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WO1990009681A1 - Particle detector - Google Patents

Particle detector Download PDF

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Publication number
WO1990009681A1
WO1990009681A1 PCT/NL1990/000015 NL9000015W WO9009681A1 WO 1990009681 A1 WO1990009681 A1 WO 1990009681A1 NL 9000015 W NL9000015 W NL 9000015W WO 9009681 A1 WO9009681 A1 WO 9009681A1
Authority
WO
WIPO (PCT)
Prior art keywords
detector
semiconductor element
transistor
charged particles
layer
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.)
Ceased
Application number
PCT/NL1990/000015
Other languages
French (fr)
Inventor
Riccardo De Salvo
Michael Franks Robinson
John Anthony Cochrane
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.)
Optische Industrie de Oude Delft NV
Original Assignee
Optische Industrie de Oude Delft NV
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
Priority claimed from NL8900313A external-priority patent/NL8900313A/en
Priority claimed from NL8900646A external-priority patent/NL8900646A/en
Application filed by Optische Industrie de Oude Delft NV filed Critical Optische Industrie de Oude Delft NV
Publication of WO1990009681A1 publication Critical patent/WO1990009681A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/28—Measuring radiation intensity with secondary-emission detectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/39—Charge-storage screens
    • H01J29/44—Charge-storage screens exhibiting internal electric effects caused by particle radiation, e.g. bombardment-induced conductivity
    • 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
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/29—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to radiation having very short wavelengths, e.g. X-rays, gamma-rays or corpuscular radiation
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/29—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to radiation having very short wavelengths, e.g. X-rays, gamma-rays or corpuscular radiation
    • H10F30/298—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to radiation having very short wavelengths, e.g. X-rays, gamma-rays or corpuscular radiation the devices being characterised by field-effect operation, e.g. MIS type detectors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/40—Optical elements or arrangements
    • H10F77/496—Luminescent members, e.g. fluorescent sheets
    • 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
    • H01J2237/2441—Semiconductor detectors, e.g. diodes
    • 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
    • H01J2237/2445—Photon detectors for X-rays, light, e.g. photomultipliers
    • 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
    • H01J2237/2446—Position sensitive 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
    • H01J2237/245—Detection characterised by the variable being measured
    • H01J2237/24507—Intensity, dose or other characteristics of particle beams or electromagnetic radiation

