Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-05-02
2002-05-14
Lambkin, Deborah C. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06388101
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel chemical-sensitization photoresist composition or, more particularly, to a positive-working chemical-sensitization photoresist composition used in the photolithographic patterning in the manufacture of various kinds of electronic devices.
Chemical-sensitization photoresist compositions in the prior art usually contain a resinous ingredient having high transparency to the KrF excimer laser beams of 248 nm wavelength which is mainly a polyhydroxystyrene resin, optionally, substituted for the hydroxyl groups therein by acid-dissociable solubility-reducing groups. It is a trend in recent years, however, that the KrF excimer laser beam as the exposure light is increasingly under replacement with an ArF excimer laser beam having a shorter wavelength of 193 nm in order to comply with the requirements toward finer and finer patterning in the manufacture of modern semiconductor devices.
When the photolithographic patterning process is conducted with the ArF excimer laser beams as the exposure light source, the polyhydroxystyrene-based resinous ingredient is no longer suitable as the resinous ingredient of the photoresist compositions because of the low transparency of the resin to the light of 193 nm wavelength due to the aromatic ring structure contained in the resin. In this regard, acrylic resins having no aromatic structure are highlighted as a substitute for the polyhydroxystyrene resins while acrylic resins in general have a disadvantage of low resistance against dry etching.
It is known that an acrylic resin can be imparted with increased resistance against dry etching when monomeric units derived from an alicyclic alkyl ester of acrylic acid are introduced into the molecular structure of the acrylic resin. For example, proposals have been made, in Japanese Patent Kokai 4-39665, for a polymer of an acrylic ester having a skeleton of adamantane in the ester-forming group and, in Japanese Patent Kokai 5-265212, for a copolymer of an acrylic ester having a skeleton of adamantane in the ester-forming group and tetrahydropyranyl acrylate.
Although improvements in the transparency and resistance against dry etching can be accomplished to some extent for an acrylic resin by the introduction of the monomeric units derived from an acrylic ester having a skeleton of adamantane, the improvements obtained thereby are still not quite satisfactory if not to mention the low availability and hence expensiveness of such an acrylic ester having a skeleton of adamantane along with a disadvantage of low photosensitivity of the photoresist composition formulated with such an acrylic resin not to give an excellent result of patterning.
While the photolithographic patterning process by using ArF excimer laser beams as the exposure light has an important target to form a very finely patterned resist layer with extremely fine pattern resolution of 0.2 &mgr;m or even finer, such extremely fine patterning is sometimes accompanied by a defect of pattern falling due to deficiency in the adhesion between the substrate surface and the resist layer formed thereon. As a remedy for this drawback, proposals have been made for an acrylic resin containing monomeric units derived from an acrylic ester having an oxygen-containing heterocyclic group such as 3-oxocyclohexyl acrylate (Japanese Patent Kokai 5-346668) and &ggr;-butyrolactone (Japanese Patent Kokai 7-181677).
When such an acrylic resin, into which the monomeric units of an acrylic acid ester having an oxygen-containing heterocyclic group are introduced, is used as a resinous ingredient of a photoresist composition to be used for patterning exposure with ArF excimer laser beams, however, a patterned resist layer having high fidelity cannot be obtained in the puddle development treatment as a major current in the manufacture of semiconductor devices due to insufficient affinity of the photoresist composition with the aqueous alkaline solution as the developer solution, even though an improvement to some extent can be obtained in the adhesion of the photoresist layer to the substrate surface. Therefore, one of the important subject matters in the technological field of photoresist compositions is to develop a photoresist composition for patterning exposure to light such as the ArF excimer laser beams exhibiting excellent adhesion between the resist layer and the substrate surface and having high affinity with an aqueous alkaline developer solution suitable for a puddle development treatment.
SUMMARY OF THE INVENTION
The present invention accordingly has an object to provide, in view of the above described situations in the prior art, a chemical-sensitization photoresist composition having high transparency to the ArF excimer laser beams and suitable for a puddle development treatment with high affinity to an aqueous alkaline developer solution to give a patterned resist layer with high photosensitivity having an excellently orthogonal cross sectional profile and exhibiting excellent adhesion to the substrate surface and resistance against dry etching.
Thus, the present invention provides a chemical-sensitization positive-working photoresist composition which comprises, as a uniform solution in an organic solvent:
(A) 100 parts by weight of an acrylic resin of which the solubility in an aqueous alkaline solution is subject to an increase in the presence of an acid; and
(B) from 0.5 to 30 parts by weight of a radiation-sensitive acid-generating agent capable of releasing an acid when irradiated with actinic rays,
the acrylic resin as the component (A) being a copolymer consisting of monomeric units derived from (meth)acrylic acid esters, of which from 20% to 80% by moles are the monomeric units having an oxygen-containing heterocyclic group represented by the general formula
in which R
1
is a hydrogen atom or methyl group, R
2
, R
3
and R
4
are each, independently from the others, a hydrogen atom, lower alkyl group having 1 to 4 carbon atoms or lower alkoxy group having 1 to 4 carbon atoms and n is 0 or 1.
The (meth)acrylic acid ester compounds, from which the the monomeric units represented by the general formula (I) given above are derived, are each a novel compound not known in the prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The component (A) in the inventive photoresist composition defined above is a specific acrylic resin of which the solubility in an aqueous alkaline solution is increased in the presence of an acid. Such an acrylic resin in general is a copolymer of monomeric compounds including (a) a derivative of (meth)acrylic acid substituted by a group capable of increasing the resistance of the resin against dry etching or an acid-dissociable protective group, (b) an ethylenically unsaturated carboxylic acid and, optionally, (c) at least one kind of other copolymerizable monomers.
Of the above mentioned three classes of the monomeric compounds, the monomeric compound of the first class (a) is a derivative of (meth)acrylic acid which can be selected from the (meth)acrylic acid derivatives conventionally used in the prior art chemical-sensitization photoresist compositions with an object to enhance the resistance of the resist layer against dry etching or to introduce acid-dissociable protective groups to the resin.
Examples of such a (meth)acrylic acid derivative belonging to the class (a) include:
(a1) acrylic or methacrylic acid substituted for the carboxylic hydrogen atom by an acid-dissociable protective group such as tert-butyl group, 2-tetrahydropyranyl group, 2-tetrahydrofuranyl group, 1-methylcyclohexyl group, 1-methyladamantyl group, 1-ethoxyethyl group and 1-methoxypropyl group as well as an ester of acrylic or methacrylic acid with 2-hydroxy-3-pinanone; and
(a2) acrylic or methacrylic acid substituted for the carboxylic hydrogen atom by an acid-undissociable group such as adamantyl group, cyclohexyl group, naphthyl group, benzyl group, 3-oxocyclohexyl group, bicyclo [2.2.1] heptyl group, tricyclodecanyl group and acetonyl group as well as an
Hada Hideo
Komano Hiroshi
Sato Kazufumi
Lambkin Deborah C.
Tokyo Ohka Kogyo Co. Ltd.
Wenderoth Lind & Ponack LLP
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