Reliability test analysis method and system for MOSFET

Abstract

The invention belongs to the technical field of test analysis, and provides a reliability test analysis method and system for an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), and the method comprises the steps: dividing the MOSFET into a plurality of sub-regions, carrying out the single avalanche energy test of the sub-regions, and judging whether the sub-regions will have avalanche breakdown or not; applying the same pulse amplitude sequence to different positions of the sub-region, carrying out multiple avalanche energy tests, evaluating the reliability of the sub-region under an avalanche condition, and positioning a breakdown position in the sub-region; measuring the thickness of a breakdown position in the sub-region when multiple avalanche energy tests are carried out through a spectrum ellipsometer, and judging whether the reliability of the sub-region is low under an avalanche condition due to non-uniform thickness of the sub-region by carrying out uniformity analysis on the thickness of different breakdown positions of the sub-region; according to the invention, the reliability of the MOSFET sub-region under the extreme avalanche condition is enhanced, and the performance consistency and the long-term working stability of the device are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of testing and analysis, and in particular relates to a reliability testing and analysis method and system for MOSFET. Background Art

[0002] In the field of power semiconductor devices, the avalanche reliability of MOSFET directly affects its application safety in scenarios such as overvoltage protection and switching power supplies.

[0003] Existing technologies for MOSFET avalanche reliability testing have significant shortcomings. Firstly, there is a lack of quantitative stability indicators, making it difficult to objectively reflect the discreteness of breakdown characteristics through numerical means. Secondly, failure analysis lacks systematic testing of material thickness uniformity, often blindly attributing factors such as temperature and interface state density, resulting in inefficient analysis. Furthermore, process optimization relies on empirical settings, and a precise control model for thickness and deposition power has not been established, making it difficult to eliminate reliability risks at the source of production. These deficiencies make existing technologies unable to meet the device stability requirements of high-power applications in MOSFET avalanche reliability assessment.

[0004] To this end, the present invention provides a reliability testing and analysis method and system for MOSFET. Summary of the Invention

[0005] In order to make up for the deficiencies of the prior art, at least one technical problem raised in the background technology is solved.

[0006] In a first aspect, the present invention provides a reliability testing and analysis method for MOSFET, comprising: By dividing the MOSFET into several sub-regions, a single avalanche energy test is performed on the sub-region to determine whether avalanche breakdown will occur in the sub-region; If avalanche breakdown occurs in a sub-region, the same pulse amplitude sequence is applied to different locations in the sub-region and multiple avalanche energy tests are performed to evaluate the reliability of the sub-region under avalanche conditions and locate the breakdown position in the sub-region; If the reliability of a sub-region under avalanche conditions is low, the thickness of the breakdown position in the sub-region is measured by spectroscopic ellipsometer during multiple avalanche energy tests. The thickness of the sub-region at different breakdown positions is analyzed for uniformity to determine whether the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region. If the reliability of the sub-region under avalanche conditions is low due to uneven thickness of the sub-region, the thickness uniformity of the sub-region with low reliability under avalanche conditions is regulated to enhance the reliability of the MOSFET sub-region under avalanche conditions.

[0007] As a further solution of the present invention, the specific process of determining whether avalanche breakdown will occur in a sub-region is as follows: Based on any sub-region, the drain current at the monitoring time point is extracted. If the drain current is greater than or equal to the drain current standard value, the corresponding monitoring time point is recorded as the breakdown time point; otherwise, the corresponding monitoring time point is recorded as the non-breakdown time point. All monitoring time points are integrated into a monitoring time series including breakdown time points and non-breakdown time points in chronological order. The monitoring time series is traversed, and the intervals in which breakdown time points appear continuously are recorded as continuous segments. The longest continuous segment is extracted, and the proportion of the number of breakdown time points in the longest continuous segment among the monitoring time points is calculated to obtain the avalanche occurrence value; if it is greater than or equal to the avalanche occurrence threshold, it means that avalanche breakdown has occurred in the sub-area.

