JPS63291890A - Method for removing nosing occurring in zone melting of raw material polycrystal - Google Patents

Abstract

PURPOSE:To completely remove the titled nosing without giving bad influence to obtained semiconductor, by arranging a cathode formed using a specific material closely near nosing arising when a raw material polycrystal is melted by a floating zone melting process and carrying out arc discharge. CONSTITUTION:A cathode 11 formed using a material containing an element having <=1 segregation coefficient, preferably W or Mo is arranged closely near nosing 5 occurring when rolling convection 3 of a protecting gas arising near a zone melting area 2 in melting of a raw material polycrystal by a floating zone melting process passes through a slit gap 10a between both ends of a heat coil 10 and collides with a shoulder part 1a of the polycrystal 1 and then arc discharge is carried out to melt and remove the titled nosing 5.

Description

Detailed Description of the Invention "Industrial Field of Application" The present invention is directed to the treatment of foreign matter or local "Nose discharge" that occurs due to excessive cooling, etc.
Regarding the removal method.

"Prior Art" The FZ method is conventionally known, in which a rod-shaped raw material polycrystal is zone-melted using a surrounding high-frequency induction heating coil, and the polycrystal is purified or a single crystal is grown. Generally, the process is carried out in an atmosphere of argon gas or other protective gas, so as shown in Figure i1, an entrainment convection 3 of the protective gas occurs near the belt-shaped melting zone 2 of the polycrystalline raw material 1, and the entrainment convection 3 causes the heating The polycrystalline shoulder 1 passes through the slit gap 10a formed between both ends of the coil 10.
a, the shoulder portion 1a may be locally cooled and unmelted.

In the FZ method, a ring-shaped belt-shaped melting zone 2 is sequentially formed every relative rotation of the heating coil 10. Therefore, when an unmelted portion as described above occurs, the melting zone 2 is formed as a result of the progress of heating and melting. Unmelted portions are left behind, resulting in icicle-like so-called "nose discharges" 5.

In addition to the local cooling caused by entrainment convection 3 as described above, such "nose discharge" 5 is mainly caused when cracks exist in raw material polycrystal 1 or when the surface shape is not a perfect circle. A part of the crystal remains as an unmelted part at the lower end of the polycrystal, and
Nasal discharge"5 may occur.

When such a "nosing" 5 occurs, the heating coil 10 is formed so that its inner diameter is smaller than the polycrystalline outer diameter in order to concentrate the heating energy on the belt-shaped melting zone 2. Therefore, when the coil 10 is relatively moved toward the raw material polycrystal 1 polycrystal heating area 4 side, the heating coil 10 is
A problem arises in that the coil 10 collides with the tip of the nose protrusion 5, making it impossible to pass the coil 10 through it, and as a result, production has to be stopped at that position.

For this reason, in the past, the "nose bulge" 5 was broken off with a magic hand or the like, but in this mechanical removal method, the root part of the "nose bulge" 5 remains, and the root part "Nose discharge" 5 is more likely to occur again, and the problem could not be completely solved.

SUMMARY OF THE INVENTION In view of the drawbacks of the prior art, it is an object of the present invention to provide a method for removing ``snot'' that can completely remove the ``snot'' without adversely affecting semiconductors to be manufactured.

The present invention focuses on the fact that the raw material polycrystal 1 is melted by the FZ method in an argon gas atmosphere where discharge is easy, and the segregation coefficient of tungsten or molybdenum, etc. The cathode 11 is formed using a material containing an element with a smaller than 1, and the cathode 11 is placed close to the 5 portions of the nose to generate an arc discharge. The main point is that ``5'' is removed by melting.

In this case, since silicon, germanium, etc. which are the constituent materials of the raw material polycrystal 1 become conductors at a predetermined temperature or higher,
The "nose" 5 side is an anode, and the negative electrode 11 and the "nose" 5 are connected as an anode.
The configuration may be such that the "nose bulge" 5 is melted and removed by an arc discharge between the two electrodes, a negative electrode 11 and a positive electrode 12, sandwiching the "nose bulge" 5 portion. may be arranged, and the "nose discharge" 5 may be melted and removed by arc discharge generated between both electrodes 11 and 12.

According to a preferred embodiment of the present invention, after the arc discharge, it is preferable that at least the negative electrode 11 is quickly evacuated or the arc voltage is quickly lowered or cut off.

"Function" According to this technical means, since the "nasal bulge" 5 is a needle-like microdiameter extending like an icicle, the "nasal bulge" 5 is instantly moved to the root by the arc discharge. The disadvantages of the prior art described above are completely eliminated.

At this time, the cathode material is discharged from the cathode 11 due to the arc discharge, and the cathode material adheres to the melting zone or single crystal growth region, but the tungsten, molybdenum, etc. that constitute the cathode 11 have a segregation coefficient. Since it is an element smaller than 1 and difficult to incorporate into semiconductor single crystals, it does not poison semiconductors and does not have the same adverse effect on the quality of manufactured single crystals.

It should be noted that those skilled in the art will naturally understand that it is preferable for the cathode constituent material to be formed using high-purity tungsten or molybdenum.

