A novel ion-implanted arc-shaped passivated dielectric terminal 4H-SiC avalanche photodetector

Abstract

The present invention discloses a novel 4H-SiC avalanche photodetector with an arc-shaped passivated dielectric terminal of ion implantation, wherein the terminal structure for suppressing the electric field strength at the edge of the avalanche photodetector is an arc-shaped passivated dielectric terminal. The terminal of the present invention forms an arc-shaped passivated dielectric terminal table through regional ion implantation and high-temperature oxidation process, which solves the shortcomings of small process window and poor reliability of the small-angle inclined table preparation process in the prior art of SiC APD, effectively suppresses the electric field gathering effect at the edge of SiC APD, is simple to prepare, and has good reliability.

Description

Technical Field

[0001] The invention relates to a novel 4H-SiC avalanche photoelectric detector with an ion-implanted arc-shaped passivation medium terminal, belonging to the technical field of semiconductor optoelectronic devices. Background Art

[0002] Ultraviolet detection has important applications in defense, industry, communications, scientific research, and civil use. Currently, common photon ultraviolet detectors on the market can be divided into two categories: vacuum photoelectric devices represented by PMT and solid-state ultraviolet detectors represented by Si, GaN, and SiC. Among them, vacuum photoelectric devices have the advantages of high sensitivity and high technical maturity, but their large size, high operating voltage, and fragility restrict the further application of this type of device. Solid-state ultraviolet detectors have the advantages of small size, high quantum efficiency, high reliability, and easy integration. They have been widely used in many applications such as environmental monitoring, ultraviolet disinfection, and ultraviolet curing. In these application scenarios, the intensity of ultraviolet radiation is relatively strong, generally in the range of mW / cm 2 Above, even reaching tens of W / cm 2 , most UV detectors are gain-free semiconductor UV detectors. In many core and emerging application areas, such as corona detection, biological detection, and fire alarm, weak UV light detection and even single photon detection are required, which requires UV detectors to have high gain and even single photon detection capabilities. High-performance UV avalanche photodiodes can have nanosecond response speeds and 10 5 With the above gain, it can even work in single-photon detection mode (Geiger mode), making it an ideal detector for measuring weak ultraviolet signals.

[0003] At present, the semiconductor materials commonly used in the preparation of ultraviolet detection are the first-generation semiconductor material Si and the third-generation semiconductor materials GaN and SiC. Among them, the band gap width of Si is 1.12eV, and the band response range covers the near-infrared-visible-ultraviolet range. It has a strong response to visible light. When used for ultraviolet detection, it is necessary to use expensive and large-area ultraviolet filters. In addition, Si materials have a strong absorption effect on ultraviolet light, resulting in extremely low quantum efficiency of Si detectors in the ultraviolet band. When preparing ultraviolet detectors, special ultraviolet enhanced structure design and special process flow design and improvement are required. As representative materials of the third-generation semiconductors, GaN and SiC materials have the advantages of large band gap, high electron drift velocity, high critical breakdown field strength, high thermal conductivity, excellent chemical stability, and no response to visible light. They are ideal materials for preparing ultraviolet detectors. Compared with Si-based UV detectors, GaN and SiC-based UV detectors have the following features: 1. Higher sensitivity; 2. No need to install UV filters, directly achieving visible light blindness and no response to visible light; 3. Able to work in harsh environments such as high temperature and strong radiation.

[0004] Silicon carbide (SiC) is a new third-generation semiconductor material with large bandgap, high electron drift velocity, high critical breakdown field strength, high thermal conductivity and excellent chemical stability. SiC material has great application potential in high temperature, high power, optoelectronics and radiation resistance.

[0005] The bandgap width of 4H-SiC semiconductor material is 3.26eV, and the corresponding light wavelength is 380nm. According to the principle of semiconductor photodetectors, semiconductor photodetectors will respond to light only when the energy of light is greater than the bandgap width of semiconductor materials. Therefore, 4H-SiC will respond only when the energy of light is greater than 3.26eV, that is, 4H-SiC only responds to light with a wavelength less than 380nm, and has no response to visible light. In addition, 4H-SiC material has the characteristics of large bandgap width and high critical displacement energy, which makes 4H-SiC have better radiation resistance and better long-term stability under high power density light intensity. At present, the growth technology of 4H-SiC material is mature and the crystal defects are relatively few, which is an ideal material for preparing high-performance avalanche ultraviolet detectors.

