WO2007049347A1 - Procede d'usinage a faible reflectivite pour un substrat en silicium de pile solaire et ledit substrat - Google Patents

Procede d'usinage a faible reflectivite pour un substrat en silicium de pile solaire et ledit substrat Download PDF

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Publication number
WO2007049347A1
WO2007049347A1 PCT/JP2005/019727 JP2005019727W WO2007049347A1 WO 2007049347 A1 WO2007049347 A1 WO 2007049347A1 JP 2005019727 W JP2005019727 W JP 2005019727W WO 2007049347 A1 WO2007049347 A1 WO 2007049347A1
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Prior art keywords
silicon substrate
solar cell
plasma treatment
processing method
plasma
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PCT/JP2005/019727
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English (en)
Japanese (ja)
Inventor
Yoshihiro Nakashima
Minoru Tahara
Nobuo Asahi
Hiroshi Otsubo
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Shinryo Corporation
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Priority to PCT/JP2005/019727 priority Critical patent/WO2007049347A1/fr
Publication of WO2007049347A1 publication Critical patent/WO2007049347A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

Definitions

  • the present invention relates to a method for processing low reflectance of a silicon substrate for solar cells and forming a rough surface on a roughened surface to achieve low reflectance, and a silicon substrate for solar cells.
  • the surface of the silicon substrate is roughened to reduce the reflectance of sunlight and increase the light absorption efficiency.
  • a chemical etching method has been proposed (for example, Japanese Patent Application Laid-Open No. 1-111887).
  • the present invention has been made in view of strong circumstances, and reduces the reflectance by easily and uniformly forming fine irregularities on the surface of a single crystal or polycrystalline silicon substrate used in a solar cell.
  • An object of the present invention is to provide a low-reflectance processing method for a silicon substrate for solar cells and a silicon substrate for solar cells.
  • a low reflectance processing method for a solar cell silicon substrate according to the first invention that meets the above-mentioned object is a method for processing a surface of a single crystal or polycrystalline silicon substrate used in a solar cell to a low reflectance.
  • the surface of the silicon substrate is roughened by chemical or physical treatment.
  • the chemical treatment refers to an etching treatment of the surface of a silicon substrate using a chemical such as alkali or acid
  • the physical treatment refers to mechanical fine unevenness processing (for example, a fine abrasive material bough). Last or Kensho IJ).
  • the first plasma treatment forms a turbulent layer or an oxide layer having a disordered crystal structure on the surface layer of the silicon substrate to modify the surface of the silicon substrate.
  • the first and second plasma treatments are performed at a frequency of 10 MHz to 50 MHz and 0.2 WZcm 2 per unit area of the electrode.
  • a high frequency power of 1.5 WZcm 2 or less is applied for a period of 30 seconds to 300 seconds.
  • the frequency is less than 10 MHz, the density of the generated plasma is low, and if the frequency exceeds 50 MHz, the production cost of the apparatus is undesirably high.
  • the high-frequency power per unit area of the electrode is less than 0.2 WZcm 2 in the first plasma treatment, the surface modification of the silicon substrate is insufficient, and if it exceeds 1.5 WZcm 2 the surface of the silicon substrate is modified. The quality is excessive, and it becomes difficult to form fine irregularities by the second plasma treatment.
  • the high-frequency power per unit area of the electrode is less than 0.2 WZcm 2 in the second plasma treatment, the density of the generated plasma is low and it becomes difficult to form fine irregularities, and if it exceeds 1.5 WZcm 2 , it reacts with the substrate. This is not preferable because the property becomes too large to control the formation of fine irregularities.
  • a low reflectance processing method for a solar cell silicon substrate according to the second invention according to the second object is a method for processing a surface of a single crystal or polycrystalline silicon substrate used for a solar cell to a low reflectance. Because
  • the surface of the roughened silicon substrate is subjected to the roughening treatment by generating plasma while supplying a mixed gas of a halogen-based gas and an oxygen gas under a reduced pressure of more than 0.05 Torr but not more than lTorr. And a second step of forming fine irregularities on the surface of the silicon substrate by plasma treatment.
