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
  • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
  • H01J37/06—Electron sources; Electron guns
  • H01J37/073—Electron guns using field emission, photo emission, or secondary emission electron sources
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
  • G02B27/0927—Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
  • H01J1/02—Main electrodes
  • H01J1/30—Cold cathodes, e.g. field-emissive cathode
  • H01J1/304—Field-emissive cathodes
  • H01J1/3042—Field-emissive cathodes microengineered, e.g. Spindt-type
  • H01J1/3044—Point emitters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
  • H01J1/02—Main electrodes
  • H01J1/34—Photo-emissive cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J19/00—Details of vacuum tubes of the types covered by group H01J21/00
  • H01J19/02—Electron-emitting electrodes; Cathodes
  • H01J19/24—Cold cathodes, e.g. field-emissive cathode
• • 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
  • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
  • H01J37/06—Electron sources; Electron guns
• • 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
• • 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
  • H01J40/00—Photoelectric discharge tubes not involving the ionisation of a gas
  • H01J40/02—Details
  • H01J40/04—Electrodes
  • H01J40/06—Photo-emissive cathodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J40/00—Photoelectric discharge tubes not involving the ionisation of a gas
  • H01J40/16—Photoelectric discharge tubes not involving the ionisation of a gas having photo- emissive cathode, e.g. alkaline photoelectric cell
  • H01J40/18—Photoelectric discharge tubes not involving the ionisation of a gas having photo- emissive cathode, e.g. alkaline photoelectric cell with luminescent coatings for influencing the sensitivity of the tube, e.g. by converting the input wavelength
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/30—Cold cathodes
  • H01J2201/304—Field emission cathodes
  • H01J2201/30403—Field emission cathodes characterised by the emitter shape
  • H01J2201/30407—Microengineered point emitters
  • H01J2201/30411—Microengineered point emitters conical shaped, e.g. Spindt type
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/30—Cold cathodes
  • H01J2201/304—Field emission cathodes
  • H01J2201/30446—Field emission cathodes characterised by the emitter material
  • H01J2201/30449—Metals and metal alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/30—Cold cathodes
  • H01J2201/304—Field emission cathodes
  • H01J2201/30446—Field emission cathodes characterised by the emitter material
  • H01J2201/3048—Semiconductor materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/30—Cold cathodes
  • H01J2201/308—Semiconductor cathodes, e.g. having PN junction layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/34—Photoemissive electrodes
  • H01J2201/342—Cathodes
  • H01J2201/3421—Composition of the emitting surface
  • H01J2201/3423—Semiconductors, e.g. GaAs, NEA emitters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/34—Photoemissive electrodes
  • H01J2201/342—Cathodes
  • H01J2201/3421—Composition of the emitting surface
  • H01J2201/3425—Metals, metal alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2201/00—Electrodes common to discharge tubes
  • H01J2201/34—Photoemissive electrodes
  • H01J2201/342—Cathodes
  • H01J2201/3421—Composition of the emitting surface
  • H01J2201/3426—Alkaline metal compounds, e.g. Na-K-Sb
• • 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
  • H01J2237/06—Sources
  • H01J2237/063—Electron sources
  • H01J2237/06325—Cold-cathode sources
  • H01J2237/06333—Photo emission
• • 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
  • H01J2237/245—Detection characterised by the variable being measured
  • H01J2237/24507—Intensity, dose or other characteristics of particle beams or electromagnetic radiation
  • H01J2237/24514—Beam diagnostics including control of the parameter or property diagnosed
  • H01J2237/24521—Beam diameter
• • 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
  • H01J2237/245—Detection characterised by the variable being measured
  • H01J2237/24592—Inspection and quality control of devices
• • 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
  • H01J2237/26—Electron or ion microscopes
  • H01J2237/28—Scanning microscopes
  • H01J2237/2813—Scanning microscopes characterised by the application
  • H01J2237/2817—Pattern inspection
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
  • H01L21/67005—Apparatus not specifically provided for elsewhere
  • H01L21/67242—Apparatus for monitoring, sorting or marking
  • H01L21/67288—Monitoring of warpage, curvature, damage, defects or the like

Definitions

• This disclosure relates to protective films for electron emitters.
• Fabricating semiconductor devices typically includes processing a semiconductor wafer using a large number of fabrication processes to form various features and multiple levels of the semiconductor devices.
• lithography is a semiconductor fabrication process that involves transferring a pattern from a reticle to a photoresist arranged on a semiconductor wafer. Additional examples of semiconductor fabrication processes include, but are not limited to, chemical-mechanical polishing (CMP), etch, deposition, and ion implantation.
