Automated polishing and cleaning of semiconductor substrates

Abstract

This invention provides a wafer processing system and method that improves the efficiency of the wafer manufacturing process without damaging the wafers by automating the loading, unloading, and cleaning processes. [Solution] A semiconductor wafer processing system for processing a set of semiconductor wafers comprises a controller, a transport robot 108 controlled by the controller, a wet bath 110 for containing cleaning solution, and a cassette 112 positioned in the wet bath for holding a set of wafers. The transport robot transports the wafers from the transfer position to the cassette, and the controller controls the transport robot during transport.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims priority based on U.S. Patent Application No. 116 / 947,157, filed on July 21, 2020. All disclosures of the application on which the priority is based are hereby incorporated by reference in their entirety into this application.

[0002] The field of the present disclosure relates to the processing of semiconductor substrates, particularly methods and systems for automated polishing and cleaning of semiconductor wafers.

[0003] Semiconductor wafers are typically used in the manufacture of integrated circuit (IC) chips on which circuits are printed. First, circuits are printed in a miniaturized state on the surface of the wafer. Then, the wafer is diced into circuit chips. For these miniaturized circuits, in order to ensure proper printing of the circuits over the entire surface of the wafer, the front and back surfaces of each wafer are required to be extremely flat and substantially defect - free. To achieve this, after the wafer is cut from an ingot, a polishing process to improve the flatness of the front and back surfaces of the wafer is commonly used. When the wafer is polished as a preparation for printing the miniaturized circuits on the wafer by an electron beam lithography process or a photolithography process (hereinafter, "lithography"), a particularly good and defect - free finish is required.

[0004] After the wafers are polished, they are washed in a wet bath to remove any debris generated during polishing. Typically, wafers are manually transported from the polishing machine to the wet bath using a vacuum pencil that holds the wafer during transport. That is, the operator typically picks up the wafer using the vacuum pencil and places it in the wet bath. Automating the transport process improves the efficiency of the wafer manufacturing process and reduces manufacturing costs. However, the conventional robots that transport wafers in the manufacturing facility and the conventional wet baths that wash the wafers are not designed for the precise handling required to safely place the wafers in the wet bath without scratching or otherwise damaging them during the transport process.

[0005] This section is intended to introduce readers to various aspects of the technology that may be relevant to the various aspects of the disclosure described and / or claimed below. This discussion is intended to be useful in providing readers with background information to better understand the various aspects of the disclosure. Therefore, these statements should be read in this context and should not be understood as an admission of prior art. [Overview of the project]

[0006] One aspect of the present disclosure relates to a semiconductor wafer processing system for processing a set of semiconductor wafers. The system comprises a controller, a transport robot controlled by the controller, a wet bath containing a cleaning solution, and a cassette positioned in the wet bath for holding a set of wafers. The transport robot transports the wafers from a transfer position to the cassette, and the controller controls the transport robot during transport.

[0007] Other aspects of the present disclosure relate to a wafer processing system for processing wafers. The system comprises a transport robot, a wet bath, a cassette, an automated guided vehicle (AGV), and a cassette holder. The wet bath has walls and defines a container for holding a cleaning solution. The cassette is positioned within the wet bath to hold wafers. The transport robot transports wafers from a transfer position to the cassette. The AGV has robotic arms for positioning the cassette in the wet bath and removing the cassette from the wet bath. The cassette holder is mounted on a wall and maintains the position of the cassette within the wet bath. The AGV positions the cassette within the cassette holder and removes the cassette from the cassette holder.

[0008] Further aspects of this disclosure relate to a method for processing wafers. This method includes positioning a cassette in a wet bath using an automated guided vehicle (AGV). This method includes transporting a wafer from a transfer position to the cassette using a transport robot. This method further includes removing the cassette and wafer from the wet bath using an AGV.

