Polymer blend and associated methods of preparation and use

Details Polymer blend and associated methods of preparation and use Polymer blend and associated methods of preparation and use

2002-03-04

2004-09-21

Ashton, Rosemary (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

C430S325000, C430S326000, C430S907000, C526S281000, C526S242000, C526S232100, C526S219600, C526S332000

Reexamination Certificate

active

06794110

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to the fields of lithography and semiconductor fabrication. More particularly, the invention relates to the use of certain novel polymer blends that are especially useful in photoresist compositions, including ultraviolet, electron-beam, and x-ray photoresists.
BACKGROUND
There is an ongoing need in the electronics industry for increasingly higher circuit densities in microelectronic devices made using lithographic techniques. One method of increasing the number of components per integrated circuit (“chip”) is to decrease the minimum feature size on the chip, which requires higher lithographic resolution. This decrease in feature size has been accomplished over the past twenty years by reducing the wavelength of the imaging radiation from the visible (436 nm) down through the ultraviolet (365 nm) to the deep ultraviolet (DUV; <248 nm). Development of commercial lithographic processes using ultra-deep ultraviolet radiation, particularly at 193 nm or 157 nm, is now of increasing interest. See, for example, Allen et al. (1995), “Resolution and Etch Resistance of a Family of 193 nm Positive Resists,”
J. Photopolym. Sci. and Tech.
8(4):623-636, and Abe et al. (1995), “Study of ArF Resist Material in Terms of Transparency and Dry Etch Resistance,”
J. Photopolym. Sci. and Tech.
8(4):637-642.
Attempts have been made to develop 157 nm resists, for example by using heavily fluorinated materials such as polytetrafluoroethylene (e.g., Teflon AF®; see Endert et al. (1999),
Proc. SPIE
-
Int. Soc. Opt. Eng,
3618:413-17) or hydridosilsesquioxanes (see U.S. Pat. No. 6,087,064 to Lin et al.). These materials do not, however, have reactivity or solubility characteristics suitable for lithographic manufacturing processes. The challenge in producing chemically amplified resists for 157 nm lithography is to achieve suitable transparency at this wavelength in polymers that have acid-labile functionalities, and that can be developed with industry-standard developers in either exposed or unexposed areas depending on whether the resist is positive or negative.
Homo- and copolymers of methyl &agr;-trifluoromethylacrylate (MTFMA) and its derivatives have been found to be surprisingly transparent at 157 nm, with an optical density (OD) of less than 3/&mgr;m, whereas poly(methyl methacrylate) (PMMA) is highly absorbing (OD=6/&mgr;m) (see, for example, Ito et al. (2001), “Polymer Design for 157 nm Chemically Amplified Resists,”
Proc. SPIE
4345: 273-284; Ito et al. (2001) “Novel Fluoropolymers for Use in 157 nm Lithography,”
J. Photopolym. Sci. Technol.
14:583-593, and Chiba et al. (2000), “157 nm Resist Materials: a Progress Report,”
J. Photopolym. Sci. Technol
13:657-664.)
Unfortunately, MTFMA and its derivatives do not readily undergo radical homopolymerization, and polymers can be made only by anionic polymerization (see Ito et al. (1981), “Methyl &agr;-Trifluoroacrylate, an E-Beam and UV Resist,” IBM Technical Disclosure Bulletin 24(2): 991). Although MTFMA-methacrylate copolymers using anionic polymerization are highly useful as 157 nm resist polymers, it is still desirable to identify comonomers that polymerize with &agr;-trifluoromethylacrylic monomers by radical initiation. Radical polymerization is easy to run and economical, and is a preferred process for preparation of resist polymers.
Several polymers have now been identified as suitable components of 157 nm resist polymers. For example, copolymers of t-butyl-&agr;-trifluoromethylacrylate (TBTFMA) and bicyclo[2.2.1]hept-5-ene-2-(1,1,1-trifluoro-2-trifluoromethylpropan-2-ol) (NBHFA) have been shown to be particularly suitable. See, for example, Ito et al. (2001)
Proc. SPIE
4345: 273-284, supra; Ito et al. (2001)
J. Photopolym. Sci. Technol.
