Apparatus for alignment of automated workpiece handling systems Number:6,763,281 from the United States Patent and Trademark Office (PTO) owispatent

Title: Apparatus for alignment of automated workpiece handling systems

Abstract: An alignment tool, method and system are provided for aligning a robot blade in a workpiece handling system, in which the tool comprises a frame or fixture adapted to be supported by a transfer chamber support surface or other support surface in the system, in which the frame has one or more non-contact distance sensors positioned to measure the distance of a workpiece or robot blade from the sensor or a predetermined reference point or surface. In one embodiment, the frame is used to align a robot blade relative to a robot support alignment surface in a robot chamber. In another embodiment, the frame emulates a workpiece cassette and the distance sensors provide an output to align the robot blade to a cassette support alignment surface. As a consequence, accidental scratching and breakage of workpieces such as semiconductor wafers and display substrates may be reduced or eliminated. In another embodiment, positions of distance sensors may be readily repositioned to accommodate alignment procedures for different sized wafers or other workpieces.

Patent Number: 6,763,281 Issued on 07/13/2004 to Schauer,   et al.

---

Inventors:	Schauer; Ronald Vern (Gilroy, CA), Lappen; Alan Rick (San Martin, CA)
Assignee:	Applied Materials, Inc (Santa Clara, CA)
Appl. No.:	09/881,854
Filed:	June 13, 2001

---

Current U.S. Class:	700/218 ; 206/710; 414/222.02; 414/937
Current International Class:	B23Q 17/24 (20060101); B23Q 3/18 (20060101); H01L 21/68 (20060101); H01L 21/00 (20060101); H01L 21/67 (20060101); H01L 21/677 (20060101); H01L 21/673 (20060101)
Field of Search:	700/213,214,218 414/217,222.01,222.02,222.13,226.05,935,936,937,938,939,940 206/454,711,710 356/400

---

References Cited [Referenced By]

---

U.S. Patent Documents

	3877134		April 1975		Shanahan
	3934733		January 1976		Worden
	4176751		December 1979		Gillissie
	4178113		December 1979		Beaver, II et al.
	4493418		January 1985		Johnson
	4687097		August 1987		Mortensen
	4759681		July 1988		Nogami
	4770590		September 1988		Hugues et al.
	4819167		April 1989		Cheng et al.
	4836733		June 1989		Hertel et al.
	4951601		August 1990		Maydan et al.
	4952299		August 1990		Chrisos et al.
	4955780		September 1990		Shimane et al.
	5042671		August 1991		Bischoff et al.
	5111936		May 1992		Kos
	5149244		September 1992		Webber et al.
	5186594		February 1993		Toshima et al.
	5186718		February 1993		Tepman et al.
	5217341		June 1993		Webber et al.
	5225691		July 1993		Powers et al.
	5227708		July 1993		Lowrance
	5292393		March 1994		Maydan et al.
	5387067		February 1995		Grunes
	5418382		May 1995		Blackwood et al.
	5436721		July 1995		Pence et al.
	5438418		August 1995		Fukui et al.
	5443346		August 1995		Murata et al.
	5447409		September 1995		Grunes et al.
	5452521		September 1995		Niewmierzycki
	5454170		October 1995		Cook
	5483138		January 1996		Shmookler et al.
	D368802		April 1996		Gallagher et al.
	5510892		April 1996		Mizutani et al.
	5516732		May 1996		Flegal
	5525024		June 1996		Freerks et al.
	5530550		June 1996		Nikoonahad et al.
	5556248		September 1996		Grunes
	5563798		October 1996		Berken et al.
	5570994		November 1996		Somekh et al.
	5604443		February 1997		Kitamura et al.
	5605428		February 1997		Birkner et al.
	5610102		March 1997		Gardopee et al.
	5611655		March 1997		Fukasawa et al.
	5615988		April 1997		Wiesler et al.
	5636960		June 1997		Hiroki et al.
	5644400		July 1997		Mundt
	5655277		August 1997		Galdos et al.
	5706201		January 1998		Andrews
	5713711		February 1998		McKenna et al.
	5740059		April 1998		Hirata et al.
	5769588		June 1998		Toshima et al.
	5783834		July 1998		Shatas
	5785186		July 1998		Babbs et al.
	5905302		May 1999		Lane et al.
	5980188		November 1999		Ko et al.
	5980194		November 1999		Freerks et al.
	6010009		January 2000		Peterson et al.
	6019563		February 2000		Murata et al.
	6036031		March 2000		Ishikawa
	6039186		March 2000		Bhatt et al.
	6047480		April 2000		Powers
	6060721		May 2000		Huang
	6063196		May 2000		Li et al.
	6082950		July 2000		Altwood et al.
	6085125		July 2000		Genov
	6095335		August 2000		Busby
	6126380		October 2000		Hillman
	6178361		January 2001		George et al.
	6197117		March 2001		Li et al.
	6286688		September 2001		Mimken et al.
	6298280		October 2001		Bonora et al.
	6300644		October 2001		Beckhart et al.
	6307211		October 2001		Beckhart et al.
	6388436		May 2002		Nodot et al.
	6390753		May 2002		De Ridder
	6390754		May 2002		Yamaga et al.
	6401554		June 2002		Mori et al.

