Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-01-11
2001-08-14
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C156S345420, C118S712000
Reexamination Certificate
active
06273023
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma processing apparatuses and electrostatic attract-and-hold vacuum chucking methods employed therein, and in particular to plasma processing apparatuses electrostatically attracting and holding semiconductor wafers to fix the semiconductor wafers and electrostatic attract-and-hold vacuum chucking methods employed therein.
2. Description of the Background Art
In recent years, electrostatic chuck technology has been increasingly used for apparatuses which process semiconductor wafers as desired, such as plasma etching apparatuses, plasma film-forming apparatuses. Electrostatic chuck technology can prevent deposition of foreign matters at the perimeter of a semiconductor wafer that have been conventionally often produced at a wafer clamp clamping the perimeter of the semiconductor wafer. This ensures that the most outer peripheral portion of a semiconductor device fabricated on the semiconductor wafer can be provided as a product to increase yield. Electrostatic chuck technology is a technology that can be utilized for various semiconductor manufacturing apparatuses in the future.
Referring to
FIG. 1
, a conventional plasma processing apparatus
60
which employs electrostatic chuck technology includes a vacuum chamber
21
blocking the external atmosphere from the internal for maintaining the internal atmosphere.
Vacuum chamber
21
includes a lower electrode
24
, a dielectric film
23
formed on a surface of lower electrode
24
to attract a semiconductor wafer
22
through electrostatic force, a gas supply port
25
for introducing a desired gas into vacuum chamber
21
from e.g. a gas cylinder (not shown), an upper electrode
26
arranged opposite to lower electrode
24
for diffusing the gas introduced via gas supply port
25
to introduce the gas into vacuum chamber
21
and also functioning as an electrode, an exhaust port
27
provided to exhaust the gas in the vacuum chamber
21
by means of a vacuum pump (not shown), and an insulator
33
formed on lower electrode
24
to maintain the insulation between lower electrode
24
and the gas in vacuum chamber
21
.
Plasma processing apparatus
60
also includes an electrostatic chuck power supply
31
for applying a desired voltage to dielectric film
23
via lower electrode
24
, a control signal unit
32
receiving a value of an electrostatic chuck voltage Vs (described hereinafter) stored in a processing-condition memory unit
62
described hereinafter to control a voltage output from electrostatic chuck power supply
31
and thus apply electrostatic chuck voltage Vs from electrostatic chuck power supply
31
to lower electrode
24
, a high-frequency power supply
29
for applying high-frequency electric power to lower electrode
24
, a high-frequency cutting filter
30
provided to prevent the high-frequency electric power from sneaking from high-frequency power supply
29
, and a matching transformer
28
for achieving the matching/integrity between high-frequency power supply
29
and lower electrode
24
.
A desired gas introduced into vacuum chamber
21
is electromagnetized by high-frequency power supply
29
to produce a plasma
34
.
Plasma processing apparatus
60
also includes a processing-condition memory unit
62
for storing the conditions for producing plasma
34
desired, such as gas flow, the pressure in vacuum chamber
21
, the magnitude of high-frequency electric power (referred to as “processing conditions” hereinafter), and the voltage applied from electrostatic chuck power supply
31
to lower electrode
24
, or electrostatic chuck voltage Vs.
A plasma
34
producing operation effected in plasma processing apparatus
60
will now be described briefly and electrostatic attract-and-hold vacuum chuck operation will then be described.
Plasma Producing Operation
Semiconductor wafer
22
is transported into vacuum chamber
21
via a transport device (not shown) and mounted on lower electrode
24
with dielectric film
23
interposed therebetween. Depending on the processing conditions stored in processing-condition memory unit
62
, a predetermined amount of gas is introduced from gas supply port
25
via upper electrode
26
into vacuum chamber
21
. Simultaneously, a predetermined amount of gas is exhausted from exhaust port
27
. Thus, the pressure inside vacuum chamber
21
is adjusted to have the value of a pressure determined by the processing conditions. Then, high-frequency power supply
29
applies high-frequency electric power to lower electrode
24
via matching transformer
28
. Associated with the application of high-frequency electric power, plasma
34
is produced inside vacuum chamber
21
. Then, desired processes, such as etching, film-forming, are applied to semiconductor wafer
22
.
Electrostatic Attract-and-Hold Vacuum Chucking Operation
When semiconductor wafer
22
is mounted on dielectric film
23
and plasma
34
is produced in vacuum chamber
21
, an equivalent circuit, such as shown in
FIG. 2
, is formed.
The equivalent circuit shown in
FIG. 2
includes electrostatic chuck power supply
31
having one end connected to the ground and the other end connected to lower electrode
24
for applying electrostatic chuck voltage Vs to lower electrode
24
, dielectric film
23
formed on lower electrode
24
, semiconductor wafer
22
mounted on dielectric film
23
, and an equivalent plasma resistance
70
having one end connected to semiconductor wafer
22
and the other end connected to the ground, and formed of plasma
34
.
When electrostatic chuck power supply
31
applies negative (−) direct current voltage to lower electrode
24
, positive (+) and negative (−) electric charges are induced at an interface between lower electrode
24
and dielectric film
23
and between dielectric film
23
and semiconductor wafer
22
. As a result, the attraction referred to as Coulomb force or Johnsen-Rahbeck force is caused between semiconductor wafer
22
and dielectric film
23
and semiconductor wafer
22
is thus attracted onto dielectric film
23
. Thus, conventional plasma process apparatus
60
can reliably attract semiconductor wafer
22
onto dielectric film
23
when the characteristics of plasma
34
formed are constant.
In plasma processing apparatus
60
, the difference between the electron current and iron current that flow onto semiconductor wafer
22
causes a self-bias voltage Vdc. The value of self-bias voltage Vdc varies depending on the condition of plasma
34
.
Referring to
FIG. 3
, the relation represented as equation (1) is established between self-bias voltage Vdc, a voltage V1 caused between semiconductor wafer
22
and dielectric film
23
, and electrostatic chuck voltage Vs:
Vs=V1+Vdc (1)
As has been mentioned above, the value of self-bias voltage Vdc varies depending on the condition of plasma
34
. In conventional plasma processing apparatus
60
, however, the value of electrostatic chuck voltage Vs is fixed. Accordingly, for conventional plasma processing apparatus
60
, the value of voltage V1 decreases as the value of self-bias voltage Vdc increases. Thus, the force to attract and hold semiconductor wafer
22
is reduced this disadvantageously.
FIG. 4
shows respective experiment results of a self-bias voltage Vdc and a minimal voltage Vmin required to attract and thus hold wafer
22
of 8″&phgr; on dielectric film
23
when the high-frequency electric power output from high-frequency power supply
29
is varied. Minimal voltage Vmin is a voltage applied from electrostatic chuck power supply
31
to lower electrode
24
to attract and hold semiconductor wafer
22
on dielectric film
23
. The graph shows that as that self-bias voltage Vdc has a more negative value, minimal voltage Vmin also has a more negative value. For example, when electrostatic chuck voltage Vs is set at −450V, it is understood that semiconductor wafer
22
can be attracted and held for a high-frequency electric power of no more than 400 W whereas semic
Hanazaki Minoru
Tsuchihashi Masaaki
Alejandro Luz
McDermott & Will & Emery
Mills Gregory
Mitsubishi Denki & Kabushiki Kaisha
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