Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-08-26
2003-05-27
Zalukaeva, Tatyana (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S259000, C526S270000, C526S271000, C526S272000, C526S313000, C526S348400, C430S296000, C430S270210
Reexamination Certificate
active
06569971
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to photoresist monomers, polymers formed therefrom, and photoresist compositions containing same, more specifically, photoresist monomers, polymers and a photoresist compositions suitable for photolithography processes employing DUV (deep ultraviolet) light sources such as KrF(249 nm) and ArF(193 nm); EUV; VUV; E-beam; ion-beam; and X-ray.
BACKGROUND OF THE INVENTION
Recently, chemical amplification type DUV photoresists have been investigated in order to achieve high sensitivity in minute image formation processes for preparing semiconductor devices. Such photoresists are prepared by blending a photoacid generator and matrix resin polymer having acid labile group.
According to the reaction mechanism of such a photoresist, the photoacid generator generates acid when it is illuminated by a light source, and the main chain or branched chain of the resin is reacted with the generated acid to be decomposed or crosslinked. The polarity change of the resin induces solubility differences between the exposed portion and unexposed portion in the developing solution, to form a predetermined pattern.
In the lithography process, resolution depends upon the wavelength of the light source—the shorter the wavelength, the more minute pattern can be formed.
In general, a photoresist (hereinafter, abbreviated to as “PR”) must satisfy various requisites such as excellent etching resistance, heat resistance and adhesiveness, and more preferably, it should be developable in 2.38% aqueous tetramethylammonium hydroxide (TMAH) solution. However, it is very difficult to synthesize a polymer that satisfies all of these requisites. For example, a polymer having a polyacrylate main chain can be easily synthesized, but it has poor etching resistance and has difficulties in the developing process. In order to secure-etching resistance, it has been considered to add an alicyclic unit to the main chain. However, in this case, it is very difficult to form a copolymer wherein the main chain is comprised entirely of alicyclic units.
As an attempt to solve the problems described above, Bell Research Center developed a polymer having the following chemical structure, wherein the main chain is substituted with norbornene, acrylate and maleic anhydride units.
However, the above polymer has a problem in that the maleic anhydride moiety (‘A’ portion), which is employed to polymerize alicyclic olefin groups, is readily dissolved in 2.38 wt % aqueous TMAH solution even in an unexposed condition. Thus, in order to inhibit the dissolution of the polymer in the unexposed section, the ratio of ‘Y’ portion having tert-butyl substituent should be increased, but this results in a relative decrease of the ‘Z’ portion (which has a role of increasing adhesiveness to the substrate), and therefore the PR might be easily separated from the substrate at the time of patterning.
In order to solve the problem, cholesterol type dissolution inhibitors have been added to the polymer to form a two-component system. However, since the amount of the dissolution inhibitor is very high [about 30%(w/w) of the resin], reappearance is low and the production cost is high, thereby making the system unsuitable as a PR.
SUMMARY OF THE INVENTION
An object of the present invention is to provide PR monomers which can form polymers having excellent etching resistance, adhesiveness and photosensitivity, and processes for preparing the same.
Another object of the present invention is to provide PR polymers having excellent etching resistance, adhesiveness and photosensitivity, wherein the unexposed portion is not easily dissolved by developing solution, and processes for preparing the same.
Another object of the present invention is to provide photoresist compositions using the novel photoresist polymers described above, and processes for preparing the same.
In order to achieve the aforementioned objects, the present invention provides a photoresist monomer represented by the following Chemical Formula 1.
wherein, m is 1 or 2.
In order to achieve the other objects, the present invention provides photoresist copolymer comprising said monomer of Formula 1. Preferably, photoresist copolymers of the present invention comprise (i) a compound represented by the above mentioned Chemical Formula 1 as a first comonomer, and (ii) as a 2
nd
comonomer, a compound represented by the following Chemical Formula 2:
wherein,
R* is an acid-labile group, and
l is 1 or 2.
In order to achieve further objects of the present invention, a photoresist composition is provided which includes (i) a photoresist copolymer according to the present invention, (ii) a photoacid generator and (iii) an organic solvent.
DETAILED DESCRIPTION OF THE INVENTION
It has been found that polymers formed from the monomer represented by Chemical Formula 1 below (i) shows good etching resistance since it is a cycloolefin compound, (ii) has a good adhesiveness to a semiconductor substrate and (iii) has the preferred photosensitivity.
wherein, m is 1 or 2.
Considering the characteristics of the compound represented by the above Chemical Formula 1, we have found that a copolymer which comprises (i) the compound represented by Chemical Formula 1 as a first monomer, and (ii), as a second comonomer, the compound represented by the following Chemical Formula 2, which functions as an dissolution inhibitor, is suitable for photolithography employing short-wavelength light sources.
wherein,
R* is an acid-labile group, and
l is 1 or 2.
In the Chemical formula 2, the R* is released when it is reacted with the acid generated by the photoacid generator. Thus, while the photoresist polymer in the exposed region becomes soluble in the developing solution, the polymer in the unexposed region is not dissolved in the developing solution because acid is not generated therein and thus the acid labile groups are still bound to the photoresist polymer. As the result, a predetermined pattern is formed.
In this way, the compound of Chemical Formula 2 has a role of enhancing photosensitivity of the photoresist polymer by increasing the difference in solubility in the developing solution between the exposed portion and the unexposed portion of the photo resist.
Though the acid labile group R* can have any structure that can be dissociated from the main alicyclic structure by reacting with an acid, preferable acid labile groups are tert-butyl, 2-tetrahydrofuranyl, 2-tetrahydropyranyl, 2-ethoxyethyl or t-butoxyethyl.
The photoresist copolymer according to the present invention can be prepared by using a polymerization initiator or by using a metal catalyst. In the case of synthesis using a polymerization initiator, maleic anhydride(Chemical formula 3) or maleimide derivatives can be added as a polymerization-enhancing monomer which makes the polymerization reaction between cycloolefin compounds more efficient. However, when performing polymerization using a metal catalyst, such polymerization-enhancing monomer is not necessarily required.
A compound having alcohol groups, as represented by the following Chemical Formula 4, can be further added as a monomer in order to intensify adhesion of the photoresist to the substrate. In addition, a monomer having at least one carboxylic acid group which is represented by the following Chemical Formula 5 may be added to the polymer in order to intensify photosensitivity.
wherein,
R
1
is —OH or —R—OH,
wherein R is substituted or non-substituted (C
1
-C
10
) alkyl, substituted or non-substituted (C
1
-C
10
) ether, substituted or non-substituted (C
1
-C
10
) ester or, substituted or non-substituted (C
1
-C
10
) ketone,
R
2
is H or R
1
,
R
3
is H or —COOR
and n is 1 or 2.
wherein,
R4 is —COOH or —R—COOH,
k is 1 or 2 and
R is as same as defined in the Chemical Formula 4.
Preferably, the average molecular weight of the photoresist copolymer according to the present invention is between 3,000 to 100,000.
A synthesizing method using a polymerization initiator is performed by reacting the comonomers, including at least one of
Jung Jae Chang
Roh Chi Hyeong
Hyundai Electronics Industries Co,. Ltd.
Townsend and Townsend / and Crew LLP
Zalukaeva Tatyana
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