Self-powered field plate structure of silicon carbide power diode and preparation method thereof

Abstract

This invention provides a self-powered field plate structure for a silicon carbide power diode and its fabrication method. The self-powered field plate structure is composed of silicon dioxide and the thermoelectric material polyvinylidene fluoride (PVDF). Utilizing the pyroelectric effect of PVDF in the field plate structure, it senses temperature changes, releases charge, and generates a strong electric field whose direction changes with temperature. This extends the diode's depletion region, increases the breakdown voltage, and achieves the self-powered field plate function. Furthermore, the electric field generated after polarization can be maintained for a long time. The two electrodes of the PVDF main material in the field plate structure are graphene and aluminum. Multiple power supply modules are connected together using a combination of series and parallel connections to solve the problem of insufficient voltage and current output from a single module. The field plate structure proposed in this invention improves the spatial distribution of the internal electric field and increases the breakdown voltage of the device without an external power supply. Moreover, the fabrication of this structure is relatively simple and cost-effective, and it is stable and easy to control.

Description

Technical Field

[0001] This invention relates to the field plate structure of power diodes, and more particularly to a self-powered field plate structure for silicon carbide power diodes and its fabrication method. Background Technology

[0002] With the development of semiconductor material and device fabrication technology, the first generation of semiconductor materials was represented by silicon (Si). After the 1990s, second-generation semiconductors, such as gallium arsenide and indium phosphide, with high mobility, gradually emerged. As second-generation semiconductor materials approached the limits of their material properties, third-generation wide-bandgap semiconductor materials emerged, with silicon carbide (SiC) as a typical representative. Compared to silicon (Si), SiC possesses significant advantages, including high electron saturation drift velocity, high thermal conductivity, high critical breakdown electric field, and strong radiation resistance. This makes it ideal for fabricating high-voltage, high-power, and high-temperature semiconductor power devices, thus becoming a research hotspot in the field of semiconductor power devices in recent years. Among the many SiC-based semiconductor power devices, silicon carbide power diodes, due to their faster switching speed and stronger high-current handling capability, are widely used in lighting, solar energy, electric vehicles, and other fields, making them the most widely used SiC-based power devices.

[0003] The importance of power diodes is self-evident due to their wide range of applications; therefore, improving their performance is crucial for the development of the power semiconductor device industry. However, a common problem in power semiconductor devices is the curved junction surface of PN junctions. Because the electric field is stronger at curved junctions, devices are prone to breakdown at these locations. Therefore, to improve the breakdown voltage, the electric field distribution on the surface or interface can be adjusted and controlled by changing the morphology of the device's edge surface or by fine-tuning the device structure. Common methods for changing the edge morphology include mesa etching and wafer beveling. Fine-tuning the device structure commonly involves adding field plates and floating field rings. This invention utilizes field plate (FP) technology, employing methods similar to... Figure 5Adding field plates can improve the electric field distribution and increase the breakdown voltage of devices. In modern semiconductor processes, a common method for fabricating junctions is to use silicon dioxide or similar materials as a mask on the silicon surface, and then use liquid-phase diffusion or low-energy ion implantation to dope impurities into the silicon at the window. We hope that the mask window can precisely control the doping range; however, in reality, due to the uncontrollable movement direction of impurities, they will also move laterally below the mask as they penetrate vertically. Therefore, the PN junctions formed in actual processes will all have curved junctions. Curved junctions can generally be divided into two types: cylindrical junctions formed at the mask window boundary and spherical junctions formed at the window corner. The potential and electric field distribution of these curved junctions can be approximated by solving the Poisson equations in cylindrical and spherical coordinates. Based on these results, the magnitude of the maximum electric field at several junction surfaces is: spherical junction > cylindrical junction > planar junction. Therefore, to improve the breakdown voltage of devices, effective solutions should focus on these weak interfaces where high electric fields are easily formed. For a PN junction, the primary voltage-carrying region is the space charge region, also known as the depletion region. Because the edges of the diffusion-formed P-region are curved (taking the formation of a P-region by doping in the N-region as an example),... Figure 5 The corresponding depletion region is the curved surface. Therefore, if the depletion region can be "flattened," it is equivalent to turning the curved junction into a planar junction. Thus, the width of the depletion region can be controlled by applying voltages in different directions on both sides of the diode. By applying sufficient potential to the field plate, the radius of curvature of the depletion region boundary can be lengthened, the boundary electric field can be reduced, and its breakdown resistance can be improved.

[0004] However, in power devices, although the field plate structure can effectively improve the breakdown voltage, in practice, due to the additional package termination and the cost associated with bias circuitry, providing a separate power supply and bias for the field plate is impractical. In actual circuits, we want to use as few independent power supplies and as few leads as possible. Therefore, an alternative approach is to use P... + The contact metal of the region extends onto the field oxide at the junction edge to form a field plate. In this case, for P... + Applying a negative voltage to the region to reverse bias the PN junction also provides a negative bias to the field plate, extending the depletion region boundary. However, these methods have certain drawbacks. For example, adding an extra layer affects the device size, increasing the space occupied by the device; moreover, power devices typically operate at very high voltages, making them unsafe to use and prone to breakdown at the oxide layer. Furthermore, the potential difference between the field plate and silicon carbide at the field plate edge is very large, resulting in a high electric field strength, causing breakdown to occur prematurely at lower voltages, and potentially at the surface. Therefore, providing additional power to traditional field plate structures yields undesirable results.

