JPH04159552A - Radiation sensitive polymer and pattern forming method using this polymer - Google Patents

Abstract

PURPOSE:To improve sensitivity and resolution by using a specified radiation sensitive polymer. CONSTITUTION:The radiation sensitive polymer expressed by formula I is used and a radiation sensitive polymer soln. essentially consisting of the radiation sensitive polymer is applied on a substrate to form a thin film and thereafter, the film is irradiated with radiation and the reactive parts are selectively developed by a wet developing method or dry developing method, by which patterns are formed. In the formula I, R<1> denotes a condensed arom. ring consisting of 2 to 5 pieces of benzene rings which may be substd. with at least one kind among a cyano group, alkyl group, alkoxy group, halogen atom, halogenated alkyl group, and sulfonic acid group; R<2> denotes 1 to 10C alkylene group; X denotes at least one kind among a sulfonate group, oxygen atom, carboxyester group, and sulfone amide group; (n) denotes >=10 integer. The patterning with the high sensitivity and high resolution and at a high aspect ratio is executed in this way.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is directed to improving dry etching resistance in a semiconductor lithography process using a radiation source (ultraviolet rays, deep ultraviolet rays, electron beams, high energy rays such as X-rays). Excellent in
Providing a resist material with high sensitivity and capable of ultra-fine processing.
This invention relates to a radiation-sensitive polymer having an aromatic ring and a pattern forming method using the polymer.

[Prior Art/Problems to be Solved by the Invention] With the spread of large computers and high-performance small computers, there is a need for faster calculation functions, increased memory functions, and miniaturization.

In order to improve these functions, it is necessary to increase the integration, increase the capacity, and reduce the size of the semiconductors that support these functions. Due to the reduction in the area of semiconductor chips, it has become difficult to achieve high integration and form large-capacity memories, and the current challenge is how to draw fine patterns.

Therefore, in order to draw fine patterns, a pattern transfer method using multilayer film formation is being considered.

This method involves forming a thick planarization layer on a semiconductor substrate, forming several thin film layers including a resist layer on top of it, and then sequentially transferring the pattern on the upper layer to the lower layer using a method such as dry etching. Usually, a three-layer system (see Fig. 1) is the most popular method. A three-layer system is a lower resist layer (4) having halogen gas plasma resistance formed on a flattening layer (5) formed on a semiconductor substrate (6), and a lower resist layer (4) having oxygen plasma etching resistance formed thereon. An intermediate layer resist (3) is formed thereon, and an upper layer resist (2) (not resistant to dry etching) is formed thereon.The upper layer resist is formed by irradiating radiation through a mask (1). The pattern (2) is transferred to the intermediate layer resist (3) by dry etching using a gas containing fluorine, and the pattern of the intermediate layer resist (3) is transferred to the lower layer resist (4) by oxygen plasma etching.
In this method, the pattern of the lower resist (4) is further transferred to the flattening layer (5) by plasma etching using a gas containing fluorine or the like. However, in this method, it is necessary to perform dry etching several times in order to transfer the pattern, resulting in a problem that the number of processes is large and complicated.

Therefore, a two-layer resist process has been developed in which a resist layer (7) having dry etching resistance is formed on a flattening layer (5) as shown in FIG.

As this two-layer resist process, a process using chloromethylated polydiphenylsiloxane, chloromethylated polyphenylmethylsilane, etc. as a resist having dry etching resistance is being considered. However, since it is difficult to control the reaction during the chloromethylation reaction in these resists, the molecular weight distribution widens due to a decrease in molecular weight, resulting in a decrease in resolution. Another problem is that quality control is difficult because characteristics tend to vary between synthetic lots.

By the way, organic resists with excellent film-forming properties, photosensitivity to specific wavelengths, and developability include polymethyl methacrylate (hereinafter referred to as PMMA), polyglycidyl methacrylate, polyhydroxystyrene, polyethersulfone, novolac resin, etc. A two-component system using a polymer as a binder and an appropriate photosensitizer added thereto, or a three-component system in which an appropriate acid generator is added to the two-component system to further cause chemical amplification. The system is being researched and developed.

