Method and system for reducing reverse leakage current of diode

Abstract

According to the method and system for reducing the reverse leakage current of the diode, the tail end of an electrode is designed to be of a multi-stage stepped structure, the physical path of potential change is prolonged, and electric field gradient distribution is smoother; meanwhile, an electrically isolated annular auxiliary electrode is arranged on the periphery of the main electrode, an intermediate potential is applied, a transverse electric field component is introduced, and edge electric field distribution is reconstructed after the transverse electric field component is superposed with a longitudinal electric field; according to the method, on the premise of not changing a semiconductor material and a doping process, electric field distribution is synergistically optimized from two dimensions of an electrode structure and potential configuration; the stepped structure enables the geometric contour of the electrode tail end to be gradually transited, potential mutation is avoided, and the local electric field peak value is remarkably reduced; the transverse electric field generated by the annular auxiliary electrode guides the electric field lines to diffuse outwards, the concentration density towards the interior of the semiconductor is reduced, the intensity of the synthesized electric field in the edge area is integrally reduced, and the maximum field intensity point is effectively restrained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of diodes, and particularly relates to a method and system for reducing reverse leakage current of a diode. BACKGROUND

[0002] In a semiconductor device, the reverse leakage current of a diode is one of the key factors affecting its performance and reliability. When the diode is in a reverse bias state, the edge of the PN junction depletion region is prone to electric field concentration due to geometric structure mutation and uneven electric field distribution. The local high electric field significantly enhances the collision ionization effect of carriers, leading to an increase in reverse leakage current, and even causes avalanche breakdown, thereby reducing the working stability and voltage resistance of the device.

[0003] In the prior art, a uniform planar electrode structure is usually adopted, and the electrode edge is aligned with the semiconductor boundary. In this structure, the potential change is concentrated in a narrow area at the end of the electrode under high reverse voltage, forming a strong electric field gradient and aggravating the edge field concentration problem. Although some solutions attempt to alleviate the electric field concentration through a passivation layer or a field plate structure, the regulation capacity is limited, and it is difficult to effectively disperse the potential change path of the electrode edge and inhibit the leakage current.

[0004] Therefore, how to reduce the edge electric field strength of the diode under reverse bias and reduce the reverse leakage current has become a technical problem to be solved. SUMMARY

[0005] The purpose of the application is to provide a method and system for reducing the reverse leakage current of a diode, effectively dispersing the electric field concentration at the electrode edge, making the maximum electric field strength lower than the material breakdown threshold, thereby significantly inhibiting the generation of reverse leakage current and improving the voltage resistance performance and working reliability of the device, to solve the problems raised in the background.

[0006] To achieve the above purpose, the application adopts the following technical scheme: a method for reducing the reverse leakage current of a diode, comprising the following steps: Set the geometric size of the P region and the N region of the diode, define the lateral length and the PN junction position, and provide a spatial reference for subsequent potential distribution analysis; Based on the geometric size and in combination with the net doping concentration of the P region and the N region, calculate the built-in potential, and apply a reverse bias voltage to form a total applied potential difference as an electrode boundary condition input; According to the total applied potential difference, cover the metal electrode A grounded at the top of the P region and the metal electrode B applied with a reverse bias voltage at the bottom of the N region, to construct a rectangular electrode structure with the electrode edge aligned with the semiconductor edge; Based on the rectangular electrode structure, solve the Poisson equation under the depletion layer approximation, calculate the potential distribution, and derive the electric field strength to identify the high field concentration point in the electrode edge region. For the high-field concentration point, the end of the original rectangular electrode is modified to a multi-stage ladder structure, and the total extension length is determined by the number of steps and the width of a single stage to prolong the potential change path and reduce the local electric field gradient; A ring-shaped auxiliary electrode is arranged outside the stepped main electrode, with a reserved distance between its inner boundary and the edge of the main electrode, a fixed width of the ring-shaped structure, and the electrode being electrically isolated from the main electrode. The potential is set to an intermediate potential between the potential of the main electrode and the ground potential, which is used to regulate the edge electric field distribution; Based on the electric field regulation effect introduced by the ring-shaped auxiliary electrode, by adjusting the number of steps, the width of a single stage, the distance between the ring-shaped electrode and the main electrode, and the proportion of the intermediate potential relative to the reverse bias voltage, the electric field intensity of the edge region is lower than the field intensity threshold corresponding to material breakdown.

[0007] Preferably, the modification of the end of the original rectangular electrode to a multi-stage ladder structure comprises: According to the total amount of potential change required to control the identified high-field concentration point, the minimum length required for the potential change path is determined; Compare the total extension length with the minimum length to determine whether the electric field dispersion requirement is met; If the total extension length is insufficient, increase the number of steps or expand the width of a single stage to distribute the potential over more or wider steps; Verify whether the adjusted ladder structure makes the edge electric field intensity lower than the breakdown threshold, and if not, repeat the adjustment.

[0008] Preferably, the potential of the ring-shaped auxiliary electrode is provided by a voltage dividing circuit, specifically comprising: Connect the voltage dividing circuit between the main electrode and the ground to form an intermediate potential output node; Connect the intermediate potential output node to the ring-shaped auxiliary electrode to make the ring-shaped electrode obtain a stable potential, which is between the potential of the main electrode and the ground potential; The potential difference between the intermediate potential and the potential of the main electrode is distributed over the spatial distance between the ring-shaped electrode and the main electrode, and the potential difference forms a transverse electric field component after spatial distribution, which is used to change the electric field line direction of the electrode edge.

