TWI683361B - Method for etching semiconductor substrate and method for fabricating semiconductor device - Google Patents

Abstract

A method for etching a semiconductor substrate is provided. After applying an etching liquid including a phosphate compound, a silicon-containing compound, and water to a substrate exposing a SiN film and a SiO₂ film and optionally removing the SiN film such that the etching liquid boils, the etching liquid is discharged to contact the substrate.

Description

Method for etching semiconductor substrate and method for manufacturing semiconductor element

The invention relates to a method for etching a semiconductor substrate and a method for manufacturing a semiconductor element.

A silicon nitride film (SiN) can be used as a mask material for forming a known selective oxide film of silicon (Si) in a local oxidation of silicon (LOCOS) structure. A silicon nitride film (SiN) is an isolation structure formed by a selective oxidation method, and is widely used as a manufacturing technology of a metal oxide semiconductor (MOS) type capacitor. Specifically, in this technique, first, a thermal oxide film is formed on a silicon substrate. Then, a silicon nitride film is formed by chemical vapor deposition (CVD) in such a manner as to cover the above thermal oxide film. In this state, the silicon nitride film is patterned, and the silicon oxide film exposed therein is further subjected to heat treatment to selectively oxidize the region. Then, the silicon nitride film used for patterning is removed. In this way, the LOCOS structure which is the basis of the MOS type capacitor and has a difference in the thickness of the silicon oxide film can be obtained.

Recently, Shallow Trench Isolation (STI) technology has been further developed, in which a silicon nitride film is also used. In this technique, a silicon oxide film is also formed on the upper surface of a silicon substrate, and a silicon nitride film is provided by CVD in such a manner as to cover it. Then, a photoresist film is applied, patterned, and etched in the order of SiN, SiO ₂ , and Si to form trenches. Then, silicon oxide is buried in the trench. At this time, since a silicon oxide film (SiO ₂ ) is also formed outside the trench, it is removed by polishing by chemical mechanical polishing (CMP). In this CMP step, a chemical solution that does not invade SiN in the slurry is used, the silicon nitride film (SiN) functions as a stopper, and the remaining silicon oxide is removed. Finally, the silicon nitride film is removed by wet etching to obtain the desired isolation structure.

As described above, in recent semiconductor manufacturing, the silicon nitride film can be used as an indispensable mask material. On the other hand, the material is not assembled into the component, and after certain processing, it needs to be removed exactly. In particular, it is desirable to selectively remove only the silicon nitride film without damage to the silicon oxide film remaining inside the substrate.

In view of the above requirements, as a chemical solution (etching solution) for selectively removing a silicon nitride film (SiN), for example, an etching solution containing phosphoric acid and hexafluorosilicic acid is proposed (see Patent Document 1 and Patent Document 2). It is also proposed to increase the selectivity by heating the etching solution containing the above components to 150°C to 180°C.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2007-258405

[Patent Document 2] Japanese Patent Laid-Open No. 2007-318057

[Patent Document 3] Japanese Patent Laid-Open No. 2000-133631

According to the chemical solutions of the formulations shown in Patent Documents 1 to 3, the silicon nitride film (SiN) can be selectively etched with respect to the silicon oxide film (SiO ₂ ). In addition, as proposed in Patent Document 3, increasing the temperature of the chemical solution can have an effect in improving its selectivity. However, according to confirmation by the present inventors, if the chemical solution of the above formula is simply heated and applied, once the dissolved silicon oxide precipitates, a film is formed on the silicon oxide film (see FIG. 3 ).

Therefore, an object of the present invention is to provide an etching method for a semiconductor substrate that exhibits a good etching selectivity to a silicon nitride film relative to a silicon oxide film, and can suppress or prevent the precipitation of silicon oxide on the silicon oxide film and A method of manufacturing a semiconductor element using the same.

Based on the above-mentioned problems, the inventors of the present invention have analyzed in detail the operation of applying a specific formulation of a chemical solution that selectively removes a silicon nitride film relative to a silicon oxide film. By analyzing it under various conditions or formulations, the results show that if the chemical solution is not simply heated and applied, but once the chemical solution is boiled and applied, the selective etching performance of the silicon nitride film is maintained and suppressed Precipitation of silicon oxide on the silicon oxide film. In this way, it can be seen that when applied to the substrate at a specific temperature below the boiling point, there will be significant differences. Although the substrate is processed at the same temperature, the chemical solution after only one boiling state will still exert the above-mentioned silicon oxide. Precipitation prevention effect. The present invention is based on the above findings and has the following methods.

[1] A method of etching a semiconductor substrate, which prepares an etching solution containing a phosphoric acid compound, a compound containing silicon and water, and applying the etching solution to a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) exposed When the silicon nitride film is selectively removed on the substrate, after the etchant is boiled, the etchant is ejected to contact the substrate.

[2] The etching method as described in [1] above, wherein the etching solution is cooled before and after it is ejected.

[3] The etching method according to [1] or [2] above, wherein the contact temperature of the etching solution with the substrate is lower than the boiling temperature by a range of more than 0°C and 20°C or less.

[4] The etching method according to any one of the above [1] to [3], wherein the etching solution is ejected from the nozzle, dripped or flowed down to come into contact with the substrate.

[5] The etching method according to any one of [1] to [4] above, wherein the etching solution is ejected at a rate of 0.5 L/min to 3 L/min.

[6] The etching method according to any one of [1] to [5] above, wherein the boiling point of the etching solution is 110°C to 180°C.

[7] The etching method according to any one of the above [1] to [6], wherein the etching liquid is boiled in a tank holding the etching liquid before it is ejected, and then transferred to the nozzle via the flow path and from the nozzle The etching liquid is sprayed onto the substrate.

[8] The etching method according to any one of [1] to [7] above, wherein the silicon-containing compound is H ₂ SiF ₆ , (NH ₄ ) ₂ SiF ₆ , or Na ₂ SiF ₆ .

[9] The etching method according to any one of [1] to [7] above, wherein the silicon-containing compound is a compound represented by the following formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃

Formula (2): Si(OR ⁴ ) ₄

(R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ represents an alkyl group having 1 to 20 carbon atoms).

[10] The etching method according to any one of [1] to [9] above, wherein the boiling time of the etching solution is 5 minutes or more and 24 hours or less.