Foreign Patent Documents

	0425184		May., 1994		EP
	1047115		Oct., 2000		EP
	1028933		Jan., 1989		JP
	3156624		Jul., 1991		JP
	5013551		Jan., 1993		JP
	6131032		May., 1994		JP
	9162257		Jun., 1997		JP
	9199571		Jul., 1997		JP
	10 154738		Jul., 2000		JP
	9858402		Dec., 1998		WO

Other References

AMAT Manual, Chapter 3, "Wafer Handler;" section 3.1, "Robot Setup and Calibration." AMAT doc ID 042-021-03, pp. 3-33 to 3-42; predating filling date of present application by at least one year. . AMAT Manual, Chapter 3, "Wafer Handler;" section 3.2, "Loadlock Cassette and Indexer Setup and Calibration." AMAT doc ID 042-021-03, pp 3-42 to 3-54;predating filing date of present application by at least one year. . AMAT Manual, Chapter 3, "Wafer Handler;" section 3.3 through 3.6, "Wafer Handoff Calibration." AMAT doc ID 256-024-03, pp 3-54 to 3-73; predating filing date of present application by at least one year. . AMAT Manual, Chapter 7, "Wafer Handler and Wafer Handoff Setup and Calibrations;" (all). AMAT doc ID 256-024-03, pp 7-1 to 7-17; predating filing date of present application by at least one year. . AMAT Manual, Chapter 7, "Wafer Handler Setup and Calibration;" section 7.1 through 7.9. AMAT doc ID 142-351-02, pp 7-1 to 7-18; predating filing date of present application by at least one year. . AMAT Manual, Chapter 7, "Wafer Mapping;" section 7.10, "Wafer Mapping." AMAT doc ID 142-351-02, pp 7-19 to 7-26; predating filing date of present application by at least one year. . Declaration of A. Lappen, 13JL2001. . Declaration of E. Ruhland, 02DE2002. . Declaration of R. Schauer, 20JL2000. . Declaration of R. Schauer, 18NO2002. . Declaration of R. Schauer, 29MY2003. . Iscoff, Ron. "Dry Etching Systems: Gearing up for Larger Wafers," Semiconductor International, Oct. 1985, pp 48--60. . US 10/303,516 filed Nov. 25, 2002 (146 pp). . US 10/266,389 filed Oct. 8, 2002, (109 pp). . PCT/US02/18494 Search Report dated May 7, 2003..

Primary Examiner: Tran; Khoi H.
Attorney, Agent or Firm: Konrad Raynes Victor & Mann, LLP Bach; Joseph

---

Parent Case Text

---

RELATED APPLICATION

This application is a continuation-in-part of application Ser. No. 09/294,301, filed Apr. 19, 1999, which is incorporated herein by reference in its entirety.

---

Claims

---

What is claimed is:

1. An alignment tool for aligning a robot blade carrying a workpiece in a workpiece handling system, and a base plane defined by a platform of said system, comprising: a frame having a base adapted to be supported by said platform of said system, said frame further having a plurality of sensor mountings; and a plurality of non-contact distance sensors mounted to said sensor mountings; wherein said frame defines an opening positioned between said base and said sensors, said opening being sized sufficiently to admit a target carried by said robot blade between said sensors and said base and wherein said sensors are positioned by said sensor mountings to measure the orientation of said target carried by said robot blade relative to said base plane.

2. The alignment tool of claim 1 wherein said system includes a chamber having a floor and a robot carrying said robot blade, and wherein said platform includes said floor of said chamber and said floor defines said base plane.

