JPS62113792A - Production unit for band silicon crystal - Google Patents

Abstract

PURPOSE:To carry out crystal growth stably for a long period and to make high-speed pulling possible, by setting a protruded part on a straight line connecting holes bored at intervals approximately equal to width of crystal at a bottom of a crucible on the surface of the bottom of the crucible having silicon melt. CONSTITUTION:A protruded part 101 at the bottom of a crucible 1 made of carbon is positioned on a straight line connecting two holes 2a and 2b which are bored through the bottom of the crucible and used for inserting filamentous substrates and the protruded part is positioned thinly and long between the two holes 2a and 2b, namely, thinly and long in the width direction of crystal to be grown. The size of the protruded part 101 is length of <= width of crystal to be grown, the width is 5-30 times as long as crystal thickness and the height is height to make the top end of the protruded part 101 3-5mm below silicon melt level. In this device, temperature distribution wherein temperature of silicon melt 6 at the central part of the crucible 1 is lower than temperature of the silicon melt 6 in the vicinity of a wall of the crucible 1 so that crystal growth caused by solidification progress from the wall face of the crucible 1 can be carried out at high speed and stably for long hours without interruption.

Description

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

[Technical background of the invention and its problems 1 Band-shaped silicon crystals have a thin plate-like shape, so unlike ingot-shaped silicon crystals obtained by the Czochralski method, etc., band-shaped silicon crystals can remain in the obtained shape. Can be used as a substrate for semiconductor devices. In other words, there is less material loss, which is required when creating a 7IIIfi-shaped semiconductor element substrate by slicing an ingot-shaped silicon crystal grown by the Czochralski method, etc., and it is possible to realize an inexpensive semiconductor element substrate. Become.

FIG. 7 is a schematic diagram showing a conventional example of a band-shaped silicon crystal manufacturing apparatus for growing such a band-shaped silicon crystal. A silicon raw material placed in a carbon crucible 1 is heated and melted from the outside to obtain a silicon melt 6. A pair of filamentous supports 3a, 3b are placed so as to maintain a certain distance perpendicularly to the silicon melt surface from the two holes drilled at the bottom of the crucible.
is inserted, and the thin plate-like seed 4 is arranged between the pair of filamentous supports 3a and 3b so as to be in contact with the silicon melt 6.

At this time, the pair of filamentous supports 3a, 3b and the seeds 4 are composed of a substance that has good wettability with the silicon melt 6, and the silicon melt that has infiltrated between the seeds 4 and the filamentous supports 3a, 3b makes both of them adhere to. Therefore, by pulling up the seed base i4, the pair of filamentous supports 3a and 3b are also pulled up, and the silicon melt is lifted above the melt surface using the seed crystal 4 and the pair of filamentous supports 3a and 3b as support. It is crystallized and a band-shaped silicon melt 5 is grown.

The thickness of the band-shaped silicon crystal produced by the above-mentioned apparatus is mainly a function of temperature and pulling rate, and the lower the crucible heating temperature or the slower the pulling rate, the thicker the crystal becomes, as shown in Figure 8. The results shown are obtained. FIG. 8 shows the thickness of crystals with a width of about 100 m grown by varying the pulling speed. For example, to obtain a thickness of 0.5M, the crystal pulling rate was 18 shoes/min. It can be seen that in order to pull a crystal of a certain thickness at high speed, it is necessary to lower the heating temperature. This is due to the following reasons.

In other words, there is a difference between the speed V at which a crystal with a certain width and thickness is pulled and the temperature (specifically, the temperature gradients d T4/dz and d Ts /dz on the melt side and crystal side at the solid-liquid interface, respectively). There is a relationship. This is the latent heat of crystallization, KS.

KJl is the thermal conductivity of the crystal and melt, respectively, and assuming that 2 is positive in the upper direction, dTs/dz and dTJL/dz usually take negative values. The temperature of the solid-liquid interface is about 1
400℃), lowering the crucible heating temperature reduces the absolute value 1dTJl/dzl of the temperature gradient d7s/dz on the melt side in the above equation, and the speed V
becomes larger.

