JPS5882492A - Band fusing flat induction coil without crusible - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Many crucibleless zone melting apparatuses for crystal rods are equipped with four heating coils for heating the outer melting zone of the support at the end of the crystal rod in one melt chamber. The relative movement between the support and the induction heating coil causes this melting zone to move within the crystal rod. The induction heating filter can be, for example, a multi-turn cylindrical coil, but many have a single turn. A high frequency alternating current is supplied to the induction heating coil from a high frequency oscillator.

The melting chamber may be under high vacuum or filled with protective gas. Highly purified hydrogen or argon is used as protective gas, so that particularly high-quality single-crystal rods can be produced by crucible-free zone melting.

Melts not only with multi-turn coils but also with single-turn coils#
There is a tendency for discharge to occur during f-free zone melting. This discharge adversely affects the quality of the crystal rod produced by zone melting. The risk of electrical discharges occurring is particularly great in gas-filled melting chambers or when high electrical power is applied to the coil.

The purpose of this invention is to prevent such discharge from occurring.

The invention is therefore directed to a crucibleless zone melting apparatus for crystal rods, in particular semiconductor rods, in which a crystal rod is placed in a melting chamber, held at its ends on a support, and in which induction heating is applied surrounding the crystal rod. The coil heats up and creates a molten zone.

A device of this type, which was the subject of German patent no. .

In a further development of the inventive concept of point j-, the central winding part of the induction heating coil or the central winding and at least one of the bale supports are electrically conductively connected to each other. It is also possible to connect an electrically symmetrical element in parallel to the induction heating coil, the center tap of which is electrically conductively coupled to at least one of the rod supports.

FIG. 1 shows a part of this known device. l is the band l#-
A rod end support 4 is attached to a shaft 3 which is the outer wall of the chamber and passes through a recess 2 of this wall.

The retractable portion 2 is hermetically connected by a packing 5.

The shaft 3 and the rod support 4 are rotatable about the central axis and simultaneously movable in the axial direction. Each of the rod supports 4 has one end of a crystal rod 6, for example a silicon rod, fixed at 1...+1.

A molten zone 8 is created in the rod 6 by the induction heating coil 7 and moves along the rod 6 due to the relative movement between the sheath 6 and the induction heating coil 7. The melting chamber, only partially shown, can be filled with high purity hydrogen or argon, for example.

'tlj 47Jρ Capacitor 15 in parallel with heating coil 7
The capacitor 15 and the coil 7 constitute a heating vibration circuit, and electrical energy is supplied to this vibration circuit from the high frequency oscillator 10 through the coaxial cable 9. The coaxial cable 9 and the heating circuit (7, 15) are therefore coupled by a coupling coil 12 to the oscillating coil 11 of the tank circuit of the high-frequency oscillator IO.

The central part 13 of the single-turn coil 7 or the central turn of the cylindrical coil is connected to the melting chamber wall 1 by a conductor 14 . Rod support 4
The central part 13 of the coil 6 and the induction heating coil 7 are placed at the same potential since the shaft 3 and the melting chamber wall are grounded. The maximum potential difference between the induction heating coil 7 and the crystal rod 6 is therefore only half as large as it would be if the coil central section 13 were not connected to the melting chamber wall and placed at equal potential with the rod 6.

As a result, no electrical discharge is observed in ordinary silicon rods up to 2 inches in diameter.

At the beginning of the zone melting process, it is necessary to introduce a high voltage to the deheating coil and the melt to melt the seed crystal and pull up the narrow part of the bottle neck. The larger the inner diameter of the flat melting coil, the more likely glow discharge or spark discharge will occur between the coils. This phenomenon is particularly noticeable when using argon as the protective gas. This discharge leads to damage of the high frequency coil h conductor, which has a negative effect on the quality of the crystal produced by zone melting.

The recent trend of cutting rods with diameters of 3 inches, 4 inches, or even 5 inches requires new solutions to these problems.