However, organic resists have poor resistance to dry etching, which is one of the microfabrication processes. For example, PMMA, which has been studied for the earliest time as a photosensitive resist, is characterized by high resolution and low cost, but its dry etching resistance is poor and its sensitivity is low. Therefore, it has been considered to add halogen-substituted benzene to the side chain to improve the dry etching resistance (JP-A-55-18638, JP-A-60-254041, and JP-A-63-23).
4006), this also has low sensitivity and low resolution. In recent years, resists having benzene rings in their polymers, such as polyhydroxystyrene, have been studied as resists for microfabrication using high-energy rays such as radiation as a light source (see JP-A-60-4413).
It has not yet been put into practical use.

[Means for Solving the Problems] The present inventors have conducted intensive research to solve the above-mentioned problems, and as a result, have completed the present invention.

That is, the present invention provides general formula (1); general formula (1): (wherein, R1 is a cyano group, an alkyl group, an alkoxy group,
A fused aromatic ring consisting of 2 to 5 benzene rings optionally substituted with at least one of a halogen atom, a halogenated alkyl group, and a sulfonic acid group, R2 has 1 to 1 carbon atoms.
10 alkylene groups; A radiation-sensitive polymer solution containing the radiation-sensitive polymer as a main component is applied to form a thin film, and then radiation is irradiated and the reaction area is selectively developed by a wet development method or a dry development method. The present invention relates to a pattern forming method characterized by forming a pattern.

[Function] The radiation-sensitive polymer of the present invention contains many aromatic rings in its main skeleton, so it absorbs a large amount of radiation, and by using this, it can be used to produce butter with high sensitivity, high resolution, and high aspect ratio. It is possible to carry out training. In addition, the polymer of the present invention has better dry etching resistance than novolak resists due to the resonance stabilization in the condensed aromatic ring, and by using this, it is possible to form patterns by etching the underlying layer such as an inorganic oxide film. Transfer can be easily performed. Furthermore, a thin film can be formed by a simple coating method.

[Example] The radiation-sensitive polymer of the present invention is a polymer represented by general formula (1).

R1 in the general formula (+) is a cyano group; a methyl group, an ethyl group, an isopropyl group, an n-propyl group, a t-butyl group,
Alkyl groups such as isobutyl group and n-butyl group; alkoxy groups such as methoxy group, ethoxy group, propoxy group, butoxy group, and pentoxy group; halogen atoms such as fluorine atom, chlorine atom, bromine atom, and iodine atom; Benzene ring 2/- which may be substituted with one or more groups selected from a halogenated alkyl group such as a fluoromethyl group, a trichloromethyl group, and a tribromomethyl group, and a sulfonic acid group
It is a fused aromatic ring consisting of five rings. By bonding such a substituent to the condensed aromatic ring, solubility in organic solvents is improved, and a simple film forming method such as a spin coding method can be applied. Note that the alkyl group is preferably an alkyl group having 5 or less carbon atoms. If the number of carbon atoms is 6 or more, the glass transition point of the polymer decreases, and as a result, it becomes difficult to change the tack-free property after film formation (the film becomes sticky).

If R1 is not a fused aromatic ring but a Hensen ring or one ring, the sensitivity to radiation is insufficient, and 6
If the number is more than 1, the molecule itself becomes loose and steric hindrance occurs, making it difficult for the polymerization reaction to obtain the polymer represented by the general formula (1) to proceed.

R2 in the general formula (+) is an alkylene group having 1 to 10 carbon atoms, such as methylene, ethylene, propylene, butene, pentene, hexene, pentene, octene, nonene, and dekene. If the number of carbon atoms in R2 exceeds 10, the glass transition point of the molecule will be lowered, and the dry etching resistance will also be lowered.

X in general formula (1) represents at least one of a sulfonic acid ester group, an oxygen atom, a carboxy ester group, and a sulfonamide group. Due to the presence of X, radiation irradiation causes collapse or structural deterioration, and a positive pattern is formed by development.

