Electric heating – Metal heating – By arc
Reexamination Certificate
2001-06-28
2002-12-10
Paschall, Mark (Department: 3742)
Electric heating
Metal heating
By arc
C219S121540, C219S121520, C219S121580, C118S7230IR, C156S345420
Reexamination Certificate
active
06492612
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a lower electrode structure used in applying plasma processing, such as etching, to a substrate such as a semiconductor substrate. The present invention also relates to a plasma processing apparatus using the lower electrode structure.
BACKGROUND ART
In a manufacturing process for a semiconductor device etc., processing within a high vacuum, such as a plasma etching, is frequently employed. However, when processing is performed under the high vacuum, vacuum adsorption cannot be used for holding a substrate such as a semiconductor substrate (hereinafter referred to as “wafer”) since the vacuum adsorption is usually applicable in the air. For this reason, the wafer is usually held by a mechanical means such as a clamp.
When the wafer is held by the clamp, the distal end of the clamp comes into contact with an edge or a working surface of the wafer. As a result, dust is generated at the time the clamp comes into contact with the wafer and sometimes contaminates the wafer surface.
To overcome these problems, a holding means called an electrostatic chuck has been widely used.
FIG. 4
is a schematic view of a lower electrode structure having the electrostatic chuck.
A lower electrode structure
100
shown in
FIG. 4
has a susceptor
101
formed of aluminium and an electrostatic chuck
102
formed thereon.
The electrostatic chuck
102
has a dielectric layer
103
having a mounting surface for mounting a wafer W thereon and a flat electrode
104
arranged in the dielectric layer
103
. The susceptor
101
is connected to a high frequency source
106
via a matching box
105
. On the other hand, to a flat electrode
104
, a direct-current source
108
is connected by way of a low pass filter
107
.
In the lower electrode structure
100
having the aforementioned structure, when a high frequency power is supplied from the high frequency source
106
to the susceptor
101
; at the same time a direct-current voltage is applied from the direct-current source
108
to the flat electrode
104
, electrostatic attraction such as a Coulomb force is produced between the flat electrode
104
and the wafer W mounted on the dielectric layer
103
. As a result, the dielectric layer
103
attracts the wafer W and holds it.
When such a lower electrode structure
100
is arranged in a chamber of a plasma processing apparatus such as a plasma etching apparatus, and the chamber is vacuumed, and then, a high frequency power is supplied from the high frequency source
106
to the susceptor
101
, a high frequency electric field is formed in the vicinity of a working surface of the wafer W.
Thereafter, when a process gas is introduced into the chamber, a plasma of the process gas is produced due to the high frequency electric field. The plasma is applied to the wafer W to perform plasma etching.
However, if the frequency of the high-frequency power to be supplied from the high frequency source
106
to the susceptor
101
is, for example, 2 MHz or less, the dielectric layer
103
interposed between the wafer W and the susceptor
101
prevents the high frequency from passing through. As a result, the high frequency electric field is rarely converged on the wafer W, decreasing etching characteristics. In particular, when the dielectric layer
103
is formed of ceramic, this tendency is significantly observed.
Different from the lower electrode structure shown in
FIG. 4
another type of lower electrode structure shown in
FIG. 5
is known.
A lower electrode structure
110
differs from that shown in
FIG. 4. A
high frequency power
106
is connected to a flat electrode
104
via a matching box
105
and a capacitor
11
. The direct-current voltage from the direct-current source
108
is superimposed on the high frequency voltage supplied from the high frequency source
106
and then applied to the flat electrode
104
.
According to the lower electrode structure
110
mentioned above, a dielectric layer
103
can pass a high frequency through it, compared with the lower electrode structure
100
shown in
FIG. 4
, whereby the high frequency electric field can be easily converged on the wafer W.
In the meantime, the heat conductivity under the high vacuum is lower than that under normal pressure, due to the extremely low amount of heat-conductive medium. In the plasma processing performed under the high vacuum, a helium gas pipe
112
for supplying helium gas for heat transmission to a space between the wafer W and the dielectric layer
103
is arranged, as shown in FIG.
5
. Due to this, the temperature of the wafer W can be controlled even under the high vacuum.
However, the lower electrode structure shown in
FIG. 5
has a problem in that an abnormal discharge occurs within the helium gas pipe
112
when helium gas is supplied.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a lower electrode structure capable of forming a high frequency electric field which capable of applying satisfactory plasma processing on a substrate without an abnormal discharge and to provide a plasma processing apparatus using the lower electrode structure.
To attain the aforementioned object, the present invention provides a lower electrode structure for use in an apparatus for applying plasma processing to a substrate, comprising:
a base table formed of a material having a conductivity;
an electrostatic adsorption member formed on the base table and having a dielectric layer on which the substrate to be mounted and within which an electrode electrically isolated from the base table is housed;
first wiring having an end connected to the electrode of the electrostatic adsorption member
a direct-current source connected to the other end of the first wiring;
second wiring having an end connected to the base table;
a high frequency source connected to the other end of the second wiring;
a third wiring for connecting the first wiring and the second wiring; and
a first capacitor formed on the third wiring.
The present invention provides a plasma processing apparatus comprising:
a chamber for applying plasma processing to a substrate while holding airtight;
a lower electrode structure housed in the chamber and having a mounting surface for the substrate;
an upper electrode arranged in the chamber so as to face the mounting surface of the lower electrode structure;
an exhaust system for exhausting the chamber;
a process gas supply system for introducing a process gas into the chamber;
the lower electrode structure comprising
a base table formed of a conductive material
a dielectric layer formed on the base table and having a mounting surface for the substrate;
an electrostatic adsorption member formed within the dielectric layer and having an electrode electrically isolated from the base table;
first wiring having an end connected to the electrode of the electrostatic adsorption member;
a direct-current source connected to the other end of the first wiring;
second wiring having an end connected to the base table;
a high frequency source connected to the other end of the second wiring;
a third wiring for connecting the first wiring and the second wiring; and
a first capacitor formed on the third wiring,
wherein a plasma of the process gas is formed in the chamber by a high frequency power output from the high frequency source and applied to the substrate, thereby performing a predetermined plasma processing.
In the present invention, the high frequency source is connected to the base table by way of the second wiring and a high frequency voltage is applied to the base table; on the other hand, the high frequency source is connected to the first wiring which connects the electrode of the electrostatic adsorption member to the direct-current source, by way of the third wiring having a capacitor. Therefore, the high frequency voltage is superimposed on the direct-current voltage to be applied to the electrode of the electrostatic adsorption member. Since the high frequency voltage is applied not only to the base table but also the electrode of the electrostatic adsor
Nonaka Ryo
Taguchi Chihiro
Paschall Mark
Tokyo Electron Limited
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