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
2000-10-30
2003-07-08
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
C430S271100, C430S325000, C526S271000, C526S279000, C526S272000
Reexamination Certificate
active
06589705
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive-working photoresist composition for use in the production of semiconductor integrated circuit element, mask for the production of integrated circuit, printed-wiring board, liquid crystal panel, etc.
BACKGROUND OF THE INVENTION
As a method for the formation of a pattern in the production of electronic components such as semiconductor device, magnetic bubble memory and integrated circuit there has heretofore widely been practically used a method involving the use of a photoresist sensitive to ultraviolet or visible ray. These photoresists can be divided into two groups, i.e., negative-working photoresist which is rendered insoluble in a developer when irradiated with light and positive-working photoresist which is rendered soluble in a developer when irradiated with light. The negative-working photoresist exhibits a higher sensitivity and better adhesivity to the substrate and chemical resistance required to wet etching than the positive-working photoresist and thus has been mainly used so far.
However, with the enhancement of the density and the degree of integration of semiconductor device, etc., the width and distance between lines on pattern have been extremely reduced. Further, as a method for etching a substrate there has been recently employed dry etching method. Thus, the photoresist has been desired to have a high resolution and a high dry etching resistance. Therefore, positive-working photoresists have been mainly used recently.
Further, as the electronic apparatus has recently been rendered more multi-functional and advanced, it has been keenly desired to provide finer patterns for higher density and integration.
In other words, since the integrated circuit can be reduced less in its vertical dimension than in its horizontal dimension, it has been natural that the ratio of height to width of a resist pattern should be great. Accordingly, it is more difficult to depress the dimensional change of a resist pattern on a wafer having a complicated step structure as the pattern becomes finer.
Further, various exposure methods are facing problems accompanying the reduction of the smallest dimension. For example, the exposure to light has been liable to interference of reflected light due to the step structure of a substrate that greatly affects the dimensional accuracy of the resist pattern. On the other hand, the exposure to electron beam has been liable to back scattering of electrons causing a proximity effect that makes it impossible to increase the ratio of height to width of a fine resist pattern.
It has been found that the foregoing many problems can be eliminated by the use of a multi-layer resist system. For the outline of such a multi-layer resist system, reference can be made to Solid State Technology, 74 (1981). Many studies of this system have been further reported.
In general, multi-layer resist methods can be divided into two groups, i.e., three-layer resist method and two-layer resist method. The three-layer resist method comprises applying an organic flat layer to a stepped substrate, superposing an inorganic interlayer and a resist on the organic flat layer, patterning the resist, dry-etching the inorganic interlayer with the resist as a mask, and then subjecting the organic flat layer to O2RIE (reactive ion etching) with the inorganic interlayer as a mask to form a pattern. This method can be basically accomplished by conventional techniques and thus has long been studied. However, since this method involves the lamination of three layers having different physical properties, i.e., organic layer, inorganic layer and organic layer, it is disadvantageous in that the interlayer is apt to have cracks or pin-holes.
As opposed to the three-layer resist method, the two-layer resist method involves the use of a resist which acts as resist in the three-layer resist method as well as an inorganic interlayer, i.e., a resist having oxygen plasma resistance. In accordance with the two-layer resist method, the occurrence of cracks or pin-holes can be inhibited. Further, since the number of resist layers to be worked is reduced from 3 to 2, the required procedure can be simplified. However, while the three-layer resist method allows the use of a conventional resist as the upper resist, the two-layer resist method faces a problem that a resist having oxygen plasma resistance must be newly developed.
Under these circumstances, it has been desired to develop a high sensitivity and high resolution positive-working photoresist having an excellent oxygen plasma resistance which can be used as the upper layer resist for two-layer resist method, etc., particularly an alkali development process resist which can be used without changing the existing process.
In the production of VLSI (very large scale integration) requiring the working of ultrafine pattern comprising lines having a width of half micron or less, the wavelength of light from the exposure apparatus for use in lithography has been reduced more and more. The use of KrF excimer laser beam and ArF excimer laser beam has been recently considered. Such a short wavelength photolithography usually employs a so-called chemically-amplified resist.
In the case where ArF excimer laser beam is utilized in particular, it is not appropriate from the standpoint of optical transparency of film to introduce a phenol structure into the binder resin which is a main component of the resist. It is instead usual to use as a binder a resin polymer containing as an image-forming site a structure which decomposes with an acid to produce a carboxylic acid such as tertiary ester (e.g., t-butylester), 1-alkyladamantylester and THP-protected carboxylic acid.
As an example of Si-containing resist containing an image-forming site transparent to ArF excimer laser beam there is disclosed a terpolymer comprising maleic anhydride, unsaturated carboxylic acid t-butylester and allyl trimethylsilane in JP-A-5-11450 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”). This resist is excellent in the resolution for the working of ultrafine pattern but leaves something to be desired in sensitivity. Further, this resist is disadvantageous in that it exhibits a deteriorated compatibility with a photo-acid generator during the preparation of a resist solution, causing turbidity. This resist is also disadvantageous in that it undergoes precipitation of insoluble matters with time. Eventually, this resist leaves something to be desired in age stability. This resist further leaves something to be desired dependence on density (defocus latitude depended on line pitch). Since the recent devices tend to have various patterns, resists having various properties have been desired. One of these requirements is dependence on density. Devices use a pattern comprising a portion having lines densely distributed, a portion having spaces wider than lines and a lone line. Thus, it is important to resolve these lines with a high reproducibility. However, it is not necessarily easy to reproduce various lines due to optical factors. Accordingly, the method for resolving these problems by resist is not definite. In particular, the resist system containing the foregoing resin has a remarkable difference in properties between lone pattern and dense pattern and thus leaves something to be desired.
Further, this resist is excellent in the resolution for the working of ultrafine pattern but is liable to the occurrence of roughness on resist pattern. The term “edge roughness” as used herein is meant to indicate that the pattern is observed uneven at the edge as viewed from above because the top and bottom edges of the line pattern of the resist are arranged irregularly along the line and in the vertical direction due to the characteristics of the resist.
Further, this resist is disadvantageous in that it exhibits a deteriorated compatibility with a photo-acid generator during the preparation of a resist solution, causing turbidity. This resist is also disadvantageous in that it u
Mizutani Kazuyoshi
Sato Kenichiro
Yasunami Shoichiro
Ashton Rosemary
Sughrue & Mion, PLLC
Thornton Yvette C.
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