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
2000-01-27
2003-04-08
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
C430S287100, C430S326000, C430S905000, C430S910000, C430S914000
Reexamination Certificate
active
06544715
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive type photoresist composition used in an ultramicrolithography process or another photofabrication process for the production of a very large scale integrated circuit or a high capacity microchip, and more particularly to a positive type photoresist composition which can form a highly refined pattern by use of light within the range god of far ultraviolet rays including excimer laser beams, particularly light having a wavelength of 250 nm.
BACKGROUND OF THE INVENTION
In recent years, integrated circuits have been progressively increased in their integration degree, and therefore processing of ultrafine patterns having a line width of a half micron or less has become necessary in the production of semiconductor substrates for very large scale integrated circuits. For fulfilling this necessity, the wavelength of light used in exposure devices employed for photolithography becomes progressively shorter, and now, of the far ultraviolet rays, the use of excimer laser light having a short wavelength (such as XeCl, KrF or ArF) has been studied.
Used in the pattern formation of lithography in this wavelength region are chemical amplification system resists.
In general, the chemical amplification system resists can be roughly divided into three classes, commonly called as a 2-component system, a 2.5-component system and a 3-component system. In the 2-component system, a compound capable of generating an acid by photolysis (hereinafter referred to as a photo-acid generator) is combined with a binder resin. The binder resin is a resin having a group which is decomposable by the action of an acid to enhance the solubility of the resin in analkali developing solution (also referred to as an acid-decomposable group) in its molecule. The 2.5-component system further contains a low molecular weight compound having an acid-decomposable group in addition to such a 2-component system. The 3-component system up contains the photo-acid generator, an alkali-soluble resin and the above-mentioned low molecular weight compound.
The above-mentioned chemical amplification system resists are suitable for photoresists for ultraviolet or far ultraviolet ray irradiation. However, they are further required to comply with desired characteristics when used. For example, when the 248-nm light of a KrF excimer laser is used, resist compositions comprising a hydroxystyrene polymer particularly low in photoabsorption and an acetal group or ketal group is introduced as a protective group into the polymer. Examples thereof are described in JP-A-2-141636 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-2-19847, JP-A-4-219757 and JP-A-5-281745. Besides, similar compositions having t-butoxycarbonyloxy groups or p-tetrahydropyranyloxy groups as acid-decomposable groups are proposed in JP-A-2-209977, JP-A-3-206458 and JP-A-2-19847.
These compositions are suitable when the 248-nm light of a KrF excimer laser is used. However, when an ArF laser is used as a light source, they are low in sensitivity because their absorbance is substantially too high. Accompanied thereby, they further have other disadvantages, for example, the problems of deterioration of resolution, deterioration of focus latitude and deterioration of pattern profiles, so that many improvements are further required.
Accordingly, as the photoresist compositions for the ArF light source, photoresist compositions are proposed in which (meth)acrylic resins smaller in absorption than partially hydroxylated styrene resins are combined with compounds capable of generating acids with light. For example, they are described in JP-A-7-199467 and JP-A-7-252324. Above all, JP-A-6-289615 discloses resins in which each organic group of tertiary carbon is attached though an ester linkage to an oxygen atom of a carboxyl group of acrylic acid.
Further, JP-A-7-234511 discloses acid-decomposable resins having acrylates or fumarates as repeating units. However, the fact is that they are insufficient in pattern profiles and adhesion to substrates, resulting in failure to obtain their sufficient performance.
Furthermore, resins are proposed into which alicyclic hydrocarbon moieties are introduced for imparting the resistance to dry etching. However, the systems become extremely hydrophobic as an adverse effect of the introduction of the alicyclic hydrocarbon moieties. The phenomena are therefore observed that the development with aqueous solutions of tetramethylammonium hydroxide (hereinafter referred to as TMAH) which have hitherto been widely used as resist developing solutions becomes difficult, and that resists are separated from substrates during the development.
For complying with such hydrophobization of resists, a measure of mixing organic solvents such as isopropyl alcohol with the developing solutions has been studied, and results have been observed although not quite satisfactorily. However, there is fear of swelling of resist films, and the process becomes complicated. It is therefore not necessarily said that problems have been solved.
As approaches to the improvement of resists, measures in which hydrophilic groups are introduced to compensate for hydrophobic alicyclic hydrocarbon moieties have been taken.
In general, the measures have been taken by copolymerizing monomers having carboxylic acid moieties such as acrylic acid and methacrylic acid with monomers having alicyclic hydrocarbon groups. However, although there is a tendency of the adhesion to substrates to be improved with the introduction of carboxylic acid groups, many problems occur such as deterioration of the resistance to dry etching and a significant film reduction in resists. Thus, the above-mentioned problems have not been solved yet. Further, JP-A-7-234511 aims at the solution to the problem of development properties by copolymerizing monomers having hydroxyl groups or cyano groups in their molecules in place of carboxyl groups, such as HEMA or acrylonitrile, with monomers having alicyclic hydrocarbon groups, but results thereof are quite insufficient.
On the other hand, in addition to the methods of introducing the alicyclic hydrocarbon moieties into side chains of the above-mentioned acrylate monomers, methods for imparting the resistance to dry etching are also studied in which alicyclic egg hydrocarbon moieties are utilized as main chains of polymers. This system also has the above-mentioned problems, and improvements according to similar approaches have been studied.
For example, in
Journal of Phopolymer Science and Technology,
10, 529-534 (1997) and
Journal of Photopolymer Science and Technology,
10, 521-528 (1997), the introduction of hydroxyl groups into main chains of norbornene polymers has been studied from the viewpoint of giving the adhesion to substrates. However, no satisfactory results have been obtained in respect to both the development properties and the adhesion to substrates.
Further,
SPIE,
3049, 92-105 (1988) discloses compositions containing polymers obtained by ring-opening polymerization of norbornene rings or polymers having norbornene rings on their main chains, which further have carboxyl groups and t-butyl ester groups. However, the polymers obtained by these processes also have the disadvantage that both the adhesion to substrates and the standard developing solution suitability are practically insufficient.
Furthermore, EP-A-789278 discloses compositions containing polymers obtained by ring-opening polymerization of norbornene rings or polymers having norbornene rings on their main chains, which further contain acid-decomposable groups and carboxyl groups. In addition, W097/33198 discloses photoresist compositions containing resins obtained by polymerizing monomers having norbornene rings having acid-decomposable groups. JP-A-9-274318 discloses photoresist compositions in which carboxylic acids are further used.
Besides, in JP-A-9-73173, JP-A-9-90637 and JP-A-10-161313, resist materials are described in which acid-sensitive compounds containing a
Aoai Toshiaki
Kodama Kunihiko
Sato Kenichiro
Baxter Janet
Fuji Photo Film Co. , Ltd.
Lee Sim J.
Sughrue & Mion, PLLC
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