• CMP chemical-mechanical polishing
• etch etch
• deposition deposition
• ion implantation ion implantation
• Electron beams are used in a number of different applications during semiconductor manufacturing. For example, electron beams can be modulated and directed onto an electron- sensitive resist on a semiconductor wafer, mask, or other workpiece to generate an electron pattern on the workpiece. Electron beams also can be used to inspect a wafer by, for example, detecting electrons emerging or reflected from the wafer to detect defects, anomalies, or undesirable objects.
• Photocathodes also have been used to generate electron beams.
• a single light beam incident on a photocathode system can generate a single electron beam with high brightness that is capable of delivering high electron current density.
• a problem with single electron beam systems is that even with high brightness systems, single electron beam systems still have relative low throughput for inspection. Low throughput is a drawback to electron beam inspection. With currently-available electron beam sources, thousands of beams would be required.
• Alkali halide photo electron emitters are used as photocathode emitters in the ultraviolet spectral range.
• CsBr and Csl photocathodes are used for high quantum efficiency with light in the deep ultraviolet (DUV) range.
• DUV deep ultraviolet
• Photocathode electron emitters generally do not have a protective coating to protect them from oxidation or carbon build up from the vacuum environment.
• Existing protective cap layers on photocathodes are not robust to cleaning. Therefore, these cap layers cannot protect a photocathode electron emitter during operation.
• Alkali halide photocathodes such as Csl and CsBr have demonstrated photoemission from intraband states when illuminated with wavelengths much longer than their bandgap energy. So far, the illumination schemes to pump these photocathodes involve either short wavelengths with energies larger than the bandgap or longer wavelengths that first activate the color centers located at about 4.7 eV above the valence band. These schemes have been tried both in transmission and in reflection mode. For reflection mode, 257 nm and 266 nm beams have successfully activated the color centers and photogenerated electrons in vacuum. A 410 nm beam was not successful at activating defects and simultaneously transferring the electrons to vacuum.
• An electron emitter includes a photocathode structure and a protective film disposed on an exterior surface of the photocathode structure.
• the protective film includes ruthenium.
• the photocathode structure includes an alkali halide.
• the alkali halide can include CsBr or Csl.
• the photocathode may include a ruthenium layer on a side of the photocathode structure opposite from the protective film.
• the photocathode may include a metal layer on a side of the photocathode structure opposite from the protective film.
• the protective film can include an alloy of ruthenium and platinum.
• the protective film may have a thickness from 1 nm to 20 nm.
• the protective film may be free of pinholes in at least an emitting area of the photocathode structure.
• the protective film may be free of bubbles and inclusions in at least an emitting area of the photocathode structure.
• the protective film may have imperfections only with a diameter or length dimension less than 1 nm.
• the protective film may have a porosity less than or equal to 25%.
• the protective film may have a packing density of greater than or equal to 0.92.
• the protective film may have fewer than 10 4 impurities over an emitting area of the photocathode structure.
• the impurities can include carbon, oxides, oxygen as a dissolved gas, sodium, or potassium.
• An electron beam tool can include the electron emitter of the first embodiment.
• the electron beam tool can includes a detector that receives electrons generated by the electron emitter and reflected from a surface of a wafer.
• a method is provided in a second embodiment.
• a photocathode structure is provided.
• a protective film is deposited on an exterior surface of the photocathode structure.
• the depositing can include ion sputtering, magnetron sputtering, or atomic layer deposition.
• the photocathode structure may include an alkali halide.
• a method is provided in a third embodiment.
• a photocathode structure is provided.
• the photocathode includes an alkali halide and a protective film disposed on an exterior surface of the photocathode structure.
• the protective film includes ruthenium. An electron beam is generated from the photocathode structure when photons are directed at the photocathode structure. [0022] A plasma clean of the photocathode structure may be performed.
• FIG. 1 is a cross-sectional diagram of an embodiment of an electron emitter in accordance with the present disclosure
• FIG. 2 is a bandgap structure for a Csl photocathode
• FIG. 3 is a table of pumping schemes
• FIG. 4 is a flowchart of a method embodiment in accordance with the present disclosure.
• FIG. 5 is a flowchart of another method embodiment in accordance with the present disclosure
• FIG. 6 is a block diagram of an embodiment of a system in accordance with the present disclosure. DETAILED DESCRIPTION OF THE DISCLOSURE
• Ruthenium or a ruthenium alloy can be used to encapsulate one or more surfaces of a photocathode.