This invention is disclosed in, for example, West German Patent Application Publication No. 2737342.
The purpose of this invention is to create a completely new structure in terms of withstand voltage characteristics while retaining the basic concept of the known flat coil described in the above publication.

A plan view of a known flat coil that is the basis of this invention is shown in the second figure.
As shown in the figure. The coil consists of an annular inner winding 17 of elliptical cross-section and a collar-shaped outer winding 18, which windings 17 and 18 are bath welded.

The outer winding 18 has a mound-shaped protrusion 16 through which it is grounded. Current conductors 19 and 20 of the coil are internal turns 1
7, and at the same time serves as a cooling water passage indicated by an arrow 21. Generally, the outer winding portion 18 of the coil has a thick wall structure and is made of silver-plated copper, and the inner winding portion 1-7 is composed of a steel tube.

In contrast to a flat induction heating coil which is made as a hollow body but is wound around a semiconductor rod by windings provided with through holes for reducing the amount of cooling fluid, the heating coil is divided into partial coils of 1a number, and the heating coils are divided into partial coils, each of which is electrically connected to the other. It is proposed to combine the physically insulated parts into one component unit, and to provide each partial coil with its own power supply terminal and coolant connection.

With the development of this invention, the thickness between the partial coils is approx.

A spacing piece of 1 to 3 aw is provided. This spacing piece can be made of ceramic, silicone rubber, silicone resin, or polybismaleimide.

The partial coils increase in thickness from the inside to the outside, for example, in a circular or curved shape, with the inside having a radius of curvature of 0.5 to 2a, the outside having a thickness of 10 to 20 IU, and further toward the center with a diameter of about 25 IU. Advantageously, the shape forms a circular hole of 351 to 351 IjI.

The entire coil may be assembled as one mechanically strong unit, or if the semiconductor rod passing through the center is of a large diameter, a fixed part may be provided outside the partial coils to mechanically hold the partial coils together, e.g. It is reasonable to provide an i-line.

The protrusions of the partial coils are grasped with Nanamik or heat-resistant clips, and the partial coils are identified with each other.

The power supply terminal and the coolant connection port can be moved along their axes to make the inner diameter of the knife heating device variable.

It is advantageous if one or both of the partial coil and the fixed part are made of copper, silver-plated copper or silver.

In principle, the heating coil can be divided into any number of partial coils, but these partial coils must be connected in the correct phase relationship and act as a single undivided coil on the molten semiconductor rod. Therefore, the number of divisions is 2.
is optimal, and 4″ft: maximum.

When each subcoil has a connecting end in its center and is directly connected to earth potential, there are two subcoils, and the maximum voltage relative to earth potential is .

The voltage terminals can be placed at the same potential as the insulated rod support.

For the current supply to the partial coils, the high frequency power supply should be equipped with voltage dividing means, such as a secondary winding of suitable construction. It is effective to provide rM and divide the total voltage according to the number of partial coils.

The present invention will be explained in more detail with respect to the embodiment shown in FIG.

FIG. 3 shows a heating coil that is divided into two partial coils.
3, which are connected to the outer winding part of the collar or to these inner winding parts. Although this outer winding portion is not shown in the drawings, it may correspond to the collar winding 18 of FIG.

The winding parts 22,23 have annular projections 24,25 through which the partial coil can be grounded.

The current connections 26 and 27 of the first part coil and the current connections 28 and 29 of the second part/coil simultaneously serve as cooling water inlets and outlets. The flow of cooling water is indicated by arrows 30 and 31.

Between the partial coils there are spacing pieces 32 and 33, which are made of ceramic with a thickness of approximately 2 mm.

Advantageously, the coil is made of copper and/or silver and has an elliptical cross-section with an inner curvature of 1 d and an outer diameter of 1 od. However, the shapes of the partial coils can be selected to suit the intended process without departing from the gist of the invention.

The heating coil may be constructed as a complete unit or as a prefabricated coil. In the simplest example, protrusions 34.85° and 36.87 are provided on both partial coils, and these are sandwiched between clips of a ceramic sheath to connect both partial coils.

