JPS63291052A - Positive type photoresist composition - Google Patents

Abstract

PURPOSE:To obtain superior pattern shape and dry etching resistance in an exposure system using far UV as a light source by using a resist compsn. contg. an alkali-soluble resin and a polymer contg. a monomer having a specified structure. CONSTITUTION:A positive type photoresist compsn. prepd. by uniformly dissolving an alkali-soluble resin A and a polymer B contg. >=10mol.% monomer represented by formula I in a solvent in 50:50-98:2 weight ratio of A:B is used. In formula I, R1 is H, 1-4C alkyl, cyano, Cl or Br and R2 is 1-22C haloalkyl. Novolak resin obtd. by condensing a phenol compd. with aldehyde in the presence of an acidic catalyst may be used as the resin A. The resist compsn. ensures superior pattern shape and dry etching resistance in an exposure system using far UV, especially KrF (krypton-fluorine) excimer laser light as a light source.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an alkali-developable radiation-sensitive resist mainly used for pattern formation of semiconductor integrated circuits and photomasks. The present invention relates to a positive photoresist that has excellent ability to form fine patterns.

(Prior art) In semiconductor integrated circuits, 1μn1 is used for high integration.
It has become necessary to form patterns with the following dimensions. In order to form such fine patterns, improvements have been made to exposure apparatuses. Mainly due to improvements in lens performance, the resolution of reduction projection exposure equipment currently in common use is 1 μn1 or less, but it is now 0.6 to 0.5 μm.
It became clear that there was a limit. Moreover, improvements in lenses have the drawback of increasing the numerical aperture, resulting in a reduced depth of focus. However, as the design dimensions of integrated circuits are approaching optical resolution, there is an increasing need for exposure methods that can accurately form patterns even in these areas.

Among the methods for further improving the optical resolution, the most effective method at present is to shorten the wavelength of the exposure light source. This method does not have the problem of reduced depth of focus, which occurs when the numerical aperture of the lens is increased.

In addition, reactive ion etching (R[) using plasma has become mainstream, replacing the wet method of immersing the substrate in an etching solution, as an etching technique for transferring the resist pattern onto the substrate. As a result, the following performance is now required. That is, in R and TE, etching tends to proceed only in the depth direction of the substrate, so if the side walls of the resist pattern are inclined, the pattern dimensions cannot be accurately transferred. Therefore, resists are required to have the ability to form patterns that are more nearly rectangular.

Specifically, krypton-7 (KrF) excimer
- Exposure systems that use lasers as light sources are about to be put into practical use. However, when using this light source, it is not possible to expose over a wide wavelength range like a conventional mercury lamp, and the band width is only a few nm around 248 nm, so the absorbance of the resist at this emission wavelength is It has been found that this has a large effect on pattern formation.

Resist layer K conventionally used for ultra-high pressure mercury lamps
The applicability of this method to rF excimer lasers has been studied, but none has been able to meet the requirements. The problems basically boil down to dry etching resistance and resolution. First, resists that can be subjected to a dry process such as self-developing type have problems in dry etching resistance and resolution. In polystyrene derivative-based resists, the styrene skeleton strongly absorbs light at 248 am, so that only the upper layer of the resist layer is crosslinked, resulting in problems such as peeling off of the pattern during development and strong overhanging of the pattern shape. Further, resists based on polyacrylic acid ester derivatives have low absorption at 248 nm, so they do not have the same problems as polystyrene derivatives, but they have poor dry etching resistance.

Furthermore, in the case of a resist made of an alkali-soluble phenolic resin and a quinonediazide compound, the dry etching resistance is good, but although the phenolic resin has low absorption of 248 nn+, the quinonediazide compound has strong absorption both before and after exposure, so the pattern formed is There was a problem that the cross-sectional shape became pyramid-shaped.

