Nanosheet Sag Prevention via Intermediary Support Structures
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Solution Overview
Problem
In long-channel nanosheet devices, sagging of nanosheets or nanowires can occur due to their long span, reducing vertical spacing and potentially causing them to touch, which existing techniques have not effectively addressed.
Innovation Solution
The formation of supporting structures, such as pinhole or I-beam configurations, by creating a stack of alternating active and sacrificial layers, patterning features, filling with resistant materials, and selectively etching sacrificial layers to suspend active layers, thereby preventing sagging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the span of nanosheets or nanowires is made long for long-channel devices, then the channel length is increased, but the nanosheets/nanowires sag reducing vertical spacing and potentially causing them to touch
Solution Approach 1:
Support structures are formed at specific locations along the nanosheet/nanowire span before the nanosheets/nanowires are suspended. These support structures are preliminarily positioned to provide mechanical support and prevent sagging during subsequent processing steps, thereby maintaining vertical spacing in long-channel devices without requiring post-fabrication adjustments
Solution Approach 2:
Support structures serve as intermediary elements between the substrate and the suspended nanosheets/nanowires. These intermediaries provide mechanical support to counteract gravitational and stress-induced sagging, maintaining the required vertical spacing between adjacent nanosheets/nanowires throughout the device fabrication process and operation
Data Source
AI summary
Techniques for providing supporting structures for suspended nanosheets/wires in long-channel devices are provided. In one aspect, a method of forming a device structure includes: forming a series of alternating active and sacrificial layers as a stack on a substrate; patterning at least one feature through each of the active and sacrificial layers in the stack; filling the feature with a fill material that is resistant to etching performed on the sacrificial layers; and etching the sacrificial layers to selectively remove at least a portion of each of the sacrificial layers from the stack thereby suspending the active layers, wherein following the etching the fill material remains as a structure supporting the suspended active layers. Transistor devices and methods for formation thereof are also provided.