JP2016051892A - Semiconductor substrate, solar battery, method for manufacturing solar battery, and manufacturing device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize a semiconductor device such as a high-performance solar battery, which has a good surface passivation function.SOLUTION: A semiconductor substrate is arranged by the steps of: chemically processing a single crystal silicon substrate in nitric acid of a concentration of 70 wt% to form an oxide film, mainly consisting of a silicon dioxide and formed by chemical process, on a surface of the semiconductor; then, performing, by heating, an annealing treatment on the substrate in dry oxygen of 100 vol.% oxygen in a heating furnace at 925°C; and further, performing, on the substrate, an annealing treatment at 450°C in 100 vol.% hydrogen. In the single crystal silicon substrate, the lifetime of minority carriers is about 5 μs(1/e), which is a measured value immediately after formation of the oxide film. The lifetime of minority carriers is largely increased to a level of about 11100 μs(1/e) by the annealing treatments. The substrate surface passivation processing with a SiOfilm formed by a heat treatment in a predetermined oxygen/hydrogen according to a nitric acid oxidation method (NAOS) also exhibits a satisfying surface passivation function on a substrate for a solar battery.SELECTED DRAWING: Figure 1

Description

In the solar cell, an insulating film is formed on a semiconductor surface by chemical treatment, a surface stabilization film is formed, and heat annealing is performed in oxygen and hydrogen to form a base semiconductor surface and an insulating film. The present invention relates to a semiconductor substrate, a solar cell, a method for manufacturing a solar cell, and a manufacturing apparatus thereof that can improve physical properties (passivation function) at the interface.

The present inventor forms a silicon dioxide film (chemical oxide film) by immersing in concentrated nitric acid on the surface of a semiconductor substrate such as silicon (Patent Document 1), and in particular, oxidizing properties such as concentrated nitric acid having an azeotropic concentration. It has been proposed to form a thin oxide film using a chemical solution (Patent Document 2).

JP 2002-64093 A Japanese Patent Laid-Open No. 2005-313102

In recent years, in the field of highly integrated semiconductor devices and photovoltaic devices such as solar cells, ultra-thin insulating films with sub-nanometer (0.1 nm order) to several nanometer (1 nm order) levels have been formed on the silicon surface. In addition, it is required to improve the passivation function of the semiconductor surface and control and improve the minority carrier lifetime and the potential open-ended voltage [Implied Voc] with high accuracy.

An object of the present invention is to form a silicon dioxide film as an insulating film on a semiconductor surface by chemical treatment, and to improve the passivation function of the semiconductor surface by heat treatment in oxygen and / or heat treatment in hydrogen. A semiconductor substrate, a solar cell, a method for manufacturing a solar cell, and an apparatus for manufacturing the same are provided.

The present invention is a process in which an oxide film is formed on the surface of a semiconductor by chemical treatment in an oxidizing chemical solution, and then heat treatment is performed at least at 600 ° C. in oxygen and / or treatment at 400 to 500 ° C. in hydrogen. It is equipped with.

The present invention forms a silicon dioxide-based oxide film on the surface of a silicon substrate by chemical treatment in an oxidizing chemical solution, heat-treats the substrate at 600 ° C. or higher in oxygen, and further heats at 400 to 500 ° C. in hydrogen. An object of the present invention is to provide a silicon substrate that has been subjected to the annealing process.

In the present invention, a semiconductor is chemically treated in a nitric acid chemical solution having a nitric acid concentration of 70 wt% at room temperature to about 120 ° C. to form an oxide film mainly composed of silicon dioxide on the surface of the semiconductor, and then at 600 ° C. or higher in dry oxygen. An object of the present invention is to provide a semiconductor device subjected to heat treatment and / or subjected to annealing treatment in hydrogen at 400 to 500 ° C.

In the present invention, a semiconductor is chemically treated in a high concentration nitric acid chemical solution having a nitric acid concentration of 40 to 99.5% at room temperature to about 120 ° C., and an oxide film mainly composed of silicon dioxide (SiO ₂ ) is formed on the surface of the semiconductor. A semiconductor substrate, a solar cell, a method for manufacturing a solar cell, and a method for manufacturing the semiconductor substrate, which are subjected to heat treatment at 600 ° C. to 1000 ° C. in 100 vol% dry oxygen after the formation and further annealed at 400 to 500 ° C. in 100 vol% hydrogen. To provide an apparatus.

