DE2609218A1 - Masks for mfr of sub-micro integrated circuits - using copolymers of alkyl-and glycidyl-methacrylates exposed by electron beams - Google Patents

Abstract

In a material sensitive to cathode rays, contg. a polymer of an alkyl methacrylate and if required, a suitable solvent, the novelty is that the polymer is a copolymer or an alkyl methacrylate with a vinyl monomer contg. epoxy groups. The vinyl monomer is pref. glycidyl methacrylate or glycydyl acrylate, and the copolymer pref. contains methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isopropyl, isobutyl, or tert. butyl-methacrylate. The copolymer pref. has mol. wt. 500 to 10 million, esp. 100,000 to 5 million. The amt. of vinyl monomer used in the copolymer is pref. 0.001-5 mol % esp. 0.05-5.0 mol %. Used esp. for mfg. masks used in the mfr. of integrated circuits, where instead of using photoresist exposed to light, the masks are exposed to a scanning beam of electrons to make the mask. As the cathode rays have a shorter wavelength than ultraviolet light and their intensity and breadth are easily controlled, greater accuracy is attainable so smaller circuit elements can be produced, e.g. in the sub-micron range.

Description

Cathode ray sensitive materials It is common practice to to use light-sensitive polymers as photoresist materials or photoresists.

More recently, there have been further developments in the field of integrated Reached circuits (IS), which represent an active element, in which a complicated Circuit is arranged on a semiconductor substrate, and therefore is in the field the semiconductor technology an extraordinarily precise way of working has become necessary.

For this reason, a method has been proposed in which this is desired Resist image with the aid of a scanning cathode ray (scanning cathode ray) directly is made without using optical radiation.

Since the cathode radiation is known to be short wavelength in comparison with the wavelength of ultraviolet radiation, the response accuracy is one Resist material to this radiation high. Ca also the intensity, width and the like of the cathode radiation can be controlled in a simple manner also the Body can be precisely regulated to which the cathode radiation is judged. By taking advantage of this advantage, the conductor element can be very can be kept small and improvements in the characteristics of the semiconductor element can be achieved and a greater integration density of the circuit can be realized, cathode ray sensitive Materials can be divided into two types, namely positive working Materials and negative working materials. You will be dependent on that intended use selected. An insoluble film of excess from one positive working cathode ray sensitive material on a suitable Substrate is formed, when irradiated with cathode rays, in a material transferred, which in a desired solvent (developer solvent) is soluble.

The well-known cathode radiation sensitive materials of the positive working type are disadvantageous in that their sensitivity is low and the solvent resistance of the non-irradiated area is unsatisfactory is.

The invention is therefore based on the object of providing cathode ray-sensitive To provide materials of the positive working type that have high sensitivity to have cathode radiation.

These positively working, provided according to the invention, Cathode ray sensitive materials should also not be irradiated Range have satisfactory resistance to solvents.

These and other objects of the invention are evident from the following detailed description.

The invention therefore relates to materials sensitive to cathode rays, consisting essentially of a copolymer of an alkyl methacrylate and an epoxy group containing vinyl monomers exist.

The present in the novel copolymer according to the invention, a Epoxy group vinyl monomers containing, for example, glycidyl methacrylate or glycidyl acrylate be.

When a coating film of the positive working cathode ray sensitive of the present invention Material is formed on a desired substrate, so this film can through the crosslinking that occurs during the pre-curing process through the epoxy group caused to be carried over into an insoluble film. This film has strong points @ Resistance to solvents. Even if the change in this film. irradiation with a relatively small amount of cathode radiation is small, the irradiated portion of this film can be increased by using a solubilized in a strong solvent or by development for a long period of time because of the non-irradiated part of these developing conditions described above is resistant to.

If the pre-cure process is poorly carried out, i. if some of the epoxy groups do not react, intermolecular crosslinking occurs caused by the unreacted epoxy groups when the material is exposed to cathodic radiation is irradiated. The sensitivity of this reaction is higher than that of the cleavage the main chain of the copolymer.

In general, the cathode ray is at the point of impact in intense in the middle and weak in the circumference. Therefore, if the weakly pre-cured film is irradiated by the cathode ray, this film becomes the focus of the incident cathode ray due to the cleavage of the copolymer main chain into a soluble material converted. At the edge or perimeter of the point of impact is therefore the film is more insoluble because the effect of intermolecular crosslinking is greater than the main chain cleavage effect. Because of this, using a fine cathode ray pattern can be obtained on this film after development, because the film shows high resolution.

The film of the present invention also exhibits satisfactory etch resistance.

