Neutron detector based on zinc oxide / magnesium zinc oxide structure and preparation method

Abstract

The invention belongs to the technical field of semiconductor device preparation, and discloses a semiconductor neutron detector based on a zinc oxide / magnesium zinc oxide structure and a preparation method. The semiconductor neutron detector based on the zinc oxide / magnesium zinc oxide structure comprises an aluminum oxide single crystal, a high-resistance magnesium zinc oxide region, a hole conductive oxide layer region, a low-resistance zinc oxide region, an insulating layer, a collecting electrode, a gate electrode and a neutron conversion material filling region. The zinc oxide / magnesium zinc oxide neutron detector structure is designed, an effective and simple process manufacturing technology is provided, the preparation problem of the oxide neutron detector with the internal gain characteristic is solved, and development of the novel neutron detector based on the zinc oxide / magnesium zinc oxide structure is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor device preparation, and relates to a semiconductor neutron detector based on a zinc oxide / magnesium zinc oxide structure and a preparation method. BACKGROUND

[0002] The semiconductor neutron detector has excellent energy resolution and fast response characteristics, and has important applications in many key fields such as nuclear energy industry, reactor monitoring, fusion device diagnosis, boron neutron capture therapy, radioactive drug monitoring, national security and frontier scientific research. The semiconductor neutron detector prepared based on the principle of nuclear reaction mainly generates secondary charged particles through the nuclear reaction of neutrons and a specific conversion layer material, and then realizes detection by using the ionization effect of the semiconductor material. Although the commercial narrow-band semiconductor neutron detector has high sensitivity, it still has problems such as low radiation damage threshold and insufficient high-temperature stability. Therefore, it is necessary to develop a neutron detector based on a new type of wide-band semiconductor material. Oxide semiconductor materials such as zinc oxide and magnesium zinc oxide are ideal candidates for the next generation of detectors because of their wide band gap, intrinsic radiation resistance and high-temperature stability. The main problems in the development of the current oxide semiconductor neutron detector are as follows: first, it is difficult to control the electrical properties of the oxide semiconductor, that is, the material often shows high resistance or low resistance characteristics, resulting in a single type of device that can be prepared; second, the carrier signal excited by the secondary charged particles generated by the reaction of neutrons and the conversion layer in the detector is small, and due to the single structure of the above-mentioned device, there is no signal amplification structure design in the device, resulting in a low signal-to-noise ratio of the detector.

[0003] In the prior art, the conversion material is often directly coated on the surface of the electrode in the preparation of the neutron conversion layer, so that the secondary charged particles formed by the reaction of the neutrons and the conversion material need to pass through the electrode before entering the inside of the detector to induce a detection signal. In this process, the energy of the secondary charged particles is lost, causing the attenuation of the response signal. In addition, for the detection of the secondary particles, a single-layer Schottky structure or a PN, PIN-type heterojunction vertical structure is usually used to prepare the detector, which can only collect the electrons and holes generated by the signal source as the response signal and has no detection amplification function. In the present application, magnesium zinc oxide is used as the detection sensitive region. By controlling the ratio of magnesium atoms and zinc atoms, the magnesium zinc oxide material exhibits high resistance characteristics, and the resistivity and mobility are adjustable. At the same time, by designing a hole conductive layer on the magnesium zinc oxide layer, the free electrons in the magnesium zinc oxide are spontaneously depleted while ensuring that the mobility is large enough, further improving the resistivity, and thus the collection electric field strength of the device is improved. Unlike the vertical device structure, the present application designs a lateral current amplification mechanism. The contact electrode of the insulating layer on the magnesium zinc oxide is used to control the amplification current transport channel. The zinc oxide region of the electron conductive type is prepared on both sides of the magnesium zinc oxide sensitive region, and the same surface electrodes are prepared. When a voltage is applied, the resistivity near the magnesium zinc oxide region is transiently reduced due to the response signal, realizing the transient output of the amplified current signal. As can be seen, the present application directly uses magnesium zinc oxide as the detection sensitive region and adopts the neutron conversion layer direct filling method, the preparation method is simpler, the amplification signal transmission path is controllable, the high-quality amplification of the detection signal can be realized, and the technical innovation is outstanding. SUMMARY

[0004] The present application aims to solve the above-mentioned key problems of further significantly improving the performance of the semiconductor neutron detector, and proposes a neutron detector based on a zinc oxide / magnesium zinc oxide structure and a preparation method capable of realizing high-quality gain of the detection signal.