[11] The etching method according to any one of [1] to [10] above, wherein the etching solution contains 0.01 to 1% by mass of a silicon-containing compound.

[12] The etching method according to any one of [1] to [11] above, wherein the etching solution contains 60 to 95% by mass of a phosphoric acid compound.

[13] The etching method according to any one of [1] to [12] above, wherein the pH of the etching solution is -2 or more and 2 or less.

[14] The etching method according to any one of the above [1] to [13], wherein the ratio of the etching rate of the silicon nitride film [R1] to the etching rate of the silicon oxide film [R2] ([R1 ]/[R2]) is 50 or more.

[15] The etching method according to any one of [1] to [14] above, wherein the phosphoric acid compound is at least one selected from the group consisting of orthophosphoric acid, metaphosphoric acid, and pyrophosphoric acid.

[16] A method of manufacturing a semiconductor element, in which the silicon nitride film is removed by the etching method described in any one of the above [1] to [15], and the semiconductor element is manufactured from the remaining substrate.

[17] An etching solution for a semiconductor substrate, which is applied to a substrate where a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) are exposed to selectively remove the silicon nitride film, and contains a phosphoric acid compound and contains silicon The compound and water are subjected to boiling treatment by heating.

[18] The etching solution according to [17] above, wherein the silicon-containing compound is a compound represented by the following formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃

Formula (2): Si(OR ⁴ ) ₄

(R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ represents an alkyl group having 1 to 20 carbon atoms).

[19] The etching liquid according to the above [17] or [18], wherein the etching liquid contains 0.01 to 1% by mass of a silicon-containing compound.

[20] The etching solution according to [17] or [18] above, wherein the etching solution contains 60 to 95% by mass of a phosphoric acid compound.

According to the method of the present invention, it can exert a good etching selectivity to the silicon nitride film relative to the silicon oxide film, effectively remove the silicon nitride film, and can suppress or prevent the silicon oxide on the silicon oxide film Precipitate. Moreover, according to the method of the present invention, it is not necessary to maintain the boiling state for etching, but the etching solution can be applied to the substrate at a lower temperature, so it is particularly suitable for the application of the chemical solution by spraying the chemical solution on the substrate. The processing of the chip device can contribute to the improvement of manufacturing efficiency, manufacturing adaptability, and manufacturing quality.

The above-mentioned and other features and advantages of the present invention should be made clear by referring to the accompanying drawings as appropriate based on the following description.

1‧‧‧SiN layer (layer 1)

2‧‧‧SiO ₂ layer (layer 2)

3‧‧‧Si layer (layer 3)

5‧‧‧SiO ₂ precipitation layer

10, 20, 30 ‧‧‧ semiconductor substrate

11‧‧‧polysilicon layer

12‧‧‧Silicon oxide film

13‧‧‧ Silicon nitride film

14‧‧‧ Wafer

15‧‧‧fine groove part

21‧‧‧Reaction vessel

22‧‧‧rotating table

23‧‧‧Spray outlet

25‧‧‧Boiler

25a‧‧‧slot exit

100‧‧‧ substrate

200‧‧‧Semiconductor substrate products

A‧‧‧Introduction Department

fc, fd‧‧‧stream

M‧‧‧rotation drive

r‧‧‧Direction

S‧‧‧Semiconductor substrate

t‧‧‧Movement trajectory

1 is a cross-sectional view schematically showing an example (before etching) of a manufacturing process of a semiconductor substrate according to an embodiment of the present invention.

2 is a cross-sectional view schematically showing an example (after etching) of a manufacturing process of a semiconductor substrate according to an embodiment of the present invention.

3 is a cross-sectional view schematically showing an example (after etching) of a manufacturing process of a semiconductor substrate according to an embodiment for comparison.

FIG. 4 is a plan view schematically showing an example of a manufacturing process (before and after etching) of a semiconductor substrate according to another embodiment of the present invention.

5 is a device configuration diagram showing a part of a wet etching device according to a preferred embodiment of the present invention.

6 is a plan view schematically showing a movement locus of a nozzle relative to a semiconductor substrate according to an embodiment of the present invention.

First, a preferred embodiment of the etching step of the etching method of the present invention will be described based on FIGS. 1 and 2.

[Etching step]

FIG. 1 shows a diagram of a semiconductor substrate before etching. In the manufacturing example of this embodiment, a silicon layer (Si layer 3) as a specific third layer and a silicon oxide film (SiO ₂ layer 2) as a second layer are arranged in a silicon wafer, and the upper side The silicon nitride film (SiN layer 1) to be the first layer is formed. The etching solution (not shown) of this embodiment is applied to the substrate 10 in this state to remove the SiN layer 1. As a result, as shown in FIG. 2, the substrate 20 with the SiN layer 1 removed can be obtained. Needless to say, in the present invention or its preferred embodiment, etching as shown in the figure is ideal, but the residual of the SiN layer or a little corrosion of the SiO ₂ layer is appropriately allowed according to the required quality of the semiconductor device manufactured, etc. The present invention is not limitedly interpreted by this description.

On the other hand, FIG. 3 is a step explanatory diagram showing an embodiment of a comparative example that does not use the etching method of the present invention. In this comparative example, for example, a form in which a chemical solution that has not been subjected to boiling treatment is directly applied to etching can be cited. The effect of the present invention cannot be obtained by such a chemical solution, and a precipitation film 5 of silicon oxide (SiO ₂ ) is formed as shown in the figure.

In addition, when referred to as a silicon substrate or a semiconductor substrate, or simply as a substrate, it is used not only in the meaning of a silicon wafer, but also in a meaning including a substrate structure to which a circuit structure is implemented. The term “substrate member” refers to a member that constitutes the silicon substrate as defined above, and may include one kind of material or plural kinds of materials. The processed semiconductor substrate is sometimes referred to as a semiconductor substrate product. The wafers and processed products taken out by further processing and cutting as necessary are called semiconductor elements or semiconductor devices. As far as the direction of the substrate is concerned, as long as there is no special explanation, as far as FIG. 1 is concerned, the side opposite to the silicon wafer (SiN side) is called "upper" or "top", and the side of the silicon wafer (Si side) is called "lower" "Or "bottom".

[Etching solution]

Next, a preferred embodiment of the etching solution of the present invention will be described. The etching solution of this embodiment contains a phosphoric acid compound and a silicon-containing compound. In the following, each is included, and each component will be described.

