Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2001-01-29
2003-03-25
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S313000, C430S322000, C430S323000, C430S324000, C438S003000
Reexamination Certificate
active
06537732
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resist pattern and a method of forming the same, a method of forming a thin-film pattern through the use of the resist pattern, and a method of manufacturing a micro device.
2. Description of the Related Art
As disclosed in Published Unexamined Japanese Patent Application (KOKAI) Heisei 9-96909 (1997), for example, methods such as etching, liftoff, or a combination of etching and liftoff (hereinafter called a combination method) have been employed to form a thin-film pattern on a substrate through the use of a resist pattern. These methods will now be described.
FIG. 36A
to
FIG. 36D
illustrate the etching method. In this method, as shown in
FIG. 36A
, a film
202
to be patterned is formed on a substrate
201
. Next, as shown in
FIG. 36B
, a resist layer is formed on the film
202
and patterned to form a resist pattern
203
. Next, as shown in
FIG. 36C
, the film
202
is selectively etched through dry etching such as ion milling with the resist pattern
203
as a mask. A thin-film pattern
204
having a desired shape is thus obtained. Next, as shown in
FIG. 36D
, the resist pattern
203
is removed.
FIG. 37A
to
FIG. 37C
illustrate the liftoff method. In this method, as shown in
FIG. 37A
, a resist layer is formed on a substrate
211
and patterned to form a resist pattern
212
. Next, as shown in
FIG. 37B
, a film
213
to be patterned is formed over the entire surface on top of the substrate
211
and the resist pattern
212
. Next, as shown in
FIG. 37C
, the resist pattern
212
is lifted off. A thin-film pattern
214
having a desired shape is thus obtained.
FIG. 38A
to
FIG. 38E
illustrate the combination method. In this method, as shown in
FIG. 38A
, a first film
222
to be patterned is formed on a substrate
221
. Next, as shown in
FIG. 38B
, a resist layer is formed on the first film
222
and patterned to form a resist pattern
223
. Next, as shown in
FIG. 38C
, the first film
222
is selectively etched through dry etching such as ion milling with the resist pattern
223
as a mask. A first thin-film pattern
224
having a desired shape is thus obtained. Next, as shown in
FIG. 38D
, a second film
225
to be patterned is formed over the entire surface on top of the substrate
221
and the resist pattern
223
. Next, as shown in
FIG. 38E
, the resist pattern
223
is removed. A second thin-film pattern
226
having a desired shape is thus obtained. Through this combination method, the first thin-film pattern
224
and the second thin-film pattern
226
contiguous with each other are formed on the substrate
221
.
It is preferred to utilize a resist pattern having a T-shaped cross section for the foregoing methods. One of the methods for making such a resist pattern is the method utilizing a two-layer resist as disclosed in Published Examined Japanese Patent Application (KOKOKU) Heisei 7-6058 (1995), for example. The two-layer resist is a material including an upper layer made of a resist, and a lower layer made of a material being soluble in a developer used for the upper layer.
Reference is now made to
FIG. 39A
to
FIG. 39D
to describe the method of forming a resist pattern having a T-shaped cross section through the use of a two-layer resist. In this method, as shown in
FIG. 39A
, a lower layer
232
of the two-layer resist is formed on a substrate
231
. The lower layer
232
is made of polymethylglutarimide as disclosed in Published Examined Japanese Patent Application (KOKOKU) Heisei 7-6058. Next, as shown in
FIG. 39B
, an upper layer
233
of the two-layer resist is formed on the lower layer
232
. The upper layer
233
is made of a resist such as a photoresist. Next, as shown in
FIG. 39C
, the layers are exposed to ultraviolet rays, for example, through a mask
234
. Next, as shown in
FIG. 39D
, the upper layer
233
is developed to form a resist pattern made up of an upper layer pattern
236
made of the remainder of the upper layer
233
and a lower layer pattern
235
made of the remainder of the lower layer
232
. When developed, part of the lower layer
232
is dissolved. As a result, after the development, a resist pattern thus obtained has a T-shaped cross section in which the lower layer pattern
235
has a width smaller than that of the upper layer pattern
236
.
The following problems have been found in the method of forming a thin-film pattern through the use of a resist pattern having a T-shaped cross section. Although the following description illustrates an example in which the two-layer resist pattern made up of the lower layer pattern
235
and the upper layer pattern
236
, the same problems apply to the case in which a single-layer resist pattern is utilized.
Reference is now made to
FIG. 40
to describe a problem of the etching method.
FIG. 40
illustrates the way in which the film
202
formed on the substrate
201
is etched through ion milling, for example, with the two-layer resist pattern made up of the lower layer pattern
235
and the upper layer pattern
236
as a mask. During this etching, the substance making up the film
202
being etched may deposit on sidewalls of the patterns
235
and
236
and thereby form a deposition film
241
. If such a deposition film
241
is formed, the deposition layer
241
may cause burrs around the thin-film pattern after the two-layer resist pattern is removed. Defects in the thin-film pattern may thereby result, which reduces the yield of micro devices including such thin-film patterns. The micro devices mean small-size devices fabricated through the use of thin-film forming techniques. Such micro devices include semiconductor devices, thin-film magnetic heads, and transducers and actuators incorporating thin films.
Reference is now made to
FIG. 41
to describe a problem of the liftoff method.
FIG. 41
illustrates the way in which the film
213
is formed over the entire surface on top of the substrate
211
and the two-layer resist pattern made up of the lower layer pattern
235
and the upper layer pattern
236
. During the formation of the film
213
, the substance making up the film
213
may deposit on sidewalls of the lower layer pattern
235
, too, and burrs
242
may be formed around the thin-film pattern. Defects in the thin-film pattern may thereby result, which reduces the yield of micro devices including such thin-film patterns.
The combination method has both of the problems of the etching method and the liftoff method.
As thus described, the prior-art methods of forming a thin-film pattern through the use of a resist pattern having a T-shaped cross section have problems that cause defects in the thin-film pattern.
A method of forming an electrode layer is disclosed in Published Unexamined Japanese Patent Application (KOKAI) Heisei 9-282617 (1997). This method employs the liftoff method using a bridge-shaped photoresist pattern made up of a single-layer photoresist. This method using the bridge-shaped photoresist pattern is capable of avoiding the problem of the foregoing method utilizing a resist pattern having a T-shaped cross section.
With regard to a thin-film magnetic head incorporating a reproducing (read) head utilizing a magnetoresistive (MR) element, for example, it is required to precisely control the width of the portion that defines the track width of the MR element, and the amount of overhanging of the lead pattern that hangs over the MR element. Therefore, if the MR element and the lead pattern are formed through the combination method using a bridge-shaped resist pattern, it is required to control the cross-sectional shape or length of the portion of the bridge-shaped resist pattern that is located up above the film to be patterned or the base layer, and the height of this portion from the film to be patterned or the base layer, in particular, to obtain desired dimensions.
However, as disclosed in Published Unexamined Japanese Patent Application (KOKAI) Heisei 9-282617, if the bridge-shaped resist pattern is made of a single-layer photoresist, it is
Huff Mark F.
Oliff & Berridg,e PLC
Sagar Kripa
TDK Corporation
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