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
1999-01-27
2001-01-23
Baxter, Janet (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
C430S281100, C430S905000, C430S914000
Reexamination Certificate
active
06177229
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a positive photosensitive composition which can be used as a photoresist in the manufacture of a semiconductor device and to a pattern forming method using the same.
Photoresist is used in the manufacture of electronic parts requiring various types of fine processing such as semiconductor integrated circuits like LSI. Also, a demagnificating projection type mask aligner, which is generally called stepper, is used as a light exposure apparatus for forming a resist pattern. The light source used in such a light exposure apparatus includes, for example, g-line (wavelength of 436 nm), h-line (wavelength of 405 nm), and i-line (wavelength of 365 nm) of a mercury lamp and an excimer laser light of KrF (wavelength of 248 nm), ArF (wavelength of 193 nm), F
2
(wavelength of 157 nm), etc. Also, the exposure using an electron beam and an ion beam is an important technology in that, since the beam has a short wavelength, it is possible to achieve a fine processing, and in that a pattern can be formed directly. Such being the situation, it is of high importance to develop a resist adapted for such an exposure technology.
Formation of a fine pattern with a high through-put is absolutely necessary in recent years in accordance with progress in the degree of integration of semiconductor integrated circuit such as LSI. An electron beam lithography technology of a high sensitivity is also absolutely necessary as well as the resist material and process technology adapted for the lithography technology. However, the electron beam lithography necessitates a vacuum system, giving rise to problems derived from the use of the vacuum system. For example, resist containing an alkali soluble resin having an acetal group introduced therein as a protective group has a small activation energy for the deblocking reaction and, thus, is advantageous in that the resist exhibits a high sensitivity. However, where a resist film formed by coating a substrate with such a resist is irradiated with an electron beam, a layer which is unlikely to be dissolved in a developing solution is formed on the surface of the resist film, resulting in failure to form a resist pattern having a strict dimensional accuracy. In the worst case, the layer unlikely to be dissolved in the developing solution extends to cover an upper surface of the adjacent resist pattern, making it impossible to achieve resolution of the pattern.
In the light exposure using a KrF excimer laser light which does not require a vacuum system, the resist is affected by the condition such as humidity in the light exposure step after the resist coating step, making it difficult to form a resist pattern of a predetermined size at a predetermined sensitivity.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention, which has been achieved in view of the above-noted problems, is to provide a positive photosensitive composition which permits forming a resist pattern rectangular in cross section and having a predetermined dimensional accuracy at a high sensitivity in the exposure using an electron beam, and to a resist pattern forming method using the particular composition.
According to an aspect of the present invention, there is provided a positive photosensitive composition, comprising an alkali soluble resin having at least some or all of the alkali soluble groups protected by a substituent which can be decomposed by an acid, a compound which generates an acid upon irradiation with an actinic radiation, and a compound which generates water under action of an acid catalyst.
According to another aspect of the present invention, there is provided a positive photosensitive composition, comprising an alkali soluble resin having at least some or all of the alkali soluble groups protected by a substituent which can be decomposed by an acid and water, a compound which generates an acid upon irradiation with an actinic radiation, and a compound which generates water under catalytic action of the acid.
According to another aspect of the present invention, there is provided a positive photosensitive composition, comprising an alkali soluble resin having at least some or all of the alkali soluble groups protected by a substituent which can be decomposed by an acid, a compound which generates an acid upon irradiation with an actinic radiation, and a tertiary alcohol and/or a secondary alcohol.
According to still another aspect of the present invention, there is provided a resist pattern forming method, comprising the step of forming a photosensitive layer containing as a main component a positive photosensitive composition on a substrate, the step of light exposure for selectively irradiating a predetermined region of the photosensitive layer with an actinic radiation, the step of applying a heat treatment to the photosensitive layer after the light exposure, and developing the photosensitive layer after the light exposure to remove selectively the light-exposed portion of the photosensitive layer.
DETAILED DESCRIPTION OF THE INVENTION
The positive photosensitive composition of the present invention comprises an alkali soluble resin having a phenol skeleton and a weight average molecular weight of 1,000 to 50,000. The alkali soluble resin used in the present invention includes, for example, phenol novolak resin, xylenol novolak resin, vinyl phenol resin, cresol novolak resin, and copolymer between vinyl phenol and acrylic resin.
A substituent which can be decomposed by an acid is introduced into the alkali soluble resin for protection of some or all of the alkali soluble groups of the alkali soluble resin in order to control the dissolution rate in the developer. The particular substituent, which is hereinafter referred to as “dissolution inhibiting group”, includes, for example, acetal group; tert-butyl derivative substituents such as tert-butoxy carbonyl group, tert-butoxy carbonyl methyl group, and tert-butoxy carbonyl ethyl group; alkyl silyl groups such as trimethyl silyl group, triethyl silyl group and triphenyl silyl group. These dissolution inhibiting groups can be used singly or in combination.
In the case of using an alkali soluble resin having the dissolution inhibiting group, particularly acetal group, introduced therein, the present invention produces the most prominent effect. It is possible for the only acetal group to protect the alkali soluble groups of the alkali soluble resin. Alternatively, some of the alkali soluble groups may be protected by a dissolution inhibiting group other than acetal group.
The acetal group introduced into the alkali soluble resin includes, for example, linear or branched acetal groups such as 1-ethoxyethyl group, 1-propoxyethyl group, 1-n-butoxyethyl group, 1-iso-butoxyethyl group, and 1-tert-butoxyethyl group; and cyclic acetal groups such as tetrahydrofuranyl group and tetrahydropyranyl group.
It is possible to use an alkali soluble resin having the alkali soluble group protected by an acetal group in combination with another alkali soluble resin having the alkali soluble group protected by another dissolution inhibiting group.
The photosensitive composition of the present invention also comprises a compound which generates an acid upon irradiation with an actinic radiation. The particular compound, which is hereinafter referred to as an acid generating agent, includes, for example, onium salt, sulfonyl compound, sulfonic acid ester, and an organic halogen compound. The term “actinic radiation” collectively denotes an energy radiation or substance radiation capable of imparting a chemical change to the photosensitive composition and includes, for example, ultraviolet light having a short wavelength, electron beam, and X-rays.
The onium salt used as an acid generating agent in the present invention includes, for example, diazonium salt, sulfonium salt and iodonium salt each containing CF
3
SO
3
−
, p-CH
3
PhSO
3
−
, etc. as a pairing anion. Particularly, it is desirable to use triallyl sulfonium salt or diallyl iodonium salt as an acid genera
Kihara Naoko
Saito Satoshi
Ushirogouchi Toru
Baxter Janet
Kabushiki Kaisha Toshiba
Lee Sin J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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