(Phosphoric acid compound)

The etching solution of the present invention contains phosphoric acid as an essential component, and the phosphoric acid used is preferably at least one selected from the group consisting of polyphosphoric acid such as orthophosphoric acid, metaphosphoric acid, and pyrophosphoric acid.

The phosphoric acid compound preferably contains 60% by mass or more, more preferably 65% by mass or more, and particularly preferably contains 70% by mass or more with respect to the total mass of the etching solution of this embodiment. The upper limit of the content of the phosphoric acid compound is preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 85% by mass or less. By setting the content of the phosphoric acid compound to be equal to or less than the above upper limit value, excessive etching of the second layer can be further suppressed, which is preferable. From the viewpoint of etching the first layer at a sufficient rate, the content of the phosphoric acid compound is preferably equal to or greater than the above lower limit. In addition, by adjusting the amount to a preferable range, the safety of the chemical solution, the viscosity adjustment, and the improvement of the etching selectivity of the first layer can be more effectively achieved, which is preferable.

These phosphoric acid compounds may be used alone or in combination of two or more.

(Compound containing silicon)

(Hexafluorosilicic acid compound)

The silicon-containing compound is preferably a compound represented by H ₂ SiF ₆ , and examples of its salts include ammonium salts ((NH ₄ ) ₂ SiF ₆ ), sodium salts (Na ₂ SiF ₆ ), and potassium salts (K ₂ SiF ₆ ) Alkali metal salts, etc. In this specification, as a general term for hexafluorosilicic acid or its salts, it is referred to as a hexafluorosilicic acid compound.

(Alkoxysilane compound)

As another embodiment, the silicon-containing compound is preferably an alkoxysilane compound. The alkoxysilane compound is a general term for a compound in which an alkoxy group is substituted on silicon, and may further have an alkyl group or an aryl group. Among them, the alkyltrialkoxysilane represented by the following formula (1) is preferable.

Formula (1): R ² Si(OR ³ ) ₃

. R ²

R ² represents an alkyl group having 1 to 12 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms). Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, etc. are mentioned. Among them, methyl or ethyl is preferred, and methyl is particularly preferred.

. R ³

R ³ represents an alkyl group having 1 to 24 carbon atoms. Among them, a linear or branched alkyl group having 1 to 20 carbon atoms is preferred. Among them, the carbon number is preferably 1 to 10, and more preferably the carbon number is 1 to 4. Especially R ³ is ethyl, preferably ethoxy.

Examples of the alkyltrialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane. , Propyl trimethoxy silane, propyl triethoxy silane, etc.

The silicon-containing compound is also preferably tetraalkoxysilane. Among them, preferably Those shown in the following formula (2).

Formula (2): Si(OR ⁴ ) ₄

. R ⁴

R ⁴ is an alkyl group having 1 to 20 carbon atoms. Among them, the carbon number is preferably 1 to 10, and more preferably the carbon number is 1 to 4. In particular, R ⁴ is ethyl, preferably ethoxy.

Examples of tetraalkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, and tetraisobutoxysilane. Based silane, tetra-third butoxysilane, etc. Among them, tetramethoxysilane and tetraethoxysilane are preferably used.

The silicon-containing compound preferably contains 0.01% by mass or more, more preferably contains 0.02% by mass or more, and particularly preferably contains 0.05% by mass or more with respect to the total mass of the etching solution of this embodiment. The upper limit of the content of the silicon-containing compound is preferably 1% by mass or less, more preferably 0.5% by mass or less, particularly preferably 0.3% by mass or less, and particularly preferably 0.15% by mass or less. By setting the silicon-containing compound within the above range, the etching property of the first layer can be sufficiently ensured, and the etching selectivity of the first layer and the second layer can be improved, while effectively suppressing and preventing the precipitation of silicon oxide. Therefore it is better. Among them, in the silicon-containing compound containing fluorine atoms, by setting the content of the silicon-containing compound to the upper limit value or less, the effect of preventing SiO ₂ precipitation and the effect of preventing damage of the second layer become more remarkable.

The above silicon-containing compounds may be used alone or in combination of two or more. use.

In addition, in this specification, the expression of a compound (for example, when it is attached to the end and is called a compound) is used in the meaning of including its salt and its ion in addition to the compound itself. In addition, it is meant to include derivatives that change a part of the introduced substituents and the like within the range where the desired effect is exerted.

In this specification, the substitution of unsubstituted or unsubstituted substituents (the same is true for the linking group) means that the group may have any substituents. This is also synonymous for compounds that do not clearly remember substituted or unsubstituted. As a preferable substituent, the following substituent T may be mentioned.

Examples of the substituent T include the following.

