Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2001-07-23
2003-02-18
Ryan, Patrick (Department: 1745)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S298110, C204S298140, C204S298150
Reexamination Certificate
active
06521105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum processing device and particularly relates to improvements in a sputtering apparatus.
2. Description of Related Art
Reference numeral
101
in
FIG. 8
shows a related sputtering apparatus. This vacuum processing device
101
has a vacuum chamber
111
.
An exhaust opening part
118
is provided at the vacuum chamber
111
. The exhaust opening part
118
is connected to a vacuum exhaust system (not shown) so that when the vacuum exhaust system is driven, the contents of the vacuum chamber
111
can be evacuated.
A gas introduction opening part
117
is provided at the vacuum chamber
111
. This gas introduction opening part
117
is connected to a gas introduction system (not shown). Gas can also be introduced to the inside of the vacuum chamber
111
from the gas introduction opening part
117
.
A backing plate
112
is located at the ceiling of the vacuum chamber
111
and a target
113
consisting of a dielectric material is located at a side of the backing plate
112
facing the inside of the vacuum chamber
111
.
A mounting table
115
facing the target
113
is located at the inside bottom surface of the vacuum chamber
111
. The surface of the mounting table
115
is flat and a substrate can be mounted on this surface as described later.
A radio-frequency supply
114
is provided at the outside of the vacuum chamber
111
. This radio-frequency supply
114
is connected to a backing plate
112
so that when the radio-frequency supply
114
is activated, radio-frequency power can be supplied to the target
113
via the backing plate
112
.
In order to form a thin film of dielectric using sputtering techniques on a surface of a silicon substrate using a sputtering apparatus
101
of this configuration, first, the inside of the vacuum chamber
111
is evacuated, and a substrate
120
is transported towards the inside of the vacuum chamber
111
and mounted on the surface of a mounting table
115
while maintaining a vacuum atmosphere. The potential of the substrate
120
is floating at this time.
Next, a discharge occurs when radio-frequency power is supplied to the target
113
while introducing a constant amount of sputtering gas such as Argon gas etc. from the gas introduction opening part
117
. An adhesion preventing plate
119
is connected to earth so that the discharge occurring within the vacuum chamber
111
is stable.
When discharge occurs, the target
113
is sputtered. At this time, in addition to flying off in the direction of the surface of the substrate
120
, the sputtered target material also flies off in the direction of the side surface of the inside of the vacuum chamber
111
and in the direction of the inner bottom surface. However, an adhesion preventing plate
119
formed substantially in a semi-spherical shape with a circular opening part in the bottom thereof is provided on the inside of the vacuum chamber
111
. The opening part in the bottom of the adhesion preventing plate
119
is positioned close to the mounting table
115
, with the target
113
, side surface within the vacuum chamber
111
and the inner bottom surface being partitioned by the adhesion preventing wall
119
so that the sputtered target material does not become directly attached to the inside bottom surface or inside side surface of the vacuum chamber
111
. A thin film is then formed on the surface of the substrate
120
from target material reaching the surface of the substrate
120
.
However, according to the sputtering apparatus of the above configuration, in particular, while a thin film of dielectric is being formed, when a plurality of films are formed on the substrate consecutively, the distribution of the thickness of the film on the substrate surface and the film-deposition speed change. Discharge therefore cannot be maintained due to discharge becoming unstable when deposition of thin films is continued.
In order to resolve the aforementioned problems of the related art, it is therefore the object of the present invention to provide technology where, when depositing thin films using sputtering techniques, discharge is stable and film deposition speed and film thickness distribution are uniform even in cases where a plurality of dielectric films are formed consecutively on a substrate.
SUMMARY OF THE INVENTION
In order to resolve the aforementioned problems, in a first aspect of the present invention, a sputtering apparatus comprises a vacuum chamber, a target positioned within the vacuum chamber, a substrate support, located within the vacuum chamber opposite the target, capable of supporting the substrate, and an opposing electrode connected to earth located about the periphery of the substrate support with a surface thereof facing the target, the surfaces being uneven.
With a second aspect of the present invention, the opposing electrode has a through-hole at the center thereof, and the substrate support is located within the through-hole.
In a third aspect of the present invention, the unevenness is comprised of a plurality of holes formed in the surface of the opposing electrode for the sputtering apparatus according to the first aspect.
A fourth aspect of the present invention is the sputtering apparatus according to the third aspect, wherein the depth of the holes is at least twice the diameter of the holes.
In a fifth aspect of the present invention, with the sputtering apparatus according to the first aspect, the target is positioned on the side of the inside ceiling of the vacuum chamber; the opposing electrode being located at an inner bottom side of the vacuum chamber; and wherein the surface of the opposing electrode is inclined in such a manner that the height of the outer side is lower than the height of the inner side.
With a sixth aspect of the present invention, for the sputtering apparatus according to the fifth aspect, the surface of the opposing electrode is inclined by at least 10° with respect to a horizontal plane.
In a seventh aspect of the present invention, the target for the sputtering apparatus according to the first aspect is a dielectric selected from the group consisting of BaTiO
3
, SrTiO
3
, (BaSr)TiO
3
, Pb(ZrTi)O
3
, and SrBi
2
Ta
2
O
9
.
In an eighth aspect of the present invention, with the sputtering apparatus according to the first aspect, only the opposing electrode is connected to earth within the vacuum chamber.
With the related sputtering apparatus described above, when a thin film of dielectric is formed, when films are formed consecutively, the distribution of the thickness of the film on the substrate surface and the film-deposition speed change, thereby causing discharge to become unstable when forming of films is continued. The inventor conceived the present invention in order to overcome a problem where, when dielectric becomes affixed to the surface of an adhesion preventing plate located in a position close to the target or substrate during sputtering, so that a dielectric film is formed, positive charge becomes affixed to the surface of the dielectric film, and the charge distribution density of positive charge occurring at the surface of the adhesion preventing plate becomes large, the potential of the surface of the adhesion preventing plate can no longer be held at earth potential and the discharge therefore becomes unstable.
The sputtering apparatus of the present invention is conceived based on this concept and is therefore provided with an opposing electrode, held at earth potential, with a surface that is made uneven as a result of forming, for example, a plurality of holes in the surface, with the opposing electrode being located at a position at the periphery of the mounting table within the vacuum chamber. Target material therefore does not become directly attached to the inner bottom surface of the vacuum chamber when the target is sputtered because the target material instead becomes affixed to the adhesion preventing plate and the opposing electrode.
Further, the surface area of the opposing electrode is la
Saito Kazuhiko
Suu Koukou
Tani Noriaki
Armstrong Westerman & Hattori, LLP.
Cantelmo Gregg
Ryan Patrick
Ulvac Inc.
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