  • the anisotropy of the plasma treatment can be increased.
  • the oxygen gas ratio QZ (P + Q) in the mixed gas is preferably 0.1 to 0.5. If Q / (P + Q) is less than 0.1, the anisotropy becomes remarkable because the oxygen content in the plasma treatment is relatively low due to the relatively low oxygen content and the surface modification action of the silicon substrate is reduced. Not preferable.
  • the plasma treatment is performed at a frequency of 10 MHz to 50 MHz and an electrode unit area of 0.2 WZcm 2 or more. It is preferable to apply high-frequency power of 5 WZcm 2 or less for 30 seconds or more and 300 seconds or less.
  • the frequency is less than 10 MHz, the density of the generated plasma will be low, and if the frequency exceeds 50 MHz, the production cost of the device will be undesirably high.
  • the formation of the generated speed is less fine irregularities of the low density plasma treatment of the plasma with the high frequency power is less than 0. 2WZcm 2 per unit area of the electrode becomes difficult, and when it exceeds 1. 5WZcm 2 bra Zuma The process becomes too reactive and it becomes difficult to control the formation of fine irregularities. It ’s not good.
  • the plasma treatment time was set to 30 seconds or longer to form uniformly fine irregularities on the entire surface of the silicon substrate, and the period of 300 seconds or shorter was set to fine fine irregularities once formed. This is to prevent disappearance.
  • the halogen-based gas is any one of carbon tetrafluoride gas and sulfur hexafluoride gas. Or it can be 2.
  • the solar cell silicon substrate according to the third invention is a solar cell silicon substrate manufactured using the low reflectance processing method for a solar cell silicon substrate according to the first or second invention.
  • Shape force seen from the cross section Height 1 m to 30 ⁇ m
  • Base length 1 ⁇ m to 40 ⁇ m
  • Uneven surface shape force seen from the cross section Height: 0. Ol ⁇ m- It has a convex shape of 0.05 m to 0.50 m, the distance between the apexes of adjacent convex parts: 0.05 m.
  • FIG. 1 is an explanatory diagram of a plasma processing apparatus used in a low reflectance processing method for a solar cell silicon substrate according to first and second embodiments of the present invention.
  • FIG. 2 is an electron micrograph showing the crystal structure of the surface of the silicon substrate after the second plasma treatment in the low reflectance processing method for a silicon substrate for solar cells according to Example 1 of the present invention.
  • FIG. 3 is a graph showing the wavelength dependence of the reflectance of a silicon substrate obtained by the low reflectance processing method for a solar cell silicon substrate according to Examples 1 and 2 of the present invention.
  • FIG. 4 is an electron micrograph showing the crystal structure of the surface of the silicon substrate after plasma processing in the low reflectance processing method for a solar cell silicon substrate according to Example 2 of the present invention.
  • FIG. 5 is an electron micrograph showing the crystal structure of the cross section of the silicon substrate after the second plasma treatment in the low reflectance processing method for a solar cell silicon substrate according to Example 3 of the present invention.
  • FIG. 6 is an electron micrograph showing an enlargement of the crystal structure of FIG.
  • FIG. 7 is a graph showing the wavelength dependence of the reflectance of a silicon substrate obtained by the low reflectance processing method for a solar cell silicon substrate according to Example 3 of the present invention.
  • FIG. 1 is an explanatory view of a plasma processing apparatus used in the low reflectance processing method of the solar cell silicon substrate according to the first and second embodiments of the present invention.
  • the plasma processing apparatus 10 used in the low reflectance processing method for a silicon substrate for solar cells according to the first and second embodiments of the present invention includes an upper electrode 11 and an upper electrode.
  • the upper electrode 11 includes a metal cylinder 15 fixed to the top plate 14 of the chamber 13 and an upper electrode plate 17 fixed to the tip of the cylinder 15 and having a plurality of holes 16.
