JPS5849690A - Production unit for ribbonlike silicon crystal - Google Patents

Abstract

PURPOSE:A production unit for growing a ribbonlike Si crystal having a little SiC powder adhesion and a good shape in high yield, equipped with plural members for regulating temperature, capable of being brought into contact with die-setting plate and moved in parallel to the longer direction of the die in order to use the heat from a heater effectively for crystal growth. CONSTITUTION:The four members 22(22a-22d) for regulating temperature are arranged in parallel to the longer direction of the dies 13a and 13b in such a way that they all can be moved along the channels carved on the fixed plate 24. The members 22 are arranged two by two at the both sides of the thickness direction of the dies 13, and each can be moved independently. By using this construction and pulling up a ribbonlike Si crystal from the dies 13, the SiC powder attached to the crystal can be extremely reduced. The temperature distribution of the width direction of the dies 13 is corrected effectively, and a wide crystal can be grown. The Si melt 11 and the heat masking shield 14 are shown respectively in the Fig.

Description

[Detailed description of the invention] do.

Because band-shaped silicon crystals are thin-plate-shaped, they differ from the ingot-shaped silicon crystals obtained by the Czochralski method, and the obtained shape! ! It is used as a substrate for semiconductor solar cells. Therefore, it has the great feature that it is cheaper than using, for example, silicon crystal obtained by the Czochralski method as a substrate for a semiconductor solar cell.

FIG. 1 shows a schematic diagram of an example of the configuration of a furnace for growing band-shaped silicon crystals. This figure 1 shows a capillary die l″I (1″
? a, 1, 9 b) (hereinafter referred to as vinegar)
The figure shows a state in which the longitudinal direction of the bolt is parallel to the longitudinal direction of the bolt 12.

The tip of this die 13 is sharp and machined into a knife shape. 14 is a heat shielding plate, which is used for melting liquid 7Z.
The window 1 serves to weaken the thermal radiation reaching the tip of the die 13, and the window 1 exposes the tip of the die 13.
9 is open. Crucible 12 is Ka, l! The crucible holder 15 is inserted into a crucible holder 15 formed of a cylindrical tube. A pair of plate-shaped resistance heaters 16 (1'6a, 16b) are provided on the outside of the crucible holder 15.

This heater 16 is connected to the die 13 and the crucible 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 crucible 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 and silicon become a silicon melt 11, and the silicon melt 11 rises to the tip of the die 13 due to capillary action. Seed crystals (not shown) are added to this rising silicon melt 11 from above.
By bringing them into contact with each other and then gradually pulling them up, a band-shaped silicon crystal can be grown.

When the present inventor grew a band-shaped silicon crystal in the above-mentioned growth apparatus, S was deposited on both sides of the band-shaped silicon crystal.
The iC grains adhered to the substrate, making it unsuitable for use as a solar cell substrate. Further, it was difficult to grow a wide and long band-shaped silicon crystal with a good yield because the growth was biased toward one side of the die 13 or a crystal with a sufficient width could not be obtained.

Therefore, the present invention makes it possible to grow a band-shaped silicon crystal with a high yield (80% or more) on one surface of the band-shaped silicon crystal, which has few SiC grains attached and has a cross-sectional shape equivalent to the slit of the die. The present invention provides an apparatus for manufacturing band-shaped silicon crystals.

That is, the present invention includes four temperature adjusting members, such as carpin plates, which are in contact with the die fixing plate and movable in parallel to the longitudinal direction of the die so that the heat from the heater can be effectively used for crystal growth. block (called a heat screen)
By placing two of these on each side of the die in the thickness direction, it is possible to pull a wide band-shaped silicon crystal with a small number of SiC grains on one surface with a high yield.

Hereinafter, the present invention will be described in detail with reference to the drawings. Second
3 is a front view showing an apparatus according to an embodiment of the present invention, FIG. 3 is a side sectional view, and FIG. 4 is a plan view showing the arrangement of a heat screen. As shown in these figures, there are four heat screens 22 (22a) parallel to the longitudinal direction of the die.

22b, 2:lc, 22d) are installed.

Both heat screens 22 can move along grooves cut on the die fixing plate 24. This heat screen 22, like the heater 16, is made of graphite. These heat screens 22 are connected to a micrometer head (not shown) VC outside the furnace through the chamber side wall by connection jigs 23 (23a, 23b, 23c, 23d), respectively.
The movement of 2 is performed by rotation of the micrometer head, and the direction of movement is parallel to the longitudinal direction of the die 13. The upper part of the die is heated mainly by conduction from the die fixing plate 24 and radiation from the heater 16 when the heat screen 22 is in a loose state. By moving the heat screen 22 so as to block part of the radiation from the heater 16, the amount of heat reaching the upper part of the goo is reduced, and the temperature of the shaded area can be made relatively low. The heat screen 22 is the die 13
There are two on each side in the thickness direction, and each can be moved independently. The crucible holder 15 is supported by a base 25. FIG. 2 shows a band-shaped silicon crystal 26 grown above the tip of the die 13. As shown in FIG.

