Resist composition and patterning process

Details Resist composition and patterning process Resist composition and patterning process

2000-10-24

2003-12-23

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

C430S325000, C430S326000, C430S327000, C430S328000, C430S330000, C430S331000, C430S905000

Reexamination Certificate

active

06667145

ABSTRACT:

This invention relates to (1) a resist composition comprising as a base resin a polymer having highly adherent, highly rigid units and especially suited as micropatterning material for VLSI fabrication, and (2) 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.
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 a etching resistance sufficient to allow for film thickness reduction and a high resolution and substrate adhesiveness sufficient to form and retain a precise micropattern. To meet these requirements, it is crucial to develop a base resin having high transparency, high rigidity, high reactivity and firm adhesion. 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 or adhesion in that highly reactive monomers or highly adherent monomers can be introduced 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 lack substrate adhesiveness because of their highly hydrophobic backbone. Therefore, some resist compositions which are formulated using these polymers as the base resin, fail to withstand etching although they can be micropatterned. Some other resist compositions are highly resistant to etching, but the micropatterned film will peel from the substrate.
SUMMARY OF THE INVENTION
An object of the invention is to provide (1) a resist composition comprising a polymer having improved substrate adhesiveness and rigidity as a base resin and achieving significantly surpassing resolution and etching resistance over prior art compositions, and (2) a patterning process using the resist composition.
It has been found that a polymer of the following general formula (1-1) or (1-2) having a weight average molecular weight of 1,000 to 500,000 possesses both high rigidity and substrate adhesiveness, and that a resist composition using the polymer as a base resin has a high resolution and high etching resistance and is very useful in precise microfabrication.
Accordingly, the invention provides a resist composition comprising as a base resin a polymer represented by the following general formula (1-1) or (1-2) and having a weight average molecular weight of 1,000 to 500,000.
Herein
R
1
is hydrogen, methyl or CO
2
R
2
,
R
2
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms,
R
3
is hydrogen, methyl or CH
2
CO
2
R
2
,
at least one of R
4
to R
7
is a carboxyl or hydroxyl-containing monovalent hydrocarbon group of 1 to 15 carbon atoms, and the reminders are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
4
to R
7
, taken together, may form a ring, and when they form a ring, at least one of R
4
to R
7
is a carboxyl or hydroxyl-containing divalent hydrocarbon group of 1 to 15 carbon atoms, and the reminders are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms,
at least one of R
8
to R
11
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO
2
— partial structure, and the reminders are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
8
to R
11
, taken together, may form a ring, and when they form a ring, at least one of R
8
to R
11
is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO
2
— partial structure, and the reminders are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms,
R
12
is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing such a polycyclic hydrocarbon group,
R
13
is an acid labile group,
Z is a divalent group of atoms to construct a 5- or 6-membered ring which contains a carboxylate, carbonate or acid anhydride therein,
k is equal to 0 or 1, x is a number from more than 0 to 1, “a” to “d” are numbers from 0 to less than 1, satisfying x+a+b+c+d=1.
Preferably, in the polymer of the general formula (1-1) or (1-2), the acid labile group represented by R
13
contains a group of the following general formula (2) or (3).
Herein
R
14
is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or substituted or unsubstituted aryl group of 6 to 20 carbon atoms,
R
15
is a straight, branched or cyclic alkyl group of 1 to 8 carbon atoms or substituted or unsubstituted aryl group of 6 to 20 carbon atoms,
R
16
to R
25
are independently hydrogen or monovalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom, or R
16
to R
25
, taken together, may form a ring, and R
16
to R
25
represent divalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom when they form a ring, or two of R
16
to R
25
which are attached to adjoining carbon atoms may bond together directly to form a double bond,
m is a number equal to 0 or 1, n is a number equal to 0, 1, 2 or 3, satisfying 2m+n=2 or 3.
In another aspect, the invention provides a process for forming a resist pattern comprising the steps of applying a resist composition as 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.
In the polymer represented by the general formula (1-1) or (1-2), an oxygen functional group capable of imparting substrate adhesiveness is fixed to the cyclic structure to insure high polarity. This adhesivenss imparting site is attached to the fused ring directly (via nothing), that is, in a spiro form, enhancing rigidity. Accordingly, the polymer possesses high etching resistance and at the same time, satisfactory substrate adhesiveness. When the polymer is formulated as the base resin, the resulting resist composition has a high resolution and high etching resistance and eliminates the drawbacks of prior art compositions including peeling of the micropatterned film, poor resolution upon micropatterning and pattern extinction after etching.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The resist composition of the invention is defined as comprising as a base resin a polymer or high molecular weight compound of the following general formula (1-1) or (1-2) having a weight average molecular weight of 1,000 to 500,000, preferably 5,000 to 100,000.
In the above formulae, k is equal to 0 or 1. Accordingly, the formulae (1-1) and (1-2) can be represented by the following formulae (1-1-1) to (1-2-2). However, it is not excluded that k is a mixture of 0 and 1.
Herein R
1
is a hydrogen atom, methyl group or CO
2
R
2
.
R
2
is a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, examples of which include methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethyl

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