Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1999-03-08
2002-04-30
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S788000, C438S775000, C204S192100
Reexamination Certificate
active
06380058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for manufacturing a semiconductor device. More particularly, the present invention relates to a method and an apparatus for manufacturing a semiconductor device having a barrier layer.
2. Description of the Background Art
Conventionally, a semiconductor device is formed by stacking a plurality of layers each having an interconnection layer. For connecting interconnection layers included in the adjacent layers, first a through hole is formed and then a plug of tungsten or the like is filled in to the through hole. For preventing tungsten diffusion and oxidation, a barrier layer of titanium, titanium nitride or the like is generally formed on bottom and side surfaces of the through hole by sputtering.
In recent years, diameter of the through hole is gradually decreasing along with the miniaturization of the semiconductor device. The depth of the through hole, however, does not become smaller because the thickness of the layers constituting the semiconductor device does not significantly change in spite of the miniaturization of the device. Thus the aspect ratio (a ratio of the depth to the diameter) of the through hole tends to increase.
In a conventional sputtering technique, when the diameter of the through hole is small, a barrier layer is formed only at an upper portion and not on the bottom surface of the through hole. When tungsten is filled in such through hole, aluminum alloy in a lower layer changes its quality at the bottom portion of the through hole, whereby a poor connection or disconnection tends to occur in this area.
Japanese Patent Laying-Open No. 8-127870 addresses this problem by placing a target including a material of a barrier layer a distance as long as 200 mm, away from a silicon substrate on which the barrier layer is to be formed at the sputtering and forming the barrier layer on the bottom surface of the through hole as well.
The method of manufacturing the barrier layer according to the above mentioned layed-open application has the following problems.
FIG. 7
is a schematic diagram of a sputtering apparatus referenced for describing the problem of the conventional method. As shown in
FIG. 7
, in the sputtering apparatus, a silicon substrate
100
and a target
120
of titanium which is a material of the barrier layer are disposed opposite to each other. An interlayer insulation film
101
is formed on silicon substrate
100
. A through hole
102
is formed in a central area of interlayer insulation film
101
. Additionally a through hole
103
is formed in an outer peripheral area of interlayer insulation film
101
. The distance between target
120
and a surface of silicon substrate
100
is about 200 mm.
In the sputtering apparatus with such a configuration, an angle at which the target is viewed from a lower edge of a side surface
102
c
or
102
d
of through hole
102
through the opening of through hole
102
is defined as &bgr;°.
In the outer peripheral area of interlayer insulation film
101
, an angle at which target
120
is viewed from a lower edge of a side surface
103
d
on the outer peripheral side of through hole
103
is &bgr;°. An angle at which target
120
is viewed from a lower edge of a side surface
103
c
on a central side of interlayer insulation film
101
through an opening of through hole
103
is defined as &agr;°. Here, &agr;° is smaller than &bgr;°.
FIG. 8
is a sectional view of a barrier layer manufactured by the apparatus shown in FIG.
7
. Referring to
FIG. 8
, as the angle at which target
120
is viewed from the lower edge of side surface
103
c
is &agr;° which is relatively small as shown in
FIG. 7
, the number of titanium atoms colliding with side surface
103
c
becomes small, whereby a barrier layer
104
becomes thinner at side surface
103
c
and an upper portion
103
a
of through hole
103
. Conversely, as the angle at which target
120
is viewed from the lower edge of side surface
103
d
is &bgr;° which is relatively large, the number of titanium atoms colliding with side surface
103
d
becomes large, whereby barrier layer
104
becomes thicker at side surface
103
d
and at an upper portion
103
b
farther from the center of silicon substrate
100
. The center of silicon substrate
100
is located in the direction shown by an arrow
110
.
When barrier layer
104
is thin at some portions, WF
6
gas used for manufacturing a tungsten plug may react with the thin portion of barrier layer
104
in upper portion
103
a
of the through hole, thereby causing the barrier layer to be peeled off.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and an apparatus for manufacturing a semiconductor device allowing a barrier layer formation in a lower portion of a semiconductor substrate, such as a bottom portion of a through hole, with the thickness of the barrier being made uniform in an upper portion of the semiconductor substrate, such as an upper portion of the through hole, when the through hole or a recess portion with a large aspect ratio exists.
In accordance with one aspect of the present invention, in a method of manufacturing a semiconductor device, a main surface of a semiconductor substrate and a main surface of a target which is a material of a film to be formed on the main surface of the semiconductor substrate are disposed approximately parallel and opposite to each other, and the film is formed on the semiconductor substrate by sputtering the target material. The method includes the following steps.
(A) Forming a first film by sputtering on the main surface of the semiconductor substrate while maintaining a first distance between the main surface of the target and the main surface of the semiconductor substrate.
(B) Forming a second film by sputtering on and adjacent to the first film while maintaining a second distance shorter than the first distance between the main surface of the target and the main surface of the semiconductor substrate.
According to the method of manufacturing the semiconductor device including such steps, first, in the step (A), as the distance between the target and the semiconductor substrate is the first distance which is relatively long, when atoms of the target are scattered out of the target, the atoms are gravitated until they reach the semiconductor substrate. Therefore velocity component in a vertical direction gradually increases until the atoms reach the semiconductor substrate. As a result, the atoms of the target travel in a direction perpendicular to the extension of main surface of the substrate. Thus, a first layer can be formed as a barrier layer at the bottom surface of the through hole in an interlayer insulation film on the semiconductor substrate, even when the through hole has a large aspect ratio.
In the above step (B), as the distance between the target and the semiconductor substrate is the second distance which is relatively short, atoms of target tend to be scattered and directly reach the substrate in random directions. Therefore the thickness of a second layer as a barrier layer can be made uniform in the upper portion for example, of the through hole.
Preferably the first distance is at least 170 mm and the second distance is at most 80 mm. By setting the first distance at this value, the distance between the semiconductor substrate and the target is made long enough to ensure a vertical velocity component of atoms scattered from the target to become large. Therefore, the barrier layer can surely be formed in the bottom surface, for example, of the through hole. On the other hand by setting the second distance at this value, the distance between the semiconductor substrate and the target becomes short enough to allow random movement of atoms scattered from the target, whereby thickness of the barrier layer can be made uniform in the upper portion of the through hole.
On the semiconductor substrate, an interlayer insulation film having a hole is formed. Preferably, first and second films are form
Kimoto Mitsuo
Manabe Seiji
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Rocchegiani Renzo N.
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