JPH04366959A - Positive type photoresist - Google Patents

Abstract

PURPOSE:To provide the positive type photoresist high in sensitivity and resolution and, especially, excellent in profile and also superior in dry etching resistance. CONSTITUTION:The positive type photoresist contains a polymer composed partially or totally of repeating units derived from a 2-cyanoacrylate monomer, thus permitting the semiconductor integrated circuits, such as LSI or ultra-LSI, to be manufactured by using short wavelength lights for such a positive type photoresist.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a positive photoresist that is used in the manufacture of semiconductor integrated circuits such as LSIs and VLSIs and has high sensitivity, high resolution, particularly excellent profile, and excellent dry etching resistance. It is widely used in the electronic equipment industry.

0002

2. Description of the Related Art Currently, pattern formation in the manufacture of semiconductor integrated circuits is performed by photolithography. There are two types of photoresists used in photolithography: positive type and negative type. In general, positive type is superior in terms of resolution, and as patterns become finer with higher integration, positive type becomes more popular. It is becoming widely used.

[0003] As a positive photoresist, a combination of an alkali-soluble resin and a photosensitizer as a dissolution inhibitor is mainly used. Examples of the alkali-soluble resin include phenol-formaldehyde mevolac resin and cresol. Examples of photosensitizers include formaldehyde mevolac resin and polyhydroxystyrene.
Examples include compounds containing a naphthoquinone diazide group and a benzoquinone azide group.

0004

[Problems to be Solved by the Invention] However, as higher integration is required, photolithography requires shorter wavelength light, such as i-line (365 nm) and KrF (248 nm), which can be expected to improve resolution. Alternatively, excimer laser light such as ArF (193 nm) has been considered, and current positive photoresists exhibit strong absorption of such short wavelength light, making it difficult for the exposed light to reach the bottom surface. The disadvantage is that the profile becomes triangular in shape.

It has also been reported that polymethyl methacrylate, polymethyl isopropenyl ketone, and the like can be used as positive-working photoresists for short-wavelength deep ultraviolet rays, but although these exhibit high resolution, they have low sensitivity and poor durability. It also has the disadvantage of low dry etching properties.

[0006] Therefore, in order to improve the resolution by shortening the wavelength, a positive photoresist is desired which has less light absorption and an excellent profile, and which also has excellent sensitivity and dry etching resistance. The inventors,
We have conducted intensive studies to create a positive photoresist that solves the above problems.

[0007]

[Means for Solving the Problems] As a result of studies conducted by the present inventors, a positive photoresist has been found that does not have the above-mentioned problems, that is, has excellent sensitivity, resolution, and especially profile, and is also excellent in dry etching resistance. The present invention was completed.

That is, the present invention relates to a positive photoresist characterized by containing a polymer in which part or all of the constituent monomers are 2-cyanoacrylate.

Examples of the 2-cyanoacrylate as a constituent monomer of the polymer contained in the positive photoresist of the present invention include methyl 2-cyanoacrylate, ethyl 2-cyanoacrylate, propyl 2-cyanoacrylate, and isopropyl 2-cyanoacrylate. -cyanoacrylate, butyl 2-cyanoacrylate, isobutyl 2-cyanoacrylate, sec-butyl 2-cyanoacrylate, t
ert-butyl 2-cyanoacrylate, pentyl 2-
Cyanoacrylate, hexyl 2-cyanoacrylate, cyclopentyl 2-cyanoacrylate, cyclohexyl 2-cyanoacrylate, cycloheptyl 2-cyanoacrylate, 2,2,2-trifluoroethyl 2-
Examples include cyanoacrylate, 2-ethoxyethyl 2-cyanoacrylate, and the like.

Among these 2-cyanoacrylates,
Preferred for the present invention are cycloalkyl 2-cyanoacrylates such as cyclopentyl 2-cyanoacrylate, cyclohexyl 2-cyanoacrylate, and cycloheptyl 2-cyanoacrylate.

[0011] In the present invention, the polymer in which part or all of the constituent monomers are 2-cyanoacrylate refers to the above-mentioned 2-cyanoacrylate polymer.
- Homopolymers or copolymers of one or more cyanoacrylates, as well as copolymers of these 2-cyanoacrylates and monomers copolymerizable with the 2-cyanoacrylates, etc. Examples of cyanoacrylate and monomers copolymerizable with it include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, 2 , 2,2-trifluoroethyl methacrylate, tetrafluorobutyl methacrylate, phenyl methacrylate and other methacrylates, methyl 2
-Chloroacrylate, 2-chloroacrylates such as 2,2,2-trifluoroethyl 2-chloroacrylate, aromatic monomers such as styrene and α-methylstyrene, methylene malonates, vinylidene cyanide, vinylidene Examples include chloride, vinyl acetate, isopropenyl acetate, and the like.

