JPH02120746A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To improve the rectangularity of pattern shapes by treating a resist layer with an aq. alkaline soln. to form a hardly soluble layer, then subjecting the layer to pattern exposing and developing. CONSTITUTION:The photoresist layer 12 consisting of an alkaline soluble resin (A) and a photosensitive agent (B) is formed on an Si substrate 11 and the layer 12 is treated with the aq. soln. of the alkali (e.g.: tetramethyl ammonium hydroxide) to form the hardly soluble layer 13. The layer 12 including the layer 13 is then subjected to pattern exposing and developing to form the resist patterns. A novolak resin, etc., contg. Si atoms in the main chain are usable as the component A and a quinone diazide compd., etc., are usable as the component B. A cellosolve compd., etc., are usable as the solvent for these components.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a resist pattern, and more particularly to a method for forming a resist pattern useful for microfabrication of semiconductors.

[Summary of the invention]

The resist pattern forming method of the present invention improves the rectangularity of the pattern shape by treating the photoresist layer on a substrate with an alkaline aqueous solution to form a hardly soluble layer before pattern exposure of the photoresist layer on the substrate. It was planned.

[Conventional technology]

In recent years, image reverse (ImageReve) has been used as a resist pattern forming method in the semiconductor manufacturing field.
rse) method is attracting attention.

This image reversal method provides a good resist pattern in microfabrication of semiconductors using g-line and i-line, and is also a method that can be expected to be applied to excimer laser lithography.

This image reversal method involves first applying a photoresist material to a silicon substrate and drying it, then heating the resulting photoresist layer to perform so-called positive and negative reversal. A negative image is formed by the process of fully exposing and developing the photoresist layer to form a pattern on the photoresist layer.

[Problem to be solved by the invention]

However, when forming a resist pattern by this image reversal method, when an excimer laser is used as an exposure source, the resist material has extremely high absorbance, so the pattern shape obtained is an acute rectangular shape due to the side surface of the resist. There was a problem in that the pattern had a substantially triangular shape, and a pattern with good rectangularity could not be obtained.

An object of the present invention is to solve the above-mentioned problems, and to provide a method for forming a resist pattern in which the rectangularity of the pattern shape is improved.

[Means to solve the problem]

The method for forming a resist pattern of the present invention includes a step of forming a photoresist layer made of an alkali-soluble resin and a photosensitive agent on a substrate, a step of treating the photoresist layer with an alkaline aqueous solution to form a hardly soluble layer, and a step of forming a hardly soluble layer on the photoresist layer. The photoresist layer including the solubilized layer is pattern-exposed and developed to form a resist pattern.

The photoresist material used in the present invention consists of an alkali-soluble resin and a photosensitizer.

Here, examples of the alkali-soluble resin include phenol, 0-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,5-xylenol, 3
．． 4-xylenol 3.5-xylenol, or α
Examples include novolac resins obtained by condensing compounds having a phenolic hydroxyl group such as -naphthol and β-naphthol with aldehydes such as formaldehyde, acetaldehyde, and benzaldehyde, and those containing silicon atoms in the resins.

As a resin containing silicon atoms, there is a resist material previously proposed by the present applicant (Japanese Patent Application No. 61-1
No. 89821). This resist material has the following general formula (2) (In both formulas, R1 and R1 are lower alkylene groups, R2, R3
,R4,R,. , R11 and R1□ are II, OH, CI
+3 or Cl120H1P, ~R, is a lower alkyl group,
R13 is CHZ or Cl10H1P, A is phenol,
A phenol derivative having 1 to 3 substituents or (R, 4 is a lower alkylene group, R15, R16 and RI
'? represents a lower alkyl group), X represents a number greater than 0 and less than or equal to 1, and Y represents O or 1-X). Examples of the phenol derivatives constituting this resist material include o-lm- and p-cresol, xylenol, and resorcinol. In addition, in each of the above formulas, the ratio of X and Y is arbitrary, but considering the developability in organic alkaline aqueous solution, Y
is preferably 0.7 or less.

An example of manufacturing this resist material is shown below.

First, equation (3) The monomer shown was synthesized by the following method.

In a 50 Qm/volume three-necked flask equipped with a reflux condenser, 3-hydroxybenzyl alcohol
g (0.4 mol), benzyl chloride 51 g (0.4
mo/), anhydrous potassium carbonate 110 g (0.8 m.

l) and 200m6 of anhydrous acetone.
The mixture was refluxed for an hour to react. The generated benzyl ether compound was extracted with ether and dried over magnesium sulfate (
yield 90%). Next, 30 g (0,14
Dissolve 1 mol of phosphorus tribromide in carbon tetrachloride and cool with water.
After 6.7 g (0,062 mol) was added dropwise over 2 hours to react, the solution was poured into ice water to decompose unreacted substances. The produced bromide was purified by silica gel chromatography using n-hexane as a developing solvent (yield 60%). Next, a nitrogen blowing pipe, a reflux condenser, and a dropping funnel were attached to each of the 500 m7!
1.93 g of magnesium (0,
079 g atoms) and 40 mJ of anhydrous ether,
Under water cooling, 20 g (0.07 moJ) of the above bromide was dissolved in anhydrous ether to QmN and added dropwise over about 2 hours. After this, the reaction was continued for another 2 hours, and then 6.6 g (0.07 mo/) of dimethylchlorosilane was added dropwise, and after being left at room temperature for a day and night, it was purified by distillation under reduced pressure (0.6 mi + Hg
, boiling point 140°C) (yield 60%).

