JP5889083B2 - Method for cleaning member made of iron alloy and method for manufacturing solar cell element - Google Patents

Description

  The present invention relates to a method for cleaning a member made of an iron alloy containing at least one of chromium and nickel for removing at least one of nitride and silicide. Furthermore, the present invention relates to a method for manufacturing a solar cell element in which a deposited film is formed on a semiconductor substrate by a CVD (Chemical Vapor Deposition) apparatus using a plate-like member cleaned by the cleaning method.

  For example, when a silicon nitride film is formed as an antireflection film on the surface of a solar cell element, a CVD apparatus is generally used. In this CVD apparatus, a large number of diameters of about 0.5 mm to 1.0 mm (in the case of solar cells, 1000 to 1) so that the material to be deposited adheres uniformly to the surface to be deposited, both in terms of location and thickness. Parts such as shower plates or collimators with about 1500 holes) are used.

  If the film forming operation is continued, not only the surface of the shower plate but also the film forming components adhere to the holes and the hole diameter becomes small, and the original designed film cannot be obtained. Further, as the film-forming components adhering to the surface other than the holes become thicker, stress accumulates inside the film and eventually collapses to generate a large amount of dust, resulting in a decrease in quality and a decrease in yield.

  Therefore, in order to reduce the above problem, the collimator is used repeatedly while periodically removing the deposits accumulated on the surface and pores.

  The deposits are removed by either a chemical cleaning method using chemicals or a physical cleaning method using blasting. In cleaning, it is ideal to remove only the deposits without damaging the material constituting the part. If the deposit is a nitride or silicide, it is difficult to dissolve in ordinary chemicals such as hydrochloric acid, nitric acid, and sulfuric acid, and a strong corrosive material must be used for the part itself. In particular, since the collimator is used at a high temperature of 500 ° C or higher, it is necessary to use hydrofluoric acid-based chemicals even though heat-resistant alloys that are easily corroded by chemicals (for example, SUS430) are used. Reality.

  For this reason, the blast method which is a physical removal method is mainly employed as a method for removing the deposits. When cleaning with blasting, the enlargement of the hole diameter is large due to the cutting force of the blasting media, and in the case of the shower plate with the surface sprayed, the damage of the sprayed film is great, and the sprayed film is repaired for each cleaning. It is necessary to reapply a sprayed film.

  Patent Document 1 below describes the use of an oxidizable alkali molten salt for descaling metal oxide scales of various alloys such as stainless steel.

  In Patent Document 2 below, stainless steel containing 19% or more of Cr by mass% is obtained by using an alkali molten salt bath whose nitrate content is 1 to 8% by mass in terms of sodium nitrate. It is described that gloss unevenness does not occur even when descaling by the molten salt immersion method.

  Thus, Patent Documents 1 and 2 only disclose that the molten salt is used for removing the stainless steel scale.

JP 59-118890 JP-A-10-324986

  Since the shower plate has to be made with a lot of labor to open a large number of through holes of about 0.5 to 1 mm, a cleaning method that can be used repeatedly as much as possible is desired. In addition, there is a strong demand for a cleaning method that does not require re-spraying of the sprayed spray plate and that does not require re-spraying.

  Therefore, the present invention enables the repeated use of a shower plate, and even when spraying is performed, the number of re-spraying can be reduced and the number of re-spraying can be reduced. It is an object of the present invention to provide a method for cleaning a member made of an iron alloy containing at least one of chromium and nickel for removing at least one of the chemical compounds. Another object of the present invention is to provide a method for manufacturing a solar cell element in which a deposited film is formed on a semiconductor substrate by a CVD apparatus using a plate-like member cleaned by the above-described cleaning method.

  The present inventors have immersed stainless steel with silicon nitride in molten salt of sodium hydroxide, so that the stainless steel is slightly damaged (does not enlarge the through-hole diameter of the shower plate), and the deposit is removed. It was found that it could be removed and washed and the above-mentioned purpose could be achieved.

