JPS6316912B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to a photoelectric conversion element using a silicon thin film formed by a plasma reaction and consisting of a plurality of layers having different film properties, such as a PIN structure. This invention relates to manufacturing equipment. This type of photoelectric conversion element includes solar cells that use amorphous silicon formed by the glow discharge method, but in order to put low-cost solar cells into practical use, it is necessary to further improve the conversion efficiency and improve the yield rate. It is necessary to establish high-quality mass production technology.

[Prior art and its problems]

Figure 1 shows the curved structure of this type of solar cell.
_The transparent conductive film 2 is formed by sequentially forming P,
I, N amorphous silicon thin films 3, 4, and 5 are laminated, and electrode metal 6 is deposited thereon. Here, the P-type silicon thin film 3 is formed using, for example, SiH ₄
It is formed by adding a _small amount of B ₂ H ₆ gas to a mixed gas of
It is a very thin film of about 100 to 200 Å. The N-type silicon thin film 5 is formed by adding a small amount of PH ₃ gas etc. to SiH ₄ and performing glow discharge decomposition, and the film thickness is about 100 to several hundred Å. The thickness is approximately several 4 Å. This solar cell generates a photovoltaic force due to incident light 7 from the substrate 1 side.
FIG. 2 shows a case where a metal substrate 8 such as stainless steel or aluminum is used, and silicon thin films 3, 4, 5 are used.
A transparent conductive film 2 is formed thereon, and a current collecting metal electrode 9 is partially adhered thereon. There are two methods for manufacturing such a photoconversion element: a method in which P, I, and N silicon thin films are formed in the same plasma reaction chamber by switching the gas introduction circuit, and a method in which P, I, and N silicon thin films are formed as shown in FIG. N silicon thin films are placed in separate plasma reaction chambers 10, 11, each equipped with counter electrodes 13, 14 connected to a high frequency power source 16, a gas inlet 18, and a vacuum exhaust port 19, respectively.
12, a method is known in which gases of different compositions are introduced and formed on a substrate placed on a support plate 15. The method shown in Fig. 3 is excellent as a manufacturing method for mass production, and the B (boron) added to the P-type silicon layer and the P (phosphorus) added to the N-type silicon layer can be used in other areas such as the I-silicon layer. It is thought that it also has the effect of preventing the conductivity type from being mixed into the silicon layer. However, in order to further improve the characteristics (conversion efficiency, etc.) of this type of photoelectric conversion element, reduce the variation in characteristics, and increase the yield rate, the thickness of the P, I, and N silicon layers, impurities, etc. must be adjusted. It is necessary to quickly feed back the evaluation results of the formed film and precisely control it, and conventional methods are insufficient.

[Purpose of the invention]

In order to further improve the characteristics and yield rate of photoelectric conversion elements, the present invention provides a manufacturing apparatus that can precisely and minutely control characteristics such as the thickness or impurity concentration of each silicon layer of different film quality. The purpose is to

[Key points of the invention]

The photoelectric conversion element manufacturing apparatus according to the present invention provides an intermediate chamber that can be evacuated between a plurality of plasma reaction chambers for producing silicon layers of different film quality on a substrate, and separates the intermediate chamber from the plasma reaction chamber. The above object is achieved by providing an adjacent front chamber which can be evacuated and has a door for taking out defective lots in accordance with the results of intermediate evaluation in the intermediate chamber.

[Embodiments of the invention]

