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
2000-05-03
2003-07-22
Chu, John S. (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
C430S910000
Reexamination Certificate
active
06596458
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive-working photoresit composition used in an ultramicrolithography process or another photofabrication process for the production of very large scale integrated circuits or high capacity microchips, and particularly to a positive-working photoresist composition which can form highly miniaturized patterns by use of light within the range of far ultraviolet rays including excimer laser beams, particularly light having a wavelength of 250 nm.
More particularly, the invention relates to a positive-working photoresit composition in which development defects are prevented from being generated, and which is excellent in resist pattern profiles obtained and in the resolving power of contact holes.
BACKGROUND OF THE INVENTION
In recent years, integrated circuits have been progressively increased in their integration degree, and therefore processing of ultra-micro 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 fufilling this necessity, the wavelength of light used in an exposure apparatus employed for photolithography becomes progressively shorter, and now, of the far ultraviolet rays, excimer laser light having a short wavelength (such as XeCl, KrF or ArF) has been studied for the use.
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 generating an acid by photolysis (hereinafter referred to as a photoacid 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 into an alkali developing solution (also referred to as an acid-decomposable group) in its molecule. The 2.5-component system contains a low molecular weight compound further having an acid-decomposable group in addition to such a 2-component system. The 3-component system contains the photoacid generator, the alkali-soluble resin and the low molecular weight compound.
The 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 at the time when used. When a ArF excimer laser is used as a light source, photoresist compositions are proposed in which (meth)acrylic resins smaller in absorption than partially hydroxylated styrenic resins are combined with compounds generating acids by light. For example, they are described in JP-A-7-199467 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-7-252324. Above all, JP-A-6-289615 discloses resins in which each organic group of tertiary carbon is attached by an ester linkage to oxygen of a carboxyl group of acrylic acid.
Further, JP-A-7-234511 discloses acid-decomposable resins having acrylic esters or fumaric esters 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 sites are introduced for imparting dry etching resistance.
In JP-A-9-73173, JP-A-9-90637 and JP-A-10-161313, resist materials are described in which acid-sensitive compounds are used, the compounds containing alkali-soluble groups protected with alicyclic group-containing structures and structure units which make the compounds alkali-soluble by eliminating the alkali-soluble groups with acids.
Besides, in JP-A-9-90637, JP-A-10-207069 and JP-A-10-274852, resist compositions containing acid-decomposable resins having specific lactone structures are described.
In the chemical amplification system photoresists or ArF exposure, the acid-decomposable group-containing resins have been variously studied as described above. However, there is still room for improvement in the resins. That is to say, the acid-decomposable resins used in the chemical amplification system photoresists deteriorate the shape of profiles (the top shape of profiles becomes pent roof-like), the resolving power (particularly, the resolving power of contact holes) and the development properties (development defects and scumming) in some cases. Copolymerization of further monomers for solving these problems results in deterioration of the sensitivity. In particular, there is no guideline for improving development defects in the present circumstances.
Accordingly, in the present circumstances, it is not clear how the resist compositions should be designed as means for solving these problems.
As described above, the resins are proposed into which alicyclic hydrocarbon sites are introduced for imparting dry etching resistance. However, as a harmful effect of the introduction of alicyclic hydrocarbon sites, the systems become extremely hydrophobic. Accordingly, the phenomena are 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 development.
For complying with such resists made hydrophobic, it has been studied that organic solvents such as isopropyl, alcohol are mixed with developing solutions. This has produced results to some degree. However, there is a fear of swelling of resist films, and the process becomes complicated. It is therefore not necessarily said that the problems have been dissolved.
As approaches for improving the resists, many measures have been taken in which various hydrophobic alicyclic hydrocarbon sites are compensated for by the introduction of hydrophilic groups.
In general, monomers having carboxylic acid sites such as acrylic acid and methacrylic acid, or monomers having hydroxyl groups or cyano groups in their molecules such as HEMA and acrylonitrile are copolymerized with monomers having alicyclic hydrocarbon groups, thereby aiming at the solution to the problem or the development properties. However, this is utterly insufficient.
On the other hand, methods for imparting dry etching resistance utilizing alicyclic hydrocarbon sites as main chains of polymers are also studied, in addition to methods of introducing alicyclic hydrocarbon sites into side chains of the acrylate monomers. However, this system also has the above-mentioned problems, and improvements by similar approaches have been studied.
In JP-A-10-254139, resin compositions are described each of which comprises an acid-decomposable group-containing resin having an alicyclic skeleton, a radiation-sensitive acid generator and a mixed solvent comprising a straight-chain ketone and at least one selected from the group consisting of a cyclic ketone, a propylene glycol monoalkyl ether acetate land an alkyl 2-hydroxypropionate. However, this system also has the above-mentioned problems, and improvements by similar approaches have been studied.
In the chemical amplification system photoresists for far ultraviolet ray exposure, various resins containing acid-decomposable groups have been studied as described above. However, there is still room for improvement, caused by the hydrophobicity of the resins. That is to say, when the chemical amplification system photoresists are stored in the solution state, there are still the problems that particles are produced in solutions and that the resist performance is deteriorated (deterioration of the storage stability of the resist solutions) because of poor miscibility of the resins with photoacid generators.
With recent demands towards miniaturization of semiconductor chips, design patterns of the micro semiconductors have reached the micro region of 0.13 &mgr;m to 0.35 &mgr;m. However, t
Aoai Toshiaki
Kawabe Yasumasa
Kodama Kunihiko
Sato Kenichiro
Chu John S.
Fuji Photo Film Co. , Ltd.
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