[0009] Preferably, by adjusting the distance between the ring-shaped electrode and the main electrode and the proportion of the intermediate potential, the transverse electric field component and the longitudinal electric field component of the main junction region are reduced after vector superposition, specifically comprising: Determine the longitudinal electric field intensity of the edge point at the end of the main electrode according to the longitudinal electric field distribution; Adjust the proportion of the intermediate potential of the ring-shaped auxiliary electrode to make the generated transverse electric field component reach the expected regulation level; Adjusting the distance between the ring electrode and the main electrode ensures that the lateral electric field covers the high field intensity area at the end of the step structure; Calculating the vector sum of the longitudinal electric field and the lateral electric field at the edge point verifies whether the intensity of the resultant electric field is lower than the breakdown threshold.

[0010] Preferably, the height of the step structure decreases step by step, so that the electrode end gradually transitions from the main electrode plane to the uncovered area, specifically including: Determining the difference between the initial height of the main electrode and the height of the semiconductor surface, and dividing the difference into multiple decreasing amounts corresponding to the height reduction of each step; Starting from the end of the main electrode, each step decreases by one decreasing amount based on the previous step, forming a continuous descending profile that smoothly transitions the electric potential from the main electrode potential to the semiconductor surface potential.

[0011] Preferably, the ring-shaped auxiliary electrode is arranged around the stepped main electrode with a reserved distance between the inner boundary of the ring-shaped auxiliary electrode and the edge of the main electrode, including: According to the lateral range of the high field intensity area, determine the required coverage width; Set the inner boundary of the ring electrode outside the high field intensity area with a spacing distance, which ensures that the electric field influence range of the ring electrode includes the entire high field intensity area; Verify whether the lateral electric field can effectively guide the distribution of the identified electric field lines and reduce the edge peak field intensity under the spacing distance.

[0012] Preferably, it further includes: by evaluating the ratio of the electric field intensity in the edge region to the breakdown threshold, determining whether the electrode layout has sufficient safety margin, specifically including: Calculate the maximum electric field intensity in the optimized edge region, compare the maximum electric field intensity with the material breakdown threshold, and obtain the ratio; If the ratio is less than the preset safety threshold, it is determined that the layout meets the safety requirements; If the ratio is greater than or equal to the preset safety threshold, adjust the step parameters or the ring electrode parameters until the safety requirements are met.

[0013] On the other hand, the present application proposes a system for reducing the reverse leakage current of a diode, including: A semiconductor substrate containing a P region and an N region, forming a PN junction; A main electrode covering the surface of the N region, with its edge adopting a stepped structure composed of multiple continuous steps; A ring-shaped auxiliary electrode arranged around the main electrode with a physical spacing between the main electrode to achieve electrical isolation and connected to an independent potential supply source; A potential supply unit applies a reverse bias voltage to the main electrode and an intermediate potential to the ring-shaped auxiliary electrode; The package structure is used for fixing the main electrode, the ring-shaped auxiliary electrode and the semiconductor substrate, and maintaining the insulation state between the electrodes.

[0014] Preferably, in the stepped structure of the main electrode, the width of each step is consistent, and the height of each step is gradually reduced, so that the electrode end forms a gradual contour and prolongs the potential change path.

[0015] Preferably, the potential of the ring-shaped auxiliary electrode is provided by a voltage dividing circuit, so that the potential difference between the ring-shaped auxiliary electrode and the main electrode is distributed in space, forming a transverse electric field, and the transverse electric field and the longitudinal electric field of the main junction are superimposed to reduce the edge synthetic electric field strength.

[0016] The technical effects and advantages of the present application: the method and system for reducing the reverse leakage current of the diode have the following advantages compared with the prior art: The electrode end is designed as a multi-step ladder structure, the physical path of potential change is prolonged, the electric field gradient distribution is more gentle, and the ring-shaped auxiliary electrode is arranged outside the main electrode and is electrically isolated, and an intermediate potential is applied to introduce a transverse electric field component, and the transverse electric field and the longitudinal electric field are superimposed to reconstruct the edge electric field distribution. The method optimizes the electric field distribution from two dimensions of electrode structure and potential configuration without changing the semiconductor material and doping process. The ladder structure gradually transitions the geometric contour of the electrode end, avoids sudden changes in potential, and significantly reduces the local electric field peak value; the transverse electric field generated by the ring-shaped auxiliary electrode guides the electric field lines to diffuse outward, reducing the density of the semiconductor interior. The combination of the two reduces the overall synthetic electric field strength of the edge region and effectively suppresses the maximum field strength point. As a result, the carrier tunneling probability and the collision ionization rate under reverse bias are greatly reduced, fundamentally weakening the leakage current generation mechanism. The leakage current of the device is reduced under the same reverse voltage, and the device can withstand higher voltage without breakdown, and the withstand voltage is improved. At the same time, the uniformization of the electric field distribution reduces the local thermal effect and material stress concentration, prolongs the service life of the device, and improves the long-term working stability. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The flowchart of the method for reducing the reverse leakage current of the diode. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0019] The application provides a method for reducing reverse leakage current of a diode Figure 1 The application provides a method for reducing reverse leakage current of a diode The geometric size of the P region and the N region of the diode is set, the lateral length and the PN junction position are defined, and a spatial reference is provided for subsequent potential distribution analysis; by accurately setting the geometric size of the P region and the N region and defining the PN junction position, a physical space framework for potential and electric field analysis is established, which provides an accurate structure basis for subsequent electric field distribution calculation.

