Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-09-08
2001-04-10
Quach, T. N. (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S688000, C438S978000
Reexamination Certificate
active
06214723
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor devices and manufacturing methods thereof, and more particularly to a semiconductor device having a conductive layer as an interconnection layer and a manufacturing method thereof.
2. Description of the Background Art
Conventionally, aluminum is used for an interconnection layer of a semiconductor device. The problem related to a method of manufacturing the interconnection with aluminum will be described.
FIGS. 18
to
22
are cross sectional views shown in conjunction with the problem associated with the conventional manufacturing method.
Referring to
FIG. 18
, an interlayer insulating film
102
is formed on a silicon substrate
101
. A titanium nitride film
103
as a barrier layer is formed on interlayer insulating film
102
. An aluminum film (hereinafter referred to as a high-temperature aluminum film)
105
is formed on titanium nitride film
103
by sputtering at a high temperature of about 400° C.
The formation of the aluminum film at such high temperature increases planarity of high-temperature aluminum film
105
. A crystal grain size of high-temperature aluminum film
105
is larger than that of an aluminum film formed at a low temperature. Therefore, when high-temperature aluminum film
105
is cooled, a recess
106
is formed by the grain boundary, for example, due to shrinkage of a crystal.
Referring to
FIG. 19
, an anti-reflection film
109
of titanium nitride is formed on a surface of high-temperature aluminum film
105
. At the time, a thickness of anti-reflection film
109
is particularly small at a corner
106
a
of recess
106
.
Referring to
FIG. 20
, resist is applied onto anti-reflection film
109
. After the resist is exposed to light, a resist pattern
110
is formed by development using developer. As the thickness of anti-reflection film
109
is small at corner
106
a
of recess
106
, the developer melts a portion of anti-reflection film
109
and also a portion of high-temperature aluminum film
105
. Thus, recess
106
extends and an opening
107
is formed. Opening
107
is greater than the opening at anti-reflection film
109
.
Referring to
FIG. 21
, etching of anti-reflection film
109
and high-temperature aluminum film
105
is started using resist pattern
110
as a mask. At the time, etch residue
111
, formed by reaction of high-temperature aluminum film
105
and etchant, is left at a portion covered by anti-reflection film
109
in opening
107
. It is relatively difficult to etch etching residue
111
.
Referring to
FIG. 22
, when etching is further performed, etch residue
111
acts as a mask to leave high-temperature aluminum film
105
and titanium nitride film
103
thereunder. As a result, interconnection layers
112
and
113
are formed and, at the same time, residues
121
and
122
including conductive portions are formed at portions which would have essentially been free of such conductive materials.
Formation of an interlayer insulating film on residues
121
and
122
would result in insulation failure of the interlayer insulating film and reduction in reliability of the semiconductor device.
SUMMARY OF THE INVENTION
The present invention is made to solve the aforementioned problem. An object according to one aspect of the present invention is to provide a semiconductor device provided with high reliability and preventing insulation failure.
An object according to another aspect of the present invention is to provide a semiconductor device provided with high adhesion with a lower layer and preventing connection failure.
The semiconductor device according to one aspect of the present invention includes a semiconductor substrate and a conductive layer including polycrystal formed on the semiconductor substrate. A recess is formed by a grain boundary in a surface of the conductive layer. A distance between side walls of the recess becomes small as closer to the semiconductor substrate.
In the semiconductor device having such structure, as the distance between the side walls of the recess becomes small as closer to the semiconductor substrate, there would be no space for the residue caused by the etching in the recess in the conductive layer and any conductive material is not left at the unexpected portion. As a result, the semiconductor device provided with high reliability and preventing insulation failure is provided.
More preferably, the conductive layer includes first and second conductive layers. The first conductive layer is formed on the semiconductor substrate and includes a polycrystal having a first average grain size. The second conductive layer is formed with a recess on the first conductive layer and includes a polycrystal having a second average grain size which is greater than the first average grain size.
As the first average grain size is relatively small as compared with the second average grain size, adhesion between the first conductive layer of the first average grain size and a lower layer increases. Thus, the semiconductor device provided with high reliability and preventing connection failure is provided.
More preferably, the semiconductor device further includes a thin film layer formed on the conductive layer and having a material which is different from that of the conductive layer.
More preferably, the thin film layer includes titanium or silicon nitride. Then, the thin film layer can be used as a barrier layer or anti-reflection layer.
More preferably, the conductive layer includes aluminum.
More preferably, the semiconductor device further includes an insulating layer formed on the semiconductor substrate and a barrier layer formed on the insulating layer. The conductive layer is formed on the barrier layer.
Then, as the barrier layer is formed under the conductive layer, diffusion of atoms of the conductive layer can be prevented.
A semiconductor device according to another aspect of the present invention includes first, second and third conductive layers. The first conductive layer is formed on the semiconductor substrate and includes a polycrystal having a first average grain size. The second conductive layer is formed on the first conductive layer and includes a polycrystal having a second average grain size which is greater than the first average grain size. The third conductive layer is formed on the second conductive layer and includes a polycrystal having a third average grain size which is smaller than the second average grain size.
In the semiconductor device having such structure, as the average grain size of the third conductive layer formed on the second conductive layer is small, formation of a recess by a grain boundary in the third conductive layer is prevented. As there would be no space for residue caused by etching in the third conductive layer, a conductive material is not left at an unexpected portion. As a result, the semiconductor device provided with high reliability and preventing insulation failure is provided.
As a first average grain size of the first conductive layer formed on the semiconductor substrate is relatively small, adhesion with a lower layer is increased and connection failure can be prevented.
More preferably, a recess is formed in a surface of the second conductive layer by the grain boundary. A distance between side walls of the recess becomes small as closer to the semiconductor substrate.
Then, there would be no space for the residue caused by the etching in the third conductive layer covering the recess. As a result, the conductive material is not left at the unexpected portion, so that reliability of the semiconductor device is further increased.
More preferably, the semiconductor device further includes a thin film layer formed on the third conductive layer and having a material which is different from that of the third conductive layer.
More preferably, the thin film layer includes titanium or silicon nitride. Then, the thin film layer can be used as an anti-reflection film or barrier layer.
More preferably, the conductive layer includes alumin
Kamoshima Takao
Takewaka Hiroki
Yamashita Takashi
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Quach T. N.
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