Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2002-04-20
2003-08-05
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S325000, C430S326000, C430S330000, C430S510000, C430S512000, C430S514000
Reexamination Certificate
active
06602652
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 antireflective coating compositions (“ARCs”) that contain a resin binder components that effectively absorbs short-wavelength exposure radiation, including sub-200 nm radiation such as 193 nm radiation.
2. Background
Photoresists are photosensitive films used for transfer of an image 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 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 developer soluble. Photoresist compositions are known to the art and described by Deforest,
Photoresist Materials and Processes
, McGraw Hill Book Company, New York, ch. 2, 1975 and by Moreay,
Semiconductor Lithography, Principles, Practices and Materials
, Plenum Press, New York, ch. 2 and 4, both incorporated herein by reference for their teaching of photoresist compositions and methods of making and using the same.
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 more 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 variations in the radiation intensity in the photoresist during exposure, 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 not 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 give rise to resolution-limiting reflection problems.
With recent trends towards high-density semiconductor devices, there is a movement in the industry to shorten the wavelength of exposure sources to deep ultraviolet (DUV) light (300 nm or less in wavelength), KrF excimer laser light (248.4 nm), ArF excimer laser light (193 nm), electron beams and soft x-rays. The use of shortened wavelengths of light for imaging a photoresist coating has generally resulted in increased reflection from the upper resist surface as well as the surface of the underlying substrate. Thus, the use of the shorter wavelengths has exacerbated the problems of reflection from a substrate surface.
Another 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 Al and U.S. Pat. Nos. 4,910,122, 4,370,405 and 4,362,809, all incorporated herein by reference for their teaching of antireflective (antihalation) compositions and the use of the same. Such layers have also been referred to in the literature as antireflective layers or ARCs (antireflective compositions).
In Shipley Company's European Applications 542008A1 and 0813114A2 highly useful antihalation (antireflective) compositions are disclosed.
While it has been found that prior ARC compositions may be effective for many antireflective applications, prior compositions also may pose some potential performance limitations, particularly when used at short wavelength imaging applications.
It thus would be desirable to have new antireflective coating compositions. It would be particularly desirable to have new antireflective coating compositions that effectively absorb undesired reflections of short wavelength radiation, including sub-200 nm radiation such as 193 nm.
SUMMARY OF THE INVENTION
The present invention provides new light absorbing compositions suitable for use as an antireflective coating composition (“ARC”), particularly for short wavelength imaging applications, such as 193 nm imaging. The ARCs of the invention in general comprise a resin binder that effectively absorbs short wavelength exposure radiation to reduce reflections of same, and optionally comprise a crosslinker component.
Preferred resin binders of ARCs of the invention contain phenyl units, preferably pendant from a polymer backbone.
Particularly preferred ARC resin binders of the invention do not have any alkyl (e.g. optionally substituted (—CH2—)
n
where n is 1 to about 6 or 8) units interposed between the polymer backbone and a pendant phenyl group. For example, preferred pendant groups include those provided by polymerization of optionally substituted styrene, optionally substituted isopropenyl styrene, optionally substituted phenyl acrylate, and optionally substituted phenyl methacrylate. As referred to herein, references to a phenyl group being “directly pendant” from a polymer backbone indicate that no alkyl or other groups are interposed between the polymer backbone and the phenyl group, such as provided by condensation of optionally substituted styrene or isopropenyl styrene units.
Nevertheless, while less preferred, the invention also includes ARCs having resin binders that have pendant phenyl groups where an alkyl (e.g. optionally substituted (—CH2—)
n
where n is 1 to about 6 or 8) linkage is interposed between the backbone and the phenyl group, e.g. as may be provided by polymerization of 2-phenyl-1-ethyl methacrylate and the like.
The antireflective composition resin binder with phenyl chromophore moieties suitably is a copolymer and is prepared by polymerizing two or more different monomers where at least one of the monomers includes a phenyl chromophore group. For example, preferred additional ARC resin units include those provided by polymerization of acrylate monomers, e.g. hydroxy acrylates such as 2-hydroxyethylmethacrylate,2-hydroxyethylacrylate and the like; C
1-12
acrylates such as methylmethacrylate, methylacrylate, butylmethacrylate, butylacrylate and the like. Acrylate resins that contain phenyl chromophore units are generally preferred for use in ARCs of the invention. For crosslinking ARCs of the invention, preferably the ARC resin has a hydroxy or other reactive moiety for promoting a curing reaction.
The invention further provides methods for forming a relief image and novel articles of manufacture comprising substrates coated with an ARC composition of the invention alone or in combination with a photoresist composition. Other aspects of the invention are disclosed infra.
DETAILED DESCRIPTION OF THE INV
Adams Timothy G.
Blacksmith Robert F.
DoCanto Manuel
Pavelchek Edward K.
Sinta Roger F.
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Shipley Company L.L.C.
Young Christopher G.
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