It is an alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, such as methyl, ethyl, isopropyl, third butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2 -Ethoxyethyl, 1-carboxymethyl, etc.), alkenyl (preferably C2-20 alkenyl, such as vinyl, allyl, oleyl, etc.), alkynyl (preferably It is an alkynyl group having 2 to 20 carbon atoms, such as ethynyl, butadiynyl, phenylethynyl, etc.), a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, such as cyclopropyl group, Cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), aryl (preferably aryl having 6 to 26 carbon atoms, such as phenyl, 1-naphthyl, 4-methoxyphenyl, 2 -Chlorophenyl, 3-methylphenyl, etc.), heterocyclic group (preferably a heterocyclic group having 2 to 20 carbon atoms, preferably 5 members having at least one oxygen atom, sulfur atom, nitrogen atom Heterocyclic group of ring or 6-membered ring, such as 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, etc.), alkoxy ( It is preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyl Oxy, benzyloxy, etc.), aryloxy (preferably C6-26 aryloxy, such as phenoxy, 1-naphthoxy, 3-methylphenoxy, 4-methoxy Phenoxy groups, etc.), alkoxycarbonyl groups (preferably alkoxycarbonyl groups having 2 to 20 carbon atoms, such as ethoxycarbonyl group, 2-ethylhexyloxycarbonyl group, etc.), amine groups (preferably Amine groups with 0 to 20 carbon atoms, including alkylamine groups and arylamine groups, such as amine groups, N,N-dimethylamine groups, N,N-diethylamine groups, and N-ethylamine Groups, anilino groups, etc.), sulfamoyl groups (preferably sulfamoyl groups having 0 to 20 carbon atoms, such as N,N-dimethylaminosulfamoyl group, N-phenylaminosulfamoyl group, etc.) , Acyl (preferably C 1-20 acyl, such as acetyl, propyl acyl, butyl acyl, benzoyl, etc.), acyloxy (preferably C 1-20 acyl Oxygen groups, such as acetoxy, benzoyloxy, etc.), carbamoyl groups (preferably carbamoyl groups having 1 to 20 carbon atoms, such as N,N-dimethylaminomethyl amide, N-phenylamine carboxamido, etc.), carboxamido (preferably C1-20 acylamino, such as acetamido, benzylamino, etc.), sulfonamide (preferably Aminosulfonyl having 0 to 20 carbon atoms, for example, mesylate, besylate, N-methyl mesylate, N-ethylbenzenesulfonamide, etc.), alkylthio (preferably It is an alkylthio group having 1 to 20 carbon atoms, such as methylthio, ethylthio, isopropylthio, benzylthio, etc.), an arylthio group (preferably an arylthio group having 6 to 26 carbon atoms, For example, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc.), alkylsulfonyl or arylsulfonyl (preferably carbon number 1~ 20 alkylsulfonyl or arylsulfonyl, such as methylsulfonyl, ethylsulfonyl, benzenesulfonyl, etc.), hydroxyl, cyano, halogen atom (such as fluorine atom, chlorine atom, bromine Atom, iodine atom, etc.), more preferably alkyl, alkenyl, aryl, heterocyclyl, alkoxy, aryloxy, alkoxycarbonyl, amine, amide, hydroxyl or halogen atom, particularly preferred Is alkyl, alkenyl, heterocyclic, Alkoxy, alkoxycarbonyl, amine, amide or hydroxy.

In addition, the substituent T may be further substituted on each of the groups listed in these substituents T.

When the compound, substituent-linking group, etc. include alkyl-alkylene group, alkenyl-alkenyl group, etc., these may be cyclic or chain-like, and may also be linear or branched, as described above It can be substituted or unsubstituted. In addition, when an aryl group, a heterocyclic group, or the like is included, these may be a single ring or a condensed ring, and may be substituted or unsubstituted.

In this specification, starting from the choice of the substituent or the linking group of the compound, each technical item such as temperature and thickness may be combined with each other even if the lists are described separately.

(Aqueous medium)

In the etching solution of the present invention, water (aqueous medium) is preferably used as the medium, and preferably an aqueous solution in which each contained component is uniformly dissolved. The content of water is preferably set in an amount minus the amounts of the phosphoric acid compound and the silicon-containing compound, and any additives as needed. Specifically, it is preferably 1% by mass to 60% by mass, and preferably 5% by mass to 50% by mass relative to the total mass of the etching solution. The water (aqueous medium) may be an aqueous medium containing a dissolved component within a range that does not impair the effects of the present invention, or may contain an inevitable trace of a mixed component. Among them, the purified water such as distilled water, ion-exchanged water, or ultrapure water is preferably used, and ultrapure water used in semiconductor manufacturing is particularly preferably used.

(pH value)

In the present invention, it is preferable to adjust the pH of the etching solution to -2 or more. On the upper limit of the pH value, the pH value is preferably 2 or less, more preferably 1.5 or less, and particularly preferably 1 or less. By setting the pH to the above lower limit or more, not only can the SiN etching rate be brought to a practical level, but also the in-plane uniformity can be further improved, which is preferable from this viewpoint. On the other hand, it is preferable to set the pH value to the above upper limit or lower to prevent damage to SiO ₂ . In addition, in this specification, the pH value is the value measured by F-51 (trade name) manufactured by HORIBA at room temperature (25°C).

(Other ingredients)

. pH adjuster

In the present embodiment, it is preferable to set the pH of the etching solution to the above range, and use a pH adjuster for the adjustment. As a pH adjusting agent, in order to raise the pH, it is preferable to use: quaternary ammonium salts such as tetramethylammonium and choline, alkali metal hydroxide salts such as potassium hydroxide, or alkaline earth metal hydroxide salts such as calcium hydroxide , 2-aminoethanol, guanidine and other amine compounds. In order to lower the pH, mineral acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethyl Butyric acid, 2-ethylbutyric acid, 4-methylvaleric acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid Organic acids such as acids, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, lactic acid, etc.

The amount of pH adjuster used is not particularly limited, in order to adjust the pH to As long as the required range is used, the range can be used.

The pH adjuster may be used alone or in combination of two or more.

(container)

The etching solution of the present invention can be filled in any container for storage, transportation, and use as long as it is not a problem with corrosiveness or not (regardless of whether it is a set). In addition, for the purpose of use of semiconductors, those with high cleanliness of the container and low elution of impurities are preferred. Examples of usable containers include "Clean Bottle" series manufactured by AICELLO CHEMICAL Co., Ltd., and "Pure Bottle" manufactured by KODAMA PLASTICS Co., Ltd., but are not limited thereto. For these.

[Etching]

In the present invention, the etching liquid is ejected and brought into contact with the semiconductor substrate. In this embodiment, as described using FIG. 5, the etching liquid is ejected from the ejection port 23 and applied to the upper surface of the semiconductor substrate S in the reaction container 21. In the embodiment shown in FIG. 5, the etching liquid is supplied from the introduction part A, and then transferred to the discharge port 23 through the boiling tank 25 via the flow path fc. In the boiling tank, the etching solution can be kept for a certain period of time, and the boiling state can be maintained therein. The flow path fd represents a return path for reusing the chemical solution. Preferably, the semiconductor substrate S is located on the turntable 22, and rotates together with the turntable by the rotation driving part M.

In the embodiment of the present invention, etching is preferably performed by a piece-by-piece device. In the piece-by-piece etching, the semiconductor substrate is transported or rotated in a specific direction, and an etching liquid is sprayed or flowed out of its space to connect the etching liquid to the semiconductor substrate touch. In addition, in the chip-by-chip device, the etching liquid is ejected from the nozzle and applied to the substrate. The "ejection" means that the etching liquid is dripped or flowed down without pressurization in addition to the form of ejecting the etching liquid by pressure. form.

