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
2000-02-09
2002-04-09
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
C430S271100, C526S315000, C526S320000, C526S326000, C526S329700
Reexamination Certificate
active
06368768
ABSTRACT:
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is related to Korean Patent Application No. 99-14763, filed Apr. 23, 1999, and takes priority from that date.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an organic anti-reflective coating material which allows the stable formation of ultrafine patterns suitable for 64M, 256M, 1 G, 4 G and 16 G DRAM semiconductor devices. More particularly, the present invention relates to an organic anti-reflective coating material which contains a chromophore with high absorbance at the wavelengths useful for submicrolithography. A layer of said anti-reflection material can prevent back reflection of light from lower layers or the surface of the semiconductor chip, as well as eliminate the standing waves in the photoresist layer, during a submicrolithographic process using a 248 nm KrF, 193 nm ArF or 157 nm F
2
laser light sources. Also, the present invention is concerned with an anti-reflective coating composition comprising such a material, an anti-reflective coating therefrom and a preparation method thereof.
2. Description of the Prior Art
During a submicrolithographic process, one of the most important processes for fabricating highly integrated semiconductor devices, there inevitably occur standing waves and reflective notching of the waves due to the optical properties of lower layers coated on the wafer and to changes in the thickness of the photosensitive film applied thereon. In addition, the submicrolithographic process generally suffers from a problem of the CD (critical dimension) being altered by diffracted and reflected light from the lower layers.
To overcome these problems, it has been proposed to introduce a film, called an anti-reflective coating (hereinafter sometimes referred to as “ARC”), between the substrate and the photosensitive film. Generally, ARCs are classified as “organic” and “inorganic” depending on the materials used, and as “absorptive” and “interfering” depending on the mechanism of operation. In microlithographic processes using I-line (365 nm wavelength) radiation, inorganic ARCs, for example TiN or amorphous carbon coatings, are employed when advantage is taken of an absorption mechanism, and SiON coatings are employed when an interference mechanism is employed. The SiON ARCs are also adapted for submicrolithographic processes which use KrF light sources.
Recently, extensive and intensive research has been and continues to be directed to the application of organic ARCs for such submicrolithography. In view of the present development status, organic ARCs must satisfy the following fundamental requirements to be useful:
First, the peeling of the photoresist layer due to dissolution in solvents in the organic ARC should not take place when conducting a lithographic process. In this regard, the organic ARC materials have to be designed so that their cured films have a crosslinked structure without producing by-products.
Second, there should be no migration of chemical materials, such as amines or acids, into and from the ARCs. If acids are migrated from the ARC, the photosensitive patterns are undercut while the egress of bases, such as amines, causes a footing phenomena.
Third, faster etch rates should be realized in the ARC than in the upper photosensitive film, allowing an etching process to be conducted smoothly with the photosensitive film serving as a mask.
Finally, the organic ARCs should be as thin as possible while playing an excellent role in preventing light reflection.
Despite the variety of ARC materials, those which are satisfactorily applicable to submicrolithographic processes using ArF light have not been found, thus far. As for inorganic ARCs, there have been reported no materials which can control the interference at the ArF wavelength, that is, 193 nm. As a result, active research has been undertaken to develop organic materials which act as superb ARCs. In fact, in most cases of submicrolithography, photosensitive layers are necessarily accompanied by organic ARCs which prevent the standing waves and reflective notching occurring upon light exposure, and eliminate the influence of the back diffraction and reflection of light from lower layers. Accordingly, the development of such an ARC material showing high absorption properties against specific wavelengths is one of the hottest and most urgent issues in the art.
U.S. Pat. No. 4,910,122 discloses an ARC which is interposed under photosensitive layers to eliminate defects caused by reflected light. The coating described therein can be formed thinly, smoothly and uniformly and includes a light absorbing dye which eliminates many of the defects caused by reflected light, resulting in increased sharpness of the images in photosensitive materials. These types of ARCs, however, suffer from disadvantages of being complicated in formulation, extremely limited in material selection and difficult to apply for photolithography using Deep Ultraviolet (DUV) radiation. For example, the ARC of the above reference comprises 4 dye compounds, including polyamic acid, curcumin, Bixin and Sudan Orange G, and 2 solvents, including cyclohexanone and N-methyl-2-pyrrolidone. This multi-component system is not easy to formulate and may intermix with the resist composition coated thereover, bringing about undesired results.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to overcome the problems encountered in the prior art and to provide a novel organic compound which can be used as an ARC for submicrolithography using 193 nm ArF, 248 nm KrF and 157 nm F
2
lasers.
It is another object of the present invention to provide a method for preparing an organic compound which prevents the diffusion and reflection caused by the light exposure in submicrolithography.
It is a further object of the present invention to provide an ARC composition containing such a diffusion/reflection-preventive compound and a preparation method therefor.
It is a still further object of the present invention to provide an ARC formed from such a composition and a preparation method therefor.
The present invention pertains to acrylate polymer resins which can be used as an ARC. Preferred polymer resins contain a chromophore which exhibits high absorbance at 193 nm and 248 nm wavelengths. A crosslinking mechanism between alcohol groups and other functional groups is introduced into the polymer resins, so that a crosslinking reaction takes place when coatings of the polymer resins are “hard baked”, thereby greatly improving the formation, tightness and dissolution properties of the ARCs. In particular, optimum crosslinking reaction efficiency and storage stability are realized in the present invention. The ARC resins of the present invention show superior solubility in all hydrocarbon solvents, but are of so high solvent resistance after hard baking that they are not dissolved in any solvent at all. These advantages allow the resins to be coated without any problem, and the coating prevents the undercutting and footing problems which can occur upon forming images on photosensitive materials. Furthermore, the coatings made of the acrylate polymers of the present invention are higher in etch rate than photosensitive films, improving the etch selection ratio therebetween.
DETAILED DESCRIPTION OF THE INVENTION
The ARC resins of the present invention are selected from the group consisting of acrylate polymers represented by the following general formulas I, II and III:
wherein,
R, R
I
, R
II
, and R
III
are independently hydrogen or a methyl group;
R
0
is a methyl group or an ethyl group;
R
1
to R
9
, which are the same or different, each represents hydrogen, hydroxy, methoxycarbonyl, carboxyl, hydroxymethyl, or a substituted or unsubstituted, linear or branched C
1
-C
6
alkyl, alkane, alkoxyalkyl or alkoxyalkane;
x, y and z each is a mole fraction in the range from 0.01 to 0.99; and
m and n are independently an integer of 1 to 4. In a preferred compound of Formula I, m is 1 or 2 and n is an integer of 1 to 4. In
Baik Ki-Ho
Hong Sung-Eun
Jung Min-Ho
Ashton Rosemary
Hyundai Electronics Industries Co,. Ltd.
Townsend and Towsend and Crew LLP
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