JPS593094A - Device for producing belt-like silicon crystal - Google Patents

Abstract

PURPOSE:To improve the pulling speed of belt-like silicon and to prevent the generation of neck-down by providing regulators for cooling temp. which are made into a U shape so as to cover the forward end part of a die and controls the temp. by flowing cooling gas in the fine holes on the die side. CONSTITUTION:A heat shielding plate 14 plays the role of weakening the heat radiation which is radiated by a melt 11 and arrives at the forward end of a die 13, and said plate is opened with a window at which the forward end part of the die 13 is exposed. A crucible 12 is inserted into a crucible holder 15 formed of carbon. A pair of plate-like heaters 16 (16a, 16b) are provided on the outer side of a crucible holder 15. The heaters 16 are installed in parallel in the longitudinal direction of the die 13 and the holder 15, and are worked to make notches 17 alternately from the top and bottom by which the electric resistance value is controlled. A pair of U shaped regulators 19 (19a, 19b) for cooling temp. are installed at both ends in the longitudinal direction in the forward end part of the die 13 so as to oppose to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in an apparatus for manufacturing band-shaped silicon crystals.

[Technical background of the invention and its problems]

Recently, a method for growing band-shaped silicon crystals has been developed as one of the crystal manufacturing techniques, and the plan view inside the furnace in which this band-shaped silicon crystal is grown is shown in Figure 1 (a) K and A.
-A' cross-sectional view is shown in (b). This figure 1 shows silico,
A glass made of quartz glass containing the melt 11? Car at 12?
A pickpocket made of

Capillary die J3 (z3a, z
3b) (Hereinafter simply referred to as gate) t = Its long side direction is Ruth? 12 is shown installed parallel to the long side direction. The tips of the dies 13 are sharp and processed into a knife shape, and these dies 13 are strongly fixed to a heat shield plate 14 provided on the slide 12. This heat shield plate 1
Reference numeral 4 serves to weaken the thermal radiation of the melt 1 from reaching the tip of the die 13, and a window is opened to expose the tip of the die 13. The crucible 12 is inserted into a crucible holder 15 made of carbon. A pair of plate-shaped heaters 16 (16a, 16b) are provided on the outside of this lute holder 15.

This heater 16 is connected to the die 13 and the holder 1.
5 is installed in parallel to the longitudinal direction, and cuts 17 are formed alternately from above and below, thereby controlling the electrical resistance value.

18 is a chamber side wall.

Polycrystalline silicon is placed in the quartz Rudde 12 of the growth apparatus configured as described above, and the temperature of the heater 16 is set to approximately 1500°C.
to rise to. Then, the polycrystalline silicon becomes a silicon melt 11, and this silicon melt 11 rises to the tip of the dyno 3 due to capillary action. By bringing a seed crystal (not shown) into contact with the rising silicon melt 11 from above and then gradually pulling it up, a band-shaped silicon crystal can be grown.

The present inventor attempted to grow a wide silicon crystal using the above-mentioned growth apparatus, and found that the pulling rate was 5 to 10 times a day.
The seed crystal is very slow, and the width of the seed crystal is always narrow.
The process of reducing the ribbon width to about one neck (hereinafter referred to as neck-down) and then widening the ribbon width was complicated, and it was not possible to obtain long and wide crystals. Considering the mass production of band-shaped silicon crystals, the above-mentioned conventional technology causes a loss in terms of time and materials, and is not an optimal technology for mass production. The reason for this is that the temperature gradient in the pulling direction near the solid-liquid interface is low and the temperature distribution in the lateral direction is poor. The present inventor measured the temperature distribution at the solid-liquid interface using a non-contact measurement method after contacting the seed crystal with the tip of the die, and found that the seed crystal (width 100 mm) had a low temperature at the center and a high temperature at both ends. The temperature distribution at the solid-liquid interface was concave with respect to the seed width. In the case of the above temperature distribution, when growing band-shaped silicon crystals, it is difficult to start growing crystals with the same width as the seed width. This will definitely result in neck down. Furthermore, when widening after necking down, since the temperature at both ends was high, the degree of widening was slow, and there was a high probability that the core would stick to the die at the lower temperature center. Furthermore, the present inventor measured the temperature gradient in the pulling direction using a thermocouple, and found that the gradient was as gentle as 100 I at the tip of the goo. This means that the pulling speed is as slow as 5 to 10 M/min.