[0009] Various improvements exist to the features described in relation to the embodiments of this disclosure described above. Similarly, further features may be incorporated into the embodiments of this disclosure described above. These improvements and additional features may exist individually or in any combination. For example, various features described below in relation to any of the illustrated embodiments of this disclosure may be incorporated into any of the embodiments of this disclosure described above, individually or in any combination. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic block diagram of a semiconductor wafer processing system. [Figure 2] Figure 2 is a perspective view of the polishing machine and unloading robot. [Figure 3] Figure 3 shows another perspective of the polishing machine and unloading robot. [Figure 4] Figure 4 is a perspective view of a 6-axis robot. [Figure 5] Figure 5 is a perspective view of the transport robot and the handover location. [Figure 6] Figure 6 is a perspective view of the transport robot and the handover location. [Figure 7] Figure 7 is a perspective view of the transport robot and wet bath. [Figure 8] Figure 8 is a top view of the wet bath. [Figure 9] Figure 9 is a top view of the wet bath and cassette. [Figure 10] Figure 10 is a perspective view of a wet bath, which includes a cassette, multiple wafers within the cassette, and the wet bath itself. [Figure 11] Figure 11 is a schematic side view of a wet bath containing a cassette positioned on a cassette stage guide. [Figure 12] Figure 12 is another schematic side view of the wet bath, including the cassette positioned on the cassette stage guide. [Figure 13] Figure 13 is a schematic side view of an automated guided vehicle (AGV) positioned next to a wet bath. [Figure 14] Figure 14 is a perspective view of the cassette. [Figure 15] Figure 15 is a perspective view of an automated guided vehicle (AGV) positioned next to a wet bath. [Figure 16] Figure 16 is a flowchart of the wafer processing method.

[0011] Certain features of various examples may be shown in some drawings but not in others, for convenience only. Any feature of any drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0012] Unless otherwise indicated, the drawings are intended to illustrate the features of the examples of this disclosure. These features are considered applicable to various systems having one or more examples of this disclosure. The drawings are not intended to include all prior art features that would be necessary for carrying out the disclosed examples. [Modes for carrying out the invention]

[0013] Suitable substrates (sometimes referred to as semiconductors or silicon "wafers") include single-crystal silicon substrates, which are obtained by cutting wafers from ingots formed by the Czochralski process. Each substrate has a central axis, a front surface, and a rear surface parallel to the front surface.

[0014] Referring to Figure 1, the semiconductor wafer processing system 100 includes a polishing machine 102, an unloading robot 104, a transfer position 106, a transport robot 108, a wet bath 110 having a cassette 112, an automated guided vehicle (AGV) 114, and a controller 116. The polishing machine 102 polishes the wafer 118. The unloading robot 104 unloads (removes) the wafer from the polishing machine to the transfer position 106. The transport robot 108 transports the wafer from the transfer position to the cassette 112 in the wet bath 110. The AGV 114 removes the cassette from the wet bath for further processing of the wafer after it has been cleaned in the wet bath. System 100 automates unloading, loading, and cleaning by using robots 104, 108, and 114 for unloading (removing) and loading (supplying) the wafer 118, and by using a controller 116 to control the robots. Therefore, system 100 improves the overall efficiency of the wafer manufacturing process and reduces the cost of manufacturing wafers.

[0015] Referring to FIG. 2, the polishing machine 102 is a double-sided polishing machine that rough polishes or finishes polishing the wafer 118. The rough polishing and the finish polishing may be performed, for example, by chemical-mechanical planarization (CMP). CMP generally includes immersing the wafer 118 in a polishing slurry and polishing. By the combination of chemical action and mechanical action, the surface of the wafer 118 is smoothed. Generally, the polishing is performed until a chemical and thermal steady state is achieved and until the wafer 118 achieves the target shape and flatness.

[0016] The polishing machine 102 has a first polishing assembly (not shown) and a second polishing assembly (lower polishing assembly) 122. A first shaft (not shown) is attached to the first polishing assembly, and a second shaft (not shown) is attached to the second polishing assembly 122. The wafer 118 is disposed between the first polishing assembly and the second polishing assembly, and the first and second shafts rotate the first and second polishing assemblies simultaneously to polish the wafer.

[0017] Referring to FIG. 4, each of the unloading robot 104, the transfer robot 108, and the AGV 114 includes a six-axis robot. The six-axis robot has a base 126, a first arm 128, a base-first arm hinge 130, a second arm 132, a first arm-second arm hinge 134, a tip 136, and a second arm-tip hinge 138. The first arm-second arm hinge 134 movably attaches the first arm 128 to the second arm 132, and the second arm-tip hinge 138 movably attaches the second arm 132 to the tip 136.

[0018] Specifically, the base 126 rotates the first arm 128, the second arm 132, and the chip 136 about a first axis (generally indicated by arrow 140). The base-first arm hinge 130 rotates the first arm 128 about a first pivot center 142 that defines a second axis (generally indicated by arrow 144). The first arm-second arm hinge 134 rotates the second arm 132 about a second pivot center 146 that defines a third axis (generally indicated by arrow 148), and rotates the second arm about a fourth axis (generally indicated by arrow 150). The second arm-chip hinge 138 rotates the chip 136 about a third pivot center 152 that defines a fifth axis (generally indicated by arrow 154), and rotates the chip about a sixth axis (generally indicated by arrow 156).

