Raw material vaporizing and supplying apparatus equipped with raw material concentration

Abstract

An apparatus able to regulate a raw material concentration, in a mixed gas of carrier gas and raw material gas, accurately and stably to supply the mixed gas to a process chamber, with a flow rate controlled highly accurately, thereby detecting a vapor concentration of the raw material gas in the mixed gas easily and highly accurately and displaying the concentration in real time without using an expensive concentration meter, etc.

Claims

1. A raw material vaporizing and supplying apparatus comprising: a raw material concentration detection mechanism, an automatic pressure regulating device, a mass flow meter, a flow-out passage, a source tank, and a constant temperature unit, wherein the raw material vaporizing and supplying apparatus is operably arranged to supply a carrier gas G.sub.K into the source tank through a mass flow controller to release the carrier gas G.sub.K from inside the source tank and also to supply into a process chamber a mixed gas G.sub.S composed of the carrier gas G.sub.K and saturated vapor G of a raw material produced by keeping the source tank at a constant temperature with the constant temperature unit; wherein the automatic pressure regulating device and the mass flow meter are installed on the flow-out passage of the mixed gas G.sub.S from the source tank, the automatic pressure regulating device is controlled so as to open and close a control valve, thereby controlling an internal pressure P.sub.0 of the source tank to a predetermined value, wherein individual detection values of a flow rate Q.sub.1 of the carrier gas G.sub.K by the mass flow controller, the internal pressure P.sub.0 of the tank, and a flow rate Q.sub.S of the mixed gas G.sub.s by the mass flow meter are input into a raw material concentration arithmetic unit, the raw material concentration arithmetic unit is used to compute a raw material flow rate Q.sub.2 based on Q.sub.2=(Q.sub.SP.sub.M0)/P.sub.0, and a raw material concentration K of the mixed gas G.sub.S supplied to the process chamber is computed and displayed in terms of K=Q.sub.2/Q.sub.S with reference to the raw material flow rate Q.sub.2, wherein P.sub.M0 is a saturated vapor pressure of raw material vapor G at a temperature of t C. in the source tank.

2. The raw material vaporizing and supplying apparatus according to claim 1, wherein a storage device of saturated steam pressure data of the raw material in the source tank is installed on the raw material concentration arithmetic unit and also detection signals of the internal pressure P.sub.0 of the source tank and a temperature t from the automatic pressure regulating device are input into the raw material concentration arithmetic unit.

3. The raw material vaporizing and supplying apparatus according to claim 1, wherein the raw material concentration detection unit, a flow rate arithmetic and control unit of the mass flow controller, a pressure arithmetic and control unit of the automatic control device and a flow rate arithmetic and control unit of the mass flow meter are arranged so as to be assembled in an integrated manner.

4. The raw material vaporizing and supplying apparatus according to claim 1, wherein the mass flow meter is installed on the downstream side of the automatic pressure regulating device.

5. The raw material vaporizing and supplying apparatus according to claim 1, wherein the mass flow meter is installed on the upstream side of the regulating device.

6. The raw material vaporizing and supplying apparatus according to claim 1, wherein the automatic pressure regulating device is a pressure regulating device which has a temperature detector T, a pressure detector P, a control valve installed on the downstream side from the pressure detector P and a pressure arithmetic and control unit.

7. The raw material vaporizing and supplying apparatus according to claim 6, wherein the mass flow meter is installed between the pressure detector P and the control valve.

8. A raw material vaporizing and supplying apparatus comprising: a raw material concentration detection mechanism, an automatic pressure regulating device, a mass flow meter, a flow-out passage, a source tank, and a constant temperature unit, wherein the raw material vaporizing and supply apparatus is connected to supply a carrier gas G.sub.K into a source tank through a mass flow controller to release the carrier gas G.sub.K from inside the source tank and also to supply, into a process chamber, a mixed gas G.sub.S composed of the carrier gas G.sub.K and saturated vapor G of a raw material produced by keeping the source tank at a constant temperature with the constant temperature unit; wherein the automatic pressure regulating device and the mass flow meter are installed on the flow-out passage of the mixed gas G.sub.S from the source tank, the automatic pressure regulating device is controlled so as to open and close a control valve, thereby controlling an internal pressure P.sub.0 of the source tank to a predetermined value, wherein detection values of a flow rate Q.sub.1 of the carrier gas G.sub.K by the mass flow controller, the internal pressure P.sub.0 of the tank and a flow rate Q.sub.S of the mixed gas G.sub.S from the mass flow meter are input into a raw material concentration arithmetic unit, and the raw material concentration arithmetic unit is used to determine a raw material flow rate Q.sub.2 based on Q.sub.2=(CFQ.sub.S)Q.sub.1, and a raw material concentration K of the mixed gas G.sub.S supplied to the process chamber is computed and displayed in terms of K =Q.sub.2/(Q.sub.1+Q.sub.2) with reference to the raw material flow rate Q.sub.2, wherein CF is a conversion factor of the mixed gas Q.sub.2.

