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
2000-09-14
2002-12-24
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
C430S914000, C552S552000, C552S555000
Reexamination Certificate
active
06497987
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive lithocholate derivative and to a chemically amplified photoresist composition containing the same.
This application is a counterpart of, and claims priority to, Korean Application No. 99-39337, filed Sep. 14, 1999, the contents of which are incorporated herein by reference.
2. Description of the Related Art
As semiconductor devices become highly integrated, photolithography processes used in the fabrication of such devices must be capable of forming ultra-fine patterns. For example, a sub-quarter micron or smaller sized pattern is needed in a semiconductor memory device having a capacity exceeding 1 Gbit. As such, a photolithography technology has beery proposed which employs an argon fluoride (ArF) excimer laser as a new type of light source. This is because the ArF laser exhibits a wavelength (193 nm) which is shorter than the wavelength (248 nm) of a conventional krypton fluoride KrF excimer laser. Therefore, a demand has arisen for chemically amplified photoresist polymers and photoresist compositions which are suitable for use with the ArF excimer laser.
In general, a chemically amplified photoresist composition for an ArF excimer laser should exhibit the following characteristics: (1) transparency at a wavelength of 193 nm; (2) high resistance to dry etching; (3) good adhesion to underlying (and overlying) film materials; and (4) easily capable of being developed using developing solutions which are in widespread use in the manufacture of semiconductor devices.
However, a terpolymer comprising methylmethacrylate, t-butyl methacrylate and methacrylic acid monomers, which is a widely known chemically amplified photoresist polymer for the ArF excimer laser, does not exhibit all of the above-mentioned characteristics. In particular, the terpolymer has a very low resistance to dry etching, and a low adhesion to underlying film materials.
Recently, attempts have been made to increase the etching resistance of a photosensitive polymer for the ArF excimer laser by introducing alicyclic compounds, for example, isobornyl, adamantyl or tricyclodecanyl group, into the backbone of the polymers. However, these polymers also have several disadvantages. For example, their etching resistance is still not acceptable and their adhesion characteristics to underlying films are still poor, which results in lifting of photoresist patterns.
U.S. Pat. No. 5,786,131 discloses mono-, di- ortri-protected hydroxy androstane-17-alkylcarboxylate such as t-butyl-3-acetyllithocholate, t-butyl 3-trifluoroacetyllithocholate or t-butyl lithocholate as an additives for increasing the etching resistance of a resist composition having poor etching resistance. While the lithocholate derivatives disclosed in this patent can be used as an additive for increasing the etching resistance of the resist composition, they cannot by themselves be used as a main component of the resist composition since they are brittle and exhibit poor wettability against a developing solution.
SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a photosensitive compound which maintains transparency even when exposed to a short-wavelength light source of 193 nm or below, and which has improved adhesion to an underlying film or substrate, improved wettability to a developing solution and improved resistance to dry etching.
It is another objective of the present invention to provide a chemically amplified photoresist composition containing the photosensitive compound.
According to one aspect of the present invention, there is provided a photosensitive lithocholate derivative having a carboxylic acid protected with a protective group capable of being deprotected with an acid and having a hydroxy at position No. 3 substituted with a hydrophillic atliphatic compound or a hydrophillic alicyclic compound selected from the group consisting of alken glycol, poly(alken glycol), alken glycol aliphatic hydrocarbon ether and alken glycol alicyclic hydrocarbon ether, poly(alken glycol) aliphatic hydrocarbon ether and poly(alken glycol) alicyclic hydrocarbon ether.
According to another aspect of the present invention, there is provided a chemically amplified photoresist composition including a first photosensitive lithocholate derivative, a second photosensitive lithocholate derivative, or a mixture thereof, and a photoacid generator contained in an amount of 1 to 15% by weight based on the total weight of the photosensitive lithocholate, wherein the first photosensitive lithocholate derivative has a carboxylic acid protected with a protective group capable of being deprotected with an acid and having a hydroxy at position No. 3 substituted with a hydrophillic aliphatic compound or a hydrophillic alicyclic compound selected from the group consisting of alken glycol, poly(alken glycol), alken glycol aliphatic hydrocarbon ether and alken glycol alicyclic hydrocarbon ether, poly(alken glycol) aliphatic hydrocarbon ether and poly(alken glycol) alicyclic hydrocarbon ether, and the second photosensitive lithocholate derivative has a carboxylic acid protected with a protective group capable of being deprotected with anacid and has a hydroxy at position No. 3 substituted with a hydrophillic alicyclic compound selected from the group consisting of alken glycol lithocholic ether, alken glycol lithocholate ether, poly(alken glycol) lithocholic ether and poly(alken glycol) lithocholate ether.
The chemically amplified photoresist composition may further include 0.01 to 2.0% by weight of an organic base based on the total weight of the photosensitive compound.
The photosensitive compound according to the present invention maintains transparency even when exposed to a short-wavelength light source, and exhibits improved adhesion to an underlying film or substrate, improved wettability to a developing solution, and improved resistance to dry etching.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A photosensitive compound and a chemically amplified photoresist composition containing the same according to the present invention will now be described. Also, a preferred photolithography process using the chemically amplified photoresist composition will also be described. This invention may, however, be embodied in many different forms, and these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Photosensitive Compound
A photosensitive compound according to the present invention is a photosensitive lithocholate derivative having a carboxylic acid protected with a protective group capable of being deprotected with an acid and having a hydroxy at position No. 3 substituted with hydrophillic aliphatic compound or hydrophillic alicyclic compound.
The protective group causes the lithocholate derivative to exhibit insolubility to a developing solution when it is bonded thereto. However, if the protective group is deprotected, that is, decomposed by an acid generated during exposure, a lithocholic acid derivative is generated, thereby exhibiting a greater solubility to a developing solution.
Thus, in consideration of a difference in the solubility of the photosensitive compound before and after exposure, the protective group is preferably t-butyl, 2-methyladamantyl, tetrahydropyranyJ or tetrahyd-rofuranyl.
The photosensitive lithocholate derivative according to a first embodiment of the present invention has a hydroxy at position No. 3 substituted with a hydrophillic aliphatic compound or a hydrophillic alicyclic compound selected from the group consisting of alken glycol, poly(alken glycol), alken glycol aliphatic hydrocarbon ether, alken glycol alicyclic hydrocarbon ether, poly(alken glycol) aliphatic hydrocarbon ether and poly(alken glycol) alicyclic hydrocarbon ether.
Here, the alken glycol is preferably C
2
to C
6
alken glycol, more preferably ethylene glycol or propylene glycol. The number of alken glycols in poly(alken glycol) is determi
Kim Hyun-woo
Lee Sook
Woo Sang-gyun
Baxter Janet
Lee Sin J.
Samsung Electronics Co,. Ltd.
Volentine & Francos, PLLC
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