US3669431A

US3669431A - Boat pulling apparatus for diffusion furnace and method

Info

Publication number: US3669431A
Application number: US109232A
Authority: US
Inventors: Andris Lenss; Lionel A Kirton
Original assignee: Signetics Corp
Current assignee: Signetics Corp
Priority date: 1971-01-25
Filing date: 1971-01-25
Publication date: 1972-06-13
Anticipated expiration: 1989-06-13

Abstract

Boat pulling apparatus for use with a diffusion furnace having motive means, means connecting the motive means to the boat, and means for controlling the operation of the motive means whereby the boat is withdrawn at a predetermined rate of speed from the diffusion furnace.

Description

United States Patent Lenss et al. [4 June 13, 1972 [54] BOAT PULLING APPARATUS FOR 2,774,588 12/1956 Oita ..263/47 R DIFFUSION FURNACE AND METHOD 3,183,130 5/1965 Reynolds et al ..263/47 R 3,604,694 9/ 1971 Muller ..263/47 R [72] Inventors: Andras Lenss, Sunnyvale; Lionel A. Klrton,

saratoga both of Cahf' Primary Examiner-John J. Camby Assignee= signetics p i ny lif- Anomey-Flehr, Hohbach, Test, Albritton & Herbert [22] Filed: Jan. 25, 1971 [57] ABSTRACT [211 Appl. No.: 109,232

Boat pulling apparatus for use with a diffusion furnace having motive means, means connecting the motive means to the ..263/28,F22t 37Z:,/;/70l3 boat, and means for controlling the operation of the motive 58] Fieid 4 l 47 R means whereby the boat is withdrawn at a predetermined rate ofspeed from the diffusion furnace. [56] References Cited UNITED STATES PATENTS 11 Claims, 7 Drawing Figures 248,801 10/ 1881 Sebillot ..263/28 PATENTEDJUH 1 3 I972 SHEET 1- BF 4 Lu fl a? 84 INVENTORS F Apdris Lenss BY Lionel A. Kirfon 9 55m, Wing WfZM/LW Attorneys PATENTEDJUN-13 I972 SHEEI 2 I}? 4 1N VENTORS s y e m m m m 6 A $1 .54. Wn n.m AL

PATENTEDJUN 12 m2 3; 669 ,431

Andris Lenss Lionel A. Kirfon AMA W,m4

- xmorneys BACKGROUND OF THE INVENTION In the past, boats have been inserted manually and withdrawn manually from the tube in the diffusion furnace. In withdrawing or pulling out the boat, it normally has been necessary to pull out the boat at a relatively slow rate as, for example, in 4 to 6 minutes, to prevent warping of the wafers which have been diffused. In pulling out the boat, it has been necessary for the operator to stand in front of the diffusion furnace which gives off considerable heat which makes it uncomfortable for the operator and thus makes it more difficult for the operator to pull out the boat at a uniform rate. There is, therefore, a need for a new and improved method and apparatus for pulling out boats from diffusion furnaces.

SUMMARY OF THE INVENTION AND OBJECTS The boat pulling apparatus is for use with a diffusion furnace of the type which has a horizontally disposed elongate tube open at one end and adapted to have a boat inserted therein for movement longitudinally of the tube. The boat pulling apparatus consists of motive means and means for connecting the motive means to the boat and means for controlling the motive means so that the boat is withdrawn from the tube at a predetermined rate. The means connecting the motive means to the boat includes an elongate chain comprised of a plurality of interconnected links. Means is provided which is adapted to support the chain in a generally horizontal position lying in the same general plane as the bottom portion of the tube. The links in the chain are formed of quartz. The chain is formed with means which facilitates breaking the boat away from the tube when it is desired to remove the same.

In the method, the boat is removed at a predetermined rate from the diffusion tube. The pulling can be initiated automatically after a diffusion operation has been completed.

In general, it is an object of the present invention to provide a boat pulling apparatus and method which makes it possible to remove boats from diffusion furnaces at a predetermined rate.

Another object of the invention is to provide a boat pulling apparatus and method of the above character which substantially reduces or minimizes the warping of the wafers carried by the boats.

Another object of the invention is to provide a boat pulling apparatus and method of the above character which utilizes a consistent pulling rate.

Another object of the invention is to provide a boat pulling apparatus and method of the above character in which the pulling does not vary from one operator to another.

Another object of the invention is to provide a boat pulling apparatus of the above character which is relatively simple and inexpensive to manufacture.

