Silicon carbide diode with terminal structure

Abstract

A silicon carbide diode with a terminal structure relates to the technical field of semiconductors. By changing the composition structure of the inorganic passivation layer, a SiO2, SiN and SiO2 sandwich structure is designed, the thickness of each layer of SiO2 is not less than 200nm, the thickness of SiN is not less than 600nm, and the upper layer is the organic passivation layer. A sandwich-like three-layer structure enables the device to be better protected in a high-voltage H3TRB reliability project, and in the high-voltage H3TRB project, along with proceeding of the project, the inorganic passivation layer of the three-layer structure can ensure that the device can better isolate water vapor and protect a silicon carbide epitaxial layer in the experiment process, so that the high-voltage H3TRB reliability of the device is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductors, in particular to a silicon carbide diode with a terminal structure. Background Art

[0002] Today, sustainable development has become an important issue worldwide. A large part of the daily needs of human beings is provided by power electronic systems, which are widely used in various fields that require power conversion, but their high energy consumption has always been a prominent problem. Improving the conversion efficiency of power electronic systems and reducing power loss during transmission will become a powerful measure for energy conservation and emission reduction. In different application fields, electric energy needs to be converted into different forms of voltage, current and waveform, and power semiconductor devices play a key role in this. In recent years, a new generation of power devices based on silicon carbide (SiC) materials have emerged, and have gradually gained favor from academia and industry for their high breakdown voltage, low on-resistance, and fast switching speed. In the process of the advancement of silicon carbide devices, efficient device design methods, stable and low-cost wafer production processes, and the behavioral characteristics and reliability of devices under abnormal conditions all need to be carefully studied. And silicon carbide diodes are an excellent platform for studying these issues.

[0003] The most popular silicon carbide diodes include junction barrier Schottky diodes (JBS diodes) and mixed PiN junction barrier Schottky diodes (MPS diodes). They have achieved a good balance between forward conduction, reverse blocking performance and surge and avalanche reliability. Many researchers have conducted in-depth research on the relationship between the cell design and device performance of MPS / JBS diodes, and many manufacturers have developed mature commercial products.

[0004] As devices are increasingly accepted by users, users are no longer satisfied with only focusing on the static performance of the devices. Whether the devices can work stably in the system for a long time is also a problem that users are concerned about. Therefore, the reliability of the devices has become particularly prominent. Especially for customers of photovoltaics and charging piles, the high-voltage H3TRB capability is a performance that customers are very concerned about. In reliability experiments, high-voltage and high-humidity environments may cause device failures. In order to improve the reliability of the devices, it is necessary to design a new structure. Utility Model Content

[0005] In view of the above problems, the utility model provides a silicon carbide diode with a terminal structure, which ensures that the device is better isolated from water vapor during the experiment and protects the silicon carbide epitaxial layer, thereby improving the high-voltage H3TRB reliability of the device.

[0006] The technical solution of the utility model is:

[0007] A silicon carbide diode with a terminal structure comprises a back thickening metal, a back ohmic contact metal, a silicon carbide substrate and a silicon carbide epitaxial layer arranged in sequence from bottom to top;

[0008] The top surface of the silicon carbide epitaxial layer is provided with a plurality of P-type doping regions 1, a P-type doping region 2 and a plurality of P-type doping regions 3 extending downward at intervals; the P-type doping region 2 is located between the plurality of P-type doping regions 1 and the plurality of P-type doping regions 3;

[0009] The top surface of the silicon carbide epitaxial layer is provided with field oxygen passing through the P-type doping region three and extending to the P-type doping region two;

[0010] The top surface of the silicon carbide epitaxial layer is provided with a front contact electrode passing through the P-type doping region 1 and extending to the top surface of the field oxide;

[0011] The top surface of the front contact electrode is provided with a front thickened metal;

[0012] The top surface of the field oxide is provided with a passivation layer extending to the top surface of the front thickened metal; the passivation layer comprises an inorganic passivation layer and an organic passivation layer connected in sequence from bottom to top;

[0013] The inorganic passivation layer includes a passivation layer 1 7a, a passivation layer 2 7b and a passivation layer 3 7c which are sequentially connected from bottom to top.

[0014] Specifically, the end of the organic passivation layer extends downward through the inorganic passivation layer to the top surface of the front thickened metal.

[0015] Specifically, the thickness of the passivation layer 1 7a and the passivation layer 2 7c is not less than 200 nm respectively.

[0016] Specifically, the thickness of the passivation layer 7b is not less than 600nm.

[0017] Specifically, the cross section of the P-type doping region 1 is rectangular and is distributed at equal intervals in the source region.

