Funnel-Shaped Isolation Structure for Memory Reliability

Solution Overview

Problem

In semiconductor memory devices, excessively small isolation structures can cause mutual interference during programming, leading to reliability issues, while excessively large structures can decrease gate coupling ratio (GCR), thereby lowering device performance.

Innovation Solution

A memory structure with a funnel-shaped isolation structure, comprising a first and second isolation layer and a lining layer, where the second isolation layer has a recess, ensuring the top profile is shaped as a funnel, protecting the sidewall of the dielectric layer and increasing GCR.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the height of isolation structures is increased to prevent mutual interference during programming, then reliability is improved, but gate coupling ratio (GCR) decreases and device performance is lowered

Engineering Contradiction:

ImprovereliabilityVSAvoiddevice performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The isolation structure is divided into multiple segments: a first isolation layer with greater height extending beyond the dielectric layer top surface, and a second isolation layer with lesser height formed within a recess of the first isolation layer. This segmentation allows different portions to serve different functions - the taller first layer provides isolation for reliability, while the recessed second layer preserves gate coupling for performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the isolation structure are given different heights and properties. The first isolation layer has greater height at the edges to provide isolation, while the second isolation layer has lesser height in the recessed region to maintain gate coupling. This local differentiation resolves the contradiction between isolation height and gate coupling.

Inventive Principle:

Principle #3Local quality

2Productivity

If the height of isolation structures is decreased to improve gate coupling ratio, then device performance is improved, but mutual interference during programming occurs and reliability is deteriorated

Engineering Contradiction:

Improvedevice performanceVSAvoidreliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The isolation structure is divided into multiple segments: a first isolation layer with greater height extending beyond the dielectric layer top surface, and a second isolation layer with lesser height formed within a recess of the first isolation layer. This segmentation allows different portions to serve different functions - the taller first layer provides isolation for reliability, while the recessed second layer preserves gate coupling for performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the isolation structure are given different heights and properties. The first isolation layer has greater height at the edges to provide isolation, while the second isolation layer has lesser height in the recessed region to maintain gate coupling. This local differentiation resolves the contradiction between isolation height and gate coupling.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If conventional planar isolation structures are used, then manufacturing is simple, but they cannot simultaneously ensure adequate isolation height and gate coupling ratio

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidisolation effectiveness

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The isolation structure is divided into multiple segments: a first isolation layer with greater height extending beyond the dielectric layer top surface, and a second isolation layer with lesser height formed within a recess of the first isolation layer. This segmentation allows different portions to serve different functions - the taller first layer provides isolation for reliability, while the recessed second layer preserves gate coupling for performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The isolation structure transitions from a conventional planar single-layer design to a multi-layer structure with vertical dimensionality. The first isolation layer extends higher, while the second isolation layer is recessed, creating a stepped profile that adds vertical complexity to simultaneously satisfy both isolation height and gate coupling requirements.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS10847612B2Method of manufacturing memory structure

Publication Date: 2020.11.24 WINBOND ELECTRONICS CORP

AI summary

A method of manufacturing a memory structure including the following steps is provided. Stacked structures are formed on a substrate, and each of the stacked structures includes a first dielectric layer and a first conductive layer sequentially disposed on the substrate. A first opening is located between two adjacent stacked structure, and the first opening extends into the substrate. At least one isolation structure is formed in the first opening. The isolation structure covers a sidewall of the first dielectric layer. The isolation structure has a recess therein, such that a top profile of the isolation structure is shaped as a funnel. A second dielectric layer is formed on the stacked structures. A second conductive layer is formed on the second dielectric layer and fills the first opening.