Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-06-21
2002-04-09
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S165000, C524S166000, C526S282000, C526S272000, C526S317100, C526S318000, C526S318410, C526S318420, C526S319000, C526S320000, C430S270100, C430S905000, C430S914000
Reexamination Certificate
active
06369143
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a chemical amplification resist copolymer sensitive to radiation and a resist composition containing it. More particularly, the present invention relates to a radiation-sensitive copolymer useful as a matrix resin to form micro patterns, and a chemical amplification resist composition based on the copolymer, which makes it possible to perform a sub-micro lithography process using a deep UV such as a KrF excimer laser or an ArF excimer laser, an X ray such as synchrotron radiation, or charged particle beams such as electron beams.
2. Description of the Prior Art
A lithography process used in fabricating semiconductor devices generally comprises coating a resist film on a substrate such as a silicon wafer, exposing the coating to light, and developing it to form a positive or negative pattern. Certainly, the recent thrust into the high integration of semiconductor devices is greatly based on advances in microlithography. For example, ultra-fine patterns as small as sub-microns, e.g. 0.2 microns or less, in size, are required for the fabrication of ultra-LSI. Now, the light sources used to form the fine patterns become increasingly shorter in wavelength, for example, from g-line or I-line, to deep UV light, including a KrF excimer laser and an ArF excimer laser, further to an X-ray, and finally to an electron beam.
With near UV light, such as I-line, which is used in conventional lithography, micro patterns as small as sub-quarter microns (0.25 microns) are virtually impossible to realize. Such a micro pattern requires shorter wavelengths which belong to deep UV excimer lasers, X rays, and electron beams. Of them, KrF and ArF excimer lasers occupied the attention of the researchers in expressing such exquisiteness, and were developed as a light source, requiring novel photoresists. Now, chemical amplification photoresists are prevalently used for deep UV light.
A chemical amplification resist composition suitable for deep UV light fundamentally comprises a polymer with an acid-dissociable functional group, a compound which generates an acid (hereinafter referred to as “photoacid generator”), and a solvent, and avails itself of chemical amplification effect in lithography.
Japanese Pat. Laid-Open Publication No. Heisei 2-27,660 suggests a chemical amplification resist composition which is based on a mixture of a polymer containing a carbonylic acid t-butylester or phenyl t-butylcarbonate group and a photoacid generator. This composition utilizes the fact that, when being irradiated, the acid generated by the photoacid generator dissociates the t-butylester or t-butylcarbonate group from the main chain and the hydroxy group thus formed allows the exposed area to be easily dissolved by an alkaline developing solution.
Most of the chemical amplification resists utilizing KrF excimer lasers are based on phenolic resins. They are, however, unsuited to ArF excimer lasers because their aromatic rings show large absorption peaks at the wavelength of the light source (193 nm).
Thus, there is a strong demand for a material which little absorbs the light belonging to such wavelength ranges. In response to the demand, active research has been directed to the development of the chemical amplification photoresists based on polyacrylate derivatives (Japanese Pat. Laid-Open Publication No. Heisei 4-226,461; Proc. SPIE, 1996, vol. 2724, p377).
Polyacrylate derivatives show little absorbance at 193 nm, but suffer from a great disadvantage in that they are far inferior in dry etch resistance. Recently, much effort has been made to overcome this disadvantage, including the introduction of alicyclic derivatives into polyacrylate. The introduction of alicyclic derivatives certainly brings about an improvement in dry etch resistance, but causes a significant problem in a developing process because their hydrophobicity has a negative influence on the affinity for developing solutions. In forming 0.2 micron or less patterns, the adherence of a resist composition to a substrate plays an important role. Carboxylic acid was introduced into the side chains of matrix polymers for the purpose of increasing the adherence (Proc. SPIE, 1997, vol. 3049, p. 126). Carboxylic acid-grafted matrix polymers, however, require a change in the basicity of developing solutions because the carboxylic acid increases the solubility of the matrix polymers in the aqueous alkaline solutions.
It is known that copolymers of maleic anhydride and olefin can be used as matrix resins which show not only hydrophilicity, but also etch resistance (Proc. SPIE, 1997, vol. 3049, p126). In the copolymers, maleic anhydride, responsible for hydrophilicity, serves as a promoter which enables the copolymerization with olefinic monomers to be accomplished at low temperatures at low pressures.
SUMMARY OF THE INVENTION
During the development of a base resin for photoresist, carboxyl-containing norbornene derivative monomers and maleic anhydride monomers give a great contribution to their polymers in improving adherence to substrate, transparency to deep UV light, and dry etch resistance as well as photosensitivity, resolution and developability.
Therefore, it is an object of the present invention to provide a copolymer as a base resin for photoresist, with which there can be obtained sufficiently fine patterns for the high integration of semiconductor devices by using deep UV light, such as a KrF excimer laser and an ArF excimer laser.
It is another object of the present invention to provide a chemical amplification photoresist composition consisting essentially of the resin and a photoacid generator.
DETAILED DESCRIPTION OF THE INVENTION
In order to avoid the problems that conventional chemical amplification resists have in adherence to substrate, dry etch resistance and developability, a cyclic structure consisting of a maleic anhydride and norbornene derivatives is introduced into the main chain of the present invention with hydroxy groups and acid-dissociable functional groups being grafted. The cyclic structure improves dry etch resistance while the hydroxy group is responsible for increasing the adherence to substrate. The acid-dissociable functional groups take charge of improving photosensitivity and resolution. Particularly, the great advance in the perpendicularity of resist patterns and the sensitivity of resist patterns the present invention achieved, is attributed to the carboxylic acid-containing norbornene derivative introduced.
Accordingly, the present invention pertains to a polymer consisting essentially of maleic anhydride, a carboxylic acid-containing norbornene derivative, and an acid-dissociable functional group-containing norbornene derivative and to a chemical amplification positive resist composition sensitive to radiation.
More details are given of the present invention, below.
POLYMER
The polymer useful in the present invention has a repeat unit consisting of a norbornene derivative with a carboxylic acid grafted, a norbornene derivative with an acid-dissociable functional group grafted, and a maleic anhydride. The polymer itself is insoluble or hard-soluble in aqueous alkaline solutions and contains at least one protecting group which can be dissociated by acid.
The alkali solubility of the polymer is primarily determined by the content of the acid functional groups which are dissociable by acid. Accordingly, the resist properties of the polymer, including adherence to substrate, photo-sensitivity, resolution and the like, are dependent on the kind and quantity of the norbornene derivatives used in the polymer.
The polymer of the present invention is a multi-membered copolymer represented by the following general formula I:
wherein, X is an acid-dissociable grafted norbornene derivative selected from the group consisting of the following general formulas II and III; Y is a carboxylic acid-grafted norbornene derivative represented by the following formula IV:
wherein R
1
is selected from the group consisting of straight or branched al
Kim Seong-Ju
Park Joo-Hyeon
Park Sun-Yi
Seo Dong-Chul
Harlan R.
Harrison & Egbert
Korea Kumho Petrochemical Co. Ltd.
Wu David W.
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