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
2000-03-20
2002-05-21
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
C560S220000, C526S281000, C430S326000
Reexamination Certificate
active
06391520
ABSTRACT:
TECHNICAL FIELD
The present invention relates to resin compositions for photoresists (resists) suitable for forming patterns (e.g., minute processing of semiconductors) by means of ultraviolet rays or far-ultraviolet rays (including excimer laser and so on), and to compounds for photoresists useful in obtaining the same.
BACKGROUND ART
Known as resists for semiconductors are photosensitive resin compositions containing an alkali-soluble novolak resin and a diazonaphthoquinone derivative. These resin compositions have been employed as positive resists utilizing the characteristic that a diazonaphthoquinone group is decomposed by irradiation with light to form a carboxyl group, rendering an alkali-insoluble resin composition alkali-soluble. Moreover, there is known a negative resist, that is a resist which becomes insoluble on exposure to light through a photo-crosslinking reaction in the presence of an azide compound or a photopolymerization reaction in the presence of a photopolymerization initiator.
However, these resists are opaque or inactive to light at a wavelength of 200 nm or shorter due to an aromatic ring contained in a resin and therefore not suitable as photoresists processed with an ArF excimer laser having a wavelength of 193 nm.
As a photoresist for ArF excimer laser, Japanese Patent Application Laid-Open No. 73173/1997 discloses a resin having an alicyclic hydrocarbon group such as adamantane and norbornane. Since this resin has no double bond in its ring, it is transparent or active to ArF excimer laser and the alicyclic hydrocarbon group thereof makes the resin more resistant to plasma gas dry-etching used in the minute processing of semiconductors.
Usually, the photoresist resins having an alicyclic hydrocarbon group are roughly classified into the groups: (1) copolymers having a monomer unit which becomes alkali-soluble by being cleaved by an acid and a non-leaving alicyclic hydrocarbon monomer unit; (2) copolymers having a unit which becomes alkali-soluble as a result of leaving of an alicyclic hydrocarbon group therefrom caused by an acid; and (3) resins having, in the main or side chain, an alicyclic hydrocarbon unit which becomes alkali-soluble by being decomposed by an acid, with the resultant resins themselves made alkali-soluble. Of these resins, resins of the group (3) are said to be preferable. However, it is difficult to make the resin (3) alkali-soluble because the adamantane skeleton is bulky, strongly hydrophobic, and stable toward an acid.
Accordingly, an object of the present invention is to provide a photoresist resin composition useful for forming minute patterns, of which the polymer itself can be solubilized by irradiation with light even when having an adamantane skeleton, and a photoresist compound useful for providing this resin composition.
Another object of the present invention is to provide a positive photoresist resin composition of simple formula which is highly resistant to etching (particularly, resistant to dry-etching) and from which can be made minute patterns with accuracy, and a photoresist compound useful for providing this resin composition.
DISCLOSURE OF INVENTION
The inventors of the present invention made intensive and extensive studies to achieve the above objects and found that, in a specific polymer having an adamantane skeleton used in combination at least with a photoactive acid generator (photoactive acid precursor), an acid generated from the photoactive acid precursor by irradiating the combination with light hydrolyzes the functional group of the polymer to give a hydrophilic group, thereby making possible development with water or an alkali. The present invention was accomplished based on the above findings.
The photoresist compound of the present invention can be expressed by the following formula (1a):
wherein R
1
represents hydrogen atom or methyl group; R
2
, R
3
and R
4
are the same or different from each other, each representing a hydrogen atom, a halogen atom, an alkyl group, a nitro group, an amino group, an N-substituted amino group, a hydroxyl group, a hydroxymethyl group, a carboxyl group, or a functional group which forms a hydroxyl group, a hydroxylmethyl group or a carboxyl group by elimination with an acid; at least one of the groups R
2
, R
3
and R
4
is the functional group mentioned above; X represents a connecting group (or a linker); and m and n individually represent 0 or 1.
In the photoresist compound, at least two of the substituents R
2
to R
4
are preferably groups selected from hydroxyl group, hydroxymethyl group, carboxyl group, and functional groups, and at least two of the substituents R
2
to R
4
are preferably substituents of different kinds selected from hydroxyl group, alkoxy groups-, hydroxyl group protected by acetilization or hemiacetalization, carboxyl group, and alkoxycarbonyl groups, and these substituents are different from each other. X may be an ester bond.
The photoresist resin composition of the present invention comprises a polymer having a unit shown by the following formula (1) and a photoactive acid precursor:
wherein R
1
represents hydrogen atom or methyl group; R
2
, R
3
and R
4
are the same or different from each other, each representing a hydrogen atom, a halogen atom, an alkyl group, a nitro group, an amino group, an N-substituted amino group, a hydroxyl group, a hydroxymethyl group, a carboxyl group, or a functional group which forms a hydroxyl group, a hydroxymethyl group or a carboxyl group by elimination with an acid; at least one of the groups R
2
to R
4
is the functional group described above; X represents a connecting group; and m and n individually represent 0 or 1.
The present invention further includes a process for forming a pattern, comprising a step of exposing a coating layer comprising the photoresist resin composition in a predetermined pattern (i.e., a step of patter-exposing a coating layer comprising the photoresist resin composition) and a step of developing the exposed coating layer to define a latent pattern.
BEST MODE FOR CARRYING OUT THE INVENTION
In the compound (1a) and the polymer (1) each having an adamantane skeltone defined above, halogen atoms include iodine, bromine, chlorine, and fluorine atoms. Alkyl groups include C
1-6
alkyl groups (particularly, C
1-4
alkyl groups) such as methyl, ethyl, propyl, isopropyl, butyl, and t-butyl. N-substituted amino groups include mono- or di-C
1-6
alkylamino groups (preferably, mono- or di-C
1-4
alkylamino groups).
Examples of the functional group which forms hydroxyl group, hydroxymethyl group or carboxyl group by elimination with an acid are hydroxyl group protected by a protective group, hydroxymethyl group protected by a protective group, and carboxyl group protected by a protective group. The protecting group functions as a dissolution-inhibitory modifying group for preventing the polymer from dissolving before being exposed to light.
Examples of the protective group for hydroxyl group or hydroxymethyl group are alkoxycarbonyl groups (e.g., C
1-4
alkoxycarbonyl groups such as methoxycarbonyl, ethoxycarbonyl, and t-butoxycarbonyl groups); and benzyloxy group. Hydroxyl group or hydroxymethyl group may be protected by a protective group represented by the formula —CH(OR
a
)R
b
(R
a
represents hydrogen atom or a C
1-6
alkyl group, and R
b
is a residue derived from an aldehyde, such as hydrogen atom, a C
1-6
alkyl group, and an aryl group) by means of hemiacetalization or acetalization.
Adamantane in which a hydroxyl group is protected by hemiacetalization or acetalization can be expressed by, e.g., the following formula:
wherein R
a
and R
b
are the same as defined above.
Examples of an aldehyde usable for hemiacetalization or acetalization are aliphatic aldehydes (e.g., C
1-10
aldehydes such as formaldehyde, acetoaldehyde), aromatic aldehydes (e.g., benzaldehyde, anisaldehyde), and heterocyclic aldehydes (e.g., nicotinaldehyde, furfural).
As the protective group for carboxyl group, there may be exemplified alkoxy groups (C
1-6
alkoxy groups such as methoxy, ethoxy
Funaki Yoshinori
Nakano Tatsuya
Ashton Rosemary
Birch & Stewart Kolasch & Birch, LLP
Daicel Chemical Industries Ltd.
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