Memory Device Weak Cell Detection via Word Line Activation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing memory devices face challenges in detecting weak cells efficiently, leading to decreased yield and potential errors due to the high probability of weak cells in densely integrated semiconductor memory devices, which are difficult to identify through precise testing.
Innovation Solution
A memory device and operating method that activate multiple word lines together to share charges and determine weak cells based on bit line voltage, allowing for a one-time test to identify weak cells by comparing voltages, thereby shortening the test time needed to detect weak cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all memory devices including weak cells are handled as fails to ensure reliability, then device reliability is improved, but manufacturing yield decreases
Solution Approach 1:
The patent segments the memory device testing process into two phases: an initial weak cell detection phase that identifies devices with weak cells, and a subsequent reliability evaluation phase that determines whether devices with detected weak cells can still meet reliability requirements. This segmentation allows the system to distinguish between devices that truly fail reliability and those that can be salvaged, thereby improving yield while maintaining reliability standards.
Solution Approach 2:
The patent changes the evaluation parameter from a binary pass/fail based on weak cell presence to a more nuanced assessment that considers the magnitude and impact of weak cell effects on overall device reliability. By introducing new evaluation parameters such as voltage threshold deviations and retention time margins, the system can accurately assess whether weak cells actually compromise device reliability, allowing more devices to be qualified.
2Measurement precision
If traditional single word line testing is used to detect weak cells, then measurement precision is maintained, but test time increases
Solution Approach 1:
The patent merges multiple word line testing operations into a single integrated test by simultaneously activating multiple word lines and observing their combined effect on bit line voltages. This merging approach maintains detection precision because the simultaneous activation creates a cumulative voltage effect that amplifies weak cell signatures, making them easier to detect while reducing the total number of test cycles required.
Solution Approach 2:
The patent transitions from one-dimensional sequential word line testing to multi-dimensional parallel testing by activating multiple word lines simultaneously across different bit lines. This dimensional change allows the system to test multiple memory locations in parallel, effectively compressing the test time while maintaining the ability to detect weak cells through voltage analysis.
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 significantly reduces the time required to detect weak cells by grouping word lines, enhancing the reliability of semiconductor memory devices by identifying weak cells more efficiently and reducing the likelihood of errors.
Implementation Method 1
sharing charges between memory cells coupled to the same bit line among memory cells coupled to the activated word lines and the bit line
Implementation Method 2
determining whether or not a weak cell exists, based on a voltage of a bit line corresponding to the activated word lines
Data Source
AI summary
A memory device includes a plurality of word lines; a plurality of bit lines; a plurality of memory cells, each memory cell coupled to a corresponding word line among the plurality of word lines and a corresponding bit line among the plurality of bit lines; and a control block suitable for controlling at least two word lines among the plurality of word lines to be activated together, and determining whether or not a weak cell exists, based on a voltage of a bit line corresponding to the activated word lines.