[0008] As a further solution of the present invention: the specific process of evaluating the reliability of the sub-region under avalanche conditions is: Conduct multiple avalanche energy tests to determine the fluctuation values ​​of avalanche triggering time, avalanche energy, and breakdown current; The fluctuation values ​​of the avalanche triggering time point, the avalanche energy fluctuation value, and the breakdown current fluctuation value are weighted and summed to obtain the avalanche breakdown stability index; if it is greater than or equal to the avalanche breakdown stability index threshold, the reliability of the sub-region under avalanche conditions is low, and the position where the same pulse amplitude is applied in the sub-region is recorded as the breakdown position.

[0009] As a further solution of the present invention: the process of determining the fluctuation value at the avalanche triggering time point is: The breakdown time points in the continuous segment are integrated into a breakdown time point sequence according to the time sequence, and the first breakdown time point in the breakdown time point sequence is extracted and recorded as the avalanche triggering time point; All avalanche triggering time points are integrated into an avalanche triggering time point sequence according to the avalanche energy test order, and the avalanche triggering time point fluctuation values ​​of all avalanche triggering time points in the avalanche triggering time point sequence are calculated using the coefficient of variation formula.

[0010] As a further solution of the present invention: the process of determining the avalanche energy fluctuation value is: The time point when the avalanche energy test starts is recorded as the initial time point. The drain current waveform and voltage waveform between the initial time point and the avalanche trigger time point are extracted from the oscilloscope by: Calculate the avalanche energy E, where Indicates the avalanche triggering time point, It represents the voltage corresponding to the monitoring time point t between the initial time point and the avalanche triggering time point, represents the drain current corresponding to the monitoring time point t between the initial time point and the avalanche triggering time point; All avalanche energies are integrated into an avalanche energy sequence according to the avalanche energy test order, and the avalanche energy fluctuation values ​​of all avalanche energies in the avalanche energy sequence are calculated using the coefficient of variation formula.

[0011] As a further solution of the present invention: the process of determining the breakdown current fluctuation value is: The drain current corresponding to the avalanche triggering time point is recorded as the breakdown current. All breakdown currents are integrated into a breakdown current sequence according to the avalanche energy test order. The breakdown current fluctuation values ​​of all breakdown currents in the breakdown current sequence are calculated using the coefficient of variation formula.

[0012] As a further solution of the present invention, the specific process of determining whether the low reliability of the sub-region under avalanche conditions is caused by the uneven thickness of the sub-region is as follows: The thickness of the breakdown position in the sub-area during multiple avalanche energy tests is integrated into a thickness sequence according to the test order, and a uniformity analysis is performed to determine the thickness variation coefficient; The sub-regions with low reliability under avalanche conditions are extracted from all the sub-regions of the MOSFET and recorded as low-reliability regions. The Pearson correlation coefficient between the thickness variation coefficient and the avalanche breakdown stability index is calculated by taking the absolute value of the Pearson correlation coefficient formula. If it is greater than or equal to the Pearson correlation coefficient threshold, it means that the low reliability of the sub-region under avalanche conditions is caused by the uneven thickness of the sub-region.

[0013] As a further solution of the present invention: the process of determining the thickness variation coefficient is: The coefficient of variation of thickness of all thicknesses in the thickness sequence is calculated using the coefficient of variation formula.

[0014] As a further solution of the present invention: the specific process of regulating the thickness uniformity of the sub-region with low reliability under avalanche conditions is as follows: In the subsequent MOSFET production process, the thickness of different breakdown positions in the sub-region is substituted into the thickness and deposition power curve obtained by fitting, thereby obtaining the initial setting value of the deposition power at different breakdown positions in the sub-region during deposition in the low reliability region; By formula: Calculate the deposition power control value of the j-th breakdown position in the sub-region during deposition in the low reliability area The deposition power control value is sent to the deposition power adjustment module of the MOSFET to adjust the deposition power at different breakdown positions in the sub-region when depositing in the low reliability area; Where, It represents the initial setting value of the deposition power at the j-th breakdown position in the sub-region when depositing in the low reliability region, K represents the process sensitivity coefficient, Indicates the thickness standard value of the sub-area, It represents the thickness of the jth breakdown position in the sub-region when the low reliability region is deposited.

