level. For example, if the substrate <b>126</b> is to be cooled, but the susceptor <b>130</b> is at a high temperature, maintaining the pins <b>134</b> in an elevated position may be useful for cooling the substrate <b>126</b>.

P-0081[0081] As shown in FIGS. 1 and 1A, alcoves or compartments <b>148</b> in the end walls of the entrance and exit load locks are provided to accommodate an associated end of a side rail of the shuttles <b>70</b> and <b>72</b>, respectively. When the shuttle is in the target position in a load lock chamber, the side rail's ends are received and accommodated by such compartments. As noted above, the rails may be generally longer than the length of process chambers <b>54</b>A-<b>54</b>C. This allows the volume of the load locks to be correspondingly minimized. Such minimization is advantageous for, e.g., accomplishing a more convenient pump-down.

P-0082[0082] For a variety of reasons, it may be advantageous to attempt to minimize chamber volume. Reduced chamber volume facilitates faster and more economical pumping down of chambers, including reducing the capacity requirements for any vacuum pumps. Additionally, the introduction of process or inert gases is facilitated with a reduced consumption of such gases. Heating and cooling may be more easily facilitated. Process uniformity may be increased, for example, by providing a more uniform plasma in the absence of voids or cavities.

P-0083[0083] With respect to the process of chambers <b>54</b>A-<b>54</b>C, an additional benefit of providing each chamber with two valves <b>56</b>A-<b>56</b>C, <b>58</b>A-<b>58</b>C is that this allows each such valve to be located substantially adjacent the susceptor of the associated chamber. An even more important benefit is that the drive mechanism <b>100</b> of each processing chamber may be located in the outside of the cavity defined by the valve housing. This significantly reduces contamination of the chambers due to the drive mechanisms.

P-0084[0084] Advantageously, the system is configured so that certain components may be serviced or replaced with minimal disruption of the system or contamination of the system chambers. As illustrated in FIGS. 6A and 6B, the drive motors <b>102</b> and encoders <b>110</b> may be serviced or replaced from outside the island without risk of contamination. If a drive shaft <b>104</b> or any of its associated components needs to be serviced or replaced, such operation may be performed with the valves on either side of the drive mechanism closed. Thus, the interiors of the adjacent chambers will not become contaminated from such action. Any contamination will be limited to the space between the valves immediately surrounding the drive mechanism which may be more readily cleaned than the interior of the adjacent chambers.

P-0085[0085] A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the particular processes associated with fabricating a given device may advantageously be associated with different chamber arrangements and sequences of use. In this way, the types of chambers may be those employed in etching processes, physical vapor deposition, chemical vapor deposition, etc. In another modification, while three process chambers have been described here, the system may employ a single process chamber, two process chambers, or more than three process chambers. The system of the present invention, as it is modular and incremental, allows numerous modifications to suit any particular process. For example, the shuttle of the present invention may be controlled to even repeat processing steps for a particular substrate if desired. In this way, the shuttle may be controlled to be bidirectional. Accordingly, other embodiments are within the scope of the following claims.