Structural Parameter Optimization Method for Shield Gate Trench-Type Field Effect Transistor

Abstract

This application relates to a method for optimizing the structural parameters of a shield-gate trench-type field-effect transistor. The method includes: obtaining established structural parameters and initial undetermined structural parameters; extracting the peak electric field path of the transistor; intercepting a plurality of sampling points on the peak electric field path; generating a collision ionization integral distribution curve based on the collision ionization integrals of the plurality of sampling points; determining whether the number of target ionization integral values in the collision ionization integral distribution curve is less than a target threshold. If so, update the initial undetermined structural parameters and then re-perform the step of determining whether the number of target ionization integral values in the collision ionization integral distribution curve is less than the target threshold until the number of target ionization integral values is greater than or equal to the target threshold. If not, use the current undetermined structural parameters as the target structural parameters. The solution provided by this application can effectively balance the contradictory relationship between the specific on-resistance and the breakdown voltage, thereby effectively reducing the static power consumption of the transistor.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and particularly to a method for optimizing the structural parameters of a shield-gate trench field-effect transistor. Background Art

[0002] Compared with traditional trench metal-oxide-semiconductor field-effect transistors, shield-gate trench transistors have a higher channel density and a better charge compensation effect. The shield-gate structure can effectively reduce the transfer capacitance, so that the shield-gate trench transistor can have a lower specific on-resistance, smaller on and switching losses, and a higher operating frequency. Therefore, shield-gate trench transistors are widely used in important fields such as power management.

[0003] In related technologies, in order to reduce the static power consumption of shield-gate trench devices and improve the contradictory relationship between breakdown voltage and specific on-resistance, most of them modulate the electric field distribution in the breakdown voltage region, so that the peak electric field in the breakdown voltage region is evenly distributed, so as to achieve the effect of optimizing the shield-gate trench transistor. For example, the patent document with the publication number CN105957892B discloses a shield-gate power device, which utilizes the characteristic that the shielding electrode can achieve lateral depletion of the breakdown voltage region through the shielding dielectric film, designs the thickness of the shielding dielectric film along the longitudinal direction of the trench, and realizes the effect of adjusting the electric field strength in the breakdown voltage region and making the electric field strength in the breakdown voltage region more evenly distributed in the longitudinal direction through the structure with gradually increasing thickness of the shielding dielectric film, thereby improving the breakdown voltage of the device.

[0004] However, the evenness of the electric field does not mean the evenness of the breakdown points in the breakdown voltage region, nor does it mean the maximization of the breakdown voltage. Summary of the Invention

[0005] To overcome the problems existing in the related technologies, this application provides a method for optimizing the structural parameters of a shield-gate trench field-effect transistor, which can effectively balance the contradictory relationship between specific on-resistance and breakdown voltage, thereby effectively reducing the static power consumption of the transistor.

[0006] This application provides a method for optimizing the structural parameters of a shield-gate trench field-effect transistor, including:

[0007] Obtaining established structural parameters and initial to-be-determined structural parameters;

[0008] Extracting the peak electric field path of the transistor; the peak electric field path is the connection line of the electric field peak positions in the breakdown voltage region of the transistor;

[0009] Intercepting a plurality of sampling points on the peak electric field path;

[0010] Generating a collision ionization integral distribution curve based on the collision ionization integrals of the plurality of sampling points;

[0011] Determine whether the number of target ionization integral values in the collision ionization integral distribution curve is less than a target threshold. If so, update the initial undetermined structure parameters and then re - execute the step of determining whether the number of target ionization integral values in the collision ionization integral distribution curve is less than the target threshold until the number of target ionization integral values is greater than or equal to the target threshold; if not, use the current undetermined structure parameters as the target structure parameters;

[0012] The error between the target ionization integral value and the preset ionization integral value is less than a preset error threshold; the target structure parameters are undetermined structure parameters that, under the condition of meeting the established structure parameters, enable the breakdown voltage of the transistor to meet the breakdown voltage requirement.

[0013] In one implementation, generating the collision ionization integral distribution curve based on the collision ionization integrals of the several sampling points includes:

[0014] Calculate the collision ionization integrals of the several sampling points respectively;

[0015] Based on the collision ionization integrals of the several sampling points, use the least - squares method to calculate the collision ionization integral distribution curve.

[0016] In one implementation, in the process of calculating the collision ionization integrals of the several sampling points respectively, calculating the collision ionization integral of one sampling point includes:

[0017] Perform collision ionization integration on the electric field lines in the breakdown voltage region passing through the sampling point based on the following calculation formula;

[0018] I n =∫α n exp[∫(α p -α n )ds′]ds

[0019] where I n represents the collision ionization integral, α n represents the electron impact ionization rate, and α p represents the hole impact ionization rate.

