Open Digit Memory Repair Using End Array Redundancy
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Solution Overview
Problem
Open digit line architectures in semiconductor memory devices underutilize extra digit lines, leading to wasted semiconductor real estate and differing noise characteristics between wrapped and straight digit lines, which affects the performance and reliability of memory arrays.
Innovation Solution
The use of extra digit lines in full-size end arrays as repair cells to create redundant memory locations in core arrays, allowing for the repair of faulty memory cells by activating redundant memory bits in end arrays, thereby enhancing the utilization of available semiconductor space and improving signal-to-noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If open digit line architecture is used to increase memory array utilization, then core array utilization is improved, but end arrays waste semiconductor real estate by using only half of available digit lines
Solution Approach 1:
The patent applies multi-functionality by enabling end arrays to serve dual purposes: normal memory operations and repair operations. The end arrays are configured with additional digit lines that can be activated to provide repair functionality, allowing the same physical structure to fulfill multiple roles and eliminate wasted semiconductor real estate.
Solution Approach 2:
The patent implements self-service by using the memory device's own end arrays as repair resources. Instead of requiring external repair mechanisms or complete redundant blocks, the system utilizes its unused digit lines in end arrays to automatically repair faulty memory cells, making the system self-repairing and eliminating the need for additional repair infrastructure.
2Manufacturing precision
If wrapped digit lines are used in end arrays to match capacitive loading, then capacitive loading matching is improved, but noise characteristics differ from straight digit lines in core arrays
Solution Approach 1:
The patent applies local quality by configuring digit lines with different characteristics in different locations. End arrays use wrapped digit lines optimized for their specific capacitive loading requirements, while core arrays use straight digit lines. This localized optimization allows each region to have the appropriate digit line configuration for its specific needs without compromising overall system performance.
Solution Approach 2:
The patent uses sense amplifiers as intermediaries between the wrapped digit lines in end arrays and the rest of the memory system. The sense amplifiers buffer and condition the signals, isolating the noise characteristics of wrapped digit lines from the core array operations and allowing capacitive loading matching without propagating noise issues throughout the system.
3Ease of repair
If complete redundant blocks are used for repair, then repair capability is improved, but device complexity and area increase
Solution Approach 1:
The patent applies partial action by implementing repair functionality in end arrays rather than creating complete redundant blocks. Instead of duplicating entire memory blocks for repair purposes, the system activates only the necessary portions (end arrays with additional digit lines) to provide repair capability, reducing the overall complexity and area requirements while maintaining effective repair functionality.
Solution Approach 2:
The patent merges the normal operation function and repair function into the same end array structures. Rather than separating repair functionality into distinct redundant blocks, the system combines both functions in the end arrays, allowing them to serve as both operational memory and repair resources, thereby reducing device complexity and eliminating the need for separate repair infrastructure.
Data Source
AI summary
A memory with extra digit lines in full size end arrays with an open digit architecture, which can use the extra digit lines to form repair cells. In one example, folded digit sense amplifiers are connected to an end array with an open digit architecture such that each sense amplifier corresponds to a group of four digit lines. Two digit lines of the group connect to two open digit sense amplifiers and the other two digit lines connect to the corresponding folded digit sense amplifier. A repair method can be performed on memories including the end arrays with folded digit sense amplifiers. A row in a core array including a replaceable IO is activated and a row in an end array is activated. The repair cells in the end array can be sensed by the folded digit sense amplifiers to generate a replacement IO, which is selected rather than the replaceable IO.