• Photocathodes are affected by vacuum conditions that can deteriorate the field emission performance.
• the photocathode can be wholly or partly encapsulated with a ruthenium protective film.
• the ruthenium protective film renders the photocathode resistant to oxidation and carbon build up.
• the ruthenium protective film also has a relative low sputter yields and can withstand erosion by ions.
• ruthenium is a metal and may have advantages over using the photocathode by itself. For example, use of ruthenium may provide higher current stability and/or operation at higher pressures.
• Photocathodes are electron sources that emit electrons when a photocathode structure is exposed to a source of light, either in transmission or reflection mode.
• the photocathode structure can be a bulk material, a film, or series of films deposited on a substrate.
• wavelength(s) of the light can be selected to optimize the amount of emission currents and energy spread of the emitted electrons.
• the current produced by photocathodes may be more stable than the current produced by cold field emitters.
• Many materials can be used for photoemission, including silicon, silicon with a metal coating, or an alkali halide.
• FIG. 1 is a cross-sectional diagram of an embodiment of an electron emitter 100.
• the electron emitter 100 includes a photocathode structure 101.
• the photocathode structure 101 can include an alkali halide, such as CsBr or Csl.
• the photocathode structure 101 also can include other semiconductor photocathode materials.
• the photocathode structure 101 may include planar features.
• a protective film 102 is disposed on an exterior surface of the photocathode structure
• the protective film 102 includes ruthenium.
• the protective film 102 may be ruthenium or a ruthenium alloy, such as an alloy of ruthenium and platinum.
• the electron emitter 100 can optionally include a layer 103 on a side of the photocathode structure 101 opposite from the protective film 102.
• the layer 103 may include ruthenium or may be another metal.
• Introducing voltage to the protective film 102 and/or layer 103 can provide control of electron migration to desired surface. For example, if the layer 103 on the back side of the electron emitter 100 is positively charged, electrons can be made to migrate to the exit surface to enhance electron emission.
• the protective film 102 can have a thickness from 1 nm to 20 nm or from 1 nm to 10 nm, including all values to the 0.1 nm and ranges in between. This thickness can be measured from an outer surface of the photocathode structure 101 or another layer that the protective film 102 is disposed on.
• the optimal thickness of the protective film 102 can be configured for optimal electron emission. Larger thicknesses, while feasible, may affect efficiency. The thickness may depend on the electron emitter 100 extractor configuration and wavelength used for photo electron emission. If the thickness is too large, then it will absorb all the light and/or will not allow electrons to escape easily by increasing the work function.
• the protective film 102 generally provides a protective function, it can be thick enough to protect the photocathode structure 101 without affecting performance.
• the protective film 102 also can supply electrons, so the thickness can vary with the wavelength of light used for electron generation.
• the protective film 102 may be free of pinholes in at least an emitting area of the photocathode structure 101.
• the protective film 102 can have a porosity less than or equal to 25%. Protection may be compromised if the porosity is greater than 25%.
• the protective film 102 can have a packing density of greater than or equal to 0.92. Protection may be compromised with a packing density less than 0.92.
• the protective film 102 can be deposited by ion or magnetron sputtering, atomic layer deposition (ALD), or by other methods that provide a dense, pinhole-free, uniform protective film 102.
• Porosity (P) can be defined and measured using index of refraction with the following equation.
• nf is the refractive index of the protective film 102 and nb is the refractive index of the material.
• the packing density (PD) of a film is defined as the ratio of the average film density (pf) and the bulk density (P B ) using the following equation.
• the protective film 102 may be free of bubbles and inclusions in at least an emitting area.
• the protective film 102 may include imperfections only with a diameter or length dimension less than 1 nm.
• the protective film 102 may have fewer than 10 4 impurities over an emitting area.
• the impurities can include carbon, oxides, oxygen as a dissolved gas, sodium, or potassium.
• the protective film 102 can be robust for electron field emission, robust in the presence of high electric fields, robust to ion sputtering, and robust to plasma or other cleaning methods. Oxidation and/or carbon can be removed from the protective film 102 without damaging the protective film 102. For example, the protective film 102 can be cleaned to atomic levels by molecular hydrogen, hydrogen plasmas, or other plasmas.
• the protective film 102 also is resistant to oxidation and carbon contamination. Ruthenium may have the ability to break apart gas molecules that land on its surface or prevent adherence of such gas molecules to its surface. These molecules are capable of distorting the extraction field on the surface of the electron emitter 100 and causing enhanced emission which translates as noise in the beam because of the mobility and residence time of the molecule on the surface. Thus, the protective film 102 can be self-cleaning.
