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
2000-08-16
2002-05-21
Chu, John S. (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, C430S910000
Reexamination Certificate
active
06391521
ABSTRACT:
BACKGROUND OF THE INVENTION
In the microelectronics industry as well as in other industries involving construction of microscopic structures (e.g. micromachines, magnetoresistive heads, etc.), there is a continued desire to reduce the size of structural features. In the microelectronics industry, the desire is to reduce the size of microelectronic devices and/or to provide greater amount of circuitry for a given chip size.
The ability to produce smaller devices is limited by the ability of lithographic techniques to reliably resolve smaller features and spacings. The nature of optics is such that the ability to obtain finer resolution is limited in part by the wavelength of light (or other radiation) used to create the lithographic pattern. Thus, there has been a continual trend toward use of shorter light wavelengths for lithographic processes. Recently, the trend has been to move from so-called I-line radiation (350 nm) to 248 nm radiation.
For future reductions in size, the need to use 193 nm radiation appears likely. Unfortunately, resist compositions at the heart of current 248 nm lithographic processes are typically unsuitable for use at shorter wavelengths.
While a photoresist composition must possess desirable optical characteristics to enable image resolution at a desired radiation wavelength, the photoresist composition must also possess suitable chemical and mechanical properties to enable transfer to the image from the patterned photoresist to an underlying substrate layer(s). Thus, a patternwise exposed positive photoresist must be capable of appropriate dissolution response (i.e. selective dissolution of exposed areas) to yield the desired photoresist structure. Given the extensive experience in the photolithographic arts with the use of aqueous alkaline developers, it is important to achieve appropriate dissolution behavior in such commonly used developer solutions.
The patterned photoresist structure (after development) must be sufficiently resistant to enable transfer of the pattern to the underlying layer(s). Typically, pattern transfer is performed by some form of wet chemical etching or ion etching. The ability of the patterned photoresist layer to withstand the pattern transfer etch process (i.e., the etch resistance of the photoresist layer) is an important characteristic of the photoresist composition.
While some photoresist compositions have been designed for use with 193 nm radiation, these compositions have generally failed to deliver the true resolution benefit of shorter wavelength imaging due to a lack of performance in one or more of the above mentioned areas. The resist compositions disclosed in the above-referenced applications represent advancement over the prior art in that the resists are capable of delivering the lithographic performance associated with 193 nm lithography, however there remains a desire for improved photoresist compositions useful in 193 nm lithography. For example, there is a desire for resist compositions exhibiting improved development characteristics (e.g., resolution, development speed, contrast, shrinkage, etc.), improved etch resistance, and improved lithographic process window.
SUMMARY OF THE INVENTION
The invention provides resist compositions which are capable of high resolution lithographic performance, especially using 193 nm imaging radiation. The resist compositions of the invention possess the combination of imageability, developability and etch resistance needed to provide pattern transfer at very high resolutions which are limited only by the wavelength of imaging radiation. The resist compositions of the invention are generally characterized by the presence of (a) an imaging polymer comprising a monomer selected from the group consisting of a cyclic olefin, an acrylate and a methacrylate, (b) a radiation-sensitive acid generator, and (c) a bulky anhydride additive.
The invention also provides lithographic methods using the resist compositions of the invention to create resist structures and methods using the resist structures to transfer patterns to an underlying layer(s). The lithographic methods of the invention are preferably characterized by the use of 193 nm ultraviolet radiation patternwise exposure. The methods of the invention are preferably capable of resolving features of less than about 150 nm in size, more preferably less than about 115 nm in size (using 0.68 numerical aperture optics) without the use of a phase shift mask.
In one aspect, the invention encompasses a resist composition comprising:
(a) an imaging polymer comprising a monomer selected from the group consisting of a cyclic olefin, an acrylate and a methacrylate,
(b) a radiation-sensitive acid generator, and
(c) a bulky anhydride additive.
The polymers of the invention are preferably cyclic olefin polymers. The bulky anhydride additive preferably contains at least 10 carbon atoms.
In another aspect, the invention encompasses a method of creating a patterned resist structure on a substrate, the method comprising:
(a) providing a substrate having a surface layer of the resist composition of the invention,
(b) patternwise exposing the resist layer to radiation whereby portions of the resist layer are exposed to radiation, and
(c) contacting the resist layer with an aqueous alkaline developer solution to remove the exposed portions of the resist layer to create the patterned resist structure.
Preferably, the radiation used in step (b) in the above method is 193 nm ultraviolet radiation.
The invention also encompasses processes for making conductive, semiconductive, magnetic or insulative structures using the patterned resist structures containing the compositions of the invention.
These and other aspects of the invention are discussed in further detail below.
DETAILED DESCRIPTION OF THE INVENTION
The resist compositions of the invention are generally characterized by the presence of (a) an imaging polymer comprising a monomer selected from the group consisting of a cyclic olefin, an acrylate and a methacrylate, (b) a radiation-sensitive acid generator, and (c) a bulky anhydride additive. These compositions are especially capable of providing high resolution lithographic patterns using 193 nm radiation with good developability and pattern transfer characteristics.
The invention further encompasses patterned resist structures containing the resist compositions of the invention, as well as processes for creating the resist structures and using the resist structures to form conductive, semiconductive and/or insulative structures.
The resist compositions of the invention preferably comprise:
(a) an imaging polymer comprising a monomer selected from the group consisting of a cyclic olefin, an acrylate and a methacrylate,
(b) a radiation-sensitive acid generator, and
(c) a bulky anhydride additive.
The imaging polymer is preferably a polymer having substantial transparency at about 193 nm wavelength radiation. The imaging polymer may be an acrylate polymer such as described in U.S. Pat. No. 5,580,694, the disclosure of which is incorporated herein by reference. More preferably, the imaging polymer contains at least some cyclic olefin monomer. Examples of polymer containing cyclic olefin monomers may be of the so-called alternating copolymer variety such as disclosed in U.S. Pat. Nos. 5,843,624 and 6,048,664 and in U.S. patent application Ser. No. 09/566,397, filed on May 5, 2000, entitled “Copolymer Photoresist with Improved Etch Resistance”; the disclosures of these documents is incorporated herein by reference. Most preferably, the imaging polymer is a non-alternating (as opposed to alternating copolymers where polymerization preferentially occurs in alternation sequence of monomers) copolymer containing cyclic olefin monomers. Examples of such non-alternating copolymers are described in the related patent applications cross-referenced above, the disclosures of which are incorporated herein by reference. Other examples of such non-alternating copolymers are described in U.S. patent application Ser. No. 09/566,395, filed on May 5, 2000, entit
Ito Hiroshi
Varanasi Pushkara Rao
Capella Steven
Chu John S.
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