Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-10-02
2003-02-04
Trinh, Ba K. (Department: 1675)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S453000, C549S430000, C549S372000
Reexamination Certificate
active
06515150
ABSTRACT:
This invention relates to (i) a novel cyclic acetal compound or a mixture of cyclic acetal compounds useful as a monomer to form a polymer, (ii) a polymer comprising specific recurring units, (iii) a resist composition comprising the polymer as a base resin, suited in a micropatterning process, and (iv) a patterning process using the resist composition.
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.
For resist materials for use with a 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 containing aliphatic cyclic compounds in the backbone are under investigation. All these polymers have advantages and disadvantages, and none of them have been established as the standard base resin.
More particularly, resist compositions using derivatives of polyacrylic or polymethacrylic acid have the advantages of high reactivity of acid-decomposable groups and good substrate adhesion and give relatively satisfactory results with respect to sensitivity and resolution, but have extremely low etching resistance and are impractical because the resin backbone is weak. On the other hand, resist compositions using polymers containing alicyclic compounds in their backbone have a practically acceptable level of etching resistance because the resin backbone is robust, but are very low in sensitivity and resolution because the reactivity of acid-decomposable protective groups is extremely low as compared with those on the acrylic polymers. Since the backbone of the resin is too robust, substrate adhesion is poor. These compositions are thus impractical as well. While a finer pattern rule is being demanded, there is a need to have a resist material which is satisfactory in sensitivity, resolution, and etching resistance.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide (i) a novel cyclic acetal compound and a mixture of cyclic acetal compounds useful as a monomer, (ii) a polymer having improved reactivity, robustness and substrate adhesion, (iii) a resist composition comprising the polymer as a base resin, which is improved in adhesion and transparency when processed by photolithography using light having a wavelength of less than 300 nm, especially ArF excimer laser light and which has a higher resolution and etching resistance than conventional resist compositions, and (iv) a patterning process using the resist composition.
The inventors have found that novel cyclic acetal compounds of the formula (i), or mixtures of a 5-membered ring acetal compound of the formula (i) and a 6-membered ring acetal compound of the formula (v), all shown below, are easily produced in high yields by the method to be described later; that polymers obtained from the cyclic acetal compounds or the mixtures of cyclic acetal compounds are highly transparent at the exposure wavelength of an excimer laser; and that a resist composition using the polymer as a base resin is improved in adhesion to substrates. It has also been found that novel polymers comprising recurring units of the formula (1-1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000, which are produced from the cyclic acetal compounds or the mixtures of cyclic acetal compounds by the method to be described later, have improved reactivity, robustness or rigidity and substrate adhesion; that a resist composition comprising the polymer as the base resin has a high resolution and etching resistance; and that this resist composition lends itself to precise micropatterning.
In a first aspect, the invention provides a cyclic acetal compound of the following general formula (i), and especially formula (ii).
Herein k is 0 or 1 and n is an integer from 0 to 6.
The invention also provides a cyclic acetal compound mixture comprising a 5-membered ring acetal compound of the general formula (i) and a 6-membered ring acetal compound of the general formula (v), and especially a 5-membered ring acetal compound of the general formula (ii) and a 6-membered ring acetal compound of the general formula (vi).
Herein k and n are defined above.
In a second aspect, the invention provides a polymer comprising recurring units of the following general formula (1-1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000.
Herein R is hydrogen or methyl, k and n are as defined above.
In a preferred embodiment, the polymer further includes recurring units of the following general formula (1′-1) or (1′-2).
Herein R, k and n are as defined above.
In another preferred embodiment, the polymer includes, in addition to the recurring units of formula (1-1), recurring units of the following general formula (2-1).
Herein k is as defined above; R
1
is hydrogen, methyl or CH
2
CO
2
R
3
; R
2
is hydrogen, methyl or CO
2
R
3
; R
3
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms; R
4
is an acid labile group; R
5
is selected from the class consisting of a halogen atom, a hydroxyl group, a straight, branched or cyclic alkoxy, acyloxy, alkoxycarbonyloxy or alkylsulfonyloxy group of 1 to 15 carbon atoms, and a straight, branched or cyclic alkoxyalkoxy group of 2 to 15 carbon atoms, in which some or all of the hydrogen atoms on constituent carbon atoms may be substituted with halogen atoms; Z is a single bond or a straight, branched or cyclic (h+2)-valent hydrocarbon group of 1 to 5 carbon atoms, in which at least one methylene may be substituted with oxygen to form a chain-like or cyclic ether or two hydrogen atoms on a common carbon may be substituted with oxygen to form a ketone; and h is 0, 1 or 2.
In a further preferred embodiment, the polymer includes, in addition to the recurring units of formula (1-1), recurring units of the following general formulae (2-1) and (3).
Herein k, h and R
1
to R
5
are as defined above.
In a still further preferred embodiment, the polymer includes, in addition to the recurring units of formula (1-1), recurring units of the following general formula (2-1) and/or recurring units of the following general formula (4), and recurring units of the following general formula (3).
Herein k, h and R
1
to R
5
are as defined above.
The polymer of any of the preferred embodiment may further include recurring units of the general formula (11-1).
In an alternative embodiment, the polymer includes, in addition to the recurring units of formula (1-2), recurring units of the following general formula (2-2).
Herein k, h and R
1
to R
5
are as defined above. The polymer may further include recurring units of the general formula (1′-2).
In a third aspect, the invention provides a resist composition comprising the polymer defined above.
In a fourth aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the resist composition onto a substrate to form a coating; heat treating the coating and then exposing it to high-energy radiation or electron beams through a photo mask; and optionally heat treating the exposed coating and developing it with a developer.
The polymers comprising recurring units of formula (1-1) or (1-2) have high rigidity since bridged aliphatic rings are incorporated in the backbone. They show improved substrate adhesion since they have on a side chain a five or six-membered ring cyclic acetal structure with a high polarity in addition to an ester structure and are thus rich in oxygen functional groups. A spacer of appropriate l
Hasegawa Koji
Hatakeyama Jun
Kinsho Takeshi
Nakashima Mutsuo
Nishi Tsunehiro
Millen White Zelano & Branigan P.C.
Trinh Ba K.
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