JP3221909B2 - Photoresist material and pattern forming method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photoresist material and a pattern forming method using the same.

In recent years, integration of semiconductor integrated circuits has been advanced, and LSIs and VLSIs have been put into practical use. At the same time, the minimum line width of a wiring pattern has reached the submicron range, and there has been a tendency toward further miniaturization. . Here, to form a fine pattern, a resist is coated on the substrate to be processed on which a thin film has been formed, a selective exposure is performed, and then development is performed to form a resist pattern. Using this as a mask, dry etching is performed. It is indispensable to use a photolithography technique for obtaining a thin film pattern by dissolving and removing the film. Ultraviolet light was initially used as the light source for this photolithography technique, but resolution of submicron width was impossible due to wavelength limitations. Resolution of submicron width has been performed using a line as a light source. The present invention relates to these radiation resist materials.

[0003]

2. Description of the Related Art Conventionally, many resists based on phenolic resins have been developed. However,
Since these materials contain an aromatic ring, they absorb a large amount of light, and therefore, with such materials, it is not possible to obtain a pattern accuracy enough to cope with miniaturization.

On the other hand, the use of polymethyl methacrylate (PMMA) or polyisopropenyl ketone (PMIPK) as a resin having low light absorption has been studied. However, since these materials do not contain an aromatic ring, Does not have sufficient dry etching resistance.

[0005]

As described above, in order to realize a submicron fine pattern, it is necessary to have excellent transparency to ionizing radiation, particularly far ultraviolet light, and to have sufficient dry etching resistance. A photosensitive material is required, and the present invention provides a photoresist having both of these characteristics.
It is an object of the present invention to put a test material into practical use.

[0006]

SUMMARY OF THE INVENTION The present invention, in order to solve the above problems, a photo made with an ester portion of a copolymer of the polymer or the esters of acrylic acid esters or α-substituted acrylic acid ester substituted with norbornyl group cash register
Provide a strike material.

A resist made of the photoresist material of the present invention is coated on a substrate to be processed to form a resist layer, and the resist layer is selectively exposed to radiation and then developed to form a resist pattern. can do.

We have already proposed a radiation-sensitive material having an adamantane structure in the ester moiety. In the present invention, a norbornane structure is introduced in place of the adamantane structure, and a material excellent in transparency and dry etching properties has been successfully obtained.

The acrylate ester particularly useful in the present invention is norbornyl acrylate. A typical example of the comonomer constituting the copolymer useful in the present invention is a monomer having a structure that generates an alkali-soluble group by the action of an acid generator. Examples of such a monomer include t-butyl methacrylate and tetrahydropyranyl. Methacrylate can be mentioned. It is particularly advantageous to use such a copolymer together with an acid generator as the photoresist material of the present invention.

Further, when forming a pattern using a photoresist material of the present invention, a resist composed of the photoresist <br/> material to form a resist layer by coating on the substrate to be processed, the resist layer Is selectively exposed to radiation and then developed after pre-baking to insolubilize, or a resist layer is formed, and the resist layer is selectively exposed to radiation and baked and then developed. .

[0011]

According to the present invention, an acrylic acid ester having an ester moiety substituted with a norbornyl group is used as a photosensitive material having excellent transparency to ionizing radiation, particularly to deep ultraviolet light, and having sufficient etching resistance. Alternatively, a material comprising a polymer of an α-substituted acrylate or a copolymer of such an ester is used.

The following formula:

Embedded image Norbornane (C ₇ H ₁₂ ) having the structure represented by is chemically stable and excellent in heat resistance. The present inventors have paid attention to the fact that a polymer containing a norbornane skeleton in the ester portion has excellent etching resistance despite having no aromatic ring, and has low absorption for ionizing radiation, particularly, far ultraviolet light. Then, taking advantage of this feature, nor the ester portion
The present invention has been achieved by using a polymer of an acrylate ester or an α-substituted acrylate ester substituted with a bornyl group or a copolymer of such an ester as a photosensitive material.

Since such a photosensitive material has excellent etching resistance and excellent transparency, a submicron pattern can be accurately formed by using the photosensitive material as a radiation resist material.

[0014]

The present invention will be further described below with reference to examples. Example 1

Embedded image After distilling norbornyl methacrylate having the structure of
After preparing a 5 mol% solution using toluene as a reaction solvent, azobisisobutyronitrile (A) was used as a polymerization initiator.
IBN) was added at 2 mol%. Next, the temperature was raised and polymerization was performed at 75 ° C. for 6 hours. After completion of the reaction, precipitation purification was performed with methanol. As a result, the weight average molecular weight was 80,000,
A polymer of 1.9 was obtained.

After this polymer was converted into a xylene solution, it was coated on a quartz substrate to a thickness of 1 μm, and the transparency to far ultraviolet light (248 nm) was examined. ). The transmittance of PMMA was 98%, and that of phenol novolak resin was 30%.

