# US 9,437,341 B2 · Method and apparatus for generating high current negative hydrogen ion beam > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,437,341 B2 - Document ID: US9437341B2 - Status: Granted - Kind: B2 - Application number: 13/800,979 - Filed: 2013-03-13 - Published: 2013-10-03 - Granted: 2016-09-06 - Earliest claimed: 2012-03-30 - Assignees: Varian Semiconductor Equipment Associates, Inc. - Applicants: Varian Semiconductor Equipment Associates, Inc. - Inventors: Shengwu Chang - Web page: https://patentgrep.com/patent/US9437341B2 ## CPC - G21K 5/00: Irradiation devices (discharge tubes for irradiating H01J37/00) - H01J 27/028: {Negative ion sources} - H01J 37/08: Ion sources; Ion guns - H01J 37/302: Controlling tubes by external information, e.g. program control (H01J37/304 takes precedence) - H01J 37/3171: {for ion implantation} - G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract An apparatus to generate negative hydrogen ions includes an ion source operative to generate positive hydrogen ions, a first component to adjust positive molecular hydrogen ion species in the ion source, a second component to adjust extraction voltage for extraction of the positive molecular hydrogen ions from the ion source, and a charge exchange cell comprising charge exchange species to convert the extracted positive molecular hydrogen ions to negative hydrogen ions. The adjusted extraction voltage is effective to generate an ion energy to maximize negative ion current yield in the charge exchange cell based upon a product of extraction efficiency of the positive molecular hydrogen ions and a peak in charge exchange efficiency for converting a species of the positive molecular hydrogen ions to negative hydrogen ions through charge exchange between the extracted hydrogen ions and charge exchange species. ## Claims ### Claim 1 An apparatus to generate negative hydrogen ions, comprising: an ion source operative to generate positive molecular hydrogen ions; a first component operative to adjust positive molecular hydrogen ion species in the ion source; a charge exchange cell comprising charge exchange species to convert the extracted positive molecular hydrogen ions to negative hydrogen ions, and an extraction voltage tuner component comprising logic operative to set an adjusted extraction voltage for extraction of the positive molecular hydrogen ions from the ion source, wherein the adjusted extraction voltage lies in a first range between a peak voltage and 30% higher than the peak voltage, the peak voltage corresponding to a peak in charge exchange efficiency for converting H3+ ions to negative hydrogen ions through charge exchange between the molecular hydrogen ions and the charge exchange species when a fraction of H3+ ions to total positive hydrogen ions is above a given threshold; the adjusted extraction voltage effective to generate an ion energy to maximize negative ion current yield in the charge exchange cell based upon a product of extraction efficiency of the positive molecular hydrogen ions and a peak in charge exchange efficiency for converting a species of the positive molecular hydrogen ions to negative hydrogen ions through charge exchange between the extracted hydrogen ions and charge exchange species. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the first component operative to generate a plasma comprising H3+ ions in the ion source. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the first component operative to adjust gas flow to the ion source to increase H3+ concentration. ### Claim 4 (depends on 2) The apparatus of claim 2, wherein the first component operative to adjust source power to the ion source to increase H3+ ion concentration. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the charge exchange species comprising magnesium, and the extraction voltage ranging from 20 to 40 kV. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the charge exchange species comprising cesium, NH3, Xe or H2O. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the second component operative to adjust extraction voltage based upon a fraction of the positive hydrogen ions that are H3+ ions. ### Claim 8 A method for providing a negative hydrogen ion beam, comprising: generating positive molecular hydrogen ions in an ion source; providing a charge exchange species in a charge exchange cell, the charge exchange species operative to transform the positive hydrogen ions into negative hydrogen ions; and extracting the positive hydrogen molecular ions at an extraction voltage effective to maximize negative ion current yield in the charge exchange cell based upon a product of extraction efficiency of the positive molecular hydrogen ions and charge exchange efficiency for converting a species of the positive molecular hydrogen ions to negative hydrogen ions through charge exchange between the extracted