End effector for carrying wafer or wafer assembly

Abstract

To provide an end effector for carrying a wafer or a wafer assembly placed thereon.SOLUTION: The end effector is integrated with or may attach to a robotic arm. The end effector includes a peripheral mount radially outside of a base portion, the peripheral mount including at least a first mount section and a second mount section. The base portion has a substantially flat horizontal upper surface. Each mount section of the peripheral mount has a substantially flat horizontal upper surface being elevated with respect to the upper surface of the base portion. The end effector is configured to hold a wafer assembly bridging the upper surfaces of the mount sections at a first height above the base portion.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention generally relates to an end effector for transferring individual wafers and wafer assemblies before, after, or during processing. The present invention also relates to a semiconductor processing apparatus incorporating such an end effector, and a method for transferring wafers and wafer assemblies.

Background Art

[0002] Wafers to be processed are typically transferred by a robotic arm with an end effector that supports and transports those wafers. When applied to plasma dicing, the wafers to be diced tend to be attached to a carrier suitable for holding the individual semiconductor dice after separation. Such wafer assemblies include those that support the wafer on a film / tape within a frame, and those that place the wafer on a silicon or glass substrate.

[0003] In the handling and transfer of wafer assemblies, a dedicated robotic arm with an end effector appropriately configured to operate with a specific type, size, and shape of wafer carrier tends to intervene. In the case where the wafer is supported on a film / tape and a frame, the end effector tends to contact the frame or the tape and the frame while avoiding contact with the tape under the wafer, thereby preventing the dice from being inadvertently displaced after dicing. One advantage of using a dedicated robotic arm is the avoidance of cross-contamination between separate wafer assemblies.

[0004] Patent Document 1 describes a method and apparatus for plasma dicing a semiconductor wafer, in which a wafer supported on a tape and a frame is transferred into and out of a process chamber by a transfer arm. Since the transfer arm has a central depression, the transfer arm can touch the frame while avoiding contact with the tape directly under the substrate wafer.

[0005] Patent Document 2 describes an arrangement in which a wafer carrier ring is supported by prongs on an end effector, with the prongs in contact with the ring but avoiding contact with the wafer substrate on the carrier. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 9,343,365 [Patent Document 2] U.S. Patent No. 9,446,522 [Patent Document 3] Japanese Patent Application Publication No. 08-55814 [Patent Document 4] U.S. Patent Application Publication No. 2016 / 343603 [Patent Document 5] Chinese Patent Application Publication No. 113113340 [Patent Document 6] U.S. Patent No. 6,077,026 Summary of the Invention [Problem to be solved by the invention]

[0007] There is a need in the art for a multi-purpose end effector that can operate with a variety of wafer and wafer assemblies without the need for reconfiguration or retrofitting, while still protecting the wafers from contamination. Such a multi-function end effector would be particularly useful in in-vacuum transfer applications where reconfiguring tooling can be more difficult and / or expensive. [Means for solving the problem]

[0008] In a first aspect of the present invention, there is provided an end effector for transporting a wafer or a wafer assembly placed thereon, which is integrated with a robot arm or configured to be attachable to the robot arm. The end effector includes peripheral mounts circumferentially arranged around a base portion, and the peripheral mounts include at least a first loading portion and a second loading portion. The base portion has a substantially flat and horizontal upper surface, and each loading portion of the peripheral mounts is located at a position higher than the upper surface of the base portion and has a substantially flat and horizontal upper surface. By doing so, the end effector is configured to hold a wafer assembly bridging the upper surfaces of these loading portions at a first height above the base portion. There is a step region between each loading portion and the base portion - peripheral mount. By making each step region have a support surface located at a position higher than the upper surface of the base portion, the end effector is configured to hold a wafer bridging the support surfaces at a second height above the base portion.

[0009] According to the present invention, thereby, an end effector capable of transporting both a wafer and a wafer assembly (although not necessarily simultaneously) is provided. That is, the present invention provides a dual - function end effector that does not require tooling changeover during wafer bonding, etching, and other processes. According to the end effector of the present invention, since a quick switch can be made between the wafer - transport application and the wafer - assembly - transport application, versatility superior to that of the prior - art end effectors is provided, and time and costs in semiconductor production are saved.

