Semiconductor Feedback Capacitance Assessment via On-Resistance Ratios
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Solution Overview
Problem
Measuring feedback capacitance in semiconductor elements is time-consuming and prone to variations, leading to potential short-circuiting issues in bridge circuits due to manufacturing inconsistencies.
Innovation Solution
An assessment method that acquires and correlates avalanche voltage and on-resistance characteristics to accurately assess feedback capacitance, using ratios and distributions to screen semiconductor elements and reduce variations, thereby minimizing defects and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback capacitance is directly measured, then measurement accuracy is improved, but measurement time increases
Solution Approach 1:
The patent introduces an intermediary assessment method that uses easily measurable parameters (gate charge Qg, threshold voltage Vth, on-resistance Rds(on)) as mediators to indirectly evaluate feedback capacitance Crss. Instead of directly measuring Crss which is time-consuming, the method measures these intermediary parameters and uses their correlations to assess Crss, thereby reducing measurement time while maintaining assessment accuracy.
Solution Approach 2:
The patent changes the measurement parameters from directly measuring feedback capacitance Crss to measuring gate charge Qg, threshold voltage Vth, and on-resistance Rds(on). By changing to these alternative parameters that have strong correlations with Crss and can be measured more quickly, the patent resolves the contradiction between measurement accuracy and measurement time.
2Ease of manufacture
If feedback capacitance variations are not controlled, then manufacturing simplicity is maintained, but reliability deteriorates due to short-circuiting
Solution Approach 1:
The patent performs preliminary assessment of feedback capacitance characteristics before the semiconductor elements are assembled into bridge circuits. By measuring Qg, Vth, and Rds(on) and assessing Crss variations in advance, the patent identifies and excludes elements with excessive variations. This preliminary action prevents reliability issues from occurring in the first place, while maintaining manufacturing simplicity by using straightforward measurement and assessment procedures.
Solution Approach 2:
The patent implements a feedback mechanism where assessment results of Qg, Vth, and Rds(on) are used to evaluate Crss variations, and this information feeds back into the selection process for bridge circuit assembly. Elements that do not meet the assessment criteria are excluded, ensuring that only elements with acceptable Crss variations are used, thereby maintaining both manufacturing simplicity and high reliability.
3Reliability
If all semiconductor elements are screened, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent applies partial screening rather than screening every single element with exhaustive testing. By using the correlation between Qg, Vth, Rds(on), and Crss, the patent screens elements based on these measurable parameters and assesses Crss variations for a representative sample or selectively for elements that fail initial checks. This partial action approach maintains high reliability by catching defective elements while preserving productivity by avoiding unnecessary exhaustive screening of all elements.
Data Source
AI summary
To easily assess a feedback capacitance of a semiconductor element. An assessment method of assessing a feedback capacitance of a semiconductor element is provided, the assessment method including:acquiring a first characteristic correlated with the feedback capacitance and a second characteristic correlated with the feedback capacitance; andassessing the feedback capacitance based on the first characteristic and the second characteristic. The first characteristic may be a characteristic that corresponds to a withstanding voltage of the semiconductor element, and the second characteristic may be an on-resistance of the semiconductor element. In the assessing, the feedback capacitance may be assessed based on a ratio between the first characteristic and the second characteristic.