[0020] In one implementation, updating the initial undetermined structure parameters includes:

[0021] Calculate the position of the ionization integral value with the smallest error from the preset ionization integral value on the peak electric field path;

[0022] Adjust the initial undetermined structure parameters based on the lateral distance between the position and the shielding gate, and use the adjusted initial undetermined structure parameters to overwrite the original initial undetermined structure parameters.

[0023] In one embodiment, adjusting the initial to-be-determined structural parameters based on the lateral distance between the position and the shielding gate includes:

[0024] Determine whether the lateral distance is greater than half of the transistor width. If so, adjust the initial to-be-determined structural parameters according to the first optimization strategy; if not, adjust the initial to-be-determined structural parameters according to the second optimization strategy.

[0025] In one embodiment, updating the initial to-be-determined structural parameters includes:

[0026] Adjust the initial to-be-determined structural parameters once according to the first optimization strategy;

[0027] Calculate the number of adjusted target ionization integral values;

[0028] Determine whether the number of adjusted target ionization integral values is greater than the number of target ionization integral values before adjustment. If so, continue to adjust the initial to-be-determined structural parameters according to the first optimization strategy; if not, adjust the initial to-be-determined structural parameters according to the second optimization strategy.

[0029] In one embodiment, the first optimization strategy includes: shortening the thickness of the breakdown voltage region, reducing the doping concentration of the breakdown voltage region, or shortening the depth of the oxide layer;

[0030] The second optimization strategy includes: increasing the thickness of the breakdown voltage region, increasing the doping concentration of the breakdown voltage region, or increasing the depth of the oxide layer.

[0031] In one embodiment, among the several sampling points, the lateral distance between any two sampling points is greater than the sampling interval threshold.

[0032] In one embodiment, before determining whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold, it further includes:

[0033] Determine whether the average slope of the impact ionization integral distribution curve is lower than the slope threshold. If so, perform the step of determining whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold.

[0034] In one embodiment, before determining whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold, it further includes:

[0035] If the average slope of the impact ionization integral distribution curve is not lower than the slope threshold, then after updating the initial to-be-determined structural parameters, re-perform the step of determining whether the average slope of the impact ionization integral distribution curve is lower than the slope threshold until the average slope of the impact ionization integral distribution curve is lower than the slope threshold.

[0036] The technical solution provided by this application may include the following beneficial effects:

[0037] The structural parameter optimization method of the shield gate trench type field effect transistor provided by this application uses the connection line of the electric field peak positions in the transistor breakdown voltage region as the sampling path, that is, the peak electric field path. Several sampling points are intercepted on this path to calculate the impact ionization integral, and then an impact ionization integral distribution curve that can represent the impact ionization integral distribution in the transistor breakdown voltage region is obtained. According to the impact ionization integral distribution in the transistor breakdown voltage region, it can be known how strong the impact ionization is at each position in the breakdown voltage region when the transistor is in forward blocking, so as to evaluate the reliability of the device; by adjusting the doping concentration in the breakdown voltage region, the thickness of the breakdown voltage region or the depth of the oxide layer, the impact ionization integral distribution tends to be uniform. Specifically, it is manifested as: the number of target ionization integral values in the impact ionization integral distribution curve is greater than or equal to the target threshold. Since the target ionization integral value is the ionization integral value whose error from the preset ionization integral value is less than the preset error threshold, therefore, when the number of target ionization integral values is greater than or equal to the target threshold, it means that the electric field lines at most positions on the peak electric field path can reach the highest impact ionization integral, which means that the impact ionization degree in the breakdown voltage region is strong. Correspondingly, the breakdown voltage of the transistor at this time is also higher. The transistor obtained with the established structural parameters and to-be-determined structural parameters of the current transistor as the design parameters of the transistor can achieve a high avalanche breakdown voltage at a given breakdown voltage region thickness; or achieve a low specific on-resistance at a given breakdown voltage. Using the structural parameter optimization method of this application to optimize the structural parameters of the shield gate trench type field effect transistor can effectively balance the contradictory relationship between the specific on-resistance and the breakdown voltage, thereby effectively reducing the static power consumption of the shield gate trench type field effect transistor.

[0038] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Brief Description of the Drawings

[0039] By describing the exemplary embodiments of this application in more detail in conjunction with the drawings, the above and other objects, features, and advantages of this application will become more obvious. Among them, in the exemplary embodiments of this application, the same reference numerals generally represent the same components.

[0040] Figure 1 It is a flowchart showing the structural parameter optimization method of the shield gate trench type field effect transistor shown in the embodiments of this application;

[0041] Figure 2 is a schematic flowchart of a method for adjusting initial to-be-determined structural parameters shown in an embodiment of the present application;

[0042] Figure 3 is another schematic flowchart of a method for adjusting initial to-be-determined structural parameters shown in an embodiment of the present application;

[0043] Figure 4 is another schematic flowchart of a method for optimizing structural parameters of a shield-gate trench-type field-effect transistor shown in an embodiment of the present application. Detailed Description of the Embodiment

[0044] The preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0045] The terms used in the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "said", and "the" used in the present application and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0046] It should be understood that although the terms "first", "second", "third", etc. may be used in the present application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality" means two or more unless otherwise specifically defined.

