# US 2020/0403370 A1 · Controlling pressure in a cavity of a light source > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2020/0403370 A1 - Document ID: US20200403370A1 - Status: Published application - Kind: A1 - Application number: 16/719,868 - Filed: 2019-12-18 - Published: 2020-12-24 - Earliest claimed: 2019-06-18 - Assignees: KLA Corporation - Applicants: KLA Corporation - Inventors: Igor Germanenko - Web page: https://patentgrep.com/patent/US20200403370A1 ## CPC - H01S 3/027: {comprising a special atmosphere inside the housing} - H01S 3/036: Means for obtaining or maintaining the desired gas pressure within the tube, e.g. by gettering, replenishing; Means for circulating the gas, e.g. for equalising the pressure within the tube {(H01S3/031 takes precedence)} - G01L 15/00: Devices or apparatus for measuring two or more fluid pressure values simultaneously - G01L 19/0007: {Fluidic connecting means} - G02F 1/3501: {Constructional details or arrangements of non-linear optical devices, e.g. shape of non-linear crystals} - H01S 3/109: Frequency multiplication, e.g. harmonic generation - H10P 72/0616: {Monitoring of warpages, curvatures, damages, defects or the like} - G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - H01S 3/02: Constructional details {(housings or packages of fibre lasers H01S3/06704)} - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL - G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G) - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) ## Abstract Methods and systems for controlling pressure in a cavity of a light source are provided. One system includes a barometric pressure sensor configured for measuring pressure in a cavity of a light source. The system also includes one or more gas flow elements configured for controlling an amount of one or more gases in the cavity. In addition, the system includes a control subsystem configured for comparing the measured pressure to a predetermined range of values for the pressure and, when the measured pressure is outside of the predetermined range, altering a parameter of at least one of the one or more gas flow elements based on results of the comparing. ## Claims ### Claim 1 A system configured to control pressure in a cavity of a light source, comprising: a barometric pressure sensor configured for measuring pressure in a cavity of a light source; one or more gas flow elements configured for controlling an amount of one or more gases in the cavity; and a control subsystem configured for comparing the measured pressure to a predetermined range of values for the pressure and, when the measured pressure is outside of the predetermined range, altering a parameter of at least one of the one or more gas flow elements based on results of said comparing. ### Claim 2 (depends on 1) The system of claim 1, further comprising an illumination subsystem configured for directing light generated by the light source to a specimen, a detection subsystem configured for detecting light from the specimen, and a computer subsystem configured for detecting defects on the specimen based on output responsive to the detected light generated by the detection subsystem. ### Claim 3 (depends on 2) The system of claim 2, wherein the specimen is a wafer. ### Claim 4 (depends on 1) The system of claim 1, wherein the light source is a laser configured to generate single wavelength light. ### Claim 5 (depends on 1) The system of claim 1, wherein the light source is a laser configured to generate narrowband light. ### Claim 6 (depends on 1) The system of claim 1, wherein the cavity is a harmonic generation cavity of the light source. ### Claim 7 (depends on 1) The system of claim 1, wherein the cavity is an infrared cavity of the light source. ### Claim 8 (depends on 1) The system of claim 1, wherein the cavity is a main cavity of the light source. ### Claim 9 (depends on 1) The system of claim 1, wherein the one or more gas flow elements comprise: a first gas flow conduit coupled to the cavity and a clean dry air source; and a second gas flow conduit coupled to the cavity and an exhaust, and wherein the first and second gas flow conduits, the clean dry air source, and the exhaust are configured to cause a positive pressure in the cavity. ### Claim 10 (depends on 9) The system of claim 9, wherein the one or more gas flow elements further comprise a purge conduit coupled to the cavity and a proportional valve coupled to the purge conduit, and wherein the parameter altered by the control subsystem is a parameter of the proportional valve. ### Claim 11 (depends on 10) The system of claim 10, wherein the barometric pressure sensor is located in a position external to the cavity and the light source and is coupled to the purge conduit. ### Claim 12 (depends on 10) The system of claim 10, wherein the barometric pressure sensor, at least one of the one or more gas flow elements, and the control subsystem are included in a back pressure regulator coupled to the purge conduit, and wherein the parameter altered by the control subsystem is a parameter of the back pressure regulator. ### Claim 13 (depends on 9) The system of claim 9, wherein the one or more gas flow elements further comprise a purge conduit coupled to the cavity and a back pressure regulator coupled to the purge conduit, and wherein the parameter altered by the control subsystem is a parameter of the back pressure regulator. ### Claim 14 (depends on 1) The system of claim 1, further comprising an additional barometric pressure sensor configured for measuring pressure in an additional cavity of the light source and one or more additional gas flow elements configured for controlling an amount of one or more gases in the additional cavity, wherein the control subsystem is further configured for comparing the measured pressure in the additional cavity to a predetermined range of values for the pressure in the additional cavity, and when the measured pressure in the additional cavity is outside of the predetermined range of values for the pressure in the additional cavity, altering a parameter of at least one of the one or more additional gas flow elements based on results of comparing the measured pressure in the additional cavity. ### Claim 15 (depends on 14) The system of claim 14, wherein the cavity is a harmonic generation cavity of the light source, and wherein the additional cavity is a main cavity of the light source. ### Claim 16 (depends on 1) The system of claim 1, wherein the control subsystem is further configured for altering the parameter using a proportional-integral-derivative control loop. ### Claim 17 (depends on 1) The system of claim 1, wherein the barometric pressure sensor is located inside the cavity of the light source. ### Claim 18 (depends on 1) The system of claim 1, wherein the barometric pressure sensor and at least one of the one or more gas flow elements are located inside the cavity of the light source. ### Claim 19 (depends on 18) The system of claim 18, wherein the control subsystem comprises firmware configured for controlling operation of a servo loop. ### Claim 20 A non-transitory computer-readable medium, storing program instructions executable on a computer system for performing a computer-implemented method for controlling pressure in a cavity of a light source, wherein the computer-implemented method comprises: measuring pressure in a cavity of a light source; controlling an amount of one or more gases in the cavity with one or more gas flow elements; comparing the measured pressure to a predetermined range of values for the pressure; and when the measured pressure is outside of the predetermined range, altering a parameter of at least one of the one or more gas flow elements based on results of the comparing. ### Claim 21 A computer-implemented method for controlling pressure in a cavity of a light source, comprising: measuring pressure in a cavity of a light source; controlling an amount of one or more gases in the cavity with one or more gas flow elements; comparing the measured pressure to a predetermined range of values for the pressure; and when the measured pressure is outside of the predetermined range, altering a parameter of at least one of the one or more gas flow elements based on results of the comparing.