Patent 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.

Full Description:
This is a National Phase Application in the United States of International Patent Application No. PCT/JP2012/004559 filed Jul. 17, 2012, which claims priority on Japanese Patent Application No. 2011-194285, filed Sep. 6, 2011. The entire disclosures of the above patent applications are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention relates to an improvement in a raw material vaporizing and supplying apparatus for semiconductor manufacturing equipment using so-called metalorganic chemical vapor deposition (hereinafter, referred to as MOCVD), and, also, to a raw material vaporizing and supplying apparatus equipped with a raw material concentration detection mechanism, capable of controlling a raw material concentration of a raw material mixed gas supplied to a process chamber highly accurately and quickly, and also capable of displaying the raw material gas concentration in real time. 
     Description of the Related Art 
     Conventionally, as this type of raw material vaporizing and supplying apparatus for semiconductor manufacturing equipment, a raw material vaporizing and supplying apparatus which utilized a so-called bubbling method has been used in many applications. In vaporizing and supplying of a raw material according to the bubbling method, there has been a strong demand for, such as, realizing significant downsizing of the raw material vaporizing and supplying apparatus, an increased supply quantity of a raw material, quick and highly accurate control of a mixture ratio of carrier gas and raw material gas, and direct display of a raw material gas concentration in the mixed gas supplied to a chamber. 
     Therefore, various types of research and development have been made for the bubbling-type raw material vaporizing and supplying apparatus. For example, techniques in the fields of controlling a flow rate of a mixed gas supplied to a process chamber and a raw material gas concentration in the mixed gas are disclosed in Japanese Published Unexamined Patent Application Publication No. H07-118862, Japanese Patent No. 4605790, etc. 
       FIG. 6  is a drawing that describes the structure of a reaction gas control method described in Japanese Published Unexamined Patent Application Publication No. H07-118862 given above. In  FIG. 6 , reference numeral  31  denotes a closed tank,  32  denotes a heater,  33  denotes a mass flow controller,  34  denotes an injection pipe,  35  denotes an ejection pipe,  36  denotes a mass flow meter, L 0  denotes a liquid raw material (TEOS, or tetraethyl orthosilicate), G K  denotes a carrier gas (N 2 ), G m  denotes a mixed gas (G+G K ), G denotes a raw material gas, Q 1  denotes a carrier gas flow rate, Q 2  denotes a raw material gas flow rate, Q S  denotes a mixed gas flow rate,  37  denotes a flow rate setting circuit,  38   a  denotes a concentration calculation circuit,  38   b  denotes a concentration setting circuit,  38   c  denotes an electric current control circuit, Q S0  denotes a set flow rate, and K S0  denotes a set concentration. 
     The present invention is to control a temperature of the liquid raw material L 0 , thereby regulating a produced flow rate Q 2  of a raw material gas G to keep the concentration of the raw material gas G in a mixed gas G m  constant. More specifically, computation is made for the produced flow rate Q 2  of the raw material gas with reference to a mixed gas flow rate Q S  from the mass flow meter  36  and a carrier gas flow rate Q 1  from the mass flow controller  33 . 
     Further, the thus computed Q 2  (the produced flow rate of the raw material gas) is used to determine Q 2 /Q S , thereby computing a raw material gas concentration K S  in the mixed gas G m . 
     The thus computed raw material gas concentration K S  is input into the concentration setting circuit  38   b  and by comparing with a set concentration K S0 , a difference between them (K S0 −K S ) is subjected to feedback to the electric current control circuit  38   c . Where such a relationship of K S0 &gt;K S  is obtained, the heater  32  is operated so as to raise its temperature, thereby increasing the produced flow rate Q 2  of the raw material gas G. Where such a relationship of K S0 &lt;K S  is obtained, the heater is operated so as to lower its temperature, thereby decreasing the produced flow rate Q 2 . 
     Further, the mixed gas flow rate Q S  from the mass flow meter  36  is compared with the set mixed gas flow rate Q S0  on the flow rate setting circuit  37 , thereby regulating the flow rate Q 1  from a mass flow controller so that a difference between them becomes zero. 
     However, the method for regulating the raw material gas concentration as shown in  FIG. 6  increases the produced flow rate Q 2  of a raw material gas by heating the liquid raw material L 0 , (or decreases the produced flow rate Q 2  of the raw material gas by lowering a temperature of the liquid raw material L 0 ). Therefore, there is a problem that the method is very low in response characteristics with respect to regulation of concentration and extremely low in response characteristics with respect to a decrease in concentration of the raw material gas. 
