WO2025202056A1 - Système à faisceaux d'électrons multiples pour inspection avec des électrons rétrodiffusés - Google Patents

Système à faisceaux d'électrons multiples pour inspection avec des électrons rétrodiffusés

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Publication number
WO2025202056A1
WO2025202056A1 PCT/EP2025/057781 EP2025057781W WO2025202056A1 WO 2025202056 A1 WO2025202056 A1 WO 2025202056A1 EP 2025057781 W EP2025057781 W EP 2025057781W WO 2025202056 A1 WO2025202056 A1 WO 2025202056A1
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WO
WIPO (PCT)
Prior art keywords
electron
backscattered
detector
photon
lens
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2025/057781
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English (en)
Inventor
Dirk Zeidler
Thomas Schmid
Felix MENKE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Carl Zeiss Multisem GmbH
Original Assignee
Carl Zeiss Multisem GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Carl Zeiss Multisem GmbH filed Critical Carl Zeiss Multisem GmbH
Publication of WO2025202056A1 publication Critical patent/WO2025202056A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/244—Detectors; Associated components or circuits therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/26—Electron or ion microscopes; Electron or ion diffraction tubes
    • H01J37/28—Electron or ion microscopes; Electron or ion diffraction tubes with scanning beams
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/244—Detection characterized by the detecting means
    • H01J2237/2443—Scintillation detectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
    • H01J2237/244—Detection characterized by the detecting means
    • H01J2237/24475—Scattered electron detectors

Definitions

  • the disclosure relates to a multi electron-beam system with a detector for detection of backscattered electrons. of the invention
  • a collection efficiency of light or photons generated within the backscattered electron detector is increased.
  • photon optical field lens photons excited from the plurality of electron detection elements are guided to a common overlapping or pupil area, where an imaging lens may be arranged to collect the photons.
  • the array lenses for each of the electron detection elements, the collection efficiency of the isotropically excited photons is increased.
  • the at least one photon optical lens attached to or in vicinity of the backscattered electron detector therefore increases a collection efficiency of photons generated by backscattered electrons, and thus increases throughput or reduces noise.
  • the multi-beam system is comprising a beam tube segment having a conic shape with decreasing diameter in direction of propagation of the plurality of primary electron beamlets.
  • the beam tube segment of conic shape can be arranged within an upper pole shoe of the at least one electron optical imaging lens. Thereby, a collection efficiency of light generated within the backscattered electron detector is even further increased.
  • the backscattered electron detector is connected to a lower pole shoe of the at least one electron optical imaging lens, and wherein the lower pole shoe is electrically insulated from the upper pole shoe.
  • a voltage VE is provided to the lower pole shoe in electrical connection to the backscattered electron detector to generate a decelerating or accelerating electrical field between backscattered electron detector and the beam tube segment.
  • a voltage for decelerating or accelerating of electrons can be provided to the backscattered electron detector.
  • the upper pole shoe and the lower pole shoe form an axial gap.
  • the backscattered electron detector comprises a Nickel-Steel alloy. Thereby, a magnetic field can be confined within an area between the lower pole shoe and the upper pole shoe.
  • At least one of the photon detectors is connected to a corresponding electron detection element by a light guide.
  • a light guide can be integrated within the backscattered electron detector or formed on the upper side of it.
  • the at least one electron optical imaging lens is a magnetic lens with an axial gap, and wherein the backscattered electron detector is arranged between a lower pole shoe of the magnetic lens and the image plane.
  • the backscattered electron detector can comprise a conducting coating on the upper side which faces the incident primary electron beamlets.
  • the conductive coating is connected to ground. Thereby, a generation of surface charges is avoided.
  • the conducting coating can be formed as transparent coating such as an ITO-coating for covering at least one of the arrays of photon optical array lenses, the photon optical field lens or a light guide.
  • At least one of the apertures of the backscattered electron detector is inclined by an inclination angle with respect to a normal N to the image plane.
  • a primary electron beamlet is then inclined accordingly.
  • a maximum of the backscattered electron distribution is impinging on the backscattered electron detector adjacent to an aperture and a backscattered electron collection is increased.
  • the inclination angle of the apertures increases with increasing distance to an optical axis of the at least one electron optical imaging lens. Thereby, inclination angles are for example adjusted to align with a Larmor rotation of primary electron beamlets within a magnetic field lens.
  • Fig. 1 shows a sectional view of a multi-beam electron beam system with a backscattered electron detector according to an example
  • Fig. 7a, b show an example of a backscattered electron detector with increased backscattered electron efficiency
  • each primary electron beamlet (3.1, 3.2, 3.3) is one of the plurality of primary electron beamlets (3). It is understood that details or features of the examples can be combined or modified without hindrance.
  • FIG. 1 is a schematic illustration of a multi-beam electron imaging system 1 (in short also multi-beam system 1) according to an embodiment.