4 and 5 show an embodiment of the present invention, and parts common to those in FIG. 3 are given the same reference numerals. This equipment includes a preheating chamber 20, a P-type film forming plasma reaction chamber 10, a P-type film evaluation chamber 21, and an I
Film forming plasma reaction chamber 11, I film evaluation chamber 22, N
A mold film forming plasma reaction chamber 12 and a cooling chamber 23 are arranged adjacent to each other, and each chamber has an exhaust port 1 having a valve.
The chambers are connected to a vacuum exhaust system via 9, and each chamber is partitioned off by shutters 17a to 17f, and the outside of the apparatus is partitioned off by shutters 24 and 25. Further, the P-type film evaluation chamber 21 and the I-film evaluation chamber 22 are provided with front chambers 26 and 27 via a shutter 28 adjacent to the side from the arrangement direction of the respective chambers for taking out defective lots. These front chambers have shutters 29 between them and the outside of the device. This device is operated by a working system as shown in FIG. The numbers written in FIG. 6 are the numbers of the rooms where the work is performed with a dash added. First, support plate 1 on which the board is placed
5 is placed in the preheating chamber 20, evacuated, and heated to a required temperature (for example, 200° C.). Next, the support plate 15 is sent by a mechanism such as a roller conveyor to the evacuated P-type film forming plasma reaction chamber 21 by opening and closing the shutter 17a, and then SiH ₄ , CH ₄ , B ₂ H ₆ , etc. are introduced from the gas inlet 18. A mixed gas is introduced and discharge power is applied between the electrodes 13 and 14 to perform plasma decomposition to grow a P-type film (film thickness: 100 Å, for example) on the substrate. Next, shutter 17b
Open and close the support plate with the substrate on it in the P-type film evaluation chamber 2.
Send to 1. The evaluation chamber 29 is evacuated in advance, and the P-type film is evaluated here.The film thickness is important as an evaluation item for the P-type film, and the film thickness evaluation method is the fluorescence X-ray method or the optical method. Both methods may be used in combination. In the fluorescence X-ray method, a method can be used in which a sealed X-ray source or an RI (radioisotope) source is used as the radiation source, and the fluorescence X-ray intensity of SiKα generated from the sample is measured and converted into film thickness. . However, with this method, in the case of photoelectric conversion elements with glass substrates,
Because SiKα radiation is generated, use a stainless steel substrate or
It is necessary to insert an Al substrate or the like as a monitor for film thickness measurement. For film thickness measurement by an optical method, a method can be used in which a He--Ne laser or the like is used as a light source and the film thickness is converted from the measured transmittance of a monitor sample of a glass substrate. In both cases, the radiation source (or light source) and detector are installed in the P-type film evaluation room 2.
1, and the measurement is carried out while the sample is being evacuated, and a mechanism for moving the monitor sample to a predetermined position during measurement is provided as necessary. For example, an arm-shaped automatic handling mechanism may be used as the moving mechanism for this purpose. Good products are sorted out based on the film thickness measurement results, and defective lots are taken out of the apparatus through the front chamber 26 adjacent to the P-type film evaluation chamber 21. Although not shown, the front chamber 26 can be connected to an evacuation system and is evacuated in advance. Defective lots are sent from the evaluation chamber 21 to the front chamber 26 by opening the shutter 28, and after closing the shutter 28, they are sent to the shutter 29. Since it will be opened and taken out, evaluation room 21
is not exposed to the outside air. At the same time, the film thickness measurement data is fed back as shown by the arrow 40, and the film forming conditions of the P-type film, such as the film forming time, are also controlled.

Next, the shutter 17c is opened and closed to send the substrate to the I-type film forming plasma reaction chamber 11, and an I-type silicon thin film (film thickness is, for example, 5000 Å) is formed by glow discharge decomposition of a gas containing SiH ₄ as the main component. . Next, the shutter 17d is opened and closed to send it to the I film evaluation room 22. The I film evaluation chamber has also been evacuated in advance, and the I film will be evaluated here. Film thickness is also important as an evaluation item for I films, and as a film thickness evaluation method, a fluorescent X-ray method or an optical method can be used as in the case of P-type films. Based on the film thickness data, defective lots are removed from the non-defective product sorting chamber 27 and the film forming conditions of the I film are controlled. Next, the N-type film forming plasma reaction chamber 12
An N-type film is formed by glow discharge decomposition of SiH ₄ gas to which PH ₃ is added, and finally it is cooled in a cooling chamber 23 to complete the silicon thin film formation process.

By selecting non-defective products based on such intermediate evaluation of P-type films and I films and feedback control of film-forming conditions,
The manufacturing yield of solar cells is improved, and the average characteristics of the solar cells are also improved. In particular, if the thickness of the P-type film used as the window layer on the light incident side is too thick, it will increase light absorption loss and affect device characteristics (conversion efficiency, etc.).
If it is too thin, the I/P junction becomes non-uniform, which also reduces the characteristics. Therefore, evaluation, selection, and film thickness control of P-type films using such methods are highly effective. Optimization of the thickness of the I film is also important for improving device characteristics and lifespan, and film thickness control including feedback is of great significance. The film formation rate is determined by the discharge power of the plasma reaction chamber,
Affected by many conditions such as gas pressure and gas flow rate,
It is difficult to control these conditions completely and constantly. Therefore, it is difficult to control the film thickness to be constant over a long period of time (or for a long period of time) simply by keeping the film formation time constant, and such monitoring and feedback of film thickness is effective.
is necessary. Furthermore, since it is difficult to measure the film thickness inside the plasma reaction chamber because, for example, a crystal oscillator cannot be used due to noise from the plasma, it is effective to install an intermediate evaluation chamber.

