Method for realizing high-conductivity gallium nitride substrate through neutron irradiation

Abstract

The invention provides a method for realizing a high-conductivity gallium nitride substrate through neutron irradiation. The method comprises the following steps: preparing an unintentionally doped gallium nitride single crystal substrate; performing neutron irradiation treatment on the gallium nitride single crystal substrate by using a neutron irradiation device so as to modify part of gallium elements into germanium elements, thereby obtaining a germanium-doped gallium nitride wafer; and cutting the germanium-doped gallium nitride wafer into a plurality of slices to obtain a plurality of high-conductivity gallium nitride substrates. A neutron irradiation treatment mode is used for replacing a traditional doping growth mode, and neutron irradiation is a technology which utilizes a neutron transmutation doping technology to enable neutrons to interact with materials in the aspect of material modification so as to change the material performance. Compared with a conventional Ge-doped chemical process, the neutron irradiation mode in the scheme can accurately control uniform distribution of germanium elements; the neutron irradiation device is used, mass production can be achieved, and efficiency is high.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for realizing a high-conductivity gallium nitride substrate by neutron irradiation. Background Art

[0002] In recent years, the third-generation wide bandgap semiconductor, gallium nitride (GaN), has been widely used in power and radio frequency device applications due to its wide bandgap, high breakdown electric field, high thermal conductivity, stable chemical properties, and radiation resistance. However, due to the limitations of traditional growth conditions, gallium nitride materials cannot be grown high and thick with uniform carrier concentration.

[0003] The existing growth of high-thickness and uniformly doped gallium nitride single crystal substrates has certain difficulties: (1) It is generally activated by doping with impurities such as Ge, Si, and C, but the doping uniformity is poor and it is difficult to achieve uniform doping; (2) The growth of high-thickness GaN is inefficient and costly. Summary of the invention

[0004] The purpose of the present invention is to provide a method for realizing a high-conductivity gallium nitride substrate by neutron irradiation, so as to improve the uniformity of germanium doping and the production efficiency.

[0005] The present invention provides a method for realizing a high-conductivity gallium nitride substrate by neutron irradiation, comprising:

[0006] preparing a non-intentionally doped gallium nitride single crystal substrate;

[0007] Using a neutron irradiation device to perform neutron irradiation treatment on the gallium nitride single crystal substrate so that part of the gallium element is modified into germanium element, thereby obtaining a germanium-doped gallium nitride wafer;

[0008] The germanium-doped gallium nitride wafer is cut into a plurality of thin slices to obtain a plurality of high-conductivity gallium nitride substrates.

[0009] Optionally, the neutron transmutation doping reaction occurring during the neutron irradiation treatment of the gallium nitride single crystal substrate by using a neutron irradiation device is:

[0010] 71 Ga+n→ 72 → 72 Ge;

[0011] in, 71 Ga is the 71st isotope of gallium, n is the neutron, 72 Ga is the 72nd isotope of gallium. 72 Ge is the 72nd isotope of germanium.

[0012] Optionally, the doping chemical reaction includes:

[0013] Neutron capture reaction: Stable gallium isotope 71 reacts with neutrons to produce unstable gallium isotope 72;

[0014] β decay: The unstable gallium isotope 72 undergoes β decay to form the stable germanium isotope 72.

[0015] Optionally, the reaction time of the neutron capture reaction is 45h-75h.

[0016] Optionally, the reaction time of the β decay is 10h-20h.

[0017] Optionally, the thickness of the unintentionally doped gallium nitride single crystal substrate is 200 μm-1000 μm.

[0018] Optionally, the thickness of the high-conductivity gallium nitride substrate after cutting is 50 μm-150 μm.

[0019] Optionally, the neutron irradiation device is the China Advanced Research Reactor of the China Institute of Atomic Energy, and the conditions for the neutron irradiation treatment are an injection energy of 50 MeV and a neutron dose of 3×10 12 cm -2 -5×10 12 cm -2 .

[0020] Optionally, the neutron irradiation treatment is to vertically irradiate the gallium surface of the gallium nitride single crystal substrate.

[0021] Optionally, the neutron irradiation device performs neutron irradiation treatment on multiple gallium nitride single crystal substrates simultaneously.

[0022] The present invention also provides a method for modifying gallium nitride by neutron irradiation, comprising:

[0023] Part of the gallium element in gallium nitride is modified into germanium element through neutron irradiation treatment to obtain modified high-conductivity gallium nitride.

