Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2001-04-26
2002-06-11
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S128000
Reexamination Certificate
active
06403823
ABSTRACT:
This invention relates to novel ester compounds useful as monomers to form base resins for use in chemically amplified resist compositions adapted for micropatterning lithography, and a method for preparing the same.
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. 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.
The resist materials for use in photolithography using light of an excimer laser, especially ArF excimer laser having a wavelength of 193 nm, are, of course, required to have a high transmittance to light of that wavelength. In addition, they are required to have an etching resistance sufficient to allow for film thickness reduction, a high sensitivity sufficient to eliminate any extra burden on the expensive optical material, and especially, a high resolution sufficient to form a precise micropattern. To meet these requirements, it is crucial to develop a base resin having a high transparency, rigidity and reactivity. None of the currently available polymers satisfy all of these requirements. Practically acceptable resist materials are not yet available.
Known high transparency resins include copolymers of acrylic or methacrylic acid derivatives and polymers containing in the backbone an alicyclic compound derived from a norbornene derivative. All these resins are unsatisfactory. For example, copolymers of acrylic or methacrylic acid derivatives are relatively easy to increase reactivity in that highly reactive monomers can be introduced and acid labile units can be increased as desired, but difficult to increase rigidity because of their backbone structure. On the other hand, the polymers containing an alicyclic compound in the backbone have rigidity within the acceptable range, but are less reactive with acid than poly(meth)acrylate because of their backbone structure, and difficult to increase reactivity because of the low freedom of polymerization. Additionally, since the backbone is highly hydrophobic, these polymers are less adherent when applied to substrates. Therefore, some resist compositions which are formulated using these polymers as the base resin fail to withstand etching although they have satisfactory sensitivity and resolution. Some other resist compositions are highly resistant to etching, but have low sensitivity and low resolution below the practically acceptable level.
SUMMARY OF THE INVENTION
An object of the invention is to provide a novel ester compound useful as a monomer to form a polymer for use in the formulation of a photoresist composition which exhibits a high reactivity and transparency when processed by photolithography using light with a wavelength of less than 300 nm, especially ArF excimer laser light as the light source. Another object is to provide a method for preparing the ester compound.
The inventor has found that an ester compound of formula (1) can be prepared in high yields by a simple method, that a polymer obtained from this ester compound has high transparency at the exposure wavelength of an excimer laser, and that a resist composition comprising the polymer as a base resin is improved in sensitivity and resolution.
The invention provides an ester compound of the following general formula (1).
Herein R
1
is hydrogen or a straight, branched or cyclic alkyl group of 1 to 6 carbon atoms, R
2
is an acyl or alkoxycarbonyl group of 1 to 15 carbon atoms in which some or all of the hydrogen atoms on the constituent carbon atoms may be substituted with halogen atoms, R
3
is an acid labile group, k is 0 or 1, and m is an integer from 0 to 5.
Preferably the ester compound has the following general formula (2) or (3).
Herein m and R
2
are as defined above, R
4
is hydrogen or methyl, R
5
to R
8
are independently selected from straight, branched or cyclic alkyl groups of 1 to 15 carbon atoms, the sum of carbon atoms in R
5
, R
6
and R
7
is at least 4, and Z is a divalent hydrocarbon group of 4 to 15 carbon atoms which forms a ring with the carbon atom to which it is connected at opposite ends.
A method for preparing the ester compound forms another aspect of the invention, which involves the steps of effecting addition reaction of a metal enolate of acetate of the following formula (5) to a carbonyl compound of the following formula (4) to form a &bgr;-hydroxyester compound of the following formula (6), and effecting acylation or alkoxycarbonylation of the hydroxyl group of the &bgr;-hydroxyester compound.
Herein k, m, R
1
and R
3
are as defined above, M is Li, Na, K, MgY or ZnY, and Y is a halogen atom.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The ester compounds of the invention are of the following general formula (1).
Herein R
1
is hydrogen or a straight, branched or cyclic alkyl group of 1 to 6 carbon atoms. Exemplary alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, and cyclohexyl. R
2
is an acyl or alkoxycarbonyl group of 1 to 15 carbon atoms in which some or all of the hydrogen atoms on the constituent carbon atoms may be substituted with halogen atoms. Exemplary of R
2
are formyl, acetyl, ethylcarbonyl, pivaloyl, methoxycarbonyl, ethoxycarbonyl, tert-butoxycarbonyl, trifluoroacetyl, trichloroacetyl, and 2,2,2-trifluoroethylcarbonyl. R
3
is an acid labile group. The letter k is 0 or 1, and m is an integer from 0 to 5 (i.e., 0≦m≦5), and preferably from 0 to 3.
The preferred acid labile group represented by R
3
are those of the following formulas.
R
5
to R
8
and Z are as defined below.
Preferred among the ester compounds of formula (1) are ester compounds of the following general formula (2) or (3).
Herein m and R
2
are as defined above. R
4
is hydrogen or methyl. R
5
to R
8
are independently selected from straight, branched or cyclic alkyl groups of 1 to 15 carbon atoms. The total number of carbon atoms in R
5
, R
6
and R
7
is at least 4. Examples of the straight, branched or cyclic alkyl groups of 1 to 15 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclohexylmethyl, cyclohexylethyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.2]octyl, bicyclo[3.3.1]nonyl, bicyclo[4.4.0]decanyl, tricyclo[5.2.1.0
2,6
]decanyl, tetracyclo[4.4.0.1
2,5
.1
7,10
]dodecanyl, and adamantyl. Z stands for divalent hydrocarbon groups of 4 to 15 carbon atoms, such as alkylene and alkenylene groups, which each forms a ring with the carbon atom to which it is connected at opposite ends. Examples of the rings that Z forms include cyclopentane, cyclopentene, cyclohexane, cyclohexene, bicyclo[2.2.1]heptane, bicyclo[4.4.0]decane, tricyclo[5.2.1.0
2,6
]decane, tetracyclo[4.4.0.1
2,5
.1
7,10
]-dodecane, and adamantane.
Illustrative, non-limiting, examples of the ester compounds of formula (1) and formulas (2) and (3) are given below.
As seen from the reaction scheme shown below, the ester compound of formula (1) can be prepared by the first step of causing a base to act on a corresponding acetate of formula (7) (where X is hydrogen) or a corresponding haloacetate of formula (7) (where X is halogen) to form a metal enolate of formula (5) and effecting nucleophilic addition reaction of the metal enolate to a carbonyl compound of formula (4) to form a &bgr;-hydroxyester compound of formula (6), and the second step of effecting acylation or alkoxycarbonylation (or esterification) of the hydroxyl group on the &bgr;-hydroxester compound.
1st step
2nd step
Herein, k, m, R
1
, R
2
and
Hasegawa Koji
Hatakeyama Jun
Kinsho Takeshi
Nakashima Mutsuo
Nishi Tsunehiro
Geist Gary
Millen White Zelano & Branigan P.C.
Reyes Hector
Shin-Etsu Chemical Co. , Ltd.
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