[0010] Furthermore, in the end effector according to the present invention, since the wafer and the wafer assembly are supported on separate horizontal planes, metal cross - contamination between the wafer and the wafer assembly being transported on the apparatus is prevented. Moreover, in the end effector of the present invention, by providing a vertical separation between the wafer or wafer assembly placed on the apparatus and the base portion, disturbance to the wafer substrate is minimized.

[0011] In the context of the present invention, a "wafer" is to be understood as including a wafer placed on a support wafer, for example a silicon wafer placed on a glass wafer, and it can also be removed. The support wafer can typically be of the same or a similar size as the wafer, for example having a diameter of 200 mm or 300 mm. The wafer can preferably be a circular wafer.

[0012] In the context of the present invention, a "wafer assembly" is to be understood as including that in which a wafer is placed on a film / tape supported within a frame, and it can preferably be a substantially circular wafer assembly, for example that in which a circular wafer is supported on a substantially circular frame.

[0013] The base portion may be substantially circular in shape or may include a circular portion, for example with the sides cut off. The upper surface of the base portion may include a continuous flat surface or may have one or more notch regions. The loading portions may be arranged on the opposite side of the base portion, for example they may be diagonally opposed on the upper surface of the base portion. Alternatively, they may be non-diagonally opposed, for example arranged at 90° to each other around the virtual center point of the base portion. In the context of the present invention, "opposite side" is to be understood as meaning at separate circumferential locations around the periphery of the base portion.

[0014] There may be more than two, for example more than three, loading portions. They may be provided in a single continuum or may be individual loading portions.

[0015] The loading portions and the corresponding stepped regions may be symmetric around the base portion.

[0016] This end effector may be provided with two prongs extending from a connector body and spaced apart spatially, and the connector body may be configured to be attachable to a robot arm.

[0017] The connector body may include teeth (i.e., notches in the end face) for connection to a robotic arm having a complementary connection surface. Alternatively, the connector body may include a different type of connector for attachment to the robotic arm.

[0018] The connector body may include a mounting portion, and each prong may include an additional mounting portion (as well as a separate portion of the base portion). Each additional mounting portion may be at a distal end from the connector body.

[0019] The prongs may narrow from the connector body toward the distal end.

[0020] The boundary between the step region and the base portion may be defined by a circumferential arc. In arrangements where the end effector is configured (i.e., appropriately sized and shaped) to carry a 300 mm wafer or 300 mm wafer assembly, the radius of the circumferential arc may be 146-150 mm from an imaginary center point of the base portion.

[0021] The boundary between the step region and the peripheral mount may be defined by a circumferential arc. In arrangements where the end effector is configured (i.e., appropriately sized and shaped) to carry a 300 mm wafer or 300 mm wafer assembly, the radius of the circumferential arc may be 150-154 mm from an imaginary center point of the base portion.

[0022] The upper surface of the peripheral mount may extend at least 15 mm, e.g., 20 mm, along a direction parallel to the central longitudinal axis of the end effector beyond the step region-to-peripheral mount boundary line. The at least 15 mm length allows for support and transfer of various types and sizes of wafer assemblies (e.g., non-standard size frames).

[0023] The first height may be 1 to 5 mm. The second height may be 0.1 to 3 mm. The first height is preferably greater than the second height.

[0024] The support surface may be provided with a shelf. The length of the shelf along a direction parallel to the central long axis of the present end effector may be 0.2 to 0.6 mm, for example, 0.4 mm.

[0025] With a length of at least 0.2 mm, it is sufficient to support the edge of the wafer while minimizing the overall dimensions of the present end effector.

[0026] The support surface may include a convex surface. The convex surface may allow the tape of the wafer assembly supported on the present end effector to rest on a smooth surface and may prevent the presence of sharp edges or corners below the tape.

[0027] The shelf may be near the base portion, and the convex surface may be adjacent to the shelf and the peripheral mount.

[0028] The convex surface may be defined by an arc with a radius of 2.5 to 3.5 mm.

[0029] The base portion may have a depth (thickness) of 3 mm along a direction perpendicular to its upper surface.

[0030] The present end effector may be formed of a ceramic material. The present end effector may be formed of a metal.

[0031] The present end effector may be formed of a metal coated with an electrostatic discharge material.

