JPS63234250A - Positive photoresist composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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.

BACKGROUND ART Conventionally, it has been reported that a condensation product of formaldehyde and a co-condensation component of m-cresol, p-cresol and 2,5-xylenol is used as an alkali-soluble novolak resin (Japanese Patent Laid-Open No. 185741/1983). . 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 that the molecular weight of the resulting resin decreases and the heat resistance of the resist decreases. In addition, it is known that the molecular weight can be increased by making the charging molar ratio of pol-11 aldehyde (F) and phenolic compound (P), F/P ratio, closer to 1.0, so this method can be used to increase the molecular weight. It is possible to solve the problem. 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 and a specific photosensitizer, the inventors have discovered that the problems of pattern thinning and heat resistance can be solved at the same time, and have completed the present invention.

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 It is a condensation product of formaldehyde and a phenol component in which 3,5-xylenol is at least 10 mol % in the total phenol component, and the photosensitizer is a 0- Naphthoquinone diazide-5-sulfone late ester, with an average esterification rate of 2.0 to
3.5 is provided.

The composition of the co-condensed component of the alkali-soluble novolac resin in the present invention is 20 to 80 mol% of m-cresol in the preparation.
, 10 to 50 mol% of p-cresol.

Xylenol is 10-60 mol%. However, 3,5-xylenol must be at least 10 mol% of the total phenol components. Also, 03,5 in xylenol
-Xylenol is usually more than 50%.

The 3,5-xylenol content in xylenol is preferably 60 mol% or more, more preferably 80 mol% or more, in order to suppress fluctuations in the condensation reaction rate and fluctuations in the alkali dissolution rate of the resulting resin due to other isomers. good. 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 xylenol content is less than 10 mol%, the property of good resolution will be lost, and if it exceeds 60 mol%, the alkali solubility of the resin will be 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.

In particular, m-cresol is preferably 30 to 50 mol%, p-cresol is 20 to 40 mol%, and xylenol is 20 to 40 mol%, and 3,5-xylenol in xylenol is preferably 60% or more, particularly 80% or more. In this range, 3,5-xylenol exhibits excellent resolution, the resulting resin has appropriate alkali solubility, and the molecular weight can be controlled without increasing the F/P ratio. It is possible to obtain a resist resin with good heat resistance without the problem of generation of.

As the formaldehyde, formalin and rose formaldehyde are used.

As a catalyst for the condensation reaction of alkali-soluble novolak,
Examples include sulfuric acid, hydrochloric acid, phosphoric acid, and oxalic acid.

The number average molecular weight of the alkali-soluble novolak resin is 800 to 1,800, preferably 900 to 1,300. If the molecular weight is small, the heat resistance will be poor, and if the molecular weight is large, the heat resistance will be good, but the resolution will be poor. Furthermore, various phenolic compounds remaining after the condensation reaction, especially p-cresol, can be reduced to 3% or less, preferably 2%, using a method such as vacuum distillation.
It is necessary to do the following. If there is a large amount of residual cresol, the heat resistance of the resist will deteriorate and the resolution will also deteriorate.

The photosensitizer in the present invention includes 2,3,4,4'-tetrahydroxybenzophenone and 0-naphthoquinonediazide.
It is an esterified product of 5-sulfonic acid, and has an average esterification rate of 2.0 to 3.5, preferably 2.8 to 3.2. If the average esterification rate is too large, the sensitivity will deteriorate,
If it is too small, the line width of the pattern will become thin.

As a photosensitizer, a sulfonic acid esterification reaction product (A
), 2.2', 4.4'-tetrahydroxybenzophenone and 0-naphthoquinonediazide sulfonic acid chloride sulfonic acid esterification reaction product (B) is also known, but in the case of compound A, Development residues tend to occur in exposed areas, resulting in poor resolution, and in the case of compound B, the solubility in engraving in solvents is low compared to the compounds of the present invention.