     Further, the mass flow meter (thermo-flowmeter)  36  undergoes a great fluctuation in measured flow rate value when a type of mixed gas G m  or a mixture ratio thereof is changed. Therefore, the method shown in  FIG. 6  has such a problem that, irrespective of whether a type of mixed gas G m  is changed or the type is the same, a great change in a mixture ratio (concentration of raw material gas) will result in a drastic decrease in the measuring accuracy of a flow rate Q S . 
     Still further, the change in temperature of heating the liquid raw material L 0  will raise a pressure inside the closed tank  31 , thereby inevitably resulting in a fluctuation in primary side pressure of the mass flow meter  36 . As a result, the mass flow meter  36  will have an error in the measured flow rate value, thus revealing a problem of decreasing the control accuracy of a flow rate and concentration of raw material gas. 
     On the other hand,  FIG. 7  is a drawing which shows the structure of a raw material gas supplying apparatus of Patent No. 4605790 which has been described above. The apparatus is able to supply a mixed gas having a predetermined concentration of raw material gas to a process chamber, with a flow rate thereof being controlled highly accurately with high responsive characteristics. 
     In  FIG. 7 , reference numeral  21  denotes a closed tank,  22  denotes a constant temperature device,  23  denotes a mass flow controller,  24  denotes an injection pipe,  25  denotes an ejection pipe,  26  denotes an automatic pressure regulator for the closed tank,  26   a  denotes an arithmetic and control unit,  26   b  denotes a control valve, L 0  denotes a liquid raw material, G K  denotes a carrier gas, Q 1  denotes a carrier gas flow rate, G denotes a raw material gas, G m  denotes a mixed gas (G+G K ), and Q S  denotes a mixed gas flow rate. 
     In the raw material gas supplying apparatus, first, the constant temperature device  22  is used to heat the closed tank  21 , a main body of the automatic pressure regulator  26  for the closed tank and a piping line L to a predetermined temperature. Thereby, an internal space of the closed tank  21  is filled with saturated steam (raw material gas) G of a raw material. 
     Further, the carrier gas G K  at a flow rate Q 1  controlled by the mass flow controller  23  is released from a bottom of the closed tank  21 . A mixed gas G m  of the carrier gas G K  and the saturated steam (or vapor) G of the raw material is supplied through the control valve  26   b  of the automatic pressure regulating device  26  to outside (process chamber). 
     The mixed gas G m  is regulated for the flow rate Q S  by controlling a pressure of the mixed gas in the closed tank  21  by the automatic pressure regulator  26 . A set flow rate Q S0  is compared with a computation flow rate Q S  computed with reference to measurement values obtained from a pressure gauge P 0  and a temperature gauge T 0  at an arithmetic and control unit  26   a  of the automatic pressure regulator  26 . And, the control valve  26   b  is opened and closed so that a difference between them (Q S0 −Q S ) becomes zero, thereby controlling a flow rate Q S  of supplying the mixed gas G m  to a set flow rate Q S0 . 
     The raw material gas supplying apparatus shown in  FIG. 7  is able to supply the mixed gas G m  having a constant raw material gas concentration which is determined in response to a heating temperature of the liquid raw material L 0  by regulating an internal pressure of the closed tank, with a flow rate thereof controlled highly accurately with high response characteristics, thereby providing excellent effects of controlling a flow rate of the mixed gas having a predetermined and constant raw material gas concentration. 
     Although the raw material gas supplying apparatus is able to measure a flow rate Q S  of the mixed gas G m  highly accurately and with high response characteristics, it has a basic problem that the mixed gas G m  is not measured for a raw material gas concentration highly accurately and cannot display a measurement value thereof. As a matter of course, if a heating temperature of the closed tank  21 , a flow rate of the carrier gas G K , a level height of the raw material liquid L 0 , etc., are determined, it is possible to estimate a raw material gas concentration K S  in the mixed gas G m  to some extent. However, a technique has not yet been developed that a raw material gas concentration of the mixed gas G m  supplied to a process chamber can be continuously and automatically measured and displayed without using a complicated and expensive concentration meter, etc., in a less expensive and economical manner. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Published Unexamined Patent Application Publication No. H07-118862 
