BACKGROUND

Field

[0001] Embodiments of the present disclosure generally relate to a method and apparatus for transfer of substrates, such as solar panel substrates, flat panel substrates, or semiconductor substrates, to and from a susceptor or substrate support.

Description of the Related Art

[0002] In the manufacture of solar panels or flat panel displays, many processes are employed to deposit thin films on substrates, such as semiconductor substrates, solar panel substrates, and liquid crystal display (LCD) and/or organic light emitting diode (OLED) substrates, to form electronic devices thereon. The deposition is generally accomplished by introducing a precursor gas into a vacuum chamber having a substrate disposed on a temperature controlled substrate support. The precursor gas is typically directed through a gas distribution plate situated near the top of the vacuum chamber. The precursor gas in the vacuum chamber may be energized (e.g., excited) into a plasma by applying a radio frequency (RF) power to the chamber from one or more RF sources coupled to the chamber. The excited gas reacts to form a layer of material on a surface of the substrate that is positioned on the temperature controlled substrate support.

[0003] The size of the substrates for forming the electronic devices now routinely exceeds 1 square meter in area, and the substrate support is sized similarly or includes a slightly larger surface area. Typically, the substrate support includes a plurality of lift pins disposed thereon or therethrough that are utilized to facilitate transfer of substrates to and from a surface thereof. For example, the lift pins are utilized to space the substrate away from a support surface of the substrate support so a robot blade or end effector may pass therebetween. Each lift pin has a lift pin head that is typically located in a recessed pocket of the substrate support. The presence of the lift pin heads on the substrate support facilitates temperature differences across the substrate support and/or radio frequency (RF) coupling deltas across the substrate support. For example, the position of the lift pins may cause portions of the substrate in proximity therewith to be cooler than other areas of the substrate. In another example, the position of the lift pins may cause the portions of the substrate in proximity therewith to have a lesser ground potential which changes plasma coupling conditions.

[0004] Uniformity is generally desired in the thin films deposited on the substrates. For example, an amorphous silicon film, such as microcrystalline silicon film, or a polycrystalline silicon film is usually deposited on a substrate for forming p- n junctions required in transistors or solar cells. The quality and uniformity of the amorphous silicon film or polycrystalline silicon film, as well as metal oxide films, are important for commercial operation. One or both of the non-uniformity of temperature and RF coupling may change properties of films deposited on the substrate, resulting in non-uniform deposition. In addition, the lift pins may scratch or otherwise damage the surface of the substrate during contact therewith.

[0005] Thus, there exists a need for a substrate support that minimizes film non- uniformity and/or damage.

SUMMARY

[0006] Embodiments of the present disclosure generally relate to a method and apparatus for transferring a substrate. In one embodiment, a substrate transfer device is provided that includes a substrate support having a perimeter, a plurality of central support members positioned outside of the perimeter, and an edge support member positioned on opposing sides of the substrate support.

[0007] In another embodiment, a plasma processing system is described. The plasma processing system includes a chamber, a substrate support having a perimeter disposed in the chamber, and a substrate transfer device positioned within the chamber. The substrate transfer device comprises a plurality of central support members positioned outside of the perimeter, and an edge support member positioned on opposing sides of the substrate support. [0008] In another embodiment, a method for transferring a substrate to a substrate receiving surface of a substrate support is described. The method includes providing a substrate to a chamber, supporting the substrate by central regions thereof using one or more central support members, supporting the substrate by two opposing edges thereof using edge support members, rotating the one or more central support members past a perimeter of the substrate support, and lowering the two opposing edges of the substrate toward the substrate receiving surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0010] Figure 1A is a schematic cross-sectional view of a plasma processing system having one embodiment of a substrate transfer device.

[0011] Figure 1 B shows the substrate transfer device of Figure 1A retracted, which places the substrate on the substrate receiving surface of the substrate support for processing.

[0012] Figures 2A-8B are various views of one embodiment of a substrate transfer device depicting one embodiment of a substrate transfer process.

[0013] Figures 9A-15B are various views of another embodiment of a substrate transfer device depicting another embodiment of a substrate transfer process.

[0014] Figure 16A is an isometric plan view of the substrate support having the edge support members positioned on opposing sides of the substrate support. [0015] Figure 16B is an isometric view of a portion of the substrate support shown in Figure 16A.

[0016] Figure 16C is a partial side cross-sectional view of the substrate support and the edge support member positioned thereon

[0017] To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. It is contemplated that elements and/or process steps of one embodiment may be beneficially incorporated in other embodiments without additional recitation.