[0019] Referring to FIGS. 2 and 3, the unloading robot 104 has a vacuum attachment 158 attached to the chip 136 for holding the wafer 118 during transfer between the polishing machine 102 and the transfer position 106. Referring to FIGS. 5 through 7, the transfer robot 108 has a wafer end effector 160 attached to the chip 136 for holding the wafer 118 during transfer between the transfer position 106 and the wet bath 110. Referring to FIG. 15, the AGV 114 has a cassette transfer attachment 162 attached to the chip 136 for loading the cassette 112 into the wet bath 110 and unloading the cassette 112 from the wet bath 110.

[0020] Referring to FIGS. 5 and 6, the transfer position 106 has a wafer holder 164 for temporarily holding the wafer 118 during transport between the polishing machine 102 and the wet bath 110. The wafer holder 164 has plungers 218 for holding the wafer 118. The wafer holder 164 is preferably made of aluminum, and the plungers 218 are preferably made of a polyether ether ketone (PEEK) material. In the illustrated embodiment, the wafer holder 164 has four plungers 218. However, in alternative embodiments, the wafer holder 164 may include any number of plungers that allow the wafer holder to operate as described.

[0021] The wet bath 110 holds the cassette 112 and wafer 118 and cleans the wafer 118. Referring to Figures 7 to 13, the wet bath 110 has multiple walls 166 defining a container 168 for holding cleaning fluid. The wet bath 110 has at least one cassette holder 170, at least one cassette stage guide 172, a fluid trap 174, and at least one AGV centering guide 176. The cassette stage guide 172 and the AGV centering guide 176 help the AGV 114 position the cassette 112 in the wet bath 110. The cassette holder 170 holds the cassette 112 in the wet bath 110, the fluid trap 174 holds the cleaning fluid in the container 168, and the AGV 114 removes the cassette from the wet bath.

[0022] As shown in Figures 8 to 10, the cassette holder 170 is attached to two of the walls 166 of the wet bath 110 and comprises a first holder 178 rotatably mounted on the first wall 180 and a second holder 182 rotatably mounted on the second wall 184 opposite the first wall. Each of the first and second holders 178 and 182 has a cassette latch 220 for engaging with and holding the cassette 112 and a plurality of extensions 186 for engaging with and holding the wafer 118. The AGV 114 positions the cassette 112 in the wet bath 110, and the first and second holders 178 and 182 rotate to engage the cassette latch 220 with the cassette 112 and the extensions 186 with the wafer 118, thereby holding the cassette and wafer in the wet bath during the cleaning process.

[0023] As shown in Figures 11 and 12, the cassette stage guide 172 is positioned on the bottom wall 188 of the container 168 and guides the cassette 112 into place when the AGV 114 loads the cassette into the wet bath 110. The cassette stage guide 172 comprises a guide base 190 and an inclined guide 192 extending from the guide base. The guide base 190 is attached to the bottom wall 188, and the inclined guide 192 is attached to and extends from the guide base. The inclined guide 192 is oriented at a first angle α1 with respect to the bottom wall 188 and guides the cassette 112 onto the guide base 190 when the AGV 114 positions the cassette into the wet bath 110.

[0024] Referring to Figure 13, the fluid trap 174 has a platform 194 rotatably mounted on at least one of the walls 166 at a trap pivot center 196. Specifically, the platform 194 is mounted on the wall 166 adjacent to the AGV 114 and rotates around the trap pivot center 196 to capture and hold the cleaning fluid dripping from the cassette 112 when the cassette is unloaded from the wet bath 110 by the AGV. More specifically, the platform 194 rotates from a first or storage configuration 198 to a second or deployment configuration 200 when the AGV 114 unloads the cassette 112 from the wet bath 110. The platform 194 is oriented at a second angle α2 with respect to the surface 202 of the cleaning fluid and directs the cleaning fluid back into the container 168.

