Polymers and photoresist compositions using the same

Details Polymers and photoresist compositions using the same Polymers and photoresist compositions using the same

1999-07-23

2002-05-21

Ashton, Rosemary E. (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

C430S326000, C526S272000, C526S281000, C526S219600, C526S227000, C528S298000, C528S306000

Reexamination Certificate

active

06391518

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a photoresist polymer that is employed in a photolithography process for the manufacture of a semiconductor device, more specifically, a photolithography process using extremely short wavelength-light such as ArF and KrF, which would be applied to the manufacture of 1 G or 4 G DRAM semiconductor devices.
BACKGROUND OF THE INVENTION
Recently, the trend towards the high integration of semiconductor devices has accelerated, and this is much affected by the development of techniques for forming a micro-pattern using photoresist polymers. In order to prepare a micro-pattern, a minute pattern is formed on a photoresist (hereinafter, sometimes abbreviated as “PR”), which is widely used as a mask in a preparation of a semiconductor device, and therefore a suitable photoresist is an indispensable requirement for these processes.
Up to the present time, methods that have been suggested for forming an ultramicroscopic pattern of not more than 0.5 &mgr;m include: (1) a contrast enhancement layer (here-in-after, abbreviated to as “CEL”) method wherein an additional film is formed on a wafer to enhance the image contrast, (2) a method of using a phase reversal mask, and (3) a method of silylating the surface of a PR film. However, these methods have several disadvantages, such as complicated processes and insufficient yield.
A popular method of increasing the resolution of the PR pattern is to use a light source of the deep ultraviolet band of the light spectrum (hereinafter referred to as “DUV”) which requires a PR polymer adapted for use with such a light source.
A chemical amplified-type PR composition, which is prepared by blending a photoacid generator (PAG) and a polymer having a structure of sensitively reacting with an acid, are widely used as a PR for DUV. According to the reaction mechanism of the chemical amplified-type PR, the photoacid generator generates acid when it is illuminated by the light source, and substituents on the main chain or branched chain of the PR polymer are decomposed or crosslinked in a reaction with the generated acid. This change in the polymer creates a solubility difference between the exposed portion and unexposed portion to the developing solution, to form a PR pattern. In view of the reaction mechanism, a PR for DUV, in particular for ArF radiation (193 nm), requires low light absorption at a wavelength of 193 nm, etching resistance, adhesiveness and developing ability in 2.38 wt % aqueous TMAH (tetramethylammonium hydroxide) solution.
Prior art research has been focused on novolac-type resins because of their high transparency at 193 nm and good etching resistance. As an example of such research, the compound represented by Chemical Formula 1 shown below has been developed by Bell Laboratory.
However, the ‘A’ portion of the compound (that is, maleic anhydride), which is employed to polymerize alicyclic olefin groups, is readily dissolved in 2.38 wt % aqueous TMAH solution even in unexposed regions of the PR film, so that a good pattern cannot be formed. In order to prevent the phenomenon, the amount of the monomer including the tert-butyl group (the ‘y’ portion) should be increased, but this results in relative decrease of ‘z’ portion and lowers adhesiveness with the substrate and sensitivity. In order to solve the problem, a cholesterol-type dissolution inhibitor has been added to the PR composition. However, since the amount of the dissolution inhibitor is typically very high [about 30%(w/w) of the resin], reappearance is low and the production cost are high, thereby making the composition unsuitable as a PR composition.
SUMMARY OF THE INVENTION
The present invention relates to a PR which solves the problems described above. The invention provides novel photoresist polymers having good etching resistance and adhesiveness, are developable in 2.38 wt % aqueous TMAH solution, and are suitable for a photoresist having high sensitivity, and a process for preparing the same. The present invention also provides photoresist compositions and semiconductor devices employing the novel photoresist polymers, and a process for preparing the same.
The present invention provides a novel photoresist polymer comprising a monomer represented by following Chemical Formula 2:
wherein, R1 and R2 are independently —COOH or —R—COOH; and R is a substituted or unsubstituted (C1-C10) alkyl.
The present invention also provides a photoresist polymer represented by the following Chemical Formula 100.
wherein, R1 and R2 are independently —COOH or —R—COOH; R is a substituted or unsubstituted (C1-C10) alkyl;
R3 is —COOR* or —R′—COOR*; R* is an acid labile group; R′ is a substituted or unsubstituted (C1-C10) alkyl;
R4 is H or R3;
R5 is a substituted or unsubstituted (C1-C10) alkyl; and
a, b and c are independently polymerization ratios of each comonomer.
In addition, the present invention also provides a photoresist composition containing (i) a photoresist copolymer of Chemical Formula 100 above, (ii) a photoacid generator, and (iii) an organic solvent.


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Alexander A. Dobrev, Emile Perez, Jean

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