# US 8,785,879 B1 · Electron beam wafer inspection system and method of operation thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,785,879 B1 - Document ID: US8785879B1 - Status: Granted - Kind: B1 - Application number: 13/945,299 - Filed: 2013-07-18 - Granted: 2014-07-22 - Earliest claimed: 2013-05-06 - Assignees: ICT Integrated Circuit Testing Gesellschaft für Halbleiterprüftechnik mbH - Applicants: Jürgen Frosien - Inventors: Jürgen Frosien - Web page: https://patentgrep.com/patent/US8785879B1 ## CPC - H01J 37/145: Combinations of electrostatic and magnetic lenses - H01J 37/265: {Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination} - H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract An electron beam wafer imaging system is described. The system includes an emitter for emitting an electron beam; a power supply for applying a voltage between the emitter and the column housing of at least 20 kV; an objective lens for focusing the electron beam on a wafer, wherein the magnetic lens component and the electrostatic lens component substantially overlap each other, wherein the electrostatic lens component has a first electrode, a second electrode and a third electrode; and a control electrode positioned along an optical axis from the position of the third electrode to the position of a specimen stage, wherein the control electrode is configured for control of signal electrons; a controller to switch between a first operational mode and a second operational mode, wherein the controller is connected to a further power supply for switching between the first operational mode and the second operational mode. ## Claims ### Claim 1 An electron beam wafer imaging system, comprising: an emitter for emitting an electron beam, wherein the emitter is a cold field emitter, a thermally assisted field emitter, or a Schottky emitter; a power supply for applying a voltage between the emitter and the column housing of at least 20 kV; an objective lens for focusing the electron beam on a wafer, wherein the objective lens has a magnetic lens component and an electrostatic lens component, wherein the magnetic lens component and the electrostatic lens component substantially overlap each other, wherein the electrostatic lens component has a first electrode, a second electrode and a third electrode; and a control electrode positioned along an optical axis from the position of the third electrode to the position of a specimen stage, wherein the control electrode is configured for control of signal electrons; a controller to switch between a first operational mode and a second operational mode, wherein the controller is connected to a further power supply for switching between the first operational mode and the second operational mode, where said first operational mode corresponds to moderate landing energies and said second operational mode corresponds to low landing energies. ### Claim 2 (depends on 1) The electron beam wafer imaging system according to claim 1, wherein the further power supply is connected to the second electrode. ### Claim 3 (depends on 1) The electron beam wafer imaging system according to claim 1, wherein the first electrode is connected to ground. ### Claim 4 (depends on 2) The electron beam wafer imaging system according to claim 2, wherein the first electrode is connected to ground. ### Claim 5 (depends on 1) The electron beam wafer imaging system according to claim 1, wherein the further power supply is connected to the second electrode and is a bipolar power supply for providing voltages from −7 kV to +7 kV. ### Claim 6 (depends on 1) The electron beam wafer imaging system according to claim 1, wherein the first electrode is provided in form of a beam guiding tube for guiding the electron beam through at least 50% of the length of the system along the optical axis. ### Claim 7 (depends on 1) The electron beam wafer imaging system according to claim 1, further comprising an acceleration electrode for acceleration of the electron beam emitted from the emitter, wherein the acceleration electrode is connected to a power supply for providing a potential of −5 kV to +5 kV or wherein the acceleration electrode is connected to ground. ### Claim 8 (depends on 1) The electron beam wafer imaging system according to claim 1, wherein the second electrode is mounted in the system attached to an insulator, which is further attached to the first electrode. ### Claim 9 (depends on 1) The electron beam wafer imaging system according to claim 1, wherein the control electrode is mounted in the system attached to a further insulator, which is further attached to the third electrode. ### Claim 10 A multi-beam wafer imaging system, comprising a wafer imaging system comprising: an emitter for emitting an electron beam, wherein the emitter is a cold field emitter, a thermally assisted field emitter, or a Schottky emitter; a power supply for applying a voltage between the emitter and the column housing of at least 20 kV; an objective lens for focusing the electron beam on a wafer, wherein the objective lens has a magnetic lens component and an electrostatic lens component, wherein the magnetic lens component and the electrostatic lens component substantially overlap each other, wherein the electrostatic lens component has a first electrode, a second electrode and a third electrode; and a control electrode positioned along an optical axis from the position of the third electrode to the position of a specimen stage, wherein the control electrode is configured for control of signal electrons; a controller to switch between a first operational mode and a second operational mode, wherein the controller is connected to a further power supply for switching between the first operational mode and the second operational mode, where said first operational mode corresponds to moderate landing energies and said second operational mode corresponds to low landing energies; the multi-beam wafer imaging system further comprises: at least one further emitter for emitting an electron beam, wherein the at least one further emitter is a cold field emitter, a thermally assisted field emitter, or a Schottky emitter; wherein the objective lens comprises at least one further electrostatic lens component; wherein the at least one further electrostatic lens components has at least one further first electrode, at least one further second electrode and at least one further third electrode; and at least one further control electrode positioned along at least one further optical axis from the respective position of the respective third electrode to the position of a specimen stage, wherein the at least one further control electrode is configured for control of signal electrons. ### Claim 11 (depends on 10) The electron beam wafer imaging system according to claim 10, wherein the further power supply is connected to the second electrode. ### Claim 12 (depends on 10) The electron beam wafer imaging system according to claim 10, wherein the first electrode is connected to ground. ### Claim 13 (depends on 10) The electron beam wafer imaging system according to claim 10, wherein the further power supply is connected to the second electrode and is a bipolar power supply for providing voltages from −7 kV to +7 kV. ### Claim 14 A method of operating an electron beam wafer imaging system, comprising: emitting an electron beam having a brightness of 5×107 A/m2/sr/eV or above; guiding the electron beam through an electron beam column with an energy of 20 keV or above; focusing the electron beam on a wafer with a magnetic field and an electrostatic field, wherein the magnetic field and the electrostatic field substantially overlap each other, wherein the electrostatic field is provided by a first electrode, a second electrode and a third electrode, and wherein the electrostatic field is configured to be switched between a first operational mode and a second operational mode by varying the focal length of the electrostatic lens component, where said first operational mode corresponds to moderate landing energies and said second operational mode corresponds to low landing energies; and controlling the extraction field for signal electrons at the wafer with a control electrode. ### Claim 15 (depends on 14) The method according to claim 14, wherein the electron beam is emitted at a positive potential of the emitter with respect to ground of 20 kV or more, and wherein the electron beam is guided through an electron beam column at ground potential. ### Claim 16 (depends on 14) The method according to claim 14, wherein the second electrode providing the electrostatic field is at a potential of −7 kV to +7 kV as compared to the first electrode providing the electrostatic field for switching between the first operational mode and the second operational mode. ### Claim 17 (depends on 14) The method according to claim 14, wherein the third electrode providing the electrostatic field and/or the wafer is at a potential of +50 V to +2 kV as compared to the potential of the emitter tip. ### Claim 18 (depends on 17) The method according to claim 17, wherein the third electrode providing the electrostatic field and/or the wafer is at a potential of +50 V to +1 kV as compared to the potential of the emitter tip. ### Claim 19 (depends on 14) The method according to claim 14, wherein the control electrode is biased to a potential of +2 kV to −2 kV as compared to the potential of the specimen or wafer. ### Claim 20 (depends on 19) The method according to claim 19, wherein the control electrode is biased to a potential of +2 kV to −1 kV as compared to the potential of the specimen or wafer.