[0015] In a second aspect, the present invention further provides a reliability testing and analysis system for MOSFET, the system comprising: Single test module: By dividing the MOSFET into several sub-regions, a single avalanche energy test is performed on the sub-region to determine whether avalanche breakdown will occur in the sub-region; Reliability judgment module: If avalanche breakdown occurs in a sub-region, the same pulse amplitude sequence is applied to different locations in the sub-region, and multiple avalanche energy tests are performed to evaluate the reliability of the sub-region under avalanche conditions and locate the breakdown position in the sub-region; Uniformity Analysis Module: If the reliability of a sub-region under avalanche conditions is low, the thickness of the breakdown position in the sub-region is measured by spectroscopic ellipsometer during multiple avalanche energy tests. By performing uniformity analysis on the thickness at different breakdown positions in the sub-region, it is determined whether the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region; Regulation and Analysis Module: If the reliability of a sub-region under avalanche conditions is low due to uneven thickness of the sub-region, the thickness uniformity of the sub-region with low reliability under avalanche conditions is regulated to enhance the reliability of the MOSFET sub-region under avalanche conditions.

[0016] The beneficial effects of the present invention are as follows: 1. The present invention achieves accurate judgment of the working consistency of the device under extreme working conditions through weighted synthesis of multi-dimensional fluctuation characteristics, providing an objective quantitative basis for reliability assessment under extreme conditions; on the other hand, the size of the index is used to characterize the discrete degree of the breakdown characteristics during the avalanche breakdown process. The smaller the index, the lower the discreteness of the sub-region's triggering time, energy release, and current conduction characteristics in multiple avalanche tests, and the higher the reliability. The breakdown position can then be located based on the index threshold, providing precise guidance for device process optimization, design improvement, and failure analysis, effectively improving the efficiency and accuracy of MOSFET reliability assessment under avalanche conditions, and reducing the risk of failure in practical applications.

[0017] 2. The present invention uses high-precision thickness measurement and coefficient of variation analysis, combined with the significance test of the Pearson correlation coefficient, to accurately determine whether uneven thickness is the cause of low avalanche reliability, thereby improving the efficiency of failure analysis; based on the fitting curve of thickness and deposition power, the deposition power is dynamically controlled by the process sensitivity coefficient to achieve precise repair of thickness uniformity in low-reliability areas, eliminate the avalanche breakdown instability problem caused by thickness differences from the source of the production process, effectively enhance the reliability of MOSFET sub-areas under extreme avalanche conditions, and improve device performance consistency and long-term working stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 This is a flowchart of a reliability test and analysis method for MOSFET according to an embodiment of the present invention; Figure 2 The present invention is a system block diagram of a reliability testing and analysis system for MOSFET according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below in conjunction with specific implementation methods.