[0005] The technical scheme of the present application is as follows:

[0006] A neutron detector based on a zinc oxide / magnesium zinc oxide structure, comprising an aluminum oxide (Al2O3) single crystal 1 (thickness 360 μm), a high-resistance magnesium zinc oxide (MgZnO) region 2 (thickness 10 μm-100 μm, resistivity 10 6 -10 12 Ω·cm), a hole conductive (P-type, hole concentration 1×10 17 cm -3 -5×10 18 cm -3 ) oxide layer region 3 (thickness 0.01 μm-5 μm), and a low-resistance zinc oxide (ZnO) region 4 (thickness 10 μm-100 μm, resistivity 10 -1 -10 5Ω·cm), an insulating layer 5 (thickness 0.01-10 μm), a collecting electrode 6 (thickness 0.01-3 μm), a gate electrode 7 (thickness 0.01-3 μm), and a neutron conversion material filling region 8 (thickness 3-360 μm).

[0007] The surface of the alumina single crystal 1 is composed of a step structure of a high-resistance magnesium zinc oxide (MgZnO) region 2 and a hole-conducting oxide layer region 3 from bottom to top; the two sides of the step structure are low-resistance zinc oxide (ZnO) regions 4, and the upper surface of the low-resistance zinc oxide (ZnO) region 4 is flush with the upper surface of the hole-conducting oxide layer region 3; the upper surfaces of the hole-conducting oxide layer region 3 and the low-resistance zinc oxide (ZnO) region 4 are insulating layers 5, and holes are opened in the insulating layers 5, where the collecting electrodes 6 are located and in contact with the low-resistance zinc oxide (ZnO) region 4; the gate electrode 7 is above the insulating layer 5 directly above the hole-conducting oxide layer region 3, and the size of the gate electrode 7 is smaller than that of the hole-conducting oxide layer region 3; the neutron conversion material filling region 8 is located in the alumina single crystal 1, and its upper surface area is the same as the lower base area of the high-resistance magnesium zinc oxide (MgZnO) region 2.

[0008] The thickness ratio of the high-resistance magnesium zinc oxide (MgZnO) region 2 to the hole-conducting (P-type, hole concentration 1×10 17 cm -3 -5×10 18 cm -3 ) oxide layer region 3 is between 1000:1 and 10:1.

[0009] The ratio of magnesium atoms to zinc atoms in the MgZnO is between 1000:1 and 1:100.

[0010] A method for preparing a zinc oxide / magnesium zinc oxide structure neutron detector, comprising the following steps:

[0011] Step 1: sequentially epitaxially growing a high-resistance magnesium zinc oxide (MgZnO) region 2 and a hole-conducting oxide layer region 3 on an alumina single crystal 1;

[0012] Step 2: using photoresist mask and then using dry etching or wet etching to make a step structure;

[0013] Step 3: after cleaning, preparing a low-resistance zinc oxide (ZnO) region 4 by physical deposition or chemical vapor deposition;

[0014] Step 4: using chemical mechanical polishing or dry etching to smooth the surface;

[0015] Step 5: using physical deposition to prepare an insulating layer 5;

[0016] Step 6: Prepare a photoresist mask, and groove the insulating layer 5 on the low-resistance zinc oxide (ZnO) region 4 by dry etching or wet etching to expose part of the ZnO;

[0017] Step 7: Prepare a photoresist mask, and prepare the collecting electrode 6 by physical deposition and mask stripping;

[0018] Step 8: Prepare a photoresist mask, and prepare the gate electrode 7 by physical deposition and mask stripping.

