JPS6311654B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ionizing radiation sensitive resist useful in microfabrication techniques for manufacturing semiconductor devices, photomasks, and the like.

Currently the most widely used positive radiation resist [polymethyl methacrylate (PMMA)]
Although it has excellent resolution, the electron beam sensitivity is 5.
×10 ^-5 C/cm ² and X-ray sensitivity is low, about 500 mJ/cm ² .For example, a normal X-ray device requires about 2 hours of irradiation time per wafer. In addition, polybutene-1-sulfone (PBS) and polyfluorinated alkyl methacrylate (e.g. FBM), which are thought to have the highest sensitivity performance among positive radiation resists, have improved sensitivity by more than an order of magnitude compared to PMMA. However, X-rays still require at least 5 to 10 minutes of irradiation time. Moreover, in the case of these resists, the former has poor dry etching resistance due to its tendency to thermally decompose, and the latter has shortcomings in its basic properties as a resist, such as poor heat resistance due to its low glass transition temperature. are doing.

On the other hand, negative-tone radiation resists have higher sensitivity than positive-tone resists; for example, polyglycidyl methacrylate (PGMA) and glycidyl methacrylate-ethyl acrylate copolymer (COP) have an electron beam sensitivity of about 4×10 ^-7 C/cm ² , X-ray sensitivity 10mJ/
It is about ^cm2 . However, even with these negative resists, for example, in the case of X-rays, it is difficult to cut down the irradiation time to 1 minute per wafer, and furthermore, the resolution is poor due to bridges and scum peculiar to negative resists, and submicron Patterning is not easy.

In this way, positive resists have excellent resolution but have drawbacks in sensitivity and other resist properties, while negative resists have superior sensitivity compared to positive resists but are extremely inferior in resolution. Thus, it has been difficult to perform submicron patterning with conventional resists even with high sensitivity (low dose).

The present invention was developed in view of the above circumstances, and has ultra-high sensitivity (irradiation dose of approximately 4×10 ^-7 C/cm ² or less for electron beams, and approximately 10 mJ/cm ² or less for X-rays) and is capable of producing submicron The object of the present invention is to provide an ionizing radiation-sensitive negative resist that can form a high-density resist pattern.

That is, the ionizing radiation sensitive negative resist of the present invention has the general formula [However, in the formula, R is H or CH ₃ , X is F, Cl,
Indicates a halogen atom such as Br. ] A polymer represented by [ ] or a copolymer of a monomer of this polymer and another monomer [ ]
It is characterized by consisting of the following.

As the negative resist of [] above, for example, poly(2,3-difluoroallyl acrylate),
poly(2,3-dichloroallyl methacrylate),
poly(2,3-dibromoallyl acrylate),
Poly(2,3-dibromoallyl methacrylate)
etc. can be mentioned.

The other monomers in the above copolymer [] may be any monomer that can be copolymerized with the monomer of the polymer [], such as styrene, α-methylstyrene glycidyl methacrylate, methyl methacrylate, ethyl acrylate, acrylonitrile, etc. can be mentioned.
In this case, the monomer content of the polymer [] in the copolymer is desirably 30 mol % or more from the viewpoint of maintaining high sensitivity performance.

Next, a method for forming a pattern using the ionizing radiation-sensitive negative resist of the present invention will be explained by showing an example.

First, a resist solution is prepared by dissolving a negative resist sensitive to ionizing radiation in an appropriate solvent such as a cellosolve solvent or an aromatic hydrocarbon solvent. Next, this resist solution is applied uniformly onto the semiconductor substrate or mask substrate using a spinner or the like to coat a resist film of the desired thickness, and then the remaining solvent is removed to increase the adhesion to the substrate. Perform pre-bake treatment. Next, the desired portion of the resist film is exposed to ionizing radiation such as electron beams and X-rays according to a conventional method, and then developed with an appropriate developer such as an aromatic hydrocarbon solvent or an amide solvent. Then, only the non-irradiated portions of the resist film are selectively dissolved and removed, and further, a rinsing process is performed with a rinsing liquid such as an alcohol solvent to form a resist pattern. Thereafter, using the resist pattern as a mask, the exposed portion of the substrate is etched by dry or wet etching to form an etched pattern.

