A design and optimization method of SiC power diode based on Fermi-like function
By using a Fermi-like function to control the JTE structure design of SiC power diodes, the problems of numerous variables, large computational load, and long simulation time in traditional designs are solved, achieving more efficient breakdown voltage optimization and device performance simulation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANTONG UNIV
- Filing Date
- 2022-11-02
- Publication Date
- 2026-04-10
AI Technical Summary
The breakdown voltage of existing SiC power diodes is affected by the concentration effect of the edge electric field. Traditional JTE structures have many design variables, large computational load, are difficult to optimize, have long simulation time, and low efficiency.
By employing Fermi-like functions to control the number of junctions and the junction center location, the doping concentration and length of the JTE region in SiC power diodes can be simulated by changing the values of these parameters, thereby reducing simulation variables and improving design efficiency.
It significantly reduces device performance simulation time, improves the design efficiency and breakdown voltage optimization speed of SiC power diodes, and reduces R&D and production costs.
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Figure CN115659545B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a power diode, in particular to a design and optimization method of a SiC power diode with high breakdown voltage. BACKGROUND
[0002] Power electronics technology is a high-tech technology for efficient conversion, control, management and use of electric energy, and power electronic devices based on semiconductor materials are the core of power electronics technology. The working characteristics of high-voltage and high-power devices indirectly determine the efficiency of the entire power electronics system. The physical limitations of traditional power electronic devices based on Si materials are increasingly apparent. Currently, SiC material has advantages such as wide band gap, high critical electric field, and high thermal conductivity, and is more suitable for preparing high-voltage and high-power devices used in various complex and harsh environments. It is recognized as the next generation of power electronic device material, meeting the requirements of high voltage, high temperature, radiation resistance and other requirements in the fields of high-speed rail transportation, new energy vehicles, smart grids, aerospace and other fields.
[0003] For an ideal SiC power device, its reverse withstand voltage is only related to the thickness and doping concentration of the i region, and the high voltage is mainly borne by the thick depleted i region. However, for actual devices, the core factor that restricts the breakdown voltage of the device is the edge field concentration effect. Because the thermal diffusion coefficient of the doping atoms in SiC is small, the curvature of the PN junction edge is very small. Due to the existence of curvature effect, the electric field is concentrated at the edge of the PN junction, which causes the reverse blocking capability of the power semiconductor device to be seriously degraded, the device breaks down prematurely, and the reliability decreases.
[0004] Junction termination extension technology is to improve the breakdown voltage of the device by the depletion effect of the lightly doped P-type JTE. As the reverse bias increases, the lightly doped P-type JTE will be gradually depleted, and the edge of the main junction P+ will be affected by the ionized negative electrically charged impurity atoms. The electric field concentration at the edge corner is effectively alleviated, and the peak electric field of the JTE edge will be coupled with the peak electric field of the P+ edge to make the macroscopic electric field distribution of the device uniform, thereby improving the breakdown voltage of the device and improving the voltage withstanding capability and reliability of the device. Introducing a PN junction to modulate the electric field distribution at the edge of the device is a common terminal technology solution, namely the Junction Termination Extension (JTE) terminal. The main requirements for the design of the terminal structure are two aspects: on the one hand, to improve the voltage withstanding capability of the terminal structure, so that its voltage withstanding capability is as close as possible to the theoretical voltage value of the device; on the other hand, the length of the designed terminal should be as short as possible. If the length of the terminal is too large, it will result in a large chip area, thereby greatly increasing the cost of the chip and affecting the integration level of the chip. Therefore, improving the voltage withstanding capability of the terminal structure and reducing the length of the terminal are the main two directions of the terminal structure research. Figure 6JTE is a junction termination extension structure, which extends the depletion region of the P+ main junction by its own depletion, and then reduces the electric field concentration phenomenon at the main junction.
