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
2000-05-05
2001-06-26
Ashton, Rosemary E. (Department: 1756)
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
Reexamination Certificate
active
06251560
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 photolithographic 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 photolithographic 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, photoresist compositions at the heart of current 248 nm photolithographic 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 photoresist compositions which are capable of high resolution lithographic performance using 193 nm imaging radiation (and possibly also with other imaging radiation). The photoresist compositions of the invention possess an improved 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 photoresist compositions of the invention enable an improved lithographic process window.
The invention also provides lithographic methods using the photoresist compositions of the invention to create photoresist structures and methods using the photoresist 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 130 nm in size without the use of a phase shift mask.
In one aspect, the invention encompasses a photoresist composition comprising: (a) a cyclic olefin polymer, and (b) a photosensitive acid generator, the cyclic olefin polymer comprising:
i) cyclic olefin monomer units each having an acid-labile moiety that inhibits solubility in aqueous alkaline solutions, and
ii) cyclic olefin monomer units each having a lactone moiety, the monomer having no oxygen atoms intervening between the lactone moiety and a ring of the cyclic olefin.
The photoresist compositions of the invention preferably also contain a bulky hydrophobic additive component which is substantially transparent to 193 nm ultraviolet radiation. The cyclic olefin polymers of the invention preferably contain at least about 5 mole % of units ii).
In another aspect, the invention encompasses a method of creating a patterned photoresist structure on a substrate, the method comprising:
(a) providing a substrate having a surface layer of the photoresist composition of the invention,
(b) patternwise exposing the photoresist layer to radiation whereby portions of the photoresist layer are exposed to radiation, and
(c) contacting the photoresist layer with an aqueous alkaline developer solution to remove the exposed portions of the photoresist layer to create the patterned photoresist 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 photoresist 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 photoresist compositions of the invention are generally characterized by the presence of cyclic olefin polymers which contain a cyclic olefin monomer having a lactone moiety, the monomer having no oxygen atoms intervening between the lactone moiety and a ring of the cyclic olefin. These compositions are capable of providing high resolution photolithographic patterns using 193 nm radiation with improved developability and pattern transfer characteristics. The invention further encompasses patterned photoresist structures containing the photoresist compositions of the invention, as well as processes for creating the photoresist structures and using the photoresist structures to form conductive, semiconductive and/or insulative structures.
The photoresist compositions of the invention generally comprise (a) a cyclic olefin polymer, and (b) a photosensitive acid generator, the cyclic olefin polymer comprising:
i) cyclic olefin monomer units each having an acid-labile moiety that inhibits solubility in aqueous alkaline solutions, and
ii) cyclic olefin monomer units each having a lactone moiety, the monomer having no oxygen atoms intervening between the lactone moiety and a ring of the cyclic olefin.
Cyclic olefin units i) may be any cyclic olefin monomeric unit having an acid labile moiety that inhibit solubility in aqueous alkaline solutions. Examples of cyclic olefin monomers include the following monomers illustrated by structure (I) below where R
1
represents an acid-labile protecting moiety and n is zero or some positive integer (preferably n is 0 or 1):
More preferably, the cyclic olefin units i) are selected from:
where R
1
represents an acid-labile protecting moiety. Preferred acid-labile protecting moieties are selected are selected from the group consisting of tertiary alkyl (or cycloalkyl) carboxyl esters (e.g., t-butyl, methyl cyclopentyl, methyl cyclohexyl, methyl adamantyl), ester ketals, and ester acetals. Tertiary butyl carboxyl ester is a most preferred acid-labile protecting moiety. If desired, combinations
Allen Robert D.
Brock Phillip Joe
DiPietro Richard Anthony
Ito Hiroshi
Truong Hoa Dao
Ashton Rosemary E.
Capella Steven
International Business Machines - Corporation
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