A method for optimizing parameters of a super junction structure in a given temperature range

Abstract

The application belongs to the technical field of semiconductor devices, and provides a super-junction structure parameter optimization method in a given temperature range, so that the optimized super-junction structure meets the expected withstand voltage value in the given temperature range, and ensures that the specific on-resistance is minimum under the same condition, so that the energy consumption of the super-junction structure is minimum; first, a design withstand voltage fitting expression is constructed, the design withstand voltage BV design in the given temperature range is obtained by re-fitting the fitting expression require , so that the actual BV value of the optimization result in the actual application is higher than the expected withstand voltage BV require , thereby ensuring that the device will not break down in advance, and has the minimum specific on-resistance; then, by using a newly proposed effective collision ionization rate model, an analytical expression of the structure parameters (doping depth optimization value W opt and doping concentration optimization value N opt ) related to the design withstand voltage BV design , the aspect ratio AR and the maximum temperature T max is given, which provides a more convenient solving way for the parameter optimization of the super-junction structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, relates to super junction structure parameter design, and specifically provides a super junction structure parameter optimization method within a given temperature range. Background Art

[0002] Power semiconductor devices have a wide range of applications in the current era of rapid development of power electronics technology due to their excellent electric energy transformation and circuit control capabilities. As two important parameters of power semiconductor devices, breakdown voltage (BV) and specific on-resistance (R on,sp ) is the key to the development of power devices. It is usually hoped to reduce the specific on-resistance as much as possible under the premise of high withstand voltage, so as to achieve low energy consumption, but this compromise is limited by the silicon material itself, namely the "silicon limit".

[0003] In order to solve the above problems, a superjunction structure was proposed in the literature "Theory of a novel voltage sustaining (CB) layer for power devices [J]. Chinese Journal of Electronics, 1998, 7 (3): 211-216". Figure 1 As shown, by using alternating horizontally arranged n-type pillars (n pillars) and p-type pillars (p pillars), ideally, the vertically aligned electric lines within the n pillars are partially absorbed by the negatively charged acceptor ions in the p pillars. This transitions the voltage withstand method from a single vertical withstand method to a combination of both horizontal and vertical withstand methods. This allows the drift region doping concentration to be increased at the same withstand voltage, thereby reducing the specific on-resistance and energy consumption. However, in the parameter optimization design of the aforementioned superjunction structure, as the operating temperature range of power semiconductor devices continues to widen, higher requirements are placed on the accuracy and simplicity of the optimization process. However, the prior art does not provide a definitive technical solution for the parameter optimization methods and optimization criteria for superjunction structures within a given temperature range. Summary of the Invention

[0004] The object of the present invention is to provide a method for optimizing parameters of a super junction structure within a given temperature range, so that the optimized super junction structure can be optimized within the given temperature range [T min ,T max ] all meet the expected withstand voltage value BV require , and ensure that the on-resistance is minimum under the same conditions, so that the energy consumption of the super junction structure is minimized.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for optimizing superjunction structure parameters within a given temperature range, comprising the following steps:

[0007] Step 1: Obtain the aspect ratio AR and expected withstand voltage BV of the superjunction structure according to the design goals require And the operating temperature range [T min ,T max ], T min With T max are the minimum and maximum temperatures respectively;

[0008] Step 2: According to the expected withstand voltage value BV require , aspect ratio AR and maximum temperature T max , put it into the design withstand voltage value fitting expression for fitting, and get the design withstand voltage value BV design ;

[0009] Step 3: According to the design withstand voltage value BV design , aspect ratio AR and maximum temperature T max , put the analytical expression of doping depth and doping concentration into the analytical expression, and get the optimized value of doping depth W opt and the optimized doping concentration N opt .

[0010] Furthermore, in step 2, the design voltage withstand value fitting expression is specifically:

[0011]

[0012] Furthermore, in step 3, the analytical expression of doping depth is specifically:

[0013] W opt =γ(T max ) 0.17 ·(BV design ) 1.17 AR -0.17 (AR+16.1) 0.17 ,

[0014] γ(T)=1.94×10 -34 -7.88×10 -37 T+8.48×10 -40 ·T 2 ,

[0015] Where T is the temperature.

[0016] Furthermore, in step 3, the analytical expression of the doping concentration is specifically:

[0017] N opt =1.76×107 · gamma (T max ) -0.33 · (BV design ) -1.33 · AR 1.33 (AR+16.1) -0.33 ,

[0018] gamma (T) = 1.94 x 10 -34 -7.88 x 10 -37 · T + 8.48 x 10 -40 · T 2 ,

[0019] wherein T is temperature.