     Patent Document 2: Japanese Patent No. 4605790 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The main object of the present invention is to solve problems of the raw material vaporizing and supplying apparatus described in Japanese Published Unexamined Patent Application Publication No. H07-118862 and Japanese Patent No. 4605790. That is, the former case has the following problems, for example. (A) The raw material vaporizing and supplying apparatus is increased or (decreased) in produced flow rate Q of a raw material gas by heating or cooling a liquid raw material L 0 , thereby regulating a raw material gas concentration K S  in a mixed gas G m . Thus, the apparatus is relatively low in response characteristics for controlling the raw material gas concentration and also required to have expensive additional equipment for increasing the response characteristics. Thereby, the raw material gas supplying apparatus has increased manufacturing costs and dimensions. (B) Where the mixed gas G m  is changed in the type of mixed gas or the mixture ratio thereof, the mass flow meter undergoes a great fluctuation in the measured flow rate value. Then, a mixed gas flow rate Q S  is decreased in accuracy of measurement, resulting in a great decrease in accuracy of computing the raw material gas concentration K S . (C) Change in heating temperature will result in a fluctuation in pressure in the closed tank  31 . Thereby, the mass flow meter  35  has decreased accuracy of measurement to decrease the accuracy of computing a measurement value of the flow rate Q S  and the raw material concentration K S . Further, the latter case has the following problem, for example. (A) It is not possible to measure a raw material gas concentration in the mixed gas G m  highly accurately and display the concentration in real time. Therefore, the present invention seeks to provide a raw material vaporizing and supplying apparatus equipped with a raw material concentration detection mechanism in which the raw material gas concentration K S  in a mixed gas G m  of carrier gas G K  and raw material gas G supplied to a process chamber is measured and displayed continuously and automatically Furthermore, in place of a concentration meter, etc., high in cost and complicated in structure, a device low in cost and simple in structure can be used for extremely economical control and display of the raw material gas concentration in the mixed gas G m . 
     Means for Solving the Problems 
     The invention according to the first aspect is a raw material vaporizing and supplying apparatus which supplies a carrier gas G K  into a source tank  5  through a mass flow controller  3  to release the carrier gas G K  from inside the source tank  5  and also supplies into a process chamber a mixed gas G S  composed of the carrier gas G K  and saturated steam G of a raw material  4  produced by keeping the source tank  5  at a constant temperature by a constant temperature unit  6 , and the raw material vaporizing and supplying apparatus in which an automatic pressure regulating device  8  and a mass flow meter  9  are installed on a flow-out passage of the mixed gas G S  from the source tank  5 , the automatic pressure regulating device  8  is controlled so as to open and close a control valve  8   a , thereby controlling an internal pressure P 0  of the source tank  5  to a predetermined value, individual detection values of a flow rate Q 1  of the carrier gas G K  by the mass flow controller  3 , the internal pressure P 0  of the tank and a flow rate Q S  of the mixed gas G S  by the mass flow meter  9  are input into a raw material concentration arithmetic unit  10 , the raw material concentration arithmetic unit  10  is used to compute a raw material flow rate Q 2  based on Q 2 =Q S ×P M0 /P 0  (however, P M0  is a saturated steam pressure of the raw material steam G at a temperature of t° C. in the source tank), and a raw material concentration K of the mixed gas G S  supplied to the process chamber is computed and displayed in terms of K=Q 2 /Q S  with reference to the raw material flow rate Q 2 . 
     The invention according to the second aspect is the invention according to the first aspect, in which a storage device of saturated steam pressure data of the raw material in the source tank  5  is installed on the raw material concentration arithmetic unit  10  and also detection signals of an internal pressure P 0  of the source tank  5  and a temperature t from the automatic pressure regulating device  8  are input into the raw material concentration arithmetic unit  10 . 
     The invention according to the third aspect is a raw material vaporizing and supplying apparatus which supplies a carrier gas G K  into a source tank  5  through a mass flow controller  3  to release the carrier gas G K  from inside the source tank  5  and also supplies to a process chamber a mixed gas G S  composed of the carrier gas G K  and saturated steam G of a raw material  4  produced by keeping the source tank  5  at a constant temperature by a constant temperature unit  6 , and the raw material vaporizing and supplying apparatus in which an automatic pressure regulating device  8  and a mass flow meter  9  are installed on a flow-out passage of the mixed gas G S  from the source tank  5 , the automatic pressure regulating device  8  is controlled so as to open and close a control valve  8   a , thereby controlling an internal pressure P 0  of the source tank  5  to a predetermined value, individual detection values of a flow rate Q 1  of the carrier gas G K  by the mass flow controller  3 , the internal pressure P 0  of the tank and a flow rate Q S  of the mixed gas G S  from the mass flow meter  9  are input into a raw material concentration arithmetic unit  10 , and the raw material concentration arithmetic unit  10  is used to determine a raw material flow rate Q 2  based on Q 2 =CF×Q S ′−Q 1  (however, CF is a conversion factor of the mixed gas Q 2 ), and a raw material concentration K of the mixed gas G S  supplied to the process chamber is computed and displayed based on K=Q 2 /(Q 1 +Q 2 ) with reference to the raw material flow rate Q 2 . 