[0005] Therefore, to solve the above problems, we propose a self-powered field plate structure for silicon carbide power diodes and its fabrication method. This invention addresses the difficulty of providing a separate power source for the field plate structure by introducing a pyroelectric material, polyvinylidene fluoride (PVDF), to achieve the self-powered function of the field plate structure. This achieves the functions of a traditional field plate structure without requiring an external power source. PVDF and its composites are among the most important pyroelectric materials, and their preparation is relatively simple and cost-effective, thus they have been extensively studied in pyroelectric fields. The role of PVDF in this invention is as follows: the ferroelectric polymer polyvinylidene fluoride molecules, possessing [-CH2-CF2-], carbon-hydrogen bonds, and polar carbon-fluorine bonds, undergo a non-piezoelectric α-phase during sufficiently slow cooling of the solution. Under voltage or polarization, the α-phase transforms into the β-phase. In the β-phase, PVDF exhibits a pyroelectric effect due to its ferroelectric properties. Therefore, when a power device is operating, the temperature change during operation allows one part of the thermoelectric material to provide the voltage and current required for polarization to another part. This generated voltage and current polarizes the thermoelectric material, ultimately producing an electric field of a certain strength. This "flattens" the depletion region, increasing the device's breakdown voltage and achieving the field plate function. Figure 5 It is known that the maximum voltage released by a single module composed of this PVDF material is 24V, which does not meet the necessary conditions for polarization of the material. Therefore, multiple PVDF materials need to be connected in series and parallel to solve the problem that the voltage and current generated by a single polyvinylidene fluoride film module are insufficient to polarize the polarization module (4). In addition, the maximum strength of PVDF material after polarization can reach 10. 9 The ultra-strong electric field of V / m is 2-3 orders of magnitude higher than the maximum electric field strength inside the device. This is sufficient to completely replace the traditional field plate structure in terms of electric field control, achieving the same function as the traditional field plate structure. Furthermore, the Curie temperature of PVDF is 180℃ higher than its melting point, so the temperature of the fabricated device will not exceed its Curie temperature during normal operation, and the polarization intensity of the material will not be lost as a result. Summary of the Invention

[0006] The purpose of this invention is to provide a self-powered field plate structure for silicon carbide power diodes. This technology improves the device's breakdown voltage while addressing the problem of traditional field plate structures being inconvenient for providing a separate power supply. It also optimizes the increased device size inherent in traditional field plate structures and solves the problem of uneven electric field distribution at the boundaries of power devices. This invention utilizes field plate technology and PVDF materials to jointly form a self-powered field plate structure. To successfully realize the field plate function, on the one hand, we utilize the change in device operating temperature to connect a portion of the power supply modules composed of multiple pyroelectric materials (PVDF) together to generate sufficient current and voltage, causing the other polarization modules to polarize. On the other hand, after polarization, the PVDF will generate a maximum intensity of up to 10.9 The ultra-strong electric field of V / m is sufficient to change the radius of curvature of the depletion region boundary of the power diode, improve the electric field distribution at the interface, and increase the breakdown voltage of the power device.

[0007] The technical solution to achieve the objective of this invention is:

[0008] A self-powered field plate structure for a silicon carbide power diode, consisting of N0, N1, N2, N3, N4, N5, N6, N7, N8, N9, N10, N11+ Type I SiC substrate, Type I SiC epitaxial layer, P + SiC layer;

[0009] The uppermost field plate structure layer of the silicon carbide power diode contains a polarization module made of polyvinylidene fluoride material that provides an electric field inside the device.

[0010] The field plate structure layer of the silicon carbide power diode also contains a power supply module that provides voltage and current to the polarization module to polarize it.

[0011] The P + The edge of the SiC layer also has a ring-shaped JTE layer extension structure, which is a uniformly doped JTE layer;

[0012] The P + A metal top electrode is led out above the SiC layer; the N + A metal bottom electrode is led out from below the SiC substrate.

[0013] Furthermore, by utilizing a self-powered field plate structure, the P inside the device... + An electric field of a certain intensity is applied at the vertical interfaces between the Type I SiC layer and the JTE layer, between several JTE layers, and between the JTE layer and the Type I SiC epitaxial layer.

[0014] Furthermore, the field plate structure layer includes a polarization module composed of polyvinylidene fluoride thin film modules and a power supply module composed of multiple polyvinylidene fluoride thin film modules connected together.

[0015] Furthermore, the external electric field applied to the device is generated by the pyroelectric effect of the polarization module, and the interaction between the internal and external electric fields makes the electric field distribution inside the device more uniform.

[0016] Furthermore, the power diode can adopt a symmetrical cylindrical structure, with the field plate structure layers arranged in concentric circles, and SiO2 is used to isolate and protect the polarization module and power supply module. The field plate structure can also be modified according to the structure of the power diode.