DETAILED DESCRIPTION

[0018] Embodiments of the present disclosure generally relate to a method and apparatus for transferring substrates to or from a substrate support without the use of conventional lift pins. In the description that follows, reference will be made to a plasma enhanced chemical vapor deposition (PECVD) chamber for forming films on large area substrates, but it is to be understood that the embodiments herein may be practiced in other chambers as well, including physical vapor deposition (PVD) chambers, etching chambers, semiconductor wafer processing chambers, solar cell processing chambers, and organic light emitting display (OLED) processing chambers to name only a few. Suitable chambers that may be used are available from AKT America, Inc., a subsidiary of Applied Materials, Inc., Santa Clara, California. It is to be understood that the embodiments discussed herein may be practiced in chambers available from other manufacturers as well.

[0019] Embodiments of the present disclosure are generally utilized in processing rectangular substrates, such as substrates for liquid crystal displays or flat panels, and substrates for solar panels. Other suitable substrates may be circular, such as semiconductor substrates. However, the present disclosure provides particular advantage in substrates having a plan surface area of about 15,600 cm ² and including substrates having a plan surface area of about a 90,000 cm ² surface area (or greater). [0020] Figure 1A is a schematic cross-sectional view of one embodiment of a plasma processing system 100. The plasma processing system 100 is configured to process a large area substrate 105 using plasma in forming structures and devices on the large area substrate 105 for use in the fabrication of liquid crystal displays (LCD's), flat panel displays, organic light emitting diodes (OLED's), or photovoltaic cells for solar cell arrays. The substrate 105 may be thin sheet of metal, plastic, organic material, silicon, glass, quartz, or polymer, among others suitable materials. The substrate 105 may have a surface area greater than about 1 square meter, such as greater than about 2 square meters. In other embodiments, the substrate 105 may include a plan surface area of about 15,600 cm ² , or greater, for example about a 90,000 cm ² plan surface area (or greater). The structures may be thin film transistors which may comprise a plurality of sequential deposition and masking steps. Other structures may include p-n junctions to form diodes for photovoltaic cells.

[0021] The plasma processing system 100 may be configured to deposit a variety of materials on the large area substrates 105, including but not limited to dielectric materials {e.g., S1O2, SiOxN _y , derivatives thereof or combinations thereof), semiconductive materials {e.g., Si and dopants thereof), barrier materials {e.g., SiN _x , SiOxNy or derivatives thereof). Specific examples of dielectric materials and semiconductive materials that are formed or deposited by the plasma processing system 100 onto the large area substrates may include epitaxial silicon, polycrystalline silicon, amorphous silicon, microcrystalline silicon, silicon germanium, germanium, silicon dioxide, silicon oxynitride, silicon nitride, dopants thereof {e.g., B, P, or As), derivatives thereof or combinations thereof. The plasma processing system 100 is also configured to receive gases such as argon, hydrogen, nitrogen, helium, or combinations thereof, for use as a purge gas or a carrier gas {e.g., Ar, H ₂ , N ₂ , He, derivatives thereof, or combinations thereof). One example of depositing silicon thin films on the large area substrate 105 using the system 100 may be accomplished by using silane as a processing gas in a hydrogen carrier gas.

[0022] As shown in Figure 1A, the plasma processing system 100 generally comprises a chamber body 1 10 including a bottom 1 15 and sidewalls 120 that at least partially defines a processing volume 125. A substrate support 130 is disposed in the processing volume 125. The substrate support 130 is coupled to an actuator 135 adapted to move the substrate support at least vertically to facilitate transfer of the substrate 105 and/or adjust a distance between the substrate 105 and a showerhead assembly 140. The substrate support 130 is adapted to support the substrate 105 on a substrate receiving surface 145 during processing.

[0023] The plasma processing system 100 includes a substrate transfer device 150 that is adapted to lift or lower the substrate 105 from the substrate receiving surface 145 of the substrate support 130. In the view if Figure 1A, the substrate 105 is shown lifted from the substrate receiving surface 145 by the substrate transfer device 150. A space between a backside surface 155 of the substrate 105 and the substrate receiving surface 145 of the substrate support 130 is provided for a conventional robot or end effector (both not shown) to pass therebetween. The substrate 105 may be transferred into or out of the chamber body 1 10 through a transfer port 160 when the substrate transfer device 150 is in the position shown in Figure 1A.

