PROCESSING LIQUID FOR SUPPRESSING PATTERN COLLAPSE OF MICROSTRUCTURE, AND METHOD FOR PRODUCING MICROSTRUCTURE USING SAME

TECHNICAL FIELD

The present invention relates to a processing liquid for suppressing pattern collapse of a microstructure, and a method for producing a microstructure using the processing liquid.

BACKGROUND ART

The photolithography technique has been employed as a formation and processing method of a device having a microstructure used in a wide range of fields of art including a semiconductor device, a circuit board and the like. In these fields of art, reduction of size, increase of integration degree and increase of speed of a semiconductor device considerably proceed associated with the highly sophisticated demands on capabilities, which bring about continuous miniaturization and increase of aspect ratio of a resist pattern used for photolithography. However, the progress of miniaturization of the resist pattern causes pattern collapse as a major problem.

It has been known that upon drying the resist pattern to remove a processing liquid used in wet processing (which is mainly a rinsing treatment for washing away a developer solution) therefrom after developing the resist pattern, the collapse of the resist pattern is caused by the stress derived by the surface tension of the processing liquid. For preventing the collapse of the resist pattern, such methods have been proposed as a method of replacing the rinsing liquid by a liquid having a low surface tension using a nonionic surfactant, a compound soluble in an alcohol solvent, or the like (see, for example, Patent Documents 1 and 2), and a method of hydrophobizing the surface of the resist pattern (see, for example, Patent Document 3).

In a microstructure formed of a metal, a metal nitride, a metal oxide, a silicon oxide, silicon or the like (except for a resist; hereinafter defined in the same way unless otherwise specified) by the photolithography technique, the strength of the material itself constituting the structure is larger than the strength of the resist pattern itself or the bonding strength between the resist pattern and the substrate, and therefore, the collapse of the structure pattern is hard to occur as compared to the resist pattern. However, associated with the progress of reduction of size, increase of integration degree and increase of speed of a semiconductor device and a micromachine, the pattern collapse of the structure is becoming a major problem due to miniaturization and increase of aspect ratio of the pattern.

Under these circumstances, in order to solve the problem of pattern collapse of the microstructure, there has been proposed the method of forming a hydrophobic protective film using a surfactant (see, for example, Patent Document 4). However, in Patent Document 4, there are no descriptions concerning details of the surfactant including kind (nonionic, anionic or cationic, etc.), product names, concentrations or the like.

PRIOR ART DOCUMENTS
Patent Documents

Patent Document 1: JP-A-2004-184648

Patent Document 2: JP-A-2005-309260

Patent Document 3: JP-A-2006-163314

Patent Document 4: JP-A-2010-114467

SUMMARY OF THE INVENTION
Problems to be Solved by the Invention

As described above, the current situation is that no effective technique for suppressing pattern collapse has been known in the field of microstructures (in particular, microstructures formed of polysilicon) such as a semiconductor device and a micromachine.

The present invention has been developed under the circumstances, and an object thereof is to provide a processing liquid that is capable of suppressing pattern collapse of a microstructure formed of polysilicon, such as a semiconductor device and a micromachine, and a method for producing a microstructure using the processing liquid.

Means for Solving the Problems

As a result of earnest investigations made by the inventors for achieving the object, it has been found that the object can be achieved with a processing liquid including at least one compound selected from the group consisting of pyridinium halides containing an alkyl group having 12, 14 or 16 carbon atoms.

The present invention has been accomplished on the basis of the above finding. Accordingly, the present invention relates to the following aspects.

1. A processing liquid for suppressing pattern collapse of a microstructure formed of polysilicon, including a pyridinium halide containing at least one alkyl group selected from the group consisting of those alkyl groups having 12, 14 and 16 carbon atoms, and water.

2. The processing liquid as described in the above aspect 1, wherein the alkyl group having 12 carbon atoms is a dodecyl group, the alkyl group having 14 carbon atoms is a tetradecyl group, and the alkyl group having 16 carbon atoms is a hexadecyl group.