It is difficult to control the in-plane uniformity of the wafer when processing by the dipping type (batch type) device relative to the above-mentioned piece-by-piece type device, and the adhered matter attached to the wafer is easily re-attached to another in the solution Of wafers. Furthermore, regarding the temperature management, if the boiling temperature is maintained, the deterioration of the chemical solution is significant. If the temperature is lowered to a specific temperature, a roundabout step management is necessary. In this respect, it is preferably processed by a piece-by-piece device.

In the present invention, the etching liquid is applied to the substrate after boiling at least once. Thereby, the effective etching property of SiN can be maintained, and on the other hand, the precipitation of SiO ₂ can be effectively suppressed. The reason for this is not clear, but it is speculated that by bringing the temperature of the etching solution to the boiling point, a certain change is given to the contained components until the performance of the above-mentioned chemical solution is exhibited. The boiling temperature (Tbp) varies depending on the composition of the chemical solution, and for example, it is preferably 100°C or higher, and more preferably 110°C or higher. The upper limit of the boiling temperature is preferably 180°C or lower, more preferably 170°C or lower, particularly preferably 160°C or lower, and particularly preferably 150°C or lower.

The boiling treatment time (time to maintain the boiling temperature after boiling) is not particularly limited, but is preferably 5 minutes or more, and more preferably 10 minutes or more. The upper limit of the boiling treatment time is preferably 24 hours or less, and more preferably 12 hours or less. In order to suppress the deactivation of the etching solution more preferably, the boiling time is preferably 120 minutes or less, and more preferably 60 minutes or less. Such boiling time control can be performed, for example, by temporarily storing the etching solution in the boiling tank (reservoir) 25 shown in FIG. 5 and adding Proceed hot. Then, the etching liquid can be transferred to the nozzle 23 and applied to the substrate S. In addition, this boiling treatment time means that it can be ensured continuously or intermittently, and it can be performed while increasing the temperature, etc., and its setting can be changed as appropriate within the scope of exerting the effects of the present invention.

Regarding the temperature at which the etching is performed (application temperature (Tap) on the substrate), in the temperature measurement method shown in the examples described later, it is preferably 80°C or higher, more preferably 100°C or higher, and particularly preferably 110°C or higher . The upper limit of the etching temperature is preferably 170°C or lower, and more preferably 150°C or lower. By setting the etching temperature to be equal to or higher than the above lower limit, a sufficient etching rate for the SiN layer can be ensured, and the precipitation of SiO ₂ can be effectively suppressed, which is preferable. By setting the etching temperature to be equal to or lower than the above upper limit value, the stability of the etching treatment rate over time can be maintained, which is preferable.

In the present invention, the boiled etching solution can be directly applied to the substrate in a boiling state, and even if it is applied at a temperature lower than its boiling point (Tbp), the desired effect can be obtained. Regarding the difference between the boiling point (Tbp) and the substrate application temperature (Tap) (ΔT=Tbp-Tap), considering the ejection application by the piece-by-piece device, it is preferably more than 0°C, and more preferably 5°C or more. As the upper limit of the temperature difference, considering the etching efficiency, it is preferably 20° C. or lower, and more preferably 10° C. or lower. In addition, when the treatment is performed at the boiling point, the boiling point of the chemical liquid becomes the same value as the boiling treatment temperature described later, but when the treatment is performed at a temperature lower than the boiling point, the boiling treatment temperature includes a temperature lower than that.

Here, if the form of cooling of the etching liquid is described, in this embodiment, it is performed before and after the etching liquid is discharged. That is, while being transferred from the slot outlet 25a to the nozzle discharge port 23, it further reaches from the discharge port 23 to the base of the discharge During the period up to the plate S (refer to the flight time to be described later), the etching solution was cooled. By optimizing the transfer time, the cooling temperature can be controlled. In addition, as a mechanism that can adjust the temperature of the turntable 22, as described above, the cooled etching solution can stably act on the material to be etched on the substrate at a desired application temperature (Tap). Furthermore, if necessary, the temperature can be adjusted by applying a heating mechanism to the flow path from the above-mentioned groove outlet 25a to the nozzle ejection outlet 23, and the circulating etching liquid can be maintained at a specific temperature or the like.

The supply rate of the etching solution is not particularly limited, but it is preferably 0.3 L (liter)/minute to 4 L (liter)/minute, and more preferably 0.5 L/minute to 3 L/minute. By setting the supply rate to be equal to or higher than the above lower limit value, the uniformity of the etched surface can be more satisfactorily obtained, which is preferable. By setting the supply speed to be equal to or lower than the above upper limit value, stable processing performance can be ensured during continuous processing, which is preferable. When rotating the semiconductor substrate, the rotation speed also depends on the size and the like. From the same viewpoint as above, it is preferable to rotate at 300 rpm to 1000 rpm.

The time until the nozzle comes into contact with the substrate can be calculated based on the flow velocity and the distance between the substrate and the nozzle. In the present invention, it is preferable to set the flight time (which may be droplets or liquid flow) from the nozzle to the contact with the substrate to more than 0 seconds, preferably 1 millisecond or more. The upper limit of time is preferably 2 seconds or less, and preferably 1 second or less. The distance between the nozzle and the substrate is not particularly limited, but is usually in the range of 5 mm to 50 mm.

In the piece-by-piece etching according to the preferred embodiment of the present invention, it is preferable that the semiconductor substrate is transported or rotated in a specific direction, and the etching solution is sprayed in The etchant is in contact with the semiconductor substrate. The supply speed of the etching solution or the rotation speed of the substrate is the same as described above.

In the structure of the piece-by-piece type apparatus according to a preferred embodiment of the present invention, as shown in FIG. 6, it is preferable to supply the etching solution while moving the ejection port (nozzle). Specifically, in this embodiment, when an etching solution is applied to the semiconductor substrate S having a SiN layer, the substrate is rotated in the r direction. On the other hand, the ejection port moves along a movement locus t extending from the center to the end of the semiconductor substrate. In this way, in the present embodiment, the rotation direction of the substrate and the movement direction of the ejection port are set to different directions, thereby moving the two relative to each other. As a result, there is a configuration in which the etching solution can be supplied to the entire surface of the semiconductor substrate without omission, and the uniformity of etching is preferably ensured.