The photosensitizer of the present invention is produced by Gentabe Nagamatsu and Hideo Inui, "Photosensitive Polymer", Kodansha Scientific (1980), 11
Page 7 or DeForest (mouth e-Forest)
), “Photoresist J”
t) +1975, Tuna 1 Sihil (phylum cGrow-1
1i11), New York), page 50. The compounding amount of the photosensitizer is 10 to 100 parts by weight of novolac resin.
The amount is 100 parts by weight, preferably 20 to 35 parts by weight. If the amount is too large, the sensitivity decreases and at the same time, development residues are likely to occur in the exposed areas. If the amount 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 also 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 fine patterns with extremely high dimensional accuracy without line width clumps and has extremely excellent heat resistance can be used without impairing sensitivity or other characteristics. You can get it without.

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 m-cresol 78g, p-cresol 60g.

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, while heating and stirring, water was distilled off at normal pressure, and unreacted monomers were further distilled off under reduced pressure (final resin temperature 180°C, degree of vacuum approximately 10 mmmm1).
l. The product was removed from the reactor and cooled to yield 148 g of resin. The residual cresol was analyzed by gas chromatography to be 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 co-condensation component and catalyst used in Reference Example 1. The number average molecule m of the obtained novolak resin is shown in Table 1.

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

Residual cresol was 1.2-1.8%.

Below is a margin reference example 6 2.3,4.4'-tetrahydroxybenzophenone 9
．． 8g and 32.2g of 0-naphthoquinonediazide-5-sulfonic acid chloride and 420g of 1,4-dioxane.
145 g of a 10% 1.4-dioxane solution of triethylamine was added dropwise over 30 minutes under stirring while heating in a 40°C water bath.After stirring for 2 hours, the reaction mixture was poured into 8 kg of water. The mixture was poured while stirring, and the precipitated powder was separated by filtration, washed with water, and vacuum-dried at 40°C to obtain 32.8 g of an esterified product.

Reference Example 7 2.3.4-) Lyhydroxybenzophenone 12.
7 g of Naphthoquinone diazido 5-sulfonic acid chloride were dissolved in 380 g of 1,4-dioxane, and while stirring while heating in a 40°C water bath, 117 g of a 10% solution of triethylamine in 1.4-dioxane was dissolved in 30 g of 10% 1.4-dioxane solution.
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 filtered off, washed with water, and dried under vacuum at 4θ°C to obtain esterified product 2.
9.0g was obtained.

Examples 1 to 3 and Comparative Examples 1 to 3 In Examples 1 to 3, the novolak resins of Reference Examples 1 to 3 and the photosensitizer obtained in Reference Example 6 were dissolved in ethyl cellosolve acetate, and a 0.2 μm Teflon membrane filter was prepared. - to obtain a resist composition. The composition is shown in Table 2.

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

Then 1.06m with a reduction projection exposure device (NAo, 35)
It was exposed through a reticle having a line-and-space pattern from 1 to 0.6 μm in 0.05 μm increments. At the same time, a 6 μml vs. I line and space pattern was also exposed. This wafer was paddle developed with a 2.4% tetramethylammonium hydroxide (TMAHO) aqueous solution, and the following evaluations were performed.

Sensitivity is expressed in m5ec units as the maximum number of exposure seconds required for a 5 μm pattern to pass through, and the minimum resolution line width is 2 from the sensitivity.
It represents the line width of the narrowest 1:1 lined space pattern that can be resolved when the exposure time is increased by 0 m5 ec to 400 m5 ec.

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

Heat resistance was evaluated as (0) if the fractured surface shape of the 5 μm pattern after processing the wafer on a hot plate at 130° C. or 150° C. for 200 seconds maintained a rectangular shape, and (x) if it was rounded. A scanning electron microscope was used for the above observations. The results of the evaluation are shown in Table 2.

In Comparative Examples 1 to 3, 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.

In Comparative Examples 1 and 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.

It can be seen that the composition of the present invention not only has good resolution of y and fine line widths, but also has good pattern shape and heat resistance, and has little pattern thinning.

In particular, from the comparison between Example 1 and Comparative Example 3, it can be seen that the specific photosensitizer of the present invention has much better resolution and heat resistance than when a photosensitizer with a similar structure is used.

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
It is a condensation product of formaldehyde and a phenol component consisting of m-cresol, p-cresol and xylenol, in which 3,5-xylenol is at least 10 mol% of the total phenol component, and the photosensitizer is 2,3
, O-naphthoquinonediazide-5-sulfonic acid ester of 4,4'-tetrahydroxybenzophenone, and has an average esterification rate of 2.0 to 3.5.