  • the lower electrode 12 includes a lower electrode plate 18 on which the silicon substrate A is directly mounted, an introduction electrode 20 that supports the lower electrode plate 18 and has a cooling water passage 19 formed therein, and an introduction electrode.
  • An insulating member that covers the base of 20 and has an outer peripheral side fitted into an opening provided in the bottom plate 21 of the chamber 13 so that the introduction electrode 20 is electrically insulated from the bottom plate 21 of the chamber 13. And 22.
  • the proximal end portion of the introduction electrode 20 is connected to the positive electrode side of the high-frequency power source 24 via the matching box 23, and the inlet side and the outlet side of the flow channel 19 are the outlet side and the inlet side of the cooling water circulator 25 equipped with a cooler. Connected to each side.
  • the space 26 surrounded by the top plate 14, the cylindrical body 15, and the upper electrode plate 17 can be formed in the upper electrode 11. Then, by grounding the chamber 13 side and the negative electrode side of the high-frequency power source 24, a discharge space is formed between the lower electrode plate 18 and the upper electrode plate 17 while cooling the lower electrode plate 18 on which the silicon substrate A is placed. Can be formed.
  • the plasma processing apparatus 10 includes an oxygen gas supply means 29 for supplying oxygen gas from the oxygen gas source 27 to the space portion 26 via the first mass flow meter 28, and an example of a halogen-based gas.
  • Halogen-based gas supply means 32 for supplying a certain sulfur hexafluoride gas from a norogen-based gas source 30 via a second mass flow meter 31 and an exhaust provided in the bottom plate 21 of the chamber 13 in the chamber 13
  • Exhaust means 34 provided with a vacuum pump for exhausting through port 33 is provided. It is.
  • the inside of the chamber 13 is in a reduced pressure state (for example, , 0.05 Torr and lTorr or less) in an oxygen gas atmosphere, a sulfur hexafluoride gas atmosphere, or a mixed gas atmosphere of oxygen gas and sulfur hexafluoride gas.
  • a reduced pressure state for example, 0.05 Torr and lTorr or less
  • the low-reflectance processing method for the solar cell silicon substrate includes a first step of performing a chemical treatment to roughen the surface of the single crystal or polycrystalline silicon substrate, and a roughening treatment.
  • a third step of forming fine irregularities on the surface of the silicon substrate by performing plasma treatment This will be described in detail below.
  • the first step is a degreasing process for removing oils and fats adhering to the untreated silicon substrate, and a surface layer removing process for uniformly removing the altered layer and the contaminated layer of the surface layer part of the silicon substrate subjected to the degreasing process.
  • an alkali etching process which is an example of a roughening process for forming irregularities on the surface of the silicon substrate that has been subjected to the surface layer removal process, and a water washing process that removes the aqueous alkali solution that has adhered to the silicon substrate that has been subjected to the alkali etching process Have.
  • the degreasing treatment is performed, for example, by immersing an untreated silicon substrate in a degreasing tank in which an organic solvent is stored on a substrate holder.
  • an organic solvent examples include ketone solvents such as acetone and methyl ethyl ketone, alcohol solvents such as ethanol and methanol, and halogen solvents such as dichloromethane and chloroform. Of these, acetone is particularly preferred.
  • the silicon substrate mounted on the substrate holder after finishing the surface layer removal treatment is immersed in an etching treatment tank in which an alkaline aqueous solution is stored.
  • an alkaline aqueous solution for example, 1 to 3% by weight sodium hydroxide aqueous solution heated to 65 to 85 ° C, or 1 to 3% by weight hydroxylated water heated to 65 to 85 ° C.
  • a potassium aqueous solution or a mixed solution obtained by adding isopropyl alcohol to an alkaline aqueous solution (the mixing volume ratio is, for example, isopropyl alcohol 1 to L0 with respect to the alkaline aqueous solution 100) can be used.
  • the treatment time is 10 to 60 minutes, preferably 20 to 40 minutes.
