Dielectric Layer EOT Measurement Using AC Scanning Capacitance
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Solution Overview
Problem
Conventional capacitance-voltage measurements to determine equivalent oxide thickness (EOT) of dielectric layers are inaccurate due to leakage currents induced by direct-current (DC) voltages.
Innovation Solution
A method using scanning capacitance microscopy to calculate EOT without DC voltages by employing impedance ratios and silicon dioxide layers to determine the impedance ratio of silicon dioxide layers and high-k dielectric layers, avoiding leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC voltage is applied to measure equivalent oxide thickness by conventional capacitance-voltage measurement, then the measurement can be performed, but leakage current is generated which makes the analysis result inaccurate
Solution Approach 1:
The patent extracts and eliminates the DC voltage component from the measurement system, retaining only AC voltage. This removes the source of leakage current while preserving the capacitance measurement capability through AC impedance analysis at different frequencies
Solution Approach 2:
The patent replaces the conventional DC-based capacitance measurement system with an AC-based impedance measurement system. By using AC voltage and analyzing impedance at different frequencies, the system achieves equivalent oxide thickness measurement without generating leakage current
2Ease of manufacture
If conventional capacitance-voltage measurement is used to determine equivalent oxide thickness, then the measurement process is simple, but the result is affected by leakage current and becomes inaccurate
Solution Approach 1:
The patent changes the measurement parameters from DC voltage to AC voltage with varying frequencies. By measuring impedance at multiple frequencies and analyzing the frequency-dependent behavior, the system accurately determines equivalent oxide thickness while avoiding leakage current issues
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
Accurately determines EOT of dielectric layers without DC voltage interference, expanding the applicability of scanning capacitance microscopy.
Implementation Method 1
By the scanning capacitance microscopy, a modulation voltage is applied to the first semiconductor capacitor and the second semiconductor capacitor to periodically vary the widths of the first depletion region and the second depletion region and a first scanning capacitance microscopic signal and a second scanning capacitance microscopic signal respectively corresponding to the first semiconductor capacitor and the second semiconductor capacitor are measured
Data Source
Figure 1(a)
Figure 1(b)
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AI summary
In a method for obtaining the equivalent oxide thickness of a dielectric layer, a first semiconductor capacitor including a first silicon dioxide layer and a second semiconductor capacitor including a second silicon dioxide layer are provided and a modulation voltage is applied to the semiconductor capacitors to measure a first scanning capacitance microscopic signal and a second scanning capacitance microscopic signal. According to the equivalent oxide thicknesses of the silicon dioxide layers and the scanning capacitance microscopic signals, an impedance ratio is calculated. The modulation voltage is applied to a third semiconductor capacitor including a dielectric layer to measure a third scanning capacitance microscopic signal. Finally, the equivalent oxide thickness of the dielectric layer is obtained according to the equivalent oxide thickness of the first silicon dioxide layer, the first scanning capacitance microscopic signal, third scanning capacitance microscopic signal, and the impedance ratio.