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
2001-04-26
2002-12-10
Baxter, Janet (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
C430S285100, C430S296000, C528S298000, C528S300000, C528S302000
Reexamination Certificate
active
06492090
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to (i) a polymer comprising units having an acid labile blocking carboxylic acid and a polar group, (ii) a resist composition comprising the polymer, having a high dissolution contrast before and after exposure and sufficient substrate adhesion, and in particular, suitable as micropatterning material for VLSI fabrication, and (iii) 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.
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, robustness 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 robustness because of their backbone structure. On the other hand, the polymers containing an alicyclic compound in the backbone have robustness 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, the backbone is highly hydrophobic, so that these polymers are less adherent to substrates when applied thereto. 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 (i) a polymer featuring reactivity and substrate affinity, (ii) a resist composition comprising the polymer, having a significantly higher sensitivity, resolution, and substrate adhesion than prior art resist compositions, and (iii) a patterning process using the resist composition.
It has been found that a polymer comprising units of formulas (1) and (2) to be defined below and having a weight average molecular weight of 1,000 to 500,000 is characterized in that the units have a highly reactive, acid labile blocking carboxylic acid and a highly polar group, so that a resist composition comprising the polymer has a significantly high sensitivity, resolution, and substrate adhesion and is thus quite useful in precise micropatterning.
In a first aspect, the invention provides a polymer comprising units of the following general formula (1) and units of the following general formula (2) and having a weight average molecular weight of 1,000 to 500,000.
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, R
4
is hydrogen, a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, a straight, branched or cyclic alkoxyalkyl group of 2 to 15 carbon atoms, or a straight, branched or cyclic acyl group of 1 to 15 carbon atoms, R
5
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, Y is a divalent hydrocarbon group of 4 to 15 carbon atoms which may contain a hetero atom and which forms a ring with the carbon atom to which it is connected at opposite ends, Z is a trivalent hydrocarbon group of 1 to 10 carbon atoms, Z may form a ring with R
1
, with the proviso that R
1
is methylene and Z is a tetravalent hydrocarbon group of 1 to 10 carbon atoms when they form a ring, and k is 0 or 1. W is —O— or —(NR)— wherein R is hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms.
Typical of the units of formula (1) are units of the following general formula (3) or (4).
Herein R
1
to R
5
, Z, and k are as defined above. R
6
to R
15
are independently hydrogen or monovalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom, two or more of R
6
to R
15
may form a ring with the proviso that they are divalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom, or two of R
6
to R
15
which are attached to adjoining carbon atoms may bond together directly to form a double bond, m is equal to 0 or 1, n is equal to 0, 1, 2 or 3, and 2m+n is equal to 2 or 3.
The polymer may further include units of at least one of the following formulas (5) to (8).
Herein R
1
, R
2
and k are as defined above. At least one of R
18
to R
21
is a carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms, and the reminders are independently hydrogen or straight, branched or cyclic alkyl groups of 1 to 15 carbon atoms, or R
18
to R
21
, taken together, may form a ring, and when they form a ring, at least one of R
18
to R
21
is a carboxyl or hydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms, and the reminders are independently single bonds or straight, branched or cyclic alkylene groups of 1 to 15 carbon atoms. At least one of R
22
to R
25
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO
2
— partial structure, and the reminders are independently hydrogen or straight, branched or cyclic alkyl groups of 1 to 15 carbon atoms, or R
22
to R
25
, taken together, may form a ring, and when they form a ring, at least one of R
22
to R
25
is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO
2
— partial structure, and the reminders are independently single bonds or straight, branched or cyclic alkylene groups of 1 to 15 carbon atoms. R
26
is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing such a polycyclic hydrocarbon group. R
27
is an acid labile group. X is —CH
2
— or —O—.
In a second aspect, the invention provides a resist composition comprising the polymer defined above.
In a third 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 units of formula (1) have carboxylic acid capped with an acid-decomposable blocking group and serve to establish a differential dissolution rate between the exposed and unexposed areas. These units are more reactive with acid than conventional units. In general, a polymer containing an alicyclic compound in its backbone tends to blunt the reactivity of acid-decomposable blocking groups with acid probably due to the hindrance by its steric str
Hasegawa Koji
Hatakeyama Jun
Kinsho Takeshi
Nakashima Mutsuo
Nishi Tsunehiro
Baxter Janet
Clarke Yvette M.
Millen White Zelano & Branigan P.C.
Shin-Etsu Chemical Co. , Ltd.
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