  • a substrate holder on which an alkali-etched silicon substrate is mounted is pulled up from the etching tank and immediately immersed in a water-washing tank to perform a water-washing process, thereby removing the aqueous alkali solution on the surface of the silicon substrate.
  • the reason why the silicon substrate is washed with water immediately after the alkali etching treatment is to prevent non-uniform etching from proceeding to the surface portion of the silicon substrate. Therefore, the water washing treatment should be performed within 30 seconds, preferably within 10 seconds after the alkali etching treatment.
  • the substrate holder is lifted from the washing tank and inserted into a dryer, and water adhering to the surface of the silicon substrate is removed by evaporation.
  • the chamber 13 of the plasma processing apparatus 10 is opened, and the silicon substrate subjected to the first step is placed in the center of the upper surface of the lower electrode plate 18. Then, after adjusting the distance of the discharge space formed between the upper electrode plate 17 and the lower electrode plate 18 to 15 to 65 mm, preferably the lower limit value is 35 mm and the upper limit value is 55 mm, the chamber 13 is adjusted. close. Then, the exhaust means 34 to the chamber one 13 via the exhaust port 33, the pressure in the chamber one 13, for example, is evacuated until 1 X 10- 5 ⁇ 5 X 10- 5 Torr, the upper electrode Oxygen gas is supplied from the oxygen gas supply means 29 into the chamber 13 through the holes 16 provided in the plate 17. Then, pressure is 7.
  • the upper limit preferably 0. upper limit value in lower limit value of 0.5 03Torr 75 Torr, more preferably the lower limit is 0. 08Torr
  • the exhaust amount of the exhaust means 34 is adjusted so that the value becomes 0.6 Torr, and the first mass meter 28 is adjusted to blow into the chamber 13 through the hole 16.
  • the purity of oxygen gas is preferably 99.0% or more.
  • the frequency between the lower electrode plate 18 and the upper electrode plate 17 from the high frequency power supply 24 was 10 to 50 MHz
  • the lower limit is 10 MHz and the upper limit is 15 MHz
  • the lower limit is 13 MHz and the upper limit is 14 MHz
  • the power per unit area of the electrode is 0.2 to 1.5 W / cm 2
  • the lower limit There 0. 3W / cm 2 at the upper limit value of lW / cm 2
  • a high frequency power upper limit value is 0. 6W / cm 2 and more preferably the lower limit is at 0. 4W / cm 2
  • 30 ⁇ 600 seconds preferably Apply the time when the lower limit is 45 seconds and the upper limit force is 50 seconds, more preferably the lower limit is 60 seconds and the upper limit is 300 seconds.
  • sulfur hexafluoride gas is supplied from the halogen-based gas supply means 32 into the chamber 13 through the holes 16 of the upper electrode plate 17. Then, pressure is 7. 5 X 10- 3 ⁇ 1 in chamber one 13. 5 Torr, preferably the lower limit is the upper limit value is 0. 75 Torr at 0. 03Torr, the upper limit more preferred properly lower limit is 0. LTorr Adjust the exhaust capacity of the exhaust means 34 so that becomes 0.6 Torr.
  • the purity of sulfur hexafluoride gas is preferably 99% or more.
  • the frequency between the lower electrode plate 18 and the upper electrode plate 17 from the high frequency power supply 24 was 10 MHz or more. 50 MHz or less, preferably lower limit 10 MHz and upper limit 15 MHz, more preferably lower limit 13 MHz and upper limit 14 MHz, power per unit area of electrode 0.2 to 1.5 W, preferably lower limit 0. 3WZcm 2 at the upper limit value LWZcm 2, the RF power upper limit value is 0. 6WZcm 2 and more preferably the lower limit is at 0. 4WZcm 2, 30 ⁇ 600 seconds, the upper limit force preferably the lower limit is 45 seconds Apply for 50 seconds, more preferably for a time with a lower limit of 60 seconds and an upper limit of 300 seconds.
  • a discharge is generated between the lower electrode plate 18 and the upper electrode plate 17, and oxygen gas is discharged.