[0047] Embodiment 1

[0048] In the related art, in order to reduce the static power consumption of shield-gate trench-type devices and improve the contradictory relationship between the breakdown voltage and the specific on-resistance, most of them modulate the electric field distribution in the breakdown voltage region, so that the peak electric field in the breakdown voltage region is evenly distributed, so as to achieve the effect of optimizing the shield-gate trench-type transistor. However, the even electric field does not mean the even breakdown points in the breakdown voltage region, nor does it mean the maximization of the breakdown voltage.

[0049] In view of the above problems, an embodiment of the present application provides a method for optimizing the structural parameters of a shielded-gate trench field-effect transistor, which can effectively balance the contradictory relationship between the specific on-resistance and the breakdown voltage, thereby effectively reducing the static power consumption of the transistor.

[0050] The technical solutions of the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0051] Figure 1 It is a flowchart showing a method for optimizing the structural parameters of a shielded-gate trench field-effect transistor shown in an embodiment of the present application.

[0052] See Figure 1 , a method for optimizing the structural parameters of a shielded-gate trench field-effect transistor, including:

[0053] 101. Obtain established structural parameters and initial to-be-determined structural parameters;

[0054] In the embodiment of the present application, in a shielded-gate trench field-effect transistor, the doping concentration of the breakdown voltage region, the thickness of the breakdown voltage region, and the depth of the oxide layer belong to the important structural parameters of the transistor, and the transistor performance has a high response sensitivity to the changes in these parameters. Therefore, when optimizing the structural parameters of a shielded-gate trench field-effect transistor to achieve a high breakdown voltage and a low specific on-resistance, these three parameters are usually adjusted to achieve the goal.

[0055] In the embodiment of the present application, the established structural parameters are one or more of the doping concentration of the breakdown voltage region, the thickness of the breakdown voltage region, and the depth of the oxide layer. Due to the limitations of actual production conditions or production requirements, the values of these one or more parameters have been predetermined. Correspondingly, the to-be-determined structural parameters are the parameters to be determined among the doping concentration of the breakdown voltage region, the thickness of the breakdown voltage region, and the depth of the oxide layer. During the process of optimizing the structural parameters, an initial value of the to-be-determined structural parameter, that is, the initial to-be-determined structural parameter, is given in advance. By adjusting the initial to-be-determined structural parameter, the breakdown voltage of the finally obtained shielded-gate trench field-effect transistor meets the requirements, thereby determining the determined value of the to-be-determined structural parameter.

[0056] It can be understood that if the established structural parameter is the doping concentration of the breakdown voltage region, then correspondingly, the to-be-determined structural parameters are the thickness of the breakdown voltage region and the depth of the oxide layer; if the established structural parameter is the thickness of the breakdown voltage region, then correspondingly, the to-be-determined structural parameters are the doping concentration of the breakdown voltage region and the depth of the oxide layer.

[0057] The above descriptions of the established structural parameters and the to-be-determined structural parameters are only examples given in the embodiments of the present application and do not serve as the sole limitation to the present application.

[0058] In the embodiments of the present application, an initial undetermined structural parameter needs to be set first as the basis for parameter optimization. The initial undetermined structural parameter can be obtained according to the initial value pre-stored in the system, or determined based on the structural parameter data imported by the user when obtaining the established structural parameter.

[0059] 102. Extract the peak electric field path of the transistor;

[0060] In the embodiments of the present application, the peak electric field path is the connection line of the positions of the peak electric fields in the breakdown voltage region of the transistor.

[0061] The breakdown voltage of the traditional shield-gate trench power device is limited by its electric field spike. Therefore, the connection line of the positions of the peak electric fields in the breakdown voltage region of the transistor is extracted as the sampling path of the present application, so that the sampling points are representative to a certain extent and can represent the impact ionization situation in the breakdown voltage region.

[0062] 103. Intercept a plurality of sampling points on the peak electric field path;

[0063] In the embodiments of the present application, the plurality of sampling points can be set at equal intervals or unequal intervals along the path, that is, whether the sampling intervals between the plurality of sampling points are equal is not the only limitation to the present application.

[0064] In order to ensure that the impact ionization integral distribution of the entire breakdown voltage region can be obtained based on the plurality of sampling points, the situation where the sampling points are concentrated in a certain area needs to be avoided. Therefore, in the embodiments of the present application, the lateral distance between any two sampling points among the plurality of sampling points, that is, the sampling interval, is limited, and it is set that all of them are greater than the sampling interval threshold.

