JPH01207310A - Macromolecular material absorbing short-wave light - Google Patents

Abstract

PURPOSE:To obtain the title material absorbing excimer laser beam capable of etching with a short time exposure and having resistances to etching, consisting of methacrylate, fluoromonomer and a specific aromatic monomer. CONSTITUTION:The aimed material expressed by the formula (R1, R3 and R5 are H, methyl and ethyl, respectively; R2 is 1-5C alkyl; R4 is fluoroalkyl at least one H is substituted with F within 1-8C alkyl) R6 is a group containing aromatic chain such as naphthalene ring, anthracene ring; l, m and n >=1, respectively and 30<=(l+m)/n<=200). The material is preferably obtained by copolymerization with plasma polymerization method of the three; methacrylate such as methyl methacrylate, fluoro-monomer such as trifluoroethyl acrylate and a monomer such as vinyl naphthalene which has a group containing aromatic chain, simultaneously.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention absorbs short wavelength light of 400 nm or less (ultraviolet rays, electron beams, X-rays), particularly -F laser light (249 nm), and The present invention relates to a short-wavelength light-absorbing polymer material that is resistant to etching agents such as liquids and HF gas.

(Prior art and problems to be solved) Conventionally, a mercury lamp such as a 356 nm high-pressure mercury lamp or a xenon lamp is used as a light source for resist materials, and long-time exposure of 5 to 10 minutes is performed. was. When such a long exposure is performed, it is difficult to obtain a clear image due to effects such as a shift in focus and vibrations of the measuring table during measurement. Recently, photoresists, that is, microfabrication (10 μI or less) using an excimer laser irradiation method have been attracting attention as short-time exposure. However, a polymeric material for photoresist suitable for this method has not yet been developed. In particular, short wavelengths in the ultraviolet region (208 nm - 193 nn+), such as excimer lasers, allow for high lens numerical apertures (NA).
ture), there is a problem that the depth of focus becomes shallow. For this reason, it is necessary to make the photoresist polymer material 1 μm or less, preferably 5000 Å or less, but a material design suitable for such thin film formation has not yet been found.

The present invention relates to improvements in polymeric materials for increasing the resolution of photolithography. By the way, the resolution R of photolithography is determined by the following equation.

λ R=−NA Here, λ is the wavelength of the light source (reduction projection exposure device Nischiper), NA is the aperture coefficient, and k is a constant determined by the resist and its process.

From this equation, we can see that in order to increase the resolving power R, (1) shorten the wavelength of the light source (decrease λ), (2) aperture coefficient of the optical lens (N
A) Increase. (3) Improvements in resist materials and processes (reducing k) can be considered.

The recent trend toward shorter wavelengths has led to active development of excimer laser steppers. However, with shorter wavelength and higher NA
If this is done in a similar manner, there will be a drawback that the depth of focus (DOF) will be shallow. Focus DOF when using a stepper = 2N
°°゛゛°°°゛°゛(2) It is expressed as Φ period P. In particular, increasing the NA is a big problem because the effect is squared. In order to deal with this problem, this patent has developed an ultra-thin film that allows excimer laser light to effectively pass through the polymer lithography material even if the numerical aperture (NA) of the lens is narrowed down (for example, on the order of several thousand people). This makes it a major feature. This ultra-thin film was achieved by making the film ultra-high molecular weight.

If the depth of focus is shallow, a phenomenon of partial distortion (out of focus) will occur, which will lead to a corresponding reduction in process margin.It is desirable to use a thin film of typically ±1 μm or less. However, with conventional resist materials, making such a thin film causes pinholes and a decrease in etching resistance, so the trend has been to make the film thicker.

In the present invention, these problems can be solved by (1) increasing the degree of polymerization of the methacrylate compound to an ultra-high molecular weight of the order of 106 to 107, thereby making it possible to form an ultra-thin film (on the order of several thousand). (2) By adding a fluorine compound to the compound in (1), resistance (HF liquid or HF gas) can be imparted. (3) Excimer laser (ultraviolet light region) XeC1 (308 nm), Kr
F (249nm), ArF (193nm), etc. 400
Short wavelength light of nm or less (ultraviolet rays, electron beams, X-rays), especially K
This problem was solved by chemically bonding a sensitizer that highly absorbs rF (249 nm) laser light. The purpose of the present invention is to provide light-absorbing polymeric materials. The present invention solves the above problems and uses excimer laser light (
(ultraviolet absorption light), especially -F laser light (249nm)
The object of the present invention is to provide a polymer lithography material that absorbs HF and has resistance to etching agents such as HF liquid and HF gas.

(Means for solving problems) That is, the present invention is based on the general formula %formula%() It is a short-wavelength light-absorbing polymer material represented by

In this general formula, if the value of (Ω10m)/n is less than 3071, polymerization will not occur sufficiently and it will be difficult for the light to reach the inside of the film during laser light irradiation, while on the other hand, if it is more than 10010.5, it will not be absorbed during laser light irradiation. This is because the reaction will be delayed. Therefore, in order to form these polymers (1)
Copolymerized to a methacrylic acid ester having the structure (I
I) As a seven-member structure: hexafluoroisopropyl methacrylate CH.

