Flow control device equipped with flow monitor

Abstract

A flow control device equipped with flow monitor includes a build-down type flow monitor unit provided on an upstream side, a flow control unit provided on a downstream side of the build-down type flow monitor unit, a signal transmission circuit connecting the build-down type flow monitor unit and the flow control unit and transmitting a monitored flow rate of the build-down type flow monitor unit to the flow control unit, and a set flow rate value adjustment mechanism being provided in the flow control unit and adjusting a set flow rate of the flow control unit based on the monitored flow rate from the build-down type flow monitor unit.

Claims

1. A flow control device equipped with flow monitor, comprising: a build-down type flow monitor unit provided on an upstream side; a flow control unit provided on a downstream side of the build-down type flow monitor unit; a signal transmission circuit connecting the build-down type flow monitor unit and the flow control unit and transmitting a monitored flow rate of the build-down type flow monitor unit to the flow control unit; and a set flow rate value adjustment mechanism for adjusting a set flow rate of the flow control unit based on the monitored flow rate from the build-down type flow monitor unit, wherein the flow control unit comprises a control valve, an orifice or a critical nozzle provided on the downstream side of the control valve, a pressure sensor for detecting a pressure between the control valve and the orifice or the critical nozzle, and a flow rate calculation control unit configured to calculate a flow rate of gas flowing through the orifice or the critical nozzle based on a measurement output from the pressure sensor and control the control valve, and the flow control unit comprises an additional pressure sensor provided on a downstream side of the orifice or the critical nozzle.

2. The flow control device equipped with flow monitor according to claim 1, wherein the set flow rate value adjustment mechanism further includes a comparator for the monitored flow rate and the set flow rate, the set flow rate value adjustment mechanism being configured to automatically correct the set flow rate to the monitored flow rate when a difference between the monitored flow rate and the set flow rate exceeds a preset value.

3. The flow control device equipped with flow monitor according to claim 1, wherein a flow rate calculation control unit of the flow control unit and a monitored flow rate calculation control unit of the build-down type flow monitor unit are integrally formed.

4. The flow control device equipped with flow monitor according to claim 1, wherein the build-down type flow monitor unit includes: a primary side opening/closing switching valve for opening and closing a flow of gas from a gas supply source; a build-down capacity connected to an outlet side of the primary side opening/closing switching valve and having a predetermined internal volume; a temperature sensor for detecting a temperature of the gas flowing through the build-down capacity; a pressure sensor for detecting a pressure of the gas flowing through the build-down capacity; and a monitored flow rate calculation control unit which controls opening and closing of the primary side opening/closing switching valve and also which opens the primary side opening/closing switching valve to set a gas pressure in the build-down capacity to a set upper limit pressure value, and then closes the primary side opening/closing switching valve to reduce the gas pressure to a set lower limit pressure value after passage of predetermined time to thereby calculate and output a monitored flow rate by a build-down system, and the monitored flow rate is calculated by an equation below in which T denotes a gas temperature (° C.), V denotes an internal volume (liter) of the build-down capacity, ΔP denotes a pressure drop range (Torr) which is a difference between the set upper limit pressure value and the set lower limit pressure value, and Δt denotes time (second) from the closing to the opening of the primary side opening/closing switching valve, $Q=\frac{1000}{760}\times 60\times \frac{273}{\left(273+T\right)}\times V\times \frac{\Delta p}{\Delta t}.$

5. The flow control device equipped with flow monitor according to claim 4, wherein the predetermined internal volume of the build-down capacity is 0.5 to 20 cc, the set upper limit pressure value is 400 to 100 kPa abs., and the set lower limit pressure value is 350 kPa abs. to 50 kPa abs., and the time Δt is 0.5 to 5 seconds.

6. The flow control device equipped with flow monitor according to claim 4, wherein the primary side opening/closing switching valve is a piezoelectric drive type metal diaphragm valve or an electromagnetic direct acting type electric operated valve, and a gas pressure recovery time from the set lower limit pressure value to the set upper limit pressure value by opening of the primary side opening/closing switching valve is shorter than a gas pressure drop time from the set upper limit pressure value to the set lower limit pressure value.

