CN118315248A - An electron source structure capable of regulating supply current - Google Patents

Abstract

The present invention relates to the technical field of vacuum micro-nano electron sources, and more specifically, to an electron source structure capable of regulating supply current, comprising a substrate, a first insulating layer, a first electrode, a second insulating layer, and a second electrode, wherein the substrate is a P-type doped semiconductor, the first electrode and the second electrode are provided with microholes with spatial overlapping areas, an emitter is provided on the substrate, and the emitter is accommodated in the microhole; the first electrode potential is used to regulate the type, concentration and depletion layer width of the carriers on the substrate surface, thereby regulating the electron current that the substrate can supply to the emitter; the second electrode potential is used to induce electrons to tunnel from the top of the emitter into a vacuum; in the structure, the first electrode and the second electrode are vertically constructed, the integration is high, the structure is simple, the process is mature, the first electrode can shield the effect of the second electrode on the carriers on the substrate surface, the stability of the first electrode's ability to regulate the supply current is improved, and a stable emission current that can be regulated at a low voltage is provided.

Description

An electron source structure capable of regulating supply current

Technical Field

The present invention relates to the technical field of vacuum micro-nano electron sources, and more specifically, to an electron source structure capable of regulating supply current.

Background technique

Field emission electron sources have the advantages of small size, low power consumption, fast response speed, high current density, and concentrated electron energy. They have broad application prospects in national defense, aviation, industrial production, and scientific research. Many vacuum electronics application fields have higher requirements for the stability and controllability of electron beams. For example, microthrusters for small spacecraft require high thrust control accuracy and need to be equipped with charge neutralizers with stable and continuously adjustable outgoing electron beams. Field emission electron sources prepared on P-type semiconductor substrates have saturated emission characteristics and high emission current stability, and can be used as high-performance electron sources in the above fields.

The commonly used field emission electron source based on a P-type semiconductor substrate controls the electron supply and tunneling emission simultaneously by a single electrode. When the electrode is placed at a positive potential relative to the substrate, the electrons at the top of the emitter are induced to tunnel into the vacuum. At the same time, the potential acts on the metal end of the metal-insulator-semiconductor (MIS) structure composed of the electrode-insulating layer-P-type semiconductor substrate. Since the voltage required to induce electron emission is generally much higher than the threshold voltage of the MIS structure, an electron inversion layer and a carrier depletion layer are formed on the surface of the substrate. The heat-generated electrons in the depletion layer are extracted to the surface inversion layer by the built-in electric field, and then diffused and transported to the emitter to supply field emission. The heat-generated current is determined by the area and thickness of the depletion layer, and the area of the depletion layer is approximately equal to the area of the control electrode and is a constant. Due to the shielding effect of the electrons in the surface inversion layer, the electric field penetrating into the semiconductor surface changes little with the potential of the control electrode, so the thickness of the depletion layer is basically unchanged, and the maximum current that the substrate can supply to the emitter is basically a constant. When the electrode potential is low, the emission current is less than the maximum current that the substrate can supply to the emitter. The emission current is determined by the external electric field and is greatly affected by surface potential fluctuations caused by factors such as gas adsorption/desorption and atomic migration on the electron emission surface. The emission current stability is poor. When the electrode potential is high, the emission current is determined by the maximum current that the substrate can supply to the emitter. The device enters the saturated working area. The emission current is highly stable but the current intensity cannot be adjusted.

