Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – By reaction with substrate
Reexamination Certificate
2000-11-06
2001-09-04
Mills, Gregory (Department: 1763)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
By reaction with substrate
C427S575000, C427S059000, C427S571000
Reexamination Certificate
active
06284674
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing device for subjecting an object such as a semiconductor wafer to a predetermined process such as film formation.
The invention also relates to a method of subjecting an object such as a semiconductor wafer to a predetermined process such as film formation by using a plasma.
With recent development in enhancing integration density and miniaturization of semiconductor products, plasma processing devices have been used in some cases in order to perform processes such as film formation, etching and ashing in steps of manufacturing the semiconductor products. In particular, a microwave plasma device tends to be used, since it can create a stable plasma even in a high vacuum state with a relatively low pressure of about 0.1 to 10 mTorr. In the microwave plasma processing device, a high-density plasma is created by combining microwaves and a magnetic field generated from a ring-shaped coil.
For example, there is known a conventional microwave plasma device wherein a plasma generating chamber having magnetic field generating means is provided with a microwave introducing port and an electron cyclotron resonance space is produced. Ions are extracted from the plasma generating chamber, and a process gas in a reaction chamber is activated by the plasma, thus performing various processes such as film formation.
FIG. 1
is a schematic diagram showing the structure of such a conventional plasma processing device. In the figure, a process chamber
11
is formed of, e.g. aluminum in a cylindrical shape. A table
12
for mounting of a semiconductor wafer W as an object to be processed is provided within the process chamber
11
. An upper part of the process chamber
11
is narrowed in a stepwise fashion and a plasma chamber
13
is formed in the upper part. A reaction chamber
14
is formed below the plasma chamber
13
.
A ceiling cover
15
of, e.g. quartz for sealing a ceiling portion of the process chamber
11
is airtightly provided on the upper part of the plasma chamber
13
. The ceiling cover
15
constitutes a microwave introducing window
16
. A conical taper waveguide
17
is connected in a member to face the microwave introducing window
16
. A rectangular waveguide
18
is connected to a top portion of the taper waveguide
17
. A microwave generator
19
for generating microwaves of, e.g. 2.45 GHz is provided on the rectangular waveguide
18
. Microwaves generated by the microwave generator
19
are introduced into the plasma chamber
13
through the microwave introducing window
16
via the rectangular waveguide
18
and taper waveguide
17
.
Ring-shaped main coils
20
and sub-coils
21
are disposed outside the plasma chamber
13
of process chamber
11
and below the bottom of the chamber, respectively. Each coil
20
,
21
generates a downward magnetic field and thereby a downward mirror field is produced within the entire process chamber
11
. In this case, the downward magnetic field and microwaves are set to meet the condition for electron cyclotron resonance. Specifically, if the frequency of microwaves is 2.45 GHz, the magnitude of the magnetic field is set at about 875 gauss.
Thus, the plasma gas, e.g. argon gas, introduced into the plasma chamber
13
is made into a plasma by electron cyclotron resonance caused by synergetic effect of applied microwaves and magnetic field. The generated plasma activates a process gas, e.g. silane gas and oxygen used as film formation gas, supplied to a lower part of the plasma chamber
13
. The activated process gas reacts and a reaction product deposits on the surface of the wafer as a thin film.
In the meantime, when the condition for electron cyclotron resonance is satisfied, the frequency of microwaves and the magnitude of magnetic field are definitively determined by setting the potential, mass, etc. of charged particles. However, if the frequency of microwaves is set at 2.45 GHz, as mentioned above, the main coils
20
and the sub coils
21
for obtaining the corresponding field intensity of 875 gauss become very large in size. For example, the weight of the main coil
20
becomes 100 Kg or more. Consequently, the cost for the plasma processing device increases, the maintenance work for the plasma processing device is time-consuming and the space for installation of the apparatus cannot be decreased.
In particular, in the case of a plasma processing device for processing 12-inch wafers, the diameter of the table
12
further increases, as compared to the apparatus for processing 8-inch wafers. Consequently, the size of the coil further increases, and the weight thereof becomes, for example, about 200 Kg. Under the circumstances, with an increase in diameter of the wafer, there is a demand for reducing the size of the coil.
In addition, when microwaves are supplied into the process chamber
11
, an impedance variation of the plasma will inevitably occur due to a variation, etc. in density of the generated plasma. Thus, all microwave power output from the microwave generator
19
is not supplied into the process chamber
11
, and some reflection power will occur due to mismatching of impedance.
In this case, an effective power contributing to plasma generation is equal to a difference between the output power and reflection power. In the prior art, however, no measure is conducted to control reflection power, and only output power is controlled. Thus, different powers may be supplied to wafers, depending on the impedance state of plasma. Consequently, reproducibility of process may deteriorate.
Furthermore, such reflection power is wasted since it does not contribute to plasma generation. From the standpoint of power consumption, the presence of reflection power is not desirable.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a plasma process apparatus with a small-sized electromagnetic coil. Another object of the invention is to provide a plasma process apparatus capable of reducing reflection power of microwaves. Still another object of the invention is to provide a plasma process method in which a small-sized coil can be used. Still another object of the invention is to provide a plasma process method capable of reducing reflection power of microwaves.
According to an aspect of the present invention, there is provided a plasma process apparatus which permits generating microwaves and a magnetic field so as to bring about electron cyclotron resonance and, thus, to generate a plasma which is applied to an object to be processed, comprising:
microwave generating means for generating said microwaves;
microwave transmitting means for transmitting the microwaves;
a process chamber having said object arranged therein, the microwaves being introduced into said process chamber through said microwave transmitting means;
process gas supply means for supplying a process gas into said process chamber; and
magnetic field generating means for generating a magnetic field within the process chamber,
wherein the frequency of the microwave falls within a range between a lower limit of a cutoff frequency determined by the inner diameter of the process chamber and an upper limit of a maximum frequency at which a standing wave of the microwave does not occur on the surface of the object.
This invention also provides a plasma process apparatus for processing an object by using a plasma produced by electron cyclotron resonance which is caused by generating microwaves and producing a magnetic field, said apparatus comprising:
microwave generating means for generating the microwaves;
microwave transmission means for transmitting the microwaves;
a process chamber in which the microwaves are introduced via the microwave transmission means and said object is disposed;
process gas supply means for supplying a process gas into the process chamber;
magnetic field generating means for generating a magnetic field in the process chamber; and
matching means for freely varying the impedance of the microwaves in the microwave transmission means, wherein
Kawakami Satoru
Toraguchi Makoto
Mills Gregory
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
Zervigon Rudy
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