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
2001-05-18
2004-05-25
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
C430S326000, C430S905000, C430S921000
Reexamination Certificate
active
06740467
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new photoresist compositions that contain a blend of ionic and nonionic photoacid generator compounds. Compositions of the invention are highly useful as deep U.V. photoresists (including imaging at 193 nm and 248 nm) with the capability of forming highly resolved features of submicron dimensions.
2. Background
Photoresists are photosensitive films for transfer of images to a substrate. They form negative or positive images. After coating a photoresist on a substrate, the coating is exposed through a patterned photomask to a source of activating energy such as ultraviolet light to form a latent image in the photoresist coating. The photomask has areas opaque and transparent to activating radiation that define an image desired to be transferred to the underlying substrate. A relief image is provided by development of the latent image pattern in the resist coating. The use of photoresists is generally described, for example, by Deforest, Photoresist Materials and Processes, McGraw Hill Book Company, New York (1975), and by Moreau, Semiconductor Lithography, Principals, Practices and Materials, Plenum Press, New York (1988).
Known photoresists can provide features having resolution and size sufficient for many existing commercial applications. However for many other applications, the need exists for new photoresists that can provide highly resolved images of submicron dimension.
Various attempts have been made to alter the make-up of photoresist compositions to improve performance of functional properties. Among other things, a variety of photoactive compounds have been reported for use in photoresist compositions. See, e.g., U.S. Pat. No. 4,450,360 and European Application 615163.
Relatively recently interest has increased in photoresists that can be photoimaged with deep U.V. radiation. Such photoresists offer the potential of forming images of smaller features than may be possible at longer wavelength exposure. As is recognized by those in the art, “deep U.V. radiation” refers to exposure radiation having a wavelength in the range of about 350 nm or less, more typically in the range of about 300 nm or less. While a number of deep U.V. resists have been reported, the need clearly exists for new deep U.V. resists that can provide highly resolved fine line images as well as acceptable photospeed and other lithographic properties. Particular interest exists in resists that can be imaged with sub-250 nm wavelengths such as KrF radiation (ca. 248 nm) or sub-200 nm wavelengths such as ArF radiation (193 nm).
SUMMARY OF THE INVENTION
We have now discovered novel blends of photoacid generators compounds (“PAGs”) that can formulated in photoresist compositions to provide excellent lithographic properties, particularly chemically-amplified positive-acting resists. Preferred PAG blends can be photoactivated upon exposure to deep U.V. radiation, particularly 248 nm and/or 193 nm exposure wavelengths.
PAG blends of the invention comprise at least one ionic PAG and at least one non-ionic PAG. For example, typical ionic PAGs include onium salts such as iodonium salts, sulfonium salts and the like. Suitable non-ionic PAGs include e.g. imidosulfonates, sulfonate esters, halogenated compounds that generate a halo-acid (e.g. HBr) upon photoactivation, and the like.
As referred to herein, the terms ionic and non-ionic with respect to PAGS are used in accordance with their-art recognized meaning, i.e. an ionic PAG includes in the PAG molecule an ionic bond that involves an electrostatic attraction between oppositely charged ions, whereas a non-ionic PAG does not have any such ionic bonds, but rather typically has all covalent-type bonds. See, for example, Morrison and Boyd,
Organic Chemistry
, pages 3-5 (3
rd
ed., 1981).
The invention also provides photoresist compositions that comprise a blend of an ionic PAG and a non-ionic PAG. The PAG blend can be used in a variety of resist systems, and preferably a PAG blend is employed in a resist composition that comprises an acrylate-containing polymer as a resin binder component. In particular, the PAG blend is preferably formulated in a chemically-amplified positive-acting resist, where the resist contains a polymer with photoacid-labile groups, particularly pendant acid-labile groups such as can be provided by condensation of alkyl acrylate monomers, e.g. an alkyl acrylate-phenol copolymer, or a polymer that contains alkyl acrylate repeat units and that is essentially or completely free of phenyl or other aromatic units. Unless otherwise indicated, the term acrylate as used herein refers to vinyl esters in general, including substituted compounds such as methacrylate and the like.
The invention also provide methods for forming relief images of the photoresists of the invention, including methods for forming highly resolved patterned photoresist images (e.g. a patterned line having essentially vertical sidewalls) of sub-micron and even sub-half micron dimensions.
The present invention further provides articles of manufacture comprising substrates such as a microelectronic wafer or a flat panel display substrate having coated thereon the photoresists and relief images of the invention. Other aspects of the invention are disclosed infra.
DETAILED DESCRIPTION OF THE INVENTION
As discussed above, PAG blends of the invention comprise at least one ionic PAG and at least one non-ionic PAG.
A variety of ionic PAGs can be employed in the PAG blends and photoresist compositions of the invention.
Onium salts are generally preferred ionic PAGs for use in accordance with the invention. Examples of suitable onium salts include those that contain halogen complex anions of divalent to heptavalent metals or non-metals, for example, Sb, Sn, Fe, Bi, Al, Ga, In, Ti, Zr, Sc, D, Cr, Hf, and Cu as well as B, P, and As. Examples of suitable onium salts are diaryl-diazonium salts and onium salts of group Va and B, Ia and B and I of the Periodic Table; for example, halonium salts, quaternary ammonium, phosphonium and arsonium salts, aromatic sulfonium salts and sulfoxonium salts or selenium salts. Onium salts have been described in the literature such as in U.S. Pat. Nos. 4,442,197; 4,603,101; and 4,624,912.
Generally preferred onium salts are iodonium salt photoacid generators, such as those compounds disclosed in published European application 0 708 368 A1. Such salts include those represented by the following formula:
where Ar
1
and Ar
2
each independently represents a substituted or unsubstituted aryl group. A preferred example of the aryl group includes a C
6-14
monocyclic or a condensed ring aryl group. Preferred examples of the substituent on the aryl group include an alkyl group, a haloalkyl group, a cycloalkyl group, an aryl group, an alkoxy group, a nitro group, a carboxyl group, an alkoxycarbonyl group, a hydroxyl group, mercapto group, and a halogen atom.
Two particularly suitable iodonium PAGs are the following PAGS 1 and 2:
Such compounds can be prepared as disclosed in European Patent Application 96118111.2 (publication number 0783136), which details the synthesis of above PAG 1. Briefly, PAG 1 can be prepared by reaction of a mixture of potassium iodate, t-butylbenzene and acetic anhydride with sulfuric acid added dropwise to the mixture with ice-bath cooling. The reaction mixture is then stirred at room temperature for approximately 22 hours, water added with cooling to about 5-10° C. and then washing with hexane. The aqueous solution of diaryliodium hydrogensulfate is then cooled to about 5-10° C. and then (+/−)-10-camphorsulfonic acid added followed by neutralization with ammonium hydroxide.
Also suitable are the above two iodonium compounds complexed with anions other than the above-depicted camphorsulfonate groups. In particular, preferred anions include those of the formula RSO
3
−
where R is adamantane, alkyl (e.g. C
1-12
alkyl) and perfluoroalkyl such as perfluoro (C
1-12
alkyl), particularly perfluoro counter anions of perfluorooctanesulfonate, perf
Ashton Rosemary
Corless Peter F.
Edwards & Angell LLP
Frickey Darryl P.
Shipley Company L.L.C.
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