JPH0334057B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photosensitive material for negative resists, and more particularly to a photosensitive material suitable for microfabricated negative resists. In recent years, in the field of microelectronics,
As the degree of integration becomes larger and more complex, processing accuracy reaching the sub-micron range is required.
Electron beam lithography began to be adopted. The electron beam lithography method has excellent processing accuracy and also functions as a pattern generator, so it is used for manufacturing master masks.
However, at present, the electron beam lithography method is not suitable as a means for producing large quantities of the same pattern because its lithography speed is slow. For this reason, there is a need for a technique for highly accurate transfer from a master mask created by electron beam lithography. Ultraviolet light with a relatively long wavelength of 3300-4500Å (called near ultraviolet light)
Conventional photolithography using 1 μm or less is impossible because it involves light diffraction and interference. For this reason, transfer methods using X-rays or electron beams are also being researched, but no practical device has been developed yet. By the way, in 1975 BJ Lin reported that 2000-2600 Å
Ultraviolet rays with relatively short wavelengths (deep ultraviolet rays)
announced that it is possible to transfer submicron patterns by using UV (BJLin: Deep UV LITHOGRAPHY).
Journal of Vacuum Science and Technology,
vol.12, No.6, 1975, pp1317-1320). This new transfer technology is called deep ultraviolet lithography and is distinguished from conventional photolithography, but as it is an extension of conventional technology, research is progressing rapidly as a technology with high feasibility, and it has already been Practical exposure equipment has been developed. However, Deep
Even with UV lithography, sufficient resolution cannot be obtained by using conventional photoresists as they are. BJ Lin obtained the above results using polymethyl methacrylate (PMMA), which is known as a high-resolution electron beam resist. There are two types of resists: negative resists, in which the areas exposed to light remain as reliefs after development, and positive resists, in which the areas exposed to light are removed as non-image areas. The aforementioned PMMA is a positive resist. A practically satisfactory negative resist for deep UV lithography has not yet been developed. In microfabrication, it is advantageous to use both positive and negative resists depending on the process, and there is a need to develop a practical negative deep UV resist. In general, photosensitive materials for negative resists are made by chemically bonding a crosslinking group to a film-forming substance (mainly a high molecular compound) as a base material, or by adding a crosslinking agent (low-molecular compound) to a film-forming substance (mainly a polymer compound). It can be produced by mixing with substances. From this point of view, the inventors of the present invention have conducted intensive research and found that a specific polymer compound has a deep
It exhibits extremely high sensitivity to UV, and is highly stable to visible light, heat, moisture, etc., and is a negative type.
We have found that this product is extremely suitable as a photosensitizing agent for deep UV resists, and is also effective as a photosensitizing component for electron beam resists, leading to the completion of the present invention. An object of the present invention is to provide a photosensitive material that can be suitably used for negative-tone deep UV resists or electron beam resists. The present invention is as follows. (1) A polymer with a molecular weight of about 500 to 500,000, and o
-Chlorbenzoic acid residue, p-chlorobenzoic acid residue, 2,4-dichlorobenzoic acid residue, 2,6-
Any group of dichlorobenzoic acid residue from 1 to
A photosensitive material for a negative resist, characterized in that it contains 100 mol% of a polymer compound bound thereto as a film-forming photosensitive component. (2) The film-forming photosensitive component is a vinyl monomer having a benzene nucleus such as styrene, vinyltoluene, α-methylstyrene, vinylnaphthalene, vinylcarbazole, or acenaphthylene 20 to 90
