Electric heating – Metal heating – By arc
Reexamination Certificate
2003-06-02
2004-10-19
Van, Quang T (Department: 3742)
Electric heating
Metal heating
By arc
C219S121400
Reexamination Certificate
active
06806437
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for generating inductively coupled plasma (ICP), and more particularly, to an ICP generating apparatus incorporating a double-layered coil antenna to improve uniformity of plasma density around a substrate within a reaction chamber.
2. Description of the Related Art
Low voltage and low temperature plasma technology is used in the manufacture of semiconductor devices and flat display panels. Plasma is used for etching or depositing certain materials on the surfaces of wafers for fabricating semiconductor devices, or substrates for fabricating liquid crystal display (LCD) panels. Particularly, in etching or thin film deposition processes for manufacturing highly integrated semiconductor devices, the use of plasma equipment is increasing. Therefore, development of plasma generating apparatuses appropriate for etching, deposition, or other processes is important for the development of semiconductor manufacturing processes and equipment. The most important factors in the development of plasma equipment for semiconductor manufacturing processes are the capability to operate on large substrates in order to enhance production yield, and capability to perform processes for fabricating highly integrated devices. Specifically, in accordance with a recent increase in wafer size from 200 mm to 300 mm, enhancing uniformity of wafer treatment processes as well as keeping high plasma density have become very important.
Various types of plasma equipment have been used in conventional semiconductor manufacturing processes, e.g., a capacitive coupled plasma (CCP) type, an electron cyclotron resonance (ECR) type, a helicon type, an inductively coupled plasma (ICP) type, and a hybrid type combining two or more of the foregoing types. Among the various types of plasma equipment, the ICP type equipment is considered to be the best equipment for the 300 mm large-size wafers because the ICP equipment can generate plasma with high density and high uniformity and has a simple structure compared to the other types of plasma equipment. However, development of ICP equipment for 300 mm wafers is not easily achieved by simply changing the dimensions of existing ICP equipment for 200 mm wafers. There are plenty of limitations due to difficulties in designing antennas that are essential to ICP discharges.
FIG. 1
shows the structure of a conventional ICP generating apparatus. As shown in
FIG. 1
, the ICP generating apparatus includes a reaction chamber
10
including a space for generating plasma. An electrostatic chuck
12
for supporting a substrate, e.g., a wafer, is provided at a lower portion Within the reaction chamber
10
, and a dielectric window
16
is formed in an upper cover
11
of the reaction chamber
10
. A gas supply port
14
for supplying reaction gas into the reaction chamber
10
is formed at a sidewall of the reaction chamber
10
, and a plurality of gas distribution ports
15
connected to the gas supply port
14
are provided within the reaction chamber
10
. A vacuum suction port
18
is formed at the bottom of the reaction chamber
10
and connected to a vacuum pump
19
for evacuating the inside of the reaction chamber
10
. Further, a coil antenna
20
for generating plasma within the reaction chamber
10
is provided above the dielectric window
16
.
The coil antenna
20
is connected with a power source (not shown) for supplying radio frequency (RF) current. As the RF current flows in the coil antenna
20
, a magnetic field is produced around the coil antenna
20
, and in accordance with variation of the magnetic field as a function of time, an electric field is induced within the reaction chamber
10
. At the same time, the reaction gas is supplied into the reaction chamber
10
through the gas distribution ports
15
, and is ionized by collisions with electrons accelerated by the induced electric field to generate plasma within the reaction chamber
10
. The generated plasma chemically reacts with the surface of the wafer W so that the wafer W is subject to a desired process, e.g., etching. Meanwhile, an additional RF power source (not shown) is generally connected to the electrostatic chuck
12
for supplying a bias voltage to increase the energy of ions derived from the plasma and collided with the wafer W.
FIG. 2
shows an example of a conventional spiral coil antenna, and
FIGS. 3A and 3B
show electric field distribution and density of plasma generated within the reaction chamber shown in
FIG. 1
by the spiral coil antenna shown in
FIG. 2
, respectively. As shown in
FIG. 2
, the spiral coil antenna
30
is typically comprised of a single spirally wound conductive coil. However, the spiral coil antenna
30
has a disadvantage in that the magnitude of the electric field induced thereby is not uniform. That is, as shown in
FIG. 3
a
, the electric field is relatively weak at the edge portion of the spiral coil antenna, and is strong at the center portion thereof. Therefore, the density of the plasma generated is highest at the center portion of the reaction chamber.
The most densely generated plasma at the center portion of the reaction chamber is diffused toward a wafer placed near the bottom of the reaction chamber. Consequently, the density of the plasma in an area near the wafer surface where reaction between the plasma and the wafer occurs is high at the center portion of the area near the wafer surface, and is low at the edge portions of the area near the wafer surface. Such irregular distribution of the plasma density causes a problem of the depth to which the wafer or substrate is etched or the thickness to which a material is deposited on the wafer or substrate being non-uniform over the surface thereof. As the diameter of the reaction chamber is increased to accommodate larger wafers, this non-uniformity problem becomes more serious. Further, in order to keep the plasma density sufficiently high within the reaction chamber, the radius of the antenna
30
and the number of turns of the coil should be increased to conform to the increased size of the ICP equipment. However, increasing the number of turns of the coil causes another problem in that the self-inductance of the antenna increases, and accordingly, the efficiency of the plasma discharges is degraded.
FIGS. 4A through 4C
show various antennas that have been proposed to solve the above-described problems of coil antennas.
FIG. 4A
shows an antenna
40
disclosed in U.S. Pat. No. 5,401,350, which includes a spiral coil antenna
40
a
placed on the upper portion of a reaction chamber
42
, and an additional solenoid-type antenna
40
b
wound around the outer surfaces of the sidewalls of the reaction chamber
42
. The antenna
40
shown in
FIG. 4A
compensates for the low plasma density at the edge portions of the reaction chamber
42
to solve the problem of the non-uniform plasma density distribution that is encountered with the conventional spiral coil antenna described above. However, since the additional antenna
40
b
is wound around the outer surfaces of the sidewalls of the reaction chamber
42
, the portions of the reaction chamber
42
corresponding to the antenna
40
b
should be made of a dielectric substance. Further, an additional coolant passage should be provided for cooling the antenna
40
b
. Therefore, the antenna as shown in
FIG. 4A
has a problem in that the entire size of the apparatus increases.
FIG. 4B
shows another antenna
50
disclosed in U.S. Pat. No. 6,291,793, which includes a plurality of spiral coils
52
,
54
, and
56
branching off in parallel. The multiple and parallel type antenna
50
shown in
FIG. 4B
has a merit in that the self-inductance of the antenna
50
can be lowered as the number of branching off coils
52
,
54
, and
56
increases. However, such multiple and parallel type antenna has disadvantages in that the density of the plasma generated at the center portion of the antenna
50
is low, and parameters for controlling the uniformity of the plasma density
Samsung Electronics Co,. Ltd.
Van Quang T
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