US3046029A - Seed crystal holding chucks - Google Patents

Description

United States Patent cc 3,046,029 SEED CRYSTAL HOLDING CHUCKS Joseph R. Weber, Chicago, and Svend E. Hauritz, Deerfield, Ill., assignors to Hoffman Electronics Corporation, a corporation of California Filed Aug. 7, 1959, Ser. No. 832,379 2 Claims. (Cl. 279-37) The present invention relates to mechanical chucks, and more particularly to chucks able to align the axis of the object being held relative to the axis of the chuck and the shaft which supports the chuck.

In growing crystals, particularly of semiconductor materials such as silicon, it is the practice to dip a single crystal seed of the material into a crucible containing similar material in a molten state. The seed is rotated and with drawn slowly to produce a large single crystal from the molten mass. In the past the seed crystal has been secured to the rotating shaft by a molybdenum wire. If the seed has any shape imperfections it may be supported off the axis of the supporting shaft and upon rotation of that shaft the seed will execute an eccentric motion with a resulting production of a defective crystal or none at all.

Therefore, it is an object of this invention to provide improved supporting means for a seed crystal in crystal growing apparatus.

It is a further object of the present invention to provide a novel seed-holding chuck.

It is another object of the present invention to provide a seed-holding chuck that can position the object being held in axial alignment with the shaft supporting the chuck.

According to one embodiment of the present invention, a chuck is constructed so that as its jaws, which are pivotally connected, approach each other, a clamp that is pivotally connected to one of the jaws engages the object to be held in the chuck and pivots to press the object against the opposing jaw. A sleeve is adapted to slide over the jaws and press them tightly towards each other so that the axis of the object is maintained coaxial with the axis of the chuck and the shaft which supports the chuck.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawings, in which,

FIGURE 1 is a cross sectional view of a chuck accord ing to the present invention.

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

FIGURE 3 is a cross sectional view taken along line 3--3 of FIGURE 1.

Referring now to the drawings, FIGURE 1 shows jaws 11 and 12 pivotally suspended from lift rod 13 by pins 14. The lower extremity of jaw 11 contains guide pin 15 in hole 16. The lower extremity of jaw 12 contains clamp 21 pivotally connected to jaw 12 in opening 22 by pin 23. Sleeve 24 slidably engages lift rod 13 and jaws 11 and 12. The lower extremity of the inner surface of sleeve 24 is tapered so as to mate slidably with the upper extremity of the outer surfaces of jaws 11 and 12. The upper extremity of the inner surface of sleeve 24 is cylindrically shaped to mate with cylindrical lift rod 13 in slidable relationship. Crystal growing seed 31 contains a notch 32 circumscribed about each of its four corners. The lower end of seed 31 is inserted in silicon melt 33 contained in crucible 34.

FIGURE 2 shows the configuration of jaws 11 and 12 by means of a cross sectional view. Seed 31 is held im- Federated July 24, 1962 mobile between jaw 11 and clamp 21, which pivots about pin 23 until it is aligned with seed 31.

FIGURE 3 shows the mating relationship between sleeve 24 and jaws 11 and 12 by means of a cross sectional view. The operation of the chuck shown in FIG- URES 1, 2 and 3 will now be described.

Sleeve 24 is slid up along lift rod 13 so as to enable jaws 11 and 12 to be spread apart by pivoting them in opposite directions about pins 14. Seed 31 is inserted between jaws 11 and 12 so that notch 32 is aligned with guide pin 15. The lower extremities of jaws 11 and 12 are then pressed towards each other until seed 31 is held securely between jaw 11 and clamp 21. Clamp 21 pivots about pin 23 to engage seed 31 and to press it against jaw 11. Guide pin 15 helps to prevent vertical movement between seed 31 and jaws 11 and 12. Sleeve 24 is then slid down lift rod 13 and along jaws 11 and 12, pressing jaws 11 and 12 towards each other, until seed 31 is held tightly. The entire apparatus can then be lowered until seed 31 is inserted into melt 33 in crucible 34. Lift rod 13 and crucible 34 are slowly rotated in opposite directions. Lift rod 13 is then very slowly and steadily raised vertically while rotating. Sleeve 24 prevents lateral movement of jaws 11 and 12 with respect to lift rod 13, and since the parts of the chuck are symmetrical, the axis of seed 31 is coaxial with the axis of lift rod 13, and seed 31 does not wobble. As seed 31 slowly rises vertically, melt 33 continues to solidify in the region of seed 31. This process is continued until a large single crystal of silicon has been lifted out of melt 33. If desired, crucible 34 can be lowered instead of lift rod 13 being raised.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

We claim:

1. A seed holding chuck for drawing a polygonal crystal vertically out of a melt, comprising a lift means having a vertical axis, a plurality of elongate vertical gripping jaws for grasping a seed crystal, means pivotally mounting the upper end of each of said gripping jaws upon said lift means, the outer surface of each of said gripping jaws being tapered at the end which is pivoted to said lift means, and the inner surface of the lower end of each of said jaws being profiled for firm engagement with the corners of the seed crystal through a substantial lengthwise extent thereof to position the crystal in accurate alignment with said vertical axis; and a sleeve mounted for sliding movement along said lift means and over the tapered ends of said gripping jaws whereby said gripping jaws are brought together to grip the corners of a crystal firmly therebetween as said sleeve is moved towards the free ends of said gripping jaws; the free end of one of said gripping jaws being provided with a cutout portion, and a clamp pivotally mounted in said cutout portion, said clamp having a surface for crystal-gripping cooperation with the inner surface of another one of said other gripping jaws.

2. A chuck as set forth in claim 1, in which one of said gripping jaws is provided with a protruding pin for aligning said gripping jaws with a notch in the crystal held between said jaws.

References Cited in the file of this patent UNITED STATES PATENTS 662,905 Banan Dec. 4, 1900 820,073 Spanogle May 8, 1906 1,575,149 Craig et al. Mar. 2, 1926 2,081,142 Branarnan May 25, 1937

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