GB2138775A - Transferring e.g. semi- conductor wafers between carriers - Google Patents

Abstract

A mechanism for transferring semi-conductor wafers 35 between carriers 28, 29 includes an elevator means, e.g. a rod 34 which projects up into a carrier and lifts wafers to a position where they may be temporarily suspended by a pair of opposed wafer support elements 32, 33 which are movable toward each other and have elements which are inserted below the horizontal centerline of the wafers to support the wafers. The carriers are mounted on a horizontally reciprocable carriage 27, and carrier 29 is moved into the position vacated by carrier 28 to receive wafers therefrom, the wafers being lowered into position again using the rod 34. <IMAGE>

Description

SPECIFICATION Robot This invention relates to robots and more particularly to robots for transferring wafers.

In recent years wafers have been transferred between furnace boats and process carriers by automatic machines, such as the robot nnanufactured by Ruska Instrument Corporation of Houston, Texas, which has been used since 1981 and which is shown in our copending application Serial No. 265,633, filed May 20, 1981 for "Transfer Apparatus".

The principal object of this invention is to provide an improved version of the robot shown in our above identified application.

Another object is to reduce the possibility of contamination of wafers during handling.

Another object is to be able to lift wafers from a dissimilar pair of carriers with a single elevator.

Another object is to be able to easily adjust the travel of the transfer system and the spacing of the arms of the suspending means as well as the elevation of the suspending means to accommodate different sized wafers in the same robot.

Another object is to be able to control the travel of the transfer system and the elevator to accomodate different designs and sizes of carriers.

Another object is to be able to handle wafers in any desired design of carrier.

Another object is to move wafers a minimum distance and gently transfer them between carriers.

Another object is to provide for easy adjustment of the transfer arms of the suspending machine and make each independently operable.

Another object is to translate the wafer carriers relative to the suspension means instead of translating the suspension means to eliminate the possibility of the translating system causing contamination of the wafers.

Other objects, features and advantages of this invention will appear from the drawings, the specification and the claims.

In the drawings wherein an illustrative embodiment of this invention is shown, and wherein like reference numerals indicate like parts: Figure 1 is a front elevational view of a robot embodying this invention; Figure 2 is a side elevational view taken along the lines 2-2 of Figure 1; Figure 3 is a top elevational view taken along the lines 3-3 of Figure 1; Figure 3 is a detail view on an enlarged scale taken along the line 3A of Figure 3; Figure 4 is a fragmentary front elevational view illustrating translation of the carriage for the wafer carriers to a second position:: Figure 5 is a bird's eye view taken along the lines 5-5 of Figure 1; Figure 6 is a front elevational view taken along the lines 6-6 of Figure 5; Figure 7 is a worm's eye view taken along the lines 7-7 of Figure 6; Figure 8 is a worm's eye view of a portion of the structure shown in Figure 6 taken along the lines 8-8 of Figure 6; Figure 9 is a front elevational view on an enlarged scale of a portion of the structure shown in Figure 6 illustrating the cam in one elevated position and in dashed lines in a second elevated position; Figure 10 is a view of the cam of Figure 9 and its associated microswitches taken at 90 to Figure 9; Figure 11 is a fragmentary worm's eye view of the carriage translation mechanism and the slot through which the mechanism is attached to the carriage;; Figure 12 is a fragmentary front elevational view taken along the lines 12-12 of Figure 11 showing the carriage translation device and a portion of the carriage in dashed lines and the lower portion of the stop rod for controlling downward movement of the suspending means; Figure 13 is a fragmentary side elevational view similar to Figure 2 and on an enlarged scale of the suspending means; Figure 14 is a fragmentary front elevational view of the suspending means and on an enlarged scale as compared to Figure 1; Figure 15 is a top plan view on an enlarged scale as compared to Figure 3 of the suspension means and illustrating the indexing means for indexing the suspension means in a fore and aft direction, as illustrated by the arrows; and Figures 16 through 21 are successive schematic illustrations of transferring wafers between a process carrier and a furnace carrier.