3. The alignment tool of claim 2 wherein said base includes a plurality of legs adapted to engage said floor.

4. The alignment tool of claim 3 wherein said base includes a base plate carried by said plurality of legs, said frame further including a top plate carrying said sensor mountings, and a plurality of brackets spacing said top plate above said base plate.

5. The alignment tool of claim 1 wherein said target defines a plane and said plurality of non-contact distance sensors includes three sensors, each sensor being positioned to measure the distance between that sensor and a separate location on said target plane to determine the spatial orientation of said target plane relative to said base plane.

6. The alignment tool of claim 5 wherein each sensor includes an optical sensor.

7. The alignment tool of claim 6 wherein each sensor includes a laser adapted to emit a laser beam onto said target.

8. An alignment tool for aligning a robot blade carrying a workpiece in a workpiece handling system, and a base plane defined by a platform of said system, said platform having a support surface, comprising: a frame adapted to be supported by said platform support surface, said frame having a reference surface and a first support surface positioned to engage said platform support surface and to support said reference surface a first predetermined distance from said platform support surface; and a first distance sensor positioned to measure the distance of said reference surface from said sensor and to measure the distance of a target from said sensor, wherein said target is adapted to be carried by said robot blade.

9. The alignment tool of claim 8 wherein said distance sensor is carried within said frame.

10. The alignment tool of claim 8 wherein said distance sensor includes a laser head.

11. The alignment tool of claim 8 wherein said first distance sensor is positioned to measure the distance of a first location of said reference surface from said sensor and to measure the distance of a first location of said target from said sensor, said tool further comprising a second distance sensor positioned to measure the distance of a second location of said reference surface from said second sensor and to measure the distance of a second location of said target from said second sensor.

12. The alignment tool of claim 11 wherein said system has a mechanism for adjusting the orientation of said robot blade along a first direction, wherein said first and second sensors are disposed along a line parallel to said first direction.

13. The alignment tool of claim 12 further comprising a third distance sensor positioned to measure the distance of a third location of said reference surface from said third sensor and to measure the distance of a third location of said target from said third sensor.

14. The alignment tool of claim 13 wherein said system has a mechanism for adjusting the orientation of said robot blade along a second direction, wherein said second and third sensors are disposed along a line parallel to said second direction.

15. An alignment tool for aligning a robot blade carrying a workpiece in a robot chamber of a workpiece handling system, and a base plane defined by a floor surface of said chamber of said system, comprising: a frame adapted to be supported by said floor surface, said frame having a plurality of legs adapted to engage said floor surface to support said frame above said floor surface; and a distance sensor attached to said frame and positioned to measure the distance of a target carried by said robot blade in said chamber, from said sensor.

16. An alignment tool for aligning a robot blade carrying a workpiece in a chamber of a workpiece handling system, and a base plane defined by a support surface of said system, comprising: a frame adapted to be supported by said system support surface; and a plurality of non-contact distance sensors positioned within said frame to measure the tilt orientation of a target carried by said robot blade relative to a reference plane within said frame.

17. An alignment tool for aligning a robot blade carrying a workpiece in a chamber of a workpiece handling system, and a base plane defined by a support surface of said system, comprising: a frame adapted to be supported by said system support surface; and a plurality of non-contact distance sensors positioned within said frame to measure the orientation of a target carried by said robot blade relative to a reference plane within said frame wherein said system has a chamber which has a floor which defines a base plane and said frame has a reference surface which defines said reference plane at a predetermined height above said base plane.

18. The tool of claim 17 wherein said reference plane is substantially parallel to said base plane.

19. The tool of claim 18 wherein said reference surface includes three separate and coplanar subsurfaces.

20. The tool of claim 16 wherein said plurality of distance sensors are positioned to measure the distances of a plurality of locations on a target carried by said robot blade relative to said reference plane.

21. The tool of claim 20 wherein each of said sensors comprises a laser distance sensor carried by said frame and positioned to measure one of said distances of said plurality of locations on said target carried by said robot blade relative to said reference plane.

22. The tool of claim 20 further comprising a display for displaying a numerical representation of each of said measured distances of said plurality of locations on said target carried by said robot blade relative to said reference plane.

23. The tool of claim 16 further comprising a display for displaying at least one of a numerical representation and a graphical representation of said measured orientation of said reference plane relative to said target carried by said robot blade.

24. The tool of claim 20 further comprising a calculator for calculating a difference between selected measured distances of selected locations of said plurality of locations on said target carried by said robot blade relative to said reference plane.

