JP2014082330A - METHOD FOR REMOVING SiN FILM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing a SiN film using a novel etching material.SOLUTION: A method for removing a SiN film includes the steps of: coating an etching material on a silicon nitride (SiN) film by means of a printing method, the etching material containing at least one boron compound selected from among a Lewis acid containing, in the structure thereof, boron and halogen bonded to the boron, a salt of the Lewis acid, and a compound generating the Lewis acid; and removing the SiN film by heating.

Description

  The present invention relates to a method for removing (etching) an inorganic thin film made of silicon nitride (SiN) or the like.

Inorganic thin films such as silicon oxide (SiO ₂ ) and SiN are used in various semiconductor elements, solar cells, and the like as interlayer insulating films, passivation films, antireflection films, and the like.
For example, in some solar cells, an antireflection film made of a SiN film is formed on the light receiving surface side and a passivation film is formed on the surface opposite to the light receiving surface in order to improve conversion efficiency.

In the manufacture of a crystalline silicon solar battery cell that is generally used as a solar battery, a phosphorus diffusion layer that becomes an n + layer is formed on the surface layer of a p-type silicon wafer, and a pn junction is formed between the lower p layer. Thereafter, after forming an antireflection film on the n + layer, electrodes are formed on the light receiving surface side and the back surface side, and a passivation film is formed as necessary.
In the manufacture of solar cells, electrodes are often connected to the n + layer after the formation of an antireflection film or a passivation film, and thus it is necessary to provide openings in these inorganic thin films.

One method for providing an opening in an inorganic thin film is an etching method. As an etching method, a method using a photoresist is generally used. However, each step of resist film formation, exposure, development, etching, and resist removal is necessary, and since many materials are used, it is not efficient.
There is also a method of forming an opening with a laser. However, since the processing position control is complicated and requires processing time, productivity is not sufficient. In addition, there is a possibility that the n + layer, the wafer, and the like below are damaged by the laser.
In addition, conventionally, the most common manufacturing method is to apply a conductive paste containing a compound that constitutes glass, such as a metal serving as an electrode and silicon oxide, to cause fire through (fired penetration) by heating, and inorganic There is a method of forming an opening in a thin film and simultaneously connecting an electrode and an n + layer. However, since this method requires high-temperature treatment at 250 ° C. or higher, the n + layer and the wafer may be damaged and power generation efficiency may be reduced.
In addition, although the method of forming an inorganic thin film in the pattern form from the beginning is considered, it is not efficient because the process is complicated, and it is not sufficient in terms of the accuracy of pattern formation.

On the other hand, a method has been proposed in which an etching paste is printed to form a pattern or the like on an inorganic thin film, and then heated to form an opening below the etching paste.
As a component (etching component) for removing the inorganic thin film, for example, Patent Document 1 describes an etching medium containing phosphoric acid or phosphate. However, since the optimum etching temperature is as high as 250 ° C. or higher, the n + layer, the wafer, and the like may be damaged.

  In addition, as an etching component, at least one fluorine selected from the group consisting of ammonium, alkali metal and antimony fluorides, ammonium, alkali metal and calcium acid fluorides, alkylated ammonium, and potassium tetrafluoroborate A method using a compound and, optionally, an etching medium containing a predetermined inorganic mineral acid and organic acid is described (see Patent Document 2). However, an etching medium in which a fluorine compound and an acid are mixed has a problem of extremely high toxicity.

JP 2005-506705 gazette Special table 2008-527698

  The present inventors have found that a predetermined Lewis acid or derivative thereof is effective for removing the SiN film. An object of the present invention is to provide a method for removing a SiN film using a new etching material.

