JPH06191815A - Silicon thin plate manufacturing method - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for manufacturing a silicon thin plate capable of forming a PN junction at the same time as manufacturing. A crucible 40 is placed in a reaction tube 20 replaced with argon gas, a p-type single crystal silicon plate 70 is melted using a tin flux in the crucible, and the silicon melt and a gas phase are formed. Is a method for producing a thin plate 80 of crystalline silicon by cooling the interface of the above and precipitating silicon at this interface, characterized in that PH ₃ gas which is an n-type dopant gas is introduced into the reaction tube only in the initial stage of cooling. And
According to this method, n is formed on the initial growth surface of the obtained thin plate 80.
Since the bulk body becomes p-type silicon with the type dopant mixed therein, it is possible to manufacture a silicon thin plate having a PN junction at the same time as manufacturing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a crystalline silicon thin plate applicable to a substrate for solar cells, etc.
The present invention relates to a method for manufacturing a silicon thin plate which has good productivity and can reduce manufacturing cost.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of protecting the global environment, a solar cell has been attracting attention as a power generation means replacing thermal power generation, nuclear power generation and the like. In other words, this solar cell is expected to be a clean energy source because it generates power when exposed to sunlight and does not emit carbon dioxide or radioactive waste at all.

However, the cost of power generation by a solar cell is still high, and it is necessary to significantly reduce the manufacturing cost in order for the solar cell to be widely popularized.

By the way, as a typical example of this solar cell,
An example is a crystalline silicon solar cell manufactured by processing a single crystal silicon substrate or a polycrystalline silicon substrate. And, in the former, from a single crystal silicon ingot obtained by pulling from the silicon melt by the Czochralski method, etc., a single crystal silicon wafer is cut out with a diamond saw as a solar cell substrate, and,
In the latter case, a polycrystalline silicon ingot is produced by a casting method or the like, and a cast silicon wafer is cut out with a diamond saw to obtain a solar cell substrate.

However, in these methods, since the growth rate of the crystalline silicon ingot is slow, the productivity thereof is poor, and a cutting step with a diamond saw is required, which increases the manufacturing cost accordingly. There was a drawback that

As a solution to the above-mentioned problems associated with the production of crystalline silicon solar cells, thin-film solar cells typified by amorphous silicon have been eagerly studied. However, in terms of cost and performance, the crystalline silicon-based solar cell has not been surpassed as a material for a solar cell for electric power.

Therefore, some methods of manufacturing a polycrystalline silicon thin plate have been proposed which do not require the above cutting step with a diamond saw.

As an example, an EFG (Edge-defined Fil) is used to pull up a ribbon-shaped silicon thin plate from a silicon melt.
m-fed Growth) method [eg, “EFG cry
stalgrowth technology for low cost terrestrial pho
tovoltaics: review andoutlook ”, FVWald et al., Sol
ar Energy Materials and Solar Cells, vol.23, p.175 (1
992), see]. In this method, as shown in FIG. 6, a crystalline silicon thin plate c is pulled up from a bath b of molten silicon a in a direction perpendicular to the silicon melt surface to manufacture. In FIG. 6, d is a ribbon and e is a die.

However, in this manufacturing method, the crystal growth of silicon occurs only at the interface between the silicon melt and the silicon thin plate, and therefore, in order to obtain crystalline silicon of a quality usable as a solar cell, the growth rate is at most several. It has to be limited to about centimeters / minute, and therefore has the drawbacks of poor productivity, low cost of solar cells, and difficulty in mass production.

As another example, a method in which a tape made of a heat resistant material such as carbon fiber cloth or graphite sheet is passed through a molten silicon bath to deposit crystalline silicon on the tape. Have also been developed [eg, “Growth of Poly sheets on
a carbon shaper by the RAD process ”, C.Belouetet a
l., Journal of Crystal Growth, vol.61, p.615 (1983), see]. In this method, a heat-resistant tape is passed through the surface of molten silicon or the surface of molten silicon, and the silicon melt adhering to the tape is solidified to obtain polycrystalline silicon. In this method, the crystallization of silicon does not necessarily have to occur at the silicon melt interface and can be performed in the heat treatment process after attaching to the tape. Has the advantage that the growth rate can be increased.

