Chemical amplification type positive resist

Details Chemical amplification type positive resist Chemical amplification type positive resist

2000-03-24

2002-02-19

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

C430S914000, C430S921000, C568S028000, C568S035000, C568S077000

Reexamination Certificate

active

06348297

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a chemical amplification type positive resist.
The fine processing in the production of semiconductor has usually been performed by adopting the lithography process using a resist composition. In the lithography process, principally, resolution can be improved by shortening wavelength for exposure, as indicated by the Rayleigh's equation for limit of diffraction. Accordingly, wavelength of the light source for lithography process used in the production of semiconductors has become shorter and shorter in such order as g-ray at a wavelength of 436 nm, i-ray at a wavelength of 365 nm. KrF excimer laser at a wavelength of 248 nm. ArF eximer laser at a wavelength of 193 nm is expected as a next generation light source, and some kinds of resists for ArF eximer laser is now being put to practical use.
Since lenses in exposing machines using ArF excimer laser have a shorter lifetime as compared with the lenses for the conventional exposing light source, the shorter time for exposing such lenses to ArF excimer laser ray is preferred. In order to make the exposure time shorter, sensitivity of the resists is to be increased, and for such purpose, so called chemical amplification type resists are used. The chemical amplification type resist contains a resin having a group cleavable by the action of an acid. and utilizes a catalytic action of the acid generated by exposure to the ray.
It has been known that resins used in resists to be exposed to ArF excimer laser preferably have no aromatic ring in order to insure the transmittance of the resists and have an alicyclic ring in place of an aromatic ring in order to confer a dry etching resistance. Various resins have been known as resins meeting such requirements. For example, D. C. Hofer, J. Photopolym. Sci. Technol., Vol. 9. No. 3, pages 387-398 (1996) describes such resins.
S. Takeuchi et al., J. Photopolym. Sci. Technol., Vol. 9, No. 3, pages 475-487 (1996) and JP-A-9-73173 also describe that, when polymers or copolymers of 2-methyl-2-adamantyl methacrylate are used as resins for chemical amplification type resist, a positive working action is realized by cleavage of 2-methyl-2-adamantyl group by the action of an acid and a high dry etching resistance, high resolution and a good adherence to substrate are obtained. JP-A-10-274852 also describes that the adherence to substrate is Improved by using a resin having a butyrolactone residue in a part of polymerization units, as a resin composing a chemical amplification type positive resist composition. In addition, JP-A-10-319595 describes a positive resist composition using a resin having a carboxyl group protected by &ggr;-butyrolactone-3-yl residue.
On the other hand, since the chemical amplification type resists utilizes the action of an acid, the profiles are liable to be bottom-tailed by deactivation of the acid when the substrate is of a basic nature. It is known that this problem can be resolved by adding a much amount of a basic quencher substance. Addition of a much amount of such quencher substance, however, results in decrease of the sensitivity. When ArF eximer laser is used as the light for exposure, the resist is often applied on a substrate having a low reflection, such as an organic or inorganic anti-reflection film. When such a substrate having a low reflection is used, the profile of the resist generally deteriorated to a taper shape, although dimension uniformity is effectively improved.
It is contemplated that a reduced quantity of an acid generator in a resist composition In order to lessen light absorption, but in this case, a sensitivity generally decreases. As other methods to lessen light absorption, the use of aliphatic sulfonium salts having a high transparency is contemplated, as described in JP-A-7-25846, JP-A-7-28237, JP-A-7-92675 and JP-A-8-27102. With such well-known aliphatic sulfonium salts, however, no sufficient resolution is achieved. In addition the problem of bottom-tailed profile on a substrate of a basic nature is not solved either. In such a way, a chemical amplification type resist using a conventional acid generator has had the problem that its performance, in particular a resist pattern profile, are varied depending on the kinds of the substrate.
An object of the present invention is to provide a chemical amplification type positive resist composition, containing a resin component and an acid generator, suitable for the ArF or KrF excimer laser lithography and the like, particularly lithography using a light of a wavelength of 220 nm or shorter such as the ArF excimer laser lithography, and not only excellent in resist performances such as sensitivity, resolution and adhesion to a substrate, but producing a good pattern profile on any kind of substrate with a little dependence on kinds of substrate, even being used with a basic substrate and a low reflectance substrate.
Another object of the present invention is to provide a compound useful as an acid generator for the chemical amplification type positive resist composition.
The present inventors has found that resolution of a chemical amplification type positive resist composition is improved and further, a pattern profile thereof is also improved even on a basic substrate and a low reflectance substrate, when certain kinds of acid generators are in combination or an acid generator of a specific structure selected from the certain kinds are used. Thus, the present invention has been completed.
SUMMARY OF THE INVENTION
The present invention provides a chemical amplification type positive resist composition (hereinafter referred to as composition A) which comprises
(1) an acid generator comprising
an aliphatic sulfonium salt represented by the following formula (I):
wherein Q
1
represents an alkyl group, Q
2
represents an alkyl or a residue of an alicyclic hydrocarbon and m represents an integer of 1 to 8; and at least one onium salt selected from triphenylsulfonium salts represented by the following formula (IIa) and diphenyiodonium salts represented by the following formula (IIb):
wherein Q
3
, Q
4
, Q
5
, Q
6
and Q
7
each independently represent a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and q and p represent a integer of 4 to 8; and
(2) a resin which has a polymerization unit with a group unstable to an acid, and is insoluble or barely soluble in alkali by itself but changes soluble in alkali by an action of the acid.
Aliphatic sulfonium salts represented by the formula (I) wherein m is in the range of 4 to 8 are conspicuous in effects to improve a resolution and a pattern profile and furthermore, impart an excellent resolution and a good pattern profile even when the onium salt selected from triphenylsulfonium salts and diphenyiodonium salts represented by the formulae (IIa) and (IIb), respectively.
Therefore, the present invention provides a chemical amplification type positive resist composition (hereinafter referred to as composition B) which comprises
(1) an acid generator comprising
an aliphatic sulfonium salt represented by the following formula (Ia):
wherein Q
1
and Q
2
are as defined above and n represents an integer of 4 to 8; and
(2) a resin which has a polymeriation unit with a group unstable to an acid, and is insoluble or barely soluble in alkali by itself but changes soluble in alkali by an action of the acid.
It is more effective to use an aliphatic sulfonium salt represented by the formula (Ia) and at least one onium salt selected from triphenylsulfonium salts and diphenyiodonium salts represented by the formulae (IIa) and (IIb), respectively, in combination.
The present Invention further provides a sulfonium salt represented by the formula (Ia).
PREFERRED EMBODIMENT OF THE INVENTION
An acid generator used in a chemical amplification type resist composition decomposes to generate an acid under radiation such as light or an electron beam to the acid generator itself or a resist composition including the acid generator. In the

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