JP2000056479A - Side wall removing liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a side wall removing liquid capable of easily removing the side wall occurring at the time of dry etching in semiconductor- manufacturing process from a semiconductor substrate without corroding a wiring material. SOLUTION: The side wall is removed from the semiconductor substrate by using a generally used side wall removing liquid after immersing the semiconductor substrate into an aqueous solution of nitric acid, preferably, in a nitric acid concentration of 0. 1-80 weight %, preferably, in an immersing time of 1 sec-1 hr, and rinsing it with water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing a sidewall, and more particularly, to a method for removing a sidewall generated during dry etching in a semiconductor manufacturing process without eroding a wiring material. Things.

[0002]

2. Description of the Related Art Conventionally, a semiconductor device has been manufactured, for example, by the following steps. A metal layer such as Al serving as a wiring material is formed on an insulating layer such as SiO ₂ . A photoresist layer is formed thereon. Further, a photomask is superposed thereon and exposed. A resist pattern is formed by performing a developing process. The exposed metal layer is etched. A metal wiring pattern is obtained by removing and removing the resist pattern.

In recent years, it has become necessary to form finer patterns in order to increase the density of integrated circuits. Conventionally, chemical etching using a chemical has been performed in etching, but dry etching using a halogen-based gas has been frequently used for forming finer patterns. In dry etching, sidewalls (sidewall protective films) are generated, which enables anisotropic etching. The sidewalls are generated by a chemical reaction between a photoresist, a wiring material, and an etching gas during dry etching. As a result, the sidewall is a compound having a complex composition including an organic substance derived from a photoresist, an inorganic substance derived from a wiring material, and a halide derived from an etching gas.

Since the conventional stripping solution is designed for stripping an organic photoresist, such a sidewall cannot be sufficiently stripped and removed. Further, halogen radicals and halogen ions generated during dry etching with a halogen-based gas are confined in the sidewalls, and an acid is generated by moisture in the air to corrode the wiring material (after-corrosion). Therefore, the sidewall must be completely removed.

[0005] However, it is difficult to remove the side wall with a commonly used resist stripping solution. For example, in the case of an alkylbenzenesulfonic acid-based acidic stripper, 100
It is difficult to remove the sidewalls even when heated to a high temperature of ° C. In addition, since these acidic stripping solutions have low solubility in water, rinsing with a water-soluble organic solvent such as 2-propanol (hereinafter referred to as IPA) is required before washing with water, which complicates the process. . On the other hand, even with an organic amine-based alkaline stripping solution, it is difficult to remove the sidewalls even when heated to a high temperature of 100 ° C. Also, if you wash immediately,
It exhibits strong alkalinity due to the action of the organic amine component and water, and causes corrosion of wiring materials. Therefore, it is necessary to perform rinsing with IPA or the like prior to washing with water, which complicates the process.

[0006] JP-A-6-202345 proposes a highly crosslinked or cured photoresist stripping composition comprising a stripping solvent such as 2-pyrrolidinone, an amine, and a weak acid. Japanese Patent Application Laid-Open No. 7-219240 proposes a positive resist stripping solution in which a carboxyl group-containing organic compound is mixed with a resist stripping composition comprising a nitrogen-containing organic hydroxyl compound. It is difficult to remove the sidewall with the liquid. Further, an acid such as hydrochloric acid or sulfuric acid, or a base such as an aqueous solution of an alkylamine or an alkanolamine can remove the sidewall by dissolving aluminum of the wiring material, but cannot prevent corrosion of the wiring material. .

JP-A-7-201793, JP-A-7-201793
Japanese Patent Application Laid-Open No. 249607/1989 proposes using nitric acid to remove the sidewalls. Nitric acid is effective in preventing corrosion by forming a passive film due to its oxidizing power, but it is sufficient to completely remove the sidewalls. is not. Therefore, in order to remove the sidewalls only by washing with nitric acid, it is necessary to select strictly strict conditions (a narrow range), and even if such conditions are selected, the sidewalls cannot be completely removed in many cases.

[0008]

As described above, a sidewall formed by dry etching after the formation of a photoresist, such as a sidewall formed as a result of a chemical reaction between a photoresist, a wiring material, and an etching gas. Removal of sidewalls having a compound having a complex composition including a photoresist-derived organic substance, an inorganic substance derived from a wiring material, a halide derived from an etching gas, etc. from a semiconductor substrate without corroding the wiring material. There is a need for method development. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of easily removing a side wall generated during dry etching in a semiconductor manufacturing process from a semiconductor substrate without corroding a wiring material.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems. As a result, the semiconductor substrate was immersed in a nitric acid aqueous solution, washed with water, and then subjected to a side wall generally used. By performing the removal treatment with the removal liquid, that is, by leaving the nitric acid pretreatment for anticorrosion and the removal treatment for sidewall removal to separate chemical solutions,
The present invention has been found that the corrosion of the wiring material can be significantly suppressed by the effect of nitric acid as compared with the conventional method, and the sidewall can be removed from the semiconductor substrate without corroding the wiring material.