[0020] Based on the geometric size and in combination with the net doping concentration of the P region and the N region, the built-in potential is calculated, and a reverse bias voltage is applied to form a total applied potential difference as an electrode boundary condition input; the built-in potential is calculated in combination with the net doping concentration, and the reverse bias voltage and the built-in potential are collectively used as the total applied potential difference, which truly reflects the electrical boundary conditions in the working state of the device, and improves the accuracy of electric field simulation and optimization.

[0021] According to the total applied potential difference, a metal electrode A is covered on the top of the P region and grounded, and a metal electrode B is covered on the bottom of the N region and applied with a reverse bias voltage, to construct a rectangular electrode structure with the electrode edge aligned with the semiconductor edge; the rectangular electrode structure with the electrode edge aligned with the semiconductor edge is constructed to ensure that the potential application mode is consistent with the actual device, so that the identification of the high field strength region is representative, and a reliable starting point is provided for subsequent targeted optimization of the electrode form. The series of steps collectively guarantee the integrity and authenticity of the entire method in structure modeling and electrical condition setting, and lay a foundation for effectively suppressing reverse leakage current.

[0022] Based on the rectangular electrode structure, the Poisson equation is solved under the depletion layer approximation, the potential distribution is calculated, and the electric field strength is derived to identify the high field strength concentration point of the electrode edge region; for the high field strength concentration point, the original rectangular electrode end is modified into a multi-stage ladder structure, and the total extension length is determined by the number of steps and the single-stage width, so as to prolong the potential change path and reduce the local electric field gradient; this structure changes the aggregation trend of the electric field lines, makes the electric field distribution gradually transition along the ladder profile, significantly reduces the local electric field peak strength, weakens the impact ionization and tunneling effect, and suppresses the generation of reverse leakage current from the source, thereby improving the voltage withstand performance and working stability of the device.

[0023] The end of the original rectangular electrode is modified into a multi-stage stepped structure, including: determining the minimum length required for the potential change path according to the total amount of potential change required for control of the identified high field strength concentration point; comparing the total extension length with the minimum length to determine whether the electric field dispersion requirement is met; if the total extension length is insufficient, increasing the number of steps or expanding the width of a single stage to distribute the potential on more or wider steps; verifying whether the adjusted stepped structure makes the edge electric field strength lower than the breakdown threshold, and repeating the adjustment if it does not meet the standard.

[0024] By establishing a quantitative matching relationship between the length of the potential change path and the electric field dispersion requirement, it is ensured that the stepped structure has sufficient physical extension to carry the potential gradient; based on the minimum length requirement, the number of steps or the width of a single stage is dynamically adjusted to achieve targeted optimization of structure parameters, avoiding insufficient electric field regulation or overdesign; through a cyclic verification mechanism, the optimization result is continuously evaluated to ensure that the final structure can make the edge electric field strength stable below the breakdown threshold, improving device reliability and design robustness.

[0025] The height of the stepped structure decreases step by step, making the electrode end gradually transition from the main electrode plane to the uncovered area, specifically including: determining the difference between the initial height of the main electrode and the height of the semiconductor surface, dividing the difference into multiple decreasing amounts corresponding to the height reduction value of each step; starting from the end of the main electrode, each step reduces by one decreasing amount based on the previous step, forming a continuous descending profile that smoothly transitions the potential from the main electrode potential to the semiconductor surface potential.

[0026] By gradually decreasing the height of the steps to form a smooth geometric transition profile, abrupt height changes between the electrode end and the semiconductor surface are avoided, effectively reducing electric field concentration caused by structural mutations; the continuous descending form promotes the smooth release of potential along the steps, reducing the peak value of the potential gradient at the interface, further weakening the acceleration effect of local strong electric field on carriers, thereby significantly suppressing the generation of reverse leakage current, improving the uniformity of the electric field distribution and the insulation reliability of the device.

[0027] An annular auxiliary electrode is provided around the stepped main electrode, with an inner boundary spaced from the edge of the main electrode, including: determining the required coverage width according to the lateral range of the high field strength area; setting the inner boundary of the annular electrode outside the high field strength area with a spacing distance, which ensures that the electric field influence range of the annular electrode includes the entire high field strength area; verifying whether the lateral electric field can effectively guide the distribution of the identified electric field lines to reduce the peak field strength at the edge under the spacing distance.

[0028] By reasonably setting the position of the annular auxiliary electrode, its electric field action range accurately covers the high field strength area of the edge of the main electrode, fully exerting the electric field regulation effect; the inner boundary is located outside the high field strength area and maintains an appropriate interval, which is conducive to forming a stable transverse electric field component, guiding the outward diffusion of the electric field lines, and avoiding their intensive convergence at the end of the main electrode; this layout strengthens the active intervention ability of the edge electric field distribution, significantly weakens the peak field strength, and improves the uniformity of the electric field distribution, thereby effectively reducing the reverse leakage current and enhancing the working stability and voltage resistance of the device under high voltage.