25. The tool of claim 24 further comprising a display for displaying a numerical representation of said calculated difference between selected measured distances of selected locations of said plurality of locations on said target carried by said robot blade relative to said reference plane.

26. An alignment tool for aligning a robot blade carrying a workpiece in a workpiece handling system, with respect to a base plane defined by a platform of said system, comprising: means for measuring the orientation of a target carried by said robot blade relative to said base plane, said measuring means including a plurality of distance sensor means for measuring the distances between said target and each of said sensor means, and frame means having a base, for mounting said sensor means and supporting said sensor means above said platform of said system, said frame means having opening means for admitting a target carried by said robot blade between said sensor means and said base.

27. The alignment tool of claim 25 wherein said system platform includes a chamber having a floor and wherein said frame means base has means for positioning said base on said floor of said chamber.

28. The alignment tool of claim 22 wherein said base plane is defined by said chamber floor.

29. The alignment tool of claim 27 wherein said base positioning means includes a plurality of legs adapted to rest on said floor.

30. The alignment tool of claim 26 herein said frame means includes reference surface means for providing a reference plane parallel to and a predetermined distance above said base plane; and said measuring means includes means for measuring the orientation of said target carried by said robot blade relative to said reference plane.

31. The alignment tool of claim 26 herein said sensor means includes laser means for emitting a laser beam and detector means for detecting a laser beam.

32. The alignment tool of claim 30 wherein a first sensor means includes means for measuring the distance of a first location of said reference surface from said first sensor means and measuring the distance of a first location of said target from said first sensor means; a second sensor means includes means for measuring the distance of a second location of said reference surface from said second sensor means and measuring the distance of a second location of said target from said second sensor means; and a third sensor means includes means for measuring the distance of a third location of said reference surface from said third sensor means and measuring the distance of a third location of said target from said third sensor means.

33. The alignment tool of claim 32 further comprising display means for displaying a numerical representation of each of said measured distances of said plurality of locations on said target carried by said robot blade relative to said reference surface.

34. The alignment tool of claim 26 further comprising display means for displaying at least one of a numerical representation and a graphical representation of said measured orientation of said target carried by said robot blade relative to said base plane.

35. The alignment tool of claim 32 further comprising calculating means for calculating a difference between selected measured distances of selected locations of said plurality of locations on said target carried by aid robot blade relative to said reference surface.

36. The alignment tool of claim 35 further comprising display means for displaying a numerical representation of said calculated difference between selected measured distances of selected locations of said plurality of locations on said target carried by said robot blade relative to said reference surface.

37. An alignment tool for aligning a robot blade carrying a target wafer in a transfer chamber, and a base plane defined by a floor of said transfer chamber, comprising: a frame having a plurality of legs adapted to be supported by said floor of said transfer chamber, said frame further having a first plate which defines at least three triangularly spaced, coplanar reference surfaces, said frame further having at least three triangularly spaced sensor mountings, a second plate carrying said sensor mountings, and a plurality of brackets spacing said first plate and said second plate; and at least three laser distance measuring sensors, each sensor being mounted to a sensor mounting and positioned facing a reference surface on said first plate; wherein said frame defines an opening positioned between said reference surfaces and said sensors, said opening being sized sufficiently to admit a target wafer carried by said robot blade between said sensors and said reference surfaces and wherein said sensors are positioned by said sensor mountings to measure the orientation of said target wafer carried by said robot blade relative to said coplanar reference surfaces.

---

Description

---

FIELD OF THE INVENTION

The present invention relates to automated workpiece handling systems, and more particularly, to methods and devices for aligning a cassette for workpieces and for aligning a robot for transferring workpieces in an automated workpiece handling system.

BACKGROUND OF THE INVENTION

In order to decrease contamination and to enhance throughput, semiconductor processing systems often utilize one or more robots to transfer semiconductor wafers, substrates and other workpieces between a number of different vacuum chambers which perform a variety of tasks. An article entitled "Dry Etching Systems: Gearing Up for Larger Wafers", in the October, 1985 issue of Semiconductor International magazine, pages 48-60, describes a four-chamber dry etching system in which a robot housed in a pentagonal-shaped mainframe serves four plasma etching chambers and a loadlock chamber mounted on the robot housing. In order to increase throughput, it has been proposed to utilize two loadlock chambers as described in U.S. Pat. No. 5,186,718. In such a two-loadlock chamber system, both loadlock chambers are loaded with full cassettes of unprocessed wafers. FIG. 1 of the present application illustrates two typical loadlock chambers LLA and LLB, each having a cassette 190 therein for holding unprocessed wafers 192 to be unloaded by a robot 194 in a transfer chamber 195 and transferred to various processing chambers 196 attached to a mainframe 198.

