JPS6113734B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radiation-sensitive composition, and more particularly to a radiation-sensitive composition that prevents a reaction from continuing even after radiation irradiation has stopped.

Conventionally, in optical lithography in which a photosensitive material is used as a photoresist for microfabrication, it is obvious that there is a limit to the machining accuracy on the order of the wavelength of light. In order to perform higher precision processing, electron beam,
Lithography using extremely short wavelength radiation such as X-rays has been proposed. When used as a resist, such a radiation-sensitive material sensitive to radiation is called an electron beam resist, an X-ray resist, or the like.

In the early stages of research, photoresists were sometimes used as electron beam resists, but specialized resists with desirable properties for electron beam or X-ray exposure are being developed.

As is well known, among these radiation resists, there are two types: positive type, in which molecular chains are cut by radiation irradiation, resulting in a decrease in molecular weight, and negative type, in which crosslinking occurs upon radiation irradiation, resulting in an increase in molecular weight. In general, polymeric substances with low molecular weight have high solubility in solvents, so by irradiating a resist coated on a substrate with radiation in a desired pattern and then immersing it in an appropriate solvent,
The part with relatively low molecular weight is dissolved and removed,
A relatively high content portion remains. Therefore,
When a specific pattern is irradiated with radiation, the resist pattern obtained after development will have the irradiated portion remaining in the negative resist pattern, and a pattern that is the inverse of that in the positive resist pattern. The sensitivity of a resist is difficult to determine uniquely because it depends on the development method, but the basic question is how many cuts or crosslinks occur in response to a certain amount of radiation irradiation.

When the present inventors attempted precision processing using a negative resist containing repeating units containing epoxy groups, they discovered that the reaction of this material continued even after radiation irradiation was stopped. , published some of the results. (Proceedings of the 11th Semiconductor/Integrated Circuit Technology Symposium, 72-
Page 77 (1976) This fact shows that when precise drawing is performed on a substrate, and it takes a considerable amount of time to draw by irradiation, there is a difference in the dimensions of the initially drawn part and the final drawn part. It means to occur. In order to suppress this undesirable phenomenon, the present inventors have already proposed a composition in which a radical scavenger is added to a negative resist containing repeating units containing epoxy groups.

As a result of further research, the present inventors recognized the fact that even in negative-tone resists in which the crosslinking reaction occurs due to azide groups, the reaction proceeds even after irradiation has stopped, and this unnecessary reaction after irradiation is stopped by radical scavenging. The present invention was achieved by successfully suppressing the reaction effectively by adding a reaction inhibitor such as a reaction inhibitor.

That is, in the present invention, a reaction inhibitor is contained in a material whose molecular weight increases due to crosslinking by azide groups caused by radiation irradiation, in order to prevent the reaction from continuing even after radiation irradiation is stopped. A radiation-sensitive composition is provided.

According to the present invention, by preventing the reaction from proceeding after the irradiation is stopped, fine processing can be realized without a large error from the intended design value. Furthermore, when performing precise drawing on a substrate, even if it takes a considerable amount of time to draw by irradiation, there will be no difference in size between the initially drawn part and the last drawn part.

The present invention will be explained in detail with the following examples.

Reference example JSR resist manufactured by Japan Synthetic Rubber Co., Ltd. was used for drawing by electron beam irradiation without adding a reaction inhibitor.
This resist contains cyclized polybutadiene in solution.
Contains 14% by weight of 2,6-di-(4'acidobenzal)cyclohexanone as an azide crosslinker to increase sensitivity. is added. Apply this resist onto a chrome blank using a spinner (6000 rpm) and
℃, prebake for 15 minutes,
A uniform film of 0.7 μm was obtained. Using an electron beam exposure device, various patterns with varying line widths and line spacings were drawn at an acceleration voltage of 20 KV and a radiation dose of 8 x 10 ^-7 coulombs/cm ² . After repeating drawing under exactly the same conditions at different positions on the same substrate after some time, the chrome blank substrate was taken out from the exposure device and stirred in JSR developer (manufactured by Japan Synthetic Rubber Co., Ltd.) for 60 seconds. It was immersed and developed, and then immersed in n-butyl acetate for 30 seconds for rinsing to obtain a resist pattern.

When we closely observed this resist pattern, we found that
Items that have been irradiated for 30 minutes (i.e., were held in a vacuum exposure device for 30 minutes), items that have been exposed for 1 hour, 2 hours, 3 hours, 5 hours, and 20 hours. It was found that the pattern gradually became thicker even though the pattern was irradiated under the same conditions, and it was found to be inconvenient if it took more than 30 minutes to draw by irradiation.

Example 1 A composition was prepared in which 5% by weight of 1,1-diphenyl-2-picrylhydrazyl (DPPH) was added and mixed with the polymer component of the JSR resist used in the reference example. When we conducted an experiment using exactly the same method as described in the reference example, we found that the irradiation dose was insufficient. In this case, it was necessary to increase it to 1.4×10 ^-6 coulombs/cm ² . A resist pattern was obtained by changing only this condition and otherwise performing the same procedure as in the reference example.

When we closely observed this resist pattern, we found that
A pattern with a uniform line width was obtained within a range of up to 20 hours after irradiation.

Example 2 The same effect as in Example 1 was obtained by adding 5% by weight of galvinoxyl to the polymer component of the resist of Reference Example.

