Memory Access Line Structure Reducing Disturb

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Solution Overview

Problem

DRAMs experience significant access line disturb due to voltage on active access lines affecting inactive memory cells, leading to inefficiencies in memory operations.

Innovation Solution

The solution involves reshaping the access line saddle profile, repositioning active chop mask areas, and altering fin shape and size to reduce the distance between passing and active access lines, using different materials for shallow trench isolation regions and forming shallower access lines to minimize disturb effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the access line saddle profile is reshaped and the distance between passing and active access lines is reduced, then memory cell isolation is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvememory cell isolationVSAvoidaccess line structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The access line structure is segmented into distinct regions: active access line portions and passing access line portions. This segmentation allows each portion to be optimized independently - the active portions maintain proper voltage levels for memory cell operation while the passing portions are positioned at greater distances or with modified profiles to minimize disturb effects on inactive memory cells.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the access line are given different geometric qualities and positioning. The active access line portions have profiles optimized for electrical performance, while the passing access line portions use modified saddle profiles with adjusted curvature and positioning to reduce capacitive coupling and voltage disturb to inactive memory cells.

Inventive Principle:

Principle #3Local quality

2Object-affected harmful factors

If shallower access lines are formed to minimize disturb effects, then access line disturb is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improveaccess line disturbVSAvoidaccess line depth control

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent employs preliminary isolation structures and sacrificial layers that are formed before the access lines. These pre-formed structures define the precise depth and profile of the access lines, allowing shallower passing access lines to be formed with controlled depth without requiring extreme precision in the access line formation process itself.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Intermediary structures such as isolation materials and sacrificial layers are introduced between the substrate and the access lines. These intermediaries serve as depth references and physical barriers that automatically limit the depth of passing access lines, reducing disturb effects while transferring precision requirements to the formation of these intermediary structures rather than the access lines themselves.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS9761590B1Passing access line structure in a memory device

Publication Date: 2017.09.12 MICRON TECHNOLOGY INC

AI summary

A method for memory device fabrication includes forming a plurality of continuous fins on a substrate. An insulator material is formed around the fins. The continuous fins are etched into segmented fins to form exposed areas between the segmented fins. An insulator material is formed in the exposed areas wherein the insulator material in the exposed areas is formed higher than the insulator material around the fins. A metal is formed over the fins and the insulator material. The metal formed over the exposed areas is formed to a shallower depth than over the fins.