[0032] In a second aspect of the present invention, a semiconductor processing apparatus including a robot arm and an end effector is provided. The end effector is integrated with or attached to the robot arm. The end effector is provided with a peripheral mount located radially outward of the base portion, and the peripheral mount includes at least a first loading portion and a second loading portion. The base portion has a substantially flat and horizontal upper surface, and each loading portion of the peripheral mount is located at a position higher than the upper surface of the base portion and has a substantially flat and horizontal upper surface. The end effector is configured to hold a wafer assembly bridging the upper surfaces of those loading portions at a first height above the base portion. Each loading portion has a step region between the base portion and the peripheral mount. Each step region has a support surface located at a position higher than the upper surface of the base portion. The end effector is configured to hold a wafer bridging those support surfaces at a second height above the base portion.

[0033] In a third aspect of the present invention, a method for transferring a wafer using a semiconductor processing apparatus including a robot arm and an end effector according to the first aspect of the present invention is provided. The end effector is integrated with or attached to the robot arm. The method includes a step of placing the wafer on the end effector such that the wafer bridges the support surface of each step region, and a step of transferring the wafer by moving the robot arm.

[0034] In a fourth aspect of the present invention, a method for transferring a wafer assembly using a semiconductor processing apparatus including a robot arm and an end effector according to the first aspect of the present invention is provided. The end effector is integrated with or attached to the robot arm. The method includes a step of placing the wafer assembly on the end effector such that the wafer assembly bridges the upper surface of each loading portion, and a step of transferring the wafer assembly by moving the robot arm.

[0035] Hereinafter, embodiments of the present invention will be described solely by way of example with reference to the accompanying schematic drawings.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0037] The wafer 1a to be transferred (FIG. 1) includes a circular silicon wafer 3a and a circular glass substrate 4 thereunder. The diameter d1 of the silicon wafer is 300 mm. The glass substrate 4 has a corresponding diameter d2 of 300 mm (although in alternative embodiments it may have a diameter larger than that of the wafer 3a). Alternative embodiments may include those in which the wafer 3a is not supported, or those supported on another carrier, such as on a silicon substrate. Also, in another embodiment, the wafer may have a different size, for example, the wafer may include a circular wafer with a diameter of 200 mm.

[0038] The wafer assembly 1b to be transferred (Fig. 2) includes a 300 mm circular silicon wafer 3b, which is stationary on a tape 5 (i.e., tape and frame assembly 4) supported within a frame 7. The wafers 3b, tape 5, and frame 7 are concentrically arranged, with the frame 7 placed on the tape 5, and the diameter d3 of the circular inner peripheral edge of the frame 7 being 350 mm. In this exemplary embodiment, the outer peripheral edge of the frame 7 is circular with a chamfered edge and has a thick edge along opposite transverse directions (x, y) across the assembly (i.e., the outer peripheral edge of the frame 7 is not strictly circular). The maximum diameter d4 of the non-circular outer peripheral edge of the frame 7 is 400 mm. The wafer frame can, for example, conform to the SEMI G87 or G74 300 mm wafer frame specifications. Also, in another embodiment, the wafer assembly can be sized and shaped to hold wafers of another size. For example, in an embodiment where the wafer is a 200 mm circular silicon wafer, the wafer frame can have a circular inner peripheral edge with a diameter of 250 mm and an outer peripheral edge with a maximum diameter of 300 mm.

[0039] An end effector 11 (Fig. 3) according to an exemplary embodiment of the present invention is configured to alternately transport the above-described wafer 1a and wafer assembly 1b. The end effector 11 of this exemplary embodiment is formed of titanium coated with an anti-electrostatic discharge coating, and the wafer 1a and wafer assembly 1b are shaped to be supported on separate horizontal planes and contact separate portions of the end effector 11. In this exemplary embodiment, the anti-electrostatic discharge coating contains diamond-like carbon, although in alternative embodiments, it may contain another anti-electrostatic discharge material. In another embodiment, the end effector may be formed of aluminum or other materials.

[0040] The end effector 11 includes a peripheral mount 13 provided as three separate loading portions 13a, 13b, 13c around a recessed base portion 15. The base portion 15 is generally flat and has a flat upper surface 17 along a first horizontal plane. Each loading portion 13a, 13b, 13c of the peripheral mount has flat upper surfaces 19a, 19b, 19c along a second horizontal plane at a higher position.

[0041] The end effector 11 has a fork shape. The end effector 11 includes a connector body 21 that is integral with and extends outward from the first loading portion 13a of the peripheral mount along a central long axis L. The connector body 21 includes a toothed end section 23 that is shaped to be interconnected with a complementary shape connector (not shown) of a robotic arm.

