Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Forming nonplanar surface
Reexamination Certificate
2001-02-13
2003-10-14
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Forming nonplanar surface
C430S005000
Reexamination Certificate
active
06632593
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a method for forming a pattern using a photomask in a fine processing process, and a pattern-forming apparatus.
Recently, as a semiconductor memory has become larger in its capacity and a CPU processor has become faster and more integrated, finer photolithographic techniques have been essentially required. In general, the lower limit of fine processing in a photolithography apparatus is about the wavelength of the light used. The wavelength of light used in a photolithography apparatus has, therefore, become shorter. Now, a near ultraviolet laser is used, allowing us to conduct fine processing to about 0.1 &mgr;m.
Although photolithography has become finer, there are many problems to be solved such as a further shorter wavelength of the laser and development of a lens for such a shorter wavelength band, for fine processing of 0.1 &mgr;m or less.
On the other hand, there has been proposed an apparatus for fine processing utilizing a configuration of a nearfield optical microscope (hereinafter, referred to as an “SNOM”)for achieving fine processing of 0.1 &mgr;m or less with light. It is a technique in which a photoresist is subjected to a local exposure over a light wavelength limit using evanescent light leaking out from a fine aperture of 0.1 &mgr;m or less.
However, in any lithography apparatus with an SNOM configuration, fine processing is conducted like pen writing, using a single processing probe or several processing probes, so that throughput may not be improved much.
To solve the above-described problem, there has been suggested a technique that a photomask having a pattern in which evanescent light leaks out between shielding films is tightly placed on a photoresist on a substrate and is subjected to exposure, whereby a fine pattern on the photomask is transferred to the photoresist at one time (Japanese Patent Application Laid-Open No. 11-145051).
A pattern required in actual lithography is a combination of patterns with various sizes. For example, it is often a combination of patterns larger than an exposure wavelength with small patterns formed by evanescent-light exposure.
Thus, when attempting exposure using a mask where apertures with sizes for both evanescent-light exposure and propagating-light exposure are provided on a single matrix, a sensitivity level of the photoresist is dispersed depending on a pattern, so that it is difficult to form a uniform pattern because the light intensity of the evanescent light is much weaker than that of the propagating light.
The phenomenon will be detailed with reference to
FIGS. 9A
to
9
C.
FIG. 9A
shows a mask in which an aperture
213
is disposed near an aperture
214
. In this case, the photoresist is a positive type, and when a negative type photoresist is used, the same result is obtained.
The aperture
213
through which the evanescent light is transmitted as a main exposure component gives a considerably smaller quantity of transmitted light than that of incident light, depending on its width, shape and its spatial relationship with other patterns.
When the above-described mask is used for exposure while controlling a quantity of the incident light to the mask such that the photoresist reacts by a quantity of the evanescent light, the quantity of light from the aperture
214
is so excessive that a photoresist pattern
217
by exposure from the aperture may become larger than the mask pattern and may cover a portion of a photoresist pattern by the exposure from the minute aperture as shown in FIG.
9
B.
On the other hand, the above-described mask is used for exposure while controlling a quantity of the incident light to the mask such that the photoresist reacts by a quantity of the propagating light from the aperture
214
, and the quantity of the evanescent light from the aperture
213
is so small that the photoresist may inadequately react, whereby a photoresist reaction portion by the evanescent light may not be formed, as shown in FIG.
9
C.
Similarly, when a photoresist is made thicker, its reaction state may become uneven in a photoresist reaction portion
206
by the evanescent light and in a photoresist reaction portion
207
by the propagating light, along the depth direction of a photoresist
203
and along the plane direction of a substrate
204
, as shown in FIG.
3
A. As a result, only the photoresist reaction portion
207
by the propagating light is formed by development after exposure, as shown in FIG.
3
B. Furthermore, the photoresist reaction portion
207
by the propagating light may expand on the substrate
204
.
In such a case, patterns may be formed by separate processes; a fine pattern is formed by exposure to evanescent light and then a larger pattern is formed by exposure to usual propagating light. However, it may lead to a higher cost and a lower throughput due to an increase in the numbers of masks and of process steps.
SUMMARY OF THE INVENTION
In light of the above-described problems, an object of this invention is to provide a method for forming patterns by using a photomask capable of forming uniform large and small patterns, and an apparatus for forming such patterns.
The above-described object can be attained by a method for forming a fine pattern using a photomask having a combination of a minute aperture where the main component of transmitted light is evanescent light and an aperture where the main component of transmitted light is propagating light, comprising the steps of: forming a photoresist with a film thickness of a width or less of the minute aperture on a substrate to be processed; and exposing the photoresist by irradiating it with light for exposure.
The object of this invention can also be achieved by an apparatus for forming patterns on a substrate to be processed, the apparatus comprising:
a sample stand for placing the substrate to be processed having a photoresist with a thickness of an exposure wavelength or less formed thereon;
a stage for placing a photomask having a shielding film formed on a photomask substrate, the shielding film having the combination of an aperture having the first width where the main component of light transmitted through the aperture is evanescent light and another aperture having the second width where the main component of light transmitted through the other aperture is propagating light;
a light source for exposure which generates light for exposure; and
means for controlling a distance between the substrate to be processed and the photomask.
These details will be later described in Examples.
REFERENCES:
patent: 4464460 (1984-08-01), Hiraoka et al.
patent: 4576475 (1986-03-01), Kitagawa et al.
patent: 4659429 (1987-04-01), Isaacson et al.
patent: 5413884 (1995-05-01), Koch et al.
patent: 5858621 (1999-01-01), Yu et al.
patent: 5958632 (1999-09-01), Sekiguchi
patent: 6171730 (2001-01-01), Kuroda et al.
patent: 6187482 (2001-02-01), Kuroda et al.
patent: 2001/0036581 (2001-11-01), Inao et al.
patent: 11-145051 (1999-05-01), None
Kuroda Ryo
Yamaguchi Takako
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Huff Mark F.
Sagar K.
LandOfFree
Pattern-forming method using photomask, and pattern-forming... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pattern-forming method using photomask, and pattern-forming..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pattern-forming method using photomask, and pattern-forming... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3140080