[0017] Furthermore, there are at least two polarization modules, located at P respectively. +Between the Type I SiC layer and the JTE layer, and between the JTE layer and the Type I SiC epitaxial layer. The power supply module is connected to both polarization modules and simultaneously provides voltage to both polarization modules.

[0018] Furthermore, the power supply module connects multiple polyvinylidene fluoride film modules together by using different connection methods between the two electrodes, thereby increasing the total current and voltage generated to solve the problem that the voltage and current generated by a single module are insufficient to polarize the polarization module.

[0019] Furthermore, the power supply module contains multiple polyvinylidene fluoride thin film modules. By connecting the two electrodes of several modules together, the modules are connected in parallel to increase the total current generated between the positive and negative electrodes when the temperature changes.

[0020] Furthermore, in the power supply module, the electrodes on both sides of multiple polyvinylidene fluoride thin film modules that are connected in parallel are interconnected to realize series connection between multiple modules, thereby increasing the total voltage generated between the positive and negative electrodes when the temperature changes.

[0021] Furthermore, the two electrodes of the polyvinylidene fluoride film in the polarization module and the power supply module are graphene and aluminum, respectively, and the thickness-to-base ratio of the polyvinylidene fluoride film to the graphene electrode is approximately 5.8 to keep the graphene film active.

[0022] Furthermore, when a voltage of approximately 45V is applied to the polarization module via the power supply module, a maximum intensity of up to 10 is generated. 9 An electric field of V / m, the maximum external electric field strength is 2-3 orders of magnitude higher than the maximum electric field strength inside the device, which is sufficient to achieve the purpose of controlling the electric field distribution inside the device.

[0023] The method for parallel connection of multiple polyvinylidene fluoride thin film modules in the power supply module includes the following steps:

[0024] S1: First, an aluminum electrode is deposited on the silicon carbide power diode;

[0025] S2: Next, a SiO2 layer is deposited on the surface of the type I SiC epitaxial layer using a plasma-enhanced chemical vapor deposition device;

[0026] S3: Then, using photoresist as a mask, SiO2 is dry etched;

[0027] S4: Place the sample in the reaction chamber and use Cl2 and BCl3 to etch aluminum metal to form the bottom aluminum electrode required for the power supply module. Then remove the SiO2 layer and photoresist on the surface of the type I SiC epitaxial layer.

[0028] S5: Then, multiple polyvinylidene fluoride films are prepared on the electrodes of the power supply module using a coating method;

[0029] S6: A SiO2 layer is deposited on the sample surface using a plasma-enhanced chemical vapor deposition device, and then the SiO2 on the surface of the polyvinylidene fluoride film is dry etched using a photoresist as a mask.

[0030] S7: Next, a screen printing device is used to screen print graphene electrodes on multiple polyvinylidene fluoride films of the power supply module. Finally, excess photoresist and SiO2 on the device surface are removed, thereby realizing the parallel connection between multiple polyvinylidene fluoride film modules in the power supply module.

[0031] Furthermore, the method for connecting multiple polyvinylidene fluoride (PVDF) thin film modules in a power supply module is characterized by the following: when etching the aluminum electrode of the power supply module, only one place needs to be etched, so that the parallel PVDF thin film modules are connected through the aluminum electrode; the PVDF thin film modules whose aluminum electrodes have been etched are connected together through printed graphene electrodes, thereby realizing the series connection of multiple PVDF thin film modules.

[0032] The working principle of the self-powered field plate structure of the aforementioned silicon carbide power diode is as follows:

[0033] The basic structure of a SiC-based PiN power diode consists of three semiconductor layers: highly doped SiCN... + N-type substrate, a low-doped N-type drift region obtained by epitaxial growth on the substrate, and a P-type anode obtained by secondary epitaxial growth or ion implantation. + The PN junction has a curved surface, where the electric field is stronger, making the device more prone to breakdown. For a PN junction, the main voltage-carrying region is the space charge region, also known as the depletion region. The width of the depletion region can be controlled by applying voltages in different directions across the diode. Therefore, research has considered adding a field plate structure to "flatten" the depletion region, thus adjusting and controlling the electric field distribution on the device's surface or interface. However, achieving this function using a field plate structure often requires applying an external power supply to the field plate, providing a separate bias. This significantly increases the cost of the field plate structure and the additional impact on the device, severely limiting its effectiveness.

[0034] To address the aforementioned issues and minimize the adverse effects of providing additional power to the field plate structure while effectively realizing its function, this invention introduces a self-powered field plate structure. In this structure, the working mechanism is as follows: when the temperature changes during device operation, a power supply module composed of pyroelectric PVDF material within the field plate structure layer generates current and voltage. This polarization causes the polarization module to become polarized, generating an electric field of a certain intensity. Through the interaction between the internal and external electric fields, the electric field distribution at the power diode interface can be improved, thereby increasing the breakdown voltage of the power device.