Therefore, as shown in the general formula, the ionizing radiation-sensitive negative resist of the present invention has an ester side chain moiety of an acrylic or methacrylic polymer that has an allyl group that is highly crosslinking-reactive due to radiation, which also has high reactivity due to radiation. Since it has a halogenated allyl group bonded to a halogen atom, it exhibits extremely high crosslinking reactivity to radiation. Furthermore, resist properties can be improved by copolymerizing with other polymers with high glass transition temperatures, or with polymers with excellent resolution and dry etching resistance, such as polystyrene. By forming a copolymer, it is possible to obtain a resist material that has not only high sensitivity but also high resolution and excellent dry etching resistance.

Next, examples of the present invention will be described.

Example 1 Poly(2,3-dibromoallyl acrylate)
A resist solution was prepared by dissolving in ethyl cellosolve acetate. This resist solution was applied onto a silicon wafer using a spinner to cover a resist film with a thickness of 1 μm, and was further prebaked at 80° C. for 30 minutes in nitrogen. Subsequently, soft X-rays (AlKα rays, wavelength 8.34 Å) are applied to desired portions of the resist film through a silicon X-ray mask with a gold pattern.
After selective irradiation with an irradiation dose of 2 mJ/cm ² , a resist pattern was formed by developing with xylene for 1 minute and rinsing with isopropanol for 30 seconds. When the obtained resist pattern was observed using a scanning electron microscope (SEM), it was found that a good resist pattern with few bridging and scum was formed.
It was confirmed that the image had a resolution of

Example 2 A resist solution was prepared by dissolving a 2,3-dibromoallyl acrylate-styrene copolymer (2,3-dibromoallyl acrylate content: 50 mol %) in ethyl cellosolve acetate. This resist solution was applied onto a chromium mask substrate using a spinner to cover a resist film with a thickness of 7000 Å, and further prebaked at 80° C. for 30 minutes in nitrogen. Subsequently, a desired portion of the resist film was exposed to 3×10 ^-7 C/cm ² using an electron beam drawing device (acceleration voltage 20 kV).
After pattern drawing was performed with a dose of irradiation, the same development and rinsing treatments as in Example 1 were performed to form a resist pattern. After that, the exhaust pressure is 3×10 ^-1 Torr,
When the chromium film exposed from the resist pattern was etched for 4 minutes by reactive ion etching using a mixed gas of C Cl ₄ and O ₂ at an output of 200 W, a good photomask with a submicron chromium film pattern was obtained.

Example 3 A resist solution was prepared by dissolving poly(2,3-dichloroallyl methacrylate) in monochlorobenzene. Coating and prebaking were performed in the same manner as in Example 1 to form a 1 μm thick resist film on a silicon wafer. Subsequently, in the same manner as in Example 1, soft X-rays were applied to the desired portion of the resist film at 5 mJ/
After selective irradiation with a dose of cm ² , a resist pattern was formed by developing with dimethylformamide for 1 minute and rinsing with isopropanol for 30 seconds. When the obtained resist pattern was observed using SEM, it was found that a resist pattern with good sharpness and excellent edge linearity was formed.
It was confirmed that it has a resolution of 0.7 μm space).

Example 4 A resist solution was prepared by dissolving a 2,3-dichloroallyl acrylate-glycidyl methacrylate copolymer (2,3-dichloroallyl acrylate content: 50 mol%) in monochlorobenzene. Coating and prebaking were performed in the same manner as in Example 2 to form a resist film with a thickness of 7000 Å on the chrome mask substrate. Subsequently, in the same manner as in Example 2, 1×
After performing electron beam writing at an irradiation dose of 10 ^-7 C/cm ² , a resist pattern was formed by developing with dimethylformamide for 1 minute and then rinsing with isopropanol for 30 seconds. Thereafter, the chromium film exposed from the resist pattern was etched in the same manner as in Example 2, and a good photomask having a submicron chromium film pattern was obtained.

As detailed above, the present invention has extremely high sensitivity to ionizing radiation (4× in the case of electron beams)
It is possible to provide an ionizing radiation-sensitive negative resist that can form a submicron high-density resist pattern with an irradiation dose of about 10 ^-7 C/cm ² or less, or about 10 mJ/cm ² or less in the case of X-rays).

Claims (1)

[Claims] 1. General formula [However, in the formula, R is H or CH ₃ , X is F, Cl,
Indicates a halogen atom such as Br. ] An ionizing radiation-sensitive negative resist characterized by comprising a polymer represented by: or a copolymer of a monomer of this polymer and another monomer.