CH,=C " C00C) I (CF3).

trifluoroethyl methacrylate Cl-13 CH2=C ■ C00CH, CF.

Trifluoroethyl acrylate CH2=CH-C00CH2CF3 Hexafluoroisopropyl acrylate CH,=CH-
Fluorine-containing vinyl salts such as C00CH(CF, )2
It is. Or hexafluorobutene CF3C=CCF.

Hexafluorobutadiene 1.3 CF2=CFCF=
C.F.

These include fluorine-containing olefin compounds such as hexafluoropropane CF and CF=CF.

Therefore, methyl methacrylate and the fluorine atom-containing monomer may be copolymerized in a desired ratio within the above-mentioned range.

Furthermore, examples of the monomer having the (m) structure containing a group having a naphthalene ring, anthracene, biphenyl, and fluorene include vinylnaphthalene, vinylanthracene, vinylbiphenyl, and vinylfluorene. Other compounds with polynuclear aromatic nuclei include phenanthrene,
Examples include compounds such as triphenylene, chrysene, and pyrene. It may have a side chain having a (chilphen)Li÷+←) chain and form a copolymer with the above-mentioned acrylate and a fluorine atom-containing monomer. Then, these monomers may be copolymerized within the above-mentioned range, and in this case, the king may be copolymerized at the same time, or the king may be copolymerized first, and then the remaining monomers may be added and copolymerized. The method of monomer copolymerization in which the former king is simultaneously bonded is preferred.As the copolymerization method, any of the usual copolymerization methods for vinyl compounds can be applied, but in particular plasma irradiation in the presence of a radical polymerization initiator is preferred. Most preferred is plasma polymerization. As the radical polymerization initiator, any initiator used in general radical polymerization may be used, such as benzoyl peroxide, dicumyl peroxide, and azobisisobutyronitrile. The amount of radical polymerization initiator added to the seven polymers varies depending on the type of monomer, polymerization temperature, polymerization of the polymer to be obtained, etc., but if you add more radical polymerization initiator than necessary, the polymerization initiator will remains in the produced polymer, which is undesirable.

In addition, the plasma used in the plasma polymerization method is preferably non-equilibrium plasma, especially low-temperature plasma generated by glow discharge, and the low-temperature plasma is used under reduced pressure, e.g.
It is obtained by applying a voltage of 20 to 100 υ, preferably 30 to 50 Ill, to a gas under a pressure of OHHg. The electrodes used include external or internal parallel plate electrodes or coiled electrodes, preferably external parallel plate electrodes. The plasma source gas may be any gas such as hydrogen, methane, nitrogen, argon, ethylene, or the monomer gas itself.

The resulting copolymer can be made into an ultra-thin film (thousands of layers) by increasing its degree of polymerization to an ultra-high molecular weight of the order of 10' to 107, and is also highly resistant by containing fluorine atoms. (11F liquid or 14F gas), and excimer laser (ultraviolet light region) such as Xe-CQ (308
(nm), Kr-F (249 nm), Ar-F, etc.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Experiment Example 1) Methyl methacrylate (HMA) 2.67+ was placed in a Pyrex glass polymerization tube (capacity 42 mQ) with an inner diameter of 15 Io11.
a Q (2,50X 10”” no Q), hexafluoroisopropyl methacrylate CHFIPHA)
4.54mm (2,50X 10-2ffloQ)
, 2-vinylnaphthalene (2VNP) 0.096g (6
,25
-'mo Q /g), the polymerization tube was connected to a vacuum line, and frozen with liquid nitrogen. This thread is 10-'Torr
After degassing, the MM in the system was sent out and melted again. After repeating this operation three times, the cock was closed, and when a portion of the monomer in the polymerization tube began to dissolve, plasma was generated in the gas phase. 501i plasma treatment was performed for 1.60 seconds using a 13.56 MHz high frequency generator.

The polymerization tube was sealed and allowed to stand at 25°C, and post-polymerization was carried out for 10 days. The obtained polymerization reaction product was dissolved in 1ooIIIQ of acetone and reprecipitated with 2.0Q of ethanol to prepare N to obtain a white polymer. The weight of the obtained polymer is 0.70g
(The yield was 8.2% by weight). In addition, the intrinsic viscosity [η] was measured at 25°C by dissolving this polymer in acetone.
was 3.70 x 10''. In addition, in the Mark and Horwink equation [η] = KMα, by substituting = 7.5 x 10-3 and α = 0.70 for the coefficient regarding polymethacrylic acid, [η] The average molecular weight determined from
It was 10'.

(Example 1) A 1% by weight methyl isobutyl ketone solution of the polymer obtained in Experimental Example 1 was coated with a spin coater (IH-
02 type) to a thickness of 300 nm on a silicon wafer.
After coating with a thin polymer film and baking (170° C. for 30 minutes), the etching resistance with hydrofluoric acid was examined. (Reference Figure 1) Etching resistance was determined by dropping a 50% hydrofluoric acid aqueous solution onto the wafer using a cotton swab, and leaving it at 25°C for 5 minutes. I observed the surface after washing with water, but
No degeneration or erosion was observed.