[Purpose of the invention]

An object of the present invention is to provide an apparatus for producing band-shaped silicon crystals that is suitable for mass production and that greatly increases the pulling speed, prevents the occurrence of neck-down, and makes it possible to pull wide band-shaped crystals from the start of growth. It's about doing.

[Summary of the invention]

As a result of extensive research aimed at improving the drawbacks of the prior art described above, the present inventor has developed a method to make the temperature distribution at the solid-liquid interface convex immediately after the start of growth, and at the same time to steepen the temperature gradient in the pulling direction. It has been found that the drawbacks of the prior art can be improved.

Therefore, in the present invention, a pair of cooling temperature regulators are installed near the solid-liquid interface. This cooling temperature regulator is U-shaped so as to cover the tip of the die, and has small holes on the die side to flow cooling gas to control the temperature near the solid-liquid interface. In addition, the cooling temperature regulator is made of, for example, molybdenum in consideration of heat resistance, and molybdenum, tube, or stainless steel pipe is welded to the cooling temperature regulator as a cooling gas supply means. Furthermore, it is preferable that the cooling temperature regulator has a structure that allows it to be moved in the longitudinal direction of the die from outside the furnace during the growth of the band-shaped silicon crystal, so that the temperature distribution at the solid-liquid interface can be arbitrarily controlled. The molybdenum or stainless steel pipe is supported, for example, on the side of the chamber, and the cooling temperature regulator is configured to slide on a heat shield plate. The cooling temperature regulator can be moved manually or automatically by a motor.

〔Effect of the invention〕

According to the present invention, by installing two cooling temperature regulators in the longitudinal direction at the tip of the goo, the temperature distribution at the solid-liquid interface immediately after pulling can be formed in a convex shape, and the solid-liquid interface Since the surrounding temperature can be made sufficiently lower than in the prior art, heat dissipation from the band-shaped silicon crystal surface is improved, and the temperature gradient in the pulling direction becomes steeper. Therefore, it is possible to pull a band-shaped silicon crystal with the same width as the seed crystal without causing neckdown immediately after pulling, and because the temperature gradient in the pulling direction becomes steep, this is not possible with conventional techniques. This enables high-speed pulling. Therefore, time and material losses are reduced,
Due to the increased speed, the production amount of band-shaped silicon crystals will increase significantly. Another effect is that since the gas is ejected near the solid-liquid interface, the tip of the die can be isolated from the atmosphere inside the furnace 1 and the surrounding air, which prevents scrap from floating in the silicon melt at the tip of the goo. can.

[Embodiments of the invention]

FIG. 2 is a plan view showing a schematic configuration of an embodiment of the present invention, and FIG. 2(b) is a sectional view taken along line AA'.

Note that the same parts as in FIG. 1 are given the same reference numerals, and detailed explanation thereof will be omitted. The difference between this embodiment device and the conventional device shown in FIG. 1 is that a pair of U-shaped cooling temperature regulators x9 (19ar1e
b") are installed facing each other. This cooling temperature regulator 19 is made of molybdenum in consideration of heat resistance.
Furthermore, molybdenum or stainless steel pipes 20 (20a, 20b) serve as flow paths for aluminum gas, which is a cooling gas.
are connected by welding. This pipe 20 is the chamber 1
8 and a flexible pipe 22 outside the chamber.
(,?,?A.

22b). The shape of the cooling temperature regulator 19 depends on the width of the die 13, but in the case of a die width of 100 mm, the width is 20 w, the length is 60 mm, and the thickness is 10 mm. There is a pore 23 with a diameter of 5. Movement of the cooling temperature regulator 19 (arrow “21” in the figure)
a.

21b) slides on the heat shield plate 14 by moving the cooling rod 20 manually or by a motor (not shown) outside the chamber.

゛The present inventor used this example device to measure the temperature distribution at the solid-liquid interface between the seed crystal and the silicon melt at the tip of the die.

Figure 3 shows the data. Figure 3(a) shows the temperature distribution of the conventional device, which shows a temperature distribution of 1427±1 at the center of the die (point 0 in the figure).
℃, 1434±1℃ on the right side (point R), 1 on the left side (point L)
It had a concave shape with a temperature of 434±2°C. (b) shows the temperature distribution according to this embodiment, when each cooling temperature regulator 19 is set at a position moved about 20 mg from the center of the die. The flow rate of argon gas is 5 l/mi each.
It is n. Temperature distribution is 1440±1℃ at 0 point, 1 at R point
The temperature was 434±1℃, and the convex f was 1434±2℃ at the L point.

