Ceramic end effector for micro circuit manufacturing

Abstract

An end effector for installation on a robotic arm for transporting a plurality of semiconductor wafers from one location to another features a ceramic end effector body portion that includes a plurality of wafer engaging fingers that each feature wafer support pads. The wafer support pads are adapted to support a semiconductor wafer surface, and at least one of the support pads has a vacuum orifice. The pads are replaceable and/or removable in case of damage or contamination. The support pads are attached to the body in such a way as to allow differential thermal expansion so as to prevent introduction of stress into the components. Typically, a wire spring is employed to secure the pad to the end effector. The body portion features an interior vacuum passageway having a first end that is adapted to connect to a vacuum source and a second end that terminates at the vacuum orifices such that a reduced gas pressure at the first end causes a vacuum to be exerted at the vacuum orifices. The interior passageway is formed from a groove in the end effector body portion and an end effector backplate that is sealingly connected to the end effector body portion to completely cover the groove from the first end to the second end. The ceramic body portion can be made of alumina or silicon carbide.

Description

TECHNICAL FIELD

The present invention relates generally to semiconductor wafer processing and more specifically to an end effector for handling semiconductor wafers during processing.

BACKGROUND OF THE INVENTION

Thermal processing systems are widely used in various stages of semiconductor fabrication. Basic thermal processing applications include chemical deposition, diffusion, oxidation, annealing, silicidation, nitridation, and solder re-flow processes. Many of these thermal processes involve extremely high temperatures. For example, vertical rapid thermal processing (RTP) systems comprise a vertically oriented processing chamber that is heated by a heat source such as a resistive heating element or a bank of high intensity light sources. The heat source is capable of heating the interior of the processing chamber to temperatures in the range of 450-1400 degrees Centigrade at ramp rates of up to about 50 degree C./sec.

Semiconductor thermal processing must be performed in an environment that is relatively free of contamination. One source of contamination that is detrimental to thermal processes is metal. For example, metals such as iron, sodium, and chromium in concentrations as little as 1×e¹⁰ atoms per cubic centimeter will significantly lower the yield from a wafer. Some vacuum type end effectors have metal components such as vacuum lines that make them susceptible to metal contamination within the processing chamber.

To maximize throughput and minimize contamination, all of the operations that occur during thermal processing of semiconductor wafers are automated. Robotic handlers routinely move wafers into and out of processing chambers. These handlers often employ end effectors disposed at the end of a robotic arm to grip and manipulate the wafer. Key features of end effectors include reliable gripping and minimal impact on the wafer surface. One type of end effector features one or more vacuum devices mounted on the end effector that use suction to grip the wafer and to give a positive indication that the wafer is positioned properly. Some existing vacuum type end effectors have plastic components such as wafer support pads that are not suitable for high temperature thermal processes because they would melt on contact with the heated wafer.

SUMMARY OF THE INVENTION

A ceramic end effector with an interior passage for vacuum provides relatively low cost, lightweight, and contaminate free wafer handling for high temperature thermal processing applications.

An end effector for installation on a robotic arm for transporting a plurality of semiconductor wafers from one location to another is provided that features a ceramic end effector body portion that includes a plurality of wafer support pads. The wafer support pads are adapted to support a semiconductor wafer surface, and at least one of the support pads has a vacuum orifice.

The support pads are secured to the end effector utilizing a unique spring which through its action forces the support pad in a downward direction against the body portion. The spring additionally forces that pad forward against an angled surface on the body. The pad is thus forced downward and into contact with the body at the angled interface as well. The surface of the bottom of the pad and that of the mating surface of the body are ground to a high degree of flatness to effect a seal that has very low leakage. The pad and body in this configuration may expand or contract at different rates as well as move relative to each other without affecting the seal or introducing stressed into either component. The underside of the vacuum pad features a counterbore which when exposed to negative pressure results in a net downward force against the end effector body thus improving the effectiveness of the seal between the pad and the end effector body. The pads are conveniently removable and/or replaceable in the event of damage or contamination.