     The invention according to the fourth aspect is the invention according to the third aspect, in which a conversion factor CF of the mixed gas Q S  is given as 1/CF=C/CF A +(1−C)/CF B  (however, CF A  is a conversion factor of the carrier gas G K , CF B  is a conversion factor of the raw material gas G, and C is a volume ratio of carrier gas (Q 1 /(Q 1 +Q 2 )). 
     The invention according to the fifth aspect is the invention according to the first aspect or the third aspect, in which the raw material concentration detection unit  10 , a flow rate arithmetic and control unit  3   b  of the mass flow controller  3 , a pressure arithmetic and control unit  8   b  of the automatic control device and a flow rate arithmetic and control unit  9   b  of the mass flow meter  9  are arranged so as to be assembled in an integrated manner. 
     The invention according to the sixth aspect is the invention according to the third aspect, in which the raw material concentration arithmetic unit  10  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 K . 
     The invention according to the seventh aspect is the invention according to any one of the first aspect to the sixth aspect, in which the mass flow meter  9  is installed on the downstream side of the automatic pressure regulating device  8 . 
     The invention according to the eighth aspect is the invention according to any one of the first aspect to the sixth aspect, in which the mass flow meter  9  is installed on the upstream side of the automatic pressure regulating device  8 . 
     The invention according to the ninth aspect is the invention according to any one of the first aspect to the sixth aspect, in which the automatic pressure regulating device  8  is a pressure regulating device which has a temperature detector T, a pressure detector P, a control valve  8   a  installed on the downstream side from the pressure detector P and a pressure arithmetic and control unit  8   b.    
     The invention according to the tenth aspect is an invention in which the mass flow meter  9  is installed between the pressure detector P and the control valve  8   a.    
     In the present invention, the raw material vaporizing and supplying apparatus is arranged so that a flow rate Q 1  of supplying the carrier gas G K  from the mass flow controller  3 , a flow rate Q S  of supplying the mixed gas G S  from the mass flow meter  9  and an internal pressure of the tank from the automatic pressure regulating device  8  in the source tank, etc., are input into the raw material concentration arithmetic unit  10 , and the mixed gas G S  is supplied to the chamber at a constant pressure and, at the same time, a raw material gas concentration K in the thus supplied mixed gas G S  is computed and displayed on the raw material concentration arithmetic unit  10  in real time. Therefore, the mixed gas G S  can be supplied at a more stable raw material concentration K. It is also possible to display the raw material concentration K of the mixed gas G S  in a digital form and carry out stable process treatment which is high in quality. 
     Further, it is acceptable that the raw material concentration arithmetic unit  10  is simply added. Thereby, as compared with a case where the above-described expensive gas concentration meter is used, the raw material gas concentration K in the mixed gas G S  can be detected and displayed reliably and in a less-expensive manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         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. 
         FIG. 2  is a drawing which describes test equipment used for studying a relationship between a raw material gas flow rate Q 2 , a mixed gas flow rate Q S , a carrier gas flow rate Q 1 , a source tank pressure P 0  and a source tank temperature t. 
         FIG. 3  is a drawing which shows a relationship between the internal pressure P 0  of the tank, the mixed gas flow rate Q S , the raw material gas flow rate Q 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 S  and (b) shows a state of change in the raw material gas flow rate Q 2 . 
         FIG. 4  is a line drawing which shows a relationship between a measurement value, with the carrier gas flow rate Q 1  kept constant (mixed gas flow rate Q S −carrier gas flow rate Q 1 ) and the raw material gas flow rate Q 2  calculated with reference to Formula (2). 
         FIG. 5  is a schematic diagram which shows a system of supplying a raw material gas. 
         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). 
