Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-08-27
2004-05-18
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S326000, C526S329500
Reexamination Certificate
active
06737492
ABSTRACT:
TECHNICAL FIELD
This invention relates to a radiation absorbing polymer which has chemically bonded thereto an organic chromophore, a coating composition containing the radiation absorbing polymer and an anti-reflective coating formed from the coating composition and, more particularly, to a radiation absorbing polymer capable of forming a radiation absorbing coating such as an anti-reflective coating useful in manufacturing integrated circuit elements by lithography, a composition containing the radiation absorbing polymer, and a radiation absorbing coating such as an anti-reflective coating formed from the composition.
BACKGROUND ART
In the field of manufacturing integrated circuit elements, patterning technology to form finer patterns by lithographic process has made progress and, in recent years, in order to attain a higher degree of integration, the development of patterning technology enabling quarter micron fine patterning has been studied. In such a lithographic process, a photoresist is applied to a substrate, a latent image of a mask pattern is created in the photoresist using a reduction projection exposure apparatus, then the latent image is developed using a proper developer solution to obtain a patterned resist with the desired width and pattern. However, many substrates used in the field of manufacturing integrated circuit elements have such a high reflectivity that, upon exposure, exposing light passing through the photoresist layer is reflected on the surface of the substrates and is again incident into the photoresist layer, which causes the problem that desired patterns are not obtained or that patterns with some defects are formed due to exposure by the reflected light of photoresist areas which are not to be exposed. These are called problems of standing wave or notching. Various techniques have been investigated to solve the problems caused by such reflection. For example, there have been attempted a technique of dispersing a dye having radiation absorption at the same exposure wavelength as in the photoresist, a technique of forming a radiation absorbing coating of an inorganic compound such as titanium nitride according to a CVD method, vacuum evaporation method or the like, a technique of forming a radiation absorbing coating by applying a dispersion or solution of a radiation absorbing dye in an organic polymer solution on to a substrate, and a technique of forming a radiation absorbing coating by applying to a substrate a radiation absorbing polymer having chemically bonded thereto a chromophore. Of the above-described techniques, the technique of dispersing a radiation absorbing dye in a photoresist has the problems of reduction in photoresist sensitivity, thinning of the resist layer during development processing, sublimation of the dye upon baking, and the like. The technique of using an inorganic anti-reflective coating has the various problems of difficulty in accurate control of coating thickness, difficulty of forming a coating with uniform coating thickness, requirement for a special apparatus for conducting, vapor deposition, poor adhesion with a resist film, a requirement for separately providing a step of transferring a pattern by dry etching, and the like. Further, the technique of dispersing a radiation absorbing dye in the anti-reflective coating involves the problems of separation of the polymer and the dye from each other upon formation of the anti-reflective coating by spin-coating, elution of the dye into a resist solvent, sublimation of the dye into the resist layer upon baking, and the like. On the other hand, the technique of using a radiation absorbing polymer does not involve such problems, and hence this technique has been noted in recent years. Methods of using radiation absorbing polymers as anti-reflective coatings and materials to be used for the methods are described in, for example, Japanese Laid-open Patent Publication Nos. H6-75378 and H6-118656, WO 9412912, U.S. Pat. Nos. 4,910,122 and 5,057,399, etc. Of the radiation absorbing polymers, those polymers wherein a radiation absorbing chromophore is chemically bonded to the polymer skeleton have recently been considered most promising, and methods of using them and their application, have already been studied. Particularly in the process of using radiation having a wavelength not longer than that of an eximer laser, an anti-reflective coating is considered to be necessary, and it has been desired to provide an anti-reflective coating having good properties.
On the other hand, there exists a requirement that, upon formation of a photoresist coating on a substrate having a large unevenness, an undercoating layer or an intermediate layer is first coated on the substrate to make the surface even for forming a resist image with high dimensional accuracy. Investigation for meeting such a requirement is also necessary.
Formation of resist patterns using a radiation absorbing intermediate coating such as an anti-reflective coating between a photoresist layer and a substrate before forming a resist pattern is conducted as follows. That is, a composition for a radiation absorbing coating such as an anti-reflective coating solution is first coated to a substrate and, after baking the coating to be made insoluble in a resist solvent, the resist coating is formed by a coating method on the radiation absorbing coating, such as the anti-reflective coating, and is then subjected to the processes of exposure, development processing, etc. to form a resist pattern, followed by removing the coating such as the anti-reflective coating in the resist-free areas, by dry etching or the like.
The above-described radiation absorbing polymers wherein a dye is chemically bonded to a skeletal polymer, generally have a low solubility in solvents for resists, and hence solvents different from those used for resists, such as cyclohexanone, are often employed as a solvent for the radiation absorbing polymer. In case that a solvent used for forming a radiation absorbing coating, such as an anti-reflective coating, is different from that for resist, there may arise problems that process steps for forming the anti-reflective coating in manufacturing integrated circuits increase in number and, in some cases, properties of the resist layer themselves are adversely affected. In addition, in the case that the anti-reflective coating and the photoresist layer are formed by using the same coating apparatus and the anti-reflective coating materials are insoluble in the solvent for resist, there arises a problem that the anti-reflective coating material might be precipitated due to the influence of mixing of the resist coating waste and the anti-reflective coating solution. The precipitate thus formed might close up pipes for waste liquor, or might scatter as fine powder, resulting in pattern defects. Further, an additional pipe line for feeding a solvent for washing the backside and periphery of substrate might be required. As is described above, an anti-reflective coating composition containing a low molecular weight dye dispersed in a polymer has also been developed. Such composition, however, often causes unevenness in coating thickness when coated on a surface of a substrate with topography, that is, it provides poor coverage, which should desired to be improved. In addition, in conducting the resist process on a substrate with areas with topography, coating of the resist is, in some cases, difficult or it is difficult to make the thickness of the resist uniform, due to difference in the level of the surface. There is also a requirement on planarization of the substrate surface by a film-forming material to get uniform thickness of the resist coating formed thereon for improving the accuracy of the formed resist pattern, as well as preventing reflection. Thus, it has been desired to provide an anti-reflecting coating material which can provide high performance, which enables one to control coverage properties on a surface of a substrate with topography, which undergoes no change in the properties of the anti-
Kang Wen-Bing
Kimura Ken
Kudo Takanori
Padmanaban Munirathna
Pawlowski Georg
Clariant Finance (BVI) Limited
Kass Alan P.
Lipman Bernard
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