[0021] Example 1 See also Figure 1 As shown, a reliability test and analysis method for MOSFET according to an embodiment of the present invention includes the following steps: Step 1: Divide the MOSFET into several sub-regions and perform a single avalanche energy test on the sub-regions to determine whether avalanche breakdown will occur in the sub-regions. MOSFET is a planar device, usually composed of multiple cells in parallel. A plasma cleaner (O2 / Ar gas mixture) is used to remove organic contaminants on the surface, and a conductive layer (such as gold / platinum, 10–20 nm thick) is sprayed to eliminate charge accumulation effects (suitable for low-voltage SEM imaging). The cell array layout was observed using a scanning electron microscope, and scanning electron microscope images were acquired. Image noise reduction and contrast enhancement were performed on the scanning electron microscope images using ImageJ. The Canny or Sobel operator was applied to extract the cell boundaries. A coordinate system was established in the scanning electron microscope images, and the coordinates of the geometric center and boundary vertices of each cell were recorded. Subregions were then cut along the coordinates of the cell boundary vertices using a focused ion beam. For any sub-area, set the initial test voltage and the maximum test voltage, gradually increase the voltage and pulse amplitude with a fixed step size (e.g., 1V each time), and use an oscilloscope to record the drain current and the corresponding voltage after each increase in pulse amplitude. Preset a monitoring period, divide the monitoring period into several monitoring time points with equal time intervals, extract the drain current at the monitoring time point, and compare the drain current at the monitoring time point with the drain current standard value: If the drain current at the monitoring time point is greater than or equal to the drain current standard value, the corresponding monitoring time point is recorded as the breakdown time point; If the drain current at the monitoring time point is less than the drain current standard value, the corresponding monitoring time point is recorded as a non-breakdown time point; It should be noted that the drain current standard value is set by those skilled in the art based on data characteristics and historical experience; All monitoring time points are integrated into a monitoring time series that includes breakdown time points and non-breakdown time points in chronological order. The monitoring time series is traversed, and the intervals where breakdown time points appear continuously are recorded as continuous segments. The longest continuous segment is extracted, and the number of breakdown time points in the longest continuous segment is counted. The proportion of breakdown time points in the longest continuous segment among the monitoring time points is calculated to obtain the avalanche occurrence value. For example, assuming that the monitoring time sequence is [N, N, B, B, N, B, B, B, B, N, B, B, B, N, B, N, N, N, N, N, N], N represents a non-breakdown time point, B represents a breakdown time point, the continuous segments in the monitoring time sequence are [B, B], [B, B, B, B], [B, B, B], the longest continuous segment is [B, B, B, B], and the number of consecutive breakdown time points in the longest continuous segment is 4; In some embodiments, the avalanche occurrence value is compared to an avalanche occurrence threshold: If the avalanche occurrence value is greater than or equal to the avalanche occurrence threshold, it means that avalanche breakdown occurs in the sub-region; If the avalanche occurrence value is less than the avalanche occurrence threshold, it means that no avalanche breakdown has occurred in the sub-region, and the pulse amplitude continues to increase; It should be noted that after continuing to increase the pulse amplitude to the maximum test voltage, the drain current is still less than the drain current standard value, and the MOSFET needs to be checked; Step 2: If avalanche breakdown occurs in the sub-region, apply the same pulse amplitude sequence to different locations in the sub-region and perform multiple avalanche energy tests to evaluate the reliability of the sub-region under avalanche conditions and locate the breakdown position in the sub-region; It should be noted that applying the same pulse amplitude sequence to different positions of the sub-region means dividing the sub-region into a plurality of different positions and applying the same pulse amplitude sequence to the different positions of the sub-region; Based on any avalanche energy test, the breakdown time points in the continuous segments are integrated into a breakdown time point sequence in chronological order. The first breakdown time point in the breakdown time point sequence is extracted and recorded as the avalanche triggering time point. The avalanche triggering time point refers to the critical time point when the sub-area suddenly changes from the normal working state to the avalanche breakdown state. The time point when the avalanche energy test starts is recorded as the initial time point. The drain current waveform and voltage waveform between the initial time point and the avalanche trigger time point are extracted from the oscilloscope by: Calculate the avalanche energy E, where Indicates the avalanche triggering time point, It represents the voltage corresponding to the monitoring time point t between the initial time point and the avalanche triggering time point, represents the drain current corresponding to the monitoring time point t between the initial time point and the avalanche triggering time point; Conduct multiple avalanche energy tests, integrate all avalanche trigger time points into an avalanche trigger time point sequence according to the avalanche energy test order, calculate the standard deviation of the avalanche trigger time point sequence using the standard deviation formula, calculate the mean of the avalanche trigger time point sequence using the mean formula, and use the coefficient of variation formula to compare the standard deviation and mean of the avalanche trigger time point sequence to obtain the avalanche trigger time point fluctuation value; All avalanche energies are integrated into an avalanche energy sequence according to the avalanche energy test order. The standard deviation of the avalanche energy sequence is calculated using the standard deviation formula. The mean of the avalanche energy sequence is calculated using the mean formula. The standard deviation and mean of the avalanche energy sequence are then compared using the coefficient of variation formula to obtain the avalanche energy fluctuation value. The drain current corresponding to the avalanche triggering time point is recorded as the breakdown current. All breakdown currents are integrated into a breakdown current sequence according to the avalanche energy test order. The standard deviation of the breakdown current sequence is calculated using the standard deviation formula. The mean of the breakdown current sequence is calculated using the mean formula. The standard deviation and mean of the breakdown current sequence are compared using the coefficient of variation formula to obtain the breakdown current fluctuation value. The avalanche breakdown stability index is obtained by weighted summing the fluctuation value of the avalanche triggering time point, the fluctuation value of the avalanche energy, and the fluctuation value of the breakdown current; In some embodiments, the avalanche breakdown stability index is compared to an avalanche breakdown stability index threshold: If the avalanche breakdown stability index is less than the avalanche breakdown stability index threshold, the reliability of the sub-region under avalanche conditions is high, and the position in the sub-region where the same pulse amplitude is applied is recorded as the normal position; If the avalanche breakdown stability index is greater than or equal to the avalanche breakdown stability index threshold, the reliability of the sub-region under avalanche conditions is low, and the position in the sub-region where the same pulse amplitude is applied is recorded as the breakdown position; The setting of the avalanche