JPS58101478A - Manufacture of polycrystalline silicon solar battery - Google Patents

Abstract

PURPOSE:To obtain a battery having excellent electric characteristics by plasma etching a polycrystalline Si substrate under low pressure, then covering by a reduced pressure CVD method the etched substrate with an insulating film containing impurity, heat treating it, diffusing the impurity in the substrate, thereby forming a P-N junction and then heat treating it in H2 plasma, and eliminating the opportunity of exposing to the atmosphere. CONSTITUTION:Many P type polycrystalline Si substrates a1 which are sufficiently cleaned are contained in a cassette C1 in a preliminary chamber Y1, and the chamber Y1 is evacuated. An etching chamber A, a PSG film forming unit B, a phosphorus diffusing unit C, an etching unit D and a hydrogen plasma unit E which are isolated via gate valves G1-G7 are arranged at the downstream of the chamber Y1, the substrate a1 is passed therein while sequentially opening and closing the valves G1-G7, performing the prescribed treatments, and are contained in a cassette C2 in a preliminary chamber Y3. In this manner, all treatments can be performed without contact with the atmosphere, thereby shortening the period of the steps and eliminating the contamination.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method of manufacturing a solar cell using polycrystalline silicon.

TECHNICAL BACKGROUND OF THE INVENTION Polycrystalline silicon has long been viewed as promising as a material with high feasibility for early realization as a material for use in low-cost solar cells. Generally, after cleaning, processing, and etching polycrystalline silicon solar cell lines and polycrystalline silicon substrates, PEG or BSG GL is formed by atmospheric pressure CVD, and then heat treated to form a P-N junction, or P by thermal diffusion. - form an N junction;
Next, electrodes are formed on both sides by vacuum evaporation or the like.

Problems with the background technology In the conventional method, the substrate must be exposed to the atmosphere at each step, and the grain boundaries of polycrystalline silicon have a large number of crystal defects and a high density of localized levels due to the accumulation of impurities. Because of the existence of these particles, the lifetime of the carriers decreases at the grain boundaries, making it difficult to produce solar cells with excellent electrical characteristics at low cost.

OBJECTS OF THE INVENTION The present invention provides a method for manufacturing a polycrystalline solar cell, which employs a dry process in a series of steps to improve reliability, reduce costs, and improve characteristics.

SUMMARY OF THE INVENTION The present invention involves drying a series of manufacturing steps for polycrystalline silicon solar cells, etching a polycrystalline silicon substrate under low pressure, and removing impurities from the polycrystalline silicon substrate. A step of forming an insulating film containing a oxide, a step of diffusing impurities from the insulating film to form a PN junction on a polycrystalline silicon substrate, and a step of treating the polycrystalline silicon substrate with hydrogen plasma are performed by exposing the substrate to the atmosphere. It is characterized by being performed continuously.

Effects of the Invention According to the present invention, since a series of processing steps are carried out continuously without exposing the substrate to the atmosphere, it is possible to shorten the time required for the solar cell manufacturing process, and there is less contamination of the substrate. Embodiment of the invention that improves reliability, reduces costs, and improves characteristics FIG. 1 schematically shows a manufacturing apparatus according to an embodiment of the invention. A P-type polycrystalline silicon substrate (doped with 1.5 O-1) a, which has been cleaned with an organic solvent or an acid, is set in a cassette c1 in the preliminary chamber Y and evacuated.

When the pressure in the preliminary chamber Y reaches ~X 10 Torr, the dirt pulp G located between it and the etching apparatus A is opened in order to etch the silicon substrate. One of the silicon substrates (a) contained in the cassette (a) is carried to the etching apparatus iA by a transport mechanism as will be described later, and is placed on the RF electrode S, and the pulp (r-) pulp G is placed on the RF electrode S.
, close. Etching device A at 5X10-'Torr
After exhausting the air to a pressure of
The P-type polycrystalline silicon substrate a2 is etched by about 2 μm by generating a TorrRF power source. After the etching has been completed, the silicon substrate a2 is subjected to P8G film formation. Open the Gutpalg G2 and transport the silicon substrate 1□ to the PEG film forming apparatus B using the transport mechanism. At this time, the susceptor wire 2 for holding the substrate can be heated and can be moved up and down as shown by the arrow. The silicon substrate a2 can be easily placed on the susceptor because it is at the same height as the transport mechanism. Move the finished P-type polycrystalline silicon substrate a placed on the susceptor 2 upwards and fix it in place. -) Close pulp G2. And in this device B there is a sg2 for example 8iH4.
＋PH.

