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
1998-02-25
2001-10-16
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
C430S905000, C430S907000, C430S909000, C430S910000
Reexamination Certificate
active
06303263
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. In one aspect of the present invention, the positive-tone resist comprises an aqueous base soluble polymer resin wherein the polar functional groups of the polymer resin are blocked, i.e. protected, with at least two different acid labile protecting groups. Such a polymer composition is referred to herein as a “dual blocked polymer resin” since the polymer resin contains at least two different protecting groups. The present invention also provides a chemically amplified resist system comprising the dual blocked polymer resin 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 resists is an aqueous base soluble polymer where the polar functional groups are protected by acid labile protecting (or so-called blocking) groups. The presence of such protecting groups converts the aqueous base soluble polymer into an insoluble resin. Acid catalyzed deprotection of the protected sites converts the polymer 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 are believed to induce a cascade of subsequent chemical transformations of the resist 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. No. 4,491,628 to Ito; U.S. Pat. No. 5,252,435 to Tani, et al.; U.S. Pat. No. 5,258,257 to Sinta, et al.; U.S. Pat. No. 5,352,564 to Takeda, et al.; U.S. Pat. No. 5,210,000 to Thackeray, et al.; and U.S. Pat. No. 5,585,220 to Breyta.
The acid labile protecting groups used with the aqueous base soluble polymer resins 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 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 resists containing low activation energy protecting groups, a post-exposure baking step 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 resist 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 resist 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, yet highly manufacturable method of formulating high performance positive-tone resists that combine all of the best 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 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 providing an aqueous base soluble polymer resin having polar functional groups thereon wherein some, but not all, of said polar functional groups are blocked with at least two different protecting groups. These so-called “dual blocked polymers” may contain either low activation energy protecting groups, high activation energy protecting groups, or mixtures thereof with the proviso that it contains at least two different protecting groups.
A further aspect of the present invention is directed to a positive-tone chemically amplified resist system which comprises (a) the polymer resin of the present invention, i.e. dual blocked polymer; (b) an acid generator; (c) a solvent for said polymer resin; 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 for said dual blocked polymer and/or (f) a surfactant.
DETAILED DESCRIPTION OF THE INVENTION
As stated above, the present invention provides a dual protected polymer resin which comprises an aqueous base soluble polymer resin having polar functional groups thereon, wherein some, but not, all of said polar functional groups are protected with at least two different acid labile protecting groups.
The aqueous base soluble polymer resins employed in the present are typically well known to those skilled in the resist material art. Generally, the aqueous base soluble polymer resins employed in the present invention are homopolymers containing one monomeric repeating unit or higher polymers, i.e. copolymers, terpolymers, etc., containing two or more monomeric repeating units that are soluble in an alkaline solution. Moreover, the aqueous soluble base polymer resins employed in the present invention are those that contain polar functional groups that readily ionize. The polar functional groups of the polymer resins are generally hydroxyl or carboxyl functionalities.
Illustrative examples of suitable homopolymers that can be utilized in the present invention include, but are not limited to: phenolic-containing resins such as poly(hydroxystyrene) including the para-, meta-, and ortho-substituted forms and phenol formaldehydes; poly
Chen Kuang-Jung
Dellaguardia Ronald A.
Huang Wu-Song
Katnani Ahmad D.
Khojasteh Mahmoud M.
Capella, Esq. Steven
Chu John S.
International Business Machines Machines
Scully Scott Murphy & Presser
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