IGBT ON Voltage Uniformity via Annealing Feedback
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Solution Overview
Problem
Variations in ON voltages of main chips obtained from a semiconductor wafer pose a challenge in manufacturing semiconductor devices, as they affect the performance and efficiency of devices like IGBT elements.
Innovation Solution
The method involves forming recombination centers on a semiconductor wafer using prescribed radioactive rays or ions, measuring ON voltages of smaller semiconductor elements, and controlling annealing treatments to stabilize and equalize the ON voltages of larger semiconductor elements, ensuring uniformity and desired performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If recombination centers are formed by emitting radioactive rays or ions to define lifetimes of semiconductor elements, then lifetimes can be controlled, but variations in ON voltages of main chips still occur
Solution Approach 1:
The patent applies parameter changes by systematically varying annealing treatment parameters (temperature, time, atmosphere) to control the recovery degree of carrier lifetimes. By adjusting these parameters, the invention achieves precise control over ON voltage values, transforming the relationship between lifetime recovery and electrical characteristics to eliminate variations in main chips' ON voltages.
Solution Approach 2:
The patent implements feedback control by measuring the ON voltages of second semiconductor elements (test elements) and using these measurements to determine the appropriate annealing treatment parameters for the first semiconductor elements (main chips). This closed-loop approach ensures that variations in main chips are eliminated by continuously adjusting the annealing process based on actual measured values from test elements.
2Duration of action of stationary object
If annealing treatment is applied to recover lifetimes after recombination center formation, then carrier lifetimes are restored, but ON voltage variations among chips persist
Solution Approach 1:
The patent applies local quality by differentiating the treatment approach between test elements and main chips. Second semiconductor elements (test elements) are used to locally assess the actual lifetime recovery status through ON voltage measurements, while first semiconductor elements (main chips) receive customized annealing treatment based on these local measurements. This localized quality control approach ensures each main chip achieves the desired ON voltage specification.
Solution Approach 2:
The patent implements preliminary action by first forming recombination centers to define baseline lifetime characteristics, then performing preliminary annealing treatment to recover lifetimes. Subsequent measurements of test elements guide further adjustments, ensuring that main chips receive the precise treatment needed before final characterization. This staged preliminary approach prevents ON voltage variations by addressing issues before final device completion.
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
This approach effectively reduces variations in ON voltages, leading to more uniform and efficient semiconductor devices with improved performance, particularly in applications like three-phase motors.
Implementation Method 1
Prescribed radioactive rays or prescribed ions are emitted all over the surface of the semiconductor wafer. Recombination centers are formed in the first semiconductor elements and the second semiconductor elements.
Implementation Method 2
The semiconductor wafer is subjected to a prescribed annealing treatment. The lifetimes of the first semiconductor elements and the lifetimes of the second semiconductor elements are recovered.
Data Source
AI summary
A semiconductor wafer having IGBT elements and transistors formed on a surface thereof is prepared. Electron beams are emitted all over the surface of the semiconductor wafer. Recombination centers are formed in the IGBT elements and the transistors. ON voltages of the transistors are measured by a measurement device, and lifetimes defined in the IGBT elements and the transistors are recovered by a prescribed annealing treatment. When the lifetimes are recovered, a control device controls an annealing treatment amount in the annealing treatment based on the measured ON voltages of the transistors such that ON voltages of the IGBT elements are each equal to a desired ON voltage. Variations in the ON voltages of a plurality of IGBT elements obtained from the semiconductor wafer are reduced.