Introduce +02 gas and keep the pressure at 0.5 Torr.
A P2O film was formed on the 15001 silicon substrate &3 by heating the RF coil with an RF power supply and performing low pressure CVD, and then the same pressure was applied in 81H4+ 0□ gas.
．． 5 Torr % At a substrate temperature of 400°C, P
An 8i02t"1000X film is formed on the 8G film to form a nine-dimensional film. After the PSG and 8102 films are formed, the silicon substrate a lowers the susceptor 2, and
- Open the pulp G, and transport it to the reserve 1i1Y under low pressure by the conveying mechanism.f-) Close the pulp G.

The transported P-type polycrystalline silicon substrate a4 on which the P8O and 8102 films are formed is cooled in this pre-chamber Y2.

The cooled silicon substrate a4 is processed into y-topulp G4.
The carried silicon substrate a, which is opened and carried into the phosphorus diffusion apparatus C by a transport mechanism, is placed on a susceptor that can be moved up and down as shown by the arrow in the PSG film forming apparatus, and is placed at a predetermined position. It can be raised to f) Pulp G4
is closed. Then, a gas odor, for example, N2+0□, is introduced into this apparatus C, and under a pressure of 10 Torr, RF
It is heated to 800°C by an RF coil powered by a power supply, and 0.8μ of phosphorus in P2O5 is added to the inside of the silicon substrate a5.
Diffusion to form a PN junction. Thereafter, after cooling the silicon substrate a5, the r-) pulp G5 is opened and transported to the etching device using the same transport mechanism, and the RF electrode S
Etching of the PSG and SlO□ films placed on the substrate 4 and after completion of diffusion is performed in this apparatus. That is, an etching gas G4, for example, CF4+H2, is introduced into this equipment, and the pressure is reduced to 0.
．． Generate sideraz i using an RF power supply at 4 Torr to etch the 810□ and PSG films.
After the etching is completed, the silicon substrate a4 is opened in the r-) pulse G4, carried to the hydrogen plasma processing apparatus E by a transport mechanism, and placed on a sussegrator 15 which can be moved up and down as shown by the arrow and which can heat the silicon substrate a7. The treatment is hydrogen gas g.

was introduced, and the pressure was increased to 1. OTorr s Substrate temperature 1i: 30
Generate H2f lasma by RF power supply under 0c,
In addition, the monocrystalline silicon bK bias, which is the cathode, is set to 1, for example.
Plasma processing is performed while applying 00V. After the plasma treatment is completed, the silicon substrate a7 is cooled, and f-) the pulp G is opened and placed in the preliminary chamber Y.

Do this continuously until the
is taken out from the preliminary chamber Y, and the next step, electrode formation, is carried out to complete the solar cell.

By the way, in order to carry out a series of steps without exposing the substrate to the atmosphere, the mechanisms for moving the substrate from one device to another must be superimposed, and Figure 2 shows an example of such a transfer mechanism. .

1m, Ib is f-) pulp, 8a is a PSG film forming device, and 8b is a phosphorus diffusion device. The substrate holder 4 holding the substrate 3 is moved by the movement of the belt 6 by the rotation of the belt drive device as shown by the arrow.
Move on guide 2 in the direction of the arrow. Further, the holder 4 can be rotated by the shaft 7 by 1800 rotations as shown by the arrow, and can change direction as well as move up and down. Moreover, it is possible to provide a vacuum pumper in the transfer chamber 5. To give a simple example of using this transport mechanism, when moving the PSG film forming apparatus B shown in Fig. 1 to the phosphorus diffusion apparatus @C, this transport mechanism is provided in the preliminary chamber Y2. . After the completion of PEG g formation, the date pulp 1a is opened to carry out the substrate from the PSG film forming apparatus 8m. At this time, the substrate holder 4 is facing the device 8a. Belt drive device 9a.