Referring first to Figures 1-3 and 16-21, the illustrated robot is mounted on and in a cabinet 25 which contains a microprocessor, not shown, and the control panel, indicated generally at 26, for controlling operation of the robot.

The robot includes a carriage, indicated generally at 27, for horizontal translation to alternately position the process boat 28 and the furnace boat 29 below the suspension means, indicated generally at 31. The suspension means 31 reciprocates vertically and has a pair of suspension arms, indicated generally at 32 and 33, which are movable toward and away from each other to support wafers therebetween.

An elevator, indicated generally at 34 (see Figures 17 and 20), is extensible up through the wafer carriers 28 and 29 to transfer wafers 35 between the carriers 28 or 29 and the suspension means 31.

Figures 16-21 illustrate one step in the operation. As shown in Figure 16, a process boat 28 has been placed on the robot and contains wafers 35. An empty furnace carrier 29 is also in position. The robot is activated and the suspension means arms 32 and 33 move away from each other, as shown in Figure 17, and the elevator 34 lifts the wafers 35 up to a position between the suspension arms 32 and 33. As shown in Figure 18, these arms are then moved toward each other and the suspension means moved upwardly to support the wafers between the arms and lift the wafers from the carrier 28.

The carrier carriage 27 is then shifted to the left, as shown in Figure 19, to position the furnace carrier 29 below the wafers 35. The suspension means is then lowered and the elevator 34 raised to support the wafers, as shown in Figure 20. Thereafter the arms 32 and 33 are opened, as shown in Figure 20, to release the wafers. The elevator 34 then lowers to transfer the wafers to the furnace boat 29.

While the suspension system illustrated moves vertically to position the suspension arms 32 and 33 immediately above each of the boats, it will be appreciated that the boats and/or the carriage could be movable vertically and the suspension system held in fixed position and accomplish the same results.

As will be understood by those skilled in the art, the reversed operation may also be carried out to transfer wafers from the furnace carrier to the process carrier and the robot is provided with an indexing system for relatively moving the suspension means 31 and the carriage so that an additional group of wafers may be transferred from a third carrier into one of the carriers to thus transfer the contents of two carriers into a single carrier.

For instance, two carriers each containing twenty-five wafers may have their contents transferred into alternate slots of another carrier, as will be understood by those skilled in the art.

From Figures 17, 18 and 20 it will be noted that the wafers have a flat side. There is provided on the side of the cabinet 25 an aligner, indicated generally at 37, on which a carrier may be positioned and the aligner activated to align all of the wafers 35 with their flat sides on the bottom, as shown in Figure 20.

Referring particularly to Figures 1-4, the carriage 27 includes a slide block 38 mounted for sliding reciprocal mnovement on guide bar 39 to alternately position the wafer carriers, such as 28 and 29, below the suspending means.

A carrier, indicated generally at 41, is supported on the slide bar. The carrier may take any desired form and is designed to support a wafer carrier, such as the furnace boat 29.

For this purpose the carriage support has a platform 42 on which a furnace carrier may rest. Referring particularly to Figure 3, the carrier support 41 has a back stop 40 against which the boat is urged by the crank arm 43 at the front of the carrier support. This arm is rotated between the lower out of the way position illustrated and an upper position in which it engages the wafer carrier 29 and holds the wafer carrier firmly against the stop 40. The crank arm 43 is rotated by the motor 44 acting through the slip clutch 45. As best seen in Figure 3, a switch 46 is depressed by the rear of the carrier 29 when the carrier is urged to the rear of the machine to signal the microprocessor that the furnace boat is in proper position on its carrier.

As the furnace carrier 29 is normally made of quartz and it relatively light, it is preferred to provide the crank arm 43 for ensuring that the carrier stays in proper position on its support.

