Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – Having glow discharge electrode gas energizing means
Reexamination Certificate
2000-09-19
2003-04-22
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
Having glow discharge electrode gas energizing means
C156S345470, C118S7230ER, C204S298370
Reexamination Certificate
active
06551445
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a plasma processing system for processing the surface of a semiconductor substrate (semiconductor wafer) or the like through physical action or chemical reaction of particles activated by conversion of a starting gas into a plasma.
A parallel plate ECR (electron cyclotron resonance) plasma system using UHF (ultrahigh frequency) is described in Japanese Patent Laid-Open No. 321031/1997 (corresponding U.S. Pat. No. 5,891,252). According to the invention set out in the publication, the problems to solve are to achieve processing of a high speed, a high selection ratio and a high aspect ratio, and a stable etching characteristic over a long time. For solving the problems, an electron cyclotron resonance phenomenon with an electromagnetic wave from a UHF power supply is used to form a plasma wherein the electromagnetic wave is radiated from a circular conductor plate located at a position in face-to-face relation with a substrate to be processed.
It will be noted that an etching system using a permanent magnet is disclosed, for example, “1988 Dry Process Symposium”, 1988, pp. 54-57. The etching system disclosed in this literature is called magnetron RIE system wherein a permanent magnet is located over a processing chamber so as to permit RF power (13.54 MHz) only to a wafer, thereby generating a plasma on a main surface of the wafer.
We have made studies on a plasma etching system particularly shown in
FIG. 13
, based on the plasma processing system disclosed in the publication.
FIG. 13
is a view showing an arrangement of a parallel plate ECR plasma processing system for etching a substrate (semiconductor wafer) to be processed. In
FIG. 13
, a processing chamber
1
has therein a planar plate
2
provided with a shower plate
10
, a dielectric substance, and a processing mount
9
. A process gas is introduced into the processing chamber
1
from a gas feed port
5
provided at the planar plate
2
via the shower plate
10
. A ultra-high-frequency (UHF) electromagnetic wave of 300 MHz to 1 GHz generated in a high frequency power supply
11
is introduced into the etching chamber from the planar plate
2
through a tuner
13
wherein a gas is converted to a plasma. In order to permit the UHF electromagnetic wave to be efficiently transmitted into the processing chamber, the outer diameter of the planar plate
2
and the type of dielectric substance
3
are, respectively, determined so that the high frequency is resonated at a desired mode (TM
01
mode herein) between the planar plate
2
and an earth
4
.
The UHF electromagnetic wave is resonated between the planar plate
2
and the earth
4
and transmitted from the periphery of the dielectric substance
3
toward the processing chamber
1
. For high efficiency discharge, a solenoid coil
17
for generating a magnetic field is disposed around the processing chamber
1
, and a coil current is so controlled that a magnetic field ranging from 0 gauss to 360 gausses is generated beneath the shower plate
10
. Eventually, there is generated a high density plasma having an electron density of 10
11
electrons/cm
3
or over by use of electron cyclotron resonance (ECR). A substrate
8
to be processed is set on the processing mount
9
and etched by means of the plasma. The etching gas is introduced into the etching chamber
1
through a gas feed port
5
and exhausted to outside of the etching chamber by means of an exhaust pump.
A high frequency bias of from 100 kHz to 15 MHz is applied from a high frequency power supply
15
via a tuner
16
to the processing mount
8
on which the substrate
8
to be processed is mounted. The distance between the substrate
8
to be processed and the shower plate
10
can be changed from 20 mm to 150 mm by use of a vertically moving mechanism for the mount
9
. The processing mount
9
has such a structure that enables one to provide a focus ring
7
with a width of about 30 mm around the substrate
8
to be processed. The focus ring
7
is so arranged that a high frequency is applied thereto as branched from 10 to about 50% of the high frequency power applied from the high frequency power supply
15
to the substrate
8
to be processed. Usually, the focus ring
7
is made of aluminium (Al) at the lower portion thereof and crystalline silicon (Si) at the upper portion thereof, and may be made of impurity-doped Si, silicon carbide (SiC) or Al at the upper portion thereof.
The planar plate
2
may be applied with a frequency (ranging from 10 kHz to 27 MHz), different from that from the high frequency power supply
11
, from a high frequency power supply
12
via a tuner
14
. This shower plate
10
is in contact with the planar plate
2
, and a coolant is introduced into the planar plate
2
from a coolant inlet
6
to control the temperature of the shower plate
10
.
In the system shown in
FIG. 13
, uniformity is optimized by changing an electric current mainly passing through the solenoid coil
17
to control the position of magnetic field intensity serving as an ECR condition.
In this arrangement, the plasma can be generated in a high efficiency, and the thus generated plasma is transported to the surface of a substrate to be processed with the aid of a magnetic field in an efficient manner, thus enabling one to make highly efficient processing. Moreover, the arrival of the plasma at the processing container walls is suppressed by the action of the magnetic field, thus making it possible to suppress the variation in processing conditions as will be accompanied by the change in the state of the processing container walls.
Our studies revealed that further problems to solve were involved in the above-stated plasma processing system.
The plasma processing system shown in
FIG. 13
has no problem on uniformity when the ion current flux ranges from low to medium levels and exhibits a linear characteristic relative to making power. However, when the making power is increased to obtain a high plasma density (of 10
11
/cm
3
or over), the wafer uniformity of the etching rate becomes 10% or over, and thus, a further improvement has been necessary. More particularly, the distribution of the etching rate is such that, as shown in
FIG. 5
, the rate becomes smaller only in the vicinity of the wafer center. This is ascribed to the uniformity of the plasma density, which has been a problem to solve.
In
FIG. 3
, there are shown a magnetic field vector (a) and an electric field vector of an electromagnetic wave by the influence of the solenoid coil
17
beneath the planar plate in the etching system shown in FIG.
13
. It has been uncovered that when using the etching system shown in
FIG. 13
, the angle of intersection between the direction of electric line of force (electric field vector (b)) and the magnetic line of flux (magnetic field vector (a)) is smaller at the center of the planar plate, thus the efficiency of plasma generation being low. More particularly, there is a portion, in which the magnetic field vector (a) is coincident with the electric field vector (b), at the center of the planar plate. Thus, this is considered to cause the non-uniformity under such high plasma density conditions as mentioned above.
SUMMARY OF THE INVENTION
An object of the invention is to provide a parallel plate ECR plasma processing system, which ensures uniform processing of a substrate to be processed in a low density to high density plasma condition.
Another object of the invention is to provide a method for making a semiconductor device, which includes the etching step capable of reducing an in-plane variation of a semiconductor wafer.
The parallel plane ECR plasma system of the invention includes a solenoid coil as a first magnetic-field-forming means and a second magnetic field-forming means located in the vicinity of a planar plate so as to from a local magnetic field. The magnetic field formed by the first magnetic field-forming means is influenced by the magnetic field from the second magnetic field-forming means so that an angle of intersection of an electr
Izawa Masaru
Momonoi Yoshinori
Negishi Nobuyuki
Tachi Shinichi
Yokogawa Ken'etsu
Dang Thi
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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