Cassette structure and related methods for batch processing in epitaxial deposition processes.

Abstract

A cassette support system is disclosed, in one embodiment, a pedestal assembly comprising a shaft; a plurality of arms coupled to the shaft and extending radially from the shaft, wherein at least two radially adjacent arms included in the plurality of arms are separated by an angle of about 130 degrees or more; a plurality of cassette support arms, each cassette support arm extending from the end of an arm included in the plurality of arms; and one or more substrate support rings, each substrate support ring including a ridge defined along the inner circumference of the substrate support ring and configured to receive a substrate.

Description

Technical Field

[0001] The present disclosure relates to a cassette structure and related methods for batch processing in an epitaxial deposition process.

Background Art

[0002] Semiconductor substrates are processed for a wide variety of applications, including the manufacture of integrated devices and microdevices. However, processes (such as epitaxial deposition processes) can be long, costly, inefficient, and may have limited capacity and throughput. The processes can also be limited with respect to film growth rate. Moreover, the hardware can involve relatively large dimensions that occupy a greater floor space in manufacturing facilities. Further, the processes can involve obstacles related to temperature control, gas control, and / or substrate center-edge control and adjustability. Such obstacles can worsen in relatively complex processing steps and / or in steps that require single-sided deposition.

[0003] Thus, there is a need for improved apparatus and methods in semiconductor processing.

Summary of the Invention

[0004] The present disclosure relates to a cassette structure and related methods for batch processing in an epitaxial deposition process.

[0005] A cassette support system is disclosed, in one embodiment, a pedestal assembly comprising a shaft; a plurality of arms coupled to the shaft and extending radially from the shaft, wherein at least two radially adjacent arms included in the plurality of arms are separated by an angle of about 130 degrees or more; a plurality of cassette support arms, each cassette support arm extending from the end of an arm included in the plurality of arms; and one or more substrate support rings, each substrate support ring including a ridge defined along the inner circumference of the substrate support ring and configured to receive a substrate.

[0006] In another embodiment, a cassette support system is provided. This cassette support system includes a pedestal assembly comprising a shaft, a plurality of arms coupled to the shaft and extending radially from the shaft, wherein at least two radially adjacent arms included in the plurality of arms are separated by an angle of about 130 degrees or more, a plurality of cassette support arms, wherein each cassette support arm extends from another arm included in the plurality of arms, and at least one substrate support ring, which includes a ridge defined along the inner circumference of each of the at least one substrate support ring.

[0007] In another embodiment, a cassette support system is provided. This cassette support system includes a pedestal assembly having a shaft, three or more arms coupled to the shaft and extending radially from the shaft, wherein two radially adjacent arms included in the three or more arms are separated by an angle of about 130 degrees or more, three or more cassette support arms, wherein each cassette support arm extends from another arm of the three or more arms, three or more substrate support rings, each having ridges defined along the inner circumference of each substrate support ring, and three or more substrate support rings, each comprising a first set of spacers disposed between a first substrate support ring and a second substrate support ring, each spacer being disposed around a corresponding vertical cassette support arm, and a second set of spacers disposed between a second substrate support ring and a third substrate support ring, each spacer being disposed around a corresponding vertical cassette support arm.

[0008] To allow the above-described features of this disclosure to be understood in detail, a more detailed description of this disclosure, which has been briefly summarized above, may be made by reference to embodiments some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings are merely illustrative embodiments and should not be considered limiting in scope, as this disclosure may allow for other equally valid embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional side view of a processing apparatus having multiple substrates in a processing position in a cassette, according to one or more embodiments. [Figure 2] This is a schematic cross-sectional side view of the apparatus shown in Figure 1 in the unloading position, according to one or more embodiments. [Figure 3]Figure 2 shows a schematic side cross-sectional view of the apparatus shown in one or more embodiments, in which a substrate is placed on two fingers of a robotic arm and lifted by a lift pin to be removed from the chamber. [Figure 4] Figures 2 and 3 show schematic side cross-sectional views of the apparatus shown in Figures 2 and 3, according to one or more embodiments, in which a substrate is positioned on two fingers of a robotic arm and a lift pin is retracted. [Figure 5] This is a perspective view of the upper portion of a pedestal assembly used to support the cassettes shown in Figures 1 to 4, according to one or more embodiments. [Figure 6] This is a plan view of the upper portion of a pedestal assembly used to support the cassettes shown in Figures 1 to 4, according to one or more embodiments. [Figure 7] This is a perspective view of a cassette according to one or more embodiments. [Figure 8] This is a schematic side cross-sectional view of a cassette containing multiple circuit boards according to one or more embodiments. [Figure 9] This is a partially cross-sectional, plan view showing the pedestal, lift pins, substrate, and the upper portion of the robot arm and fingers. [Modes for carrying out the invention]

[0010] For ease of understanding, the same reference numerals are used to designate the same elements common to the figures where possible. It is intended that elements and features of one or more embodiments may be usefully incorporated into other embodiments without further description.