The key to regulating the emission current is to regulate the current supplied from the substrate to the emitter. A common method for regulating the supply current in the field is to integrate the emitter in series with the conductive channel of a planar transistor (such as a metal-oxide-semiconductor field effect transistor, MOSFET, or a thin film transistor, TFT), and to regulate the field emission supply current by regulating the transistor channel current. However, in this scheme, the planar transistor occupies a certain substrate area, which reduces the integration of the electron source; the high voltage of the electron extraction electrode acts on the emitter and the transistor drain surface at the same time, which easily leads to reverse breakdown of the PN junction formed by the transistor drain-body substrate, and failure of the transistor gate control current capability; and the preparation of the integrated transistor includes multiple pattern definition and doping processes, which require cumbersome steps. Therefore, this method has technical problems such as low electron source integration, cumbersome preparation process of the integrated transistor, and unstable transistor gate control current capability.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, such as low integration of electron sources, unstable transistor gate current capability and complicated preparation process of integrated transistors, and to provide an electron source structure with adjustable supply current.

In order to solve the above technical problems, the technical solution adopted by the present invention is:

An electron source structure with adjustable supply current, characterized in that: it includes a substrate, a first insulating layer, a first electrode, a second insulating layer and a second electrode stacked in sequence from bottom to top, the first electrode and the second electrode are provided with micropores with spatial overlapping areas, an emitter is provided on the substrate, the emitter penetrates the first insulating layer and the second insulating layer and is accommodated in the micropores; the shortest distance from the first electrode to the top of the emitter is greater than the shortest distance from the second electrode to the top of the emitter; the substrate is a P-type doped semiconductor material; the first electrode can adjust the carrier type, concentration and depletion layer width on the surface of the substrate by potential, thereby adjusting the electron current supplied by the substrate to the emitter; the second electrode is placed at a positive potential relative to the substrate, inducing the electrons supplied by the substrate to the emitter to tunnel from the top surface of the emitter into a vacuum.

The structure principle of an electron source capable of regulating supply current of the present invention is as follows:

The first electrode-first insulating layer-P-type semiconductor substrate constitutes a metal-insulator-semiconductor (MIS) structure. Placing the first electrode at different potentials can change the working state of the above-mentioned MIS structure, thereby regulating the maximum electron current that the substrate can supply to the emitter. The second electrode is placed at a positive potential relative to the substrate, and the electrons supplied by the substrate to the emitter are extracted into a vacuum, so that the device enters a stable working state with saturated emission current. Specifically, when the first electrode potential is lower than the flat band voltage of the MIS structure, the substrate surface is in a hole accumulation state, and the electron current that the substrate can supply to the emitter is extremely small, and the electron source is controlled to be turned off. When the first electrode potential is raised to a level higher than the flat band voltage, the holes on the substrate surface are depleted, but the depletion layer width is small, the heat generated electrons provided are small, and the surface electron concentration is small. The electron current supplied by the substrate to the emitter is small, and the saturated emission current is small. Continue to raise the first electrode potential, the depletion layer will be widened, the surface electron concentration will increase, the electron current supplied by the substrate to the emitter will increase, and the saturated emission current will increase accordingly. Further increasing the potential of the first electrode to a voltage greater than the threshold voltage of the MIS structure, the substrate surface reaches a strong electron inversion state, effectively shielding the external electric field, the depletion layer width hardly changes with the change of the first electrode potential, and the supplied thermal generation current reaches the maximum value. Therefore, in the working range between the flat band voltage and the threshold voltage of the MIS structure, the change of the first electrode potential can lead to a change in the current supplied by the substrate to the emitter. The first electrode and the second electrode work together to provide a stable emission current that can be controlled at a low voltage.

The present invention discloses an electron source structure with adjustable supply current, wherein the first electrode can effectively shield the influence of the second electrode voltage on the surface working state of the MIS structure, thereby improving the stability of the first electrode's ability to regulate supply current; meanwhile, the distance from the second electrode to the top of the emitter is closer than the distance from the first electrode to the top of the emitter, and the electric field at the top of the emitter is mainly controlled by the second electrode voltage, so the first electrode and the second electrode can respectively control the supply current and electron emission, and coupling interference is relatively weak; the first electrode and the second electrode are vertically integrated in space, and the occupied substrate areas overlap, thereby ensuring that the device has a high degree of integration; the structure has a simple preparation process, and can be prepared by a mature "self-alignment" process method, thereby effectively solving the technical problems of low electron source integration, complicated preparation process of integrated transistors, and unstable transistor gate control current capability in the existing integrated planar transistor field emission regulation technology.