[0024] Figure 1 B shows the substrate transfer device 150 retracted, which places the substrate 105 on the substrate receiving surface 145 for processing. The substrate transfer device 150 may include a plurality of support members adapted to contact the backside surface 155 of the substrate 105. The plurality of support members may include edge support members 162 (only one is shown in Figures 1A and 1 B) and central support members 164. The edge support members 162 may be utilized to contact and support edges of the substrate 105. The central support members 164 may be utilized to contact and support regions of the substrate 105 interior of the edges of the substrate 105. The edge support members 162 and the central support members 164 are adapted to move laterally and/or rotationally relative to the substrate support 130 (in an X-Y plane). The edge support members 162 and the central support members 164 are adapted to move vertically (in the Z direction) relative the substrate support 130.

[0025] The edge support members 162 may be coupled to first actuators 166. The edge support members 162 may be coupled to the first actuators 166 by a support shaft 165. The support shafts 165 may be positioned outside of a perimeter of the substrate support 130 in some embodiments, as shown. In other embodiments, the support shafts 165 may alternatively or additionally be positioned such that the support shafts 165 pass through the substrate support 130. The central support members 164 may be coupled to support shafts 167 that are positioned outside of the perimeter of the substrate support 130.

[0026] The central support members 164 may be coupled to second actuators 168. Each of the first actuators 166 may be a linear drive device adapted to move the edge support members 162 in a vertical direction (the Z direction). Each of the second actuators 168 may be a linear and rotational drive device adapted to move the central support members 164 up and down (in the Z direction) as well as movement of the central support members 164 in an X-Y plane.

[0027] In operation, the showerhead assembly 140 is configured to supply a processing gas to the processing volume 125 from a processing gas source 170. The plasma processing system 100 also comprises an exhaust system 172 configured to apply negative pressure to the processing volume 125. The showerhead assembly 140 is generally disposed opposing the substrate support 130 in a substantially parallel relationship.

[0028] The showerhead assembly 140 comprises a gas distribution plate 174 and a backing plate 176. The backing plate 176 may function as a blocker plate to enable formation of a gas volume between the gas distribution plate 174 and the backing plate 176. The gas source 170 is connected to the gas distribution plate 174 by a conduit 178. In one embodiment, a remote plasma source 180 is coupled to the conduit 178 for supplying a plasma of activated gas through the gas distribution plate 174 to the processing volume 125. The plasma from the remote plasma source 180 may include activated gases for cleaning chamber components disposed in the processing volume 125. In one embodiment, activated cleaning gases are flowed to the processing volume 125. Suitable gases for cleaning include fluorine (F ₂ ), nitrogen trifluoride (NF ₃ ), sulfur hexafluoride (SF ₆ ) and carbon/fluorine containing gases, such as fluorocarbons, for example octofluorotetrahydrofuran (C ₄ F ₈ 0), carbonyl fluoride (COF ₂ ), hexafluoroethane (C ₂ F ₆ ), tetrafluoromethane

(CF ₄ ), perfluoropropane (C ₃ F ₈ ), and combinations thereof. Although carbon and oxygen containing gases may be used, the gases are not favorable due to possible carbon and/or oxygen contamination.

[0029] The gas distribution plate 174, the backing plate 176, and the conduit 178 are generally formed from electrically conductive materials and are in electrical communication with one another. The chamber body 1 10 is also formed from an electrically conductive material. The chamber body 1 10 is generally electrically insulated from the showerhead assembly 140. In one embodiment, the showerhead assembly 140 is mounted on the chamber body 1 10 by an insulator 182.

[0030] In one embodiment, the substrate support 130 is also made of an electrically conductive material, and the substrate support 130 and the showerhead assembly 140 are configured to be opposing electrodes for generating a plasma 184 of processing gases therebetween during processing and/or a pre-treatment or post- treatment process. Additionally, the substrate support 130 and the showerhead assembly 140 may be utilized to support a plasma of cleaning gases during a cleaning process. The substrate support 130 may also be heated, such as by resistive heating elements (not shown) and/or include fluid channels (not shown) for circulating a fluid to control temperature of a substrate positioned thereon.

[0031] A radio frequency (RF) power source 186 is generally used to generate the plasma 184 between the showerhead assembly 140 and the substrate support 130 before, during and after processing. In some embodiments, the substrate support 130 is at ground potential. The RF power source 186 may also be used to maintain energized species or further excite cleaning gases supplied from the remote plasma source 180. An impedance matching circuit 188 may be coupled between the power source 186 and the showerhead assembly 140. In some embodiments, a frame member 190 (shown in Figure 1 B) may be placed about the periphery of the substrate 105. The frame member 190 may be utilized to confine gases over the substrate 105 during processing. [0032] Figures 2A-8B are various views of the substrate transfer device 150 showing one embodiment of a substrate transfer process. Figures 2A, 3A, 4A, 5A, 6A, 7A and 8A are top plan views of a substrate 105 and a substrate support 130 while Figures 2B, 3B, 4B, 5B, 6B, 7B and 8B are elevation views illustrating the process depicted in Figures 2A, 3A, 4A, 5A, 6A, 7A and 8A.

