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
2001-06-21
2003-10-21
Baxter, Janet (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
C430S281100, C430S286100, C430S287100, C430S288100
Reexamination Certificate
active
06635401
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 with 193 nm radiation lithography on the immediate horizon.
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). For example, the ability of the resist to wet and adhere to the underlying substrate must be adequate especially where relatively thin resist layers are employed to enhance resolution performance. The resist must also be relatively stable with good shelf life such that the required radiation dose to image the resist composition remains predictable.
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 often 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.
SUMMARY OF THE INVENTION
The invention provides resist compositions which are capable of high resolution lithographic performance with (a) improved stability/shelf-life, (b) improved etch resistance, (c) improved wettability, and/or (d) improved thin film adhesion. 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 2-cyano acrylic monomer units (hereafter also referred to as “CNA monomer”). The CNA monomer preferably is an acrylic acid or has a pendant ester group COO—R where R contains one or more functional and/or non-functional moieties such as acid-labile moieties, polar moieties, and/or non-acid-labile, non-polar moieties. The CNA monomer is generally capable of copolymerizing with cyclic olefins under free radical polymerization conditions.
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 at least some monomeric units. 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 imaging polymers containing CNA monomer.
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 CNA monomer units. These compositions are preferably capable of providing high resolution lithographic patterns using 193 nm radiation with (a) improved stability/shelf-life, (b) improved etch resistance, (c) improved wetability, and/or (d) improved thin film adhesion. 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 imaging polymers containing CNA monomer.
The resist compositions of the invention generally comprise (a) an imaging polymer, and (b) a radiation-sensitive acid generator, the imaging polymer comprising CNA monomer units. Preferred CNA monomeric units may be represented by the structure:
where R is H or COO—R is an ester group.
R preferably contains one or more moieties such as acid-labile moieties, polar moieties, and/or non-acid-labile, non-polar moieties.
The acid-labile moieties preferably act to inhibit solubility of the resist composition in aqueous alkaline solutions. The acid-labile moieties are preferably selected from the group consisting of tertiary alkyl (or cycloalkyl) esters (e.g., t-butyl, methyl cyclopentyl, methyl cyclohexyl, methyl adamantyl), ketals, and acetals. Tertiary butyl ester and methyl cyclopentyl ester are most preferred acid-labile protecting moieties.
Polar moieties preferably promote the solubility of the resist in aqueous alkaline solutions. Preferred polar moieties are selected from the group consisting of carboxylic acids, lactones, amides, imides, sulfonamides, —CH(CF
3
)OH, and —C(CF
3
)
2
OH.
The non-acid-labile, non-polar moieties are preferably selected from the group consisting of primary and secondary linear, branched, and cyclic alkyls, and/or aryls. The non-acid-labile, non-polar moieties preferably have 1-12 carbons. The alkyls are more preferred.
R may further include other moieties such as spacer groups between the functional moieties described above and the oxygen of the ester. Preferred spacers are C
x
H
2x
and C
x
H
2x
O
y
moieties where x and y are preferably 1-6.
The imaging polymer may be a homopolymer of the CNA monomer described above or may contain other monomeric units in addition to the CNA monomer. For example, the imaging polymer may contain one or more of the following: (a) cyclic olefin monomers containing acid labile moieties which inhibit the solubility of the resist in aqueous alkaline solutions, (b) cyclic olefin monomeric units having polar moieties w
Li Wenjie
Varanasi Pushkara Rao
Baxter Janet
Capella Steven
Gilliam Barbara
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