[0025] As shown in Figure 8, the AGV centering guide 176 extends from the bottom wall 188 of the container 168 and has a tubular guide 204 for guiding the cassette 112 onto the guide base 190 when the AGV 114 positions the cassette in the wet bath 110. The tubular guide 204 has a hollow tube that engages with the cassette 112 and defines a tube opening 206 for guiding the cassette 112 into the wet bath 110. More specifically, as shown in Figure 15, the cassette transport attachment 162 has at least one centering rod 208 for guiding the cassette 112 onto the guide base 190 when the AGV 114 positions the cassette in the wet bath 110. In the illustrated embodiment, the wet bath 110 has two AGV centering guides 176 for each cassette 112, and the cassette transport attachment 162 has two corresponding centering rods 208. The centering rod 208 slides into the tube opening 206 when the AGV 114 lowers the cassette 112 into the wet bath 110, positioning the cassette 112 on the guide base 190.

[0026] In this embodiment, the cleaning solution comprises a non-abrasive fluid, such as deionized water that is substantially free of silicon dioxide. More specifically, the cleaning solution comprises deionized water. In alternative embodiments, the cleaning solution may comprise any fluid that enables the wet bath 110 to operate as described herein.

[0027] Referring to Figure 14, the cassette 112 has a curved base 210 and two circular ends 212. The curved base 210 has a plurality of wafer slots 214 for holding wafers 118 and a plurality of engagement slots 216 for engaging with cassette latches 220 of first and second holders 178,182. The transport robot 108 positions the wafers 118 in the wafer slots 214 so that the wafers are held in the wet bath 110. After the AGV 114 positions the cassette 112 in the wet bath 110, the first and second holders 178,182 are rotated so that the cassette latches 220 engage with the engagement slots 216 and the extensions 186 mesh between the wafers 118 so that the cassette and wafers are held in the wet bath.

[0028] The controller 116 automatically controls the polishing machine 102, the unloading robot 104, the transport robot 108, the wet bath 110 having first and second holders 178, 182 and a fluid trap 174, and the AGV 114. This allows the controller 116 to automate the processes of polishing the wafer 118, transporting the wafer to the wet bath 110, cleaning the wafer, and removing the cassette 112 containing the wafer from the wet bath.

[0029] During operation, the wafer 118 is positioned between the first polishing assembly and the second polishing assembly 122, which rotate to polish the wafer. The unloading robot 104 removes the wafer 118 from the polishing machine 102 and places the wafer on the wafer holder 164 at the transfer position 106. Specifically, the unloading robot 104 positions its first arm 128 and second arm 132 so that the vacuum attachment 158 ​​contacts the wafer 118. While the unloading robot 104 is transporting the wafer to the transfer position 106, the vacuum attachment 158 ​​generates a suction force to keep the wafer 118 on the vacuum attachment 158. The controller 116 controls the unloading robot 104 during the transport process so that the unloading robot automatically transports the wafer 118 without operator intervention.

[0030] The AGV 114 picks up the cassette 112 and positions the cassette in the wet bath 110. Specifically, the AGV 114 attaches the cassette transport attachment 162 to the cassette 112, and the first arm 128 and second arm 132 of the AGV 114 position the cassette above the wet bath 110. The AGV 114 lowers the cassette 112 into the wet bath 110 so that the centering rod 208 slides into the pipe opening 206 of the tubular guide 204 of the AGV centering guide 176. The AGV centering guide 176 positions the cassette 112 in the wet bath 110 while the AGV 114 is lowering the cassette into the wet bath. In addition, the tilt guide 192 of the cassette stage guide 172 positions the cassette 112 in the wet bath 110 while the AGV 114 is lowering the cassette into the wet bath. More specifically, the tilting guide 192 engages with the circular end 212 of the cassette 112 to guide the cassette to the guide base 190 of the wet bath 110. Together, the AGV centering guide 176 and the cassette stage guide 172 ensure that the AGV 114 positions the cassette 112, including the wafer 118, in the wet bath 110 with sufficient precision to prevent scratching or damage to the wafer or cassette. After the AGV 117 positions the cassette 112 in the wet bath 110, the cassette holder 170 is rotated so that the extension 186 engages between the wafers 118 and the cassette latch 220 engages with the engagement slot 216. The cassette holder 170 maintains the position of the cassette 112 and wafer 118 in the wet bath 110. The controller 116 controls the AGV 114 during the transport process so that the AGV automatically transports the cassette 112 without operator intervention.

[0031] The transport robot 108 retrieves the wafer 118 from the transfer position 106 and positions the wafer in the wafer slot 214 of the cassette 112. Specifically, the transport robot 108 positions its first arm 128 and second arm 132 so that the wafer end effector 160 holds the wafer 118 while the transport robot 108 is transporting the wafer to the cassette 112. The controller 116 controls the transport robot 108 during the transport process so that the transport robot automatically transports the wafer 118 without operator intervention.