Further, the number of repetitions (n) of intermolecular polycondensation is 10 or more, preferably 10-50, and more preferably 10-3o from the viewpoint of tri-etching resistance. n
If it is less than 10, the film forming property is poor and a uniform thin film cannot be obtained. Moreover, when it exceeds 50, the crystallinity of the polymer tends to increase and the solubility in a solution tends to decrease. The average molecular weight of the polymer is 2000 to 30,000, and even 5000 to 20
,000 is preferred.

Specific examples of the polymer of the present invention include poly(2
-ethyl-6-nafdosulfonate), poly(1-carboxylic acid-2-isopropyl-6-nafdosulfonate)
, poly(1-hydroxy-2-ethyl-7-anthrasulfonate), poly(1-hydroxy-2-ethyl-
6-anthrasulfonate), poly(1-carboxylic acid-
2-isopropyl-6-anthrasulfonate), poly(1-hydroxy-2-ethyl-8-naphthasesulfonate), poly(1-hydroxy-2-ethyl-9-naphthasesulfonate), poly(l-carboxylic acid) -2-
isopropyl-9-naphthasesulfonate), poly(j
-hydroxy-2-ethyl-7-pyrosulfonate),
Poly(1-hydroxy-2-ethyl-6-pyrosulfonate), poly(1-hydroxy-2-ethyl-8-pyrosulfonate), poly(1-carboxylic acid-2-isopropyl-8-pyrosulfonate), poly (1-carboxylic acid-2-isopropyl-9-pyrosulfonate) sulfonic acid ester polymer.

Poly(2-ethyl-6-nafdoether), poly(1-
carboxylic acid-2-isopropyl-6-nafdoether)
, poly (1-hydroxy-2-ethyl-7-anthraether), poly (1-hydroxy-2-ethyl-6
-anthraether), poly(1-carboxylic acid-2-isopropyl-6-anthraether), poly(1-hydroxy-2-ethyl-8-naphthaceether), poly(1-hydroxy-2-ethyl-9 -naphthacetether), poly(1-carboxylic acid-2-isopropyl-9-naphtacetether), poly(1-hydroxy-2-ethyl to 7-biroether), poly(1-hydroxy-2-ethyl-6 -pyroether), poly(1-hydroxy-
2-ethyl-8-pyroether), poly(1-carphonic acid-2-isopropyl-8-pyroether), poly
Ether polymer with (1-carboxylic acid-2-isopropyl-9-pyroether) ), poly(1-hydroquine-2-,
ethyl-7-anthracarboxyester), poly(
1-hydroxy-2-ethyl-6-anthracarboxyester), poly(1-carboxylic acid-2-isopropyl-6-anthracarboxyester), poly(1-hydroquine-2-ethyl-8-naphthacecarboxyester) , poly(hydroxy-2-ethyl-9-naphthacecarboxyester), poly(1-carphonic acid-2-isopropyl-9-naphthacetate carboxyester), poly(
1-hydroquine-2-ethyl-7-pyrocarboxyester), poly(1-hydroxy-2-ethyl-6-pyrocarboxyester), poly(l-hydroxy-2-ethyl-8-pyrocarboxyester), poly (I-carboxylic acid-2-isopropyl-8-pyrocarboxyester), poly(1-carboxylic acid-2-isopropyl-9-
Carboxyester polymers such as poly(1-aminoethyl-6-naphthosulfonamide), poly(1-carboxylic acid-2-isopropyl-
8-naphthosulfonamide), poly (1-hydroxy-2-ethyl-7-anthrasulfonamide), poly
(1-hydroxy-2-ethyl-6-anthrasulfonamide), poly(l-carboxylic acid-2-isopropyl-
6-anthrasulfonamide), poly(1-hydroxy-2-ethyl-8-naphthasesulfonamide), poly(
1-hydroxy-2-ethyl-9-naphthasesulfonamide), poly(1-carboxylic acid-2-isopropyl-9)
-naphthasesulfonamide), poly(1-hydroxy-
2-ethyl-7-pyrosulfonamide), poly(1-hydroxy-2-ethyl-6-pyrosulfonamide), poly(I-hydroxy-2-ethyl-8-pyrosulfonamide), poly(1-carbon acid-2-isopropyl-8
-pyrosulfonamide), poly(I-carboxylic acid-2-
Examples include sulfonamide F-based polymers such as isopropyl-9-pyrosulfonamide).

