3D Memory Backside Passivation Structure for Crack Resistance

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Solution Overview

Problem

Existing three-dimensional memory devices face challenges in achieving a crack-resistant backside passivation structure, which is crucial for maintaining device reliability and performance.

Innovation Solution

The proposed solution involves a three-dimensional memory device with a backside passivation structure that includes a backside isolation layer with specific horizontally-extending portions and connecting portions, and a backside connection pad structure with a unique configuration to enhance mechanical stability and reduce stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional backside passivation structure is used, then the device structure is simple, but cracks and voids occur in the passivation dielectric material reducing reliability

Engineering Contradiction:

Improvedevice reliabilityVSAvoidbackside passivation structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The backside isolation layer is divided into multiple horizontally-extending portions (first, second, third portions) with different lateral extents, creating a segmented structure that distributes stress and prevents crack propagation while maintaining device reliability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The backside connection pad structure includes a connecting portion that extends laterally beyond the vertically-extending portion, adding a horizontal dimension to the pad structure. This lateral extension provides stress relief and prevents void formation in the passivation dielectric material

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Strength

If the backside connection pad structure is made larger to improve stability, then mechanical stability improves, but the lateral distance between inner and outer sidewalls increases creating more void space

Engineering Contradiction:

Improvemechanical stabilityVSAvoidvoid space in passivation dielectric

Core Design Contradiction:

StrengthVSVolume of stationary object

Solution Approach 1:

The backside isolation layer is configured with different horizontal extents at different locations: the first portion extends further laterally than the second portion, which in turn extends further than the third portion. This localized variation provides stress distribution without creating excessive void space

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20250169070A1Three-dimensional memory device including crack-resistant backside passivation structure and methods of forming the same

Publication Date: 2025.05.22 SANDISK TECHNOLOGIES LLC

AI summary

A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers, a three-dimensional array of memory elements embedded in the alternating stack, a dielectric material portion located adjacent to the alternating stack, connection via structures vertically extending through the dielectric material portion, a backside connection pad cavity vertically extending through the source layer, a backside isolation layer, and a backside connection pad structure including a proximal portion contacting end surfaces of the connection via structures. The backside connection pad structure includes a tapered connecting portion overlying a stepped connecting portion of the backside isolation layer, or dummy regions which do not contact the end surfaces of the connection via structures.