[0029] An annular auxiliary electrode is arranged outside the stepped main electrode, the inner boundary of which is spaced apart from the edge of the main electrode, the width of the annular structure is fixed, the electrode is electrically isolated from the main electrode, and the potential is set to an intermediate potential between the potential of the main electrode and the ground potential, for regulating the edge electric field distribution; Specifically, the potential of the annular auxiliary electrode is provided by a voltage dividing circuit, which specifically includes: connecting the voltage dividing circuit between the main electrode and the ground to form an intermediate potential output node; connecting the intermediate potential output node to the annular auxiliary electrode to make the annular electrode obtain a stable potential, which is between the potential of the main electrode and the ground potential; the potential difference between the intermediate potential and the potential of the main electrode is distributed on the spatial distance between the annular electrode and the main electrode, and the potential difference forms a transverse electric field component after spatial distribution, which is used to change the direction of the electric field lines at the edge of the electrode.

[0030] By setting the electrically isolated annular auxiliary electrode and applying a controllable intermediate potential, an independent electric field regulation path is constructed, avoiding interference with the working state of the main electrode; a stable intermediate potential is provided by a voltage dividing circuit to ensure the accuracy and long-term consistency of the potential of the annular electrode, improving the reliability of the electric field regulation; the potential difference between the main electrode and the annular electrode forms a directional transverse electric field in the reserved interval, effectively changing the distribution direction of the electric field lines in the edge region of the electrode from vertical dense distribution to inclined or divergent form, significantly reducing the electric field line density and local field strength peak; this transverse electric field cooperates with the longitudinal electric field regulation of the stepped structure to realize multi-dimensional electric field optimization, further suppress the edge electric field concentration, reduce the probability of carrier tunneling and impact ionization, thereby significantly reducing the reverse leakage current and improving the insulation performance and voltage resistance level of the device.

[0031] Based on the electric field regulation effect introduced by the annular auxiliary electrode, by adjusting the number of steps, the width of each step, the distance between the annular electrode and the main electrode, and the proportion of the intermediate potential to the reverse bias voltage, the electric field strength in the edge region is lower than the field strength threshold corresponding to material breakdown.

[0032] Further, by adjusting the distance between the annular electrode and the main electrode and the proportion of the intermediate potential, the synthetic electric field intensity of the edge point is reduced after the vector superposition of the transverse electric field component and the longitudinal electric field component of the main junction region, specifically including: determining the longitudinal electric field intensity of the edge point at the end of the main electrode according to the longitudinal electric field distribution; adjusting the proportion of the intermediate potential of the annular auxiliary electrode to make the generated transverse electric field component reach the expected regulation level; adjusting the distance between the annular electrode and the main electrode to ensure that the transverse electric field covers the high field strength area at the end of the stepped structure; and calculating the vector sum of the longitudinal electric field and the transverse electric field at the edge point to verify whether the synthetic electric field intensity is lower than the breakdown threshold.

[0033] Through multi-parameter coordinated regulation, fine control of the edge electric field distribution is realized; optimization of the number of steps and the single-stage width further prolongs the potential transition path and reduces the longitudinal electric field gradient; the coordinated adjustment of the distance between the annular electrodes and the proportion of the intermediate potential accurately matches the transverse electric field intensity and the action range with the high field strength area; the vector superposition of the transverse electric field component and the longitudinal electric field component at the edge point effectively offsets part of the longitudinal field strength and significantly reduces the peak value of the synthetic electric field; by quantitatively verifying the relationship between the synthetic electric field intensity and the breakdown threshold, it is ensured that the optimization result meets the safety margin requirement, which fundamentally suppresses the carrier multiplication effect induced by the electric field, greatly reduces the reverse leakage current, and improves the working reliability and stability of the device under high reverse voltage.

[0034] By evaluating the ratio of the electric field intensity of the edge region to the breakdown threshold, it is determined whether the electrode layout has sufficient safety margin, specifically including: calculating the maximum electric field intensity of the optimized edge region, comparing the maximum electric field intensity with the material breakdown threshold, and obtaining the ratio; if the ratio is less than the preset safety threshold, it is determined that the layout meets the safety requirement; if the ratio is greater than or equal to the preset safety threshold, the step parameters or the annular electrode parameters are adjusted until the safety requirement is met.

[0035] By quantifying the ratio of the maximum electric field intensity of the edge region to the material breakdown threshold, a clear safety margin evaluation standard is established to objectively determine the optimization effect of the electrode structure; this evaluation mechanism can identify layouts with insufficient electric field control in a timely manner and trigger further adjustment of the number of steps, the single-stage width, the distance between the annular electrodes, or the proportion of the intermediate potential, forming a closed-loop optimization process; it ensures that the final structure can maintain an electric field intensity below the critical value under various working conditions, effectively avoiding the risk of local breakdown; and improves the reliability and robustness of the device design, ensuring the long-term stable operation of the diode under high reverse voltage.