Definitions

  • This invention relates to a detector for detecting charged particles moved by an electric field directly or indirectly to said detector, and to an apparatus comprising such a particle detector.
  • a detector for charged particles for example, electrons
  • a detector for charged particles is for example the anode of a photomultiplier tube, or the anode of an image intensifier tube, but also the target plate of a television camera tube or the anode of a klystron.
  • the electrons which reach the anode come indirectly from the cathode, because a number of dynodes are disposed between the cathode and the anode, which by means of secondary emission cause a multplication of the original number of electrons emitted by the cathode.
  • image intensifier tube which may or may not be of the proximity-focus type
  • secondary emission effects it is also possible to use secondary emission effects, and the same can be done in a television camera tube.
  • an image intensifier tube for example, a so-called multi-channel plate can be used.
  • a detector for detecting charged particles of the type described above is characterized in that the detector comprises at least one multi-layer semiconductor element which in operation collects the charged particles and converts them into a corresponding electric output signal.
  • Fig. 1 diagrammatically shows an example of a modified photomultiplier tube comprising a particle detector according to the present invention
  • Fig. 2 illustrates diagrammatically, and by way of example, the construction of a transistor of a detector as shown in Fig. 1;
  • Fig. 3 shows an equivalent diagram of the apparatus shown in Fig.l
  • Fig. 4 shows an equivalent diagram of a variant of an apparatus illustrated in Fig. 1;
  • Fig. 5 shows diagrammatically the construction of a GaAs PIN diode suitable for use in the variant of Fig. 4;
  • Fig. 6 shows a modification of Fig. 3
  • Figs. 7 and 8 show equivalent diagrams of two further variants of the apparatus of Fig. 1;
  • Fig. 9 shows diagrammatically an image intensifier tube of the proximity focus type including a detector according to the present invention.
  • Fig. 1 shows diagrammatically an example of a modified photomultiplier tube including a detector according to the present invention with a transistor.
  • the modified photomultiplier tube comprises a housing 1 with an input window 2.
  • input window 2 is provided on the inside with a photocathode 3 which in response to incident light 4 emits electrons 5.
  • the electron detector 8 comprises at least one multi-layer semiconductor element which, in the example shown, is a transistor.
  • the transistor may, for example, be a silicon npn transistor or a GaAs transistor.
  • the tube When such a bipolar transistor is used, the tube is given such an efficiency that the conventional dynodes may be omitted. Accordingly, the tube shown could also be regarded as a modified image intensifier tube. Owing to the use of a transistor as the electron detector, a tube with a fast response and a relatively high gain is obtained, while in addition, owing to the absence of dynodes, a compact construction is possible. Such tubes are very suitable for use as photodetectors .
  • Fig. 3 shows an equivalent electric diagram of the apparatus shown in Fig. 1.
  • the electrons 5 emitted by photocathode 3 under the influence of incident light 4 are moved by a suitable electric field to electron detector 8.
  • the electron detector is formed as an npn transistor, for example, a silicon transistor or a GaAs transistor.
  • the electrons 5 penetrate through emitter 9 and generate electron-hole pairs in base 10. This is what activates the transistor.
  • each electron-hole pair is formed in the semiconductor material of the base.
  • an incident electron may have an energy of a large number of times 3.6 eV, for example, 20 keV, each electron generates a large number of electron-hole pairs.
  • the action of a transistor produces an extra gain, so that a very high total gain can be obtained.
  • the transistor is adjusted in the conventional manner by means of a collector voltage Vc.
  • the emitter is grounded through an emitter impedance 12.
  • the output signal appears across the emitter impedance and, if desired, may be intensified further within or without the tube by means of a suitable intensifier.
  • Fig. 2 shows, by way of example, the construction of a suitable transistor.
  • a collector formed on a substrate 13, in known manner, are a collector, a base and an emitter.
  • Emitter 9 may consist of a relatively thin layer of n-type material.
  • Base 10 may consist of a thicker layer of p-type material, and collector 11, again, of a relatively thick layer of n-type material.
  • the substrate 13 may consist of p-type material.
  • the emitter 9 may consist of a thin layer of GaAlAs n-type material.
  • the base may consist of a thicker layer of GaAs p-type material, and collector 11, again, of a relatively thick layer of GaAs n- type material or GaAlAs n-type material .
  • the substrate may in this case consist of GaAs p-type material.
  • a contact layer of, for example, n-type material may be provided on emitter 9 and between collector 11 and substrate 13.
  • the contact layer may consist of GaAs material.
  • Such contact layers are indicated schematically at 14 and 15 in Fig. 2. Layers 14 and 9 should permit the passage of incident electrons. and are therefore made relatively thin.
  • pnp transistors may be used for detecting positively charged particles, such as protons or positive ions.
  • the detection method described is also suitable for detecting negatively charged particles other than electrons.
  • diodes may be used, if so desired.
  • Fig. 4 shows a variant of Fig. 3, using a GaAs PIN diode 20, reversely biased , as the electron detector.
