JPS63234249A - Positive type photoresist composition - Google Patents

Abstract

PURPOSE:To improve the fine pattern forming capacity and heat resistance of a photoresist by using specified alkali-soluble novolak resin. CONSTITUTION:The titled compsn. consists of alkali-soluble novolak resin and a sensitizer. The novolak resin is a product produced by condensing phenol components with formaldehyde. The phenol components are m-cresol, p-cresol and xylenol and the amt. of 3,5-xylenol is >=10mol.% of the total amt. of the phenol components. A quinoneazido compd. may be used as the sensitizer. When the compsn. is used, a fine resist pattern can be formed with high dimensional accuracy without narrowing the line width and the heat resistance of the resist is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an alkali-developable radiation-sensitive resist mainly used for patterning semiconductor integrated circuits, photomasks, etc. This invention relates to a positive photoresist with excellent properties.

Prior Art Conventionally, rn-cresol, p-cresol and 2,5-
It is known to use a condensation product of a co-condensed component of xylenol and formaldehyde as an alkali-soluble novolac resin (Japanese Patent Laid-Open No. 186741/1983). However, according to our knowledge, novolac resins using 2°5-xylenol as a co-condensation component have the following drawbacks.

2.5-xylenol has low cocondensation reactivity, so
In order to co-condense an amount such that the effect of 2,5-xylenol is sufficiently exhibited on the properties of the resulting resin, the amount of highly reactive m-cresol must be increased. However, since both m-cresol and 2,5-xylenol are components that increase the alkali solubility of the resulting resin, a problem arises in that the line width of the developed pattern becomes narrower. Therefore, it is possible to increase the amount of p-cresol, which is a component that reduces the alkali solubility of the resulting resin.
- Since cresol has low cocondensation reactivity, there is a problem in that the molecular weight of the resulting resin decreases and the heat resistance of the resist decreases. In addition, the charging molar ratio of formaldehyde (F) and phenolic compound (P), F/P ratio, was 1.0.
It is known that the molecular weight can be increased by increasing the molecular weight to a value close to However, when the F/P ratio is increased, gels tend to form, making it extremely difficult to control the molecular weight. As described above, it is difficult to balance the characteristics of the resin with manufacturing problems, and no material has been obtained that satisfies pattern forming ability and heat resistance at the same time.

Problems to be Solved by the Invention As a result of intensive research in order to solve the above-mentioned drawbacks, the present inventors have found that at least 10 mol% of m-cresol and p-cresol are used as co-condensation components of an alkali-soluble novolac resin.
, 5-xylenol was used to solve the problems of pattern cohesion and heat resistance at the same time, and the present invention was completed.

Means for Solving the Problems Thus, according to the present invention, in a composition comprising an alkali-soluble novolak resin and a photosensitizer, the alkali-soluble novolak resin comprises m-cresol, p-cresol and xylenol, and A positive-working photoresist composition is provided, characterized in that it is a condensation product of a phenol component and formaldehyde, in which 3,5-xylenol is at least 10 mol % of the total phenol component.

The composition of the phenolic component constituting the alkali-soluble novolac resin in the present invention is usually 20 to 80 mol% of m-cresol and 10 to 50 mol% of p-cresol.
, xylenol is 10 to 60 mol%. However, 3゜5-xylenol is 10 mol% of the total phenolic components.
Must be above. Also, 3 in xylenol,
5-xylenol is usually 50% or more. The content of 3,5-xylenol in xylenol is preferably 60% or more, more preferably 80% or more, in order to suppress fluctuations in the condensation reaction rate due to other isomers and fluctuations in the alkali dissolution rate of the resulting resin. However, although it is economically disadvantageous, there is no problem in using 3,5-xylenol and other specific isomers mixed at a certain ratio. If the amount of xylenol is less than 10 mol %, the characteristic of good resolution is lost, and if it exceeds 60 mol %, the alkali solubility of the resin becomes too low, making it unsuitable for use in a resist for alkaline development. m-cresol and p-cresol can be selected so that the alkali solubility of the resulting resin is appropriate depending on the amount of xylenol. However, if the amount of p-cresol increases, the alkali solubility of the resulting resin becomes too low, so the amount is preferably 50 mol% or less. Especially m-cresol 3
0-50 mol%, p-cresol 20-40 mol%, xylenol 20-40 mol%, 3,
80% or more of 5-xylenol is preferred. In this range, 3,5-xylenol exhibits excellent resolution,
The alkali solubility of the produced resin is also appropriate, and F/P
Since the molecular weight can be controlled without increasing the ratio, there is no problem of gel formation during the manufacturing process, and a resist resin with good heat resistance can be obtained.