The moving speed of the ejection port (nozzle) is not particularly limited, but is preferably 0.1 cm/s or more, and more preferably 1 cm/s or more. On the other hand, the upper limit of the moving speed is preferably 30 cm/s or less, and more preferably 15 cm/s or less. The moving trajectory may be a straight line or a curved line (for example, a circular arc shape). In either case, the moving speed can be calculated based on the actual trajectory distance and the time it takes to move.

[Workpiece]

The material etched by applying the etchant of this embodiment may be any material, but a substrate having a first layer containing SiN and a second layer containing SiO ₂ is used. The formation of the SiN layer can be performed by CVD. The specific composition of the SiN layer is Si ₃ N ₄ , but the present invention is not limited to this. In addition, when it is described as SiN, it means that SixNy is broadly included (x and y are arbitrary). This is common in this specification, and it is the same for other metal compounds. The first layer contains SiN as its main component, but it may also contain other components within the scope of exerting the effects of the present invention. This is the same for other layers such as the second layer. In addition, the SiO ₂ layer may be prepared according to the usual practice. For example, it can be suitably produced by a method called Chemical Vapor Deposition (CVD) or Atomic Layer Deposition (ALD).

The silicon oxide film (SiO ₂ layer) is preferably a film obtained by heating and oxidizing the silicon film (Si layer).

The first layer is preferably etched at a high etching rate. The thickness of the first layer is not particularly limited, and when considering the structure of a general device, it is actually about 0.005 μm to 0.3 μm. The etching rate [R1] of the first layer is not particularly limited, and considering production efficiency, it is preferably 30Å/min or more, more preferably 50Å/min or more, and particularly preferably 70Å/min or more. The upper limit of the etch rate [R1] of the first layer is not special, but it is actually 500Å/min or less

The thickness of the second layer is not particularly limited, and when considering the structure of a general device, it is actually about 0.005 μm to 0.3 μm. The etching rate [R2] of the second layer (SiO ₂ layer) is not particularly limited, and it is preferably not removed as much as possible, preferably 10Å/min or less, more preferably 5Å/min or less, and particularly preferably 1Å/min or less . The lower limit of the etching rate [R2] is not special, and is actually 0.001Å/min or more.

The ratio of the etching rate [R1] of the silicon nitride film to the etching rate [R2] of the silicon oxide film ([R1]/[R2]) is preferably 50 or more, and more preferably 100 or more. Moreover, when it is set to a high etching rate, it is preferably 200 or more, more preferably 300 or more on. The upper limit of the speed ratio is not special, and is actually less than 100,000. If the more practical side of the applied material is considered, it may be 10,000 or less, 5,000 or less, or 1,000 or less.

[Manufacture of semiconductor substrate products]

In this embodiment, it is preferable to manufacture a semiconductor substrate product having a desired structure through the following steps: making a semiconductor substrate on which a first layer and a second layer are formed on a silicon wafer; applying to the semiconductor substrate The etchant selectively removes the first layer. At this time, the etching uses the above-mentioned specific etching solution.

In addition, in this specification, each step of etching and a method of manufacturing a semiconductor substrate are allowed to be applied by appropriately changing the order of steps within the scope of exerting the effects of the present invention. In this specification, when it is called "preparation", it means that in addition to preparations such as synthesizing or blending specific materials, it also includes supplying specific persons through purchase or the like. In addition, the case of using the etching solution of each material of the semiconductor substrate to be etched is referred to as "application", but this embodiment is not particularly limited. For example, it broadly includes contacting the etching solution with the substrate. Specifically, it can be etched by a batch type immersion and etched by a piecewise type spray.

FIG. 4 is a plan view schematically showing the steps of a Terabit Cell Array Transistor (TCAT) of a NAND flash memory. The silicon nitride film has been used in the manufacturing of MOS as described above, but it has also recently been effectively used in the manufacturing process of flash memory and the like. In the manufacturing process of this embodiment, the silicon oxide film 12 and the silicon nitride film 13 are arranged on the left and right sides of the wafer 14 on the upper side. Moreover, the left and right silicon oxide films 12 and silicon nitride films 13 are respectively The polysilicon layer 11 serving as an electrode is arranged on both sides, and on the other hand, the two types of layers are alternately arranged in the front-rear direction. One pattern (line width) is formed at the nanometer level. The above etching solution is applied to the substrate 100 having such a fine pattern. Then, only the silicon nitride film is preferably removed to form the semiconductor substrate product 200 with the remaining silicon oxide film 12 and the polysilicon layer 11. By using a large number of fine grooves 15 formed on the substrate, a trap layer, a barrier layer, and a metal gate are respectively arranged thereon, and a high-performance and large-capacity flash memory can be formed. According to the etching method of the present invention, the selective removal of the silicon nitride film in an element having such a fine structure can be handled particularly well.

The direction of the semiconductor substrate is not particularly limited, and for convenience of description, in this specification, the SiN side is set to be upper and the Si side is set to be lower. In the accompanying drawings, the structure of the semiconductor substrate or its members is simplified and illustrated, and it may be explained in a necessary form as necessary.

[Example]

Hereinafter, the present invention will be described in more detail with examples, but the present invention is not limited to the following examples. In addition, the specification of the amount or ratio shown in an Example is a quality standard unless there is special notice.

<Example 1, Comparative Example 1>

The composition shown in Table 1 (mass %) contains the components shown in Table 1 below and is adjusted to an etching solution. In addition, the rest is water (ultra-pure water).

(Manufacturing method of substrate)

A silicon oxide film (SiO ₂ layer) is formed on a commercially available 300 mm silicon substrate by thermal oxidation. Then, a silicon nitride film (SiN layer) is formed by CVD. The silicon nitride film on the silicon substrate is set to a thickness of 300 nm, and the silicon oxide film on the silicon substrate is set to a thickness of 300 nm.

(Etching test)

The above-mentioned test substrate was etched by a piece-by-piece device (manufactured by SPS-Europe B.V., POLOS (trade name)) under the following conditions, and an evaluation test was carried out.

. Substrate application temperature (Tap): refer to Table 1

. Spray volume: 1L/min

. 5 minutes

. Wafer speed 500rpm

(Measurement method of processing temperature)

A radiation thermometer IT-550F (trade name) manufactured by Horiba Manufacturing Co., Ltd. was fixed at a height of 30 cm above the wafer in the above-mentioned piece-by-piece device. The temperature is measured on the wafer center (Tap-c) and the wafer surface 250 mm (Tap-e) from the center of the wafer while flowing a chemical solution to the thermometer. The temperature is digitally output by the radiation thermometer and continuously recorded by the computer. The temperature stabilized for 10 seconds was averaged, and the obtained value was taken as the temperature on the wafer (Tap).