(Problems to be solved by the invention) As a result of intensive research to solve the above-mentioned drawbacks, the present inventors have found that
By using a resist composition consisting of an alkali-soluble resin and a polymer containing a monomer represented by the general formula (I), it is possible to improve the pattern shape in an exposure system using deep ultraviolet light, especially K r F excimer laser, as a light source. It was discovered that the problem of dry etching resistance could be solved, and based on this knowledge, the present invention was completed.

(Means for Solving the Problems) Thus, according to the present invention, a polymer (E) containing at least 10 moles of an alkali-soluble resin (Shu and a monomer represented by general formula (I)) is uniformly added to a solvent. It dissolves,
A positive photoresist composition is provided, characterized in that the weight ratio of A:B is in the range of 50:50 to 98=2.

I CH2-C-C=O(I) body -R2 (R1 in the formula is hydrogen or an alkyl group having 1 to 4 carbon atoms.

Examples of the alkali-soluble resin in the present invention include novolak. This is usually obtained by condensing a phenol compound and an aldehyde under an acidic catalyst. As the phenol compound, phenol, cresol, xylenol, argylphenol such as t-butylphenol, bisphenol, naphthol, etc. may be used alone or in combination. As the aldehyde, formaldehyde is generally used, but other aldehydes may also be used. As the acidic catalyst, inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, etc., or organic acids such as sialic acid, p-toluenesulfonic acid, etc. are used, but the strength of the acidity can be adjusted depending on the reactivity of the phenol and aldehyde used. You need to choose.

As the alkali-soluble resin in the present invention, homopolymers or copolymers of vinylphenol and isopropenylphenol can also be used.

In the case of copolymers, styrene derivatives that do not have phenolic hydroxyl groups are not preferred because they increase absorption at 248 nm, but monomers such as acrylic esters and acrylonitrile may be used as long as they do not lose their alkali solubility. It can be used in copolymerization in any desired proportion. However, these copolymers reduce dry etching resistance, so
It is preferable to use it in a range of less than 50 mol%.

Among the alkali-soluble resins, the number average molecular weight of novolak is 800 to 2000, preferably 90.
A value of 0 to 1600 is preferable. In the RIE process, the temperature of the resist surface increases, so if the molecular weight is too small, the heat resistance will deteriorate and the pattern will flow. Conversely, if the molecular weight is too large, the resist will have good heat resistance but poor resolution. In the case of vinylphenol, isopropenylphenol homopolymers or copolymers, the number average molecular weight is 1.
000 to 50,000 is preferable.

The compound of general formula (I) is an ester of acrylic acid, α-alkyl acrylic acid (e.g. methacrylic acid), α-cyanoacrylic acid, α-chloroacrylic acid, α-bromoacrylic acid, etc., and as an ester residue It has a haloalkyl group. Among these acids, methacrylic acid, α-cyanoacrylic acid, and α-chloroacrylic acid are preferable because they have low absorption at 248 nm and good sensitivity.

The number of carbon atoms in the haloalkyl group of R2 is preferably 1 to 8.Those within this range have good sensitivity and resist heat resistance.

Examples of the halogen in the haloalkyl group include fluorine, chlorine, and bromine. A specific example of R2 is -CH20
F2C'HF21-CH2(CF2)3C! HF2. −
C(CH3)2CF2CHF2. -C(CH3)2(C
F2)3CHF2. -CH2CF2CFHCF3. -C
H(CH3)CF2CFHCF3. -CH(CH2CH
3) CF2CFHCF3. -CH(CH2CF2CHa
) CF2CFHCF3. -C(CH3)2CF2CFH
CF3. -C(CH3)(C2H5)CF2CFHCF
3. -CH2C(CH3)2CF2CFHCF3,
CH2CH20mF2m CFa (" is an integer from 0 to 21), -CH2CH2X, -CH2C
F2. -CH2CX3. -CH2CI(2CH2X
, -CH2CH2CH2X.

-CH2CH2CH22, CH2CH2CX3. -C
H2CH2CH2CH2X.