According to the present invention, the following SiN film removal method is provided.
1. An etching material containing at least one boron compound selected from a Lewis acid containing boron and a halogen bonded to the boron in the structure, a salt of the Lewis acid, and a compound that generates the Lewis acid is printed by a printing method. Applying on the silicon nitride (SiN) film;
Removing the SiN film by heating. A method for removing the SiN film.
2. 2. The method of removing an SiN film according to 1, wherein the boron compound is liquid at the heating temperature or is dissolved in a liquid substance at the heating temperature.
3. 3. The method for removing a SiN film according to 1 or 2, wherein a melting point of the boron compound is not higher than the heating temperature and is nonvolatile.
4). The removal method of the SiN film in any one of 1-3 whose said printing method is plate printing.
5. The removal method of the SiN film in any one of 1-3 whose said printing method is plateless printing.
6). The method for removing an SiN film according to any one of 1 to 3, wherein the printing method is plate printing and plateless printing.
7). The SiN film is formed on a silicon film or a silicon oxide (SiO ₂ film), or any one of 1 to 6 formed on a silicon substrate or a silicon oxide (SiO ₂ film) substrate The method for removing the SiN film described in 1.

  According to the present invention, a method of removing a SiN film using a new etching material can be provided. According to the present invention, the inorganic thin film can be removed at a lower temperature than in the prior art.

The SiN film removal method of the present invention includes the following printing process and etching process.
Printing step Etching material containing at least one boron compound selected from a Lewis acid containing boron and a halogen bonded to the boron in the structure, a salt of the Lewis acid, and a compound that generates the Lewis acid, Process for applying and etching on silicon nitride (SiN) film by printing method Process for removing SiN film by heating Hereinafter, each process will be described.

1. Printing Step In this step, an etching material is applied on the silicon nitride (SiN) film by a printing method.
The etching material contains at least one boron compound selected from a Lewis acid containing in its structure boron and a halogen bonded to the boron, a salt of the Lewis acid, and a compound that generates the Lewis acid.
The boron compound is a component that erodes and removes the inorganic thin film. This component is liquefied by heating to dissolve and remove the inorganic thin film, particularly the SiN film.

Specific examples of the boron compound include triphenylcarbenium tetrafluoroborate, N-fluoro-N′-chloromethyltriethylenediaminebis (tetrafluoroboric acid), and 1- (chloro-1-pyrrolidinyl tetrafluoroborate. Methylene) pyrrolidinium, tropylium tetrafluoroborate, di-n-butylammonium tetrafluoroborate, tetraethylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, tetramethylammonium tetrafluoroborate, trimethyloxotetrafluoroborate , Triethyloxonium tetrafluoroborate, 1,3-bis (2,4,6-trimethylphenyl) -4,5-dihydroimidazolium tetrafluoroborate, 1-butyl-3-methyli Midazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium Tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-methyl-3-octylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate Acid salt, 1,3-di-tert-butylimidazolinium tetrafluoroborate, 1-butyl-1-methylpiperidinium tetrafluoroborate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butylpyridinium tetrafluoroborate, tetrafluoroboric acid 2 4,6-trimethylpyridinium, 1-butyl-1-methylpyrrolidinium tetrafluoroborate, 1-ethyl-1-methylpyrrolidinium tetrafluoroborate, 1-ethyl-1-methylpiperidinium tetra Tetrafluoroboric acid organic base salts such as fluoroborate and tricyclopentylphosphine tetrafluoroborate,
Tetrafluoroborate halogen salts such as lithium tetrafluoroborate,
Tetrafluoroborate metal salts such as copper tetrafluoroborate and zinc tetrafluoroborate,
Potassium methyltrifluoroborate, potassium (morpholin-4-yl) methyltrifluoroborate, potassium (3,3-dimethylbutyl) trifluoroborate, potassium 4-iodophenyltrifluoroborate, 4-fluorophenyltri Potassium fluoroborate, potassium phenyltrifluoroborate, potassium pyridine-3-trifluoroborate, potassium vinyltrifluoroborate, (4-methyl-1-piperazinyl) methyltrifluoroborate, [(N-tert -Butylammonio) methyl] alkyl trifluoroborate such as trifluoroboric acid,
Boron trifluoride monoethylamine complex, boron trifluoride-acetic acid complex, boron trifluoride tetrahydrofuran complex, boron trifluoride phenol complex, boron trifluoride diethyl ether complex, boron trifluoride acetonitrile complex and boron trifluoride methanol Boron trifluoride complex compounds such as complexes,
Examples thereof include nitronium tetrafluoroborate, boron triiodide, tris (pentafluorophenyl) borane, tetrakis (pentafluorophenyl) borate ethyl ether complex, and the like.