Furthermore, since the removal of the "nose discharge" 5 by the arc discharge is instantaneous, it has a particularly bad effect on the induction radio waves of the heating coil IO! Since there is no IS, the heating temperature to zone 2 does not fluctuate.

"Embodiments" Hereinafter, preferred embodiments of the present invention will be described in detail by way of example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in this example are not intended to limit the scope of this invention, but are merely illustrative examples. It's nothing more than that.

FIGS. 1 and 2 show a silicon single crystal manufacturing apparatus incorporating a "snot discharge" removing apparatus according to an embodiment of the present invention. Upper shaft 6
A single-turn flat heating coil 10 is arranged to be movable in the axial direction between the two shafts 6 and 7, and a high-frequency power source (not shown) is connected to the coil 10. It is configured to allow high frequency induced current to circulate. On the other hand, a voltage-adjustable DC power supply 9 is arranged outside the furnace 8, with its e-terminal side connected to the upper shaft 6, and its e-terminal side connected to the drive mechanism 13.
A needle-shaped tungsten electrode 11 housed in the furnace 8
Connect to each. The drive mechanism 13 moves the tungsten electrode 11 to the vicinity of the tungsten electrode 11 when the "bleep" 5 occurs, and is composed of, for example, a multi-column shaft whose movement can be controlled from outside the furnace 8.

According to this device, first, a rod-shaped raw material polycrystalline l is held in the upper shaft 6, a single crystal seed with a small diameter is held in the lower shaft 7, and one end of the polycrystalline 1 is first melted by a heating coil 10 surrounded by the rod-shaped raw material polycrystal l. After fusing and seeding the seed crystal IA, the raw material polycrystal 1 is made non-dislocated by seed squeezing, and the coil 10 is raised in the axial direction while rotating the polycrystal 1.
is zone-melted to produce semiconductor single crystals.

If a "bleep" 5 occurs due to the presence of foreign matter in the polycrystalline raw material or local heating during the zone melting, the tungsten electrode 11 is moved to the vicinity of the tungsten electrode 11 and the DC power source 9 is applied to the Apply power. At this time, the above-mentioned "nade" 5 is a polycrystalline raw material! It is connected to the ■ terminal side of the DC power supply 8 via the upper shaft B, and since the inside of the furnace 8 is under an argon gas atmosphere where discharge is easy, there is no connection between the tungsten electrode 11 and the "nose" 5. Arc discharge occurs, and the "nose discharge" 5 is instantly melted and removed by the arc discharge. After the melting and removal, the voltage of the DC power source 8 is lowered.

Note that when the temperature is high in the raw material polycrystal 1 such as silicon polycrystal, it acts as a conductor and the arc discharge acts smoothly, but when a long material is used as the raw material polycrystal 1, the upper axis 6 Since the temperature of the raw material polycrystal 1 in the vicinity becomes low and the resistance of that part increases, the arc discharge may not proceed smoothly.

In such a case, as shown in Fig. 3, the DC type 1! Another electrode 12 connected to the ■terminal side of A9 is placed on the opposite side of the tungsten electrode 11,
What is necessary is just to arrange so that an arc discharge may be performed between both electrodes 11 and 12.

"Effects of the Invention" As described above, according to the present invention, the "nasal bleed" can be completely removed with a simple structure without adversely affecting the semiconductor to be manufactured, and the "nasal bleed" can be completely removed. Even if it occurs,
It is possible to smoothly purify polycrystals and manufacture single crystals.

It has various effects such as

[Brief explanation of drawings]

Figures 1 and 2 show a silicon single crystal manufacturing apparatus incorporating a "nasal bleed" removal device according to an embodiment of the present invention, and Figure 2 is an overall view of the device, and Figure 1 is an enlarged view of its main parts. be. FIG. 3 is an enlarged view of main parts showing another modification. Fig. 1 Fig. 3 Fig. 2 Procedures Manual (spontaneous) July 30, 1988

Claims (1)

[Claims] 1) In a method for removing "snot" that occurs when melting a raw material polycrystal by a floating zone melting method, a negative electrode is formed using a material containing an element with a segregation coefficient of less than 1, and 2) A method for removing nasal discharge, characterized in that the cathode is placed close to the nasal discharge and arc discharge is performed, and the arc discharge melts and removes the nasal discharge. 3) A method for removing a "nasal bleed" according to claim 1, wherein the negative electrode is formed of a material containing tungsten or molybdenum.
4) A method for removing a "nasal bleed" according to claim 1 or 2, in which the "nasal bleed" is melted and removed by arc discharge between The "nasal discharge" according to claim 1 or 2, wherein two electrodes consisting of an electrode and a positive electrode are arranged, and the "nasal discharge" is melted and removed by arc discharge generated between both electrodes. "Removal method 5) "Nose discharge" removal method 5) according to any one of claims 1 to 3, wherein at least the one electrode is immediately evacuated after the arc discharge. The method for removing "nasal discharge" according to any one of claims 1 to 3, wherein the arc voltage is quickly lowered or cut off after the arc discharge.