The required amount of epoxy groups is at least one group per one molecule of the copolymer. Therefore, if the molecular weight of the copolymer is about 10 million (degree of polymerization about 100,000), the epoxy group should vinyl monomer unit containing in each molecule of the copolymer more than 0.001 Nol- amount. When such copolymers are crosslinked with one another by heating, so the molecular weight of the copolymer becomes enormous and the copolymer becomes insoluble.

When the molecular weight of the copolymer is more than about 10 million this copolymer is insoluble from the start.

In this regard, the molecular weight should be in the range of about 500 to about 10 million, preferably between about 100,000 and about 5 million lie.

The molar fraction of the epoxy group-containing vinyl monomeric unit in in the copolymer in the copolymer should be in the range of about 0.001 to 5 mol- preferably about 0.05 to 5 minor larvae. The invention will be made more preferred in the following Embodiments described '.

For examples of suitable alkyl methacrylates, which one of the monomer units of the copolymer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, Butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate and tert-butyl methacrylate.

The copolymers of methyl methacrylate and the comonomer are preferred, because they are easily soluble in solvents.

Examples of epoxy group-containing vinyl monomers which are used as Comonomers present include glycidyl acrylate and glycidyl methacrylate.

The use of a copolymer obtained by copolymerizing the above indicated alkyl methacrylate and a comonomer has been obtained, can to a fine positive pattern when using about one seventh the amount of radiation the cathode radiation lead that for usual, positive working people cathode ray sensitive polymers is required.

The invention is explained in more detail by the following examples, without that it should be limited to this.

Example 1 200 cm3 of water passed through an ion exchange resin was placed in a reaction vessel and 1 g of sodium auryl sulfate as an emulsifier was dissolved in the water. 25 g methyl methacrylate and 0.5 mol% glycidyl methacrylate, based on the total amount of monomers, were mixed into the solution after the atmosphere in the reaction vessel has been displaced by gaseous nitrogen was to achieve oxygen-free conditions. 0.1 g of potassium persulfate and 0.1 g of sodium bisulfite were added to the mixture and the mixture was then taken for about 6 hours Stirring held at 2300. There was then about 15 grams of sodium chloride in the reaction mixture dissolved to salt out the copolymer. The precipitated copolymer was recovered washed with methyl alcohol and water, reprecipitated three times with toluene and methyl alcohol and then dried in vacuo at room temperature.

The resulting copolymer contained about 0.5 mole of glycidyl methacrylate and had a molecular weight of about 5 million.

Following the procedure described above, copolymers produced which have a molar proportion of glycidyl methacrylate of approximately 1 mol%, about 3 mole percent and about 5 mole percent respectively, but with manufacture the molar proportions of the glycidyl methacrylate used as monomers at 1, 3 respectively.

5 ol, based on the total monomers, were kept.

The copolymers were dissolved in toluene and each of these solutions was applied to a thin chrome film that has been vapor-deposited onto a glass substrate was. After heating at 11,000 for 5 minutes, insoluble copolymer films had one Thickness of about 5 microns.

In Table 1, when irradiated with an electron beam the amount of radiation applied and the developer required are shown, to apply a fine cathode ray image of the positive type to the corresponding pre-cured To produce films with the aid of an electron beam of 15 KV. , In the table For comparison, a polymer is listed which does not contain glycidyl methacrylate contain, i.e. a methyl methacrylate polymer.

The results indicate that by using the copolymer which Contains 0.5 mol% glycidyl methacrylate units, a fine cathode ray image of the positive type achieved using about one seventh the amount of radiation which is necessary for conventional polymers and that in use of copolymers in which the molar proportion of glycidyl methacrylate is in the range of 1 mol% to 5 mol%, a fine image with about a fifth of the amount of radiation which is required for conventional polymers can be achieved.

Copolymers in which the molar proportion of glycidyl methacrylate is more than 5 mol% do not lead to fine and exact images because of the epoxy groups form numerous cross-links.