The loadlock chamber LLA, for example, is a pressure-tight enclosure which is coupled to the periphery of the mainframe 198 by interlocking seals which permit the loadlock chamber to be removed and reattached to the mainframe as needed. The cassette 190 is loaded into the loadlock chamber LLA through a rear door, which is closed in a pressure-tight seal. The wafers are transferred between the mainframe 198 and the loadlock chamber LLA through a passageway 199 which may be closed by a slit valve to isolate the loadlock chamber volume from the mainframe volume.

As shown in FIG. 2, a typical cassette 190 is supported by a platform 200 of a cassette handler system 208, which includes an elevator 210, which elevates the platform 200 and the cassette 190. The platform 200 has a top surface, which defines a base plane 220 on which the cassette 190 rests. As the cassette includes a plurality of "slots" 204 or wafer support locations, the elevator moves the cassette to sequentially position each of the slots with the slit valves to allow a robot blade to pass from the mainframe, through the slit valve, and to a location to "pick" or deposit a wafer in a wafer slot.

The slots 204 of the cassette may be initially loaded with unprocessed wafers or other workpieces before the cassette is loaded into the loadlock chamber LLA. The number of unprocessed wafers initially loaded into the cassette may depend upon the design of the cassette. For example, some cassettes may have slots for 25 or more wafers.

After the loadlock access door is closed and sealed, the loadlock chamber is then pumped by a pump system down to the vacuum level of the mainframe 198 before the slit valve is opened. The robot 194 which is mounted in the mainframe 198 then unloads the wafers from the cassette one at a time, transferring each wafer in turn to the first processing chamber. The robot 194 includes a robot hand or blade 206, which is moved underneath the wafer to be unloaded. The robot 194 then "lifts" the wafer from the wafer slot supports supporting the wafers in the cassette 190. By "lifting," it is meant that either the robot blade 206 is elevated or the cassette 190 is lowered by the handler mechanism 208 such that the wafer is lifted off the cassette wafer supports. The wafer may then be withdrawn from the cassette 190 through the passageway and transferred to the first processing chamber.

Once a wafer has completed its processing in the first processing chamber, that wafer is transferred to the next processing chamber (or back to a cassette) and the robot 194 unloads another wafer from the cassette 190 and transfers it to the first processing chamber. When a wafer has completed all the processing steps of the wafer processing system, the robot 194 returns the processed wafer back to the cassette 190 from which it came. Once all the wafers have been processed and returned to the cassette 190, the cassette in the loadlock chamber is removed and another full cassette of unprocessed wafers is reloaded. Alternatively, a loaded cassette may be placed in one loadlock, and an empty one in the other loadlock. Wafers are thus moved from the full cassette, processed, and then loaded into the (initially) empty cassette in the other loadlock. Once the initially empty cassette is full, the initially full cassette will be empty. The full "processed" cassette is exchanged for a full cassette of unprocessed wafers, and these are then picked from the cassette, processed, and returned to the other cassette. The movements of the robot 194 and the cassette handler 208 are controlled by an operator system controller 222 (FIG. 1), which is often implemented with a programmed workstation.

As shown in FIGS. 2 and 3, the wafers are typically very closely spaced in many wafer cassettes. For example, the spacing between the upper surface of a wafer carried on a moving blade and the lower surface of an adjacent wafer in the cassette may be as small as 0.050 inches. Thus, the wafer blade is often very thin, to fit between wafers as cassettes are loaded or unloaded. As a consequence, it is often preferred in many processing systems for the cassette and the cassette handler 208 to be precisely aligned with respect to the robot blade and wafer to avoid accidental contact between either the robot blade or the wafer carried by the blade and the walls of the cassette or with other wafers held within the cassette.