breakdown stability index has the following effects: Function 1: By integrating the fluctuation characteristics of avalanche trigger time, avalanche energy, and breakdown current, the stability of the sub-region under avalanche conditions is converted into a single value, which is used to judge the working consistency of the device under extreme working conditions; Function 2: The avalanche breakdown stability index represents the degree of discreteness of the breakdown characteristics during the avalanche breakdown process. The smaller the avalanche breakdown stability index, the lower the discreteness of the breakdown characteristics during the avalanche breakdown process. The sub-region has performed stably in multiple avalanche tests, indicating that the sub-region has high reliability under avalanche conditions. The technical solution of this embodiment is as follows: by dividing the MOSFET into several sub-regions, a single avalanche energy test is performed on the sub-region to determine whether avalanche breakdown will occur in the sub-region; if avalanche breakdown occurs in the sub-region, the same pulse amplitude sequence is applied to different positions of the sub-region, and multiple avalanche energy tests are performed to evaluate the reliability of the sub-region under avalanche conditions and locate the breakdown position in the sub-region; the present invention realizes accurate judgment of the working consistency of the device under extreme working conditions through weighted synthesis of multi-dimensional fluctuation characteristics, and provides an objective quantitative basis for reliability evaluation under extreme conditions; on the other hand, the size of the index is used to characterize the discreteness of the breakdown characteristics during the avalanche breakdown process. The smaller the index, the lower the discreteness of the triggering time, energy release and current conduction characteristics of the sub-region in multiple avalanche tests, and the higher the reliability. The breakdown position can then be located based on the index threshold, providing precise guidance for device process optimization, design improvement and failure analysis, effectively improving the efficiency and accuracy of the reliability evaluation of MOSFET under avalanche conditions, and reducing the failure risk in practical applications; Example 2 See also Figure 1 As shown, a reliability test and analysis method for MOSFET according to an embodiment of the present invention further includes the following steps: Step 3: If the reliability of the sub-region under avalanche conditions is low, the thickness of the breakdown position in the sub-region during multiple avalanche energy tests is measured using spectroscopic ellipsometer. The thickness of the sub-region at different breakdown positions is analyzed for uniformity to determine whether the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region. The thickness of the breakdown position in the sub-area during multiple avalanche energy tests is integrated into a thickness sequence according to the test order. The standard deviation of the thickness sequence is calculated using the standard deviation formula, the mean of the thickness sequence is calculated using the mean formula, and the coefficient of variation formula is used to calculate the ratio of the standard deviation of the thickness sequence to the mean to obtain the thickness variation coefficient. Extract the sub-regions with low reliability under avalanche conditions from all the sub-regions of MOSFET and record them as low reliability regions by: Calculate the Pearson correlation coefficient r between the thickness variation coefficient and the avalanche breakdown stability index, where represents the thickness variation coefficient of the i-th low reliability area, represents the mean coefficient of variation of thickness in all low reliability areas, The avalanche breakdown stability index indicating the low reliability region, represents the mean value of avalanche breakdown stability index of all low reliability regions; In some embodiments, the Pearson correlation coefficient between the thickness variation coefficient and the avalanche breakdown stability index is compared to a Pearson correlation coefficient threshold: If the Pearson correlation coefficient between the thickness variation coefficient and the avalanche breakdown stability index is greater than or equal to the Pearson correlation coefficient threshold, it means that the reliability of the sub-region under avalanche conditions is low due to the uneven thickness of the sub-region; If the Pearson correlation coefficient between the thickness variation coefficient and the avalanche breakdown stability index is less than the Pearson correlation coefficient threshold, it means that the low reliability of the sub-region under avalanche conditions is not caused by the uneven thickness of the sub-region, and further judgment is needed on other influencing factors, including temperature and interface state density; Step 4: If the reliability of the sub-region under avalanche conditions is low due to uneven thickness of the sub-region, the thickness uniformity of the sub-region with low reliability under avalanche conditions is controlled to enhance the reliability of the MOSFET sub-region under avalanche conditions; In the subsequent MOSFET production process, the thickness of different breakdown positions in the sub-region is substituted into the thickness and deposition power curve obtained by fitting, thereby obtaining the initial setting value of the deposition power at different breakdown positions in the sub-region during deposition in the low reliability region; By formula: Calculate the deposition power control value of the j-th breakdown position in the sub-region during deposition in the low reliability area The deposition power control value is sent to the deposition power adjustment module of the MOSFET to adjust the deposition power at different breakdown positions in the sub-region during deposition in the low-reliability region, thereby improving the thickness uniformity of the sub-region with low reliability under avalanche conditions and enhancing the reliability of the MOSFET sub-region under avalanche conditions. Where, It represents the initial setting value of the deposition power at the j-th breakdown position in the sub-region when depositing in the low reliability region. K represents the process sensitivity coefficient, which is calibrated through experiments. The thickness standard value of the sub-area is set by those skilled in the art based on historical experience. represents the thickness of the jth breakdown position in the sub-region when depositing in the low reliability region; The technical solution of this embodiment is as follows: if the reliability of a sub-region under avalanche conditions is low, the thickness of the breakdown position in the sub-region is measured by spectroscopic ellipsometer during multiple avalanche energy tests, and the thickness of different breakdown positions in the sub-region is analyzed for uniformity to determine whether the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region; if the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region, the thickness uniformity of the sub-region with low reliability under avalanche conditions is regulated to enhance the reliability of the MOSFET sub-region under avalanche conditions; the present invention uses high-precision thickness measurement and coefficient of variation analysis, combined with a significance test of the Pearson correlation coefficient, to accurately determine whether uneven thickness is the cause of low avalanche reliability, thereby improving the efficiency of failure analysis; based on a fitting curve of thickness and deposition power, the deposition power is dynamically controlled by the process sensitivity coefficient to achieve precise repair of the thickness uniformity of the low-reliability region, eliminate the avalanche breakdown instability problem caused by thickness differences at the source of the production process, effectively enhance the reliability of the MOSFET sub-region under extreme avalanche conditions, and improve the device performance consistency and long-term operating stability.

