阅读说明：本技术 一种电子成像探测器及其制备方法和电子显微成像系统 (Electron imaging detector, preparation method thereof and electron microscopic imaging system ) 是由 邓智 李任恺 魏桐 于 2020-06-01 设计创作，主要内容包括：本发明公开了一种电子成像探测器及其制备方法,以及采用该电子成像探测器的电子显微成像系统。该电子成像探测器包括：探测器灵敏区,由金刚石材料构成,具有相对而设的第一表面和第二表面；平面电极,设置于第一表面；像素电极,设置于第二表面。本发明中,由于探测器灵敏区所采用的金刚石材料在室温下具有禁带宽度大、电阻率高、抗辐照性能强等特点,因此,不需要通过掺杂等工艺形成的PN结,降低了制备复杂程度。同时,由于金刚石材料的原子序数小、电子散射小,进而降低了电子成像探测器中电子的散射,提高了电子探测的位置分辨率,从而能够获得更加清晰的图像。(The invention discloses an electronic imaging detector, a preparation method thereof and an electronic microscopic imaging system adopting the electronic imaging detector. The electronic imaging detector includes: the detector sensitive area is made of diamond materials and is provided with a first surface and a second surface which are arranged oppositely; the planar electrode is arranged on the first surface; and the pixel electrode is arranged on the second surface. In the invention, because the diamond material adopted by the sensitive region of the detector has the characteristics of large forbidden band width, high resistivity, strong radiation resistance and the like at room temperature, a PN junction formed by doping and other processes is not needed, and the preparation complexity is reduced. Meanwhile, because the diamond material has small atomic number and small electron scattering, the scattering of electrons in the electronic imaging detector is reduced, the position resolution of electronic detection is improved, and a clearer image can be obtained.)

1. An electronic imaging detector, comprising:

the detector comprises a detector sensitive area, a first electrode and a second electrode, wherein the detector sensitive area is made of diamond materials and is provided with a first surface and a second surface which are arranged oppositely;

a planar electrode disposed on the first surface; and the number of the first and second groups,

and the pixel electrode is arranged on the second surface.

2. The electronic imaging detector of claim 1, wherein:

the number of the pixel electrodes is multiple, and the pixel electrodes are distributed on the second surface in a two-dimensional array.

3. The electronic imaging detector of claim 2, further comprising:

and the protective ring is arranged on the second surface and positioned outside the pixel electrode.

4. The electronic imaging detector of claim 2, further comprising:

and the protective grid is arranged on the second surface and positioned outside the pixel electrodes and between the adjacent pixel electrodes.

5. The electronic imaging detector of claim 2, wherein:

the pixel electrode is connected to the readout circuit chip by flip-chip bonding.

6. The electronic imaging detector of claim 5, wherein:

the readout circuit chip includes a plurality of pixel circuits electrically connected to the plurality of pixel electrodes in a one-to-one manner.

7. The electronic imaging detector of claim 6, wherein:

the pixel circuit is a single electron detection mode circuit, a continuous charge integration mode circuit and/or a pulse charge integration mode circuit.

8. The electronic imaging detector of claim 1, wherein:

the diamond material is single crystal and/or polycrystalline diamond crystals.

9. A method of making an electronic imaging detector, comprising:

preparing a detector sensitive area of diamond material;

and respectively depositing a planar electrode and a pixel electrode on a first surface and a second surface which are arranged opposite to the sensitive area of the detector.

10. An electron microscopy imaging system characterized in that an electron imaging detector according to any of claims 1 to 8 is used.

Technical Field

The invention relates to the technical field of electron microscopic imaging, in particular to an electron imaging detector, a preparation method thereof and an electron microscopic imaging system adopting the electron imaging detector.

Background

Typical electron microscopy imaging systems include Transmission Electron Microscopes (TEM), Scanning Transmission Electron Microscopes (STEM), and electron diffraction imaging, and are widely used in research fields such as materials, biology and life sciences, and industrial fields such as semiconductor micromachining.

In electron microscopy imaging systems, it is necessary to detect the transmitted or diffracted electron two-dimensional intensity distribution to reconstruct an image of a sample and to obtain structural information. Fig. 1 shows a basic structure of a transmission electron microscope imaging system, which mainly includes an electron source, an electron lens system, a sample chamber, a detector, a data acquisition system, a computer, and the like. The electrons are bundled by the focusing lens and then pass through a sample in the sample chamber, and the emergent electrons which have the action with the sample reach a detection plane through an objective lens, a middle lens, a projection lens and the like, are detected by an electronic imaging detector and finally are collected in a computer to reconstruct a sample image. Among them, the electronic imaging detector is an important link for determining the resolution of the final image. Electronic detector technology has experienced a development stage from first-generation film, second-generation scintillator-Coupled CCD (Charge Coupled Device) detectors, to third-generation active CMOS (Complementary Metal Oxide Semiconductor) pixel detectors, which are also referred to as direct imaging detectors, and hybrid Semiconductor pixel detectors. Compared with the second generation CCD detector, the third generation direct electronic imaging detector has the advantages of high position resolution, high detection efficiency, high integration degree, large dynamic range, quick reading, good radiation resistance and the like.