[0006] The common 4H-SiC APD structure is mainly a pn (pin) structure APD (avalanche photodetector). This type of device needs to work in a high electric field mode. Therefore, a reliable terminal structure is the key to achieving stable operation of the device. Due to the constraints of SiC processes such as epitaxy, diffusion, and ion implantation, it is impossible to achieve an effective guard ring and junction terminal extension (JTE) structure in the SiC APD device structure. Existing SiC APDs all use a method called "small angle beveled mesa" to form a terminal structure. This type of device structure uses a photoresist reflow process to form a mesa with a very small inclination angle. The purpose of making a small angle mesa is to suppress the peak electric field around the mesa and prevent the device from breaking down prematurely under high bias. Although the small-angle tilted table can effectively suppress the peak electric field at the edge of the SiC APD device table, there are also many problems: (1) The preparation process window is small, the device size cannot be freely changed, and high-performance SiC APD with high-performance ultra-large or ultra-small pixels cannot be achieved; (2) The device preparation process is complex and requires etching, damage repair and other processes, and there are many defects and poor reliability at the deposited passivation layer / SiC interface of the tilted table. Summary of the invention

[0007] The present invention provides a novel 4H-SiC avalanche photodetector with ion-implanted arc-shaped passivation dielectric terminal, which aims to solve the shortcomings of the existing SiC APD technology, such as low filling factor of small-angle inclined table, small preparation process window and poor reliability, and effectively suppress the SiC APD edge electric field concentration effect, improve the device avalanche uniformity, and expand the SiC APD chip preparation window.

[0008] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0009] A novel 4H-SiC avalanche photodetector with an ion-implanted arc-shaped passivation dielectric terminal is a PN junction (PIN) structure. The terminal structure for suppressing the electric field strength at the edge of the avalanche photodetector is an arc-shaped passivation dielectric terminal.

[0010] The arc-shaped passivation dielectric terminal is arranged at the periphery of the SiC active region.

[0011] The above-mentioned 4H-SiC avalanche photodetector does not require the production of a "small-angle tilted table", which significantly expands the SiCAPD chip preparation window.

[0012] In order to simplify the preparation process, the arc-shaped passivation dielectric terminal is prepared based on an ion implantation method and a high-temperature oxidation method.

[0013] The above-mentioned novel 4H-SiC avalanche photodetector with arc-shaped passivation dielectric terminal of ion implantation adopts selective ion implantation of SiC to form regional amorphous SiC. By utilizing the characteristic that the oxidation rate of amorphous SiC at high temperature is greater than that of single crystal SiC, SiC is oxidized in a high temperature environment to form an arc-shaped passivation dielectric terminal in the ion implanted SiC region. The arc-shaped passivation dielectric terminal can effectively expand the depletion layer width of the avalanche layer at the edge of the APD table, and effectively suppress the electric field concentration at the edge of the SiC APD avalanche layer, which can effectively overcome the various problems existing in the existing small-angle inclined table.

[0014] The above-mentioned ion implanted SiC elements include: H, Ar, Al, N and / or O elements.

[0015] In order to further ensure the performance of the device, the depth of ion implantation in SiC is: 0.2-5mm, preferably 0.5-1.5μm; the width of ion implantation is: 0.05-500mm, preferably 1-3mm. The energy of ion implantation in SiC is: 10-100keV; the dose of ion implantation in SiC is: 1×10 12 / cm 2 ~1×10 14 / cm 2 .

[0016] After the above ion implantation, high temperature oxidation ions are implanted into the SiC region to form an arc-shaped passivation dielectric terminal with a thickness of 0.1-1 mm, preferably 0.3-0.9 mm, where the aforementioned thickness refers to the maximum thickness of the arc-shaped passivation dielectric terminal (along the longitudinal direction, i.e., consistent with the depth direction of ion implantation).

[0017] In order to improve device reliability, the temperature of the arc-shaped passivation dielectric terminal formed by the high-temperature oxidation ion implantation into the SiC region is 1000° C.-1500° C. and the time is greater than 0.5 h.