According to the present invention, after forming an oxide film mainly composed of silicon dioxide (SiO ₂ ) on the surface of the semiconductor by chemical treatment in an oxidizing chemical solution, the semiconductor is heat-annealed at 600 ° C. or higher in dry oxygen and / or Alternatively, by annealing at 400 to 500 ° C. in hydrogen, for example, the (1 / e) minority carrier lifetime (measured value) of the silicon substrate surface becomes several thousand μs (microseconds) or more, and 600 ° C. in dry oxygen. The minority carrier lifetime (measured value) immediately after the formation of the oxide film, which was not subjected to the above-described heat annealing treatment and / or annealing treatment in hydrogen at 400 to 500 ° C., is significantly larger than that of about 5 μs. As a result of experiments, such as the phenomenon of significant minority carrier lifetime improvement being observed, the performance of semiconductor devices such as solar cells with enhanced semiconductor surface passivation functions has been demonstrated. It became possible.

According to the present invention, after an oxide film is formed on the surface of the semiconductor by chemical treatment in an oxidizing chemical solution, a heat annealing treatment is performed at 600 ° C. or higher in 100 vol% dry oxygen and / or 400 to 500 ° C. in hydrogen. By performing this annealing process, it is possible to realize a semiconductor device manufacturing apparatus such as a solar cell having a high semiconductor surface passivation function.

Further, according to the present invention, a semiconductor is chemically treated in a high concentration nitric acid chemical solution having a nitric acid concentration of 40 to 99.5% to form an oxide film mainly composed of silicon dioxide on the surface of the semiconductor, and then 100 vol% dry oxygen. By providing a heat annealing treatment at a temperature of 600 ° C. or higher and a hydrogen annealing treatment at a temperature of 400 to 500 ° C. in a 100 vol% hydrogen, there is a significant increase in minority carrier lifetime, It can contribute to realization of a solar cell.

It is a characteristic view of 1 / e minority carrier lifetime measured value of Example 1 of this invention. It is a characteristic diagram of 1 / e ² minority carrier lifetime measurements of the present invention Example 1. It is a characteristic view of the oxide film thickness of the silicon dioxide (SiO ₂₎ of the present invention embodiment. It is a characteristic view of 1 / e minority carrier lifetime measurement value of Example 2 of this invention. It is a characteristic diagram of 1 / e ² minority carrier lifetime measurements of the present invention Example 2. It is a characteristic view of 1 / e minority carrier lifetime measured value of Example 3 of this invention. It is a characteristic diagram of 1 / e ² minority carrier lifetime measurements of the present invention Example 3. It is a characteristic view of the minority carrier lifetime measured value of the n + / p-Si / n + substrate of Example 4 of the present invention. It is a characteristic view of the measured value of the potential open end voltage (Implied Voc) in the n + / p-Si / n + board | substrate of Example 4 of this invention. It is a measurement figure of the minority carrier lifetime in the n + / p-Si / n + board | substrate in this invention Example 5. FIG. It is a characteristic view of the measured value of the potential open end voltage (Implied Voc) in the n + / p-Si / n + board | substrate of this invention Example 5. FIG. It is a characteristic view of the measured value of the minority carrier lifetime in the p <+> / n-Si / p + board | substrate of this invention Example 6. FIG. It is a characteristic view of the measured value of the potential open end voltage (Implied Voc) in the p <+> / n-Si / p + board | substrate of Example 6 of this invention. It is a characteristic view of the measured value of the minority carrier lifetime in the n <+> / n-Si / n + board | substrate of Example 6 of this invention. It is a characteristic view of the measured value of the potential open end voltage (Implied Voc) of the n <+> / n-Si / n + board | substrate of Example 6 of this invention.

Next, an example which is an embodiment of the present invention will be described in detail below.

In a first example which is an embodiment of the present invention, an n-type single crystal silicon substrate having a (100) plane, resistivity: 8-12 Ω · cm, and thickness of 725 μm is cut into a size of 50 mm × 50 mm. First, RCA cleaning was performed in a 300 cc solution in a quartz beaker at a temperature of 70 ° C. for 10 minutes, washed with running water for 2 minutes, and dried with nitrogen (N 2) blow.