However, when crystal growth is performed using the conventional apparatus shown in Figure 7, when the heating temperature of the crucible is lowered below a certain temperature, the silicon melt starts to solidify from the crucible wall surface, and eventually the solidification reaches the crystals and the crystals become fixed. and growth is interrupted. If the crucible heating temperature is increased to prevent this, the crystals will no longer stick and solidify from the crucible wall, allowing crystal growth to continue, but as the crucible heating concentration is increased, the temperature of the silicon melt will rise again, resulting in a high rate of growth. This will impede lifting.

As mentioned above, in the conventional device, a certain thickness, for example, 5
There was a problem in that it was not possible to produce crystals of 00μ at a speed higher than the above-mentioned speed (20aS 1 minute or higher).

(Objective of the Invention) The present invention has been made in view of the above-mentioned problems, and is capable of stable crystal growth for a long period of time without being interrupted by the progress of solidification from the crucible wall surface, and capable of high-speed pulling. The purpose of the present invention is to provide a band-shaped silicon crystal manufacturing device that is possible.

[Summary of the Invention] The present invention provides a convex portion on the upper surface of the bottom of the crucible for storing silicon melt on a straight line connecting the hole for inserting the filamentous support formed in the bottom of the crucible, thereby reducing the temperature inside the crucible. The distribution is made so that the concentration is lower in the center of the crucible where crystals grow than in the vicinity of the crucible walls, and crystal growth is maintained at high speed and stably for a long time without interrupting crystal growth due to solidification progressing from the crucible walls. This is a possible band-shaped silicon crystal manufacturing device.

[Embodiments of the Invention] FIG. 1 shows a schematic diagram of a crucible for producing band-shaped silicon crystals according to the present invention. That is, the protrusion 101 on the bottom of the carbon-made Luppo 1 is located on a straight line connecting the two holes 2a, 2b for inserting the filamentous support formed in the bottom of the crucible, and the two holes 2a, 2b are connected to each other. In other words, they are arranged in an elongated manner in the width direction of the crystal to be grown. The size of the convex portion 101 is less than or equal to the crystal width to be grown, and the width is 5 to 5 times the crystal thickness.
The range of 30 times and the height are set so that the upper end of the convex portion 101 is 3 to 5 aw below the silicon melt.

An example of manufacturing a band-shaped silicon crystal using the crucible 1 described above will be described below.

A band-shaped silicon crystal having a width of 10 G was grown using a band-shaped silicon crystal manufacturing apparatus configured as shown in FIG. In Figure 2,
The same parts as in FIG. 7 are given the same reference numerals, and the explanation thereof will be omitted.

In this example, the protrusion 101 on the bottom of the crucible was rectangular, with a length of 98IWi and a width of 5M. Further, the height of the convex portion 101 was set to 20 m from the upper surface of the bottom of the crucible, using a crucible 1 having a depth of 30 s. FIG. 3 shows the results of growing a band-shaped silicon crystal 5 using this crucible 1. In Figure 3, the horizontal axis shows the pulling speed (m/min), and the vertical axis shows the crystal thickness (m).
), and there is no protrusion on the top surface of the bottom of the conventional crucible A
In order to obtain a crystal with a crystal thickness of 500 cxm, the pulling speed was approximately 20 d/min, but in B, in which a convex portion was provided on the top surface of the bottom of the crucible according to the present invention, the pulling speed was 30 m/min.
Crystals with a thickness of about 500 μm could be obtained in minutes.