  • the intensification realised in the PIN diode is exclusively the result of the fact that an incident electron leads to a large number of electron-hole pairs in the diode.
  • the output signal of the diode may be intensified further, if so desired, by means of one or ' more suitable intensifiers 21 within and/or without the tube.
  • Fig. 5 illustrates, by way of example, the construction of a suitable PIN diode.
  • the diode comprises a layer of p-type GaAs material 22 which forms the cathode of the diode.
  • a layer 23 of non-doped GaAs material forms the junction area between the cathode layer 22 and an anode layer 24 consisting of n- type GaAs material.
  • the incident electrons pass layer 22, lose their energy in the junction area and there form electron-hole pairs.
  • a thin contact layer 25 of p-type GaAs material may be provided on layer 22.
  • Fig. 6 shows another variant of Fig. 3, in which an extra intensifying step in the form of a transistor 26 is used in the tube. As in Fig. 3, the adjusting resistors are not shown.
  • Transistor 26 is preferably of the same type as the semiconductor element 8. When the semiconductor element 8 is a GaAs transistor, the transistor 26 is therefore preferably also a GaAs transistor.
  • the multi-layer semiconductor element may be provided with a layer of material which converts the incident electrons into light having a suitable wavelength.
  • the light is again converted into electron-hole pairs by the semiconductor element, which in that case functions as a photosensitive element, and as a result of which an electric output signal is again formed in the manner described above, which signal may or may not be intensified further.
  • a phosphor screen providing light of a suitable wavelength for example, a red emitting phosphor screen of the P22 type, which may be provided direct on the semiconductor element .
  • Fig. 7 shows an equivalent electric diagram of such a configuration.
  • a phosphor screen 27 collects the electrons 5 emitted by cathode 3 and emits (red) light.
  • the light passes the emitter of the semiconductor element, which in the example shown is a GaAs transistor, and is absorbed and converted into electron-hole pairs in the transistor base.
  • the emitter may consist, for example, of n-type GaAlAs material permitting the passage of red light.
  • the base can then consist of p-type GaAs material which is not transparent to red light, and the collector of n-type GaAs material.
  • the resulting output signal can be intensified further, if so desired.
  • a GaAs diode may be used instead of a transistor.
  • One advantage of the use of a phosphor screen or other screen luminescing under the influence of incident particles is that the screen may provide an extra intensification.
  • the electrons emitted are collected by means of a conductive collector plate 30 connected to the control electrode of a transistor element, such as a field effect transistor 31.
  • the intensification is in this case limited to the intensification provided by the transistor element.
  • a field effect transistor like a bipolar transistor, may be used to collect charged particles directly, which are again converted into electron-hole pairs and provide an electric output signal .
  • the particle detector may be constructed as a matrix of detector elements of one of the types described. The electric output signals of the various elements then jointly represent a two-dimensional picture.
  • Fig.9 shows, by way of example, and schematically, an image intensifier tube of the proximity-focus type, comprising a housing 40 with a cathode window 41 carrying on the inside a photosensitive or, more generally, radiation-sensitive cathode 42. Disposed in opposition to the cathode, there is further provided an anode which comprises a matrix 43 of multi-layer semiconductor elements according to the present invention. Connecting wires for the matrix 43 are shown diagrammatically at 44. Shown diagrammatically at 45 is further an integrated control circuit for reading the signals provided by the matrix.
  • a multi-channel plate may be interposed between the cathode and the detector, as shown at 46.
  • a GaAs cathode in combination with a GaAs semiconductor element for example, a GaAs transistor as described above, may be used with advantage, so that the cathode material and the material of the electron detector cannot adversely affect each other.
  • a GaAs transistor as described above
  • the electric output signals provided by a detector can be intensified and/or processed further in various ways.
  • the various layers of the transistors may be sub-divided into thinner layers, doped in various ways, by means of techniques known for the purpose.
  • integrated reading electronics may be used on the same chip, if so desired, as is also used, for example, in CCD arrays.
  • a detector according to the invention could be used in analysis techniques in vacuo, such as in scanning electron microscopes, in which a substrate to be investigated is bombarded with electrons from an electron gun, and electrons emitted by the substrate have to be detected.
  • the electrons could reach the base from the collector side.
  • transistors described instead of the types of transistors described, other types of transistors may be used. Instead of a PIN diode, as shown in Fig. 4, a different type of diode could be used.
  • PIN diode as shown in Fig. 4
  • suitable multi-layer semiconductor elements are bipolar junction transistors made of silicon and heterojunction transistors made of InP/GalnAsP. Such modifications are considered to fall within the scope of the present invention.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
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  • Chemical & Material Sciences (AREA)
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  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)