[0065] In the actual application process, the specific value of the sampling interval threshold can be set according to the actual situation and is not limited here.

[0066] 104. Generate an impact ionization integral distribution curve based on the impact ionization integrals of the plurality of sampling points;

[0067] In the embodiments of the present application, for example:

[0068] Calculate the impact ionization integrals of the plurality of sampling points respectively;

[0069] Among them, taking the calculation of the impact ionization integral of one sampling point as an example:

[0070] Perform impact ionization integration on the electric field line of the breakdown voltage region passing through the sampling point based on the following calculation formula;

[0071] I n =∫α n exp[∫(α p -α n )ds′]ds

[0072] Among them, I n represents the impact ionization integral, and α n represents the impact ionization rate of electrons, and α p represents the impact ionization rate of holes. s and s′ indicate that the integration paths of the above formulas are along the same electric field line direction.

[0073] Based on the impact ionization integrals of the several sampling points, the impact ionization integral distribution curve is calculated using the least squares method.

[0074] In the embodiments of the present application, the more the number of sampling points, the more accurate the impact ionization integral distribution curve obtained by using the least squares method, that is, the more the impact ionization integral distribution curve fits the actual situation. However, the increase in the number of sampling points will inevitably lead to an increase in the calculation amount, thereby resulting in a decrease in the system processing efficiency. Therefore, in the actual application process, the number of sampling points can be adjusted according to different calculation requirements.

[0075] It should be noted that the above calculation process is the calculation of the impact ionization integral based on the Chynoweth model. In the actual application process, other impact ionization integrals can also be selected for calculation, such as the Fulop model. For the sake of accuracy, the Chynoweth model is preferably used in the embodiments of the present application.

[0076] 105. Based on the comparison result between the number of target ionization integral values in the impact ionization integral distribution curve and the target threshold, the target structural parameters of the shield gate trench type field effect transistor are obtained.

[0077] Specifically:

[0078] Judge whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold. If so, update the initial to-be-determined structural parameters and then re-execute the step of judging whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold until the number of target ionization integral values is greater than or equal to the target threshold; if not, use the current to-be-determined structural parameters as the target structural parameters;

[0079] In the embodiments of the present application, the target ionization integral value is the ionization integral value whose error from the preset ionization integral value is less than the preset error threshold; the target structural parameter is the to-be-determined structural parameter that makes the breakdown voltage of the transistor meet the breakdown voltage requirement under the condition of meeting the established structural parameters.

[0080] In the actual application process, the target threshold, the preset error threshold, and the breakdown voltage requirement can all be preset in the system and called during the structural parameter optimization process of the shield gate trench type field effect transistor; or they can be reset by the user before executing step 105.

[0081] It should be noted that there are no strict limitations on the above-mentioned target threshold, preset error threshold, and breakdown voltage requirement in this application, and they can be adjusted according to the actual situation.

[0082] In the embodiment of this application, during the process of updating the initial to-be-determined structural parameters, the initial to-be-determined structural parameters can be adjusted and updated according to the optimization strategy set in the system; or the user can adjust the initial to-be-determined structural parameters by themselves to optimize the structural parameters of the transistor.

[0083] When the number of target ionization integral values in the impact ionization integral distribution curve is greater than or equal to the target threshold, it indicates that there are already enough impact ionization integrals of the electric field lines near the highest impact ionization integral, that is, the impact ionization integral distribution in the transistor breakdown voltage region tends to be uniform. At this time, it can be considered that the shield-gate trench field-effect transistor is operating under the performance that meets the requirements of specific on-resistance and breakdown voltage. Therefore, the current to-be-determined structural parameters are used as the target structural parameters, and combined with the established structural parameters, the structure of the shield-gate trench field-effect transistor is optimized to obtain a shield-gate trench field-effect transistor that meets the requirements.

[0084] The structural parameter optimization method of the shield-gate trench field-effect transistor provided in this application uses the connection line of the peak electric field positions in the transistor breakdown voltage region as the sampling path, that is, the peak electric field path. Several sampling points are intercepted on this path to calculate the impact ionization integral, and then an impact ionization integral distribution curve that can represent the impact ionization integral distribution in the transistor breakdown voltage region is obtained. According to the impact ionization integral distribution in the transistor breakdown voltage region, it can be known the strength of impact ionization at each position in the breakdown voltage region when the transistor is in forward blocking, so as to evaluate the reliability of the device; by adjusting the doping concentration, thickness of the breakdown voltage region, or depth of the oxide layer, the impact ionization integral distribution tends to be uniform. Specifically, it is manifested as: the number of target ionization integral values in the impact ionization integral distribution curve is greater than or equal to the target threshold. Since the target ionization integral value is the ionization integral value whose error from the preset ionization integral value is less than the preset error threshold, when the number of target ionization integral values is greater than or equal to the target threshold, it means that the electric field lines at most positions on the peak electric field path can reach the highest impact ionization integral, which means that the impact ionization degree in the breakdown voltage region is strong. Correspondingly, the breakdown voltage of the transistor at this time is also higher. The transistor obtained by using the established structural parameters and to-be-determined structural parameters of the current transistor as the design parameters of the transistor can achieve a high avalanche breakdown voltage at a given breakdown voltage region thickness; or achieve a low specific on-resistance at a given breakdown voltage. Using the structural parameter optimization method of this application to optimize the structural parameters of the shield-gate trench field-effect transistor can effectively balance the contradictory relationship between the specific on-resistance and the breakdown voltage, thereby effectively reducing the static power consumption of the shield-gate trench field-effect transistor.