Specific experimental data will be explained below. Die used 1
3 has a width of 100 mm and has 4 heat screens 22
The arrangement can be moved so that the two mirror surfaces intersect at the center of the die 13 in a symmetrical relationship. The heat screen 22 can be placed sufficiently away from the die 13, and at this time, it can be placed in a position that does not impede heat radiation from the heater 16 reaching the top of the die 13 at all. First, the two heat screens 22c and 22d on one side of the die 13 in the thickness direction are fixed at a position where they do not block thermal radiation, and the two heat screens 22a and 22b on the other side are fixed.
Crystal growth was performed while moving the . The positions of the heat screens 22a and 22b are expressed as distances from the center of the die I3, and it was confirmed that the positions had sufficient reproducibility.

FIG. 5 shows two heat screens 22a from the center of the die 13.

The distance to the tip of 22b is X mm and Y
ntm, and the table below shows the combinations of X and Y, the number of SiC grains attached to the surface of the grown silicon band, and the maximum width of the silicon band.

As is clear from this table, heat screen 22*,
By placing 22b and providing a temperature difference in the thickness direction of the die 13, the number of 810 pieces could be reduced by about one order of magnitude on one side (the side without heat isolation). Further, by arranging the heat screens 22* and 22b at appropriate positions, the effect of correcting the temperature distribution in the longitudinal direction of the die 13 was also obtained, which contributed to widening the band-shaped silicon crystal. However, it was difficult to widen the die to a width of about 77 meters or more for a die with a width of 100 m. Therefore, two heat screens 22c were placed between the dies and fixed on opposite sides.

22d is also brought closer to die 13 and X = 43 ttm,
The heat screens 22a and 22b that have been used for a long time are placed in the position of Y = 51, and the positions of X = 26 and Y =
When placed at a position of 38 mm, a silicon strip with a maximum width of 97 mm could be grown on a die with a width of 100 mm. The number of SiC at this time is about 0.09 on the small side.
pcs/Ca.

Next, a solar cell was created using a band-shaped silicon crystal manufactured using the apparatus of this embodiment and a crystal manufactured using a conventional apparatus, and their performances were compared. In the former crystal, a pn junction was formed on the side to which less SiC grains were attached, and this was used as a light-receiving surface. As a result, it was found that the former was superior to the latter by about 30 to 50 units in terms of solar cell conversion efficiency.

Furthermore, in the case of thick band-shaped silicon crystals (~0.8+a), irregular grain boundaries that bisect the thickness were occasionally observed in the past, but in this embodiment, a temperature difference was created in the thickness direction of the die. As a result, these irregular grain boundaries disappeared and improved crystallinity was also confirmed. Particularly when high-speed pulling is performed, it is necessary to maintain good crystallinity, and the apparatus of this embodiment is considered to function effectively.

As explained above, according to the present invention, at the top of the die,
By installing four temperature adjustment members that control heat radiation from the heater, it is possible to set a temperature gradient in the thickness direction of the die, and the 84
In one aspect, which is essential for improving the solar wheel-pond conversion efficiency, it was possible to significantly reduce the number of grains.

It is also effective in correcting the temperature distribution in the width direction of the die.
□It is now possible to grow wide crystals. Compared to the case where the same effect is achieved electrically using an auxiliary heater, this method has the advantage that a new power source is not required, and the control mechanism is relatively simple, so that the growth apparatus can be made smaller. Therefore, the apparatus of the present invention makes it possible to produce wide band-shaped silicon crystals with good crystallinity at a high yield and at a lower cost, which greatly contributes to lowering the cost of solar cells.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the inside of the furnace showing a conventional apparatus for growing band-shaped silicon crystals, and Figures 2 and 3 are
FIG. 1 is a front view of the inside of the furnace and a cross-sectional view from the side of an embodiment of the present invention in which a heat screen is incorporated into the apparatus, FIG. 4 is a plan view showing the arrangement of the heat screen, and FIG. 5 is a heat screen. It is a figure which shows how to determine the position of a screen. 11...Silicon melt, 12...Quartz glass lugs, 13L, 13b l...Gui, 14...Heat shield &, rs...Rutsuga holder, 16a, 16b.
...Resistance heater, 17... Notch, 18... Chamber side wall, x9-B, 22a, 22b, 22c. 22d... Heat screen (temperature adjustment member), 23
a, 23 b, 23' c, 23 d
-' Connecting jig, 24... Gui fixing plate, 25... Crucible holder is stand, 26... Band-shaped silicon crystal. Applicant's representative Patent attorney Takehiko Suzue = 11- Stomach

Claims (2)

[Claims] (1) A capillary die having a slit is arranged in a luge containing a silicon melt, a seed crystal is brought into contact with the melt rising through the slit, and the band-shaped silicon crystal is pulled by pulling up the seed crystal. A resistance heating type pulling device W for lifting the die includes a fixing plate for fixing the die and a heat shielding plate having a fixed space above the die and a window for exposing the tip of the die above the die. An apparatus for producing a band-shaped silicon crystal, characterized in that four temperature adjustment members that are in contact with a fixed plate and movable in parallel to the longitudinal direction of the die are arranged, two on each side of the die in the 1V direction. . (2) The apparatus for producing a band-shaped silicon crystal according to claim 1, wherein the temperature adjusting member is a heat screen made of a block made of Kaden.