Next, in a fluororesin beaker, washing was performed with a hydrofluoric acid solution having a concentration of 0.5 wt% and 300 cc for 2 minutes, followed by washing with water at room temperature for 2 minutes and then drying with nitrogen (N2) blow.

Subsequently, a solution treatment at 70 ° C. for 10 minutes in a 70 wt% nitric acid solution was performed in a fluorine-based resin beaker to form a silicon dioxide (SiO ₂ ) film on the silicon surface by a chemical oxidation method. The thickness of the silicon dioxide (SiO ₂ ) film was 1 to 1.3 nm as measured by XPS.

At this stage, the (1 / e) minority carrier lifetime immediately after the formation of the silicon dioxide (SiO ₂ ) film was measured using a measuring device (μ-PCD); Kobelco Research Institute / LTA.1510 (part number). , About 5 μs.

Next, after forming a silicon dioxide (SiO ₂ ) film by the above-described chemical oxidation method, the temperature is 700 ° C., 800 ° C., 850 ° C., 900 ° C. in a dry atmosphere composed of 100 vol% oxygen in a thermal oxidation furnace. Each temperature was selected as 925 ° C. and 1000 ° C., and each was subjected to a thermal oxidation annealing treatment for 10 minutes, followed by a hydrogen annealing treatment for 30 minutes at 450 ° C. in a 100 vol% hydrogen atmosphere.

In a dry atmosphere composed of 100 wt% oxygen, a thermal oxidation annealing process at a temperature of 700 ° C. to 1000 ° C. and a hydrogen annealing process at 450 ° C. in a 100 vol% hydrogen atmosphere were performed by a chemical oxidation method. Each minority carrier lifetime measurement result when the formed silicon dioxide (SiO ₂ ) film is present / not present (so-called, with NAOS / without NAOS) is shown in FIG. 1 as a measurement value of 1 / e minority carrier lifetime. FIG. 2 shows a comparison of measured values of 1 / e ² minority carrier lifetime.

As is apparent from FIGS. 1 and 2, for example, with a silicon dioxide (SiO ₂ ) film formed by a chemical oxidation method (so-called NAOS is present), after heat annealing at 925 ° C. in dry oxygen, 100 vol% in the case of hydrogen annealing process 450 ° C. in hydrogen, 1 / e minority carrier lifetime (Figure 1), 1 / ^{e 2} minority carrier lifetime (Figure 2) is, (1 / e) value at maximum 11.1Ms ( (Millisecond) and (1 / e ² ) values increased significantly to 16.0 ms.

The increase in the minority carrier lifetime described above due to the hydrogen annealing treatment is considered to be caused by the reduction in interface state density promoted by hydrogen termination of dangling bonds in the silicon substrate.

FIG. 3 shows the thickness of a silicon dioxide (SiO ₂ ) film in a 10-minute thermal oxidation annealing process selected in a temperature range of 700 ° C. to 1000 ° C. in a dry atmosphere consisting of 100 vol% oxygen in a heating furnace. Shows the results obtained by ellipsometry measurement, the horizontal axis is a plot of processing temperatures of 700 ° C., 800 ° C., 850 ° C., 900 ° C., 925 ° C., 950 ° C. and 1000 ° C., and the vertical axis is a silicon dioxide (SiO ₂ ) film. The thickness of was expressed.

In FIG. 3, when a silicon dioxide (SiO ₂ ) film initially formed by a chemical oxidation method (so-called NAOS treatment) is present (with NAOS in the figure; indicated by a solid line), and when there is not (FIG. 3) In any of the cases without NAOS in the middle; indicated by a dotted line), the silicon dioxide (SiO ₂ ) film on the surface of each silicon substrate is grown by thermal oxidation annealing, but the minority carrier lifetime is as shown in FIGS. Although no numerical values are shown, all of them are in the range of about 5 to 50 μs, and there was almost no effect on the fluctuation of the minority carrier lifetime.