[0033] Figures 2A and 2B show an end effector 200 having a plurality of fingers 205 at least partially supporting a substrate 105 above a substrate support 130. The edge support members 162 may be utilized to support sides of the substrate 105 while the central support members 164 may be utilized to support areas of the substrate 105 inward of the sides of the substrate 105. The edge support members 162 and the central support members 164 may comprise a ceramic material. The edge support members 162 and the central support members 164 may comprise AI2O3, for example. Surfaces of the edge support members 162 and the central support members 164 in contact with the substrate 105 may be AI2O3, anodized aluminum or graphite. The edge support members 162 may be utilized to support all four sides of the substrate 105 or only two sides of the substrate 105. The edge support members 162 are positioned outside of the fingers 205 as to not interfere with the operation of the end effector 200. At least a portion of the central support members 164 may be offset {e.g., "L" shaped) to not interfere with the fingers 205 of the end effector 200.

[0034] The end effector 200 may transfer the substrate 105 to the position above the substrate support 130 shown in Figure 2A. Thereafter, the edge support members 162 and central support members 164 may be actuated to the positions shown in Figure 2B.

[0035] Figure 3A shows the end effector 200 of Figures 2A and 2B retracted and Figure 3B shows the edge support members 162 and the central support members 164 supporting the substrate 105 above the substrate support 130. As shown in Figure 3B, the edge support members 162 and central support members 164 may be raised slightly from the substrate support 130 so the fingers 205 are clear of the backside surface of the substrate 105 in order to prevent scratching. [0036] Figures 4A and 4B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 3B. Additionally, an inner set 400 of central support members 164 is rotated to a position outside of the perimeter of the substrate 105.

[0037] Figures 5A and 5B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 4B. The center portion of the substrate 105 is brought into closer proximity to the substrate support 130.

[0038] Figures 6A and 6B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 5B. Additionally, a central set 600 of central support members 164 is rotated to a position outside of the perimeter of the substrate 105. The center portion of the substrate 105 is brought into closer proximity to the substrate support 130 as compared to the view shown in Figure 5B.

[0039] Figures 7A and 7B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 6B. Additionally, an outer set 700 of central support members 164 is rotated to a position outside of the perimeter of the substrate 105. The center portion of the substrate 105 is brought into contact with the substrate support 130. Sides of the substrate 105 remain supported by the edge support members 162 while all central support members 164 are rotated outside of the perimeter of the substrate 105.

[0040] Figures 8A and 8B shows the substrate 105 lowered onto the substrate support 130. The lowering is accomplished by lowering the edge support members 162 toward the substrate support 130. In some embodiments, the edge support members 162 are lowered into a recess along an edge of the substrate support 130. In this embodiment, the edge support members 162 are positioned between the substrate 105 and the substrate support 130.

[0041] Figures 9A-15B are various views of another embodiment of the substrate transfer device 150 showing another embodiment of a substrate transfer process. Figures 9A, 10A, 1 1A, 12A, 13A, 14A and 15A are top plan views of a substrate 105 and a substrate support 130 while Figures 9B, 10B, 1 1 B, 12B, 13B, 14B and 15B are elevation views illustrating the process depicted in Figures 9A, 10A, 1 1A, 12A, 13A, 14A and 15A.

[0042] The substrate transfer sequence is substantially similar to the embodiment depicted in Figures 2A-8B with the exception of a central edge support member 900 between the central support members 164 and the edge support members 162.

[0043] Figures 9A and 9B show an end effector 200 having a plurality of fingers 205 at least partially supporting a substrate 105 above a substrate support 130. The edge support members 162 as well as the central edge support members 900 may be utilized to support sides of the substrate 105 while the central support members 164 may be utilized to support areas of the substrate 105 inward of the sides of the substrate 105. The central edge support members 900 may comprise a ceramic material. The edge support members 162 are positioned outside of the fingers 205 as to not interfere with the operation of the end effector 200. The central edge support members 900 are positioned between the fingers 205 as to not interfere with the operation of the end effector 200.

[0044] Figure 10A shows the end effector 200 of Figures 9A and 9B retracted and Figure 10B shows the edge support members 162 and the central support members 164 supporting the substrate 105 above the substrate support 130. As shown in Figure 3B, the edge support members 162 and central support members 164 may be raised slightly from the substrate support 130 so the fingers 205 are clear of the backside surface of the substrate 105 in order to prevent scratching.