Next, the inventor used a thermocouple to measure the temperature gradient in the pulling direction between the conventional device and the device of this embodiment. In the case of the conventional device, the temperature was 100″C/cm directly above the die, whereas in the device of this embodiment, the temperature was 200° C.h.

Furthermore, the present inventor conducted a pulling experiment with the temperature distribution shown in FIGS. 3(a) and 3(b). In this case, the die width was 102 m, and the seed crystal width was 98+m. In that situation, the seed crystal 41 (41&, 41b) and the band-shaped silicon crystal 4 at the initial stage of pulling
2 (42&, 42b) are shown in Figure 3 (a) and (b).
) in Fig. 4(a).

Shown in (b). In case of (a), approximately 25m+1 immediately after lifting
It takes about 2 to narrow the width to about 1, and widen it to 100 mm in width.
m, it takes about 1.5 hours, and the width is 100WII.
The average pulling speed during stable growth after widening at t is 10 to 15
It was 1 minute. In the case of (b), approximately 51
With 1II+, the width was increased to 100 mm, and the pulling speed during stable growth was 20 to 25 tons/min on average, which is about twice as high as that of the conventional technology. Also, as the crystal grows, the field width of (,) changes, but in the case of (), it is possible to control the width of 100 ± 1 + a++ by finely adjusting the position of the cooling temperature regulator. Ta. If a cold temperature regulator is used as in the device of this embodiment shown in FIG. 2, the temperature distribution at the solid-liquid interface can be controlled relatively easily. It is possible to widen the width to the desired width immediately after the start of pulling without causing any cracks, and it is also possible to pull at a speed approximately twice as high as that of conventional equipment. Therefore, it saves time and materials. Loss is significantly reduced, the production amount of band-shaped silicon crystals is greatly improved, mass production is possible, and costs can be significantly reduced when used in elements such as solar cells.

The inventor of the present invention attempted to control other control elements, that is, speed and heater power for pulling, with a conventional device, but the pulling control was extremely complicated, the probability of failure in pulling was high, and it was difficult to resolve the neckdown. was not achieved.

Another effect of the present invention is that when the belt-shaped silicon crystal is growing stably, if the sheather or pulling speed changes due to external noise, etc., and the width of the crystal changes, the width of the crystal changes. By changing the setting position of the cooling temperature regulator, the width can be controlled easily and quickly.

In addition, as a means of controlling the temperature distribution at the solid-liquid interface, it is possible to install a small heater near the guipure, but there is a discharge phenomenon that depends on the shape of the heater, the distance between the guipure and the heater, and a time delay due to the 9W control. Considering the above, the present invention can be controlled relatively easily and does not require a control system for power control, so it can be manufactured at low cost. Further, although the heater can control the temperature distribution at the solid-liquid interface, it cannot improve the speed at which the bow 1 is raised.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a plan view and a sectional view showing a conventional device, FIGS. Figure (IL), (b)
and Figure 4(a). (b) U is a diagram for explaining the effects of the conventional device and the device of this embodiment. 11... Silicon melt, 12... Quartz glass Lu-113h, 13b... Gui, 14... Heat shielding plate,
15... Ruth is holder, 16m, 16b... Heater, 17... Notch, 18... Chasono 9 side wall, 1
9m. 19b...Cooling temperature regulator, j Oa e j Ob
...Cooling pipe, 21m, 21b...Movement direction of cooling temperature regulator, 22g, 22b...Flexible pipe, 4'1 ae4ib''・Seed crystal, 4
2a e 42b... Band-shaped silicon crystal. Applicant's agent Patent attorney Hiko Suzu Etake Figure 3 (b) 1! :ja
IMD Figure 4-111]~1″'

Claims (1)

[Scope of claims] A pair of dies each having a slot into which one end is immersed, and a heating source for heating the silicon melt and the die, a seed crystal is brought into contact with the silicon melt rising through the slot of the die, and the seed crystal is brought into contact with the silicon melt rising through the slot of the die. In an apparatus for manufacturing a band-shaped silicon crystal that grows a band-shaped silicon crystal by pulling up a seed crystal, the device covers the tip of the goo protruding on the heat shielding plate and has a pore on the die side that serves as an inlet and an inlet for cooling gas. An apparatus for manufacturing a band-shaped silicon crystal, characterized in that a pair of U-shaped cooling temperature regulators are installed. (2) The cooling temperature regulator has a mechanism that can move in the longitudinal direction of the die. (3) The apparatus for manufacturing a band-shaped silicon crystal according to Claim 1, wherein the cooling temperature regulator is made of molybdenum, and the cooling gas is argon gas.