  • the multi-beam system 1 uses a plurality of electron beams for forming an image of an object 7.
  • the multi-beam system 1 generates a plurality of J primary particle beams 3 which strike the object 7 to be examined in order to generate interaction products, e.g. backscattered electrons, which emanate from the object 7 and are subsequently detected.
  • the multi-beam system 1 is of an electron microscope, which uses a plurality of primary electron beams 3 which are incident on a surface of the object 7 at a plurality of locations and generate there a plurality of primary electron beam focus spots 5, that are spatially separated from one another.
  • the plurality of focus spots 5 of the primary electron beamlets 3 form a regular raster arrangement of incidence locations, which are formed in the object plane 101.
  • the number J of primary beamlets 3 may be five, twenty-five, or more.
  • Exemplary values of the pitch P between the incidence locations are 1 micrometer, 10 micrometers, or more, for example 40 micrometers.
  • only three primary beamlets 3.1, 3.2 and 3.3 with corresponding focus points 5.1, 5.2 and 5.3 are shown in figure 1.
  • the detector 601 is comprising a plurality of detection elements, arranged in the vicinity of the plurality of apertures.
  • Detection elements can for example be diodes such as PMDs, or CMOS detection elements, and can be provided with electron-to-light conversion elements, or can be formed as direct electron detection elements.
  • the detector 601 comprises an electron-to-light conversion element, such as formed by scintillating material, by which backscattered electrons are converted into light, and a plurality of light detection elements.
  • the combination of the electron-to-light conversion element and the plurality of light detection elements hereby form together a plurality of electron detection elements.
  • the detector or image sensor 601 can further comprise a relay optical system for imaging and guiding the photons generated by the electron to photon conversion unit on dedicated photon detection elements, such as a plurality of photomultipliers or avalanche photodiodes (not shown).
  • the primary particle beams 3 are generated in a beam generation apparatus 300 comprising at least one electron emitter 301, at least one collimation lens 303, a multi-aperture arrangement 305 and a first electron optical field lens 331 and a second electron optical field lens 333.
  • the electron emitter 301 is connected to a voltage supply for providing an emitter voltage VK to the emitter 301 and generates at least one diverging electron beam 309, which is at least substantially collimated by the at least one collimation lens 303, and which illuminates the multi-aperture arrangement 305.
  • the multi-aperture arrangement 305 comprises at least one first multi-aperture or filter plate, which has a plurality of J openings formed therein in a first raster arrangement.
  • a multi-aperture arrangement 305 usually comprises further array elements, for example an electron optical lens array, a stigmator array or an array of electron optical deflection elements.
  • the particle beam 309 is perfectly collimated by collimation lens 303.
  • the multi-aperture arrangement 305 focuses each of the primary beamlets 3 in such a way that focal points are formed in an intermediate image surface.
  • the intermediate image surface can be real or virtual.
  • the intermediate image surface can be curved to pre-compensate a field curvature and image plane tilt of the electron imaging system arranged downstream of the intermediate image surface.
  • the multi-pole corrector deflector 110 is driven by a multi-electron beamlet control unit 860. Additionally, the multi-beam system 1 can comprise further static deflectors and multipole elements 112 configured to adjust the position and beam shapes of the plurality of the primary beamlets 3.
  • the multi-beam electron imaging system 1 furthermore comprises a control unit 800 configured both for controlling the individual particle optical components of the multiple electron beam system and for evaluating and analyzing the signals obtained by the detector 601.
  • the control or controller unit 800 can be constructed from a plurality of individual electronic computers or electronic components.
  • the control unit 800 comprises a control operation processor 880 and a control module 830 for the control of the electron-optical elements of the primary beamlet generation unit 300.
  • the control unit 800 further comprises a stage control module 850 for positioning the sample surface 25 or sample 7 by stage 500 within the object plane 101.
  • the control unit 800 further comprises a control module to adjust a sample voltage VS, which is connected to a module 503 for supplying the sample voltage VS to the sample 7, said sample voltage VS also being referred to as extraction voltage.
  • a control module to adjust a sample voltage VS, which is connected to a module 503 for supplying the sample voltage VS to the sample 7, said sample voltage VS also being referred to as extraction voltage.
  • an extraction field is generated between the backscattered electron detector 601 and the surface 25 of the object 7.
  • the extraction field decelerates the primary electrons of the primary electron beamlets 3 before the sample surface 25 is reached and generates an additional focusing effect on the plurality of primary electron beamlets 3.
  • the extraction field serves during use to accelerate the backscattered electrons from the surface 25 of the object 7 to the backscattered electron detector 601.
  • the detector 601 comprises a plurality of sets of detection elements with one set of detection elements for each primary electron beamlet 3. During use, each set of detection elements is configured to record the intensity signal of the assigned backscattered electrons. The plurality of intensity signals for the plurality of backscattered electrons is transferred to the image data acquisition unit or imaging control module 810, where the image data is processed and stored in memory 890.