[0085] Embodiment 2

[0086] In the actual application process, the process of updating the initial to-be-determined structure parameters can adjust and update the initial to-be-determined structure parameters according to the optimization strategy set in the system; or the user can adjust the initial to-be-determined structure parameters by himself to optimize the structure parameters of the transistor.

[0087] The embodiment of the present application adopts the technical solution of adjusting and updating the initial to-be-determined structure parameters according to the optimization strategy set in the system.

[0088] The technical solution of the embodiment of the present application will be described in detail below with reference to the drawings.

[0089] Figure 2 It is a schematic flowchart of the method for adjusting the initial to-be-determined structure parameters shown in the embodiment of the present application.

[0090] See Figure 2 , the method for adjusting the initial to-be-determined structure parameters shown in the embodiment of the present application includes:

[0091] 201. Determine whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold.

[0092] If so, sequentially execute step 202 and step 203 and then return to execute step 201;

[0093] If not, execute step 204;

[0094] In the embodiment of the present application, preferably, in the embodiment of the present application, the preset ionization integral value is taken as 1.

[0095] In the embodiment of the present application, the target ionization integral value refers to the ionization integral value whose error from the preset ionization integral value is less than the preset error threshold. When the number of target ionization integral values is greater than or equal to the target threshold, it means that there are already enough impact ionization integrals of the electric field lines near the highest impact ionization integral, and it can be considered that the impact ionization integral distribution in the breakdown voltage region of the transistor tends to be uniform.

[0096] In the actual application process, the preset error threshold can be set according to the actual situation and is not limited here.

[0097] 202. Calculate the position of the ionization integral value with the smallest error from the preset ionization integral value on the peak electric field path;

[0098] In the embodiment of the present application, starting from the end far from the shielding gate along the peak electric field path towards the end close to the shielding gate, sampling points are extracted and the impact ionization integration is calculated. The sampling point that first reaches the preset ionization integration value, or the sampling point with the earliest sampling time among the sampling points whose ionization integration values are closest to 1 is used as the judgment basis for step 203.

[0099] 203. Adjust the initial undetermined structural parameters based on the lateral distance between the position and the shielding gate, and overwrite the original initial undetermined structural parameters with the adjusted initial undetermined structural parameters.

[0100] Specifically:

[0101] Judge whether the lateral distance is greater than half of the transistor width. If so, adjust the initial undetermined structural parameters according to the first optimization strategy; if not, adjust the initial undetermined structural parameters according to the second optimization strategy.

[0102] The lateral distance is the distance between the position of the sampling point in step 202 and the boundary of the shielding gate in the transistor width direction.

[0103] Among them, the first optimization strategy includes: shortening the thickness of the breakdown voltage region, reducing the doping concentration of the breakdown voltage region, or shortening the oxide layer depth; the second optimization strategy includes: increasing the thickness of the breakdown voltage region, increasing the doping concentration of the breakdown voltage region, or increasing the oxide layer depth.

[0104] Taking the breakdown voltage region thickness with established structural parameters as an example, the undetermined structural parameters include the doping concentration of the breakdown voltage region and the oxide layer depth:

[0105] Taking the width direction of the transistor as the horizontal axis, with the starting point of the horizontal axis being the sampling starting point of the peak electric field path, when in the impact ionization integration distribution curve, the position of the sampling point that first reaches the preset ionization integration value, or the first sampling point whose ionization integration value is closest to 1 is located in the front half axis of the horizontal axis, then the initial undetermined structural parameters are adjusted by reducing the doping concentration of the breakdown voltage region or shortening the oxide layer depth, so that the position of the sampling point that reaches the preset ionization integration value, or the sampling point whose ionization integration value is closest to 1 moves backward. In the above example, "first" corresponds to the first in sampling time.

[0106] 204. Take the current undetermined structural parameters as the target structural parameters.

