System for manufacturing a semiconductor device

Details System for manufacturing a semiconductor device System for manufacturing a semiconductor device

1999-02-26

2001-08-14

Mills, Gregory (Department: 1763)

Coating apparatus

Control means responsive to a randomly occurring sensed...

Responsive to condition of coating material

C118S715000

Reexamination Certificate

active

06273954

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for manufacturing a semiconductor device, and more specifically, it relates to a system for forming a thin film on a surface of a sample or etching the surface of the sample with plasma.
2. Description of the Prior Art
FIG. 12
illustrates the structure of a plasma system described in Japanese Patent Laying-Open No. 7-263353 (1995). As shown in
FIG. 12
, the plasma system includes a reaction chamber
1
, a stage
12
for receiving a sample
11
thereon, a pulse gas valve
20
, a gas introduction tube
141
, a pressure detector
142
, a pressure controller
143
and a pressure regulator
144
.
The gas introduction tube
141
supplies a gas from a gas cylinder (not shown) into the pulse gas valve
20
. The pressure detector
142
and the pressure regulator
144
are connected to intermediate portions of the gas introduction tube
141
. The pressure controller
143
drives the pressure regulator
144
on the basis of a signal from the pressure detector
142
.
The gas introduced from the gas introduction tube
141
is supplied into the pulse gas valve
20
and pulsatively introduced into the reaction chamber
1
. The pressure detector
142
sequentially detects the pressure in the gas introduction tube
141
and feeds back the same to the pressure controller
143
. The pressure controller
143
controls the pressure regulator
144
for maintaining the pressure in the gas introduction tube
141
at a prescribed value.
Even if the back pressure of the pulse gas valve
20
fluctuates, therefore, the flow rate of an etching gas introduced into the reaction chamber
1
can be kept under prescribed conditions for maintaining the pressure in the reaction chamber
1
at a prescribed value.
However, the aforementioned conventional plasma system has the following problems:
In the aforementioned gas supply system, the flow rate of the gas supplied from the pulse gas valve
20
into the reaction chamber
1
is univocally determined by the pressure at the inlet of the pulse gas valve
20
. In order to stably pulsatively supply the gas at a prescribed flow rate, therefore, the pressure at the inlet of the pulse gas valve
20
must be maintained constant through the pressure controller
143
. The pressure controller
143
must be employed also for changing the gas flow rate. However, the gas flow rate cannot be correctly controlled or finely regulated through the pressure controller
143
.
Further, the flow rate of the gas supplied into the reaction chamber
1
, which is controlled by the pressure controller
143
, must be calculated from the pressure in the reaction chamber
1
. Therefore, the correct gas flow rate cannot be immediately recognized.
The pressure controller
143
controlling the pressure through the feedback signal from the pressure detector
142
is effective for slow pressure change. However, the pressure controller
143
cannot cope with abrupt pressure change, and hence it is difficult to maintain the gas flow rate at a constant value when remarkable pressure change takes place.
In case of supplying a gaseous mixture into the reaction chamber
1
through the single pulse gas valve
20
, the gas mixing ratio (flow ratio partial pressure ratio) is determined through the ratios of the specific heat of the gases and the pressure at the inlet of the pulse gas valve
20
. When the difference between the ratios of specific heat of the gases or the pressure difference between the gases is remarkable, therefore, it is difficult to obtain a desired mixing ratio.
In case of employing a plurality of pulse gas valves
20
or exchanging the pulse gas valve
20
, gases are supplied at different flow rates even if the valves
20
are pulsatively driven under the same conditions, due to the individual difference between the opening degrees thereof. It is difficult to obtain a desired gas flow rate also in this case.
When supplying a gas into a plurality of reaction chambers
1
from a single gas cylinder and starting processing in one of the reaction chambers
1
during processing in another reaction chamber
1
, the pressure in a pipe temporarily fluctuates to change the flow rate of the gas supplied into the reaction chambers
1
. It is difficult to obtain a desired gas flow rate also in this case.
SUMMARY OF THE INVENTION
The present invention has been proposed in order to solve the aforementioned various problems, and an object thereof is to control the flow rate of a gas supplied into a reaction chamber at a desired value under all situations.
Another object of the present invention is to control the mixing ratio of gases supplied into a reaction chamber
1
at a desired value under all situations.
A manufacturing system according to the present invention includes a reaction chamber, a gas supply system, a pulse valve, a gas flow controller, a back pressure controller, and a control part. The gas supply system supplies a gas into the reaction chamber. The pulse valve is provided on the gas supply system and pulsatively supplies the gas into the reaction chamber. The gas flow controller is provided on the gas supply system and controls the flow rate of the gas supplied to the pulse valve. The back pressure controller is provided on the gas supply system and controls the back pressure of the pulse valve. The control part controls the operations of the pulse valve, the gas flow controller and the back pressure controller.
The gas flow rate can be finely regulated by providing the gas flow controller as described above. The back pressure controller can suppress fluctuation of the back pressure of the pulse valve, for suppressing fluctuation of the gas flow rate resulting from fluctuation of the back pressure. Consequently, the gas flow rate can be correctly controlled and finely regulated. Further, the gas flow rate can be immediately detected due to employment of the gas flow controller. Even if the difference between ratios of specific heat of gases or pressure difference between gases is remarkable, a desired mixing ratio can be obtained by employing the gas flow controller as well as the back pressure controller, and the gas flow rate can be controlled despite individual difference between pulse valves or fluctuation of the pressure in a pipe. The problems of the prior art can be solved in the aforementioned manner, while the gas flow controller and the back pressure controller can be controlled to compensate for mutual disadvantages. This also can contribute to correct control of the gas flow rate.
The back pressure controller is preferably connected to an inlet of the gas flow controller.
Thus, a gas controlled at a constant pressure can be supplied to the gas flow controller, for stably supplying a prescribed volume of gas into the reaction chamber. This is particularly effective for abrupt pressure change.
The gas flow controller preferably includes a flow meter and a variable flow control valve. The back pressure controller preferably includes a pressure gauge and a pressure control valve. The control part preferably selects at least either flow control by the variable flow control valve or back pressure control by the pressure control valve in response to change of the gas flow rate detected by the flow meter.
Thus, the preferable control system can be selected in response to change of the gas flow rate, whereby the flow rate of the gas can be correctly and readily controlled.
The control part may select at least either the flow control by the variable flow control valve or the back pressure control by the pressure control valve in response to the pressure of the gas detected by the pressure gauge.
Also in this case, the flow rate of the gas can be correctly and readily controlled similarly to the above.
Preferably, the gas flow controller is a mass flow controller. In this case, the pulse valve and the mass flow controller are preferably integrated or directly connected with each other.
Thus, it is possible to prevent difference between a value indicated by the mass flow controller an

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