  Among the above, triphenylcarbenium tetrafluoroborate, tropylium tetrafluoroborate, di-n-butylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, trimethyloxonium tetrafluoroborate, tetrafluoroboric acid Triethyloxonium, 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate, 1-butyl-1-methylpyrrolidinium tetrafluoroborate, potassium methyltrifluoroborate, 4-iodophenyltrifluoro Potassium borate, potassium (4-methyl-1-piperazinyl) methyltrifluoroborate, tricyclopentylphosphine tetrafluoroborate, boron trifluoride monoethylamine complex, pyridine-3-trifluoroboric acid Potassium, nitronium tetrafluoroborate, triiodide, boron, tris (pentafluorophenyl) borane, lithium tetrakis (pentafluorophenyl) ethyl ether complex borate is preferred. Further, di-n-butylammonium tetrafluoroborate, tetrabutylammonium tetrafluoroborate, and boron trifluoride monoethylamine complex are preferable, and boron trifluoride monoethylamine complex is particularly preferable.

The melting point of the boron compound is the heating temperature in the etching step, and is preferably non-volatile when liquefied. Thereby, the etching component can be liquefied independently at the removal temperature of the inorganic thin film, and deformation of the pattern due to evaporation of the etching component can be suppressed.
In the present invention, “nonvolatile” means that an etching component of 50% by mass or more can remain without volatilization during the processing time at the etching temperature, and has a boiling point of at least the etching temperature, preferably Means a case where the vapor pressure at the etching temperature is 350 Pa or less.

  The boron compound may be liquid or solid at room temperature (25 ° C.), but is preferably solid. It is preferable to adjust so that it may become liquid in the temperature of 100 to 250 degreeC which is the temperature at the time of etching. Here, the liquid state can be exemplified by the fact that the boron compound itself melts into a liquid at the above temperature, or a state in which the boron compound is dissolved in a compound that becomes liquid at the etching temperature.

The etching material preferably contains a solvent in addition to the boron compound described above. By using a solvent, the viscosity and printability of the etching material can be improved. The solvent is not particularly limited as long as the above-described boron compound can be dispersed. When the etching material of the present invention is printed using screen printing, if the viscosity changes due to volatilization of the solvent during printing, the printability changes, so the vapor pressure at 25 ° C. is 1.34 × 10. ^It is less than ³ Pa, preferably less than 1.0 × 10 ³ Pa · s.
Solvents include aliphatic hydrocarbon solvents such as nonane, decane, dodecane, and tetradecane; aromatic hydrocarbon solvents such as ethylbenzene, anisole, mesitylene, naphthalene, cyclohexylbenzene, diethylbenzene, phenylacetonitrile, phenylcyclohexane, benzonitrile, and mesitylene Solvent; ester solvent such as isobutyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, glycol sulfite, ethyl lactate, ethyl lactate; alcohol solvent such as 1-butanol, cyclohexanol, glycerin; terpineol, Terpineol C, dihydroterpineol, dihydroterpinel acetate, tersolve DTO-210, tersolve THA-90, tersolve THA-70, tersolve TOE-10 Terpene solvents such as dihydroxyterpinyloxyethanol, terpinylmethylether, dihydroterpinylmethylether, and tersolve MTPH; cyclohexanone, 2-hexanone, 2-heptanone, 2-octanone, 1,3-dioxolane-2 Ketone solvents such as -one, 1,5,5-trimethylcyclohexen-3-one; diethylene glycol ethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether , Propylene glycol monomethyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol propyl acetate Teracetate, diethylene glycol isopropyl ether acetate, diethylene glycol butyl ether acetate, diethylene glycol-t-butyl ether acetate, triethylene glycol methyl ether acetate, triethylene glycol ethyl ether acetate, triethylene glycol propyl ether acetate, triethylene glycol isopropyl ether acetate, triethylene glycol Alkylene glycol solvents such as butyl ether acetate, triethylene glycol-t-butyl ether acetate, dipropylene glycol dimethyl ether, dipropylene glycol monobutyl ether; dihexyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene Ether solvents such as benzyl ethyl ether; carbonate solvents such as propylene carbonate and ethylene carbonate; amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone, and nitrile solvents such as malononitrile Can be illustrated.
Of these, terpineol, γ-butyrolactone, N-methylpyrrolidone, glycol sulfite, and propylene carbonate are preferable.
These solvents can be used alone or in combination of two or more.