9. The raw material vaporizing and supplying apparatus according to claim 8, wherein a conversion factor CF of the mixed gas Q.sub.2 is 1/CF=C/CF.sub.A+(1-C)/CF.sub.B wherein, CF.sub.A is a conversion factor of the carrier gas G.sub.K, CF.sub.B is a conversion factor of the raw material gas G and C is a volume ratio of the carrier gas, namely, Q.sub.1/(Q.sub.1+Q.sub.2).

10. The raw material vaporizing and supplying apparatus according to claim 8, wherein the raw material concentration arithmetic unit is provided with a storage device of individual data on conversion factors of the raw material gas G in the source tank and conversion factors of the carrier gas G.sub.K.

11. The raw material vaporizing and supplying apparatus according to claim 8, wherein the raw material concentration detection unit, a flow rate arithmetic and control unit of the mass flow controller, a pressure arithmetic and control unit of the automatic control device and a flow rate arithmetic and control unit of the mass flow meter are arranged so as to be assembled in an integrated manner.

12. The raw material vaporizing and supplying apparatus according to claim 8, wherein the mass flow meter is installed on the downstream side of the automatic pressure regulating device.

13. The raw material vaporizing and supplying apparatus according to claim 8, wherein the mass flow meter is installed on the upstream side of the regulating device.

14. The raw material vaporizing and supplying apparatus according to claim 8, wherein the automatic pressure regulating device is a pressure regulating device which has a temperature detector T, a pressure detector P, a control valve installed on the downstream side from the pressure detector P and a pressure arithmetic and control unit.

15. A raw material vaporizing and supplying apparatus, comprising: a source tank for containing source material; a constant temperature unit disposed to keep the source tank at a constant temperature t C.; a source of carrier gas G.sub.K; a mass flow controller disposed to control a flow of carrier gas G.sub.K from the source of carrier gas G.sub.K into the source tank at a flow rate Q.sub.1; an outflow passage disposed to deliver a mixed gas G.sub.S, composed of the carrier gas G.sub.K and a saturated vapor G of a raw material, from the source tank at a flow rate Q.sub.S; a raw material concentration detection mechanism; a control valve disposed to control the internal pressure P.sub.0 of the source tank; an automatic pressure regulating device disposed and arranged to regulate the internal pressure P.sub.0 of the source tank to a predetermined value; a mass flow meter disposed in the outflow passage to measure flow rate Q.sub.s of mixed gas G.sub.S; a process chamber disposed to receive mixed gas G.sub.S composed of the carrier gas G.sub.K and the saturated vapor G of the raw material from said outflow passage; a raw material concentration arithmetic unit, configured to receive data and compute (a) a raw material flow rate Q.sub.2 based on Q.sub.2=(Q.sub.SP.sub.M0)/P.sub.0, wherein P.sub.M0 is a saturated vapor pressure of raw material vapor G at a temperature of t C. in the source tank, and (b) a raw material concentration K of the mixed gas G.sub.S supplied to the process chamber of K=Q.sub.2/Q.sub.S with reference to the raw material flow rate Q.sub.2.

16. A raw material vaporizing and supplying apparatus, comprising: a source tank for containing source material; a constant temperature unit disposed to keep the source tank at a constant temperature t C.; a source of carrier gas G.sub.K; a mass flow controller disposed to control a flow of carrier gas G.sub.K from the source of carrier gas G.sub.K into the source tank at a flow rate Q.sub.1; an outflow passage disposed to deliver a mixed gas G.sub.S, composed of the carrier gas G.sub.K and a saturated vapor G of a raw material, from the source tank at a flow rate Q.sub.S; a raw material concentration detection mechanism; a control valve disposed to control the internal pressure P.sub.0 of the source tank; an automatic pressure regulating device disposed and arranged to regulate the internal pressure P.sub.0 of the source tank to a predetermined value; a mass flow meter disposed in the outflow passage to measure flow rate Q.sub.S of mixed gas G.sub.S; a process chamber disposed to receive mixed gas G.sub.s composed of the carrier gas G.sub.K and the saturated vapor G of the raw material from said outflow passage; a raw material concentration arithmetic unit, configured to receive data and compute (a) a raw material flow rate Q.sub.2 based on Q.sub.2=(CFQ.sub.S)Q.sub.1, wherein CF is a conversion factor of the mixed gas Q.sub.2, and (b) a raw material concentration K of the mixed gas G.sub.S supplied to the process chamber based on K=Q.sub.2/(Q.sub.1+Q.sub.2) with reference to the raw material flow rate Q.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a systematic diagram which shows the structure of a raw material vaporizing and supplying apparatus equipped with a raw material concentration detection mechanism according to a first embodiment of the present invention.