[0107] After it is determined in step 201 that the current undetermined structural parameters can make the number of target ionization integration values in the impact ionization integration distribution curve reach the target threshold, then the current undetermined structural parameters are taken as the target structural parameters, and the shielding gate trench field effect transistor is structurally optimized in combination with the established structural parameters.

[0108] The embodiment of the present application provides a method for adjusting initial undetermined structural parameters. According to the lateral distance between the position where the ionization integral value with the smallest error from the preset ionization integral value is located and the shielding gate, the adjustment direction of the initial undetermined structural parameters is determined, thereby avoiding invalid adjustments and validations due to incorrect adjustment directions and wasting processing time; adjusting the initial undetermined structural parameters after determining the optimization strategy can improve the optimization efficiency.

[0109] Embodiment III

[0110] In the actual application process, the process of updating the initial undetermined structural parameters can adjust and update the initial undetermined structural parameters according to the optimization strategy set in the system; or the user can adjust the initial undetermined structural parameters by himself to optimize the structural parameters of the transistor.

[0111] Relatively to the solution shown in the above Embodiment II, the embodiment of the present application adopts another technical solution for adjusting and updating the initial undetermined structural parameters according to the optimization strategy set in the system.

[0112] The technical solution of the embodiment of the present application will be described in detail below with reference to the drawings.

[0113] Figure 3 It is another flow diagram of the method for adjusting the initial undetermined structural parameters shown in the embodiment of the present application.

[0114] See Figure 3 , the method for adjusting the initial undetermined structural parameters shown in the embodiment of the present application includes:

[0115] 301. Determine whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold.

[0116] If so, sequentially execute steps 302, 303, and 304;

[0117] If not, execute step 305;

[0118] 302. Make a first adjustment to the initial undetermined structural parameters according to the first optimization strategy;

[0119] In the embodiment of the present application, a first pre-adjustment is made to the initial undetermined structural parameters to verify whether the current optimization strategy meets the optimization requirements of the transistor, so as to determine whether to continue to adjust the initial undetermined structural parameters with the current optimization strategy in the future. If not, the optimization strategy is changed in time to avoid invalid adjustment actions.

[0120] 303. Calculate the number of adjusted target ionization integral values;

[0121] In the embodiments of the present application, the target ionization integral value refers to the ionization integral value whose error from the preset ionization integral value is less than the preset error threshold.

[0122] 304. Determine whether the number of adjusted target ionization integral values is greater than the number of target ionization integral values before adjustment.

[0123] If so, after executing step 306, return to execute step 301.

[0124] If not, after executing step 307, return to execute step 301.

[0125] 305. Take the current to-be-determined structure parameter as the target structure parameter.

[0126] 306. Continue to adjust the initial to-be-determined structure parameter according to the first optimization strategy.

[0127] 307. Adjust the initial to-be-determined structure parameter according to the second optimization strategy.

[0128] After a preliminary adjustment of the initial to-be-determined structure parameter, if step 304 determines that the number of target ionization integral values after the preliminary adjustment has increased compared with the original, it indicates that the current optimization strategy is effective. Therefore, the initial to-be-determined structure parameter will continue to be adjusted according to the current optimization strategy.

[0129] Otherwise, it indicates that the preliminary adjustment is an ineffective adjustment, and the optimization strategy should be changed.

[0130] Among them, the first optimization strategy includes: shortening the thickness of the breakdown voltage region, reducing the doping concentration of the breakdown voltage region, or shortening the depth of the oxide layer; the second optimization strategy includes: increasing the thickness of the breakdown voltage region, increasing the doping concentration of the breakdown voltage region, or increasing the depth of the oxide layer.

[0131] The embodiments of the present application provide a method for adjusting the initial to-be-determined structure parameter. After a preliminary adjustment of the initial to-be-determined structure parameter, it is determined whether the number of target ionization integral values after the preliminary adjustment has increased compared with that before adjustment to determine whether the effect of the current optimization strategy is positive or negative, so as to determine an effective optimization strategy, avoid ineffective adjustments and verifications due to wrong adjustment directions, and consume processing time; after determining the optimization strategy, adjusting the initial to-be-determined structure parameter can improve the optimization efficiency.

[0132] Embodiment 4

[0133] In the actual application process, in order to further ensure the uniformity of the impact ionization integral distribution in the breakdown voltage region of the transistor, in addition to setting requirements for the number of target ionization integral values, further, the uniformity of the impact ionization integral distribution can be judged by increasing the verification of the shape of the impact ionization integral distribution curve, so as to ensure the reliability of the target structure parameter.

[0134] The technical solutions of the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0135] Figure 4 It is another schematic flow chart of the method for optimizing the structural parameters of the shielded gate trench type field effect transistor shown in the embodiments of the present application.

[0136] Refer to Figure 4 , the method for optimizing the structural parameters of the shielded gate trench type field effect transistor shown in the embodiments of the present application includes:

[0137] 401. Obtain the established structural parameters and the initial undetermined structural parameters;

[0138] In the embodiments of the present application, step 401 is the same as step 101 in Embodiment 1, and will not be elaborated here.