The polymer used in the present invention can be easily obtained from 2-cyanoacrylate and a monomer copolymerizable with 2-cyanoacrylate by conventional anionic or radical polymerization.

[0013] As the anionic polymerization method, a method in which the polymerization is carried out in a solvent such as acetone, tetrahydrofuran, or toluene using a basic compound such as amines, phosphines, or sulfides as a catalyst is preferred. In addition, as a radical polymerization method, azobisisobutyronitrile or the like is used as a catalyst to
Bulk polymerization or solution polymerization methods carried out at ~70°C are preferred.

In the polymer of the present invention, it is preferable that the amount of 2-cyanoacrylate constituting the polymer is 20 wt% or more;
If it is less than 0 wt%, sensitivity and dry etching resistance will decrease, so it is preferably avoided.

The molecular weight of the polymer is preferably 10,000 to 4,000,000, more preferably 50,000 to 2,000,000, particularly preferably 100,000 to 1,000,000 as determined by gel permeation chromatography as a polystyrene equivalent weight average molecular weight.
It belongs to ten thousand people. If the molecular weight is too large, a solvent with good solubility may not be available when applying a thin film, a gel may form in the solution, making it impossible to filter it, or a uniform thin film may not be obtained. Furthermore, if the molecular weight is too small, it becomes difficult to obtain a uniform thin film with an appropriate thickness.

The positive photoresist of the present invention usually has the following properties:
It is used by dissolving the component polymer in a solvent, and examples of the solvent include methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, isobutyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, toluene, xylene, 1,2- Dichloroethane etc. are used.

The type and amount of the solvent to be used may be determined depending on the composition and degree of polymerization of the polymer to facilitate thin film coating, and is usually adjusted to a viscosity of about 10 to 100 cps. Ru.

The positive photoresist of the present invention also contains a sensitizer such as p-tert-butylbenzoic acid, a development accelerator such as tetrabutylammonium perchlorate, a dye,
Additives such as plasticizers, adhesion promoters, and surfactants can also be used in combination.

The positive photoresist solution thus obtained can be coated in a thin film onto a wafer of silicon or the like using an ordinary spin coater. After applying a thin film of photoresist solution and prebaking at an appropriate temperature, exposure to deep ultraviolet rays is performed through a required mask using a reduction projection exposure device or the like. Far-UV light sources include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury arcs, Xe short arcs, and Xe
-Hg short arc, etc., as well as Kr F, Ar
An excimer laser such as F can be used. The exposed polymer undergoes decomposition of its main chain by the energy of deep ultraviolet rays and its molecular weight decreases, resulting in a difference in solubility between the exposed and unexposed areas. Therefore, by treating the substrate exposed to deep ultraviolet rays with a suitable developer, the exposed portions are selectively dissolved and removed, and an image with irregularities corresponding to the mask pattern can be obtained.

[0020] The appropriate developing solution used at this time may be any developer as long as it can distinguish between exposed and unexposed areas and selectively dissolve the exposed areas. Selected from combinations of solvents and poor solvents. Examples of good and poor solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, tetrahydrofuran, ethyl acetate, isobutyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, acetonitrile, nitromethane, N-methylpyrrolidone, γ-butyrolactone, Toluene, xylene, 1,2-dichloroethane, etc. are good solvents, methanol, ethanol,
Poor solvents include isopropyl alcohol, ethyl cellosolve, water, hexane, and cyclohexane.

[0021] Immediately after development, rinsing is performed, and then post-baking is performed to complete a concavo-convex image in accordance with the exposed mask pattern. After forming the uneven image, the substrate can be dry etched using the resist film as a mask to form a pattern on the substrate. For example, if an uneven image of the positive photoresist of the present invention is formed on a silicon wafer having an oxide film of appropriate thickness, and then reactive sputter etching with carbon tetrafluoride is performed,
Only the portions of the oxide film where there is no resist film can be selectively etched. The type and conditions of dry etching may be appropriately selected depending on the type of substrate for pattern formation.

[0022]

[Function] The positive photoresist of the present invention exhibits the following excellent functions. A photoresist film of the present invention with a thickness of 0.5 μm formed on a silicon wafer having an oxide film of 0.5 μm was exposed to light using a low-pressure mercury lamp through a mask, and a residual film sensitivity curve was determined.
A sensitivity of cm2 was obtained. Furthermore, when a 0.5 μm line and space pattern was tested, a line and space pattern with a steep boundary between exposed and unexposed areas and a good profile was obtained. Furthermore, by dry etching, it was possible to form a pattern that matched the dimensions of the resist.

