Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
2001-07-13
2003-04-15
Ashton, Rosemary (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S270100
Reexamination Certificate
active
06548229
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel positive-working chemical-amplification photoresist composition capable of giving a very finely patterned resist layer having an excellently orthogonal cross sectional profile with high photosensitivity and pattern resolution on a substrate surface by patterning exposure using a KrF excimer laser beam and to a method for efficiently forming a very finely patterned resist layer of an isolated pattern having an excellently orthogonal cross sectional profile with fidelity to a photomask pattern by using the above mentioned photoresist composition.
As a trend in the manufacturing technology of semiconductor devices and liquid crystal display panels in recent years, extensive investigations are now under way to establish a photolithographic patterning process of a resist layer having a pattern resolution of as fine as 0.25 &mgr;m or even finer by the use of a positive-working chemical-amplification photoresist composition. Turning now to the problem of the light source for the pattern-wise exposure of the photoresist layer to comply with the requirement in the manufacture of semiconductor devices to accomplish finer and finer patterning, a photolithographic patterning technology for obtaining a patterned resist layer of 0.15 to 0.22 &mgr;m fineness by using a KrF excimer laser beam is the current target of the development works.
With an object to comply with the above mentioned requirements, a proposal is made in Japanese Patent Kokai 7-209868 for a positive-working chemical-amplification photoresist composition containing, as the film-forming resinous ingredient, a copolymeric resin consisting of hydroxyl group-containing styrene units, styrene units and tert-butyl (meth)acrylate units in a molar ratio of 40:20:40 or 33:17:50. The there proposed photoresist composition using a copolymeric resin with a relatively small amount of the hydroxyl group-containing styrene units or a relatively large amount of the tert-butyl (meth)acrylate units is not quite satisfactory when an extremely fine patterned resist layer with 0.15 to 0.22 &mgr;m fineness is formed therewith because the cross sectional profile of the patterned resist layer is not fully orthogonal as desired.
SUMMARY OF THE INVENTION
The present invention accordingly has an object to provide a novel positive-working chemical-amplification photoresist composition capable of giving a finely patterned resist layer with 0.15 to 0.22 &mgr;m fineness and an excellently orthogonal cross sectional profile with high photosensitivity and pattern resolution by the pattern-wise exposure with a KrF excimer laser beam and a method for efficiently forming a very finely patterned resist layer of an isolated pattern with high fidelity to the photomask pattern having an excellently orthogonal cross sectional profile by using the above mentioned photoresist composition.
Thus, the positive-working chemical-amplification photoresist composition provided by the present invention is a uniform blend which comprises, as a solution in an organic solvent:
(A) 100 parts by weight of a copolymeric resin capable of being imparted with increased solubility in an aqueous alkaline solution in the presence of an acid, which consists of from 50 to 85% by moles of hydroxyl group-containing styrene units, from 15 to 35% by moles of styrene units and from 2 to 20% by moles of tert-butyl (meth)acrylate units; and
(B) from 1 to 20 parts by weight of a radiation-sensitive acid-generating agent capable of releasing an acid by decomposition under irradiation with actinic rays.
Further, the method for the formation of a patterned resist layer is provided by the present invention which comprises the steps of:
(a) forming, on the surface of a substrate, a layer of the above defined positive-working chemical-amplification photoresist composition;
(b) subjecting the photoresist layer to a first heat treatment at a temperature in the range of from 100° C. to 110° C.;
(c) subjecting the photoresist layer to pattern-wise exposure to actinic rays;
(d) subjecting the photoresist layer to a second heat treatment at a temperature in the range of from 100° C. to 110° C. and
(e) subjecting the photoresist layer to a development treatment with an aqueous alkaline solution.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The film-forming base ingredient as the component (A) in the inventive photoresist composition is a resin capable of being imparted with increased solubility in an aqueous alkaline solution in the presence of an acid, which is a ternary copolymeric resin consisting of three kinds of the monomeric units including (a) from 50 to 85% by moles of hydroxyl group-containing styrene units, (b) from 15 to 35% by moles of styrene units and (c) from 2 to 20% by moles of tert-butyl (meth)acrylate units, the total of the molar fractions of the monomeric units (a), (b) and (c) being 100%. In this ternary copolymeric resin as the component (A), the monomeric unit of the first class (a) is a unit derived from a styrene compound having at least one hydroxyl group bonded to the aromatic nucleus in the molecule in order to impart the copolymeric resin with good solubility in an aqueous alkaline solution as the developer solution. Examples of such a monomeric unit include a hydroxystyrene unit and &agr;-methyl hydroxystyrene unit.
The monomeric unit of the third class (c) in the copolymeric resin is a tert-butyl (meth)acrylate unit, of which the tert-butyl group protects the carboxylic group of (meth)acrylic acid to reduce the solubility of the resin in an aqueous alkaline solution, while this tert-butyl group is eliminated to regenerate the carboxyl group by the interaction with an acid generated from the acid-generating agent as the component (B) when the photoresist layer is exposed pattern-wise to actinic rays resulting in an increase in the solubility of the resin in an aqueous alkaline solution to give a patterned resist layer in the development treatment.
The copolymeric resin as the component (A), which consists of the monomeric units of the three classes (a), (b) and (c) in a specified molar proportion, is advantageous as compared with a resin having solubility-reducing groups introduced into a part of the monomeric units of a polyhydroxystyrene resin in respect of the larger solubility-reducing effect and smaller thickness reduction of the resist layer by a development treatment in the unexposed areas to give a patterned resist layer having an excellently orthogonal cross sectional profile.
In the inventive photoresist composition comprising the copolymeric resinous ingredient as the component (A), which can be either one or a combination of two kinds or more of copolymeric resins falling within the definition of the above described ternary copolymeric resins, it is preferable that the component (A) is a combination of a first copolymeric resin (Al) consisting of from 62 to 68% by moles of the monomeric units of the first class (a), from 15 to 25% by moles of the monomeric units of the second class (b) and from 12 to 18% by moles of the monomeric units of the third class (c) and a second copolymeric resin (A2) consisting of from 62 to 68% by moles of the monomeric units of the first class (a), from 25 to 35% by moles of the monomeric units of the second class (b) and from 2 to 8% by moles of the monomeric units of the third class (c) in a weight proportion in the range from 9:1 to 5:5 or, preferably, from 8:2 to 6:4 in respect of the superiority in the photosensitivity, pattern resolution and orthogonality of the cross sectional profile of the patterned resist layer.
It is preferable that the copolymeric resin as the component (A) has a weight-average molecular weight in the range from 3000 to 30000 as determined by the gel permeation chromatographic (GPC) method by making reference to known polystyrene resins. When the weight-average molecular weight of the component (A) is too low, the photoresist composition cannot be fully film-forming while, when the weight-average molecular weight of the resin is too h
Oomori Katsumi
Sato Kazufumi
Uchida Ryusuke
Yukawa Hiroto
Ashton Rosemary
Tokyo Ohka Kogyo Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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