  • a discharge is generated in the discharge space, which becomes a plasma source, and the sulfur hexafluoride gas is ionized to form ions and fluorine radicals F * in the discharge space.
  • the generated radical ions are accelerated by the voltage applied between the upper electrode 11 and the lower electrode 12, and move toward the lower electrode 12 and move in the discharge space, and are placed on the lower electrode 12. It collides with the surface of the silicon substrate. Thereby, fine unevenness (secondary texture structure) is uniformly formed on each uneven surface of the primary texture structure formed on the silicon substrate.
  • the low reflectance processing method of the solar cell silicon substrate according to the second embodiment of the present invention is the same as the low reflectance processing method of the solar cell silicon substrate according to the first embodiment.
  • the surface of the roughened silicon substrate was supplied with a mixed gas of sulfur hexafluoride gas and oxygen gas, which is an example of a halogen-based gas, under a reduced pressure of more than 0.05 Torr and less than lTorr.
  • a mixed gas of sulfur hexafluoride gas and oxygen gas which is an example of a halogen-based gas
  • a mixed gas of sulfur hexafluoride gas and oxygen gas is used instead of the sulfur hexafluoride gas, as compared with the second plasma treatment in the first embodiment. Except for the use, it is essentially the same as the second plasma treatment method. For this reason, the description of the low reflectance processing method of the silicon substrate for solar cells according to the second embodiment is omitted.
  • the ratio of oxygen gas in the mixed gas is in the range of 0.1 to 0.5, preferably the lower limit is 0.12, the upper limit is 0.3, and more preferably the lower limit is 0.15. The upper limit is 0.25.
  • a single crystal silicon substrate was immersed in a degreasing tank in which acetone was stored for 300 seconds for degreasing treatment, and then dried with a dryer.
  • the silicon substrate was immersed for 60 seconds in an alkaline tank in which 3% by weight of sodium hydroxide / sodium hydroxide aqueous solution heated to 80 ° C was stored, and the silicon substrate subjected to surface layer removal treatment was removed from the alkaline tank. It was pulled up and immersed in a washing tank within 10 seconds to remove the sodium hydroxide aqueous solution, and the washing tank was pulled up and loaded into a dryer to be dried.
  • an alkali was immersed for 30 minutes in the etching treatment tank mixture of isopropyl alcohol Mizusani ⁇ aqueous sodium and 5 vol 0/0 of the silicon substrate 1 by weight%, which is heated to 75 ° C is stored etched After performing the treatment, immerse it in a water washing tank within 10 seconds and wash it with water. The aqueous solution of sodium hydroxide was removed from the treated and roughened silicon substrate, and the washing tank was also pulled up and loaded into a dryer to dry it (first step). As a result, irregularities having a shape force height of 1 m to 15 m and a base length of 1 m to 30 ⁇ m as viewed from the cross section are formed on the surface of the silicon substrate.
  • the roughened silicon substrate is placed on the lower electrode plate of the lower electrode of the plasma processing apparatus, the distance between the lower electrode plate and the upper electrode plate is adjusted to 45 mm, and oxygen gas is placed in the chamber.
  • the pressure inside the chamber is maintained at 0.5 Torr, and the frequency is 13.56 MHz between the upper electrode and the lower electrode from the high frequency power supply, and the high frequency power of 0.45 W / cm 2 per unit area of the electrode is 300.
  • the first plasma treatment was performed by applying a second to generate an oxygen plasma by discharge between the lower electrode and the upper electrode (the second step).
  • a mixed gas having a ratio of oxygen gas of 0.2 is supplied into the chamber 1, the pressure in the chamber 1 is maintained at 0.5 Torr, and the high frequency power supply A high frequency power of 0.456 W Zcm 2 per unit area of the electrode is applied for 180 seconds between the lower electrode and the upper electrode, and plasma is generated by discharge between the lower electrode and the upper electrode.
  • the second plasma treatment was performed (the third step).
  • the shape viewed from the cross-section has a height of 1 ⁇ m to 15 ⁇ m and the bottom surface length is 1 ⁇ m to 30 ⁇ m.