There are no particular limitations on the method for producing the polymer, and it can be synthesized by various methods.
I) ■2 (wherein R, R are the same as above, R3 represents a carboxylic acid group, a halogenated carbonic acid group, a sulfonic acid group or a halokenated sulfonic acid group), a compound represented by the general formula (Ill) : % Formula % (In the formula, R, 17, I? are the same as above) or general formula (IV): ) (0- R2- R1-Y (IV)
(In the formula, I?, I? are the same as above, Y is a chlorine atom,
(represents a halogen atom such as a bromine or iodine atom)
Examples include a method of condensation polymerization of a compound represented by

Since the polymer of the present invention has excellent resistance to both oxygen dry etching and halocarbon gas dry etching, it can also be used as a single layer resist.

Next, a pattern forming method using the above polymer will be explained.

In the pattern forming method of the present invention, a radiation-sensitive polymer solution (resist solution) containing the above polymer as a main component or a simple method such as a spin code method is applied onto a semiconductor substrate such as Si, and a film is A thin film with a thickness of about 0.2 to 10 μm is formed.

Specific examples of solvents used to prepare the resist solution include esters such as methyl cellosolve acetate, ethyl cellosolve acetate, and butyric acid esters, and ketones such as acetone, methyl ethyl ketone, 2-hexanone, methyl isobutyl ketone, and 2-heptanone. , ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether, halogenated hydrocarbons such as chlorohensen and bromobenzene, hydrocarbon solvents such as toluene, xylene, ethylbenzene, and butylhensen, and organic solvents such as dimethylformamide. Can be used as a solvent.

The concentration of radiation-sensitive polymer in the resist solution is between 5 and 25
% (weight %, hereinafter the same).

Adhesion improvers, acid generators, alkali generators, and other additives are added to the resist solution as necessary. The alkali generator may be added in an amount of 3 to 8 mol % based on the polymer.

Next, the thin film is irradiated with high-energy rays such as ultraviolet rays, deep ultraviolet rays, electron beams, and X-rays, and the reaction areas are selectively developed by wet development or dry development to form a desired pattern.

The wet development method is not particularly limited, and any conventional method may be used, such as dip development, spray development, paddle development, etc., in which the thin film is immersed in a developer after being irradiated with high-energy rays.

Specific examples of the developer used in the wet development method include alkaline solutions such as trimethylammonium hydroxide that are soluble in the reaction part; acidic solutions such as dilute hydrochloric acid and dilute sulfuric acid; dichloromethane, 1,1-dichloroethane;
1.2-dichloroethane, 1.1.1-trichloroethane, 1,1.2-1-dichloroethane, 1,1,1.2
-tetrachloroethane, 1,1,2.2-tetrachloroethane, methanol, ethanol, 2-propanol,
Organics such as 2-butanol, isobutyl alcohol, 3-methyl-butanol, benzyl alcohol, cyclohexanol, hexane, heptane, toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, isobutyl acetate, isoamyl acetate Examples include solvents. These solvents are
They may be used alone or in combination of two or more, if necessary.

There are no particular limitations on the dry development method, and the usual methods include a development method that uses ablation by high-energy ray irradiation, and a method that develops the exposed area by dry etching after high-energy ray irradiation (pattern baking is done later). The following method can be used.

If the resist film after forming the pattern as described above is used as a mask, the pattern can be transferred to the underlying material by dry etching.

Next, the present invention will be explained based on Examples, but the present invention is not limited to these Examples.