[0011] This disclosure relates to a cassette structure and related methods for batch processing in an epitaxial deposition process.

[0012] Figure 1 is a schematic cross-sectional side view of a processing apparatus with multiple substrates located at processing positions in a cassette, in one mounting configuration. The processing apparatus 100 includes a processing chamber having a chamber body 130 that defines a processing space 124, as well as an upper heat source 106 and a lower heat source 138.

[0013] The processing apparatus 100 includes a plurality of gas injection passages 182 formed in the chamber body 130 and fluidly connected to the processing space 124, and one or more gas exhaust passages 172 (multiple are shown in Figure 1) formed in the chamber body 130 on the opposite side of the plurality of gas injection passages 182. One or more gas exhaust passages 172 are fluidly connected to the processing space 124. Each of the plurality of gas injection passages 182 and one or more gas exhaust passages 172 are formed through one or more side walls of the chamber body 130 and through one or more liners 120 that line one or more side walls of the chamber body 130.

[0014] The processing apparatus 100 includes a flow guide structure 150 positioned in the processing space 124. The flow guide structure 150 includes one or more first flow dividers 151 that divide the processing space into a plurality of flow levels 153. During a process (such as during an epitaxial deposition process), one or more process gases P1 are supplied to the processing space 124 through a supply conduit system 121 and through a plurality of gas injection passages 182. One or more process gases P1 are supplied from one or more gas sources 196 that are fluidly connected to the plurality of gas injection passages 182. Each of the gas injection passages 182 is configured to direct one or more process gases P1 generally radially inward toward the cassette 230. Thus, in one or more embodiments, the gas injection passages 182 may be part of a cross-flow gas injector. The flow of one or more process gases P1 is divided into a plurality of flow levels 153. Dividing the process gas (one or more) into multiple flow levels 153 facilitates uniform processing (e.g., deposition) on the substrate, center-edge uniformity, and process tunability.

[0015] The processing apparatus 100 includes an exhaust conduit system 190. One or more process gases P1 can be discharged to an optional common exhaust box and then to the outside through the conduit using one or more pumping devices 197 (such as one or more vacuum pumps).

[0016] The cassette 230 is positioned in the processing space 124 and at least partially supported by the pedestal assembly 300. In various embodiments, the cassette 230 supports multiple substrates 255a, 255b, 255c for simultaneous processing (e.g., epitaxial deposition). In the embodiment shown in Figure 1, the cassette 230 supports three substrates. However, the cassette 230 can support other numbers of substrates, including, but not limited to, two substrates 255, three substrates 255, six substrates 255, twelve substrates 255, and so on.

[0017] The processing apparatus 100 includes a window 193, such as a dome, positioned above the cassette 230 and below the upper heat source 106. The heat sources 106 and 138 are positioned to provide uniform heating of the substrate 255. One or more heat sources may be radiant heat sources, such as lamps. For example, halogen lamps and / or other heat sources may be used (in addition to or instead of lamps) for the various heat sources described herein. In other examples, resistance heaters, light-emitting diodes (LEDs), and / or lasers may be used for the various heat sources described herein.

[0018] The processing apparatus 100 includes a pedestal assembly 300 disposed in the processing space 124. One or more liners 120 are disposed in the processing space 124 and surround the pedestal assembly 300. The one or more liners 120 facilitate protecting the chamber body 130 from the processing chemistry in the processing space 124. The one or more liners 120 are disposed between the processing space 124 and the chamber body 130. Further, a sealing ring 350 disposed on the pedestal assembly 300 below the cassette 230 hermetically protects the chamber body 130 from process gases when the cassette is in the processing position in the chamber. In the illustrated embodiment, the ring 350 seals adjacent gas inlets and exhaust structures to the shield ring 111 during processing.