  In addition, by immersing stainless steel on which nickel aluminum alloy has been sprayed in a molten salt of sodium hydroxide and sodium silicate, deposits can be removed and washed with minimal damage to the sprayed film. I also got the knowledge.

  The present invention has been completed based on these findings, and has been completed. The present invention provides a method for cleaning a member made of the following iron alloy and a method for manufacturing a solar cell element.

(I) Cleaning method for members made of iron alloy
(I-1) A member made of an iron alloy containing at least one of chromium and nickel, to which at least one of nitride and silicide is attached, is immersed in a molten salt bath containing an alkali metal, and the nitride and the silica are immersed. A method for cleaning a member made of an iron alloy, comprising a step of removing at least one of the chemicals.
(I-2) The method for cleaning a member made of an iron alloy according to (I-1), wherein the nitride is silicon nitride.
(I-3) A method for cleaning a member made of an iron alloy according to (I-1) or (I-2), wherein the iron alloy is stainless steel.
(I-4) The method for cleaning a member made of an iron alloy according to (I-3), wherein the stainless steel is SUS430.
(I-5) A method for cleaning a member made of an iron alloy according to (I-1) or (I-2), wherein the iron alloy is 42 alloy.
(I-6) The member made of the iron alloy is sprayed on the surface, and at least one of the nitride and the silicide is attached to the sprayed film, (I-1) to (I-5) ) A method for cleaning a member made of an iron alloy according to any one of the above.
(I-7) The method for cleaning a member made of an iron alloy according to any one of (I-1) to (I-6), wherein the molten salt bath contains sodium hydroxide.
(I-8) The method for cleaning a member made of an iron alloy according to (I-7), wherein the molten salt bath further contains sodium silicate.
(I-9) The method for cleaning a member made of an iron alloy according to any one of (I-1) to (I-8), wherein the member made of the iron alloy is a plate-like member having a plurality of through holes.

(II) Manufacturing method of solar cell element
(II-1) The plate-shaped member cleaned by the method according to (I-9) is used as a member for introducing a reaction gas into the CVD apparatus from the through hole, and is disposed in the CVD apparatus. A method for manufacturing a solar cell element, comprising a step of forming a deposited film having a component of the reaction gas on a semiconductor substrate for a battery element by a CVD method.

  According to the above cleaning method, since the nitride and silicide can be removed in a state where damage to the iron alloy containing at least one of chromium and nickel is slight, the iron alloy containing at least one of chromium and nickel It is possible to repeatedly use a shower plate made of metal. Further, according to the cleaning method of the present invention, even when the thermal spraying is performed on the iron alloy containing at least one of chromium and nickel, the nitride and the silicide are removed with a slight damage to the sprayed film. Therefore, the number of times of re-spraying and re-spraying can be reduced.

  Furthermore, in the production of solar cell elements, the concentration of impurities in the antireflection film can be reduced by using the cleaning method of the present invention to remove the film deposited on the surface of the electrode plate of the CVD apparatus. Impurity diffusion to the wafer surface is reduced, and the photoelectric conversion efficiency of the solar cell element can be improved.

It is the perspective view seen from the side which showed the structural example of CVD apparatus typically. FIG. 2 is an enlarged perspective view of an upper part of a film forming chamber in the CVD apparatus of FIG. 1. (a) is a plan view schematically showing an example of an electrode plate of a CVD apparatus, and (b) is a cross-sectional view showing an example of a cross section along line AA of (a).

  Hereinafter, embodiments of the present invention (hereinafter referred to as the present embodiment) will be described in detail with reference to the drawings. In addition, drawing is shown typically and the size of each structure, positional relationship, etc. are not shown correctly.

Method of cleaning member made of iron alloy The method of cleaning a member made of iron alloy according to the present embodiment is a member made of an iron alloy containing at least one of chromium and nickel, to which at least one of nitride and silicide is attached. Dipping in a molten salt bath having an alkali metal to remove at least one of the nitride and the silicide.