[0035] Pyroelectric materials, as an important subclass of piezoelectric materials, have attracted widespread attention due to their unique pyroelectric effect caused by spontaneous polarization. Their various electrical responses resulting from temperature changes over time suggest broad application prospects. The pyroelectric effect refers to the spontaneous polarization caused by temperature fluctuations in certain polar materials. The principle of the pyroelectric effect is as follows: Figure 8 As shown, many electric dipoles superimpose to form spontaneous polarization (P) perpendicular to the flat surface of the pyroelectric material. s In pyroelectric materials, the stable spontaneous polarization attracts nearby light particles with positive or negative charges. When the surface of the pyroelectric material is covered by two conductive electrodes, the spontaneously generated field within the material induces electrostatic induction, producing equal charges of opposite polarities on the two electrodes through an external circuit. When the temperature of the pyroelectric material increases (dT / dt>0), the oscillation of the electric dipoles strengthens, thereby weakening the spontaneous polarization and driving electron migration in the external circuit to reach a new electrostatic equilibrium state. Similarly, when dT / dt<0, it strengthens the spontaneous polarization, disrupting the electrical equilibrium again, leading to reverse electron migration. Compared to the thermoelectric effect, the pyroelectric effect is caused by temperature changes (dT / dt≠0), while the thermoelectric effect is caused by changes in spatial temperature (dT / dx≠0). Because the current is only the rate of change of surface charge, the generated pyroelectric current is proportional to the surface area of ​​the material and independent of its thickness and volume.

[0036] In this invention, to enhance the performance of PVDF films, a PVDF / CuO composite film (with copper oxide nanoparticles of approximately 60 nm in size) was used and prepared. During the synthesis process, the incorporation of copper oxide nanoparticles led to a faster crystallization rate. The surface of the copper oxide nanoparticles can serve as nucleation centers for the electroactive β phase, and the interaction between the copper oxide and PVDF chain ionic dipoles induces the formation of a pyroelectric β-phase PVDF film. By controlling the amount of copper oxide added, a series of PVDF / CuO composite materials were prepared using solution. The results showed that after adding copper oxide nanoparticles, the interfacial area between the copper oxide nanoparticles and the PVDF polymer was the highest, achieving a maximum β-phase fraction of 90% in the pyroelectric composite film, thus achieving optimal pyroelectric performance. The electrodes used in this invention are graphene and aluminum (Al), serving as two asymmetric electrodes primarily for heat collection. The graphene electrode exhibits high thermal radiation absorptivity and conductivity. Furthermore, under the same experimental conditions, the pyroelectric device based on Graphene / PVDF / Al exhibits significantly higher short-circuit current and open-circuit voltage, exceeding those based on Al / PVDF / Al by 750% and 340%, respectively. The Curie temperature of PVDF material is 180℃. Figure 7 In the middle, as the material temperature approaches T CThe polarization phenomenon will also begin to disappear rapidly. After polarization, PVDF materials will exhibit a maximum strength of up to 10. 9 The ultra-strong electric field of V / m is more than sufficient for controlling the electric field distribution inside the device. In addition, PVDF is highly cost-effective compared to other types, and it has a variety of derivative materials, such as copolymers of trifluoroethylene (VDF-TRFE) and vinylidene fluoride.

[0037] In addition to the points mentioned above, it is also important to note that the presence of negative charges in the oxide can compensate for the positive charges on the ionized donor, allowing the depletion layer to extend along the surface. The presence of positive charges has the opposite effect on the surface depletion layer; therefore, by applying a bias voltage to the metal, the electric field at the edge of the planar junction can be modulated. Without applying a bias voltage to the field plate, the depletion region boundary has a cylindrical junction, such as... Figure 5 Curve A. When a positive bias is applied relative to the N-type substrate, it attracts electrons to the surface, such as... Figure 5 As shown in Figure B. This reduces the extension of the depletion layer along the surface, enhances the electric field at the junction, and thus lowers the breakdown voltage. On the other hand, if a negative bias is applied to the field plate, it will cause electrons to move away from the device surface, resulting in expansion of the surface depletion region, such as... Figure 5 As shown by curve C, this will lead to a decrease in the electric field at the junction, thereby increasing the breakdown voltage. In this invention, the self-powered module can generate a maximum strength of up to 10 by utilizing the temperature change during device operation. 9 An ultra-strong electric field of around V / m is used to realize the field plate function and improve the electric field distribution inside the device.

[0038] By adopting the above technical solution, the present invention has the following beneficial effects:

[0039] (1) The self-powered field plate structure proposed in this invention is used, which can generate a maximum strength of 10 by utilizing the temperature change of the device itself during operation. 9 The ultra-strong electric field of around V / m increases the breakdown voltage of the power diode, thus eliminating the need for a separate power supply for the field plate structure layer, which improves the performance and safety of the power diode.

[0040] (2) After the PVDF material in the polarization module is polarized, its polarization state can be maintained for a long time, and the strong electric field generated after polarization can also be maintained for a long time. Therefore, there is no need to continuously provide voltage to polarize it.

[0041] (3) The voltage and current generated by the pyroelectric material PVDF used in this invention are proportional to the rate of temperature change. Therefore, it can provide protection for the device according to the speed of temperature change of the device itself. The faster the temperature changes, the stronger the electric field generated by PVDF polarization, and the better the protection of the device. Moreover, the time required to generate the electric field is very short.

