Method for simulating crack propagation and thermal stress after irradiation and thermal cycle of high-voltage and high-power device
By constructing a three-dimensional crack model using the finite element method, the problem of real-time monitoring of microcrack propagation in high-voltage, high-power devices was solved by traditional experiments. This enabled accurate reliability assessment and performance prediction of the devices during thermal cycling, reducing costs and time.
Patent Information
- Application Number
- CN202511440840.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-10
- Publication Date
- 2026-03-17
AI Technical Summary
Existing traditional experimental methods are difficult to monitor and accurately predict the formation and propagation of microcracks in high-voltage, high-power devices during thermal cycling in real time, which makes it difficult to assess the long-term stability and reliability of the devices, and also results in high costs and long cycles.
A three-dimensional crack model was constructed by combining the finite element method with thermal load and material properties. The crack was observed by an ultra-depth-of-field microscope. Based on the device's geometry and material properties, the stress distribution of the device under microcrack conditions was evaluated, and the long-term impact of crack propagation on device performance was simulated.
It enables accurate prediction of stress distribution and crack propagation of high-voltage, high-power devices under actual working conditions, reducing R&D costs and time, improving the accuracy of reliability assessment, and avoiding sudden failures and safety hazards caused by crack propagation.
Smart Images
Figure CN121683305A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of device reliability testing and analysis, and in particular relates to a simulation method for crack propagation and thermal stress of high-voltage, high-power devices after irradiation and thermal cycling. Background Technology
[0002] As the integration of electronic devices continues to increase, these devices often face complex operating environments in practical applications, including the coupled effects of thermal cycling and irradiation. In this environment, the materials of the devices, especially metallic materials, experience heat concentration and energy deposition after irradiation, leading to changes in their mechanical properties. Further thermal cycling experiments cause these unstable regions to be subjected to repeated thermal expansion and contraction, resulting in the formation and propagation of microcracks. These cracks can affect the long-term performance of the devices and even lead to device failure. Therefore, accurately predicting the reliability of devices during thermal cycling has become one of the key issues in device design and optimization.
[0003] Existing traditional experiments typically require lengthy testing periods. While they offer some reliability assessment, they are costly, time-consuming, and lack real-time feedback on internal stress distribution and crack development. Therefore, finite element simulation combined with thermal load and material properties for device performance prediction and analysis has become an efficient and accurate evaluation method. Although traditional irradiation and thermal cycling coupled experiments can provide some reliability assessment, in practical applications, the thermal load processes experienced by devices are complex and varied, making it difficult to monitor and accurately predict the formation and propagation of microcracks in real time. Furthermore, traditional experimental methods are time-consuming and costly, and cannot obtain real-time information on the internal stress state and crack development of the device during the experiment. This method is limited to laboratory environments and cannot comprehensively reflect the thermal stress effects of devices under actual operating conditions.
[0004] In some cases, even if microcracks appear inside a device, its electrical performance may degrade. However, because the cracks have not yet developed to the level of significant failure criteria, traditional thermal cycling tests cannot detect this potential problem in real time. In such cases, the device may still continue to operate, but its long-term stability and reliability have deteriorated, making it prone to unexpected failures during later use. This not only increases the cost of equipment maintenance but may also lead to system safety hazards. Summary of the Invention
[0005] Objective: This invention aims to provide a simulation method for crack propagation and thermal stress in high-voltage, high-power devices after irradiation and thermal cycling. The method involves irradiation and high / low temperature cycling experiments to test the degradation of electrical performance, observing cracks using a super-depth-of-field microscope, and simulating the stress distribution in the top metal region of the device after cracking. The core of this method lies in accurately constructing a three-dimensional simulated crack model. Through calculation, combined with the device's geometry and material properties, the stress distribution of the device under microcrack conditions is evaluated. This method can help to gain a deeper understanding of the long-term impact of crack propagation on device performance.