An electronic direct imaging detector module comprises a detector and a reading circuit, wherein the detector is used for converting incident electrons into current signals; the reading circuit amplifies, processes and reads the current signal. The detector is typically divided into an array of micro-cells, each cell being referred to as a detector pixel. In order to realize high position resolution, the typical size of a detector pixel is in the order of 1-100 microns. Since each pixel requires an independent readout, the readout circuitry must be implemented using integrated circuit technology. In an active CMOS pixel detector, the detector and the readout circuitry are integrated on the same silicon chip, and the pixel size can be several microns. In a hybrid semiconductor pixel detector, the detector and the readout circuitry are fabricated separately and connected by flip-chip bonding, so that the detector and circuitry can be optimized separately, e.g., using different thicknesses or even different materials. But limited to the flip-chip process, the pixel size of hybrid semiconductor pixel detectors is typically over 50 microns.

At present, a hybrid semiconductor pixel detector mainly adopts silicon as a detector material, but a detector adopting the silicon material has high intrinsic carrier concentration and large dark current at room temperature, and must be made into a PN junction to increase the resistivity. In addition, electrons scatter more heavily in silicon detectors, thereby affecting the position resolution. This problem can be alleviated to some extent by reducing the thickness of the detector, but is also more difficult to achieve.

Disclosure of Invention

In view of this, the present invention provides an electron imaging detector, a method for manufacturing the same, and an electron microscopy imaging system, so as to reduce scattering of electrons, improve the position resolution of electron detection, and obtain a clearer image.

The technical scheme of the invention is realized as follows:

an electronic imaging detector comprising:

the detector comprises a detector sensitive area, a first electrode and a second electrode, wherein the detector sensitive area is made of diamond materials and is provided with a first surface and a second surface which are arranged oppositely;

a planar electrode disposed on the first surface; and the number of the first and second groups,

and the pixel electrode is arranged on the second surface.

Furthermore, the number of the pixel electrodes is multiple, and the pixel electrodes are distributed on the second surface in a two-dimensional array.

Further, the electronic imaging detector further comprises:

and the protective ring is arranged on the second surface and positioned outside the pixel electrode.

Further, the electronic imaging detector further comprises:

and the protective grid is arranged on the second surface and positioned outside the pixel electrodes and between the adjacent pixel electrodes.

Further, the pixel electrode is connected to the readout circuit chip by flip-chip bonding.

Further, the readout circuit chip includes a plurality of pixel circuits electrically connected to the plurality of pixel electrodes in a one-to-one manner.

Further, the pixel circuit is a single electron detection mode circuit, a continuous charge integration mode circuit and/or a pulse charge integration mode circuit.

Further, the diamond material is single crystal and/or polycrystalline diamond crystals.

A method of making an electronic imaging detector, comprising:

preparing a detector sensitive area of diamond material;

and respectively depositing a planar electrode and a pixel electrode on a first surface and a second surface which are arranged opposite to the sensitive area of the detector.

An electron microscopy imaging system employing an electron imaging detector as claimed in any one of the preceding claims.

According to the scheme, in the electronic imaging detector, the preparation method thereof and the electronic microscopic imaging system, the adopted diamond material has the characteristics of large forbidden band width, high resistivity, strong irradiation resistance and the like at room temperature, so that a PN junction formed by doping and other processes is not needed, and the preparation complexity is reduced. Meanwhile, because the diamond material has small atomic number and small electron scattering, the scattering of electrons in the electronic imaging detector is reduced, the position resolution of electronic detection is improved, and a clearer image can be obtained.

Drawings

FIG. 1 is a schematic diagram of the basic structure of a transmission electron microscope imaging system;

FIG. 2 is a schematic cross-sectional structural view of an electronic imaging detector in accordance with an embodiment of the present invention;

FIG. 3 is a schematic diagram of a pixel electrode side of an electronic imaging detector according to an embodiment of the invention;

FIG. 4 is a schematic diagram of a pixel electrode side having a guard ring according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a pixel electrode with a protective grid according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a single electron detection mode circuit according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a continuous charge integration mode circuit according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of a pulse charge integration mode circuit according to an embodiment of the present invention;

FIG. 9 is a flowchart of a method for manufacturing an electronic imaging detector according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and examples.