Next, 5 g (0,019 mol) of this distilled product was
If a compound with a % para-substance is used, a monomer corresponding to this compound can be obtained.

Next, 5.4 g (0,0156 moff) of the monomer of formula (3) above, which is a siloxane-based phenol, 1.14 g of formalin (37% water soluble?&), 6 g of ethyl cellosolve acetate, and 27 mg of oxalic acid dihydrate. 10
0ml! The reaction product was placed in a large capacity eggplant-shaped flask, heated and stirred at 110° C. for 8 hours to react, and the reaction product was washed with water and purified under reduced pressure to obtain a polymer mainly represented by formula (4).

Examples of photosensitizers include quinonesia (in the formula, R1 and R2 each represent an alkyl group having 1 to 3 carbon atoms, whether the same or different) such as naphthoquinonediazide sulfonyl chloride. Compounds (wherein R3 and R4 may be the same or different and each represents an alkyl group having 1 to 3 carbon atoms) can be mentioned.

Furthermore, examples of the solvent in which the photoresist material is prepared include cellosolve solvents and mixed solvents of these and other solvents.

The formation of the hardly soluble layer in the present invention is carried out before pattern exposure, and is carried out by immersing the two-layer structure consisting of the substrate and the photoresist layer in an alkaline aqueous solution. As the alkaline aqueous solution, an aqueous solution of tetramethylammonium hydroxide is used.

For the pattern exposure in the present invention, a normal exposure method may be applied. The light source for this exposure uses a photosensitizer of 300~
Since they have spectral absorption at about 450 nm, arc lamps, mercury lamps, and metal halide lamps are used, for example.

The resist pattern of the present invention may be formed by applying a normal developing method after the pattern exposure described above. Examples of this developer include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate,
Inorganic alkalis such as ammonia water, ethylamine, n-
Aqueous solutions of secondary amines such as propylamine and di-n-propylamine, tertiary amines such as triethylamine and methyldiethylamine, and quaternary amines such as tetramethylammonium hydroxide and trimethylhydrokine ethylammonium hydroxide; Alternatively, alcohol, surfactant, etc. may be added to this.

In addition, in the resist pattern forming method of the present invention, in addition to the above-described steps, a resist pattern with better rectangularity can be formed by performing heat treatment after pattern exposure and before development.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Developed for 5 seconds at 20°C using a 3.2% aqueous solution of H (
Figure 1D).

As a result of this development, it was confirmed that a hardly soluble layer was formed on the surface of the photoresist layer, the development speed of which was five times slower than that of the bulk.

〔Example〕

Example 1 This example will be described based on the drawings. First, the resist material shown in the above manufacturing example was placed on a silicon substrate with a thickness of 0.4 μm.
It was coated to a thickness of m and then the whole was dried at 90° C. for 90 seconds (Fig. 1A).

The resulting two-layer structure consisting of the resist layer and the substrate was treated with 3.5% of tetramethylammonium hydroxide (TMAH).
．． After immersing it in a 2% aqueous solution at 20°C for 3 minutes, it was washed with water and dried to form a hardly soluble layer (Figure 1B).

The resist layer including the obtained hardly soluble layer was exposed to ultraviolet light (wavelength: 4
36 nm) pattern exposure (intensity: 200 mJ/c
nl) L (Figure 1C), then the same resist material as used in Example 1 was applied onto the silicon substrate to a thickness of 0.4 μm, and then the entire surface was coated with a thickness of 90''. It was dried at C for 90 seconds.

The resulting two-layer structure consisting of the resist layer and the substrate is TM
After being immersed in a 3.2% aqueous solution of AH at 20° C. for 3 minutes, it was washed with water and dried to form a hardly soluble layer.

The resist layer including the obtained hardly soluble layer was exposed to ultraviolet light (wavelength: 2
48 nm) with lines/spaces of 0.5 μm, and then developed using a 3.2% aqueous solution of TMA H at 20° C. for 1 minute.

It was confirmed that the obtained resist pattern had better rectangularity than that obtained by a conventional method.

In addition, the remaining film rate in the unexposed area is 97% when using the normal method.
It was also confirmed that the method according to the present invention has an improvement of 99%.

Next, a resist pattern was prepared in the same manner as in Example 1, except that 0FPR800 (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was used as the photoresist material and NMD-3 (trade name) was used as the alkaline treatment aqueous solution and developer. Formation was performed.

It was confirmed that the resulting resist pattern had reduced film slippage in low exposure areas and improved T-characteristics.

Note that the sensitivity hardly changed.

〔Effect of the invention〕

As detailed above, according to the resist pattern forming method of the present invention, it is possible to form a resist fine pattern with significantly improved rectangularity compared to conventional forming methods, and it is also effective for microfabrication. It is also possible to apply the present invention to excimer laser lithography, which is currently attracting attention, and is extremely useful in the field of semiconductor manufacturing, for example, and has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a side view sequentially showing an embodiment of the present invention. In addition, in the reference numerals used in the drawings, 11-.
----1.--Photoresist layer 13 ---
------------- It is a hardly soluble layer.

Claims (1)

[Scope of Claims] A method comprising: forming a photoresist layer made of an alkali-soluble resin and a photosensitive agent on a substrate; treating the photoresist layer with an alkaline aqueous solution to form a hardly soluble layer; and comprising the hardly soluble layer. 1. A method for forming a resist pattern, comprising the steps of exposing and developing a photoresist layer in a pattern to form a resist pattern.