7. A flow control device equipped with flow monitor, comprising: a build-down type flow monitor unit provided on an upstream side; a flow control unit provided on a downstream side of the build-down type flow monitor unit; a signal transmission circuit connecting the build-down type flow monitor unit and the flow control unit and transmitting a monitored flow rate of the build-down type flow monitor unit to the flow control unit; and a set flow rate value adjustment mechanism being provided in the flow control unit and adjusting a set flow rate of the flow control unit based on the monitored flow rate from the build-down type flow monitor unit, wherein the build-down type flow monitor unit includes a build-down chamber and the chamber is configured so that an inner cylinder and an outer cylinder are concentrically arranged and fixed, a space between the inner cylinder and the outer cylinder which form the chamber is used as a gas flow passage, and a pressure sensor is provided in the chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic configuration view of a test device for measuring a flow monitoring characteristic of a pressure-type flow control device with build-down type flow volume monitor.

(2) FIG. 2 is an explanation view of a pressure drop state of the build-down type flow monitor.

(3) FIG. 3 shows an example of a pressure recovery characteristic curve when measuring a build-down flow rate.

(4) FIG. 4 is a partially enlarged view of FIG. 3.

(5) FIG. 5 shows a pressure recovery characteristic curve in Test 1.

(6) FIG. 6 shows the form of the pressure drop characteristic (Controlled flow rate=100 sccm).

(7) FIG. 7 shows the form of the pressure drop characteristic (Controlled flow rate=50 sccm).

(8) FIG. 8 shows the form of the pressure drop characteristic (Controlled flow rate=10 sccm).

(9) FIG. 9 is a diagram showing the relationship between the lapsed time from closing of a primary side opening/closing switching valve (upstream side valve) AV and flow rate stability (Build-down capacity BC=1.78 cc).

(10) FIG. 10 is a diagram showing the relationship between the lapsed time from closing of the primary side opening/closing switching valve (upstream side valve) valve AV and flow rate stability (Build-down capacity BC=9.91 cc).

(11) FIG. 11 shows the flow rate accuracy when repeatedly performing measurement 10 times.

(12) FIG. 12 is a diagram showing the basic configuration of a pressure-type flow control device equipped with flow monitor according to the present invention.

(13) FIG. 13 is a vertical cross-sectional schematic view of the build-down-type pressure-type flow control device equipped with flow monitor according to the present invention.

(14) FIG. 14 is a diagram showing the relationship between a gas flow rate sccm and the pressure drop inclination kPa/sec when the measurable time is set to 1 second or less in each of chambers A to E used in this example.

(15) FIG. 15 shows the form of the pressure drop characteristic when the pressure drop inclination of each of the chambers A to E used in this example is 20 kPa(s)/sec.

(16) FIG. 16 is a diagram showing the relationship of the lapsed time from closing of the primary side opening/closing switching valve (upstream side valve) AV and flow rate stability of each of the chambers A to E used in this example.

(17) FIG. 17 is a diagram showing the relationship between flow rate accuracy % S.P. and the flow rate sccm in the repeated measurement of the chamber A and the chamber B used in this example.

(18) FIG. 18 is a diagram showing the relationship between the flow rate accuracy % S.P. and the pressure drop inclination kPa/sec in the repeated measurement of the chamber A and the chamber B used in this example.

(19) FIG. 19 is the basic configuration view of a former pressure-type flow control device.

(20) FIG. 20 is the basic configuration view of a former pressure-type flow control device equipped with flow monitor.

DETAILED DESCRIPTION OF THE INVENTION

(21) Hereinafter, an embodiment of the present invention is described based on the drawings.

(22) FIG. 12 is a diagram showing the basic configuration of a pressure-type flow control device equipped with flow monitor according to the present invention. The flow control device equipped with flow monitor is configured from a signal transmission circuit (Digital-communication circuit) CT which connects a build-down unit BDM and a pressure-type flow control unit FCS.