         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 
     Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 
       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. 
     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 1  denotes a carrier gas flow rate of Ar, etc., Q 2  denotes a flow rate of the raw material saturated steam (raw material gas flow rate), Q S  denotes a mixed gas flow rate of the carrier gas flow rate Q 1  and the raw material steam flow rate Q 2 , P denotes a pressure detector of the mixed gas G S , T denotes a temperature detector of the mixed gas G S ,  3   a  denotes a sensor unit of the mass flow controller,  8   a  denotes a piezoelectric element driving control valve,  9   a  denotes a sensor unit of the mass flow meter, and  9   b  denotes an arithmetic and control unit of the mass flow meter  9   a . The mass flow controller  3  is made up of the sensor unit  3   a  and a flow rate arithmetic and control unit  3   b  of the sensor unit  3   a . The automatic pressure regulator  8  of the source tank is made up of the control valve  8   a , a pressure arithmetic and control unit  8   b , the pressure detector P and the temperature detector T. 
     It is noted that N 2  is generally used as the carrier gas G K . However, the carrier gas G K  is not limited to N 2  but includes various types of gas such as H 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. 
     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. 
     Further, in  FIG. 1 , reference numeral G K  denotes a carrier gas, G denotes raw material steam (raw material gas), G S  denotes a mixed gas, P 0  denotes an internal pressure of the source tank (kPa abs.), P M0  denotes a raw material steam pressure in the source tank (kPa abs.),  3   e  denotes a flow rate display signal,  8   d  denotes a control valve control signal,  8   c  denotes a pressure detection signal,  8   f  denotes a temperature detection signal,  8   e  denotes a pressure display signal,  9   c  denotes a mixed gas flow rate detection signal, and  9   e  denotes a mixed gas flow rate display signal. The display signal  3   e  of the flow rate Q 1  of the carrier gas G K  and the display signal  9   e  of the flow rate Q S  of the mixed gas G 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 S  is computed and displayed here. It is noted that  10   K  denotes a raw material concentration display signal. 
     It is noted that in the embodiment shown in  FIG. 1 , the flow rate arithmetic and control unit  3   b  of the mass flow controller  3 , the pressure arithmetic and control unit  8   b  of the automatic pressure regulating device  8 , the flow rate arithmetic and control unit  9   b  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  3   b ,  8   b ,  9   b  and the raw material concentration arithmetic unit  10  are individually installed. 
     Next, a description will be given of operation of the raw material vaporizing and supplying apparatus. 
     In the raw material vaporizing and supplying apparatus, first, a pressure PG 1  of the carrier gas G 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 1  thereof is also set so as to give a predetermined value by the thermal type mass flow control system  3  (mass flow controller). 
     Further, the constant temperature unit  6  is operated to keep parts in constant temperature excluding the source tank  5 , the arithmetic and control unit  8   b  of the automatic pressure regulating device  8 , etc. 
     As described so far, the supply quantity Q 1  of the carrier gas G 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 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 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  8   a , and the flow rate Q S  of the mixed gas G S  is measured here with high accuracy. 
     Further, the source tank  5 , the control valve  8   a  of the automatic pressure regulating device  8 , etc., are kept at constant temperature. Therefore, a pressure P M0  of the raw material saturated steam G in the source tank  5  is kept stable and the internal pressure P 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 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 S  is kept stable. 
     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 0  (kPa abs.), the raw material steam pressure is given as P M0 , the flow rate of the carrier gas G K , is given as Q 1  (sccm), the flow rate of the mixed gas G S  supplied to the chamber is given as Q 2  (sccm) and the flow rate of the raw material steam G is given as Q 2  (sccm), the flow rate Q S  of supplying the mixed gas G S  to the chamber is expressed as Q S =Q 1 +Q 2  (sccm). 
     That is, the raw material flow rate Q 2  is proportional to the raw material steam pressure P M0  in the source tank, and the flow rate of supplying the mixed gas G S , that is, Q S =Q 1 +Q 2 , is proportional to the internal pressure P 0  of the source tank. Therefore, the following relationship is obtained. Raw material flow rate Q 2 : mixed gas supplying flow rate Q S =raw material steam pressure P M0 : internal pressure P 0  of source tank. 
     That is, 
     [Formula 1]
 