  The member made of an iron alloy in the present embodiment is preferably used as a plate-like member having a plurality of through holes (also referred to as a shower plate or an electrode plate in the present specification). When used as a plate-like member having a plurality of through holes, the diameter of the hole of the member made of an iron alloy is usually about 0.3 to 3.0 mm, preferably about 0.5 to 1.0 mm. When used as a plate-like member having a plurality of through-holes, the thickness of the member made of an iron alloy is usually about 2 to 5 mm, preferably about 3 to 4 mm. As the member made of the iron alloy of this embodiment, stainless steel, 42 alloy or the like is preferably used.

  The type of stainless steel used in the present embodiment is not particularly limited as long as the effect can be obtained in the present embodiment, and any of ferrite, martensite, austenite, ferrite-austenite, and precipitation hardening systems can be used. Although it may be present, SUS430 is preferable.

  Further, the member made of the iron alloy used in the present embodiment may be sprayed on the surface, and in this case, at least one of nitride and silicide adheres to the sprayed film. Such a sprayed coating provides an effect of preventing the peeling of film forming components. Examples of the metal used for thermal spraying include an alloy containing aluminum, a nickel aluminum alloy, and nickel. The composition of the nickel-aluminum alloy can be appropriately set, but is usually 80 to 95% by mass of Ni and 20 to 5% by mass of Al (or 65 to 90 mol% of Ni and 35 to 10 mol% of Al). The thickness of the sprayed film is usually about 10 to 40 μm. Thermal spraying can be performed by a conventional method such as plasma spraying.

The object to be removed from the member made of the iron alloy by the method of the present embodiment is at least one of the deposited nitride and silicide. For example, such a nitride adheres to a shower plate (a member made of an iron alloy) when forming a film using a shower plate with a vacuum evaporation apparatus in a part of a manufacturing process of a semiconductor or a solar cell. is there. Examples of the nitride include silicon nitride, aluminum nitride, titanium nitride, and magnesium nitride, and silicon nitride (particularly, Si ₃ N ₄ ) is preferable. Examples of the silicide include molybdenum silicide, tantalum silicide, tungsten silicide, titanium silicide, nickel silicide, copper silicide, and cobalt silicide.

  The molten salt bath used in this embodiment has an alkali metal. By immersing a member made of an iron alloy containing at least one of chromium and nickel to which at least one of nitride and silicide is attached to such a molten salt, the member made of the iron alloy adheres in a slight state. It is possible to remove at least one of nitride and silicide. Moreover, even when the member made of an iron alloy has a sprayed film, it is possible to remove at least one of nitride and silicide adhered with a slight damage to the sprayed film.

  The molten salt bath used in the present embodiment preferably contains an alkali metal salt and / or an alkali metal hydroxide.

  The alkali metal salt is not particularly limited as long as the effect can be obtained in the present embodiment, and examples thereof include alkali metal halides, alkali metal nitrates, alkali metal sulfates, and specific compounds include nitric acid. Sodium is mentioned. These can be used alone or in combination of two or more.

  The alkali metal hydroxide is not particularly limited as long as the effect can be obtained in this embodiment, and examples thereof include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide and the like. These can be used singly or in combination of two or more.

  As the molten salt bath used in the present embodiment, one containing sodium hydroxide is particularly preferred, and one containing sodium hydroxide and sodium silicate can also be suitably used. When both sodium hydroxide and sodium silicate are contained, the content in each molten salt is preferably 80 to 95% by mass and 20 to 5% by mass.

  The content of the alkali metal salt and / or alkali metal hydroxide in the molten salt bath used in the present embodiment is preferably 70% by mass or more, more preferably 85% by mass or more.