The body portion features an interior vacuum passageway having a first end that is adapted to connect to a vacuum source and a second end that terminates at the vacuum aperture such that a reduced gas pressure at the first end causes a vacuum to be exerted at the vacuum aperture. In one embodiment, the interior passageway is formed from a groove in the end effector body portion and an end effector backplate that is sealingly connected to the end effector body portion to completely cover the groove from the first end to the second end. The ceramic body portion can be made of alumina or silicon carbide. In an exemplary embodiment, the end effector has three wafer engaging fingers, two of which have wafer support pads that include vacuum orifices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview drawing of a robot featuring an end effector constructed according to an embodiment of the present invention loading an RTP process chamber;

FIG. 2 is a perspective view of the body portion of an end effector constructed in accordance with an embodiment of the present invention;

FIG. 2A is a bottom view of an end effector showing the vacuum channels constructed in accordance with an embodiment of the present invention;

FIG. 3 is a close-up top view of a vacuum support pad cavity of the end effector body of FIG. 2 constructed in accordance with an embodiment of the present invention;

FIG. 4 is a cross-sectional view of the vacuum support pad cavity of FIG. 3;

FIG. 5 is a top view of a non-vacuum support pad cavity of the end effector body of FIG. 2 constructed in accordance with an embodiment of the present invention;

FIG. 6 is a cross-sectional view of the non-vacuum support pad cavity of FIG. 5;

FIG. 7 is a close-up top view of a vacuum support pad mounted in its operating position constructed in accordance with an embodiment of the present invention;

FIG. 8 is a cross-sectional view of the vacuum support pad cavity of FIG. 7;

FIG. 9 is a close-up top view of a non-vacuum support pad mounted in its operating position constructed in accordance with an embodiment of the present invention; and

FIG. 10 is a cross-sectional view of the non-vacuum support pad cavity of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an overview of an end effector 20 installed on a typical wafer handling robot 15 that is loading an RTP machine 30. The end effector 20 grips a wafer 17 and installs it through a slot 36 into the RTP processing chamber. Upon completion of the thermal process, the end effector is inserted into the processing chamber and retrieves the wafer 17 for transport to the next step in fabrication.

FIGS. 2-6 show the end effector 20 according to the present invention in more detail. The end effector 20 includes a body portion 25 that is made of a ceramic material such as, alumina, or silicon carbide, but preferably alumina. The body portion 25 is generally planar in shape and features a robot arm mounting end 19, and two outer wafer engaging fingers 27 and a center wafer support finger 29 at an axial end. The outer wafer engaging fingers 27 and support 29 each have a wafer support pad cavity which houses a wafer support pad that support the wafer during handling without damaging the wafer surface. The wafer supporting end of each wafer engaging finger 27 includes a flared wall portion 27a in the same plane as the finger 27. This flared wall region 27a encompasses the vacuum support pad cavity 31. The center wafer supporting finger 29 includes a non-vacuum support pad cavity 81.

Within the body portion 25, an interior vacuum passageway 37 (shown in phantom in FIG. 2) passes from the robot mounting end 19 to vacuum apertures 34 located on each wafer engaging finger 27. The vacuum passageway 37 is formed from a groove that is machined in the surface of the body portion 25 that is opposite the surface that includes the wafer vacuum support pads 33 (FIGS. 7 and 8). A backplate 35 (FIG. 2b) is fused to the body portion over the groove 37 to seal the passageway so that vacuum can pass from the robot mounting end 19 to the vacuum apertures 34. Known vacuum fittings are located in the robot mounting end 19 to connect the interior vacuum passageway to an exterior vacuum supply 21. Of course, exterior vacuum lines (not shown) could be used in conjunction with or in lieu of the interior vacuum passageways described herein in accordance with the present invention. The center support 29 does not include vacuum grooves. The center support 29 does include a non-vacuum support pad cavity 81 which houses a non-vacuum support pad 77

FIGS. 3 and 4 show the details of the vacuum support pad cavity 31. The vacuum support pad cavity 31 is a substantially circular cavity, the bottom of which is a flat vacuum sealing surface 57. The vacuum support pad cavity 31 further includes a front beveled wall portion 54 which angles into the body of the support finger 27 and away from a central axis of the vacuum support pad cavity 31. This makes the opening cavity diameter smaller than the diameter of the cavity along the vacuum sealing bottom portion 57. As described, a vacuum passageway 37 runs the length of the supporting finger 27 and terminates at a vacuum aperture 34 in the sealing surface 57 of the vacuum support pad cavity 31. In this configuration, vacuum is supplied to the vacuum support pad cavity 31 through the vacuum aperture 34.