However, this method also has the following drawbacks.

First, in this method, silicon crystallizes on a heat resistant tape such as carbon. At this time, during cooling from the growth temperature (1410 ° C. or higher which is the melting point of silicon) to room temperature, cracks or various crystal defects occur in the silicon due to the difference in thermal expansion coefficient between the silicon and the heat resistant tape. Easy to do. Then, these cracks and crystal defects in the silicon cause the characteristics to be greatly deteriorated when applied to the solar cell.

The heat resistant tape such as carbon must be of high purity. This is because if the heat-resistant tape contains impurities, these impurities will be diffused into the silicon during the growth and crystallization process of silicon and will cause a significant deterioration in its characteristics when applied to solar cells. .

As described above, the EFG method of pulling up the ribbon-shaped silicon thin plate has a difficulty in productivity, and the manufacturing method of growing silicon on the heat-resistant tape deteriorates the characteristics of the solar cell. was there.

Under such a technical background, a new manufacturing method has been proposed in which a supporting base material such as the above heat-resistant tape is not required and a crystalline silicon thin plate is required at high speed. For example, in Japanese Unexamined Patent Publication No. 57-205395, a cooling plate is arranged near the silicon melt in the crucible to cool the interface between the silicon melt and the vapor phase, and to cool the solid phase. A method for depositing silicon is disclosed, and Japanese Patent Application Laid-Open No. 55-140791 discloses a method for spraying a cooling gas onto the surface of the silicon melt to deposit solid phase silicon.

These methods of cooling the interface between the silicon melt and the vapor phase to precipitate solid phase silicon require a silicon thin plate in a one-step process, have a high raw material utilization rate, and have the above-mentioned cutting. It was a method having excellent advantages as compared with the other manufacturing methods described above, such as no steps required.

[0017]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention By the way, it has been disclosed in the above publication that a cooling plate is arranged in the vicinity of the above-mentioned silicon melt or a cooling gas is sprayed to cool the interface between the silicon melt and the vapor phase. In the conventional method, a silicon melt obtained by melting silicon has been applied.

Therefore, the silicon thin plates manufactured by these conventional methods become intrinsic silicon or p-type or n-type silicon corresponding to the type of silicon raw material applied, and PN junctions are previously formed in these silicon thin plates. It was difficult to form.

Therefore, when a solar cell is formed by using the manufactured silicon thin plate, another step for forming the PN junction is required, and there is a problem that productivity is deteriorated accordingly.

The present invention has been made by paying attention to such problems, and an object thereof is to provide a method for manufacturing a silicon thin plate capable of forming a PN junction at the same time as manufacturing the silicon thin plate. To do.

[0021]

That is, the invention according to claim 1 arranges a crucible in a tube replaced with hydrogen or an inert gas, and cools an interface between a silicon melt and a vapor phase in the crucible. And, and on the premise of the method for producing a silicon thin plate to produce a crystalline silicon thin plate by precipitating silicon at this interface, hydrogen or hydrogen into the tube in the initial stage of cooling the interface between the silicon melt and the gas phase. The n-type or p-type dopant gas is introduced together with the inert gas, and the introduction of the n-type or p-type dopant gas is stopped during the deposition of silicon to partially mix the n-type or p-type dopant on one surface side thereof. It is characterized by producing a thin plate of the crystalline silicon thus obtained.

According to such technical means, it is possible to manufacture a thin plate of crystalline silicon in which an n-type or p-type dopant is partially mixed on one surface side thereof. Therefore, it is easy to adjust the silicon raw material to be applied. It becomes possible to form a PN junction part in the.

For example, p-type or n-type silicon raw material manufactured in advance is put into the crucible and melted to obtain a silicon melt, and the interface between the silicon melt and the vapor phase is cooled to obtain silicon. By depositing an n-type or p-type dopant gas during the deposition, it is possible to manufacture a silicon thin plate having a PN junction in advance.
The p-type or n-type silicon raw material is not particularly limited, and for example, a block-shaped silicon material or a powder-shaped silicon material can be applied, and a single crystal silicon plate (polycrystalline silicon plate) described below can be used. Etc. are also applicable.

