Scanning Probe Microscope with Feature Point Voltage Detection
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Solution Overview
Problem
Scanning nonlinear dielectric microscopes (SNDMs) face disturbances from stray capacitance and charging issues, leading to reduced measurement sensitivity and variability in results due to ambient environment effects.
Innovation Solution
A scanning probe microscope configuration that includes a probe, positioning unit, excitation unit, resonance unit, frequency demodulator, lock-in amplifier, and feature point voltage detecting unit, which generates a differential capacitance signal and applies a DC bias voltage to minimize disturbance impact, allowing for accurate electrical characteristic measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SNDM is used to detect small capacitance changes, then measurement sensitivity is improved, but measurement results become highly sensitive to ambient environment and disturbance
Solution Approach 1:
The patent applies preliminary action by performing a calibration measurement on a reference sample before measuring the actual sample. The system first measures the capacitance of a reference sample with known characteristics, establishes a baseline relationship between applied voltage and capacitance, and uses this calibration data to compensate for subsequent measurements. This preliminary calibration step eliminates the need for repeated measurements and ensures consistent results regardless of ambient environmental changes.
Solution Approach 2:
The system implements feedback by continuously monitoring the measured capacitance values and comparing them against expected values based on the measurement voltage. When deviations are detected (indicating environmental disturbances or drift), the system adjusts the measurement parameters or applies correction factors to maintain measurement accuracy. This feedback mechanism ensures that measurement results remain reliable even when ambient conditions change.
2Ease of manufacture
If surface charging occurs during polishing or oxide film formation, then sample processing is completed, but C-V curve shifts in voltage direction and differential capacitance signal changes
Solution Approach 1:
The patent measures the flat-band voltage of the sample before performing any surface processing such as polishing or oxide film formation. This preliminary measurement establishes the initial voltage reference point. After processing, the system compares the new C-V curve against this reference and calculates the voltage shift caused by surface charging. This allows the system to compensate for the charging effects and maintain measurement accuracy throughout the manufacturing process.
3Reliability
If multiple measurements are performed to ensure accuracy, then measurement reliability improves, but measurement time increases
Solution Approach 1:
The patent performs a single calibration measurement on a reference sample to establish the voltage-capacitance relationship, rather than requiring multiple repeated measurements for each sample. The calibration data obtained from this preliminary action is then used to rapidly assess subsequent samples. This approach reduces the total measurement time while maintaining high reliability through the use of standardized reference comparisons.
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 configuration enables precise measurement of electrical characteristics with reduced impact from disturbances, ensuring consistent results even for charged samples by detecting and compensating for voltage shifts, thereby stabilizing the measurement process.
Implementation Method 1
a resonance unit configured to output a frequency modulation signal obtained by converting a change of a capacitance of the measurement sample or the standard sample into a change of a resonant frequency
Implementation Method 2
a lock-in amplifier configured to output a differential capacitance signal obtained by extracting a frequency component and a harmonic component of the excitation frequency included in the demodulated signal
Data Source
AI summary
A scanning probe microscope that includes a probe, a positioning unit configured to position a probe on a measurement sample, an excitation unit configured to excite the measurement sample at a predetermined frequency, a resonance unit configured to output a frequency modulation signal by converting a change of a capacitance of the measurement sample, a lock-in amplifier configured to output a differential capacitance signal obtained by extracting a predetermined frequency component and a harmonic component of the predetermined frequency of the demodulated signal, a conversion unit configured to output data indicative of a relationship between a voltage applied to the measurement sample and the capacitance, a detecting unit that detects a voltage value corresponding to a feature point of the relationship data, and a main measurement control unit that measures electrical characteristics of the measurement sample subjected to a DC bias voltage substantially equal to the feature point voltage.