# US 2008/0185509 A1 · Particle-optical apparatus for simultaneous observing a sample with particles and photons > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0185509 A1 - Document ID: US20080185509A1 - Status: Published application - Kind: A1 - Application number: 12/027,245 - Filed: 2008-02-06 - Published: 2008-08-07 - Earliest claimed: 2007-02-06 - Assignees: FEI Company - Inventors: William Ralph Knowles - Web page: https://patentgrep.com/patent/US20080185509A1 ## CPC - H01J 37/228: {whereby illumination or light collection take place in the same area of the discharge} - H01J 37/244: Detectors; Associated components or circuits therefor - H01J 37/256: using scanning beams - H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} - H01J 2237/188: Differential pressure - H01J 2237/2608: with environmental specimen chamber - H01J 2237/2808: Cathodoluminescence - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) ## Abstract A particle-optical apparatus, such as an ESEM®, for simultaneous observing a sample with particles and photons. A pressure limiting aperture (PLA) is placed in a diaphragm between the objective lens of the ESEM® and the sample position. The distance between the sample position and the aperture is sufficiently small to allow a large collection angle of the photons through this aperture. A mirror is placed between the diaphragm and the objective lens. Due to the large collection angle for photons a large NA is achieved. The small distance between sample position and aperture also result in less scattering of electrons than occurs in ESEM's where a mirror is placed between aperture and sample position, as the electrons have to travel through only a limited length in a high pressure area. Embodiments describe combinations where e.g. an immersion lens is used. ## Claims ### Claim 1 Particle-optical apparatus comprising: a vacuum chamber, a particle-optical column mounted on the vacuum chamber for producing a particle beam round a particle-optical axis, said particle-optical column comprising a particle source, a sample carrier located in the vacuum chamber for carrying a sample at a sample position, said sample position located on the particle-optical axis, a mirror for collecting light emitted from the sample position or focussing light on the sample position, said mirror showing a through-hole round the particle-optical axis, and evacuation means for evacuating the apparatus, characterized in that a diaphragm is placed between the sample position and the mirror, said diaphragm dividing a first volume within the vacuum chamber in which the sample position is located from a second volume, said diaphragm showing an aperture round the particle-optical axis for passing particles produced by the particle-optical column and for passing light between the mirror and the sample position, the aperture limiting the gas flow from the first volume to the second volume to such a value, that, when the pressure at the sample position is the equilibrium pressure of a fluid with an equilibrium pressure above 1 mbar, the evacuation means can evacuate the second vacuum to a pressure sufficiently low to cause negligible scattering of the particle beam in the second volume when compared to the scattering in the first volume, the distance between the aperture and the sample position can be adjusted to be, or is fixed at, less than four times the diameter of the aperture, and the mirror is located between the diaphragm and the particle source. ### Claim 2 (depends on 1) The particle optical apparatus according to claim 1 in which the distance between the aperture and the sample position can be adjusted to be, or is fixed at, less than twice the diameter of the aperture. ### Claim 3 (depends on 1) The particle optical apparatus according to claim 1 in which the diameter of the aperture is less than 1 mm. ### Claim 4 (depends on 1) The particle optical apparatus according to claim 1 in which the diameter of the aperture is less than 300 μm. ### Claim 5 (depends on 1) The particle optical apparatus according to claim 1 in which the evacuation means can evacuate the second volume to a pressure sufficiently low to cause negligible scattering of the particle beam compared to the scattering occurring in the first vacuum when the pressure in the first volume is above approximately 6 mbar. ### Claim 6 (depends on 1) The particle optical apparatus according to claim 1 further comprising a charged particle detector, said detector located in the second volume. ### Claim 7 (depends on 1) The particle optical apparatus according to claim 1 further comprising a charged particle detector, said detector located in the first volume. ### Claim 8 (depends on 1) The particle optical apparatus according to claim 1 further comprising a charged particle detector, in which the diaphragm is part of said charged particle detector. ### Claim 9 (depends on 1) The particle optical apparatus according to claim 1 further comprising a photon detector for detecting light emanating from the sample position. ### Claim 10 (depends on 9) The particle optical apparatus according to claim 9 further comprising a light block placed on the light-optical path between the photon detector and the mirror, said light block showing a hole for passing light, the mirror imaging the sample position on the hole, as a result of which light emanating from other places than the sample position does not significantly contribute to the amount of light detected by the photon detector ### Claim 11 (depends on 1) The particle optical apparatus according to claim 1 in which the apparatus is equipped with a gas injector, said gas injector admitting gas or vapour to the first volume. ### Claim 12 (depends on 1) The particle optical apparatus according to claim 1 in which the diaphragm shows a protrusion in the form of a truncated cone pointing to the sample position, and where the aperture is formed in the end of the cone closest to the sample position. ### Claim 13 (depends on 1) The particle optical apparatus according to claim 1 in which the light