[0036] On the other hand, the present application proposes a system for reducing the reverse leakage current of a diode, comprising: a semiconductor substrate comprising a P region and an N region, forming a PN junction; a main electrode covering the surface of the N region, the edge of which adopts a stepped structure composed of multiple continuous steps; a ring-shaped auxiliary electrode arranged outside the periphery of the main electrode, physically separated from the main electrode to achieve electrical isolation, and connected to an independent potential supply source; a potential supply unit configured to apply a reverse bias voltage to the main electrode and an intermediate potential to the ring-shaped auxiliary electrode; a packaging structure configured to fix the main electrode, the ring-shaped auxiliary electrode and the semiconductor substrate, and maintain the insulating state between the electrodes.

[0037] Preferably, in the stepped structure of the main electrode, the width of each step is consistent, and the height of each step decreases gradually, so that the electrode end forms a gradual profile and prolongs the potential change path.

[0038] Preferably, the potential of the ring-shaped auxiliary electrode is provided by a voltage dividing circuit, so that the potential difference between the main electrode and the ring-shaped auxiliary electrode is distributed in space, forming a transverse electric field, which, after superimposed with the longitudinal electric field of the main junction, reduces the edge synthetic electric field strength.

[0039] The system realizes effective regulation of the edge electric field through the above electrode layout design, without changing the characteristics of the semiconductor body, and achieves the goal of suppressing the leakage current. The whole scheme is logically rigorous, and each step is closely linked, forming a complete technical path from initial modeling to final evaluation. The proposed stepped structure and ring-shaped electrode work together to solve the fundamental problem of edge electric field concentration in traditional design from two dimensions of geometric shape and potential distribution. By prolonging the potential change path and introducing a transverse electric field component, the local field strength is significantly reduced, thereby suppressing the unintended transport of carriers and improving the performance of the diode under reverse bias.

[0040] In addition, the system components described above are also used to implement other steps of the above-mentioned method for reducing the reverse leakage current of a diode, as follows: Step 1: Determine the initial geometric parameters and electrical boundary conditions of the diode body structure Set the geometric dimensions of the P-type and N-type semiconductor regions of the diode, including the lateral length of the P region and the N region and the position coordinates of the interface between them (i.e., the PN junction) . Set the axis to extend in the lateral direction, with the origin located at the left end boundary of the P region, then . This setting is used to establish a one-dimensional spatial coordinate system to facilitate subsequent mathematical description of potential and electric field.

[0041] By clearly defining the spatial coordinates and region division, a clear geometric basis is provided for the modeling of potential distribution. This coordinate system will be used throughout the subsequent analysis process to ensure that all physical quantities are expressed in a unified framework.

[0042] In semiconductor devices, the potential distribution is directly dependent on the spatial location, especially near the PN junction, the potential gradient determines the electric field strength. Therefore, establishing an accurate spatial coordinate system is the prerequisite for analyzing the electric field behavior.

[0043] Given the net doping concentration of P and N regions, respectively denoted as and , with units of . Assuming uniform doping distribution, i.e., within their respective regions (when ), (when ). This setting is used to determine the initial expression of the space charge density .

[0044] The uniform doping assumption simplifies the charge distribution model, making the potential equation analytically solvable, while still reflecting the main electrical characteristics of the actual device. The space charge density is contributed by the doping ions, which dominates the source term of the Poisson equation within the depletion layer. Clearly is the key first step to solve the potential distribution.

[0045] Based on the doping concentration and temperature (set to 300K), the built-in potential is calculated, whose expression is: ; where is the Boltzmann constant, is the electron charge amount, is the intrinsic carrier concentration. This value represents the potential difference on both sides of the PN junction under zero bias, which is the reference for the superimposed reverse bias voltage. The built-in potential determines the initial level of the depletion layer width and the maximum electric field strength, which is an important input parameter for subsequent electric field analysis. This formula is derived from the principle of Fermi level alignment, reflecting the natural potential barrier formed by the difference in carrier concentration between the P and N regions.

[0046] Apply a reverse bias voltage ( ), at this time the total applied potential difference is . This voltage will widen the depletion layer and enhance the electric field strength near the junction region, especially in the edge region where field concentration phenomenon is prone to occur. This condition is set as the boundary input for subsequent electric field distribution calculation. Reverse bias is the main working state for leakage current generation, and clearly value can simulate the electric field behavior in actual application scenarios. The applied reverse voltage increases the potential difference within the depletion layer, resulting in a stronger electric field, which in turn increases the tunneling probability and leakage current level. Therefore, it is necessary to evaluate the edge field strength under this condition.

[0047] Step two: Establish the initial electrode layout and calculate the electric field distribution in the edge region After the basic structure and boundary conditions are set, the next step is to construct a standard planar electrode structure and derive the electric field strength in the edge region using the potential equation, identifying the high field concentration points to provide target areas for subsequent electrode shape optimization.

[0048] Design standard rectangular electrode structure: P region top covered with metal electrode A, N region bottom covered with metal electrode B, electrode lateral width consistent with semiconductor region, both , and electrode edges aligned with semiconductor edges. Electrode A is grounded (0V), and electrode B applies voltage (relative to ground).

[0049] This structure is a traditional design, which is convenient as a comparison benchmark to highlight the advantages of subsequent optimization schemes.

[0050] Electrode voltage directly sets the potential value of the semiconductor boundary, thereby affecting the internal potential distribution. The aligned edge structure is common in manufacturing, but it easily leads to edge field concentration.