FIG. 7 is a schematic diagram (plan view) showing another embodiment, and FIG. 8 is a work system diagram thereof, and the same reference numerals as in FIG. 6 are given. Here, waiting rooms 30 and 31 are newly provided, and these waiting rooms 3
0, 31 and I film forming chamber 11 are made larger than other rooms. This is because the I film is more than 10 times thicker than the P-type film and the N-type film, so it takes a long time to form the film, so by increasing the size of these three chambers, the aim is to improve mass productivity. Waiting room 30, 31
Therefore, it is desirable to heat the substrate (for example, to 200°C), which will prevent damage to the film caused by plasma during film formation and prevent P.
Damage caused by X-rays used for mold film evaluation can also be removed by annealing. In this respect, it is better to use an optical method to evaluate the thickness of the type I film than a method using X-rays.

FIG. 8 shows a case where an analytical evaluation is included in addition to the film thickness evaluation as an intermediate evaluation of the P-type film and the i-type film.
This is because, in addition to the film thickness, the composition and impurity concentration (including the concentration distribution in the film thickness direction) of these films are important in determining whether the P-type film or I-type film is good or bad. In a P-type film, the concentration of hydrogen, carbon, boron, etc. as well as components mixed in from the substrate affect the film quality. In the I film, the concentration of hydrogen, trace additive elements, trace impurities, etc. and the concentration distribution in the thickness direction affect the characteristics. Feedback control based on analytical data is considered to be the best way to precisely control these concentrations and concentration distributions. Methods for performing these analytical evaluations include secondary ion mass spectrometry (SIMS), Auger electron spectroscopy (AES), photoelectron spectroscopy (ESCA),
Fourier transform infrared absorption method (ET-IR) is effective. Sampling of samples for performing these analyzes and evaluations is carried out in the defective lot extraction chambers 26 and 27.
By attaching an analysis sample sampling mechanism to the device, only the sample for analysis can be sampled without exposing other films and substrates to the atmosphere.

In particular, it is very difficult to evaluate the P-type film after it has been laminated with the PIN in a three-layer structure, both in terms of film thickness and analytical evaluation, and the significance of evaluation at such an intermediate stage and the feedback control that results from it. is big. Note that optical evaluation (optical bandcap, etc.) and electrical evaluation (photoconductivity, etc.) can be added to the intermediate evaluation items for the I film.

In the example shown in FIG.
If you can do it in 0.31, mid-term evaluation room 2
1 and 22 can be omitted. In this case, the front chambers 26 and 27 are provided adjacent to the waiting chambers 30 and 31. Further, in any of the embodiments, one of the P-type film intermediate evaluation chamber 21 and the I-film intermediate evaluation chamber 22 can be omitted.

〔Effect of the invention〕

As described above, in the present invention, an intermediate evaluation chamber is provided between each plasma reaction chamber, and the intermediate evaluation is used to select non-defective products and control the film forming conditions through feedback. The device can be efficiently manufactured with a high yield rate, and the characteristics of the device can be improved as a whole (on average). That is,
It is an excellent manufacturing method for high-quality mass production. In addition, compared to the conventional apparatus shown in Fig. 3, this method allows for more complete separation of the three chambers, the P-type film formation chamber, the I-type film formation chamber, and the N-type film formation chamber. It can be said that this method is also excellent in preventing source gas from entering the I-type film forming chamber during N-type film formation.

Furthermore, the present invention can be effectively used as an apparatus for manufacturing amorphous silicon photoreceptors, sensors, and other photoelectric conversion elements.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views of typical amorphous silicon solar cells, FIG. 3 is a side view of a conventional solar cell manufacturing apparatus, and FIG. 4 is a side cross-sectional view of an embodiment of the present invention. , FIG. 5 is a plan sectional view of the same, FIG. 6 is a working system diagram using the same, FIG. 7 is a plan sectional view of another embodiment, and FIG. 8 is a working system diagram using the same. . 10... P-type film forming plasma reaction chamber, 11...
I film forming plasma reaction chamber, 12...P type film forming plasma reaction chamber, 19...vacuum exhaust port, 21...P
Type film evaluation intermediate room, 22...I film evaluation intermediate room, 2
6,27...front room.

Claims (1)

[Claims] 1 In a device having a plurality of plasma reaction chambers, each of which can be evacuated and equipped with a counter electrode for generating glow discharge, an intermediate chamber that can be evacuated and provided between the plasma reaction chambers, and a plasma reaction chamber in the intermediate chamber. 1. A photoelectric conversion element manufacturing apparatus comprising: a front chamber which is provided adjacently on one side not in contact with the front chamber and which can be evacuated and has a door between it and the outside.