Further, with respect to the p-type or n-type single crystal silicon plate (polycrystalline silicon plate), it is dissolved in a flux such as indium, tin or gallium to obtain a silicon melt, and this silicon melt is used. When the interface with the vapor phase is cooled to deposit silicon, it is possible to manufacture a silicon thin plate having a PN junction in advance by introducing an n-type or p-type dopant gas.

In the latter method in which the flux is applied, the p-type or n-type single-crystal silicon plate (polycrystalline silicon plate) that has been put into the melt is melted from the melt. It may surface. In such a case, it is necessary to provide a fixing means for fixing the solid silicon in the crucible.

The n-type dopant gas described above is PH ₃ (phosphine) gas, AsH ₃ (arsine) gas, and the p-type dopant gas is B.
₂ H ₆ (diborane) gas or the like can be applied.

[0027]

According to the invention of claim 1, n-type or p-type dopant gas is introduced into the tube together with hydrogen or an inert gas in the initial stage of cooling the interface between the silicon melt and the vapor phase,
In addition, the introduction of the n-type or p-type dopant gas is stopped during the deposition of silicon to manufacture a thin plate of crystalline silicon in which the n-type or p-type dopant is partially mixed on one surface side.

Therefore, by appropriately adjusting the silicon raw material to be applied so that the type of the deposited silicon thin plate is p-type or n-type, PN can be produced at the same time as the production of the silicon thin plate.
It is also possible to form a joint.

[0029]

Embodiments of the present invention will now be described in detail with reference to the drawings.

The manufacturing apparatus used in this embodiment is shown in FIG.
As shown in FIG. 1, an electric furnace 10 is provided, and a length of 40 cm and a diameter of 10 are fixedly arranged on a support 100 in the electric furnace 10.
cm quartz reaction tube 20 and a quartz crucible 40 arranged in the reaction tube 20 via a graphite crucible stand 30.
A member 50 for taking out a thin plate made of quartz, which is arranged in the reaction tube 20 and has a fork-shaped tip portion housed in the crucible 40, and the base end side of which serves as a lever, and the crucible 40 in the reaction tube 20. Air supply pipe 6 placed near the
1 and a cooler 60 made of glassy carbon provided with an exhaust pipe 62, the main part of which is formed.
The base end side of 1 and the front end side of the exhaust pipe 62 are slidably attached through an opening (not shown) of a lid 21 provided at the opening of the reaction tube 20, and for removing the thin plate. Member 50
The base end side of is also slidably attached to the opening (not shown) of the lid 21.
0 and the fork-shaped tip portion of the thin plate extracting member 50 can be moved in the vertical direction. Further, above the reaction tube 20, the inside of the reaction tube 20 is evacuated and the reaction tube 2
Introducing port 22 for introducing high-purity argon gas into 0
And the exhaust port 23 are attached respectively. In addition, 90 in FIG. 1 shows a heat insulating material.

As shown in FIGS. 2 and 3, the cooler 60 is composed of a rectangular hollow body 63 having a bottom shape of 45 mm × 45 mm, and the air supply pipe 61 is provided in the hollow body 63.
The refrigerant (nitrogen gas set to normal temperature) is circulated through the exhaust pipe 62.

On the other hand, the quartz crucible 40 is shown in FIG.
As shown in (A) to (B), the bottom surface has a closed diameter of 80.
It is composed of a cylindrical body having a height of 72 mm and a height of 72 mm, and a fixing member 42 composed of two protrusions is attached to the lower side of the inner wall surface thereof.

The silicon plate 70 put into the crucible 40 has a disc shape as shown in FIGS. 5A to 5B, and a fixing member attached to the inner wall surface of the crucible 40. A band-shaped cutout portion 71 is formed at a portion corresponding to 42. The cutout portion 71 is pushed into the crucible 40 aligned with the position of the fixing member 42, and the disc-shaped silicon plate 70 is placed in either The disc-shaped silicon plate 70 is prevented from floating by rotating the disc-shaped silicon plate 70 by rotating it in the direction of and shifting the positions of the notch 71 and the fixing member 42.