3. The processing liquid as described in the above aspect 1, wherein the pyridinium halide containing an alkyl group having 12, 14 or 16 carbon atoms is at least one compound selected from the group consisting of dodecyl pyridinium chloride, tetradecyl pyridinium chloride, hexadecyl pyridinium chloride, 1-dodecyl-4-methylpyridinium chloride, 1-tetradecyl-4-methyl pyridinium chloride and 1-hexadecyl-4-methylpyridinium chloride.

4. The processing liquid as described in the above aspect 1, wherein a content of the pyridinium halide containing an alkyl group having 12, 14 or 16 carbon atoms in the processing liquid is from 10 ppm to 10%.

5. A method for producing a microstructure formed of polysilicon, comprising the steps of:

subjecting a structure to wet etching or dry etching to obtain the microstructure; and

rinsing the microstructure obtained by the wet etching or dry etching with a processing liquid for suppressing pattern collapse, the processing liquid comprising a pyridinium halide containing at least one alkyl group selected from the group consisting of those alkyl groups having 12, 14 and 16 carbon atoms, and water.

6. The method as described in the above aspect 5, wherein the microstructure is a semiconductor device or a micromachine.

ADVANTAGES OF THE INVENTION

According to the present invention, there are provided a processing liquid that is capable of suppressing pattern collapse of a microstructure, such as a semiconductor device and a micromachine, and a method for producing a microstructure using the processing liquid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(
a) to FIG. 1(h) are schematic cross sectional views showing respective production steps of a microstructure.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

(Processing Liquid for Suppressing Pattern Collapse)

The processing liquid of the present invention (i.e., a processing liquid for suppressing pattern collapse) is used for suppressing pattern collapse of a microstructure formed of polysilicon, and includes at least one compound selected from the group consisting of pyridinium halides containing an alkyl group having 12, 14 or 16 carbon atoms.

The term “microstructure formed of polysilicon” as used herein means a microstructure in which a portion to be processed with the processing liquid is formed of polysilicon.

It is considered that the pyridinium halide containing an alkyl group having 12, 14 or 16 carbon atoms used in the processing liquid of the present invention is adsorbed to the material used in the pattern of the microstructure, thereby hydrophobizing the surface of the pattern. The hydrophobization as used in the present invention means that the contact angle of the material having been processed with the processing liquid of the present invention with respect to water is 70° or more.

The alkyl group having 12 carbon atoms is preferably a dodecyl group, the alkyl group having 14 carbon atoms is preferably a tetradecyl group, and the alkyl group having 16 carbon atoms is preferably a hexadecyl group. The compounds having such a straight chain alkyl group can be adsorbed to a polysilicon material with a high density as compared to those compounds having a branched alkyl group.

In view of practical use, among the halides, preferred is chlorine.

Preferred examples of the pyridinium halide containing an alkyl group having 12, 14 or 16 carbon atoms include dodecyl pyridinium chloride, dodecyl pyridinium bromide, dodecyl pyridinium iodide, tetradecyl pyridinium chloride, tetradecyl pyridinium bromide, tetradecyl pyridinium iodide, hexadecyl pyridinium chloride, hexadecyl pyridinium bromide, hexadecyl pyridinium iodide, 1-dodecyl-4-methylpyridinium chloride, 1-dodecyl-4-methylpyridinium bromide, 1-dodecyl-4-methylpyridinium iodide, 1-tetradecyl-4-methylpyridinium chloride, 1-tetradecyl-4-methyl pyridinium bromide, 1-tetradecyl-4-methylpyridinium iodide, 1-hexadecyl-4-methylpyridinium chloride, 1-hexadecyl-4-methylpyridinium bromide and 1-hexadecyl-4-methylpyridinium iodide. Among these pyridinium halides, especially preferred are dodecyl pyridinium chloride, tetradecyl pyridinium chloride, hexadecyl pyridinium chloride, 1-dodecyl-4-methylpyridinium chloride, 1-tetradecyl-4-methylpyridinium chloride and 1-hexadecyl-4-methylpyridinium chloride.

The processing liquid for suppressing pattern collapse according to the present invention may be used in the form of an aqueous solution. Preferred examples of the water used for preparation of the aqueous solution include water, from which metallic ions, organic impurities, particles and the like are removed by distillation, ion exchange, filtering, adsorption treatment or the like, and particularly preferred examples thereof include pure water and ultrapure water.