 Q   2   ×P   0   =Q   S   ×P   M0    (1)
 
With reference to Formula 1, the raw material flow rate Q 2  is expressed as follows:
 
[Formula 2]
 
 Q   2   =Q   S   ×P   M0   /P   0    (2)
 
     As apparent from Formula 2 given above, the raw material flow rate Q 2  is determined by the mixed gas flow rate Q S , the source tank pressure P 0  and the raw material steam pressure (partial pressure) P M0 . Further, the internal pressure P 0  of source tank is determined by the temperature t in the source tank. 
     In other words, the raw material concentration K in the mixed gas G S  is determined by parameters such as the carrier gas flow rate Q 1 , the internal pressure P 0  of source tank and the temperature t in the source tank. 
     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  8   a.    
     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). 
     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. 
     Further, where the mass flow meter  9  is installed between the pressure detector P and the control valve  8   a , 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  8   a,  thereby affecting the response characteristics for pressure control. 
       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 2  was used as the carrier gas G K . A relationship between the internal pressure P 0  of the tank and the flow rate Q S  of the mixed gas G S  was regulated, with the tank temperature t given as a parameter (−10° C., 0° C., 10° C., 20° C.). 
       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 2  of the raw material acetone. 
     
       
         
               
             
               
               
             
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Raw material acetone: Carrier gas N 2  (50 sccm) 
               
             
          
           
               
                 Temperature of 
                   
               
               
                 constant temperature 
                   
               
               
                 water bath (° C.) 
                 Internal pressure P 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 
               
               
                   
               
             
          
         
       
     
     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. 
     
       
         
               
               
               
             
               
             
               
               
               
             
               
             
               
               
               
             
           
               
                   
                 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 
               
               
                   
               
             
          
         
       
     
       FIG. 4  is a drawing which shows a relationship of a difference between an N 2  converted detection flow rate Q S ′ of the mixed gas G S  and the carrier gas flow rate Q 1 , Q S ′−Q 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 1 ) kept constant and the tank temperature t (−10° C. to 20° C.) given as a parameter (that is, an N 2  converted raw material gas flow rate Q 2 ′=Q S ′−Q 1 ) with respect to an acetone flow rate (Q 2  sccm) calculated with reference to Formula (2). In this drawing, (a) covers a case where the carrier gas flow rate Q 1  is equal to 50 sccm, (b) covers a case where Q 1  is equal to 100 sccm and (c) covers a case where Q 1  is equal to 10 sccm. 
     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 S ′−carrier gas flow rate Q 1 ) by using the mass flow meter and a calculated acetone flow rate Q 2 . As a result, the carrier gas flow rate Q 1  is measured by using the mass flow controller  3  and the mixed gas flow rate Q S  is measured by using the mass flow meter  9 , respectively, to determine Q S −Q 1 . Thereby, it is possible to calculate the raw material gas flow rate Q 2 . 
     Next, a description will be given of calculation of a raw material gas flow rate Q 2  and a concentration K of the raw material gas G in the mixed gas Gs. 
     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 2  equivalent to a concentration K and a carrier gas G K  (N 2 ) at a flow rate Q 1  (that is, Q 2 +Q 1  sccm) are supplied to the mass flow meter  9  to give a detection flow rate (N 2 -based conversion) of mixed gas Gs at this time as Q S ′ (sccm), the raw material gas flow rate Q 2  and the raw material gas concentration K in the mixed gas can be obtained with reference to the formulae given below. 
     [Formula 3]
 
