Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-11-04
2002-01-22
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S671000, C438S725000, C438S782000, C438S947000, C438S948000, C438S949000, C438S951000, C438S952000
Reexamination Certificate
active
06340635
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resist pattern, to a process for the formation thereof, and to a process for the formation of a wiring pattern. More particularly, it relates to a technique for the formation of a resist pattern which is stable in shape, dimensions, accuracy and other characteristics. Furthermore, it relates to a process for the formation of a fine wiring pattern by plating or by a lift off process. The resist pattern, the process for the formation of the resist pattern, and the process for the formation of a wiring pattern can be suitably employed for a semiconductor device manufacturing process or electronic parts manufacturing process which require fine patterning.
2. Description of the Related Art
As processes for the formation of a thick fine wiring having a thickness exceeding 1 &mgr;m, there may be mentioned a semi-additive (plating) process as shown in
FIGS. 9A
to
9
G, and a lift off process as illustrated in
FIGS. 10A
to
10
F.
Initially, the semi-additive process will now be described. According to this process, a feed film
32
(or plating base) of a metallic material is formed on a substrate
31
(FIG.
9
A), and then a positive resist
33
is applied onto the feed film
32
(FIG.
9
B). Subsequently, the resist
33
is exposed to ultraviolet radiation through an aperture
34
a
of a photomask
34
(FIG.
9
C), and then is subjected to development (FIG.
9
D). A region of the resist
33
exposed to ultraviolet radiation becomes soluble, and the exposed region is hence dissolved by development to give a resist pattern
35
rectangular in cross section.
After this step, a voltage is applied to the feed film
32
to conduct electroplating, and a plating metal is precipitated on the feed film
32
in a region not covered by the resist pattern
35
(FIG.
9
E), to form a plated film
36
. After the completion of plating, the resist pattern
35
is stripped (
FIG. 9
F), and the feed film
32
is removed by etching in a region not covered by the plated film
36
to give a target wiring pattern
37
on the substrate
31
(FIG.
9
G).
Next, the lift off process will be described. According to this process, a negative resist
42
is applied (
FIG. 10B
) onto the surface of such a substrate
41
as shown in
FIG. 10A
, and the resist
42
is then exposed to ultraviolet radiation through an aperture
43
a
of a photomask
43
(FIG.
10
C), and the exposed resist is subjected to development (FIG.
10
D). The resist
42
in a region exposed to ultraviolet radiation becomes insoluble, and the exposed region remains even after the development to give a resist pattern
44
which is of a reversed taper shape in cross section.
Next, an electrode material
45
is deposited all over the substrate
41
from above the resist pattern
44
(FIG.
10
E), and the resist pattern
44
and the electrode material
45
deposited on the resist pattern
44
are stripped off to give a target wiring pattern
46
on the substrate
41
(FIG.
10
F).
As is apparent from the aforementioned explanation, both the semi-additive process and lift off process require forming a resist pattern having a thickness greater than the thickness of a target wiring, as their operations demonstrate, and thus require forming a comparatively thick resist pattern. In addition, the resist pattern formed by the semi-additive process must be rectangular in cross section, and that formed by the lift off process must be of a reverse taper shape in cross section.
Furthermore, both of the semi-additive process and lift off process are characterized in that a film of a wiring material is formed after the formation of a resist pattern to give a wiring pattern. The dimensions, shape and accuracy of the wiring pattern therefore reflect the dimensions, shape and accuracy of the resist pattern. Consequently, it is important to retain the shape of the resist pattern until the formation of a film of the wiring material is completed in order to provide a fine wiring pattern sufficiently having target dimensions, shape and accuracy.
According to conventional processes for the formation of a resist pattern, however, the following results, for example, occur when the thickness of a resist film to be formed is increased:
(1) volumetric shrinkage of the resist pattern due to degassing (gas emission) when the resist is baked in a photolithography step,
(2) defective film of the wiring material because of a collision between flying particles of the wiring material and gas particles, which gas particles are derived from degassing with increasing temperature in the formation of a film of the wiring material, and
(3) stress of the wiring material. The resist sags or deforms because of these results, and an ideal shape of the resist cannot be maintained, and in consequence, a target fine wiring pattern cannot be obtained when a film of the wiring material is formed.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the aforementioned technical problems, and its object is to provide a process for the formation of a wiring pattern, which can yield a fine wiring pattern having target dimensions, shape and accuracy while suppressing the deformation of a resist pattern due to heat or stress.
The resist pattern according to the present invention includes a plurality of depressions formed on its surface, the depressions not reaching the back of the resist pattern.
As the present resist pattern has a plurality of depressions formed on its surface, which depressions neither penetrate the pattern nor reach the back of the resist pattern, the volume of the resist pattern can be smaller and the surface area thereof can be greater than normal. Since the volume of the resist pattern can be decreased by forming depressions on the resist pattern as thus described, the volume of degassing upon baking of the resist pattern can be reduced, and the volumetric shrinkage of the resist pattern can therefore be decreased. Furthermore, by making the resist pattern pectinate or comb-like in cross section, a stress applied from the wiring pattern can be decreased and hence deformation due to the stress in the resist pattern can be mitigated.
In addition, as the surface area of the resist pattern is increased, gas can sufficiently be emitted from the resist pattern when the resist pattern is baked. The volume of emitted gas in the film formation step can therefore be reduced to avoid scattering of flying particles of the wiring material by gas particles emitted from the resist pattern and to ensure attachment of a film on the substrate. Consequently, the deformation of the resist pattern due to, for instance, volumetric shrinkage of the resist pattern can be suppressed, and the formation step of a film of the wiring material is not hindered by gas emission from the resist pattern, resulting in the formation of a precise and satisfactory wiring pattern. In this connection, as the depressions do not reach the back of the resist pattern, they do not affect the pattern shape of the wiring pattern.
In particular, a thick resist having a thickness of 2 &mgr;m or more often suffers volumetric shrinkage and/or deformation, and the application of the configuration to a resist having a thickness of 2 &mgr;m or more yields marked advantages.
A process for the formation of a resist pattern according to the present invention includes the steps of: exposing a resist through a photomask and developing the exposed resist, the photomask having a pattern whose line width is equal to or less than a resolution limit, to form depressions on the surface of a resist pattern, the depressions not reaching the back of the resist pattern.
According to the present process for the formation of a resist pattern, depressions can be formed on the surface of a resist pattern in a conventional manner, which depressions do not reach the back of the resist pattern, only by the use of a photomask having a pattern whose line width is equal to or less than the resolution limit. Consequently, conventional exposu
Hasegawa Masayuki
Koshido Yoshihiro
Toyota Yuji
Gurley Lynne A.
Murata Manufacturing Co. Ltd.
Niebling John F.
Ostrolenk Faber Gerb & Soffen, LLP
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