Adjustable Induction Coil For Heating Semiconductor Rods

Abstract

An adjustable induction coil is made up of several component parts, some of which may be disassembled from the remainder in order effectively to enlarge the inner diameter of the coil, or to remove the coil from association with a semiconductor rod passing through the coil, and which is heated by the coil. The coil is provided with conduits adapted to support a fluid flow for cooling the coil during operation.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to induction coils and more particularly to induction coils which are employed in the process of treating semiconductor rods by the floating zone melting process.

2. The Prior Art

It is frequently desirable to purify rods consisting of semiconductor material by subjecting them to a so-called floating zone melting process, employing an induction coil which heats the semiconductor rod by induction. A melting zone is established within the rod, which is encircled by the coil, and this melting zone is shifted along the length of the rod from one end to another, by moving the rod relative to the coil. In this manner, impurities are transported to one end of the rod, leaving the remaining structure more free of impurities than before. The floating zone melting process is also used for the breeding of single crystals by melting a core crystal to one end of the rod, and guiding a melting zone from the core crystal to the other end of the rod.

It is desirable to use a variety of sizes of induction coils in carrying out some heating processes, and it is therefore necessary sometimes to remove the coil from association with the rod, and to replace it with one of a different size. When a conventional coil construction is employed, the coil can be removed only by disconnecting an end of the semiconductor rod from the apparatus which supports the rod during its movement relative to the coil. This is undesirable, especially when relatively large diameter rods such as 50 to 80 millimeters in diameter, are being treated. The disconnecting procedure is cumbersome and expensive and it is desirable to avoid this procedure, if possible.

SUMMARY OF THE INVENTION

A principal object of the present invention is to provide an induction heating coil which is constructed in a way which permits it to be dismounted from a semiconductor rod which it is adapted to heat.

Another object of the present invention is to provide a coil which has means for adjusting its inner diameter without removing it from a semiconductor rod which it is adapted to heat.

These and other objects and advantages of the present invention will become manifest upon an inspection of the following description and the accompanying drawings.

In one embodiment of the present invention there is provided a coil having two components which are selectively connectable with each other and which are adapted to be separated from each other to permit removal of the coil from the semiconductor rod.

In another embodiment the coil consists of one or more loops with a ring shaped inner part formed of two components adapted to be separated from each other and from the coil loops.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings in which:

FIG. 1 is a perspective view of a coil incorporating an illustrative embodiment of the present invention, shown in separated condition;

FIG. 2 is a plan view of the coil of FIG. 1, shown in assembled condition;

FIG. 3 is a perspective view of an alternative embodiment of the present invention;

FIG. 4 is a plan view of a further embodiment of the present invention;

FIG. 5 is a vertical cross-sectional view of the coil of FIG. 4, taken along a plane V--V;

FIG. 6 is a plan view of yet another embodiment of the present invention; and

FIG. 7 is a vertical cross-sectional view of the coil of FIG. 6, taken along a plane VII--VII.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, and in particular to FIGS. 1 and 2, a coil 1 is shown which is adapted to be used for heating a semiconductor rod and which is selectively separable from the rod. The coil 1 consists of a single loop, and is provided with a pair of hollow conductive terminals 34 and 35, which may be connected to a suitable source of electric potential to establish an electric current within the coil. The terminals 34 and 35 are also connected to a source of cooling fluid and to a sink therefor, respectively. The coil 1 is composed of copper or silver or some other metal with good conducting properties. It is formed of two component sections 2 and 3, which are in electrical contact with each other along the end surfaces thereof 4 and 5.

The two sections 2 and 3 each have an interior conduit 31 connected at one end to the interior of the hollow terminals 34 and 35, and at the other end to each other via a sealing arrangement which prevents leakage of the fluid at the joint between the sections 2 and 3. A flange 32 is provided on each of the sections 2 and 3 and each flange 32 having aligned bolt holes 6, 7 and 8 by which the flanges 32 may be bolted together by bolts 6a and 7a. An O-ring 9 surrounds the joint between the conduits 31 to insure a fluid-tight sealing relationship between the two flanges 32 when the same are bolted together. The surfaces of the two flanges 32 are spaced slightly from the planes of the surfaces 4 and 5, to accomodate the thickness of the O-ring 9, permitting good electrical connection between the surfaces 4 and 5. In one coil, the inner diameter is about 30 millimeters and the outer diameter is between 80 millimeters and 120 millimeters. Of course the sizes of the coil diameters depend on the rod sizes which are to be used with the coil. When it is desired to remove the coil 1 from the rod with which it is associated, it may be readily separated into two parts by disconnecting the nuts and bolts associated with the bolt holes 6, 7 and 8, after which the two sections 2 and 3 may be withdrawn separately from the semiconductor rod. Of course, the fluid flow is stopped prior to disconnection to avoid spillage.