Based on the technical route of the hybrid semiconductor pixel detector, the silicon material in the detector adopted in the existing electron microscope or electron diffraction imaging system is replaced by the diamond material, and optimization is carried out according to the characteristics of the diamond material and the signal characteristics of the diamond material. The diamond has the characteristics of large forbidden band width and high resistivity at room temperature, so that a PN junction does not need to be formed by doping and other processes. Therefore, the detector pixel can be formed by manufacturing the metal pixel electrodes in a two-dimensional array on the surface of the diamond material. The thickness of the detector, the pixel size and the like are determined and optimized according to the response of electrons with different energies in the diamond detector. On the basis of the embodiment of the invention, a special reading circuit chip is further designed according to different requirements of an electron microscope, electron diffraction imaging and the like and signal characteristics of the diamond detector, wherein each pixel circuit corresponds to a pixel electrode of the detector one by one, and the extraction of information such as electron energy or intensity and the like is realized. Reading out the electron beam at a high counting rate by adopting a charge integration mode, and taking the charge amount integrated in a period of time as the measurement of the incident electron intensity; whereas at low count rates the deposited energy of a single electron can be measured, etc.

The electronic imaging detector of the embodiment of the invention is placed on an imaging plane to realize transmitted two-dimensional electron intensity distribution detection, and as shown in fig. 2, the electronic imaging detector of the embodiment of the invention mainly comprises a detector sensitive area 11, a plane electrode 12 and a pixel electrode 13. The detector sensitive region 11 is made of a diamond material, and the detector sensitive region 11 has a first surface (e.g., an upward surface in fig. 1, hereinafter referred to as an upper surface) and a second surface (e.g., a downward surface in fig. 1, hereinafter referred to as a lower surface) that are opposite to each other. The planar electrode 12 is disposed on a first surface, such as an upper surface. The pixel electrode 13 is disposed on a second surface, for example, a lower surface.

In an alternative embodiment, the diamond material is single crystal and/or polycrystalline diamond crystals, wherein, preferably, the crystal planes of the single crystal diamond material are (100) planes. The thickness of the detector sensitive area 11 can be optimized according to the diamond material characteristics and its signal characteristics, for example 0.05mm to 0.5 mm.

Wherein there is no PN junction in the detector sensitive area 11.

The number of the pixel electrodes 13 is plural, and the pixel electrodes are distributed on the second surface (lower surface) in a two-dimensional array.

Fig. 3 shows a structure in which an electron imaging detector of an embodiment of the present invention is located on the pixel electrode side. In an alternative embodiment, the pixel electrodes 13 are two-dimensional arrays arranged periodically, and in an alternative embodiment, each pixel electrode 13 is a square as shown in fig. 3, and adjacent pixel electrodes 13 are arranged at intervals.

In alternative embodiments, the material of the planar electrode 12 may be aluminum, titanium, chromium, silver, gold, and the like, and the material of the pixel electrode 13 may be aluminum, titanium, chromium, silver, gold, and the like.

In an alternative embodiment the size of the pixel electrode 13 is in the order of hundreds of microns.

In the arrangement structure of the pixel electrodes 13 shown in fig. 3, there is a leakage current around the pixel electrodes 13. In order to reduce leakage current around the pixel electrode 13, in an alternative embodiment, the electron imaging detector further comprises a guard ring 14, as shown in fig. 4. The guard ring 14 is disposed on the second surface (lower surface) and outside the pixel electrode 13. The leakage current of the peripheral pixel electrode 13 can be reduced by adjusting the bias of the guard ring 14.

In the arrangement structure of the pixel electrodes 13 as shown in fig. 3, each pixel electrode 13 collects electrons during operation, and the gap existing between the adjacent pixel electrodes 13 is not covered with metal, the lateral drift electric field is weak, and it takes a long time for the electrons to be collected when they drift to the gap between the adjacent pixel electrodes 13, thereby reducing the charge collection efficiency of the pixel electrodes 13. In order to increase the charge collection efficiency, as shown in fig. 5, in an alternative embodiment, the electronic imaging detector further includes a protective Grid (Grid)15 (also referred to as a Grid), and the protective Grid 15 is disposed on the second surface (lower surface) and located outside the pixel electrodes 13 and between the adjacent pixel electrodes 13. The protective grid 15 isolates each of the pixel electrodes 13 from each other, and thus charge collection efficiency for each of the pixel electrodes 13 can be increased by adjusting the bias voltage of the protective grid 15.

In alternative embodiments, the material of the protection ring 14 and the protection grid 15 may be aluminum, titanium, chromium, silver, gold, or other metal materials.

With continued reference to fig. 2, in the electronic imaging detector according to the embodiment of the present invention, the pixel electrodes 13 are connected to the readout circuit chip 2 by flip-chip bonding (indicated by a dashed box area a in fig. 2). The readout circuit chip 2 includes a plurality of pixel circuits electrically connected to the plurality of pixel electrodes 13 in a one-to-one manner.