Referring now to FIGS. 7 and 8, a vacuum support pad 33 is secured in the vacuum support pad cavity 31 by a removable nickel-chromium alloy wire spring 50, typically Inconel wire. The arrangement of the vacuum support pad 33 and wire 50 permit differential thermal expansion between the vacuum support pad 33 and the end effector body 27 while maintaining the integrity of the seal between the vacuum support pad 33 and the base 57. The vacuum support pads 33, in turn, are consumable and/or replaceable in the event that they become damaged or contaminated.

The wire spring 50 extends through a first section of the flared wall portion 27a in a bore 53a. The bore 53a terminates at the outer peripheral edge of the vacuum support pad cavity 31 thus exposing the wire spring 50 to the vacuum support pad cavity 31. The wire spring 50 further extends across the entire length of the vacuum support pad cavity 31 into a bore 53b in a second section of the flared wall portion 27a. The bore 53b extends through the second section of the flared wall portion 27b providing a path for the wire spring 50 to extend through and protrude out of the flared wall portion 27b. The area of the wire spring 50 that is exposed in the vacuum support pad cavity 31 provides torsional forces on a vacuum support pad 33 within the vacuum support pad cavity 31. The torsional forces from the spring 50 are a result of the vacuum support pad 33 in the vacuum support pad cavity 31 displacing the wire spring 50 from its natural position within the vacuum support pad cavity 31. In this arrangement, the wire spring 50 forces the vacuum support pad 33 forward and downward to make contact the beveled wall 54 of the vacuum support pad cavity 31.

FIG. 8 shows the vacuum support pad 33 in its proper operating position. The vacuum support pad 33 includes top surface 61 having a raised annular wafer engaging surface 63. A vacuum enhancing chamber is created between the top surface 61 and the raised annular surface 63 which aids in securing a wafer against the annular surface 63 during operation and movement of the robotic arm. At the central axis of the vacuum support pad 33 is a vacuum orifice 65 which extends completely through the body of the vacuum support pad 33. The outside perimeter of the vacuum support pad 33 includes a beveled wall 67 which angles away from the central axis A of the vacuum support pad 33 from the top of the annular surface 63 to the bottom of the vacuum support pad 33. When the vacuum support pad 33 is positioned in the vacuum support pad cavity 31 as described above, the wire spring 50 applies a torsional force that urges the vacuum support pad 33 towards the beveled wall portion 54 of the interior of the vacuum support pad cavity 31. The beveled wall 67 of the vacuum support pad 33 is caused to come into contact with the beveled wall 54 of the interior of the vacuum support pad cavity 31 in manner that locks a portion of the vacuum support pad 33 within the vacuum support pad cavity 31. The wire spring 50 rests on the outer perimeter of the pad including the bevel which causes the wire spring 50 to further exert a downward force on the vacuum support pad 33.

The pad further includes a bottom surface 71 having a portion of which is raised creating an annular sealing surface 73. The sealing surface 73 sealingly engages the bottom surface 57 of the vacuum support pad cavity 31. Both the annular sealing surface 73 of the vacuum support pad 33 and the bottom surface 57 of the vacuum support pad cavity 31 are ground to a relatively high degree of flatness to provide a seal with very low leakage. The bottom surface 71 further includes a counter bore area 75 having the vacuum orifice 65 generally it's center. During operation, the vacuum aperture 34 is in fluid communication with the vacuum orifice 65 of the vacuum support pad 33 such that a vacuum pressure can be communicated through the vacuum support pad 33 to a wafer contacting the wafer engaging surface 63. Further, the counter bore area 75 when exposed to the negative pressure of the vacuum enhances the net downward force of the vacuum support pad 33 resulting in the annular sealing surface 73 of the vacuum support pad 33 to sealingly engage with very low leakage the bottom 57 surface of the vacuum support pad cavity 31.

FIGS. 5 and 6 illustrate the pad holding end of the central support finger 29. As with the holding end of the wafer engaging fingers 27, the support finger 29 includes a non-vacuum support pad cavity 81 which is used to house a non-vacuum support pad 77. The non-vacuum support cavity 81 further includes the front bevel wall 54 and a flat bottom 61. However, the wafer support finger 29 does not include vacuum passageways and for this reason, the flat bottom 61 of the vacuum support pad cavity 31 does not include a vacuum aperture.