(Etching speed)

The etching rate (ER) was calculated by measuring the film thickness before and after the etching process using an ellipsometer (spectroscopy ellipsometer, J.A. Woollam JAPAN Co., Ltd., Vase). The average value of 5 points was used (measurement conditions are measurement range: 1.2 eV-2.5 eV, measurement angle: 70 degrees, 75 degrees).

(Other conditions)

The pure water rinse process after etching is performed at 2 L/min. 60 sec. 500 rpm. The drying process is carried out at 1500rpm 60sec.

The test was carried out by spraying the liquid in the tank after reaching the boiling point (Tbp) and maintaining the temperature for 10 minutes. The estimated flight time based on the supply speed and the nozzle-substrate distance is 0.01 seconds.

The precipitation on the silicon oxide film was evaluated using COMPLUS 3T of Applied Materials.

Drugs used: Phosphoric acid, Phosphorus Phosphorus Chemicals, Inc. semiconductor grade EL-S phosphoric acid; for others, the test was conducted using reagents manufactured by Aldrich in the following table.

(Note of table)

A test starting with C as a comparative example

Si-compounds: compounds containing silicon

Tbp: temperature in the tank (boiling treatment temperature)

Tap-c: temperature on the wafer (wafer center)

Tap-e: temperature on the wafer (250mm from the center of the wafer)

SiN[R1]: etching rate of SiN layer

SiO ₂ [R2]: etch rate of SiO ₂ layer

Precipitation of SiO _2: SiO ₂ is deposited on the SiO ₂ layer

1Å=0.1nm

a: H ₂ SiF ₆ , product number 01302 made by sigma-aldrich company

b: Na ₂ SiF ₆ , product number 250171 made by Sigma-Aldrich

c: (NH ₄ ) ₂ SiF ₆ , product number 204331 made by Sigma-Aldrich

d: (C ₂ H ₅ O) ₄ Si, Tetra ethoxy silane (Tetra ethoxy silane), product number 333859 manufactured by Sigma-Aldrich

e: (CH ₃ O) ₃ CH ₃ Si, trimethoxy methyl silane (Trimethoxy methyl silane), product number 246174 made by Sigma-Aldrich

From the above results, it can be seen that according to the present invention, SiN can be selectively removed and the precipitation of SiO ₂ in the SiO ₂ layer can be effectively suppressed.

In addition, when the liquid in the tank reaches the boiling point (Tbp) and maintains the temperature longer than 10 minutes, and then ejects to perform the same test as above, it can also be obtained Get the same effect.

The present invention and its embodiments have been described together, but we believe that unless otherwise specified, any specific part of the description does not limit our invention, and does not deviate from the spirit and scope of the invention shown in the scope of the attached patent application. Under the circumstances, a wide range of explanations should be possible.

This application claims priority based on Japanese Patent Application No. 2012-249674 for which a patent application was filed in Japan on November 13, 2012, and the contents thereof are incorporated by reference as part of the description of this specification.

1‧‧‧SiN layer (layer 1)

2‧‧‧SiO ₂ layer (layer 2)

3‧‧‧Si layer (layer 3)

10‧‧‧Semiconductor substrate

Claims (34)