A known high frequency ring current and a resonant circuit 40 are used for power supply. The secondary side of this circuit has a total voltage of 1000V for example.
The voltage is divided into two equal voltages of 00 V each. Terminals 41 and 42 and 43 and 44 of the feed transformer are connected to current connection ends 2B and 2 through high frequency cable 45°46.
7 and 28°29.

Connections in the circuit should be made with the correct phase relationship and arrows 47
A high frequency ring current flows as shown at and 48 to create the same electric field as in the case of an undivided single turn coil within the semiconductor bar.

When the heating coil is divided into two partial coils, half of the total voltage is applied to the tube partial coil. Furthermore, when the midpoint of each partial coil is grounded, the voltage of each partial coil is divided into two equal parts. Therefore, the voltage between the melting zone and the high frequency heating coil drops to %. If the heating coil voltage is 1υ00V, a voltage of 25' OV is applied to the problematic coil locations 49.50 and 51.52 with respect to the half-bar molten zone.

[Brief explanation of the drawing]

Figure 1 shows a part of the semiconductor rod zone melting apparatus to which the present invention is applied, Figure 2 is a plan view of the flat induction heating coil used in the apparatus shown in Figure 1, and Figure 3 is a plan view of this device. FIG. 2 is a plan view of an embodiment of the invention. In FIG. 3, 22 and 23 are semi-annular inner winding portions, and 32 and 33 are spacing pieces between the partial coils.

Claims (1)

[Claims] l) The heating coil is divided into a plurality of segment-shaped partial coils, the partial coils electrically insulated from each other constitute one structural unit, and each partial coil has its own power supply. Fringeless zone melting of a semi-reflective rod made as a hollow body or having cooling current flow holes and having a winding (b) annularly surrounding the semiconductor rod, characterized by having an end and a cooling liquid connection port. Flat induction coil for use. 2) The coil according to claim 1, characterized in that a spacing piece is provided between the partial coils. 3) A coil according to claim 1 or 2, characterized in that the 11111 septa have an edge width of about 1 to La. 4) Coil according to one of claims 1 to 3, characterized in that the one-opening septum is made of ceramic, silicone rubber, silico/resin or polybismaleimide. 5) The partial coil exhibits a thickness increasing from the inside to the outside, e.g. in a conical manner.
The coil according to one of items 1 to 4. 6) Coil according to one of claims 1 to 5, characterized in that the partial coil has a radius of curvature of 0.5 to 2'' on its inside. 7) The outer thickness of the partial coil is between lO and 20. The coil according to any one of claims 1 to 81!6, characterized in that it is a fin. 8) The partial coil has a diameter of approximately 26 to 8511 mm toward the center.
A coil according to one of claims M1 to 7, characterized in that eleven circular holes are formed. 9) The coil according to any one of claims 1 to 8, characterized in that the partial coil has a fixed part, for example, a protrusion on the outside thereof, and is mechanically collectively held by this fixed part. . 10) Ceramic clip grips the fixed part. 10. A coil according to claim 1, wherein the partial coils are collectively held by the coil. 11) Claims 1 to 10, characterized in that the partial coil is made of copper, silver-plated copper, or silver.
A coil described in one of the sections. 12) Coil according to one of claims 1 to 1v, characterized in that the fixing part is made of copper, silver-plated steel or silver. 13) Coil according to one of claims 1 to 12, characterized in that the flat coil is divided into two partial coils. 14) Claims 1 to 1, characterized in that each partial coil has a voltage connection end in the center of the coil.
A coil according to one of item 3. 15) Coil according to one of claims 1 to 14, characterized in that the high-frequency oscillator with Pk@ is provided with a device for dividing the total supply voltage according to the number of partial coils. 16) The coil according to one of the claims 1 to 15, characterized in that the secondary winding of the feed transformer is configured to perform a predetermined voltage division.