Furthermore, each of the first electrode and the second electrode is provided with only one, and the micropores are provided in a plurality on the first electrode and the second electrode, respectively. By providing a plurality of micropore emitters, the total current carrying capacity is improved. A single first electrode regulates the supply current of multiple emitters, and low-voltage regulation of a large emission current can be achieved, which can be applied to ultra-high vacuum ionization gauges, microthruster charge neutralizers, mass spectrometers and other fields.

Furthermore, the first electrodes are provided in a plurality of discrete portions, the second electrode is provided in a single portion, and the plurality of first electrodes are provided with a single or a plurality of microholes. The supply current of a plurality of emitters is regulated independently or in groups by the plurality of discrete first electrodes, and electrons are extracted from all emitters into a vacuum by a single second electrode, which can be applied to frontier fields such as parallel electron beam lithography and parallel electron beam microscopic detection.

Furthermore, the sum of the thicknesses of the first insulating layer and the first electrode is less than half of the emitter height, and the sum of the thicknesses of the first insulating layer, the first electrode, the second insulating layer and the second electrode is greater than 60% of the emitter height and less than 150% of the emitter height.

Furthermore, the material constituting the substrate is one or more of P-type doped elemental silicon, elemental germanium, gallium arsenide, gallium nitride, silicon carbide, indium phosphide, gallium oxide, zinc oxide, and diamond.

Furthermore, the P-type doping concentration of the substrate is higher than the intrinsic carrier concentration of the material of the substrate at room temperature and is lower than 10 ²⁰ cm ^-3 .

Furthermore, the emitter is a field electron emitter, and its structure is one of a micro-cone, a nanowire, a nanotube, a micro-pyramid, and an upright two-dimensional film.

Furthermore, the material of the first insulating layer and the second insulating layer is one or more of silicon dioxide, hafnium oxide, silicon nitride, and aluminum oxide.

Furthermore, the material of the first electrode and the second electrode is an alloy consisting of two or more materials selected from the group consisting of gold, silver, aluminum, chromium, molybdenum, nickel, niobium, tantalum, graphite, heavily doped polysilicon, and lanthanum hexaboride.

The present invention also provides an application of an electron source structure capable of regulating supply current in a vacuum electronic device.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention discloses an electron source structure with adjustable supply current, wherein two electrodes are vertically integrated on a P-type doped semiconductor substrate, wherein the potential of the first electrode controls the type, concentration and depletion layer width of carriers on the substrate surface, thereby adjusting the electron current that the substrate can supply to the emitter; the second electrode is placed at a positive potential relative to the substrate, thereby inducing the electrons supplied by the substrate to the emitter to tunnel from the top surface of the emitter into a vacuum, thereby saturating the emission current; in this structure, the first electrode and the second electrode are vertically constructed, with high integration, simple structure and mature process; the first electrode can shield the effect of the second electrode on the carriers on the substrate surface, thereby improving the stability of the first electrode's ability to regulate the supply current, and providing a stable emission current that can be regulated at a low voltage, thereby effectively solving the technical problems of low electron source integration, complicated integrated transistor preparation process and unstable transistor gate control current capability in the existing integrated transistor field emission current regulation technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of an electron source structure with adjustable supply current according to Embodiment 1;

FIG2 is a schematic diagram of the structure of an electron source structure capable of simultaneously regulating the supply current of multiple emitters according to Embodiment 2;

FIG3 is a schematic diagram of the structure of an electron source structure capable of regulating the supply current of multiple emitters one by one or in groups according to the third embodiment;

In the accompanying drawings: 1. substrate; 2. first insulating layer; 3. first electrode; 4. second insulating layer; 5. second electrode; 6. micropore; 7. emitter.