Another object of the invention is to provide a boat pulling apparatus of the above character which can readily withstand high temperatures encountered in the difi'usion furnace.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front elevational view of a diflusion furnace having a boat pulling apparatus incorporating the present inven' tion mounted thereon.

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2.

FIG. 4 is an enlarged cross-sectional view taken along the line 4-4 of FIG. 2.

FIG. 5 is a cross-sectional view taken along the line 5-5 of FIG. 2.

FIG. 6 is a cross-sectional view taken along the line 6-6 of FIG. 2.

FIG. 7 is a cross-sectional view taken along the line 7-7 of FIG. 4.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT The boat pulling apparatus 11 incorporating the present invention is particularly adapted for use with a diffusion furnace 12 of a conventional type. The diffusion furnace is provided with a housing which includes a front wall 13 that is provided with an opening 14 therein. A plate or bulkhead 16 is secured to the front wall 13. The bulkhead I6 is provided with an opening 17 which opens into the opening 14. The diffusion furnace I2 is also provided with an elongate tube 18 formed of a suitable material such as quartz which is disposed horizontally within the diffusion furnace and is supported in the diffusion furnace so that it is in general alignment with the opening 14in the front wall 13 and also the opening 17 in the bulkhead 16. As can be seen particularly'from FIG. 2, the front end of the tube 18 has an open end 19 which is disposed slightly to the rear of the front wall 13. The tube 18 is of such a size that it can accommodate boats of a type conventionally used for diffusion operations.

The boat 21 can take various forms. For example, it can be in the form of a carrier 22 which carries a plurality of cassettes 23. The carrier 22 can be fonned of a suitable material such as quartz; for example, it can be formed of a long quartz rod 24 which has been bent to an elongate U with both legs of the U being parallel and of the same length. Thus, there is provided a loop 26 in the rod 24 and two spaced parallel legs 27. At spaced intervals, laterally extending pieces 28 formed of a suitable material such as square quartz rod are mounted between the legs 27. The pieces 28 have slots 29 formed therein extending laterally of the legs 27 which are adapted to receive test wafers between the cassettes.

Each of the cassettes 23 consists of a rectangular structure 31 formed of a suitable material such as square quartz rod. The rectangular structure is provided with spaced parallel sides 32 and spaced parallel ends 33. The sides 32 are provided with a plurality of spaced slots 34 which are adapted to receive the sides of wafers 36 (see FIGS. 4 and 7). The rectangular structure 31 is supported by a plurality of semi-circular members 37 also formed of a suitable material such as cylindrical quartz rod. A rectangular quartz member 38 is mounted inside the semicircular members 37 spaced at the lower end of extremity of the same and spaced equi-distant between the sides 32. The member 38 is provided with a-plurality of upwardly facing slots 39 which are in alignment with the slots 34 provided in the sides 32. In order to facilitate positioning of the cassette 23 upon the carrier 22, the pair of cylindrical rods 41 are secured to the semi-circular member on the outer surfaces of the same on opposite sides of the rectangularmember 38. These rods 41 are adapted to rest upon the carrier 22 as shown particularly in FIGS. 4 and 7. As can be seen from FIG. 7, the cassettes are each adapted to carry a plurality of spaced wafers 36 which are disposed in a direction which is at right angles to the longitudinal axis of the large quartz tube 18. It also can be seen that the carrier 22, the cassettes 23 with the wafers therein are adapted to be readily positioned within the open end 19 of the tube 18 so that diffusion operations can be carried out in a conventional manner.

The boat pulling apparatus 11 is provided for removing the boat 21 from the tube 18 and consists of an L-shaped main support bracket 51 which is secured to the bulkhead 16 in such a manner that it can be adjusted vertically. Thus, there has been provided screws 52 with washers 53. The screws 52 extend through elongate slots 54 provided in the L-shaped main support bracket 51. The screws 52 also extend through holes 56 provided in the bulkhead and are threaded into a reinforcing plate 57 which is secured to the bulkhead 13 by suitable means such as welding. The elongate slots 54 permit vertical adjustment of the main support bracket relative to the opening 17 provided in the bulkhead.