  • the stage 500 is continuously moved at least in a first or x-direction, and after the acquisition of an image patch, the stage 500 is moved to the next image patch to be acquired.
  • the stage 500 is continuously moved in a first or x-direction while an image is acquired by scanning of the plurality of primary electron beamlets 3 with the raster scanner 110 in a first direction.
  • Stage movement and stage position is monitored and controlled by sensors known in the art, such as Laser interferometers, grating interferometers, confocal micro lens arrays, or similar.
  • control unit 800 is configured to trigger the image sensor 601 to detect in predetermined time intervals a plurality of timely resolved intensity signals from the plurality of backscattered electrons, and the digital image of an image patch is accumulated and stitched together from all positions of the plurality of primary electron beamlets 3.
  • FIG 2 illustrates examples of the backscattered electron detector 601. Same reference numbers are used as in figure 1 and reference is made also to the description of figure 1.
  • a backscattered electron detector 601 is arranged between the pole shoe 165 of magnetic objective lens 102 and the image plane 101, in which a surface 25 of a wafer 7 is placed by wafer stage 500.
  • the primary electron beamlets 3 pass an electron beam tube 151 at a given kinetic energy.
  • the beam tube 151 is connected to a tube potential VT, which is for example given by ground potential.
  • the backscattered electron detector 601 is connected to a potential VE, which generates a decelerating force to the primary electrons of the primary electron beamlets 3.1 to 3.3.
  • the backscattered electron detector 601 comprises a plurality of apertures 85.1 to 85.3, thereby passing the plurality of primary electron beamlets 3.1 to 3.3.
  • the backscattered electron detector 601 is arranged at distance D above the image pane 101, in which by stage 500 (not shown) a surface (25) of a wafer 7 is arranged.
  • Electron beamlets 3.1 to 3.3 are focused by objective lens 102 by a magnetic field generated by coil 161, to which a current I is provided.
  • the magnetic lens 102 with pole shoe 165 forms an axial gap lens, wherein the gap 167 between the lower pole shoe and higher pole shoe for forming a magnetic field is oriented in axial direction almost perpendicular to the image plane 101.
  • the pole shoe may not be formed by a single piece but can be formed by two electrically isolated parts forming an upper and a lower pole shoe.
  • backscattered electron detection higher landing energies are as well possible, for example voltage VL provided to the wafer 7 can be adjusted for landing energies of more than 2keV, more than 5 keV, for example even up to 50 keV.
  • voltage VL provided to the wafer 7 can be adjusted for landing energies of more than 2keV, more than 5 keV, for example even up to 50 keV.
  • backscattered electrons are generated (not shown), which are backscattered from the wafer surface 25 at kinetic energies like the landing energy. Backscattered electrons are then accelerated to the backscattered electron detector 601 and partially focused into detecting areas of the backscattered electron detector 601 (see below).
  • VE the kinetic energy of backscattered electrons when impinging onto the backscattered electron detector 601 can be adjusted.
  • FIG. 2b illustrates another example.
  • a backscattered electron detector 601 is arranged between the lower pole shoe 169 of magnetic objective lens 102.
  • the primary electron beamlets 3 pass the beam tube 151 at a given kinetic energy.
  • the beam tube 151 is connected to a tube potential VT, which is for example given by ground potential.
  • the magnetic lens 102 with pole shoe 165 forms a radial gap lens, wherein the gap 167 between the lower pole shoe 169 and higher pole shoe for forming a magnetic field has an extension almost parallel to the image plane 101.
  • the focusing magnetic field is thus generated directly above the surface 25 of a wafer 7.
  • Such a magnetic lens 102 is sometimes also called an immersion lens.
  • the backscattered electron detector 601 is thus arranged within the magnetic field of the immersion lens.
  • the backscattered electron detector 601 can be connected to a potential VE, which optionally generates a decelerating force to the primary electrons of the primary electron beamlets 3.1 to 3.3 before entering the backscattered electron detector 601.
  • the backscattered electron detector 601 comprises a plurality of apertures 85.1 to 85.3, thereby passing the plurality of primary electron beamlets 3.1 to 3.3.
  • the wafer is further connected to a voltage supply 503, configured for providing during use a voltage VL to the wafer 7. Thereby, primary electrons are decelerated before reaching the wafer surface 25.
  • Primary electrons are therefore focused by the magnetic immersion lens of magnetic lens 102 and decelerated in in at least one step by voltage VL provided to the wafer, such that the primary electrons impinge on the surface 25 of the wafer 7 at landing energies below 2keV, below 1 keV or even less, for example 300 eV or 200eV.
