Super junction structure parameter optimization method in given temperature range

Abstract

The invention belongs to the technical field of semiconductor devices, and provides a method for optimizing parameters of a super-junction structure in a given temperature range, so that the optimized super-junction structure meets an expected withstand voltage value in the given temperature range, the specific on-resistance is ensured to be minimum under the same condition, and the energy consumption of the super-junction structure is enabled to be minimum. The method comprises the following steps: firstly, constructing a design withstand voltage value fitting expression, and re-fitting through the fitting expression to obtain a design withstand voltage value BVdesign in a given temperature range, so that an actual BV value of an optimization result in actual application is higher than an expected withstand voltage value BVdesign, thereby ensuring that a device cannot be broken down in advance and has minimum specific on-resistance; and then, by using a newly proposed effective collision ionization rate model, an analytical expression of correlation between structure parameters (a doping depth optimization value Wopt and a doping concentration optimization value Nopt) and a designed withstand voltage value BVdesign, a depth-to-width ratio AR and a highest temperature Tmax is given, and a more convenient solution approach is provided for 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, the breakdown voltage (BV) and the 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 relationship is limited by the silicon material itself, namely the "silicon limit".

[0003] 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 the laterally alternately arranged n-type pillars (n pillar) and p-type pillars (p pillar), in an ideal case, the electric lines originally arranged vertically in the n pillars are partially absorbed by the negatively charged acceptor ions in the p pillars, and the withstand voltage mode is changed from the original single longitudinal withstand voltage to a combination of lateral and longitudinal withstand voltage, so that under the same withstand voltage, the doping concentration of the drift region can be increased, thereby reducing the specific on-resistance and reducing energy consumption. However, in the parameter optimization design of the above-mentioned superjunction structure, as the operating temperature range of power semiconductor devices becomes wider and wider, higher requirements are placed on the accuracy and simplicity of the optimization process, and the prior art does not provide a definite technical solution for the parameter optimization method and optimization criteria of the superjunction structure within a given temperature range. Summary of the invention

[0004] The object of the present invention is to provide a method for optimizing super junction structure parameters 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 minimized 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 super junction structure parameters within a given temperature range, characterized in that it comprises the following steps:

[0007] Step 1: Obtain the aspect ratio AR and expected withstand voltage value BV of the super junction structure according to the design goal 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 , substituting the analytical expression of doping depth and the analytical expression of doping concentration, the corresponding optimized value of doping depth W is obtained 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 temperature.

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

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

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

[0019] Where T is temperature.

[0020] In terms of working principle:

[0021] The present invention provides a method for optimizing super junction structure parameters within a given temperature range. To illustrate its working principle, an exemplary description is given below.

[0022] In the traditional superjunction structure parameter optimization method, the design target voltage value BV is usually used. require As design value BV design , the superjunction structure parameters are optimized at three temperatures of 218K, 298K, and 398K, and applied to a given temperature range [218K, 398K]. The results are as follows Figure 2 As shown in the figure, since the collision ionization rate coefficient increases as the temperature decreases, when the optimization result at a certain temperature is applied to an environment below the temperature, the actual withstand voltage value will be less than the expected withstand voltage value BV require , which leads to premature breakdown of super junction devices and failure to meet withstand voltage standards;

[0023] It can be seen that in order to make the super junction structure meet the withstand voltage performance (BV require ), it is necessary to increase the design value BV at each temperature design , so that BV can be met even at low temperatures require To solve this problem, the present invention uses the dichotomy method to apply the optimization result to the actual withstand voltage value of low temperature equal to the withstand voltage value BV require As the termination condition of the dichotomy method, find the withstand voltage design value BV that meets the termination condition design ; Based on the dichotomy method, using MATLAB numerical fitting, we get BV design The fitting expression of Figure 3 As shown, the average relative error between the fitting results and the dichotomy results is less than 1%;

[0024] Further, such as Figure 4 As shown, when the withstand voltage value 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, if 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 applied to a given temperature range [218K, 398K]. It can be seen from the figure that the optimization result at high temperature shows a 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 needs to be within 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 this condition, it can be ensured that the optimization results meet the voltage resistance performance while minimizing power consumption when applied.

[0027] On this basis, the present invention proposes an effective collision ionization rate model based on a given temperature range suitable for traditional superjunction structures by MATLAB fitting. The model can greatly simplify the collision 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' of the superjunction structure Through the full depletion condition and collision ionization integration conditions The analytical expression of the optimization parameter 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, through the Chynoweth collision ionization rate integral model, that is, To optimize the superjunction structural parameters, the electric field and composite integral in the form of series make the solution process of this method too complicated, and it needs to be solved with the help of tools such as MALTAB. In the present invention, a temperature-based numerical analytical method is provided. Under the premise of ensuring the accuracy of the results, this method uses the effective collision ionization rate model obtained by fitting to derive a concise analytical expression of the superjunction structural parameters, which greatly simplifies the optimization process of the superjunction structural 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 refitting the fitting expression. design , so that the optimization results meet the actual BV value higher than the expected withstand voltage value BV in practical application require , so as 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 opt and the optimized doping concentration N opt ) and 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 takes the expected withstand voltage value BV require As design value BV design The optimization results are applied to the actual withstand voltage value (BV) diagram at different temperatures.

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

[0036] Figure 4 is a plurality of expected withstand voltage values ​​BV in the present invention require The designed withstand voltage value BV is obtained by fitting design Figure 3 shows the actual withstand voltage value (BV) of the optimization results.

[0037] Figure 5 is a plurality of expected withstand voltage values ​​BV in the present invention require The designed withstand voltage value BV is obtained by fitting design The optimization result is 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 solution 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, which specifically includes the following steps:

[0042] Step 1: Taking the conventional use conditions and process level of the super junction structure as a reference, the aspect ratio of the super junction structure is preset to AR = 10, and the expected withstand voltage value BV is require =600V, and the device’s operating temperature range 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 , substituting the analytical expression of doping depth and the analytical expression of doping concentration, the corresponding optimized value of doping depth W is obtained 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 implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the 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 value BV of the super junction structure according to the design goal 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 design withstand voltage value BV design , Aspect Ratio AR and Maximum Temperature T max , substituting the analytical expression of doping depth and the analytical expression of doping concentration, the corresponding optimized value of doping depth W is obtained opt and the optimized doping concentration N opt .

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

3. The method for optimizing super junction structure parameters within a given temperature range according to claim 1, characterized in that: In step 3, the 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 , Where T is temperature.

4. The method for optimizing super junction structure parameters within a given temperature range according to claim 1, characterized in that: In step 3, 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 temperature.

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