Abstract

A detector for detecting charged particles moved by an electric field directly or indirectly to said detector. The detector comprises a multi-layer semiconductor element which in operation collects the charged particles and converts them into a corresponding electric signal. The semiconductor element may be a matrix.

Description

Title: Particle detector.
This invention relates to a detector for detecting charged particles moved by an electric field directly or indirectly to said detector, and to an apparatus comprising such a particle detector. A detector for charged particles, for example, electrons, is for example the anode of a photomultiplier tube, or the anode of an image intensifier tube, but also the target plate of a television camera tube or the anode of a klystron. In the case of a photomultiplier tube, the electrons which reach the anode come indirectly from the cathode, because a number of dynodes are disposed between the cathode and the anode, which by means of secondary emission cause a multplication of the original number of electrons emitted by the cathode. In sn image intensifier tube, which may or may not be of the proximity-focus type, it is also possible to use secondary emission effects, and the same can be done in a television camera tube. Furthermore, in an image intensifier tube, for example, a so-called multi-channel plate can be used.
It is an object of the present invention to provide an improved detector for detecting charged particles with a relatively high efficiency and a fast response, which is capable of detecting incident charged particles and provide a corresponding electric output signal. For this purpose, a detector for detecting charged particles of the type described above is characterized in that the detector comprises at least one multi-layer semiconductor element which in operation collects the charged particles and converts them into a corresponding electric output signal.
Some embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings. In said drawings,
Fig. 1 diagrammatically shows an example of a modified photomultiplier tube comprising a particle detector according to the present invention;
Fig. 2 illustrates diagrammatically, and by way of example, the construction of a transistor of a detector as shown in Fig. 1;
Fig. 3 shows an equivalent diagram of the apparatus shown in Fig.l;
Fig. 4 shows an equivalent diagram of a variant of an apparatus illustrated in Fig. 1;
Fig. 5 shows diagrammatically the construction of a GaAs PIN diode suitable for use in the variant of Fig. 4;
Fig. 6 shows a modification of Fig. 3;
Figs. 7 and 8 show equivalent diagrams of two further variants of the apparatus of Fig. 1; and
Fig. 9 shows diagrammatically an image intensifier tube of the proximity focus type including a detector according to the present invention.
Fig. 1 shows diagrammatically an example of a modified photomultiplier tube including a detector according to the present invention with a transistor. The modified photomultiplier tube comprises a housing 1 with an input window 2. In operation, a vacuum prevails in the housing. In the conventional manner, input window 2 is provided on the inside with a photocathode 3 which in response to incident light 4 emits electrons 5. By means of focussing and acceleration electrodes 6,7, the emitted electrons are targeted onto a detector 8 which in this example is indeed arranged to detect electrons. According to the invention, the electron detector 8 comprises at least one multi-layer semiconductor element which, in the example shown, is a transistor. The transistor may, for example, be a silicon npn transistor or a GaAs transistor. When such a bipolar transistor is used, the tube is given such an efficiency that the conventional dynodes may be omitted. Accordingly, the tube shown could also be regarded as a modified image intensifier tube. Owing to the use of a transistor as the electron detector, a tube with a fast response and a relatively high gain is obtained, while in addition, owing to the absence of dynodes, a compact construction is possible. Such tubes are very suitable for use as photodetectors .
Fig. 3 shows an equivalent electric diagram of the apparatus shown in Fig. 1. The electrons 5 emitted by photocathode 3 under the influence of incident light 4 are moved by a suitable electric field to electron detector 8. The electron detector is formed as an npn transistor, for example, a silicon transistor or a GaAs transistor. The electrons 5 penetrate through emitter 9 and generate electron-hole pairs in base 10. This is what activates the transistor.
For each 3.6 eV of energy, approximately ,of an incident electron, approximately one electron-hole pair is formed in the semiconductor material of the base. As an incident electron may have an energy of a large number of times 3.6 eV, for example, 20 keV, each electron generates a large number of electron-hole pairs. In addition, the action of a transistor produces an extra gain, so that a very high total gain can be obtained.
The transistor is adjusted in the conventional manner by means of a collector voltage Vc. The emitter is grounded through an emitter impedance 12. The output signal appears across the emitter impedance and, if desired, may be intensified further within or without the tube by means of a suitable intensifier.
Fig. 2 shows, by way of example, the construction of a suitable transistor. Formed on a substrate 13, in known manner, are a collector, a base and an emitter. Emitter 9 may consist of a relatively thin layer of n-type material. Base 10 may consist of a thicker layer of p-type material, and collector 11, again, of a relatively thick layer of n-type material. The substrate 13 may consist of p-type material.
When a GaAs transistor is used, the emitter 9 may consist of a thin layer of GaAlAs n-type material. The base may consist of a thicker layer of GaAs p-type material, and collector 11, again, of a relatively thick layer of GaAs n- type material or GaAlAs n-type material . The substrate may in this case consist of GaAs p-type material.
Additionally, a contact layer of, for example, n-type material may be provided on emitter 9 and between collector 11 and substrate 13. In the case of a GaAs transistor, the contact layer may consist of GaAs material. Such contact layers are indicated schematically at 14 and 15 in Fig. 2. Layers 14 and 9 should permit the passage of incident electrons. and are therefore made relatively thin. It is noted that pnp transistors may be used for detecting positively charged particles, such as protons or positive ions.
