3D Memory Source Layer Isolation Using Backside Trenches

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Solution Overview

Problem

Existing three-dimensional memory devices face challenges in effectively isolating source lines laterally, which affects the electrical performance and integration of memory elements.

Innovation Solution

The implementation of source line isolation structures and methods that involve forming alternating stacks of insulating and conductive layers laterally spaced by backside trenches, with specific trench fill structures and contact via configurations to achieve electrical isolation of source layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If source lines are laterally isolated using source line isolation structures with backside trenches and trench fill structures, then electrical isolation performance is improved, but device structure complexity increases

Engineering Contradiction:

Improveelectrical isolation performanceVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The source layer is divided into multiple isolated source line portions by introducing backside trenches that laterally separate them. Each source line portion is independently formed over different sets of memory openings, achieving lateral electrical isolation through physical segmentation of the source layer structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the device are assigned different structures: some backside trenches are filled with conductive material to form backside contact via structures that electrically connect to the source layer, while other backside trenches are filled with insulating material to provide electrical isolation. This local differentiation of trench fill properties enables both connectivity and isolation functions.

Inventive Principle:

Principle #3Local quality

2Productivity

If alternating stacks of insulating and conductive layers are formed laterally spaced by backside trenches, then memory element integration is improved, but manufacturing process complexity increases

Engineering Contradiction:

Improvememory element integrationVSAvoidmanufacturing process complexity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The backside trenches are formed and filled with appropriate materials (conductive or insulating) before the final source layer is completed. This preliminary preparation of the trench fill structures enables subsequent formation of the alternating stacks of insulating and conductive layers with proper lateral spacing, simplifying the overall manufacturing sequence.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The alternating stacks of insulating and conductive layers are formed within the spaces laterally defined by the backside trenches. The trench structures serve as lateral boundaries that contain and organize the alternating layer stacks, creating a nested configuration where the alternating layers are positioned within the trench-defined regions.

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS12456687B2Three-dimensional memory device with source line isolation and method of making the same

Publication Date: 2025.10.28 SANDISK TECHNOLOGIES LLC

AI summary

A memory device includes a horizontal source layer which is laterally separated into laterally isolated portions located in adjacent memory blocks by a dielectric backside trench fill structure or a source isolation dielectric structure.