[0023]

[Examples] The present invention will be explained below with reference to Examples.
The present invention is not limited to this.

Example 1 200 ml of acetone and 50 g of cyclohexyl 2-cyanoacrylate were placed in a three-necked flask equipped with a stirring bar, a thermometer, and a drying tube, and the mixture was cooled to 0° C. while stirring. In this liquid,
A solution of 0.1 g of N,N-dimethyl-p-toluidine dissolved in 20 ml of acetone was quickly added. After stirring for 3 hours, 5 g of acetic acid was added, and the mixture was poured into 1100 ml of petroleum ether to precipitate a polymer. After rinsing thoroughly with petroleum ether, it was dried under reduced pressure at about 60°C. The polymer was purified by reprecipitation with an acetone/petroleum ether system and dried again under reduced pressure at about 60°C. The yield was 90%, and the weight average molecular weight determined by gel permeation chromatography was 380,000. 40 g of this polymer was dissolved in 760 g of cyclohexanone and filtered under pressure through a 0.2 μm Teflon membrane filter to obtain a photoresist solution of the present invention. This solution was spin-coated at 1000 rpm onto a silicon wafer having an oxide film of 0.5 μm, and then prebaked at 120° C. for 30 minutes to obtain a uniform thin film of 0.5 μm. Next, this thin film was exposed to light using a low-pressure mercury lamp through a mask, and a residual film sensitivity curve was determined using a methyl isobutyl ketone-isopropanol developer. 20℃
The residual film sensitivity was 100 mJ/cm2 and the γ value was immersed in a methyl isobutyl ketone-isopropanol solution with a volume ratio of 1/1 for 2 minutes, rinsed with hexane for 20 seconds, and post-baked at 140°C for 10 minutes. 2.6 was obtained. In addition, in a thin film prepared in the same way,
16 with 0.5 μm line and space pattern
Exposure was performed using a low pressure mercury lamp at 0 mJ/cm2. Methyl isobutyl ketone-isopropanol (volume ratio 1/1)
By immersing it in water for 2 minutes and developing it, rinsing it and post-baking it in the same way, a concavo-convex image with a good profile was obtained. Furthermore, when reactive sputter etching was performed using carbon tetrafluoride, the resist edge did not recede, and after the resist was peeled off, an oxide film pattern that matched the dimensions of the resist was obtained.

Example 2 In a sealed tube, cyclohexyl 2-cyanoacrylate and butyl methacrylate were mixed at a ratio of 70/30 (mole ratio), and 0.5 wt% of the monomer K azobisisobutyronitrile was added. Radical copolymerization was performed as an agent. It was purified using an acetone/petroleum ether system and vacuum dried at about 60°C. The yield was 85%, and the weight average molecular weight determined by gel permeation chromatography was 410,000. Also, NM
The copolymerization ratio determined from R was 68/32 (molar ratio). 40g of this polymer and 760g of cyclohexanone
The photoresist solution of the present invention was obtained by dissolving the photoresist solution in water and filtering it under pressure through a 0.2 μm Teflon membrane filter. This solution was spin-coated at 1000 rpm onto a silicon wafer having an oxide film of 0.5 μm, and then prebaked at 120° C. for 30 minutes to obtain a uniform thin film of 0.5 μm. When the residual film sensitivity curve was obtained in the same manner as in Example 1, the sample was immersed in methyl isobutyl ketone-isopropanol (volume ratio 1/1) for 1 minute, rinsed with hexane for 20 seconds, and post-baked at 140°C for 10 minutes. Depending on the conditions, a residual film sensitivity of 80 mJ/cm2 and a γ value of 2.0 were obtained. In addition, in a thin film prepared in the same way,
15 with a 0.5μm line and space pattern
Exposure was performed using a low pressure mercury lamp at 0 mJ/cm2. Methyl isobutyl ketone-isopropanol (volume ratio 1/1)
By immersing it in water for 1 minute and developing it, rinsing it and post-baking it in the same way, a concavo-convex image with a good profile was obtained. Furthermore, when reactive sputter etching was performed using carbon tetrafluoride, the resist edge did not recede, and after the resist was peeled off, an oxide film pattern that matched the dimensions of the resist was obtained.

[0026]

[Effects of the Invention] According to the present invention, a positive photoresist is obtained which has high sensitivity to short wavelength light, high resolution, excellent profile, and excellent dry etching resistance.
Semiconductor integrated circuits with small pattern dimensions can be manufactured. Therefore, the role played by the present invention in increasing the degree of integration of LSIs and VLSIs is enormous.

Claims (1)

[Claims] [Claim 1] Part or all of the constituent monomers are 2-
A positive photoresist characterized by containing a polymer that is cyanoacrylate.