Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-08-23
2003-11-04
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S272000, C526S281000, C526S317100, C526S320000, C430S270100
Reexamination Certificate
active
06642336
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive polymer.
2. Description of the Related Art
As semiconductor devices become highly integrated, photolithography processes used in the manufacture of such devices must be capable of fine pattern formation. Further, as a result of sub-quarter micron or smaller sized patterns which are needed in semiconductor memory devices having capacities exceeding 1 Gbit, a photolithography technique has been proposed in which an argon fluoride (ArF) excimer laser (wavelength: 193 nm) is used as a new type of exposure light source. The use of the ArF excimer laser stems from the fact that its wavelength is less than that of the more conventional krypton fluoride (KrF) excimer laser (wavelength: 248 nm). As a result, there is an increasing demand for new chemically amplified photoresist polymers and photoresist compositions which are suitable for use with the ArF excimer laser.
In general, a chemically amplified photoresist composition for an ArF excimer laser should preferably exhibit the following characteristics: (1) transparency at a wavelength of 193 nm; (2) excellent thermal properties (for example, high glass transition temperature); (3) good adhesion to underlying and overlying film materials; (4) high resistance to dry etching; and (5) easily capable of being developed using developing solutions which are in widespread use in the manufacture of semiconductor devices, for example, 2.38% by weight of tetramethyl ammonium hydroxide (TMAH).
However, a terpolymer comprising methylmethacrylate, t-butyl methacrylate and methacrylic acid, which is a widely known chemically amplified photoresist polymer for the ArF excimer laser, does not exhibit all of the above-described characteristics. In particular, the terpolymer has a very low resistance to dry etching and a low adhesion to underlying and overlying film materials.
Recently, attempts have been made to prepare photosensitive polymers for the ArF excimer laser having increased etching resistances using (meth)acrylate which has alicyclic compounds, for example, isobornyl, adamantyl or tricyclodecanyl group, as a substitutent or t-butyl norbornene carboxylate. However, these polymers also have several disadvantages. For example, their etching resistance and adhesion characteristics to film materials are still poor, which results in lifting of photoresist patterns.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a photosensitive polymer which maintains transparency even when exposed to a short-wavelength light source of 193 nm or below, and which has improved adhesive, contrast, and resistance to dry etching characteristics.
It is another objective of the present invention to provide a chemically amplified photoresist composition containing the photosensitive polymer.
Accordingly, to achieve the above objective, there is provided a photosensitive polymer including a first monomer which is an alicyclic hydrocarbon carboxylate having an acid-labile C
8
to C
20
tertiary alicyclic hydrocarbon group as a substituent, and a second monomer which is capable of free radical polymerization.
Preferably, the alicyclic hydrocarbon carboxylate is norbornene carboxylate, the second monomer is maleic anhydride, and the C
8
to C
20
tertiary alicyclic hydrocarbon group is 2-methyl-2-norbornyl, 2-methyl-2-isobornyl, 8-ethyl-8-tricyclo[5.2.1.0
2,6
]decanyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl or 1-adamantyl-1-methyl ethyl.
The photosensitive polymer according to present invention is polymerized with one or more monomers selected from the group consisting of a third monomer, a fourth monomer and a fifth monomer, in addition to the first and second monomers, wherein the third monomer is a monomer having a secondary cyclic alcohol group bonded to its backbone; wherein the fourth monomer is a monomer selected from the group consisting of (meth)acrylic acid, (meth)acrylate having C
1
to C
12
aliphatic alcohol as a substituent, (meth)acrylate having an acid-labile group as a substituent, and (meth)acrylate having a dissolution inhibitor group as a substituent; and wherein the fifth monomer is a monomer selected from the group consisting of norbornene, norbornene-ol, norbornene having C
1
to C
12
aliphatic alcohol as a substituent, norbornene carboxylic acid, norbornene dicarboxylic anhydride, norbornene carboxylate having C
1
to C
12
aliphatic alcohol as a substituent, norbornene carboxylate having a lactone group as a substituent, norbornene carboxylate having an acid-labile group as a substituent, and norbornene carboxylate having a dissolution inhibitor group as a substituent.
Preferably, the third monomer is secondary polycyclic alcohol.
The photosensitive polymer according to the preferred embodiment of the present invention has a cyclic backbone, and an acid-labile C
8
to C
20
tertiary alicyclic hydrocarbon group is bonded to the backbone. Thus, a photoresist composition containing the same exhibits a high resistance to etching. Also, since there is a large difference in the solubility before and after exposure, the contrast is excellent.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A photosensitive polymer and a chemically amplified photoresist composition containing the same according to the present invention will now be described. Also, a preferred photolithography process using the chemically amplified 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.
Photosensitive Polymer
A photosensitive polymer according to the present invention includes a first monomer which is an alicyclic hydrocarbon carboxylate having an acid-labile C
8
-C
20
tertiary alicyclic hydrocarbon group as a substituent and a second monomer capable of free radical polymerization. The weight average molecular weight of the photosensitive polymer is preferably in the range of 1,000 to 100,000.
Suitable alicyclic hydrocarbons constituting a backbone of the first monomer include norbornene, isobornene, adamantene and the like.
2-methyl-2-norbornyl, 2-methyl-2-isobornyl, 8-ethyl-8-tricyclo[5.2.1.0
2,6
]decanyl, 2-methyl-2-adamantyl, 2-ethyl-2-adamantyl or 1-adamantyl-1-methylethyl is preferably used as the C
8
-C
20
tertiary alicyclic hydrocarbon group, which can be expressed by the formula below. Since the alicyclic hydrocarbon group is a tertiary alkyl group, it is acidolyzed.
Suitable second monomers capable of free radical polymerization to introduce a first monomer into the photosensitive polymer include maleic anhydride.
The photosensitive polymer according to the present invention has a cyclic backbone like in an alicyclic hydrocarbon or maleic anhydride. Also, since a C
6
-C
20
tertiary alicyclic hydrocarbon group is bonded to the backbone of the polymer, the etching resistance of the photosensitive polymer is much larger than that of the conventional photosensitive polymer.
The etching resistance of a polymer is generally known to be inversely proportion to an Ohnishi parameter, which is calculated by the following formula (1):
Ohnishi parameter=N
T
/N
c
−N
o
wherein N
T
is the total number of atoms in the polymer, N
c
is the number of carbon atoms in the polymer and N
o
is the number of oxygen atoms in the polymer.
Table 1 lists Ohnishi parameters calculated by the formula (1) in the prior art polymer and in the polymer of the present invention.
TABLE 1
Classification
Ohnishi parameter
Prior art
Poly(methyladamantylacrylate-cyclo-
3.59
polymer
pentanoate acrylate)
Poly(t-butylnorbornenecarboxylate-
3.73
maleic anhydride)
Present
Poly(2-methyl-2-norbornyl norbornene
3.32
invention
carboxylate-maleic anhydride)
polymer
Poly(2-methyl-2-isobornyl norbornene
3.29
carboxylate-maleic anhydride)
Poly(8-ethyl-8-tricyclo[5.2.1.0
2,6
]-
3.18
decanyl norbornene carboxylate-maleic
Choi Sang-jun
Jung Dong-won
Kim Hyun-woo
Kwon Ki-young
Lee Si-hyeung
Pezzuto Helen L.
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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