Positive working photoresist composition

Details Positive working photoresist composition Positive working photoresist composition

2000-06-01

2002-05-28

Ashton, Rosemary (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, C430S325000, C430S326000, C430S921000, C568S018000, C568S077000

Reexamination Certificate

active

06395450

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a positive working photoresist composition with high sensitivity and resolution, and with good photosensitivity to various radiations, such as KrF excimer laser light. More particularly, the present invention relates to a positive working photoresist composition which comprises at least one thermally cross-linkable photoacid generator, a binder polymer, and a solvent in which the binder polymer and photoacid generator are dissolved.
BACKGROUND OF THE INVENTION
A positive photoresist composition for precise processing is an important material in the microlithography which leads to an improved integration of LSI semiconductors. The photoresists should have etching resistance to form relief images on the substrate upon exposure to actinic radiation, such as UV, deep UV or X-ray radiation, or to electron beams.
The integration of LSI semiconductors has been rapidly improved in recent years, and the improvement of the integration can be achieved through precise processing. For this purpose, the photoresists should have high resolution, sensitivity, and etching resistance. A conventional method of forming a precise pattern shall be described as follows:
A photoresist composition is coated by spin coating on a silicon wafer, the coated Si wafer is baked at high temperature, and the resist is exposed to actinic radiation through a pattern mask. The exposed resist on the Si wafer is post-exposure baked at high temperature again, and the Si wafer is developed in a developer solution to form a resist pattern. A dry etching or wet etching is conducted on the resist pattern so formed. When the exposed area of the resist is dissolved in a developer solution, the resist is called as positive working resist. When the exposed area of the resist is not dissolved in a developer solution (i.e., when the unexposed area of the resist is dissolved), it is called as negative working resist.
High sensitivity is required of a resist in order to increase productivity. High resist sensitivity can be achieved through chemical amplification based upon acid catalyst reaction in the resist. Such a chemical amplification resist includes a photoacid generator in its composition. An acid is produced by the photoacid generator during exposure, and amplified during post-exposure bake (PEB) to produce a catalyst reaction such as degradation and cross-linking. As the amplification distance of the acid is as short as about 5 nm, a resist having high resolution and sensitivity can be obtained.
Recently a new chemical amplification type resist has been disclosed, which is based upon a thermal cross-linking reaction of acid labile vinyl ether groups and a degradation reaction of the acid labile groups. This type of resist includes as a binder a polymer of phenol resin having vinyl ether groups partially on the side chain, and a photoacid generator. The resist film, coated on a Si wafer, is cross-linked by a thermal cross-linking reaction of the vinyl ether groups with the phenol portion during post-apply bake (PAB). When being exposed to actinic radiation, the photoacid generator produces acid, which is amplified during PEB to cause a degradation reaction of the acetal-based cross-linked network. Accordingly, a positive-tone chemically amplified resist is obtained. An onium salt is used as a photoacid generator. However, the onium salt produces a hydrophobic compound during degradation, which will inhibit the solubility of the resist on the exposed portion so as to degrade the sensitivity and resolution of the resist.
The present inventors filed patent applications in Korea (Korean Patent Application Nos. 97-53062 and 97-52797) on new photoresist compositions in which a triphenyl sulfonium salt having vinyl ether groups therein is employed as a thermal cross-linking photoacid generator, and polyhydroxystyrene as a binder polymer. The sulfonium salt functions not only as a photoacid generator, but also as a cross-linking agent. The vinyl ether groups of the photoacid generator react with the Brönsted acid of the binder polymer during PAB to form an acetal-based cross-linked network. Upon exposure to actinic radiation, the sulfonium salt forming the acetal-based cross-linked network is degraded, resulting in increased solubility of the exposed portion. Also, the exposure to actinic radiation causes photodegradation of the photoacid generator to produce acid. The acid is amplified during PEB to produce a degradation reaction of the acetal-based cross-linked network by the action of the acid catalyst. Accordingly, the exposed portion is dissolved. The photoacid generator provides a photodegradable product having hydrophilic hydroxyl groups after photodegradation thereof. Consequently, the resist compositions of the foregoing Korean patent applications are distinguished from the conventional chemical amplification resist and have high sensitivity and resolution which are obtained through direct photodegradation and chemical amplification.
However, the aforementioned resist compositions have lower transmittance due to the use of large amounts of the photoacid generator. Further, a high temperature is required at the PAB step to accomplish the chemical cross-linking reaction. Furthermore, the photoacid generators usable in the resist compositions are limited to triflic acids, methanesulfonic acids, and halogenic acids.
A need exists for a new photoresist composition with high contrast and resolution and good photosensitivity.
SUMMARY OF THE INVENTION
A feature of the present invention is the provision of a positive working photoresist composition with high contrast and resolution, and with good photosensitivity to various radiations such as KrF excimer laser light.
Another feature of the present invention is the provision of a positive working photoresist composition with high transmittance.
A further feature of the present invention is the provision of a positive working photoresist composition with which the post-apply bake (PAB) is conducted at a from about temperature of about 90 to about 140° C.
A further feature of the present invention is the provision of a positive working photoresist composition in which various photoacid generators can be used.
In accordance with one aspect of the present invention, a photoresist composition is provided that includes at least one thermally cross-linkable photoacid generator, a binder polymer, and a solvent in which the binder polymer and photoacid generator are dissolved.
The thermally cross-linkable photoacid generator is represented by the general formula (I):
wherein
X is methanesulfonate, trifluoromethanesulfonate, 4-toluenesulfonate, 10-camphorsulfonate, cyclohexane sulfamate, perfluoro-1-butanesulfonate, perfluorooctanesulfonate, F, Cl, Br, SbF
6
, BF
4
, PF
4
, or AsF
6
,
R
1
is hydrogen or methyl, and
R
2
is alkyl of C
1-10
or vinyloxyethyl.
In more specific embodiments, R
2
in the thermally cross-linkable photoacid generator is methyl.
The binder polymer is represented by the general formula (II):
wherein R
1
and R
2
are different from each other and are selected from the group consisting of acid labile groups, hydrogen, methoxy, ethoxy, n-butoxy and t-butoxy, R
3
is hydrogen or alkyl of C
1-10
, R
4
is hydrogen or methyl, 0<o<1, 0≦p≦0.7, 0≦q≦0.7, and 0≦r≦0.3, wherein p, q and r are not 0 simultaneously.
In more specific embodiments, R
1
and R
2
in the binder polymer are groups such as 1-ethoxyethoxy, 1-isobutoxyethoxy, 1-cyclohexyloxyethoxy, 1-chloroethoxyethoxy, tetrahydropyranyloxy, t-butoxycarbonyloxy, trimethylsilyloxy, vinyloxyethyl, hydrogen, methoxy, ethoxy, n-butoxy or t-butoxy. R
3
in more specific embodiments is a group such as n-butyl or t-butyl.
The thermally cross-linkable photoacid generator preferably is employed in an amount from about 0.05 to about 15% by weight based on the weight of the binder polymer.
In accordance with another aspect of the present invention, a thermally cross-linkable photoacid generator as set forth above is provided.
In accordance with a fur

Affiliated with

Also associated with

Rating

Positive working photoresist composition does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Positive working photoresist composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Positive working photoresist composition will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2888520