Two chamber plasma processing apparatus

Details Two chamber plasma processing apparatus Two chamber plasma processing apparatus

1998-03-26

2001-01-02

Gorgos, Kathryn (Department: 1741)

Coating apparatus

Gas or vapor deposition

With treating means

C118S715000, C118S7230ER, C422S186040

Utility Patent

active

06167835

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma processing apparatuses, and more particularly, to a plasma processing apparatus that forms a thin film On the surface of an object of interest or that etches the surface of an object taxing advantage of plasma.
2. Description of the Background Art
FIG. 4
is a schematic sectional view of a conventional plasma processing apparatus disclosed in, for example, Japanese Patent Laying-Open No. 2-9452. Referring to
FIG. 4
, the conventional plasma apparatus includes a vacuum vessel
101
a first electrode
103
on which an object
102
to be processed is placed, and a second electrode
104
arranged opposite to first electrode
103
Etching gas is introduced through a gas inlet
105
into vacuum vessel
1
and exhausted through an exhaust port
106
. A high frequency power source
107
is connected to first electrode
103
via a matching circuit
108
. A permanent magnet
109
is arranged at the atmosphere side of second electrode
104
. A cooling mechanism
110
is connected to first electrode
103
. In
FIG. 4
, E indicates the electric field and B is the component of the magnetic field induced by magnet
109
, parallel to first electrode
103
.
The operation of the plasma processing apparatus of the above structure will be described hereinafter. When etching gas is introduced into the plasma chamber of vacuum vessel
101
from gas inlet
105
, plasma is generated between first and second electrodes
103
and
104
by the high frequency power applied to first electrode
103
.
The apparatus shown in
FIG. 4
is directed to achieve high electron density even at a low pressure by magnetron discharge. The apparatus of
FIG. 4
is set so that the magnetic flux density at the surface of first electrode
103
is approximately 200 G.
At the sheath region (the region where plasma is in contact with first electrode
103
), the charged particles (electrons and ions) drift in the direction of E×B while moving cycloidally under the influence of the sheath electric field and magnetic field.
As a result, the probability of collision between an electron and a neutron (molecule, atom) increases to promote ionization. Accordingly, plasma of high density is generated even at a low pressure to achieve a high etching rate. In this case, plasma loss is reduced by the magnetic field caused by permanent magnet
109
. Therefore, the high density plasma is maintained to allow etching of object
102
of interest.
It is now necessary to generate uniform plasma over a large area for the purpose of processing objects of large diameter such as 8 inch or 10 inch in size. However, the magnetic flux density in the lateral direction (parallel between electrodes) at the surface of second electrode
104
of the above-described plasma processing apparatus with the arrangement of a single permanent magnet is low at the center and becomes higher uniformly in the radial direction as shown in FIG.
5
(B). The overall magnetic flux density is not uniform. It is therefore difficult to form a magnetic field of uniform intensity in the proximity of the object to be processed.
It is not easy to generate plasma uniformly despite its homogeneous action by diffusion. FIG.
5
(A) shows a permanent magnet of 200 mm in diameter and 50 mm in height with the surface magnetic flux density entirely uniform at 3 kG. FIG.
5
(B) is a graph of the magnetic field distribution in the lateral direction at the surface of second electrode
104
remote from the permanent magnet of FIG.
5
(A) by 35 mm. The magnetic field intensity B⊥(G) in the lateral direction is plotted along the ordinate, and the distance r(mm) from the center is plotted along the abscissa.
The magnetic field distribution at the surface of the object to be processed placed on first electrode
103
is also not uniform. Since the movement of a charged particle is greatly affected by the magnetic field distribution, the flux of the incident charged particles at the surface of the object to be processed is also not uniform, reflecting the nonuniform magnetic field distribution. As a result, the distribution of the charge density is disturbed at the surface of the object to be processed to damage the device.
In the event that a plurality of permanent magnets are used, the magnetic field distribution will be nonuniform similar to the above case with a single magnet if the permanent magnets are arranged so that adjacent magnets have the same polarity. Therefore, the uniformity of the plasma was not sufficient even if the homogeneous action by plasma diffusion is taken into account.
The aforementioned Japanese Patent Laying-Open No. 2-9452 also discloses arrangement of a plurality of rod-like permanent magnets with the polarity between adjacent magnets being the opposite, as shown in the sectional view of FIG.
6
(A). When the polarity is altered alternately, the distribution in the radial direction of the lateral magnetic flux density B⊥ at the surface of second electrode
104
is indicated by the waveform of FIG.
7
(B) according to the arrangement of permanent magnets
109
of FIG.
7
(A).
It is appreciated from FIGS.
7
(A) and
7
(B) that the position of the peak can be controlled by altering the distance between the magnets although B⊥ is not uniform radially. Homogeneity can be achieved by generating the plasma in such a magnetic field coordination since the plasma is spread by diffusion even to the region where the magnetic field is weak. Because of reduction in loss in contrast to the case where there is no magnet, uniform plasma of high density can be obtained.
In the parallel arrangement of a plurality of rod-like permanent magnets
109
as shown in FIG.
6
(A), magnetic fields B
1
and B
2
are generated as shown in FIG.
6
(B). At region (A) in the proximity of the object to be processed, the plasma drifts in the direction piercing the plane of the drawing sheet by the E×B drift caused by electric field E and magnetic field B
1
. At the region of (B), plasma drifts in the opposite direction by electric field E and magnetic field B
2
to become locally dense.
Focusing on the movement of the charged particles at the sheath portion at the surface of second electrode
104
, the direction of drift (indicated by arrows) differs for every pair of adjacent permanent magnets
109
due to the E×B drift as shown in FIG.
8
. The region of the shaded area indicated by × in the drawing has high density due to the high plasma density portion corresponding to the direction of the drift. As a result, nonuniformity occurs in the plasma density with the parallel arrangement. This means that uniformity in the etching rate is degraded. This is a critical problem in the parallel arrangement of permanent magnets.
FIG. 9
shows a schematic structure of another conventional plasma processing apparatus having the plasma generation chamber and the processing chamber divided. Such a plasma processing apparatus is disclosed in Japanese Patent Laying-open No. 51-88182, for example. Referring to
FIG. 9
, a processing chamber
121
is evacuated by a diffusion pump
132
via a main valve
131
and an auxiliary rotary pump
133
. A plasma generation chamber
122
is provided above processing chamber
121
. Counter electrodes
118
and
119
are connected to ground at plasma generation chamber
122
. Counter electrode
119
with a plurality of holes
20
is provided as a partition wall to divide plasma generation chamber
122
and processing chamber
121
. A raw material gas cylinder
134
is connected to a gas conduit
115
.
The operation of the plasma processing apparatus of the above structure will be described hereinafter. The etching gas introduced into plasma generation chamber
122
through gas conduit
115
passes through processing chamber
122
to be output by a vacuum pump. Difference in pressure between plasma generation chamber
122
and processing chamber
121
is generated by the conductance of holes
120
provided between plasma generation chamber
122
and

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