At the other end of the slide block 38 a support 47 is provided for a wafer carrier. The carrier illustrated is a process carrier. Process carriers are normally made of plastic and are much heavier than furnace carriers and their weight is depended upon to hold the carrier in position on the support 47. The platform 48 on which the carrier rests is contoured to fit the lower surface of the carrier 28 and, as illustrated, the mating contours of the platform 48 and the carrier hold the carrier in position and in alignment. A stop, such as illustrated at 49, is engaged by the end surface of the carrier 28 and correctly positions the fore and aft relationship of the carrier with the support 47. A suitable switch, such as indicated at 49a, is depressed when the carrier 28 is properly positioned to signal the microprocessor that the process carrier is in position.

A means is provided for reciprocating the slide block 38. Preferably, this means is substantially inside of the cabinet 25 to isolate it from the wafers as much as possible to thus reduce the possibility of contamination of the wafers by the translating device and to reduce the possibility of injury to operators by exposed niechanism.

The translating system for the slide block 38 is illustrated in Figures 6, 7, 11 and 12.

Suspended below the top 51 of the cabinet are journal blocks 52 and 53. These journals support the horizontally extending lead screw 54 which is driven by motor 55 through slip clutch 56.

A nut 57 travels on the lead screw 54 with translation thereof and is secured through its support plate 5a to an angle member 59 which carries the standard 61 (which extends through slot 60) to which the slide block 38 of the carriage is attached, as best seen in Figures 5 and 12. Thus, by driving the motor 56 in opposite directions, the carriage 27 is reciprocated to position the support for the wafer carriers in two alternate positions in which the wafer carriers on supports 41 and 47 are positioned below the suspending means.

Suitable stops 62 and 63 depend from the cabinet top and preferably carry swiitches 64 and 65 to signal the micro-processor that the carriage is at the end of its travel.

The system for shifting the gripping means vertically is shown in Figure 2.

A standard 66 extends vertically upwardly from the cabinet top 51 and carries a slide bar, shown in dashed lines at 67. A vertically movable slide block 68 is supported on the slide bar 67. A yoke 69 is carried by the slide block 68 and extends rearwardly on each side of the standard 66. The yoke 69 carries a nut 71 which runs on the lead screw 72 supported in a journal block 73 at its upper end and a journal block 74 at its lower end. The lead screw 72 is driven through a brake 75 and clutch 76 by a motor shown in dashed lines at 77.

Control of the motor and other equipment is effected through leads, such as the flexible lead 78 to the motor.

Mounted on the rear of the standard 66 is a switch rod block 79 which supports a slide rod 81 on which the switches 82, 83 and 84 are adjustably mounted. These switches sense the position of the yoke 69 and signal the microprocessor when the yoke is in the full up position and in its two selective down positions where the suspending means is properly positioned relative to a wafer carrier.

Suitable adjustable stops are provided to control the vertical movement of the slide block 68. At the top of the standard 66 an adjustable stop 85 is engaged by the yoke 69 at the top of its travel. The housing 86 has a slot 87 in its upper end to permit the yoke 69 to engage the stop 85.

Downward travel of the slide block 68 is controlled by a pair of rods 88 and 89 (see Figure 4).

Downward travel of the slide block 68 in its full lower position where the suspending means cooperates with the low level furnace carrier is controlled by the stop 89. The stop 89 is a rod which is threadedly carried in the top 51 of the cabinet and engages a stop block 91 carried on the slide block 68 (see Figure 4). This stop could be carried by either the table or the block and a slight adjustment may be provided for by moving the block 91 on the slide block and by substituting different length stops, particularly for large differences in desired travel. While this stop rod could be carried by or engage the carriage 38, it is simpler and preferred to permit the bar to be carried by or engage the top of the cabinet.