[0005] When the dopant dose is too low, the JTE is fully depleted at low reverse bias, and its role in alleviating the main junction corner electric field concentration is greatly weakened, resulting in the edge peak electric field in the JTE region being significantly higher than the edge peak electric field outside the JTE region, and the device will break down at the edge of the JTE region in advance; when the dopant dose is too high, the excess negative charge prevents the depletion of the JTE, at this time the JTE can be regarded as an extension of the main junction, and the electric field concentration occurs at the edge outside the JTE region, that is, the edge peak electric field outside the JTE region is much higher than the electric field on the inside of the JTE region, and the breakdown will occur at the edge outside the JTE. Under the single-zone JTE structure, the breakdown voltage is very sensitive to the doping concentration, the injection window is small, and the process is difficult. In order to improve the dose sensitivity of the single-zone JTE, the concept of traditional two-zone junction termination extension structure (Two Zone-JTE, TZ-JTE) is proposed. The two-zone JTE structure has a different doping concentration distribution compared to the single-zone JTE structure, and the same partition is generally uniformly doped, and generally speaking, the closer to the main junction, the higher the doping concentration, so the two-zone JTE structure can alleviate the local electric field concentration effect while improving the breakdown voltage of the device. Although the two-zone JTE structure can obtain a higher breakdown voltage compared to the single-zone JTE structure, it is still too low compared to the breakdown voltage that can be obtained in the related literature. Therefore, on the basis of the two-zone JTE structure, a three-zone junction termination extension region is proposed. In order to improve the breakdown voltage of the device at a higher JTE doping concentration, the doping concentration in the three-zone JTE structure must decrease, that is, the farther away from the main junction, the lower the doping concentration. The three-zone JTE structure can further improve the breakdown voltage of the device while reducing the peak electric field of the main junction due to its longer terminal region length and multiple partitions with different doping concentrations. However, when using a multi-zone junction termination extension structure to improve the breakdown voltage, the number of JTE regions is limited. Even though the breakdown voltage obtained by the four-zone JTE structure is higher, it has the disadvantage of requiring multiple ion implantations to form, so the four-zone JTE structure is not considered for the time being.
[0006] When facing the problem of determining the maximum ideal breakdown voltage of SiC power diode, the doping concentration and length of JTE structure are needed. For three-junction structure, at least six variables are needed for three JTE regions, and at least twelve variables are needed for comparison of single-junction, double-junction and three-junction structure. The traditional method of determining breakdown voltage has the disadvantages of many variables and large amount of calculation, which makes it difficult to optimize the results, and the device simulation time is long, and the efficiency of obtaining SiC power diode structure with ideal breakdown voltage is low. Based on this, in the invention, a Fermi-like function is introduced, which is controlled by the number of junction parameters and the center position of the junction parameters. The size of the number of junction parameters is changed to realize the change of the doping concentration of the JTE region, and the single, double and three-junction JTE structure is determined according to the continuity of the doping concentration. The size of the center position of the junction is changed to realize the movement of the center position of the JTE and the change of the length of the JTE. Two parameters are used to replace the twelve variables needed for comparison of single-junction, double-junction and three-junction structure breakdown voltage, so that the design method in the invention greatly reduces the device performance simulation time compared with the traditional design method of device JTE structure, and improves the design efficiency of SiC power diode with ideal breakdown voltage. SUMMARY
[0007] The purpose of the present application is to provide a design and optimization method of SiC power diode based on Fermi-like function, which improves the disadvantages of many variables and large amount of calculation in the traditional design method of device JTE structure. The present application realizes optimization design based on Fermi-like function, and takes the number of junction parameters and the center position of the junction parameters as the change standard. The breakdown voltage of single, double and three-junction JTE structure is simulated by changing the values of the number of junction parameters and the center position of the junction parameters, and the two-dimensional graph of the breakdown voltage of the device with the number of junction parameters and the center position of the junction parameters as the coordinates is obtained. The SiC power diode determined by the doping concentration and the length of JTE corresponding to the maximum breakdown voltage point in the two-dimensional graph is the optimal solution of the optimization design, and the corresponding λ and μ are the optimal number of junction parameters and the optimal center position of the junction parameters.
[0008] The technical steps to achieve the purpose of the present application are:
[0009] A design and optimization method of SiC power diode based on Fermi-like function, characterized in that: the Fermi-like function is controlled by the number of junction parameters and the center position of the junction parameters.
[0010] The size of the number of junction parameters is changed to realize the change of the distribution and size of the doping concentration of the JTE region, and the single, double and three-junction JTE structure of the SiC power diode is determined according to the continuity of the doping concentration.
[0011] The size of the center position of the junction is changed to realize the change of the length of the JTE region and the movement of the center position of the JTE.