[0018] The atmosphere of the arc-shaped passivation dielectric terminal formed by the high-temperature oxidation ion implantation in the SiC region is dry oxygen, wet oxygen, or the alternating use of the two atmospheres.

[0019] The 4H-SiC avalanche photodetector with ion implanted arc passivation dielectric terminal comprises, from top to bottom, an upper electrode 4H-SiC ohmic contact layer (p-type / n-type heavily doped), a 4H-SiC transition layer (p-type / n-type), an i-type 4H-SiC avalanche layer, a lower electrode 4H-SiC ohmic contact layer (n-type / p-type heavily doped), a 4H-SiC substrate (n-type / p-type) and a lower metal contact electrode (n-type / p-type), the upper electrode 4H-SiC ohmic contact layer (n-type / p-type heavily doped), and the lower metal contact electrode (n-type / p-type). An upper metal contact electrode (p-type / n-type) and an arc-shaped passivation dielectric terminal are provided on the ohmic contact layer, an ion-implanted SiC high-resistance region is provided below the arc-shaped passivation dielectric terminal, and a passivation layer is deposited on the upper electrode 4H-SiC ohmic contact layer except for the upper metal contact electrode (p-type / n-type), that is, a passivation layer is also provided on the surface of the arc-shaped passivation dielectric terminal, and the arc-shaped passivation dielectric terminal extends from the upper electrode 4H-SiC ohmic contact layer to at least the i-type 4H-SiC avalanche layer.

[0020] During the preparation, a lower electrode 4H-SiC ohmic contact layer (n-type / p-type heavily doped), an i-type 4H-SiC avalanche layer, a 4H-SiC transition layer (p-type / n-type) and an upper electrode 4H-SiC ohmic contact layer (p-type / n-type heavily doped) are sequentially deposited on a 4H-SiC substrate (n-type / p-type), and then ion implantation and high-temperature oxidation are sequentially performed to form an arc-shaped passivation dielectric terminal, wherein the ion implantation depth is at least to the i-type 4H-SiC avalanche layer, and the deepest can reach the lower electrode 4H-SiC ohmic contact layer (n-type / p-type heavily doped), and then high-temperature oxidation is performed, the oxidation rate of the SiC ion implantation area is faster, and an arc-shaped passivation dielectric terminal similar to an ellipsoid will be spontaneously formed, and then surface passivation is performed to form a passivation layer, and finally the passivation layer in the optical window area is removed by wet etching, and an electrode layer is deposited.

[0021] For the preparation techniques not mentioned in this application, reference is made to the preparation of existing avalanche photodetectors.

[0022] In order to take into account the device volume and performance requirements, the thickness of the upper electrode 4H-SiC ohmic contact layer is 0.1-0.3mm, the thickness of the 4H-SiC transition layer is 0.1-0.3mm, the thickness of the i-type 4H-SiC avalanche layer is 0.3-2mm, the thickness of the lower electrode 4H-SiC ohmic contact layer is 1-10mm, the thickness of the 4H-SiC substrate is 200-400mm, the thickness of the upper metal contact electrode and the lower metal contact electrode are both 0.1-2mm, and the thickness of the passivation layer is 0.5-1μm. The upper electrode and the lower electrode are single-layer or multi-layer metal composite structures, and the metal composition of the upper electrode and the lower electrode contact can be the same or different, and can be a composite structure of one or more metals among Ti, Al, Ni, Au, and Pt metals, preferably a composite structure, and more preferably a multi-layer structure of Ni / Ti / Al / Au connected in sequence.

[0023] To ensure device performance, the average doping concentration of the upper electrode 4H-SiC ohmic contact layer is between 3×10 18 -2×10 19 cm -3 The average doping concentration of the 4H-SiC transition layer is between 1×10 17 -5×10 18 cm -3 The average doping concentration of the i-type 4H-SiC avalanche layer is between 1×10 14 -1×10 17 cm -3 The average doping concentration of the lower electrode 4H-SiC ohmic contact layer is between 5×10 17 -2×10 19 cm -3 The average doping concentration of 4H-SiC substrate is between 5×10 17 -2×10 19 cm -3 The material used for the passivation protection layer is at least one of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide or hafnium oxide.

