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
2000-11-01
2002-09-24
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
C430S905000, C430S322000, C430S909000, C522S109000, C522S038000, C525S060000, C525S074000
Reexamination Certificate
active
06455226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to photoresist polymers and photoresist compositions comprising the same. Photoresist polymers and photoresist compositions of the present invention are suitable for a photolithography process employing a deep ultraviolet light source, preferably vacuum ultraviolet(VUV, 157 nm) or extreme ultraviolet (EUV, 13 nm).
2. Description of the Background Art
A photoresist (PR) polymer for an ArF or VUV photolithography process should have a variety of physical characteristics, such as low absorbency of 193 nm and 157 nm wavelengths, and excellent etching resistance and adhesiveness. In addition, the photoresist should be easily developable in a commercially readily available developing solution, such as 2.38 wt % or 2.6 wt % aqueous tetramethylammonium hydroxide (TMAH) solution.
There has been much research done on resins having a high transparency at a wavelength of 193 nm and dry etching resistance similar to Nobolac resin. However, most of the photoresists are not suitable for VUV due to their poor transmittance at 157 nm wavelength. Photoresists containing fluorine and silicon have good transmittance at these wavelengths. Unfortunately, most photoresists containing fluorine with a polyethylene or polyacrylate polymer backbone have weak etching resistance, low solubility in an aqueous TMAH solution and poor adhesiveness to the silicon wafer. In addition, these photoresists are difficult to mass-produce and are expensive. Furthermore, during a post-exposure bake (PEB) process these photoresist can generate HF which can contaminate a lens or corrode a device. Thus, these photoresists are generally not suitable for commercial use. On the other hand, photoresists containing silicon require a 2-step process such as HF treatment and O
2
treatment during the etching process. And because it is difficult to remove HF completely, these types of photoresists are generally not suitable in the production of semiconductor devices.
SUMMARY OF THE INVENTION
An object of the present invention is to provide photoresist polymers having a good transmittance at wavelengths of 157 nm or 13 nm, etching resistance, adhesiveness and photosensitivity, and a process for preparing the same.
Another object of the present invention is to provide photoresist compositions comprising the PR polymers described above, and a process for preparing the same.
Still another object of the present invention is to provide a semiconductor element produced by using the photoresist composition.
DETAILED DESCRIPTION OF THE INVENTION
One aspect of the present invention provides a photoresist polymer of the Formula:
wherein
Y is H;
R
1
is a hydroxy protecting group; and
the ratio of a:b:c is 10-90 mol %:5-45 mol %:5-45 mol %, preferably 50 mol %:5-45 mol %:5-45 mol %. The terminal groups in Formula 4 depends on the polymerization initiator and polymerization terminator.
As used throughout this disclosure, it should be appreciated that the order of each monomeric units represented in a polymer formula of the present invention does not necessarily indicate the actual order of such monomeric units in the actual polymer. The monomeric units represented in polymer formulas are intended to simply indicate the presence of such monomeric unit in the polymer. Moreover, the variables represent the total relative ratio of each units. For example, the total amount “a” of polymeric units derived from norborylene of Formula 4 above can be inter dispersed throughout the polymer (not necessarily in same concentrations) or all or majority of such polymeric unit can be concentrated in one particular location of the polymer.
Variety of hydroxy protecting groups are known to one of ordinary skill in the art. Exemplary hydroxy protecting groups can be found in, for example,
Protective Groups in Organic Synthesis,
3rd edition, T. W. Greene and P. G. M. Wuts, John Wiley & Sons, New York, 1999, which is incorporated herein by reference in its entirety. Preferably, the hydroxy protecting group is an acetal. More preferably, the hydroxy protecting group is of the formula: —CH(CH
3
)OR
4
, where each R
4
is independently optionally substituted linear or branched (C
1
-C
20
) alkyl or aryl, or 5-7 membered cyclic lactam.
Examples of preferred polymers of the present invention include, but are not limited to:
wherein the ratio of a:b:c is 10-90 mol %:5-45 mol %:5-45 mol %.
Polymers of the present invention can be prepared by a variety of methods. In one particularly preferred method, polymers of the present invention are prepared by (1) synthesizing a copolymer of alicyclic monomer and maleic anhydride (or a derivative of maleic anhydride; (2) esterifying the copolymer; and (3) reducing the esterified copolymer to lower light absorbency in the wavelength of 157 nm.
In one particular embodiment of the present invention, a process for preparing photoresist polymer of the Formula 4 comprises the steps of:
(a) polymerizing norbornylene and a maleic anhydride derivative to produce a polymer of Formula 1;
(b) contacting the polymer of Formula 1 with an alcohol to produce a polymer of Formula 2;
(c) contacting the polymer of Formula 2 with a reducing agent to produce a polymer of Formula 3; and
(d) reacting the polymer of Formula 3 with a hydroxy protecting group precursor to produce at least a partially hydroxy protected polymer of Formula 4.
wherein,
Y is H; and
the ratio of a:d is 10-90 mol %:10-90 mol %.
The alcohol in step (b) is preferably a lower alcohol of the formula R
5
OH, where R
5
is (C
1
-C
5
) alkyl, more preferably, the alcohol is methanol. The degree of esterification is generally determined by the amount of R
5
OH used. For example, when an excess amount of R
5
OH is used in step (b), theoretically all the carboxylic acid groups in Formula 1 can be esterified. However, it is possible that 5% or less of carboxylic acid group remains unesterified depending on a variety of factors such as reaction conditions including the purity of R
5
OH.
In one embodiment, the reducing agent in step (c) is preferably NaBH
4
.
Alternatively, the polymer of Formula 3 can be prepared from the polymer of Formula 1 by reducing the polymer of Formula 1 directly. In such a process, the reducing agent is preferably LiAlH
4
.
As used herein, the term “hydroxy protecting group precursor” refers to a compound which when reacted with a hydroxy functional group results in the protection of the hydroxy functional group. Such hydroxy protecting group precursors are well known to one of ordinary skill in the art and include compounds that are disclosed in the above disclosed
Protective Groups in Organic Synthesis,
3rd edition, which was previously incorporated by reference in its entirety. In one particular embodiment, the hydroxy protecting group precursor is a (C
1
-C
20
) alkyl or aryl vinyl ether compound, including tert-butylvinylether, ethylvinylether and cyclohexylvinylether.
The polymerization can be conducted in an organic solvent. Preferably, the polymerization solvent is selected from the group consisting of tetrahydrofuran, dimethylformamide, dimethylsulfoxide, dioxane, benzene, toluene and xylene. The polymer can be separated and/or purified by crystallization. Preferably the polymer crystallization solvent is selected from the group consisting of diethylether, petroleum ether, water, lower alcohols (such as methanol, ethanol, and isopropanol), and mixtures thereof.
One particular embodiment for preparing photoresist polymers of the present invention is illustrated in Reaction Scheme 1:
where R
1
, R
5
, Y, a, b, c, and d are those defined above.
Another aspect of the present invention provides polymers of Formulas 2 and 3. These polymers can be used as intermediate polymers in the preparation of photoresist polymers of Formula 4.
Yet another aspect of the present invention provides a photoresist composition comprising a photoresist polymer described above, a photoacid generator, and an organic solvent.
Preferred photoacid generators have a relatively low light absorbency
Baik Ki Ho
Jung Jae Chang
Kim Hyeong Soo
Lee Geun Su
Baxter Janet
Clarke Yvette M.
Hyundai Electronics Industries Co,. Ltd.
Townsend and Townsend / and Crew LLP
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