Detailed ways

The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the accompanying drawings may be omitted.

The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

Embodiment 1

FIG. 1 shows a first embodiment of an electron source structure with controllable supply current according to the present invention.

An electron source structure capable of regulating supply current comprises a substrate 1, a first insulating layer 2 (silicon dioxide with a thickness of 100 nm in this embodiment), a first electrode 3 (chromium with a thickness of 100 nm in this embodiment), a second insulating layer 4 (silicon dioxide with a thickness of 1200 nm in this embodiment) and a second electrode 5 (chromium with a thickness of 100 nm in this embodiment) which are stacked in sequence from bottom to top, the first electrode 3 and the second electrode 5 are provided with micropores 6 (overlapping circular holes with a diameter of 2000 nm in this embodiment) with spatially overlapping regions, an emitter 7 (silicon micro-cone with a height of 1500 nm in this embodiment) is provided on the substrate 1, the emitter 7 penetrates the first insulating layer 2 and the second insulating layer 4 and is accommodated in the micropore 6; the shortest distance from the first electrode 3 to the top of the emitter 7 is greater than the shortest distance from the second electrode 5 to the top of the emitter 7; the substrate 1 is a P-type doped semiconductor material (boron-doped silicon with a doping concentration of 10 ¹⁵ cm ^-3 in this embodiment). ); the first electrode 3 can regulate the type, concentration and depletion layer width of the carrier on the surface of the substrate 1 by potential, thereby regulating the electron current supplied by the substrate 1 to the emitter 7; the second electrode 5 is placed at a positive potential relative to the substrate 1, inducing the electrons supplied by the substrate 1 to the emitter 7 to tunnel from the top surface of the emitter 7 into the vacuum.

In this embodiment, as shown in FIG. 1 , the first electrode 3-the first insulating layer 2-the P-type semiconductor substrate 1 constitutes a metal-insulator-semiconductor (MIS) structure. In this embodiment, an ideal MIS structure device physical model is used to calculate its working state, and the influence of fixed charges in the insulator on the device is ignored. In this embodiment, the emitter 7 is grounded, the work function of the metal (chromium) is 4.5 V, the Fermi potential of the substrate 1 (P-type silicon) = thermoelectric potential × ln (doping concentration/intrinsic carrier concentration) = 0.347 V, the work function of the substrate 1 = silicon electron affinity + 0.5 × bandgap width + Fermi potential = 4.96 V, and the flat band voltage of the MIS structure = the work function difference between the metal and the semiconductor = -0.46 V; when the potential of the first electrode 3 is equal to -0.46 V, the substrate There is no electric field in the substrate 1. When the potential of the first electrode 3 is lower than -0.46V, there is an electric field pointing from the body to the surface in the substrate 1, holes accumulate on the surface of the substrate 1, and the electron current supplied by the substrate 1 to the emitter 7 is extremely small, and the electron source is in the off state; when the potential of the first electrode 3 is increased to higher than -0.46V, there is an electric field pointing from the surface to the body in the substrate 1, the holes on the surface of the substrate 1 are depleted, forming a carrier depletion layer, and the heat-generated electrons in the depletion layer are transported to the emitter 7 to supply field emission; as the potential of the first electrode 3 increases, an electronic inversion layer is formed on the surface of the substrate 1. When the surface electron concentration increases to be equal to the hole concentration in the body of the substrate 1, the surface density of the stored charge in the depletion region is (4×silicon dielectric constant×Fermi potential×electron charge×doping concentration)^0.5＝1.38× ^10-8 C/ ^cm2 . The threshold voltage of the MIS structure = depletion layer storage charge surface density × insulating layer thickness / insulating layer dielectric constant + flat band voltage + 2 × Fermi potential = 0.24V; when the potential of the first electrode 3 is higher than 0.24V, due to the shielding effect of the inversion layer electrons, the depletion layer width reaches a maximum value, and the heat generation current supplied by the substrate 1 to the emitter 7 reaches a maximum value; when the potential of the first electrode 3 is higher than -0.46V and lower than 0.24V, the depletion layer width changes with the voltage electrode potential, and then the heat generation current supplied by the substrate 1 to the emitter 7 is regulated by the potential of the first electrode 3; the second electrode 5 is placed at a sufficiently high potential (>30V) to induce the electrons supplied by the substrate 1 to the emitter 7 to tunnel into the vacuum, and the device enters a current saturated working state, and the first electrode 3 and the second electrode 5 work together to provide an adjustable stable emission current.