The processing liquid for suppressing pattern collapse according to the present invention includes the at least one compound selected from the group consisting of pyridinium halides containing an alkyl groups having 12, 14 or 16 carbon atoms, and water, and may also contain various kinds of additives that are ordinarily used in processing liquids for suppressing pattern collapse in such a range that does not impair the advantages of the processing liquid.

The content of the at least one compound selected from the group consisting of pyridinium halides containing an alkyl group having 12, 14 or 16 carbon atoms (when using two or more kinds of compounds, it means a total content thereof) in the processing liquid of the present invention is preferably from 10 ppm to 10%. When the content of the compound is in the range, the advantages of these compound may be sufficiently obtained, and in consideration of handleability, economy and foaming, the content is preferably 5% or less, more preferably from 10 to 2,000 ppm, and more preferably from 10 to 1,000 ppm. In the case where the compounds do not have sufficient solubility in water to cause phase separation, an organic solvent, such as an alcohol, may be added, and an acid or an alkali may be added to enhance the solubility. Even in the case where the processing liquid is simply turbid white without phase separation, the processing liquid may be used in such a range that does not impair the advantages of the processing liquid, and may be used while stirring to render the processing liquid homogeneous. Furthermore, for avoiding the white turbidity of the processing liquid, the processing liquid may be used after adding an organic solvent, such as an alcohol, an acid or an alkali thereto as similar to the above case.

The processing liquid for suppressing pattern collapse according to the present invention may be suitably used for suppressing pattern collapse of a microstructure, such as a semiconductor device and a micromachine. Preferred examples of the pattern of the microstructure include those patterns obtained from polysilicon.

The microstructure may be patterned on an insulating film species, such as TEOS (a tetraethoxy ortho silane oxide film) and SiOC-based low dielectric constant films (such as “Black Diamond 2” (tradename) available from Applied Materials Inc., and “Aurora 2.7” and “Aurora 2.4” (tradenames) both available from ASM International N.V.), in some cases, or the insulating film species may be contained as a part of the microstructure in some cases.

The processing liquid for suppressing pattern collapse according to the present invention can exhibit excellent pattern collapse suppressing effect to not only an ordinary microstructure, but also a microstructure with further miniaturization and higher aspect ratio. The aspect ratio as referred herein is a value calculated from (height of pattern/width of pattern), and the processing liquid of the present invention may also exhibit excellent pattern collapse suppressing effect to a pattern that has a high aspect ratio of 3 or more, and further 7 or more. The processing liquid for suppressing pattern collapse according to the present invention has excellent pattern collapse suppressing effect to a finer pattern with a pattern size (pattern width) of 300 nm or less, further 150 nm or less, and still further 100 nm or less, and with a pattern size of 50 nm or less and a line/space ratio of 1/1, and similarly to a finer pattern with a pattern distance of 300 nm or less, further 150 nm or less, still further 100 nm or less, and still further 50 nm or less and a cylindrical hollow or cylindrical solid structure.

[Method for Producing Microstructure]

The method for producing a microstructure formed of polysilicon according to the present invention includes, after wet etching or dry etching, a rinsing step using the processing liquid for suppressing pattern collapse according to the present invention. More specifically, in the rinsing step, it is preferred that the pattern of the microstructure is made in contact with the processing liquid of the present invention by dipping, spray ejecting, spraying or the like, then the processing liquid is replaced by water, and the microstructure is dried. In the case where the pattern of the microstructure and the processing liquid of the present invention are in contact with each other by dipping, the dipping time is preferably from 10 seconds to 30 minutes, more preferably from 15 seconds to 20 minutes, still more preferably from 20 seconds to 15 minutes, and especially preferably from 30 seconds to 10 minutes, and the temperature condition is preferably from 10 to 80° C., more preferably from 15 to 60° C., still more preferably from 25 to 50° C., and especially preferably from 25 to 40° C. The pattern of the microstructure may be rinsed with water before making in contact with the processing liquid of the present invention. The contact between the pattern of the microstructure and the processing liquid of the present invention enables suppression of collapse of the pattern through hydrophobization of the surface of the pattern.

