Method for forming fine patterns by thinning developed...

Details Method for forming fine patterns by thinning developed... Method for forming fine patterns by thinning developed...

2001-06-27

2002-10-15

Chaudhuri, Olik (Department: 2813)

Semiconductor device manufacturing: process

Chemical etching

Combined with coating step

C438S708000, C430S313000, C430S329000

Reexamination Certificate

active

06465356

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for fabricating a semiconductor device; and, more particularly, to a method for fabricating fine photoresist pattern to form a fine line width of about 0.1 &mgr;m or less.
DESCRIPTION OF THE PRIOR ART
Generally, with the development of highly integrated circuits, the minimum feature size required to manufacture a semiconductor device has become increasingly smaller and line width has depended on the resolution of step-and-repeat projection equipment (stepper). The resolution of the current stepper may form a line width of 0.28 &mgr;m when the i-line of 365 nm-wavelength is applied to the lithography process. In case of DUV (Deep Ultra Violet) of 275 nm-wavelength, the stepper may form a line width of 0.18 &mgr;m.
The stepper has employed a DUV light source from KrF-Excimer laser generating 248 nm-wavelength light or a scanning method has been employed.
As of now, although many techniques are combined in order to increase of the resolution in the DUV-Lithography process, it is impossible to form a fine pattern of 0.1 &mgr;m or less. Accordingly, new light sources such as electron beam, X-ray and EUV (Extreme Ultra Violet), have been developed.
However, the lithography process using the electron beam is not suitable to increase the throughput of semiconductor devices and, in case of the X-ray, there are many problems to be solved in connection with masks, arrangement, resist materials and the yield of devices.
On the other hand, photoresist patterns have been removed by plasma that is generated from the RF or microwave equipment. That is, the photoresist layers are removed by the chemical reaction on ions or radicals in the plasma, which physically strike against the components in the photoresist patterns.
However, this photoresist removing method involves a physical method, in which the ion and radical collisions are employed, and an additional chemical method. As a result, this methodology may cause an exposed semiconductor substrate or other layers formed on the semiconductor substrate to be damaged because many layers are exposed between the photoresist patterns. Also, heavy metal ions such as Na+ infiltrate into the semiconductor layer together with plasma components, causing the semiconductor layer to be seriously damaged. Frequently, this seriously damaged semiconductor layer results in the devices being discarded.
FIGS. 1A and 1B
are cross-sectional views illustrating a prior art method for forming photoresist patterns.
Referring to
FIG. 1A
, a conducting layer
12
is formed on a semiconductor substrate
11
and an ARC (Anti-Reflective Coating) layer
13
is formed on the conducting layer
12
. Photoresist patterns
14
are formed on the ARC layer
13
using a KrF-Excimer laser stepper. The photoresist patterns
14
are formed at a constant distance (S) and height (H) and in a constant width (W). Typically, the photoresist patterns
14
may have a width of 170nm in the KrF-Excimer laser stepper.
Referring to
FIG. 1B
, final fine patterns are formed by developing the photoresist patterns
14
to which the exposure process has been applied. However, in case where the ratio for the height to the width of each photoresist pattern
14
is in excess of four, the photoresist patterns
14
may collapse after wet-treating the photoresist patterns
14
in the developing process. Furthermore, the depth of the photoresist patterns
14
may be decreased at the time of treatment in a plasma asher with their size shift.
SUMMARY OF THE DISCLOSED METHOD AND DEVICE
The disclosed method and device provides a method for forming fine patterns capable of surpassing resolution of a stepper by using a KrF-Excimer laser and an O
3
-asher in semiconductor fabricating processes.
The disclosed method and device also provides a method for forming fine patterns to guarantee the throughput of devices in semiconductor fabricating processes.
In accordance with one aspect of the present invention, a method for forming fine photoresist patterns in a semiconductor device is provided which comprises forming photoresist patterns over a semiconductor substrate using a stepper; and ashing the photoresist patterns using oxygen radicals in order to decrease line width of the photoresist patterns. In the disclosed method and device, the oxygen radicals are formed by a thermal decomposition of an ozone gas in an ozone asher.


REFERENCES:
patent: 4806456 (1989-02-01), Katoh
patent: 5876901 (1999-03-01), Ishimaru
patent: 6316169 (2001-11-01), Vahedi et al.
patent: 2001/0050386 (2001-12-01), Suzuki et al.
Ghandi, Sorab,; “VLSI Fabrication Principles-Silicon and Galium Arsenide”; 1994 by John Wiley & Sons Inc.; Second Edition; pp. 664-669, 673-676 and 685-687.

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