[0012] The Fermi-like function is as follows:
[0013]
[0014] Wherein, F(x) represents the doping concentration size at the position x of the JTE structure, x represents the distance from the main junction in the JTE structure, the range of x is 0 to the preset total length of JTE; the variable parameter μ is the junction center position parameter, the value range is 0-10 4 ; the variable parameter λ is the junction number parameter, the value range is 0-600; D1 is the preset initial doping concentration of the JTE region, D1+D2 is the preset highest doping concentration of the JTE region, the value range of D1-D1+D2 is 1×10 12 cm -3 -1×10 19 cm -3 .
[0015] Further, the structure of the SiC power diode used in the design and optimization method based on the Fermi-like function includes a Ti / Au metal bottom electrode layer (1), an N+ type SiC substrate layer (2) above the Ti / Au metal bottom electrode layer (1), and an N- type SiC epitaxial layer (3) above the N+ type SiC substrate layer (2).
[0016] Further, a P+ type SiC layer (4) is arranged above the left upper side of the N- type SiC epitaxial layer (3).
[0017] Further, a P type junction termination extension region (5) is arranged in a concentric circle shape from inside to outside at the right side of the P+ type SiC layer (4), which is a JTE region (5) under a single junction structure, is a JTE1 region (51) and a JTE2 region (52) under a double junction structure, and is a JTE1 region (51), a JTE2 region (52) and a JTE3 region (53) under a triple junction structure.
[0018] Further, an N+ field stop ring (6) is arranged at the right side of the P type junction termination extension region (5), and the N+ field stop ring (6) is not adjacent to the P type junction termination extension region (5).
[0019] Further, a Ti / Au metal top electrode layer (7) is arranged above the P+ type SiC layer (4), and a passivation dielectric layer (8) is arranged above the P type junction termination extension region (5).
[0020] Further, in order to make the JTE region of the SiC power diode a single junction structure, the junction number parameter λ is equal to 10 4 (enough large), at this time, the function exponential term part always tends to 1, which is a uniform doping single junction structure; and the junction number parameter λ is 60-100, which is a gradual doping single junction structure.
[0021] Further, in the single-junction structure, when the junction center position parameter μ in the Fermi-like function varies from 0 to the total length of the JTE, the length of the JTE region of the single-junction structure is unchanged, and the junction center position moves to the right.
[0022] Further, in order to make the JTE region of the SiC power diode a double-junction structure, the junction number parameter λ is set to be equal to 0, at this time, the exponential term of the JTE1 part function always tends to 0, and the exponential term of the JTE2 part function always tends to infinity, which is a double-junction structure in which JTE1 and JTE2 are uniformly doped.
[0023] Further, in the double-junction structure, when the junction center position parameter μ in the Fermi-like function varies from 0 to the total length of the JTE, the length of the JTE1 region increases, the length of the JTE2 region decreases, and the junction center position moves to the right.
[0024] Further, in order to make the JTE region of the SiC power diode a triple-junction structure, the junction number parameter λ is set to be between 1 and 60, at this time, the exponential term of the JTE1 part function always tends to 0, and the exponential term of the JTE3 part function always tends to infinity, which is a triple-junction structure in which JTE1 and JTE3 are uniformly doped, and JTE2 is gradually doped.
[0025] Further, in the triple-junction structure, when the junction center position parameter μ in the Fermi-like function varies from 0 to the total length of the JTE, the length of the JTE1 region increases, the length of the JTE2 region is unchanged, and the length of the JTE3 region decreases, and the junction center position moves to the right.
[0026] Further, taking the different lengths and different doping concentration distributions determined by the junction number parameter and the junction center position parameter as the variation standards, the breakdown voltage of the single-junction, double-junction and triple-junction JTE structures is simulated by changing the values of the junction number parameter and the junction center position parameter, that is, the JTE structure is simulated in a scanning mode.
[0027] Further, a two-dimensional graph with the junction number parameter and the junction center position parameter as the coordinates is obtained, in which the SiC power diode determined by the doping concentration and the JTE length corresponding to the maximum breakdown voltage point is the optimal solution, and the corresponding λ and μ are the optimal junction number parameter and the optimal junction center position parameter.