The processing liquid for suppressing pattern collapse according to the present invention may be applied widely to a production process of a microstructure irrespective of the kind of microstructure, with the production process having a step of wet etching or dry etching, then a step of wet processing (such as etching, cleaning or rinsing for washing away the cleaning liquid), and then a drying step. For example, the processing liquid of the present invention may be suitably used after the etching step in the production process of a semiconductor device or a micromachine, for example, (i) after wet etching of an insulating film around an electroconductive film in the production of a DRAM type semiconductor device (see, for example, JP-A-2000-196038 and H-A-2004-288710), (ii) after a rinsing step for removing contamination formed after dry etching or wet etching upon processing a gate electrode in the production of a semiconductor device having a transistor with a fin in the form of strips (see, for example, JP-A-2007-335892), and (iii) after a rinsing step for removing contamination formed after etching for forming a cavity by removing a sacrifice layer formed of an insulating film through a through hole in an electroconductive film upon forming a cavity of a micromachine (electrodynamic micromachine) (see, for example, JP-A-2009-122031).

EXAMPLES

The present invention will be described in more detail with reference to Examples, etc., below, but the present invention is not limited to these Examples.

<<Preparation of Processing Liquid>>

Processing liquids for suppressing pattern collapse of a microstructure were prepared according to the formulation compositions (% by mass) as shown in Table 1.

TABLE 1

Number of

carbon atoms

in alkyl

Kind
group*¹
Content

Processing
Dodecyl pyridinium chloride
12
500 ppm

liquid 1

Processing
Dodecyl pyridinium chloride
12
8%

liquid 2

Processing
1-Dodecyl-4-methyl
12
300 ppm

liquid 3
pyridinium chloride

Processing
1-Dodecyl-4-methyl
12
10%

liquid 4
pyridinium chloride

Processing
Tetradecyl pyridinium chloride
14
100 ppm

liquid 5

Processing
Tetradecyl pyridinium chloride
14
5%

liquid 6

Processing
1-Tetradecyl-4-methyl
14
50 ppm

liquid 7
pyridinium chloride

Processing
1-Tetradecyl-4-methyl
14
3%

liquid 8
pyridinium chloride

Processing
Hexadecyl pyridinium chloride
16
30 ppm

liquid 9

Processing
Hexadecyl pyridinium chloride
16
1%

liquid 10

Processing
1-Hexadecyl-4-methyl
16
10 ppm

liquid 11
pyridinium chloride

Processing
1-Hexadecyl-4-methyl
16
1,000 ppm

liquid 12
pyridinium chloride

*¹Number of carbon atoms in an alkyl group contained in respective compounds

Examples 1 to 12

As shown in FIG. 1(a), silicon nitride 103 (thickness: 100 nm) and silicon oxide 102 (thickness: 1,200 nm) were formed as films on a silicon substrate 104, then a photoresist 101 was formed, and the photoresist 101 was exposed and developed, thereby forming a tubular (chimney-shaped) opening 105 (diameter: 125 nm, distance between circles: 50 nm), as shown in FIG. 1(b). The silicon oxide 102 was etched by dry etching with the photoresist 101 as a mask, thereby forming a cylindrical hole 106 reaching the layer of silicon nitride 103, as shown in FIG. 1(c). The photoresist 101 was then removed by asking, thereby providing a structure having the silicon oxide 102 with the cylindrical hole 106 reaching the layer of silicon nitride 103, as shown in FIG. 1(d). The cylindrical hole 106 of the resulting structure was filled and deposited with polysilicon 107 (FIG. 1(e)), and an excessive portion of the polysilicon 107 on the silicon oxide 102 was removed by chemical mechanical polishing (CMP), thereby providing a structure having the silicon oxide 102 with a cylindrical hollow 108 of polysilicon embedded therein, as shown in FIG. 1(f). The silicon oxide 102 of the resulting structure was removed by dissolving with hydrofluoric acid, and then the structure was processed by making into contact with pure water, the respective processing liquids 1 to 12, and pure water in this order, followed by drying, thereby providing a structure shown in FIG. 1(g).

The resulting structure had a microstructure with a tubular (chimney-shaped) pattern formed of polysilicon (diameter: 125 nm, height: 1,200 nm (aspect ratio: 9.6), distance between the cylindrical hollows: 50 nm), and 70% or more of the pattern was not collapsed.