[0020] In terms of working principle:

[0021] The application provides a super-junction structure parameter optimization method in a given temperature range, in order to illustrate the working principle, the following is exemplarily described;

[0022] In the conventional super-junction structure parameter optimization method, the breakdown voltage BV require of the design target is usually taken as the design value BV design , the super-junction structure parameters are optimized at 218K, 298K and 398K, and the optimized results are applied to the given temperature range [218K, 398K], and the results are shown in Figure 2 Since the collision ionization rate coefficient increases with the decrease of temperature, when the optimized result at a certain temperature is applied to the environment lower than the temperature, the actual breakdown voltage will be less than the expected breakdown voltage BV require , thereby causing the super-junction device to break down in advance and the breakdown voltage performance to be substandard;

[0023] Therefore, in order to make the super-junction structure meet the breakdown voltage performance (BV require ) in the given temperature range [218K, 398K], the design value BV design at each temperature needs to be improved, so that BV require can also be met at low temperature; in view of the problem, the application uses bisection method, and the actual breakdown voltage when the optimized result is applied to low temperature is equal to the breakdown voltage BV require , the breakdown voltage design value BV design that meets the termination condition is found as the termination condition of the bisection method; based on the bisection method, the MATLAB numerical fitting is used to obtain the fitting expression of BV design , as shown in Figure 3 The average relative error of the fitting result and the bisection result is less than 1%;

[0024] Further, as shown in Figure 4 , when the breakdown voltage BVrequire When the voltage is 400V, 600V and 900V respectively, at each design temperature (218K, 298K and 398K), the withstand voltage design value BV is design Based on the fitting expression, it is improved in sequence; at the corresponding withstand voltage design value BV design The superjunction structure parameters are optimized under the given temperature range [218K, 398K]. As can be seen from the figure, the actual BV values ​​of the optimized superjunction structure in the given temperature range are higher than the expected BV. require ;

[0025] Furthermore, Figure 5 As shown in the figure, for the specific on-resistance, the superjunction structure parameters are optimized at three temperatures of 218K, 298K, and 398K, and then applied within a given temperature range [218K, 398K]. As can be seen from the figure, the optimization results at high temperature show lower specific on-resistance when applied. Therefore, optimizing the design at high temperature helps to obtain the lowest specific on-resistance, that is, the lowest energy consumption;

[0026] In summary, the present invention only requires the maximum value T in a given temperature range. max The withstand voltage design value BV is obtained by fitting the expression design , at the withstand voltage design value BV design By optimizing the superjunction structure parameters under these conditions, it can be ensured that the optimized results meet the voltage resistance performance while minimizing power consumption when applied.

[0027] On this basis, the present invention proposes an effective impact ionization rate model based on a given temperature range that is applicable to traditional superjunction structures by MATLAB fitting. This model can greatly simplify the impact ionization solution steps, and its expression is:

[0028] ∫α eff ds=∫(1.9762×10 -34 -7.9586×10 -37 ×T+8.4577×10 -40 ×T 2 )·E 7 ds=1

[0029] Using the single exponential expression of the electric field at AA' in the superjunction structure Through the full depletion condition and collision ionization integration conditions The analytical expression of the optimization parameters can be derived, as shown in step 3;

[0030] When the withstand voltage value BV requireWhen the voltage is 600V, the aspect ratio AR is set to 10, 20, and 30 respectively. The error between the optimization result (Analytic) obtained by the analytical expression of the present invention and the optimization result (Conventional) obtained by the traditional method is as follows: Figure 6 As shown, for the optimized thickness W opt and doping concentration N opt , the present invention can better fit the optimization results of the traditional method, with average errors of 1.96% and 1.01% respectively; however, compared with the traditional optimization method, as described in the patent document with publication number CN 114781309 A, the traditional optimization method uses the series expression of the electric field at AA' of the superjunction structure and the Chynoweth impact ionization rate integral model, that is, When optimizing the superjunction structure parameters, the series form of electric field and composite integrals make the solution process of this method too complicated and require the use of tools such as MALTAB for solution. In the present invention, a temperature-based numerical analytical method is provided. While ensuring the accuracy of the results, this method uses the fitted effective collision ionization rate model to derive a concise analytical expression for the superjunction structure parameters, greatly simplifying the optimization process of the superjunction structure parameters.