[0022] Example 3 See also Figure 2 As shown, a reliability test and analysis system for MOSFET according to an embodiment of the present invention includes the following modules: Single test module: By dividing the MOSFET into several sub-regions, a single avalanche energy test is performed on the sub-region to determine whether avalanche breakdown will occur in the sub-region; Reliability judgment module: If avalanche breakdown occurs in a sub-region, the same pulse amplitude sequence is applied to different locations in the sub-region, and multiple avalanche energy tests are performed to evaluate the reliability of the sub-region under avalanche conditions and locate the breakdown position in the sub-region; Uniformity Analysis Module: If the reliability of a sub-region under avalanche conditions is low, the thickness of the breakdown position in the sub-region is measured by spectroscopic ellipsometer during multiple avalanche energy tests. By performing uniformity analysis on the thickness at different breakdown positions in the sub-region, it is determined whether the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region; Regulation and Analysis Module: If the reliability of a sub-region under avalanche conditions is low due to uneven thickness of the sub-region, the thickness uniformity of the sub-region with low reliability under avalanche conditions is regulated to enhance the reliability of the MOSFET sub-region under avalanche conditions.

[0023] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A reliability test and analysis method for MOSFET, characterized by: include: By dividing the MOSFET into several sub-regions, a single avalanche energy test is performed on the sub-region to determine whether avalanche breakdown will occur in the sub-region; If avalanche breakdown occurs in a sub-region, the same pulse amplitude sequence is applied to different locations in the sub-region and multiple avalanche energy tests are performed to evaluate the reliability of the sub-region under avalanche conditions and locate the breakdown position in the sub-region; If the reliability of a sub-region under avalanche conditions is low, the thickness of the breakdown position in the sub-region is measured by spectroscopic ellipsometer during multiple avalanche energy tests. The thickness of the sub-region at different breakdown positions is analyzed for uniformity to determine whether the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region. If the reliability of the sub-region under avalanche conditions is low due to uneven thickness of the sub-region, the thickness uniformity of the sub-region with low reliability under avalanche conditions is regulated to enhance the reliability of the MOSFET sub-region under avalanche conditions.