is formed by photons from the group of infra-red, visible light, ultra-violet and X-ray photons. ### Claim 14 (depends on 1) The particle optical apparatus according to claim 1 claims in which a pole piece of a particle-optical lens is situated between the sample position and the mirror. ### Claim 15 (depends on 14) The particle optical apparatus according to claim 14 in which the pole piece is the diaphragm. ### Claim 16 (depends on 1) The particle optical apparatus according to claim 1 in which the mirror is located between the particle-optical column and the aperture. ### Claim 17 (depends on 1) A Kit for upgrading an existing microscope to a microscope according to claim 1. ### Claim 18 (depends on 1) A method of operating a particle-optical apparatus, the method comprising: providing an apparatus according to claim 1, mounting a sample at the sample position, evacuating the first volume to a pressure between 1-50 mbar, evacuating the second volume to a pressure below 0.1 mbar adjusting the distance between the sample and the aperture to a distance less than twice the diameter of the aperture, passing a beam of particles through the aperture, and passing a beam of photons through the aperture. ### Claim 19 (depends on 18) The method according to claim 18 in which the beam of photons emanates from the sample. ### Claim 20 (depends on 18) The method according to claim 18 in which the beam of photons is focused on the sample. ### Claim 21 (depends on 18) The method according to claim 18 in which the first volume is evacuated to a pressure between approximately 1 mbar and approximately 20 mbar. ### Claim 22 (depends on 18) The method according to claim 18 in which the first volume is evacuated to a pressure between approximately 6 and approximately 10 mbar. ### Claim 23 A particle-optical apparatus comprising: a vacuum chamber; a particle-optical column mounted on the vacuum chamber for producing a particle beam round a particle-optical axis, said particle-optical column comprising a particle source; a sample carrier located in the vacuum chamber for carrying a sample at a sample position, said sample position located on the particle-optical axis; a mirror located between the particle source and the sample position, the mirror for collecting light emitted from the sample position or focussing light on the sample position, and said mirror showing a through-hole around the particle-optical axis; a pump for evacuating the apparatus; diaphragm located between the sample position and the mirror, said diaphragm dividing a first volume within the vacuum chamber in which the sample position is located from a second volume, said diaphragm having an aperture for passing particles produced by the particle-optical column and for passing light between the mirror and the sample position, the distance between the aperture and the sample position fixed at, or capable of being adjusted to be, less than four times the diameter of the aperture; the aperture positioned so that said particle-optical axis passes through the aperture, and the aperture further limiting the gas flow from the first volume to the second volume to such a degree, that, when the pressure at the sample position is at the equilibrium pressure of a fluid with an equilibrium pressure above 1 mbar, the pump can evacuate the second vacuum to a pressure sufficiently low to cause negligible scattering of a particle beam passing through the second volume when compared to the scattering of a particle beam passing through the first volume. ### Claim 24 (depends on 23) The apparatus of claim 23 in which the distance between the aperture and the sample position fixed at, or capable of being adjusted to be, less than two times the diameter of the aperture. ### Claim 25 A method of operating a particle-optical apparatus, the method comprising: (a) providing a particle-optical apparatus comprising: (i) a vacuum chamber; (ii) a particle-optical column mounted on the vacuum chamber for producing a particle beam round a particle-optical axis, said particle-optical column comprising a particle source; (iii) a sample carrier located in the vacuum chamber for carrying a sample at a sample position, said sample position located on the particle-optical axis; (iv) a mirror located between the particle source and the sample position, the mirror for collecting light emitted from the sample position or focussing light on the sample position, and said mirror showing a through-hole around the particle-optical axis; (v) a pump for evacuating the apparatus; (vi) diaphragm located between the sample position and the mirror, said diaphragm dividing a first volume within the vacuum chamber in which the sample position is located from a second volume, said diaphragm having an aperture for passing particles produced by the particle-optical column and for passing light between the mirror and the sample position, the distance between the aperture and the sample position fixed at, or capable of being adjusted to be, less than four times the diameter of the aperture; and (vii) the aperture positioned so that said particle-optical axis passes through the aperture, and the aperture further limiting the gas flow from the first volume to the second volume to such a degree, that, when the pressure at the sample position is at the equilibrium pressure of a fluid with an equilibrium pressure above 1 mbar, the pump can evacuate the second vacuum to a pressure sufficiently low to cause negligible scattering of a particle beam passing through the second volume when compared to the scattering of a particle beam passing through the first volume; (b) mounting a sample on the sample carrier at the sample position; (c) evacuating the first volume to a pressure between 1-50 mbar; (d) evacuating the second volume to a pressure below 0.1 mbar; (e) adjusting the distance between the sample and the aperture to a distance less than twice the diameter of the aperture; (f) passing a beam of particles through the aperture and onto the sample; and (g) passing a beam of photons through the aperture.