[0024] The technologies not mentioned in the present invention are all referred to the prior art.

[0025] The novel ion-implanted arc-shaped passivation dielectric terminal 4H-SiC avalanche photodetector of the present invention breaks the disadvantages of "the traditional 4H-SiC APD technology uses etching to form an inclined table terminal structure, which has a low filling factor and a small process window". 4H-SiC is ion-implanted to form an amorphous material, and the oxidation rate of amorphous 4H-SiC is greater than that of single-crystal 4H-SiC. An arc-shaped passivation dielectric terminal is formed at the edge of the 4H-SiCAPD table, and the depletion layer width of the avalanche layer at the table edge is expanded to effectively suppress the electric field concentration at the table edge. At the same time, the flexibility of the ion implantation technology and the wide process window are combined to effectively improve the filling factor of the 4H-SiCAPD device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The structure diagram of the conventional inclined table-terminated 4H-SiC APD device in Comparative Example 1;

[0027] Figure 2 The schematic diagram of the formation of the novel ion implantation arc passivation dielectric terminal in Example 1 (the upper figure is a schematic diagram of the ion implantation, and the lower figure is a schematic diagram of the finished product structure);

[0028] Figure 3 The figure is a field intensity distribution diagram inside the conventional inclined table-terminated 4H-SiC APD device in comparative example 1, wherein the left figure is a cross-sectional two-dimensional distribution diagram of field intensity variation; the right figure is a field intensity variation curve in the horizontal direction at the junction of the p-layer and the i-layer;

[0029] Figure 4 The figure is a field intensity distribution diagram inside the 4H-SiC APD device with a novel ion-implanted arc-shaped passivation dielectric terminal in Example 1, wherein the left figure is a cross-sectional two-dimensional distribution diagram of field intensity variation; the right figure is a field intensity variation curve in the horizontal direction at the junction of the p-layer and the i-layer;

[0030] Figure 5 is a simplified structural diagram of the ion-implanted arc-shaped passivation dielectric terminal 4H-SiC APD in Example 2, and the device is prepared on a p-type SiC substrate material;

[0031] In the figure, 101 is a lower metal contact electrode, 102 is an n-type 4H-SiC conductive substrate, 103 is an n-type 4H-SiC ohmic contact layer, 104 is an i-type 4H-SiC avalanche layer, 105 is a p-type doped 4H-SiC transition layer, 106 is a p+ type heavily doped 4H-SiC metal contact layer, 107 is a passivation layer, 108 is an upper metal contact electrode, 109 is an inclined table terminal, 202 is a p-type 4H-SiC conductive substrate, 203 is a p-type SiC contact layer, 205 is an n-type SiC transition layer, 206 is an n+ type SiC ohmic contact layer, 209 is an arc-shaped passivation dielectric terminal, and 210 is an ion-implanted SiC high-resistance region. DETAILED DESCRIPTION

[0032] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0033] The directional terms such as up and down, top and bottom, vertical, etc. in this application are all based on the relative orientation or position relationship shown in the drawings and should not be understood as absolute limitations on this application.

[0034] Embodiment 1:

[0035] like Figure 2 As shown in the figure below, a novel ion-implanted arc-shaped passivation dielectric terminal 4H-SiC APD is prepared on an n-type 4H-SiC substrate material, and includes, from bottom to top, a lower metal contact electrode (n-type contact electrode) 101, an n-type 4H-SiC conductive substrate 102, an n-type 4H-SiC ohmic contact layer 103, an i-type 4H-SiC avalanche layer 104, a p-type doped 4H-SiC transition layer 105, and a p+ type heavily doped 4H-SiC metal contact layer 106, a p-type upper metal contact electrode 108, and an arc-shaped passivation dielectric terminal 209 are both arranged on the p+ type On the heavily doped 4H-SiC metal contact layer 106, the arc-shaped passivation dielectric terminal 209 extends from the p+ type heavily doped 4H-SiC metal contact layer 106 to the i-type 4H-SiC avalanche layer 104, with a total depth of 0.4μm, and the ion-implanted SiC high-resistance region 210 extends to the n-type 4H-SiC ohmic contact layer, with a total depth of 1μm. The p+ type heavily doped 4H-SiC metal contact layer 106 is provided with a passivation layer 107 except for the p-type upper metal contact electrode 108.