In the second example, which is an embodiment of the present invention, the texture structure unevenness (111) surface is formed on the surface of the n-type single crystal silicon substrate (100) surface on the sample substrate, and the resistivity is 1.7 Ωcm. , 130 μm thick, sample size; using a 5 cm × 5 cm substrate, as in Example 1 and Example 2, first RCA cleaning, then surface cleaning with 0.5 wt% hydrofluoric acid solution for 2 minutes Subsequently, a silicon dioxide (SiO ₂ ) film by a chemical oxidation method (so-called NAOS treatment) was formed on the surface of the silicon substrate by treatment at 70 ° C. for 10 minutes in a nitric acid solution having a concentration of 70 wt%. At this stage, the thickness of the silicon dioxide (SiO ₂ ) film was 1-1.3 nm.

Next, in the above-described n-type single crystal silicon substrate, after forming a silicon dioxide (SiO ₂ ) film by a chemical oxidation method, using a thermal oxidation furnace, 925 ° C. in dry oxygen composed of 100 vol% oxygen, After performing thermal oxidation annealing treatment for 10 minutes, hydrogen annealing treatment was performed at 450 ° C. for 30 minutes in 100 vol% hydrogen, and minority carrier lifetime was measured. Silicon dioxide formed by a chemical oxidation method For the presence / absence of the (SiO ₂ ) film (so-called, with / without NAOS), the measurement results of the minority carrier lifetimes are shown in FIG. And 1 / e ² minority carrier lifetime values are compared and shown. As a minority carrier lifetime measuring apparatus (μ-PCD), Kobelco Research Institute / LTA.1510 (product number) was used.

As shown in FIGS. 4 and 5, after performing thermal oxidation annealing treatment at 925 ° C. for 10 minutes in dry oxygen composed of 100 vol% oxygen, hydrogen annealing treatment at 450 ° C. for 30 minutes in 100 vol% hydrogen. As a result, the minority carrier lifetime was significantly increased even in the presence / absence of the silicon dioxide (SiO ₂ ) film formed by the chemical oxidation method (with / without NAOS in the figure).

The increase in the minority carrier lifetime described above due to the hydrogen annealing treatment is considered to be caused by the reduction in interface state density promoted by hydrogen termination of dangling bonds in the silicon substrate.

Furthermore, in the third example, which is an embodiment of the present invention, a resistance in which a texture structure is formed on the surface of the n-type solar cell single crystal silicon substrate (100) surface of the sample substrate, as in Example 2. Rate: 1.7 Ωcm, thickness 130 μm, sample size: using a 5 cm × 5 cm substrate, as in Examples 1 and 2, first RCA cleaning, then 0.5 wt% concentration of fluorine. The surface was cleaned with an acid solution for 2 minutes.

Next, a silicon nitride (SiN _x ) film was formed on the above-described n-type single crystal silicon substrate by a plasma vapor deposition (P-CVD) method. In forming this SiN _X film, a two-layer structure was selected, one layer having a high hydrogen composition on the silicon substrate side and two layers having a low hydrogen composition on the air side. The film formation conditions are as follows: plasma generation input RF; 50 (W), gas component 20% SiH ₄ N ₂ ) / NH ₂ / N ₂ / H ₂ : 50/9/260/0, pressure (Pa ): 80, temperature 150 ° C., film forming speed nm / min: 19.3, film thickness 40 nm, refractive index (n): 2.097, plasma generation input on the second layer RF: 100 (W), gas component 20% SiH ₄ N ₂ ) / NH ₂ / N ₂ / H ₂ : 13/0/1000/270, pressure (Pa): 133, temperature 300 ° C., film formation rate nm / Min: 12.6 was selected, and the film thickness was 50 nm and the refractive index (n) was 2.07. The above silicon nitride film was formed on the above substrate. After the formation, heat treatment was performed at 730 ° C. for several seconds in air corresponding to the firing treatment.

Next, in the above-described n-type single crystal silicon substrate, a thermal oxidation furnace is used to perform a thermal oxidation annealing treatment at 925 ° C. for 10 minutes in dry oxygen composed of 100 vol% oxygen, and then in 100 vol% hydrogen. Hydrogen annealing treatment at 450 ° C. for 30 minutes was performed. Thereafter, the above silicon nitride film was formed, and the above baking process was performed.

Next, after forming a silicon dioxide (SiO ₂ ) film by a chemical oxidation method on the above-described n-type single crystal silicon substrate, using a thermal oxidation furnace, 925 ° C., 10 ° C. in dry oxygen composed of 100 vol% oxygen. After performing a thermal oxidation annealing treatment for 30 minutes, a hydrogen annealing treatment was performed in 100 vol% hydrogen at 450 ° C. for 30 minutes. Thereafter, the above silicon nitride film was formed, and the above baking process was performed.