[0042] (4) PVDF is one of the best piezoelectric polymer materials discovered to date. It has good flexibility, high sensitivity and relatively simple preparation process, and excellent and stable performance, which reduces the cost of producing and preparing power diode devices. Attached Figure Description

[0043] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein...

[0044] Figure 1 This is a schematic diagram of the structure of a self-powered field plate for a silicon carbide power diode according to the present invention.

[0045] Figure 2 This is a top view of a self-powered field plate structure for a silicon carbide power diode according to the present invention.

[0046] Figure 3 This is a three-dimensional schematic diagram of a self-powered field plate structure for a silicon carbide power diode according to the present invention.

[0047] Figure 4 This is a cross-sectional view of a silicon carbide power diode with a self-powered field plate structure according to the present invention.

[0048] Figure 5 A cross-sectional view of a planar junction with a biased field plate added to a field oxide.

[0049] Figure 6 This is a schematic diagram showing the voltage generated by the PVDF material as a function of time.

[0050] Figure 7 This is a schematic diagram showing the change in polarization intensity of PVDF material with temperature.

[0051] Figure 8 This is a schematic diagram of the pyroelectric effect.

[0052] Figure 9 A schematic diagram of the process flow for manufacturing the power supply module.

[0053] Figure 10 A comparison diagram of the electric field distribution of a conventional diode and the diode with a self-powered field plate structure proposed in this invention.

[0054] Figure 11 The image shows the IV characteristic curves of a conventional diode and a silicon carbide power diode with a self-powered field plate structure according to the present invention.

[0055] The attached figure is labeled N. + Type I SiC substrate 1, Type I SiC epitaxial layer 2, and P +3. Type SiC layer; 4. Polarization module that generates electric field; 5. Power supply module that provides polarization voltage and current; 6. JTE layer; 7. Metal top electrode; 8. Metal bottom electrode. Detailed Implementation

[0056] (Example 1)

[0057] This embodiment describes a self-powered field plate structure for a silicon carbide power diode, such as... Figure 1 As shown, the power diode has a symmetrical cylindrical structure, thus providing sufficient space during actual device fabrication to design the number of self-powered modules to meet the device's requirements. From bottom to top, the number is N. + Type I SiC substrate 1, Type I SiC epitaxial layer 2, P + Type SiC layer 3;

[0058] The uppermost field plate structure layer of the silicon carbide power diode contains a polarization module 4 made of polyvinylidene fluoride material that provides an electric field inside the device.

[0059] The field plate structure layer of the silicon carbide power diode also contains a power supply module 5 that provides voltage and current to the polarization module 4 to polarize it;

[0060] The P + The edge of the SiC layer 3 also has a JTE layer ring structure, which is a uniformly doped JTE layer 6;

[0061] The P + A metal top electrode 7 is led out from above the SiC layer 3; the N + A metal bottom electrode 8 is led out from below the SiC substrate layer 1.

[0062] The self-powered electric field board structure can apply an electric field of a certain intensity to the vertical interface between the P+ type SiC layer 3 and JTE layer 6 inside the device, between several JTE layers 6, and between the JTE layer 6 and the I type SiC epitaxial layer 2.

[0063] The field plate structure layer includes a polarization module 4 composed of polyvinylidene fluoride thin film modules and a power supply module 5 composed of multiple polyvinylidene fluoride thin film modules connected together.

[0064] The polarization module 4 and the power supply module 5 contain multiple polyvinylidene fluoride thin film modules. The power supply module 5 achieves series and parallel connection between modules by utilizing different connection methods between the two electrodes of several modules.

[0065] The external electric field applied to the device by the self-powered electric field board structure is generated by the pyroelectric effect of the polarization module 4. The interaction between the internal and external electric fields makes the electric field distribution inside the device more uniform.

[0066] The field plate structure layer is concentric, and SiO2 is used to isolate and protect the polarization module 4 and the power supply module 5 therein.

[0067] The power supply module 5 connects multiple polyvinylidene fluoride film modules together by using different connection methods between the two electrodes to increase the total current and voltage generated, thereby solving the problem that the voltage and current generated by a single module are insufficient to polarize the polarization module 4.

[0068] The power supply module 5 contains multiple polyvinylidene fluoride thin film modules. By connecting the two electrodes of several modules together, the modules are connected in parallel to increase the total current generated between the positive and negative electrodes when the temperature changes.

[0069] In the power supply module 5, the electrodes on both sides of multiple polyvinylidene fluoride thin film modules that have been connected in parallel are connected to each other to realize the series connection between multiple modules, thereby increasing the total voltage generated between the positive and negative electrodes when the temperature changes.

[0070] The two electrodes of the polyvinylidene fluoride film in the polarization module 4 and the power supply module 5 are graphene and aluminum, respectively, and the thickness-to-base ratio of the polyvinylidene fluoride film to the graphene electrode is about 5.8 to keep the graphene film active.

