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
2001-04-27
2003-03-18
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, C430S323000
Reexamination Certificate
active
06534239
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, photoresist compositions at the heart of current 248 nm lithographic processes are typically unsuitable for use at shorter wavelengths.
While a resist composition must possess desirable optical characteristics to enable image resolution at a desired radiation wavelength, the resist composition must also possess suitable chemical and mechanical properties to enable transfer to the image from the patterned resist to an underlying substrate layer(s). Thus, a patternwise exposed positive resist must be capable of appropriate dissolution response (i.e. selective dissolution of exposed areas) to yield the desired resist structure. Given the extensive experience in the lithographic arts with the use of aqueous alkaline developers, it is important to achieve appropriate dissolution behavior in such commonly used developer solutions.
The patterned resist 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 resist layer to withstand the pattern transfer etch process (i.e., the etch resistance of the resist layer) is an important characteristic of the resist composition.
While some resist 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 resist 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. There is especially a desire for resist compositions having improved shrinkage characteristics.
SUMMARY OF THE INVENTION
The invention provides resist compositions which are capable of high resolution lithographic performance with (a) reduced shrinkage upon exposure and/or post-exposure bake, (b) improved dissolution characteristics, and/or (c) improved formulation/applied film homogeneity. The resists of the invention are preferably imageable using 193 nm imaging radiation (and possibly also with other imaging radiation).
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 130 nm in size without the use of a phase shift mask.
In one aspect, the invention encompasses a resist composition comprising: (a) an imaging polymer, and (b) a radiation-sensitive acid generator, the imaging polymer comprising monomer units having group pendant from the polymerizing portion of the monomer, the pendant group containing plural acid labile moieties (hereafter also referred to as “PALM” group). The PALM group may be pendant from cyclic olefin monomer units or from other desired monomer units forming the backbone of the imaging polymer. The PALM group preferably has a bulky end group such as an alicyclic group and/or a medium chain hydrocarbon (e.g., C
6
-C
10
). In the absence of generated acid, the PALM group preferably inhibits solubility of the resist in aqueous alkaline solutions.
Preferably, the imaging polymer contains (i) cyclic olefin monomeric units in the polymer backbone (i.e., the polymerizable portion of monomeric units making up the polymer), and/or (ii) alicyclic moieties as bulky end groups on the end of the PALM group. In the absence of generated acid, the imaging polymer is preferably substantially insoluble in aqueous alkaline solutions such that the resist is a positive resist.
In another aspect, the invention encompasses the PALM-containing monomers and the imaging polymers containing the PALM-containing monomers.
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 imaging 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 an imaging polymer which contains monomer units having a pendant PALM group. These compositions are preferably capable of providing high resolution lithographic patterns using 193 nm radiation with (a) reduced shrinkage upon exposure and/or post-exposure bake, (b) improved dissolution characteristics, and/or (c) improved formulation/applied film homogeneity. 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 invention also encompasses polymerizable monomers having a pendant PALM group.
The resist compositions of the invention generally comprise (a) an imaging polymer, and (b) a radiation-sensitive acid generator, the imaging polymer comprising monomer units having a pendant PALM group. Preferred monomeric units containing the PALM group may be represented by the structure:
wherein:
(i) X is a component that forms at least one acid-labile bond with an oxygen of each neighboring carboxyl moiety and/or itself contains plural acid labile moieties,
(ii) M is a preferably polymerizing backbone moiety independently selected from the group consisting of an ethylenic moiety and a cyclic olefin moiety, or other suitably polymerizable moiety,
(iii) Z is a moiety independently selected from the group consisting of cycloalkyl, linear alkyl (C
1
-C
3
), or other compatible spacer moiety,
(iv) p is independently equal to 0 or 1, and
(v) Q is a
Lawson Margaret C.
Li Wenjie
Varanasi Pushkara Rao
Ashton Rosemary
Capella Steven
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