JP5195527B2 - Flow control device and process device - Google Patents

Description

  The present invention relates to a flow rate control device that controls the flow rate of a reaction gas supplied to a process device. In particular, the present invention relates to a flow rate control device that controls the flow rate of a reaction gas in a process device including a gas supply source in a reduced pressure state.

In recent years, the use of ozone (element symbol: O ₃ ) has been developed in various fields including water and sewage treatment using its strong oxidizing power. In particular, in the field of manufacturing semiconductor devices, application to Si wafer cleaning and TEOS-CVD (Tetra Ethyl Ortho Silicon-Chemical Vapor Deposition) is being studied. In Si wafer cleaning, ozone water in which ozone gas is dissolved in pure water is used as a cleaning liquid, and it has been announced that heavy metals and organic substances on Si wafer can be removed by using together with dilute hydrofluoric acid aqueous solution (electronic material 1999). March issue PP. 13-18). TEOS-CVD is used to form an interlayer insulating film when a semiconductor element is formed into a multilayer wiring, and is characterized in that the unevenness of the wafer surface caused by the electrodes can be planarized by the insulating film. It has been reported that the planarization performance is improved by adding ozone to the TEOS-CVD (Jpn. J. Appl. Phys. Vol. 32 (1993) PP. L110-L112).

  These are examples using ozone gas with a relatively low concentration of about 10%, but by using ozone gas with a relatively high concentration of 80% or more, there is a possibility of a new application that could not be considered by conventional ozone gas usage. Has begun to be pointed out. As an example, there is an oxide film formation of a Si semiconductor disclosed in JP-A-8-335576. According to this publication, it is possible to form an oxide film at a relatively low temperature, which is impossible with the conventional thermal oxidation method, and to form a high-quality oxide film with less suboxide layer and defect structure. Has been.

  By the way, a silent discharge system is generally used to generate ozone gas. This generates a mixed gas of ozone and oxygen from oxygen gas by electric discharge. Due to the limit of generation efficiency and danger of explosion, it is difficult to generate ozone gas of about 10% by volume or more under normal temperature and pressure. It was.

  Thus, Japanese Patent Publication No. 5-17164 introduces a method of generating high-concentration ozone gas of 80% or more by liquefying and storing the generated ozone gas and then vaporizing it. This method will be described with reference to the liquid ozone production apparatus shown in FIG.

  This apparatus for producing liquid ozone is composed of an ozone gas generator and an exhaust device 1 and a liquid ozone generator 2 for liquefying ozone. Oxygen gas is sent from the oxygen cylinder 3 to the ozonizer 5 through the pressure adjustment valve 4. In the ozonizer 5, the oxygen gas becomes an ozone-containing oxygen gas in which ozone gas is mixed with oxygen by silent discharge, and passes through a mass flow controller 6 for controlling the flow rate and a particulate removal filter 7 for removing particulates in the ozone-containing gas. It is introduced into a liquid ozone generator 2 that liquefies ozone gas.

  In the liquid ozone generator 2, as shown in detail in FIG. 4, the ozone-containing oxygen gas obtained by mixing the ozone gas with the oxygen gas introduced from the ozone gas generator 1 is supplied with the flow rate adjusting valve 8 and the ozone-containing oxygen gas introduction pipe. 25 is introduced into the ozone chamber 9. The ozone chamber is thermally coupled to a cold head 19 that has been cooled by a refrigerator 20 that is driven in advance by a compressor 21, and a temperature within 0.1 K by a temperature sensor 24, a heater 23, and a temperature control device 22. The temperature can be precisely controlled with accuracy, and is kept at a low temperature of 80K to 100K.

  The principle of liquefaction of ozone gas is to liquefy only ozone gas by the difference in vapor pressure between ozone and oxygen. For example, at 1 atmosphere, ozone has a boiling point of 161K, while oxygen has a boiling point of 90K. Therefore, if it is cooled to a temperature of 90K or more and less than 161K, most of ozone is in a liquid state and most of oxygen is in a gaseous state, so that only ozone can be separated as a liquid.

  Actually, since it is handled under reduced pressure conditions for safety against explosive properties of high-concentration ozone, the separation conditions are determined by the difference between the vapor pressures of ozone and oxygen under the temperature and pressure conditions. For example, if the temperature is 90 K and the pressure is 10 mmHg (= 13.3 hPa), the ozone vapor pressure is almost 0 mmHg (= 0 Pa) at 90 K, but oxygen is about 690 mmHg (= 918 hPa), and only ozone is under this condition. Liquefied.