[0036] Comparative Example 1

[0037] like Figure 1FIG. 1 is a schematic diagram of a conventional inclined terrace terminal SiC APD structure, which is prepared on an n-type 4H-SiC substrate material and includes, from bottom to top, a lower metal contact electrode (n-type contact electrode) 101, an n-type 4H-SiC conductive substrate 102, an n-type 4H-SiC ohmic contact layer 103, an i-type 4H-SiC avalanche layer 104, a p-type doped 4H-SiC transition layer 105, and a p+-type heavily doped 4H-SiC metal contact layer 106. Starting from the p+-type heavily doped 4H-SiC metal contact layer 106, the inclined terrace is etched downward to the i-type 4H-SiC avalanche layer 104, and the etching depth is 0.4 μm in total, that is, the i-type 4 Part of the height of the H-SiC avalanche layer 104 (the height of 0.1 mm at the top), the p-type doped 4H-SiC transition layer 105 (0.2 μm) and the p+ type heavily doped 4H-SiC metal contact layer 106 (0.1 μm) together form an inclined table top that tapers from bottom to top and is larger at the bottom and smaller at the top. A passivation layer is provided on the side of the inclined table top to form an inclined table top terminal 109. A p-type upper metal contact electrode 108 is provided on the top of the p+ type heavily doped 4H-SiC metal contact layer 106. A passivation layer 107 is provided on the top of the p+ type heavily doped 4H-SiC metal contact layer 106 except for the p-type upper metal contact electrode 108.

[0038] Figure 2 Shown with Figure 1 The device structure corresponds to the improved novel ion-implanted arc-shaped passivation dielectric terminal 4H-SiC APD of the present application. The substrate material, the lower electrode 4H-SiC ohmic contact layer, the i-type 4H-SiC avalanche layer, the doping concentration, the doping type and the metal contact electrode of the device are the same as those of the conventional inclined table terminal SiC APD of Example 1. The difference is that: Figure 2 The mesa terminal of the device shown is an arc-shaped passivated dielectric terminal. The terminal preparation process is similar to Figure 1 The device structures shown are also different.

[0039] On an n-type 4H-SiC conductive substrate 102, an n-type 4H-SiC ohmic contact layer 103, an i-type 4H-SiC avalanche layer 104, a p-type doped 4H-SiC transition layer 105, and a p+-type heavily doped 4H-SiC metal contact layer 106 are sequentially grown, and then an arc-shaped passivation dielectric terminal is prepared. Figure 2 The preparation of the arc-shaped passivation dielectric terminal of the SiC APD shown in the figure includes: regional ion implantation and high temperature oxidation. The arc-shaped passivation dielectric terminal is formed by regional ion implantation and high temperature oxidation. The depth of the arc-shaped passivation dielectric terminal reaches the inside of the i-type 4H-SiC avalanche layer 104. The specific process and parameters are: Ar is implanted in three steps on the SiC epitaxial surface through selective ion implantation. The implantation energy and dose are: (1) 50 keV, 5×10 14 cm -2; (2) 130keV, 2×10 15 cm -2 ; and (3) 300keV, 5×10 15 cm -2 The ion implantation direction is vertical downward, the ion implantation depth is 1 μm, and the implantation region width is 2 μm (cylindrical with a diameter of 2 μm). The regional ion implantation SiC epitaxial wafer is placed in a wet oxygen environment and subjected to high temperature oxidation at a temperature of 1150° C. for 6 hours to form a Figure 2 The (ellipsoidal) curved passivation dielectric termination is shown with a maximum thickness (maximum height) of 400 nm. Figure 1 The SiC APD terminal preparation method shown includes high temperature photoresist reflow and inclined terrace etching process, and an inclined terrace terminal is formed by etching photoresist pattern transfer technology, and its depth reaches into the i-type 4H-SiC avalanche layer 104.