Example] 2-Hydroxyethyl-
A solution 101 of 10 mmol of 6-naphthosulfonic acid in hexamethylphosphoramide was gradually added dropwise. After refluxing for about 2 hours without stirring, 10 mmol of aluminum chloride was added and the mixture was refluxed for an additional 2-3 hours. After cooling, it was washed with water, then washed with a 5% aqueous sodium hydroxide solution and water, filtered, and purified by vacuum drying the solid to obtain poly(2-ethyl-6-nafdosulfonate). (yield 80%, My: 20,000, IR (cm
-1): 1348 (νasSo),
1.160 (ν So ), 80
5 (0) C'112) ).

2 s2 Example 2 The polymer obtained in Example 1 was dissolved in ethyl cellosolve acetate to make a 15% solution, applied to a silicon wafer by a spin code method, and prebaked at 100°C for 30 minutes in a conventional oven. The film thickness is about 10
A thin film of μm was formed. Electron beam (25KeV)
, 5 nA), and then developed with a 2.38% trimethylammonium hydroxide (TMAI+) aqueous solution at room temperature for 1 minute to form a resist pattern. Sensitivity is 2μC/Cm2, contrast is 3
, 5, the resolution was 0.25 μm.

Examples 3 to 14 Using the sulfonic acid ester polymers shown in Table 1 obtained by the same reaction as in Example 1, patterns were formed and evaluated in the same manner as in Example 2.

The results are shown in Table 1.

Example 15 0.2 mol of 2-chloroethyl-6-naphthol and 0.2 mol of sodium hydroxide were added to ether 501 and reacted at room temperature for 2 to 3 hours. After the reaction was completed, the mixture was washed with dilute hydrochloric acid and water in that order, and after filtering and separation, the solid was dried under vacuum heating at 60°C to obtain poly(2-ethyl-6-nafdoether) (yield 100%, My: 10,500 ,IR(em-1)
:1124 (ν C-0), 1026 (ν C
-0), 805 (ωaS
5CH2)).

Example 16 The polymer obtained in Example 15 was dissolved in methyl ethyl ketone to make a 15% solution, coated on a silicon wafer by a spin-coating method, and heated in a conventional oven.
A thin film having a thickness of about 1.0 μm was formed by prebaking at 90° C. for 30 minutes. Electron beam (25KeV,
After exposure (5 nA), a pattern was formed by developing with a 2.38% THAN aqueous solution. Sensitivity is 2.5μC
/Cm2, contrast is 30, resolution is 0.25μm
Met.

Examples 17 to 28 Using the ether polymers shown in Table 1 obtained by the same reaction as in Example 15, patterns were formed and evaluated in the same manner as in Example 16. The results are shown in Table 1.

Example 29 Boron trifluoride Nieteller 1.5 in ethanol 501
After dissolving mmol of 2-hydroxyethyl-6
-35 mmol of naphthocarboxylic acid were added and the mixture was refluxed overnight. After cooling, water j001 was added to precipitate the polymer, which was washed with a saturated aqueous sodium chloride solution, then water, and washed and purified with methanol.
Hydroxyethyl-0-naphthocarboxyester) was obtained (yield 80%, Mw: 18,000, IR (cm
'): 3510 (νOH), 1080 (ν
C-0), 1741 (ν C-0
), 1253 (ν asaS
5C-O) ).

Example 30 The polymer obtained in Example 29 was dissolved in ethyl cellosolve acetate to make a 15% solution, applied to a silicon wafer by a spin code method, and prebaked at 100°C for 30 minutes in a conventional oven. The film thickness is approximately 1.
A thin film of 0 μm was formed. The thin film was coated with an electron beam (25Ke
V, 5 nA) After exposure, 2.38%T
A pattern was formed by developing with M A I+ aqueous solution. Sensitivity is 185μClCl112, contrast is 3.8,
The resolution was 0.25 μm.

Examples 31 to 42 Using a carboxyester polymer obtained by the same reaction as in Example 29, patterns were formed and evaluated in the same manner as in Example 30. The results are shown in Table 1.