  Thus, in the ozone chamber 9, only ozone gas is liquefied by the difference in vapor pressure between ozone and oxygen at the cooled temperature. When the ozone gas is liquefied, the valve 15 between the oxidation treatment container 16 is closed and the valve 10 connected to the ozone killer 11 is opened. Oxygen gas that is not liquefied through the ozone discharge pipe 26 and the valve 10 connected to the ozone chamber is introduced into the ozone killer 11 that is heated and converted into oxygen so that the remaining ozone gas is not discharged to the outside, and is heated by the ozone killer 11. A gas cooler 12 for cooling the generated oxygen gas and a liquid nitrogen trap 13 for preventing contamination and mixing of the ozone chamber by carbides from the vacuum pump 14 and the like are discharged to the outside by the vacuum pump 14.

  When the liquefied liquid ozone 27 is used for the purpose of oxidation or the like in the oxidation treatment container 16, the flow rate adjusting valve 8 and the valve 10 are closed and the valve 15 is opened. By raising the temperature of the ozone chamber thermally coupled to the cold head 19 by the temperature sensor 24, the heater 23 and the temperature control device 22, liquid ozone is vaporized and oxidized as ozone gas through the ozone discharge pipe 26 and the valve 15. It is introduced into the processing container 16. In addition, the safety valve 18 is for expelling liquid ozone or high-concentration ozone gas.

  In addition, when a process such as surface oxidation or film formation by CVD is performed, the flow rate of the gas used is one of the most important parameters. Therefore, as shown in Patent Documents 1 and 2, flow control has always been performed with stability and good reproducibility.

JP-A-6-318116 Japanese Patent No. 3247758

  FIG. 5 shows a configuration diagram of a process apparatus using high-concentration ozone. Since the high-concentration ozone gas may cause an explosion when the gas pressure becomes high, the pressure in the liquid ozone chamber in FIG. 5 must always be maintained in a reduced pressure state (a state below atmospheric pressure). For this reason, the ozone gas supply line to the process apparatus is also in a reduced pressure state.

  As described in the prior art, when performing processes such as surface oxidation and film formation by CVD, the gas flow rate to be used is one of the most important parameters. . Usually, a mass flow controller is used for such flow rate control.

  However, when supplying high-concentration ozone gas, a general mass flow controller uses a piezoelectric valve, so that the pressure loss in the controller portion becomes large, and there is a problem that the pressure on the supply side is set to atmospheric pressure or higher.

  Further, a general mass flow controller uses a sensor utilizing gas specific heat as a flow rate sensor, but there are problems that the sensor part is easily corroded by ozone and that measurement cannot be performed without a pressure of about atmospheric pressure.

  Recently, a process using a liquid source has been used in CVD or the like, and there is a flow control device 42 configured as shown in FIG. 6 as a mass flow controller that can be used even in a reduced pressure supply source.

  FIG. 7 shows a configuration diagram when the flow rate control device 42 is applied to a process device 28 that supplies the process chamber 16 from the high-concentration ozone gas supply device 2, for example.

  As shown in FIG. 7, when the high-concentration ozone chamber 9 is in a reduced pressure state, the process chamber 16 is provided with a vacuum pump 29. Then, the ozone accumulated in the ozone chamber 9 is supplied to the process chamber 16 through the valve 15, the flow control device 42, and the valve 30 by evacuation.

  The flow rate control device 42 is provided to obtain a stable flow rate. Specifically, as shown in FIG. 6, the variable conductance valve 39 is controlled so that the pressure measured by the internal pressure gauge 40 becomes constant, and the pressure loss is reduced by the flow restrictor 41 at the tip of the internal pressure gauge 40. A stable flow rate is obtained by making it happen.

  In the case of this system, when a conductance change from the flow rate control device 42 to the process chamber 16, a change in exhaust speed in the process chamber 16, a mixing with other gas in the process chamber 16, etc. occur, the mounting portion of the internal pressure gauge 40 The pressure at changes. Therefore, it is necessary to calibrate the control input / output of the flow control device 42 by measuring the correspondence between the gas flow rate and the pressure of the internal pressure gauge 40 for each process condition.

  This method has no problem as long as it is a process apparatus that always performs the same simple process. However, stable control is difficult in an apparatus having a plurality of chambers such as a multi-chamber process apparatus or a multilayer film forming apparatus that changes gas mixing in a complicated manner.

