Wordline RC Time-Constant Tracking Using Memory-Cell Thresholds
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Solution Overview
Problem
Existing memory devices face challenges in accurately measuring the RC time constant of individual wordlines due to limited access points, leading to unknown RC time constants for most wordlines, which hinders performance optimization and defect detection.
Innovation Solution
Implementing control logic within the memory device to internally measure the RC time constant by applying a measurement programming pulse to each wordline and reading the threshold voltage of memory cells along the wordline, using a lookup table to determine the RC time constant for each wordline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional external measurement methods are used for RC time constant, then measurement accessibility is limited, but measurement precision remains insufficient for individual wordlines
Solution Approach 1:
The patent introduces memory cells as intermediary elements to measure the RC time constant of wordlines. By programming memory cells with specific threshold voltages and reading their states after a predetermined time period, the system can indirectly measure the RC time constant of individual wordlines without requiring direct external access to the wordline electrical characteristics. This intermediary approach enables precise per-wordline measurement that would otherwise be inaccessible through traditional external methods.
Solution Approach 2:
The memory device performs self-measurement of its own RC time constants by utilizing its internal memory cells and control logic. The control logic programs specific memory cells, waits for a predetermined time period, then reads the cell states to determine RC time constants. This self-service capability eliminates the need for external measurement equipment and enables comprehensive characterization of all wordlines within the memory device.
2Productivity
If RC time constant measurement is implemented for all wordlines, then performance optimization improves, but device complexity increases
Solution Approach 1:
The patent makes the memory cells serve multiple functions: data storage and RC time constant measurement. The same memory cells used for storing user data are also utilized as measurement probes for characterizing wordline RC time constants. This multi-functionality approach avoids adding dedicated measurement hardware, thereby improving performance optimization capability while minimizing increases in device complexity.
Solution Approach 2:
The control logic dynamically adjusts programming parameters (threshold voltages, programming pulses) and measurement parameters (wait time periods, read voltages) to optimize RC time constant measurements for different wordlines. By changing these parameters based on measured RC values, the system achieves comprehensive performance optimization across all wordlines without requiring complex dedicated measurement circuitry for each wordline.
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
Enables precise determination and storage of RC time constants for each wordline, improving memory device performance by monitoring degradation, detecting defects, optimizing overdrive and underdrive performance, and optimizing programming time.
Implementation Method 1
Tracking RC time constant by wordline in memory devices - the RC time constant is a measure of the time it takes for a capacitor to charge or discharge through a resistor
Implementation Method 2
Tracking RC time constant by wordline in memory devices - the RC time constant is a measure of the time it takes for a capacitor to charge or discharge through a resistor
Data Source
AI summary
A memory device includes a memory array comprising a plurality of wordlines, and control logic, operatively coupled with the memory array. The control logic causes a measurement programming pulse to be sequentially applied to each of the plurality of wordlines of the memory array and determines respective threshold voltages stored in a number of memory cells associated with each of the plurality of wordlines. The control logic further determines a difference in the respective threshold voltages based on a location of the number of memory cells within each wordline and determines a respective resistance-capacitance (RC) time constant for each of the plurality of wordlines in view of the difference in the respective threshold voltages.