• the protective film 102 on the photocathode structure 101 can control
• Electromigration can be controlled with the protective film 102 on one surface of the photocathode structure 101 and ruthenium or another metal on an opposite surface of the photocathode structure 101.
• the protective film 102 also may provide improved angular spread of the electron beam.
• Photocathodes generally can operate at approximately 10 "11 Torr. With a protective film 102, the electron emitter 100 may be able to operate at approximately 10 "9 Torr.
• the protective film 102 is transparent to UV wavelengths. This can enable operation of the electron emitter 100 in both transmission and reflection modes.
• Embodiments of the electron source 100 can be used as the electron source in reticle and wafer inspection systems.
• embodiments of the electron source 100 can be used as the electron source in electron beam wafer or reticle inspection systems using single or multiple electron sources, electron beam wafer or reticle review systems using single or multiple electron sources, or electron beam wafer or reticle metrology systems using single or multiple electron sources.
• Embodiments of the electron source 100 also can be used in systems that generate x-rays using single or multiple electron sources in wafer or reticle metrology, review, or inspection.
• Multiple wavelengths can be applied to the photocathode structure 101 that includes an alkali halide, such as CsBr or Csl.
• the multiple wavelengths can be applied in both reflection and transmission mode to activate and pump intraband states (e.g., color centers) of the alkali halide.
• the multiple wavelengths can activate the centers and transfer electrons to vacuum.
• Use of multiple wavelengths can increase quantum efficiency and/or achieve the same quantum efficiency as with a single wavelength while producing less heat.
• Less complex lasers systems can be used to generate multiple wavelengths than a single wavelength. For example, a longer wavelength can use a less complex laser system or optics. Less energy spread of the photogenerated electrons and lower emittance can be achieved.
• the proposed pumping schemes are: activate color centers with ⁇ and pump the cathode with ⁇ 2; activate with ⁇ , pump with ⁇ and ⁇ 2; and/or pump with ⁇ and ⁇ 3.
• FIG. 2 illustrates the conduction band (CB) and valence band (VB).
• the third pumping scheme using two wavelengths may be an equivalent to electromagnetically-induced transparency (EIT) where ⁇ blocks the color centers from absorbing ⁇ 3, which can enable electrons to be pumped directly from the valence band to vacuum.
• EIT electromagnetically-induced transparency
• the dual wavelength pumping scheme can minimize required optical power per photogenerated electron, which can provide higher quantum efficiency. Heat dissipation per photogenerated electron also can be minimized. A dual wavelength pumping scheme also can provide improve localization of induced current.
• Dual wavelength pumping schemes can be performed concurrently in transmission and reflection mode, which can optimize efficiency.
• Longer photocathode and optics lifetimes can be achieved with longer wavelength illumination, such as those using a dual wavelength pumping scheme.
• Lower emittance and energy spread also can be achieved using longer wavelengths, such as with a dual wavelength pumping scheme.
• FIG. 4 is a flowchart of a method 200.
• a photocathode structure is provided at 201.
• the photocathode structure includes an alkali halide.
• a protective film that includes ruthenium is deposited on an exterior surface of the photocathode structure at 202.
• the deposition can include ion sputtering, magnetron sputtering, or ALD.
• the deposition can provide the desired film density, conformal nature, and amount of pinhole defects.
• FIG. 5 is a flowchart of a method 250.
• a photocathode structure is provided at 251.
• the photocathode structure includes an alkali halide and a protective film disposed on an exterior surface of the photocathode structure.
• the protective film includes ruthenium.
• An electron beam is generated from the photocathode structure at 252 when photons are directed at the photocathode structure. Electron generation may occur at approximately 10 "5 Torr or less. A plasma clean can optionally be performed on the photocathode structure after the electron beam is generated.
• the electron beam produced using the photocathode structure with the protective film can have a higher quantum efficiency than a photocathode structure without the protective film.
• FIG. 6 is a block diagram of an embodiment of a system 300.
• the system 300 includes a wafer inspection tool (which includes the electron column 301) configured to generate images of a wafer 304.
• the wafer inspection tool includes an output acquisition subsystem that includes at least an energy source and a detector.
• the output acquisition subsystem may be an electron beam- based output acquisition subsystem.
• the energy directed to the wafer 304 includes electrons
• the energy detected from the wafer 304 includes electrons.
• the energy source may be an electron beam source.
• the output acquisition subsystem includes electron column 301, which is coupled to computer subsystem 302.
• a chuck (not illustrated) may hold the wafer 304.