[0032] The wet bath 110 cleans the wafer 118 in the cassette 112. After the wafer 118 is cleaned, the platform 194 of the fluid trap 174 rotates around the trap pivot center 196 from the first configuration 198 to the second configuration 200. Furthermore, the cassette holder 170 is rotated so that the extension 186 is disengaged from the wafer 118 and the cassette latch 220 is disengaged from the engagement slot 216, and the cassette holder 170 no longer maintains the position of the cassette 112 in the wet bath 110.

[0033] The AGV 114 picks up the cassette 112 containing the wafer 118 and transports the cassette and wafer downstream for further processing. Specifically, the AGV 114 attaches the cassette transport attachment 162 to the cassette 112, and the first arm 128 and second arm 132 of the AGV 114 operate to remove the cassette from the wet bath 110. The AGV 114 pulls the cassette 112 out of the wet bath 110 so that the centering rod 208 slides out of the tube opening 206 of the tubular guide 204 of the AGV centering guide 176. Furthermore, the tilting guide 192 of the cassette stage guide 172 guides the cassette 112 out of the wet bath 110 as the AGV 114 pulls the cassette 112 out. More specifically, the tilting guide 192 engages with the circular end 212 of the cassette 112 to guide the cassette away from the guide base 190. The AGV centering guide 176 and the cassette stage guide 172 together ensure that the AGV 114 removes the cassette 112 containing the wafer 118 from the wet bath 110 with sufficient precision to prevent scratching or damage to the wafer or cassette. The controller 116 controls the AGV 114 during the transport process so that the AGV automatically transports the cassette 112 without operator intervention. The processing system 100 described herein automates the processes of polishing, loading, unloading, and cleaning without damaging the wafer. As a result, the processing system 100 described herein improves the efficiency of the wafer manufacturing process and reduces the overall wafer manufacturing cost without damaging the wafer.

[0034] Figure 16 shows a wafer processing method 300. Method 300 includes polishing the wafer with a polishing machine 302. Method 300 includes transporting the wafer from the polishing machine to a transfer position with an unloading robot 304. Method 300 further includes positioning the cassette in a wet bath with an AGV 306. Positioning the cassette in a wet bath with an AGV 306 may include centering the cassette in the wet bath with an AGV centering guide and a centering rod 308. After the AGV has positioned the cassette in the wet bath, Method 300 includes rotating the cassette holder 310 so that the extensions interlock between the wafers. Method 300 includes maintaining the position of the cassette in the wet bath with the cassette holder 312. Method 300 includes transporting the wafer from the transfer position to the cassette with a transport robot 314. Method 300 further includes removing the cassette and wafer from the wet bath using an AGV 316.

[0035] Generally, as disclosed herein, a semiconductor wafer processing system for processing a set of semiconductor wafers automatically loads each wafer into a wet bath for cleaning the wafers after polishing. In one example, the system comprises a polishing machine for polishing the wafers, an unloading robot for unloading the wafers from the polishing machine, a transport robot for transporting the wafers to the wet bath, a cassette positioned in the wet bath for holding and transporting the wafers, and an automated guided vehicle (AGV) for positioning the cassette in the wet bath and removing the cassette from the wet bath. The system automatically polishes the wafers, automatically loads the wafers into the cassette and the wet bath for cleaning, and automatically unloads the cassette containing the wafers for post-processing. The unloading robot, transport robot, and AGV automatically transport the wafers during the polishing and cleaning processes, thereby automating the polishing and cleaning processes. The wet bath has AGV centering guides and cassette stage guides for guiding the cassette in and out of the wet bath with sufficient precision to prevent scratches or other damage to the wafers during the transport process. Automating the loading, unloading, and cleaning processes improves the efficiency of the wafer manufacturing process without damaging the wafers, thereby reducing the overall wafer manufacturing cost.

[0036] As used herein, the terms “about,” “substantially,” “essentially,” and “approximately,” when used in relation to a range of dimensions, density, temperature, or other physical or chemical properties or characteristics, mean to include any variations that may exist in the upper and / or lower limits of the property or characteristic. Such variations include, for example, variations resulting from rounding, measurement methods, or other statistical variations.