[0019] In some embodiments, the pedestal assembly 300 can be raised to a first position so that the cassette 230 is positioned within the processing space 124. The pedestal assembly 300 can be lowered to a second position such that the cassette 230 of the chamber body 130 is where one or more substrates 255 can be loaded onto and / or unloaded from the cassette 230.

[0020] Separate from the pedestal assembly 300, there is a lift pin assembly 360. In the illustrated embodiment, the lift pin assembly 360 is disposed outside the pedestal assembly 300 with a coaxial shaft 365 that is axially movable independently of the pedestal shaft 305. From the shaft 365, three arms 370a, 370b, 370c (FIG. 9) extend, each having a vertical lift pin 372a, 372b, 372c at their distal ends. As will be described below with reference to FIGS. 1-4, the lift pins 372 are utilized to lift and lower the (one or more) substrates when the substrate 255 is loaded onto and / or unloaded from the cassette 230.

[0021] Figures 2 to 4 show the operation and movement of the substrate 255 from the cassette after processing. Figure 2 is a schematic cross-sectional side view of the processing apparatus 100 shown in Figure 1, with the cassette 230 in the unloading position. In various embodiments, the lift pin assembly 360 and lift pins 370a, 370b, and 370c are positioned below the cassette 230 in the processing position so that the substrate 255 is loaded into the cassette 230 from top to bottom and unloaded from bottom to top.

[0022] In Figure 2, the lower substrate 255c has been removed, and the lift pin assembly 360 is ready to lift the central substrate 255b to a position adjacent to an opening 136, where the central substrate 255b can be accessed by a robotic arm 375 (not shown). The opening 136 is formed through one or more side walls of the chamber body 130. The opening 136 can be used to transport the substrate 255 into or out of the cassette 230, for example, in and out of the processing space 124. In one or more embodiments, the opening 136 includes a slit valve. In one or more embodiments, the opening 136 can be connected to any suitable valve that allows a passage for the substrate 255 through it. In some embodiments, the cassette 230 is rotatable during processing. In such embodiments, the cassette 230 has a loading / unloading position in which the cassette 230 is oriented in the position shown in Figure 9, allowing the substrate 255 to be loaded and unloaded through the opening 136 without interference by the cassette support arm 315.

[0023] FIG. 3 is a schematic side cross-sectional view of the processing apparatus 100 of FIG. 2 with the substrate 255b lifted by the lift pins 372a, 372b, 372c at a position in front of the opening 136 and immediately above the robot arm 375. (Shown in FIG. 9) The robot arm 375 including two fingers 375a, 375b is constructed and arranged to straddle the lift pin 372a and position itself immediately below the substrate 255b. At this position, the split fingers of the robot arm 375 are ready to receive the substrate 255b when the lift pins 372a, 372b, 372c are lowered.

[0024] In FIG. 3, the lift pin assembly 360 raises the lower substrate 255c for removal by the robot arm 375. When the lower substrate 255c is removed, the lift pin assembly 360 is raised through the inside of the lower substrate support ring 320c to lift the central substrate 255b from the central substrate support ring 320b for removal by the robot arm 375. This process is then repeated to lift the upper substrate 255a for removal.

[0025] FIG. 4 is a schematic top cross-sectional view of the processing apparatus 100 shown in FIGS. 2 and 3 with the second substrate 255b placed on the robot arm 375 and the lift pins 372a, 372b, 372c retracted. The substrate 255b can then be removed from the processing space 124 by the robot through the opening 136. This process will be repeated until the remaining substrate 255a is removed and the cassette 230 is empty. The above process is described as being repeated three times to remove the substrates 255a, 255b, and 255c, but in various embodiments, the process can be repeated any number of times, such as two, four, six, or twelve times, depending on how many substrates the cassette 230 can hold.

[0026] The processing apparatus 100 may include one or more temperature sensors 191, 192, such as an optical pyrometer, for measuring one or more temperatures within the processing apparatus 100 (such as on the surface of the window 193, on one or more surfaces of the substrate 255 and / or the cassette 230). In some embodiments, one or more temperature sensors 191, 192 are disposed on the lid 104.

[0027] The processing unit 100 includes a controller 1070 configured to control the processing unit 100 or its components. For example, the controller 1070 may control the operation of the components of the processing unit 100 by using direct control of those components or by controlling controllers associated with those components. During operation, the controller 1070 enables data acquisition and feedback from each chamber to coordinate and control the performance of the processing unit 100.