(2) FIG. 2 is a drawing which describes test equipment used for studying a relationship between a raw material gas flow rate Q.sub.2, a mixed gas flow rate Q.sub.S, a carrier gas flow rate Q.sub.1, a source tank pressure P.sub.0 and a source tank temperature t.

(3) FIG. 3 is a drawing which shows a relationship between the internal pressure P.sub.0 of the tank, the mixed gas flow rate Q.sub.S, the raw material gas flow rate Q.sub.2 and the tank temperature t measured by using the test equipment given in FIG. 2, in which (a) shows a state of change in the mixed gas flow rate Q.sub.S and (b) shows a state of change in the raw material gas flow rate Q.sub.2.

(4) FIG. 4 is a line drawing which shows a relationship between a measurement value, with the carrier gas flow rate Q.sub.1 kept constant (mixed gas flow rate Q.sub.Scarrier gas flow rate Q.sub.1) and the raw material gas flow rate Q.sub.2 calculated with reference to Formula (2).

(5) FIG. 5 is a schematic diagram which shows a system of supplying a raw material gas.

(6) FIG. 6 is a drawing which describes one example of a conventional raw material vaporizing and supplying apparatus according to the bubbling method (Japanese Published Unexamined Patent Application Publication No. H07-118862).

(7) FIG. 7 is a drawing which describes another example of a conventional raw material vaporizing and supplying apparatus according to the bubbling method (Japanese Patent No. 4605790).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(9) FIG. 1 is a systematic diagram which shows the structure of a raw material vaporizing and supplying apparatus equipped with a raw material concentration detection mechanism according to the first embodiment of the present invention.

(10) In FIG. 1, reference numeral 1 denotes a carrier gas supply source, 2 denotes a decompression unit, 3 denotes a thermal type mass flow control system (mass flow controller), 4 denotes a raw material (organometallic compound (MO material), etc.), 5 denotes a source tank, 6 denotes a constant temperature unit, 7 denotes an induction pipe, 8 denotes an automatic pressure regulating device in the source tank, 9 denotes a mass flow meter, 10 denotes a raw material concentration arithmetic unit, Q.sub.1 denotes a carrier gas flow rate of Ar, etc., Q.sub.2 denotes a flow rate of the raw material saturated steam (raw material gas flow rate), Q.sub.S denotes a mixed gas flow rate of the carrier gas flow rate Q.sub.1 and the raw material steam flow rate Q.sub.2, P denotes a pressure detector of the mixed gas G.sub.S, T denotes a temperature detector of the mixed gas G.sub.S, 3a denotes a sensor unit of the mass flow controller, 8a denotes a piezoelectric element driving control valve, 9a denotes a sensor unit of the mass flow meter, and 9b denotes an arithmetic and control unit of the mass flow meter 9a. The mass flow controller 3 is made up of the sensor unit 3a and a flow rate arithmetic and control unit 3b of the sensor unit 3a. The automatic pressure regulator 8 of the source tank is made up of the control valve 8a, a pressure arithmetic and control unit 8b, the pressure detector P and the temperature detector T.

(11) It is noted that N.sub.2 is generally used as the carrier gas G.sub.K. However, the carrier gas G.sub.K is not limited to N.sub.2 but includes various types of gas such as H.sub.2 and Ar. Further, the raw material includes an organometallic compound (MO material) but shall not be limited to an organometallic material. The raw material also includes any liquid and solid materials as long as they are capable of attaining a predetermined saturated steam pressure in a source tank.

(12) The mass flow controller 3 is publicly known and, therefore, a detailed description thereof will be omitted here. The automatic pressure regulating device 8 of the source tank is also publicly known in Japanese Patent No. 4605790, etc., with a detailed description thereof omitted here.

(13) Further, in FIG. 1, reference numeral G.sub.K denotes a carrier gas, G denotes raw material steam (raw material gas), G.sub.S denotes a mixed gas, P.sub.0 denotes an internal pressure of the source tank (kPa abs.), P.sub.M0 denotes a raw material steam pressure in the source tank (kPa abs.), 3e denotes a flow rate display signal, 8d denotes a control valve control signal, 8c denotes a pressure detection signal, 8f denotes a temperature detection signal, 8e denotes a pressure display signal, 9c denotes a mixed gas flow rate detection signal, and 9e denotes a mixed gas flow rate display signal. The display signal 3e of the flow rate Q.sub.1 of the carrier gas G.sub.K and the display signal 9e of the flow rate Q.sub.S of the mixed gas G.sub.S from the mass flow meter 9 are input into the raw material concentration arithmetic unit 10, and a raw material gas concentration K in the mixed gas G.sub.S is computed and displayed here. It is noted that 10.sub.K denotes a raw material concentration display signal.