[0139] 402. Extract the peak electric field path of the transistor;

[0140] In the embodiments of the present application, step 402 is the same as step 102 in Embodiment 1, and will not be elaborated here.

[0141] 403. Intercept a plurality of sampling points on the peak electric field path;

[0142] In the embodiments of the present application, step 403 is the same as step 103 in Embodiment 1, and will not be elaborated here.

[0143] 404. Generate a collision ionization integral distribution curve based on the collision ionization integrals of the plurality of sampling points;

[0144] In the embodiments of the present application, step 404 is the same as step 104 in Embodiment 1, and will not be elaborated here.

[0145] 405. Determine whether the average slope of the collision ionization integral distribution curve is lower than the slope threshold. If so, execute step 407;

[0146] If not, execute step 406 and then re - execute step 405.

[0147] The slope represents the degree of inclination of a straight line or the tangent of a curve. In the embodiments of the present application, to ensure excellent performance of the specific on-resistance and breakdown voltage of the transistor, it is necessary to make the integral distribution of impact ionization in its breakdown voltage region uniform. For the integral distribution curve of impact ionization, as many target ionization integral values as possible are required. Further, requirements can also be set for the shape of the integral distribution curve of impact ionization. For example, in order to make the impact ionization integrals of as many sampling points as possible at the same level, it is determined whether the average slope of the integral distribution curve of impact ionization is less than a slope threshold. If so, it indicates that the shape of the integral distribution curve of impact ionization is flat, that is, the impact ionization integrals of a sufficient number of sampling points are at the same level, and then the determination of the number of target ionization integral values can be continued; if not, the initial to-be-determined structural parameters need to be adjusted and updated in advance until the shape of the integral distribution curve of impact ionization is flat.

[0148] 406. Update the initial to-be-determined structural parameters;

[0149] In the embodiments of the present application, the steps of updating the initial to-be-determined structural parameters have been described in detail in Embodiment 2 or 3, and will not be elaborated here.

[0150] 407. Based on the comparison result between the number of target ionization integral values in the integral distribution curve of impact ionization and the target threshold, obtain the target structural parameters of the shielded-gate trench-type field-effect transistor.

[0151] In the embodiments of the present application, Step 407 is the same as Step 105 in Embodiment 1, and will not be elaborated here.

[0152] The embodiments of the present application provide a method for optimizing the structural parameters of a shielded-gate trench-type field-effect transistor, which not only judges the number of target ionization integral values, but also requires the shape of the integral distribution curve of impact ionization. Then, on the condition that the integral distribution curve of impact ionization is flat, that is, the impact ionization integrals of a sufficient number of sampling points are at the same level, it is ensured that the number of sufficient target ionization integral values is greater than or equal to the target threshold, and further it is ensured that the electric field lines at most positions on the peak electric field path can reach the highest impact ionization integral, which indicates that the impact ionization degree in the breakdown voltage region is strong. Correspondingly, the breakdown voltage of the transistor at this time is also relatively high. The transistor obtained by using the established structural parameters and the to-be-determined structural parameters of the current transistor as the design parameters of the transistor can achieve a large avalanche breakdown voltage at a given breakdown voltage region thickness; or achieve a small specific on-resistance at a given breakdown voltage.

[0153] The solution of the present application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not described in detail in a certain embodiment, reference may be made to the relevant descriptions of other embodiments. Those skilled in the art should also be aware that the actions and modules involved in the specification are not necessarily essential to the present application. In addition, it can be understood that the steps in the method embodiments of the present application can be adjusted, combined, and deleted according to actual needs, and the modules in the device embodiments of the present application can be combined, divided, and deleted according to actual needs.

[0154] In addition, the method according to the present application can also be implemented as a computer program or a computer program product, which includes computer program code instructions for performing some or all of the steps in the above method of the present application.

[0155] Alternatively, the present application can also be implemented as a non-transitory machine-readable storage medium (or computer-readable storage medium, or machine-readable storage medium), on which executable code (or computer program, or computer instruction code) is stored. When the executable code (or computer program, or computer instruction code) is executed by a processor of an electronic device (or an electronic device, a server, etc.), the processor is caused to execute some or all of the steps of the above method according to the present application.

[0156] Those skilled in the art will also understand that the various exemplary logical blocks, modules, circuits, and algorithm steps described in connection with the applications herein can be implemented as electronic hardware, computer software, or a combination of both.