2. A reliability testing and analysis method for MOSFET according to claim 1, characterized in that: The specific process of determining whether avalanche breakdown will occur in a sub-region is as follows: Based on any sub-region, the drain current at the monitoring time point is extracted. If the drain current is greater than or equal to the drain current standard value, the corresponding monitoring time point is recorded as the breakdown time point; otherwise, the corresponding monitoring time point is recorded as the non-breakdown time point. All monitoring time points are integrated into a monitoring time series including breakdown time points and non-breakdown time points in chronological order. The monitoring time series is traversed, and the intervals in which breakdown time points appear continuously are recorded as continuous segments. The longest continuous segment is extracted, and the proportion of the number of breakdown time points in the longest continuous segment among the monitoring time points is calculated to obtain the avalanche occurrence value; if it is greater than or equal to the avalanche occurrence threshold, it means that avalanche breakdown has occurred in the sub-area.

3. A reliability testing and analysis method for MOSFET according to claim 1, characterized in that: The specific process of evaluating the reliability of the sub-area under avalanche conditions is as follows: Conduct multiple avalanche energy tests to determine the fluctuation values ​​of avalanche triggering time, avalanche energy, and breakdown current; The fluctuation values ​​of the avalanche triggering time point, the avalanche energy fluctuation value, and the breakdown current fluctuation value are weighted and summed to obtain the avalanche breakdown stability index; if it is greater than or equal to the avalanche breakdown stability index threshold, the reliability of the sub-region under avalanche conditions is low, and the position where the same pulse amplitude is applied in the sub-region is recorded as the breakdown position.

4. A reliability testing and analysis method for MOSFET according to claim 3, characterized in that: The process of determining the fluctuation value at the avalanche triggering time point is as follows: The breakdown time points in the continuous segment are integrated into a breakdown time point sequence according to the time sequence, and the first breakdown time point in the breakdown time point sequence is extracted and recorded as the avalanche triggering time point; All avalanche triggering time points are integrated into an avalanche triggering time point sequence according to the avalanche energy test order, and the avalanche triggering time point fluctuation values ​​of all avalanche triggering time points in the avalanche triggering time point sequence are calculated using the coefficient of variation formula.

5. A reliability testing and analysis method for MOSFET according to claim 4, characterized in that: The process of determining the avalanche energy fluctuation value is as follows: The time point when the avalanche energy test starts is recorded as the initial time point. The drain current waveform and voltage waveform between the initial time point and the avalanche trigger time point are extracted from the oscilloscope by: Calculate the avalanche energy E, where Indicates the avalanche triggering time point, It represents the voltage corresponding to the monitoring time point t between the initial time point and the avalanche triggering time point, represents the drain current corresponding to the monitoring time point t between the initial time point and the avalanche triggering time point; All avalanche energies are integrated into an avalanche energy sequence according to the avalanche energy test order, and the avalanche energy fluctuation values ​​of all avalanche energies in the avalanche energy sequence are calculated using the coefficient of variation formula.