(23) In FIG. 12, PV.sub.1 denotes an inlet side switching valve, PV.sub.2 denotes an outlet side switching valve, BC denotes a build-down capacity, P.sub.3 denotes a pressure difference detecting pressure sensor, CPb denotes a monitored flow rate calculation control unit, VB.sub.1 denotes a monitor inlet side block, and VB.sub.2 denotes a monitor outlet side block.

(24) In FIG. 12, CV denotes a control valve, CPa denotes a flow rate calculation control unit, OL.sub.1 denotes a small-diameter orifice, OL.sub.2 denotes a large-diameter orifice, P.sub.1 denotes a first pressure sensor, P.sub.2 denotes a second pressure sensor, VB.sub.3 denotes a flow control unit inlet side block, VB.sub.4 denotes a flow control unit outlet side block, VB.sub.5 denotes a connecting block, and SK denotes connecting gaskets of a connection portion.

(25) Furthermore, the pressure-type flow control unit FCS is provided with a set flow rate adjustment mechanism Q.sub.s R, in which, when a preset flow rate value Q.sub.s is compared with a build-down flow rate Q input through the signal transmission circuit CT by a comparator (not illustrated), and a difference between the values reaches a specified flow rate value, the set flow rate value Q.sub.s is automatically corrected to Q.sub.s′, and the flow control value of the pressure-type flow control unit FCS is adjusted to be coincident with the build-down flow rate Q. More specifically, the actual flow rate is adjusted to be coincident with the build-down flow rate Q.

(26) In FIG. 12, the temperature detection sensor T, the filter F, and the like are omitted and it is a matter of course that the pressure-type flow control unit FCS may be any type, e.g., one orifice is provided. The basic configurations themselves of the pressure-type flow control unit FCS and the build-down type flow monitor unit BDM are known, and therefore a detailed description thereof is omitted herein.

(27) Referring to FIG. 12, gas having a pressure of 500 to 320 kPa abs. flowing into the build-down type flow rate monitor unit BDM from a gas inlet 1 flows through the inlet side piezoelectric switching valve PV.sub.1, the build-down capacity BC of a chamber type, and the outlet side piezoelectric switching valve PV.sub.2 in this order, the monitored flow rate Q is calculated in the monitored flow rate calculation control unit CPb, and then the calculated value is input into the set flow rate adjustment mechanism Q.sub.sR of the pressure-type flow control unit FCS.

(28) The gas flowing out of the build-down type flow monitor unit BDM passes through the control valve CV and the small-diameter orifice OL.sub.1 and/or the large diameter orifice OL.sub.2, and then flows out of a gas outlet 2. During the passing of the gas, the flow rate calculation control unit CPa calculates the orifice flow gas flow rate and also controls the opening/closing of the control valve CV and the opening/closing of the orifice switching valve OLV.

(29) Furthermore, in the set flow rate adjustment mechanism Q.sub.s R of the flow rate calculation control unit CPa, when the monitored flow rate Q from the build-down type flow monitor unit BDM and the orifice flow rate (i.e., controlled flow rate in the flow rate calculation control unit CPa) are compared and a difference between the flow rates exceeds a preset value defined beforehand, the set flow rate Q.sub.s is adjusted so that the controlled flow rate of the pressure-type flow control unit FCS is coincident with the monitored flow rate Q, and then automatically corrected to Q.sub.s′.

(30) More specifically, the build-down type flow monitoring control unit CPb forming a principal portion of the present invention controls the opening/closing of the inlet side (upstream side) piezoelectric switching valve PV.sub.1 and calculates the build-down flow rate Q from the difference pressure detection pressure sensor P.sub.3, the temperature detection sensor T (omitted in FIG. 12), the volume V of the buildup capacity BC between the switching valve PV.sub.1 and PV.sub.2, and the like, and then outputs the calculated build-down flow rate Q to the flow rate calculation control unit CPa.

(31) As described above, in the flow control device equipped with flow monitor according to the present invention, the measurement of the pressure drop rate ΔP/Δt and the calculation of the monitored flow rate Q are performed in the build-down type flow monitor unit BDM and a command signal and/or a setting signal is input into the monitored flow rate calculation control unit CPb through an external input/output circuit PIO, whereby the monitored flow rate is displayed on a monitor at a rate of at least 1 time for 1 second and also the correction and the compensation of the controlled flow rate value of the pressure-type flow control unit FCS are automatically performed.

