Memory Array Redundancy Selector for In-System Field Repair
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Solution Overview
Problem
Existing methods for in-system repair of memory arrays on integrated circuits are ineffective for addressing new failures that occur after the circuits have been operational for some time, as they do not allow for modification of redundancy information to substitute unused redundancy elements for failing array elements.
Innovation Solution
A method and apparatus for in-system redundant array repair on integrated circuits, which includes a control data selector between the fuse box and memory arrays, allowing external alternate control data to be applied, enabling the substitution of unused redundancy elements for failing ones, and is compatible with the IEEE1149.1 standard for in-system testing and diagnostics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuse information is decoded and transferred to memory arrays using a serial scan chain during manufacturing test, then redundant wordlines or bitlines can be substituted for failing elements, but the procedure is ineffective for fixing new failures that occur in the field
Solution Approach 1:
The patent makes the redundancy configuration dynamic by introducing a control data selector that can switch between fuse-loaded control data and externally supplied alternate control data. This allows the system to adapt to new failures in the field by updating the control data selector with new redundancy information, transforming a static manufacturing-time repair mechanism into a dynamic field-updatable system.
Solution Approach 2:
The control data selector acts as an intermediary component between the fuse box and the memory arrays. It receives control data from either the fuse box (during manufacturing) or an external source (in the field), and routes the appropriate control data to the memory arrays. This intermediary enables field repair capability without disrupting the original manufacturing test procedure.
2Manufacturing precision
If control data is fixed during manufacturing test, then redundancy elements can be configured for initial failures, but unused redundancy elements cannot be substituted for newly failing array elements
Solution Approach 1:
The control data selector enables dynamic reconfiguration of redundancy elements in the field. When a new failure occurs, external control data can be supplied to the selector, which then routes this new control data to the memory arrays, allowing unused redundancy elements to be substituted for newly failing elements while maintaining manufacturing precision.
Solution Approach 2:
The control data selector serves multiple functions: it routes control data from the fuse box during manufacturing test, and routes alternate control data from external sources in the field. This multi-functionality enables both manufacturing precision and field repairability through a single unified component.
3Adaptability or versatility
If a control data selector is added between the fuse box and memory arrays, then field repair capability is enabled, but device complexity increases
Solution Approach 1:
The control data selector is designed to perform multiple functions within a single component: it can receive control data from the fuse box during manufacturing and from external sources in the field. This multi-functionality minimizes the increase in device complexity while maximizing adaptability and repair capability.
Solution Approach 2:
The control data selector acts as a simple intermediary that adds minimal complexity to the system. It provides a clean interface between the existing fuse box/manufacturing infrastructure and new field repair capabilities, isolating the complexity of field repair functionality from the core memory array design.
Data Source
AI summary
Disclosed is a method of repairing an integrated circuit of the type comprising of a multitude of memory arrays and a fuse box holding control data for controlling redundancy logic of the arrays. The method comprises the steps of providing the integrated circuit with a control data selector for passing the control data from the fuse box to the memory arrays; providing a source of alternate control data, external of the integrated circuit; and connecting the source of alternate control data to the control data selector. The method comprises the further step of, at a given time, passing the alternate control data from the source thereof, through the control data selector and to the memory arrays to control the redundancy logic of the memory arrays.