According to a first aspect of the present invention, there is provided a method of removing side walls generated during dry etching in a semiconductor manufacturing process from a semiconductor substrate, wherein the semiconductor substrate is immersed in a nitric acid aqueous solution. A method of removing a sidewall, which comprises removing the sidewall with a sidewall removing liquid after a water washing process.

According to a second aspect of the present invention, in the method for removing a sidewall according to the first aspect, the concentration of the nitric acid aqueous solution is 0.1 to 80% by weight.

According to a third aspect of the present invention, in the method for removing a sidewall according to the first or second aspect, the immersion time in the nitric acid aqueous solution is 1 second to 1 hour.

[0013]

Embodiments of the present invention will be described below in detail. Usually, the removal of the sidewall is performed by an etching process,
This is performed after the ashing step. Usually, in the step of removing the side wall, after the treatment with the removing solution, rinsing with a water-soluble organic solvent (the rinsing with the organic solvent is not performed in some cases) and finally washing with pure water Complete. The side wall removing step of the present invention is constituted by first immersing the semiconductor substrate in an aqueous nitric acid solution, washing the substrate with water, and then removing the side wall from the semiconductor substrate with a normal side wall removing liquid.

The nitric acid concentration of the aqueous nitric acid solution used in the present invention is preferably 0.1 to 80% by weight. If the amount is less than 0.1% by weight, the effect of the present invention may not be sufficiently obtained. On the other hand, if the amount exceeds 80% by weight, no further improvement in the effect is observed, and the burden of waste liquid treatment is undesirably increased.

The immersion time of the semiconductor substrate in the aqueous nitric acid solution used in the present invention is preferably between 1 second and 1 hour. If the time is shorter than 1 second, the effect of the present invention may not be sufficiently obtained. On the other hand, if the time is longer than 1 hour, productivity is poor and not practical, which is not preferable.

The side wall removing solution used in the present invention is not particularly limited, and any commonly used removing solution can be applied. Commonly used side wall removing liquids include stripping agents (acidic components, basic components, ammonium fluoride, etc.), organic solvents, anticorrosives (catechols, reducing sugars, etc.), additives (surfactants, chelates) Agents), water and the like.

Examples of the above-mentioned stripping agent that constitutes a commonly used side wall removing solution include acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, formic acid, lactic acid, benzoic acid, methanesulfonic acid, and benzenesulfonic acid. , Ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, alkylamines such as triethylamine, n-propylamine and isopropylamine, alkanols such as monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine and dimethylmonoethanolamine Examples include amines, organic bases such as tetramethylammonium hydroxide, and fluorides such as hydrofluoric acid and ammonium fluoride. These may be used alone or in combination of two or more.

As the organic solvent, any organic solvent can be used as long as it is uniformly compatible with the other components. Generally, the organic solvent is often water-soluble, but is not particularly limited.
As the organic solvent, specifically, for example, methanol, ethanol, n-propanol, 2-propanol, n-butanol, sec-butanol, tert-
Alcohols such as butanol, ethylene glycol,
Propylene glycol, 1,3-propanediol,
1,2-butanediol, 2,3-butanediol,
Diols such as 1,3-butanediol and 1,4-butanediol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol Monoisopropyl ether,
Ether alcohols such as diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, formamide, N-methylformamide, N, N-dimethylformamide;
N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N
Amides such as -methylpropionamide, 2-pyrrolidone, N-methylpyrrolidone, dimethyl sulfoxide,
And sulfolane. These may be used alone or in combination of two or more,
It does not have to be used.

Specific examples of the above anticorrosive include sugars such as glucose, mannose, galactose, sorbitol, mannitol and xylitol, sugar alcohols, phenol, cresol, catechol, and the like.
Aromatic hydroxy compounds such as resorcinol, 2,3-pyridinediol, pyrogallol, salicylic acid, and gallic acid, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,6- Dimethyl-4-
Octin-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,5-dimethyl-1-hexyn-3-ol, 2-butyne-1,4
-Alkyne alcohols such as diols, benzotriazole, o-tolyltriazole, m-tolyltriazole, p-tolyltriazole, carboxybenzotriazole, 1-hydroxybenzotriazole, nitrobenzotriazole, and triazoles such as dihydroxypropylbenzotriazole. I can give it. These may be used alone, may be used in combination of two or more, or may not be used.

Examples of the above additives include a surfactant and a chelating agent. These may be added alone, may be added in combination of two or more, or may not be added. Water is usually used.

FIGS. 1A to 1E are explanatory views for explaining a sidewall removing method of the present invention for removing a sidewall from a semiconductor substrate using a sidewall removing liquid. Although the principle of the present invention is not clear, the inventors presume as follows. The mechanism of removing the sidewall is presumed to be such that the metal component of the wiring material is slightly dissolved to peel off the sidewall on the outside thereof. On the other hand, the mechanism of corrosion prevention is presumed to be due to the oxidation of the metal surface of the wiring material by the oxidizing action of nitric acid to form a passivation film.