  • VL voltage provided to the wafer
  • backscattered electrons are generated (not shown), which are backscattered from the wafer surface 25 at kinetic energies similar to the landing energy. Backscattered electrons are then accelerated to the backscattered electron detector 601 and partially focus into detecting areas of the backscattered electron detector 601 (see below).
  • the backscattered electron detector 601 comprises paramagnetic materials with a permeability pR close to one, such as Aluminum, Magnesium or Tungsten. Other paramagnetic materials are given by paramagnetic semiconductors.
  • backscattered electron detector 601 is comprises diamagnetic material such as Bismuth or Copper.
  • backscattered electron detector 601 is comprises quartz (SiO2). Thereby, a magnetic field of objective lens 102 is at least partially transferred or increased through the backscattered electron detector 601.
  • the backscattered electron detector 601 comprises Nickel-Iron alloys such as Permanorm with higher permeability pR of for example pR about 10000.
  • FIG. 2c An example is illustrated in Figure 2c, where the backscattered electron detector 601 forms an extension of the lower pole shoe of the magnetic objective lens 102.
  • the magnetic field generated by objective lens 102 is confined within a region between objective lens 102 and backscattered electron detector 601.
  • a magnetic field between backscattered electron detector 601 and surface 25 of the wafer 7 is reduced and Larmor rotation of the electron beamlets below the backscattered electron detector 601 is reduced.
  • the backscattered electron detector 601 comprises hard magnetic materials, such as Samarium Cobalt, Ferrite or Neodymium. Thereby, a magnetic field from the objective lens 102 is modified. Thereby, for example a Larmor rotation of electrons within or between the backscattered electron detector 601 and the surface 25 of the wafer 7 is reduced.
  • Each primary electron beamlet 3 is focused by objective lens 102 (see Figure 1 and 2) and by decelerating fields generated by voltages VL and VE and transmits the corresponding aperture 85.1 to 85.7.
  • Each primary electron beamlet 3 impinges on the surface 25 of wafer 7 at focus points 5, including focus points 5.1 to 5.3 in figure 3a.
  • At each focus point 5, some electrons are scattered back and form backscattered electrons 9 including backscattered electrons 9.1 to 9.3.
  • Backscattered electrons 9.1 to 9.3 as propagating in direction of backscattered electron detector 601.
  • backscattered electrons 9.1 to 9.3 are accelerated and slightly focused and impinge on detection elements 607.1 to 607.7 arranged on the backside 611 of backscattered electron detector 601.
  • At least one detection element 607 is assigned to each aperture 85 and is for example arranged as circular detection element 607 of ring shape around each corresponding aperture 85.
  • backscattered electrons 9 can be detected for each primary beamlet 3 individually and separately.
  • electron detection elements 607 comprise a scintillating material. Within a scintillating material, photons are generated by backscattered electrons 9 within the scintillating material. An example is illustrated in figure 4a.
  • 607.1 to 607.3 are comprising scintillating material and are connected to optical light-guides
  • Photons excited within the electron detection elements 607.1 to 607.3 are guided within lightguides 609.1 to 609.3 to photon detectors 613.1 to 613.3.
  • Photon detectors 613.1 to 613.3 are connected to imaging control module 810, configured to capture image data corresponding to the backscattered electron count received by backscattered electron detector 601.
  • the lightguides 609.1 to 609.3 can be small in cross section of about few urn and can be formed by well-known planar fabrication techniques of integrated optics, for example by structured ion exchange within glass, or as SiO2-structures within of a conducting semiconductor sample.
  • the lightguides 609.1 to 609.3 have the advantage that they are formed by linear dielectric material and photons do not have any interaction with electrons and electrical or magnetic fields present in vicinity of the apertures 85.
  • the bulk material of the backscattered electron detector 601 is comprising conducting material such as doped silicon or Permanorm. The bulk material is connected to voltage supply for providing voltage VE to assist the generation of the accelerating or decelerating electrical field between backscattered electron detector 601 and wafer surface 25. Using a conductive material also prevents the backscattered electron detector 601 from charging up during exposure with for example backscattered electrons.
  • the lightguides 609.1 to 609.3 can be embedded (as shown in Figure 4a) within the conductive material.
  • lightguides 609.1 to 609.3 can be covered by a conductive coating formed by for example ITO or Aluminum to avoid a buildup of surface charges on exposed surfaces of the lightguides 609.1 to 609.3.
  • FIG. 4b A further example is illustrated in figure 4b.
  • the electron detection elements 607.1 to 607.3 are comprising scintillating material and are directly connected to photon detectors 613.1 to 613.3.
  • Photon detectors 613.1 to 613.3 are connected by embedded and isolated electrical connections 619.1 to 619.3 to imaging control module 810, configured to capture image data corresponding to the backscattered electron count received by backscattered electron detector 601.
  • Embedded electrical connections 619.1 to 619.3 can be formed by local regions of doped semiconductors of metal lines embedded within for example an isolating SiO2-structure.