As can be seen, the main support bracket extends outwardly in a horizontal direction from the bulkhead. A generally horizontal tray support member 61 is provided with a depending side portion 61a. Depending side portion 61a is provided with a pair of slots 62 which receive screws 63 which are threaded into the mainsupport bracket 51. As can be seen from FIG. 3, the position of the tray support member 61 relative to the main support bracket 51 can be adjusted in a vertical direction because of the slots 62. A tray support 66 formed of a suitable material such as stainless steel is secured to the tray support member by suitable means such as crews 67 which are countersunk in the tray support 66 and are threaded into the tray support member 61. As can be seen from FIG. 3, the tray support member 61 and the tray support 66 extend into the diffusion furnace through the opening 17 in such a manner, that the tray support 66 is generally horizontal and slightly underlies the front end of the tube 18. The tray support 66 is generally planar as shown in FIG. 3 but is provided with upturned and outwardly extending side wall portions 66a which are inclined at an angle of approximately 45 with respect to the horizontal. The tray support 66 is also provided with a tab 68 at the outer extremity thereof formed integral therewith and which extends downwardly and outwardly at an angle of approximately 45. The tab 68 is provided with an elongate or oval-shaped hole 69 which is utilized for a purpose hereinafter described.

The boat pulling apparatus 11 also consists of a chain 71 which is formed of a plurality of interconnected links 72. The chain 71 is formed of a material which can be placed within the diffusion furnace. Thus, in the present embodiment of the invention, the links 72 of the chain have been formed of quartz. By way of example, such a chain can be formed by tak ing 6 mm. quartz rod which is 3 or 4 ft. in length and winding it about a carbon rod approximately one-half inch in diameter. To do this, the carbon rod is inserted in a lathe and istumed slowly. The quartz rod is heated and is wrapped about the carbon rod to form a helix. Each turn of the helix is cut apart. The

individual turns are then looped together and have their ends fused to provide the interconnected links for the chain.

Particularly novel means is provided for securing the chain to the boat and consists of a hook-like member 73 which is also formed of a suitable material such as quartz. The hooklike member 73 is provided with an eye 74 which is interconnected with the last link 72 at one end of the chain 71. The hook-like member 73 is provided with a hook 76 which is formed integral with the eye 74' and lies in the same general plane as the eye. A rod-like cross member 77 which serves as a rocker or fulcrum is secured to the hook 76 generally intermediate the ends of the hook. As can be seen, the cross member 77 serves to position the hook 76 in such a manner that its outer extremity extends upwardly in a vertical direction (see FIG. 4), so that it will stay engaged with the loop 26 of the carrier 22 of the boat 21.

A clevis 81 formed of a suitable material such as stainless steel is secured into the last link 72 of the other end of the chain 71 and has connected thereto a stainless steel cable 82. The cable 82 passes over an idler pulley 84 which is provided with a centrally disposed annular groove 86 in which the cable 82 is adapted to travel. The pulley 84 is provided with spaced parallel flanges 87' which are adapted to accommodate the quartz chain 71. Thus, the idler pulley 84 is provided with means whereby it can accommodate the stainless steel cable 82 and also the chain 71. The idler pulley 84 is rotatably mounted upon a pin 88 which is carried by a U-shaped support member 89. The pin 88 is inserted through a hole 89 in the U- shaped member and is then extended through the idler pulley 84 and is then seated in a hole92 in the U-shaped support member. The U-shaped support member is then secured to the main support bracket 51 by screws 94, which also hold the pin 88 in place. 7

Motive means is provided for retracting the cable 82 after it has travelled over the pulley 84 and consists of an electric motor 96 of a suitable type such as a 60 cycle a.c. motor which has an output shaft 97 that rotates at a suitable speed such as three revolutions per minute. The motor 96 is mounted on the mounting plate 98 by screws 99. The mounting plate 98 is secured to the main support bracket 51 by screws 101.

A motor clutch key 102 is secured to the shaft 98 by a set screw 103. The motor clutch key 102 is provided with a cylindrical portion 102a which is rotatably mounted in one end of a flanged driver pulley 104. A driver pulley key 106 is also mounted in the pulley and is secured thereto by a pin 107 extending through the pulley 104 and the key 106. Cooperative mating means is carried by the driver pulley key 106 and the motor clutch key 102 to permit a driving relationship to be established between the same. This means consists of a protruding male portion 102b provided on the motor clutch key 102 and a female slot 108 provided on the driver pulley key 106.

