JPS6316404B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a novel novolak resin, and more particularly to a novolak resin whose dry etching resistance is greatly improved by incorporating silicon atoms into its structure. (Prior Art and its Problems) In the manufacturing process of electronic devices such as integrated circuits and bubble memory elements, polymeric materials are often used in the process. In recent years, due to manufacturing requirements, there has been a strong demand for these polymer materials to be resistant to dry etching processes, and research has begun on polymers with high dry etching resistance. The inventors were the first to demonstrate the chemotactic correlation between the chemical composition of these polymeric materials and their etching resistance. (J.Electrochem.Soc.) No.
Volume 130, page 143 (1983). The results showed that in ion beam etching, which aims at anisotropic etching, the carbon content in the organic matter is the dominant factor in etching resistance. This result implied that carbon itself is the organic substance with the highest etching resistance, and that if higher resistance is desired, it is necessary to introduce inorganic elements. The inventors have developed a material in which silicon is introduced into polystyrene, namely polytrimethylsilylstyrene, and a material containing trimethylsilylstyrene as a repeating unit in the structure (Proceedings of the 23rd Symposium on Semiconductor Integrated Circuit Technology, p. 18,
57, and JP-A-59-15243 and JP-A-59-15419). However, with regard to novolac resins, which are important as electronic materials, no material containing silicon has been found to be satisfactory. (Object of the Invention) An object of the present invention is to provide a novel novolak resin having extremely high dry etching resistance, particularly oxygen dry etching resistance. (Structure of the Invention) According to the present invention, the structure represented by the general formula A is
~80 mol% molecular weight included in the main chain as a repeating unit
300-6000 novolak resin is obtained. General formula A: (In the formula, n represents 1 to 3, and R represents a hydrogen atom or an alkyl group.) (Detailed description of the structure) The present invention has solved the problems of the prior art by adopting the above-mentioned structure. The configuration of the present invention will be explained in detail below. The novolak resin of the present invention is characterized in that it contains at least a unit structure represented by the general formula A shown in the claims;
In addition to the unit structure shown in