[0024] The method of neutron irradiation of this scheme to achieve a high conductivity gallium nitride substrate uses neutron irradiation treatment instead of traditional doping growth methods. In terms of material modification, neutron irradiation is a technology that uses neutron transmutation doping technology to allow neutrons to interact with materials, thereby changing the material properties. The advantages of high-thickness and uniformly doped GaN are: (1) reducing device stress and defects and improving device performance. (2) High crystal quality, which helps to prepare high-performance RF and optoelectronic devices. (3) Reduce self-heating effects, better reduce thermal resistance, and improve device reliability. Compared with the conventional chemical process of doping Ge, the neutron irradiation method of this scheme can accurately control the uniform distribution of germanium elements; using neutron irradiation equipment, it can be mass-produced with high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of neutron-nuclear conversion of gallium nitride materials in this scheme;

[0026] Figure 2 This is a model diagram of the local chemical structure of the gallium nitride single crystal substrate before irradiation;

[0027] Figure 3 This is a model diagram of the local chemical structure of a germanium-doped gallium nitride wafer after irradiation. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two components. For ordinary technicians in this field, the specific meanings of the terms in the present invention can be understood according to specific circumstances.

[0030] This embodiment provides a method for modifying gallium nitride by neutron irradiation, comprising: modifying part of gallium elements in gallium nitride into germanium elements by neutron irradiation treatment to obtain modified high-conductivity gallium nitride.

[0031] See also Figure 1 This embodiment provides a method for realizing a high-conductivity gallium nitride substrate by neutron irradiation, comprising:

[0032] S1. Prepare a 500 μm non-intentionally doped gallium nitride single crystal substrate;

[0033] S2, using a neutron irradiation device to perform neutron irradiation treatment on the gallium nitride single crystal substrate to modify part of the gallium element into germanium element, thereby obtaining a germanium-doped gallium nitride wafer;

[0034] The neutron transmutation doping reaction that occurs when the gallium nitride single crystal substrate is neutron irradiated by the neutron irradiation device is:

[0035] 71 Ga+n→ 72 → 72 Ge;

[0036] in, 71 Ga is the 71st isotope of gallium, such as Figure 2 As shown in the figure, before irradiation, the large atom is Ga atom, the small atom is N atom; n is neutron, 72 Ga is the 72nd isotope of gallium. 72 Ge is the 72nd isotope of germanium, such as Figure 3 As shown, after irradiation, the large atoms are Ge atoms, the middle atoms are Ga atoms, and the small atoms are N atoms.

[0037] Specifically, the doping chemical reactions include:

[0038] Neutron capture reaction: When irradiated with neutrons, the stable gallium isotope 71 reacts with neutrons for 60 hours to produce the unstable gallium isotope 72.

[0039] β decay: Stop neutron irradiation. Under natural conditions, the unstable gallium isotope 72 undergoes β decay with a reaction time of 14 hours to produce the stable germanium isotope 72.

[0040] In this embodiment, the neutron irradiation device is the China Advanced Research Reactor (CARR) of the China Institute of Atomic Energy, also known as the "Yanlong" pool reactor. The conditions of the neutron irradiation treatment are an injection energy of 50 MeV and a dose of 3×10 12 cm -2 -5×10 12 cm -2 .

[0041] The neutron irradiation treatment is to vertically irradiate the gallium surface of the gallium nitride single crystal substrate. Gallium nitride is a complete crystal, but to the naked eye, it has a front and back side, divided into a gallium side and a nitrogen side. We irradiate the Ga side (actually the entire side has been irradiated).

[0042] The neutron irradiation device can simultaneously perform neutron irradiation treatment on multiple gallium nitride single crystal substrates. (2) By using a doping device equipped with GaN, several wafers can be placed in a vertical irradiation hole, which can be mass-produced with high efficiency.

[0043] The process of generating neutron pulses in the Yanlong device is as follows: first, the reactor is brought close to delayed criticality by adjusting the control rods and control rods, and a burst pulse is generated to produce precursor neutrons. Then, the reaction is stopped by controlling the main safety block. When the precursor neutrons decay to the allowable level, the main safety block is controlled to make the reactor reach a super-prompt critical state, and a fission chain is established. The fission in the reactor increases very quickly. At this time, the reactor temperature rises and the volume expands, resulting in a continuous decrease in the reactor reactivity, and the fission rate also decreases, forming a neutron pulse. The Yanlong reactor has the characteristics of being able to flexibly switch between pulse working mode and steady-state working mode, and can carry out research on transient or continuous neutron irradiation. The irradiation field is clean, without shock waves and electromagnetic pulses, etc. It is an ideal laboratory irradiation platform for conducting neutron irradiation-related research.

[0044] Preparation for irradiation experiment: Place the sample on the device table, then transport the sample to be irradiated to the irradiation room through the transmission system. Then, set the neutron irradiation related parameters (energy is 50MeV, dose is 5×1012cm-2, neutron irradiation time is 60h) through the control system and leave it for 24h to make GaN undergo β decay and make the outward radiation reach the safety standard.