  The content of the boron compound may be appropriately adjusted in consideration of the properties of the etching material at the time of use. Although it is preferable that the content of the boron compound as an etching component is high, it is important to adjust the viscosity and paste properties in consideration of applying the composition by a printing method. The content of the boron compound is preferably 30 to 80% by mass and particularly preferably 50 to 70% by mass with respect to the entire etching material.

  The content of the solvent may be appropriately adjusted in consideration of the properties of the composition at the time of use. Usually, it is preferable that it is 15-65 mass% with respect to the whole etching material, and it is especially preferable that it is 25-50 mass%.

The boron compound as an etching component preferably has a particle size before mixing of 100 μm or less in order to improve printability.
In addition, the particle size here is a number average particle size, and is obtained as an average value of 100 randomly selected without overlapping in the SEM observation image. Specifically, a carbon adhesive tape is affixed on the SEM sample stage, and an etching component is sprinkled thereon. Of the etching components on the sample stage, those that are not adhered are blown off with an air gun. Using a vacuum sputtering apparatus (for example, ION SPUTTER, manufactured by Hitachi High-Technologies), Pt is sputtered to a thickness of 10 to 20 nm on the SEM sample stage to which the etching component is adhered to obtain a sample for SEM. The sample for SEM is observed with an SEM apparatus (for example, ESEM XL30, manufactured by Philips) at an overload voltage of 10 kV. The magnification is selected so that the average conductive particle diameter occupies about 10% of the field of view. 100 particles are randomly selected from the observed particle images that are overlapped and the outer shape cannot be confirmed, and parallel two lines selected so as to have the maximum distance among the two parallel lines circumscribing each etching component image. Measure the distance between straight lines. An average value is obtained for these 100 values and is defined as the number average particle diameter. When 100 particles cannot be selected from one field of view, measurement is performed from a plurality of fields.

The particle size (dispersed particle size) of the boron compound after dispersion is preferably 100 μm or less from the viewpoint of screen printing accuracy, and preferably 0.01 μm or more from the point of viscosity characteristics.
The dispersed particle diameter is obtained as a volume average particle diameter using a laser scattering particle size distribution analyzer. Specifically, using a laser scattering particle size distribution measurement device (for example, LS13 320, manufactured by Beckman Coulter) equipped with a universal liquid module, the main body is turned on for 30 minutes to stabilize the light source, and then the liquid module is used. Only the solvent used in the etching material is introduced from the measurement program by the Rinse command, and De-bubble, Measurement Offset, Align, and Measurement Background are performed from the measurement program. Subsequently, using the measurement program Measurement Loading, the etching material is added to the liquid module until the measurement program reaches the OK from the sample amount Low. Thereafter, Measurement is performed from the measurement program to obtain a particle size distribution. As settings of the laser scattering method particle size distribution measuring apparatus, Pump Speed: 70%, Include PIDS data: ON, and Run Length: 90 seconds are used. For the refractive index of the dispersion medium and the dispersoid, the refractive indexes of the boron compound and the solvent are used, respectively.