[0006] Technical solution: The present invention provides a simulation method for crack propagation and thermal stress of high-voltage, high-power devices after irradiation and thermal cycling, comprising the following steps:
[0007] Step 1: Conduct electron irradiation experiments on the target high-voltage high-power device, and then continue with high and low temperature cycling experiments; to evaluate the degradation trend and performance changes of the device under irradiation and long-term alternating high and low temperature conditions. By controlling the temperature change range, the device is subjected to multiple accumulations of thermal stress.
[0008] Step 2: Test the electrical performance of the device using a testing platform;
[0009] Step 3: Observe the lifting phenomenon that appears in the top metal region of the device;
[0010] Step 4: Use finite element analysis software to build a three-dimensional simulation model of the device. The model includes the device's geometric structure and the mechanical properties of the material.
[0011] Step 5: Establish a spatial coordinate system. Create a basic model of the random crack and set the coordinate system of the crack. The X-axis is the direction of crack propagation, and the Z-axis is the length of the crack.
[0012] Step 6: In the model, model the top metal region of the device and add random cracks to reflect the degradation behavior of the device during high and low temperature cycling.
[0013] Step 7: Simulate the temperature change of the device during alternating high and low temperatures by applying a temperature load;
[0014] Step 8: The thermal module is used as the output and transmitted to the stress module to simulate the stress distribution and crack propagation in a real-world scenario.
[0015] Step 9: Solve the device model to obtain the stress distribution in the top metal region and the stress intensity factor at the tip of the texture.
[0016] Step 10: By comparing the changing trends of the crack tip factor under different crack lengths, the crack resistance of the material is determined;
[0017] Step 11: In the simulation results, compare the stress distribution in the top metal region of the device with the crack-free model to study the change in stress field after the addition of random cracks.
[0018] Furthermore, step 3 specifically involves: using a super depth-of-field microscope to observe the lifting phenomenon of the top metal region of the device, indicating that during the irradiation and thermal cycling coupling process, the local area is affected by thermal stress, but the overall device does not completely fail; using experimental data as input, combined with simulation results for comparison, the crack propagation and stress change model during the irradiation and thermal cycling coupling experiment is optimized.
[0019] Furthermore, in step 4, the mechanical properties include elastic modulus, Poisson's ratio, and coefficient of thermal expansion.
[0020] Furthermore, step 5 specifically involves setting the origin of the local coordinate system as the starting position of the crack, determining the coordinates of the crack starting point through a preset position in the model, defining the X-axis of the local coordinate system as the crack propagation direction, and the Z-axis of the local coordinate system as the crack length direction, representing the direction from the crack starting point to the crack tail.
[0021] Furthermore, in step 6, the top metal region of the device is modeled. Specifically, the gate metal pad is connected to the gate pin through bonding wires, the drain metal pad is connected to the substrate through an adapter plate to increase its heat dissipation, and the source metal pad and drain metal pad are connected to each other through a cross comb structure to achieve uniform current distribution and heat dissipation.
[0022] Furthermore, in step 7, the range of alternating high and low temperatures is from 150°C to -25°C.
[0023] Furthermore, in step 9, the device model is solved to obtain the stress distribution in the top metal region. Specifically, with the periodic change of temperature, the bonding force between the layers will undergo a certain thermal expansion. The thermal expansion coefficients of Au and GaN are 14.2 × 10⁻⁶ and 14.2 × 10⁻⁶, respectively. -6 / K and 5.59×10 -6 The significant mismatch in the thermal expansion coefficients of the material ( / K) leads to stress accumulation. Under alternating temperatures, the mechanical strain in the top metal region increases significantly, and this high mechanical strain is further amplified at high temperatures. Therefore, the thermal stress is primarily caused by the thermal expansion of the material, calculated using the following formula: ; in, E represents thermal stress, and E is the elastic modulus of the material. It is the coefficient of thermal expansion of the material. Represents strain in the x-direction. It represents the amount of temperature change.
[0024] The present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method of the present invention.
[0025] The present invention also discloses a computer-readable storage medium having a computer program / instructions stored thereon, which, when executed by a processor, implements the steps of the method of the present invention.