  • 05 / ⁇ ⁇ ⁇ 0.20 ⁇ m a silicon substrate having a convex shape with the distance between the vertices of adjacent convex parts being 0.1.lO ⁇ m-0.30 m is obtained.
  • a silicon substrate obtained by performing the same roughening treatment as in Example 1 in the first step is subjected to plasma treatment. It is placed on the lower electrode plate of the lower electrode of the control device, the distance between the lower electrode plate and the upper electrode plate is adjusted to 45 mm, and the oxygen gas ratio in the mixed gas of sulfur hexafluoride gas and oxygen gas is 0
  • the mixed gas of 2 is supplied into the chamber 1 and the pressure in the chamber 1 is maintained at 0.5 Torr.
  • the frequency is 13.56 MHz between the upper electrode and the lower electrode from the high frequency power source, and the unit area of the electrode is 0
  • a plasma treatment was performed by applying high-frequency power of 45 WZcm 2 for 180 seconds to generate oxygen plasma by discharge between the lower electrode and the upper electrode (the second step).
  • the shape viewed from the cross section has a height of 1 111 to 15 111 and the bottom length of 1 ⁇ to 30 / ⁇ ⁇ , and the shape viewed from the cross section has a height of 0.01.
  • a silicon substrate having a convex shape with / ⁇ ⁇ to 0.10 m and a distance between vertices of adjacent convex portions of 0.10 m to 0.30 m can be obtained.
  • the polycrystalline silicon substrate was degreased by immersing it in a degreasing tank in which acetone was stored for 300 seconds, and then dried with a dryer.
  • the silicon substrate was immersed for 10 minutes in an alkaline tank in which a 5 wt% sodium hydroxide aqueous solution heated to 80 ° C was stored, and the silicon substrate subjected to surface layer removal treatment was removed from the alkaline tank.
  • it was immersed in a washing tank to remove the aqueous solution of sodium hydroxide, and then pulled up from the washing tank and loaded into a dryer to dry it (the first step).
  • irregularities having a height of 1111 to 15111 and a base length of 1 ⁇ m to 40 ⁇ m are formed on the surface of the silicon substrate.
  • the roughened silicon substrate is placed on the lower electrode plate of the lower electrode of the plasma processing apparatus, the distance between the lower electrode plate and the upper electrode plate is adjusted to 45 mm, and oxygen gas is placed in the chamber.
  • the pressure in the chamber is kept at 0.15 Torr, and the frequency is 13.56 MHz between the upper electrode and lower electrode from the RF power source, and RF power of 0.6 W / cm 2 per unit area of the electrode is applied for 300 seconds.
  • Applied, and oxygen is released between the lower and upper electrodes by discharge.
  • a first plasma treatment was performed by generating a plasma (the second step).
  • a mixed gas having an oxygen gas ratio of 0.2 is supplied into the chamber 1, the pressure in the chamber 1 is maintained at 0.20 Torr, and the high frequency power supply
  • a high frequency power of 13.56 MHz and 0.3 W / cm 2 per unit area of the electrode is applied for 300 seconds between the lower electrode and the upper electrode, and plasma is generated by discharge between the lower electrode and the upper electrode.
  • the second plasma treatment was performed (the third step).
  • the shape viewed from the cross section has a height force of SO.30 / ⁇ ⁇ ⁇ 0.0 to the uneven surface with a height of 1 to 15 m and a base length of 1 to 40 ⁇ m.
  • a silicon substrate having a convex shape of 50 ⁇ m and a distance force between the vertices of adjacent convex portions of 0.10 / ⁇ ⁇ to 0.30 ⁇ m is obtained.
  • the present invention is not limited to this embodiment, and can be modified without changing the gist of the invention.
  • the present invention also includes a case where a low-reflectance processing method for a silicon substrate for solar cells and a silicon substrate for solar cells according to the present invention are configured by combining some or all of these embodiments and modifications. It is.
  • alkali etching is performed as a chemical treatment, but acid etching may be performed.