The measured value of 1 / e minority carrier lifetime after each of the above-described processes is shown in FIG. 6, and the measured value of 1 / e ² minority carrier lifetime is compared in FIG. As a minority carrier lifetime measuring apparatus (μ-PCD), Kobelco Research Institute / LTA.1510 (product number) was used.

FIG. 6 shows a case with a silicon dioxide (SiO ₂ ) film (so-called NAOS), after performing thermal oxidation annealing treatment at 925 ° C. for 10 minutes in dry oxygen in 100 vol% oxygen and then 100 vol% hydrogen. In the middle, hydrogen annealing treatment was performed at 450 ° C. for 30 minutes, and the highest minority carrier lifetime was obtained after the baking treatment of the silicon nitride film.

Also in FIG. 7, after performing thermal oxidation annealing treatment at 925 ° C. for 10 minutes in dry oxygen composed of 100 vol% oxygen with NAOS treatment, hydrogen annealing treatment at 450 ° C. for 30 minutes in 100 vol% hydrogen is performed. When the silicon nitride film was formed and baked, the minority carrier lifetime showed the highest value.

From the results of this example, the minority carrier lifetime is greatly increased by performing thermal oxidation annealing treatment and / or hydrogen annealing treatment and baking treatment after forming a silicon nitride film on the n-type single crystal silicon substrate after NAOS treatment. It was found that the electrical and optical characteristics of semiconductors and solar cells were significantly improved. Furthermore, by continuously performing these processes within a predetermined time, it is possible to improve the stability of characteristics, the reduction of variations, the manufacturing stability, and the manufacturing speed.

In the fourth example which is an embodiment of the present invention, a texture structure is formed on both sides of a single crystal silicon substrate (100) surface for a p-type solar cell on a silicon substrate, resistivity: 2 Ωcm, thickness 190 μm, Sample size: A substrate of 5 cm × 5 cm was used. As in Examples 1, 2, and 3, RCA cleaning was first performed, and then surface cleaning was performed with a hydrofluoric acid solution having a concentration of 0.5 wt% for 2 minutes.

Subsequently, a coating agent for forming a film made of organic silica containing P2O5 was dropped and applied for 30 seconds at a spin coat of 3000 rpm. This coating process was performed on both sides.
Thereafter, heat treatment was performed at 150 ° C. for 30 minutes in an oven, followed by treatment in oxygen at 600 ° C. for 30 minutes using a thermal diffusion furnace to vitrify and form a PSG film. Thereafter, the atmosphere was replaced with nitrogen and held for 5 minutes. Thereafter, PSG was diffused in nitrogen at 910 ° C. for 20 minutes to form an n-type diffusion layer. The sheet resistance of the n-type diffusion layer was about 70Ω / □. Thereafter, the PSG film was removed by treatment with 5% hydrofluoric acid for 2 minutes. Using the p-type substrate with an n-type diffusion layer (n + / p-Si / n +) thus produced, the process treatment experiment was continued as follows.

Subsequently, a silicon dioxide (SiO ₂ ) film was formed on the surface of the silicon substrate by a chemical oxidation method (NAOS method) in a 70 wt% nitric acid solution at 70 ° C. for 10 minutes. At this stage, the thickness of the silicon dioxide (SiO ₂ ) film was 1-1.3 nm.

Next, in the above-described p-type single crystal silicon substrate, a thermal oxidation furnace is used to perform a thermal oxidation annealing treatment at 700 ° C. to 925 ° C. for 10 minutes in dry oxygen composed of 100 vol% oxygen, and then 100 vol. Hydrogen annealing treatment was performed in% hydrogen at 450 ° C. for 30 minutes.

FIG. 8 and FIG. 9 show the measurement results of minority carrier lifetime and potential open-ended voltage (Implied Voc (mV)) using a measuring device (WCT-120) manufactured by Synton after these treatments.
From these results, it is possible to control and improve the minority carrier lifetime by appropriately using the nitric acid oxidation method (NAOS), dry oxidation annealing, and 100 wt% hydrogen treatment method, and control and improve the Implied Voc to 625 mV or more. It turns out that it can be achieved. As a result, a good surface passivation treatment can be realized, and the performance of a solar cell using a p-type substrate can be greatly improved.