Control of downward movement of the slide block 68 to stop the block and position the suspension means relative to a high wafer carrier, such as carrier 28, is provided for by the stop rod 88 which is carried by a mounting block 92. The rod 88 depends from the mounting block and is in register with a hole 93 extending through the top 51 of cabinet 25 (Figure 5). The stop rod 88 is free to extend through this hole 93 and to move downwardly when the slide block 68 is moving down to associate the suspension means with the furnace carrier 29, as shown in Figure 4. In this position of the carriage the stop 89 arrests downward movement of the slide block.

When the downward movement of the slide block 68 is to be arrested to position the suspension means with the tall wafer carrier 28, the carriage 27 is provided with a means for arresting downward movement of the stop rod 88. This means or stop plate may be provided in any desired manner, such as by the stop plate assembly shown in Figures 7, 11 and 12.

The stop plate could be a simple plate passing under the hole 93 in cabinet top 51 when the carriage 27 is in the position shown in Figure 1. Due to interference of parts as the carriage reciprocates, it is preferred to provide a swinging stop plate 94 carried on the support plate 58 and swinging about pivot 95.

Due to the downward force exerted by the motor on the vertical slide block 68, it is preferred to support the stop plate 94 and for this purpose a stepped plate 96 is carried on the under surface of cabinet top 51. The stepped portion of plate 96 which overlies the hole 93 is spaced from the cabinet top 51.

As the carriage 27 moves to the right, as viewed in Figure 7, the stop plate 94 strikes the stepped plate 96 causing the plate 94 to rotate about the pivot 95 to the position shown in Figure 11 and to at the same time pass between the cabinet top 51 and the spaced portion of plate 96, as shown in Figure 11, so that the stop plate 94 now underlies the hole 93 and is supported by the stepped plate 96. In this position the downward force exerted by the slide block is transmitted through the stop plate 94 to the step plate 96 and thus to the cabinet top 51, and substantially no downward force is absorbed by the carriage 27.

The stop plate 94 is urged to the position shown in Figure 7 where it will not interfere with reciprocation of the carriage by the spring 97.

Referring now particularly to Figures 2, 3, 4, 13, 14 and 15, the suspending means 31 and its mounting are illustrated. The suspending means is supported and carried on the slide block 68 for vertical movement. Secured to the slide block 68 is an angle support 98 which supports the slide bed 99. Mounted in this bed for fore and aft sliding movement is the slide block 101 (Figure 15). Above the slide block a cam motor bracket 102 supports a motor 103 and a slip coupling 104. The slip coupling carries a yoke 105 having its fingers 106 and 107 on opposite sides of the cam follower 108, which is mounted on the slide block 101.Thus, with rotation of the motor 1 Q3 in opposite directions the slide block 101 is caused to reciprocate fore and aft of the machine, as indicated in Figure 15, between suitable stops to shift the suspending means the distance between the centerline of a pair of adjacent slot ways in the suspending means to position the suspending means for engagement with alternate groups of wafers in the wafer carriers, as will be understood by those skilled in the art.

The slide block 101 supports a spacing bar 109. The two suspending systems, indicated generally at 32 and 33, are secured to the spacing bar. From Figure 14 it will be noted that the spacing bar 109 has a pair of slots 11 2 in which the suspending elements 32 and 33, respectively, are secured by fasteners, one of which is shown in Figure 2 at 11 3. Thus provision is made for spacing the suspending elements 32 and 33 at different points along the spacing bar to permit them to suspend wafers of different diameter.

Referring to the suspending element 33, an adjusting block 114 is secured to the spacing bar 109 and carries the slip coupling 115 and motor 116 which drives through the slip coupling. The output from the slip coupling is to a shaft 117 on which the arm 118 is mounted for rotation between the positions shown in Figures 16 and 17. Such rotation moves the free end of the arm 118 which carries the slotted wafer support 119. Rotation of the arm 118 in a clockwise position, as viewed in Figure 14, is limited by the stop 121 engaging the block 122.

The other support system 32 is a mirror image of system 32 and thus the free ends of the two wafer supports move toward and away from each other to support a plurality of wafers.