(14) It is noted that in the embodiment shown in FIG. 1, the flow rate arithmetic and control unit 3b of the mass flow controller 3, the pressure arithmetic and control unit 8b of the automatic pressure regulating device 8, the flow rate arithmetic and control unit 9b of the mass flow meter 9 and the raw material concentration arithmetic unit 10 are formed on a single substrate in an integrated manner. As a matter of course, it is also acceptable that the control units 3b, 8b, 9b and the raw material concentration arithmetic unit 10 are individually installed.

(15) Next, a description will be given of operation of the raw material vaporizing and supplying apparatus.

(16) In the raw material vaporizing and supplying apparatus, first, a pressure PG.sub.1 of the carrier gas G.sub.K supplied into the source tank 5 is set so as to give a predetermined pressure value by the decompression unit 2 and a supplying flow rate Q.sub.1 thereof is also set so as to give a predetermined value by the thermal type mass flow control system 3 (mass flow controller).

(17) Further, the constant temperature unit 6 is operated to keep parts in constant temperature excluding the source tank 5, the arithmetic and control unit 8b of the automatic pressure regulating device 8, etc.

(18) As described so far, the supply quantity Q.sub.1 of the carrier gas G.sub.K is kept at a set value by the thermal type mass flow control system 3, the temperature of the source tank 5 is kept at a set value, and the internal pressure P.sub.0 of the source tank 5 is kept at a set value by the automatic pressure regulating device 8, respectively. Thereby, the mixed gas G.sub.S with a constant flow rate is allowed to flow into the mass flow meter 9 at a fixed mixture ratio through the control valve 8a, and the flow rate Q.sub.S of the mixed gas G.sub.S is measured here with high accuracy.

(19) Further, the source tank 5, the control valve 8a of the automatic pressure regulating device 8, etc., are kept at constant temperature. Therefore, a pressure P.sub.M0 of the raw material saturated steam G in the source tank 5 is kept stable and the internal pressure P.sub.0 of the source tank 5 is controlled so as to give a set value by the automatic pressure regulating device 8. It is, thereby, possible to measure and display the raw material gas concentration K in the mixed gas G.sub.S on the raw material concentration arithmetic unit 10 as described later, while the concentration K of the raw material gas G in the mixed gas G.sub.S is kept stable.

(20) And, in the raw material vaporizing and supplying apparatus shown in FIG. 1, where the internal pressure of the source tank is given as P.sub.0 (kPa abs.), the raw material steam pressure is given as P.sub.M0, the flow rate of the carrier gas G.sub.K, is given as Q.sub.1 (sccm), the flow rate of the mixed gas G.sub.S supplied to the chamber is given as Q.sub.2 (sccm) and the flow rate of the raw material steam G is given as Q.sub.2 (sccm), the flow rate Q.sub.S of supplying the mixed gas G.sub.S to the chamber is expressed as Q.sub.S=Q.sub.1+Q.sub.2 (sccm).

(21) That is, the raw material flow rate Q.sub.2 is proportional to the raw material steam pressure P.sub.M0 in the source tank, and the flow rate of supplying the mixed gas G.sub.S, that is, Q.sub.S=Q.sub.1+Q.sub.2, is proportional to the internal pressure P.sub.0 of the source tank. Therefore, the following relationship is obtained. Raw material flow rate Q.sub.2: mixed gas supplying flow rate Q.sub.S=raw material steam pressure P.sub.M0: internal pressure P.sub.0 of source tank.

(22) That is,

(23) [Formula 1]
Q.sub.2P.sub.0=Q.sub.SP.sub.M0 (1)
With reference to Formula 1, the raw material flow rate Q.sub.2 is expressed as follows:
[Formula 2]
Q.sub.2=Q.sub.SP.sub.M0/P.sub.0 (2)

(24) As apparent from Formula 2 given above, the raw material flow rate Q.sub.2 is determined by the mixed gas flow rate Q.sub.S, the source tank pressure P.sub.0 and the raw material steam pressure (partial pressure) P.sub.M0. Further, the internal pressure P.sub.0 of source tank is determined by the temperature t in the source tank.

(25) In other words, the raw material concentration K in the mixed gas G.sub.S is determined by parameters such as the carrier gas flow rate Q.sub.1, the internal pressure P.sub.0 of source tank and the temperature t in the source tank.