A copolymer with a molecular weight of about 5,000 to 200,000 consisting of mol % and one or more other vinyl monomers, and a polymer compound having 2 to 50 mol % of the aforementioned groups bonded. A photosensitive material in range 1 of (3) The film-forming photosensitive component is a polymeric compound having 0.2 to 3 _C2-6 fatty acid residues bonded to each of the above-mentioned groups. photosensitive material. With the photosensitive material for negative resist of the present invention,
Deep UV resists and electron beam resists can be obtained, and in particular, practical negative-tone deep UV resists with excellent sensitivity, film formability, adhesion to substrates, resolution, corrosion resistance, and stability can be obtained. Suitable film-forming photosensitive components in the present invention are the following polymer compounds. It has a molecular weight of about 5000 and consists of 20 to 90 mol% of vinyl monomers having a benzene nucleus such as styrene, vinyltoluene, α-methylstyrene, vinylnaphthalene, vinylcarbazole, and acenaphthylene, and one or more other vinyl monomers. ~
200,000 copolymer having 2 to 50 mol% of the groups listed above. The above polymer compounds can be processed by plasma etching,
It has excellent resistance to so-called dry etching such as reactive ion etching. When the ratio of vinyl monomers having benzene nuclei as described above increases, cracks tend to occur when formed into a thin film, and the adhesion to the substrate tends to deteriorate. Note that rubber-based polymers such as polybutadiene tend to swell with organic solvents, making it difficult to obtain a resist with high resolution. Furthermore, since resists are often used at high temperatures of 100° C. or higher, it is not preferable to use a resist that contains a large amount of monomer that lowers the softening temperature of the polymer. Furthermore, monomers containing fluorine atoms tend to deteriorate adhesion to the substrate. The base material of the polymer compound in the present invention preferably has a functional group such as an epoxy group, a hydroxyl group, a carboxyl group, or a carboxylic acid halide group. In the case of negative resists, the base material, and even
As the molecular weight of the polymer compound decreases, the resolution tends to improve, but at the same time, the sensitivity decreases in proportion to the molecular weight. Furthermore, if the molecular weight is too small, the mechanical strength of the coating film tends to deteriorate, and therefore the molecular weight cannot be made extremely small. From this point of view, the molecular weight range of the base material and, by extension, the polymer compound is determined. The polymer compound in the present invention has a molecular weight of about
500 to 500,000, preferably about 5,000 to 200,000, and contains 1 to 100 mol%, preferably 2 to 50 mol% of any of the above-mentioned benzoic acid residues.
It is something that is combined and possessed. If the molecular weight is less than 500, the mechanical strength of the coating film will decrease and the photosensitivity will also decrease. If it exceeds 500,000, a commensurate improvement in mechanical strength and sensitivity cannot be obtained. In addition, the binding amount of the above residue is 1 mol%
If it is less than 100 mol %, a resist with high resolution cannot be obtained, and if it exceeds 100 mol %, a commensurate improvement in photosensitive properties cannot be obtained. The production of the polymer compound in the present invention will be described. The above groups may be bonded to a monomer in advance, or may be bonded to a polymer by reaction. A known method may be used for the reaction method of bonding the group as a side chain of a monomer or polymer.
There are no particular limitations. Other suitable polymer compounds in the present invention include 0.2 to 0.2 to 6 C _2-6 fatty acid residues per group shown above.
It is a high molecular compound having three molecules bonded together. By combining fatty acid residues ( _C2-6 ) in addition to the above-mentioned benzoic acid residues, a photosensitive material with even more excellent properties can be obtained. The effect of the fatty acid residue is mainly to improve the resolution of the resist by suppressing the swelling of the resist during development. This fatty acid has 2 to 6 carbon atoms.
saturated or unsaturated fatty acids. Examples of such fatty acids are acetic acid, propionic acid, butenoic acid, crotonic acid, vinylacetic acid,
Acrylic acid, methacrylic acid, and two of these acids
There are more than one species. The amount of fatty acid residue bound is 0.2 to 3 fatty acid residues per one benzoic acid residue shown above.