As shown in Figure 15, each of the wafer supports 119 has a plurality of vertical slots extending from top to bottom of the supports 119. Every other slot has in its lower section opposed wafer supporting surfaces which extend upwardly and outwardly away from each other. Preferably, these support surfaces conform generally to the curvature of the wafers that they are to support, but it will be appreciated that they do not have to be mirror images of the periphery of the wafer but only need to be an upwardly facing shoulder which will engage the wafer below the horizontal centerline of the wafer and support it against the force of gravity. For a disclosure of a suitable type wafer support, see our copending application for United States patent identified hereinabove.

As in the above identified application, the suspending means could be designed to have the systems 32 and 33 move toward each other in their entirety, or rotate as shown, or in some other manner be capable of moving the supporting surfaces under the wafer. Any desired manner of moving the systems 32 and 33 may be employed to support and release wafers.

The elevator system for lifting the wafers from the wafer carriers is shown in Figures 6 through 9. The elevator system, indicated generally at 34, includes the elevator bar 123 which is raised and lowered from a low position, shown in Figure 6, to a full raised position, shown in Figure 17, and an intermediate raised position, shown in Figure 20.

A vertically extending slide bed 124 is mounted in the cabinet and a slide 125 is vertically reciprocal therein. A rack 126 is carried on the slide 125 and is driven vertically by the motor 127 through the slip coupling 128 and the drive gear 129. Thus, by operating the motor 127 to rotate the drive gear 129 in opposite directions, the elevator bar 123 may be lowered to a full lower position and raised to a full upper position and an intermediate upper position.

To control operation of the elevator, a cam 131 is carried on the rack 126 and has a stop 132 provided by the upper end of the cam and a stop 133 provided by a step in the cam. These two stop surfaces cooperate with a slide block stop 134 which in the position shown in Figures 6, 8 and 9 blocks upward movement of the cam beyond the point at which the upper end of the cam 132 engages the stop 134, as shown in Figure 9. When the motor 127 drives the elevator up to the point that the stop 132 engages the slide block stop 134, the elevator is raised to its intermediate position, at which point the wafers are lifted from the furnace carrier, as shown in Figure 20.

By sliding the slide block stop 134 to an out of the way position, the cam may be driven up to the point where the stop surface 133 on the cam strikes the slide block stop 134. This relationship is shown in dashed lines in Figures 8 and 9 in which the cam 131 is above the slide block stop 134 and when the cam is driven upwardly the stop surface 133 will strike the slide block stop 134. When the slide has been shifted to the left, as viewed in Figure 8, sufficient to clear the upper end 132 of the cam 131, it will be in a position to be engaged by the cam stop surface 133, shown in dashed lines in Figure 8, and arrest upward movement of the elevator bar.

The slide block 134 is suitably supported in a slide bed 136 and is urged to a position overlying the cam 131 by spring 135. The support plate 137 on which the slide bed 135 is mounted has a pivot pin 138 about which the rock arm 139 pivots. The rock arm 139 has a slide point 141 which engages the end face of the slide block 134 and slides there along to shift the block between the solid and dotted line positions shown in Figure 8. The rock arm 139 has a standard 142 which extends up through the upper surface 51 of the cabinet, as shown in Figures 6 and 9, and is engageable by a contact block 143 carried on the carriage 38 (Figure 6). This standard 142 carries an actuator stud 144 which is engaged by the block 143 on the carriage 38 as the carriage moves to the right, as viewed in Figure 6, to position the process wafer carrier 28 below the suspension means.As the carriage moves to this position, the arm 139 is rotated to the position shown in dashed lines in Figure 8 to permit the stop 132 of the cam to bypass the slide block 34 and the cam to move upwardly until the stop 133 engages the slide block 134 and limits further upward movement of the elevator.

By reference to Figure 10 it will be noted that the cam has cam surfaces 145, 146 and 147 which engage, respectively,. with switches 148, 149 and 151 to indicate the vertical position of the elevator system.