(32) The pressure-type flow control device FCS and the build-down type flow monitor unit BDM themselves are known, and therefore a detailed description thereof is omitted herein.

(33) When a difference equal to or higher than a preset value arises between the monitored flow rate output Q (flow rate output from the monitored flow rate calculation control unit CPb) and the flow rate output (flow rate output from the pressure-type flow rate calculation control unit CPa) of the pressure-type flow control unit FCS, an alarm about the abnormalities in the flow rate can be issued or, as necessary, a cause and a generation place of the abnormalities in the flow rate can be specified by performing so-called flow rate self-diagnosis of the pressure-type flow control device FCS and furthermore, when a flow rate difference equal to or higher than a preset value arises, zero point adjustment and the like of the pressure-type flow control unit FCS itself can be carried out, for example.

(34) In this embodiment, as the inlet (upstream) side switching valve and the like, a piezoelectric drive type valve is used but a direct acting type electromagnetic driving valve may be used. The internal volume V of the build-down capacity BC is selected in the range of 1.78 to 9.91 cc. This embodiment has a configuration in which the pressure drop range ΔP is selected in 20 kPa abs. (350 to 320 kPa abs.) and the monitored flow rate is output 1 or more times for at least 1 second. In addition, as the temperature detection sensor T (not illustrated), an outer surface attaching type temperature measuring resistance type temperature sensor is used but a thermostat type thermometer which is inserted into the monitor inlet side block VB.sub.1 or the monitor outlet side block VB.sub.2 can be used.

(35) In this embodiment, a chamber equipped with pressure sensor is used as the build-down capacity BC as described later. However, a configuration may be acceptable in which the build-down capacity BC is formed corresponding to the internal volume of a gas flow passage and the internal diameter and the length of the flow passage are selected as appropriate, whereby the build-down capacity BC having a desired internal volume V is obtained.

EXAMPLE

(36) FIG. 13 is a vertical cross-sectional schematic view of a flow control device equipped with build-down type flow monitor according to Example of the present invention. In this example, a chamber CH equipped with pressure sensor is used as the build-down capacity BC and the internal diameter of each of gas passages L.sub.1, L.sub.2, and L.sub.4 of the build-down type flow monitor unit BDM is set to a small diameter of 1.8 mm. On the downstream side of the orifices OL.sub.1 and OL.sub.2, a second pressure sensor P.sub.2 is separately formed. Furthermore, a pressure difference detecting pressure sensor P.sub.3 is provided in the chamber CH.

(37) More specifically, this example has a configuration in which the pressure chamber CH of a small size is provided between the inlet side switching valve PV.sub.1 and the outlet side switching valve PV.sub.2, and the internal volume V of the build-down capacity BC is adjusted by adjusting the internal volume of the pressure chamber CH. In order to increase the opening/closing rate of both the switching valves PV.sub.1 and PV.sub.2, a piezoelectric drive metal diaphragm type normal closing valve is used. The piezoelectric drive metal diaphragm type normal closing valve itself is known, and therefore a description thereof is omitted.

(38) The pressure chamber CH is formed with two cylinders of an outer cylinder CHa and an inner cylinder CHb and the gap G between the outer and inner cylinders CHa and CHb is selected to be 1.8 mm in this example. This example has a configuration in which the internal volume of the pressure chamber CH is selected to be about 1.3 to 12 cc, and the pressure difference detecting pressure sensor P3 is attached thereto.

(39) In this example, the volume of the pressure chamber CH can be freely selected, the diameter of all of the gas flow passages L.sub.1, L.sub.2, L.sub.4, etc. can be uniformly set to the same small diameter (for example, 1.8 mmφ), and the internal volume of the build-down capacity BC can be correctly and easily set to a predetermined capacity value.

(40) Specifically, five kinds of chambers having sizes shown in Table 3 in which the gap G was set to 1.8 mm to 3.6 mm were created as a chamber CH for test. The chambers were applied to the test device of FIG. 1, and then the relationship of the gas flow rate (sccm), the pressure drop inclination (kPa/sec), and the pressure drop time (sec) and the like, and the like were examined.