As described above, by providing the convex portion 101 on the upper surface of the bottom of the silicon containing crucible 1 according to the present invention on the straight line connecting the holes 2a and 2b drilled in the bottom of the crucible, the center of the crucible 1 where crystal growth is performed is formed. By creating a temperature distribution such that the temperature of the silicon melt 6 in that part is lower than the temperature of the silicon melt 6 near the wall of the crucible 1, crystal growth due to progress of solidification from the wall of the crucible 1 is not interrupted. Crystal growth can now be performed at high speed and stably for long periods of time. In addition, as another effect of the present invention, the temperature distribution of the silicon melt surface in the part where the crystal is grown in the center of the crucible becomes almost uniform, and as a result, a flat band-shaped silicon crystal with a substantially uniform thickness is obtained. When this was made into a device as a substrate for a solar cell, it was possible to obtain a device with good characteristics. - [Other embodiments of the invention] In the above embodiments, the convex shape at the bottom of the crucible was rectangular,
Even with other shapes, almost the same effects as in the above example were obtained. Examples of the shape of the convex portion on the upper surface of the bottom of the crucible are the fourth factor and the fifth factor.
As shown in the figure. In FIG. 4, the convex portion 101 is shaped like a triangular prism, and in FIG. 5, the center portion of the convex portion 101 is shaped like a convex lens, bulging toward both side walls of the crucible. In the shape shown in FIG. 5, the temperature of the silicon melt at the center in the width direction of the crystal is lower than the temperature at the ends of the crystal, and crystal growth proceeds from the center of the crystal toward the ends in the width direction. This allows the strain that occurs during crystal growth to escape to both ends of the crystal, and when used as a substrate for semiconductor devices, by removing both ends of the crystal with a lot of distortion, a high quality substrate for semiconductor devices can be obtained, and the growth The resulting crystals can be used effectively.

Alternatively, as shown in FIG. 6, by dropping the upper portions of both ends of the crucible bottom upper surface convex portion 101 in the crystal width direction obliquely,
The temperature distribution was such that the temperature of the silicon melt at the center of the crystal was lower than the temperature at the ends of the crystal, and the same effect as above was obtained. In other shapes as well, the same effect as above can be obtained by dropping both ends of the convex portion obliquely.

I also tried growing the crucible by making the crucible longer than the width of the crystal in order to grow the convex part on the top surface of the bottom, but the temperature of the silicon melt at the filamentous supports at both ends of the crystal decreased and the crystal grew at high speed. When the heating temperature of the crucible was lowered for this reason, the filamentous support portions became fixed and crystal growth was interrupted.

[Effects of the Invention] As described above, according to the present invention, the temperature of the silicon melt contained in the crucible is lower than that of the silicon melt at the center in the crystal width direction. By setting the temperature lower than Manufacturing equipment can be provided.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing an example of a crucible according to the present invention;
FIG. 2 is a schematic cross-sectional view showing an embodiment of the belt-shaped silicon crystal manufacturing apparatus of the present invention, FIG. 3 is a diagram showing an example of the pulling speed crystal thickness characteristics of the present invention in comparison with the conventional one, and FIG. 5 and 6 are schematic perspective views showing other embodiments of the present invention, FIG. 7 is a schematic cross-sectional view of a conventional belt-shaped silicon crystal manufacturing apparatus, and FIG. 8 is a drawing speed-crystal thickness of the conventional apparatus. FIG. DESCRIPTION OF SYMBOLS 1...Carbon crucible, 2a, 2b...Thread-like support insertion hole, 3a, 3b...Thread-like support, 4...
Seed, 5... Band-shaped silicon crystal, 6... Silicon melt, 101... Convex portion. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) A pair of filamentous supports are passed perpendicularly to the surface of the silicon melt through holes drilled at the bottom of the crucible containing the silicon melt at approximately equal intervals to the width of the band-shaped silicon crystal to be grown. and bringing the seeds into contact with the pair of filamentous supports and the silicon melt between the pair of filamentous supports,
The device for manufacturing band-shaped silicon crystals by pulling up the seeds, characterized in that a convex portion is provided on the upper surface of the bottom of the crucible containing the silicon melt in a linear shape connecting holes drilled in the bottom of the crucible. A device for producing band-shaped silicon crystals. (2) The device for producing a band-shaped silicon crystal according to claim 1, wherein the convex portion on the upper surface of the bottom of the crucible containing the silicon melt is set to be less than or equal to the width of the band-shaped silicon crystal to be grown.