Raw material gas flow rate  Q   2  (sccm)= CF  of mixed gas×detected flow rate (N 2 -based conversion)  Q   S ′ (sccm)−carrier gas flow rate  Q   1  (sccm)   (3)
 
[Formula 4]
 
Raw material gas concentration  K =Raw material gas flow rate  Q   2  (sccm)/Carrier gas flow rate  Q   1  (sccm)+Raw material gas flow rate  Q   2  (sccm)   (4)
 
     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. 
     [Formula 5]
 
1 /CF=C/CF   A +(1 −C )/ CF   B   (5)
 
     However, in Formula (5), CF A  denotes a conversion factor of gas A, CF B  denotes a conversion factor of gas B, C denotes a volume ratio (concentration) of the gas A and (1−C) 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). 
     Now, in  FIG. 5 , where CF A  of the carrier gas G K  (N 2 ) is given as 1 and CF B  of the raw material gas G is given as α, the concentration of the raw material gas is expressed as Q 2 /(Q 1 +Q 2 ) and the concentration of the carrier gas is expressed as Q 1 /(Q 1 +Q 2 ). Thus, CF of the mixed gas Q 2  is expressed by Formula (5) as follows. 
                     1   CF     =           1   1     ×       Q   1         Q   1     +     Q   2           +       1   α     ·       Q   2         Q   1     +     Q   2             =         α   ⁢           ⁢     Q   1       +     Q   2         α   ⁡     (       Q   1     +     Q   2       )                   [     Formula   ⁢           ⁢   6     ]               
Thus, the following formula is obtained.
 
     
       
         
           
             
               
                 
                   CF 
                   = 
                   
                     
                       α 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             Q 
                             1 
                           
                           + 
                           
                             Q 
                             2 
                           
                         
                         ) 
                       
                     
                     
                       
                         α 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           Q 
                           1 
                         
                       
                       + 
                       
                         Q 
                         2 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     7 
                   
                   ] 
                 
               
             
           
         
       
     
     Therefore, the N 2  converted detection flow rate Q S ′ of the mixed gas G S  detected by the mass flow meter  9  is expressed as follows. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           Qs 
                           ’ 
                         
                         = 
                           
                         ⁢ 
                         
                           
                             
                               Q 
                               1 
                             
                             + 
                             
                               Q 
                               2 
                             
                           
                           CF 
                         
                       
                     
                   
                   
                     
                       
                         = 
                           
                         ⁢ 
                         
                           
                             ( 
                             
                               
                                 Q 
                                 1 
                               
                               + 
                               
                                 Q 
                                 2 
                               
                             
                             ) 
                           
                           × 
                           
                             
                               ( 
                               
                                 
                                   α 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   
                                     Q 
                                     1 
                                   
                                 
                                 + 
                                 
                                   Q 
                                   2 
                                 
                               
                               ) 
                             
                             / 
                             
                               α 
                               ⁡ 
                               
                                 ( 
                                 
                                   
                                     Q 
                                     1 
                                   
                                   + 
                                   
                                     Q 
                                     2 
                                   
                                 
                                 ) 
                               
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         = 
                           
                         ⁢ 
                         
                           
                             ( 
                             
                               
                                 α 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 
                                   Q 
                                   1 
                                 
                               
                               + 
                               
                                 Q 
                                 2 
                               
                             
                             ) 
                           
                           / 
                           α 
                         
                       
                     
                   
                   
                     
                       
                         = 
                           
                         ⁢ 
                         
                           
                             Q 
                             1 
                           
                           + 
                           
                             
                               Q 
                               2 
                             
                             α 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     8 
                   
                   ] 
                 
               
             
           
         
       
     