[0037] When describing elements of this disclosure or embodiments thereof, the articles “a,” “an,” “the,” and “said” are intended to indicate that there is one or more elements. The terms “comprising,” “including,” “containing,” and “having” are intended to indicate comprehensiveness and mean that additional elements other than those listed may exist. The use of terms indicating specific orientations (e.g., “top,” “bottom,” “side”) is for explanatory convenience and does not require a specific orientation of the described article. Because various modifications are possible in the above-described structure and method without departing from the scope of this disclosure, all matters included in the above description and shown in the accompanying drawings are intended to be interpreted as illustrative rather than restrictive.

Claims

1. A semiconductor wafer processing system for processing a set of semiconductor wafers, Controller and A transport robot controlled by the aforementioned controller, A wet bath for containing the cleaning solution, A cassette positioned in the wet bath and for holding the set of wafers Equipped with, A wafer control system comprising a transport robot that transports the wafer from the transfer position to a cassette, and a controller that controls the transport robot during transport.

2. The wafer processing system according to claim 1, wherein the transport robot includes a six-axis robot, and the six-axis robot is fitted with a wafer end effector for holding the wafer during transport between the transfer position and the wet bath.

3. The wafer processing system according to claim 1, further comprising an unloading robot for transporting the wafer from the polishing machine to the transfer position.

4. The wafer processing system according to claim 3, wherein the unloading robot includes a 6-axis robot.

5. The wafer processing system according to claim 3, wherein the unloading robot has a vacuum attachment for holding the wafer during transport between the polishing machine and the transfer position.

6. The wafer processing system according to claim 3, wherein the polishing machine includes a double-sided polishing machine, and the set of semiconductor wafers includes at least five semiconductor wafers.

7. The wafer processing system according to claim 1, further comprising an automated guided vehicle (AGV) having a robotic arm for positioning the cassette in the wet bath and removing the cassette from the wet bath.

8. The wafer processing system according to claim 7, wherein the AGV is attached to the robot arm and has a cassette transport attachment for attaching the AGV to the cassette.

9. The aforementioned cassette transport attachment is, A cassette clip for attaching the cassette transport attachment to the cassette, When the AGV positions the cassette in the wet bath, a centering rod that positions the cassette in the wet bath and A wafer processing system according to claim 8, having the following features.

10. A wafer processing system for processing wafers, Transport robots and A wet bath having walls and defining a container for holding cleaning solution, A cassette positioned within the wet bath for holding the wafer, and the transport robot transports the wafer from the transfer position to the cassette. An automated guided vehicle (AGV) including a robotic arm for positioning the cassette in the wet bath and for removing the cassette from the wet bath, A cassette holder mounted on the wall for maintaining the position of the cassette within the wet bath and Equipped with, The AGV is a wafer processing system that positions the cassette within the cassette holder and removes the cassette from the cassette holder.

11. The cassette holder includes an extension that engages with the wafer, The wafer processing system according to claim 10, wherein the cassette holder is rotated so that the extension engages with the wafers after the AGV positions the cassette in the wet bath.

12. The wafer processing system according to claim 10, further comprising a cassette stage guide for guiding the cassette to a predetermined position when the AGV positions the cassette in the wet bath.

13. The wafer processing system according to claim 10, further comprising a fluid trap for holding the cleaning fluid in the wet bath when the AGV removes the cassette from the wet bath, wherein the fluid trap is movable between a storage configuration and an expansion configuration.

14. The wet bath is further equipped with an AGV centering guide extending from the bottom, The wafer processing system according to claim 10, wherein the AGV centering guide includes a tube that defines an opening.

15. The AGV includes a cassette transport attachment including a centering rod, The wafer processing system according to claim 14, wherein the centering rod slides into the opening of the AGV centering guide when the AGV positions the cassette in the wet bath, thereby positioning the cassette in the wet bath.

16. A wafer processing method, An automated guided vehicle (AGV) is used to position the cassette inside the wet bath. The transport robot transports the wafer from the transfer position to the cassette. The AGV removes the cassette and the wafer from the wet bath. A method that includes doing so.

17. The wafer is polished using a polishing machine. The unloading robot transports the wafer from the polishing machine to the transfer position. The method according to claim 16, further comprising the following:

18. The method according to claim 17, wherein positioning the cassette in the wet bath by the AGV includes centering the cassette in the wet bath using an AGV centering guide and a centering rod.

19. The method according to claim 16, further comprising maintaining the position of the cassette in the wet bath with a cassette holder.

20. The cassette holder includes an extension for engaging with the wafer, The method according to claim 19, further comprising the AGV positioning the cassette in the wet bath, and then rotating the cassette holder so that the extensions interlock between the wafers.

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