However, typical prior methods for aligning the handler and cassette to the robot blade have generally been relatively imprecise, often relying upon subjective visual inspections of the clearances between the various surfaces. Some tools have been developed to assist the operator in making the necessary alignments. These tools have included special wafers, bars or reference "pucks" which are placed upon the robot blade and are then carefully moved into special slotted or pocketed receptacles which are positioned to represent the tolerance limits for the blade motions. However, many of these tools have a number of drawbacks. For example, some tools rely upon contact between the blade or a tool on the blade and the receptacle to indicate a condition of nonalignment. Such contact can be very detrimental to high precision mechanisms for moving the blade as well as to the blade itself. Also, many such tools do not indicate the degree of alignment or nonalignment but merely a "go/no-go" indication of whether contact is likely.

In aligning the handler mechanism to the robot blade, one procedure attempts to orient the cassette to be as level as possible with respect to the robot blade. One tool that has been developed to assist in the leveling procedure has dual bubble levels in which one bubble level is placed on the blade and the other is placed on the cassette. The operator then attempts to match the level orientation of the blade to that of the cassette. In addition to being very subjective, such bubble tools have also often been difficult to see in the close confines of the cassette and handler mechanisms.

In addition to aligning the robot blade with respect to a cassette handler, in many systems the robot blade should be properly aligned with respect to the various chambers of the system in which the blade operates including the buffer, transfer and pass through chambers. Here too, prior procedures have typically relied upon subjective measurements including using tape measures to measure the distances of various portions of the robot blade to surfaces of the chamber. Other techniques have utilized mechanical gauges, which rely upon visual inspections which again, are typically very subjective.

As a consequence of these and other deficiencies of the prior alignment procedures and tools, alignments have often tended to be not only imprecise but also inconsistent from application to application. These problems have frequently led to the breakage or scratching of very expensive wafers and equipment as well as to the generation of damaging particulates in the systems.

SUMMARY OF THE INVENTIONS

The present inventions are, in one aspect, directed to an alignment tool, method and system for aligning a robot blade in a workpiece handling system, in which the tool comprises a frame or fixture adapted to be supported by a support surface in the system, and in which the frame has one or more distance sensors positioned to measure the distance of a workpiece or robot blade from the sensor or a predetermined reference point or surface. In one embodiment, the frame is placed on a chamber floor reference surface so that non-contact type distance sensors can directly measure the spatial orientation of a workpiece held by the robot blade within a frame opening relative to the chamber. In another embodiment, the frame emulates a workpiece cassette and the distance sensors provide a numerical output of the distance to the workpiece. As explained in greater detail below, these distance measurements facilitate accurately leveling the robot blade. As a consequence, accidental scratching and breakage of workpieces such as semiconductor wafers and display substrates may be reduced or eliminated.

In another aspect of the present inventions, the tool is adapted to facilitate ready repositioning of the distance sensors to accommodate aligning robot blades for wafers or other workpieces of different sizes. In the illustrated embodiment, releasable fasteners are removed and the distance sensors are reversed in orientation and refastened to the tool to shift the field of view of the sensors.

In another aspect of the present inventions, the frame has a predetermined reference surface positioned opposite the distance sensors of the frame. In a preferred embodiment, the frame reference surface is accurately positioned by the frame to be at a predetermined orientation and distance from a base reference point or surface such as a chamber floor or a cassette handler support surface. As a consequence, as explained in greater detail below, distance measurements to the workpiece or robot blade may be output as offsets from this predetermined frame reference surface which significantly facilitates calibrating the distance sensors.

In yet another aspect of the present inventions, a preferred embodiment includes a computer operated graphical user interface which can significantly facilitate rapid and accurate performance of alignment and setting procedures utilizing the alignment frame of the present inventions. Actual measurements may be compared to preferred values calculated or otherwise provided and appropriate adjustments made.

There are additional aspects to the present inventions. It should therefore be understood that the preceding is merely a brief summary of some embodiments and aspects of the present inventions. Additional embodiments and aspects of the present inventions are referenced below. It should further be understood that numerous changes to the disclosed embodiments can be made without departing from the spirit or scope of the inventions. The preceding summary therefore is not meant to limit the scope of the inventions. Rather, the scope of the inventions is to be determined by appended claims and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described with reference to the accompanying drawings which, for illustrative purposes, are schematic and not drawn to scale.

FIG. 1 is a schematic top view of a typical deposition chamber having two loadlock chambers.

FIG. 2 is a schematic front view of a typical wafer cassette disposed on a platform of a cassette handling system.

FIG. 3 is a partial view of the wafer cassette of FIG. 2, depicting a wafer resting in a slot and a wafer picked up from a slot.

FIG. 3A is an enlarged partial view of the wafer cassette of FIG. 3, depicting a wafer resting in a slot and a wafer picked up from a slot.