     Thereby, the flow rate Q 2  of the raw material gas G is expressed as Q 2 =α(Q S ′−Q 1 ). However, in this case, α is a conversion factor of the raw material gas G. 
     Table 3 below shows results obtained by comparing a raw material gas flow rate Q 2  calculated by using a conversion factor CF determined with reference to Formula (5) above with a raw material gas flow rate Q 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). 
     It is noted that in Table 1, acetone is supplied as a raw material gas G and N 2  is supplied as a carrier gas G K  at a flow rate Q 1 =500 sccm and calculation is made, with the temperature t given as a parameter. The raw material gas flow rate Q 2  determined with reference to a pressure ratio between Formula (1) and Formula (2) and the raw material gas flow rate Q 2  determined with reference to a conversion factor CF according to Formula (5) are approximate in flow rate value with each other. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 CF of acetone: 0.341, Constant temperature water bath set at 20° C., Flow rate of N 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 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 s   
                 MIN 
                 sccm 
                 87.8 
                 78.9 
                 73.2 
                 69.6 
                 67.1 
                 64.9 
                 63.3 
               
               
                 (N 2 -based 
               
               
                 conversion): Q s ′ 
               
             
          
           
               
                 Raw material gas flow 
                 sccm 
                 38.3 
                 29.5 
                 23.8 
                 20.1 
                 17.5 
                 15.3 
                 13.7 
               
               
                 rate (N 2 -based 
               
               
                 conversion) Q 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) 
               
               
                   
               
             
          
         
       
     
     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 1  of N 2  as a carrier gas G K  being changed. 
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Flow rate of N 2 : 100 sccm 
               
             
          
           
               
                   
                 Internal pressure P 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 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Flow rate of N 2 : 50 sccm 
               
             
          
           
               
                   
                 Internal pressure P 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 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Flow rate of N 2 : 10 sccm 
               
             
          
           
               
                   
                 Internal pressure P 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 
               
               
                   
               
             
          
         
       
     
     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 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 M0 ) is required, in addition to a measured flow rate value Q 1  from the mass flow controller  3 , a measurement value of internal pressure P 0  of the tank from the automatic pressure regulating device  8  and a measured flow rate Q 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 M0 . 
     Further, also in a case where a CF method according to Formula (5) is used to determine a raw material gas flow rate Q 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 S  are in advance prepared in a table form. 
     As a matter of course, the raw material gas steam flow rate Q 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. 
     Further, as a matter of course, the raw material gas steam concentration K can be raised or lowered by controlling a tank pressure P 0  and/or a tank temperature t. 
     INDUSTRIAL APPLICABILITY 
     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 
     
         
           1 : carrier gas supply source 
           2 : decompression unit 
           3 : mass flow control system 
           3   a:  sensor unit of mass flow controller 
           3   b:  flow rate arithmetic and control unit of mass flow controller 
           3   e:  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 
           8   a:  control valve 
           8   b:  pressure arithmetic and control unit 
           8   c:  pressure detection signal 
           8   d:  control valve control signal 
           8   e:  pressure display signal 
           8   f:  temperature detection signal 
           9 : mass flow meter 
           9   a:  sensor unit of mass flow meter 
           9   b:  arithmetic and control unit of mass flow meter 
           9   c:  mixed gas flow rate detection signal 
           9   e:  display signal of mixed gas flow rate 
           10 : raw material concentration arithmetic unit 
           10   K : concentration detection signal 
         CF: conversion factor of mixed gas 
         CF A : conversion factor of gas A 
         CF B : conversion factor of gas B 
         C: volume ratio of gas A 
         G K : carrier gas 
         G: raw material gas 
         G S : mixed gas 
         P 0 : internal pressure of source tank 
         P M0 : raw material steam partial pressure in source tank 
         Q 1 : carrier gas flow rate 
         Q S : mixed gas flow rate 
         Q S ′: detection flow rate of mass flow meter (N 2 -based conversion) 
         Q 2 : raw material gas flow rate 
         Q 2 ′: raw material gas flow rate (N 2 -based conversion) 
         K: raw material gas steam concentration 
         P: pressure gauge 
         T: temperature gauge 
         t: tank temperature (raw material temperature)

Technology Classification (CPC): 5