  • physical treatment instead of chemical treatment, for example, unevenness may be mechanically formed on the surface of the silicon substrate.
  • Carbon tetrafluoride gas can be used in place of sulfur hexafluoride gas as halogen-based gas, and mixed gas of carbon tetrafluoride gas and oxygen gas, sulfur hexafluoride gas, carbon tetrafluoride It is possible to use a mixed gas of gas and oxygen gas.
  • the second plasma treatment is performed on the silicon substrate whose surface has been modified by the first plasma treatment.
  • Plasma etching is performed, and fine and deep irregularities can be uniformly and efficiently formed on the surface of the roughened silicon substrate, and the single crystal or the reflectivity is greatly reduced.
  • a polycrystalline silicon substrate can be mass-produced with high productivity and stable production.
  • the first and second plasma treatments are performed at a frequency of 10 MHz or more and 50 MHz or less and per unit area of the electrode.
  • high frequency power of 2 WZcm 2 or more and 1.5 WZcm 2 or less is applied for 30 seconds or more and 300 seconds or less, respectively, the density of the generated plasma can be maintained high.
  • this plasma treatment it is possible to efficiently modify the surface of the silicon substrate, and in the second plasma treatment, it is possible to form fine irregularities.
  • the anisotropy of the plasma treatment can be increased, and the roughening treatment can be performed by adjusting the mixing ratio of oxygen. It is possible to promote the formation of fine irregularities on each irregular surface of the surface of the treated silicon substrate.
  • the plasma treatment is performed at a frequency of 10 MHz to 50 MHz and an electrode unit area of 0.2 WZcm 2 or more.
  • high-frequency power of 5 WZcm 2 or less is applied for a period of 30 seconds or more and 300 seconds or less, so the reaction with the substrate can be controlled, so the surface modification and plasma etching of the silicon substrate can be performed in parallel. Can be performed.
  • the halogen-based gas is selected from carbon tetrafluoride gas and sulfur hexafluoride gas 1 or 2
  • fluorine radicals and ions derived from carbon tetrafluoride or sulfur hexafluoride can be generated, and chemical etching by fluorine radicals on the silicon substrate surface and sputter etching by ions are caused. Is possible.
  • the silicon substrate for solar cells according to the third invention the silicon substrate for solar cells having a lower reflectance can be provided by the above-described stable manufacturing method.

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Abstract

Le problème à résoudre dans le cadre de la présente invention consiste à proposer un procédé d'usinage à faible réflectivité pour un substrat en silicium de pile solaire, par lequel la réflectivité peut être réduite en formant de manière stable de fines irrégularités sur la surface d'un substrat en silicium monocristallin ou polycristallin devant être utilisé pour une pile à combustible, et à proposer un tel substrat fabriqué par un tel procédé. La solution proposée consiste en un procédé qui est prévu pour usiner la surface du substrat en silicium monocristallin ou polycristallin (A) devant être utilisé pour la pile solaire pour apporter une faible réflectivité. Le procédé comprend une première étape consistant à rendre rugueuse la surface du substrat en silicium (A) par un traitement chimique ou physique ; une deuxième étape consistant à réaliser un premier traitement au plasma sur la surface dudit substrat rendu rugueux (A) par l'utilisation d'oxygène gazeux dans un état dépressurisé ; et une troisième étape consistant à former de fines irrégularités sur la surface dudit substrat (A) par un second traitement au plasma sur la surface dudit substrat (A) après le premier traitement au plasma, dans un état dépressurisé par l'utilisation d'halogène gazeux.
PCT/JP2005/019727 2005-10-26 2005-10-26 Procede d'usinage a faible reflectivite pour un substrat en silicium de pile solaire et ledit substrat WO2007049347A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2476959C2 (ru) * 2008-01-23 2013-02-27 Солвей Флуор Гмбх Способ изготовления солнечных элементов
EP3104418A1 (fr) * 2015-06-08 2016-12-14 Meyer Burger (Germany) AG Procédé et dispositif destinés à texturer une surface en silicium

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