[0042] The end effector 11 includes two prongs 25a, 25b extending from the first loading portion 13a along a direction parallel to the central long axis L. The end effector 11 is symmetric about the central long axis L. Each prong 25a, 25b includes individual portions 15a, 15b of the base portion 15. Each prong 25a, 25b includes loading portions 13b, 13c at an end 26 distal from the connector body 21. The second and third loading portions 13b, 13c have rounded end faces 27.

[0043] Overall, in this exemplary embodiment for transferring a 300 mm wafer and a 300 mm wafer assembly, the length L1 of the end effector 11 is 410 - 450 mm, the width W1 is 100 - 175 mm, and the depth (thickness) D1 is 6 mm. The width W1 of the end effector is constant along its length. The width W2 of each prong 25a, 25b decreases with the distance from the connector body 21 towards the distal end 26. In other words, the lateral separation between the prongs increases towards the distal end. According to other embodiments of the present invention, the dimensions of the end effector can be adjusted appropriately for transferring wafers / wafer assemblies of different sizes, such as 200 mm wafers / wafer assemblies.

[0044] The depth of the end effector 11 varies along its length. The horizontal plane constituting the upper surface 17 of the base portion 15 is recessed compared to the horizontal plane constituting the upper surface of the peripheral mount 13. More specifically, the horizontal plane constituting the upper surface 17 of the base portion 15 is recessed compared to the horizontal planes constituting the upper surfaces 19a, 19b, 19c of the loading portions 13a, 13b, 13c of the peripheral mount 13.

[0045] The end effector 11 includes a stepped region 29 between the base portion 15 and the peripheral mount 13 (FIG. 4). Among the peripheral portions of the base portion 15, the places where each of the two prongs 25a, 25b is provided in the top view are defined by a circle having a radius of 152 mm (from the virtual center point of the base portion 15). The circle is cut off at each of the upper side 31 and the lower side 33 of the present end effector, and thus the base portion 15 is defined by the middle lobe portion of the circle. In other words, the impression of the base portion 15 is within a virtual circle having a radius of 152 mm. The stepped region 29 has a ring with a width of 4 mm, and the ring is bounded on the inner peripheral edge 35 side by the base portion 15 and on the outer peripheral edge 37 side by the peripheral mount 13.

[0046] In the cross-sectional side view (Figure 5), the step region 29 includes an inner square step 39 having a flat upper surface 41 (i.e., a horizontal shelf) and an outer rounded step 43 having a top surface 45 defined by an arc with a radius of 3 mm. The base portion 15 has a constant depth D2 of 3 mm. Each of the loading portions 13a, 13b, 13c has a constant depth D1 of 6 mm. The connector body 21 (best shown in Figure 3) has a constant depth of 3 mm that extends below the horizontal plane constituting the upper surface 13a. The square step 39 (referring again to Figure 5) has a depth D3 of 3.4 mm (i.e., the upper surface 41 of the square step 39 is at a height 0.4 mm above the upper surface 17 of the base portion 15). The top surface 45 of the rounded step 43 forms a convex surface that projects outward from the peripheral mount 13, and it meets the square step 39 at the inner edge 47 and forms a trapezoidal portion together with the upper surface 19a of the first loading portion 13a. The length L2 between the inner edge 47 and the step edge 49 in the square step 39 is 0.4 mm. The step region 29 has the same profile at each of the loading portions 13a, 13b, 13c and faces inward toward the base portion 15. Since the step regions related to the second and third loading portions 13b, 13c are arranged symmetrically and face the step region related to the first loading portion 13a, the upper surfaces of the square steps are on the same horizontal plane at the same height. The upper surfaces 19a, 19b, 19c of each of the loading portions 13a, 13b, 13c are on the same horizontal plane, and that horizontal plane is at a higher position compared to the upper surface 41 of each square step 39.

[0047] In use, the wafer 1a will be supported and transferred on the end effector 11 (FIG. 6). The first edge region 51 of the wafer 1a stays on the upper surface 41 of the square step 39 related to the first loading portion 13a. The second and third edge regions of the wafer 1a stay on the upper surfaces of the square steps related to the second and third loading portions (not shown in FIG. 6). In this way, the wafer 1a is supported on the end effector 11 in a horizontal plane at a height of 0.4 mm above the upper surface 17 of the base portion 15. In other words, there is a gap 53 above the base portion 15, and the wafer 1a is suspended above it. In the present exemplary embodiment of the invention, the length L2 of the square step 39 is 0.4 mm, and according to the findings, this provides an optimal contact area, and thus the wafer can be supported while being held at a certain distance above the upper surface 17 of the base portion 15.