  The bath temperature when the member made of an iron alloy to which at least one of nitride and silicide is attached is immersed in the molten salt bath is appropriately set according to conditions such as the type of the molten salt to be used, preferably It is 300-500 degreeC, More preferably, it is 330-400 degreeC. The time for immersing the member made of an iron alloy to which at least one of nitride and silicide is attached is appropriately set according to conditions such as bath temperature, but is preferably 20 to 60 minutes, more preferably 30 to 45. Minutes. Thus, by immersing the member made of iron alloy in the molten salt bath, at least one of nitride and silicide is dissolved in the molten salt, and at least one of nitride and silicide from the member made of iron alloy Is removed.

  After the member made of an iron alloy is immersed in the molten salt bath, it is desirable to perform water washing or the like to remove the molten salt.

  According to the cleaning method of this embodiment, at least one of nitride and silicide can be removed from a member made of iron alloy in a state where damage to the member made of iron alloy (e.g., enlargement of the diameter of the hole) is slight. Therefore, unlike conventional methods (dissolution cleaning method using chemicals and physical cleaning method using blasting), an iron alloy shower plate containing at least one of chromium and nickel can be used repeatedly.

  Further, according to the cleaning method of the present embodiment, even when the member made of the iron alloy is sprayed, at least one of the nitride and the silicide is removed in a state where damage to the sprayed film is slight. As a result, it is possible to correct the thermal spraying and reduce the number of re-spraying.

Method for Manufacturing Solar Cell Element The method for manufacturing a solar cell element according to the present embodiment introduces a reaction gas into the CVD apparatus from the through hole, through the plate-like member having the plurality of through holes cleaned by the above method. The method includes a step of forming a deposited film having a component of the reaction gas by a CVD method on a semiconductor substrate for a solar cell element disposed in the CVD apparatus.

  One embodiment of the CVD apparatus according to the present embodiment is a plasma including a pair of electrode plates disposed opposite to each other in a reaction chamber, and a plate for placing a film formation substrate disposed between the electrode plates. It is a CVD apparatus (plasma chemical vapor deposition apparatus).

  In FIG. 1, 1 is a semiconductor substrate, 2 is a transfer cart, 3 is a load lock chamber, 4 is a film forming chamber, 5 is an unload lock chamber, 6 is a transfer mechanism, 7 is an electrode plate, 8 is power supply means, 9 Is a mass flow controller, 10 is a vacuum pump, 11 is ground, and 12 is a heater.

  Concerning the transport mechanism: The transport cart 2 on which the semiconductor substrate 1 is placed is carried into the load lock chamber 3 by the transport mechanism 6, exhausted from the atmospheric state to a vacuum state, and heated to a predetermined temperature. Then, the substrate 1 and the transfer cart 2 are transferred to the film forming chamber 4 while being heated, and are formed in the film forming chamber 4. Then, after film formation, it is carried to the unload lock chamber 5 and is purged from the vacuum state to the atmospheric state and carried out.

  Deposition film deposition: The film deposition chamber 4 is evacuated by a vacuum pump 10 and RF power is applied from a power supply means 8 such as an RF power source while introducing a gas from the mass flow controller 9 into the film deposition chamber 4. Thus, the introduced gas is excited to an active state, and plasma is generated between the electrode plate 7 and the transport cart 2 on the ground 11 side. As a result, a thin film such as an antireflection film can be formed on the upper surface of the semiconductor substrate 1 placed on the plate 17 on the transport cart 2.

  FIG. 2 is an enlarged perspective view of the upper part of the film forming chamber of the CVD apparatus of FIG. 1, wherein 13 is a gas supply and 14 is an electrode plate. A plate-like member (electrode plate 14) having a plurality of through holes cleaned by the cleaning method of the present invention is set at the lower part of the electrode plate 7, supplied with gas 13 from above the electrode plate 7, and penetrates the electrode plate 14. A reactive gas is supplied from the hole into the CVD apparatus.

