Dummy Fin Isolation Etching for Lower-Aspect-Ratio Semiconductor Fabrication
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Solution Overview
Problem
Current semiconductor device fabrication processes face challenges in scaling down device sizes, leading to increased complexity and defects, which affect device performance and fabrication costs, particularly in non-planar transistor architectures like FinFETs and GAAFETs, where precise etching and isolation are critical.
Innovation Solution
A three-step etching process is employed to form semiconductor devices, including a first etch to align the top surface of semiconductor fins with the isolation region, a second etch to create a recess in the isolation region adjacent to the fins, and a third etch to remove the fins and etch into the substrate, reducing the aspect ratio and improving the process window and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional single-step etching process is used to remove fins and etch substrate, then the process is simple and fast, but the aspect ratio is high leading to poor process window and low yield
Solution Approach 1:
The etching process is divided into three sequential steps: (1) first etch to remove top portions of fins, (2) second etch to recess isolation region, and (3) third etch to remove remaining fins and etch substrate. This segmentation reduces the aspect ratio during fin removal, improving the process window and yield while maintaining overall productivity.
Solution Approach 2:
The first etch step performs preliminary removal of top portions of fins before the main fin removal step. This preliminary action reduces the fin height that needs to be removed in the third etch, thereby reducing the aspect ratio and improving the process window for the critical substrate etching step.
2Productivity
If device geometry size is scaled down to increase functional density, then production efficiency increases and costs decrease, but device performance degradation and fabrication complexity increase
Solution Approach 1:
The multi-step etching process segments the fin removal and substrate etching operations, allowing precise control at each stage. This segmentation enables maintaining reliable fin structures during scaling by carefully controlling the aspect ratio reduction, thereby preserving device performance while enabling continued scaling for high productivity.
Solution Approach 2:
The process changes physical parameters (etch depth, etch selectivity, aspect ratio) through sequential steps. By adjusting these parameters in each etch step, the process maintains optimal conditions for fin integrity and substrate etching quality, ensuring device reliability even as geometry scales down.
3Device complexity
If the isolation region is not recessed before fin removal, then the process is simpler, but the aspect ratio for fin removal is high reducing yield
Solution Approach 1:
The second etch step performs a preliminary recession of the isolation region before the main fin removal and substrate etching. This preliminary action creates a tapered profile that reduces the aspect ratio, improving yield. The principle of performing preparatory action in advance is applied to optimize the subsequent critical etching step.
Data Source
AI summary
A semiconductor device includes a semiconductor substrate; an isolation region disposed on the semiconductor substrate; a plurality of dummy fins disposed over the isolation region and partially extending into the isolation region; and a dielectric material disposed between the plurality of dummy fins, and partially extending through the isolation region and partially into the semiconductor substrate.