[0028] The controller 1070 generally includes a central processing unit (CPU) 1071, memory 1072, and support circuitry 1073. The CPU 1071 may be one of any form of general-purpose processor that may be used in an industrial setting. Memory 1072, or non-temporary computer-readable medium, is accessible by the CPU 1071 and may be one or more of the following types of memory: random access memory (RAM), read-only memory (ROM), floppy disk, hard disk, or any other form of local or remote digital storage. Support circuitry 1073 is coupled to the CPU 1071 and may include a cache, clock circuitry, input / output subsystems, power supply, etc.

[0029] The various methods and processes disclosed herein can generally be implemented under the control of the CPU 1071 by the CPU 1071 executing computer instruction code stored, for example, as software routines in memory 1072 (or in the memory of a particular processing chamber). When the computer instruction code is executed by the CPU 1071, the CPU 1071 controls the components of the processing chamber 100 to operate according to the various methods and processes described herein. In one embodiment, which may be combined with other embodiments, memory 1072 (a non-temporary computer-readable medium) contains instructions stored therein that, when executed, cause the methods and processes described herein to be performed. The controller 1070 may communicate with the heat source, gas source, and / or (one or more) vacuum pumps of the processing unit 100, for example, to cause multiple processes to be performed.

[0030] Figure 5 is a perspective view of the upper portion of a pedestal assembly 300 used to support the cassette 230 shown in Figures 1 to 4. Figure 6 is a plan view of the pedestal assembly 300. The pedestal assembly 300 includes a vertical shaft 305 extending from a motor 164 (not shown) configured to independently raise, lower, and / or rotate the cassette 230. At the upper end of the shaft 305 are a plurality of outwardly extending arms 310a, 310b, and 310c, each of which is provided with upright cassette support arms 315a, 315b, and 315c at their distal ends. The pedestal assembly may be a single-piece or monolithic design made from a material such as quartz to allow a compact surface area to fit within the processing chamber. In the illustrated embodiment, the support arms are integrally formed on the arms.

[0031] As shown in Figure 6, distinct angles A, B, and C are formed between adjacent pairs of arms 310a, 310b, and 310c. In various embodiments, angle A between arms 310a and 310b is greater than angle B formed between arms 310b and 310c and angle C formed between arms 310c and 310a, respectively. Increasing angle A relative to angles B and C facilitates the lateral passage of the substrate 255 to the cassette 230 through the two cassette support arms 315a, 315b. Thus, both the lengths of arms 310a, 310b, and angle A between arms 310a and 310b, result in a minimum distance between support arms that is wide enough to allow passage of the substrate 255 between arms 310a and 310b and to the cassette 230, exceeding the outer diameter of the substrate 255. Angle A can be greater than 120 degrees, such as greater than 130 degrees, greater than 150 degrees, greater than 170 degrees, etc., to ensure that the pedestal assembly remains compact but is still large enough to allow the substrate to be transported to the cassette 230. For example, in the case of a substrate with an outer diameter of 300 mm, the inner distance between arms 310a and 310b will exceed 300 mm. While this example is for a 300 mm substrate, it should be understood that the arms can be designed to exceed the outer diameter of a substrate with a diameter greater than 100 mm, such as a 200 mm diameter or a 400 mm diameter, or any other diameter.

[0032] The purpose of the vertical cassette support arms 315a, 315b, 315c located at the distal ends of each horizontal arm 310a, 310b, 310c of the pedestal assembly 300 is to support various levels of the cassette 230, each level housing a substrate 255 for processing. The cassette in Figure 7 includes, for example, three levels. Each level consists of substrate support rings 320a, 320b, 320c, each ring including inwardly facing ridges 325a, 325b, 325c on the inner circumference of the substrate support ring. The ridges 325 of each ring 320 have an inner diameter slightly smaller than the outer diameter of the substrate 255. Thus, the inner diameter of the ring 320 is slightly larger than the outer diameter of the substrate, but the smaller inner diameter of the ridges 325 supports the substrate. In this way, each substrate can be held in place in the cassette 230 during processing.

