Dummy Word Line Capacitive Coupling for SRAM Read/Write Assist

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Solution Overview

Problem

Integrated circuits, particularly memory chips like SRAM, face challenges in read and write operations due to process variations, leading to difficulties at certain corners (e.g., slow-fast and fast-slow corners), which existing read/write assist techniques often address at the cost of increased chip area and power consumption.

Innovation Solution

The integration of a dummy word line (DWL) capacitively coupled with the word line (WL) to assist in voltage control during read and write operations, using capacitive coupling to boost or reduce the WL voltage, thereby enhancing the performance without significant area or power penalties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dummy word line is added to provide read/write assist, then memory operation reliability is improved, but chip area increases

Engineering Contradiction:
Improvememory operation reliabilityVSAvoidchip area
Core Design Contradiction:
ReliabilityVSArea of stationary object

Solution Approach 1:

The patent introduces a dummy word line arranged in a different spatial dimension (parallel to the original word line) to provide capacitive coupling assistance. This dimensional addition enables read/write assist functionality without interfering with the original memory cell structure, resolving the contradiction between reliability improvement and area consumption.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Productivity

If existing read/write assist techniques are implemented, then memory performance is improved, but power consumption increases

Engineering Contradiction:
Improvememory performanceVSAvoidpower consumption
Core Design Contradiction:
ProductivityVSUse of energy by moving object

Solution Approach 1:

The dummy word line acts as an intermediary element that provides capacitive coupling to assist memory operations. By using this intermediate structure, the patent achieves improved memory performance through voltage boosting during read/write operations while consuming less power compared to traditional assist techniques that directly modify memory cell transistors.

Inventive Principle:
Principle #24Intermediary (Mediator)

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 improves the read and write assist capabilities of SRAMs by reducing the access time and increasing the noise margin, while maintaining efficiency and minimizing the impact on chip area and power consumption.

Implementation Method 1

a dummy word line arranged with the word line to have a capacitance therebetween

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 2

dummy word line means for affecting a voltage applied to the word line through a capacitive coupling therebetween

Methodology Applied
Scientific EffectCapacitive coupling: Capacitance

Data Source

PatentEP3050061B1Read/write assist for memories
Publication Date: 2017.04.19 QUALCOMM INC
  • EP3050061B1 patent drawingFigure 1
  • EP3050061B1 patent drawingFigure 2
  • EP3050061B1 patent drawingFigure 3

AI summary

An integrated circuit includes one or more bit cells, a word line coupled to the one or more bit cells, and a dummy word line arranged with the word line to have a capacitance therebetween. The capacitance provides a voltage boost or reduction of the word line to assist read and write operations.