Example 3 For the polymer component of the resist used in the reference example,
The composition to which 10% by weight of iodine was added showed an inhibitory effect on the reaction after the irradiation was stopped, but the effect was not as great as that of Example 1. However, the required irradiation dose was 1×10 ⁻⁶ coulomb/cm ² and did not show a significant increase. The crosslinking reaction that continues to occur even after the irradiation has stopped is thought to be because radicals generated by the irradiation do not disappear even after the irradiation has stopped, causing a chain reaction. The experimental facts regarding this post-irradiation effect are already well known in the field of radiochemistry. (For example, see "Radiation Polymerization" by Yoneho Tabata (Sangyo Tosho, published in 1962).) Therefore, the application of the present invention is not limited to the examples listed above, but also to polymers that do not contain an azide group. 2,6-di-(4'-azidobenzal)-4, which can be expected to have exactly the same effect as an azide crosslinking agent.
-methylcyclohexanone, 4,4'-diazidochalcone, 4,4'-diazidodiphenylmethane, etc.
It goes without saying that the invention also extends to compositions comprising materials well known to those skilled in the art. Although it is possible that a polymer that does not contain an azide group does not contain a group that directly causes crosslinking upon irradiation with radiation, a polymer that contains such a group has better efficiency against irradiation. In addition to the cyclized polybutadiene used in the examples, suitable polymers that do not contain azide groups and can be crosslinked by irradiation include polystyrene, styrene-polybutadiene copolymers, polydiallyl orthophthalate, and polydimethylsiloxane. It is.

Further, polymer substances in which an azide group is bonded to the side chain of a polymer substance, such as polyazidobenzoic acid, are also included in the present invention because crosslinking occurs by the same mechanism. In addition, as a secondary effect of the present invention,
Materials containing azide groups are extremely unstable to light, and this reaction inhibitor works to weaken that sensitivity.

Regarding these materials mainly composed of azide groups,
For example, there is a useful description in ``Photosensitive Resin'' by Takahiro Tsunoda (published by the Institute of Printing Publishing Department in 1972). Among reaction inhibitors, radical scavengers include tri-p-nitrophenylmethyl, di-p-fluoroaniline, N-(3N-oxyanilino-1,3-dimethylbutylidene), in addition to those listed in Examples. ) Stable radicals such as aniline oxide, substituted products and homologs thereof, alkyl iodides, quinones such as p-benzoquinone, anthraquinone, and chloranil, polyhydroxy compounds such as hydroquinone, catechol, and p-butylcatechol, pyridine,
Methylaniline, p-phenylenediamine, N,
Amino compounds such as N'-tetraethyl-p-phenylenediamine, m-dinitrobenzene, 2,4
-Dinitrotoluene, 2,4-dinitrophenol, nitro compounds such as picric acid, nitroso compounds such as nitrosobenzene, nitroso-β-naphthol, dithiobenzoyl sulfide, p,p'-ditolyl trisulfide, p, Organic sulfur compounds such as p'-ditolyltetrasulfide, metal chlorides such as ferric chloride, cupric chloride, titanium trichloride, and nickel dichloride are known.

Although these reaction inhibitors may have different suppressive effects on the reaction after radiation irradiation has stopped, those with a significant suppressive effect tend to increase the irradiation dose, that is, lower the sensitivity. The user can select the amount or type of additive depending on the required pattern accuracy. It is also known that when two or more types are added in combination, a remarkable synergistic effect appears. Therefore, the reaction inhibitor is not limited to those described in the examples, but all radical reaction inhibitors and scavengers as inhibitors known in the field of radiochemistry are included within the scope of the present invention. It is clear that

As described above, by adding a reaction inhibitor to a material whose molecular weight increases due to crosslinking by azide groups caused by radiation irradiation, the reaction after irradiation is stopped can be suppressed.

Claims (1)

[Scope of Claims] 1. A radiation-sensitive composition comprising a material whose molecular weight increases due to crosslinking by azide groups caused by radiation irradiation, and a reaction inhibitor in an amount of 5% by weight or more and 20% by weight or less based on the above material. . 2. The radiation-sensitive composition according to claim 1, wherein the material is a polymeric substance that essentially contains an azide group-containing unit in its polymerized repeating unit. 3. The radiation-sensitive composition according to claim 1, wherein the material is a polymer containing no azide group and an azide crosslinking agent. 4. The radiation-sensitive composition according to claim 3, wherein the polymer is a polymer that undergoes crosslinking upon irradiation. 5. The radiation-sensitive composition according to claim 4, wherein the polymer that undergoes crosslinking upon irradiation is polystyrene, cyclized polybutadiene, styrene-butadiene copolymer, polydiallyl orthophthalate, or polydimethylsiloxane. 6. The radiation-sensitive composition according to claim 1, wherein the reaction inhibitor is a radical scavenger. 7. The radiation-sensitive composition according to claim 6, wherein the radical scavenger is a stable radical. 8 Stable radicals include diphenylpicrylhydrazyl, tri-p-nitrophenylmethyl, di-p-
-fluoroaniline, N-(3N-oxyanilino-1,3 dimethylbutylidene)aniline oxide or galbinoxyl, or substituted products thereof, or homologues thereof. 9. The radiation-sensitive composition according to claim 7, wherein the radical scavenger is iodine or alkyl iodide. 10. The radiation-sensitive composition according to claim 1, wherein the reaction inhibitor is a combination containing two or more types of radical scavengers.