Means is provided for supporting the driver pulley key 106 to permit rotational and slidable movement of the same and consists of an L-shaped support arm 111 which is secured to the motor mounting plate 98 by screws 1 12. A flanged bushing 113 is mounted in a hole 114 provided in the arm 111. The driver pulley key 106 is mounted in this bushing 113. Means is provided for yieldably urging the driver pulley key 106 and the driver pulley 104 mounted thereon to the right as viewed in FIG. 5 and consists of a spring 116 which has one end engaging the driver pulley 104 and has the other end engaging a Teflon washer 107 which engages the arm 111. Means is provided for shifting thedriver pulley key 106 against the force of the spring 116 and consists of a cam member 118 which is pivotally mounted on the driver pulley key 106 by a pin 1 19. The cam member 118 is provided with a curved cam surface 121 as shown particularly in FIG. 5. A handle 122 has one end threaded into the cam member 118 as shown in FIG. 5 and is provided for manually operating the .cam member.

A housing 126 covers the motor 96 and is secured to the motor mounting plate 98 by screws 127. The cable 82 is secured to the driver pulley 104 in a suitable manner such as by extending the cable through a hole 128 (see FIG. 5), the driver pulley end then forming a knot in the cable so that it will not slip through the hole.

Means is provided for controlling the operation of the motor 96 and includes a control box 131 which is mounted on the bulkhead 16. Such a control box can include a timer 132 of a conventional type which will, after a predetermined time has elapsed, operate contacts to open the same. Such a control box also includes

terminals

133 and 134 which are connected to the contacts controlled by the timer and which are connected by wires 136 to the motor 96. The control box also includes a start push button 137. The housing 126 can also have mounted thereon an off-on switch 138 a fuse 139 and a light 141 to indicate when power is being supplied to the motor. A microswitch 143 is mounted on the tray support and is adapted to be operated by the chain 71.

A door 146 is provided for closing the opening 17. The door 146 is mounted on the bulkhead 16 in such a manner that it can be opened to permit removal and cleaning of the cylindrical tube 18. Thus, the door is mounted on a rod 147 by screws 148. The rod 147 is provided with cylindrical ends which are disposed in inclined slots 149 provided in blocks 151that are secured to the bulkhead 16 by suitable means such as screws (not shown). The door 146 is provided with an opening 152 which opens through the bottom end of the door to accommodate the tray support and the chain 72. From the construc tion shown, it can be seen that the door 146 can either be positioned so that it will remain open as shown in FIG. 3 or, alternatively, will swing closed. I

Operation and use of the boat pulling apparatus in performing the method may now be briefly described as follows. Let it be assumed that it is desired to load the diffusion furnace with a boat consisting of the carrier with a plurality of cassettes on the carrier and with a plurality of wafers carried by each of the cassettes. The operator places the loaded boat with the wafers on the tray support 66. The operator, either before or after placing the boat on the tray support, operates the handle 22 to move it from the solid-line position to the broken-line position shown in FIG. 5 to disengage the driver pulley key from the motor clutch key. The operator is then free to pull the chain 71 which will cause the cable 82 to unwind from the driver pulley 104. The operator continues to pull the chain 71 until it is possible for the operator to hook the hook-like member 73 into the loop 26 of the carrier 22 as shown in FIG. 4. The operator then uses a push rod to push the boat from the tray support 66 into the open end 19 of the cylindrical tube 18 so that it is substantially centered along the length of the tube 18. As this is occurring, the chain 72 is pulled with the boat and additional cable is unwound from the pulley 104.

After the boat has been pushed into the proper position, the operator makes sure that the hook is generally in the position shown in FIG. 4. In other words, the part of the hook that is attached to the chain is in a raised position. The operator then operates the lever arm 122 to permit the spring to urge the driver pulley key into engagement with the motor clutch key or, in other words, to cause the clutch to become engaged. The desired diffusion operation is then commenced. At the same time, the timer 132 is set so that after a predetermined time in which the desired diffusion operation has been carried out, the boat will be removed from the tube 18. With the use of the timer 132 after the predetermined time, contacts are closed which cause energization of the motor 96. As the motor 96 starts operating, it tensions the cable 82 and the chain 71. As the chain is tensioned, it will pull downwardly on the eye 74 using the cross member 77 as a fulcrum. This will case the hook to lift upwardly on the looped portion 26 of the boat to cause the boat to break loose from the quartz tube 18 in the event it may have become stuck during the heating occurring during the diffusion operation. As soon as the boat has been broken loose, the hook-like member 73 will assume a horizontal position and will start pulling out the boat. The boat will be pulled out at a predetermined uniform rate of speed as, for e xample, one foot per minute longitudinally of the tube. It is important that the boat be pulled slow enough so that the wafers will not warp. The wafers must come into contact very gradually with the cooler air. It is desirable that the temperature transition be gradual. The boat is pulled out of the tube 18 and onto the tray support 66 and this movement continues until the chain 71 engages the Microswitch 143 to operate the same .to deenergize the motor 96. The boat can them remain on the tray support 66 to cool sufficiently so that it may be handled by hand. As soon as this is the case, the operator takes the hook-like member 73 and removes it from the tray and places it in the hole 69 on the tray support. The boat can then be removed and taken to a work station where it can be unloaded.