  • Embedded electrical connections 609.1 to 609.3 can be smaller in diameter compared to optical light guides 609, for example 1pm or even less.
  • the backside 411 of backscattered electron detector 601 is covered by reflective coating 621, for example comprising a thin Aluminum coating.
  • Aluminum has a low stopping power to backscattered electrons, but it reflects photons generated in electron detection elements 607.1 to 607.3 and thus reduces light loss from electron detection elements 607.1 to 607.3.
  • electron detection elements 607.1 to 607.3 are completely encapsulated by a reflection coating except for an aperture opening to a lightguide 609 or a photon detector 613.
  • Each photon optical array lens 629.1 to 629.3 is arranged at the upper side 603 of backscattered electron detector 601, opposing at least one of the detection elements
  • Photons generated within a detection element 607 are thus collimated by an photon optical array lens 629 and collection efficiency by photon optical lens system 627 is increased even when limited within the electron beam tube 151.
  • a photon optical folding mirror 651 is arranged with aperture 653 for passing the plurality of electron beamlets comprising beamlets 3.1 to 3.3.
  • Primary electron beamlets 3.1 to 3.3 are propagating through aperture 653 arranged at the electron beam cross over 108 and are further through beam tube 151.
  • electron objective lens 102 not shown here, see figure 1 or 2
  • primary electron beamlets 3.1 to 3.3 are focused and are passing apertures
  • Backscattered electrons 9.1 to 9.3 are scattered back from focus points 5.1 to 5.3 or primary electron beamlets 3.1 to 3.3 and directed in direction of individual electron detection elements 607.1 to 607.3. Backscattered electrons
  • Photon optical array lenses 629.1 to 629.3 can be formed by optical transparent lens material such as Silicon dioxide or fused silica and can be formed by usual planar fabrication techniques of photon optical micro-lens arrays for example for CMOS sensors.
  • An aperture 85 is formed through each of the photon optical array lenses 629.1 to 629.3.
  • Lens surfaces including the open surfaces within the apertures 85 of the photon optical array lenses 629.1 to 629.3 can be covered by conducting materials such as ITO to prevent charges to stick on the surface of the isolating lens material.
  • Figure 5b shows another example of an photon optical imaging lens system 627 with a photon optical field lens 623 arranged on the upper side 603 of backscattered electron detector 601.
  • Photon optical field lens 623 and photon optical array lenses 629 can also be combined. Thereby, collection efficiency is further increased.
  • a photon optical field lens 623 can for example be formed from fused silica and connected to backscattered electron detector 601 by wringing or using Van-der-Waals-forces.
  • Apertures 85 can be formed in a photon optical field lens for example by directional RIE etching. Open surfaces of photon optical field lens 623, including the open surfaces within the apertures 85, can be covered by a conductive coating 633 comprising conducting materials such as ITO to prevent charges to stick on the surface of the isolating lens material.
  • Photon optical folding mirror 651 can be a mirror with a high reflective metal coating such as an aluminum or silver coating. Folding mirror 651 and photon optical lenses of imaging optical system 627 are connected to ground, such that no charges are build up within the light optical system.
  • Figure 5c illustrates an example with increased collection efficiency for light generated within the backscattered electron detector 601.
  • photon optical array lenses 629 for collimating light and the function of photon optical field lens 623 is combined within the spatially variable photon optical array lenses 629, such that photon optical lenses with a larger distance to axis 105.1 have a larger prismatic power to refract light in direction of axis
  • Electron optical objective lens 102 has an upper pole shoe 163, which has an inner section of conic shape with increasing diameter in direction of light along the negative z-direction. Inside the upper pole shoe 163, a conic section of electron beam tube
  • a plurality of apertures 85 is provided and in vicinity of each aperture 85, an optically transparent electron detection element 607 comprising scintillating material is provided.
  • the lower pole shoe is set to a potential by voltage VE, such that primary electrons are for example decelerated before passing the apertures 85 of backscattered electron detector 601.
  • primary electron beamlets 3.1 to 3.3 can be scanned across the surface 25 by multipole deflector element 110 within a limited range according to diameters of apertures 85.1 to 85.3.
  • a scanning range of 2pm, 3pm or even more is possible.
  • a typical aperture angle of a primary beamlet 3 is less than lOmrad, such that a diameter of a beamlet at 100pm from the wafer surface 25 is about 1pm.
  • an aperture diameter of for example 4pm of apertures 85 of the backscattered electron detector 601 a scanning range of for example 2pm is possible.
  • a spatially resolved backscattered electron image of a closed segment of the surface 25 of a wafer 7 is acquired by repetitive image scanning and stitching.
  • FIG. 6 illustrates an example of a photon optical imaging system.