• the electron column 301 includes an electron beam source
• the electron beam source 303 may include, for example, an embodiment of the electron source 100 of FIG. 1.
• the one or more elements 305 may include, for example, a gun lens, an anode, a beam limiting aperture, a gate valve, a beam current selection aperture, an objective lens, and a scanning subsystem, all of which may include any such suitable elements known in the art.
• Electrons returned from the wafer 304 e.g., secondary electrons
• One or more elements 306 may include, for example, a scanning subsystem, which may be the same scanning subsystem included in element(s) 305.
• the electron column also may include any other suitable elements known in the art.
• the electron column 301 is shown in FIG. 6 as being configured such that the electrons are directed to the wafer 304 at an oblique angle of incidence and are scattered from the wafer 304 at another oblique angle
• the electron beam may be directed to and scattered from the wafer 304 at any suitable angles.
• the electron beam-based output acquisition subsystem may be configured to use multiple modes to generate images of the wafer 304 (e.g., with different illumination angles, collection angles, etc.). The multiple modes of the electron beam-based output acquisition subsystem may be different in any image generation parameters of the output acquisition subsystem.
• Computer subsystem 302 may be coupled to detector 307 such that the computer subsystem 302 is in electronic communication with the detector 307 or other components of the wafer inspection tool.
• the detector 307 may detect electrons returned from the surface of the wafer 304 thereby forming electron beam images of the wafer 304 with the computer subsystem 302.
• the electron beam images may include any suitable electron beam images.
• the computer subsystem 302 includes a processor 308 and an electronic data storage unit 309.
• the processor 308 may include a microprocessor, a microcontroller, or other devices.
• FIG. 6 is provided herein to generally illustrate a configuration of an electron beam-based output acquisition subsystem that may be used in the embodiments described herein.
• the electron beam-based output acquisition subsystem configuration described herein may be altered to optimize the performance of the output acquisition subsystem as is normally performed when designing a commercial output acquisition system.
• the systems described herein may be implemented using an existing system (e.g., by adding functionality described herein to an existing system).
• the methods described herein may be provided as optional functionality of the system (e.g., in addition to other functionality of the system).
• the system described herein may be designed as a completely new system.
• the computer subsystem 302 may be coupled to the components of the system 300 in any suitable manner (e.g., via one or more transmission media, which may include wired and/or wireless transmission media) such that the processor 308 can receive output.
• the processor 308 may be configured to perform a number of functions using the output.
• the wafer inspection tool can receive instructions or other information from the processor 308.
• the processor 308 and/or the electronic data storage unit 309 optionally may be in electronic communication with another wafer inspection tool, a wafer metrology tool, or a wafer review tool (not illustrated) to receive additional information or send instructions.
• the computer subsystem 302, other system(s), or other subsystem(s) described herein may be part of various systems, including a personal computer system, image computer, mainframe computer system, workstation, network appliance, internet appliance, or other device.
• the subsystem(s) or system(s) may also include any suitable processor known in the art, such as a parallel processor.
• the subsystem(s) or system(s) may include a platform with high speed processing and software, either as a standalone or a networked tool.
• the processor 308 and electronic data storage unit 309 may be disposed in or otherwise part of the system 300 or another device.
• the processor 308 and electronic data storage unit 309 may be part of a standalone control unit or in a centralized quality control unit. Multiple processors 308 or electronic data storage unit 309 may be used.
• the processor 308 may be implemented in practice by any combination of hardware, software, and firmware. Also, its functions as described herein may be performed by one unit, or divided up among different components, each of which may be implemented in turn by any combination of hardware, software, and firmware. Program code or instructions for the processor 308 to implement various methods and functions may be stored in readable storage media, such as a memory in the electronic data storage unit 309 or other memory.
• the system 300 of FIG. 6 is merely one example of a system that can use embodiments of the electron source 100 or embodiments of the method 250. Embodiments of the electron source 100 may be part of a defect review system, an inspection system, a metrology system, or some other type of system. Thus, the embodiments disclosed herein describe some configurations that can be tailored in a number of manners for systems having different capabilities that are more or less suitable for different applications.
• each of the steps of the method may be performed as described herein.
• the methods also may include any other step(s) that can be performed by the processor and/or computer subsystem(s) or system(s) described herein.
• the steps can be performed by one or more computer systems, which may be configured according to any of the embodiments described herein.
• the methods described above may be performed by any of the system embodiments described herein.

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• Analysing Materials By The Use Of Radiation (AREA)
• Testing Or Measuring Of Semiconductors Or The Like (AREA)
• Electron Sources, Ion Sources (AREA)

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