(26) In FIG. 1, the mass flow meter 9 is installed on the downstream side of the automatic pressure regulating device 8. It is acceptable that their positions are exchanged so that the automatic pressure regulating device 8 is installed on the downstream side of the mass flow meter 9. It is also acceptable that the mass flow meter 9 is installed between the pressure detector P and the control valve 8a.

(27) As shown in FIG. 1, where the automatic pressure regulating device 8 is installed on the upstream side of the mass flow meter 9, a control pressure of the automatic pressure regulating device 8 is in agreement with an internal pressure of the source tank. It is, therefore, possible to control the internal pressure of the source tank accurately. However, such a problem is posed that a supply pressure of the mass flow meter 9 is influenced by a secondary side (process chamber side).

(28) On the other hand, where the mass flow meter 9 is installed on the upstream side of the automatic pressure regulating device 8, the mass flow meter 9 is in a range of pressure control by the automatic pressure regulating device 8. Thus, the mass flow meter 9 is made stable in supply pressure, thus enabling highly accurate measurement of a flow rate. However, the mass flow meter 9 undergoes pressure loss, thereby causing a difference between the control pressure of the automatic pressure regulating device 8 and the internal pressure of the source tank.

(29) Further, where the mass flow meter 9 is installed between the pressure detector P and the control valve 8a, the control pressure of the automatic pressure regulating device 8 is in agreement with the internal pressure of the source tank and the mass flow meter 9 is also in a range of pressure controlled by the automatic pressure regulating device 8. Therefore, the mass flow meter 9 is made stable in supply pressure, enabling highly accurate measurement of a flow rate. However, such a problem is posed that the mass flow meter 9 causes pressure loss between the pressure detector P and the control valve 8a, thereby affecting the response characteristics for pressure control.

(30) FIG. 2 is a drawing which describes test equipment used for confirming the establishment of a relationship between Formula 1 and Formula 2 given above. Acetone (steam pressure curve is close to that of TMGa) was used as the raw material 4, a water bath was used as the constant temperature unit 6 and N.sub.2 was used as the carrier gas G.sub.K. A relationship between the internal pressure P.sub.0 of the tank and the flow rate Q.sub.S of the mixed gas G.sub.S was regulated, with the tank temperature t given as a parameter (10 C., 0 C., 10 C., 20 C.).

(31) FIG. 3 shows results of the test carried out by using the test equipment of FIG. 2. Further, Table 1 below shows results obtained by using Formula 2 to compute the raw material gas flow rate Q.sub.2 of the raw material acetone.

(32) TABLE-US-00001 TABLE 1 Raw material acetone: Carrier gas N.sub.2 (50 sccm) Temperature of constant temperature water bath ( C.) Internal pressure P.sub.0 of tank (kPa abs) and Measure- raw material flow rate Q (sccm) Setting ment 120 150 180 210 240 270 300 20 19.4 12.43 9.56 7.70 6.44 5.59 4.92 4.36 10 9.8 7.34 5.68 4.67 3.94 3.42 3.02 2.69 0 0.5 4.12 3.25 2.67 2.27 1.99 1.77 1.57 10 11.0 2.21 1.74 1.44 1.23 1.08 0.96 0.86

(33) Table 2 shows comparison between steam pressure of acetone as a raw material and steam pressure of TMGa (trimethyl gallium) as a generally-used MO material. Since these two substances are remarkably approximate in steam pressure, calculation values obtained by using acetone in Table 1 can be said to indicate those of TMGa used as a raw material.

(34) TABLE-US-00002 TABLE 2 kPa Torr Steam pressure of acetone 10 5.39 40.4 0 9.36 70.2 10 15.53 116.5 20 24.74 185.6 30 38.03 285.3 40 56.64 424.9 50 81.98 615.1 Steam pressure of TMGa 10 5.20 39.0 0 8.97 67.3 10 14.91 111.8 20 23.92 179.4 30 37.21 279.1 40 56.26 422.0 50 82.93 622.0

(35) FIG. 4 is a drawing which shows a relationship of a difference between an N.sub.2 converted detection flow rate Q.sub.S of the mixed gas G.sub.S and the carrier gas flow rate Q.sub.1, Q.sub.SQ.sub.1 which are measured by using a mass flow meter installed on the test equipment of FIG. 2, with a carrier gas flow rate (Q.sub.1) kept constant and the tank temperature t (10 C. to 20 C.) given as a parameter (that is, an N.sub.2 converted raw material gas flow rate Q.sub.2=Q.sub.SQ.sub.1) with respect to an acetone flow rate (Q.sub.2 sccm) calculated with reference to Formula (2). In this drawing, (a) covers a case where the carrier gas flow rate Q.sub.1 is equal to 50 sccm, (b) covers a case where Q.sub.1 is equal to 100 sccm and (c) covers a case where Q.sub.1 is equal to 10 sccm.