hydrogen ions and charge exchange species, wherein the extraction voltage lies in a first range between a peak voltage and 30% higher than the peak voltage, the peak voltage corresponding to a peak in charge exchange efficiency for converting H3+ ions to negative hydrogen ions through charge exchange between the molecular hydrogen ions and the charge exchange species when a fraction of H3+ ions to total positive hydrogen ions is above a given threshold. ### Claim 9 (depends on 8) The method of claim 8, further comprising: determining the peak voltage; and setting the extraction voltage at a voltage approximately equal to the peak voltage. ### Claim 10 (depends on 8) The method of claim 8, further comprising generating a plasma comprising H3+ ions in the ion source. ### Claim 11 (depends on 8) The method of claim 8, comprising adjusting gas flow to the ion source to increase H3+ concentration. ### Claim 12 (depends on 8) The method of claim 8, comprising adjusting source power to the ion source to increase H3+ ion concentration. ### Claim 13 (depends on 8) The method of claim 8, comprising adjusting a magnetic field or electric field applied to the ion source to increase H3+ ion concentration. ### Claim 14 (depends on 8) The method of claim 8, comprising: providing magnesium as the charge exchange species; and setting the extraction voltage between 20 kV to 40 kV. ### Claim 15 (depends on 8) The method of claim 8, comprising providing cesium, NH3, Xe, or H2O as the charge exchange species. ### Claim 16 (depends on 8) The method of claim 8, further comprising: determining a fraction of H3+ ions in the positive hydrogen ions of the ion source; and adjusting the extraction voltage based upon the determined fraction of H3+ ions. ### Claim 17 (depends on 16) The method of claim 16, comprising setting the extraction voltage to about 15-20 kV when the fraction of H2+ ions of total positive hydrogen ions in the ion source is above a threshold. ### Claim 18 An ion implantation system to generate a proton beam, comprising: an ion source operative to generate a plasma and extract ions from the plasma as positive molecular hydrogen ions; a charge exchange cell operative to receive the positive molecular hydrogen ions and convert the extracted positive molecular hydrogen ions to negative hydrogen ions using a charge exchange species; an extraction voltage tuner component comprising logic operative to set an adjusted extraction voltage for extraction of the positive molecular hydrogen ions from the ion source, wherein the adjusted extraction voltage lies in a first range between a peak voltage and 30% higher than the peak voltage, the peak voltage corresponding to a peak in charge exchange efficiency for converting H3+ ions to negative hydrogen ions through charge exchange between the molecular hydrogen ions and the charge exchange species when a fraction of H3+ ions to total positive hydrogen ions is above a given threshold; and a tandem accelerator to convert the negative hydrogen ions into a beam of protons. ### Claim 19 (depends on 18) The ion implantation system of claim 18 wherein the adjusted extraction voltage lies in a second range between a second peak voltage and 30% higher than the second peak voltage, the second peak voltage corresponding to a peak in charge exchange efficiency for converting H2+ ions to negative hydrogen ions through charge exchange between the molecular hydrogen ions and charge exchange species when the fraction of H3+ ions to total positive hydrogen ions is below the given threshold. ### Claim 20 (depends on 18) The ion implantation system of claim 18, further comprising a hydrogen ion species tuner component is operative to adjust gas flow and/or to plasma energy and/or magnetic field and/or electric field in the ion source to increase H3+ concentration. ### Claim 21 (depends on 18) The ion implantation system claim 18, wherein the extraction voltage tuner component is operative to adjust magnetic field and/or electric field applied to the ion source to increase H3+ concentration. ### Claim 22 (depends on 18) The ion implantation system of claim 18, wherein the charge exchange species comprising magnesium, cesium, NH3, Xe or H2O. ### Claim 23 (depends on 19) The ion implantation system of claim 19, wherein the threshold corresponds to 50% fraction of H2+ ions to total positive hydrogen ions. ### Claim 24 (depends on 18) The ion implantation system of claim 18, wherein the charge exchange species comprises Mg, and wherein the voltage range is between 25 kV and 30 kV. ### Claim 25 (depends on 19) The ion implantation system of claim 19, wherein the charge exchange species comprises Mg, and wherein the second voltage range is between 15 kV and 20 kV. ### Claim 26 (depends on 18) The ion implantation system of claim 18, the logic to set the adjusted extraction voltage based upon a pressure of the ion source.