CH2CH2CH2CH2X (bromine or a mixture thereof), etc.

The monomer of general formula (I) can be used by copolymerizing with other monomers. 0 As a copolymerizable monomer, 1 is α,
Examples include β-unsaturated carboxylic acids and α,β-unsaturated carboxylic acid esters, α,β-unsaturated carboxylic acid halides, acrylonitrile, and acrolein.

Specifically, (meth)acrylic acid alkyl esters,
(meth)acrylic acid-β-hydroxyethyl, (meth)
Acrylic acid chloride, α-chloroacrylic acid alkyl esters, (meth)acrylic acid, (meth)acrylic acid anhydride, α-chloroacrylic acid, maleic anhydride, maleic acid alkyl esters, phthalic acid, phthalic acid alkyl esters crotonic acid, crotonic acid alkyl esters, itaconic acid, itaconic acid alkyl esters, etc. Also, reactive groups such as glycidyl groups are added to the ester residues of the above α,β-unsaturated carboxylic acids. You can also use

The polymer (Bl) has a monomer ratio of general formula (I) of 10 to
It is necessary to have a composition in which the amount is more than 100 moles. Meta- and α-haloacrylic acids and their esters can be used to obtain polymers with a high content of these acids, but the general formula (I
) If the monomer content is less than 10 mol %, sensitivity to deep ultraviolet rays is insufficient. When the proportion of the monomer of general formula (I) is 30 mol or more, sensitivity is high and it is particularly preferable.

The compound of general formula (I) is synthesized from acrylic acid, α-alkyl acrylic acid, α-cyanacrylic acid, α-chloroacrylic acid, α-bromoacrylic acid, and 10genated alcohol. J, D, Lazθrtθ, J for synthesis of halogenated alcohols.

Amer, Chem, Soc,, 77.910 (1
955) etc. Polymer (B) is also produced by a radical polymerization method.

The blending composition of alkali-soluble resin (polymer (Bl) is A:B of 50:50 to 98:2.If the ratio of B exceeds 50%, the dry etching resistance will decrease, and if the ratio of B exceeds 2. If it is less than %, the sensitivity to far ultraviolet rays is insufficient.

Of course, the alkali-soluble resin and the polymer may be used alone or in combination. In addition, a polymer other than the polymer of the present invention can be used in combination with the monomer of the general formula (I) in an amount of 10 moles or more, but the point is that using the polymer of the present invention alone has better resolution. It is preferable.

The resist composition of the present invention is obtained by uniformly dissolving a solid substance in an organic solvent. Examples of solvents include alcohols such as gropanol and butanol, ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, acetate esters such as ethyl acetate, butyl acetate, and inamyl acetate, cyclic ethers such as tetrahydrofuran and dioxane, butyl cellosolve, and ethyl cellosolve. , butyl cellosolve, and further examples include ethyl cellosolve acetate, butyl cellosolve acetate, γ-butyrolactone, and the like. Further, aromatic hydrocarbons such as xylene and toluene may be mixed. The content of solids is usually about 10 to 40 parts by weight.

The resist composition of the present invention may contain additives such as surfactants, dyes, and sensitizers.

After the resist composition of the present invention is spin-coated onto a substrate,
A resist film of about 1 μm is formed by heat treatment at around 0° C., and then exposed and developed to form a pattern. The composition of the present invention can be used as a single-layer resist by coating it on a semiconductor substrate on which a pattern is to be formed, or can be used as a two-layer or six-layer resist by coating another resist as an underlying layer. can also be used. Exposure is normally preferably carried out using a deep ultraviolet exposure device such as a contact aligner, projection aligner, or stepper, but electron beams, X-rays, ion beams, etc. can also be used. Development is preferably carried out by immersing the exposed substrate in a developer for about 1 minute, or by leaving the developer still on the substrate. As the developer, inorganic alkalis such as sodium hydroxide, potassium hydroxide, and sodium metasilicate, and organic alkalis such as tetramethylammonium hydroxide and choline are used. Moreover, amines, alcohols, ethers, surfactants, etc. can also be used in combination.