In the above-mentioned MIS structure, due to the shielding effect of the first electrode 3, the carrier type, concentration and depletion zone width on the surface of the substrate 1 will not be affected by the potential of the second electrode 5; the shortest distance from the first electrode 3 to the top of the emitter 7 (~1640nm) is greater than the shortest distance from the second electrode 5 to the top of the emitter 7 (~1000nm), and the potential of the first electrode 3 is much lower than the potential of the second electrode 5, so the local electric field strength at the top of the emitter 7 is mainly regulated by the potential of the second electrode 5; the first electrode 3 and the second electrode 5 respectively regulate the current supplied by the substrate 1 to the emitter 7 and the electron tunneling emission at the top of the emitter 7, and the coupling interference is weak, ensuring the reliability of the electron source current regulation mechanism.

Embodiment 2

FIG. 2 shows a second embodiment of an electron source structure with controllable supply current according to the present invention.

This embodiment is similar to the first embodiment, except that only a single first electrode 3 and a single second electrode 5 are provided, and a plurality of micropores 6 are provided on the first electrode 3 and the second electrode 5 .

In this embodiment, as shown in FIG. 2 , by providing a plurality of microholes 6 and utilizing a plurality of emitters 7 to improve the total current carrying capacity, a single first electrode 3 regulates the supply current of a plurality of emitters 7, thereby achieving regulation of a large emission current, and can be applied to ultra-high vacuum ionization gauges, microthruster charge neutralizers, mass spectrometers and other fields.

Embodiment 3

FIG. 3 shows a third embodiment of an electron source structure with controllable supply current according to the present invention.

This embodiment is similar to the first embodiment or the second embodiment, except that: a plurality of first electrodes 3 are provided separately, a single second electrode 5 is provided, and a plurality of first electrodes 3 are respectively provided with a single or a plurality of micropores 6 .

In this embodiment, as shown in FIG3 , the supply current of different emitters 7 is regulated by a plurality of discrete first electrodes 3, and the electrons of each emitter 7 are extracted into a vacuum by a single second electrode 5. The emission current of a plurality of emitters 7 can be regulated independently or in groups, and can be applied to cutting-edge fields such as parallel electron beam lithography and parallel electron beam microscopy.

Embodiment 4

This embodiment is the fourth embodiment of an electron source structure capable of regulating supply current of the present invention.

This embodiment is similar to any one of embodiments 1 to 3, except that the sum of the thicknesses of the first insulating layer 2 and the first electrode 3 is less than half the height of the emitter 7, and the sum of the thicknesses of the first insulating layer 2, the first electrode 3, the second insulating layer 4 and the second electrode 5 is greater than 60% of the height of the emitter 7 and less than 150% of the height of the emitter 7.

In this embodiment, the material constituting the substrate 1 is one or more of P-type doped elemental silicon, elemental germanium, gallium arsenide, gallium nitride, silicon carbide, indium phosphide, gallium oxide, zinc oxide, and diamond.

In this embodiment, the doping concentration of the P-type semiconductor substrate 1 is higher than the intrinsic carrier concentration of the material of the substrate 1 at room temperature and is lower than 10 ²⁰ cm ⁻³ .

In this embodiment, the emitter 7 is a field electron emitter, and its structure is one of a micro-cone, a nanowire, a nanotube, a micro-pyramid, and a vertical two-dimensional film.