14:583-593, supra, and Chiba et al. (2000), supra. As norbornene copolymers based on NBHFA are made by metal-mediated addition polymerization, copolymers that can be readily prepared via a conventional radical mechanism have also been sought. Unfortunately, it is difficult to incorporate more than 50 mol % NBHFA in the copolymer, and the OD of P(TBTFMA-NBHFA) ranges from 3.2 to 2.7/&mgr;m, depending on the molecular weight (see the aforementioned references).
Although the lowest OD achieved with P(TBTFMA-NBHFA) may be adequate for some purposes, it is still desirable to increase the transparency of the polymer for 157 nm applications. Furthermore, resist polymers must possess many properties in addition to good transparency at the exposure wavelength. In fact, the ability of the resist polymer to be developed in aqueous base is critically important in generating high-resolution images. Unfortunately, however, resists based on copolymers such as poly(TBTFMA-co-NBHFA) do not develop well in aqueous base due to their low hydrophilicity.
SUMMARY OF THE INVENTION
While two different polymers do not, in general, mix homogeneously, it has now been discovered and is herein disclosed that certain copolymers—such as the TBTFMA-NBHFA copolymer, copolymers of (4-(1-hydroxy-2,2,2-trifluoro-1-trifluoromethyl)ethylstyrene) (STHFA) with t-butyl methacrylate (TBMA) (PF-ESCAP) and with TBTFMA (PF
2
-ESCAP), and certain TBTFMA-vinyl ether copolymers—are capable of blending substantially homogeneously with other polymers, such as a homopolymer of NBHFA (PNBHFA). The blending of a lipophilic copolymer with a transparent, hydrophilic polymer improves aqueous base development and increases transparency, to allow for the generation of high-resolution images.
Accordingly, it is a primary object of the invention to address the above-described need in the art by providing a substantially homogeneous polymer blend that is suitable for use in lithographic photoresist compositions.
It is another object of the invention to provide a lithographic photoresist composition containing a substantially homogeneous polymer blend.
It is still another object of the invention to provide a method for generating a resist image on a substrate using a photoresist composition as described herein.
It is a further object of the invention to provide a method for forming a patterned structure on a substrate by transferring the aforementioned resist image to the underlying substrate material, e.g., by etching.
It is still a further object of the invention to provide a method of preparing a copolymer suitable for use in lithographic photoresist compositions.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.
In one aspect of the invention a substantially homogeneous polymer blend comprising a first polymer and second polymer is provided. Alternatively, a third polymer may be included in the blend. The first polymer is comprised of monomer units having the structure of formula (I):
wherein R
1
is C
1-12
alkyl or C
1-12
fluoroalkyl, R
2
is C
1-12
fluoroalkyl, and L is C
1-6
alkylene or C
1-6
fluoroalkylene. In preferred embodiments, the second polymer is a copolymer comprising:
a first monomer unit having the structure of formula (II):
wherein R
3
is H, F, CN, CH
3
or C
1-6
fluoroalkyl (with fluorinated methyl groups, i.e., CF
2
H, CFH
2
, and CF
3
, being preferred C
1-6
fluoroalkyl substituents), R
4a
and R
4b
are H or F, and R
5
is CN or COOR, wherein R is selected from the group consisting of H, C
1-12
alkyl, and C
1-12
fluoroalkyl, or is selected so as to render R
5
acid-cleavable; and a second monomer unit selected from the group consisting of:
wherein in formulae (I) and (IV), R
1
, R
2
, and L are as defined previously, and in formula (III), R
6
is H, C
1-12
alkyl, C
1-12
fluoroalkyl, C
3-15
alicyclic, or fluorinated C
3-15
alicyclic, R
7
is C
1-12
alkyl C
1-12
alkyl substituted with 1-12 fluorine atoms and 0-2 hydroxyl groups, C
3-15
alicyclic, or fluorinated C
3-15
alicyclic, or R
6
and R
7
together form a five-, six-, or s

Affiliated with

Also associated with

Rating

Polymer blend and associated methods of preparation and use does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Polymer blend and associated methods of preparation and use, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymer blend and associated methods of preparation and use will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3267534