[0051] Under the depletion layer approximation, solve the one-dimensional Poisson equation to obtain the potential distribution . In the P region depletion layer ( ) and N region depletion layer ( ), the equation is: ; where is the semiconductor dielectric constant, approximately constant in the depletion region (sudden change junction can be simplified to ).

[0052] This equation describes how the charge distribution affects the second-order change in potential, which is the core of electric field calculation.

[0053] Poisson's equation is a basic equation of electrostatics that connects charge density and potential curvature, and its solution directly determines the electric field .

[0054] Integrate the above equation twice and apply the boundary conditions to obtain the potential function. Then take the derivative to get the electric field distribution: ; where is the integration constant determined by the junction position and doping. The maximum electric field occurs at , i.e. , is the total depletion layer width. This expression reveals the relationship between the maximum electric field and doping concentration, dielectric constant, and depletion layer width, providing a quantitative basis for subsequent optimization. In the abrupt junction model, the electric field is linearly distributed, with the peak value at the junction center.

[0055] The edge field enhancement is analyzed by introducing a two-dimensional effect. The curvature effect at the electrode edge is considered, and the edge field amplification factor is estimated by conformal transformation or numerical method , whose empirical expression is ; where is the effective curvature radius of the electrode edge (tends to 0 in rectangular structure, leading to ). Therefore, the edge field is much higher than that in the central region. This formula quantifies the edge field enhancement phenomenon and explicitly points out that sharp edges are the source of high field strength. In electrostatic field, the greater the curvature of the conductor edge (the smaller the radius), the higher the charge density, leading to a sharp rise in local electric field. This is the physical source of leakage current concentration.

[0056] Step three: design a stepped electrode edge structure to disperse the edge charge density In view of the edge field concentration problem identified in step two, this step proposes a stepped electrode edge layout, which changes the geometry of the electrode end, prolongs the potential change path, and thus reduces the local electric field gradient.

[0057] The right-angle edge of the original rectangular electrode is modified to a multi-step ladder structure. Suppose the electrode end is divided into steps along the horizontal direction, each step has a width of , and the height decreases by . The total extension length is . This structure gradually transitions from the main electrode area to the electrode-free area. The stepped structure increases the effective curvature radius of the electrode edge, avoiding potential sudden changes. The potential on the conductor surface must be continuous, and the stepped edge forces the potential to change over a longer path, thus reducing the electric field strength.

[0058] Establish an equivalent potential distribution model for the ladder area. Suppose the potential of the step is , since the metal electrode is an equipotential body, all step potentials are the same, all . But the potential of the semiconductor surface below it gradually decreases as it moves away from the main junction area. Introduce the horizontal distance (from the main junction to the edge), then the surface potential satisfies: ; where is the potential decay length, which is related to the characteristics of the depletion layer. This formula describes the exponential decay behavior of the potential in the edge region. This model reflects the trend of the electric field weakening away from the junction area, providing a distance basis for the ladder design. In the edge region, the electric field lines diverge outward, leading to a slow change in potential, which can be approximated by an exponential function.

[0059] Calculate the local electric field under the stepped structure. In the End of step, transverse electric field component Decided by potential gradient: ; Where . Since changes smoothly, and is limited, significantly lower than the theoretical infinity of the right-angle edge. Limited step width disperses the potential difference into multiple small segments, avoiding single-point drastic changes. The electric field is the spatial derivative of the potential, and the discretization process converts the derivative into a difference, limiting its maximum value.

[0060] Optimize step number and single-step width . Set the goal to make the maximum edge electric field lower than the breakdown threshold . From ; require , we get . This condition is used to guide the selection of structure parameters. This inequality provides a lower limit for design, ensuring that the electric field is controlled within a safe range.

[0061] The total potential difference is shared by steps, each step undertakes about voltage drop, spanning , so the electric field is inversely proportional to .

[0062] Step Four: Introduce a ring-shaped auxiliary electrode to guide the uniform distribution of electric field lines To further improve the electric field distribution, this step adds a ring-shaped auxiliary electrode to the periphery of the main electrode, which guides the direction of electric field lines through its potential setting, reducing the tendency to concentrate towards the edge.

[0063] Set a ring-shaped conductive structure, denoted as electrode C, around the periphery of the main electrode (electrode B), with its inner boundary from the edge of the main electrode, and the ring width is . Electrode C is electrically isolated from the main electrode and can independently apply a potential .

[0064] Electrode C serves as an electric field control element and does not participate in the main current path, but is only used for electrostatic field shaping.

[0065] The potential of the external conductor will affect the internal electric field distribution. By reasonably setting , the divergence direction of the electric field lines can be changed.

[0066] Connect electrode C to a voltage divider circuit so that its potential is between the potential of the main electrode and the ground potential 0V. Set , where This intermediate potential makes electrode C a "buffer zone" for the electric field lines.

[0067] The intermediate potential avoids a direct jump from to 0, making the electric field lines transition smoothly.

[0068] Electric field lines start at high potential and end at low potential. Setting an intermediate potential point can attract some of the electric field lines, reducing their concentration towards the physical edge.

[0069] Analyzing the effect of electrode C on the electric field distribution. Let the potential difference between the main electrode edge point A and a point B on electrode C be , and the distance between the two points be . Then the average electric field is: ; When approaches 1, decreases, lowering, meaning that electrode C effectively shields the strong field of the main electrode edge. By adjusting , the edge electric field strength can be dynamically controlled. Reducing the potential difference directly reduces the electric field, while provides adjustable freedom.

