JPS5950636B2 - Band-shaped silicon crystal manufacturing equipment - Google Patents

Description

[Detailed description of the invention] [Technical field of invention] TECHNICAL FIELD The present invention relates to an improvement in an apparatus for producing band-shaped silicon crystals.

[Technical background of the invention and its problems]

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 cross-sectional view of the interior of the furnace for growing band-shaped silicon crystals.

This figure 1 shows a slit (gap) made of carbon in a quartz glass crucible 12 that houses a silicon melt 11.
Capillary die 13 (13a, 13b) with
(hereinafter referred to as single nigui) with its long side as crucible 1
3 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 support plate 14 and further to a heat shield plate 15.

This heat shielding plate 15 serves to weaken the thermal radiation of the melt 11 from reaching the tip of the die 13, and has a window that exposes the tip of the die 13.

The crucible 12 is a crucible holder 1 made of carbon.
It is inserted in 6.

A pair of plate-shaped heaters 17 (17a, 17b) are provided on the outside of the crucible holder 16.

This heater 17 is connected to the die 13 and the crucible holder 1.
6 is installed parallel to the longitudinal direction, and cuts are made alternately from the top and bottom, thereby controlling the electrical resistance value.

Note that 18 in the figure indicates a band-shaped silicon crystal.

Further, FIG. 2 is a view of the apparatus shown in FIG. 1 from above, and 19 (19a, 19b) is a chamber H.
It shows a regular wall.

Polycrystalline silicon is put into the quartz crucible 12 of the belt-shaped silicon crystal production apparatus constructed as described above, and the temperature of the heater 17 is raised to about 1500 [° C.].

Then, the polycrystalline silicon becomes a silicon melt 11, and this silicon melt 11 rises to the tip of the die 13 due to capillary action.

By bringing a seed crystal (not shown) into contact with the rising silicon melt 11 from above and gradually pulling up the seed crystal, a band-shaped silicon crystal can be grown.

Ru.

However, this type of apparatus has a problem in that the crystal growth rate is slow.

When the present inventor actually grew a band-shaped silicon crystal using the apparatus shown in FIG.
00, [mm], thickness 0. 5 (mm) of crystals were obtained, but the pulling growth rate could not exceed 15 (mm/min).

When aiming to reduce the cost of solar cell substrates, increasing the amount of crystal growth per unit time is an important means, and now that the crystal width has reached 100 (mm)1, there is a demand for increasing the pulling growth rate. has been done.

On the other hand, as a means of increasing the pulling growth rate of crystals,
Cool the band-shaped silicon crystal by blowing gas directly on it, or place the band-shaped silicon crystal in a metal block.

Attempts have been made to increase the temperature gradient over the die.

However, in the former case, it is extremely difficult to control the cooling temperature, and in the latter case, there are problems such as poor cooling efficiency.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for producing a silicon crystal band, which can increase the pulling growth rate of the silicon crystal band, increase the amount of crystal growth per unit time, and improve the manufacturing yield. be.

[Summary of the invention]

The gist of the present invention is how to increase the temperature gradient on the die and slit and improve the temperature controllability.

The temperature of the area under the heat shield plate where the heater, silicon melt, etc. are housed is 1500 [°C] or more.

At the upper end of the die and slit, the silicon must be in a molten state and must be maintained at a temperature of about 1420 ['C] or higher.

In order to obtain a large temperature gradient directly above the die tip, it is necessary to minimize the heat flowing onto the heat shield plate.

Moreover, in order to control crystal pulling, the solid-liquid interface must be visible, and it is not permissible to make the heat shield plate unnecessarily thick.

The present invention focuses on such points, and one end of a capillary and a die having a slit is immersed in a heated and melted silicon melt housed in a crucible, and the silicon melt rises through the slit of the capillary and die. In an apparatus for producing band-shaped silicon crystals, which grows and forms band-shaped silicon crystals by bringing a seed crystal into contact with a seed crystal and pulling up the seed crystal, the capillary is placed on a heat shielding plate provided at the top of the crucible, and a protrusion near the upper end of the die is formed. A receiving plate having a section is disposed, and a gas cooling block for cooling a portion above the solid-liquid interface of the silicon melt is disposed on the receiving plate.

〔Effect of the invention〕

According to the present invention, since there is a heat retention effect on the high-temperature portion at the bottom of the heat shielding plate, no more heating power than before is required.

Moreover, since the gas is blown in the direction of the protrusion near the tip of the die on the receiving plate, the cooling effect can be exerted even closer to the band-shaped silicon crystal.

As a result, the pulling growth rate, which conventionally could not exceed 15 mm/min, reached 30 cm/min, making it possible to significantly increase the amount of crystal growth per unit time.

In addition, rather than directly blowing cooling gas onto the band-shaped silicon crystal, the flow rate and direction of the cooling gas used for crystal cooling is regulated by the receiving plate having the convex portion, making temperature control relatively easy. This allows for highly uniform cooling.

Therefore, manufacturing yield can also be improved.

[Embodiments of the invention]

FIG. 3 is a schematic sectional view showing a band-shaped silicon crystal manufacturing apparatus according to an embodiment of the present invention, and FIG. 4 is a plan view of the apparatus as viewed from above.

Note that the same parts as in FIGS. 1 and 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

This embodiment differs from the conventional device in that the heat shield plate 15
A receiving plate 20 is placed on the receiving plate 20, and a gas cooling block 21 (21a, 21b) is arranged on this receiving plate 20.