The etching material is preferably a non-volatile liquid at the etching temperature, and preferably contains a compound (component (A)) that dissolves the boron compound. Thereby, the choice of the compound which can be used as an etching component can be increased. Further, the etching temperature can be lowered, and the etching rate is also improved.
Examples of the component (A) include a Lewis acid containing boron and a halogen bonded to the boron in the structure, a salt of the Lewis acid, a compound that generates the Lewis acid, a super acid, or an ionic liquid.
The Lewis acid containing boron and halogen directly bonded to boron in the structure, the salt of the Lewis acid, the compound that generates the Lewis acid by heating, and the superacid are the same as the etching component described above. What is necessary is just to select what melt | dissolves an etching component from the said example.

As the ionic liquid (ionic liquid), known ones can be used, but it is preferable that the anion of the ionic liquid contains fluorine. Specifically, examples of the anion include tetrafluoroborate ion and hexafluorophosphate ion.
Examples of the cation of the ionic liquid include an imidazolium cation and a pyridinium cation.

Specific examples of the component (A) include 1,3-bis (2,4,6-trimethylphenyl) -4,5-dihydroimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoro Borate, 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-2,3-dimethylimidazolium tetrafluoroborate 1-hexyl-3-methylimidazolium tetrafluoroborate, 1-methyl-3-octylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1, 3-di-tert-butylimidazolinium tetrafluoroborate, 1-ethyl-3-methylimidazole Ium hexafluorophosphate, 1-methyl-3-imidazolium salts such as octyl imidazolium hexafluorophosphate,
1-butyl-3-methylpyridinium tetrafluoroborate, 1-butylpyridinium tetrafluoroborate, 2,4,6-trimethylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium hexafluorophosphate Pyridinium salt, etc.
Piperidinium salts such as 1-butyl-1-methylpiperidinium tetrafluoroborate, 1-ethyl-1-methylpiperidinium tetrafluoroborate, 1-butyl-1-methylpiperidinium hexafluorophosphate ,
Pyrrolidinium such as 1-butyl-1-methylpyrrolidinium tetrafluoroborate, 1-ethyl-1-methylpyrrolidinium tetrafluoroborate, 1-butyl-1-methylpyrrolidinium hexafluorophosphate Salts and the like are preferred.

  It is preferable that the content rate of a component (A) is 3.0-64.0 mass% with respect to the whole liquid composition, and 5.0-56.0 mass% is especially preferable.

  In addition to the above-mentioned components, the etching material is optionally improved as necessary to prevent thixotropic properties, a substrate wettability adjuster, a particle dispersant, a defoaming agent, a cocoon skin, etc. Additives (leveling agents), additives such as additives for promoting uniform drying, viscosity adjusting materials (fine particles, solvents, additives), doping agents, pH adjusting agents, and the like can be added.

  For example, depending on the printing method, it is preferable to impart thixotropy for fine line drawing. Examples of the method for imparting thixotropy include a method using a thixotropic agent and a method for dispersing fine particles. These methods may be used in combination.

As the thixotropic agent, ethyl cellulose, BYK-405, 410, 411, 415, 420, 425, 420, 430, 431, etc. (Bic Chemie Co., Ltd.), Disparlon thixotropic agent series (Enomoto Kasei) and the like are commercially available. Are listed. The thixotropic agent is not particularly limited as long as the solvent to be used and the desired thixotropy can be obtained.
In addition, polysiloxane, polyacryl, polyamide, polyvinyl alcohol, alkyl-modified cellulose, peptide, polypeptide, and a copolymer having two or more of these structures are also preferable.

  Examples of the fine particles include organic fine particles and inorganic fine particles such as metal oxide particles. By adding fine particles, viscosity and thixotropy can be appropriately adjusted, and printability (for example, fine line drawing property and shape retention) and etching property can be controlled. Further, when heated to the etching temperature of the inorganic thin film, the etching component becomes liquid, but the fluidity is suppressed by the particles and the shape of the printed SiN liquid composition is prevented from being deformed.

Examples of the organic fine particles include polystyrene beads, polyethylene particles, acrylic particles, polysiloxane resin particles, isoprene rubber particles, and polyamide particles.
Examples of the inorganic fine particles include metal oxide particles such as copper oxide, copper hydroxide, iron oxide, alumina, zinc oxide, lead oxide, magnesia, tin oxide, calcium carbonate, carbon, silica, mica, and smectite. .
Further, if the surface is an electrically attracting particle, a similar effect can be expected because a pseudo-aggregation is formed in the liquid composition.