[0033] In some embodiments, these levels are separated vertically by utilizing hollow spacers 330 that are coaxially positioned around the cassette support arms 315a, 315b, 315c (Figure 5). In Figure 7, for example, the cassette 230 has three levels for housing three substrates 255. Its arrangement utilizes two sets of spacers 330 to facilitate the separation of the two upper levels, for example, rings 320a, 320b. The lower substrate support ring 320c may include three holes (not shown) corresponding to the three vertical cassette support arms 315a, 315b, 315c. The three holes will be coaxially aligned around the cassette support arms 315a, 315b, 315c so that the lower substrate support ring 320c can be positioned relative to the upper surfaces of each horizontal arm 310a, 310b, 315c. Next, the first set of spacers 330 is positioned around each of the corresponding vertical cassette support arms 315a, 310b, and 310c such that the lower surface of each spacer 330 is positioned relative to the upper surface of the lower substrate support ring 320c.

[0034] The intermediate substrate support ring 320b may include three through holes that align with the three holes in the lower substrate support ring 320c. The three through holes will be coaxially aligned around the cassette support arms 315a, 315b, 315c so that the intermediate substrate support ring 320b can be positioned relative to the upper surface of each of the first set of spacers 330. This process is then repeated for the second set of spacers 330 and the upper support ring 320a. The vertical distance between the support rings can be predetermined by selecting the height of the spacers 330. The current embodiment is shown to have three vertical cassette support arms 315a, 315b, 315c and three support rings 320a, 320b, 320c. It should be understood that the cassette 230 may have more than three vertical cassette support arms 315, such as four or five vertical cassette support arms 315, and may have more or fewer than three support rings 320, such as two, six, or twelve support rings 320. In general, any combination of the number of vertical cassette support arms 315 and the number of board support rings 320 can be implemented, such as five vertical cassette support arms 315 and two board support rings 320, or three vertical cassette support arms 315 and twelve board support rings 320. It should be further understood that there may be any number of holes through each board support ring, and any number of spacers 330 between each pair of adjacent board support rings.

[0035] Figure 8 is a schematic side view of the cassette 230, in partial cross-section. The right side of Figure 8 shows the cassette support arm 315c of the cassette, with two spacers 330 stacked on top of it, and the substrate support ring 320b held between its pair of spacers 330. Two additional support rings 320a, 320c are shown, one below the lower spacer adjacent to the sealing ring 350, and the other at the upper end of the upper spacer 330, where the support ring 320a is held in place by a fastener 317. A total of three support rings 320 are shown, each having inward-facing ledges 325a, 325b, 325c for supporting the substrate 255. A second cassette support arm 310b is visible toward the rear of the cassette 230, along with its own spacer 300 (the third vertical member is not visible in Figure 8).

[0036] Figure 9 is a partially cross-sectional, plan view showing the pedestal arms 310a, 310b, and 310c, along with their connections to their cassette support arms (spacers 330 and fasteners 317 obscure the figure) and the substrate support ring 320a. Lift pins 372a, 372b, and 372c are also shown. A robotic arm 375 with two branched fingers 375a and 375b, and a substrate 255 are shown by dotted lines.

[0037] Figure 9 shows, in general, how the substrate 255 is loaded into the cassette 230 having the pedestal design disclosed herein in various embodiments (note arrow 905). As shown, the substrate 255 is insertable (or removable) by taking advantage of the enlarged angle A formed between the cassette support arms 315 at the ends of the horizontal arms 310a, 310b. Considering Figure 9 together with Figure 6, it can be understood that the lengths of the horizontal arms 310a, 310b and the angle A between the horizontal arms 310a and 310b result in dimension 901, the inner distance between the cassette support arms 315a and 315b. Comparing dimension 901 to dimension 902, the outer diameter of the substrate 255, the difference, dimension 903, can be understood to provide sufficient space for lateral insertion of the substrate into the cassette 230, as long as the pedestal assembly 300 is in the rotational position shown in Figure 9.

[0038] Furthermore, the lift pins 372a, 372b, and 372c are also radially positioned in loading / unloading positions so as not to interfere with the branched robotic fingers 375a, 375b that extend to the cassette 230 to position the substrate 255 onto the lift pins 372 when they are raised to lift the substrate from the fingers. The lift pins 372 then lower the substrate 255 to its predetermined position in the substrate support ring 320a of the cassette 230. The same process is repeated for each substrate to be batched in the chamber. Each time a new substrate is to be loaded, the cassette axially aligns the next empty support ring with the opening 136.