  • the photon optical imaging lens system 627 is hereby formed by a first photon optical field lens 623.1 arranged at the backscattered electron detector 601, an intermediate photon optical imaging lens 625 and a second photon optical field lens 623.1 arranged in front of the spatially resolving detector 635 with several detection areas including detection area 633 assigned to the different individual primary electron beamlet 3.1 and the backscattered electrons generated by this beamlet 3.1.
  • the photon optical imaging lens system 627 is schematically illustrated in an unfolded system with photon optical mirror plane 651, at which the system is folded by a half folding angle of for example 20°, 30° or 45°, or more.
  • the photon optical folding mirror 651 is again placed at the beam cross over 108, such that primary electron beamlets can transmit the photon optical mirror 651 at an aperture 653 of small size.
  • the primary electron beamlets 3 forms close to the image plane 101 a telecentric bundle of beamlets 3, meaning that all electron beamlets 3 are parallel to each other.
  • the telecentricity property does not require the beamlet to be perpendicular to the image plane 101, in which the surface 25 of a wafer 7 is arranged.
  • the telecentric bundle of primary electron beamlets 3 is inclined with respect to the optical axis 105 by inclination angle 17, wherein the optical axis 105 is perpendicular to the image plane 101.
  • apertures 85 can be arranged within the backscattered electron detector 601 at the same angle 17 to allow transmission of oblique primary electron beamlets 3.1 to 3.3.
  • electron detection elements 607.1 to 607.3 can be arranged for example only on one side of the apertures 85 in direction of the angle of incidence 17.
  • the principle of using oblique primary electron beamlets is not limited to telecentric bundles but can as well be applied to homocentric bundles of primary electron beamlets 3. It is understood that for example within an immersion lens field, electron beamlets are further inclined to the optical axis 105 perpendicular to the wafer surface 25 by the Larmor rotation with increasing inclination angle with respect to the optical axis 105. In the example illustrated in Figure 7b, inclination angles 17.2 and 17.3 of apertures 85.2 and 85.3 are individually adjusted to compensate such an increasing inclination of each corresponding electron beamlet due to the Larmor rotation.
  • the inclination of apertures is here shown in the x-z-plane, it is however understood that a Larmor-Rotation typically leads to an inclination angle of primary and backscattered electron beamlets in azimuthal direction, i.e. in the illustration in figure 7b, the oblique apertures can be inclined in y- direction perpendicular to the x-z-plane with radially increasing inclination angle 17.
  • FIG 8 shows another example of a multi-beamlet charged-particle system 1.
  • backscattered electron detector 601 comprises an array of apertures 85, in each of which an electron source 301 is arranged. Only two electron sources 301.1 and 301.2 are shown, but there can be many more, for example 469 electron sources 301 forming 469 beamlets.
  • the backscattered electron detector 601 further comprises a plurality of isolating layers 693 and extracting electrode layer 697. By providing appropriate voltages to the extracting electrode layer 697, electrons are accelerated from the electron sources 301.1, 303.3 and focused by electrostatic lens fields within the apertures 85 formed by lens electrode layer 698.
  • Electron beamlets 3.1 and 3.2 are impinging on the surface 25 of wafer 7 and cause backscattered electrons to be directed backwards in direction of backscattered electron detector 601.
  • Backscattered electron detector 601 comprises electron detection elements 607.1 and 607.2, each arranged in vicinity of an aperture 85. Electron detection elements 607.1 and 607.2 comprise scintillating material to convert electrons into photons. Photons emitted from the electron detection elements 607.1, 607.2 are then imaged by photon optical imaging lens system 627 onto spatially resolving photon detector 635.
  • the example of figure 8 has the advantage that the detection of backscattered electrons by conversion of backscattered electrons into photons within the localized and confined electron detection elements 607.1, 607.2 does not need any electrical connection. Photons are inert to interaction within linear material and can be imaged without interference with electron-optical elements or charged particles.
  • a typical photon detector is formed by a spatially resolving image sensor 635 such as a CMOS sensor.
  • An image field of a multi-beam system 1 for example has a diameter of 100pm or more.
  • photon optical system 627 further comprises a photon optical beam-splitter for guiding focused excitation light to specific positions at the photocathode to excite electrons at the source position within the apertures 85.
  • Figure 9 illustrates another example of a backscattered electron detector 601. Same reference numbers as within the previous figures are used and reference is also made to the description of the previous figures.
  • the apertures 85.1 to 85.5 are formed as elongated slits to allow for a larger scanning range of the primary electron beamlets (see figure 8b).
  • primary electrons are scanned in y-direction which the wafer 7 is continuously moved by stage 500 in x-direction. Thereby, a complete surface area of a surface 25 of a wafer 7 can be imaged by parallel scanning of the plurality of beamlets 3 in a first direction while moving the wafer 7 in a second direction.
  • Figure 10 illustrates another example of a multi-beamlet charged-particle system 1 with a backscattered electron detector 601.
