Polymer and chemically amplified resist composition...

Details Polymer and chemically amplified resist composition... Polymer and chemically amplified resist composition...

2000-02-23

2001-06-12

Le, Hoa Van (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

C430S905000, C430S910000, C526S279000, C526S313000

Reexamination Certificate

active

06245482

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemically amplified photoresist composition, and more particularly, to a chemically amplified photoresist composition composed of a silicon-containing polymer compound.
2. Description of the Related Art
As semiconductor devices become highly integrated and complicated to manufacture, fine pattern formation is required. Accordingly, there is a great demand for new photoresists to be used in photolithography. Further, as the capacity of a semiconductor memory device exceeds 1 Gbit, a new photoresist material capable of being developed into a sharp pattern after exposure by an ArF excimer laser (193 nm) is necessary.
A photoresist that is intended for use with an ArF laser may be either a single layer resist (SLR) or a bi-layer resist (BLR), depending on the semiconductor fabrication process. Generally, the photoresist patterning process is simpler using an SLR than using a BLR. However, there are many problems associated with using an SLR. Foremost among them is the low dry etch resistance of the SLR. Another problem with SLR is the collapse of patterns having a high aspect ratio.
Although the patterning process is more complicated when a BLR is used, the BLR has a significantly higher dry etching resistance than the SLR due to the presence of silicon in the photoresist. During dry etching by O
2
plasma, the silicon atoms in the BLR material crystallize into glass to form a hard layer over the surface of the photoresist layer. This hard layer acts as an etching mask during subsequent dry etching, thereby permitting the formation of a sharp pattern even if the aspect ratio is high.
The content of silicon in a polymer that is to be used in a photoresist composition is an important factor in fabricating the BLR. One example of a silicon containing polymer used in a bi-layer photoresist intended for use in an ArF excimer laser lithography process, is disclosed in Akiko Kotachi et al., “Si-containing Positive Resist for ArF Excimer Laser Lithography”, J. Photopolymer Science and Technology, Vol. 8, No. 4, p 615, 1995. However, the silicon content in the polymer disclosed in the above reference, poly (TMSMMA-RMA), is only about 8 wt %. It is recognized that a silicon content of at least 10 wt % is necessary to attain a high enough aspect ratio, therefore the conventional silicon-containing polymers are not adequate to provide the high dry etching resistance that is required to form a sharp photoresist pattern at the high aspect ratio. Further, the silicon polymer described in Kotachi et al. for use with an ArF excimer laser in photolithography has inadequate adhesion characteristics, which means that the resist layer formed using the polymer may lift from the underlying layer, thus forming a photoresist pattern that is not sharp enough.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide polymers having a new structure and containing enough silicon to be useful in ArF excimer laser photolithography. It is another objective of the present invention to provide a chemically amplified photoresist composition containing the polymer.
Accordingly, to achieve the first objective, the present invention provides a polymer for use in a chemically amplified photoresist that is represented by the following chemical formula (CF1):
wherein R′ is one selected from the group comprising:
 in which R
1
is one selected from the group comprising —H and —CH
3
; m and n are integers; m/(m+n)=0.1-0.6; and
wherein R
2
is one selected from the group comprising —H and —CH
3
; R
3
is one selected from the group comprising —H and —CH
3
; R
4
is one selected from the group comprising —H; —CH
3
and —CH
2
CH
2
OH; p, q and r are integers; p/(p+q+r)=0.1 to 0.7; q/(p+q+r)=0.1 to 0.7; and r/(p+q+r)=0.1 to 0.5.
To achieve the second objective, the present invention provides a photoresist composition having the polymer represented by CF1, and a photoacid generator (PAG).
The polymer has a weight-average molecular weight of from 5,000 to 100,000.
The photoresist composition comprises from 1 to 15 weight percent of the PAG based on the weight of the polymer.
The PAG is selected from the group comprising triarylsulfonium salts, diaryliodonium salts, sulfonates and any combination thereof.
The photoresist composition further comprises an organic base which is present in an amount of from 0.01 to 2.0 weight percent of the polymer; the organic base is one selected from the group comprising triethyl amine, diethyl amine, triethanol amine, and any combination thereof.
The present invention also provides a polymer that has a silicon-containing acid-labile group, and a photoresist composition containing the polymer. The polymer according to the present invention, therefore, has a greater content of silicon than conventional polymers, and it has excellent adhesion to other films.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The preferred embodiments of the present invention will now be described. In general, the present invention provides a polymer for use in a chemically amplified photoresist that is represented by the following chemical formula (CF1):
wherein R′ is one selected from the group comprising:
 in which R
1
is one selected from the group comprising —H and —CH
3
; m and n are integers; m/(m+n)=0.1-0.6; and
wherein R
2
is one selected from the group comprising —H and —CH
3
; R
3
is one selected from the group comprising —H and —CH
3
; R
4
is one selected from the group comprising —H; —CH
3
and —CH
2
CH
2
OH; p, q and r are integers; p/(p+q+r)=0.1 to 0.7; q/(p+q+r)=0.1 to 0.7; and r/(p+q+r)=0.1 to 0.5.
A photoresist composition is provided in which the polymer represented by CF1 is combined with a photoacid generator (PAG). The polymer has a weight-average molecular weight of from 5,000 to 100,000. The photoresist composition comprises from 1 to 15 weight percent of the PAG based on the weight of the polymer. The PAG is selected from the group comprising triarylsulfonium salts, diaryliodonium salts, sulfonates and combinations thereof.
The photoresist composition further comprises an organic base which is present in an amount of from 0.01 to 2.0 weight percent of the polymer. The organic base is one selected from the group comprising triethyl amine, diethyl amine, triethanol amine, and any combination thereof.
The polymer has a silicon-containing acid-labile group, and therefore has a greater content of silicon than conventional polymers, while also providing excellent adhesion to other films.
The embodiments of the present invention will now be described in greater detail with reference to the following examples.


REFERENCES:
patent: 4491628 (1985-01-01), Ito et al.
patent: 5981141 (1999-11-01), Choi et al.
patent: 6045970 (2000-04-01), Choi et al.
Akiko Kotachi et al., “Si-Containing Positive Resist for ArF Excimer Laser Lithography” Photopolym Sci. Technol., vol. 8, No. 4, 1995, pp. 615-622.

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