Charge Carrier Lifetime Measurement Probe
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Solution Overview
Problem
Current methods for measuring the lifetime of charge carriers in semiconductor on insulator structures face challenges such as improper electrical field definition, high leakage currents, and difficulty in separating substrate and semiconductor material contributions, leading to inaccurate results.
Innovation Solution
An apparatus and method that utilize a measuring probe with a predetermined spatial relationship between electrodes and the semiconductor structure to apply a well-defined bias voltage, combined with ultraviolet radiation to create excess minority carriers, and a microwave detector to measure reflectivity changes, while maintaining controlled electric field distribution and surface passivation to reduce recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a bias voltage is applied to measure charge carrier lifetime in semiconductor on insulator structures, then the measurement sensitivity is improved, but leakage currents increase causing measurement inaccuracy
Solution Approach 1:
The patent segments the electrical field application by using multiple electrodes positioned at specific locations (front surface and back surface of the semiconductor layer) to create a localized and controlled electric field only in the semiconductor layer, preventing field penetration into the insulator layer that would cause leakage currents while maintaining measurement sensitivity
Solution Approach 2:
The patent applies local quality by creating a controlled electric field distribution through strategically positioned electrodes that generate an electric field confined to the semiconductor layer region, providing local field enhancement for carrier separation while avoiding field-induced leakage in the insulator layer
2Reliability
If the electric field is not properly defined in the semiconductor structure, then the device complexity is reduced, but the measurement reliability deteriorates
Solution Approach 1:
The patent extracts the electric field generation function from a complex distributed system and implements it through discrete electrodes at specific positions, taking out only the essential field-generation points needed to define the electric field in the semiconductor layer without requiring complex field distribution structures
Solution Approach 2:
The patent applies preliminary action by pre-positioning electrodes at optimized locations before measurement to establish a well-defined electric field configuration, and by pre-passivating the semiconductor layer surface to eliminate surface recombination effects before the actual lifetime measurement begins
3Measurement precision
If substrate and semiconductor material contributions are not separated, then the measurement process is simplified, but the measurement precision of volume recombination lifetime deteriorates
Solution Approach 1:
The patent segments the signal contribution from substrate and semiconductor layer by using the insulator layer as an electrical barrier that prevents carrier injection from the substrate, and by positioning electrodes to generate electric field only in the semiconductor layer, enabling separate measurement of volume recombination lifetime in the semiconductor material
Solution Approach 2:
The patent uses the insulator layer as an intermediary element that electrically isolates the substrate from the semiconductor layer, preventing substrate carriers from interfering with the measurement, and using it as a reference structure to separate and identify the semiconductor layer's volume recombination characteristics
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 allows for precise measurement of charge carrier lifetime by ensuring a well-defined electric field and reduced leakage currents, providing accurate volume recombination lifetime measurements.
Implementation Method 1
irradiating the semiconductor structure with ultraviolet radiation... A laser pulse is applied to the wafer to generate electron-hole pairs in the wafer
Implementation Method 2
The reflectance of the wafer for the microwave radiation which is related to the concentration of charge carriers in the wafer, is monitored by measuring an intensity of the reflected microwave radiation
Implementation Method 3
the excess minority carriers can recombine with majority carriers, which leads to a decay of the reflectivity of the wafer for the microwave radiation
Data Source
AI summary
An apparatus for measuring a lifetime of charge carriers that has a measuring probe and a component for directing ultraviolet radiation to a measuring position. The measuring probe also includes at least one electrode provided at a predetermined spatial relationship to the measuring position. A microwave source is adapted to direct microwave radiation to the measuring position, a microwave detector is adapted to measure an alteration of an intensity of microwave radiation reflected at the measuring position in response to the ultraviolet radiation and a semiconductor structure holder is adapted to receive a semiconductor structure and to provide an electric contact to a portion of the semiconductor structure. Additionally, a device for moving the substrate holder relative to the measuring probe is provided for positioning at least one portion of the semiconductor structure at the measuring position. The apparatus includes a power source adapted to apply a bias voltage between the semiconductor structure holder and the electrode.