[0026] The present invention also discloses a computer program product, including a computer program / instructions that, when executed by a processor, implement the steps of the method of the present invention.
[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:
[0028] 1. This invention introduces a random crack model into the finite element simulation model to simulate the stress distribution and crack tip strength factor changes of a device after experiencing irradiation and thermal cycling loads, thereby evaluating the stability and reliability of the device under actual operating conditions. This technology is applicable to the thermodynamic behavior analysis and reliability optimization of electronic components, semiconductor devices, packaging materials, and other fields.
[0029] 2. This invention proposes a stochastic crack model based on the finite element method, focusing on the accelerated performance degradation of high-voltage, high-power devices under thermal cycling and irradiation coupling. By inputting the metal layer lift height measured in irradiation and thermal cycling experiments into the simulation model, a thermodynamic coupling model and a stochastic crack model are used to accurately predict the thermal stress distribution of the device under microcrack conditions. This simulation method can comprehensively evaluate the gradual impact of cracks on device performance under different thermal cycling conditions and further analyze the potential threat of microcrack propagation to electrical performance.
[0030] 3. By combining finite element simulation with irradiation and thermal cycling experiments, the thermal stress distribution and microcrack propagation effects of high-voltage, high-power devices under crack conditions can be predicted. Simultaneously, by improving the accuracy of reliability experiments, sudden failures and potential safety hazards caused by crack propagation can be effectively avoided. Furthermore, obtaining stress distribution and crack propagation information during the simulation phase reduces the need for physical experiments, thereby lowering R&D costs and time. Attached Figure Description
[0031] Figure 1 This is a flowchart illustrating the implementation of the present invention.
[0032] Figure 2 The figures show the electrical characteristics as a function of the number of thermal cycles after the irradiation experiment. (a) Transfer characteristics, (b) Output characteristics.
[0033] Figure 3The height of the top metal region was measured under irradiation and thermal cycling coupling experimental conditions. (a) Overall schematic diagram of the top metal region, (b) gate, (c) drain, (d) test results of the height difference between the source metal pads.
[0034] Figure 4 The stress distribution of the drain metal region under the conditions of irradiation and thermal cycling coupling experiment with added cracks is shown in (a) 25℃, (b) -25℃, and (c) 150℃.
[0035] Figure 5 This is a schematic diagram of crack propagation. (a) Stress intensity factor distribution at the crack tip, (b) Stress intensity factor at the crack tip as a function of length.
[0036] Figure 6 The stress distribution in the drain metal region under thermal cycling conditions is shown as follows: (a) 25℃, (b) -25℃, (c) 150℃. Detailed Implementation
[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings.
[0038] like Figure 1 As shown, this invention proposes a simulation method for crack propagation and thermal stress in high-voltage, high-power devices after irradiation and thermal cycling, comprising the following steps:
[0039] (1) The selected high-voltage, high-power device was first subjected to an electron irradiation experiment with an irradiation dose of 2 Mrad (Si), and then subjected to 1000 cycles of high and low temperature cycling. The purpose of the experiment was to evaluate the degradation trend and performance changes of the device under irradiation and long-term alternating high and low temperature conditions. By controlling the temperature variation range and cycling 1000 times, the device was subjected to multiple accumulations of thermal stress.
[0040] (2) First, the electrical performance of the device was tested in detail using a testing platform. During the test, the present invention monitored the IV characteristics to assess the phenomenon of device performance degradation, specifically a decrease in saturation leakage current. However, despite the significant degradation in device performance, the device remained in a conducting state, indicating that even under performance degradation, the device could still continue to operate and perform its basic functions, such as... Figure 2 As shown.