The primary particle shape of the fine particles can be selected from a substantially spherical shape, a needle shape, a plate shape, a rice grain shape, and the like. In particular, for the purpose of imparting thixotropy, a needle shape, a plate shape, a rice grain shape, or a bead shape is preferable.
For dispersion of the fine particles, a dispersion aid or a dispersion stabilizer can be added as long as the target function is not impaired.
The major axis (long side) of the fine particles is preferably 10 nm to 10 μm. The major axis (long side) of the fine particles can be obtained by a method similar to the method for obtaining the particle size of the etching component from the SEM observation image.

  The content of the thixotropic agent is preferably 0.1 to 5.0% by mass with respect to the entire etching material. If it is less than 0.1% by mass, a sufficient effect for thixotropic expression may not be obtained. On the other hand, if it exceeds 5.0 mass%, the viscosity may become too high. The content of the thixotropic agent is particularly preferably 1.0 to 4.0% by mass.

An etching material can be manufactured by mixing the boron compound mentioned above, the solvent mix | blended as needed, the said additive, etc.
In order to improve the uniformity of the etching material, propeller agitation, ultrasonic dispersion device (eg, Nippon Seiki Seisakusho, Ultrasonic Homogenizer), revolving mixer (eg, Sinky, Awatake Rentaro), high-speed emulsification / dispersion It is preferable to mix using a disperser such as a machine (eg, TK homomixer series manufactured by PRIMIX Co., Ltd.), a rake machine, a three-roll mill, a bead mill, a sand mill, or a pot mill. In addition, dispersion | distribution can implement these apparatuses individually or in combination.

  When air bubbles are generated in the mixed composition after dispersion, the air bubbles in the composition can be removed by standing under reduced pressure, stirring and degassing under reduced pressure, or the like.

The etching material prepared as described above is printed on the SiN film by a printing method.
The SiN film is used as an interlayer insulating film of a semiconductor element such as a CMOS, a passivation film, an antireflection film of a solar cell, or the like. The SiN film is formed by a known method such as chemical vapor deposition (CVD). “SiN” does not mean that the stoichiometric ratio (Si: N) is 1: 1.

As the printing method, known plate printing and plateless printing can be employed.
For example, plate printing includes screen printing, flexographic printing, microcontact printing, and the like. Plateless printing includes inkjet printing, slit printing, dispenser printing, and the like.
A printing method capable of patterning without contact is preferable because damage to the substrate due to application of printing pressure can be avoided.

Since the viscosity of the etching material depends on the printing method and the printing apparatus, it is not particularly limited and can be prepared so as to be suitable for each printing method.
For example, in screen printing, the viscosity at 25 ° C. is preferably 100 mPa · s or more, and particularly preferably 1 Pa · s or more.
In inkjet printing, 3 to 20 mPa · s is generally a preferred range.

  In the printing process, a desired pattern on the SiN film is formed by using the above-described printing method.

  After printing, if necessary, the solvent of the etching material is volatilized and removed by heating or decompression. The removal of the solvent may be combined with the heating in the etching step, but is appropriately selected because each temperature condition may be different.

2. Etching Step In the etching step, the SiN film coated with the etching material in the printing step is heated at 100 to 250 ° C., more preferably 100 to 200 ° C. for 1 to 60 minutes. When the temperature exceeds 250 ° C., for example, in the case of a solar cell, the dopant doped in the n + layer or the like diffuses, and an interdiffusion layer is formed at the P-type / N-type interface, which may deteriorate the characteristics of the solar cell. is there.
The boron compound liquefied by heating etches the SiN film located under the pattern.

If there is a residue after the etching process, a cleaning process is provided to remove the residue.
Examples of the cleaning step include ultrasonic cleaning using pure water, brush cleaning, spray cleaning, running water cleaning, and the like.

