SRAM SWT Redundancy Using Spare Circuits for Yield Recovery

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Solution Overview

Problem

Existing memory designs fail to effectively detect and repair defective synchronous-write-through (SWT) circuits, leading to overkill in SRAM yield due to treating such defects as fatal, despite their non-impact on normal SRAM function.

Innovation Solution

A memory design with built-in SWT redundancy and a modified test flow that includes fault analysis and soft repair using spare SWT circuits, optimizing area usage through hardware sharing and employing a cooperative-optimized scheme.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If a logic test is performed to detect defective SWT circuits, then test coverage is improved, but SRAM yield deteriorates because defective SWT circuits are treated as fatal defects

Engineering Contradiction:

Improvetest coverageVSAvoidSRAM yield

Core Design Contradiction:

Difficulty of detecting and measuringVSProductivity

Solution Approach 1:

The test flow is segmented into distinct phases: logic test phase for detecting SWT circuit defects, fault analysis phase for determining defect location, and memory test phase for assessing SRAM functionality. This segmentation allows selective repair based on defect location, preventing unnecessary discarding of functional SRAMs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A spare SWT circuit is introduced as an intermediary component to replace defective SWT circuits. The spare SWT circuit acts as a backup that can be activated through soft repair, allowing the SRAM to continue functioning even when the original SWT circuit is defective.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If spare SWT circuits are added to replace defective ones, then SRAM yield is improved, but device complexity increases

Engineering Contradiction:

ImproveSRAM yieldVSAvoidcircuit complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The spare SWT circuit is designed to be universally applicable, serving as a replacement for any defective SWT circuit in the array. This multi-functional design allows a single spare circuit to protect against multiple potential failure points, reducing the overall number of spare circuits needed.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Instead of discarding entire SRAMs with defective SWT circuits, the system recovers functionality by activating spare SWT circuits through soft repair. This approach discards only the defective SWT circuit component while recovering the overall SRAM functionality.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS12482529B2Memory with built-in synchronous-write-through redundancy and associated test method

Publication Date: 2025.11.25 MEDIATEK INC

AI summary

A memory with built-in synchronous-write-through (SWT) redundancy includes a plurality of memory input/output (IO) arrays, a plurality of SWT circuits, and at least one spare SWT circuit. The at least one spare SWT circuit is used to replace at least one of the plurality of SWT circuits that is defective.