After the disk-shaped silicon plate 70 (p-type single crystal silicon plate having a specific resistance of 1 Ω · cm) for supplying the raw material is placed in the crucible 40 according to the above-mentioned procedure,
Into the crucible 40, about 1500 g (gram) of high-purity tin (99.9999%) was charged. Then, the system inside the reaction tube 20 is evacuated through the exhaust port 23 to 10 ⁻⁶ Torr.
After that, high-purity argon from which oxygen and water were removed by passing through the purification column was introduced from the inlet 22 at 200 cc / min to bring the pressure in the system to normal pressure (1 atm).

Next, the temperature of the entire system is set to 950 in the electric furnace 10.
The temperature was raised to 0 ° C., and this temperature was maintained for 1 hour to dissolve silicon in the molten tin until saturation was reached.

Next, the cooler 60 is arranged at a position 5 mm from the liquid surface of the tin melt in which silicon is dissolved, and from 2 minutes before the introduction of the refrigerant into the cooler 60 until 2 minutes after the introduction. 1% PH ₃ / A together with high-purity argon (200 cc / min) introduced into the reaction tube 20 for a total of 4 minutes.
After introducing the r-balanced gas at a flow rate of 20 cc / min,
The interface between the tin melt and the vapor phase was continuously cooled with the introduction gas switched to only high-purity argon, and silicon was deposited at the interface.

After 30 minutes, the cooler 60 and the thin plate removing member 50 are pulled up (silicon deposited by this operation is pulled up from the tin melt), and the electric furnace 10 is turned off to bring the inside of the reaction tube 20 to room temperature. After cooling, the deposited silicon thin plate 80 was taken out to the outside using the above-mentioned thin plate taking-out member 50.

The thin plate 80 produced has an outer dimension of approximately 40 m.
This is a polycrystalline silicon plate having a size of m × 40 mm and a thickness of about 0.5 mm. The initially grown surface of the thin plate 80 is n-type doped with about 0.1 Ω · cm according to the measurement result of the spreading resistance. The bulk resistivity excluding this surface is approximately 1Ω.
-Cm p-type silicon.

[0039]

According to the invention of claim 1, at the initial stage of cooling the interface between the silicon melt and the gas phase, an n-type or p-type dopant gas is introduced into the tube together with hydrogen or an inert gas, In addition, the introduction of the n-type or p-type dopant gas is stopped during the deposition of silicon to manufacture a thin plate of crystalline silicon in which the n-type or p-type dopant is partially mixed on one surface side.

Therefore, by appropriately adjusting the silicon raw material to be applied so that the type of the deposited silicon thin plate is p-type or n-type, PN can be produced simultaneously with the production of the silicon thin plate.
Since it is possible to form a joint portion, there is an effect that the manufacturing cost of the solar cell can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a manufacturing apparatus used in an example.

FIG. 2 is a partially enlarged view of FIG.

3 (A) is a plan view of the cooler, and FIG. 3 (B) is a sectional view taken along the line BB of FIG. 3 (A).

4A is a cross-sectional view of the crucible, and FIG. 4B is a plan view of the crucible.

FIG. 5 (A) is a plan view of a silicon plate, and FIG. 5 (B).
Is this cross section.

FIG. 6 is a perspective view according to a conventional example of manufacturing a silicon thin plate.

[Explanation of symbols]

 40 Crucible 60 Cooler 61 Air Supply Pipe 62 Exhaust Pipe 70 Silicon Plate 80 Thin Plate

Claims (1)

[Claims] 1. A crucible is placed in a tube replaced with hydrogen or an inert gas, the interface between the silicon melt and the vapor phase in the crucible is cooled, and silicon is deposited at this interface to crystallize. In a method for manufacturing a silicon thin plate for manufacturing a silicon thin plate, an n-type or p-type dopant gas is introduced into the tube together with hydrogen or an inert gas at an early stage of cooling an interface between a silicon melt and a vapor phase, and The silicon is characterized in that the introduction of the n-type or p-type dopant gas is stopped during the deposition of silicon to produce a thin plate of crystalline silicon in which the n-type or p-type dopant is partially mixed on one surface side thereof. Method for manufacturing thin plate.