  3A is a plan view of an example of an electrode plate of a CVD apparatus, FIG. 3B is a cross-sectional view showing the structure along the AA line of FIG. 3A, 15 is a through hole, 16 is a base material, and 17 is sprayed. The membrane is shown. As an example of the plate-like member (electrode plate 14) having a plurality of through holes of the present embodiment, stainless steel having a plurality of through holes 15 having a diameter of 0.5 to 1.0 mm and a thermal spray film 17 such as nickel alumite. Of the base material 16.

When forming an SiN _x film (a composition ratio (x) having a width with a center on Si ₃ N ₄ stoichiometry) as an antireflection film on a semiconductor substrate for a solar cell element, from the mass flow controller 9, A predetermined amount of monosilane gas (SiH ₄ ) and ammonia gas (NH ₃ ) are supplied, and the introduced gas is excited by applying RF power from the power supply means 8, thereby conveying the electrode plate 7 and the ground 11 side. Plasma is generated between the carts 2. Thereby, a thin film of SiN _x is formed on the upper surface of the substrate 1 placed on the transport cart 2.

  In this film formation process, the temperature of the substrate 1 is raised to about 400 to 500 ° C., and the frequency of the RF power to be applied is a relatively low frequency of about 100 to 600 kHz. It is desirable because the effect can be increased.

  Conditions such as gas amount, RF power output value and time in this film formation process are optimally determined by measuring the refractive index and film thickness of the formed antireflection film and the output characteristics of the completed solar cell element. It ’s fine.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not restrict | limited by this Example. The “%” below indicates “% by mass” unless otherwise specified.

Example 1
A shower plate with through-holes with Si ₃ N ₄ adhered to a thickness of about 25 μm during solar cell production was immersed in molten salt (liquid temperature 350 to 420 ° C.) made of caustic soda (NaOH) for 45 minutes and then washed with water. However, Si ₃ N ₄ was completely removed from both the surface of the shower plate and the inside of the through hole. The hole diameter of the through hole was 0.98 mm on average before cleaning, but it was almost unchanged at 0.97 mm on average.

  However, since the surface was oxidized and slightly turned gray, the oxide film was removed with an alkaline rust inhibitor.

  Under the same conditions, film formation → cleaning was repeated 10 times, but the average diameter of the through holes was 0.99 mm, and it was demonstrated that the shower plate could be used further.

Comparative Example 1
The shower plate formed under the same conditions as in Example 1 was washed with 25% hydrofluoric acid. After 4 hours, Si ₃ N ₄ adhering to the surface was completely removed, but about 1/3 of Si ₃ N ₄ in the through hole remained. When the immersion time was further extended by 1 hour, Si ₃ N ₄ in the through hole was also cleaned. The average hole diameter of the through holes before cleaning was 0.98 mm, but after cleaning, the average hole diameter increased to an average of 1.703 mm.

Subsequently, Si ₃ N ₄ was deposited and washed in the same manner as described above. As a result, the diameter of the through-holes increased to an average of 2.279 mm, so the shower plate was discarded after two uses.

Example 2
After spraying about 25 μm of Ni 90% Al 10% on a shower plate made of SUS430, a Si ₃ N ₄ film was formed as in Example 1. When this was immersed in molten salt (350-400 ° C) of 85% caustic soda and 15% sodium oxalate for 45 minutes and then washed with water, both the surface of the shower plate and the Si ₃ N ₄ in the through hole were completely washed. It was. Moreover, the sprayed coating coated on the surface remained almost without being destroyed. The average hole diameter of the through-holes before cleaning was 0.930 mm on average, and the average was 0.930 mm after cleaning with almost no change.

  However, since the surface was oxidized and turned slightly gray, the oxide film was removed with an acid rust inhibitor.

  Without re-spraying, the film formation under the same conditions as in Example 1 and the cleaning under the same conditions as described above were repeated 10 times. As a result, the thermal sprayed film was reduced by about 30%, but the average diameter of the through-holes was only 0.984 mm. For this reason, the remaining NiAl sprayed film was once peeled off and then resprayed, so that the reuse could be continued without discarding the shower plate.