【formula】

【formula】

【formula】

[Formula] etc. may be included. Also,
According to experiments conducted by the present inventors, the degree of polymerization of this novolak resin does not exceed 20. When adding a photosensitive substance to the novolak resin of the present invention and using it as a resist composition, the resin needs to be soluble in some solvent in order to be coated, and also needs to be soluble in a solvent suitable for development (e.g. Since the novolak resin needs to be soluble in an aqueous solution containing an alkaline substance, the content of general formula A in the novolak resin is preferably 80 mol% or less. Further, in order to provide sufficient dry etching resistance, the content of general formula A is preferably 20 mol % or more. The diazo compound added to the novolac resin as a photosensitizer can be changed from a state insoluble in an alkaline aqueous solution to a state soluble in an alkaline aqueous solution by irradiating it with electron beams, X-rays, deep ultraviolet rays, ultraviolet rays, or visible light. For optical exposure, quinonediazide compounds are preferred. This compound can also be used with electron beams, X-rays, and deep ultraviolet light. Examples of quinonediazide compounds include low-molecular and high-molecular compounds containing naphthoquinonediazide groups and benzoquinonediazide groups, such as condensation products of naphthoquinonediazide sulfonic acid chloride and benzoquinonediazide sulfonic acid chloride and low-molecular and high-molecular compounds having hydroxyl groups. It will be done. Here, examples of low molecular weight compounds having a hydroxyl group include hydroquinone, resorcinol, phloroglucin, 2,4-dihydroxybenzophenone, 2,
Examples of the polymer compound include 3,4-trihydroxybenzophenone and the like, and examples of the polymer compound include phenolic resin and polyhydroxystyrene. The amount of the photosensitizer added is preferably in the range of 5 to 100 grams, more preferably in the range of 15 to 50 grams, per 100 grams of the resin of the present invention. In addition to the photosensitizer, additional additives such as small amounts of additional resins (for example, to improve adhesion with organic films), plasticizers, pigments, dyes (light absorbers), etc. are added. Good too. Next, a method for forming a pattern will be explained in detail. After a thick organic film is spin-coated as the first layer and evaporated to dryness, a resist composition of the present invention is spin-coated onto the organic film. Solvents for coating include xylene, isoamyl acetate, cellosolve ethyl acetate, cellosolve methyl acetate, cellosolve acetate, and mixtures thereof. It is necessary to select a solvent that does not dissolve or deform the first layer organic film. After coating, the resist composition of the present invention is heated and dried under appropriate conditions, and then exposed to electron beams, X-rays,
A predetermined resist pattern can be drawn by exposing to deep ultraviolet rays, ultraviolet rays, visible light, etc. and developing it. As a developer suitable for developing the resist composition of the present invention, sodium hydroxide and potassium hydroxide are used. This includes all aqueous solutions that exhibit alkalinity, such as inorganic alkali aqueous solutions such as, tetramethylammonium hydroxide, and aqueous solutions containing organic alkalis such as choline. In addition to the alkaline substance, additional additives such as surfactants may be added. Using the resist pattern obtained by development as a mask, the first thick organic layer is etched by a dry etching method such as reactive ion etching using oxygen or oxygen ion beam etching. Thereafter, a thick organic layer with fine patterns is obtained. (Example) 200mL with reflux condenser and dropping funnel attached
In a three-neck flask, add 100 mL of ethanol, 4.6
g of metallic sodium was added thereto and stirred with a magnetic stirrer. When the solution became homogeneous, 22 g of resorcinol was added and stirring was continued for 1 hour while refluxing. 24.5 g of trimethylsilylchloromethane was added dropwise from the dropping funnel over 2 hours under reflux, and after the addition was complete, reflux was continued for an additional 24 hours. After cooling, remove ethanol under reduced pressure, add 30 mL of water, make slightly acidic with concentrated hydrochloric acid, and extract with chloroform (30 mL x 4).
The extracts were combined and washed with water (30 mL x 4).
After drying the chloroform solution over anhydrous magnesium sulfate, vacuum distillation was performed to obtain 12.6 g of a component distilled at a boiling point of 86° C. at 0.2 torr. This fraction has nuclear magnetic resonance properties (in CDCl ₃ , δ0.1 (9H, S, 3CH ₃ ),
3.5 (2H, S, CH ₂ ), 5.0 (1H, S, OH), 6.0−
7.3 (4H, m, Ar)), infrared absorption characteristics (KBrdisk,
3350 (OH), 1255 (SiCH ₃ )), elemental analysis value (C,
61.3%:H, 8.3%), it was confirmed that it was 3-(trimethylsilylmethoxy)phenol (hereinafter abbreviated as 1-). 2-methyl-3-
(Trimethylsilylmethoxy)phenol (hereinafter abbreviated as 2), (boiling point: 81℃/0.15torr. Elemental analysis value: C, 62.8%; H, 8.8%), 3-(3-trimethylsilylpropoxy)phenol (hereinafter 3- ), (boiling point: 117℃/0.1torr. Elemental analysis value:
C, 64.4%; H, 8.9%) were synthesized. Subsequently, 5.0 g of 1-, 2.1 g of 2-methylresorcin, and 3.7 g of 35% formalin were dissolved in 21 g of ethanol, 10 drops of concentrated hydrochloric acid was added, and the mixture was heated under reflux to carry out an addition condensation reaction. 500m of water after 12 hours
7.6 g of pale yellow powder was obtained. The obtained novolac-based resin (hereinafter abbreviated as P1~) is
It was soluble in organic solvents such as alcohol, chloroform, cellosolve ethyl acetate, and acetone, as well as in 1N aqueous sodium hydroxide solution and 1N aqueous tetramethylammonium hydroxide solution. Addition condensation was carried out while changing the ratio of 1-,2-methylresorcin and formalin to obtain resins (hereinafter abbreviated as P2-, P3-, P4-, P5- and P6-, respectively). Furthermore, in the above addition condensation reaction, 2~ or 3~ was used in place of 1~ to give resins P7~ and P8~. The results are shown in Table-1.

【table】

[Table] In order to confirm the oxygen dry etching resistance of these polymers, resin P1 was dissolved in ethyl acetate cellosolve, applied on a silicon substrate using a spinner, and dried at 80°C for 30 minutes. An experiment was conducted in comparison with MP-1300 (Shipley Co., Ltd.) whose main component is novolak resin. In reactive oxygen ion etching, under the conditions of oxygen flow rate of 5 sccm, oxygen pressure of 1.5 Pa, and high frequency output of 100 W, MP-1300 etches at a rate approximately 15 times faster than P1~, that is, while P1~ is etched by 1000 Å.
MP-1300 was etched to approximately 15,000 Å. In addition, in oxygen ion beam etching,
Accelerating voltage 100V, ion current density 0.25mA/cm ² ,
Under the condition of oxygen pressure 2.6Pa, P1~ is of MP-1300.
It showed more than 20 times more resistance. That is, P1~ is 1000Å
During etching, MP-1300 was etched by more than 20,000 Å. Polymers P2 to P8 showed similarly high etching resistance, proving that these new silicon-containing novolac resins are materials with high etching resistance, as intended. (Effects of the Invention) According to the present invention, a novel phenolic resin containing silicon atoms was obtained. It was found that this resin is a material that exhibits extremely high etching resistance in the dry etching process.

Claims (1)

[Scope of Claims] 1. A novolak resin having a molecular weight of 300 to 6,000 and containing a structure represented by general formula A as a repeating unit of 20 to 80 mol % in the main chain. General formula A: (In the formula, n represents 1 to 3, and R represents a hydrogen atom or an alkyl group.) 2. The novolak resin according to claim 1, wherein the general formula A has a structure represented by the general formula C. General formula C: (In the formula, n is 1 to 3, R represents a hydrogen atom or a methyl group)