MOS Capacitor Interface State Density Measurement via Frequency-Dependent Series Resistance
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Solution Overview
Problem
Current methods for measuring interface state density, such as the charge pumping method, face challenges in accuracy due to small recombination currents and current leakage in semiconductor devices with decreasing critical dimensions and high-k dielectric materials, leading to inaccurate average measurements.
Innovation Solution
A conductance technique is employed that models a series resistor relevant to frequency, allowing for the optimization of parasitic component modeling and elimination of interference, enabling accurate simulation and measurement of interface state density by biasing a MOS capacitor structure and using a Gp-G model to calculate series resistor values at predetermined scanning frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the charge pumping method is used to measure interface state density, then the measurement can be performed on semiconductor devices, but the measurement accuracy deteriorates due to small recombination currents and current leakage in devices with decreasing critical dimensions and thin gate oxide
Solution Approach 1:
The patent extracts and separates the gate oxide leakage current from the total measured current by measuring it independently through a separate capacitor structure with identical gate oxide. This allows the leakage current to be subtracted from the charge pumping current, eliminating its harmful effect on measurement accuracy in devices with thin gate oxide
Solution Approach 2:
The patent introduces an auxiliary capacitor structure as an intermediary to measure the gate oxide leakage current. This intermediary structure has identical gate oxide characteristics but without the interface states being measured, serving as a reference to isolate and quantify the leakage component
2Measurement precision
If the charge pumping method is used to measure interface state density, then the measurement can be performed on semiconductor devices, but the measurement accuracy deteriorates due to insufficient device accuracy in small devices with decreasing critical dimensions
Solution Approach 1:
The patent segments the total current into distinct components: charge pumping current, gate oxide leakage current, and displacement current. By measuring and separating these components individually, the method achieves accurate interface state density measurement even when the recombination current is very small in devices with decreasing critical dimensions
3Measurement precision
If the conventional conductance technique with fixed parasitic components is used, then the measurement can be performed, but the measurement accuracy deteriorates due to the influence of series components and inability to measure interface state inside high-k dielectric material
Solution Approach 1:
The patent transforms the fixed, frequency-independent parasitic component model into a dynamic, frequency-dependent model. By measuring the capacitor structure at multiple frequencies and extracting the series resistance value that minimizes the real part of impedance, the method adapts to different measurement conditions and accurately characterizes interface states in high-k dielectric materials
Solution Approach 2:
The patent changes the measurement parameter from fixed parasitic components to frequency-dependent series resistance. By varying the measurement frequency and corresponding the series resistance value to each frequency, the method achieves accurate measurement of interface state density in high-k dielectric materials where fixed component models fail
Data Source
AI summary
The present invention provides a method for measuring the interface state density by a conductance technique. In particular, the method comprises: biasing a MOS capacitor structure to be measured in an accumulation region, measuring the MOS capacitor structure under a fixed bias voltage and at predetermined scanning frequencies in the accumulation region by using a Gp-G model, and calculating the values of the series resistor at respective predetermined scanning frequencies to obtain a series resistor model; obtaining an accurate model in an inversion region from the series resistor model varying with the predetermined scanning frequencies obtained in the accumulation region and obtaining the measurement results of interface state according to the accurate model.