FIG. 4 is a schematic pictorial view of a cassette alignment tool system in accordance with an embodiment of the present invention.

FIG. 5 is a side view of the metrology cassette of FIG. 4.

FIGS. 6A, 6B and 6C are a schematic partial cross-sectional top views of the metrology cassette of FIG. 5, showing distance sensors in various configurations.

FIG. 7 is a schematic view of display of the interface controller of the system of FIG. 4.

FIG. 7A is a view of the computer display of FIG. 4, depicting an input-output screen used in a calibration procedure.

FIG. 8 is a front view of the metrology cassette of FIG. 4.

FIG. 9 is a view of the computer display of FIG. 4, depicting an input-output screen used in a calibration and leveling procedure.

FIG. 10 is an enlarged view of a portion of the screen of FIG. 9, graphically depicting the leveling inputs for a typical cassette handler platform.

FIG. 11 is a schematic view of the display of the interface controller of the system of FIG. 4, during a wafer level measurement procedure.

FIG. 12a is a top view of the metrology cassette of FIG. 4.

FIG. 12b is a side view of the metrology cassette of FIG. 4.

FIG. 12c is a front view of the metrology cassette of FIG. 4.

FIG. 12d is a bottom view of the metrology cassette of FIG. 4.

FIG. 13 is a partial schematic view of a wafer resting on the reference surface of the metrology cassette in an inverted position.

FIG. 14 is a front view of the metrology cassette of FIG. 4, showing the metrology cassette in an inverted position.

FIG. 15 is a schematic pictorial view of a robot blade alignment tool system in accordance with an alternative embodiment of the present inventions.

FIG. 16 is a top view of the transfer chamber of FIG. 1 with the blade alignment tool of FIG. 15 disposed in the chamber.

FIG. 17 is a top view of the metrology tool of FIG. 15.

FIG. 18 is a rear view of the metrology tool of FIG. 15.

FIG. 19 is a view of the computer display of FIG. 15, depicting an input-output screen used in a calibration procedure.

FIG. 20 is a side view of the metrology tool of FIG. 15.

FIG. 21 is a view of the computer display of FIG. 15, depicting an input-output screen used in a leveling procedure.

FIG. 22 is a schematic diagram of the interface controller signal processing circuit for sampling signals from the laser head sensors.

FIG. 23a is a top view of an alternative embodiment depicting the distance sensors in a first position.

FIG. 23b is a top view of the tool of FIG. 23a depicting the distance sensors in a second position.

FIG. 24a is a side view of the tool of FIG. 23a depicting the distance sensors in the first position.

FIG. 24b is a side view of the tool of FIG. 23b depicting the distance sensors in the second position.

DETAILED DESCRIPTION

A cassette alignment tool system in accordance with a preferred embodiment of the present invention is indicated generally at 400 in FIG. 4. The cassette alignment tool 400 comprises a metrology cassette 410, cassette controller 412 coupled by communication cables 414 to the metrology cassette 410, and a computer 416 coupled by a communication cable 418 to the cassette controller 412. The metrology cassette 410 is secured to the cassette handler platform 200 in the same manner as an actual wafer cassette such as the cassette 190 of FIG. 2 and thus emulates the wafer cassette 190. For example, the metrology cassette has alignment and registration surfaces including an H-bar 430 and side rails 570 which are received by the cassette handler to align the cassette with respect to the handler. In addition, the metrology cassette 410 approximates the size and weight of a production wafer cassette full of wafers.

The cassette alignment tool system 400 may be used with processing systems having one or many processing chambers and one or more workpiece handling systems for transferring workpieces from one or more cassettes in one or more loadlock chambers to one or more of the processing chambers. Once a particular handling system has been properly aligned and calibrated to the robot blade and workpiece, the metrology cassette 410 may be removed from the handler and processing of workpieces may begin using a standard workpiece cassette which was emulated by the metrology cassette 410. However, it is preferred that all handlers of a particular processing system be properly aligned prior to initiating processing of production workpieces.

In accordance with one aspect of the illustrated embodiments, the metrology cassette 410 has a distance measurement device 500 which can provide precise measurements of the position of a wafer or other workpiece being held by the robot blade within the metrology cassette 410. As explained in greater detail below, these wafer position measurements can be used to accurately align an actual wafer cassette such as the cassette 190 to the robot blade in such a manner as to reduce or eliminate accidental contact between the blade or the wafer held by the blade and the cassette or wafers held within the wafer cassette.