(41) In the examination using the test device of FIG. 1, the flow sensor T was attached and fixed to the outer surface of the chamber CH. The volume of the gas flow passages L.sub.2 and L.sub.4 other than the chamber CH is 0.226 cc.

(42) TABLE-US-00003 TABLE 3 Chamber A Gap 1.8 mm Height 14.0 mm Diameter 18.0 mm Chamber 1.58 cc Another flow passage volume 0.226 cc Actual total volume 2.31 cc Chamber B Gap 1.8 mm Height 92.0 mm Diameter 18.0 mm Chamber 8.72 cc Another flow passage volume 0.226 cc Actual total volume 9.70 cc Chamber C Gap 2.4 mm Height 92.0 mm Diameter 18.0 mm Chamber 11.15 cc Another flow passage volume 0.226 cc Actual total volume 11.55 cc Chamber D Gap 3.0 mm Height 92.0 mm Diameter 18.0 mm Chamber 13.35 cc Another flow passage volume 0.226 cc Actual total volume 13.91 cc Chamber E Gap 3.6 mm Height 92.0 mm Diameter 18.0 mm Chamber 15.31 cc Another flow passage volume 0.226 cc Actual total volume 15.45 cc

(43) FIG. 14 shows the results obtained by measuring the relationship between the gas flow rate (sccm) and the pressure drop inclination (kPa/sec) when the pressure drop time (b) in FIG. 2 was set to be within 1 second about each of the chambers A to E and the actual buildup capacity of each chamber in the state where the chamber was attached to the test device was 2.31 cc to 15.45 cc.

(44) As is clear from FIG. 14, it is found that, when the pressure drop range ΔP was set to 20 kPa/sec, the flow measurement can be achieved as follows: 25.2 sccm in the case of the chamber A, 106.6 sccm in the case of the chamber B, and 169.0 sccm in the case of the chamber E.

(45) In the test device of FIG. 1, FIG. 15 shows the linearity of the pressure drop when the gas flow rate was adjusted so that the pressure drop inclination was 20 kPa/sec and is the same diagram as those of FIG. 6 to FIG. 8 described above. The measurement data are acquired by the data logger NR of FIG. 1.

(46) As is clear from FIG. 15, it is found that, in the case of the chamber CH in which the internal volume V of the build-down capacity BC is small (i.e., chambers A and B and the like), the linearity of the pressure drop characteristic becomes good.

(47) In FIG. 16, the flow measurement error due to the deviation from the linearity of the pressure drop characteristic curve is determined by measuring the flow rate at five points every 0.25 second within the flow rate measurable time (b) within 1 second in the same manner as in the cases of FIG. 9 and FIG. 10 and it is found that the flow rate error decreases at an early stage after the start of the pressure drop in the chambers A and B having a small buildup capacity BC (i.e., it can be said that the linearity of the pressure drop characteristic is excellent).

(48) FIG. 17 shows the results of examining the reproducibility of the flow measurement accuracy about the chamber A and the chamber B and the examination was performed for the same purpose as that of FIG. 11.

(49) In the reproducibility test of the flow measurement accuracy, the primary side change opening/closing valve (upstream side valve) AV is closed, and then the measurement is performed after a predetermined waiting time in order to stabilize the pressure drop inclination and the measurement is performed over a long period of time in order to obtain reproducibility but the flow rate output time is set to be within 1 second in any case.

(50) As is clear from FIG. 17, it is found that, in the case of the chamber A, the flow rate 3 to 50 sccm is the applicable range and, in the case of the chamber B, the flow rate 30 to 300 sccm is the applicable range in terms of reproducibility.

(51) Table 4 shows the basic data used for the creation of the diagram showing the reproducibility of the flow measurement accuracy shown in the FIG. 17 and the chamber A (Internal volume V of the build-down capacity BC=2.31 cc) and the chamber B (Internal volume V of the build-down capacity BC=9.47 cc) were the test targets.

