Wiggled Backside Contact Vias for 3D Memory Stress Distribution
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Solution Overview
Problem
Current three-dimensional memory devices face challenges in efficiently forming backside contact via structures that provide adequate mechanical stability and prevent die cracking, particularly due to stress accumulation from deposited metallic layers and substrate thinning.
Innovation Solution
The implementation of wiggled backside contact via structures, which laterally offset along a second horizontal direction perpendicular to the primary direction, and the use of multiple planes with laterally offset backside contact via structures, helps in distributing stress and preventing die cracking by creating a more uniform stress distribution across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional straight backside contact via structures are used, then the manufacturing process is simple, but stress accumulates and causes die cracking
Solution Approach 1:
The backside contact via structure is segmented into multiple lateral portions offset along the second horizontal direction, creating a stepped or zigzag pattern that distributes stress across different locations rather than concentrating it in a single straight path
Solution Approach 2:
The via structure is extended from a single-dimensional straight line into a multi-dimensional offset pattern by adding lateral displacement along the second horizontal direction, effectively using an additional spatial dimension to distribute mechanical stress
2Area of stationary object
If substrate is thinned to reduce device size, then device footprint is reduced, but mechanical stability decreases and die cracking increases
Solution Approach 1:
The offset via structure is designed in advance to compensate for the reduced mechanical strength caused by substrate thinning, creating a stress-distributing geometry that cushions against potential die cracking before it occurs
3Reliability
If metallic layers are deposited to form contacts, then electrical connectivity is improved, but stress accumulation increases leading to die cracking
Solution Approach 1:
The metallic contact layers are segmented into multiple offset portions along the second horizontal direction, distributing the stress from deposited metallic layers across different locations rather than concentrating it along a single straight contact path
Data Source
AI summary
A three-dimensional memory device includes a plurality of planes, each having a respective alternating stack, strings of memory stack structures which extends through the respective alternating stack, and backside contact via structures vertically extending through the respective alternating stack, extending generally along the first horizontal direction, and laterally separating neighboring pairs of strings of memory stack structures along a second horizontal direction. A first plane includes a first plurality of strings that are laterally spaced apart along the second horizontal direction by a first plurality of backside contact via structures. A second plane laterally shifted from the first plane along the first horizontal direction and including a second plurality of strings that are laterally spaced apart along the second horizontal direction by a second plurality of backside contact via structures which are laterally offset with respect the first plurality of backside contact via structures along the second horizontal direction.