A method for etching a semiconductor substrate, comprising: preparing an etching solution containing a phosphoric acid compound, a compound containing silicon and water; and after boiling the etching solution, spraying the etching solution on a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) On the exposed substrate, the etching solution is brought into contact with the substrate to remove the silicon nitride film. The etching solution contains 0.01% by mass to 1% by mass of the silicon-containing compound, and the silicon-containing compound is ( NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , compounds represented by the following formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃ Formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ represents an alkyl group having 1 to 20 carbon atoms. The method of etching a semiconductor substrate as described in item 1 of the scope of the patent application, wherein the etching solution is cooled before and after it is ejected. The method for etching a semiconductor substrate as described in item 1 of the patent application range, wherein the contact temperature of the etching solution with the substrate is lower than the boiling temperature by more than 0°C And the range below 20 ℃. The method for etching a semiconductor substrate as described in item 1 of the patent application range, wherein the etching solution is ejected from a nozzle, dripped or flowed down to come into contact with the substrate. The method for etching a semiconductor substrate as described in item 1 of the scope of the patent application, wherein the etching solution is ejected at a rate of 0.5L/min~3L/min. The method for etching a semiconductor substrate according to any one of claims 1 to 5 of the patent application, wherein the boiling point of the etching solution is 110°C to 180°C. The method for etching a semiconductor substrate according to any one of the first to fifth patent applications, wherein the etching liquid is boiled in a tank holding the etching liquid before it is ejected, and then transferred to a nozzle via a flow path, Then, the etching liquid is ejected from the nozzle toward the substrate. The method for etching a semiconductor substrate according to any one of claims 1 to 5, wherein the boiling time of the etching solution is 5 minutes or more and 24 hours or less. The method for etching a semiconductor substrate according to any one of claims 1 to 5, wherein the etching solution contains 60 to 95% by mass of the phosphoric acid compound. The method for etching a semiconductor substrate according to any one of claims 1 to 5, wherein the pH value of the etching solution is -2 or more and 2 or less. The method of etching a semiconductor substrate as described in any one of the first to fifth patent application ranges, wherein the ratio of the etching rate of the silicon nitride film [R1] to the etching rate of the silicon oxide film [R2] ([R1]/[R2]) is 50 or more. The method for etching a semiconductor substrate according to any one of claims 1 to 5, wherein the phosphoric acid compound is at least one selected from the group consisting of orthophosphoric acid, metaphosphoric acid, and pyrophosphoric acid. A method of manufacturing a semiconductor element, wherein the silicon nitride film is removed by the etching method of a semiconductor substrate as described in any one of claims 1 to 12, and the semiconductor element is manufactured from the remaining substrate. An etching solution for a semiconductor substrate, which is applied to a substrate where a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) are exposed to selectively remove the silicon nitride film, and contains a phosphoric acid compound and a silicon-containing compound And water, and performing boiling treatment by heating, the etching solution contains 0.01% by mass to 1% by mass of the silicon-containing compound, the silicon-containing compound is (NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , and The compound represented by formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃ Formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms ; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ is an alkyl group having 1 to 20 carbon atoms. The etching solution for a semiconductor substrate as described in item 14 of the patent application range, wherein the etching solution contains 60% by mass to 95% by mass of the phosphoric acid compound. A method for etching a semiconductor substrate, comprising: preparing an etching solution containing a phosphoric acid compound, a compound containing silicon and water; and after boiling the etching solution, spraying the etching solution on a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) On the exposed substrate, the etching liquid is brought into contact with the substrate to remove the silicon nitride film, wherein the etching liquid is boiled in a tank holding the etching liquid before it is ejected, and then transferred to the nozzle through the flow path , And the etching solution is ejected from the nozzle toward the substrate. The etching method of the semiconductor substrate is to etch piece by piece. The piece by piece etching is to transport or rotate the substrate in a specific direction. The etching solution is sprayed or flows out of the space to contact the etching solution with the substrate. The silicon-containing compound is (NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , as shown in the following formula (1) or formula (2) Compound: Formula (1): R ² Si(OR ³ ) ₃ Formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms ; R ⁴ is an alkyl group having 1 to 20 carbon atoms. An etching method of a semiconductor substrate as described in item 16 of the patent application range, wherein the etching solution is cooled before and after the discharge. The method for etching a semiconductor substrate according to item 16 of the patent application range, wherein the contact temperature of the etching solution with the substrate is lower than the boiling temperature by a range of 0°C to 20°C or less. The method for etching a semiconductor substrate as described in Item 16 of the patent application range, wherein the etching solution is ejected from a nozzle, dripped or flowed down to contact the substrate. The method for etching a semiconductor substrate as described in item 16 of the patent application range, wherein the etching solution is ejected at a rate of 0.5L/min~3L/min. The method for etching a semiconductor substrate according to any one of claims 16 to 20, wherein the boiling point of the etching solution is 110°C to 180°C. The method for etching a semiconductor substrate according to any one of claims 16 to 20, wherein the boiling time of the etching solution is 5 minutes or more and 24 hours or less. According to the method of etching a semiconductor substrate as described in item 16 of the patent application range, the etching solution contains 0.01% by mass to 1% by mass of the silicon-containing compound. The method for etching a semiconductor substrate according to any one of claims 16 to 20, wherein the etching solution contains 60 to 95% by mass of the phosphoric acid compound. The semiconductor as described in any one of patent application items 16 to 20 A method of etching a substrate, wherein the pH of the etching solution is -2 or more and 2 or less. The method for etching a semiconductor substrate as described in any one of claims 16 to 20, wherein the ratio of the etching rate of the silicon nitride film [R1] to the etching rate of the silicon oxide film [R2] ([R1]/[R2]) is 50 or more. The method of etching a semiconductor substrate according to any one of claims 16 to 20, wherein the phosphoric acid compound is at least one selected from the group consisting of orthophosphoric acid, metaphosphoric acid, and pyrophosphoric acid. A method for etching a semiconductor substrate, comprising: preparing an etching solution containing a phosphoric acid compound, a compound containing silicon and water; and after boiling the etching solution, spraying the etching solution on a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) On the exposed substrate, the etching solution is brought into contact with the substrate to remove the silicon nitride film, wherein the etching solution contains 60% by mass to 95% by mass of the phosphoric acid compound, and the silicon-containing compound is (NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , compounds represented by the following formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃ Formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ represents an alkyl group having 1 to 20 carbon atoms. A method for etching a semiconductor substrate, comprising: preparing an etching solution containing a phosphoric acid compound, a compound containing silicon and water; and after boiling the etching solution, spraying the etching solution on a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) On the exposed substrate, the etching solution is brought into contact with the substrate to remove the silicon nitride film, wherein the pH value of the etching solution is -2 or more and 2 or less, and the silicon-containing compound is (NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , compounds represented by the following formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃ Formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ represents an alkyl group having 1 to 20 carbon atoms. An etching solution for a semiconductor substrate, which is applied to a substrate where a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) are exposed to selectively remove the silicon nitride film, and contains a phosphoric acid compound and a silicon-containing compound And water, and performing boiling treatment by heating, wherein the etching liquid is boiled in a tank holding the etching liquid before it is sprayed, and then transferred to a nozzle through a flow path, and the etching liquid is sprayed from the nozzle to the substrate , The silicon-containing compound is (NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , the compound represented by the following formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃ formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ represents an alkyl group having 1 to 20 carbon atoms. An etching solution for a semiconductor substrate as described in item 30 of the patent application range, wherein the etching solution contains 0.01% by mass to 1% by mass of the silicon-containing compound. The etching solution for a semiconductor substrate according to item 30 of the patent application range, wherein the etching solution contains 60% by mass to 95% by mass of the phosphoric acid compound. An etching solution for a semiconductor substrate, which is applied to a substrate where a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) are exposed to selectively remove the silicon nitride film, and contains a phosphoric acid compound and a silicon-containing compound And water, and performing boiling treatment by heating, wherein the etching solution contains 60% by mass to 95% by mass of the phosphoric acid compound, and the silicon-containing compound is (NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , the following The compound represented by formula (1) or formula (2): Formula (1): R ² Si(OR ³ ) ₃ Formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ represents an alkyl group having 1 to 24 carbon atoms; R ⁴ is an alkyl group having 1 to 20 carbon atoms. An etching solution for a semiconductor substrate, which is applied to a substrate where a silicon nitride film (SiN) and a silicon oxide film (SiO ₂ ) are exposed to selectively remove the silicon nitride film, and contains a phosphoric acid compound and a silicon-containing compound And water, and performing boiling treatment by heating, wherein the pH of the etching solution is -2 or more and 2 or less, and the silicon-containing compound is (NH ₄ ) ₂ SiF ₆ , Na ₂ SiF ₆ , and the following formula ( 1) or a compound represented by formula (2): Formula (1): R ² Si(OR ³ ) ₃ Formula (2): Si(OR ⁴ ) ₄ R ² represents an alkyl group having 1 to 12 carbon atoms; R ³ Represents an alkyl group having 1 to 24 carbon atoms; R ⁴ is an alkyl group having 1 to 20 carbon atoms.

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