(Effects of the Invention) Thus, according to the present invention, a positive photoresist composition is provided which has excellent pattern shape and dry etching resistance in an exposure system using deep ultraviolet light, particularly a KrF excimer laser, as a light source.

The present invention will be explained in more detail with reference to Examples below. Note that parts and sections in Examples and Comparative Examples are based on weight unless otherwise specified.

Example 1 Monomer of formula (II) CH2=CH1(■) 0-C-0-CH2CH2(CF2)IICF3107
r (0,15 mol) and methyl methacrylate 85f (0,
85 mol) and azobisisobutyronidolyl (AIBN
) 0.669 (4.0 mmol) and benzene 642y were placed in a flask, dissolved at room temperature, nitrogen was blown into the flask for 60 minutes, and then the temperature in the flask was raised to 80° C. under a nitrogen stream and polymerization was carried out with stirring for 5 hours. 5 while stirring the reactants! The precipitated polymer was filtered and dried under vacuum to obtain a 97y polymer. G.P.
The polystyrene equivalent weight average molecular weight of C is 11,000
Met. This polymer has a number average molecular weight of 4.51 and 1400.
50f of cresol formaldehyde resin (ff+-cresol/p-cresol=6/d) was dissolved in cellosolve acetate 147y. This solution was filtered through a 0.2 μm Teflon membrane filter to obtain a resist composition.

This resist composition was applied to a silicon mirror wafer using a spin coulter and prebaked in an air oven at 120°C for 60 minutes to give a resist film thickness of 1.2 μm. A pattern was exposed using a krypton-fluorine gas system under the following conditions.

The exposure energy per pulse was 20mJ/am''.0.05μm from 1.0μ to 0.45μ〃1
Contact exposure was carried out through a photomask having a 1:1 line and space pattern in increments. 5 μn at the same time
A 1 line and ψ space pattern was also exposed. This wafer was developed at room temperature with a 2.4% tetramethylammonium hydroxide aqueous solution, and the following evaluations were performed.

Sensitivity represents the minimum exposure energy required to pass through a 5 μn+ pattern, and the minimum resolution line width is determined by increasing the exposure energy by 20 mJ/c and the exposure time by 400 m from the exposure energy corresponding to the sensitivity.
The line width of the narrowest one-to-one line-and-space pattern that can be resolved when increasing the line width to J/am”.The pattern shape is determined by observing the fractured surface of the pattern with the minimum resolution line width. And, rectangular ones are 01 trapezoidal ones are ×
And so. A scanning electron microscope was used for these evaluations.

1.2μ on an oxide film silicon substrate with a spin coater? +
A resist film of No. 1 was formed, a 5 μm line and space pattern was drawn, and the substrate was etched. Electrode spacing was 3511 m using an EM-451T dry etching device manufactured by Nichiden Anelva.

13.75MHz, 500W, CF4/H2=25/
Tri-etching resistance was evaluated under conditions of 8 (volume ratio). The dry etching resistance was expressed as a relative value with the etching rate of the resist of Comparative Example 1 being 1.0.

The smaller the value, the better the dry etching resistance.

Sensitivity: 1120 mJ/cm”, minimum resolution line width: 0
．． 45 ttm, the pattern shape was ○, and the dry etching resistance was 1.1.

Example 2 The cresol formaldehyde resin in Example 1 was replaced with polyvinylphenol 41.1F having a number average molecular weight of 8900 and the same polymer 5.・62
The evaluation was carried out in the same manner as in Example 1, except that the sample was dissolved in cellosolve acetate 1261.

Sensitivity is 80 mJ/c, minimum resolution line width is 0.45 μ
1. Pattern shape is ○, dry etching resistance is 1.2
Met.