(52) TABLE-US-00004 TABLE 4 Chamber A (BC = 2.31 cc) Flow rate sccm 1 2 3 5 10 20 30 50 Temperature ° C. 22.7 23.0 23.1 22.8 22.6 22.6 22.6 22.7 Inclination kPa/sec 0.8 1.6 2.4 4.0 7.9 16.1 23.4 39.2 Measurement kPa 370 370 370 370 370 370 370 370 start pressure abs. Measurement kPa 368 365 365 363 355 350 350 350 end pressure abs. Measurement kPa 2 5 5 7 15 20 20 20 pressure range Measurement sec 2.73 3.42 2.28 1.91 2.05 1.37 0.91 0.55 time Chamber B (BC = 9.47 cc) Flow rate sccm 5 10 20 30 50 100 200 300 400 Temperature ° C. 22.7 23.0 22.4 22.4 22.5 22.5 22.5 22.6 22.59 Inclination kPa/sec 0.9 1.9 3.8 5.7 9.4 18.9 37.7 57.3 77.204 Measurement kPa 370 370 370 370 370 370 370 370 370 start pressure abs. Measurement kPa 368 367 365 360 350 350 350 350 350 end pressure abs. Measurement kPa 2 3 5 10 20 20 20 20 20 pressure range Measurement sec 2.24 1.68 1.40 1.87 2.24 1.12 0.56 0.37 0.28 time *Measurement was performed while changing the time and the pressure range in such a manner as not to exceed 10000 data.

(53) FIG. 18 shows the results of examining the relationship between the pressure drop inclination kPa/sec and the error % S.P. of the chamber A and the chamber B from the data of Table 4 and shows that, when the pressure drop inclination is within the range of 2 to 60 kPa/sec, the flow measurement error % S.P. is within the range of ±1%.

INDUSTRIAL APPLICABILITY

(54) The present invention can be applied to a gas supplying facility for a semiconductor manufacturing apparatus and also can be widely applied to a gas supplying facility for a chemical manufacturing device insofar as it is a pressure-type flow control device employing an orifice or a critical nozzle.

EXPLANATION OF REFERENCE NUMERALS

(55) BDM Build-down type flow monitor unit FCS Pressure-type flow control unit (pressure-type flow control device) AV Primary side opening/closing switching valve (upstream side valve) BC Build-down capacity V Internal volume of build-down capacity RG Pressure regulator N.sub.2 N.sub.2 supply source T Temperature sensor (temperature measuring resistor) P.sub.1, P.sub.2 Pressure sensor P.sub.3 Pressure difference detecting pressure sensor CV Control valve OL Orifice OL.sub.1 Small diameter orifice OL.sub.2 Large diameter orifice OIP External input/output circuit OLV Orifice switching valve VB.sub.1 Monitor inlet side block VB.sub.2 Monitor outlet side block VB.sub.3 Flow control unit inlet side block VB.sub.4 Flow control unit outlet side block VB.sub.5 Connection portion gasket CT Signal transmission circuit (digital communication circuit) CP Calculation control unit CPa Flow rate calculation control unit CPb Monitored flow rate calculation control unit E.sub.1 Power supply for pressure-type flow control device E.sub.2 Power supply for calculation control unit E.sub.3 Power supply for electromagnetic valve ECV Electric operated driving unit NR Data logger S Signal generator PC Calculation displaying unit PV.sub.1 Inlet side switching valve (inlet side piezoelectric switching valve) PV.sub.2 Outlet side switching valve (outlet side piezoelectric switching valve) L.sub.1 Gas inlet side passage of inlet side piezoelectric switching valve L.sub.2 Gas outlet side passage of inlet side piezoelectric switching valve L.sub.3 Gas inlet side passage of outlet side piezoelectric switching valve L.sub.4 Gas outlet side passage of outlet side piezoelectric switching valve Cu Cupper bar piece Q Monitored flow rate (build-down flow rate) CH Chamber CHa Outer cylinder CHb Inner cylinder Q.sub.sR Set flow rate value adjustment mechanism Q.sub.s Set flow rate Q.sub.s′ Adjusted flow rate 1 Gas inlet 2 Gas outlet