[0070] Optimizing the combination of and . After the introduction of electrode C, the maximum electric field at the edge must satisfy: ; where is the target suppression ratio, is the edge field strength without electrode C. Through numerical simulation or approximate calculation, determine the range of that satisfies the condition.

[0071] This condition ensures that the performance improvement reaches the expected target. The effect of electrode C weakens as the distance increases, but needs to be adjusted with to maintain the shielding effect.

[0072] Step Five: Implementing Composite Electric Field Control by Combining Step Ladder Structure and Ring Electrode Combine the step ladder main electrode of step three with the ring auxiliary electrode of step four to form a composite electrode layout, achieving multi-dimensional electric field control and further reducing the peak value of the electric field in the edge region.

[0073] Take the step ladder electrode in step three as the main electrode (electrode B), which has stages at the end. On this basis, arrange the ring electrode C in step four around the entire main electrode periphery, with the inner boundary of the ring electrode maintaining a distance The staircase structure processes the local potential gradient, and the ring electrode controls the overall electric field direction. The combination of local geometry optimization and global potential guidance can more comprehensively suppress the electric field concentration.

[0074] Set the potential of the ring electrode C , where According to the optimization results, the potential difference from the outermost step of the main electrode to the electrode C is , which is distributed at a distance of , forming a transverse electric field: ; the direction of this electric field is perpendicular to the main junction electric field, which plays a role in transverse stretching and reduces the edge vertical field strength.

[0075] The transverse electric field changes the direction of the electric field lines, making them more parallel to the surface and reducing the vertical component. The electric field is a vector, and its direction is determined by all charges. The introduction of a transverse component by the external electrode can offset part of the vertical concentration.

[0076] Calculate the total electric field strength under the composite structure. At the edge point P, the electric field is composed of three parts: the main junction longitudinal field , the transverse field caused by the staircase structure , and the transverse field caused by the ring electrode . The synthesized electric field mode is: ; By design, the is large enough to significantly reduce the , even if the is unchanged. The vector synthesis effect allows the total field strength to be weakened by increasing the transverse component. The electric field strength is determined by the vector sum, and increasing the orthogonal component can change the direction and size of the resultant force.

[0077] Verify the stability of the composite structure. When the reverse voltage changes, check whether always remains below . Define the safety margin ; All working require . If not met, adjust until standards are met. Ensure that the device operates safely within the entire working range. When the reverse voltage increases, all electric field components are enhanced, and sufficient margin needs to be reserved.

[0078] Step six: complete the electrode layout and evaluate the leakage current suppression effect After completing the electrode structure optimization, the final step is to integrate all design parameters to form the final layout and estimate the degree of leakage current reduction based on the electric field distribution.

[0079] Summarize all structure parameters: the main electrode uses Stages, each stage wide ; annular auxiliary electrode C from the main electrode , wide , the potential is set to ; semiconductor parameters remain unchanged, the maximum edge electric field after optimization is estimated .

[0080] Combined with the vector model and the ladder voltage division effect, we have: ; this formula combines the longitudinal depletion field and the transverse control field to evaluate the total field strength.

[0081] Based on the electric field strength to estimate the reverse leakage current . The leakage current is mainly contributed by tunneling and thermal excitation, and its field-dependent relationship is: ; where is a constant related to the material. It can be seen that is extremely sensitive to .

[0082] Calculate the leakage current suppression ratio : ; If , then , indicating that the leakage current is significantly reduced. This ratio quantifies the performance gain of the proposed scheme, completing the final evaluation. By using the field strength sensitivity of the leakage current, even a small decrease in the electric field can result in a significant suppression of the current.

[0083] Finally, it should be pointed out that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the scope of the present application should be included in the protection scope of the present application.

Claims

1. A method for reducing reverse leakage current of a diode, characterized in that: The following steps are involved: Set the geometric dimensions of the P and N regions of the diode, define the lateral length and PN junction position, and provide a spatial reference for subsequent potential distribution analysis; Based on the geometric dimensions and the net doping concentrations of the P region and the N region, a built-in potential is calculated, and a reverse bias voltage is applied to form a total applied potential difference as an input for the electrode boundary condition; Based on the total applied potential difference, a grounded metal electrode A is placed on the top of the P region, and a metal electrode B to which a reverse bias voltage is applied is placed on the bottom of the N region, thereby constructing a rectangular electrode structure in which the electrode edges are aligned with the semiconductor edges. Based on the rectangular electrode structure, the Poisson equation is solved under the depletion layer approximation to calculate the potential distribution, deduce the electric field strength, and identify the high field strength concentration point in the electrode edge area; For the high field intensity concentration point, the original rectangular electrode end is modified into a multi-step structure. The total extension length is determined by the number of steps and the width of a single step, so as to extend the potential change path and reduce the local electric field gradient. A ring-shaped auxiliary electrode is set around the stepped main electrode, with a spacing reserved between its inner boundary and the edge of the main electrode. The width of the ring structure is fixed, the electrode is electrically isolated from the main electrode, and the potential is set to an intermediate potential between the main electrode potential and the ground potential to regulate the edge electric field distribution; Based on the electric field regulation effect introduced by the annular auxiliary electrode, the electric field strength in the edge area is lower than the field strength threshold corresponding to material breakdown by adjusting the number of steps, the width of a single step, the distance between the annular electrode and the main electrode, and the ratio of the intermediate potential to the reverse bias voltage.