It will be apparent that other means of controlling the elevator could readily be utilized, such as, for instance, a stepping motor which would step the cam to the desired position on command from a microprocessor.

While all of the activating motors have been shown to be operable through slip couplings and suitable switches are activated by movement of the several moving parts to signal the microprocessor when the moving part has reached a station, it will be apparent that other shifting means could be utilized in all of these translating systems.

Reference is made to the above identified United States application to illustrate a typical manner of programming the microprocessor to carry out the several functions of the system.

Of course, as the instant invention differs in the elements which are translated and the provision for raising the elevator to two levels instead of one, the system would be different but it would be obvious to one skilled in the art to modify the microprocessor program to carry out the functions of this invention which were earlier explained in conjunction with the sequential operations shown in Figures 16 through 21.

As each sequential step is carried out, as shown in Figures 16 through 21, a switch is energized which signals to the microprocessor that the apparatus has reached the desired position and the microprocessor then signals the next appropriate motor to carry out the next step.

Wafers may be shifted in either direction between any desired design of wafer carriers and the content of two wafer carriers may be transferred to one wafer carrier and vice versa, as will be understood by those skilled in the art.

The foregoing disclosure and description of the invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

Claims (10)

1. A robot for transferring wafers between carriers comprising: suspending means for supporting a plurality of wafers; horizontally movable carriage means having spaced wafer carrier supports for alternately positioning a pair of carriers below said suspending means; elevator means movable vertically for extending up into carriers on said carrier supports and lifting and lowering wafers to and from said carriers to a position where they may be engaged by said suspending means; and means for moving said suspending means and said carriage means toward and away from each other.

2. The robot of claim 1 including means for arresting movement of said suspending means and carriage toward each other at different elevations in response to the carriage means alternately positioning the wafer carrier supports below the suspending means.

3. The robot of claim 1 including means for indexing the suspending means in a horizontal plane perpendicular to the plane of movement of the carriage means.

4. The robot of claim 2 including means for indexing the suspending means in a horizontal plane perpendicular to the plane of movement of the carriage means.

5. The robot of claim 1 wherein the elevator means rises to a first position with the carriage in a selected first position and wherein the elevator means rises to a second position with the carriage in a selected second position.

6. A robot for transferring wafers between carriers comprising: vertically movable suspending means for lifting and lowering a plurality of wafers; horizontally movable carriage means having spaced wafer carrier supports for alternately positioning a pair of carriers below said suspending means; vertically movable elevator means extending upwardly into a carrier on said carriage means and lifting and lowering wafers between said carrier and a position where they may be engaged by said suspending means; means for arresting downward movement of said suspending means at different elevations in response to the carriage means alternately positioning the wafer carrier supports below the suspending means; and means for controlling movement of said elevator means in response to movement of said carriage means to alternately position the pair of carriers below the suspending means.

7. The robot of claim 6 wherein means responsive to vertical movement of said elevator means signals the arrival of said elevator means at said selected elevations.

8. The robot of claim 6 wherein the suspending means includes: a vertical travelling member; a crossbar is mounted at selected vertical positions on said travelling member; and a pair of lifting means are mounted at selected spaced apart points on said crossbar; said lifting means including upwardly and outwardly extending surfaces adapted to engage a wafer at points below the horizontal centerline of the wafer; and means for moving said surfaces horizontally toward and away from each other to engage and disengage wafers.

9. The robot of claim 6 wherein the suspending means includes a pair of arms pivotally mounted at one end for swinging movement about parallel substantially horizontally extending axes and supporting upwardly and outwardly inclined surfaces for supporting wafers by engaging their periphery at points below their horizontal centerline when the arms are pivoted towards each other and releasing wafers when the arms are pivoted away from each other.

10. A robot for transferring wafers between carriers substantially as hereinbefore described with reference to and as shown in the accompanying drawings.