Photoresist compositions

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

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C430S287100, C430S326000, C430S905000, C430S914000, C526S270000, C526S326000, C526S333000

Reexamination Certificate

active

06258507

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to photoresist compositions suitable for lithography using high energy radiation such as a far ultraviolet ray from an eximer laser and the like, electron beam, X-ray or radiated light, and to resins useful as an ingredient of the same compositions.
2. Description of the Related Art
Recently, pattern formation on a quarter micron order has been required with increased high integration of integrated circuits. Eximer laser lithography particularly draws attention since it enables production of the 64 M DRAM and the 256 M DRAM. As a resist suitable for a eximer laser lithography process, a so-called chemical amplification type photoresist utilizing an acid catalyst and a chemical amplification effect is suggested. In a resist film made from a chemical amplification type photoresist, the solubility of irradiated portions in an alkaline developer changes by way of a reaction using an acid as a catalyst, which acid is generated from an acid generating agent in portions irradiated with a radiation. By this reaction, the chemical amplification type photoresist gives a positive type or negative type pattern.
In the production of semiconductor integrated circuits, photolithography is conducted on various substrates. Usually, a photoresist is required to have high transparency against the radiation used for irradiation. However, when lithography is conducted on a substrate having a significantly high reflection ratio against the radiated light, it may be necessary to decrease the transparency of a photoresist to a certain degree in order to avoid unnecessary exposure of the photoresist to the reflected light from the substrate. In this case, a pigment component having a lower molecular weight is usually added to the resist. However, when such a pigment component is added, the basic ability of the resist tends to decrease.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a raw material for a photoresist composition which reduces transparency of the photoresist composition but does not give adverse affects to the various properties of the photoresist composition such as sensitivity, resolution, heat resistance, film retention ratio, applicability and profile and, as a result, to provide a photoresist composition that is particularly excellent in its pattern forming properties.
The present inventors have intensively studied for attaining such an object, and found that a specific resin can reduce the transparency of a positive type photoresist composition without producing an adverse affects on the properties of the positive type photoresist composition. The present invention has thus been completed.
The present invention provides a photoresist composition which comprises, as one component of the photoresist composition, a resin having a structural unit represented by the following formula (I):
wherein R
1
, R
2
ad R
3
each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R
4
represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms and R
5
represents a hydrogen atom, alkyl group or aryl group, or R
4
and R
5
join together to form a ring, which may be heterocyclic; and R
6
represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or a hydroxyl group.
By including the resin having a structural unit represented by the formula (I) into a photoresist, transparency of the photoresist can be controlled and a photoresist composition having a reduced transparency but having excellent properties is obtained.
This resin can be advantageously produced by allowing polyvinylphenols having a structure represented by the following formula (II):
wherein R
1
, R
2
and R
3
are as defined above to react with an acid halide represented by the following formula (III):
wherein R
4
, R
5
and R
6
are as defined above, and X represents a halogen for esterifying a part of hydroxyl groups in the polyvinylphenols of formula (II).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The photoresist referred to in the present invention is a radiation-sensitive coating material which is used for forming a film on a substrate and conducting selective irradiation (exposure) and development to form a pattern, and generally contains, as a binder, a resin component having a radiation-sensitive group, or contains, as a binder, a resin component and a radiation-sensitive component. Photoresists are classified according to positive type resists in which irradiated portions are dissolved in a developer and non-irradiated portions remain as a pattern and negative type resists in which non-irradiated portions are dissolved in a developer and irradiated portions are cured and remain as a pattern. In both cases, a novolak resin, an acrylic resin, a polyvinylphenol resin and the like have been used as a binder resin. A resin having a structural unit represented by the formula (I) can be applied to any of such resists containing a novolak resin, an acrylic resin, a polyvinylphenol resin or the like. In particular, a resin having a structural unit of formula (I) is effective for controlling the transparency of a so-called chemical amplification type photoresist, which contains an acid-generating agent and utilizes catalytic action of an acid generated from the acid-generating agent in irradiated portions. In such a chemical amplification type photoresist, a resin having a structural unit of formula (I) can on occasion also be used as a binder resin.
A chemical amplification type photoresist contains a resin component and an acid generating agent, and the acid generating agent generates an acid in irradiated portions, and catalytic action of the acid is utilized to from a pattern. In a chemical amplification type positive photoresist, acid generated in irradiated portions disperses by subsequent heat treatment (post exposure bake, sometimes abbreviated as PEB), which allows a protecting group of the resin to be released and re-produces an acid to make the irradiated portions soluble in an alkali.
Chemical amplification type positive photoresists are classified according to (i) resists which comprise an alkali-soluble resin component, an acid generating agent and a dissolution inhibitor which has a protecting group cleavable by the action of an acid and has itself an ability of inhibiting alkali-solubility of the alkali-soluble resin, but allows the resin to be alkali-soluble after cleavage of the protecting group by the action of an acid, and to (ii) resists which comprise an acid generating agent and a resin component which has a protecting group cleavable by the action of an acid, and which resin itself is insoluble or poorly soluble in an alkali and becomes alkali-soluble after cleavage of the above-described protecting group by the action of an acid.
A chemical amplification type negative photoresist comprises a resin component which is usually alkali-soluble, an acid generating agent and a cross-linking agent. In this chemical amplification type negative photoresist, an acid generated in irradiated portions disperses by PEB, acts on a cross-linking agent to cure a binder resin in the irradiated portions. In a chemical amplification type photoresist thus acting, a group corresponding to an acid generating agent, namely a group which is cleaved by the action of a light and generates an acid, may be sometimes appended to a side chain of the resin.
A resin having a structural unit of formula (I) is particularly effective for a chemical amplification type positive photoresist comprising a resin component, which has a protecting group cleavable by the action of an acid and that is itself insoluble or poorly soluble in an alkali and becomes alkali-soluble after cleavage of said protecting group by the action of an acid.
In such types of a chemical amplification photoresist compositions, a main resin is itself insoluble or poorly soluble in an alkali and becomes alkali-solu

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