Turning now to FIGS. 9 and 10, a support finger 29 is illustrated. The support finger 29 includes a non-vacuum support pad cavity 81 at a portion of the support finger 29 distal to the robot mounting end 19. The non-vacuum support pad cavity 81 is generally circular in shape. The non-vacuum support pad 77 is held in place within the non-vacuum support pad cavity 81 in the same manner as described for the wafer engaging finger 27. The cavity wall 29a includes bores 83a and 83b, extending through the entire wall 29a. A spring clip 50 extends through a first section of the cavity wall 29a, across the entire length of the non-vacuum support pad cavity 81 and further through the second section of the cavity wall 29b, as shown. The spring clip 50 is exposed to the non-vacuum support pad cavity 84 and, as described with respect to the wafer-engaging finger 27, arranged to make torsional contact with the non-vacuum support pad 77.

The non-vacuum support pad cavity 81 extends partially into the body of the support finger 29 and includes a wall bevel 85 that angles into the body and away from the central axis of the non-vacuum support pad cavity 81. The non-vacuum support pad 77 includes a wafer engaging surface 87 and a support engaging surface 89. The support engaging surface 89 has a greater diameter than the wafer engaging surface 87 creating the wall bevel 85 around the outer perimeter of the non-vacuum support pad 77. When the non-vacuum support pad 77 is in its operational location, the wire spring 50 rests on the bevel 85 providing torsional force to the non-vacuum support pad 77. This force, because of the bevel, causes the non-vacuum support pad 77 to be forced downward against the non-vacuum support pad cavity bottom 91 and forward into the beveled wall 85. The bevel on the outer perimeter of the non-vacuum support pad 77 interlocks with the wall bevel 85 in the non-vacuum support pad cavity wall, thus locking the non-vacuum support pad 77 in the non-vacuum support pad cavity 81. The support finger 29 does not include a vacuum passageway and, as such, the non-vacuum support pad 77 does not require a vacuum orifice nor does the cavity bottom 91 include a vacuum aperture. The non-vacuum support pad 77 merely supports a portion of a wafer during operation of the robotic arm 20.

Although the present invention has been described with a degree of particularity, it is the intent that the invention include all modifications and alterations from the disclosed design falling within the spirit or scope of the appended claims.

Claims

1. For use in the processing of semiconductor wafers, an end effector for installation on a robotic arm for transporting a plurality of semiconductor wafers from one location to another, the end effector comprising: a ceramic end effector; a plurality of removable wafer support pads disposed at a distal end of said end effector said support pads being adapted to support a semiconductor wafer surface, wherein at least one of the support pads comprises a vacuum orifice in communication with a vacuum source for exerting a vacuum on the wafer surface; and a retaining structure for removably securing the removable support pads to the end effector.

2. The end effector of claim 1 wherein said end effector body includes an interior vacuum passageway having a first end that is adapted to connect to a vacuum source and a second end that terminates at a vacuum aperture, said aperture communicating with the support pad vacuum orifice such that a reduced gas pressure at the first end causes a vacuum to be exerted at the vacuum orifice of the support pad.

3. The end effector of claim 2 wherein the interior passageway is formed from a groove in the end effector body portion and an end effector backplate that is sealingly connected to the end effector body portion to completely cover the groove from the first end to the second end.

4. The end effector of claim 1 wherein the ceramic body is made of alumina.

5. The end effector of claim 1 wherein the ceramic body is made of silicon carbide.

6. The end effector of claim 1 wherein the end effector body comprises a plurality of wafer engaging fingers at the distal end.

7. The end effector of claim 6 wherein the wafer support pads are disposed at an axial end of the wafer engaging fingers.

8. The end effector of claim 6 comprising three wafer engaging fingers, two of which comprise wafer support pads that include vacuum orifices.

9. The end effector of claim 6 wherein at least one of the wafer engaging fingers includes a cavity which houses a vacuum support pad.

10. The end effector of claim 1 wherein said retaining structure is a spring clip, said spring clip extending through a portion of the body of the wafer engaging finger, into said cavity and making torsional engagement with the vacuum pad such that said spring clip secures the pad in the cavity.