Next, an experiment of the passivation effect by the SiN (silicon nitride) film lamination of the fifth example which is an embodiment of the present invention was conducted.
In the fourth embodiment, after NAOS treatment, heat treatment in dry oxygen (925 ° C.) and heat treatment in 100 vol% hydrogen, PECVD SiN film was deposited to 90 nm, and then in the air in a mass production belt furnace. Minority carrier lifetime and potential open-ended voltage [Implied Voc (mV)] using a measuring device (WCT-120) manufactured by Synton Co., Ltd. when firing at 860 ° C. for several seconds. It shows in FIG. 10, FIG. From these results, by using NAOS treatment, dry oxidation, 100 wt% hydrogen treatment and SiN film lamination treatment, a good surface passivation treatment can be realized, and a p-type solar cell substrate has an extremely high value of 644 mV as Implied Voc. It was. Therefore, the performance of the solar cell using the p-type substrate can be further greatly improved.

In the sixth example which is an embodiment of the present invention, a texture structure is formed on both sides of the surface of an n-type solar cell single crystal silicon substrate (100) on a silicon substrate, resistivity: 2 Ωcm, thickness 130 μm, sample Size: A substrate of 5 cm × 5 cm was used. First, RCA cleaning was performed, and then surface cleaning was performed for 2 minutes with a hydrofluoric acid solution having a concentration of 0.5 wt%.

Subsequently, in order to form the same n-type diffusion layer on both sides and the same p-type diffusion layer on both sides, a coating agent for forming a film made of organic silica containing P2O5 and a film made of organic silica containing B2O3 Each of the forming coating agents was dropped and applied by spin coating at 3000 rpm for 30 seconds. The coating process was performed on both sides.
Thereafter, heat treatment was performed in an oven at 150 ° C. for 30 minutes, followed by treatment in oxygen at 600 ° C. for 30 minutes using a thermal diffusion furnace, and vitrified to form a PSG film and a BSG film on both surfaces. Thereafter, it was replaced with nitrogen, and held for 5 minutes. Thereafter, PSG was diffused in nitrogen at 910 ° C. for 20 minutes and BSG was diffused at 950 ° C. for 20 minutes to form n-type and p-type diffusion layers. The sheet resistance of the n-type diffusion layer was 60Ω / □, and the sheet resistance of the p-type diffusion layer was 60Ω / □. Thereafter, the film was treated with 5% hydrofluoric acid for 2 minutes to remove the film. Using the n-type substrate with the double-sided n-type diffusion layer (n + / n-Si / n +) and the n-type substrate with the double-sided p-type diffusion layer (p + / n-Si / p +) thus prepared, So that the process treatment experiment continued.

Subsequently, a silicon dioxide (SiO ₂ ) film was formed on the surface of the silicon substrate by a chemical oxidation method (NAOS method) in a 70 wt% nitric acid solution at 70 ° C. for 10 minutes. At this stage, the thickness of the silicon dioxide (SiO ₂ ) film was 1-1.3 nm.

Next, in the above-described p-type single crystal silicon substrate, a thermal oxidation furnace is used to perform a thermal oxidation annealing treatment at 925 ° C. for 10 minutes in dry oxygen composed of 100 vol% oxygen, and then in 100 vol% hydrogen. Hydrogen annealing treatment at 450 ° C. for 30 minutes was performed.

12 and 13 minority carrier lifetime and potential open-circuit voltage performed using a measuring device (WCT-120) manufactured by Synton on a p + / n-Si / p + substrate using the process of Example 6 in FIGS. The measurement result of [Implied Voc (mV)] is shown. The meaning of 100% H2 in FIG. 12 means that 100 vol% hydrogen treatment was performed after dry oxidation (925 ° treatment) (the same applies to FIGS. 13, 14, and 15). In particular, the Implied Voc was controlled and improved to 611 mV by NAOS treatment, dry oxidation at 925 ° C. and 100 vol% hydrogen treatment. If these treatments can realize a good surface passivation treatment, it is possible to greatly improve the performance of a solar cell using an n-type substrate.