[0040] Figure 1 and 2 The SiC APD metal electrode and passivation layer preparation method shown includes: surface passivation, n-type and p-type ohmic contact electrode preparation, surface passivation forms a passivation layer by PECVD, the passivation layer is deposited on the upper electrode 4H-SiC ohmic contact layer except the upper metal contact electrode 108, that is, the surface of the arc-shaped passivation medium terminal 209 is also provided with a passivation layer, and then the passivation layer in the optical window area is removed by wet etching, and the electrode layer is deposited, wherein the lower metal contact electrode (back electrode metal ohmic contact layer) 101 and the upper metal contact electrode (upper electrode metal ohmic contact layer) 108 are both multi-layer metal composite structures, which are deposited on the back of the n-type 4H-SiC conductive substrate 102 and the surface of the p+ type heavily doped 4H-SiC metal contact layer 106 by evaporation or sputtering process, and then formed by high temperature annealing.

[0041] contrast Figure 1 and Figure 2 There are obvious differences in device structure and device terminals. Since the ion implantation process has higher precision, the processing accuracy is higher in the preparation of device terminals, and the terminal structure size control is more flexible. At the same time, 4H-SiC APD with ultra-small avalanche zone can be prepared; while the tilted table terminal is restricted by the photoresist reflow process and the etching process window, the tilted table angle cannot be flexibly controlled, and is affected by the large difference in etching rate between photoresist and SiC (the etching rate ratio of photoresist to SiC>4:1), and 4H-SiC APD with ultra-small avalanche zone cannot be prepared.

[0042] The purpose of preparing the terminal of SiC APD is to effectively weaken the electric field spike around the table. The advantages of the new ion-implanted arc-shaped passivation dielectric terminal 4H-SiC APD will be further illustrated by Silvaco device simulation data.

[0043] Figure 2 , Figure 3 The specific structural parameters of the device are set as follows: the doping concentration of the conductive n-type 4H-SiC substrate 102 is 5×10 18 cm -3 , thickness 300 μm; the doping concentration of the lower electrode n-type 4H-SiC ohmic contact layer 103 is 1×10 19 cm -3 , the thickness is 2 μm, the doping concentration of the i-type 4H-SiC avalanche layer 104 is 1×10 15 cm -3 , thickness 0.6 μm; the doping concentration of the p-type 4H-SiC transition layer 105 is 5×10 17 cm -3 , thickness 0.2 μm; the doping concentration of the p+ type SiC ohmic contact layer 106 is 1×10 19 cm -3 , thickness 0.1μm, the surface passivation layer 107 of the device is silicon dioxide with a thickness of 0.8μm; the lower metal contact electrode (n-type contact electrode) 101 and the upper metal contact electrode (p-type contact electrode) 108 of the detector are both multi-layer structures based on metal Ni / Ti / Al / Au (35 / 50 / 150 / 100nm), that is, including a Ni layer with a thickness of 35nm, a Ti layer with a thickness of 50nm, an Al layer with a thickness of 150nm and an Au layer with a thickness of 100nm, wherein the Au layer of the lower metal contact electrode 101 is located at the bottom layer, and the Au layer of the upper metal contact electrode 108 is located at the top layer.

[0044] Figure 3 The tilt angle of the mesa SiCAPD ( Figure 1 ), where the left figure is a 2D cross-sectional distribution of field intensity changes, and the right figure is a curve of field intensity changes along the horizontal direction of the interface between the p-layer and the i-layer. The mesa etching depth is 0.4 μm, which has penetrated into the i-type SiC avalanche layer 104.

[0045] From the results of device simulation calculation, it can be seen that under the reverse bias voltage of 190V, the maximum electric field strength in the tilted mesa SiC APD device is located at the junction of the i-type SiC avalanche layer 104 and the p-type SiC transition layer 105 and close to the edge of the mesa (left figure). From the specific distribution of the electric field strength along the boundary line between the i-type SiC avalanche layer 104 and the p-type SiC transition layer 105 (right figure), it can be seen that when using the tilted mesa structure, the electric field peak at the edge of the SiCAPD mesa is only 0.22MV / cm higher than the internal field strength, indicating that the small tilt angle (tilt angle of 8°) mesa can effectively suppress the electric field spike at the edge of the SiC APD mesa.

