Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2002-08-26
2004-08-17
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S907000, C430S914000, C526S247000, C526S281000, C526S329600
Reexamination Certificate
active
06777162
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive polymer and a photoresist composition thereof.
2. Description of the Related Art
A smaller sized pattern design rule of not greater than 0.2 &mgr;m is necessary in a semiconductor memory device having a capacity exceeding 1 Gbit. A photolithographic technique has been proposed in which an argon fluoride excimer laser (“ArF”) capable of forming 0.1 &mgr;m patterns and having a wavelength of 193 nm, which is even shorter than that of a conventional krypton fluoride excimer laser (“KrF”) having a wavelength of 248 nm, and a F
2
excimer laser capable of forming 0.07 &mgr;m patterns and having a wavelength of 157 nm, are used as a new type of exposure light source. According to the change in exposure light source, there is an increasing demand for developing new photoresist materials having transparency at a shorter wavelength of 193 nm or less; high resistance to dry etching; good adhesion to layer materials above or below; easily capable of being developed using conventional aqueous developing solutions; and excellent in annealing effect during baking.
However, compared to the conventional KrF resist materials, known ArF or F
2
resist materials pose many problems for practical use. For example, poly(methyl methacrylate-t-butyl methacrylate-methacrylic acid), a terpolymer known in the art, is weak in resistance to dry etching.
In the case of a cycloolefin-maleic anhydride (“COMA”) alternating polymer having the following formula, the production cost of raw material is cheap, whereas yield of the polymer sharply decreases. In addition, the transmittance of the polymer is very low at a short wavelength region, such as, for example, at 193 nm. The above COMA synthetic polymers have alicyclic hydrocarbon in their backbone, which shows prominent hydrophobicity, and thus the adhesiveness to neighboring material layers below is very poor.
The copolymer has a glass transition temperature of 200° C. or more due to the structural characteristic of the backbone. As a result, it is difficult to achieve an annealing effect for eliminating a dynamic volume from the resist layer formed of the polymer with the above structure during baking. Accordingly, the resist layer has poor environmental resistance. As a result, when the polymer contacts a basic contaminant in the atmosphere, acid (“H
+
”) generated from a photoacid generator (“PAG”) by exposure cannot participate in acidolysis in the polymer and is quenched. Also, the acid is easily diffused into a non-exposed portion, thereby producing a photoresist pattern having a poor profile, such as, for example, a T-top profile. In addition, the resist layer is deformed due to e-beam while the photoresist pattern is observed by V-SEM, thus making it difficult to determine a good or bad state of the pattern. Also, these polymers do not have satisfactory transmittance.
SUMMARY OF THE INVENTION
The above and other drawbacks and disadvantages of the prior art are addressed by embodiments of the present disclosure that provide a photosensitive polymer which has a high enough glass transition temperature to acquire an annealing effect during baking while satisfying requirements as a main component of a resist material.
It is another advantage of the present invention to provide a photoresist composition containing the photosensitive polymer, suitable for an exposure light source having a shorter wavelength of 193 nm or less.
Accordingly, to achieve the above advantage, there is provided a photosensitive polymer including 10 to 90 mol % of an alkyl vinyl ether monomer having the formula, and 10 to 90 mol % of at least one monomer selected from the group consisting of an acrylate derivative, methacrylate derivative, fumarate derivative and 4-hydroxy styrene derivative, having an acid-labile hydrocarbon with from 4 to 20 carbon atoms, or at least one monomer selected from the group consisting of acrylonitrilie derivative and norbornene derivative, having an acid-labile substituent group with from 4 to 20 carbon atoms, and the photosensitive polymer has a weight average molecular weight of 3,000 to 50,000:
where x is an integer from 3 to 6 inclusive, R
1
and R
2
are independently alkyl having from 1 to 20 carbon atoms, fluorinated alkyl having from 1 to 10 carbon atoms or perfluoronated alkyl having from 1 to 10 carbon atoms.
In another aspect of the present invention, a photosensitive polymer includes 10 to 90 mol % of an alkyl vinyl ether monomer having the formula, and not greater than 50 mol % of a maleic acid anhydride monomer, wherein the photosensitive polymer has a weight average molecular weight of 3,000 to 50,000.
Preferably, the photosensitive polymer further includes at least one monomer selected from the group consisting of an acrylate derivative, methacrylate derivative, fumarate derivative and 4-hydroxy styrene derivative, having an acid-labile hydrocarbon with from 4 to 20 carbon atoms, or at least one monomer selected from the group consisting of acrylonitrilie derivative and norbornene derivative, having an acid-labile substituent group with from 4 to 20 carbon atoms.
According to another aspect of the present invention, there is provided a photoresist composition including at least one polymer selected from the above photosensitive polymers, and 1.0 to 15 wt % of a photoacid generator (“PAG”) based on the weight of the photosensitive polymer.
Preferably, the PAG includes a triarylsulfonium salt, diaryliodonium salt, sulfonate or a mixture of these materials.
The resist composition may include 0.01 to 20 wt % by weight an organic base based on the weight of the photosensitive polymer.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
A photosensitive polymer and a photoresist composition thereof are provided and described. Also, a preferred photolithography process using the photoresist composition will be described. This invention may, however, be embodied in many different forms, and these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In formulas, the same characters denote the same functional groups.
A photosensitive polymer according to an exemplary embodiment of the present disclosure includes 10 to 90% by mole of a hydroxy alkyl vinyl ether monomer, and thus has vinyl ether as a main component of its backbone. The vinyl ether backbone is more flexible than a conventional alicyclic hydrocarbon backbone, contributing to lowering a glass transition temperature of the photosensitive polymer. The vinyl ether is preferably substituted by a C
1
-C
20
hydroxy alkyl group to further increase the flexibility of the photosensitive polymer. More preferably, the vinyl ether is substituted by a C
1
-C
10
hydroxy fluoroalkyl group or a C
1
-C
10
hydroxy perfluoroalkyl group to increase transmittance with respect to an exposure light source of 157 nm. Since the substituent includes a hydroxy group (—OH), the adhesion and wettability of the photosensitive polymer against layer materials can be enhanced. The vinyl ether monomer can be expressed by the following formula 2:
wherein x is an integer in the range of 3 to 6 inclusive, R
1
and R
2
are individually C
1
to C
20
alkyl, C
1
to C
10
fluoronated alkyl or C
1
to C
10
perfluoronated alkyl.
Since the hydroxy alkyl vinyl ether monomer has an electron-donating property, it is polymerized with one or more other monomers having an electron-withdrawing property to facilitate polymerization, thereby forming a photosensitive polymer. Usable monomers capable of being polymerized with the hydroxy alkyl vinyl ether monomer include monomers selected from the group consisting of an acrylate derivative, methacrylate derivative, fumarate derivative and 4-hydroxy styrene derivative, having an acid-labile hydrocarbon with from 4 to 20 carbon atoms, or monomers selected from the group consisting of acrylonitrilie derivative and norbornene derivative, having an acid-labile substituent group
F. Chau & Associates LLC
Samsung Electronics Co,. Ltd.
Schilling Richard L.
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