Method and apparatus

1. A method of depositing a film on a substrate, comprising:

(a) providing an evaporation vessel comprising a chamber containing a precursor compound to be vaporized, the evaporation vessel having a gas inlet and a gas outlet, a carrier gas feed line in fluid communication with the gas inlet, a gas control valve in the gas feed line, and a gas exit line in fluid communication between the gas outlet and a plurality of vapor deposition reactors, the gas exit line having a pressure transducer and a concentration transducer, each of the gas control valve, pressure transducer and concentration transducer in electrical connection with a controller;

(b) conveying a gaseous mixture comprising vaporized precursor compound and a carrier gas to the plurality of vapor deposition reactors;

(c) maintaining a substantially constant concentration of the precursor compound in the gaseous mixture by the steps selected from the group consisting of:

(1) sensing a concentration of the vaporized precursor compound in the gaseous mixture in the gas exit line;

comparing the sensed concentration (c) with a reference concentration (c o ) to provide a concentration differential (c−c o );

generating a signal in the controller utilizing the concentration differential;

transmitting the signal to the gas control valve wherein the signal adjusts the gas control valve to adjust total pressure within the evaporation vessel in order to maintain a substantially constant concentration of the vaporized precursor compound in the gaseous mixture in the gas exit line;

(2) providing the evaporation vessel with a temperature sensing means, the temperature sensing means located so as to sense temperature of the precursor compound;

sensing the temperature of the precursor compound;

comparing the sensed temperature (T) with a reference temperature (T o ) to provide a temperature differential (T−T o );

generating a signal in the controller utilizing the temperature differential;

transmitting the signal to the gas control valve wherein the signal adjusts the gas control valve to adjust total pressure in the evaporation vessel in order to maintain a substantially constant concentration of the vaporized precursor compound in the gaseous mixture in the gas exit line;

and

(3) a combination of (1) and (2); and

(d) subjecting the gaseous mixture to conditions in the plurality of deposition reactors sufficient to deposit a film.

2. The method of claim 1 wherein the signal generated in step (c)(1) utilizes the equation

p

=

p

o

+

B

⁢

∫

time

⁢

(

c

-

c

o

)

where p is a total pressure, p o is a reference pressure, and B is a calibration constant.

3. The method of claim 1 wherein the signal generated in step (c)(2) utilizes the equation p=p o +D(T−T o ) where p is a total pressure, p o is a reference pressure, and D is a calibration constant.

4. The method of claim 1 wherein the precursor compound is a metalorganic compound.

5. The method of claim 4 wherein the metalorganic compound comprises a metalloid.

6. The method of claim 1 wherein the precursor compound is selected from trimethylgallium, triethylgallium, trimethylaluminum, trimethylindium, dimethylzinc, silane, dichlorosilane, boron trichloride, isobutyl germane, germanium tetrachloride.

7. The method of claim 1 wherein a second gas control valve is present in the gas exit line.

8. The method of claim 1 wherein step (c)(2) is used to maintain a substantially constant concentration of the precursor in the gaseous mixture.

9. A method of depositing a film on a substrate, comprising:

(a) providing an evaporation vessel comprising a chamber containing a precursor compound to be vaporized, the evaporation vessel having a gas inlet and a gas outlet, a carrier gas feed line in fluid communication with the gas inlet, a gas control valve in the gas feed line, and a gas exit line in fluid communication between the gas outlet and one or more vapor deposition reactors, the gas exit line having a pressure transducer and a concentration transducer, each of the gas control valve, pressure transducer and concentration transducer in electrical connection with a controller;

(b) conveying a gaseous mixture comprising vaporized precursor compound and a carrier gas to the one or more vapor deposition reactors;

(c) maintaining a substantially constant concentration of the precursor compound in the gaseous mixture by

providing the evaporation vessel with a temperature sensing means, the temperature sensing means located so as to sense temperature of the precursor compound;

sensing the temperature of the precursor compound;

comparing the sensed temperature (T) with a reference temperature (T o ) to provide a temperature differential (T−T o );

generating a signal in the controller utilizing the temperature differential;

transmitting the signal to the gas control valve wherein the signal adjusts the gas control valve to adjust total pressure in the evaporation vessel in order to maintain a substantially constant concentration of the vaporized precursor compound in the gaseous mixture in the gas exit line; and

(d) subjecting the gaseous mixture to conditions in the one or more deposition reactors sufficient to deposit a film.

10. The method of claim 9 wherein the gas exit line is in fluid communication between the gas outlet and a plurality of vapor deposition reactors.

11. The method of claim 9 wherein signal generated utilizes the equation p=p o +D(T−T o ) where p is a total pressure, p o is a reference pressure, and D is a calibration constant.