[0046] Figure 4 The arc-shaped passivated dielectric mesa SiC APD ( Figure 2 ), where the left figure is a 2D cross-sectional distribution of field intensity changes, and the right figure is a horizontal field intensity change curve along the interface between the p-layer and the i-layer. The arc-shaped passivation medium has a depth of 0.4 μm, penetrating into the i-type SiC avalanche layer 104.

[0047] From the results of device simulation calculation, it can be seen that under the reverse bias voltage of 190V, the maximum electric field strength in the arc-shaped passivated dielectric table SiCAPD device is located at the junction of the i-type SiC avalanche layer 104 and the p-type SiC transition layer 105 and close to the edge of the table (left figure). From the specific distribution of the electric field strength along the boundary line of the i-type SiC avalanche layer 104 and the p-type SiC transition layer 105 (right figure), it can be seen that when using the arc-shaped passivated dielectric table structure, the electric field peak at the edge of the SiC APD table is only 0.2MV / cm higher than the internal field strength, indicating that the arc-shaped passivated dielectric terminal can also effectively suppress the electric field spike at the edge of the SiC APD table, which is similar to the electric field spike suppression effect of the inclined table terminal on the edge of the SiC APD table.

[0048] Table 1 shows the tilted table SiC APD ( Figure 1 ) and curved passivated dielectric mesa SiC APD ( Figure 2 Comparison of the field strength change at the edge of the table, the maximum tolerable overload bias, and the maximum avalanche current (see figure below).

[0049] Tilted table SiC APD Curved passivated dielectric table SiC APD Electric field strength increment at the edge of the table +0.22MV / cm +0.2MV / cm Maximum overload bias voltage +2V +5V Maximum avalanche current <![CDATA[1×10 -5 A]]> <![CDATA[1×10 -3 A]]>

[0050] Note: Since the device structure is symmetrical, Figure 1 Only the right half of the device is shown. Figure 3 , Figure 4 Only the right half of the device cross section is drawn as a schematic diagram.

[0051] Example 2

[0052] Figure 5 This is a simplified structural diagram of another arc-shaped passivated dielectric terminal SiC APD device proposed by the present invention. The device is prepared on a p-type 4H-SiC conductive substrate material. The basic components of the device include: a p-type 4H-SiC conductive substrate 202. On the p-type 4H-SiC conductive substrate 202, grown in sequence: a p-type SiC contact layer 203, an i-type SiC avalanche layer 104, an n-type SiC transition layer 205, and an n+ type SiC ohmic contact layer 206; the thickness and doping concentration of each layer are consistent with the thickness and doping concentration of the corresponding layer in Example 1. The surface passivation layer 107, the upper contact electrode 108 and the lower contact electrode 101 are Figure 2 The structure is consistent. Figure 5 The mesa structure of the device Figure 2 The structure is also completely consistent, that is, the table is an arc-shaped passivation dielectric terminal, and its depth at least reaches the i-type SiC avalanche layer 104.

[0053] Figure 5 The arc-shaped passivated dielectric terminal SiC APD device shown in Figure 2 The SiCAPD devices with mid-arc passivated dielectric termination are identical in physical mechanism, except that one is a nip structure from top to bottom and the other is a pin structure from top to bottom. Due to the symmetry of the structure and the distribution of conductive polarity and doping concentration of each layer, Figure 5 The device structure shown also has the effect of suppressing the electric field spike at the edge of the APD table. The corresponding conclusion is also supported by the device simulation calculation results, which will not be repeated here.

Claims

1. A 4H-SiC avalanche photodetector with an ion-implanted arc-shaped passivation dielectric terminal, which has a PN junction structure and is characterized by: The terminal structure for suppressing the electric field strength at the edge of the avalanche photodetector is an arc-shaped passivated dielectric terminal; The preparation method of the arc-shaped passivation dielectric terminal is as follows: after depositing a lower electrode 4H-SiC ohmic contact layer, an i-type 4H-SiC avalanche layer, a 4H-SiC transition layer and an upper electrode 4H-SiC ohmic contact layer on a 4H-SiC substrate in sequence, ion implantation and high-temperature oxidation are performed in sequence to form an arc-shaped passivation dielectric terminal, wherein the depth of the ion implantation is at least to the i-type 4H-SiC avalanche layer and can reach the bottom electrode 4H-SiC ohmic contact layer at the deepest. After the ion implantation is completed, high-temperature oxidation is performed to spontaneously form an ellipsoidal arc-shaped passivation dielectric terminal.

2. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 1, characterized in that: The arc-shaped passivation dielectric terminal is manufactured based on ion implantation and high temperature oxidation methods.

3. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 1 or 2, characterized in that: The elements implanted by ions include H, Ar, Al, N and / or O elements.

4. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 1 or 2, characterized in that: The depth of ion implantation is 0.2-5 mm; the width of ion implantation is 0.05-500 mm; the energy of ion implantation into SiC is 10-100 keV; the dose of ion implantation into SiC is 1×10 12 / cm 2 ~1×10 14 / cm 2 .

5. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 1 or 2, characterized in that: After ion implantation, the ion implanted area is oxidized at high temperature to form an arc-shaped passivation dielectric terminal with a thickness of 0.1-1 mm.

6. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 1 or 2, characterized in that: The temperature of high temperature oxidation is 1000°C-1500°C, and the time is greater than 0.5 h; the atmosphere during high temperature oxidation is dry oxygen, wet oxygen, or the alternating use of the two atmospheres.

7. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 1 or 2, characterized in that: The invention comprises, from top to bottom, an upper electrode 4H-SiC ohmic contact layer, a 4H-SiC transition layer, an i-type 4H-SiC avalanche layer, a lower electrode 4H-SiC ohmic contact layer, a 4H-SiC substrate and a lower metal contact electrode. An upper metal contact electrode and an arc-shaped passivation dielectric terminal are arranged on the upper electrode 4H-SiC ohmic contact layer. A passivation layer is arranged on the upper electrode 4H-SiC ohmic contact layer except for the upper metal contact electrode. The arc-shaped passivation dielectric terminal extends from the upper electrode 4H-SiC ohmic contact layer to at least the i-type 4H-SiC avalanche layer.

8. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 7, characterized in that: The preparation method comprises the following steps: depositing a lower electrode 4H-SiC ohmic contact layer, an i-type 4H-SiC avalanche layer, a 4H-SiC transition layer and an upper electrode 4H-SiC ohmic contact layer on a 4H-SiC substrate in sequence, and then performing ion implantation and high-temperature oxidation in sequence to form an arc-shaped passivation dielectric terminal, wherein the depth of the ion implantation is at least to the i-type 4H-SiC avalanche layer and can reach the lower electrode 4H-SiC ohmic contact layer at the deepest; performing high-temperature oxidation after the ion implantation to spontaneously form an ellipsoidal arc-shaped passivation dielectric terminal, and then performing surface passivation to form a passivation layer, and finally preparing an upper metal contact electrode and a lower metal contact electrode.

9. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 7, characterized in that: The thickness of the upper electrode 4H-SiC ohmic contact layer is 0.1-0.3 mm, the thickness of the 4H-SiC transition layer is 0.1-0.3 mm, the thickness of the i-type 4H-SiC avalanche layer is 0.3-2 mm, the thickness of the lower electrode 4H-SiC ohmic contact layer is 1-10 mm, the thickness of the 4H-SiC substrate is 200-400 mm, the thickness of the upper metal contact electrode and the lower metal contact electrode are both 0.1-2 mm, and the thickness of the passivation layer is 0.5~1μm.

10. The 4H-SiC avalanche photodetector with ion implanted arc-shaped passivation dielectric termination according to claim 7, characterized in that: The average doping concentration of the upper electrode 4H-SiC ohmic contact layer is between 3×10 18 -2×10 19 cm -3 The average doping concentration of the 4H-SiC transition layer is between 1×10 17 - 5×10 18 cm -3 The average doping concentration of the i-type 4H-SiC avalanche layer is between 1×10 14 - 1×10 17 cm -3 The average doping concentration of the lower electrode 4H-SiC ohmic contact layer is between 5×10 17 -2×10 19 cm -3 The average doping concentration of 4H-SiC substrate is between 5×10 17 -2×10 19 cm -3 The material used for the passivation layer is at least one of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide or hafnium oxide.

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