A co-injection based method for p-type doping of ga2o3

Abstract

The present application relates to a kind of Ga2O3-based P-type doping methods based on co-implantation, including ion implantation, post annealing and surface polishing, ion implantation is to the epitaxial layer grown on semiconductor substrate is successively implanted nitrogen element and divalent metal element and with multiple energy injection to form uniform doping, nitrogen element and divalent metal element are to provide hole, form acceptor-doped impurity, while the injection of nitrogen element also reduces the self-trapping effect of hole caused by the high electronegativity of oxygen element, can increase the hole mobility of Ga2O3 P-type region, while the introduction of another acceptor-doped impurity can make the acceptor-doped concentration increase, post annealing is by placing the wafer after implantation into high temperature annealing furnace to anneal at a certain temperature to repair lattice damage and activate doping element, surface polishing is to the wafer that has been implanted twice ion and annealed is polished to a certain thickness with downward facing to reduce the roughness of wafer surface after ion implantation while eliminating the surface doping inhomogeneity caused by doping element outward diffusion after high temperature annealing.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a P-type doping method based on co-injection of Ga2O3. Background Technology

[0002] In recent years, the world has placed increasing emphasis on energy conservation and emission reduction, which has placed higher demands on loss control and efficiency improvement of large power electronic equipment. As an important component of power electronic equipment, semiconductor power devices have received widespread attention from the industry.

[0003] Breakdown voltage is a crucial indicator of semiconductor power devices, representing the maximum voltage the device can withstand. Power devices have evolved from early silicon-based devices to the current third-generation semiconductor material SiC, whose large bandgap makes it particularly suitable for power applications. However, SiC's development in terms of voltage withstand capability has reached a bottleneck, leading to the development of ultra-wide bandgap semiconductors. These semiconductors offer even wider bandgap and higher breakdown field strength, making them particularly suitable for high-voltage applications. Among them, Ga2O3 shows great potential to become a fourth-generation semiconductor. N-type doping of Ga2O3 is relatively easy and can be controlled within a reasonable and precise range. However, P-type doping generally cannot achieve an effective and usable P-type doping concentration through implantation. The lack of P-type doping severely limits the development of power devices based on this novel semiconductor material. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a P-type doping method based on co-injection of Ga2O3, which has the advantages of increasing the doping concentration of acceptor impurities and improving hole mobility, and can quickly solve existing doping problems.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] According to an embodiment of the present invention, a P-type doping method based on co-implantation of Ga2O3 is proposed, comprising three parts: ion implantation, post-annealing, and surface polishing. The method is characterized in that an N-type epitaxial layer is grown on a semiconductor substrate, and then P-type doping of the semiconductor is performed by implantation. Finally, lattice repair is performed by annealing. The acceptor doping elements implanted into the N-type epitaxial layer are nitrogen and divalent metal elements.

[0007] Preferably, the doping concentration of the nitrogen and divalent metal elements is two orders of magnitude or more than the donor doping concentration of the N-type epitaxial layer.

[0008] Preferably, the implantation method includes using multi-energy implantation to form uniform doping.

[0009] Preferably, the annealing method includes using 800-1200℃ to activate the acceptor dopant and prevent the diffusion of the acceptor dopant during annealing.

[0010] Preferably, the surface polishing includes polishing the injected surface after annealing.

[0011] Another method for P-type doping of Ga2O3 based on co-implantation according to an embodiment of the present invention is characterized by comprising the following steps: implanting high concentrations of nitrogen and divalent metal elements into the epitaxial layer of the substrate; annealing the wafer in an annealing furnace to repair lattice damage and form P-type doping; and then polishing the implanted surface.

[0012] According to an embodiment of the present invention, another p-type doping method based on co-implantation of Ga2O3 is proposed, comprising three parts: ion implantation, post-annealing, and post-annealing polishing. The method is characterized by including ion implantation, post-annealing, and post-annealing polishing. Ion implantation includes implanting nitrogen and divalent metal elements into the epitaxial layer of a semiconductor substrate, wherein the nitrogen and divalent metal elements provide holes to form acceptor-doped impurities. Post-annealing includes annealing the implanted substrate in an annealing furnace at a temperature of 800-1200°C. Post-annealing polishing includes polishing the annealed surface to eliminate the increase in surface roughness and defects caused by the two implantations.

[0013] The proposed p-type doping method for Ga2O3 based on co-implantation, compared to traditional implantation processes, employs two acceptor elements to achieve an effective and usable doping concentration. It reduces electronegativity in the crystal lattice by significantly implanting nitrogen (N) to replace oxygen (O), while simultaneously increasing hole mobility. The doping concentration is further enhanced by introducing the second doping element. Post-annealing polishing is performed on the implanted surface after implantation to reduce surface roughness and defects. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a structural diagram of a p-type doping method proposed in an embodiment of the present invention;

[0016] Figure 2 This is a flowchart of an embodiment of a p-type doping method proposed in this invention;

[0017] Figure 3This is a flowchart of a second embodiment of a p-type doping method proposed in this invention;

[0018] Figure 4 This is a polishing schematic diagram of a P-type doping method proposed in an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of the structure of a P-type doping method proposed in an embodiment of the present invention before polishing;

[0020] Figure 6 This is a schematic diagram showing the concentration distribution of implanted N and divalent metal elements in a P-type doping method proposed in an embodiment of the present invention.