6. A reliability testing and analysis method for MOSFET according to claim 4, characterized in that: The process of determining the breakdown current fluctuation value is as follows: The drain current corresponding to the avalanche triggering time point is recorded as the breakdown current. All breakdown currents are integrated into a breakdown current sequence according to the avalanche energy test order. The breakdown current fluctuation values ​​of all breakdown currents in the breakdown current sequence are calculated using the coefficient of variation formula.

7. A reliability testing and analysis method for MOSFET according to claim 3, characterized in that: The specific process of determining whether the low reliability of the sub-region under avalanche conditions is caused by the uneven thickness of the sub-region is as follows: The thickness of the breakdown position in the sub-area during multiple avalanche energy tests is integrated into a thickness sequence according to the test order, and a uniformity analysis is performed to determine the thickness variation coefficient; The sub-regions with low reliability under avalanche conditions are extracted from all the sub-regions of the MOSFET and recorded as low-reliability regions. The Pearson correlation coefficient between the thickness variation coefficient and the avalanche breakdown stability index is calculated by taking the absolute value of the Pearson correlation coefficient formula. If it is greater than or equal to the Pearson correlation coefficient threshold, it means that the low reliability of the sub-region under avalanche conditions is caused by the uneven thickness of the sub-region.

8. A reliability testing and analysis method for MOSFET according to claim 7, characterized in that: The process of determining the thickness variation coefficient is as follows: The coefficient of variation of thickness of all thicknesses in the thickness sequence is calculated using the coefficient of variation formula.

9. A reliability testing and analysis method for MOSFET according to claim 7, characterized in that: The specific process of regulating the thickness uniformity of the sub-region with low reliability under avalanche conditions is as follows: In the subsequent MOSFET production process, the thickness of different breakdown positions in the sub-region is substituted into the thickness and deposition power curve obtained by fitting, thereby obtaining the initial setting value of the deposition power at different breakdown positions in the sub-region during deposition in the low reliability region; By formula: Calculate the deposition power control value of the j-th breakdown position in the sub-region during deposition in the low reliability area The deposition power control value is sent to the deposition power adjustment module of the MOSFET to adjust the deposition power at different breakdown positions in the sub-region when depositing in the low reliability area; Where, It represents the initial setting value of the deposition power at the j-th breakdown position in the sub-region when depositing in the low reliability region, K represents the process sensitivity coefficient, Indicates the thickness standard value of the sub-area, It represents the thickness of the jth breakdown position in the sub-region when the low reliability region is deposited.

10. A reliability test and analysis system for MOSFET, characterized in that: The system is used to perform the method according to any one of claims 1 to 9, and the system comprises: Single test module: By dividing the MOSFET into several sub-regions, a single avalanche energy test is performed on the sub-region to determine whether avalanche breakdown will occur in the sub-region; Reliability judgment module: If avalanche breakdown occurs in a sub-region, the same pulse amplitude sequence is applied to different locations in the sub-region, and multiple avalanche energy tests are performed to evaluate the reliability of the sub-region under avalanche conditions and locate the breakdown position in the sub-region; Uniformity Analysis Module: If the reliability of a sub-region under avalanche conditions is low, the thickness of the breakdown position in the sub-region is measured by spectroscopic ellipsometer during multiple avalanche energy tests. By performing uniformity analysis on the thickness at different breakdown positions in the sub-region, it is determined whether the low reliability of the sub-region under avalanche conditions is caused by uneven thickness of the sub-region; Regulation and Analysis Module: If the reliability of a sub-region under avalanche conditions is low due to uneven thickness of the sub-region, the thickness uniformity of the sub-region with low reliability under avalanche conditions is regulated to enhance the reliability of the MOSFET sub-region under avalanche conditions.

Images