[0028] The working principle of the above-mentioned design and optimization method of the SiC power diode based on the Fermi-like function is as follows:
[0029] Power semiconductor as an important part of power electronic system, its performance directly affects the operation of the whole system. For ideal SiC power device, its reverse withstand voltage is only related to the thickness and doping concentration of i region, and high voltage is mainly relied on thick depleted i region. But for actual device, the key factor restricting the breakdown voltage of the device is the edge field concentration effect. Because the thermal diffusion coefficient of the doping atoms in SiC is small, the curvature of the PN junction edge is very small. Due to the existence of curvature effect, the electric field is concentrated at the edge of PN junction, which causes the reverse blocking capability of power semiconductor device to be seriously degraded, and the device breaks down in advance. In order to alleviate the edge electric field concentration effect, the junction termination extension structure is proposed.
[0030] When using the junction termination extension structure to improve the breakdown voltage, the number of JTE regions is limited. When the number of JTE regions is large, the process is more complex and needs to be implanted multiple times to form; when the number of regions is small, the JTE dopant dose window cannot be effectively expanded when high breakdown voltage is achieved. The doping concentration of JTE structure is also very critical. Exceeding the optimal JTE doping concentration will cause the breakdown voltage to decrease rapidly, and slightly less than a certain JTE doping concentration cannot improve the breakdown voltage value. The length of JTE structure is also a key variable. When the length of JTE region extends to the width of the parallel plane junction depletion region, the breakdown voltage is greatly improved compared with the breakdown voltage of cylindrical junction, but when the length of JTE region increases far more than this length, the breakdown voltage will not be further improved, at the same time, the space of the device edge is consumed and the reliability of the device is affected. Traditional single-zone, double-zone and triple-zone JTE structure needs JTE length, doping concentration and other parameters to determine the maximum ideal breakdown voltage, and at least twelve variables are needed to compare single-junction, double-junction and triple-junction structure. There are many variables and large amount of calculation, which makes it difficult to optimize the results, and the device simulation time is long, and the efficiency of obtaining SiC power diode structure with ideal breakdown voltage is low.
[0031] In order to solve the above problems, a Fermi-like function is introduced in the present application, which is controlled by the number of junction parameters and the center position parameters of the junction. The Fermi-like function of a single curve is used to simulate the doping dose distribution in the three JTE regions of SiC power diode, and only two parameters need to be modified to obtain JTE doping concentration and JTE length, which can significantly reduce the device performance simulation time and improve the efficiency of device structure design, which is quite meaningful.
[0032] In the present application, in order to successfully determine the design scheme of SiC power diode with ideal breakdown voltage, the transformation of single-junction, double-junction and triple-junction structure is realized by the junction Fermi function.
[0033] In order to obtain single-junction structure, the number of junction parameters λ is equal to 10 4(Enough large), at this time the function exponential term part always tends to 1, it is a single junction JTE structure of uniform doping, at this time the doping concentration is determined by the Fermi-like function as D1+D2 / 2; let the junction number parameter λ be 60-100, it is a single junction JTE structure of gradual doping. In order to obtain a double junction structure, let the junction number parameter λ be equal to zero, at this time the JTE1 part function exponential term always tends to 0, the doping concentration is determined by the Fermi-like function as D1+D2, the JTE2 part function exponential term always tends to infinity, the doping concentration is determined by the Fermi-like function as D1, it is a double junction structure in which JTE1 and JTE2 are both uniform doping. In order to obtain a triple junction structure, let the junction number parameter λ be located at 1-60, the JTE1 part function exponential term always tends to 0, the doping concentration is determined by the Fermi-like function as D1+D2, the JTE3 part function exponential term always tends to infinity, the doping concentration is determined by the Fermi-like function as D1, the JTE2 part is gradual doping from D1+D2 to D1, it is a triple junction structure in which JTE1 and JTE3 are both uniform doping and the JTE2 part is gradual doping. The doping concentration changes of single junction, double junction and triple junction JTE structures are shown in Figs. 1-3. Figure 5 The junction center position parameter in the Fermi-like function changes from 0 to the total length of JTE, under a single junction structure, the length of JTE region is unchanged, the junction center position moves to the right, and the doping concentration distribution of the SiC power diode obtained by changing the junction center position is shown in Fig. 4. Figure 7 Under a double junction structure, the length of JTE1 region increases, the length of JTE2 region decreases, the junction center position moves to the right, and the doping concentration distribution of the SiC power diode obtained by changing the junction center position is shown in Fig. 5. Figure 8 Under a triple junction structure, the length of JTE1 region increases, the length of JTE2 region is unchanged, the length of JTE3 region decreases, the junction center position moves to the right, and the doping concentration distribution of the SiC power diode obtained by changing the junction center position is shown in Fig. 6. Figure 9 The main reason for selecting the Fermi-like function composed of the junction number parameter and the junction center position parameter is that the efficiency of determining the SiC power diode structure design with an ideal breakdown voltage in the application is higher and faster than that of the traditional design method of the device JTE structure, the application replaces the twelve parameters originally required by the single junction, double junction and triple junction structures with the junction number parameter and the junction center position parameter, which can significantly reduce the device performance simulation time, improve the device structure design efficiency, reduce the device research and production cost, and make the application field of the SiC power diode using the Fermi-like function in the application more extensive.
