# US 2021/0242009 A1 · Laser sustained plasma light source with high pressure flow > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0242009 A1 - Document ID: US20210242009A1 - Status: Published application - Kind: A1 - Application number: 17/157,782 - Filed: 2021-01-25 - Published: 2021-08-05 - Earliest claimed: 2020-02-05 - Assignees: KLA Corporation - Applicants: KLA Corporation - Inventors: Anatoly Shchemelinin - Web page: https://patentgrep.com/patent/US20210242009A1 ## CPC - H01J 61/025: {Associated optical elements} - H01J 65/04: Lamps in which a gas filling is excited to luminesce by an external electromagnetic field or by external corpuscular radiation, e.g. for indicating {plasma display panels} - H01J 61/16: having helium, argon, neon, krypton, or xenon as the principle constituent - H01J 61/28: Means for producing, introducing, or replenishing gas or vapour during operation of the lamp - H01J 61/52: Cooling arrangements; Heating arrangements; Means for circulating gas or vapour within the discharge space {(heating or cooling arrangements to promote ionisation for starting H01J61/54)} - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A broadband radiation source is disclosed. The source may include a gas containment vessel configured to maintain a plasma and emit broadband radiation. The source may also include a recirculation gas loop fluidically coupled to the gas containment vessel. The recirculation gas loop may be configured to transport gas from one or more gas boosters configured to pressurize the low-pressure gas into a high-pressure gas and transport the high-pressure gas to the recirculation loop via an outlet. The system includes a pressurized gas reservoir fluidically coupled to the outlet of the one or more gas boosters and is configured to receive and store high pressure gas from the one or more gas boosters. The source includes a pressurized gas reservoir located between the one or more gas boosters and the gas containment vessel and is configured to receive and store high pressure gas from the one or more gas boosters. ## Claims ### Claim 1 A gas recirculation apparatus comprising: a gas containment vessel configured to receive laser radiation from a pump source to sustain a plasma within gas flowed through the gas containment vessel, wherein the gas containment vessel is configured to transport gas from an inlet of the gas containment vessel to an outlet of the gas containment vessel, wherein the gas containment vessel is further configured to transmit at least a portion of broadband radiation emitted by the plasma; a recirculation gas loop fluidically coupled to the gas containment vessel, wherein a first portion of the recirculation gas loop is fluidically coupled to the outlet of the gas containment vessel and is configured to receive heated gas or a plume from the plasma from the outlet of the gas containment vessel; one or more gas boosters, wherein the one or more gas boosters are fluidically coupled to the recirculation gas loop, wherein an inlet of the one or more gas boosters is configured to receive low pressure gas from the recirculation loop and wherein the one or more gas boosters are configured to pressurize the low-pressure gas into a high-pressure gas and transport the high-pressure gas to the recirculation loop via an outlet; and wherein a second portion of the recirculation gas loop is fluidically coupled to the inlet of the gas containment vessel and is configured to transport pressurized gas from the one or more gas boosters to the inlet of the gas containment vessel. ### Claim 2 (depends on 1) The apparatus of claim 1, further comprising: a pressurized gas reservoir located between the one or more gas boosters and the gas containment vessel, wherein the pressurized gas reservoir is fluidically coupled to the outlet of the one or more gas boosters and is configured to receive and store high pressure gas from the one or more gas boosters. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the gas pressure in the pressurized gas reservoir varies above a working temperature of the gas containment vessel. ### Claim 4 (depends on 2) The apparatus of claim 2, further comprising: a pressure regulator coupled to an outlet of the pressurized gas reservoir and configured to stabilize an output pressure of the pressurized gas reservoir and define a working pressure level of the gas containment vessel. ### Claim 5 (depends on 1) The apparatus of the claim 1, wherein the one or more gas boosters comprise one or more vessels. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein one or more walls of the one or more vessels is maintained at a temperature below a temperature of gas at an intake of the one or more gas boosters. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the one or more gas boosters include one or more temperature control elements configured to generate a temperature difference between the gas within the one or more gas boosters and one or more walls of the one or more vessels of the one or more gas boosters. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the one or more temperature control elements comprise one or more heating elements. