Flexible Decoder Reference Cell Selection for Memory Yield
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Solution Overview
Problem
Conventional fixed reference cell selection in non-volatile memory systems leads to manufacturing-related yield loss and non-ideal reference behavior due to manufacturing defects and location-dependent performance, resulting in performance degradation and increased errors during read operations.
Innovation Solution
Implementing a flexible decoder system that generates selection signals based on characteristics of interconnected cells in the reference array, allowing for programmable and adaptive selection of reference cells to optimize performance and reduce defects, thereby improving device reliability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed reference cell selection scheme is used, then the device structure is simple, but manufacturing yield is reduced and reference behavior is non-ideal
Solution Approach 1:
The patent implements a dynamic reference cell selection mechanism where the reference cell is not fixed but can be programmably selected based on operational requirements and measured characteristics. The system includes a programmable counter that can be loaded with different seed values to generate different reference cell selections, allowing the reference cell to change from static to dynamic based on actual device performance and manufacturing variations.
Solution Approach 2:
The patent changes the selection parameter from a fixed manufacturer-determined reference cell to a programmable reference cell selection based on measured characteristics such as threshold voltage distributions. The system measures actual device characteristics and uses these parameters to determine the appropriate reference cell, transforming the reference cell selection from a constant design parameter to a variable parameter that adapts to actual manufacturing results.
2Productivity
If the physical dimensions of floating gate transistors are reduced, then memory density is increased, but manufacturing defects increase
Solution Approach 1:
The patent applies local quality by measuring and characterizing specific local characteristics of individual memory cells (such as threshold voltage) and using this local information to determine appropriate reference cells for each cell. Instead of using a uniform fixed reference for all cells, the system tailors the reference cell selection to the specific characteristics of each local cell region, allowing for localized optimization that compensates for manufacturing variations introduced by dimension reduction.
Solution Approach 2:
The patent implements feedback by measuring the actual characteristics of memory cells after manufacturing and using these measurements to determine the reference cell selection. The system measures threshold voltage distributions and other characteristics, then feeds this information back into the reference cell selection process. This feedback loop allows the system to adapt to the actual quality and variations introduced by high-density manufacturing, selecting reference cells that compensate for the increased defect rates.
3Ease of manufacture
If a fixed reference cell is assigned to each operation type, then the system is easy to manufacture, but performance is degraded due to location-dependent defects
Solution Approach 1:
The patent implements self-service by enabling the system to automatically measure its own characteristics and determine appropriate reference cells without manual intervention. The system measures threshold voltage distributions and other characteristics of the memory cells, then autonomously selects the most suitable reference cells based on these measurements. This self-service approach replaces manual manufacturer assignment with an automated process that adapts to actual device characteristics, improving reference behavior accuracy while maintaining ease of manufacture through programmable selection.
Data Source
AI summary
An exemplary system includes an array of interconnected cells and a flexible decoder. The array is configured to receive a selection signal as input, select a cell based upon the selection signal, and provide an output based on the selected cell. The flexible decoder is configured to receive an input, generate a selection signal based on the input and one or more characteristics of the array of interconnected cells, and provide the selection signal to the array of interconnected cells.