Impedance measurement tool

Details Impedance measurement tool Impedance measurement tool

2001-04-26

2002-09-17

Le, N. (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S1540PB

Reexamination Certificate

active

06452408

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma treatment equipment.
2. Description of Related Art
Plasma treatment equipment shown in
FIG. 12
has been known heretofore as plasma treatment equipment.
In the plasma treatment equipment, a matching circuit is provided between a high frequency power source
1
and a plasma excitation electrode
4
. The matching circuit is a circuit for matching the impedance between these high frequency power source
1
and the plasma excitation electrode
4
.
The high frequency power is supplied from the high frequency power source
1
to the plasma excitation electrode
4
by way of a matching circuit and through a feeder plate
3
.
These matching circuit and feeder plate
3
are contained in a matching box
2
formed of a housing
21
consisting of conductive material.
A shower plate
5
having a number of holes
7
is provided under the plasma excitation electrode (cathode)
4
, and a space
6
is defined by the plasma excitation electrode
4
and the shower plate
5
. A gas guide pipe
17
is provided to the space
6
. Gas introduced from the gas guide pipe
17
is supplied to a chamber
60
defined by a chamber wall
10
through the holes
7
of the shower plate
5
.
9
denotes an insulator for insulation between the chamber wall
10
and the plasma excitation electrode (cathode)
4
. An exhaust system is omitted in this drawing.
On the other hand, in the chamber
60
, a wafer suscepter (suscepter electrode)
8
serves as a plasma excitation electrode having a base plate
16
placed thereon is provided, and a suscepter shield
12
is provided on the periphery of the wafer suscepter
8
. The wafer suscepter
8
and suscepter shield
12
are vertically movable by means of a bellows
11
so that the distance between the plasma excitation electrodes
4
and
8
is adjustable.
The second high frequency power source
15
is connected to the wafer suscepter
8
through the matching circuit contained in a matching box
14
. The DC potential of the chamber is the same as that of the suscepter shield
12
.
Another conventional plasma treatment equipment is shown in FIG.
14
.
The plasma treatment equipment shown in
FIG. 12
is a so-called double wave excitation type plasma treatment equipment, whereas, the plasma treatment equipment shown in
FIG. 14
is a single wave excitation type plasma treatment equipment. As shown in
FIG. 14
, the high frequency power is supplied only to the cathode
4
and the suscepter electrode
8
is grounded. Unlike the plasma treatment equipment shown in
FIG. 12
, there is no high frequency power source
15
and no matching box
14
. The DC potential of the suscepter electrode
8
is the same as that of the chamber wall
10
.
Yet another conventional plasma treatment equipment is shown in FIG.
15
. There is no shower plate in the plasma treatment equipment shown in
FIG. 15
, and the cathode
4
, which serves as a plasma excitation electrode, is disposed so as to face directly to the wafer suscepter
8
. A shield
20
is provided on back side periphery of the cathode
4
. This plasma treatment equipment has the same structure as that shown in
FIG. 12
excepting the above-mentioned points.
Further another conventional plasma treatment equipment is shown in FIG.
16
. The plasma treatment equipment shown in
FIG. 15
is a so-called double wave excitation type plasma treatment equipment, whereas, the plasma treatment equipment shown in
FIG. 16
is a single wave excitation type plasma treatment equipment. As shown in
FIG. 16
, the high frequency power is supplied only to the cathode
4
, and the suscepter electrode
8
is grounded. There is no high frequency power source
15
and no matching box
14
(like that shown in FIG.
15
). The DC potential of the suscepter electrode
8
is the same as that of the chamber wall
10
.
However, it is found as the result of detailed study of the conventional plasma treatment equipment that the power consumption efficiency (proportion of the power consumed in plasma to the power supplied to a plasma excitation electrode
4
) is not necessarily high, and particularly the power consumption efficiency decreases remarkably as the frequency supplied from a high frequency power source increases. Also it is found by the inventors of the present invention that the decrease in efficiency becomes more remarkable as the base plate size increases.
In conventional plasma treatment equipment shown in
FIG. 12
,
FIG. 14
,
FIG. 15
, and
FIG. 16
, the suscepter impedance (impedance between the suscepter and chamber) is high, and the impedance increases more as the frequency of high frequency power supplied from the high frequency power source
1
or
15
increases. In other words, the impedance depends on the frequency. As a result, the high frequency current of the plasma, which is connected to the suscepter impedance, decreases and the power consumption efficiency decreases remarkably as the frequency of high frequency power supplied from the high frequency power source
1
increases.
The power consumption efficiency is checked by a method as described herein under.
(1) The chamber wall of plasma treatment equipment is replaced with an equivalent circuit comprising a concentrated constant circuit.
(2) Constants of circuits are determined by measuring the impedance of chamber components using an impedance analyzer.
(3) The impedance of the whole chamber during discharge is measured by utilizing the relation that the impedance of the whole chamber during discharge is in complex conjugate to the impedance of the matching box provided with a 50 &OHgr; dummy load on the input side.
(4) The plasma space is regarded as a series circuit of a resistance R and capacitance C, and constants are calculated from values obtained in (2) and (3).
(5) Based on the equivalent circuit model of the chamber during discharge obtained by means of the above-mentioned method, the circuit calculation is performed and the power consumption efficiency is derived.
As described herein above, the conventional plasma treatment equipment is disadvantageous in that the film forming speed is low due to low power consumption efficiency and it is difficult to form an insulating film with high dielectric strength when a insulating film is formed.
The inventors of the present invention have studied the cause of low power consumption efficiency. As the result, the cause of the low power consumption efficiency described herein under has been found.
In detail, first, in the suscepter electrode
8
side of the conventional plasma treatment equipment shown in
FIG. 12
, as shown by an arrow shown in
FIG. 13
which is an enlarged view of the suscepter electrode
8
shown in
FIG. 12
, the high frequency power is supplied from the high frequency power source
1
to a coaxial cable, the matching circuit, the feeder plate
3
, and the plasma excitation electrode (cathode)
4
. On the other hand, in the case that the path of the high frequency current is addressed, the current passes the plasma space (chamber
60
) through these components, and the other electrode (suscepter electrode)
8
, the vertical part of shield
12
, the bellows
11
, the bottom
10
b
of the chamber wall
10
and the sidewall
10
s
of the chamber wall
10
. Then, the current passes the housing of the matching box
2
and returns to the earth of the high frequency power source
1
.
In the plasma treatment equipment shown in
FIG. 14
, the high frequency power from the high frequency power source
1
is supplied through the coaxial cable, the matching circuit, and the feeder plate
3
and to the cathode
4
. On the other hand, in the case that the path of the high frequency current is addressed, the current passes to the plasma space through these components, further to the other electrode (suscepter electrode)
8
, the shaft
13
, the bottom
10
b
of the chamber wall
10
, and the side wall
10
s
of the chamber wall
10
. Then, the current passes through the housing of the matching box
2
and returns to the earth of

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