2. The method for reducing diode reverse leakage current according to claim 1, wherein: The modification of the original rectangular electrode end into a multi-step structure includes: Determine the minimum length of the potential change path required based on the total amount of potential change required to control the identified high field concentration point; Compare the total extension length with the minimum length to determine whether the electric field dispersion requirements are met; If the total extension length is insufficient, increase the number of steps or expand the width of a single step so that the potential is distributed over more or wider steps; Verify whether the adjusted step structure makes the edge electric field strength lower than the breakdown threshold. If not, repeat the adjustment.

3. The method for reducing diode reverse leakage current according to claim 1, wherein: The potential of the annular auxiliary electrode is provided by a voltage divider circuit, specifically comprising: Connect the voltage divider circuit between the main electrode and the ground to form an intermediate potential output node; Connecting the intermediate potential output node to the annular auxiliary electrode so that the annular electrode obtains a stable potential between the main electrode potential and the ground potential; The potential difference between the intermediate potential and the main electrode potential is distributed over the spatial distance between the annular electrode and the main electrode. After the potential difference is distributed in space, a transverse electric field component is formed, which is used to change the direction of the electric field lines at the electrode edge.

4. The method for reducing diode reverse leakage current according to claim 1, wherein: By adjusting the distance between the annular electrode and the main electrode and the ratio of the intermediate potential, the composite electric field intensity at the edge point is reduced after the transverse electric field component and the longitudinal electric field component of the main junction region are vector-superimposed. Specifically, Determine the longitudinal electric field intensity at the end edge of the main electrode based on the longitudinal electric field distribution; Adjust the intermediate potential ratio of the annular auxiliary electrode so that the generated transverse electric field component reaches the desired control level; Adjust the distance between the ring electrode and the main electrode to ensure that the transverse electric field covers the high field strength area at the end of the stepped structure; Calculate the vector sum of the longitudinal electric field and the transverse electric field at the edge point to verify whether the composite electric field strength is lower than the breakdown threshold.

5. The method for reducing diode reverse leakage current according to claim 1, wherein: The height of the stepped structure decreases step by step, so that the electrode end gradually transitions from the main electrode plane to the uncovered area, specifically including: Determine the difference between the initial height of the main electrode and the height of the semiconductor surface, and divide the difference into a plurality of decreasing amounts corresponding to the height reduction value of each step; Starting from the end of the main electrode, each step is reduced by a decreasing amount on the basis of the previous step, forming a continuous descending profile, which makes the potential transition smoothly from the main electrode potential to the semiconductor surface potential.

6. The method for reducing diode reverse leakage current according to claim 1, characterized in that: The method of providing a ring-shaped auxiliary electrode on the periphery of the stepped main electrode, with a reserved distance between the inner boundary of the auxiliary electrode and the edge of the main electrode, includes: Determine the required coverage width based on the lateral extent of the high field strength area; The inner boundary of the ring electrode is set outside the high field strength area, and the spacing distance is maintained. The spacing distance ensures that the electric field influence range of the ring electrode includes the entire high field strength area; Verify whether the transverse electric field can effectively guide the distribution of identified electric field lines and reduce the edge peak field strength at the separation distance.

7. The method for reducing diode reverse leakage current according to claim 1, characterized in that: Also includes: By evaluating the ratio of the electric field strength in the edge area to the breakdown threshold, it is determined whether the electrode layout has sufficient safety margin, including: Calculate the maximum electric field intensity in the optimized edge area, compare the maximum electric field intensity with the material breakdown threshold, and obtain a ratio; If the ratio is less than the preset safety threshold, the layout is determined to meet the safety requirements; If the ratio is greater than or equal to the preset safety threshold, the step parameters or ring electrode parameters are adjusted until the safety requirements are met.

8. A system for reducing diode reverse leakage current by implementing the method according to any one of claims 1 to 7, characterized in that: include: The semiconductor substrate includes a P region and an N region, forming a PN junction; The main electrode covers the surface of the N region, and its edge adopts a stepped structure consisting of multiple continuous steps; The annular auxiliary electrode is arranged outside the main electrode, is physically separated from the main electrode, realizes electrical isolation, and is connected to an independent potential supply source; a potential supply unit for applying a reverse bias voltage to the main electrode and an intermediate potential to the annular auxiliary electrode; The packaging structure is used to fix the main electrode, the annular auxiliary electrode and the semiconductor substrate, and maintain the insulation state between the electrodes.

9. The system for reducing diode reverse leakage current according to claim 8, characterized in that: In the stepped structure of the main electrode, the width of each step is consistent and the height decreases step by step, so that the electrode end forms a gradual profile and extends the potential change path.

10. The system for reducing diode reverse leakage current according to claim 8, characterized in that: The potential of the annular auxiliary electrode is provided by a voltage divider circuit, so that the potential difference between it and the main electrode is distributed in space, forming a transverse electric field. The transverse electric field is superimposed on the longitudinal electric field of the main junction to reduce the edge composite electric field strength.

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