  • the backscattered electron detector 601 of figure 10 can be any of the backscattered electron detector 601 shown in figure 1 to 7 or 9.
  • multi-beamlet charged-particle system 1 comprises an electron-optical beam divider 400.
  • Beam divider 400 is separating backscattered electrons and secondary electrons 19 which pass the apertures 85 of backscattered electron detector 601 along secondary electron beam path 11 into an electron-optical detection system 200. Both types of electrons are further described without limit as secondary electrons 19.
  • Electron-optical detection system 200 comprises electron optical lenses 206, 208 and 210 to image secondary electrons 19 onto a spatially resolving detector 209, onto which focus points 15.1 to 15.3 of secondary electrons 19 are formed.
  • a spatially resolving detector 209 onto which focus points 15.1 to 15.3 of secondary electrons 19 are formed.
  • backscattered electrons 9 as well as secondary electrons 19 of typically lower kinetic energy can be detected separately and more information of a surface 25 of a wafer 7 can be acquired.
  • a multi-beam generation apparatus configured for generating a plurality of primary electron beamlets (3) from at least one electron source (301),
  • At least one electron optical imaging lens (102, 698) for forming a plurality of spatially separated electron focus spots (5) in an image plane (101) of the multi-beam system (1)
  • a wafer stage (500) configured to arrange a surface (25) of a wafer (7) in the image plane (101),
  • At least one photon detector (613, 635) for spatially resolved detecting of photons generated within each of the electron detection elements (607),
  • a photon imaging lens system (627) for imaging photons excited by the electron detection elements (607) onto the at least one photon detector (635), wherein the photon imaging lens system (627) comprises at least one photon optical lens (623, 629) attached to the backscattered electron detector (601), and wherein each aperture (85) extends through the at least one photon optical lens (623, 628).
  • Clause 2 The system of clause 1, wherein the least one photon optical lens (623, 629) is formed as a single photon optical field lens (623) arranged at an upper side (603) of the backscattered electron detector (601), wherein the upper side (603) faces the incident primary electron beamlets (3), and wherein each aperture (85) extends through the photon optical field lens (623).
  • Clause 3 The system of clause 1, wherein the least one photon optical lens (623, 629) is comprising an array of photon optical lenses (629) arranged at an upper side (603) of the backscattered electron detector (601), wherein the upper side (603) faces the incident primary electron beamlets (3), and wherein each aperture (85) extends through one photon optical lens of the array of photon optical lenses (629).
  • At least one electron optical imaging lens (102, 698) for forming a plurality of spatially separated electron focus spots (5) in an image plane (101) of the multi-beam system (1)
  • the backscattered electron detector (601) arranged parallel to the image plane (101) at a distance D, wherein the backscattered electron detector (601) comprises a plurality of apertures (85) for transmitting the plurality of primary electron beamlets (3) and a plurality of electron detection elements (607), wherein for each aperture (85), at least one electron detection element (607) is arranged adjacent to the corresponding aperture (85), wherein each of the electron detection element (607) is comprising a scintillating material configured for converting backscattered electrons (9) into photons,
  • the backscattered electron detector (601) comprises a plurality of light guides (609) for guiding photons from a lower side of the backscattered electron detector (601) to an upper side (603), wherein the upper side (603) faces the incident primary electron beamlets (3).
  • a wafer stage (500) configured to arrange a surface (25) of a wafer (7) in the image plane (101),
  • backscattered electron detector (601) arranged parallel to the image plane (101) at a distance D, wherein the backscattered electron detector (601) comprises a plurality of apertures (85) for transmitting the plurality of primary electron beamlets (3) and a plurality of electron detection elements (607), wherein the backscattered electron detector (601) comprises a conducting coating (633) on an upper side (603) which faces the incident primary electron beamlets (3).
  • a multi-beam generation apparatus configured for generating a plurality of primary electron beamlets (3) from at least one electron source (301),
  • At least one electron optical imaging lens (102, 698) for forming a plurality of spatially separated electron focus spots (5) in an image plane (101) of the multi-beam system (1)
  • a wafer stage (500) configured to arrange a surface (25) of a wafer (7) in the image plane (101),
  • the backscattered electron detector (601) arranged parallel to the image plane (101) at a distance D, wherein the backscattered electron detector (601) comprises a plurality of apertures (85) for transmitting the plurality of primary electron beamlets (3) and a plurality of electron detection elements (607), wherein for each aperture (85), at least one electron detection element (607) is arranged adjacent to the corresponding aperture (85), wherein each of the electron detection element (607) is comprising a scintillating material configured for converting backscattered electrons (9) into photons,
  • Clause 10 The system of clause 9, wherein the beam tube segment (151.2) of conic shape is arranged within an upper pole shoe (163) of the at least one electron optical imaging lens (102).