Comparative Example 2
The shower plate on which the same Si ₃ N ₄ film as in Example 2 was blasted using glass beads ^# 1 under the condition of a pressure of 5 kgf / cm ² to clean the Si ₃ N ₄ . Blasting did not leave the thermal spray in an effective state, and it was removed until thermal spraying, as was the case with the Si ₃ N ₄ film. The diameter of the through holes at this time was 0.935 mm on average before cleaning, and 1.133 mm on average after cleaning. This shower plate was sprayed again, and after film formation and cleaning by blasting were repeated four more times (5 times in total), the average diameter of the through holes was 2.012 mm and was discarded.

Comparative Example 3
The same shower plate on which Si ₃ N ₄ was formed as in Example 2 was washed with 25% hydrofluoric acid. After 3 hours, Si ₃ N ₄ was removed both from the surface of the shower plate and from the pores. However, about 80% of the sprayed film was dropped. The average pore size was 0.931 mm before cleaning, but the average was 1.356 mm after cleaning. The sprayed film remaining in an incomplete state was removed by blasting and then re-sprayed to form a film. This shower plate was discarded because the hole diameter increased to an average of 2.353 mm by the third repetition of film formation → washing.

Test example 1
The same CVD is used when the electrode plate cleaned by the method of the present invention and subjected to oxide film removal treatment is used (Example 3) and when the electrode plate cleaned by the blast method is used (Comparative Example 4). An antireflection film made of silicon nitride was formed on a 6-inch single crystal silicon wafer by an apparatus. The surface is washed with nitric acid: pure water = 1: 1, and then the antireflection film is dissolved with hydrofluoric acid. The solution is ultrapure and diluted 10 times. Quantitative analysis was performed with an (Inductively Coupled Plasma) mass spectrometer (ELAN DCRII manufactured by PerkinElmer). The results are shown in Table 1.

  By using the cleaning method of the present invention to remove the film deposited on the electrode plate surface of the CVD apparatus, it becomes possible to expose the surface of the sprayed nickel alumite sprayed film as compared with the blasted one, and the antireflection film. The impurity concentration in the medium could be reduced.

Test example 2
The same CVD is used when the electrode plate cleaned by the method of the present invention and subjected to oxide film removal treatment is used (Example 4) and when the electrode plate cleaned by the blast method is used (Comparative Example 5). An antireflection film made of silicon nitride was formed by an apparatus, and 5,000 polycrystalline silicon solar cells were produced.

  Specifically, as the semiconductor substrate 1, a polycrystalline silicon substrate manufactured by a casting method having a square side of about 156 mm and a thickness of about 200 μm in plan view was prepared. As these polycrystalline silicon substrates, polycrystalline silicon substrates exhibiting a p-type conductivity type having a specific resistance of about 1.5 Ω · cm by doping boron were used. The damaged layer on the surface of the semiconductor substrate 1 was etched using an aqueous NaOH solution, and then washed.

  Next, a concavo-convex structure was formed on the surface which becomes the light receiving surface of each prepared polycrystalline silicon substrate by using the RIE (Reactive Ion Etching) method.

Next, phosphorus is diffused by a vapor phase thermal diffusion method using phosphorus oxychloride (POCl ₃ ) as a diffusion source, and an n-type reverse conductivity type layer having a sheet resistance of about 90 Ω / □ is formed on the surface of the substrate 1. Formed. The reverse conductivity type layers formed on the side surface and the back surface (non-light receiving surface) side were removed with a hydrofluoric acid solution.

  Thereafter, the antireflection layer 4 made of silicon nitride is formed on the surface of the light receiving surface by the same CVD apparatus using the electrode plate cleaned by the blast method according to the present invention and the electrode plate cleaned by the blast method as a comparative example. did. The antireflection layer 4 had an average thickness of about 80 nm and a refractive index of about 2.0.