The pattern collapse was observed with “FE-SEM S-5500 (model number)” available from Hitachi High-Technologies Corporation, and the collapse suppression ratio was a value obtained by calculating the ratio of the not-collapsed pattern in the total pattern. Cases where the collapse suppression ratio was 50% or more were determined as “passed”. The processing liquids for suppressing pattern collapse, the processing methods and the results of collapse suppression ratios in the respective Examples are shown in Table 3.

Comparative Example 1

A structure shown in FIG. 1(g) was obtained in the same manner as in Example 1 except that after removing the silicon oxide 102 of the structure shown in FIG. 1(f) by dissolving with hydrofluoric acid, the structure was processed only with pure water. As a result, 50% or more of the pattern of the resulting structure were collapsed as shown in FIG. 1(h) (which indicated a collapse suppression ratio of less than 50%). The processing liquid, the processing method and the result of collapse suppression ratio in Comparative Example 1 are shown in Table 3.

Comparative Examples 2 to 17

Structures shown in FIG. 1(g) of Comparative Examples 2 to 17 were obtained in the same manner as in Example 1 except that after removing the silicon oxide 102 of the structures shown in FIG. 1(f) by dissolving with hydrofluoric acid and then processing the structures with pure water, the structures were processed with the respective comparative liquids 2 to 17 shown in Table 2 instead of the processing liquid 1. As a result, 50% or more of the pattern of the resulting respective structures were collapsed as shown in FIG. 1(h). The processing liquids, the processing methods and the results of collapse suppression ratios in Comparative Examples 2 to 17 are shown in Table 3.

TABLE 2

Name of substance

Comparative liquid 1
Water

Comparative liquid 2
Isopropyl alcohol

Comparative liquid 3
Diethylene glycol monomethyl ether

Comparative liquid 4
Dimethyl acetamide

Comparative liquid 5
Ammonium perfluoroalkyl sulfonate halide*¹

Comparative liquid 6
Perfluoroalkyl carboxylic acid salt*²

Comparative liquid 7
Adduct of 2,4,7,9-tetramethyl-5-decyne-4,7-diol

with ethyleneoxide*³

Comparative liquid 8
2,4,7,9-Tetramethyl-5-decyne-4,7-diol*⁴

Comparative liquid 9
Polyoxyethylene/polyoxypropylene block

polymer*⁵

Comparative liquid 10
1-Decyl-3-methyl imidazolium chloride (number

of carbon atoms in alkyl group: 10)*⁶

Comparative liquid 11
1-Hexadecyl-3-methyl imidazolium chloride

(number of carbon atoms in alkyl group: 16)*⁷

Comparative liquid 12
Dodecyl trimethyl ammonium chloride (number

of carbon atoms in alkyl group: 12)*⁸

Comparative liquid 13
Octadecyl trimethyl ammonium chloride

(number of carbon atoms in alkyl group: 18)*⁹

Comparative liquid 14
1-Decyl pyridinium chloride (number of carbon

atoms in alkyl group: 10)*¹⁰

Comparative liquid 15
Coconut oil fatty acid amide propyl betaine

(number of carbon atoms in alkyl group: 12, 14,

16)*¹¹

Comparative liquid 16
Dimethyl dodecyl amine oxide (number of carbon

atoms in alkyl group: 12)*¹²

Comparative liquid 17
Dimethyl octadecyl amine oxide (number of

carbon atoms in alkyl group: 18)*¹³

*¹“Fluorad FC-93” (tradename) available from 3M Corp.; specific gravity: 1.1 (25° C.); pH: 7 (0.1% aqueous solution); flash point: 38° C. (as measured by an open cup method); 0.01% aqueous solution

*²“Surflon S-111” (tradename) available from AGC Seimi Chemical Co., Ltd.; specific gravity: 1.0 (20° C.); flash point: 18° C. (as measured by a tag closed cup method); 0.01% aqueous solution

*³“Surfynol 420” (tradename) available from Nisshin Chemical Industry Co., Ltd.; ethyleneoxide content: 20%; 0.01% aqueous solution

*⁴“Surfynol 104” (tradename) available from Nisshin Chemical Industry Co., Ltd.; 0.01% aqueous solution

