Apparatus with optical cavity for determining process rate

Abstract

A parameter measurement system is provided. A cavity ring down device is provided comprising a first cavity ring down mirror and a second cavity ring down mirror spaced apart from the first cavity ring down mirror. At least one laser light source is optically coupled to the first cavity ring down mirror. A light detector is optically coupled to either the first cavity ring down mirror or the second cavity ring down mirror. A controller is configured to use a sample received from the processing chamber and the light from the at least one laser light source and reflected between the first and second cavity ring down mirrors to measure one or more process parameters and adjust the process based on the one or more process parameters.

What is claimed is: 
     
         1 . A parameter measurement system in fluid connection with a processing chamber for controlling a process for processing a substrate, comprising:
 a cavity ring down device, comprising:
 a first cavity ring down mirror on a first side of the cavity ring down device; and 
 a second cavity ring down mirror on a second side of the cavity ring down device spaced apart from the first cavity ring down mirror; 
   at least one laser light source optically coupled to the first cavity ring down mirror;   a light detector optically coupled to either the first cavity ring down mirror or the second cavity ring down mirror; and   a controller configured to use a sample received from the processing chamber and the light from the at least one laser light source and reflected between the first and second cavity ring down mirrors to measure one or more process parameters and adjust the process based on the one or more process parameters.   
     
     
         2 . The parameter measurement system, as recited in  claim 1 , wherein the sample includes at least one of a gas byproduct from the process and plasma that is present when the process is carried out. 
     
     
         3 . The parameter measurement system, as recited in  claim 1 , further comprising one or more heaters for heating the first and second cavity ring down mirrors to a temperature of at least 120° C.; and wherein the first cavity ring down mirror and the second cavity ring down mirror are temperature compensated to operate at a temperature of at least 120° C. 
     
     
         4 . The parameter measurement system, as recited in  claim 1 , wherein the at least one laser light source provides a first light beam at a first frequency and a second light beam at a second frequency that is different from the first frequency. 
     
     
         5 . The parameter measurement system, as recited in  claim 1 , wherein the cavity ring down device is in fluid communication with the processing chamber by receiving a gas byproduct from the processing chamber via an exhaust pump. 
     
     
         6 . The parameter measurement system, as recited in  claim 5 , wherein the parameter measurement system uses a gas byproduct and light generated by the at least one laser light source and reflected between the first and second cavity ring down mirrors to measure one or more process parameters and adjust a process based on the one or more process parameters. 
     
     
         7 . The parameter measurement system, as recited in  claim 1 , wherein the cavity ring down device is in fluid communication with the processing chamber by receiving plasma from the processing chamber, the parameter measurement system further comprising a valve for controlling flow of the plasma between the processing chamber and the cavity ring down device. 
     
     
         8 . The parameter measurement system, as recited in  claim 1 , wherein the cavity ring down device is in fluid communication with the processing chamber in that a portion of an inner volume of the processing chamber is between the first cavity ring down mirror and the second cavity ring down mirror; and wherein the inner volume includes plasma that is present when the process is carried out. 
     
     
         9 . The parameter measurement system, as recited in  claim 8 , wherein the parameter measurement system uses a gas byproduct and light generated by the at least one laser light source and reflected between the first and second cavity ring down mirrors to measure one or more process parameters and adjust a process based on the one or more process parameters. 
     
     
         10 . The parameter measurement system, as recited in  claim 1 , wherein the first cavity ring down mirror is near confocal with the second cavity ring down mirror. 
     
     
         11 . The parameter measurement system, as recited in  claim 1 , wherein the first cavity ring down mirror and the second cavity ring down mirror each have a reflectivity to light from the at least one laser light source of at least 99.99% and transmission of light from the at least one laser light source of 0.01% to 0.001%. 
     
     
         12 . The parameter measurement system, as recited in  claim 1 , wherein the first cavity ring down mirror has a first surface on a first side of the first cavity ring down mirror and a second surface on a second side of the first cavity ring down mirror, wherein the second surface of the first cavity ring down mirror faces outside the cavity ring down device and the first surface of the first cavity ring down mirror faces inside the cavity ring down device, wherein the at least one laser light source is optically coupled to the second surface of the first cavity ring down mirror. 
     
     
         13 . The parameter measurement system, as recited in  claim 12 , wherein the second cavity ring down mirror has a first surface on a first side of the second cavity ring down mirror and a second surface on a second side of the second cavity ring down mirror, wherein the second surface of the second cavity ring down mirror faces outside the cavity ring down device and the first surface of the second cavity ring down mirror faces inside the cavity ring down device, wherein the light detector is optically coupled to the second surface of the first cavity ring down mirror or the second surface of the second cavity ring down mirror. 
     
     
         14 . The parameter measurement system, as recited in  claim 1 , wherein the parameter measurement system uses a gas byproduct and light generated by the at least one laser light source and reflected between the first and second cavity ring down mirrors to measure one or more process parameters and adjust the process based on the one or more process parameters. 
     
     
         15 . The parameter measurement system, as recited in  claim 1 , wherein the first cavity ring down mirror and the second cavity ring down mirror each have a reflectivity to light from the at least one laser light source of at least 99.9% and transmission of light from the at least one laser light source of 0.01% to 0.001%.