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
2002-05-10
2004-07-27
Ashton, Rosemary (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
C430S325000, C430S326000, C430S921000
Reexamination Certificate
active
06767689
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to compositions that reduce reflection of exposing radiation from a substrate back into an overcoated photoresist layer. More particularly, the invention relates to anti-reflective coating compositions that contains an ionic thermal acid generator compound. The compositions can exhibit, inter alia, enhanced storage stability.
2. Background
Photoresists are photosensitive films used for the transfer of images to a substrate. A coating layer of a photoresist is formed on a substrate and the photoresist layer is then exposed through a photomask to a source of activating radiation. The photomask has areas that are opaque to activating radiation and other areas that are transparent to activating radiation. Exposure to activating radiation provides a photoinduced or chemical transformation of the photoresist coating to thereby transfer the pattern of the photomask to the photoresist-coated substrate. Following exposure, the photoresist is developed to provide a relief image that permits selective processing of a substrate.
A photoresist can be either positive-acting or negative-acting. For most negative-acting photoresists, those coating layer portions that are exposed to activating radiation polymerize or crosslink in a reaction between a photoactive compound and polymerizable reagents of the photoresist composition. Consequently, the exposed coating portions are rendered less soluble in a developer solution than unexposed portions. For a positive-acting photoresist, exposed portions are rendered more soluble in a developer solution while areas not exposed remain comparatively less soluble in the developer solution. Photoresist compositions are described in Deforest,
Photoresist Materials and Processes
, McGraw Hill Book Company, New York, ch. 2, 1975 and by Moreau,
Semiconductor Lithography, Principles, Practices and Materials
, Plenum Press, New York, ch. 2 and 4.
A major use of photoresists is in semiconductor manufacture where an object is to convert a highly polished semiconductor slice, such as silicon or gallium arsenide, into a complex matrix of electron conducting paths, preferably of micron or submicron geometry, that perform circuit functions. Proper photoresist processing is a key to attaining this object. While there is a strong interdependency among the various photoresist processing steps, exposure is believed to be one of the most important steps in attaining high resolution photoresist images.
Reflection of activating radiation used to expose a photoresist often poses limits on resolution of the image patterned in the photoresist layer. Reflection of radiation from the substrate/photoresist interface can produce spatial variations in the radiation intensity in the photoresist, resulting in non-uniform photoresist linewidth upon development. Radiation also can scatter from the substrate/photoresist interface into regions of the photoresist where exposure is non intended, again resulting in linewidth variations. The amount of scattering and reflection will typically vary from region to region, resulting in further linewidth non-uniformity. Variations in substrate topography also can give rise to resolution-limiting problems.
One approach used to reduce the problem of reflected radiation has been the use of a radiation absorbing layer interposed between the substrate surface and the photoresist coating layer. See for example, PCT Application WO 90/03598, EPO Application No. 0 639 941 A1 and U.S. Pat. Nos. 4,910,122, 4370,405, 4,362,809, and 5,939,236. Such layers have also been referred to as antireflective layers or antireflective compositions. See also U.S. Pat. Nos. 5,939,236; 5,886,102; 5,851,738; and 5,851,730, all assigned to the Shipley Company, which disclose highly usefull antireflective compositions.
SUMMARY OF THE INVENTION
We have now discovered new antireflective compositions for use with an overcoated photoresist layer that can exhibit enhanced properties, including enhanced storage stability (i.e. shelf life stability).
We have found that certain antireflective compositions can exhibit limited shelf life, e.g. produce particles or become turbid during storage and prior to use. More particularly, certain anti-reflective coating compositions include a thermal acid generator or an acid that limit the shelf life of the composition. Without being bound by theory, it is believed that interaction between antireflective composition components can result in less than desirable shelf life.
We have discovered that use of an ionic thermal acid generator compound can significantly enhance the storage stability of an organic solvent antireflective composition. Exemplary ionic thermal acid generators include e.g. sulfonate salts, preferably arylsulfonate salts such as toluenesulfonate acid amine salt.
Antireflective compositions of the invention suitably comprise a resin and a thermal acid generator (TAG). Preferred antireflective compositions of the invention contain a crosslinking component, and the antireflective composition is crosslinked prior to applying a photoresist composition layer over the antireflective composition layer. An antireflective composition may contain an oligiomeric or polymeric thermal acid generator as the sole resin component of an antireflective composition. It is generally preferred however that an antireflective composition contain at least one resin component in addition to any thermal acid generator component, e.g. to impart good film-forming properties to the antireflective composition.
Antireflective compositions of the invention also will contain a component that comprises chromophore groups that can absorb undesired radiation used to expose the overcoated resist layer from reflecting back into the resist layer. Generally preferred chromophores are aromatic groups, including both single ring and multiple ring aromatic groups such as optionally substituted phenyl, optionally substituted naphthyl, optionally substituted anthracenyl, optionally substituted phenanthracenyl, optionally substituted quinolinyl, and the like. Particularly preferred chromophores may vary with the radiation employed to expose an overcoated resist layer. More specifically, for exposure of an overcoated resist at 248 nm, optionally substituted anthracene is a particularly preferred chromophore of the antireflective composition. For exposure of an overcoated resist at 193 nm, optionally substituted phenyl is a particularly preferred chromophore of the antireflective composition. Preferably, such chromophore groups are linked (e.g. pendant groups) to a resin component of the antireflective composition, either a polymeric thermal acid generator component or an additional resin component distinct from the polymeric base additive.
As mentioned, preferred antireflective coating compositions of the invention can be crosslinked, e.g. by thermal and/or radiation treatment. For example, preferred antireflective coating compositions of the invention may contain a separate crosslinker component that can crosslink with one ore more other components of the antireflective composition. Generally preferred crosslinking antireflective compositions comprise a separate crosslinker component. Particularly preferred antireflective compositions of the invention contain as separate components: a resin, a crosslinker, and a thermal acid generator additive. Additionally, crosslinking antireflective compositions of the invention preferably can also contain an amine basic additive to promote elimination of footing or notching of the overcoated photoresist layer. Crosslinking antireflective compositions are preferably crosslinked prior to application of a photoresist layer over the antireflective coating layer. Thermal-induced crosslinking of the antireflective composition by activation of the thermal acid generator is generally preferred.
Antireflective compositions of the invention are typically formulated and applied to a substrate as an organic solvent solution. A variety of solvents, including protic
Pavelchek Edward K.
Trefonas, III Peter
Ashton Rosemary
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Shipley Company L.L.C.
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