FIG. 1A shows that a silicon substrate 1 is
An insulating layer ₂ such as iO2, a metal layer 3 such as Al serving as a wiring material are formed thereon, a positive photoresist layer 4 is formed thereon, and a photomask 5 is further superposed thereon and exposed. The steps will be described. The resist exposed to light becomes soluble in the alkaline aqueous solution developer.

FIG. 1B shows a step of forming a resist pattern by performing a developing process. The light-exposed portions of the resist are removed.

FIG. 1C shows a step of dry-etching the exposed metal layer 3. The side wall 6 is formed at the same time as the portion of the metal layer 3 where the resist is removed is etched. The sidewall 6 also has a role of protecting the remaining metal layer 3 from being excessively etched.

FIG. 1D shows a step of obtaining the metal wiring pattern 3 by removing the resist pattern 4 by ashing with plasma or the like.

FIG. 1E shows a step of removing the side wall 6 using a normal side wall removing liquid.
The sidewall 6 can be removed in a short time at a low temperature without corroding the wiring material by using a normal sidewall removing liquid.

[0027]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. (Preparation of Substrate) An SiO ₂ film was formed on a silicon wafer substrate, and an Al—Si—Cu layer was formed thereon. A novolak type photoresist was applied thereon, exposed and developed to form a resist pattern. After performing dry etching with a chlorine-based gas, the resist other than the sidewalls was removed by oxygen plasma ashing to obtain a test substrate.

(Examples 1 to 8) The above substrate was subjected to a nitric acid treatment (25 ° C.) and a removing solution treatment (25 ° C.) under the conditions shown in Table 1, rinsed with water, dried, and then subjected to SEM (scanning electron microscope). Was observed and evaluated. Table 1 shows the results of evaluating the removability of the sidewall and the corrosiveness of the wiring material according to the following criteria.
Shown in

Removability ：: The sidewall is completely removed. ×: The sidewall is not removed. Corrosive ○: No corrosion is observed in the wiring material. ×: Corrosion is observed in the wiring material.

(Comparative Examples 1 to 3) Under the conditions shown in Table 1, the above substrates were treated with a removing solution (25 ° C.), rinsed with water, dried, and observed and evaluated by SEM (scanning electron microscope).
Table 1 shows the results of the evaluation of the removability of the sidewall and the corrosiveness of the wiring material according to the above criteria.

[0031]

[Table 1]

From Examples 1 to 8 in Table 1, it can be seen that the sidewalls are completely removed, and the nitric acid treatment suppresses the corrosion of the wiring material in the subsequent removal liquid treatment. On the other hand, from Comparative Examples 1 to 3 in Table 1, it is found that the sidewalls are completely removed, but the treatment with only the removing solution causes corrosion of the wiring material.

[0033]

By using the method for removing a sidewall according to the present invention, the corrosion of a wiring material is greatly suppressed as compared with the conventional method, and the sidewall is easily removed from the semiconductor substrate without corroding the wiring material. It is possible.

[Brief description of the drawings]

FIG. 1A shows an insulating layer ₂ such as SiO ₂ on a silicon substrate 1, a metal layer 3 such as Al serving as a wiring material formed thereon, and a positive photoresist layer 4 formed thereon. Further, a step of exposing a photomask 5 thereon is shown, (b) shows a step of forming a resist pattern by performing a developing process, and (c) shows a step of exposing the exposed metal layer 3.
(D) shows a step of obtaining the metal wiring pattern 3 by removing the resist pattern 4 by ashing, and (e) shows a step of removing the side wall using a normal side wall removing liquid. 6 is shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Insulating layer 3 Metal layer 4 Positive photoresist 5 Photomask 6 Sidewall

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/3065 H01L 21/302 N 5F043 21/306 21/306 S 21/3213 21/88 C (72) Inventor Kuniaki Miyahara 4980, Kaiseicho, Shinnanyo-shi, Yamaguchi Prefecture Tokuyama Petrochemical Co., Ltd. (72) Inventor Koji Shimizu 4980, Kaiseicho, Shinnanyo-shi, Yamaguchi Prefecture Tokuyama Petrochemical Co., Ltd.F-term (reference) 2H095 BB14 BB18 2H096 AA25 HA23 HA30 LA01 LA30 4H003 BA12 DA15 DB03 EA03 ED02 FA15 5F004 AA08 AA09 BD01 DA26 DB09 DB12 DB26 EA10 EA28 EB02 5F033 HH09 QQ08 QQ11 QQ19 QQ20 QQ93 WW00 WW04 XX21 5F043 AA24 BB27 BB28 CC16 DD02

Claims (3)

[Claims] In a method of removing a sidewall generated during dry etching in a semiconductor manufacturing process from a semiconductor substrate, the semiconductor substrate is immersed in an aqueous nitric acid solution, washed with water, and then removed with a sidewall removing solution. A sidewall removing method. 2. The method according to claim 1, wherein the concentration of the nitric acid aqueous solution is 0.1 to 80% by weight. 3. The immersion time in the nitric acid aqueous solution is 1 second to 1 second.
3. The method according to claim 1, wherein the time is a time.
The method for removing the sidewall described in the above.