[0071] When the power supply module 5 applies a voltage of approximately 45V to the polarization module 4, the polarization module 4 will generate a maximum intensity of 10. 9 An electric field of V / m, the maximum external electric field strength is 2-3 orders of magnitude higher than the maximum electric field strength inside the device, which is sufficient to achieve the purpose of controlling the electric field distribution inside the device.

[0072] This embodiment provides a self-powered field plate structure for a silicon carbide power diode, the steps of which include:

[0073] S1: First, dissolve the polyvinylidene fluoride powder in an N,N-dimethylformamide (DMF) solution and stir vigorously until completely dissolved. See the following steps for details:

[0074] S11: First, pour 20ml of DMF solution into a beaker, then add 500mg of PVDF powder to dissolve it;

[0075] S12: Then stir vigorously in a beaker at 60°C to completely dissolve PVDF in DMF;

[0076] S2: Add a certain weight of copper oxide nanoparticles to the polyvinylidene fluoride solution, and stir vigorously to obtain a homogeneous mixture, as detailed in the following steps:

[0077] S21: First, dissolve 25 grams of CuSO4·5H2O in an appropriate amount of water, and dilute to 1L at room temperature to prepare a 0.1M copper sulfate solution;

[0078] S22: Then add 1M sodium hydroxide solution dropwise to copper sulfate solution while stirring vigorously until the pH of the synthesized solution is 13;

[0079] S23: The solution is then transferred to a stainless steel high-pressure reactor and properly sealed before being heated in a furnace at 110°C for 18 hours.

[0080] S24: After the high-pressure reactor has cooled naturally to room temperature (30°C), the resulting solution is centrifuged (4000 rpm) for about 30 minutes.

[0081] S25: Then wash the product several times properly with distilled water and ethanol to remove any remaining impurities.

[0082] S26: The solution is then dried to obtain the synthesized powder. The powder sample is stored in a vacuum dryer to completely remove the residual solvent contained in the powder, thus completing the preparation of copper oxide nanoparticles.

[0083] S27: Then, a certain weight (1-5wt%) of copper oxide nanoparticles are added to the PVDF solution, stirred vigorously for 16 hours, and then subjected to ultrasonic treatment for 30 minutes to obtain a homogeneous mixture.

[0084] S3: In N + A type I SiC epitaxial layer 2 is epitaxially grown on the type I SiC substrate layer 1, as detailed in the following steps:

[0085] S31: First, pure hydrogen gas is used to treat N + In-situ etching is performed on the SiC substrate layer 1 to eliminate damage or stress on its surface;

[0086] S32: Next, using a chemical vapor deposition system at a propane flow rate of 7 mL / min, a silane flow rate of 21 mL / min, a hydrogen flow rate of 80 L / min, a temperature of 1580 °C, and a pressure of 100 mbar, under N... + A type I SiC epitaxial layer 2 with a cross-sectional radius of 80 μm and a thickness of 8 μm is epitaxially grown on a type I SiC substrate 1.

[0087] S4: Then, P is formed on the type I SiC epitaxial layer 2 by ion implantation. + Type 3 SiC layer, see the following steps for details:

[0088] S41: First, a 2μm thick SiO2 layer is deposited on the surface of the type I SiC epitaxial layer 2 using a plasma-enhanced chemical vapor deposition device;

[0089] S42: Then, using a 1.8μm thick photoresist as a mask, SiO2 is dry etched to form an ion implantation mask;

[0090] S43: Aluminum (Al) ions at 450℃ were implanted into the type I SiC epitaxial layer 2 through a SiO2 mask window. The implantation energy was 30–150 keV, and the implantation was performed four times, ultimately forming a layer with a cross-sectional radius of 10 μm, a thickness of 0.65 μm, and a doping concentration of 2.4 × 10⁻⁶. 19 cm -3 P + Type I SiC layer 3, and remove the SiO2 layer and photoresist from the surface of Type I SiC epitaxial layer 2;

[0091] S5: Then in P + The edge of the SiC layer 3 is also formed with a uniformly doped JTE layer 6 by ion implantation, as detailed in the following steps:

[0092] S51: First, a 2μm thick SiO2 layer is deposited on the surface of the type I SiC epitaxial layer 2 using a plasma-enhanced chemical vapor deposition device;

[0093] S52: Then, using a 1.8μm thick photoresist as a mask, SiO2 is dry etched to form an ion implantation mask;

[0094] S53: Al ions at 400℃ are implanted into the type I SiC epitaxial layer 2 through a SiO2 mask window. The implantation energy is 100–800 keV, and the implantation is performed 5 times, ultimately forming a ring with a width of 20 μm, a thickness of 1.25 μm, and a doping concentration of 7 × 10⁻⁶. 18 cm -3 JTE layer 6, and remove the SiO2 layer and photoresist from the surface of the type I SiC epitaxial layer 2;

[0095] S6: After ion implantation, the device undergoes annealing treatment, as detailed in the following steps:

[0096] S61: Place the cleaned parts into the clamp pot, slowly push the clamp pot to the middle of the annealing furnace, and then close the sample opening;

[0097] S62: Turn on the mechanical pump to evacuate the chamber until the pressure inside the chamber is about 0.2 Pa. Then turn off the mechanical pump and open the nitrogen valve to introduce nitrogen gas, so that the pressure inside the chamber is slightly higher than atmospheric pressure. Then close the nitrogen valve and continue the evacuation operation. Evacuate the chamber until it is about 0.2 Pa, then turn off the mechanical pump and introduce nitrogen gas again. The purpose of repeating this operation is to ensure the purity of the nitrogen gas inside the chamber and prevent the sample from oxidizing during annealing.

