Contamination monitoring and control techniques for use with an optical metrology instrument
AssigneeMetroSol, Inc.
InventorsDale A. Harrison, Matthew Weldon
Life of this patent
Estimating the term…
Abstract
A technique is provided for generating and subsequently monitoring the controlled environment(s) within an optical metrology instrument in such a manner as to minimize absorbing species within the light path of the metrology instrument and to minimize the build-up of contaminants on the surfaces of optical elements that may result in performance degradation. Both evacuation and backfill techniques may be utilized together along with a monitoring technique to determine if the environmental is suitable for measurements or if the environment should be regenerated. The optical metrology instrument may be an instrument which operates at wavelengths that include vacuum ultra-violet (VUV) wavelengths.
Claims67
A method of controlling an atmosphere in an optical metrology tool comprising:
- providing at least a first environmentally controlled chamber and a second environmentally controlled chamber, the first and second environmentally controlled chambers configured for passage of a light beam having wavelengths below DUV wavelengths;
- lowering the concentration of an optical absorbing species in at least one of the first and second environmentally controlled chambers by utilizing vacuum evacuation techniques, the at least one of the first and second environmentally controlled chambers being a controlled atmosphere chamber;
- backfilling, with a non-absorbing gas, the controlled atmosphere chamber so as to improve optical performance by increasing a pressure within the controlled atmosphere chamber above a vacuum evacuation pressure level;
- and
- transmitting the light beam having wavelengths below DUV wavelengths while the controlled atmosphere chamber is in the backfilled state.
A method of controlling an atmosphere in an optical metrology tool comprising:
- providing at least an environmentally controlled sample chamber and an environmentally controlled optics chamber, the sample chamber and optics chamber each being configured for passage of a light beam having wavelengths below DUV wavelengths;
- decreasing from an ambient state the concentration of moisture or oxygen in at least one of the sample chamber and the optics chamber by utilizing vacuum evacuation techniques, the at least one of the sample chamber and the optics chamber in which the decreasing occurs being a controlled atmosphere chamber;
- backfilling, with a VUV non-absorbing gas, the controlled atmosphere chamber so as to decrease contaminant migration by increasing a pressure within the controlled atmosphere chamber above a vacuum evacuation pressure level;
- and
- transmitting the light beam having wavelengths below DUV wavelengths while the controlled atmosphere chamber is in the backfilled state.
A method of controlling an atmosphere in an optical metrology tool comprising:
- providing at least an environmentally controlled sample chamber and an environmentally controlled optics chamber, the sample chamber and optics chamber each being configured for passage of a light beam having wavelengths below DUV wavelengths;
- providing a sample beam optical path and a reference beam optical path, the optical path lengths of the sample beam optical path and the reference beam optical patch being matched;
- decreasing from an ambient state the concentration of moisture or oxygen in at least one of the sample chamber and the optics chamber by utilizing vacuum evacuation techniques, the at least one of the sample chamber and the optics chamber in which the decreasing occurs being a controlled atmosphere chamber;
- backfilling, with a VUV non-absorbing gas, the controlled atmosphere chamber so as to improve the optical performance by increasing a pressure within the controlled atmosphere chamber above a vacuum evacuation pressure level;
- and
- transmitting the light beam having wavelengths below DUV wavelengths while the controlled atmosphere chamber is in the backfilled state.
A method of determining an environmental contamination state in an optical metrology tool comprising:
- obtaining a first intensity measurement from a reference sample at a first time;
- obtaining a second intensity measurement from the reference sample at a second time;
- analyzing the first and second intensity measurements;
- determining from the analyzing of the first and second intensity measurements if the environmental contamination state of the optical metrology tool is suitable for further use based upon variations between the first intensity and the second intensity;
- and
- adjusting the environment of the optical metrology tool if the environmental contamination state of the optical metrology tool is determined to be unsuitable for further use.
A method of determining an environmental contamination state in an optical metrology tool comprising:
- obtaining a first intensity measurement from a reference sample at a first time;
- obtaining a second intensity measurement from the reference sample at a second time;
- analyzing the first and second intensity measurements;
- and
- determining from the analyzing of the first and second intensity measurements if the environmental contamination state of the optical metrology tool is suitable for further use based upon variations between the first intensity and the second intensity;
- wherein the variations between the first intensity measurement and the second intensity measurement are analyzed by calculating a ratio of the first and second intensity measurements;
- and
- wherein measured concentrations of the absorbing species are determined at the first time and the second time.
A method of determining an environmental contamination state in an optical metrology tool that operates at wavelengths that at least include wavelengths below DUV wavelengths, the method comprising:
- obtaining a first intensity spectrum measurement from a reference sample at a first time, the first intensity spectrum measurement comprising at least a plurality of wavelengths below DUV wavelengths;
- obtaining a second intensity measurement from the reference sample at a second time, the first intensity spectrum measurement comprising at least a plurality of wavelengths below DUV wavelengths;
- analyzing the first and second intensity measurements;
- determining from the analyzing of the first and second intensity measurements if the environmental contamination state of the optical metrology tool is suitable for further use based upon variations between the first intensity and the second intensity.
Dependencies are inferred from the claim text.