(36) As apparent from (a) to (c) in FIG. 4 as well, there is found a direct proportional relationship between a measurement value (mixed gas flow rate Q.sub.Scarrier gas flow rate Q.sub.1) by using the mass flow meter and a calculated acetone flow rate Q.sub.2. As a result, the carrier gas flow rate Q.sub.1 is measured by using the mass flow controller 3 and the mixed gas flow rate Q.sub.S is measured by using the mass flow meter 9, respectively, to determine Q.sub.SQ.sub.1. Thereby, it is possible to calculate the raw material gas flow rate Q.sub.2.

(37) Next, a description will be given of calculation of a raw material gas flow rate Q.sub.2 and a concentration K of the raw material gas G in the mixed gas Gs.

(38) Where a raw material gas supply system is expressed as given in FIG. 5 and where a raw material gas G at a flow rate Q.sub.2 equivalent to a concentration K and a carrier gas G.sub.K (N.sub.2) at a flow rate Q.sub.1 (that is, Q.sub.2+Q.sub.1 sccm) are supplied to the mass flow meter 9 to give a detection flow rate (N.sub.2-based conversion) of mixed gas Gs at this time as Q.sub.S (sccm), the raw material gas flow rate Q.sub.2 and the raw material gas concentration K in the mixed gas can be obtained with reference to the formulae given below.

(39) [Formula 3]
Raw material gas flow rate Q.sub.2 (sccm)=CF of mixed gasdetected flow rate (N.sub.2-based conversion) Q.sub.S (sccm)carrier gas flow rate Q.sub.1 (sccm) (3)
[Formula 4]
Raw material gas concentration K=Raw material gas flow rate Q.sub.2 (sccm)/Carrier gas flow rate Q.sub.1 (sccm)+Raw material gas flow rate Q.sub.2 (sccm) (4)

(40) CF given in Formula (3) above is a conversion factor of the so-called mixed gas Gs in a thermal type mass flow meter and can be obtained with reference to Formula (5) below.

(41) [Formula 5]
1/CF=C/CF.sub.A+(1C)/CF.sub.B(5)

(42) However, in Formula (5), CF.sub.A denotes a conversion factor of gas A, CF.sub.B denotes a conversion factor of gas B, C denotes a volume ratio (concentration) of the gas A and (1C) denotes a volume ratio (concentration) of the gas B (Flow rate measurement: A to Z, compiled by the Japan Measuring Instruments Federation, published by Kogyogijutsusha (pp. 176 to 178).

(43) Now, in FIG. 5, where CF.sub.A of the carrier gas G.sub.K (N.sub.2) is given as 1 and CF.sub.B of the raw material gas G is given as , the concentration of the raw material gas is expressed as Q.sub.2/(Q.sub.1+Q.sub.2) and the concentration of the carrier gas is expressed as Q.sub.1/(Q.sub.1+Q.sub.2). Thus, CF of the mixed gas Q.sub.2 is expressed by Formula (5) as follows.

(44) $\begin{array}{cc}\frac{1}{\mathrm{CF}}=\frac{1}{1}\frac{Q_1}{Q_1+Q_2}+\frac{1}{}.Math.\frac{Q_2}{Q_1+Q_2}=\frac{Q_1+Q_2}{\left(Q_1+Q_2\right)}& \left[\mathrm{Formula}6\right]\end{array}$
Thus, the following formula is obtained.

(45) $\begin{array}{cc}\mathrm{CF}=\frac{\left(Q_1+Q_2\right)}{Q_1+Q_2}& \left[\mathrm{Formula}7\right]\end{array}$

(46) Therefore, the N.sub.2 converted detection flow rate Q.sub.S of the mixed gas G.sub.S detected by the mass flow meter 9 is expressed as follows.

(47) $\begin{array}{cc}\begin{array}{c}{\mathrm{Qs}}^{}=\frac{Q_1+Q_2}{\mathrm{CF}}\\ =\left(Q_1+Q_2\right)\left(Q_1+Q_2\right)/\left(Q_1+Q_2\right)\\ =\left(Q_1+Q_2\right)/\\ =Q_1+\frac{Q_2}{}\end{array}& \left[\mathrm{Formula}8\right]\end{array}$

(48) Thereby, the flow rate Q.sub.2 of the raw material gas G is expressed as Q.sub.2=(Q.sub.SQ.sub.1). However, in this case, is a conversion factor of the raw material gas G.

(49) Table 3 below shows results obtained by comparing a raw material gas flow rate Q.sub.2 calculated by using a conversion factor CF determined with reference to Formula (5) above with a raw material gas flow rate Q.sub.2 computed by using Formula (1) and Formula (2). It is found that a value calculated with reference to Formula (1) and Formula (2) is well in agreement with a value calculated with reference to Formula (5).