As formaldehyde, formalin and paraformaldehyde are used.

Examples of catalysts for the condensation reaction of alkali-soluble novolacs include sulfuric acid, hydrochloric acid, phosphoric acid, and oxalic acid.

The number average molecular weight of the alkali-soluble novolac resin is from 800 to 1,800', preferably from 900 to 1,300. If the molecular weight is less than 800, heat resistance is poor;
When it is larger than 1800, heat resistance is good, but resolution becomes poor. The phenolic compound remaining after the condensation reaction is reduced to 3% or less, preferably 2%, using a method such as vacuum distillation.
% or less. If there is a large amount of residual cresol, the heat resistance of the resist will deteriorate and the resolution will deteriorate.

As the photosensitizer in the composition of the present invention, a photosensitizer for a positive type photoresist is used.

Typical examples are quinonediazide compounds such as orthobenzoquinonediazide compounds and orthonaphthoquinonediazide compounds, both of which can be blended as esters with compounds having free hydroxyl groups to improve compatibility with novolac resins. Of the orthobensoquinonediazide compounds and orthonaphthoquinonediazide compounds, the latter is more useful because it has superior storage stability and thermal stability. More specifically, hydroxybenzophenono or its derivatives, gallic acid or its derivatives,
Esters of orthonaphthoquinonediacidosulfonyl chloride and polymers having hydroxyl groups such as acetone-pyrogallol resins and polyhydroxystyrene are known and useful, but are not particularly limited thereto.

Quinonediazide compounds are described in Gentabe Nagamatsu and Hideo Inui, "Photosensitive Polymers", Kodansha Scientific (1980).
, page 117, or DeFores)
est), “Photoresist J”
i-8t), 1975, McGraw-Hill (McGrow-
It can be synthesized according to the method described in, for example, p. The compounding amount of the photosensitizer is 10 parts by weight per 100 parts by weight of the novolak resin.
~100 parts by weight. If the amount of the photosensitizer is too large, the sensitivity decreases and at the same time, development residues are likely to occur in the exposed areas, while if it is too small, the line width of the pattern becomes narrow and it is difficult to obtain the desired line width.

The solvent used in the present invention is propatool.

Alcohols such as butanol, methyl ethyl ketone,
Ketones such as methyl isobutyl ketone and cyclohexanone, acetate esters such as ethyl acetate, butyl acetate, and isoamyl acetate, cyclic ethers such as tetrahydrofuran and dioxane, methyl cellosolve, ethyl cellosolve, and butyl cellosolve, as well as ethyl cellosolve acetate, butyl cellosolve acetate, Examples include γ-butyrolactone. Further, aromatic hydrocarbons such as xylene and toluene may be used as a mixture, and three or more types of solvents may be used. The solid content concentration is set to about 10 to 40% so that a desired film thickness can be obtained by spin coating or the like.

The composition of the present invention may contain a sensitizer, a surfactant, a dye, etc.

The composition of the present invention can be used for ultraviolet rays, deep ultraviolet rays, and electron beams.

A pattern can be formed by irradiation with energy rays such as X-rays and ion beams. It is particularly suitable as a pattern forming material using an ultraviolet exposure method.

Effects of the Invention Thus, according to the present invention, a resist composition that can draw a fine pattern with high dimensional accuracy without bunching of line widths and has good heat resistance can be obtained without impairing sensitivity or other characteristics. be able to.

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

Reference example 1 78 g of m-cresol, 60 g of p-cresol.

A mixture of 28 g of 3.5-xylenol, 85 g of a 37% aqueous formalin solution, and 1.8 g of oxalic acid dihydrate was heated with stirring and refluxed for 3 hours. Next, water was distilled off under normal pressure while heating and stirring was continued, and unreacted monomers were further distilled off under reduced pressure (final resin temperature 180°C, degree of vacuum 10 mmH3). The product was removed from the reactor and cooled to yield 148 g of resin. The residual cresol analyzed by gas chromatography was 1.6%, and the number average molecular weight was 1090 as measured using a vapor pressure equilibrium molecular weight analyzer (Model 115, manufactured by Hitachi, Ltd.).

