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
2001-04-19
2003-07-01
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
C430S270100, C430S296000, C430S325000, C430S327000, C526S271000, C526S281000
Reexamination Certificate
active
06586157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to (i) a novel ester compound, (ii) a polymer comprising units of the ester compound which is blended as a base resin to formulate a resist composition having a high sensitivity and resolution, and in particular, suitable as micropatterning material for VLSI fabrication, (iii) a resist composition comprising the polymer, and (iv) a patterning process using the resist composition.
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 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 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 acid labile or eliminatable groups. The overall performance of resist material is adjusted by a choice from among a variety of acid eliminatable protective groups.
Exemplary acid eliminatable protective groups include tert-butoxycarbonyl (JP-B 2-27660), tert-butyl (JP-A 62-115440, JP-A 5-80515, and J. Photopolym. Sci. Technol. 7 [3], 507 (1994)), 2-tetrahydropyranyl (JP-A 2-19847, 5-80515 and 5-88367), and 1-ethoxyethyl (JP-A 2-19847 and 4-215661). While it is desired to achieve a finer pattern rule, none of these acid eliminatable protective groups are deemed to exert satisfactory performance.
More particularly, tert-butoxycarbonyl and tert-butyl are extremely less reactive with acids so that a substantial quantity of energy radiation must be irradiated to generate a sufficient amount of acid in order to establish a difference in rate of dissolution before and after exposure. If a photoacid generator of the strong acid type is used, the exposure can be reduced to a relatively low level because reaction can proceed with a small amount of acid generated. However, in this event, the deactivation of the generated acid by air-borne basic substances has a relatively large influence, giving rise to such problems as a T-top pattern. On the other hand, 2-tetrahydropyranyl and 1-ethoxyethyl are so reactive with acids that with the acid generated by exposure, elimination reaction may randomly proceed without a need for heat treatment, with the result that substantial dimensional changes occur between exposure and heat treatment/development. Where these groups are used as protective groups for carboxylic acid, they have a low dissolution inhibiting effect to alkali, resulting in a high rate of dissolution in unexposed areas and film thinning during development. If highly substituted polymers are used to avoid such inconvenience, there results an extreme drop of heat resistance. These resins fail to provide a difference in rate of dissolution before and after exposure, resulting in resist materials having a very low resolution.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide (i) a novel ester compound capable of forming an acid-decomposable polymer, (ii) a polymer which is blended as a base resin to formulate a resist composition having a higher sensitivity and resolution than conventional resist compositions, (iii) a resist composition comprising the polymer as a base resin, and (iv) a patterning process using the resist composition.
The inventor has found that a novel ester compound of the following general formula (1) obtained by the method to be described later is useful in preparing an acid-decomposable polymer; that a resist composition comprising as the base resin a novel polymer prepared from the ester compound to a weight average molecular weight of 1,000 to 500,000 has a high sensitivity and resolution; and that this resist composition lends itself to precise micropatterning.
In a first aspect, the invention provides an ester compound of the following general formula (1).
Herein 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, Z is a divalent hydrocarbon group of 2 to 20 carbon atoms which forms a single ring or bridged ring with the carbon atom and which may contain a hetero atom, m is 0 or 1, n is 0, 1, 2 or 3, and 2m+n is 2 or 3.
In a second aspect, the invention provides a polymer comprising recurring units of the following general formula (1a) derived from an ester compound of the general formula (1), and having a weight average molecular weight of 1,000 to 500,000.
Herein R
1
, R
2
, Z, m and n are as defined above.
In a preferred embodiment, the polymer further comprises recurring units of at least one of the following formulas (2a) to (10a).
Herein R
1
and R
2
are as defined above; k is 0 or 1; R
4
is hydrogen or a carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms; at least one of R
5
to R
8
is a carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms, and the remainders are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
5
to R
8
, taken together, may form a ring, and when they form a ring, at least one of R
5
to R
8
is a carboxyl or hydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms, and the remainders are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms; R
9
is a monovalent hydrocarbon group of 3 to 15 carbon atoms containing a —CO
2
— partial structure; at least one of R
10
to R
13
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO
2
— partial structure, and the remainders are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
10
to R
13
, taken together, may form a ring, and when they form a ring, at least one of R
10
to R
13
is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO
2
— partial structure, and the remainders are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms; R
14
is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing such a polycyclic hydrocarbon group; R
15
is an acid labile group; X is —CH
2
— or —O—; and Y is —O— or —(NR
16
)— wherein R
16
is hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms.
In a third aspect, the invention provides a resist composition comprising the polymer defined above, and more specifically, a resist composition comprising the polymer defined above, a photoacid generator, and an organic solvent.
In a fourth aspect, the invention provides a process for forming a resist pattern comprising the steps of applying the resist composition defined above 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 ester compound of formula (1) and the polymer comprising units of formula (1a) employ a cycloalkyl—cycloalkyl or cycloalkylcycloalkenyl group of the following formula (1b) as the acid-eliminatable protective group, thereby overcoming the drawbacks of the tert-butoxycarbonyl and tert-butyl groups having low reactivity with acid as well as the 2-tetrahydropyranyl and 1-ethoxyethyl groups having too high reactivity with acid and low resistance to alk
Hasegawa Koji
Hatakeyama Jun
Kinsho Takeshi
Nakashima Mutsuo
Nishi Tsunehiro
Ashton Rosemary
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
Thornton Yvette C.
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