JP2000064959A - Exhaust system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge a regulation range of an exhaust speed by a method wherein an exhaust impedance regulator and an exhaust pump varying an exhaust speed through drive of an inverter are arranged in series, in an exhaust device to regulate a container to a given internal pressure by effecting exhaust as gas is fed in the container. SOLUTION: When carrier gas is fed from a gas introduction pipe 12 to a reaction container 11 and exhaust operation is started, an exhaust pump 16 communicated with an exhaust pipe 14 through a control valve (an exhaust impedance regulator) 15 is started. In this case, the opening of the control valve 15 is fixed to a set value, and the frequency of an inverter 18 to drive the exhaust pump 16 is linearly increased. When the output value of a pressure gauge 13 attains a set value, a control valve 15 is slightly closed trough a pressure control part 17b by the main control part 17a of a controller 17 and a pressure value is regulated to the set value. Thereafter, when a container is brought into a steady control state, reaction gas is also introduced through a gas introduction pipe 12 to effect formation of a film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system which supplies gas into a vessel and controls the pressure in the vessel to a predetermined pressure while supplying gas into the vessel, such as a sputtering apparatus or a CVD apparatus. Since the -VPE (metal-organic vapor phase epitaxy) apparatus is used for growing a multilayer film, the conditions are wide, and therefore it is required to adjust the pumping speed in a wide range. The present invention relates to an exhaust device capable of obtaining stable pressure regulation.

[0002]

2. Description of the Related Art An example of a conventional apparatus will be described with reference to the drawings.
FIG. 3 is a diagram conceptually showing the above. In the figure, reference numeral 1 denotes, for example, a reaction vessel of a CVD apparatus, which is heated to a predetermined temperature, but has no relation to the gist of the present invention, so that the description is omitted. The reaction vessel 1 is provided with a gas introduction pipe 2, and a material gas and a carrier gas are introduced. Further, a pressure gauge 3 is provided to compare with a set value. Further, an exhaust pipe 4 is provided. At the end of the exhaust pipe 4, an exhaust device in which a control valve 5 for adjusting exhaust impedance and an exhaust pump 6 are connected in series is connected. A controller 7 is provided for controlling the control valve 5 based on the result of comparing the value of the pressure gauge 3 with the set value.

At the time of film growth, a material gas and a carrier gas are supplied at a predetermined flow rate from a gas introduction pipe 2, and an unreacted gas, a gas generated by the reaction, a carrier gas and the like are supplied from an exhaust pipe 4 via a control valve 5 to an exhaust pump 6. Exhausted by The pressure in the reaction vessel 1 is determined by the balance of the flow rate of the introduced gas, the increase / decrease due to the reaction, the pumping speed, the temperature in the reaction vessel 1, and the like. The pressure is set to an appropriate value according to the type of the film to be grown, the material gas, and the like. Therefore, when the value of the pressure gauge 3 is higher than the set value, the controller 7 opens the control valve 5 to increase the pumping speed. When the value of the pressure gauge 3 is lower than the set value, the controller 7 closes the control valve 5 to reduce the exhaust speed.

An exhaust pump 6 in this apparatus exhausts gas with almost constant power, and controls an apparent exhaust speed by a control valve 5.

[0005]

There are various types of material gases, for example, MO-VPE apparatuses for forming multi-layer films of compound semiconductors of various materials, and various films are formed.
Therefore, the flow rate of the supplied material gas and the pressure at the time of film formation are required to have a wide adjustment range, and the adjustment range is not sufficient when applying the above-described configuration to equipment. Therefore, the present invention provides an exhaust device in which the adjustment range of the exhaust speed is expanded.

[0007]

In order to solve the above-mentioned problems, an exhaust device according to the present invention is an exhaust device which exhausts gas while supplying gas to the container and adjusts the inside of the container to a predetermined pressure.
The invention is characterized in that an exhaust impedance controller and an exhaust pump whose inverter-driven variable exhaust speed is variable are arranged in series. According to this configuration, when controlling in a state where the exhaust speed is high, maintaining the state where the rotation of the exhaust pump is increased and controlling the pressure of the container with the exhaust impedance adjuster,
Conversely, the exhaust impedance adjuster was opened (low resistance)
The state may be maintained and controlled by the rotation speed of the exhaust pump.
When controlling at a low pumping speed, keep the rotation of the pump low and control the pressure of the vessel with the pump impedance adjuster, or conversely, keep the pump impedance regulator squeezed (high resistance). The pressure may be controlled by the rotation speed of the exhaust pump. By doing so, it is possible to control the exhaust speed in a wide range.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a drawing conceptually showing this. In the figure, reference numeral 11 denotes a reaction vessel of an MO-VPE apparatus which is heated to a predetermined temperature, but has no relation to the gist of the present invention, so that the description is omitted. The reaction vessel 11 is a gas introduction pipe 1
2 and a material gas and a carrier gas are introduced. Further, a pressure gauge 13 is provided to compare with a set value.
Further, an exhaust pipe 14 is provided. At the end of the exhaust pipe 14 is connected an exhaust device in which a control valve 15 for adjusting exhaust impedance and an exhaust pump 16 are connected in series. The exhaust pump 16 is driven and controlled by an inverter 18 and has a variable rotation speed. Then, the controller 17 instructs the inverter 18 on the rotation speed (exhaust speed) of the exhaust pump, compares the value of the pressure gauge 13 with the set value, and controls the control valve 15 based on the result. That is, the controller 17 includes a main controller 17a and a pressure controller 17b. The main control unit 17a controls the pressure control unit 17b and the inverter 18 and performs overall control. The pressure control unit 17b compares the value of the pressure gauge with the set value every moment, and controls the control valve 15 based on the result. To control.