  Furthermore, this method has a problem that the flow cannot be confirmed because the flow rate is displayed even when the gas inlet valve 30 of the process device 28 is closed.

  Accordingly, an object of the present invention is to always supply a gas having a calibrated flow rate even when the configuration and process conditions on the process apparatus side change.

  The flow control device of the present invention that achieves the above object includes a flow restrictor disposed in a pipe for supplying a reaction gas to a reaction vessel, and a first variable conductance disposed on the upstream side of the flow restrictor in the pipe. A valve, a second variable conductance valve disposed downstream of the flow restrictor in the piping, a pressure between the flow restrictor and the first variable conductance valve, the flow restrictor, and the second restrictor. A valve control device for controlling the first variable conductance valve and the second variable conductance valve based on a pressure between the variable conductance valves, wherein the valve control device includes the flow restrictor and the second variable conductance valve. The second variable conductance valve is controlled so that the pressure between the variable conductance valves is constant, and the conductance of the flow restrictor Based on the pressure between the flow restrictor and the second variable conductance valve, a target pressure value between the flow restrictor and the first variable conductance valve at which the reaction gas becomes a target flow is calculated, and the flow restriction The first variable conductance valve is controlled such that the pressure between the pressure sensor and the first variable conductance valve indicates the target pressure value.

  The flow control device may include a differential pressure gauge that detects a pressure between the flow restrictor and the first variable conductance valve and a pressure between the flow restrictor and the second variable conductance valve. .

  The process apparatus of the present invention that achieves the above object is the process apparatus for supplying a reaction gas to a reaction vessel and performing a reaction, wherein the flow rate control device is provided in a pipe for supplying the reaction gas. Features.

  Further, the reaction gas is ozone gas, the ozone gas is stored as liquid ozone in an ozone accumulation chamber, and ozone gas evaporated from the liquid ozone gas is supplied to the reaction vessel.

  A stable flow rate of gas can be supplied to the reaction vessel even if the pressure in the chamber is reduced.

  Therefore, according to the above invention, it is possible to always supply a gas having a calibrated flow rate even when the configuration and process conditions on the process apparatus side change.

1 is a schematic view of a flow control device according to an embodiment of the present invention. Schematic of the process apparatus provided with the flow control device concerning the embodiment of the present invention. The schematic sectional drawing of a liquid ozone manufacturing apparatus. Detailed sectional drawing of a liquid ozone manufacturing apparatus. Schematic of process equipment using high-concentration ozone. Schematic of the flow control apparatus which concerns on a prior art. Schematic of the process apparatus provided with the flow control apparatus which concerns on a prior art.

  A flow control device and a process device according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

  FIG. 1 is a schematic diagram of a flow rate control apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a process apparatus including the flow rate control apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the flow control device 37 according to the embodiment of the present invention includes a flow restrictor 36 in a pipe for supplying a reaction gas. The first variable conductance valve 32 is disposed in the upstream pipe of the flow restrictor 36 and includes a pressure gauge 34 that measures the pressure between the flow restrictor 36 and the variable conductance valve 32.

  In addition, a second variable conductance valve 33 is disposed on the downstream side of the flow restrictor 36 and includes a pressure gauge 35 that measures the pressure between the flow restrictor 36 and the variable conductance valve 33.

  The variable conductance valves 32 and 33 are controlled by a valve control device 38. Based on the conductance characteristic of the flow restrictor 36 and the pressure measured by the pressure gauge 35, the valve control device 38 calculates the pressure at the pressure gauge 34 so that the reaction gas flows at the set flow rate. Based on this, the variable conductance valve 32 is controlled.

  A control method by the flow rate control device 37 configured as described above will be described.

  First, the variable conductance valve 33 is controlled so that the pressure of the pressure gauge 35 becomes constant.

  Subsequently, the valve control device 38 uses the flow restrictor 36 and the first variable so that the reaction gas flow rate becomes a preset flow rate based on the conductance of the flow restrictor 36 and the pressure measured by the pressure gauge 35. The pressure value between the conductance valves 32 is calculated.

  The valve control device 38 controls the variable conductance valve 32 so that the pressure gauge 34 has the calculated value.

A calculation method in the valve control device 38 will be specifically described. If the flow rate required for the reaction is Q, the conductance of the flow restrictor 36 is C, and the measured values with the pressure gauges 34 and 35 are p1 and p2,
Q = C (p1-p2) (1)
It becomes.