[0021] Figure reference numerals: 1. Substrate layer; 2. Epitaxial layer; 3. Implanted layer; 4. Polished layer; 5. Unit cell; 6. Covalent bond or dangling bond; 7. N atom; 8. Divalent metal atom; 9. Distribution of N atoms in the implanted layer; 10. Distribution of divalent metal atoms in the implanted layer. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0023] like Figure 1 As shown, a p-doped structure includes a substrate layer 1, an epitaxial layer 2, an implantation layer 3, and a polished layer 4. The substrate layer 1 can be a Ga2O3 substrate, and the epitaxial layer 2 is grown on the substrate layer 1. The implantation layer 3 is implanted with nitrogen (hereinafter also referred to as N element or N atom) and divalent metal elements, and the implantation dose should be two orders of magnitude or more than the doping concentration of the epitaxial layer. In one embodiment of the present invention, the epitaxial layer concentration is 1 × 10⁻⁶. 16 cm -3 The concentration of injected nitrogen should be at least two orders of magnitude greater than the concentration of the epitaxial layer, i.e., 1 × 10⁻⁶. 18 cm -3 And above. Moreover, its injection depth can also be changed by multi-energy injection depending on the application. The polishing layer 4 is the part of the injection layer 3 that is polished and removed from the surface of the injection layer.

[0024] The implantation layer 3 is where N atoms 7 and divalent metal atoms 8 are implanted into this region to form the source of acceptor doping. At the same time, in order to obtain uniform doping after annealing, a multi-energy implantation method is used to form uniform doping by implanting N atoms 7 and divalent metal atoms 8. The polishing layer 4 is a part of the implantation layer 3 that is polished off from the surface of the implantation layer 3 to eliminate the increase in surface roughness and the increase in defects caused by multiple implantations of the two elements (i.e., N atoms 7 and divalent metal atoms 8) when forming uniform doping.

[0025] Example 1

[0026] Figure 2 The following is a basic manufacturing flowchart of Embodiment 1 of the present invention. First, N atoms 7 are implanted into the implantation layer 3. At this time, because no annealing repair process has been performed, the positions of the N atoms 7 in the implantation layer are random and not located at lattice sites. Then, divalent metal atoms 8 are implanted into the implantation layer 3. At this time, both types of atoms in the implantation layer 3 are random. Then, high-temperature annealing repair is performed, and the N atoms 7 and divalent metal atoms 8 become regularly arranged, replacing the Ga (gallium) and O (oxygen) elements in Ga2O3, respectively, to form acceptor doping. It should be noted that in one embodiment of the present invention, because of the different activation energies and diffusion degrees of N atoms 7 and divalent metal atoms 8 in Ga2O3, the annealing temperature is selected as a compromise of 950°C.

[0027] Example 2

[0028] Figure 3 The following is a basic manufacturing flowchart of Embodiment 1 of the present invention. First, N atoms 7 are injected into the implantation layer 3. At this time, the disordered N atoms will replace the O element in Ga2O3 after annealing at a temperature of 1200°C. Then, divalent metal atoms 8 are injected into the implantation layer 3, and then annealed at a high temperature of 800°C, so that the injected divalent metal atoms 8 replace the Ga element in Ga2O3. The reason for doing this is that the activation energy and diffusion degree of divalent metal atoms 8 and N atoms 7 are different in gallium oxide. This method of separately injecting and activating can effectively control their activation and prevent their diffusion, thereby improving the doping robustness of the manufactured power semiconductor device.

[0029] Figure 4 After multiple ion implantations, the semiconductor surface will have a lot of roughness. At this time, polishing is used to remove the polishing layer 4 to reduce the interface state and roughness caused by implantation, so as to improve the yield during device manufacturing.

[0030] Figure 5 This is a two-dimensional structural diagram of the final product of the present invention, including a substrate layer 1, an epitaxial layer 2, an implantation layer 3, and N atoms 7, divalent metal atoms 8 contained therein, and a polishing layer 4 that is finally removed by polishing.

[0031] Figure 6This diagram illustrates the concentration distribution of N atoms and divalent metal atoms implanted in this invention to form uniform doping. The advantage of this is that divalent metal atoms are inherently acceptor elements in gallium oxide, and implanting both elements increases the acceptor doping concentration. Furthermore, the difficulty in fabricating P-type semiconductors in oxide semiconductors like gallium oxide stems from the high electronegativity of O, which restricts hole movement in the P-type region, resulting in low mobility and a high-resistivity region. This invention effectively solves this problem by implanting a large amount of N to replace O, altering the lattice potential and reducing electronegativity, thereby increasing hole mobility in the P-type region. Simultaneously, the introduction of another dopant leads to an increase in the P-type doping concentration.

[0032] Although the invention has been described with reference to several exemplary embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A p-type doping method for Ga2O3 based on co-implantation, comprising three parts: ion implantation, post-annealing, and surface polishing, characterized in that, An N-type epitaxial layer is grown on a semiconductor substrate, followed by P-type doping via implantation. The implantation method involves co-implanting nitrogen and divalent metal elements using multi-energy ion implantation. The doping concentrations of the nitrogen and divalent metal elements are two orders of magnitude or higher than the donor doping concentration of the N-type epitaxial layer. The nitrogen and divalent metal elements provide holes to form acceptor doped impurities. The wafer is then annealed in an annealing furnace at 800–1200°C to prevent inward diffusion of dopants, repair lattice damage, and form uniform P-type doping within the Ga₂O₃ bulk. After annealing, the implanted... The surface is polished to reduce the interface states and roughness increase caused by implantation. The multi-energy ion implantation method co-implanting nitrogen and divalent metal elements and annealing the wafer in an annealing furnace at a temperature of 800–1200°C includes: firstly, implanting N atoms into the implantation layer, and then annealing the disordered N atoms at a temperature of 1200°C to replace the O elements in Ga2O3; then implanting divalent metal atoms into the implantation layer, and then annealing at a high temperature of 800°C, so that the implanted divalent metal atoms replace the Ga elements in Ga2O3, resulting in different activation energies and diffusion degrees of divalent metal atoms and N atoms in gallium oxide.

Images