Resist composition and patterning process

Details Resist composition and patterning process Resist composition and patterning process

2000-10-24

2002-06-04

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

C430S326000

Reexamination Certificate

active

06399274

ABSTRACT:

This invention relates to (1) a resist composition comprising as a base resin a polymer having highly reactive, acid lability-imparting 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 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. 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 (1) a resist composition comprising a polymer having improved reactivity and rigidity as a base resin and achieving significantly surpassing sensitivity, resolution and etching resistance over prior art compositions, and (2) a patterning process using the resist composition.
It has been found that 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 possesses both high rigidity and reactivity, and that a resist composition using the polymer as a base resin has a high sensitivity, 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 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
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
, R
4
is an acid labile group, i is an integer of 1 to 4, and k is equal to 0 or 1.
In one preferred embodiment, the polymer comprising recurring units of the general formula (1-1) or (1-2) is a polymer of the following general formula (2), (3) or (4).
Herein
R
1
to R
4
, i and k are as defined above,
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 remainder 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 are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms,
at least one of R
9
to R
12
is a monovalent hydrocarbon group of 2 to 15 carbon atoms containing a —CO2— partial structure, and the remainder are independently hydrogen or a straight, branched or cyclic alkyl group of 1 to 15 carbon atoms, or R
9
to R
12
, taken together, may form a ring, and when they form a ring, at least one of R
9
to R
12
is a divalent hydrocarbon group of 1 to 15 carbon atoms containing a —CO2— partial structure, and the remainder are independently a single bond or a straight, branched or cyclic alkylene group of 1 to 15 carbon atoms,
R
13
is a polycyclic hydrocarbon group of 7 to 15 carbon atoms or an alkyl group containing such a polycyclic hydrocarbon group,
R
14
is an acid labile group,
x is a number from more than 0 to 1, “a” to “e” are numbers from 0 to less than 1, satisfying x+a+b+c+d+e=1.
In a further preferred embodiment, the acid labile group represented by R
4
in the general formula (2), (3) or (4) contains a group of the following general formula (5) or (6).
Herein
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
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
17
to R
26
are independently hydrogen or monovalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom, or R
17
to R
26
, taken together, may form a ring, and R
17
to R
26
represent divalent hydrocarbon groups of 1 to 15 carbon atoms which may contain a hetero atom when they form a ring, or two of R17 to R
26
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 recurring units of formula (1-1) or (1-2), a spacer of 1 to 4 carbon atoms is introduced between the condensed ring skeleton and the acid labile group-blocked carboxylic acid site. This polymer is more reactive with acid as compared with prior art polymers in which the blocked carboxylic acid is directly attached to the ring. Although the reason is not well understood, it is believed that as a phenomenon inherent to polymers, the insertion of a spacer of an appropriate length into the complex intertwining of backbones enables to enhance the degree of baring or exposure of reactive sites, leading to an increased acid contact probability, as compared with the direct bond type in which reactive sites are rather buried. When the polymer is used in a resist composition, the degree of baring of carboxylic acid upon deblocking is so high that a significant improvement in dissolution rate is achieved per unit deblocking, leading to a high dissolution contrast. With respect to the spacer length, which depends on the backbone structure, extraneously increasing the number of carbon atoms gives only a little further effect after passing over a

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