[0031] Based on the above working principle and technical solution, the beneficial effects of the present invention are:

[0032] The present invention provides a method for optimizing superjunction structure parameters within a given temperature range. First, a design withstand voltage value fitting expression is constructed, and the design withstand voltage value BV within the given temperature range is obtained by re-fitting the fitting expression. design , so that the optimization results meet the actual BV value in practical application, which is higher than the expected withstand voltage value BV require The requirements of the device are met to ensure that the device will not break down prematurely and has the minimum specific on-resistance. Then, the structural parameters (optimized value of doping depth W) are derived by using the new effective impact ionization rate model. opt and the optimized doping concentration N opt ) and the design withstand voltage value BV design , aspect ratio AR, maximum temperature T max The relevant analytical expressions provide a more convenient solution for the parameter optimization of superjunction structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the structure of a traditional super junction structure.

[0034] Figure 2 The present invention uses the expected withstand voltage value BV require As the design value BV design The optimization results are applied to the actual withstand voltage (BV) diagram at different temperatures.

[0035] Figure 3 The withstand voltage value BV is designed in the present invention design A plot of the fitting results for the fitted expression.

[0036] Figure 4 The multiple expected withstand voltage values ​​BV in the present invention require The designed withstand voltage value BV is obtained by fitting design Figure 4 shows the actual withstand voltage (BV) of the optimization results.

[0037] Figure 5 The multiple expected withstand voltage values ​​BV in the present invention require The designed withstand voltage value BV is obtained by fitting design The optimization result of the specific on-resistance (R on,sp )picture.

[0038] Figure 6 This is a diagram showing the optimization results of the analytical expression for doping depth and the analytical expression for doping concentration in the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0040] Example 1

[0041] This embodiment provides a method for optimizing super junction structure parameters within a given temperature range, specifically comprising the following steps:

[0042] Step 1: Based on the conventional use conditions and process level of the super junction structure, the aspect ratio AR of the super junction structure is preset to be 10, and the expected withstand voltage value BV is require =600V, and the operating temperature range of the device is [218K, 398K];

[0043] Step 2: According to the expected withstand voltage value BV require , aspect ratio AR and maximum temperature T max , put it into the design withstand voltage value fitting expression for fitting, and get the design withstand voltage value BV design ;

[0044] T max =398K,

[0045]

[0046] Step 3: According to the design withstand voltage value BV design , aspect ratio AR and maximum temperature T max , put the analytical expression of doping depth and doping concentration into the analytical expression, and get the optimized value of doping depth W optand the optimized doping concentration N opt .

[0047] W opt =γ(T max ) 0.17 ·(BV design ) 1.17 AR -0.17 (AR+16.1) 0.17 =44.01μm,

[0048] N opt =1.76×10 7 γ(T max ) -0.33 ·(BV design ) -1.33 AR 1.33 (AR+16.1) -0.33 =7.16×10 15 cm -3 ,

[0049] γ(T)=1.94×10 -34 -7.88×10 -37 T+8.48×10 -40 ·T 2 ;

[0050] Thus, the structural parameter optimization of the super junction structure is completed, and the optimized structure is W opt =44.01μm, N opt =7.16×10 15 cm -3 .

[0051] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A method for optimizing superjunction structure parameters within a given temperature range, characterized in that: The following steps are involved: Step 1: Obtain the aspect ratio AR and expected withstand voltage BV of the superjunction structure according to the design goals require And the operating temperature range [T min ,T max ], T min With T max are the minimum and maximum temperatures respectively; Step 2: According to the expected withstand voltage value BV require , aspect ratio AR and maximum temperature T max , put it into the design withstand voltage value fitting expression for fitting, and get the design withstand voltage value BV design ; Step 3: According to the designed withstand voltage value BV design , aspect ratio AR and maximum temperature T max , put the analytical expression of doping depth and doping concentration into the analytical expression, and get the optimized value of doping depth W opt and the optimized doping concentration N opt ; The specific analytical expression of doping depth is: W opt =γ(T max ) 0.17 ·(BV design ) 1.17 ·AR -0.17 (AR+16.1) 0.17 , γ(T)=1.94×10 -34 -7.88×10 -37 ·T+8.48×10 -40 ·T 2 , The analytical expression of doping concentration is: N opt =1.76×10 7 ·γ(T max ) -0.33 ·(BV design ) -1.33 ·AR 1.33 (AR+16.1) -0.33 , γ(T)=1.94×10 -34 -7.88×10 -37 ·T+8.48×10 -40 ·T 2 , Where T is the temperature.

2. The method for optimizing superjunction structure parameters within a given temperature range according to claim 1, wherein: In step 2, the design voltage withstand value fitting expression is specifically:

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