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
2000-05-18
2002-07-02
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
C430S296000, C430S325000
Reexamination Certificate
active
06413695
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resist composition, preferably of the chemical amplification type, especially of the chemical amplification positive type, and a patterning process using the same.
2. Prior Art
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. In particular, photolithography using a KrF or ArF excimer laser as the light source is strongly desired to reach the practical level as the micropatterning technique capable of achieving a feature size of 0.3 &mgr;m or less.
For resist materials for use with KrF excimer lasers, polyhydroxystyrene having a practical level of transmittance and etching resistance is, in fact, a standard base resin. For resist materials for use with ArF excimer lasers, polyacrylic or polymethacrylic acid derivatives and polymers comprising aliphatic cyclic compounds in the backbone are under investigation. In either case, the basic concept is that some or all of alkali soluble sites of alkali soluble resin are protected with suitable acid-eliminatable groups. The overall performance of resist material is adjusted by a choice from among a variety of acid-eliminatable protective groups or by incorporating one or more low-molecular-weight components having an appropriate function separate from the resin.
One typical functional low-molecular-weight component to be formulated in resist materials is a class of compounds known as dissolution regulators. A variety of proposals have been made on the structure of dissolution regulators. A common structure has on a mother nucleus of a certain size one or plural readily alkali-soluble sites, some or all of which are blocked with acid-decomposable protective groups (see JP-A 6-266109 and JP-A 9-278699). When an appropriate amount of dissolution regulator is blended, the dissolution of the resist film in the unexposed area is restrained whereas in the exposed area, readily alkali-soluble sites which are exposed under the action of generated acid promote the dissolution of the resist film. That is, the differential dissolution rate between the exposed and unexposed areas is enhanced. Consequently, the resolution of the resist film is considerably improved.
What is required for the dissolution regulator is to keep low the dissolution rate of the resist film in the unexposed area and to allow the exposed area to quickly turn to be readily soluble in an alkali developer. These properties are largely affected by the mother nucleus and the choice of acid-decomposable sites. For the mother nucleus, sufficient hydrophobicity is essential for exerting dissolution inhibition in the unexposed area, and the mother nucleus must also have such a structure that developer affinity is insured in deblocked form for exerting dissolution promotion in the exposed area. Also, the acid-decomposable sites are required to have contradictory properties in that the acid-decomposable sites must have a high reactivity sufficient to quickly decompose even in low exposed area such as resist film deep inside, whereas they must have a low reactivity sufficient to prevent reaction from being triggered merely by exposure and a stability sufficient to prevent a sensitivity variation during storage, in order to restrain the formation of volatile decomposition products which can contaminate the optical system of an aligner. As to the mother nucleus, it is relatively easy to design the mother nucleus having hydrophobicity and developer affinity upon deblocking adequate to the purpose, by increasing the molecular weight above a certain level and optionally incorporating a cyclic structure. However, the acid-decomposable sites that fully satisfy the requirement are not yet available.
As to the currently available acid-decomposable sites, tertiary alkyl esters such as tert-butyl esters and 1-alkoxyalkyl esters such as 2-tetrahydropyranyl esters and 1-ethoxyethyl esters are known as the protected carboxylic acid; tertiary alkyl carbonates such as tert-butyl carbonate, tertiary alkyl ethers such as tert-butyl ethers, and 1-alkoxyalkyl ethers such as 2-tetrahydropyranyl ethers and 1-ethoxyethyl ethers are known as the protected phenolic hydroxyl group. Among the foregoing examples, however, the 1-alkoxyalkyl esters and 1-alkoxyalkyl ethers are excessively reactive and have the risk of causing contamination of the aligner optical system and sensitivity variation. Inversely, the remaining examples are poorly reactive and fail to fully accelerate the dissolution rate in the exposed area. In addition, many other proposals have been made on the acid-decomposable sites although they are not satisfactory in both reactivity and stability. While the pattern rule is increasingly scaled down, there is a need to have a dissolution regulator having improved acid-decomposable sites and a high sensitivity, high resolution resist material which can be realized thereby.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a resist composition comprising a dissolution regulator having both high reactivity and sufficient storage stability. Another object is to provide a process for forming a pattern using the same.
It has been found that an ester compound of the following general formula (1) obtained by a method to be described later is useful as a dissolution regulator to be blended in a resist composition. The resist composition having the ester compound blended therein has high sensitivity and resolution and is suited for precise microfabrication.
The invention provides a resist composition comprising an ester compound of the following general formula (1).
Herein R
1
is an n-valent straight, branched or cyclic, saturated or unsaturated hydrocarbon group of 4 to 40 carbon atoms which may contain a hetero atom. R
2
is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or a substituted or unsubstituted aryl group of 6 to 20 carbon atoms. R
3
to R
12
each are hydrogen or a monovalent hydrocarbon group of 1 to 15 carbon atoms which may contain a hetero atom and R
3
to R
12
, taken together, may form a ring, and when they form a ring, they represent divalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom, or two of R
3
to R
12
which are attached to adjacent carbon atoms may directly bond together to form a double bond. The letter n is an integer of 1 to 8. The formula also represents an enantiomer.
Preferably in formula (1), R
1
is an n-valent hydrocarbon group of 4 to 40 carbon atoms, in which n hydrogen atoms at arbitrary positions are eliminated to introduce valence bonds, selected from among (i) straight or branched aliphatic saturated hydrocarbons of 4 to 30 carbon atoms and alicyclic saturated hydrocarbons including
(ii) hydrocarbons belonging to (i) in which at least one hydrogen atom at an arbitrary position is replaced by a straight, branched or cyclic alkyl, (iii) hydrocarbons belonging to (i) and (ii) in which a carbon-carbon bond at an arbitrary position is unsaturated to introduce at least one double or triple bond, (iv) hydrocarbons belonging to (i) to (iii) in which at least one CH
2
, CH or C at an arbitrary position is replaced by O, N, NH, S, SO or SO
2
, and (v) hydrocarbons belonging to (i) to (iv) in which at least one hydrogen atom at an arbitrary position is replaced by a group of atoms selected from among a halogen atom, hydroxyl, alkoxy, aryloxy, formyl, alkylcarbonyl, arylcarbonyl, carboxy, alkoxycarbonyl, aryloxycarbonyl, cyano, amino, alkylamino, arylamino, mercapto, alkylthio, arylthio, carbamoyl, alkylcarbamoyl, arylcarbamoyl, alkylcarbonylamino, arylcarbonylamino, sulfo, oxo, and imino group or an alkyl or aryl containing said group of atoms;
R
2
is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or an aryl group of 6 to 20 carbon atoms which may be substituted
Hasegawa Koji
Hatakeyama Jun
Kinsho Takeshi
Nakashima Mutsuo
Nishi Tsunehiro
Ashton Rosemary
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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