(Example 2) The 9t% MIBK solution obtained in Example 1 was coated onto a silicon wafer plate using a spinner in the same manner as in Example 1 to a thickness of approximately 3000 mm.

This film substrate was prebaked at 110° C. for 30 minutes and then irradiated with a KF excimer laser (249 nm) (5 pulses, 1 pulse approximately IO+1 second). Then 17
Fine line and space line width 1 obtained by after-baking at 0°C for 30 minutes and then developing for 5 minutes at 25°C with a development solution for Freon substrates (developing solution containing 90% nibrobanol: Daiflon FBIMIO manufactured by Daikin Co., Ltd.). ．．
A 0 μm lithography pattern was obtained (reference figure -
3). As a result, it became clear that clear and delicate patterns could be drawn.

The ultraviolet absorption spectrum of the lithographic polymer material is shown in Figure 1 (■), which is a spectrum very similar to that of the (HMA-2 vinylnaphthalene) copolymer of Comparative Example 1. The transmittance in the vicinity is about 2.0%, and the absorption of this line material is extremely excellent for lithography polymer materials.

(Experimental Example 2) Methyl methacrylate 2.67m Q 2.50X 10-2+o Q Hexafluoroisopropyl methacrylate 4.54+Q2
．． 50X10-'woQ2-vinylnaphthalene 0.129g 8.33X10-'o+oQ initiator (
BPO) 0.005g 4.13X10-3a
A plasma-initiated polymerization reaction was carried out in the same manner as in Experimental Example 1 except for the charging conditions of +o12/Q.

Yield 0.54g (yield 6.41%) [711= 3.41 X 10” ([77] =
7.5 x 10-'MO, 70), MV = 4.
51 x 10' Shape White powder (Example 3) The polymer material obtained from Experimental Example 2 was baked in the same manner as in Example 1 (170°C, 30 minutes), and then baked in a 50% HF solution at 25°C for 5 minutes. I did some baking. As a result, as shown in Reference FIG. 2, no denaturation or corrosion of the resist film was observed, and it was found that the resist film had resistance. Further, the ultraviolet absorption spectrum of the lithographic polymer material is shown in FIG.

(Experimental Comparative Example 1) Methyl methacrylate 2.67m Q 2.50 X 10"-"ll1o
n2-vinylnaphthalene 0.064g 7.17 X 10''''moQ initiator (BPO) 0.005g 4.13X10-
A plasma-initiated polymerization reaction was carried out in the same manner as in Experimental Example 1 except for the charging conditions of 3moQ/(1).

Yield 0.18g (yield 75%) [η] = 5.99 x 10” ([η] = 5.2
MV=4.57X10' from
n2-vinylnaphthalene 0.129g 8.36X10-'+oQ initiator (
BPO) 0.005g 4.13XIO-3m
A plasma-initiated polymerization reaction was carried out in the same manner as in Experimental Example 1 except for the oQ/Q charging conditions. MV = 4.57 x 1
It was 0'.

This polymer material was baked (170°C) in the same manner as in Example 1.
.

30 minutes), then 50%) IF solution at 25°C.
, baking was performed for 5 minutes. Similar to Example 2, no denaturation or corrosion of the resist film was observed, indicating that the resist film had corrosion resistance. Further, the ultraviolet absorption spectrum of this lithographic polymer material is shown in Figure 1-2.

(Comparative Example 1) The polymer material obtained in Experimental Comparative Example 1 was baked (170° C., 30 minutes) in the same manner as in Example 1. then 50%
It was found that the resist film was damaged when it was baked in an HF solution at 25° C. for 5 minutes.

(Effects) As described above, the short-wavelength light-absorbing polymer material of the present invention is particularly suitable for r-F laser (249n111) irradiation, and is suitable for preventing film damage and dissolution during wet etching (acid-resistant and alkali-resistant treatment) of PMMA. This problem can be solved by chemically bonding a compound containing a fluorine atom, and the problems of pinholes and poor etching resistance caused by conventional film formation can be solved with ultra-high molecular weight PMMA. It is now possible to perform focal vibration, easy operation, and produce high-resolution fine patterns (fine patterns of 1 μm or less) with one to several irradiation times.
It is possible to provide an excimer laser-irradiated polymer lithography material that allows drawing of images.

[Brief explanation of the drawing]

FIG. 1 is an ultraviolet absorption spectrum diagram of Examples 1, 2, and 3 according to the present invention.

Claims (1)

[Claims] 1. General formula ▲ Numerical formulas, chemical formulas, tables, etc. R_4 represents a fluoroalkyl group in which at least one hydrogen atom is substituted with a fluorine atom among alkyl groups having 1 to 8 carbon atoms, and R_6 represents an aromatic group such as a naphthalene ring, anthracene ring or biphenyl. It is a group having a group chain, l, m, n are integers of 1 or more, and 30≦(
l+m)/n≦200. ] A short-wavelength light-absorbing polymer material represented by