From the foregoing, it can be seen that the boat pulling apparatus is semi-automatic. It is only necessary for the operator to place the boat in the diffusion furnace and then to place the timer 132 in operation. The boat will be removed automaticlly from the diffusion furnace and the motor will be deenergized when it is completed. This makes it possible for the operator to work with several diffusion furnaces at the same time without being concerned as to when the difiusion operation in each should be stopped. This makes it possible to produce a more consistent product without danger of warping and the like. The boat pulling apparatus also makes it possible to over-' come one of the most tedious operations which heretofore consisted of the manual removal at a slow rate of the boat from the diffusion furnace.

It is possible with the apparatus shown to stop the pulling out operation at any desired time merely by operating the switch 138.

It is apparent from the foregoing that there has been provided a boat pulling apparatus and method which makes it possible to remove boats from diffusion furnaces at a rate and at rates which will not vary from one predetermined operator to another, and thus make it possible to obtain a more uniform product. The use of the quart pulling chain makes it possible for the pulling apparatus to be utilized in high temperatures. It also will not contaminate the quartz tube in which the diffusion operation is carried out. The apparatus is constructed in such a way that the quartz chain is not contaminated. This is made possible because all the parts which can possibly come in contact with the quartz chain are formed of stainless steel.

We claim:

1. In a boat pulling apparatus for use with a diffusion furnace of the type having a horizontally disposed elongate tube open at one end and adapted to have a boat inserted therein and movable longitudinally of the tube, support means adapted to be disposed in the vicinity of the open end of the tube, said support means including a horizontally disposed tray support lying in the same general plane as the bottom portion of the tube, a chain formed of a plurality of interconnected links, means carried by one end of the chain adapted to be secured to the boat, motive means carried by the support means, and means connecting the other end of the chain to the motive means whereby as the motive means is operated the chain and the boat attached thereto are withdrawn at a predetermined rate.

2. Apparatus as in claim 1 wherein said chain is formed of material which can withstand the high temperatures encountered in a diffusion furnace.

3. Apparatus as in claim 2 wherein said chain is formed of interconnected quartz links.

4. Apparatus as in claim 1 wherein said means securing said chain to said boat includes a hook-like member and fulcrum means carried by the hook-like member positioned so that when a pulling force is applied to the chain, the hook portion of the hook-like member is moved upwardly to lift the boat upwardly away from the tube to thereby break the boat away from the tube in the event that the boat has become stuck to the tube during a diffusion operation.

5. Apparatus as in claim 1 together with timing means, said timing means including contact means and means operated by the timing means for causing operation of said contact means to deenergize the motive means after a predetermined period of time.

6. Apparatus as in claim 5 together with means carried by the support means for deenergizing the motive means.

7. Apparatus as in claim 1 wherein said means connecting the other end of the chain to the motive means includes a pulley, means for securing the pulley to the motive means and means connecting the chain to the pulley.

8. Apparatus as in claim 1 wherein said support means includes a tray having a generally horizontal portion and .upwardly extending side walls.

9. Apparatus as in claim 1 together with an idler pulley mounted on said support means and wherein said chain is adapted to travel over said idler pulley.

10. In a method for removing a boat from a diffusion furnace of the type having a horizontally disposed elongate tube open at one end and adapted to have a boat inserted therein and movable longitudinally of the tube, inserting the boat in the tube, completing a diffusion operation, removing the boat from the tube at a predetermined rate of speed and stopping movement of the boat after the boat has reached a predetermined position out of the tube.

11. A method as in claim 10 together with the step of determining the period of time that the boat is in the diffusion furnace, and automatically removing the boat from the furnace after the predetermined time has elapsed.

Claims

8. Apparatus as in claim 1 wherein said support means includes a tray having a generally horizontal portion and upwardly extending side walls.