Next, the setting of the exhaust conditions of the apparatus will be described. FIG. 2A is a graph showing the time history of the opening degree of the control valve 15, and FIG. 2B is a graph showing the time history of the output frequency of the inverter 18 (the rotation speed of the exhaust pump 16). FIG. 2C shows the pressure gauge 13.
6 is a graph showing the time course of the output values of FIG. The following conditions shown in these graphs must be set in advance. It is not necessary to set in the order of description. a) The opening F of the control valve 15 when the exhaust gas is started up: An intermediate value may be used so as not to open or close too much. b) Inverter frequency A at the start of evacuation T0: This is set to a low value because abrupt initial evacuation causes inconveniences such as winds in the reaction vessel 11 caused by air and dust soaring. c) Pressure value B to be controlled: this set value and pressure gauge 1
The control is performed by comparing with the output value of No. 3. d) Inverter frequency C at the time of control: When the pressure is controlled to be constant, it is kept constant (therefore, the capacity of the exhaust pump is fixed) and controlled by the control valve 15. At this time, the control valve 15 is used in consideration of the flow rate of the supplied gas and the pressure value to be controlled.
Is selected such that the opening degree of the control is 20 to 30% with good controllability. e) Inflection point D (time tD from T0 and frequency Df) at the start of inverter frequency: Set according to the assumed pressure reduction curve. f) Time t until point E where the inverter enters constant frequency C operation
E: Time T1 at which set pressure B is reached is later than point D at point E
Set to be earlier. g) Time toff from exhaust stop signal time T2 until exhaust pump 16 stops.

Next, the operation will be described. Gas inlet pipe 1
When the exhaust operation is started by supplying a predetermined flow rate of the carrier gas from the control valve 15, the control valve 15
Through the exhaust pump 16 via the pump. At this time, the opening of the control valve 15 is fixed at the set value F, and the frequency of the inverter 18 for driving the exhaust pump 16 starts at the initial set value A and linearly increases toward the frequency Df at the point D. Thereafter, the frequency increases with a gentler rising gradient toward the point E. When the output value of the pressure gauge 13 reaches the set value B at time T1 before reaching the point E, the main control unit 17a activates the pressure control unit 17b to start pressure control. Then, the pressure is controlled by the pressure control unit 17b, the control valve 15 is slightly closed, and the pressure is controlled to the set value B. Thereafter, the opening of the control valve 15 is adjusted according to the output value of the pressure gauge 13 every moment. Thereafter, after reaching point E, the rotation of the exhaust pump becomes constant, and the pressure adjustment is performed only by adjusting the opening of the control valve, thereby entering a steady control state. Then, a reaction gas is introduced from the gas introduction pipe 12 in addition to the carrier gas to form a film. Since the amount of the reaction gas is smaller than the amount of the carrier gas, the disturbance of the pressure is small even at the beginning of the introduction, and the control is restored immediately.

When a stop signal is given at time T2 after the completion of the predetermined film formation, the reaction gas is stopped and the set to
During the time ff, the frequency of the inverter 18 is changed to the exhaust pump 1
6 drops linearly to the point where it does not work. Then, since the exhaust capacity of the exhaust pump 16 decreases, the pressure control unit 1
The control valve 15 is fully opened by the control of 7b, but the pressure in the reaction vessel increases as the exhaust amount of the exhaust pump 16 further decreases. Then, the exhaust pump 16 stops and the operation ends.

Although the above embodiment has been described with reference to one type of film formation, if it is necessary to use different exhaust conditions for performing various types of film formation with this apparatus, the respective settings are stored and the switching application is performed. You should do it. The same applies to the case where it is used for forming a multilayer film.

According to this device, the capacity of the exhaust pump can be variably set, so that the pressure control by the control valve can be performed at the opening with the best controllability, so that stable control can be performed. Further, the controllable range is significantly widened.

[0014]

As described above, according to the exhaust system of the present invention, a wide variable range of the exhaust speed can be obtained, and a wider range of conditions can be controlled by controlling the pressure in the container.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a graph (time chart) showing the operation state, and FIG. 2 (a) shows the time course of the opening degree of the control valve. (B) shows the time history of the output frequency of the inverter 18 (the rotation speed of the exhaust pump 16). (C) shows the time history of the output value of the pressure gauge 13.

FIG. 3 is a block diagram showing a conventional device.

[Explanation of symbols]

Reference Signs List 11 reaction vessel (vessel) 12 gas supply pipe 13 pressure gauge 14 exhaust pipe 15 control valve (exhaust impedance adjuster) 16 exhaust pump 17 controller 17a main control section 17b pressure control section 18 inverter

Claims (3)

[Claims] 1. An exhaust device for adjusting the inside of a container to a predetermined pressure by exhausting gas while supplying gas to the container, wherein an exhaust impedance controller and an exhaust pump having a variable exhaust speed driven by an inverter are arranged in series. Exhaust device. 2. The exhaust device according to claim 1, wherein in a steady control state in which the pressure is controlled to be constant, the exhaust speed of the exhaust pump is fixed, and the exhaust pump is controlled by the exhaust impedance adjuster. 3. The exhaust device according to claim 1, wherein in a steady control state in which the pressure is controlled to be constant, the exhaust impedance adjuster operates in a fixed manner, and controls the exhaust speed of the exhaust pump by adjusting the exhaust speed.