The cooling block 21 includes water cooling pipes 22 (22a, 22
b) is welded.

The receiving plate 20 is made of carbon material with a thickness of 3 (mm),
The part close to the die tip is a convex part formed parallel to a part of the tipper of the die, and the distance from the die tip wall surface is about 1. 5 (mm).

This convex portion is formed to have the same height as the die tip.

The gas cooling block 21 is made of stainless steel with a wall thickness of 2 cm, and one side has 25 jet ports 23 (23a, 23b) diagonally downward, and the opposite side has a gas outlet. Pipe 24 (24a
, 24b) are attached to ν·ru.

A water-cooling pipe 22 for circulating water is welded to the opposite side of the gas-cooling hook 21 from the receiving plate 20, and the water-cooling pipe 22 and the gas introduction pipe 24 are
They are connected inside the chamber H-shaped wall 19 and have a structure that allows for easy removal.

Using the device configured as described above, Ar gas was supplied to the upper cooling mechanism of the heat shield plate 15 at a rate of 20 [1/min], and cooling water was supplied at a rate of 5 [1/min].
/minute] and the temperature was measured directly above the die.

As a result of using platinum-platinum-rhodium 13 [%] as a thermocouple, the ambient temperature directly above the die was about 900 [°C].

This temperature is significantly lower than the measured value of about 1200 [° C.] at the same position before the upper cooling mechanism of the heat shield plate 15 was installed.

Therefore, an increase in the pulling growth rate is expected.

Next, the seed crystal is brought into contact with the silicon melt at the upper end of the die,
A band-shaped silicon crystal was grown.

At this time, the seed pair needed a little more power because the seeds themselves were cooled down more, but when the steady state was reached, no more power than before was needed.

The pulling growth rate is as follows: Width 100 (mm, l, thickness 0.5
(mm) band-shaped silicon crystal up to 34 (mm/m/
The speed was constantly 30 mm/m/min.

This means that the pulling growth rate has increased by about 2.3 times compared to the conventional method, and therefore, the amount of crystal growth per unit time can also be increased by this amount.

Because the temperature gradient was steeper, the probability of solidification occurring due to temperature fluctuations was smaller, and growth was easier to control.

Moreover, no deterioration in the performance of the silicon strip as a substrate due to the installation of the upper cooling mechanism of the heat shield plate 15 was observed.

Band-shaped silicon crystals were mainly developed for use in solar cells, and now that a certain degree of quality improvement has been achieved, it is inevitable to aim for cost reduction, and improvement of the pulling growth rate is also necessary. It is expected.

Therefore, this embodiment is expected to have a wide range of applications in addition to the benefits of resource saving and energy saving.

Note that the present invention is not limited to the embodiments described above.

For example, the receiving plate placed on the heat shielding plate is made of a material other than carbon that is heat resistant and is inert to silicon vapor,
In addition, molybutton, which has a lower emissivity, may also be used.

Further, the number of the receiving plates does not need to be one, and two or more may be used in a stacked manner from the viewpoint of heat retention.

Furthermore, the material of the gas cooling block is not limited to stainless steel, but may also be the above-mentioned molybutton, and a partition may be provided inside the block to allow the gas to flow effectively;
It is also possible to provide a plurality of gas introduction vias or to change the diameter, number, direction, etc. of the gas ejection ports as appropriate.

However, when considering cost, processing system, etc., the above-mentioned example materials are a better combination.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a conventional belt-shaped silicon crystal production apparatus, FIG. 2 is a plan view of the conventional apparatus seen from above, FIG. 3 is a schematic cross-sectional view showing an embodiment of the present invention, and FIG. FIG. 2 is a plan view of the above-mentioned embodiment device viewed from above. 11... Silicon melt, 12... Crucible, 13...
・Capillary die, 15... Heat shield plate, 17a, 1
7b... Heater, 20... Receiving plate, 21a, 21b.
...Gas cooling block, 22a, 22b...Water cooling pipe, 23a, 23b...Gas outlet, 24a, 24b
−・Gas introduction via.

Claims (1)

[Claims] 1. One end of a capillary die having a slit is immersed in a heated and melted silicon melt housed in a crucible, and a seed crystal is placed in the silicon melt rising through the slit of the capillary die. In an apparatus for producing a band-shaped silicon crystal in which a band-shaped silicon crystal is grown and formed by bringing the seed crystal into contact with the seed crystal and pulling up the seed crystal, a receiver having a convex portion near the upper end of the capillary die is provided on a heat shielding plate provided on the upper part of the crucible. A band-shaped silicon crystal comprising a plate and a gas cooling block disposed on the receiving plate, the gas cooling block cooling a portion above the solid-liquid interface of the silicon melt. Manufacturing equipment. 2. The belt-shaped silicon crystal manufacturing apparatus according to claim 1, wherein the gas cooling block has a cooling water circulation pipe attached to its peripheral surface. 3. The belt-shaped silicon crystal manufacturing apparatus according to claim 1, wherein the receiving plate is made of carbon or molybdenum. 4. The belt-shaped silicon crystal manufacturing apparatus according to claim 1, wherein the gas cooling block is made of stainless steel or molybutton and has a gas outlet that blows out diagonally downward with respect to the receiving plate surface. .