[0034] In addition to the above points, it is also necessary to note in the application that when the Fermi-like function is used to design and optimize the SiC power diode, in addition to the design scheme of the SiC power diode with the maximum ideal breakdown voltage, the best design scheme of the SiC power diode with the process window width and the interface charge size as the standard can also be pursued.
[0035] With the above design scheme, the application has the following beneficial effects:
[0036] (1) Under the joint action of the junction number parameter and the junction center position parameter in the Fermi-like function, the efficiency of determining the SiC power diode structure design with an ideal breakdown voltage in the application is higher and faster than the efficiency of the traditional design method of the device JTE structure, so that the application field of the SiC power diode using the Fermi-like function in the application is more extensive.
[0037] (2) Under the action of the junction center position parameter, the SiC power diode in the application transfers three parameters of the length required by the three-zone JTE structure to the processing of the junction center position parameter, and changes the JTE length and moves the position of the JTE junction center in the SiC power diode by changing the size of the junction center position parameter.
[0038] (3) Under the action of the junction number parameter, the SiC power diode in the application transfers three parameters of the JTE region doping concentration required by the three-zone JTE structure to the processing of the junction number parameter, and changes the JTE region doping concentration in the SiC power diode by changing the size of the junction number parameter.
[0039] (4) The number of junction terminal extension structures is controlled according to the continuity of the doping concentration, so that the number of JTE junctions can be conveniently switched in single, double and triple JTE structures.
[0040] (5) The doping concentration distribution is obtained by a single curve Fermi-like function, which is faster than the traditional multi-zone JTE structure in determining the doping concentration.
[0041] (6) Due to the existence of the junction number parameter and the junction center position parameter, the application replaces the twelve parameters required by the single, double and triple junction structures with the junction number parameter and the junction center position parameter, which can significantly reduce the device performance simulation time, improve the device structure design efficiency, and reduce the device research and production cost.
[0042] (7) In addition to the design scheme of the SiC power diode with the maximum breakdown voltage, the best design scheme of the SiC power diode with the process window width and the interface charge size as the standard can also be pursued. BRIEF DESCRIPTION OF DRAWINGS
[0043] In order to make the content of the application more easily and clearly understood, the application will be further described in detail below according to specific embodiments and in conjunction with the drawings, in which:
[0044] Figure 1 The flowchart of the design and optimization method of the SiC power diode based on the Fermi-like function.
[0045] Figure 2 Cross-sectional view of SiC power diode with single junction based on Fermi- like function for the present invention.
[0046] Figure 3 Cross-sectional view of SiC power diode with double junction based on Fermi- like function for the present invention.
[0047] Figure 4 Cross-sectional view of SiC power diode with triple junction based on Fermi- like function for the present invention.
[0048] Figure 5 Variation of doping concentration with position for single, double and triple junction JTE structure.
[0049] Figure 6 Schematic diagram of junction termination extension structure.
[0050] Figure 7 Doping concentration distribution of diode with single junction structure as a function of junction center position.
[0051] Figure 8 Doping concentration distribution of diode with double junction structure as a function of junction center position.
[0052] Figure 9 Doping concentration distribution of diode with triple junction structure as a function of junction center position.
[0053] Figure 10 Variation of breakdown voltage of JTE termination structure SiC power diode as a function of junction number and junction center position.
