Method for rapidly determining an impurity level in a gas source or a gas distribution system

• US 5,714,678 A
• Filed: 11/26/1996
• Issued: 02/03/1998
• Est. Priority Date: 11/26/1996
• Status: Expired due to Fees

• Current Assignee: American Air Liquide Incorporated (L'Air Liquide SA)
• Original Assignee: American Air Liquide Incorporated (L'Air Liquide SA)
• Inventors: Jurcik, Benjamin, Znamensky, Dmitry, McAndrew, James
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Politzer, Jay L.
• Application Number:
  US08/757,752
• Time in Patent Office: 434 Days
• Field of Search: 73/31.03, 73/23.2, 73/863.83, 73/864.81
• US Class Current: 73/31.03
• CPC Class Codes: G01N 33/0004 Gaseous mixtures, e.g. polluted air

Abstract

Provided is a novel method for rapidly determining an impurity level in a gas source. A gas source and a measurement tool are provided for measuring an impurity level in a gas flowing from the gas source. The measurement tool is in communication with the gas source through a sampling line. The sampling line has a gas inlet disposed upstream from a gas outlet. The sampling line is baked according to a baking strategy, such that when baking is terminated, a concentration profile of the impurity in the sampling line contains a first region and a second region. In the first region, extending from the gas inlet to a point downstream from the inlet, the vapor phase concentration of the impurity is less than the vapor phase concentration of the impurity in the gas entering the sampling line. In the second region, located downstream from the first region and extending to the gas outlet, the vapor phase concentration of the impurity is greater than the vapor phase concentration of the impurity in the gas entering the sampling line. A method for rapidly determining an impurity level in a gas distribution system which delivers gas to a point of use is also provided. Particular applicability is found in the semiconductor processing industry to measure impurities in gases delivered to processing tools.

Claims

1. A method for rapidly determining an impurity level in a gas source, comprising:

(a) providing a gas source;

(b) providing a measurement tool for measuring an impurity level in a gas flowing from the gas source, wherein the measurement tool is in communication with the gas source through a sampling line, the sampling line having a gas inlet disposed upstream from a gas outlet; and

(c) baking the sampling line according to a baking strategy, such that when the baking is terminated, a concentration profile of the impurity in the sampling line contains a first region extending from the gas inlet to a point downstream from the inlet, in which the vapor phase concentration of the impurity is less than the vapor phase concentration of the impurity in the gas entering the sampling line, and a second region downstream from the first region extending to the gas outlet in which the vapor phase concentration of the impurity is greater than the vapor phase concentration of the impurity in the gas entering the sampling line.

2. The method for rapidly determining an impurity level according to claim 1, wherein a simulation program is employed to determine the baking strategy.

3. The method for rapidly determining an impurity level according to claim 1, wherein the measurement tool is an atmospheric pressure ionization mass spectrometer.

4. The method for rapidly determining an impurity level according to claim 1, wherein the impurity is water vapor.

5. The method for rapidly determining an impurity level according to claim 1, wherein the gas is nitrogen, helium, argon, or oxygen.

6. The method for rapidly determining an impurity level according to claim 1, wherein the impurity level is measured until the measured impurity level becomes stabilized.

7. A method for rapidly determining an impurity level in a gas distribution system, comprising:

(a) providing a gas distribution system for delivering a gas to a point of use, the gas distribution system being connected to a gas source;

(b) providing a measurement tool for measuring an impurity level in a gas flowing through the gas distribution system, wherein the measurement tool is in communication with the gas distribution system through a sampling line, the sampling line having a gas inlet disposed upstream from a gas outlet; and

(c) baking the sampling line according to a baking strategy, such that when the baking is terminated, a concentration profile of the impurity in the sampling line contains a first region extending from the gas inlet to a point downstream from the inlet, in which the vapor phase concentration of the impurity is less than the vapor phase concentration of the impurity in the gas entering the sampling line, and a second region downstream from the first region extending to the gas outlet in which the vapor phase concentration of the impurity is greater than the vapor phase concentration of the impurity in the gas entering the sampling line.

8. The method for rapidly determining an impurity level according to claim 7, wherein a simulation program is employed to determine the baking temperature.

9. The method for rapidly determining an impurity level according to claim 7, wherein the measurement tool is an atmospheric pressure ionization mass spectrometer.

10. The method for rapidly determining an impurity level according to claim 7, wherein the impurity is water vapor.

11. The method for rapidly determining an impurity level according to claim 7, wherein the point of use of the gas is a semiconductor processing tool.

12. The method for rapidly determining an impurity level according to claim 7, wherein the impurity level measurement is performed at a plurality of points along the gas distribution system.

13. The method for rapidly determining an impurity level according to claim 7, wherein the gas is nitrogen, helium, argon, or oxygen.

14. The method for rapidly determining an impurity level according to claim 7, wherein the impurity level is measured until the measured impurity level becomes stabilized.