In this embodiment, the material of the first insulating layer 2 and the second insulating layer 4 is one or more of silicon dioxide, hafnium oxide, silicon nitride, and aluminum oxide.

In this embodiment, the material of the first electrode 3 and the second electrode 5 is an alloy consisting of two or more of gold, silver, aluminum, chromium, molybdenum, nickel, niobium, tantalum, graphite, heavily doped polysilicon, and lanthanum hexaboride.

In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims (10)

1. An electron source structure capable of regulating supply current, characterized in that: it comprises a substrate (1), a first insulating layer (2), a first electrode (3), a second insulating layer (4) and a second electrode (5) stacked in sequence from bottom to top, the first electrode (3) and the second electrode (5) are provided with microholes (6) with spatial overlap areas, an emitter (7) is provided on the substrate (1), the emitter (7) penetrates the first insulating layer (2) and the second insulating layer (4) and is accommodated in the microhole (6); the first electrode (3) to the emitter The shortest distance from the top of the body (7) is greater than the shortest distance from the second electrode (5) to the top of the emitter (7); the substrate (1) is a P-type doped semiconductor material; the first electrode (3) can regulate the type, concentration and depletion layer width of the carriers on the surface of the substrate (1) by potential, thereby regulating the electron current supplied by the substrate (1) to the emitter (7); the second electrode (5) is placed at a positive potential relative to the substrate (1), inducing the electrons supplied by the substrate (1) to the emitter (7) to tunnel from the top surface of the emitter (7) into a vacuum. 2. The electron source structure with adjustable supply current according to claim 1 is characterized in that: the first electrode (3) and the second electrode (5) are each provided with only a single one, and a plurality of micropores (6) are respectively provided on the first electrode (3) and the second electrode (5). 3. The electron source structure with adjustable supply current according to claim 1 is characterized in that: a plurality of the first electrodes (3) are separately provided, a single second electrode (5) is provided, and a plurality of the first electrodes (3) are respectively provided with a single or a plurality of the micropores (6). 4. The electron source structure with adjustable supply current according to claim 1 is characterized in that the sum of the thicknesses of the first insulating layer (2) and the first electrode (3) is less than half of the height of the emitter (7), and the sum of the thicknesses of the first insulating layer (2), the first electrode (3), the second insulating layer (4) and the second electrode (5) is greater than 60% of the height of the emitter (7) and less than 150% of the height of the emitter (7). 5. The electron source structure with adjustable supply current according to claim 1 is characterized in that the material constituting the substrate (1) is one or more of P-type doped elemental silicon, elemental germanium, gallium arsenide, gallium nitride, silicon carbide, indium phosphide, gallium oxide, zinc oxide, and diamond. 6. The electron source structure with adjustable supply current according to claim 1, characterized in that the doping concentration of the P-type semiconductor substrate (1) is higher than the intrinsic carrier concentration of the material of the substrate (1) at room temperature and lower than ¹⁰²⁰ cm ^-3 . 7. The electron source structure with adjustable supply current according to claim 1 is characterized in that the emitter (7) is a field electron emitter, and its structure is one of a micro-cone, a nanowire, a nanotube, a micro-pyramid, and an upright two-dimensional film. 8. The electron source structure with adjustable supply current according to claim 1, characterized in that the material of the first insulating layer (2) and the second insulating layer (4) is one or more of silicon dioxide, hafnium oxide, silicon nitride, and aluminum oxide. 9. The electron source structure with adjustable supply current according to claim 1 is characterized in that the material of the first electrode (3) and the second electrode (5) is an alloy composed of two or more materials selected from the group consisting of gold, silver, aluminum, chromium, molybdenum, nickel, niobium, tantalum, graphite, heavily doped polysilicon, and lanthanum hexaboride. 10. The electron source structure with adjustable supply current according to any one of claims 1 to 9, characterized in that it is applied in vacuum electronic equipment.