(50) It is noted that in Table 1, acetone is supplied as a raw material gas G and N.sub.2 is supplied as a carrier gas G.sub.K at a flow rate Q.sub.1=500 sccm and calculation is made, with the temperature t given as a parameter. The raw material gas flow rate Q.sub.2 determined with reference to a pressure ratio between Formula (1) and Formula (2) and the raw material gas flow rate Q.sub.2 determined with reference to a conversion factor CF according to Formula (5) are approximate in flow rate value with each other.

(51) TABLE-US-00003 TABLE 3 CF of acetone: 0.341, Constant temperature water bath set at 20 C., Flow rate of N.sub.2, 50 sccm RT C. 24.0 24.0 23.9 23.9 24.0 24.1 23.9 Tank temperature C. 19.2 19.4 19.3 19.3 19.4 19.5 19.4 Acetone steam KPa 23.9 24.0 24.0 23.9 24.1 24.1 24.0 pressure abs Flow rate of N.sub.2 sccm 50.1 50.1 50.1 50.1 50.1 50.1 50.1 Internal pressure of KPa 120 150 180 210 240 270 300 tank abs Concentration % 19.9% 16.0% 13.3% 11.4% 10.0% 8.39% 8.0% Detection flow AVE sccm 88.4 79.6 73.9 70.2 67.6 65.4 63.8 rate of mixed MAX sccm 89.1 80.2 74.7 70.7 68.2 66.0 64.4 gas G.sub.s MIN sccm 87.8 78.9 73.2 69.6 67.1 64.9 63.3 (N.sub.2-based conversion): Q.sub.s Raw material gas flow sccm 38.3 29.5 23.8 20.1 17.5 15.3 13.7 rate (N.sub.2-based conversion) Q.sub.2 Calculated acetone sccm 12.43 9.56 7.70 6.44 5.59 4.92 4.32 flow rate (Formula 2) Mixed gas CF 0.869 0.894 0.912 0.925 0.934 0.941 0.947 Measured acetone sccm 13.08 10.05 8.13 6.86 5.98 5.23 4.68 flow rate (Formula 5)

(52) Table 4, Table 5 and Table 6 below respectively show cases in which an acetone flow rate determined by using a pressure ratio (Formula (1) and Formula (2)) is compared with an acetone flow rate determined by using a conversion factor CF (Formula 5), with a flow rate Q.sub.1 of N.sub.2 as a carrier gas G.sub.K being changed.

(53) TABLE-US-00004 TABLE 4 Flow rate of N.sub.2: 100 sccm Internal pressure P.sub.0 of tank kPaabs 120 150 180 210 240 270 300 100 sccm 20 C. Partial sccm 24.99 19.06 15.46 13.00 11.19 9.83 8.76 pressure acetone flow rate CF acetone sccm 25.91 19.83 16.06 13.60 11.63 10.22 9.10 flow rate 100 sccm 10 C. Partial sccm 14.46 11.34 9.30 7.87 6.80 6.03 5.37 pressure acetone flow rate CF acetone sccm 14.99 11.67 9.55 8.08 6.98 6.18 5.55 flow rate 100 sccm 0 C. Partial sccm 8.30 6.61 5.38 4.62 4.01 3.59 3.21 pressure acetone flow rate CF acetone sccm 8.42 6.64 5.48 4.64 4.02 3.59 3.25 flow rate 100 sccm 10 C. Partial sccm 4.36 3.46 2.84 2.43 2.12 1.88 1.70 pressure acetone flow rate CF acetone sccm 4.37 3.43 2.80 2.42 2.06 1.87 1.67 flow rate

(54) TABLE-US-00005 TABLE 5 Flow rate of N.sub.2: 50 sccm Internal pressure P.sub.0 of tank kPaabs 120 150 180 210 240 270 300 50 sccm 20 C. Partial sccm 12.43 9.56 7.70 6.44 5.59 4.92 4.36 pressure acetone flow rate CF acetone sccm 13.08 10.05 8.13 6.86 5.98 5.23 4.68 flow rate 50 sccm 10 C. Partial sccm 7.34 5.68 4.67 3.94 3.42 3.02 2.69 pressure acetone flow rate CF acetone sccm 7.69 6.01 4.93 4.18 3.64 3.24 2.88 flow rate 50 sccm 0 C. Partial sccm 4.12 3.25 2.67 2.27 1.99 1.77 1.57 pressure acetone flow rate CF acetone sccm 4.39 3.43 2.83 2.42 2.12 1.86 1.69 flow rate 50 sccm 10 C. Partial sccm 2.21 1.74 1.44 1.23 1.08 0.96 0.86 pressure acetone flow rate CF acetone sccm 2.35 1.91 1.53 1.33 1.17 1.08 0.94 flowrate