In alternative embodiments, the pixel circuit is a single electron detection mode circuit, a continuous charge integration mode circuit, and/or a pulsed charge integration mode circuit.

In operation, a high voltage is applied to the planar electrode 12, creating a drift field in the detector sensitive region 11 of diamond material. The planar electrode 12 faces the direction of the incident electrons, and the incident electrons penetrate through the planar electrode 12 to generate electron and hole pairs after energy is deposited in the sensitive region 11 of the detector, and drift towards the planar electrode 12 and the pixel electrode 13 respectively under the action of an electric field and are collected. Depending on the polarity of the high voltage applied by the planar electrode 12, the pixel electrode 13 may collect electrons or holes to generate induced current with different polarity. The pixel circuits in the readout circuit chip 2 correspond to the pixel electrodes 13 one by one, each pixel circuit includes a signal amplifying and holding circuit, and the like, and extracts and stores information such as the signal charge amount of the pixel electrodes 13. The signals stored by each pixel circuit are finally serialized and output by means of multi-path gating and the like. The electron distribution image after transmission or diffraction can be reconstructed by the signal amplitude output by each pixel circuit. The area of a single electronic direct imaging detector module is limited by the maximum area of the electronic imaging detector and the maximum area of the processing of the reading circuit chip which form the electronic direct imaging detector module, and the detector module with larger area can be formed by splicing a plurality of electronic direct imaging detector modules.

As shown in fig. 6, the single-electron detection mode circuit mainly includes an integrator circuit portion, a shaping circuit portion, a peak hold circuit portion, a gate switch, and an output drive circuit portion. In the single-electron detection mode, the high-energy electron flux of the electronic imaging detector is low, each pixel circuit can amplify and shape a current signal generated by a single high-energy electron in the electronic imaging detector of the embodiment of the invention, then the signal amplitude is extracted through the peak holding circuit, and finally the gating output is performed through the gating switch and the output driving circuit.

As shown in fig. 7, the continuous charge integration mode circuit mainly includes an integrator circuit portion, a CDS (correlated double Sampling) circuit portion, a gate switch, and an output drive circuit portion. In the continuous charge integration mode, high energy electrons continue to reach the electron imaging detector and the flux is high. Each pixel circuit cannot distinguish a single sheet, only can integrate and convert induced current generated by high-energy electrons in a period of time in the electronic imaging detector of the embodiment of the invention into a voltage signal, then sample and hold the integrated voltage value in the period of time through a CDS circuit, and finally gate and output through a gate switch and an output driving circuit.

As shown in fig. 8, the pulse charge integration mode circuit mainly includes an integrator circuit portion, a CDS circuit portion, a switched capacitor array circuit portion, a gate switch, and an output drive circuit portion. In the pulsed charge integration mode, periodic pulsed high-energy electrons reach the electron imaging detector with very narrow single pulse time, high flux, and generally low pulse repetition frequency. Each pixel circuit integrates the induced current generated by the high-energy electrons in each pulse in the electronic imaging detector of the embodiment of the invention and converts the integrated current into a voltage signal, then the voltage values corresponding to different pulses are sampled and held through the switched capacitor array circuit, and finally the gated output is performed through the gating switch and the output driving circuit.

The embodiment of the present invention further provides a method for manufacturing an electronic imaging detector, as shown in fig. 9, including:

step 1, preparing a detector sensitive area of a diamond material;

and 2, respectively depositing a first surface and a second surface which are arranged opposite to the sensitive area of the detector to form a planar electrode and a pixel electrode.

Wherein, in step 1, the diamond material may be prepared by CVD (Chemical Vapor Deposition). After a certain thickness of diamond material is prepared, the diamond material is processed into the shape required by the detector, usually a rectangular sheet.

In step 2, the planar electrode and the pixel electrode can be respectively prepared on the first surface and the second surface of the sensitive area of the detector through processes such as sputtering, etching and the like.

And after the step 2 is finished, connecting the prepared electronic imaging detector and the read-out circuit chip together through flip chip to form the electronic direct imaging detector module of the diamond material.

The embodiment of the invention also provides an electron microscopy imaging system, which adopts the electron imaging detector in any embodiment.

In the electronic imaging detector, the preparation method thereof and the electronic microscopic imaging system, the adopted diamond material has the characteristics of large forbidden bandwidth, high resistivity, strong radiation resistance and the like at room temperature, so that a PN junction formed by doping and other processes is not needed, and the preparation complexity is reduced. Meanwhile, because the diamond material has small atomic number and small electron scattering, the electron imaging detector of the embodiment of the invention reduces the electron scattering in the electron imaging detector, improves the position resolution of electron detection, and can obtain clearer images.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.