[0019] Step 9: Groove the back surface of the aluminum oxide single crystal 1 by laser etching and inductively coupled plasma etching to expose the lower surface of the high-resistance magnesium zinc oxide (MgZnO) region 2;

[0020] Step 10: Fill the neutron conversion material into the groove by deposition or spin coating, and perform necessary reinforcement.

[0021] The beneficial effects of the present application are as follows: the present application designs a zinc oxide / magnesium zinc oxide structure neutron detector structure, directly uses magnesium zinc oxide as the detection sensitive region, locally hollows the substrate, and directly fills the neutron conversion material into the lower part of the detection sensitive region, thereby significantly reducing the energy loss of secondary particles; at the same time, the magnesium zinc oxide is used as the detection sensitive region, the proportion of magnesium atoms and zinc atoms can be controlled to make the magnesium zinc oxide material present high resistance characteristics, and the resistivity and mobility are adjustable; at the same time, a hole conductive characteristic layer is designed on the magnesium zinc oxide layer, the free electrons in the magnesium zinc oxide are spontaneously depleted while ensuring that the mobility is large enough, thereby further improving the resistivity, and then the collection electric field strength of the device is improved; unlike the vertical device structure, the present application designs a lateral current amplification mechanism, the contact electrode of the insulating layer on the magnesium zinc oxide is used to control the amplification current transport channel, the zinc oxide region of the electron conductive type is prepared on both sides of the magnesium zinc oxide sensitive region, and the same surface electrodes are prepared, a voltage is applied, when the response signal causes the resistance of the magnesium zinc oxide region to be instantaneously reduced, the instantaneous output of the amplified current signal is realized. As can be seen, the present application proposes an effective and simple process manufacturing technology, solves the preparation difficulty of the oxide neutron detector with internal gain characteristics, and realizes the development of a new type of zinc oxide / magnesium zinc oxide structure neutron detector. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a zinc oxide / magnesium zinc oxide structure neutron detector.

[0023] In the figure: 1 aluminum oxide single crystal; 2 high-resistance magnesium zinc oxide region; 3 hole conductive (P-type) oxide layer region; 4 low-resistance zinc oxide (ZnO) region; 5 insulating layer; 6 collecting electrode; 7 gate electrode; 8 neutron conversion material. DETAILED DESCRIPTION

[0024] The specific implementation of the present application is further described below in combination with the technical solutions and the accompanying drawings.

[0025] Embodiment 1

[0026] A preparation method of a zinc oxide / magnesium zinc oxide structure neutron detector, comprising the following process steps:

[0027] Step 1: a 10 μm high-resistance magnesium zinc oxide region 2 with a resistivity of 10 6 Ω·cm and a 0.01 μm hole-conducting oxide layer region 3 with a hole concentration of 1×10 17 cm -3 are sequentially epitaxially grown on an alumina single crystal with a thickness of 360 μm;

[0028] Step 2: after preparing a photoresist mask, a dry etching method is used to make a ladder structure;

[0029] Step 3: after cleaning, a chemical vapor deposition method is used to prepare a 10 μm low-resistance zinc oxide region 4 with a resistivity of 1 Ω·cm;

[0030] Step 4: a chemical mechanical polishing method is used to smooth the surface, exposing the upper surface of the ladder nickel oxide;

[0031] Step 5: a magnetron sputtering method is used to prepare a 0.01 μm thick silicon dioxide insulating layer 5;

[0032] Step 6: a photoresist mask is prepared, and a wet etching method is used to groove in the insulating layer 5 on the low-resistance zinc oxide region 4, exposing part of the ZnO;

[0033] Step 7: a photoresist mask is prepared, and an electron beam evaporation and mask stripping method is used to prepare a 0.01 μm thick aluminum electrode 6;

[0034] Step 8: a photoresist mask is prepared, and an electron beam evaporation and mask stripping method is used to prepare a 0.01 μm thick aluminum electrode 7.