[0018] The present invention changes the composition structure of the inorganic passivation layer to design a sandwich structure of SiO2, SiN, and SiO2, wherein the thickness of each SiO2 layer is not less than 200nm, the thickness of SiN is not less than 600nm, and the upper layer is an organic passivation layer. The three-layer structure similar to the sandwich enables the device to be better protected in the high-voltage H3TRB reliability project. In the high-voltage H3TRB project, as the project proceeds, the three-layer inorganic passivation layer can ensure that the device is better isolated from water vapor during the experiment and protect the silicon carbide epitaxial layer, thereby improving the reliability of the high-voltage H3TRB of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of step S100 of the utility model;

[0020] Figure 2 It is a structural schematic diagram of step S200 of the utility model;

[0021] Figure 3 It is a structural schematic diagram of step S300 of the utility model;

[0022] Figure 4 It is a structural schematic diagram of step S400 of the utility model;

[0023] Figure 5 It is a schematic diagram of the structure of step S500 of the utility model;

[0024] Figure 6 It is a structural schematic diagram of step S600 of the utility model;

[0025] Figure 7 It is a structural schematic diagram of step S600 of the utility model;

[0026] Figure 8 It is a structural schematic diagram of step S700 of the utility model;

[0027] Fig. 9 It is a structural schematic diagram of step S800 of the utility model;

[0028] 1 is silicon carbide substrate, 2 is silicon carbide epitaxy,

[0029] 3a is the P-type doping region 1, 3b is the P-type doping region 2, and 3c is the P-type doping region 3.

[0030] 4 is field oxygen, 5 is Schottky contact electrode, 6 is front thickened metal, 7 is inorganic passivation layer, 7a is passivation layer one, 7b is passivation layer two, 7c is passivation layer three, 8 is organic passivation layer, 9 is back ohmic contact electrode, and 10 is thickened metal. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0032] In the description of the present invention, it should be understood that the terms "upper", "lower", "left", "right", "vertical", "horizontal", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 a limitation on the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0033] In the description of the present invention, it should be noted that, 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 a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] A silicon carbide diode with a terminal structure comprises the following steps:

[0035] S100, growing a silicon carbide epitaxial layer 2 on the silicon carbide substrate 1; Figure 1 As shown;

[0036] S200, transferring the ion implantation pattern to the hard mask by coating, photolithography and development, and then using a dry etching process to produce a P-type ion implantation area, and forming a plurality of P-type doping regions 1 3a, a P-type doping region 2 3b and a plurality of P-type doping regions 3c on the top of the silicon carbide epitaxy 2 by aluminum ion implantation and high temperature activation annealing; Figure 2 As shown;

[0037] S300, forming a field oxide 4 on the P-type doping region 2 3b and the P-type doping region 3c at the terminal by chemical vapor deposition; Figure 3 As shown;

[0038] The cross section of the P-type doping region 1 3a is rectangular and is distributed at equal intervals in the source region; the P-type doping region 2 3b is a terminal main junction withstand voltage structure; the P-type doping region 3c is a terminal voltage divider ring structure, which is distributed at non-equal intervals;

[0039] S400, sputtering metal on the P-type doping region 1 3a, the P-type doping region 2 3b and the field oxide 4, and forming a Schottky contact electrode 5 after annealing. The Schottky annealing temperature is generally 400°C-500°C; Figure 4 As shown;

[0040] S500, depositing a front thickened metal 6 on the Schottky contact electrode 5 as an anode lead; Figure 5 As shown;

[0041] S600, an inorganic passivation layer 7 and an organic passivation layer 8 are sequentially formed at the terminal position of the device, and the inorganic passivation layer 7 and the organic passivation layer 8 start from the top of the front thickened metal 6 to the end of the chip dicing road, respectively.

[0042] The inorganic passivation layer 7 is the lower layer, and the organic passivation layer 8 is the upper layer. The inorganic passivation layer 7 and the organic passivation layer 8 are collectively referred to as the passivation layer, which plays the role of isolating water vapor and protecting the terminal; Figure 6 and Figure 7 As shown;

[0043] S700, forming a back ohmic contact electrode 9 on the back side of the silicon carbide substrate 1; Figure 8 As shown;

[0044] S800, depositing thickened metal 10 on the ohmic contact electrode 9 to form a cathode, completing device manufacturing, refer to Fig. 9 shown.

[0045] Specifically, in step S200, the P-type injection is high-temperature aluminum ion injection, the injection temperature is 450°C-550°C, the injection energy is 20KV-500KV, and in order to ensure the appropriate injection morphology, it is generally divided into multiple injections. The activation temperature after silicon carbide ion injection is relatively high, the temperature is 1600-1800°C, and the time is 10min-30min. In order to prevent the precipitation of silicon atoms in high-temperature silicon carbide and cause surface carbonization, a carbon film is generally sputtered for protection before high-temperature annealing.

