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
2000-03-24
2002-09-24
Chu, John S. (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
C430S905000
Reexamination Certificate
active
06455223
ABSTRACT:
This invention relates to novel resist compositions suited for microfabrication technology and a patterning process.
BACKGROUND OF THE INVENTION
While a number of recent efforts are being made to achieve a finer pattern rule in the drive for higher integration and operating speeds in LSI devices, deep-ultraviolet lithography is thought to hold particular promise as the next generation in microfabrication technology. Deep-UV lithography is capable of achieving a minimum feature size of 0.3 &mgr;m or less and, when a resist having low light absorption is used, can form patterns with sidewalls that are nearly perpendicular to the substrate. One technology that has attracted a good deal of attention recently utilizes a high-intensity KrF excimer laser as the deep-UV light source. Resist materials with low light absorption and high sensitivity are needed to successfully apply this technology to large-volume production.
Acid-catalyzed chemically amplified resist materials which were recently developed from this standpoint are disclosed in JP-B 2-27660, JP-A 63-27829, U.S. Pat. Nos. 4,491,628 and 5,310,619. These resist materials are especially promising for deep-UV lithography because of their excellent properties such as high sensitivity and high resolution. They are known to exhibit excellent properties when exposed to electron beams (EB) and x-rays.
Chemically amplified resist materials were initially utilized in the 0.3 micron process. By way of 0.25 micron rule, their application to 0.18 micron rule for mass scale production is now started, and even their further application to 0.15 micron rule is under consideration. The evolution of KrF excimer laser lithography toward finer pattern rules is accelerating. At the same time, an actual study on the use of EB or x-ray as the light source is started, with the target placed on the next generation of microfabrication. It is required to miniaturize the pattern rule and improve the resolution of resist material.
With the progress of miniaturization, line edge roughness is now taken serious. The line edge roughness, also known as micro-roughness, represents irregularities on the side wall of a line. Upon exposure to light of a single wavelength as in the case of an excimer laser, reflection from the substrate produces standing waves, which cause irregularities to generate on the side walls. The reflection from the substrate can be suppressed to substantially 0% by disposing an anti-reflection film between the resist and the substrate, but line roughness is still observed. In the case of EB and x-ray exposure, no standing waves generate due to the lack of reflection from the substrate, but line edge roughness is yet observed. It is believed in the literature that the line edge roughness is assigned to polymer clusters. JP-A 6-266099 describes that the line edge roughness can be reduced by using low molecular weight monodisperse polymers. It is also known that line edge roughness occurs more often in negative resists than in positive resists. However, the use of low molecular weight polymers has the drawbacks associated with their low glass transition temperature (Tg). If the Tg is lower than the pre-baking temperature, heat baking must be avoided, which is impractical. Further the lower Tg of polymers leads to a decline of dry etching resistance.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel and improved resist composition having a high resolution, high sensitivity, minimized line edge roughness and satisfactory dry etching resistance. Another object of the invention is to provide a process for forming a resist pattern using the resist composition.
We have found that while the entanglement of polymer molecules is believed to constitute a cluster structure, the intensity of entanglement is in proportion to the length of the polymer backbone. When a branched polymer, and especially a star-shaped polymer having more uniformly distributed branches is used rather than a linear polymer, entanglement occurs only within the length of branches, indicating that the entanglement is mitigated without reducing the overall molecular weight. While radical polymerization is generally believed to induce branching, it is impossible to precisely control the degree of branching during radical polymerization to regulate the molecular weight and its dispersity. We have found that a star-shaped polymer can be synthesized by living anion polymerization and that polymer is applicable as the base resin of resist material.
In a first aspect, the invention provides a resist composition comprising as a base resin a dendritic or hyperbranched polymer of a phenol derivative having a weight average molecular weight of 500 to 10,000,000.
In one preferred embodiment, the polymer comprises recurring units (I) or (II) or both and recurring units (III) as shown below, the number of units (III) being 1 to 1,000.
units (I):
units (II):
Herein R
1
is hydrogen or methyl, R
2
is independently a straight, branched or cyclic alkyl group of 1 to 30 carbon atoms or aryl group of 6 to 30 carbon atoms, R
3
is an OR
4
group, R
4
is an acid labile group or acid stable group, x is 0 or a positive integer, y is a positive integer, and the sum of x and y is up to 5.
units (III):
Herein R
1
is as defined above, and R
5
is a straight, branched or cyclic alkylene group of 1 to 30 carbon atoms or arylene group of 6 to 30 carbon atoms, or a mixture thereof, which may contain an ether or ester bond. Preferably, the units (III) are of the following formula (3a):
wherein X is a valence bond or a straight or branched alkylene group of 1 to 10 carbon atoms which may contain a hydroxyl or carbonyl group. Typically, the polymer has been prepared by living anion polymerization.
In a second aspect, the invention provides a chemical amplification type positive resist composition comprising (A) a base resin constructed of the above-defined polymer which is little or no soluble in alkali, but becomes alkali soluble by reaction with acid, (B) an organic solvent, and (C) a photoacid generator. The positive resist composition may further include (D) a basic compound and (E) a dissolution regulator.
In a third aspect, the invention provides a chemical amplification type negative resist composition comprising (A′) a base resin constructed of the above-defined polymer which becomes little or no soluble in alkali by crosslinking with a crosslinker, (B) an organic solvent, (C) a photoacid generator, and (F) the crosslinker. The negative resist composition may further include (D) a basic compound.
In a fourth aspect, the invention provides a process for forming a resist pattern comprising the steps of (i) applying the chemical amplification type positive or negative resist composition onto a substrate, (ii) heat treating the coated film and then exposing it to actinic radiation having a wavelength of up to 500 nm or electron beams through a photo mask, and (iii) optionally heat treating the exposed film and developing it with a developer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Polymer
The resist composition of the invention uses as a base resin a polymer or high molecular weight compound in the form of a dendritic or hyperbranched polymer of a phenol derivative having a weight average molecular weight of 500 to 10,000,000.
Preferably the polymer is comprised of recurring units (I) and/or recurring units (II) and recurring units (III). The number of units (III) is 1 to 1,000, more preferably 1 to 500, and most preferably 1 to 200.
units (I):
units (II):
Herein R
1
is hydrogen or methyl, R
2
, which may be the same or different, is a straight, branched or cyclic alkyl group of 1 to 30 carbon atoms or aryl group of 6 to 30 carbon atoms, R
3
is an OR
4
group, R
4
is an acid labile group or acid stable group, x is 0 or a positive integer, y is a positive integer, satisfying x+y≦5.
units (III):
Herein R
1
is as defined above, and R
5
is a straight, branched or cyclic alkylene group of 1 to 30 carbon atoms or arylene group of 6 to 30 carbon atoms, or a mixtu
Hatakeyama Jun
Ishihara Toshinobu
Kobayashi Tomohiro
Takeda Takanobu
Watanabe Jun
Chu John S.
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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