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the one or more heating elements comprise: at least one of one or more metal wires, a metal grid, or a metal mash configured for heating via an electrical current. ### Claim 10 (depends on 8) The apparatus of claim 8, wherein the one or more heating elements comprise: a structure configured for heating via an external magnetic field. ### Claim 11 (depends on 8) The apparatus of claim 8, wherein the one or more heating elements comprise: a set of electrodes configured for heating via electric arc discharge. ### Claim 12 (depends on 8) The apparatus of claim 8, wherein the one or more heating elements comprise: an external optical device configured to focus light into the one or more gas boosters, wherein the external optical device comprises one or more lasers. ### Claim 13 (depends on 8) The apparatus of claim 8, wherein the one or more heating elements comprise: electromagnetic radiation source configured to transmit electromagnetic radiation into at least one of the first gas booster of the second gas booster, wherein the external optical device comprises one or more lasers. ### Claim 14 (depends on 7) The apparatus of claim 7, wherein the one or more temperature control elements comprise one or more cooling elements. ### Claim 15 (depends on 1) The apparatus of claim 1, wherein the one or more gas boosters include one or more agitators. ### Claim 16 (depends on 1) The apparatus of claim 1, wherein the one or more gas boosters comprises two or more gas boosters. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein the two or more gas boosters are connected in parallel, wherein the two or more gas boosters comprise a first gas booster and a second gas booster fluidically coupled in parallel to the recirculation gas loop and configured to receive gas from the gas containment vessel. ### Claim 18 (depends on 16) The apparatus of claim 16, wherein each of the first gas booster and the second gas booster include one or more temperature control elements. ### Claim 19 (depends on 18) The apparatus of claim 18, wherein each of the first gas booster and the second gas booster include one or more heating elements. ### Claim 20 (depends on 19) The apparatus of claim 19, wherein the first gas booster includes a first heating element and the second gas booster includes a second heating element, wherein the first heating element and the second heating element are configured for ON/OFF cycling to periodically vary the temperature and pressure of the pressurized gas from the first gas booster and the second gas booster. ### Claim 21 (depends on 19) The apparatus of claim 19, wherein at least one of the first heating element or the second heating element comprise: at least one of one or more metal wires, a metal grid, or a metal mash configured for heating via an electrical current. ### Claim 22 (depends on 19) The apparatus of claim 19, wherein at least one of the first heating element or the second heating element comprise: a structure configured for heating via an external magnetic field. ### Claim 23 (depends on 19) The apparatus of claim 19, wherein at least one of the first heating element or the second heating element comprise: a set of electrodes configured for heating via electric arc discharge. ### Claim 24 (depends on 19) The apparatus of claim 19, wherein at least one of the first heating element or the second heating element comprise: an external optical device configured to focus light into at least one of the first gas booster of the second gas booster, wherein the external optical device comprises one or more lasers. ### Claim 25 (depends on 19) The apparatus of claim 19, wherein at least one of the first heating element or the second heating element comprise: electromagnetic radiation source configured to transmit electromagnetic radiation into at least one of the first gas booster of the second gas booster, wherein the external optical device comprises one or more lasers. ### Claim 26 (depends on 18) The apparatus of claim 18, wherein the one or more temperature control elements comprise one or more cooling elements. ### Claim 27 (depends on 17) The apparatus of claim 17, wherein each of the first gas booster and the second gas booster include one or more agitators. ### Claim 28 (depends on 16) The apparatus of claim 16, wherein the two or more gas boosters are connected in series, wherein the two or more gas boosters comprise a first gas booster and a second gas booster fluidically coupled in series to the recirculation gas loop, wherein the first gas booster is configured to receive gas from the gas containment vessel and wherein the second gas booster is configured to receive heated gas from the first gas booster. ### Claim 29 (depends on 28) The apparatus of claim 28, wherein each of the first gas booster and the second gas booster comprise: an intake nozzle and an output nozzle, wherein the intake nozzle is at a lower temperature than the output nozzle. ### Claim 30 (depends on 28) The apparatus of claim 28, wherein each of the first gas booster and the second gas booster include one or more heating elements. ### Claim 31 (depends on 30) The apparatus of claim 30, wherein at least one of the first heating element or the second heating element comprise: at least one of one or more metal wires, a metal grid, or a metal mesh configured for heating via an electrical current. ### Claim 32 (depends on 30) The apparatus of claim 30, wherein at least one of the first heating element or the second heating element comprise: a structure configured for heating via an external magnetic field. ### Claim 33 (depends on 30) The apparatus of claim 30, wherein at least one of the first heating element or the second heating element comprise: a set of electrodes configured for heating via electric arc discharge. ### Claim 34 (depends on 30) The apparatus of claim 30, wherein at least one of the first heating element or the second heating element comprise: an external optical device configured to focus light into at least one of the first gas booster of the second gas booster, wherein the external optical device comprises one or more lasers. ### Claim 35 (depends on 30) The apparatus of claim 30, wherein at least one of the first heating element or the second heating element comprise: an electromagnetic radiation source configured to transmit electromagnetic radiation