Discrete Backside Openings for 3D Memory Stress Distribution
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Solution Overview
Problem
The existing methods for forming three-dimensional semiconductor devices using backside replacement openings lead to unidirectional stress on the substrate, causing distortion and reducing the process window for subsequent lithography steps due to the use of elongated backside trenches, which results in significant substrate bowing and mechanical stress issues.
Innovation Solution
The use of discrete backside openings instead of elongated backside trenches for replacing sacrificial material layers with electrically conductive layers, distributing mechanical stress omnidirectionally and reducing unidirectional stress on the substrate, thereby minimizing substrate distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If elongated backside trenches are used for replacing sacrificial material layers, then the replacement process can be completed, but unidirectional stress is applied to the substrate causing distortion and reducing the process window for subsequent lithography steps
Solution Approach 1:
The patent divides the continuous backside trench into multiple discrete, separated openings. This segmentation allows stress to be distributed omnidirectionally across the substrate rather than concentrated in a unidirectional manner, reducing substrate distortion while still enabling complete replacement of sacrificial material layers with electrically conductive layers
2Ease of manufacture
If elongated backside trenches are used, then sacrificial material can be replaced with electrically conductive layers, but significant substrate bowing and mechanical stress issues occur
Solution Approach 1:
By segmenting the backside trench into discrete openings, the mechanical stress applied to the substrate during material replacement is distributed across multiple localized points rather than applied continuously along a long trench. This maintains substrate mechanical stability while enabling complete replacement of sacrificial material
Solution Approach 2:
The discrete openings are strategically positioned and sized to provide localized stress distribution points. Each opening creates a localized replacement zone that minimizes overall substrate distortion while achieving the global goal of complete sacrificial material replacement
3Manufacturing precision
If discrete backside openings are used instead of elongated trenches, then stress is distributed omnidirectionally reducing substrate distortion, but the replacement process complexity increases
Solution Approach 1:
The segmentation of the backside trench into discrete openings simplifies the stress distribution mechanism while maintaining replacement effectiveness. Although the number of openings increases, each individual opening is simpler in geometry and easier to process than a single continuous trench, reducing overall process complexity
Data Source
AI summary
Memory openings and backside openings are formed through an alternating stack of insulating layers and sacrificial material layers over a substrate. Memory opening fill structures are formed in the memory openings, and sacrificial backside opening fill structures are formed in the backside openings. Cavities are formed in volumes of the backside openings by removing the sacrificial backside opening fill structures. Remaining portions of the sacrificial material layers are replaced with material portions including electrically conductive layers. Each electrically conductive layer is formed as a continuous material layer including holes around the backside openings. Each electrically conductive layer is singulated into a plurality of electrically conductive strips by isotropically recessing the electrically conductive layers around each backside opening. Width-modulated cavities including expanded volumes of the backside openings are formed, and are filled with width-modulated insulating wall structures.