Example 3 Hexafluorobutyl methacrylate (CH2=C(CH
3)Coo-CIJ2CH2CHFCF3) 125
f (0.5 mol) and methyl α-chloroacrylate 60
．． 3f (0,50 mol) and azobisisobutyronitrile 0.82 f/ (5,0 mmol) and benzene 58
31 was placed in a flask and polymerized in the same manner as in Example 1 to obtain Polymer 1212 of the present invention. The weight average molecular weight in terms of polystyrene determined by GPC was 13,000. This polymer 121 and the same cresol-formaldehyde resin 601 used in Example 1 were dissolved in cellosolve acetate 1852 and evaluated in the same manner as in Example 1.

Sensitivity is 120 mJ/cm”, minimum resolution line width is 0.45
μm, pattern shape is ○, dry etching resistance is 1.
It was 0.

Example 4 Hexafluorobutyl α-chloroacrylate 162.3
f (0.60 mol) and methyl methacrylate 40S' (0
, 40 mol) and azobisisobutyronenitrile 0.65
6 f (4,0 mmol) and Penzen 675 f! was placed in a flask and polymerized in the same manner as in Example 1 to obtain polymer 1292. The weight average molecular weight in terms of polystyrene by GPC was 9900. This polymer 5.5f and the cresol formaldehyde resin 60 used in Example 1
1 was dissolved in 180 g of cellosolve acetate and evaluated in the same manner as in Example 1.

Sensitivity is 90mJ/am", minimum resolution line width td 0.45
μnr, pattern shape was ○, and dry etching resistance was 1.1.

Example 5 α-cyanoacrylic acid-2,2,2-) IJ Chloroethyl 130.09 (0.60 mol) and acrylic acid 7
, 2 (0.10 mol) and β-hydroxyethyl acrylate34. El (0.30 mol) and azobisisobutyronenitrile 0.656? (4, Ommol) and benzene 573v were placed in a flask and polymerized in the same manner as in Example 1 to obtain polymer 129y. The weight average molecular weight in terms of polystyrene determined by GPC was 12,000. This polymer 242 and the cresol-formaldehyde resin 607 used in Example 1 were dissolved in cellosolve acetate 239y and evaluated in the same manner as in Example 1.

Sensitivity is 100 mJ/cm”, minimum resolution line width is 0.45
μm, pattern shape is ○, dry etching resistance is 1.
It was 2.

Comparative Example 1 2, 3.4-) IJ Hydroxybenzophenone 1.
Esterified product 267 of 0 mol and 1.8 mol of O-naphthoquinonediazide-5-sulfonic acid chloride and Example 1
The cresol-formaldehyde resin 962 used in was dissolved in cellosolve acetate 2927 and filtered through a 0.2 μm membrane filter to prepare a positive photoresist.
Evaluation was made in the same manner as in Example 1.

Sensitivity is 150 mJ/Cm'', minimum resolution line width is 0.55
μm, pattern shape is ×, dry etching resistance is 1.
It was 0.

Comparative Example 2 Evaluation was carried out in the same manner as in Example 1 except that polymethyl methacrylate having a polystyrene equivalent molecular weight of 40,000 was used as the resist.

Sensitivity is 280 mJ/cm", minimum resolution line width is 0.45
μm1 pattern shape is 0, dry etching resistance is 4.
It was 6.

It can be seen that the composition of the present invention has high resolution, good pattern shape, and excellent dry etching resistance.

Claims (1)

[Claims] An alkali-soluble resin (A) and a polymer (B) containing at least 10 mol% of a monomer represented by general formula (I)
is uniformly dissolved in a solvent, and the weight ratio of A:B is 5.
A positive photoresist composition characterized in that the ratio is in the range of 0:50 to 98:2. CH_2=C-C=O(I) (R_1 in the formula is hydrogen, an alkyl group having 1 to 4 carbon atoms. It represents either a cyano group, chlorine or bromine, and R_2 represents a haloalkyl group having 1 to 22 carbon atoms. )