FinFET Etching Uniformity via Sacrificial Layer Loading Effect
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Solution Overview
Problem
Existing FinFET devices face challenges in controlling etching uniformity due to the loading effect, which occurs when etching fin structures with different pattern densities, leading to mismatched etching rates and difficulties in maintaining uniformity of height and thickness across regions.
Innovation Solution
The implementation of a sacrificial layer with a higher-than-normal thickness over the fin structures to reduce the loading effect, maintaining a specific gap between the heights of the fin structures within a range of 0.4 nm to 4 nm, which helps in controlling the uniformity of deposited layers and improving the performance of the FinFET structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If etching is performed on fin structures with different pattern densities, then the etching process can be completed, but the loading effect causes non-uniform etching rates and difficulty in maintaining etching uniformity
Solution Approach 1:
A sacrificial layer is introduced as an intermediary material between the etching process and the fin structures. This sacrificial layer has different etching characteristics than the fin structures themselves, allowing the etching process to proceed uniformly across regions with different pattern densities. The sacrificial layer absorbs the loading effect variations, protecting the fin structures from non-uniform etching.
Solution Approach 2:
The etching process parameters are changed by performing selective etching in multiple stages. First, the sacrificial layer is etched with specific parameters optimized for that material. Then, the fin structures are etched with different parameters. This parameter change approach allows each material to be etched under optimal conditions, achieving overall process uniformity despite different pattern densities.
2Device complexity
If a normal thickness sacrificial layer is used, then the process is simpler, but the loading effect is not sufficiently reduced and fin height uniformity cannot be maintained within the desired gap range
Solution Approach 1:
A sacrificial layer with higher-than-normal thickness is deposited in advance before the fin structures are formed or before the critical etching steps. This preliminary action creates a buffer that compensates for the loading effect during subsequent etching processes. The excessive thickness ensures that even with etching variations, the final fin height uniformity remains within the desired 0.4 nm to 4 nm gap range.
Data Source
AI summary
Methods for forming the fin field effect transistor (FinFET) device structure are provided. The method includes forming first fin structures and second fin structures on a first region and a second region of a substrate, respectively, and a number of the first fin structures is greater than a number of the second fin structures. The method also includes forming a sacrificial layer on the first fin structures and the second fin structures and performing an etching process to the sacrificial layer to form an isolation structure on the substrate.