[0054] In the drawing, the reference signs are: Ti / Au metal bottom electrode layer 1, N+ type SiC substrate layer 2, N- type SiC epitaxial layer 3, P+ type SiC layer 4, P type junction termination extension region 5, JTE1 region 51, JTE2 region 52, JTE3 region 53, N+ field stop ring 6, Ti / Au metal top electrode layer 7, passivation dielectric layer 8. DETAILED DESCRIPTION
[0055] (Example 1)
[0056] The Fermi-like function is controlled by the junction number and the junction center position, and the formula of the Fermi-like function is as follows:
[0057]
[0058] The total length of the junction termination extension region is 50-600 μm, the lowest doping concentration is 1 x 10 12 cm -3 , and the highest doping concentration is 1 x 10 19 cm-3 And the best JTE length and doping concentration are obtained by gradually narrowing the length and doping concentration range.
[0059] To make the JTE region of SiC power diode a single junction structure, the junction number parameter is equal to 10 4 , that is, the doping concentration of the JTE region is 5×10 18 cm -3 ; the junction number parameter is 60-100, and the doping concentration of the JTE region is 1×10 19 cm -3 to 1×10 12 cm -3 linearly.
[0060] To make the JTE region of SiC power diode a double junction structure, the junction number parameter is equal to zero, the doping concentration of the JTE1 region is 1×10 19 cm -3 , and the doping concentration of the JTE2 region is 1×10 12 cm -3 .
[0061] To make the JTE region of SiC power diode a triple junction structure, the junction number parameter is 1-60, the doping concentration of the JTE1 region is 1×10 19 cm -3 , the doping concentration of the JTE2 region is 1×10 19 cm -3 to 1×10 12 cm -3 linearly, and the doping concentration of the JTE3 region is 1×10 12 cm -3 .
[0062] The breakdown voltage of single, double, and triple junction JTE structures is simulated by changing the values of the junction number parameter and the junction center position parameter, and the range of the total JTE length and the doping concentration is gradually narrowed to continue to obtain the breakdown voltage. The two-dimensional graph of the breakdown voltage of the device with the junction number parameter and the junction center position parameter as coordinates is obtained. The SiC power diode corresponding to the doping concentration and the JTE length of the maximum breakdown voltage point in the two-dimensional graph is the optimal solution of the design. The corresponding optimal junction number parameter is 18, the JTE is a triple junction structure, the optimal junction center position parameter is 220, the best JTE length is 300μm, the length of the JTE1 region is 50μm, the length of the JTE2 region is 100μm, the length of the JTE3 region is 150μm, and the best doping concentration range is 8×10 16 cm -3 to 2×10 17 cm -3.
[0063] The application is based on the design and optimization scheme of SiC power diode, which is a symmetrical cylindrical structure, so the device performance on both sides of the vertical central axis is completely consistent, so in the simulation process, in order to avoid a large amount of calculation, the symmetry of the SiC power diode is utilized to study only 1 / 2 of the structure cross section of the vertical central axis, and the device structure cross section is as shown in Figure 4 Although the device structure is only a part of the entire SiC power diode, the device performance of the two is completely consistent, and it is completely feasible to use 1 / 2 of the structure cross section of the vertical central axis of the entire device to replace the entire SiC power diode to study. See Figure 4 , the structure of the SiC power diode with three junctions, from bottom to top, is Ti / Au metal bottom electrode layer 1, N+ type SiC substrate layer 2, N- type SiC epitaxial layer 3;
[0064] A P+ type SiC layer 4 is arranged above the left side of the N- type SiC epitaxial layer 3;
[0065] The right side of the P+ type SiC layer 4 is adjacent to the P-type junction termination expansion region 5 which is arranged in a concentric circle shape and expands from inside to outside, including JTE1 region 51, JTE2 region 52 and JTE3 region 53;
[0066] An N+ field cutoff ring 6 is arranged on the right side of the P-type junction termination expansion region 5, and the N+ field cutoff ring 6 is not adjacent to the P-type junction termination expansion region 5;
[0067] A Ti / Au metal top electrode layer 7 is arranged above the P+ type SiC layer 4, and a passivation dielectric layer 8 is arranged above the P-type junction termination expansion region 5.
[0068] The total length of the P-type junction termination expansion region 5 is 300 μm, and the doping concentration range is 8×10 16 cm -3 ~ 2×10 17 cm -3 .