[0041] (3) Using a super depth-of-field microscope, a slight lifting phenomenon was observed in the top metal region of the device, indicating that the local area was affected by thermal stress during thermal cycling, but the overall device did not completely fail. Macroscopic observation and microscopic examination of the device surface confirmed that the device underwent deformation in the horizontal and vertical directions of the pads during thermal cycling, but did not reach the point of failure. Using the experimental data of 4 μm as the crack radius input, the crack propagation process under irradiation and thermal load was simulated. Figure 3 As shown
[0042] (4) Use finite element analysis software to establish a three-dimensional simulation model of the device. The model includes the device's geometry and the mechanical properties of the material (such as elastic modulus, Poisson's ratio, coefficient of thermal expansion, etc.).
[0043] (5) To ensure an accurate description of crack behavior, a local coordinate system needs to be set up for the crack in the global coordinate system. The relationship between this local coordinate system and the global coordinate system needs to be clearly defined in order to describe the crack propagation. The origin of the local coordinate system is usually set as the crack initiation position, and the coordinates of the crack initiation point can be determined by the preset position in the model. The X-axis of the local coordinate system is usually defined as the crack propagation direction, and the Z-axis of the local coordinate system represents the crack length direction, indicating the direction from the crack initiation point to the crack tail.
[0044] (6) In the model, the top metal region of the device is specifically modeled in detail, and random cracks are added. These cracks represent the potential occurrence of the device in actual applications. The model simulates the initial development of microcracks inside the material and can reflect the possible degradation behavior of the device during irradiation and high and low temperature cycling in the simulation.
[0045] (7) Simulate the temperature change of the device during the alternation of high and low temperatures by applying a real temperature load. This process involves dynamically applying a temperature load to the device model to simulate the temperature change cycle in actual applications. Typically, the temperature will drop from a high temperature (e.g., 150°C) to a low temperature (e.g., -25°C) and change periodically. Through accurate temperature field simulation, the simulation can reveal the changes in thermal stress, thermal expansion stress, and possible material deformation of the device at different temperatures.
[0046] (8) The thermal module is used as the output and transmitted to the stress module. The thermal stress caused by the change in temperature field is usually calculated by thermal expansion. Temperature change will cause the volume expansion of the material, which in turn will generate internal stress.
[0047] (9) Based on the above steps, the device model is solved to obtain the stress distribution under the condition of adding cracks in the top metal region, such as Figure 4 ;
[0048] (10) By comparing the trend of the crack tip factor under different crack lengths, the crack resistance of the material can be judged. If the crack tip factor grows too fast or too high, it indicates that the crack resistance of the material is poor and crack propagation is likely to occur. If the growth is relatively stable, it indicates that the material can resist crack propagation well and may have good crack resistance.
[0049] Figure 5 (a) is a schematic diagram of the crack tip factor. Figure 5 (b) is a graph showing the crack tip factor. From Figure 5 As shown in (b), the crack tip factor starts from an initial value of 0.11948 and gradually decreases with the increase of crack length, indicating that the crack tip is subjected to compressive stress, which inhibits crack propagation. Figure 5 As shown;
[0050] (11) In the simulation results, this invention focuses on analyzing the stress distribution in the top metal region of the device. By comparing with the single thermal cycling model, the change of stress field after the introduction of random cracks is studied. Figure 6 The results show that under thermal cycling conditions, the stress distribution is relatively uniform and low, compared to... Figure 4 and Figure 6 With the addition of cracks, stress concentration under the coupled irradiation and thermal cycling conditions is significantly enhanced, exceeding the concentration by approximately 27% at high temperatures. This result reveals the significant impact of cracks on local stress distribution and further emphasizes the potential threat cracks pose to device lifespan.