individual is advantageous. The photosensitive material of the present invention effectively forms a resist with light having a wavelength of approximately 2000 to 3000 Å and an electron beam, and is particularly effective against light having a wavelength of approximately 2000 to 2600 Å (Deep UV). The case where the photosensitive material of the present invention is used for a deep UV resist will be illustrated. On a substrate such as a silicon wafer, the photosensitive material of the present invention is dissolved in a suitable solvent such as ethylene glycol monomethyl ether acetate, applied uniformly using a spinner, and dried to form a resist layer with a thickness of 0.4 to 1 μm. Let it form. Next, using a light source that efficiently emits light with a wavelength of approximately 2,000 to 2,600 Å, such as a xenon-mercury lamp, exposure is performed through a mask pattern that uses a material that transmits this light, such as an artificial quartz plate, as a support. Next, by immersing this in a developer, such as a mixed solvent of methyl ethyl ketone and ethanol, and eluating the non-exposed areas, a fine pattern faithful to the mask can be obtained. Since the photosensitive material of the present invention is not sensitive to visible light, it can be handled in a bright room. Furthermore, it is stable against humidity and heat, does not require special care in handling, and has excellent storage stability. The photosensitive material of the present invention is also useful as a resist for electron beam lithography. acceleration voltage
It exhibits a sensitivity of more than 10 microcoulombs/cm ² to an electron beam of 10 to 30 KV, and can resolve a grid pattern of 0.3 μm. Next, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to these Examples. Example 1 (Synthesis of a polymer compound) A copolymer with a molecular weight of 22,000 consisting of 85 mol% styrene and 15 mol% glycidyl methacrylate was prepared as a base material, and the derivatives shown in Table 1 were added to the epoxy group to form a polymer. The binding amount was 10 mol%.
An example of the reaction used here is as follows. 28 g of the aforementioned copolymer and 12 g of 2,4-dichlorobenzoic acid were dissolved in 250 ml of methyl ethyl ketone, 0.5 g of triethylbenzylammonium chloride was added as a catalyst, and the mixture was heated under reflux for 4 hours with stirring. After cooling, the reaction solution was poured into isopropyl alcohol to recover the monomer, which was dried under reduced pressure at room temperature. A portion of the thus obtained polymer was taken and the amount of unreacted epoxy groups was determined by a conventional method. As a result, the amount of 2,4-dichlorobenzoic acid introduced was 10 mol % based on the polymer. (Preparation and use of photosensitive solution) Next, a photosensitive solution was prepared by dissolving 20 g of the polymer to which each of the derivatives shown in Table 1 was added in 100 ml of ethylene glycol monomethyl ether acetate. This photosensitive solution was applied onto a silicon wafer using a spinner and then baked at 90° C. for 30 minutes to remove the solvent and form a resist film with a thickness of 0.7 μm. This resist film was applied from a distance of 15 cm.
After exposure with a 500W xenon-mercury lamp for different times in stages, the film was developed by immersing it in a mixed solvent of methyl ethyl ketone and ethanol for 60 seconds. The sensitivity was evaluated and the results shown in Table 1 were obtained. The relative sensitivities in Table 1 are shown assuming that the sensitivity of the base polymer itself used here is 1.

[Table] Example 2 2,
4-dichlorobenzoic acid was bound to the polymer in an amount of 3 mol%, 6 mol%, and 10 mol%, respectively. The sensitivity of these photosensitive materials obtained in the same manner as in Example 1 was measured in the same manner as in Example 1, and the results shown in Table 2 were obtained.

[Etching conditions]

Etching gas: CF ₄ + H ₂ (20%) Gas pressure: 0.02 Torr Gas flow rate: 70 SCCM RF power: 200 W Example 7 20 g of the photosensitive material of Example 3 was dissolved in 100 ml of ethylene glycol monomethyl ether acetate.
A photosensitive solution prepared by filtration with a 0.2 μm membrane filter was applied onto a silicon wafer with a 5000 Å thick oxide film using a spinner, and incubated at 90°C for 30 minutes.
