Vapor mass flow control system

Claim 2

In a chemical vapor delivery system including a container partially filled with material to be vaporized and applied to a system which uses the vapor, means for ducting a carrier gas through said material to transport said vaporized material, a valve for controlling the flow of said carrier gas to said container, and means for controlling the temperature of the material in said container, an improved method comprising: providing a continuous, uniform mass flow of said vaporized material to said using system by: sensing the total gaseous pressure (P) in said container; comparing said sensed pressure (P) with a reference pressure (P o ) to provide a pressure differential (ΔP=P-P o ); generating a signal in a vapor mass flow controller utilizing said pressure differential (ΔP) in a computation by the controller wherein, as the differential becomes more positive, said computation demands an increase in carrier gas flows; and transmitting said signal to said flow control valve, said signal adjusting said flow control valve to control the carrier gas flow to provide said continuous uniform mass flow of said vaporized material.

Claim 3

The method of claim 1 including the steps of: sensing the temperature (T) of said material to be vaporized; comparing said sensed temperature (T) with a nominal temperature (T o ) to determine a temperature differential (ΔT=T-T o ); generating a signal in a vapor mass flow controller utilizing said temperature differential (ΔT) in a computation by the controller which demands an increase in carrier gas flow in response to more negative differentials; and combining said temperature differential signal with said pressure differential signal to generate said signal for providing said continuous uniform mass flow of said vaporized material.

Claim 4

The method of claim 1 or 2 including: sensing the level of said material in said container; determining changes in said sensed levels; combining said changes in said sensed levels with said pressure differential to generate said signal for providing said continuous uniform mass flow of said vaporized material.

Claim 5

A chemical vapor delivery system comprising: a bubbler container for holding a quantity of high purity liquid to be vaporized and applied to a using system; means for transporting a carrier gas through said liquid to transport the vaporized material to the using system; means for sensing the carrier gas flow rate; valve means for controlling the flow of said carrier gas; means for sensing and controlling the temperature of said liquid; means for sensing the total gaseous pressure in said container; and controller means connected to receive the sensed carrier gas flow rate, the sensed temperature and the sensed pressure and to compare the sensed pressure (P) with a reference pressure (P o ) to provide a pressure differential (ΔP=P-P o ), said controller generating a signal in a computation wherein, as the differential (ΔP) becomes more positive, said computation demands an increase in carrier gas flow rate, said signal for controlling said carrier gas flow control valve means in a manner to produce a continuous, uniform mass flow of said vaporized liquid to said using system.

Claim 6

A chemical vapor delivery system comprising: a bubbler container for holding a quantity of high purity liquid to be vaporized and applied to a using system; means for transporting a carrier gas through said liquid to transport the vaporized material to the using system; means for sensing the carrier gas flow rate; valve means for controlling the flow of said carrier gas; means for sensing and controlling the temperature of said liquid; means for sensing the total gaseous pressure in said container; and controller means connected to receive the sensed carrier gas flow rate, the sensed temperature and the sensed pressure and to compare the sensed pressure (P) with a reference pressure (P o ) to provide a pressure differential (ΔP=P-P o ), said controller generating a signal in a computation wherein, as the differential (ΔP) becomes more positive, said computation demands an increase in carrier gas flow rate, said signal for controlling said carrier gas flow control valve means in a manner to produce a continuous, uniform mass flow of said vaporized liquid to said using system.

Claim 7

A chemical vapor delivery system as claimed in claim 4, wherein said controller means is connected to compare said sensed temperature (T) with a reference temperature (T o ) to provide a temperature differential (ΔT=T-T o ), said controller generating a signal in a computation wherein, as said temperature differential becomes more negative, said computation demands an increase in carrier gas flow rate.

Claim 8

A chemical vapor delivery system as claimed in claim 4 or 5 wherein, said controller means generates said signal in said computation in accordance with the approximate formula: m*=AF.sub.c (1+BΔT-CΔP-DF.sub.c +EΔL) wherein m*=Approximate vapor mass flow F c =Carrier gas mass flow ΔT=Temperature variation from nominal (T-T o ) ΔP=Pressure variation from nominal=(P-P o ) ΔL=Change in liquid level=-∫ m*dt A,B and C=Positive constants computed for each chemical and nominal operating conditions; and D and E=Positive or negative constants computed for each chemical and nominal operating conditions.

Claim 9

A chemical vapor delivery system, said delivery system for providing a continuous uniform mass flow of vapor to a using system, including: a container partially filled with material to be vaporized and applied to said using system; means for ducting a carrier gas through said material to transport said material in a vaporized form; valve means for controlling the flow of said carrier gas; means for sensing and controlling the temperature of said material in said container; means for sensing the total gaseous pressure in said container; means for sensing the carrier gas flow rate; and means for sensing the level of material in said container, said delivery system further including controller means for utilizing the sensed temperature, pressure, flow rate, and material level to control said valve means to provide continuous uniform vapor mass flow in accordance with the approximate formula: m*=AF.sub.c (1+BΔT-CΔP-DF.sub.c +EΔL) wherein m*=Approximate vapor mass flow F c =Carrier gas mass flow ΔT=Temperature variation from nominal=(T-T o ) ΔP=Pressure variation from nominal=(P-P o ) ΔL=Change in liquid level=-∫ m*dt A,B and C=Positive constants computed for each chemical and nominal operating conditions; and D and/or E=Negative constants computed for each chemical and nominal operating conditions.

Claim 10

A chemical vapor delivery system, said delivery system for providing a continuous uniform mass flow of vapor to a using system, including: a container partially filled with material to be vaporized and applied to said using system; means for ducting a carrier gas through said material to transport said material in a vaporized form; valve means for controlling the flow of said carrier gas; means for sensing and controlling the temperature of said material in said container; means for sensing the total gaseous pressure in said container; means for sensing the carrier gas flow rate; and means for sensing the level of material in said container, said delivery system further including controller means for utilizing the sensed temperature, pressure, flow rate, and material level to control said valve means to provide continuous uniform vapor mass flow in accordance with the approximate formula: m*=AF.sub.c (1+BΔT-CΔP-DF.sub.c +EΔL) wherein m*=Approximate vapor mass flow F c =Carrier gas mass flow ΔT=Temperature variation from nominal=(T-T o ) ΔP=Pressure variation from nominal=(P-P o ) ΔL=Change in liquid level=-∫ m*dt A,B and C=Positive constants computed for each chemical and nominal operating conditions; and D and/or E=Negative constants computed for each chemical and nominal operating conditions.

Claim 11

An apparatus as claimed in claim 7, including means linked to said controller means for interrupting flow of carrier gas into said controller at a predetermined pressure.

Claim 12

An apparatus as claimed in claim 8, further including alarm means linked to said controller means for providing an alarm signal if the flow of carrier gas into said bubbler container is interrupted.

Claim 13

An apparatus as claimed in claim 8 including means for relieving pressure applied to said container at a predetermined pressure by venting said carrier gas to said using system.