*⁵“Epan 420” (tradename) available from Dai-ichi Kogyo Seiyaku Co., Ltd.; average molecular weight of a hydrophobic group (polyoxypropylene): 1,200; polyoxyethylene content: 20%; 0.01% aqueous solution

*⁶to *¹³0.01% aqueous solution

TABLE 3

Collapse

sup-
Pass

pression
or

Processing method
ratio*¹
fail

Example 1
Pure water → processing liquid 1 →
80% or
Pass

pure water → drying
more

Example 2
Pure water → processing liquid 2 →
80% or
Pass

pure water → drying
more

Example 3
Pure water → processing liquid 3 →
80% or
Pass

pure water → drying
more

Example 4
Pure water → processing liquid 4 →
80% or
Pass

pure water → drying
more

Example 5
Pure water → processing liquid 5 →
80% or
Pass

pure water → drying
more

Example 6
Pure water → processing liquid 6 →
80% or
Pass

pure water → drying
more

Example 7
Pure water → processing liquid 7 →
70% or
Pass

pure water → drying
more

Example 8
Pure water → processing liquid 8 →
80% or
Pass

pure water → drying
more

Example 9
Pure water → processing liquid 9 →
70% or
Pass

pure water → drying
more

Example 10
Pure water → processing liquid 10 →
80% or
Pass

pure water → drying
more

Example 11
Pure water → processing liquid 11 →
70% or
Pass

pure water → drying
more

Example 12
Pure water → processing liquid 12 →
70% or
Pass

pure water → drying
more

Comparative
Pure water → drying
Less than
Fail

Example 1

50%

Comparative
Pure water → comparative liquid 2 →
Less than
Fail

Example 2
pure water → drying
50%

Comparative
Pure water → comparative liquid 3 →
Less than
Fail

Example 3
pure water → drying
50%

Comparative
Pure water → comparative liquid 4 →
Less than
Fail

Example 4
pure water → drying
50%

Comparative
Pure water → comparative liquid 5 →
Less than
Fail

Example 5
pure water → drying
50%

Comparative
Pure water → comparative liquid 6 →
Less than
Fail

Example 6
pure water → drying
50%

Comparative
Pure water → comparative liquid 7 →
Less than
Fail

Example 7
pure water → drying
50%

Comparative
Pure water → comparative liquid 8 →
Less than
Fail

Example 8
pure water → drying
50%

Comparative
Pure water → comparative liquid 9 →
Less than
Fail

Example 9
pure water → drying
50%

Comparative
Pure water → comparative liquid 10 →
Less than
Fail

Example 10
pure water → drying
50%

Comparative
Pure water → comparative liquid 11 →
Less than
Fail

Example 11
pure water → drying
50%

Comparative
Pure water → comparative liquid 12 →
Less than
Fail

Example 12
pure water → drying
50%

Comparative
Pure water → comparative liquid 13 →
Less than
Fail

Example 13
pure water → drying
50%

Comparative
Pure water → comparative liquid 14 →
Less than
Fail

Example 14
pure water → drying
50%

Comparative
Pure water → comparative liquid 16 →
Less than
Fail

Example 15
pure water → drying
50%

Comparative
Pure water → comparative liquid 16 →
Less than
Fail

Example 16
pure water → drying
50%

Comparative
Pure water → comparative liquid 17 →
Less than
Fail

Example 17
pure water → drying
50%

*¹Collapse suppression ratio = [(number of cylindrical hollows not collapsed)/(total number of cylindrical hollows)] × 100 (%)

INDUSTRIAL APPLICABILITY

The processing liquid of the present invention may be suitably used for suppressing pattern collapse upon production of a microstructure, such as a semiconductor device and a micromachine (MEMS).

EXPLANATION OF REFERENCE NUMERALS

101: Photoresist; 102: Silicon oxide; 103: Silicon nitride; 104: Silicon substrate; 105: Circular opening; 106: Cylindrical hole; 107: Polysilicon; 108: Cylindrical hollows formed of polysilicon

PROCESSING LIQUID FOR SUPPRESSING PATTERN COLLAPSE OF MICROSTRUCTURE, AND METHOD FOR PRODUCING MICROSTRUCTURE USING SAME

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