A resist film having a thickness of 0.7 μm was formed by baking for a minute. A quartz mask was placed in close contact with this resist film, and after exposure for 8 seconds with a 500W xenon-mercury lamp,
By developing with a mixed solvent of isopropanol and methyl ethyl ketone at a volume ratio of 7:3 and rinsing with n-heptane, a 0.5 μm pattern could be accurately transferred. Next, the silicon wafer on which the pattern was formed was baked at 150°C for 30 minutes, and then a 30°C hydrofluoric acid buffer solution (1 part of 40% hydrofluoric acid + 6 parts of 40% ammonium fluoride aqueous solution) was used.
When etching was performed by immersing the mask in the mask pattern for 4 minutes, an etching pattern faithful to the mask pattern was obtained without seepage or peeling of the resist. Example 8 A photosensitive solution prepared by dissolving 20 g of the photosensitive material obtained in Example 4 in 100 ml of ethylene glycol monomethyl ether acetate and filtering it through a 0.2 μm membrane filter was applied to a silicon wafer using a spinner and heated at 90°C. A resist film with a thickness of 0.7 μm was formed by baking for 30 minutes. A quartz mask was brought into close contact with this resist film, and the resist film was exposed for 6 seconds with a 500 W xenon-mercury lamp, and then developed with a mixed solvent of methyl ethyl ketone and ethanol in the same manner as in Example 6, and then washed with isopropanol. The swelling of the resist image during development was very small, and an extremely accurate transfer pattern was obtained. Example 9 The photosensitive solution prepared in Example 6 was applied to a chrome substrate having a 700 Å thick chromium layer on a glass plate,
A resist film with a thickness of 0.6 μm was formed by baking at 90° C. for 30 minutes. This substrate was placed in a vacuum, the resist surface was swept with an electron beam at an acceleration voltage of 27 KV, and then taken out and developed with a mixed solvent of methyl ethyl ketone and ethanol in the same manner as in Example 6, and then washed with isopropanol. A resist image was obtained in the area irradiated with the electron beam. This resist image resolved a lattice pattern of 0.3 μm. The amount of charge irradiated at this time was 8 microcoulombs per square centimeter, and the thickness of the resist film after development was 0.35 μm. Reference example 1 Chlorstyrene (o-chlorostyrene 65%, p
- a mixture of 35% chlorostyrene) was polymerized to obtain polychlorostyrene with a molecular weight of 20,000. Dissolve 20g of this polymer in 100ml of chlorobenzene and
It was filtered with a membrane filter. Next, this polymer solution was applied onto a silicon wafer using a spinner, and then baked at 90° C. for 30 minutes to form a 0.7 μm thick polymer film. This polymer membrane was prepared in the same manner as in Example 1,
After exposure with a 500W xenon-mercury lamp, the sensitivity was measured by developing with a mixed solvent of methyl ethyl ketone and ethanol, and the sensitivity was significantly lower than that of the photosensitive materials of the examples of the present invention. The sensitivity was below 0.9.

Claims (1)

[Scope of Claims] 1. A polymer having a molecular weight of about 500 to 500,000,
- A polymer having 1 to 100 mol% of any of the following groups: chlorobenzoic acid residue, p-chlorobenzoic acid residue, 2,4-dichlorobenzoic acid residue, 2,6-dichlorobenzoic acid residue A photosensitive material for a negative resist, characterized by containing a molecular compound as a film-forming photosensitive component. 2 The film-forming photosensitive component contains 20 to 90 mol% of a vinyl monomer having a benzene nucleus such as styrene, vinyltoluene, α-methylstyrene, vinylnaphthalene, vinylcarbazole, acenaphthylene, and one or more other types. A copolymer with a molecular weight of approximately 5,000 to 200,000 consisting of a vinyl monomer of
The photosensitive material according to claim 1, which is a polymer compound having 2 to 50 mol% of the groups shown above. 3. Claim 1, wherein the film-forming photosensitive component is a polymeric compound having 0.2 to 3 _C2-6 fatty acid residues bonded to each of the aforementioned groups.
photosensitive material.