  • Clause 12 The system of clause 11, wherein the upper pole shoe (163) and the lower pole shoe (169) form an axial gap (167).
  • a multi-beam generation apparatus configured for generating a plurality of primary electron beamlets (3) from at least one electron source (301),
  • a backscattered electron detector (601) arranged parallel to the image plane (101) at a distance D, wherein the backscattered electron detector (601) comprises a plurality of apertures (85) for transmitting the plurality of primary electron beamlets (3), wherein during use, a voltage VE is provided to the backscattered electron detector (601) to generate a decelerating or accelerating electrical field.
  • Clause 14 The system of clause 13, wherein, during use, a voltage VL is provided to the wafer (7), and wherein
  • At least one electron optical imaging lens (102, 698) for forming a plurality of spatially separated electron focus spots (5) in an image plane (101) of the multi-beam system (1)
  • At least one electron optical imaging lens (102, 698) for forming a plurality of spatially separated electron focus spots (5) in an image plane (101) of the multi-beam system (1)
  • a wafer stage (500) configured to arrange a surface (25) of a wafer (7) in the image plane (101),
  • a multi-beam generation apparatus configured for generating a plurality of primary electron beamlets (3) from at least one electron source (301),

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

L'invention concerne un système d'électrons à faisceaux multiples avec un détecteur d'électrons rétrodiffusé. Dans un exemple, le détecteur d'électrons rétrodiffusés comprend une pluralité d'ouvertures ayant des régions confinées localement de matériau scintillant à proximité des ouvertures. Ainsi, des électrons rétrodiffusés sont convertis en photons, qui sont ensuite guidés par des moyens optiques tels que des guides de lumière d'un système de lentille d'imagerie optique vers un détecteur de photons à résolution spatiale.
PCT/EP2025/057781 2024-03-25 2025-03-21 Système à faisceaux d'électrons multiples pour inspection avec des électrons rétrodiffusés Pending WO2025202056A1 (fr)

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EP3579263A1 (fr) * 2018-06-07 2019-12-11 FEI Company Microscope à électrons multifaisceau améliorés
CN112987145A (zh) * 2021-04-26 2021-06-18 京东方科技集团股份有限公司 微透镜结构、显示装置以及微透镜结构的加工方法
DE102020125534B3 (de) 2020-09-30 2021-12-02 Carl Zeiss Multisem Gmbh Vielzahl-Teilchenstrahlmikroskop und zugehöriges Verfahren mit schnellem Autofokus um einen einstellbaren Arbeitsabstand
WO2023280642A1 (fr) 2021-07-05 2023-01-12 Asml Netherlands B.V. Détecteur de particules chargées
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005024881A2 (fr) 2003-09-05 2005-03-17 Carl Zeiss Smt Ag Systemes et dispositifs d'optique particulaire et composants d'optique particulaire pour de tels systemes et dispositifs
WO2007028596A1 (fr) 2005-09-06 2007-03-15 Carl Zeiss Smt Ag Procédé d’examen de particules chargées et système à particules chargées
WO2007028595A2 (fr) 2005-09-06 2007-03-15 Carl Zeiss Smt Ag Composant optique a particules
WO2007060017A2 (fr) 2005-11-28 2007-05-31 Carl Zeiss Smt Ag Composant optique a particules
WO2011124352A1 (fr) 2010-04-09 2011-10-13 Carl Zeiss Smt Gmbh Système de détection des particules chargées et système d'inspection à mini-faisceaux multiples
US8598525B2 (en) 2010-07-06 2013-12-03 Carl Zeiss Microscopy Gmbh Particle beam system
US20120273686A1 (en) * 2011-04-26 2012-11-01 Shinichi Kojima Apparatus and methods for electron beam detection
DE102013014976A1 (de) 2013-09-09 2015-03-12 Carl Zeiss Microscopy Gmbh Teilchenoptisches System
DE102013016113A1 (de) 2013-09-26 2015-03-26 Carl Zeiss Microscopy Gmbh Verfahren zum Detektieren von Elektronen, Elektronendetektor und Inspektionssystem
EP3579263A1 (fr) * 2018-06-07 2019-12-11 FEI Company Microscope à électrons multifaisceau améliorés
DE102020125534B3 (de) 2020-09-30 2021-12-02 Carl Zeiss Multisem Gmbh Vielzahl-Teilchenstrahlmikroskop und zugehöriges Verfahren mit schnellem Autofokus um einen einstellbaren Arbeitsabstand
CN112987145A (zh) * 2021-04-26 2021-06-18 京东方科技集团股份有限公司 微透镜结构、显示装置以及微透镜结构的加工方法
WO2023280642A1 (fr) 2021-07-05 2023-01-12 Asml Netherlands B.V. Détecteur de particules chargées
WO2023011824A1 (fr) 2021-08-02 2023-02-09 Asml Netherlands B.V. Dispositif optique à particules chargées

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