[0069] A preparation method of a SiC power diode based on a Fermi-like function, characterized by comprising the following steps:
[0070] S1: The doping concentration of the N+ type SiC substrate layer 2 is 5×10 18 cm -3 ~ 1×10 19 cm -3 , and the thickness of the N+ type SiC substrate layer (2) is 350-400 μm;
[0071] S2: epitaxially growing an N-type SiC epitaxial layer 3 on the N+ type SiC substrate layer 2, the doping concentration of the N-type SiC epitaxial layer 3 ranging from 1×10 14 cm -3 to 9×10 16 cm -3 , the thickness of the N-type SiC epitaxial layer 3 being 10-100 μm;
[0072] S3: forming a P+ type SiC layer 4 on the N-type SiC epitaxial layer 3 by ion implantation, the doping concentration of the P+ type SiC layer 4 ranging from 8×10 16 cm -3 to 2×10 17 cm -3 , the implantation depth being 0.8-1 μm;
[0073] S4: then forming a JTE1 region 51 on the edge of the P+ type SiC layer 4 by ion implantation as well, the length of the JTE1 region 51 being 50 μm, the doping concentration being 2×10 17 cm -3 , the implantation depth being 0.6-1 μm;
[0074] S5: then forming a JTE2 region 52 on the edge of the JTE1 region 51 by ion implantation, the length of the JTE2 region 52 being 100 μm, the doping concentration ranging from 2×10 17 cm -3 to 8×10 16 cm -3 linearly decreasing, the implantation depth being 0.6-1 μm;
[0075] S6: then forming a JTE3 region 53 on the edge of the JTE2 region 52 by ion implantation, the length of the JTE3 region 53 being 150 μm, the doping concentration being 8×10 16 cm -3 , the implantation depth being 0.6-1 μm;
[0076] S7: after the ion implantation, annealing the device;
[0077] S8: then evaporating a Ti / Au metal top electrode layer 7 on the P+ type SiC layer 4; evaporating a Ti / Au metal bottom electrode layer 1 under the N+ type SiC substrate layer 2;
[0078] S9: finally depositing a passivation oxide layer dielectric layer, thus forming a SiC power diode based on Fermi-like function junction termination extension structure.
[0079] The junction termination extension structure of the SiC power diode based on Fermi-like function of the present application is shown in Figure 6 Fig. 1.Figure 7 It can be seen that the length of the JTE region under the single-junction structure is unchanged, the junction center position moves to the right, and the distribution of the doping concentration of the SiC power diode with the change of the junction center position when the junction center position parameter in the Fermi-like function changes from 0 to the total length of the JTE. Figure 8 It can be seen that the length of the JTE1 region under the double-junction structure increases, the length of the JTE2 region decreases, the junction center position moves to the right, and the distribution of the doping concentration of the SiC power diode with the change of the junction center position when the junction number parameter is equal to zero. Figure 9 It can be seen that the length of the JTE1 region under the triple-junction structure increases, the length of the JTE2 region is unchanged, the length of the JTE3 region decreases, and the junction center position moves to the right. The distribution of the doping concentration of the SiC power diode with the change of the junction center position at this time. Figure 10 The two-dimensional graph of the breakdown voltage of the JTE terminal structure SiC power diode with the change of the junction number parameter and the junction center position parameter can be seen. With the increase of the junction number parameter λ, the breakdown voltage of the JTE increases and then decreases. With the increase of the junction center position parameter μ, the breakdown voltage of the JTE increases. The darker the color in the two-dimensional graph, the higher the breakdown voltage. Therefore, the darkest part of the two-dimensional graph is the maximum ideal breakdown voltage point, i.e. the optimal performance point of the SiC power diode, and λ and μ are the optimal junction number parameter and the optimal junction center position parameter. According to the JTE length and the doping concentration corresponding to the junction number parameter and the junction center position parameter at this time, the SiC power diode can significantly reduce the device research and production cost. In addition to pursuing the design scheme of the SiC power diode with the maximum breakdown voltage, the Fermi-like function can also be used to pursue the best design scheme of the SiC power diode with the process window width and the interface charge size as the standard. Therefore, the design efficiency of the SiC power diode structure with the ideal breakdown voltage is effectively improved, and the device performance simulation time is significantly reduced.