[0046] In step S600, the passivation layer 1 7a, the passivation layer 2 7b and the passivation layer 3 7c in the inorganic passivation layer 7 are formed by multiple chemical vapor deposition methods, wherein the thickness of SiO2 is not less than 200nm, and the thickness of SiN is not less than 600nm.

[0047] A silicon carbide diode with improved reliability comprises a back thickening metal 10, a back ohmic contact metal 9, a silicon carbide substrate 1 and a silicon carbide epitaxial layer 2 arranged in sequence from bottom to top;

[0048] The top surface of the silicon carbide epitaxial layer 2 is provided with a plurality of P-type doping regions 1 3a, a P-type doping region 2 3b and a plurality of P-type doping regions 3c extending downward at intervals;

[0049] The top surface of the silicon carbide epitaxial layer 2 is provided with a field oxide 4 passing through the P-type doping region 3c and extending to the P-type doping region 2 3b;

[0050] The top surface of the silicon carbide epitaxial layer 2 is provided with a front contact electrode 5 passing through the P-type doping region 1 3a and extending to the top surface of the field oxide 4;

[0051] The top surface of the front contact electrode 5 is provided with a front thickening metal 6;

[0052] The top surface of the field oxide 4 is provided with a passivation layer extending to the top surface of the front thickened metal 6; the passivation layer comprises an inorganic passivation layer 7 and an organic passivation layer 8 connected sequentially from bottom to top;

[0053] The inorganic passivation layer 7 includes a passivation layer 1 7a, a passivation layer 2 7b and a passivation layer 3 7c which are sequentially connected from bottom to top.

[0054] The end of the organic passivation layer 8 extends downward through the inorganic passivation layer 7 to the top surface of the front thickened metal 6 .

[0055] The passivation layer 1 7a and the passivation layer 3 7c are SiO2 passivation layer 1 7a and SiO2 passivation layer 3 7c respectively;

[0056] The second passivation layer 7b is a SiN passivation layer 7b.

[0057] The thickness of the passivation layer 1 7a and the passivation layer 3 7c are equal, wherein the thickness of SiO2 of the passivation layer 1 7a and the passivation layer 3 7c is not less than 200nm respectively, and the thickness of the SiN passivation layer 2 7b is not less than 600nm. When the thickness is less than this value, the waterproof performance of the passivation layer will be defective.

[0058] The organic passivation layer 8 is a polyimide protective layer, which acts like a sponge and absorbs water.

[0059] The preparation process of the utility model designs the passivation layer 7 into a three-layer structure similar to a sandwich, forming better density, so that in reliability tests, especially verification projects with water vapor, water vapor can be better isolated to protect the device, thereby improving the reliability of the product.

Claims

1. A silicon carbide diode with a terminal structure, characterized in that: It comprises a back thickening metal (10), a back ohmic contact metal (9), a silicon carbide substrate (1) and a silicon carbide epitaxial layer (2) which are arranged in sequence from bottom to top; The top surface of the silicon carbide epitaxial layer (2) is provided with a plurality of P-type doping regions 1 (3a), a P-type doping region 2 (3b) and a plurality of P-type doping regions 3 (3c) extending downward at intervals; the P-type doping region 2 (3b) is located between the plurality of P-type doping regions 1 (3a) and the plurality of P-type doping regions 3 (3c); The top surface of the silicon carbide epitaxial layer (2) is provided with a field oxygen (4) passing through the P-type doping region three (3c) and extending to the P-type doping region two (3b); The top surface of the silicon carbide epitaxial layer (2) is provided with a front contact electrode (5) passing through the P-type doped region 1 (3a) and extending to the top surface of the field oxide (4); The top surface of the front contact electrode (5) is provided with a front thickening metal (6); The top surface of the field oxide (4) is provided with a passivation layer extending to the top surface of the front thickened metal (6); the passivation layer comprises an inorganic passivation layer (7) and an organic passivation layer (8) connected in sequence from bottom to top; The inorganic passivation layer (7) comprises a passivation layer 1 (7a), a passivation layer 2 (7b) and a passivation layer 3 (7c) which are sequentially connected from bottom to top.

2. A silicon carbide diode with a terminal structure according to claim 1, characterized in that: The end of the organic passivation layer (8) extends downward through the inorganic passivation layer (7) to the top surface of the front thickened metal (6).

3. The silicon carbide diode with a terminal structure according to claim 1, characterized in that: The thickness of the passivation layer 1 (7a) and the passivation layer 3 (7c) is not less than 200 nm respectively.

4. The silicon carbide diode with a terminal structure according to claim 1, characterized in that: The thickness of the second passivation layer (7b) is not less than 600nm.

5. The silicon carbide diode with a terminal structure according to claim 1, characterized in that: The cross section of the P-type doped region 1 (3a) is rectangular and is evenly spaced in the source region.

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