Reference Examples 2 to 5 Alkali-soluble novolac resins were synthesized in the same manner as in Reference Example 1. However, the amounts shown in Table 1 were used instead of the amounts of the co-condensation component and catalyst used in Reference Example 1. Table 1 shows the number average molecular weight of the obtained novolak resin.

In addition, in Reference Examples 1 to 5, 3,5-xylenol and 2
, 5-xylenol of 90% grade was used.

Residual cresol is 1.2-1. E was 3%.

Below is a reference example in the margin 6 2,3.4-) Lyhydroxybenzophenone 12.
7g and 25.8g of 0-naphthoquinonediazide-5-sulfonic acid chloride were dissolved in 380g of 1.4-dioxane, and while stirring while heating in a 40°C water bath, 117g of a 10% solution of triethylamine in 1.4-dioxane was added. 30
It dripped in minutes. After stirring for 2 hours, the reaction mixture was poured into 6 kg of water with stirring, and the precipitated powder was separated by filtration, washed with water, and dried under vacuum at 40°C to obtain esterified product 2.
9.0g was obtained.

Examples 1 to 3 and Comparative Examples 1 to 2 In Examples 1 to 3, 24.0 g of the novolak resin of Reference Examples 1 to 3 and 6.5 g of the quinonediazide compound of Reference Example 6
was dissolved in 101.6 g of ethyl cellosolve acetate and filtered through a 0.2 μm Teflon membrane filter to obtain a resist composition.

In Comparative Examples 1 and 2, Reference Example 4 was used as the novolak resin.
A resist composition was obtained in the same manner as in the example except that 5 to 5 was used.

These resist compositions were applied to a silicon mirror wafer using a spin coater and prebaked in an air oven at 85° C. for 30 minutes to obtain a film thickness of 1.2 μm.

Next, a reduction projection exposure device (NAo, 35) was used to
From 0.6. 1ff14 in 0.06μm increments up to um
Exposure was through a reticle with a 1 line and space pattern. At the same time, a 5 μml to 1 line and space pattern was also exposed. This wafer was treated with 2.4% tetramethylammonium hydroxide (TMAHO).
Paddle development was performed using an aqueous solution, and the following evaluations were performed.

Sensitivity is the minimum number of exposure seconds required for a 5 μm pattern to pass through, expressed in units of 1llsec, and minimum resolution line width is the narrowest line width that can be resolved when increasing the exposure time by 20 m5ec from the sensitivity up to 400 m5ec. 1:1 Represents the line width of the lined space pattern.

The cross-sectional shape was determined by observing the fractured surface of the pattern with the minimum resolution line width, and a rectangular shape was marked (○) and a trapezoid shape was marked (x).

Pattern thinning is 1.0 μm at an exposure dose twice the sensitivity.
The dimensions of the line and space pattern were measured and evaluated. The closer the size is to 1.0 μm, the better it is; the thinner it is, the worse it is.

The heat resistance is as follows:
If the cross-sectional shape of the 5 μm pattern after second processing remained rectangular, it was marked as (0), and if it was rounded, it was marked as (x).

A scanning electron microscope was used for the above observations. The results of the evaluation are shown in Table 2.

In Comparisons 19111-2, resist compositions having the formulations shown in Table 2 were prepared in the same manner as in the examples, and evaluated in the same manner as in the examples. The results are shown in Table 2.

The following margins show that the composition of the present invention not only has good resolution of fine line widths, but also has good pattern shape and heat resistance, and has little thinning of the pattern.

Patent applicant: Zeon Corporation Same as Fujitsu Limited

Claims (1)

[Claims] (1) In a composition comprising an alkali-soluble novolak resin and a photosensitizer, the alkali-soluble novolac resin is
A positive-working photosensitive material comprising m-cresol, p-cresol and xylenol, which is a condensation product of formaldehyde and a phenol component in which 3,5-xylenol accounts for at least 10 mol% of the total phenol component. Resist composition.