Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-12-27
2001-07-31
Chu, John S. (Department: 1752)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S216000, C525S219000, C430S270100, C430S905000
Reexamination Certificate
active
06268436
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to semiconductor manufacturing and, in particular, to a high-performance irradiation sensitive positive-tone resist for use in mid-ultraviolet (UV), deep-UV, extreme UV, X-ray and e-beam lithography and to a method of formulating said positive-tone resist. In one aspect of the present invention, a polymer resin composition comprising a blend of at least two miscible aqueous base soluble polymer resins that are partially protected with different acid labile protecting groups is provided. The present invention also provides a chemically amplified resist system comprising the polymer resin composition of the present invention.
BACKGROUND OF THE INVENTION
In the field of semiconductor manufacturing, optical lithography has been the main stream approach to pattern semiconductor devices. In typical prior art lithography processes, UV light is projected onto a silicon wafer coated with a thin layer of photosensitive resist through a mask that defines a particular circuitry pattern. Exposure to UV light, followed by subsequent baking, induces a photochemical reaction which changes the solubility of the exposed regions of the photosensitive resist. Thereafter, an appropriate developer, usually an aqueous base solution, is used to selectively remove the resist either in the exposed regions (positive-tone resists) or, in the unexposed region (negative-tone resists). The pattern thus defined is then imprinted on the silicon wafer by etching away the regions that are not protected by the resist with a dry or wet etch process.
Many of the currently used resists are chemically amplified positive-tone resists which are made of two major components: The first component of such chemically amplified positive-tone resists is an aqueous base soluble polymer resin where the polar functional groups of the polymer resin are partially protected by acid labile protecting (or so-called blocking) groups. The presence of such protecting, i.e. blocking, groups makes the polymer resin base insoluble. Acid catalyzed deprotection of the protected sites converts the polymer resin back into an aqueous base soluble polymer.
The second major component of prior art chemically amplified positive-tone resists is a photoacid generator. Exposure of these resists to UV irradiation typically generates an acidic catalytic species as a result of the photochemistry of the acid precursor. The catalytic species is believed to induce a cascade of subsequent chemical transformations of the polymer resins that alter the solubility of the exposed regions. Thus, the quantum efficiency of the photochemical event is amplified hundreds or even thousands of times through the catalytic chain reaction. The most commonly employed chemical amplification involves the acid catalyzed deprotection of various partially protected poly(p-hydroxystyrene), poly(acrylic acid), or copolymers thereof for positive-tone resists. The chemical amplification of resist materials are described in detail in U.S. Pat. Nos. 4,491,028 to Ito, 5,252,435; to Tani, et al.; 5,258,257 to Sinta, et al.; 5,352,564 to Takeda, et al.; 5,210,000 to Thackeray, et al; and 5,585,220 to Breyta.
The acid labile protecting groups used with the aqueous base soluble polymers can be classified into two distinct groups: (I) High activation energy protecting groups such as t-butyl ester or t-butyl carbonyl groups; and (II) Low activation energy protecting groups such as acetal, ketal or silylether groups.
Resists containing aqueous base soluble polymer resins protected with high activation energy protecting groups generally require a post-exposure baking step to effect the deprotection and solubility switch due to the high bonding energy. In the case of polymer resins containing low activation energy protecting groups, a post-exposure baking step of the resist is not necessarily required because of the facile deprotection chemistry of this group which generally occurs at about room temperature.
Accordingly, each of the foregoing acid labile protecting groups has their own advantages and disadvantages associated therewith. For example, the high activation energy protecting groups tend to give rise to high resolution, but suffer from environmental contamination during the post-exposure delay. On the other hand, the low activation energy protecting groups tend to exhibit robust environmental stability, however they normally suffer from line width slimming and shelf-life problems.
In view of the state of prior art resists, it would be beneficial if a new polymer resin composition could be formulated which incorporates the advantages of both types of protecting groups in a single resist while eliminating the disadvantages associated with each protecting group. That is, there is a continued need to develop a new and improved polymer resin composition which exhibits high resolution upon exposure to UV irradiation, good environmental stability and that could be used to pattern semiconductor circuitries.
SUMMARY OF THE INVENTION
One object of the present invention is provide a simple and highly manufacturable method of formulating high performance positive-tone resists that combine all of the desirable features and/or properties of each of the above-mentioned protecting groups into a single resist.
Another object of the present invention is to provide a method of formulating a positive-tone resist that exhibits high resolution and good environmental stability.
A further object of the present invention is to provide a positive-tone polymer resin composition and resist system that can be used in semiconductor manufacturing, and, in particular, in the patterning of semiconductor circuitries.
These and other objects and advantages are achieved in the present invention by blending at least two miscible aqueous base soluble polymer resins having different acid labile protecting groups together. Specifically, the method of the present invention comprises the step of:
(a) blending one aqueous base soluble polymer resin that is partially protected with a low activation energy protecting group with another aqueous base soluble polymer resin that is partially protected with a high activation energy protecting group, wherein said aqueous base soluble polymer resins are miscible with one another.
In another aspect of the present invention, a polymer resin composition which is employed in fabricating and/or patterning semiconductor devices is provided. Specifically, in this aspect of the present invention, the polymer resin composition comprises a blend of at least two miscible aqueous base soluble polymer resins, wherein one of said aqueous base soluble polymer resins is partially protected with a high activation energy protecting group and the other aqueous base soluble polymer resin is partially protected with a low activation energy protecting group.
A further aspect of the present invention is directed to a positive-tone chemically amplified resist system which comprises (a) the polymer resin composition of the present invention; (b) an acid generator; (c) a solvent for said polymer resin composition; and, optionally, (d) a photosensitizer that is capable of absorbing irradiation in the mid-UV, deep-UV, extreme-UV, X-ray or e-beam range. The chemically amplified resist system of the present invention may further comprise (e) a base and/or (f) a surfactant.
DETAILED DESCRIPTION OF THE INVENTION
In one aspect of the present invention, a polymer resin composition useful in formulating a positive-tone resist which comprises a blend of at least two miscible aqueous base soluble polymer resins, wherein one of said aqueous base soluble polymer resins is partially protected with a high activation energy protecting group and the other aqueous base soluble polymer resin is partially protected with a low activation energy protecting group is provided. The term miscible, is used herein to denote polymer resins which, after mixing and processing, show no detectable phase separation under optical and/or electron microscopy.
The polymer resins employed in the
Chen Kuang-Jung
Dellaguardia Ronald A.
Huang Wu-Song
Katnani Ahmad D.
Khojasteh Mahmoud M.
Capella, Esq. Steven
Chu John S.
International Business Machines - Corporation
Scully Scott Murphy & Presser
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