[0080] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims
1. A method for design and optimization of SiC power diodes based on Fermi- like functions, characterized by: The pseudo Fermi function is controlled by a junction number parameter and a junction center position parameter; Changing the size of the junction number parameter changes the distribution and size of the JTE region doping concentration, and determines the SiC power diode to be a single-junction, double-junction or triple-junction JTE structure according to the continuity of the doping concentration. Changing the size of the junction center position parameter changes the length of the JTE region and the movement of the junction center position. The pseudo Fermi function formula is as follows: Wherein, F(x) represents the doping concentration size at the JTE structure x, x represents the distance from the main junction in the JTE structure, the change range of x is 0 to the preset JTE total length; the variable parameter μ is a junction center position parameter, the value range is 0-10 4 ; the variable parameter λ is a junction number parameter, the value range is 0-600; D1 is a preset JTE region initial doping concentration, D1+D2 is a preset JTE region highest doping concentration, the value range of D1-D1+D2 is 1×10 12 cm -3 -1×10 19 cm -3 .
2. The method for design and optimization of Fermi- like function based SiC power diodes according to claim 1, characterized in that: The SiC power diode comprises a Ti / Au metal bottom electrode layer (1), an N+ type SiC substrate layer (2) above the Ti / Au metal bottom electrode layer (1), and an N- type SiC epitaxial layer (3) above the N+ type SiC substrate layer (2). A P+ type SiC layer (4) is arranged above the left upper side of the N- type SiC epitaxial layer (3). The P+ type SiC layer (4) is adjacent to the right side of the P type junction termination extension region (5) and expands outward in a concentric circle shape, and the P type junction termination extension region (5) is a JTE region (5) in a single-junction structure, is a JTE1 region (51) and a JTE2 region (52) in a double-junction structure, and is a JTE1 region (51), a JTE2 region (52) and a JTE3 region (53) in a triple-junction structure. An N+ field stop ring (6) is arranged on the right side of the P type junction termination extension region (5), and the N+ field stop ring (6) is not adjacent to the P type junction termination extension region (5). A Ti / Au metal top electrode layer (7) is arranged above the P+ type SiC layer (4), and a passivation dielectric layer (8) is arranged above the P type junction termination extension region (5).
3. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 1, characterized in that: In order to make the SiC power diode JTE region a single junction structure, let the junction number parameter λ equal 10 4 At this time, the function exponential term part always tends to 1, which is a uniform doped single junction structure; let the junction number parameter λ be 60-100, which is a gradual doped single junction structure.
4. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 3, characterized in that: In the single-junction structure, when the junction center position parameter μ in the pseudo Fermi function changes from 0 to the total length of the JTE region, the length of the JTE region in the single-junction structure remains unchanged, and the junction center position moves to the right.
5. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 1, characterized in that: To make the JTE region of the SiC power diode a double-junction structure, the junction number parameter λ is set to zero, and at this time, the exponential term of the JTE1 part function always tends to 0, and the exponential term of the JTE2 part function always tends to infinity, which is a double-junction structure in which JTE1 and JTE2 are uniformly doped.
6. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 5, characterized in that: In the double-junction structure, when the junction center position parameter μ in the pseudo Fermi function changes from 0 to the total length of the JTE region, the length of the JTE1 region increases, the length of the JTE2 region decreases, and the junction center position moves to the right.
7. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 1, characterized in that: To make the JTE region of the SiC power diode a triple-junction structure, the junction number parameter λ is set to 1-60, and at this time, the exponential term of the JTE1 part function always tends to 0, and the exponential term of the JTE3 part function always tends to infinity, which is a triple-junction structure in which JTE1 and JTE3 are uniformly doped and JTE2 is gradually doped.
8. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 7, characterized in that: In the triple-junction structure, when the junction center position parameter μ in the pseudo Fermi function changes from 0 to the total length of the JTE region, the length of the JTE1 region increases, the length of the JTE2 region remains unchanged, the length of the JTE3 region decreases, and the junction center position moves to the right.
9. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 1, characterized in that: The breakdown voltage of the single-junction, double-junction and triple-junction JTE structures is simulated by changing the values of the junction number parameter and the junction center position parameter, which is the scanning simulation of the JTE structure.
10. The method for design and optimization of SiC power diodes based on Fermi- like functions according to claim 1, characterized in that: The breakdown voltage of the device is obtained as a two-dimensional graph with the junction number parameter and the junction center position parameter as coordinates, and the SiC power diode determined by the doping concentration and the JTE length corresponding to the maximum breakdown voltage point in the two-dimensional graph is the optimal solution of the design, and λ and μ are the optimal junction number parameter and the optimal junction center position parameter.