Claims
1. A method for simulating crack propagation and thermal stress of high-voltage high-power devices after irradiation and thermal cycling, characterized in that, The method comprises the following steps: Step 1, electronic irradiation experiment is conducted on a target high-voltage high-power device, and then high-low temperature cycle experiment is conducted; the degradation trend and performance change of the device under the coupling condition of irradiation and long-time high-low temperature alternation are evaluated, and the device is subjected to accumulation of multiple thermal stresses by controlling the temperature variation range; Step 2, the electrical performance of the device is tested by using a test platform; Step 3, the lifting phenomenon of the top metal region of the device is observed; Step 4, a three-dimensional simulation model of the device is established by using finite element analysis software, and the model comprises the geometric structure and the mechanical properties of the materials of the device; Step 5, a spatial coordinate system is established, a basic model of a random crack is established, and a coordinate system of the crack is set, wherein the X-axis is the extension direction of the crack, and the Z-axis is the length direction of the crack; Step 6, in the model, the top metal region of the device is modeled, and the random crack is added to reflect the degradation behavior of the device in the high-low temperature cycle process; Step 7, the temperature variation of the device in the high-low temperature alternation process is simulated by applying a temperature load; Step 8, the thermal module is taken as an output and is transmitted to a stress module to simulate the stress distribution and crack extension in a real scene; Step 9, the device model is solved to obtain the stress distribution of the top metal region and the stress intensity factor of the crack tip; Step 10, the anti-crack performance of the material is judged by comparing the change trend of the crack tip factor under different crack lengths; Step 11, in the simulation result, the stress distribution of the top metal region of the device is compared with that of a model without the crack, and the change of the stress field after the random crack is added is researched.
2. The method for simulating crack propagation and thermal stress of high-voltage high-power devices after irradiation and thermal cycling according to claim 1, characterized in that, Step 3 specifically comprises: the lifting phenomenon of the top metal region of the device is observed by using an ultra-depth microscope, which indicates that, in the coupling process of irradiation and thermal cycle, the local region is affected by thermal stress, but the overall device has not completely failed; experimental data are taken as input, and the crack extension and stress change model in the coupling experiment of irradiation and thermal cycle are optimized by combining the simulation result.
3. The method of claim 1, wherein the method is characterized by: In step 4, the mechanical properties comprise an elastic modulus, a Poisson's ratio and a thermal expansion coefficient.
4. The method of claim 1, wherein the method is characterized by: Step 5 specifically comprises: the origin of the local coordinate system is set as the starting position of the crack, the coordinates of the starting position of the crack are determined through a preset position in the model, the X-axis of the local coordinate system is defined as the extension direction of the crack, and the Z-axis of the local coordinate system represents the length direction of the crack, that is, the direction from the starting position of the crack to the tail end of the crack.
5. The method for simulating crack propagation and thermal stress of high-voltage high-power devices after irradiation and thermal cycling according to claim 1, characterized in that, In step 6, the top metal region of the device is modeled, specifically: the gate metal pad is connected to the gate pin through a bonding wire, the drain metal pad is connected to the substrate through a conversion plate to increase heat dissipation, and the source metal pad and the drain metal pad are connected to each other through a cross comb structure to realize uniform current distribution and heat dissipation.
6. The method for simulating crack propagation and thermal stress of high-voltage high-power devices after irradiation and thermal cycling according to claim 1, characterized in that, In step 7, the high-low temperature alternation ranges from 150°C to -25°C.
7. The method for simulating crack propagation and thermal stress of high-voltage high-power devices after irradiation and thermal cycling according to claim 1, characterized in that, In step 9, the device model is solved to obtain the stress distribution of the top metal region, specifically: with the periodic change of temperature, the binding force between each layer will expand through thermal expansion, the thermal expansion coefficients of Au and GaN are 14.2x10 -6 / K and 5.59x10 -6 / K, for the mechanical strain of the top metal region under alternating temperature, the high mechanical strain force is further amplified at high temperature, and the thermal stress is caused by the thermal expansion of the material, which is calculated by the following formula: ； wherein, represents thermal stress, E is the elastic modulus of the material, is the thermal expansion coefficient of the material, denotes the strain in the x direction, denotes the amount of temperature change.
8. A computer apparatus comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program, when executed by the processor, causes the processor to perform the method of any one of claims 1 to 7. The processor executes the computer program to realize the steps of the method in claim 1.
9. A computer readable storage medium having stored thereon computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to realize the steps of the method in claim 1.
10. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to realize the steps of the method in claim 1.