TABLE 1 Molar fraction of exposure to glycidyl methacrylate developer Electron beam (mol%) (coulomb / cm²) 0.5 7 x 10-6 butyl acetate 1 1 x 10-5 cyclohexanone 3 1 x 10-5 methyl isobutyl ketone 5 1 x 10-5 methyl isobutyl ketone 0 (comparative 5 x 10-5 methyl isobutyl ketone experiment) + isopropyl alcohol (1: 2) example 2 films obtained by applying copolymers prepared according to Example 1 were heated to 170 ° C for 5 minutes to precure them The resulting insoluble films were about 5 microns thick. If those When films were irradiated with the aid of an electron beam, the irradiated one became Proportion of films for the amount of electron beam irradiation given in Table 1 really. However, if the non-irradiated areas of these films are in solvent were immersed, such as cyclohexanone, xylene, toluene, benzene, monochlorobenzene, chloroform, Carbon tetrachloride, trichlorethylene, ethyl acetate, butyl acetate, amyl acetate, isoamyl acetate, Acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl amine, acetonitrile, tetra hydrofuran and dimethylformamide, they were subject to immersion for one day 6 no change. If the non-irradiated portions of these films go in 10 Solutions of substances such as sulfuric acid, hydrochloric acid, it.phosphoric acid, Nitric acid, ammonia, sodium hydroxide, potassium hydroxide, and hydrogen peroxide Hydrogen-ammonium fluoride, have been immersed for one hour, the films were not changed.

Example 3 200 cm3 of water passed through an ion exchange resin was placed in a reaction vessel and 1 g of sodium lauryl sulfate as an emulsifier was dissolved in the water. 25 g methyl methacrylate and 0.5 MoR% glycidyl acrylate, based on the total amount of monomers, were mixed into the solution after the atmosphere in the reaction vessel has been displaced by gaseous nitrogen was to maintain oxygen-free conditions. 0.1 g of potassium persulfate and 0.1 g Sodium bisulfite was added in the mixture, and the mixture was then stirred with stirring held at 2300 for about 6 hours.

The salt from and the work-up were carried out in the same way as in Example 1 carried out.

The copolymer formed contained about 0.5 mole glycidyl acrylate.

Copolymers containing a molar proportion of glycidyl acrylate of approximately 0.05% by mole, 1% by mole and 5% by mole, respectively, were determined in the same manner as above described, produced, with the modification that the molar proportion of glycidyl acrylate monomers has been modified.

The copolymers were dissolved in toluene and each of these solutions was applied to a thin chrome film that has been vapor-deposited onto a glass substrate was. After heating at 18,000 for 16 minutes, insoluble films of the copolytrerene had formed a thickness of about 5 microns.

In Table 2, the amount of radiation when irradiated with a Electron beam and the developer indicated that the formation of a fine positive Cathode radiation image on the. appropriate precured films using an electron beam of 15 KV are required.

These results indicate that by using a copolymer, which contains 0.05 mol%, 0.5 mol 1 mol% or 5 mol glycidyl acrylate units, a fine radiation image using about one fifth, one tenth, one Seventh resp.

half the radiation dose that can be achieved for conventional Polymers is required.

Copolymers with a molar proportion of glycidyl acrylate of more than 5 mol% cannot be used to form a fine image because form numerous crosslinks through the epoxy groups.

The films discussed above have the same behavior towards solvents as described in Example 2.

TABLE 2 Molar fraction of irradiation with; Glycidyl methacrylate developer Electron beam (mol%) (coulomb / cm2) 0.05 1 x 10-5 methyl isobutyl ketone 0.5 5 x 10-6 toluene 1 7 x 10-6 toluene 5 2 x 10-5 ethyl acetate

Claims (8)

PATENT CLAIMS 1. Containing cathode ray sensitive material a polymer of an alkyl methacrylate and optionally a suitable solvent, in that it is a copolymer of a polymer as a polymer Has alkyl methacrylate with an epoxy group-containing vinyl monomer. 2. Cathode ray sensitive material according to claim 1, characterized it is not noted that it contains a copolymer in which as epoxy group-containing Vinyl monomer glycidyl methacrylate or glycidyl acrylate is present. 3. Cathode ray sensitive material according to claim 1 or 2, in that it is used as a polymer of an alkyl methacrylate a copolymer of methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, Contains isopropyl methacrylate, isobutyl methacrylate or tert-butyl methacrylate. 4. Cathode ray sensitive * material according to one of the claims 1 to 3, in that it is a copolymer with a Contains molecular weights from about 500 to about 10 million. 5. Cathode ray sensitive material according to claim 4, characterized it is not noted that it is a copolymer with a molecular weight contains from about 100,000 to 5 million. 6. Cathode ray sensitive mater: ia: l according to one of the claims 1 to 5, characterized in that it contains a copolymer, in which the units of the epoxy group-containing vinyl monomer in a molar proportion from about 0.001 to about 5 mole percent. 7. Cathode ray-sensitive material according to one of the claims 1 to 5, noting that it contains a copolymer in which is the molar proportion of the units of the vinyl containing epoxy groups: onomers ranges from about 0.05 mole percent to about 5 mole percent. 8. Use of a cathode steel sensitive material according to one of claims 1 to 7 as a resist material for the production of cathode radiation sensitive Coating films.