[0035] Step 9: a laser etching and inductively coupled plasma etching method is used to groove on the back surface of the alumina single crystal 1, exposing the lower surface of the high-resistance magnesium zinc oxide region 2;

[0036] Step 10: a spin coating method is used to fill lithium fluoride neutron conversion material into the groove with a thickness of 3 μm, compact it and reinforce it with resin.

[0037] Embodiment 2

[0038] A preparation method of a zinc oxide / magnesium zinc oxide structure neutron detector, comprising the following process steps:

[0039] Step 1: Epitaxially grow 100 μm thick alumina single crystal with a resistivity of 10⁻⁶ on a 360 μm thick alumina single crystal. 12 High-resistivity magnesium-zinc-oxygen region 2 with Ω·cm and a thickness of 5μm and a hole concentration of 5×10 18 cm -3 Hole-conducting oxide layer region 3;

[0040] Step 2: After preparing the photoresist mask, the ladder structure is fabricated using dry etching.

[0041] Step 3: After cleaning, chemical vapor deposition is performed to prepare a film with a thickness of 100 μm and a resistivity of 10. 5 Low-resistivity zinc oxide region 4 with Ω·cm;

[0042] Step 4: Use chemical mechanical polishing to smooth the surface and expose the upper surface of the stepped nickel oxide.

[0043] Step 5: Prepare a 10 μm thick silicon dioxide insulating layer 5 using magnetron sputtering;

[0044] Step 6: Prepare a photomask and use a wet etching method to create a groove in the insulating layer 5 on the low-resistivity zinc oxide region 4 to expose part of the ZnO;

[0045] Step 7: Prepare a photoresist mask, and fabricate a 3μm thick aluminum electrode 6 by electron beam evaporation and mask stripping.

[0046] Step 8: Prepare a photoresist mask, and fabricate a 3μm thick aluminum electrode 7 by electron beam evaporation and mask stripping.

[0047] Step 9: Using laser etching and inductively coupled plasma etching methods, grooves are made on the back side of the alumina single crystal 1 to expose the lower surface of the high-resistivity magnesium zinc oxide region 2;

[0048] Step 10: Using a spin-coating method, the lithium fluoride neutron conversion material is filled into the tank to a thickness of 360 μm, compacted, and reinforced with resin.

[0049] Example 3

[0050] A method for fabricating a zinc oxide / magnesium zinc oxygen structure neutron detector includes the following process steps:

[0051] Step 1: Epitaxially grow 20 μm thick alumina single crystal with a resistivity of 10⁻⁶ on a 360 μm thick alumina single crystal. 9 High-resistivity magnesium-zinc-oxygen region 2 with Ω·cm and a thickness of 1μm and a hole concentration of 1×10 18 cm -3 P-type nickel oxide layer 3;

[0052] Step 2: After using photoresist mask, the dry etching is used to make the terrace structure;

[0053] Step 3: After cleaning, the low-resistance zinc oxide region 4 with a thickness of 20 μm and a resistivity of 10 Ω·cm is prepared by chemical vapor deposition;

[0054] Step 4: The surface is smoothed by using the chemical mechanical polishing method, and the upper surface of the terrace nickel oxide is exposed;

[0055] Step 5: The 1 μm-thick silicon dioxide insulating layer 5 is prepared by using the magnetron sputtering method;

[0056] Step 6: The photoresist mask is prepared, and the wet etching method is used to groove the insulating layer 5 on the low-resistance zinc oxide region 4 to expose part of the ZnO;

[0057] Step 7: The photoresist mask is prepared, and the 1 μm-thick aluminum electrode 6 is prepared by using the electron beam evaporation and mask stripping method;

[0058] Step 8: The photoresist mask is prepared, and the 1 μm-thick aluminum electrode 7 is prepared by using the electron beam evaporation and mask stripping method.

[0059] Step 9: The laser etching and inductively coupled plasma etching method is used to groove the back surface of the aluminum oxide single crystal 1 to expose the lower surface of the high-resistance magnesium zinc oxide region 2;

[0060] Step 10: The lithium fluoride neutron conversion material is filled into the groove by using the spin coating method, with a thickness of 150 μm, and is compacted and reinforced by using the resin.

