Word Line Resistance Sensing for Stacked Memory Reliability
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Solution Overview
Problem
As the number of stacked stages in vertically stacked nonvolatile memory devices increases, the height of metal contacts connected to word lines also increases, leading to resistance distribution issues and resistance defects, making it difficult to accurately measure line resistance and ensuring data reliability.
Innovation Solution
Incorporating a sensing capacitor and switch circuitry to measure line resistance by performing a charge sharing operation between the word line and the sensing capacitor, allowing for accurate detection of resistance defects and leakage current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of stacked stages is increased to improve integration, then memory capacity is improved, but resistance distribution increases and resistance defects occur
Solution Approach 1:
The patent applies preliminary action by measuring the line resistance of word lines before they are connected to memory cells. This pre-measurement allows defects to be detected early in the manufacturing process, before they can cause read errors during operation. The method involves temporarily connecting measurement circuitry to the open-node word lines and measuring resistance values to identify lines with abnormal resistance characteristics.
Solution Approach 2:
The patent replaces physical inspection or post-fabrication testing with an electrical measurement system. By using voltage application and current measurement circuits, the system can non-destructively assess the resistance characteristics of word lines without mechanical contact or damage to the stacked memory structure.
2Ease of operation
If traditional measurement methods are used for open node word lines, then measurement simplicity is maintained, but measurement accuracy deteriorates due to capacitive components
Solution Approach 1:
The patent applies preliminary action by pre-charging the word line to a known voltage level before performing the resistance measurement. This pre-charge step ensures that the capacitive component of the open-node word line is fully charged, allowing the subsequent measurement to accurately reflect the resistive characteristics rather than being influenced by transient capacitive effects.
Solution Approach 2:
The patent employs periodic action by using a multi-stage measurement sequence: first pre-charging the word line, then waiting for a predetermined time period to allow capacitive transients to settle, and finally measuring the voltage to calculate resistance. This time-based separation of capacitive charging from resistive measurement eliminates measurement errors caused by the capacitive nature of open-node word lines.
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 method enables the accurate measurement of line resistance and leakage current, effectively identifying potential defects in memory devices and ensuring data reliability by detecting resistive issues before they cause read errors.
Implementation Method 1
a sensing capacitor having a size proportional to a size of a word line capacitor associated with the selected word line
Implementation Method 2
performing a charge sharing operation between the selected word line and the sensing capacitor following the precharging of the selected word line, and measuring a voltage of the sensing capacitor
Data Source
AI summary
A memory device includes; a memory cell array including memory cells, a row decoder selecting a word line in response to a received address, and control logic including a sensing capacitor having a size proportional to a size of a word line capacitor associated with the selected word line. The control logic measures line resistance of the selected word line by precharging the selected word line, performing a charge sharing operation between the selected word line and the sensing capacitor following the precharging of the selected word line, and measuring a voltage of the sensing capacitor following the performing of the charge sharing operation.