[0157] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of systems and methods according to multiple embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0158] The embodiments of the present application have been described above. The above description is exemplary and not exhaustive, and is also not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for optimizing the structural parameters of a shielded gate trench-type field effect transistor, characterized in that, Including: Obtain established structure parameters and initial undetermined structure parameters; Extract the peak electric field path of the transistor; The peak electric field path is the connection line of the positions of the peak electric fields in the breakdown voltage region of the transistor; Intercept a number of sampling points on the peak electric field path; Generate a collision ionization integral distribution curve based on the collision ionization integrals of the number of sampling points; Judge whether the number of target ionization integral values in the collision ionization integral distribution curve is less than a target threshold. If so, update the initial undetermined structure parameters and then re - execute the step of judging whether the number of target ionization integral values in the collision ionization integral distribution curve is less than the target threshold until the number of target ionization integral values is greater than or equal to the target threshold; If not, use the current undetermined structure parameters as the target structure parameters; The error between the target ionization integral value and the preset ionization integral value is less than the preset error threshold; The target structure parameters are undetermined structure parameters that, under the condition of meeting the established structure parameters, enable the breakdown voltage of the transistor to meet the breakdown voltage requirements.

2. The method for optimizing the structural parameters of a shielded gate trench-type field effect transistor according to claim 1, characterized in that, The generating a collision ionization integral distribution curve based on the collision ionization integrals of the number of sampling points includes: Calculate the collision ionization integrals of the number of sampling points respectively; Based on the collision ionization integrals of the number of sampling points, use the least - squares method to calculate the collision ionization integral distribution curve.

3. The method for optimizing the structural parameters of a shielded gate trench-type field effect transistor according to claim 2, characterized in that, In the calculating the collision ionization integrals of the number of sampling points respectively, calculating the collision ionization integral of one sampling point includes: Perform collision ionization integration on the breakdown voltage region electric field line passing through the sampling point based on the following calculation formula; I n = ∫α n exp[∫(α p - α n ) ds′] ds Among them, I n represents the impact ionization integral, and α n represents the impact ionization rate of electrons, and α p represents the impact ionization rate of holes.

4. The method for optimizing the structural parameters of a shielded gate trench-type field effect transistor according to claim 1, characterized in that, The updating the initial undetermined structure parameters includes: Calculate the position of the ionization integral value with the smallest error from the preset ionization integral value on the peak electric field path; Adjust the initial undetermined structure parameters based on the lateral distance between the position and the shielding gate, and use the adjusted initial undetermined structure parameters to overwrite the original initial undetermined structure parameters.

5. The method for optimizing the structural parameters of a shielded gate trench-type field effect transistor according to claim 4, characterized in that, The adjusting the initial undetermined structure parameters based on the lateral distance between the position and the shielding gate includes: Judge whether the lateral distance is greater than half of the transistor width. If so, adjust the initial undetermined structure parameters according to the first optimization strategy; if not, adjust the initial undetermined structure parameters according to the second optimization strategy.

6. The method for optimizing the structural parameters of a shielded gate trench-type field effect transistor according to claim 1, characterized in that, The updating the initial undetermined structure parameters includes: Adjust the initial undetermined structure parameters once according to the first optimization strategy; Calculate the number of target ionization integral values after adjustment; Judge whether the number of target ionization integral values after adjustment is greater than the number of target ionization integral values before adjustment. If so, continue to adjust the initial undetermined structure parameters according to the first optimization strategy; if not, adjust the initial undetermined structure parameters according to the second optimization strategy.

7. The method for optimizing the structural parameters of a shielded gate trench-type field effect transistor according to claim 5 or 6, characterized in that, The first optimization strategy includes: shortening the breakdown voltage region thickness, reducing the doping concentration of the breakdown voltage region, or shortening the oxide layer depth; The second optimization strategy includes: increasing the breakdown voltage region thickness, increasing the doping concentration of the breakdown voltage region, or increasing the oxide layer depth.

8. The method for optimizing the structural parameters of the shielded gate trench-type field effect transistor according to claim 1, wherein, Among the number of sampling points, the lateral distance between any two sampling points is greater than the sampling interval threshold.

9. The method for optimizing the structural parameters of the shielded gate trench-type field effect transistor according to claim 1, wherein, Before determining whether the number of target ionization integral values in the impact ionization integral distribution curve is less than a target threshold, it further includes: Determine whether the average slope of the impact ionization integral distribution curve is lower than a slope threshold. If so, perform the step of determining whether the number of target ionization integral values in the impact ionization integral distribution curve is less than the target threshold.

10. The method for optimizing the structural parameters of the shielded gate trench-type field effect transistor according to claim 9, wherein, Before determining whether the number of target ionization integral values in the impact ionization integral distribution curve is less than a target threshold, it further includes: If the average slope of the impact ionization integral distribution curve is not lower than the slope threshold, update the initial undetermined structural parameters and then re-perform the step of determining whether the average slope of the impact ionization integral distribution curve is lower than the slope threshold until the average slope of the impact ionization integral distribution curve is lower than the slope threshold.

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