Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2002-11-15
2004-06-29
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S192000, C430S193000, C430S326000, C430S330000
Reexamination Certificate
active
06756178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a positive photoresist composition and a method of patterning a resist thin film for use in an inclined implantation process. More specifically, it relates to a highly sensitive positive photoresist composition that is used in photolithography using i-line (365 nm) and specifically advantageously in an inclined implantation process using a very thin resist film about 0.1 to 0.5 &mgr;m thick, as well as to a method of patterning a resist thin film for use in the inclined implantation process using the positive photoresist composition.
2. Description of the Related Art
Photoresist compositions each containing an alkali-soluble resin and a quinonediazido-group-containing compound have satisfactory definition, sensitivity, etching resistance and thermal resistance in a photolithography process using i-line (365 nm) and therefore have been applied to practical use in fabrication of semiconductor devices and liquid crystal devices.
Such resist patterns having a size smaller than the wavelength of exposing light have been believed to be hardly formed by photolithography without deteriorating the above properties. However, fine resist patterns of about 0.35 &mgr;m, smaller than the wavelength of i-line, can now be formed as a result of improvements in materials, process conditions and exposure techniques.
With increasing diameters of silicon substrates for semiconductors and glass substrates for liquid crystal display devices, increasing demands have been made on positive photoresist compositions with higher sensitivity to improve throughputs. Improvements in conventional positive photoresist compositions each containing an alkali-soluble resin and a quinonediazido-group-containing compound have therefore been proposed.
For example, Japanese Patent Laid-Open No. 3-249654 discloses a photosensitive composition containing a polymeric compound (e.g., a novolak resin) having an acid-decomposable substituent, and a 1,2-naphthoquinonediazido-4-sulfonic acid ester.
However, the photosensitive composition often invites insoluble matters to form during storage and must have higher definition and sensitivity. In addition, the photosensitive composition is readily deactivated upon contact with a basic substance in the air to vary its sensitivity and is thereby insufficient in post-coating delay (PCD; time interval between coating process and exposure process) stability and post-exposure delay (PED; time interval between exposure process to post-exposure baking (PEB) process) stability. In short, the resist composition is insufficient in “stability of latent image before development.”
Japanese Patent Laid-Open No. 5-127386 discloses a photosensitive composition containing a polymer and a photosensitive acid generator (e.g., an orthoquinonediazidosulfonic acid ester), which polymer comprises a hydrogenated alkali-soluble resin (e.g., a novolak resin) having a phenol skeleton and having dissolution inhibiting groups being unstable to acids and being combined with its phenolic hydroxyl groups.
However, the photosensitive composition must be exposed to excimer laser light and thus invites high production cost.
Japanese Patent Laid-Open No. 5-181279 discloses a photosensitive composition containing a polyhydroxystyrene polymer having an acid-decomposable substituent, and a photosensitive acid generator (e.g., an orthoquinonediazidosulfonic acid ester).
The photosensitive composition, however, often invites insoluble matters to form during storage and must have higher sensitivity and definition.
Japanese Patent Laid-Open No. 6-130665 discloses a photosensitive composition containing an alkali-soluble resin (e.g., a novolak resin) having an acid-decomposable substituent, and a photosensitive acid generator (e.g., a quinonediazide compound).
The photosensitive composition, however, must be exposed to excimer laser light and thus invites high production cost.
Japanese Patent Laid-Open No. 6-202320 discloses a photosensitive composition containing an alkali-soluble resin (e.g., a novolak resin) having an acid-decomposable substituent, and a 1,2-naphthoquinonediazido-4-sulfonic acid ester of a polyhydroxybenzophenone.
The photosensitive composition, however, often invites insoluble matters to form during storage and must have higher sensitivity and definition.
Japanese Patent Laid-Open No. 7-5682 discloses a resist composition containing a polyhydroxystyrene polymer having an acid-decomposable substituent, and a 1,2-naphthoquinonediazide compound.
However, the resist composition must be exposed to excimer laser light and thus invites high production cost.
Japanese Patent Laid-Open No. 9-179300 discloses a resist composition containing a polyhydroxystyrene polymer having an acid-decomposable substituent, a photosensitive acid generator (e.g., a quinonediazide compound), and an acid-diffusion controlling agent.
However, the resist composition must be exposed to excimer laser light and thus invites high production cost.
In addition, all the aforementioned compositions must be improved in their stability of latent image before development.
Separately, an “inclined implantation” process is proposed in, for example, Japanese Patent Laid-Open No. 8-22965. In this process, an inclined semiconductor substrate having a patterned resist mask is subjected to ion implantation to thereby selectively implant dopant ions to a surface of the semiconductor substrate.
The process is believed to be effective for selective ion implantation into a small area of the substrate directly below the patterned resist or into side walls of holes disposed on the substrate.
When an ultrafine resist pattern of about 0.35 &mgr;m is formed by the inclined implantation process, a patterned resist film serving as a mask must be very thin of about 0.1 to 0.5 &mgr;m so as not to inhibit ion implantation.
However, when very thin resist films are formed using conventional positive photoresist compositions, the resulting very thin resist films cannot yield satisfactory latent images, are reduced in thickness in unexposed portions, invite large amounts of scum, or cannot yield patterned resists having a good shape.
In addition, the patterned resist films are exposed to elevated temperatures during implantation process and must have high thermal resistance. Accordingly, the resist films are subjected to “post-baking” heat treatment after development. The positive photoresist compositions for use in the implantation process must have sufficient thermal resistance to resist deformation of patterned resist films during post-baking.
Positive photoresist compositions for use in the inclined implantation process using a patterned resist thin film about 0.1 to 0.5 &mgr;m thick must yield a patterned resist film with high definition and contrast and satisfactory shape, must have high sensitivity, invite less scum and have satisfactory stability of latent image before development and high thermal resistance.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a positive photoresist composition that has highly improved sensitivity and definition, can yield a patterned resist thin film with high contrast, invites less scum and has satisfactory stability of latent image before development and thermal resistance specifically in an inclined implantation process.
Another object of the present invention is to provide a method of patterning a resist thin film for use in an inclined implantation process using the positive photoresist composition.
After intensive investigations, the present inventors have solved the problems of the conventional technologies.
Specifically, the present invention provides, in an aspect, a positive photoresist composition including:
(A) a novolak resin containing equal to or more than 20% by mole of a m-cresol constitutional repeating unit in total phenolic constitutional repeating units and having 1-ethoxyethyl groups substituting for part of hydrogen atoms of phenolic hydroxyl groups;
(B) a quinonediazide ester repre
Doi Kousuke
Katano Akira
Kono Shinichi
Nakagawa Yusuke
Chu John S.
Tokyo Ohka Kogyo Co. Ltd.
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