[0045] Figures 1 1A and 1 1 B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 10B. Additionally, an inner set 400 of central support members 164 is rotated to a position outside of the perimeter of the substrate 105.

[0046] Figures 12A and 12B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 1 1 B. The center portion of the substrate 105 is brought into closer proximity to the substrate support 130. [0047] Figures 13A and 13B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 12B. Additionally, a central set 600 of central support members 164 is rotated to a position outside of the perimeter of the substrate 105. The center portion of the substrate 105 is brought into closer proximity to the substrate support 130 as compared to the view shown in Figure 12B.

[0048] Figures 14A and 14B shows the substrate 105 lowered toward the substrate support 130 as compared to the view shown in Figure 13B. Additionally, an outer set 700 of central support members 164 is rotated to a position outside of the perimeter of the substrate 105. The center portion of the substrate 105 is brought into contact with the substrate support 130. Sides of the substrate 105 remain supported by the edge support members 162, the central edge support members 900, and a central portion of the substrate 105 is supported by an outer set of central support members 164.

[0049] Figures 15A and 15B shows the substrate 105 lowered onto the substrate support 130. The lowering is accomplished by lowering the edge support members 162 and the central edge support members 900 toward the substrate support 130. In addition an outer set of central support members 164 are rotated outside of the perimeter of the substrate 105.

[0050] Figure 16A is an isometric plan view of the substrate support 130 having the edge support members 162 positioned on opposing sides of the substrate support 130. Additionally, the frame member 190 is shown above the substrate support 130. The central edge support members 900 are also shown positioned on the substrate support 130 on opposing sides thereof. Also shown are ceramic strips 1600 positioned on opposing sides of the central edge support members 900. While the edge support members 162 are configured to move in order to transfer the substrate 105, the ceramic strips 1600 may remain coupled to the substrate support 130. In configurations where the central edge support members 900 are not used. The ceramic strips 1600 may be one piece (i.e., not broken by the central edge support members 900). [0051] Figure 16B is an isometric view of a portion of the substrate support 130 shown in Figure 16A. The edge support member 162 and the ceramic strip 1600 are shown positioned outside of a perimeter 1605 of the substrate 105. Also shown is a recessed peripheral region 1610 of the substrate support 130 where the frame member 190 may be positioned.

[0052] Figure 16C is a partial side cross-sectional view of the substrate support 130 and the edge support member 162 positioned thereon. The edge support members 162 (only one is shown in this view) are adapted to be positioned in a recess 1615 below the substrate receiving surface 145 of the substrate support 130. The recess 1615 may be sized to receive a width of the edge support members 162. The recess 1615 may also be sized to receive a thickness of the edge support members 162 such that an upper surface 1620 of the edge support members 162 is substantially coplanar with an upper surface 1625 of the substrate 105. The frame member 190 is adapted to cover the upper surface 1620 of the edge support members 162 during processing but is spaced away from this position in order to show other elements.

[0053] Also shown is an opening 1630 in a peripheral region 1635 of the substrate support 130. The opening 1630 may be sized to receive and allow passage of a support shaft 1640. While only one opening 1630 is shown in Figure 16C, the peripheral region 1635 of the substrate support 130 may have other openings. The support shaft 1640 may be the support shaft 165 for the edge support members 162 as well as a support shaft for the central edge support members 900. The opening 1630 may be utilized for a respective support shaft 165 to contact, lift and lower the edge support member 162.

[0054] Embodiments of the substrate transfer device 150 as described herein provide many benefits. One benefit includes elimination of lift pins in the substrate support 130 as well as lift pin pockets in the substrate support 130. The substrate receiving surface 145 of the substrate support 130 does not include any through- holes (i.e., is not perforated) which reduces or eliminates cold spots on the substrate 105. The substrate edge supports (162 and 900) impact film property and has a minimum width in order to have a minimal impact on RF coupling. Another benefit of the substrate transfer device 150 includes less damage to a backside surface of a substrate 105. Conventional lift pins, which tend to scratch the substrate, are eliminated, which minimizes or eliminates scratching of the substrate. The substrate transfer device 150 places a substrate 105 on the substrate support 130 from the center of the substrate outward to the edges thereof by removing the central support members 164 from center gradually (shown in Figures 2B-8B and 9B-15B). Initial contact of the center of the substrate 105 with the substrate support 130 minimizes movement of the substrate 105 during the transfer operation. The substrate transfer device 150 also functions to maintain the shape of the substrate 105 (e.g., minimizes deformation) to control stress (for example, less than about 100 MPa).

[0055] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.