  Therefore, as shown by the equation (1), when the flow rate Q and the pressure p2 necessary for the reaction are set, the value of the pressure p1 (that is, the indicated value of the pressure gauge 34) is obtained by calculation based on the conductance characteristic of the flow restrictor 36. Can do.

  Thus, since the valve control device 38 controls the variable conductance valve 32 so that the pressure gauge 34 shows the value obtained by calculation, the flow rate always calibrated even if the process side configuration and process conditions change. Gas can be supplied.

  When an abnormality occurs in the gas piping on the process apparatus side due to malfunction or the like, an abnormality in the flow rate can be detected.

  When the difference between the pressure values detected by the pressure gauge 34 and the pressure gauge 35 is small, the pressure between the flow restrictor 36 and the variable conductance valve 32 and the flow restrictor 36 are variable instead of the pressure gauge 34 and the pressure gauge 35. A fine differential pressure gauge for detecting the pressure between the conductance valves 33 may be provided.

  Here, the process apparatus 28 provided with the flow control device 37 according to the present invention will be described in detail with reference to FIG.

  Here, a description will be given of a process device 28 that supplies a high-concentration ozone gas to the process chamber 16 and causes the reaction to occur.

  As shown in FIG. 2, the process apparatus 28 according to the present invention includes a high-concentration ozone supply apparatus 2 via a flow rate control apparatus 37. The liquid ozone accumulated in the ozone chamber 9 is supplied to the process chamber 16 via the valve 15, the flow control device 37, and the valve 30.

  The ozone chamber 9 stores liquefied ozone. By vaporizing the accumulated liquid ozone again, high-concentration ozone gas is supplied to the reactor 28.

  Since high-concentration ozone gas may explode, liquid ozone is stored in a reduced-pressure atmosphere. That is, the ozone chamber 9 is in a reduced pressure state. Therefore, the process chamber 16 is provided with a vacuum pump 29, and ozone gas is supplied by vacuum exhaust.

  With the above configuration, the process apparatus according to the present invention can always supply a high-concentration ozone gas having a calibrated flow rate to the reaction apparatus 28.

  Therefore, the flow control device 37 according to the present invention can be used even in a supply source in a reduced pressure state, and can always perform flow control that is stable and has good reproducibility. Therefore, stable gas flow rate control can be performed in an apparatus having a plurality of chambers such as a multi-chamber process apparatus or a multilayer film forming apparatus that changes gas mixing in a complicated manner.

  However, the flow control device 37 according to the present invention is not only applied to a process device that supplies ozone gas, but is also applied to a process device that uses a liquid source and a process device that uses a corrosive gas other than ozone gas. Can do.

2 ... High-concentration ozone supply device 9 ... Ozone chamber (ozone storage chamber)
16 ... oxidation treatment vessel (process chamber, reaction vessel)
28 ... Process devices 32, 33 ... Variable conductance valves 36, 41 ... Flow rate limiters 34, 35 ... Pressure gauges 37, 42 ... Flow rate limit device 38 ... Valve control device

Claims (5)

A flow restrictor disposed in a pipe for supplying the reaction gas to the reaction vessel;
A first variable conductance valve disposed upstream of the flow restrictor in the piping;
A second variable conductance valve disposed downstream of the flow restrictor of the piping;
Based on the pressure between the flow restrictor and the first variable conductance valve and the pressure between the flow restrictor and the second variable conductance valve, the first variable conductance valve and the second variable conductance valve And a valve control device for controlling
The valve control device
Controlling the second variable conductance valve so that the pressure between the flow restrictor and the second variable conductance valve is constant;
Based on the conductance of the flow restrictor and the pressure between the flow restrictor and the second variable conductance valve, the target pressure between the flow restrictor and the first variable conductance valve at which the reaction gas becomes a target flow rate. Calculate the value
A flow rate control device for controlling the first variable conductance valve so that a pressure between the flow restrictor and the first variable conductance valve indicates the target pressure value. The differential pressure gauge for detecting a pressure between the flow restrictor and the first variable conductance valve and a pressure between the flow restrictor and the second variable conductance valve, according to claim 1. Flow control device. In a process apparatus for supplying a reaction gas to a reaction vessel and performing a reaction,
In the piping for supplying the reaction gas,
A process apparatus comprising the flow rate control apparatus according to claim 1. The reaction gas is ozone gas,
This ozone gas is stored in the ozone storage chamber as liquid ozone,
The process apparatus according to claim 3, wherein ozone gas evaporated from the liquid ozone gas is supplied to the reaction vessel. The process apparatus according to claim 4, wherein the chamber is depressurized.

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