Claims

1. A neutron detector based on a zinc oxide / magnesium zinc oxygen structure, characterized in that, The structure of the zinc oxide / magnesium zinc oxygen structure-based neutron detector is as follows: The surface of the alumina single crystal (1) is composed of a high-resistivity magnesium zinc oxide region (2) and a hole-conducting oxide layer region (3) from bottom to top. On both sides of the stepped structure are low-resistivity zinc oxide regions (4), and the upper surface of the low-resistivity zinc oxide region (4) is flush with the upper surface of the hole-conducting oxide layer region (3). On the upper surface of the hole-conducting oxide layer region (3) and the low-resistivity zinc oxide region (4) is an insulating layer (5), and a hole is opened in the insulating layer (5). The opening is a collecting electrode (6), and the collecting electrode (6) is in contact with the low-resistivity zinc oxide region (4). A gate electrode (7) is located on the insulating layer (5) directly above the hole-conducting oxide layer region (3), and the size of the gate electrode (7) is smaller than that of the hole-conducting oxide layer region (3); the neutron conversion material filling region (8) is located in the alumina single crystal (1), and its upper surface area is the same as that of the lower bottom area of ​​the high-resistivity magnesium zinc oxide region (2).

2. The neutron detector based on a zinc oxide / magnesium zinc oxygen structure according to claim 1, characterized in that, The thickness of the alumina single crystal (1) is 360 μm; The thickness of the high-resistivity magnesium-zinc-oxygen region (2) is 10μm-100μm, and the resistivity is 10. 6 -10 12 Ω·cm; The thickness of the hole-conducting oxide layer region (3) is 0.01 μm-5 μm, and its hole concentration is 1 × 10⁻⁶. 17 cm -3 -5×10 18 cm -3 ; The thickness of the low-resistivity zinc oxide region (4) is 10μm-100μm, and the resistivity is 10. -1 -10 5 Ω·cm; The thickness of the insulating layer (5) is 0.01μm-10μm; The thickness of the collecting electrode (6) is 0.01 μm-3 μm; The thickness of the gate electrode (7) is 0.01 μm-3 μm; The thickness of the neutron conversion material filling region (8) is 3μm-360μm.

3. The neutron detector based on a zinc oxide / magnesium zinc oxygen structure according to claim 1, characterized in that, The thickness ratio of the high-resistivity magnesium zinc oxide region (2) to the hole-conducting oxide layer region (3) is between 1000:1 and 10:

1.

4. The neutron detector based on a zinc oxide / magnesium zinc oxygen structure according to claim 1, characterized in that, The ratio of magnesium atoms to zinc atoms in MgZnO is between 1000:1 and 1:

100.

5. A method for fabricating a zinc oxide / magnesium zinc oxygen structure neutron detector, characterized in that, The steps are as follows: Step 1: A high-resistivity magnesium zinc oxide region (2) and a hole-conducting oxide layer region (3) are epitaxially grown sequentially on an alumina single crystal (1); Step 2: After preparing the photoresist mask, the ladder structure is fabricated using dry etching or wet etching. Step 3: After cleaning, prepare low-resistivity zinc oxide regions by physical deposition or chemical vapor deposition (4); Step 4: Smooth the surface using chemical mechanical polishing or dry etching methods; Step 5: Prepare the insulating layer using physical deposition (5); Step 6: Prepare a photoresist mask and use dry etching or wet etching to create grooves in the insulating layer (5) on the low-resistivity zinc oxide region (4) to expose part of the ZnO; Step 7: Prepare a photoresist mask, and prepare the collecting electrode by physical deposition and mask stripping (6); Step 8: Prepare a photoresist mask, and fabricate the gate electrode by physical deposition and mask lift-off (7); Step 9: Using laser etching and inductively coupled plasma etching, a groove is made on the back side of the alumina single crystal (1) to expose the lower surface of the high-resistivity magnesium zinc oxide region (2); Step 10: Fill the tank with neutron conversion material using deposition or spin coating methods, and reinforce it as necessary.

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