Furthermore, the detection method described is also suitable for detecting negatively charged particles other than electrons.
Furthermore, in all cases, diodes may be used, if so desired.
Fig. 4 shows a variant of Fig. 3, using a GaAs PIN diode 20, reversely biased , as the electron detector. The intensification realised in the PIN diode is exclusively the result of the fact that an incident electron leads to a large number of electron-hole pairs in the diode. The output signal of the diode may be intensified further, if so desired, by means of one or'more suitable intensifiers 21 within and/or without the tube.
Fig. 5 illustrates, by way of example, the construction of a suitable PIN diode. The diode comprises a layer of p-type GaAs material 22 which forms the cathode of the diode. A layer 23 of non-doped GaAs material forms the junction area between the cathode layer 22 and an anode layer 24 consisting of n- type GaAs material. The incident electrons pass layer 22, lose their energy in the junction area and there form electron-hole pairs.
A thin contact layer 25 of p-type GaAs material may be provided on layer 22.
Fig. 6 shows another variant of Fig. 3, in which an extra intensifying step in the form of a transistor 26 is used in the tube. As in Fig. 3, the adjusting resistors are not shown. Transistor 26 is preferably of the same type as the semiconductor element 8. When the semiconductor element 8 is a GaAs transistor, the transistor 26 is therefore preferably also a GaAs transistor.
Alternatively, the multi-layer semiconductor element may be provided with a layer of material which converts the incident electrons into light having a suitable wavelength. The light is again converted into electron-hole pairs by the semiconductor element, which in that case functions as a photosensitive element, and as a result of which an electric output signal is again formed in the manner described above, which signal may or may not be intensified further.
Advantageously, use can be made of a phosphor screen providing light of a suitable wavelength, for example, a red emitting phosphor screen of the P22 type, which may be provided direct on the semiconductor element . Fig. 7 shows an equivalent electric diagram of such a configuration. A phosphor screen 27 collects the electrons 5 emitted by cathode 3 and emits (red) light. The light passes the emitter of the semiconductor element, which in the example shown is a GaAs transistor, and is absorbed and converted into electron-hole pairs in the transistor base. The emitter may consist, for example, of n-type GaAlAs material permitting the passage of red light. The base can then consist of p-type GaAs material which is not transparent to red light, and the collector of n-type GaAs material. The resulting output signal can be intensified further, if so desired. Furthermore, as described before, a GaAs diode may be used instead of a transistor.
One advantage of the use of a phosphor screen or other screen luminescing under the influence of incident particles is that the screen may provide an extra intensification.
According to another variant, shown schematically in Fig. 8, the electrons emitted are collected by means of a conductive collector plate 30 connected to the control electrode of a transistor element, such as a field effect transistor 31. The intensification is in this case limited to the intensification provided by the transistor element.
A field effect transistor (unipolar transistor) , like a bipolar transistor, may be used to collect charged particles directly, which are again converted into electron-hole pairs and provide an electric output signal . In all cases described, the particle detector may be constructed as a matrix of detector elements of one of the types described. The electric output signals of the various elements then jointly represent a two-dimensional picture. By means of such a matrix of transistors, a camera tube or a
(proximity-focus) image intensifier of high gain can be made in a simple manner.
Fig.9 shows, by way of example, and schematically, an image intensifier tube of the proximity-focus type, comprising a housing 40 with a cathode window 41 carrying on the inside a photosensitive or, more generally, radiation-sensitive cathode 42. Disposed in opposition to the cathode, there is further provided an anode which comprises a matrix 43 of multi-layer semiconductor elements according to the present invention. Connecting wires for the matrix 43 are shown diagrammatically at 44. Shown diagrammatically at 45 is further an integrated control circuit for reading the signals provided by the matrix.
A multi-channel plate may be interposed between the cathode and the detector, as shown at 46.
When the particles to be detected consist of electrons emitted by a photocathode, a GaAs cathode in combination with a GaAs semiconductor element, for example, a GaAs transistor as described above, may be used with advantage, so that the cathode material and the material of the electron detector cannot adversely affect each other. It is noted that, after reading the above, various modifications will readily occur to those skilled in the art. Thus the electric output signals provided by a detector can be intensified and/or processed further in various ways. Also, the various layers of the transistors may be sub-divided into thinner layers, doped in various ways, by means of techniques known for the purpose.
When a matrix of transistors is used, integrated reading electronics may be used on the same chip, if so desired, as is also used, for example, in CCD arrays.
It is further noted that a detector according to the invention could be used in analysis techniques in vacuo, such as in scanning electron microscopes, in which a substrate to be investigated is bombarded with electrons from an electron gun, and electrons emitted by the substrate have to be detected.
Furthermore, the electrons could reach the base from the collector side.
Instead of the types of transistors described, other types of transistors may be used. Instead of a PIN diode, as shown in Fig. 4, a different type of diode could be used. Other examples of suitable multi-layer semiconductor elements are bipolar junction transistors made of silicon and heterojunction transistors made of InP/GalnAsP. Such modifications are considered to fall within the scope of the present invention.

