Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2002-05-31
2003-04-08
Ghyka, Alexander (Department: 2812)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
C438S780000, C438S706000, C438S725000
Reexamination Certificate
active
06544904
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device in which a film to be subjected to anisotropic etching, another film to be subjected to isotropic etching, and a polyimide film are sequentially deposited in that order.
2. Description of the Background Art
FIGS. 13-18
are sectional views of structures at respective steps of a conventional method of manufacturing a semiconductor device. As illustrated in
FIG. 13
, a passivation film
160
comprising a silicon oxide film
130
and a silicon nitride film
140
is formed over a semiconductor substrate
110
on which a wiring process and other process(es) typically included prior to the wiring process in a semiconductor manufacturing operation have been performed. More specifically, the silicon oxide film
130
is formed over the semiconductor substrate
110
so as to cover an interconnect
120
formed on the semiconductor substrate
110
, and subsequently, the silicon nitride film
140
is formed on the silicon oxide film
130
. Next, a polyimide film
150
functioning as both a buffer layer and a coating layer is formed on the passivation film
160
, to be more exact, on the silicon nitride film
140
, as illustrated in FIG.
14
. Turning to
FIG. 15
, then, a predetermined pattern is formed in the polyimide film
150
by a photolithograpy process. For the formation of the predetermined pattern in the polyimide film
150
, when the polyimide film
150
is not photosensitive in nature, a photoresist (not shown) is applied to the polyimide film
150
, and exposure and development are performed on the applied photoresist, to form a resist pattern. By etching the polyimide film
150
using the resist pattern of the photoresist, the predetermined pattern is formed in the polyimide film
150
. Additionally, the photoresist is removed after the formation of the predetermined pattern in the polyimide film
150
. On the other hand, when the polyimide film
150
is photosensitive in nature, it is unnecessary to use a photoresist. In such case, it is possible to form the predetermined pattern in the polyimide film
150
by performing exposure and development directly on the polyimide film
150
.
Next, the passivation film
160
is etched using the patterned polyimide film
150
as a mask, to expose the interconnect
120
. More specifically, first, isotropic etching is performed on the silicon nitride film
140
using the patterned polyimide film
150
as a mask, to selectively remove the silicon nitride film
140
as illustrated in FIG.
16
. For the isotropic etching performed at that time, reactive ion etching may be employed, for example. Subsequently, referring to
FIG. 17
, anisotropic etching is performed on the silicon oxide film
130
using again the patterned polyimide film
150
as a mask while employing reactive ion etching, for example, to expose a portion of the interconnect
120
. Then, referring to
FIG. 18
, a heat treatment is carried out at a temperature in the range of approximately 300 to 450° C. The heat treatment is intended to imidize the polyimide film
150
and evaporate a solvent used in the polyimide film
150
. Further, in the case where the polyimide film
150
is photosensitive, the heat treatment is effective also in evaporating a photosensitizer in the polyimide film
150
. While not shown, a wire bonding process follows, so that the exposed portion of the interconnect
120
and an external terminal (not shown) are connected to each other via an aluminum wire or the like.
Having described the overall sequence of the conventional method, attention is now brought to the step illustrated in
FIG. 18
, where the heat treatment is performed. It is noted that the heat treatment at this step causes not only the imidization of the polyimide film
150
but also shrinkage of the polyimide film
150
. After the heat treatment, the volume of the polyimide film
150
is reduced by about 50% and the polyimide film
150
has a sloped side face. For this reason, if the heat treatment to imidize the polyimide film
150
is carried out prior to etching the passivation film
160
, to be more exact, prior to the isotropic etching on the silicon nitride film
140
illustrated in
FIG. 16
, and the passivation film
160
is etched using the imidized polyimide film
150
as a mask, it would probably result in failure to achieve a desired dimensional accuracy of the etched passivation film
160
. However, according to the conventional method of manufacturing a semiconductor device as described above, the polyimide film
150
is imidized by carrying out the heat treatment after the passivation film
160
is etched to expose the interconnect
120
. Accordingly, the volume shrinkage of the polyimide film
150
does not occur before etching the passivation film
160
. This allows for increase in the dimensional accuracy of the etched passivation film
160
.
Nevertheless, the conventional method has drawbacks. Specifically, referring to
FIG. 17
, deposits
180
are adhered to side faces of the polyimide film
150
, the silicon nitride film
140
and the silicon oxide film
130
during the anisotropic etching on the silicon oxide film
130
. As the heat treatment for imidizing the polyimide film
150
is carried out after the anisotropic etching in the conventional method, there has been likely arisen a problem such that the deposits
180
come off, or the polyimide film
150
comes unstuck from the silicon nitride film
140
as illustrated in FIG.
18
. In particular, dry etching such as reactive ion etching is mostly employed for the anisotropic etching on the silicon oxide film
130
. In such case, the etching is carried out while adhering the deposits
180
which have a high resistance to etching to the side face of the silicon oxide film
130
, in order to achieve a required etch anisotropy for the anisotropic etching on the silicon oxide film
130
. However, during the etching, the deposits
180
are also adhered to the side faces of the polyimide film
150
and the silicon nitride film
140
as mentioned above. To carry out the heat treatment for imidizing the polyimide film
150
with the deposits
180
being adhered to the respective side faces of the polyimide film
150
and the silicon nitride film
140
as well as the side face of the silicon oxide film
130
would probably cause the deposits
180
to come off due to the volume shrinkage of the polyimide film
150
and a thermal stress. Further, the deposits
180
do not shrink substantially during the heat treatment for the imidization of the polyimide film
150
during which the polyimide film
150
is shrinking. Accordingly, the volume shrinkage of the polyimide film
150
is limited by the deposits
180
on the polyimide film
150
, so that the polyimide film
150
can not completely shrink. As a result, a force that the polyimide film
150
has failed to exert for the shrinkage thereof due to the limitation imposed by the deposits
180
, in other words, a force that is saved as a result of the incomplete shrinkage of the polyimide film
150
, is applied to an interface between the polyimide film
150
and the silicon nitride film
140
. Because of this, conventionally, it has been likely that the polyimide film
150
comes unstuck from the silicon nitride film
140
.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of manufacturing a semiconductor device in which a film to be subjected to anisotropic etching, another film to be subjected to isotropic etching and a polyimide film are sequentially deposited in that order, which method prevents the polyimide film from coming unstuck from the film to be subjected to isotropic etching, as well as prevents deposits adhered to the respective side faces of the deposited films because of the anisotropic etching from coming off, during a heat treatment for imidizing the polyimide film.
According to the present invention, the method of manufacturing a semiconductor device includes the following ste
Kamiura Yuuki
Kawata Hiroyuki
Oda Kouji
Sawada Mahito
Shibata Koji
Ghyka Alexander
Ryoden Semiconductor System Engineering Corporation
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