(55) TABLE-US-00006 TABLE 6 Flow rate of N.sub.2: 10 sccm Internal pressure P.sub.0 of tank kPaabs 120 150 180 210 240 270 300 10 sccm 20 C. Partial sccm 2.53 1.93 1.56 1.30 1.13 0.99 0.88 pressure acetone flow rate CF acetone sccm 2.84 2.21 1.80 1.53 1.35 1.18 1.05 flow rate 10 sccm 10 C. Partial sccm 1.48 1.16 0.94 0.80 0.69 0.61 0.54 pressure acetone flow rate CF acetone sccm 1.68 1.34 1.11 0.96 0.86 0.76 0.70 flow rate 10 sccm 0 C. Partial sccm 0.83 0.65 0.54 0.48 0.40 0.35 0.32 pressure acetone flow rate CF acetone sccm 0.93 0.73 0.60 0.54 0.46 0.42 0.38 flow rate 10 sccm 10 C. Partial sccm 0.45 0.35 0.29 0.25 0.22 0.19 0.17 pressure acetone flow rate CF acetone sccm 0.55 0.50 0.50 0.41 0.34 0.30 0.30 flow rate

(56) As apparent from the above description as well, where a partial pressure method based on Formula (1) and Formula (2) is used to determine a raw material gas steam flow rate Q.sub.2 and a raw material gas steam concentration K, as a matter of course, a steam pressure curve of raw material (a relationship between the temperature t and steam pressure P.sub.M0) is required, in addition to a measured flow rate value Q.sub.1 from the mass flow controller 3, a measurement value of internal pressure P.sub.0 of the tank from the automatic pressure regulating device 8 and a measured flow rate Q.sub.S from the mass flow meter 9 as shown in FIG. 1. Further, the raw material concentration arithmetic unit 10 shown in FIG. 1 is required to store in advance a curve which covers the temperature t of the raw material 4 and the steam P.sub.M0.

(57) Further, also in a case where a CF method according to Formula (5) is used to determine a raw material gas flow rate Q.sub.2 and a raw material gas steam concentration K, it is desirable that conversion factors CFs for various types of raw material gas and various types of mixed gas G.sub.S are in advance prepared in a table form.

(58) As a matter of course, the raw material gas steam flow rate Q.sub.2 and the raw material gas steam concentration K which have been described previously are all computed and displayed, etc., on the raw material concentration arithmetic unit 10 shown in FIG. 1 by using a CPU, etc.

(59) Further, as a matter of course, the raw material gas steam concentration K can be raised or lowered by controlling a tank pressure P.sub.0 and/or a tank temperature t.

INDUSTRIAL APPLICABILITY

(60) The present invention is applicable not only to a raw material vaporizing and supplying apparatus used in a MOCVD method and a CVD method but also applicable to any liquid supplying apparatus arranged so as to supply gas from a pressurized storage source to a process chamber in plants for manufacturing semiconductors and chemicals.

DESCRIPTION OF REFERENCE SYMBOLS

(61) 1: carrier gas supply source 2: decompression unit 3: mass flow control system 3a: sensor unit of mass flow controller 3b: flow rate arithmetic and control unit of mass flow controller 3e: flow rate display signal 4: raw material (MO material such as organometallic compound) 5: source tank (container) 6: constant temperature unit 7: induction pipe 8: automatic pressure regulating device in source tank 8a: control valve 8b: pressure arithmetic and control unit 8c: pressure detection signal 8d: control valve control signal 8e: pressure display signal 8f: temperature detection signal 9: mass flow meter 9a: sensor unit of mass flow meter 9b: arithmetic and control unit of mass flow meter 9c: mixed gas flow rate detection signal 9e: display signal of mixed gas flow rate 10: raw material concentration arithmetic unit 10.sub.K: concentration detection signal CF: conversion factor of mixed gas CF.sub.A: conversion factor of gas A CF.sub.B: conversion factor of gas B C: volume ratio of gas A G.sub.K: carrier gas G: raw material gas G.sub.S: mixed gas P.sub.0: internal pressure of source tank P.sub.M0: raw material steam partial pressure in source tank Q.sub.1: carrier gas flow rate Q.sub.S: mixed gas flow rate Q.sub.S: detection flow rate of mass flow meter (N.sub.2-based conversion) Q.sub.2: raw material gas flow rate Q.sub.2: raw material gas flow rate (N.sub.2-based conversion) K: raw material gas steam concentration P: pressure gauge T: temperature gauge t: tank temperature (raw material temperature)