11. The end effector of claim 1 wherein the vacuum support orifice includes a counterbore to enhance a seal between the vacuum pad and end effector during expansion or contraction of the end effector components.

12. The end effector of claim 1 wherein the vacuum pad is ground flat at that portion which engages the end effector to create a vacuum seal with low leakage.

13. For use in the processing of semiconductor wafers, an end effector for installation on a robotic arm for transporting at least one of semiconductor wafers from one location to another, the end effector comprising: a ceramic end effector body portion including a plurality of wafer engaging fingers; a plurality of removable wafer support pads disposed at an axial end of the wafer engaging fingers, said support pads being adapted to support a semiconductor wafer surface, wherein at least one of the support pads comprises a vacuum orifice in communication with a vacuum source for exerting a vacuum on the wafer surface; and a retaining structure for removably securing the removable support pads to the end effector.

14. The end effector of claim 13 wherein the ceramic body is made of alumina.

15. The end effector of claim 13 wherein the ceramic body is made of silicon carbide.

16. The end effector of claim 13 wherein at least one of the wafer engaging fingers includes a cavity which houses a vacuum support pad.

17. The end effector of claim 13 wherein said retaining structure is a spring clip, said spring clip extending through a portion of the body of the wafer engaging finger, into said cavity and making torsional engagement with the vacuum pad such that said spring clip secures the pad in the cavity.

18. The end effector of claim 13 wherein the vacuum support orifice includes a counterbore to enhance a seal between the vacuum pad and end effector during expansion or contraction of the end effector components.

19. The end effector of claim 13 comprising three wafer engaging fingers, two of which comprise wafer support pads that include vacuum orifices.

20. The end effector of claim 13 wherein at least one of the wafer engaging fingers includes a cavity which houses the vacuum support pad.

21. For use in the processing of semiconductor wafers, an end effector for installation on a robotic arm for transporting at least one of semiconductor wafers from one location to another, the end effector comprising: a ceramic end effector body including three wafer engaging fingers, at least one of which comprise wafer support pads that include vacuum orifices; a plurality of removable wafer support pads disposed in a cavity at an axial end of the wafer engaging fingers, said support pads being adapted to support a semiconductor wafer surface, wherein at least one of the support pads comprises a vacuum orifice in communication with a vacuum source for exerting a vacuum on the wafer surface; and a retaining structure comprising a spring clip, said spring clip extending through a portion of the body of the wafer engaging finger, into said cavity and making torsional engagement with the pad such that said spring clip secures the pad in the cavity.

22. For use in the processing of semiconductor wafers, an end effector for installation on a robotic arm for transporting at least one of semiconductor wafers from one location to another, the end effector comprising: a ceramic end effector body including an interior vacuum passageway having a first end that is adapted to connect to a vacuum source and a second end that terminates at a first vacuum orifice such that a reduced gas pressure at the first end causes a vacuum to be exerted at the fist vacuum orifice; a plurality of removable wafer support pads secured to said end effector body portion said support pads being adapted to support a semiconductor wafer surface, wherein at least one of the support pads comprises a second vacuum orifice in communication with said first vacuum orifice such that a vacuum is exerted on the wafer surface; and a retaining structure for securing the removable support pads to the end effector.

23. A method of securing a semiconductor wafer support pad to an end effector, said end effector for use in thermal processing of the semiconductor wafer wherein the end effector is installed on a robotic arm for transporting at least one of semiconductor wafers from one location to another, the method comprising the steps of: placing a plurality of wafer support pads in contact with the end effector, wherein at least one of said pads including a vacuum orifice in communication with a vacuum source; and securing the wafer support pads to the end effector with a retaining structure.

24. The method of claim 23 wherein the end effector comprises a plurality of wafer engaging fingers.

25. The end effector of claim 24 wherein the wafer support pads are disposed at an axial end of the wafer engaging fingers.

26. The method of claim 25 wherein at least one of the wafer engaging fingers includes a cavity which houses the vacuum support pad.

27. The method of claim 26 wherein said retaining structure is a spring clip, said spring clip extending through a portion of the body of the wafer engaging finger, into said cavity and making torsional engagement with the pad such that said spring clip secures the pad in the cavity