Metrology method for transient gas flow

Patent metadata

Field	Value
Publication number	US-9778083-B2
Application number	US-201313896108-A
Country	US
Kind code	B2
Filing date	May 16, 2013
Priority date	May 16, 2013
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

A method of calculating a transient flow rate of a flowed process gas comprises flowing process gas through a mass flow controller into a chamber of known volume and measuring successive data sample points which include pressure data, temperature data, and a time value for each successive data sample point. Groups of successive data sample points are identified wherein each group shares one or more successive data sample points with another group, and ratio values are calculated for each of the successive data sample points wherein each ratio value is a ratio between the pressure data and a product of temperature and gas compressibility data for each respective time value. A line of best fit of the ratio values is determined within at least one group, and then the transient flow rate of the flowed process gas is calculated using a pressure rate of rise technique wherein the pressure rate of rise technique utilizes a ratio value determined from the line of best fit for at least one time value within the at least one group.

First claim

What is claimed is:

1. A method of calculating a transient flow rate of a flowed process gas, wherein the process gas is flowed through a mass flow controller to a chamber of a known volume, comprising:
flowing process gas through the mass flow controller into the chamber;
measuring successive data sample points which include pressure data, temperature data, and a time value for each successive data sample point;
processing the measured pressure data with a digital filter, wherein the digital filter reduces noise from the measured pressure data and provides processed pressure data;
identifying groups of successive data sample points wherein each group shares one or more successive data sample points with another group;
calculating ratio values for each of the successive data sample points wherein each ratio value is a ratio between the processed pressure data and a product of temperature and gas compressibility data for each respective time value;
determining a line of best fit of the ratio values within at least one group;
calculating the transient flow rate of the flowed process gas using a pressure rate of rise technique wherein the pressure rate of rise technique utilizes a ratio value determined from the line of best fit for at least one time value within the at least one group; and
controlling flow of the process gas through the mass flow controller into the chamber based on the calculated transient flow rate.

2. The method of claim 1 , wherein the process gas flows through the mass flow controller at a predetermined set point, the method further comprising comparing the calculated transient flow rate against the predetermined set point and determining whether any transient gas flow anomalies are detected.

3. The method of claim 2 , further comprising outputting, displaying, and/or storing the calculated transient flow rate of the flowed process gas and/or determining whether any transient gas flow anomalies are detected and outputting, displaying, and/or storing the transient gas flow anomalies of the flowed process gas.

4. The method of claim 1 , further comprising processing the measured temperature data with the digital filter before calculating the ratio values, wherein the digital filter reduces noise from the measured temperature data and provides processed temperature data.

5. The method of claim 1 , wherein the digital filter processes the pressure data using (a) a least squares curve fit, or (b) a multipoint digital filtering process.

6. The method of claim 1 , wherein each group shares (a) about 5 to 500 successive data sample points with an adjacent group; (b) about 50 to 150 successive data sample points with an adjacent group; or (c) about 100 data sample points with an adjacent group.

7. The method of claim 1 , wherein the successive data sample points are measured at a predetermined data sampling rate of (a) about 10 milliseconds, (b) about 2 milliseconds, (c) about 1 millisecond or (d) about 0.5 milliseconds.

8. The method of claim 1 , wherein each group shares (a) at least about 50% of successive data sample points with an adjacent group; (b) at least about 90% of successive data sample points with an adjacent group; or (c) at least about 99% of successive data sample points with an adjacent group.

9. The method of claim 1 , wherein the time value used to determine the ratio value from the line of best fit is (a) a median time value of the group; or (b) a mean time value of the group.

10. The method of claim 1 , wherein a control system calculates the transient flow rate of the flowed process gas.

11. The method of claim 10 , wherein the control system includes a display which displays the transient flow rate and/or transient flow anomalies.

12. The method of claim 2 , and calibrating the mass flow controller wherein the calibration includes verifying a process gas flow set point and calibrating the mass flow controller to operate within a predetermined flow tolerance of the process gas flow set point.

13. The method of claim 2 , wherein the mass flow controller undergoes a multi-point gas calibration, the multi-point gas calibration includes verification of at least ten process gas flow set points and calibrating the mass flow controller to operate within a respective predetermined flow tolerance of each process gas flow set point.

14. The method of claim 1 , wherein the flow rate of the process gas is about 0.1 sccm to about 10,000 sccm.

15. The method of claim 1 , wherein (a) the ratio values for the successive data sample points are calculated before the groups of successive data sample points are identified; or (b) the measured pressure data is processed after the groups of successive data sample points are identified.

16. The method of claim 1 , wherein operations of the method are performed by a computer program when executed by one or more processors, the computer program being embedded in a non-transitory computer-readable storage medium.

17. A method of calculating a transient flow rate of a flowed process gas, wherein the process gas is flowed through a mass flow controller to a chamber of a known volume, comprising:
flowing process gas through the mass flow controller into the chamber;
measuring successive data sample points which include pressure data, temperature data, and a time value for each successive data sample point;
identifying groups of successive data sample points wherein each group shares one or more successive data sample points with another group;
calculating ratio values for each of the successive data sample points wherein each ratio value is a ratio between the pressure data and a product of temperature and gas compressibility data for each respective time value;
determining a line of best fit of the ratio values within at least one group;
calculating the transient flow rate of the flowed process gas using a pressure rate of rise technique wherein the pressure rate of rise technique utilizes a ratio value determined from the line of best fit for at least one time value within the at least one group; and
controlling flow of the process gas through the mass flow controller into the chamber based on the calculated transient flow rate.

18. The method of claim 17 , wherein the process gas flows through the mass flow controller at a predetermined set point, the method further comprising comparing the calculated transient flow rate against the predetermined set point and determining whether any transient gas flow anomalies are detected.

19. A method of calculating a transient flow rate of a process gas flowed through a mass flow controller to a chamber, comprising:
measuring successive data sample points which include pressure data, temperature data, and a time value for each successive data sample point;
identifying groups of successive data sample points;
calculating ratio values for each of the successive data sample points wherein each ratio value is a ratio between the pressure data and a product of temperature and gas compressibility data for each respective time value;
determining a line of best fit of the ratio values within at least one group;
calculating the transient flow rate of the flowed process gas using a pressure rate of rise technique wherein the pressure rate of rise technique utilizes a ratio value determined from the line of best fit for at least one time value within the at least one group; and
controlling flow of the process gas through the mass flow controller into the chamber based on the calculated transient flow rate.

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Assignees

• Lam Res Corp

Inventors

• Spyropoulos Evangelos
• Shareef Iqbal

Classifications

• B01J2219/00216

  Parameter value calculated by equations · CPC title

• G01F25/0038

  Physics · mapped topic

• G01F25/0092

  for metering by volume · CPC title

• G01F1/34 Primary

  by measuring pressure or differential pressure · CPC title

• G01F25/0007

  Physics · mapped topic