As best seen in FIGS. 5 and 6A, in the illustrated embodiment, the distance measurement device 500 of the illustrated embodiment includes three laser sensors A, B and C, each of which includes a laser head 510b, 510r or 510y, which is clamped in a mounting 512b, 512r or 512y, respectively, carried by the metrology cassette 410. The mountings 512b, 512r and 512y are preferably color coded and mechanically keyed to reduce or eliminate inadvertent exchanges or misplacements of the laser heads in the mountings. Thus, the mountings 512b, 512r and 512y may be color coded blue, red and yellow, respectively, for example. In the illustrated embodiment, the mountings are brackets but may have a variety of other mechanical shapes, depending upon the particular application.

In the illustrated embodiment, the distance sensors are laser sensors manufactured by NaiS/Matsushita/Panasonic (Japan), model ANR12821 (high power) or ANR11821 (low power). This particular laser sensor operates based upon perpendicular beam, scattered reflection triangulation using a position sensing diode array. The beam from the light source (in this embodiment, a laser) impinges upon the target perpendicular to the surface of the target, preferably within a relatively small angle. The surface preferably provides a diffuse reflection that is visible to the sensing device over a relatively wide angle. The field of view of the sensing device is focused upon a receptor (a linear optical sensor in this embodiment), the output of which is interpreted to determine the displacement of the target surface within the field of view. The geometry of the light path therefore forms a right triangle with light from the light source traveling along the vertical edge and reflected light of the return path traveling along the diagonal. The distance between the sensor and the target may then be calculated using the Pythagorean theorem.

Although the distance sensors are described in the illustrated embodiments as three laser sensors, it is appreciated that other types and numbers of distance measuring sensors may be used. For example, there are several different techniques and methods utilized by commercial laser distance sensors. These include scattered light triangulation, reflective triangulation, perpendicular and angled beam triangulation, time delta, interference pattern deciphering, CCD array sensors, position sensing diode sensors, position sensing photoresistor sensors, etc. It is anticipated that a variety of optical and non-optical based distance measuring sensors may be suitable as well. It is preferred that the distance sensors be of the non-contact type such that there is no contact between the distance sensor and the workpiece or other target object for which the distance to the target object is being measured.

In the embodiment of FIG. 6A, the heads 510b, 510r and 510y of the laser sensors are positioned in an equilateral triangular placement which facilitates a three point plane distance determination for measuring the height of a surface such as a wafer surface. As explained in greater detail below, the laser heads may be readily repositioned to other placements including an in-line placement for blade motion mapping (FIG. 6B), and a modified right triangle placement (FIG. 6C) for on-blade measurements.

Sensor Calibration

In another aspect of the illustrated embodiments, the metrology cassette 410 includes a precision internal reference surface which defines a reference plane 520 (FIG. 5) which provides fixed reference points from which all measurements may be gauged. It is fixed at the top of the cassette whereas the laser sensors are fixed to the bottom. The laser sensor light beams 522 are intercepted by the reference surface 520 when no wafer is present inside the metrology cassette 410 and are reflected by the surface 520 back to the laser heads of the laser sensor.

In the illustrated embodiment, the metrology cassette 410 is manufactured so that the reference surface 520 is relatively flat and parallel with respect to the base plane 220 of the platform 200 of the cassette handler to a relatively high degree of precision. All subsequent distance measurements of the wafer can be made as offsets to this reference surface 520. Because of the effects of temperature and aging of electronics, the output of the laser sensors can often vary over time. Thus, the actual value of the laser measurements of the distance D.sub.REF between the laser sensors and the reference surface 520 can also vary over time even though the actual distance remains fixed. However, because all subsequent distance measurements of the wafer are made as offsets to this reference surface 520, whatever value the lasers determine the distance D.sub.REF between the laser sensors and the reference surface 520 to be, that value is considered to be the "zero" distance. Any subsequent measurement of wafer position is calculated as the difference or offset D.sub.OFF between the measured reference distance D.sub.REF and the measured wafer distance D.sub.WAF Hence, calibrating the laser sensors is simply a matter of turning the laser sensors on and after a sufficient warm up time, noting the measured reference distance D.sub.REF and assigning that value as the "zero" distance.

For example, in the illustrated embodiment, once the cassette alignment tool system 400 has powered up properly the operator will see three (3) red laser light s