Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2001-02-22
2003-03-04
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S176000, C430S270100, C430S905000, C522S031000, C522S032000
Reexamination Certificate
active
06528229
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive photoresist composition used for the production of semiconductor integrated circuit elements, masks for producing integrated circuits, printed wiring boards and liquid crystal panels.
BACKGROUND OF THE INVENTION
In order to form a pattern for the production of electronic parts such as semiconductor devices, magnetic bubble memories and integrated circuits, a method utilizing a photoresist which is sensitive to an ultraviolet ray or a visible ray has hitherto been practically used widely. The photoresist includes a negative type photoresist in which an area irradiated with a radiation is insolubilized in a developing solution and a positive type photoresist in which an area irradiated with a radiation is conversely solubilized in a developing solution. The negative type photoresist has high sensitivity in comparison with the positive type photoresist and is excellent in adhesion to a substrate and chemical resistance which are required for wet etching, so that the negative type photoresist had took the main current of photoresist until recent years.
However, keeping step with increased density and integration of semiconductor device, the linewidth and space have extremely decreased, and dry etching has come into use for etching of substrate. Thus, high resolution and high dry etching resistance have been desired for the photoresist. As a result, the positive type photoresist occupies the most part of the photoresist field, at present.
With recent multifunctionalization and advancement of electronic equipment, it has been strongly demand to make pattern fine for the purpose of further increasing the density and integration.
Specifically, since the longitudinal dimension of integrated circuit has not been decreased so much compared with reduction in the transverse dimension thereof, increase in a ratio of the height to the width of resist pattern cannot be helped. Therefore, with advance of making pattern fine, it has become more difficult to suppress change in the size of resist pattern on a wafer having a complicated structure of difference in level.
Also, in various kinds of exposure systems, problems occur in association with reduction in the minimum dimension. For example, in case of light-exposure, the interference action of reflected light based on the difference in level of substrate has greatly influenced on the dimensional accuracy, whereas in electron beam-exposure, the proximity effect due to back scattering of electrons have made it impossible to increase the ratio of the height to the width of resist pattern.
It has been found that these many problems can be solved by the use of a multilayer resist system. With respect to the multilayer resist system, the outline thereof is described in
Solid State Technology,
74 (1981). In addition, many investigations on the system have been made.
In general, a multilayer resist method includes a three-layer resist method and a two-layer resist method. The three-layer resist method is a method comprising coating a planarizing organic layer on a substrate having differences in level, overlaying an intermediate inorganic layer and a resist thereon, patterning the resist, then dry etching the intermediate inorganic layer using the patterned resist as a mask, and further patterning the planarizing organic layer using the intermediate inorganic layer as a mask by O
2
RIE (reactive ion etching). In the method, since conventional techniques can be basically used, investigations have been early initiated. However, problems are encountered in that the process is very complicated and in that cracks and pinholes are liable to occur in the intermediate layer since three layers of the organic layer, inorganic layer and organic layer different from each other in properties are overlaid with one another.
In contrast with the three-layer resist method, the two-layer resist method uses a resist having combined properties of both the resist and the intermediate inorganic layer used in the three-layer resist method, that is to say, a resist having oxygen plasma resistance. Accordingly, the occurrence of cracks and pinholes is inhibited and the process is simplified from three layers to two layers. However, the two-layer resist method has a problem in that a resist having the oxygen plasma resistance must be newly developed, although a conventional resist can be used as the upper-layer resist in the three-layer resist method.
From these circumstances, it has been desired to develop a positive type photoresist which is excellent in the oxygen plasma resistance capable of using as the upper-layer resist in the two-layer resist method and has high sensitivity and high resolution, particularly a resist of the alkali development system which can be used without changing the process now in use.
Further, in the production of VLSI which requires fabrication of an ultrafine pattern comprising linewidth of a half micron or less, a wavelength of light source for an exposure device used for lithography has become shorter and shorter, and the use of a KrF excimer laser beam or a ArF excimer laser beam is investigated. In such a photolithography using an exposure ray having a short wavelength, a so-called chemical amplification-type resist is ordinarily employed as a resist.
Particularly, in case of utilizing an ArF excimer laser beam, it is not preferred to introduce a phenol structure into a binder resin which is the main component of a resist from the standpoint of optical transparency of the resist film. Thus, a polymer containing structure which decomposes with an acid to generate a carboxylic acid, for example, a tertiary ester such as tert-butyl ester, 1-alkyladamantyl ester or a THP-protected carboxylic acid for the image-forming portion is ordinarily used as the binder resin.
However, as a result of the observation of a resist pattern formed by a scanning electron microscope (SEM) , it is found that the linewidth thereof shrinks which causes a big problem in design for device. This problem is remarkable in case of using a resin containing an alicyclic group which is particularly employed in a resin for the ArF exposure.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a positive photoresist composition which provides a resist pattern in which variation of the linewidth is suppressed when the resist pattern formed in the production of semiconductor device is observed by a scanning electron microscope (SEM).
Other objects of the present invention will become apparent from the following description.
As a result of intensive investigations made by the inventors on positive resist compositions of the chemical-amplification type, it has been found that the objects of the present invention are accomplished by using an acid-decomposable resin containing specific repeating units as copolymer components to complete the present invention.
Specifically, the present invention includes the following positive photoresist compositions:
(1) a positive photoresist composition which comprises (A) a resin which contains a repeating unit represented by formula (I) shown below and a repeating unit represented by formula (II) shown below and whose solubility in an alkaline developing solution increases by the action of an acid and (B) a compound which generates an acid upon irradiation with an actinic ray or radiation,
wherein R
1
, R
2
and R
3
, which may be the same or different, each independently represents an alkyl group, a haloalkyl group, a halogen atom, an alkoxy group, a trialkylsilyl group or a trialkylsilyloxy group; and n represents 0 or 1,
wherein M represents an atomic group necessary for forming an alicyclic structure, which may be substituted, together with the connected two carbon atoms (C—C) ; and R
11
and R
12
, which may be the same or different, each independently represents a hydrogen atom, a cyano group, a halogen atom or an alkyl group which may be substituted, and
(2) the positive photoresist composition as described in item (1) above, wherein
Chu John S.
Sughrue & Mion, PLLC
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