The method for removing a SiN film of the present invention can be applied to a substrate having a SiN film. Examples of the substrate include glass (quartz, window glass, borosilicate glass, non-alkali glass), silicon wafer, and the like when Si is the main component. Depending on the purpose of use, it may contain impurities or may be oxidized. Moreover, the shape of the surface is not ask | required.
For example, the SiN film may be formed on a silicon film or a silicon oxide (SiO ₂ film), or may be formed on a silicon substrate or a silicon oxide (SiO ₂ film) substrate.

  The substrate obtained by removing the SiN film using the method of the present invention becomes an intermediate processed product of various semiconductor devices and solar cells. For example, in the case of a solar cell, a solar cell can be produced by forming a power supply wiring (electrode) using a metal paste or the like after removing the SiN film. The n + portion may be formed by doping an exposed silicon surface with a dopant such as phosphorus.

Example 1
(1) Preparation of Etching Material Boron trifluoride monoethylamine complex (melting point: 88 ° C.) (Wako Pure Chemical Industries, Ltd.) 25 g was ground in an automatic mortar for 9 hours and passed through a 100 μm sieve to fine powder of boron trifluoride monoethylamine complex Got.
Etching material (SiN etching paste) 6.87g fine powder of boron trifluoride monoethylamine complex, silica particles (AEROSIL R202, Nippon Aerosil) 0.13g, and terpineol isomer mixture 3.5g are mixed in an agate mortar. Got.

(2) 150 nm of SiO ₂ by PE-CVD on the etching mirror surface of the print and the SiN film of SiN etching paste, and, SiN a P-type silicon wafer was 90nm laminated (1~50Ω) (Mito Seiko Co., Ltd.) an SiN film Used as an attached silicon substrate.
A 5 cm × 5 cm square and straight lines having widths of 50 μm, 75 μm, and 100 μm were printed on the SiN film by screen printing of the SiN etching paste.
The printed silicon substrate with the SiN film was heat-treated for 30 minutes on a hot plate heated to 200 ° C., then allowed to cool and ultrasonically cleaned in ultrapure water.
In the SiN-attached silicon substrate after the etching process, the SiN film at the lower part of the printing part has been removed.

Example 2
An etching material was prepared in the same manner as in Example 1 except that 0.35 g of long-grained (particle diameter 200 nm, aspect ratio 3) copper oxide nanoparticles (in-house synthesized product) was used instead of silica particles, and printing and etching were performed. did.
As a result, in the silicon substrate with SiN after the etching process, the SiN film at the bottom of the printing part was removed.

Experimental Example A small amount of the boron fluoride reagent shown in Table 1 was placed on the same SiN film as in Example 1 and heated on a hot plate at 200 ° C. for 30 minutes. Table 1 shows the state of heating (200 ° C.) and the etching results of the SiN film.

  The method for removing a SiN film of the present invention can be used in manufacturing processes of various semiconductor elements and solar cells.

Claims (7)

An etching material containing at least one boron compound selected from a Lewis acid containing boron and a halogen bonded to the boron in the structure, a salt of the Lewis acid, and a compound that generates the Lewis acid is printed by a printing method. Applying on the silicon nitride (SiN) film;
Removing the SiN film by heating. A method for removing the SiN film.   The method for removing a SiN film according to claim 1, wherein the boron compound is liquid at the heating temperature or is dissolved in a liquid substance at the heating temperature.   The method for removing a SiN film according to claim 1, wherein a melting point of the boron compound is not higher than the heating temperature and is non-volatile.   The method for removing a SiN film according to claim 1, wherein the printing method is plate printing.   The method for removing a SiN film according to claim 1, wherein the printing method is plateless printing.   The method for removing a SiN film according to any one of claims 1 to 3, wherein the printing methods are plate printing and plateless printing. The SiN film is formed on a silicon film or a silicon oxide (SiO ₂ film), or is formed on a silicon substrate or a silicon oxide (SiO ₂ film) substrate. The method for removing an SiN film according to any one of the above.