9b moves the belt 6 to the left, and at the same time, the holder 4 also moves to the left on the guide 2, and the mounting @ 8
9.Enter inside a and stop at the board position to hold the board.

Thereafter, the holder 4 is moved rightward to a predetermined position and then stopped. After this, close the pulp 1a.

Next, the substrate holder 4 is rotated 180° by 20 rotations of the shaft and is moved to a position facing the phosphorus diffusion device 8b. Here, by opening the date pulp 1b and similarly moving the belt 6 to the right by the belt drive devices 9m and 9b, the substrate holder 4 is also moved to the right on the guide 2, and the substrate of the phosphorus diffusion device 8b is moved to the right. I strike and tremble at the position. After placing the substrate in a predetermined position, the holder 4 returns to the leftward transfer chamber 5. Finally r-) Close pulp Ib and PS
The transfer from the G film forming device to the phosphorus diffusion device without disturbing the atmosphere is completed.

As described above, one example of the conveyance mechanism has been shown, but by providing such a mechanism, the series of steps of this embodiment can be performed without exposure to the atmosphere.

Specifically, the polycrystalline silicon substrate 3 is received and transferred by the substrate holder 4 as shown in FIG. 3, for example. That is, the polycrystalline silicon substrate 3 is in a state of being fixed to a fixing base 10 made of quartz with a lip, and the substrate holder 4 is U-shaped, as shown in FIG. 3(b). What is necessary is to insert it under the collar of the board 10 and lift and carry the board 3 together with the fixing base 9.

The feature of the above embodiment is that the series of steps from polycrystalline silicon etching to hydrogen plasma treatment can be carried out continuously without exposing the substrate to the atmosphere, resulting in a significant time reduction, and further exposing the substrate to the atmosphere. Since this process can always be performed in a clean state, the reliability and reproducibility of the process can be improved. Further details of the effects of the present invention are that since the etching and etching are performed in plasma, there is almost no unevenness in etching and etching, and the amount of gas and liquid etching solution used for etching and etching can be reduced. In forming a PSG film by low pressure CVD, it is possible to form a homogeneous film that is not possible with normal pressure CVD, and the impurity concentration can be easily controlled.
Since the G film can be formed at low temperature and in a short period of time, it can greatly contribute to cost reduction. Furthermore, defects and localized levels existing in polycrystalline silicon are hydrogenated by dangling bonds and impurity groups at grain boundaries by hydrogen plasma treatment.
The properties of polycrystalline silicon solar cells are improved by reducing the parsimony.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a manufacturing apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of its conveyance mechanism, and FIG. 3(a)
, (b)ti is a diagram for explaining how the board is transferred. A...Engineer, coating device, B...PEG film forming device,
C... Phosphorus diffusion device, D... Engineering, Ching device, E.
・Hydrogen glazma processing equipment, a1+ azp Iksm
*4e jL5+a6* a7+ 16...Polycrystalline silicon substrate, b...Single crystal silicon! 1411 +
62 ””Cassette %G1p G2+ G5*G4.
G5t G6. G, - Gutonol 1% g1+
g21 g31g41g5...Gas, 8,184...
RF electrode, 12+ 83+I5...susceptor, Yl,
Y2. Y...Preliminary room, RF...RF power supply, J
a, Ib...f-) Pulp, 2... Guide, 3...
・Substrate, 4...Substrate holder, 5...Transfer chamber, 6...
・Belt, 1...shirt), Jim...PSG film forming device, 8b...phosphorus diffusion device, 9m, 9b...
Belt drive.

Claims (1)

[Claims] A step of etching a polycrystalline silicon substrate in plasma under low pressure, a step of forming an insulating film containing impurities on the etched polycrystalline silicon substrate by low pressure CVD or plasma CVD, and a step of transferring the formed insulating film to the silicon substrate. A solar cell characterized in that a step of diffusing impurities to form a P-N junction and a step of heat-treating the silicon substrate in hydrogen plasma are performed continuously without exposing the silicon substrate to the atmosphere. Production method.