Example 43 10 mmol of cyclohexylcarbodiimide was added to 100 ml of dry dioxane, and further 2-aminoethyl-
8 mmol of 6-nafdosulfonic acid was added and the mixture was refluxed for 3 hours. After cooling, the crystals were filtered, the filtrate was poured into water, and the precipitated polymer was thoroughly washed with water to obtain poly(2-ethyl-6-nafdosulfonamide) (yield: 60% My: 12,
500, IR(el"-'): lH2(ν So
N), 1.14111 (ν8SO,,N)
, 326B (νas 2 NH), 805 (ωC112)).

Example 44 The polymer obtained in Example 43 was dissolved in dimethylformamide to make a 15% solution, coated on a silicon wafer by a spin code method, and incubated in a conventional oven for 15%.
Pre-bake at 30℃ for 30 minutes.

A thin film having a thickness of about 1.0 μm was formed. After exposing the thin film to an electron beam (25 KeV, 5 nA),
．． A pattern was formed by developing with 38% TMAI+aqueous solution.

Sensitivity is 1.2μC/CII+2, contrast is 38,
The resolution was 0.25 μm.

Examples 45 to 56 Using the sulfonamide polymer obtained by the same reaction as in Example 43, patterns were formed and evaluated in the same manner as in Example 44. The results are shown in Table 1.

Examples 57 to 108 The resistance of the resist patterns formed in Examples 1 to 56 to CF4 gas and oxygen gas trietching was investigated. C.F.
4 In reactive ion etching, the gas flow rate is 53CC.
M, temperature 10℃, system pressure 10Pa, gas flow rate 53CCM in oxygen reactive ion etching, temperature 10℃
, CF4 casting etching and oxygen gas dry etching were carried out under conditions of an internal system pressure of 13 Pa. The results are shown in Table 2.

Comparative Example 1 A 10% chlorobenzene polymer solution of polymethyl methacrylate was applied onto an S1 wafer by a spin code method, and prebaked for 30 minutes in a conventional oven at 125° C. to form a 1.0 μm thick thin film. The thin film was exposed to electron beam (25 KeV, 5n^). The sensitivity was 100 μC/Cl11, the contrast was 3.0, and the resolution was 0.25 μm.

Furthermore, the polymer film has a dry etching resistance of 340 persons/min, respectively, of CF4 gas and oxygen gas.
, 1890 people/min.

[Effects of the Invention] The polymer of the present invention is a radiation-sensitive polymer having excellent dry etching resistance, high sensitivity, and high resolution. According to the pattern forming method of the present invention using this, an ultra-fine pattern with a high aspect ratio can be easily formed, and an ultra-L
It is also possible to follow the trend toward higher integration with SI.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining a three-layer resist process, and FIG. 2 is a cross-sectional view for explaining a two-layer resist process. (Symbols in drawings) (1): Mask (2) Second upper layer resist (3): Intermediate layer resist (4): Lower layer resist (5): Flattening layer (6). Semiconductor substrate (7): Resist layer with tri-etching resistance 7I-1 Figure 2 Radiation Radiation 1 Mask 5, flattening layer

Claims (2)

[Claims] (1) General formula (I): ■R^2-R^1-X■_n(I) (wherein, R^1 is a cyano group, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, or a sulfone A fused aromatic ring consisting of 2 to 5 benzene rings optionally substituted with at least one of the acid groups, R^2 is an alkylene group having 1 to 10 carbon atoms, X is a sulfonic acid ester group,
A radiation-sensitive polymer represented by at least one of an oxygen atom, a carboxyester group, and a sulfonamide group, where n is an integer of 10 or more. (2) A radiation-sensitive polymer solution containing the radiation-sensitive polymer according to claim 1 as a main component is applied onto a substrate to form a thin film, and then radiation is irradiated and the reaction area is developed using a wet development method or a dry method. A pattern forming method characterized by forming a pattern by selectively developing using a developing method.