14 and 15, minority carrier lifetime and potential open-ended voltage performed using a measuring device (WCT-120) manufactured by Synton on an n + / n−Si / n + substrate using the process of Example 6 in FIGS. The measurement result of [Implied Voc (mV)] is shown. In particular, by implementing NAOS treatment, dry oxidation at 925 ° C. and 100 vol% hydrogen treatment, Implied Voc was controlled and improved, and the maximum value of 650 mV in the experiment was achieved. In particular, the hydrogen treatment improved the minority carrier lifetime by 10 times or more, and improved the Implied Voc by about 70 mV. By these treatments, a very good surface passivation treatment can be realized, and further significant performance improvement of a solar cell using an n-type substrate can be achieved.

The present invention is applicable not only to the above-mentioned n-type single crystal silicon substrate, but also to a p-type single crystal silicon substrate and n and p-type polycrystalline silicon regardless of its conductivity, and a chemical oxidation method. (HNO ₃ ) concentration of the chemical solution (high concentration nitric acid) when forming the silicon dioxide (SiO ₂ ) film by the above can be selected and used within the range of 60% to 99.5%, and the use temperature of the chemical solution It is possible to select from the range of room temperature to about 120 ° C. as appropriate, and further, the temperature of the thermal annealing treatment in oxygen after the formation of the oxide film is appropriately selected in the range of 600 ° C. to 1000 ° C. In addition, the hydrogen concentration in the annealing process in hydrogen can be selectively set at around 5 vol% and 100 vol%, the heating temperature can be appropriately set in the range of 400 ° C. to 500 ° C., and the processing time can be maximized. Of course, it is possible to obtain appropriate conditions, select and set them, and use them.

In the field of highly integrated semiconductor devices and system liquid crystal displays, or in the field of photoelectric conversion devices such as solar cells, the present invention has a thickness of sub-nanometers (0.1 nm) to several nanometers (nm) on the silicon surface. A semiconductor device that can be used by forming an ultra-thin insulating film, and its manufacturing method, to control and improve the minority carrier lifetime and potential open-ended voltage with high accuracy, and to use it to significantly improve the performance of semiconductor devices. Can do.

Claims (8)

After an oxide film is formed on the surface of the semiconductor by chemical treatment in an oxidizing chemical solution, the semiconductor is subjected to a heat annealing treatment in an oxygen atmosphere in the range of 600 ° C. to 1000 ° C. and / or hydrogen at 400 to 500 ° C. A semiconductor substrate characterized by performing an annealing treatment. An oxide film is formed on the surface of the semiconductor by chemical treatment in an oxidizing chemical solution, and then a heat annealing treatment is performed at 600 ° C. or higher in a dry oxygen atmosphere and / or a hydrogen annealing treatment at 400 to 500 ° C. A method for manufacturing a semiconductor device, comprising: The method of manufacturing a semiconductor device according to claim 1, wherein the silicon nitride film is baked. An oxide film is formed on the surface of the semiconductor by chemical treatment in an oxidizing chemical solution, and then a thermal annealing treatment in a temperature range of 600 ° C. to 1000 ° C. in oxygen and a temperature range of 400 to 500 ° C. in hydrogen. An apparatus for manufacturing a semiconductor device, comprising means for performing an annealing process. After an oxide film is formed on the surface of the semiconductor by chemical treatment in an oxidizing chemical solution, the semiconductor is subjected to a heat annealing treatment in an oxygen atmosphere in the range of 600 ° C. to 1000 ° C. and / or hydrogen at 400 to 500 ° C. A solar cell comprising an annealing treatment and / or a silicon nitride film. After an oxide film is formed on the surface of the semiconductor by chemical treatment in an oxidizing chemical solution, the semiconductor is subjected to a heat annealing treatment in an oxygen atmosphere in the range of 600 ° C. to 1000 ° C. and / or hydrogen at 400 to 500 ° C. A method for manufacturing a solar cell, characterized by performing an annealing treatment and / or forming a silicon nitride film. 6. The solar cell according to claim 5, wherein n-type and / or p-type diffusion layers are provided on the front and back surfaces of the semiconductor. The method for manufacturing a solar cell according to claim 6, wherein an n-type and / or a p-type diffusion layer is provided on the front and back surfaces of the semiconductor.