into at least one of the first gas booster of the second gas booster, wherein the electromagnetic radiation source comprises one or more lasers. ### Claim 36 (depends on 28) The apparatus of claim 28, wherein each of the first gas booster and the second gas booster include one or more agitators. ### Claim 37 (depends on 1) The apparatus of claim 1, wherein the one or more recirculation gas loops comprise one or more closed recirculation gas loops. ### Claim 38 (depends on 1) The apparatus of claim 1, wherein the gas containment vessel comprises: at least one of a plasma lamp, a plasma cell, or a plasma chamber. ### Claim 39 (depends on 1) The apparatus of claim 1, wherein the one or more recirculation gas loops is configured to flow at least one of argon, xenon, neon, nitrogen, krypton, or helium through the gas containment vessel. ### Claim 40 (depends on 39) The apparatus of claim 39, wherein the one or more recirculation gas loops is configured to flow a mixture of two or more gases. ### Claim 41 A broadband light source comprising: a pump source configured to generate laser radiation; a gas containment vessel configured to receive the laser radiation from the pump source to sustain a plasma within gas flowed through the gas containment vessel, wherein the gas containment vessel is configured to transport gas from an inlet of the gas containment vessel to an outlet of the gas containment vessel; a set of collection optics configured to receive broadband radiation emitted by the plasma sustained within the gas containment vessel; and a recirculation gas loop fluidically coupled to the gas containment vessel, wherein a first portion of the recirculation gas loop is fluidically coupled to the outlet of the gas containment vessel and is configured to receive heated gas or a plume from the plasma from the outlet of the gas containment vessel; one or more gas boosters, wherein the one or more gas boosters are fluidically coupled to the recirculation gas loop, wherein an inlet of the one or more gas boosters is configured to receive low pressure gas from the recirculation loop and wherein the one or more gas boosters are configured to pressurize the low-pressure gas into a high-pressure gas and transport the high-pressure gas to the recirculation loop via an outlet; and wherein a second portion of the recirculation gas loop is fluidically coupled to the inlet of the gas containment vessel and is configured to transport pressurized gas from the two or more gas boosters to the inlet of the gas containment vessel. ### Claim 42 (depends on 41) The broadband light source of claim 41, wherein the pump source comprises: at least one of a pulsed laser, a continuous wave (CW) laser, a pseudo-CW laser, or a modulated CW laser. ### Claim 43 An optical characterization system comprising: a broadband radiation source, wherein the broadband radiation source comprises: a pump source configured to generate laser radiation; a gas containment vessel configured to receive the laser radiation from the pump source to sustain a plasma within gas flowed through the gas containment vessel, wherein the gas containment vessel is configured to transport gas from an inlet of the gas containment vessel to an outlet of the gas containment vessel; a set of collection optics configured to receive broadband radiation emitted by the plasma sustained within the gas containment vessel; a recirculation gas loop fluidically coupled to the gas containment vessel, wherein a first portion of the recirculation gas loop is fluidically coupled to the outlet of the gas containment vessel and is configured to receive heated gas or a plume from the plasma from the outlet of the gas containment vessel; one or more gas boosters, wherein the one or more gas boosters are fluidically coupled to the recirculation gas loop, wherein an inlet of the one or more gas boosters is configured to receive low pressure gas from the recirculation loop and wherein the one or more gas boosters are configured to pressurize the low-pressure gas into a high-pressure gas and transport the high-pressure gas to the recirculation loop via an outlet; and wherein a second portion of the recirculation gas loop is fluidically coupled to the inlet of the gas containment vessel and is configured to transport pressurized gas from the one or more gas boosters to the inlet of the gas containment vessel; and a set of characterization optics configured to collect a portion of the broadband radiation from the set of collection optics of the broadband radiation source, and direct the broadband radiation onto a specimen, wherein the set of characterization optics is further configured to direct radiation from the sample to a detector assembly. ### Claim 44 (depends on 43) The system of claim 43, wherein the optical characterization system is configured as an inspection system. ### Claim 45 (depends on 43) The system of claim 43, wherein the optical characterization system is configured as a metrology system. ### Claim 46 A method comprising: directing laser radiation into a gas containment vessel in order to sustain a plasma within a gas flowing through the gas containment vessel, wherein the plasma emits broadband radiation; and recirculating the gas through the gas containment vessel via a recirculation gas loop, wherein the recirculating the gas through the gas containment vessel comprises: transporting gas from an outlet of the gas containment vessel to an inlet of one or more gas booster assemblies; pressurizing the gas within the one or more gas boosters; storing the pressurized gas from an outlet of the one or more gas boosters within a pressurized gas reservoir; and transporting pressurized gas at a selected working pressure from the pressurized gas reservoir to the gas containment vessel.