Charge Distribution Extraction in Charge-Trapping Memory
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Solution Overview
Problem
Current methods for determining the spatial distribution of charge in non-volatile charge-trapping memory devices, such as NROM, face challenges due to poor endurance and retention properties, and existing techniques like Charge-Pumping are inaccurate when interface traps are non-uniform, especially after multiple program/erase cycles.
Innovation Solution
A method involving two charge-pumping measurements with varying base-level and top-level voltage measurements is used to extract the spatial distribution of charge in the charge-trapping layer and interface traps, allowing for accurate characterization of charge retention and optimization of device performance by accounting for interface degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge-pumping measurements are used to extract lateral distribution of charge, then charge distribution information can be obtained, but measurement accuracy deteriorates due to non-uniform interface traps after multiple program/erase cycles
Solution Approach 1:
The patent divides the charge distribution extraction into two separate measurements: one for electrons and one for holes. By segmenting the measurement process and using different voltage polarities, the method can independently characterize electron and hole distributions even when interface traps are non-uniform, thereby maintaining measurement accuracy despite interface degradation
Solution Approach 2:
The patent changes the voltage polarity parameter between measurements to selectively extract different charge carrier distributions. By applying positive voltage for electron measurement and negative voltage for hole measurement, the method can distinguish between electron and hole contributions to the overall charge distribution, enabling accurate extraction despite non-uniform interface traps
2Measurement precision
If interface traps are non-uniform after multiple program/erase cycles, then device degradation occurs, but accurate charge distribution extraction becomes impossible using conventional charge-pumping techniques
Solution Approach 1:
The patent uses feedback by comparing measurements taken with different voltage polarities. By measuring charge distribution with both positive and negative voltage applications and comparing the results, the method can identify and compensate for interface trap effects, enabling accurate charge distribution extraction even when interface traps are non-uniform due to device degradation
3Ease of operation
If conventional charge-pumping technique is used, then measurement simplicity is maintained, but measurement accuracy deteriorates due to sensitivity to interface degradation
Solution Approach 1:
The patent merges two charge-pumping measurements taken with opposite voltage polarities to extract separate electron and hole distributions. By combining the information from both measurements, the method maintains operational simplicity while achieving accurate charge distribution extraction that is insensitive to interface trap non-uniformity
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 enables precise extraction of electron and hole distributions in the charge-trapping layer and interface traps, improving the understanding and optimization of charge-trapping devices by accurately accounting for electrical stress effects.
Implementation Method 1
One method to determine the lateral distribution of charge in MOSFET-type devices is the technique known as Charge-Pumping (CP). This method was initially developed to study hot-carrier-induced degradation mechanisms in MOSFET-type devices.
Implementation Method 2
Charge-pumping measurements are a powerful technique for obtaining information on the charge trapped in a MOSFET-type device by scanning the threshold voltage along the channel of the device.
Data Source
AI summary
A method is described for extracting the spatial distribution of charge stored in a charge-trapping layer of a semiconductor device. The method comprises the steps of performing a first charge-pumping measurement on a device under test using a variation of the upper level of the pulse and performing a second charge-pumping measurement on this device using a variation of the lower level of the pulse. The data obtained is combined for extracting the spatial distribution. This is done by establishing a relation between a charge pumping current Icp and a calculated channel length Lcalc of the semiconductor device by reconstructing spatial charge distribution estimates from the charge pumping curves for multiple values of the charge pumping current Icp. From these multiple values of Icp the value is obtained for which the corresponding calculated channel length Lcalc is substantially equal to the effective channel length Leff of the semiconductor device and the spatial charge distribution is reconstructed from the charge pumping curves using the obtained value of Icp.