Further, as a result of comparing the etching rate by carbon tetrafluoride gas (CF ₄ ) with that of PMMA,
The etching rate was 1100 ° / min, whereas that of polynorbornyl methacrylate was as excellent as 800 ° / min. The etching conditions were as follows: CF ₄ pressure 0.02 Torr
(100 sccm) and the power was 200 W.

Next, the obtained norbornyl methacrylate polymer is used as a crosslinking agent in the following formula:

Embedded image 4,4'-diazidophenylmethylene having the structure
Wt% to make xylene solution, 0.5μ on Si substrate
After coating to a thickness of m, prebaking was performed at 100 ° C. for 30 minutes.

Next, after exposing with a xenon-mercury (Xe-Hg) lamp for 30 seconds, development was performed with xylene for 60 seconds, and patterning characteristics were examined. As a result, a 0.6 μm line and space could be resolved.

Example 2 Instead of 4,4'-diazidophenylmethylene as a crosslinking agent, the following formula:

Embedded image The procedure of Example 1 was repeated using 4,4′-diazidophenylsulfone having the structure of In this case, similar results were obtained.

Example 3 Using AIBN as a polymerization initiator, norbornyl methacrylate and methacrylic acid were treated at 80 ° C. in 1,4-dioxane.
, And reprecipitation purification was performed using hexane. As a result, a copolymer having a weight average molecular weight of 30,000, a dispersity of 2.3, and a composition ratio of 6: 4 was obtained.

30% by weight of 4,4'-diazidophenylmethylene as a crosslinking agent is added to this polymer to form a cyclohexanone solution, which is coated on a Si substrate to a thickness of 0.5 μm,
For 30 minutes. Thereafter, exposure was performed for 30 seconds by a Xe-Hg lamp, and alkali development was performed. As a result, a 0.5 μm line and space pattern could be resolved. The etching resistance in this case was equivalent to that of polynorbornyl methacrylate.

Example 4 Norbornyl methacrylate and t-butyl methacrylate were copolymerized in the same manner as described in Example 3, and as a result, the weight average molecular weight was 18,000, the degree of dispersion was 1.9, and the composition ratio was 4:
6 was obtained. This polymer is an acid generator, the following formula,

Embedded image 5% by weight of triphenylsulfonium hexafluorophosphate having the following structure was added to form a cyclohexanone solution, which was coated on a Si substrate to a thickness of 1 μm,
Prebaking was performed for 0 minutes.

Next, exposure was performed for 20 seconds with a Xe-Hg lamp, baking was performed at 110 ° C. for 20 minutes, and development was performed with alkali. As a result, a 0.5 μm line and space pattern was resolved. The etching rate in this case was 1.2 times that in the case of polynorbornyl methacrylate, and the transmittance of the resin was equivalent to that of PMMA.

Example 5 The following formula was used as the acid generator:

Embedded image The operation of Example 4 was repeated using diphenyliodohexafluorophosphate having the structure In this case, similar results were obtained.

Example 6 Copolymerization of norbornyl methacrylate and tetrahydropyranyl methacrylate in the same manner as described in Example 3 resulted in a copolymer having a weight average molecular weight of 12,000, a dispersity of 1.7, and a composition ratio of 6: 4. was gotten.

3% by weight of triphenylsulfonium hexafluorophosphate was added to this polymer to form a cyclohexanone solution. After coating on a Si substrate to a thickness of 1 μm, prebaking was performed at 90 ° C. for 30 minutes. Then X
Exposure was performed with an e-Hg lamp for 5 seconds, baked at 110 ° C. for 20 minutes, and developed with alkali. As a result, 0.5μ
An m-line and space pattern was resolved. In this case, both the etching rate and the transmittance were the same as in the case of polynorbornyl methacrylate.

Example 7 The following formula:

Embedded image As a result of repeating the operation of Example 6 using benzoin tosylate having the structure as an acid generator, similar results were obtained with an exposure time of 3 seconds.

Example 8 As a result of repeating the operation of Example 6 using an electron beam exposure apparatus having an acceleration voltage of 20 kV instead of the Xe-Hg lamp,
A 0.7 μm line and space pattern was obtained at 1.6 μC / cm ² .

[0029]

According to the present invention, it is possible to obtain a resist pattern having high transparency to ionizing radiation and sufficient etching resistance, whereby a submicron pattern can be formed with high precision. it can.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-52050 (JP, A) JP-A-3-157657 (JP, A) JP-A-7-90227 (JP, A) JP-A-2- 97516 (JP, A) JP-A-63-314219 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 7/038 G03F 7/027 G03F 7/039 H01L 21/027

Claims (2)

(57) [Claims] [Claim 1] comprising the ester moiety of a copolymer of the polymer or the esters of acrylic acid esters or α-substituted acrylic acid ester substituted with norbornyl group Fotore
Zyst material. 2. The ester moiety is substituted by a norbornyl group.
Of acrylate or α-substituted acrylate
A resist comprising a polymer or a copolymer of the ester is applied on a substrate to be processed to form a resist layer, and the resist layer is selectively exposed to radiation and then developed to form a resist pattern. Characteristic pattern formation method.