[0048] Alternatively, in use, the wafer assembly 1b will be supported and transferred on the end effector 11 instead (FIG. 7). The first edge region 55 of the wafer assembly 1b stays on the first loading portion 13a. The second edge region of the wafer assembly 1b stays on the second loading portion 13b (not shown in FIG. 7). The third edge region of the wafer assembly 1b stays on the third loading portion 13c (not shown in FIG. 7). The frame 7 is thus supported on the end effector 11. The first edge region 55 of the wafer assembly 1b is provided with the first section 7a of the frame 7 and the first boundary portion 5a of the tape 5. The first section 7a of the frame 7 stays on the upper surface 19a of the first loading portion 13a. The first boundary portion 5a of the tape 5 stays partially on the upper surface 19a of the first loading portion 13a and partially on the top surface 45 of the rounded step 43 of the step region 29. Similar arrangements are provided for the second and third loading portions 13b, 13c. The wafer assembly 1b is firmly held in place on the end effector 11 by the friction between the lower side of the tape 5, the top surfaces 45 of the rounded steps 43 (in each loading portion), and the upper surfaces 19a, 19b, 19c of the loading portions 13a, 13b, 13c.

[0049] Of the frame 7, the inner edge 58 of the first section 7a that stays on the upper surface 19a of the first loading portion 13a recedes by a length L3 of about 20 mm from the outer edge 56 of the rounding step 43. The outer edge 59 of the first section 7a of the frame 7 recedes by a length L4 of about 40 mm from the outer edge 56 of the rounding step 43. Corresponding arrays (i.e., mirror images) are provided in the second and third loading portions 13b and 13c. Advantageously, with the sizes and shapes of the loading portions 13a, 13b, and 13c according to this design, not only standard 300 mm wafer frames but also non-standard 300 mm wafer frames can be received. The frames of non-standard 300 mm wafer assemblies can also be made to stay on the upper surfaces of the loading portions 13a, 13b, and 13c, but the amount by which the frame recedes from the outer edge 56 of the rounding step 43 can be a different amount; that is, the length L3 can vary, but still the tape and the frame will be properly supported.

[0050] In an embodiment where the wafer is a 200 mm wafer and the wafer assembly is a 200 mm wafer assembly, the dimensions of the step region and the loading portion can be comparable to an example embodiment for a 300 mm wafer, but the radius of the peripheral line defining the inner boundary of the step region (that measured from the virtual center point of the base portion) will correspondingly decrease. The overall length and width L1, W1 of the end effector will also decrease. However, the length L2 of the square step will remain the same, as will the size of the rounding step 43 and the lengths of the upper surfaces 19a, 19b, 19c of the loading portions. The length of each loading portion 13a, 13b, 13c is made long enough to receive non-standard wafer assemblies (regardless of whether it is for a 300 mm wafer assembly or a 200 mm wafer assembly).

[0051] In this example embodiment, the tape 5 within each edge region 55 of the wafer assembly 1b is leveled in the horizontal plane after being placed along the contours of the top 60 of the upper surface 19a of the first loading portion 13a and the top surface 45 of the rounding step 43. Accordingly, the tape 5 follows a smooth profile across each loading portion 13a, 13b, 13c and the corresponding rounding step 43 of the step region, and there are no sharp edges or corners under the tape 5.

[0052] Each edge region of the wafer assembly 1b stays on the upper surfaces of the mounting portions 13a, 13b, 13c and on the corresponding stepped regions (not shown). Accordingly, the wafer assembly 1b is supported on the end effector 11 in a horizontal plane at a height of 3 mm above the upper surface 17 of the base portion 15. In other words, there is a gap 57 above the base portion 15, and the wafer assembly 1b is suspended above it.