In FIG. 3, an alternative embodiment is illustrated which is like the embodiment shown in FIGS. 1 and 2 except that the separating line between the two sections 2 and 3 lies partly in the plane of the coil, rather than being transverse thereto as in the embodiment of FIGS. 1 and 2. In other words, the separating line extends through the coil and is defined by two parallel planes which extend perpendicular to the plane of the coil joined to a third plane between and perpendicular to the parallel planes. The two sections 2 and 3 are connected for good electrical contact therebetween, and with a fluid-tight seal, by means of screws 6b and 7b. The screws 6b and 7b are received in aligned apertures in the two sections 2 and 3, those in the section 3 having cooperating threads. The screws 6b and 7b are located on opposite sides of junction between the interior conduits of the two sections. The interior conduit in each section is formed so that the junction between the sections 2 and 3 is disposed solely on the horizontal surface 10, in the manner shown in FIG. 7, which is described hereinafter. This insures that a fluid-tight seal is achieved by surrounding the opening on one side or the other with a gasket member such as an O-ring.

The embodiment of FIG. 3 is preferable to that illustrated in FIGS. 1 and 2 in some circumstances, when the screws 6b and 7b, being oriented differently from the bolts 6a and 7a, are more accessible.

In FIGS. 4 and 5 an alternative embodiment of the present invention is illustrated, showing an induction heating coil or loop 11 composed of copper, silver or the like having three convolutions 12 connected between the hollow terminals 34 and 35. The coil 11 is formed of tubular material to support a stream of cooling fluid. The winding includes two arcuate inner sections 13 and 14 which are in electrical contact with the inner convolution of the coil 11. A flange 30 is attached by means of soldering, welding or the like, to the inner convolution 12 of the coil 11, and the sections 13 and 14 are connected to the flange 30 by means of screws 15-22. As illustrated in FIG. 5, a solder joint 24 fills the space between the flange 30 and the inner convolution of the coil. A gap is provided in the flange 30 between the beginning and end of the inner convolution 12, to avoid short circuiting the convolution. A gap is also provided between the sections 13 and 14 at this location for the same purpose.

When the screws 15-22 are removed, the two inner sections 13 and 14 are separated and removed, thereby increasing the inner diameter of the coil 11 from that illustrated in FIG. 4 to that illustrated in the dashed line 23, which defines the inner surface of the flange 30. The coil illustrated in FIGS. 4 and 5 may, therefore, be employed in a process which requires coils of different inner diameters during the course of the process. Of course it can also be used in a process involving a single semiconductor rod which is mounted in a way which permits the coil 11 to be removed therefrom only when its inner diameter is as large as the dashed line 23.

In FIGS. 6 and 7 another embodiment of the present invention is illustrated. This embodiment resembles that shown in FIGS. 5 and 6 except that the inner sections 13 and 14 are provided with an interior conduit for cooling purposes. The coil 11 has two convolutions 12, and the flange 30 is soldered by a solder joint 24 to the inner convolution of the coil, just as in the embodiment of FIGS. 4 and 5. As best illustrated in FIG. 7, the flange 30 has a rectangular cross-section, and includes a horizontal bore 36 communicating at one end with the interior of the inner convolution 12 of the coil 11, and at the other end with a vertical bore aligned with a vertical bore 37 provided in the sections 13 and 14 and leading to the hollow interior of the sections 13 and 14. By this means the inner convolution is connected to the inner sections at four locations, and cooling fluid flows through the hollow inner sections 13 and 14, as well as through the coil 11, as illustrated by the arrows 25. Both of the sections 13 and 14 have end walls closing off the ends of the conduit therewithin, so no sealing arrangement is needed at the vertical plane of contact between the sections 13 and 14. Four O-rings 26-29 surround the four fluid junction points between the two inner sections 13 and 14 and the ring flange 30, as best illustrated in FIG. 6, to insure a fluid-tight connection therebetween. Screws 15-22 interconnect the inner sections 13 and 14 to the ring flange 30 in the same manner as has been described in reference to FIGS. 4 and 5.

The embodiment shown in FIGS. 6 and 7 may be employed in the same manner as that illustrated in FIGS. 4 and 5, but the embodiment of FIGS. 6 and 7 achieves the additional advantage of permitting cooling of the inner sections 13 and 14.

Claims

What is claimed is:

1. An induction heating coil for use in heating a semiconductor rod comprising:

an induction coil adapted to encircle said rod and including a current conducting loop forming an outer section of said coil and a plurality of separable inner sections, whereby at least some of said inner sections may be independently separated from association with said rod;

said loop formed of a plurality of convolutions of an elongated tube;

said inner sections being removably connected with an innermost convolution of said loop, said inner sections being in substantially continuous electrical contact with said innermost convolution of said loop, said inner sections having a radially innermost surface defining a circle for surrounding said rod, said inner sections being separable from each other along a separating line;

an insulating space separating one end of said innermost convolution from the other end of said innermost convolution;

conduit means within said inner sections for supporting a fluid flow therethrough; and

means for connecting the interior of the tube of said innermost convolution with said conduit means.

2. A disassembleable induction heating arrangement for floating zone melting of semiconductor rods comprising:

a flat coil having at least two separable components contacting each other along a separating line;

means for securing said components together; a fluid passageway through each of said components; and gasket means for forming a fluid-tight connection therebetween;

said separating line extending through said coil and being defined by two parallel planes which extend perpendicular to the plane of said coil joined to a third plane between and perpendicular to said parallel planes.