[0039] The benefits of this disclosure include a reduced number of individual parts (by integrating the cassette support arm into the pedestal assembly), as well as a smaller overall footprint of the cassette assembly (for example, in terms of width), enabling the simultaneous loading, unloading, and processing of multiple circuit boards.

[0040] The foregoing applies to embodiments of the present disclosure, but other and further embodiments of the present disclosure may be devised without departing from its basic scope, the scope of which is determined by the following claims.

Claims

1. A cassette support system comprising a pedestal assembly, The pedestal assembly is The shaft and A plurality of arms connected to the shaft and extending radially from the shaft, wherein at least two radially adjacent arms included in the plurality of arms are separated by an angle of approximately 130 degrees or more. A plurality of cassette support arms, each cassette support arm extending from the end of an arm included in the plurality of arms, One or more substrate support rings, each substrate support ring is A ridge defined along the inner circumference of the substrate support ring, wherein the ridge is configured to receive the substrate. A substrate support ring comprising one or more substrate support rings A cassette support system equipped with this system.

2. The cassette support system according to claim 1, wherein the pedestal assembly includes quartz.

3. The cassette support system according to claim 1, wherein the shaft and the plurality of arms form a monolithic body.

4. The cassette support system according to claim 1, wherein the pedestal assembly comprises one or more spacers, each spacer being arranged around a corresponding cassette support arm between adjacent pairs of substrate support rings included in the one or more substrate support rings.

5. The cassette support system according to claim 1, wherein the angle is approximately 150 degrees or more.

6. The cassette support system according to claim 1, wherein the angle is approximately 170 degrees or greater.

7. The cassette support system according to claim 4, wherein the one or more substrate support rings comprises at least three substrate support rings separated by at least two sets of spacers included in the one or more spacers.

8. The cassette support system according to claim 4, wherein the one or more substrate support rings comprises at least four substrate support rings separated by at least three sets of spacers included in the one or more spacers.

9. The cassette support system according to claim 1, wherein the plurality of arms comprises at least two horizontal arms.

10. The cassette support system according to claim 1, wherein the pedestal assembly comprises at least three arms and at least three cassette support arms.

11. The cassette support system according to claim 4, wherein the distance between the substrate support rings corresponds to the height of one or more spacers disposed on the arm.

12. A processing system, Processing chamber and The cassette support system according to claim 1 and A processing system equipped with the following features.

13. The processing system according to claim 12, further comprising a lift pin assembly having a plurality of lift pins, wherein the lift pin assembly is adjustable in the vertical direction.

14. The processing system according to claim 13, wherein the shaft of the lift pin assembly is arranged coaxially to the outside of the shaft.

15. The cassette support system according to claim 1, wherein at least one of the one or more substrate support rings is provided with a plurality of through holes.

16. The cassette support system according to claim 15, wherein the plurality of cassette support arms are arranged in the plurality of through holes.

17. The cassette support system according to claim 1, wherein the angle forms the minimum distance between the ends of radially adjacent arms, and the minimum distance is greater than the diameter of the inner circumference of the substrate support ring.

18. The cassette support system according to claim 17, wherein the minimum distance is greater than 200 mm.

19. A cassette support system comprising a pedestal assembly, The pedestal assembly is The shaft and A plurality of arms connected to the shaft and extending radially from the shaft, wherein at least two radially adjacent arms included in the plurality of arms are separated by an angle of approximately 130 degrees or more. A plurality of cassette support arms, each cassette support arm extending from another arm included in the plurality of arms, At least one substrate support ring, Ridges defined along the inner circumference of each of the at least one substrate support rings A substrate support ring comprising at least one substrate support ring A cassette support system equipped with this system.

20. A cassette support system comprising a pedestal assembly, The pedestal assembly is The shaft and Three or more arms connected to the shaft and extending radially from the shaft, wherein two radially adjacent arms included in the three or more arms are separated by an angle of approximately 130 degrees or more, Three or more cassette support arms, each cassette support arm having three or more cassette support arms extending from another arm among the three or more arms, Three or more substrate support rings, Ridges defined along the inner circumference of each of the substrate support rings, A first set of spacers disposed between a first substrate support ring and a second substrate support ring, wherein each spacer is disposed around a corresponding vertical cassette support arm, A second set of spacers disposed between the second substrate support ring and the third substrate support ring, wherein each spacer is disposed around the corresponding vertical cassette support arm, and It comprises three or more substrate support rings and A cassette support system equipped with this system.

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