[0098] S63: After nitrogen is introduced, turn on the annealing furnace switch, adjust the heating time and temperature holding time, open the vent valve, and introduce nitrogen into the chamber. Set the nitrogen flow rate to 50 sccm / min and wait for the temperature to rise to 1450℃.

[0099] S64: Start the cooling process. After the annealing furnace temperature is below 600℃, turn off the annealing furnace and wait for it to cool naturally to room temperature. Then, turn off the nitrogen valve, open the annealing furnace chamber, and the annealing process is complete. Take out the device sample and proceed to the next step.

[0100] S7: An aluminum electrode is deposited on the silicon carbide power diode, and the electrodes required for the polarization module 4 and power supply module 5 are formed by etching. See the following steps for details:

[0101] S71: Open the evaporation chamber, tie the weighed Al metal to the tungsten wire, and clamp the tungsten wire with the metal attached to the electrode post of the evaporation chamber. Test the contact between the tungsten wire and the electrode. Place the silicon carbide sample covered with the electrode mold directly above the location where the tungsten wire is tied with the metal. After closing, evacuate the chamber to a pressure of 10. -3 Below Pa;

[0102] S72: Turn on the evaporation switch to evaporate Al metal. Slowly adjust the voltage knob. When the voltage reaches a certain value, you can see the tungsten filament glow. Continue to increase the voltage until the Al metal on the tungsten filament is completely evaporated. After the Al evaporation is completed, adjust the voltage knob to 0 and wait for two minutes to allow the Al vapor in the chamber to completely disappear.

[0103] S73: Turn off the molecular pump and mechanical pump, turn on the gas filling switch, and after the gas filling is complete, raise the bell jar and take out the sample after the electrode is vapor-deposited.

[0104] S74: After the electrode evaporation is completed, the electrode is annealed to form ohmic contact. The annealing equipment is a high-temperature tube furnace, the annealing temperature is 880℃, the annealing time is 5min, and the annealing atmosphere is hydrogen.

[0105] S75: A 2μm thick SiO2 layer is deposited on the surface of the type I SiC epitaxial layer 2 using a plasma-enhanced chemical vapor deposition device;

[0106] S76: Then, using a 1.8μm thick photoresist as a mask, SiO2 is dry etched;

[0107] S77: Place the sample in the reaction chamber and use Cl2 and BCl3 to etch aluminum metal to form the bottom aluminum electrode required for polarization module 4 and power supply module 5, and remove the SiO2 layer and photoresist on the surface of the type I SiC epitaxial layer 2.

[0108] S8: Then, a polyvinylidene fluoride (PVDF) film is prepared on the electrode of polarization module 4 using a coating method, and several PVDF films are prepared on the electrode of power supply module 5. See the following steps for details:

[0109] S81: First, take a certain amount of test adhesive and apply it to the electrode surface where the PVDF film needs to be grown. When applying the adhesive, spread the adhesive evenly on the crystal surface and make the thickness of the adhesive as thin as possible.

[0110] S82: Then place the coated sample in a sealed container and store it for 24 hours to allow the adhesive to fully solidify;

[0111] S83: After confirming that the glue has solidified, slowly place it into the prepared PVDF solution;

[0112] S84: If no impurities are found on the coated surface after a period of observation, take out the sample and place it in a vacuum drying oven for about 5 minutes to allow the solvent to evaporate and form a dry film. Repeat this process until a film with a thickness of about 2 μm is obtained.

[0113] S85: The device sample was then placed in a vacuum drying oven for annealing at a temperature of 100°C for 1.5 hours.

[0114] S9: Next, use a screen printing device to screen print graphene electrodes on the polyvinylidene fluoride film, as detailed in the following steps:

[0115] S91: First, a SiO2 layer is deposited on the sample surface using a plasma-enhanced chemical vapor deposition device. Then, the SiO2 on the surface of the polyvinylidene fluoride film is dry etched using a photoresist as a mask.

[0116] S92: Next, extract the relative permittivity ε. r =11 graphene ink;

[0117] S93: Then, under constant pressure, a screen printing device is used to screen print graphene electrodes with an average thickness of about 0.17 times the thickness of PVDF and uniform thickness on the PVDF film at a speed of 220 mm / s. The graphene electrodes of the power supply module 5 need to be connected together to realize series and parallel connection between modules.

[0118] S94: Finally, remove excess photoresist and SiO2 layer, and dry the sample at room temperature for one day to form graphene electrode.

[0119] S10: Next, a SiO2 passivation layer is deposited on the device surface using plasma-enhanced chemical vapor deposition equipment, and the SiO2 layer at the metal top electrode 7 is dry-etched, thereby forming a self-powered field plate structure for a silicon carbide power diode.

