Jogged Spacer NOR Flash Self-Alignment

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Solution Overview

Problem

In traditional NOR flash memory architectures using self-aligned contact (SAC) techniques, drain contacts are only self-aligned perpendicular to wordlines, requiring a masking step for isolation in the direction parallel to wordlines, which complicates the process and limits scaling.

Innovation Solution

Implementing a virtual ground architecture with staggered source contacts and jogged or kinked spacers that self-align both parallel and perpendicular to wordlines, eliminating the need for a masking step and allowing for larger contact dimensions, enabling scaling to smaller nodes like the 32 nm node.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If self-aligned contact techniques are used with traditional spacers, then vertical self-alignment is achieved, but additional masking steps are required for horizontal isolation

Engineering Contradiction:

Improvevertical self-alignment precisionVSAvoidmasking step complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The spacer structure is extended from providing only vertical self-alignment to providing both vertical and horizontal self-alignment by adding jogged or kinked portions that protrude in the horizontal direction, eliminating the need for additional masking steps

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The spacer structure performs multiple functions including vertical isolation, horizontal isolation, and self-alignment in both directions, allowing the contact holes to be self-aligned without requiring external masking processes

Inventive Principle:

Principle #25Self-service

2Ease of manufacture

If traditional spacer structures are used, then simple fabrication is maintained, but contact dimensions are limited and scaling is restricted

Engineering Contradiction:

Improvefabrication simplicityVSAvoidcontact dimension control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The spacer is divided into multiple segments including a first portion and a second portion with jogged or kinked configurations, allowing independent optimization of each segment for both fabrication ease and precise contact dimension control

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The spacer incorporates jogged or kinked portions with curved or angled geometries that enable larger contact dimensions while maintaining self-alignment, facilitating scaling to smaller nodes like 32 nm

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Device complexity

If contacts are not self-aligned in the direction parallel to wordlines, then spacer structure remains simple, but isolation requires additional masking steps

Engineering Contradiction:

Improvespacer structure complexityVSAvoidmanufacturing efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The spacer structure is designed to perform multiple functions simultaneously: vertical isolation, horizontal isolation, and self-alignment in both vertical and horizontal directions, eliminating the need for separate masking operations and improving manufacturing efficiency

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8754463B2High density NOR flash array architecture

Publication Date: 2014.06.17 MICRON TECHNOLOGY INC

AI summary

In one embodiment of the invention, a memory includes wordline jogs and adjacent spacers. Spacers from different wordlines may contact one another on either side of a drain contact and consequently isolate and self-align the contact in the horizontal and vertical directions.