Claims

1. A detector for detecting charged particles moved by an electric field directly or indirectly to said detector, characterized in that the detector comprises at least one multi-layer semiconductor element which in operation collects the charged particles and converts them into a corresponding electric output signal.
2. A detector as claimed in claim 1, characterized in that said at least one semiconductor element comprises at least one bipolar transistor.
3. A detector as claimed in claim 1, characterized in that said at least one semiconductor element comprises at least one unipolar transistor.
4. A detector as claimed in any of the preceding claims, characterized in that the detector comprises a screen disposed in front of said at least one semiconductor element, said screen comprising a material emitting light in response to incident charged particles, and that said at least one semiconductor element is capable of providing an electric output signal under the influence of light .
5. A detector as claimed in claim 4, characterized in that said screen is provided direct on said at least one semiconductor element .
6. A detector as claimed in claim 3 or 4, characterized in that said screen comprises a layer of red emitting phosphor.
7. A detector as claimed in claim 1, characterized in that said at least one semiconductor element is connected to a plate of a material which is an electric conductor, which plate, in operation, collects incident charged particles, and is electrically connected to the control electrode of a transistor.
8. A detector as claimed in claim 7, characterized in that said transistor is a field effect transistor.
9. A detector as claimed in any of the preceding claims, characterized in that the detector comprises a matrix of semiconductor elements .
10. A detector as claimed in claim 9, characterized in that the matrix of semiconductor elements is at least partly integrated with reading electronics on one chip.
11. A detector as cla.imed in any of the preceding claims, characterized in that said at least one multi-layer semiconductor element comprises a GaAs semiconductor element .
12. A detector as claimed in claim 11, characterized in that said GaAs semiconductor element comprises at least one layer of GaAlAs material.
13. A detector as claimed in claim 1, characterized in that said at least one multi-layer semiconductor element comprises a GaAs diode biased in the reverse direction.
14. Apparatus comprising at least one means which in operation emits charged particles, said means being disposed in a closed housing, characterized by a particle detector as claimed in any of claims 1-9 for collecting charged particles coming directly or indirectly from said emitting means.
15. Apparatus as claimed in claim 14, characterized by comprising a proximity-focus image intensifier tube comprising an anode screen which is an electron-sensitive particle detector formed as a matrix, as claimed in claim 9.
16. Apparatus as claimed in claim 15, characterized by a multi-channel plate disposed between the particles emitting means and the detector.
17. An analytic device for material analysis in vacuo, such as a scanning electron microscope, characterized by a detector as claimed in any of claims 1-13.
PCT/NL1990/000015 1989-02-08 1990-02-08 Particle detector Ceased WO1990009681A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
NL8900313A NL8900313A (en) 1989-02-08 1989-02-08 ELECTRON DETECTOR.
NL8900313 1989-02-08
NL8900646 1989-03-16
NL8900646A NL8900646A (en) 1989-03-16 1989-03-16 Particle detector e.g. for electron scanning microscope - has multilayer semiconductor element for collecting charged particles and producing electric signal proportional to particle density

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WO1990009681A1 true WO1990009681A1 (en) 1990-08-23

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EP0602982A1 (en) * 1992-12-17 1994-06-22 Intevac, Inc. Focused electron-bombarded detector
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TWI804837B (en) * 2020-04-10 2023-06-11 荷蘭商Ａｓｍｌ荷蘭公司 Systems and methods for signal electron detection
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