[0045] The neutron irradiation device includes a reactor, an irradiation room, a transmission system, a control system, a safety system, a ventilation system and a dose monitoring system.

[0046] Reactor: Provides neutron source and is the core part of the Yanlong neutron irradiation device.

[0047] Irradiation room: used to place irradiated items and usually has the function of shielding radiation.

[0048] Transport system: transports the irradiated items into the irradiation room and sends them out after irradiation.

[0049] Control system: monitors and controls the operation of the Yanlong neutron irradiation device, including the control of parameters such as reactor power, irradiation time, and transmission speed.

[0050] Safety system: including radiation monitoring, emergency shutdown, fire prevention and explosion prevention and other safety equipment and measures to ensure the safe operation of the Yanlong neutron irradiation device.

[0051] Ventilation system: used to remove heat and radioactive gases from the irradiation room and maintain the ambient temperature and air quality in the irradiation room.

[0052] Dose monitoring system: monitors and measures the radiation dose of the Yanlong neutron irradiation device to ensure that the radiation dose received by the irradiated items meets the requirements

[0053] S3, cutting the germanium-doped gallium nitride wafer into a number of 100-micrometer slices to obtain a number of high-conductivity gallium nitride substrates.

[0054] Compared with the traditional doping growth method of GaN, the method of realizing high conductivity GaN substrate by neutron irradiation proposed in the present invention effectively solves the current problem of difficulty in preparing high-thickness, high-quality and uniform carrier concentration n-GaN by neutron irradiation. At the same time, neutron irradiation can prepare multiple wafers at one time, which helps to reduce the manufacturing cost of devices. Any high-conductivity GaN substrate based on similar neutron irradiation is protected.

[0055] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for realizing a high-conductivity gallium nitride substrate by neutron irradiation, characterized in that: include: preparing a non-intentionally doped gallium nitride single crystal substrate; Using a neutron irradiation device to perform neutron irradiation treatment on the gallium nitride single crystal substrate so that part of the gallium element is modified into germanium element, thereby obtaining a germanium-doped gallium nitride wafer; The germanium-doped gallium nitride wafer is cut into a plurality of thin slices to obtain a plurality of high-conductivity gallium nitride substrates.

2. The method for realizing high conductivity gallium nitride substrate by neutron irradiation according to claim 1, characterized in that: The neutron transmutation doping reaction that occurs when the gallium nitride single crystal substrate is neutron irradiated by the neutron irradiation device is: 71 Ga+n→ 72 Ga → 72 Ge; in, 71 Ga is the 71st isotope of gallium, n is the neutron, 72 Ga is the 72nd isotope of gallium. 72 Ge is the 72nd isotope of germanium.

3. The method for realizing high conductivity gallium nitride substrate by neutron irradiation according to claim 2, characterized in that: The doping chemical reaction includes: Neutron capture reaction: Stable gallium isotope 71 reacts with neutrons to produce unstable gallium isotope 72; β decay: The unstable gallium isotope 72 undergoes β decay to form the stable germanium isotope 72.

4. The method for realizing high-conductivity gallium nitride substrate by neutron irradiation according to claim 3, characterized in that: The reaction time of the neutron capture reaction is 45h-75h.

5. The method for realizing high-conductivity gallium nitride substrate by neutron irradiation according to claim 3, characterized in that: The reaction time of the β decay is 10h-20h.

6. The method for realizing high-conductivity gallium nitride substrate by neutron irradiation according to claim 1, characterized in that: The thickness of the unintentionally doped gallium nitride single crystal substrate is 200 μm-1000 μm.

7. The method for realizing high-conductivity gallium nitride substrate by neutron irradiation according to claim 1, characterized in that: The thickness of the high-conductivity gallium nitride substrate after cutting is 50 μm-150 μm.

8. The method for realizing high-conductivity gallium nitride substrate by neutron irradiation according to claim 1, characterized in that: The neutron irradiation device is the China Advanced Research Reactor of the China Institute of Atomic Energy. The conditions of the neutron irradiation treatment are as follows: the injection energy is 50 MeV, the neutron dose is 3×10 12 cm -2 -5× 10 12 cm -2 。 9. The method for realizing high-conductivity gallium nitride substrate by neutron irradiation according to claim 1, characterized in that: The neutron irradiation device performs neutron irradiation treatment on multiple gallium nitride single crystal substrates at the same time.

10. A method for modifying gallium nitride by neutron irradiation, characterized in that: include: Part of the gallium element in gallium nitride is modified into germanium element through neutron irradiation treatment to obtain modified high-conductivity gallium nitride.

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