Claims

1. An end effector for transporting a wafer or a wafer assembly placed thereon, integrated with a robotic arm or configured to be attachable to a robotic arm, the end effector comprising: a peripheral mount circumferentially arranged around a base portion, the peripheral mount comprising at least a first loading portion and a second loading portion; the base portion having a substantially flat and horizontal upper surface, and each loading portion of the peripheral mount being at a higher position than the upper surface of the base portion and having a substantially flat and horizontal upper surface, whereby the wafer assembly bridging on the upper surface of the loading portion is configured to be held at a first height above the base portion; each loading portion has a step region between the base portion and the peripheral mount; each step region comprises a support surface at a higher position than the upper surface of the base portion, whereby the wafer bridging on the support surface is configured to be held at a second height above the base portion.

2. The end effector according to claim 1, comprising two prongs extending from a connector body and spaced apart spatially, the connector body being configured to be attachable to the robotic arm.

3. The end effector according to claim 2, wherein the connector body comprises a loading portion, and each prong comprises a part of the base portion and a further loading portion, the further loading portion being at the distal end as seen from the connector body.

4. The end effector according to claim 2 or 3, wherein the prong narrows towards the distal end from the connector body.

5. The end effector according to any one of claims 1 to 4, configured to transport a 300 mm wafer or a 300 mm wafer assembly, and a boundary line between the step region and the base portion being defined by a circumferential arc at a position with a radius of 146 to 150 mm from a virtual center point of the base portion.

6. An end effector according to any one of claims 1 to 5, configured to be able to carry a 300 mm wafer or a 300 mm wafer assembly, wherein a boundary line between the step region and the peripheral mount is defined by a circumferential arc at a position 150 to 154 mm in radius from a virtual center point of the base portion.

7. An end effector according to any one of claims 1 to 6, wherein an upper surface of the peripheral mount extends along a direction parallel to a central major axis of the present end effector, beyond a boundary line between the step region and the peripheral mount, over a length of at least 20 mm.

8. An end effector according to any one of claims 1 to 7, wherein the first height is 1 to 5 mm.

9. An end effector according to any one of claims 1 to 8, wherein the second height is 0.1 to 3 mm.

10. An end effector according to any one of claims 1 to 9, wherein the first height is greater than the second height.

11. An end effector according to any one of claims 1 to 10, wherein the support surface includes a shelf.

12. An end effector according to claim 11, wherein a length of the shelf along a direction parallel to a central major axis of the present end effector is 0.2 to 0.6 mm.

13. An end effector according to any one of claims 1 to 12, wherein the support surface includes a convex surface.

14. An end effector according to claim 11 or 12, wherein the support surface includes a convex surface, the shelf is in the vicinity of the base portion, and the convex surface is adjacent to the shelf and the peripheral mount.

15. An end effector according to claim 13 or 14, wherein the convex surface is defined by an arc having a radius of 2.5 to 3.5 mm.

16. An end effector according to any one of claims 1 to 15, wherein the base portion has a depth of 3 mm along a direction orthogonal to its upper surface.

17. An end effector according to any one of claims 1 to 16, formed of a ceramic material or metal.

18. An end effector according to any one of claims 1 to 17, the end effector being formed of a metal coated with an electrostatic discharge material.

19. A semiconductor processing apparatus comprising a robot arm and an end effector, wherein the end effector is integrated with or attached to the robot arm, the end effector includes a peripheral mount disposed radially outward of a base portion, the peripheral mount including at least a first loading portion and a second loading portion, the base portion has a substantially flat and horizontal upper surface, and each loading portion of the peripheral mount is at a higher position than the upper surface of the base portion and has a substantially flat and horizontal upper surface, and the end effector is configured to hold a wafer assembly bridging on the upper surface of the loading portion at a first height above the base portion, each loading portion has a stepped region between the base portion and the peripheral mount, each stepped region includes a support surface at a higher position than the upper surface of the base portion, and the end effector is configured to hold a wafer bridging on the support surface at a second height above the base portion. A semiconductor processing apparatus.

20. A method of transferring a wafer using a semiconductor processing apparatus including a robot arm and an end effector according to any one of claims 1 to 18, the end effector being integrated with or attached to the robot arm, placing the wafer on the end effector such that the wafer bridges on the support surface of each stepped region; transferring the wafer by moving the robot arm; A method having.

21. A method of transferring a wafer assembly using a semiconductor processing apparatus including a robot arm and an end effector according to any one of claims 1 to 18, the end effector being integrated with or attached to the robot arm, placing the wafer assembly on the end effector such that the wafer assembly bridges on the upper surface of each loading portion; transferring the wafer assembly by moving the robot arm; A method having.

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