  Next, a conductive paste mainly composed of aluminum is applied to the non-light-receiving surface side of the semiconductor substrate 1 by screen printing, excluding the outer peripheral portion (about 1.5 mm in width) on the back surface, and then a temperature of 750 ° C. After firing at a degree, aluminum was baked on the non-light-receiving surface side of the semiconductor substrate 1 to form a collector electrode.

  Thereafter, 10 parts by weight of silver powder and organic vehicle were added to 100 parts by weight of silver, and 5 parts by weight of glass frit was added to 100 parts by weight of silver on the antireflection layer 4 of the semiconductor substrate 1. The conductive paste was applied in a predetermined shape using a screen printing method.

  Further, a conductive paste mainly composed of silver was applied in a predetermined shape onto the collector electrode on the non-light-receiving surface side of the semiconductor substrate 1 using a screen printing method. Thereafter, these were baked at a maximum temperature of about 770 ° C. for about several minutes to form electrodes on the light receiving surface side and the back surface side.

The solar cell element was produced as described above. And the short circuit current of the solar cell element, the open circuit voltage, the fill factor (FF), and the maximum output were measured and the average was calculated | required. These characteristics were measured under the conditions of irradiation with AM (Air Mass) 1.5 and 100 mW / cm ² based on JIS C 8913.

  The results are shown in Table 2.

  Table 2 shows an index using each value as 100 when an electrode plate by the blast method is used.

  By using the cleaning method of the present invention to remove the film deposited on the electrode plate surface of the CVD apparatus, the light reflection is reduced and the diffusion of impurities to the silicon wafer surface is reduced compared to the blast treatment, and the solar cell element It was confirmed that the photoelectric conversion efficiency was improved.

  The cleaning method of the present invention is a part of a manufacturing process of a semiconductor or a solar cell, and a plate having a plurality of through holes such as a shower plate attached to obtain a uniform film formation when forming a film with a vacuum evaporation apparatus It can be used for cleaning of a member, cleaning in an industry where it is necessary to remove adhering nitride in a short time with little damage to the product.

DESCRIPTION OF SYMBOLS 1; Semiconductor substrate 2; Transfer cart 3; Load lock chamber 4; Film formation chamber 5; Unload lock chamber 6; Transfer mechanism 7; Electrode plate 8; Power supply means 9; Heater 13: Gas supply 14: Electrode plate 15: Through hole 16: Base material 17: Thermal spray film

Claims (9)

A member made of an iron alloy containing at least one of chromium and nickel, to which at least one of nitride and silicide is attached, is immersed in a molten salt bath containing an alkali metal, and at least one of the nitride and silicide is immersed in the member. the step of removing only contains,
The iron alloy is stainless steel or 42 alloy,
The molten salt bath contains an alkali metal hydroxide,
A method for cleaning a member made of an iron alloy.   The method for cleaning a member made of an iron alloy according to claim 1, wherein the nitride is silicon nitride. The method for cleaning a member made of an iron alloy according to claim 1 or 2 , wherein the stainless steel is SUS430. The member made of the iron alloy is made of the iron alloy according to any one of claims 1 to 3 , wherein the surface is sprayed, and at least one of the nitride and the silicide is attached to the sprayed film. Cleaning method for members. The method for cleaning a member made of an iron alloy according to any one of claims 1 to 4 , wherein the molten salt bath contains sodium hydroxide. The method for cleaning a member made of an iron alloy according to claim 5 , wherein the molten salt bath further contains sodium silicate. The method for cleaning a member made of an iron alloy according to any one of claims 1 to 6, wherein a bath temperature of the molten salt bath is 330 to 400 ° C. The method for cleaning a member made of an iron alloy according to any one of claims 1 to 7 , wherein the member made of the iron alloy is a plate-like member having a plurality of through holes. The plate-like member cleaned by the method according to claim 8 is used as a member for introducing a reaction gas into the CVD apparatus from the through hole, and a semiconductor substrate for a solar cell element disposed in the CVD apparatus. A method for manufacturing a solar cell element, further comprising a step of forming a deposited film having the reaction gas component by a CVD method.

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