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
2000-08-28
2001-11-20
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
C430S288100
Reexamination Certificate
active
06319651
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to the field of antireflective coatings. More specifically, the invention relates to an acid sensitive antireflective coating and its method of use.
2. Background Art
In the production of semiconductor devices, an integrated circuit substrate is coated with a film of photo patterning resist, exposed to actinic radiation, and developed to define a resist image over the integrated circuit substrate. The resist image includes both lines and spaces, wherein portions of the photo patterning resist that are removed form the spaces and the portions that remain form the lines. The resist image is transferred to the integrated circuit substrate by modifying the exposed portion of the substrate. Such modification may be performed by removal of a portion of the substrate by etching processes, by implantation of atomic species into the substrate, or by other methods known to those skilled in the art. During such processes, the photo patterning resist lines act as a mask to prevent modification of the portions of the substrate underlying the resist lines. Resolution of the image transferred to the substrate is dependent on the resolution of the resist image.
During exposure of a photo patterning resist on an integrated circuit substrate, some reflection of the actinic radiation off the integrated circuit substrate will typically occur. The reflection causes film interference effects that change the effective exposure intensity within a chip, across the wafer, and from wafer to wafer. Given the variation in effective exposure intensity, an unacceptable amount of line width variation typically occurs. This is especially true in modem manufacturing where laser exposure tools are used as the source of the actinic radiation and reflection is particularly prevalent.
To prevent reflection of actinic radiation into a photo patterning resist, one or more layers of an antireflective coating (ARC) may be provided between a substrate and a photo patterning resist film. ARCs often include a radiation adsorbing dye dispersed in a polymer binder, however, some polymers exist that contain an appropriate chromophore that sufficiently adsorbs the actinic radiation such that an additional adsorbing dye is not required. The ARC may be adapted to attenuate a particular wavelength of radiation used to expose the photo patterning resist by a selection of suitable adsorbing dies or a polymer having suitable chromophores.
Unfortunately, the use of an ARC creates its own problems. Once the photo patterning resist film is developed, exposing the underlying ARC, the ARC must be removed to expose the underlying integrated circuit substrate for subsequent modification as mentioned above. Commonly, the ARC is removed using a reactive ion etch process, however, other types of dry etching or wet etching as known to those skilled in the art may be used.
Regardless of the method selected for removing the ARC, there is a strong tendency for such processes to degrade the resist image by rounding off the comers, changing the line width, and creating other nonuniformities across the wafer or wafer to wafer. In particular, such processes may result in undercut and possible partial liftoff of the photo patterning resist film, causing etch bias, profile changes, photo patterning resist thinning, and other photo patterning resist defects as described in U.S. Pat. No. 5,635,333, issued to Petersen et al. While Petersen et al., and perhaps other references, attempt to resolve a portion of the above described problems, they are only partially effective at doing so.
Therefore there existed a need to provide a method and/or composition for forming an ARC that may be removed without degrading the resist image and that provides simplification of the complex processing steps recited by Petersen et al. and perhaps other references.
DISCLOSURE OF INVENTION
According to the present invention, a composition is provided including a water soluble resin and a cross-linker, wherein the composition may be cross-inked and will thus form an acid sensitive, water insoluble antireflective coating (ARC). By way of example, the composition may further include a dye selected from among 9-anthracene methanol and a squaric acid derivative. Also, the water soluble resin may be selected from among hydroxystyrene-sulfonated styrene copolymer, poly(2-isopropenyl-2-oxazoline), and poly(acrylic acid) and the cross-linker may be selected from among an acetal diacid and a water soluble divinyl ether. Particular advantages are achieved when the composition further includes chemical amplification components sufficient to produce a photosensitivity of less than about 900 milliJoules per square centimeter (mJ/cm
2
), especially about 100 mJ/cm
2
or less.
The present invention further provides a method including the steps of applying a radiation adsorbing layer on a substrate and forming an acid sensitive, water insoluble ARC therefrom, applying a photo patterning resist (PPR) layer on the ARC, exposing part of the PPR layer to actinic radiation, developing the PPR layer to form a resist image, rendering the ARC water soluble, and developing the ARC to uncover selected portions of the substrate. By way of example, the composition described above may be used as the radiation adsorbing layer. Also, for example, the step of developing the ARC may be performed with a water rinse. In addition, the steps of exposing the PPR layer and rendering the ARC water soluble may occur together in a single exposure to actinic radiation. Further, the steps of developing the PPR layer and developing the ARC may occur together in a single develop. Finally, the step of rendering the ARC water soluble may be accomplished by exposing the ARC to an acid solution or an acid vapor, by exposing the ARC to actinic radiation without first hardening the PPR layer, or by other methods.
The foregoing and other features and advantages of the present invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.
MODE(S) FOR CARRYING OUT THE INVENTION
According to a preferred embodiment of the present invention, a composition is provided that includes a water soluble resin and a cross-linker. Radiation adsorptive components may be provided as part of the resin or, more preferably, as a separate dye. Such a composition may be used as an acid sensitive antireflective coating (ARC), that is, the composition may be applied on a substrate as a radiation adsorbing layer and additionally cross-linked to form an acid sensitive, water insoluble ARC on which a photopatterning resist (PPR) layer may be formed. Being acid sensitive, selected portions of an ARC formed from the composition may be removed by a suitable reversal of the cross-linking followed by a develop step, preferably with an aqueous developer, more preferably de-ionized water.
The water soluble resin is preferably poly(2-isopropenyl-2-oxazoline) (hereinafter PIO), a hydroxystyrene-sulfonated styrene copolymer (hereinafter HSS copolymer), or poly(acrylic acid) (hereinafter PAA). The cross-linker is preferably an acetal diacid or a water soluble divinyl ether. The dye is preferably 2-anthracene methanol (9-AM) or a derivative of squaric acid having suitable dye properties. If a suitable photoacid generator (PAG) is included, then an ARC formed from such components may exhibit a photosensitivity similar to or even lower than that of the overlying PPR. That is, the exposure dose of actinic radiation required to cause the desired photo response in the overlying PPR layer to form a resist image is similar to the exposure dose of actinic radiation that will reverse the cross-linking of the water soluble resin in the ARC. This is a tremendous improvement over conventional ARCs, which are typically not photo sensitive.
While some attempts have been made to provide a photosensitive ARC, the ARCs are only marginally photo sensitive, requiring an exposure dose much higher than a typical PPR. F
Holmes Steven J.
Rabidoux Paul A.
Ashton Rosemary
International Business Machines - Corporation
Sabo William D.
Schmeiser Olsen & Watts
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