Transistor Internal Capacitance Measurement Without Parasitic Turn-On

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Solution Overview

Problem

There is a need to accurately measure the internal capacitances, particularly the first internal capacitance, and the electric charge stored in transistor devices like MOSFETs and IGBTs, as they influence switching characteristics and parasitic-turn-on tendencies, which are crucial for device reliability.

Innovation Solution

A method involving applying a predefined voltage between load path nodes, measuring the voltage across the control node, and using an evaluation circuit to determine the capacitance and charge stored in the internal capacitances, allowing for measurement on a wafer level before separation into individual devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a voltage is applied between load path nodes to measure internal capacitance, then the capacitance value can be determined, but the transistor device may experience unintended switching or parasitic turn-on

Engineering Contradiction:

Improveinternal capacitance measurementVSAvoidtransistor switching control

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces an evaluation circuit as an intermediary between the voltage source and the transistor device. This evaluation circuit includes a controllable current source that charges the internal capacitances in a controlled manner, and a voltage sensor that measures the resulting voltage. The intermediary circuitry allows capacitance measurement without directly applying potentially harmful voltages that could cause unintended switching or parasitic turn-on of the transistor device.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies preliminary action by first charging the internal capacitances through a controlled current source before taking measurements. The current source is activated in a predetermined manner to charge the capacitances, and only after this controlled charging process does the voltage sensor measure the resulting voltage. This preliminary controlled charging action ensures that the capacitances are charged in a safe, controlled manner that prevents unintended switching while still enabling accurate measurement.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If voltage is applied to charge internal capacitances for measurement, then capacitance values can be determined, but energy is consumed in the charging process

Engineering Contradiction:

Improvecapacitance value determinationVSAvoidenergy consumption during measurement

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the conventional approach of using a voltage source to charge capacitances with an evaluation circuit that uses a controllable current source. Instead of directly applying voltage (which consumes energy and risks unintended switching), the current source charges the capacitances in a controlled manner. This substitution of the charging mechanism allows for energy-efficient capacitance measurement while maintaining measurement precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If measurement is performed on individual transistor devices, then accurate capacitance data is obtained, but measurement time and productivity are reduced

Engineering Contradiction:

Improvecapacitance measurement accuracyVSAvoidmeasurement throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent designs the evaluation circuit to be universally applicable to multiple transistor devices. The same evaluation circuit can measure the internal capacitances of different transistor devices by simply changing the device under test while keeping the evaluation circuitry the same. This universal design allows for efficient batch measurement of multiple devices without requiring separate measurement setups for each device, thereby improving productivity while maintaining measurement precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables precise determination of internal capacitances and charges, enhancing the understanding of transistor behavior and reliability, particularly by preventing unintended switching and ensuring safe operation during measurement.

Implementation Method 1

determining at least one of an electric charge stored in a first internal capacitance or a capacitance value of a first internal capacitance

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the electric charge stored in the first internal capacitance when a certain voltage is applied

Methodology Applied

Scientific EffectElectric charge storage: Electrical Accumulator

Data Source

PatentUS20260009830A1Method for measuring an internal capacitance of a transistor device

Publication Date: 2026.01.08 INFINEON TECHNOLOGIES AG

AI summary

A method includes applying a voltage with a predefined voltage level between a first load path node and a second load path node of a transistor device; measuring a voltage between a control node and the second load path node to obtain a voltage measurement value; and determining at least one of an electric charge stored in a first internal capacitance or a capacitance value of the internal capacitance effective between the first load path node and the control node based on the first voltage measurement value and based on a capacitance value of a second internal capacitance effective between the control node and the second load path node.