[0120] A top view of the self-powered field plate structure of the silicon carbide power diode proposed in this invention is shown below. Figure 2 As shown, a three-dimensional schematic diagram of the power supply module and polarization module is as follows: Figure 3 As shown. Figure 6 The curve shows the voltage change of PVDF material over time. The maximum voltage it releases can reach 24V, and the required polarization voltage for PVDF material is approximately 45V. Therefore, series and parallel connections are needed to increase the maximum voltage and current generated by the power supply module to meet these requirements. The maximum intensity generated after polarization is approximately 10. 9 An electric field of V / m is sufficient to control the electric field of the device. Figure 7 The curve shows the polarization intensity of the pyroelectric material as a function of temperature, and the Curie temperature T of the PVDF material is also shown. c It reaches 180°C, so it will not lose its polarization function during industrial manufacturing. Figure 9 This is a schematic diagram of the manufacturing process of the power supply module proposed in this invention. Figure 10 The diagram shows a comparison of the electric field distribution of a conventional diode and the diode with a self-powered electric field plate structure proposed in this invention. It can be seen that the electric field distribution inside the device is improved, and the depletion region extends along the surface of the device. Figure 11 The image shows the IV characteristic curves of a conventional diode and a silicon carbide power diode with a self-powered field plate structure proposed in this invention. It can be seen that adding the self-powered field plate structure to the conventional silicon carbide power diode significantly improves the breakdown voltage. Therefore, this invention effectively improves the breakdown voltage of silicon carbide power diodes and solves the problems of traditional field plate structures, such as inconvenience in providing voltage independently and significant impact on device size.

[0121] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-powered field plate structure for a silicon carbide power diode, characterized by: It includes a polarization module (4) made of polyvinylidene fluoride material that provides an electric field inside the diode, and a power supply module (5) that provides voltage and current to the polarization module (4) to polarize it; the power supply module (5) includes multiple polyvinylidene fluoride materials, and the upper and lower electrodes of the multiple polyvinylidene fluoride materials are connected together to achieve parallel connection so as to achieve current superposition, and then the voltage is superposition through series connection.

2. The self-powered field plate structure of a silicon carbide power diode according to claim 1, wherein the silicon carbide power diode comprises N + Type I SiC substrate (1), Type I SiC epitaxial layer (2), P + The SiC layer (3) and JTE layer (6) are characterized in that, The polarization modules (4) are at least two, respectively located at P + between the SiC layer (3) and the JTE layer (6), and between the JTE layer (6) and the I-type SiC epitaxial layer (2).

3. The self-powered field plate structure of a silicon carbide power diode according to claim 1, wherein the self-powered field plate structure is a concentric circle structure, and SiO2 is used to isolate and protect the polarization module (4) and the power supply module (5).

4. The self-supplied field plate structure of a silicon carbide power diode according to claim 1, wherein The two electrodes of the polyvinylidene fluoride material in the polarization module (4) and the power supply module (5) are graphene and aluminum, respectively, and the thickness-to-base ratio of the polyvinylidene fluoride material to the graphene electrode is about 5.

8.

5. The self-supplied field plate structure of a silicon carbide power diode according to claim 1, wherein Utilizing a self-powered field plate structure, the P inside the silicon carbide power diode is... + An electric field of a certain intensity is applied at the vertical interface between the type SiC layer (3) and the JTE layer (6), between several JTE layers (6), and between the JTE layer (6) and the type I SiC epitaxial layer (2).

6. A method of manufacturing a self-powered field plate structure as claimed in any one of claims 1 to 5, characterized in that, The preparation of the power supply module (5) includes the following steps: S1: First, an aluminum electrode is deposited on the silicon carbide power diode; S2: Next, a SiO2 layer is deposited on the surface of the type I SiC epitaxial layer (2) using a plasma-enhanced chemical vapor deposition device; S3: Then, using photoresist as a mask, SiO2 is dry etched; S4: Place the diode device sample in the reaction chamber and use Cl2 and BCl3 to etch aluminum metal to form the bottom aluminum electrode required for the power supply module (5). Then remove the SiO2 layer and photoresist on the surface of the type I SiC epitaxial layer (2). S5: Then, multiple polyvinylidene fluoride films are prepared on the electrodes of the power supply module (5) using a coating method; S6: A SiO2 layer is deposited on the sample surface using a plasma-enhanced chemical vapor deposition device, and then the SiO2 on the surface of the polyvinylidene fluoride film is dry etched using a photoresist as a mask. S7: Next, a screen printing device is used to screen print graphene electrodes on multiple polyvinylidene fluoride films of the power supply module (5). Finally, excess photoresist and SiO2 on the device surface are removed, thereby realizing the parallel connection between multiple polyvinylidene fluoride film modules in the power supply module (5).

7. The method of claim 6, wherein: When etching the aluminum electrode of the power supply module (5), only one place needs to be etched so that the parallel polyvinylidene fluoride thin film modules can be connected through the aluminum electrode; the polyvinylidene fluoride thin film modules whose aluminum electrodes have been etched are connected together through printed graphene electrodes, thereby realizing the series connection of multiple polyvinylidene fluoride thin film modules.

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