JPS5932434B2 - Band-shaped silicon crystal production equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to an apparatus for manufacturing band-shaped silicon crystals.

Since the band-shaped silicon crystal is in the form of a thin plate, unlike the ingot-shaped silicon crystal obtained by the Czochralski method, it can be used as a substrate for a semiconductor solar cell in its obtained shape.

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.

FIG. 1 shows a capillary die 13 (13a, 13b) (hereinafter simply referred to as die) having a slit (gap) made of carbon in a quartz glass crucible 12 containing a silicon melt 11 in its longitudinal direction. It shows a state in which the crucible 12 is installed parallel to the longitudinal direction of the crucible 12.

The tip of this die 13 is sharp and processed into a knife shape.

Reference numeral 14 denotes a heat shielding plate, which serves to weaken the thermal radiation of the melt 11 from reaching the tip of the die 13. A window 19 is opened to expose the tip of the die 13. There is.

The crucible 12 is a crucible holder 1 made of carbon.
It is inserted in 5.

A pair of plate-shaped resistance heaters 16 (16a) are provided on the outside of the crucible holder 15.

16b) is provided.

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 becomes a silicon melt 11, and this silicon melt 11 flows through the die 1 due to capillary action.
It rises to the tip of 3.

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.

When the present inventor grew a band-shaped silicon crystal using the above-mentioned growth apparatus, Si was deposited on both sides of the band-shaped silicon crystal.
0 particles adhered to the substrate, making it unsuitable as a substrate for solar cells.

In addition, the growth was biased toward one side of the die 13, and crystals of sufficient width could not be obtained, resulting in poor yield (it was difficult to grow long, wide band-shaped silicon crystals).

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

That is, the present invention includes four temperature adjusting members, such as carbon 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 up a wide band-shaped silicon crystal with a small number of Si0 grains on one surface with a high yield.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 2 is a front view showing an apparatus according to an embodiment of the present invention, FIG. 3 is a lateral sectional view, and FIG. 4 is a plan view showing the arrangement of a heat screen.

As shown in these figures, four heat screens 22 (22a, 22b) are arranged parallel to the longitudinal direction of the die.

22c, 22d) are installed.

Each of the 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 connecting jigs 23, respectively.
(23a, 23b.

23c, 23d) are connected to a micrometer head (not shown) outside the furnace through the chamber side wall, and the movement of the heat screen 22 is performed by rotation of the micrometer head, and the direction of movement is parallel to the longitudinal direction of the die 13. It is.

Heating of the upper part of the die is mainly performed by conduction from the die fixing plate 24 and radiation from the heater 16 when the heat screen 22 is not provided.

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 die is reduced, and the temperature of the shaded area can be kept relatively low.

There are two heat screens 22 on both sides of the die 13 in the thickness direction.
They are arranged one by one and can be moved independently.

The crucible holder 15 is supported by one crucible holder 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.

The width of the die 130 used was 100 mm, and the arrangement of the four heat screens 22 could be moved so that the two mirror surfaces intersecting at the center of the die 13 were symmetrical.

The heat screen 22 can be placed at a sufficient distance from the die 13, and at this time, it can be placed in a position that does not at all impede heat radiation from the heater 16 that reaches the top of the die 13.

First, the two heat screens 22c and 22d on one side in the thickness direction of the die 13 are fixed in a position where they do not block thermal radiation, and the two heat screens 22a on the other side are fixed.
, 22b was moved while crystal growth was performed.

Position of heat screens 22a and 22b (Todai 13
It was confirmed that there was sufficient reproducibility of the position, expressed as the distance from the center.

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

The distance to the tip of 22b is Xvvrn, Y
The table below shows the combination of X and Y, the number of Si0 grains attached to the surface of the grown silicon band, and the maximum width of the silicon band.

As is clear from this table, the heat screen 22a
, 22b and providing a temperature difference in the thickness direction of the die 13, it was possible to reduce the number of SiC by about one order of magnitude on one side (the side without heat shielding).

Also, a heat screen 22a. By arranging 22b at an appropriate position, the effect of correcting the temperature distribution in the longitudinal direction of the die 13 was also obtained, contributing to widening of the band-shaped silicon crystal.

However, for a die with a width of 1001 m, approximately 777
It was difficult to widen the width beyond r111L.

Therefore, the die was fixed on the opposite side with two
The heat screens 22c and 22d were also placed close to the die 13 at the position of X2431Lm, Y=51, and the heat screen 22a that had been used previously.

22b was able to grow a silicon band with a maximum width of 97 mm on a die with a width of 100 mm when placed at a position of X = 26 mm and Y2 38 mm.

The number of SiC at this time was about 0.09 pieces/d on the small side.

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 times in terms of solar cell conversion efficiency.

In addition, thick band-shaped silicon crystal (~Q, 8*yn)
Conventionally, irregular grain boundaries that bisect the thickness were occasionally observed, but with the device of this embodiment, which created a temperature difference in the thickness direction of the die, these irregular grain boundaries disappeared and the crystallinity improved. An improvement was also confirmed.

In particular, 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 Si attached to the band-shaped silicon crystal can be
In one aspect, C grains, which are essential for improving the conversion efficiency of solar cells, were able to be significantly reduced.

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, there is an 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, thereby significantly contributing to cost reduction of solar cells.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of the inside of a furnace showing a conventional apparatus for growing band-shaped silicon crystals, and FIGS. 2 and 3 show an embodiment of the present invention in which a heat screen is incorporated into the apparatus of FIG. 1. A front view of the inside of the furnace and a sectional view from the side, FIG. 4 is a plan view showing the arrangement of the heat screen, and FIG. 5 is a diagram showing how to determine the position of the heat screen. 11... Silicon melt, 12... Quartz glass crucible, 13a, 13b... Die, 1
4... Heat shielding plate, 15... Crucible holder, 16a, 16b... Resistance heater, 1
7...notch, 18...chamber side wall, 19...window, 22a, 22b. 22c, 22d...Heat screen (temperature adjustment member), 23a, 23b, 23c, 23d-
-----Series tying jig, 24...Die fixing plate, 2
5... Crucible support is a stand, 26... Band-shaped silicon crystal.

Claims (1)

[Scope of Claims] 1. A capillary die having a slit is arranged in a crucible containing silicon melt melted by a heater, a seed crystal is brought into contact with the melt rising through the slit, and the seed crystal is pulled. In a resistance heating type pulling device for pulling a band-shaped silicon crystal by lifting the crucible, a fixing plate for fixing the die above the crucible and a heat shielding plate having a fixed space and a window above which the tip of the die is exposed. four heat screens, two of which are arranged on each side of the die in the thickness direction, which are in contact with the die fixing plate and movable in parallel to the longitudinal direction of the die, and which block part of the radiant heat from the heater. An apparatus for producing band-shaped silicon crystals, which is characterized by: 2. The apparatus for manufacturing a band-shaped silicon crystal according to claim 1, wherein the heat screen is a carbon block.