FinFET Fin Height Control via Dual STI Segmentation
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Solution Overview
Problem
Conventional FinFET fabrication processes result in fin-shaped structures being lower than surrounding shallow trench isolation due to over-etching, affecting the formation of epitaxial layers.
Innovation Solution
A method involving the formation of a first and second shallow trench isolation (STI) around fin-shaped structures, where part of the fin-shaped structures and first STI are removed to create a height difference, allowing the top surfaces of the fin-shaped structures to be higher than the first STI and lower than the second STI, facilitating epitaxial layer growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional FinFET fabrication process is used to form recesses after removing part of fin-shaped structures, then epitaxial layer growth space is provided, but the fin-shaped structures become lower than the surrounding shallow trench isolation due to over-etching
Solution Approach 1:
The shallow trench isolation is divided into two distinct types: a first STI formed between fin-shaped structures and a second STI formed around the fin-shaped structures. This segmentation allows different height levels for different STI regions, enabling the fin-shaped structures to be positioned at appropriate heights relative to each STI type without over-etching damage.
Solution Approach 2:
Different regions of the isolation structure are given different properties: the first STI is removed partially to create a lower top surface, while the second STI is maintained at a higher top surface. This local differentiation in height and material removal allows the fin-shaped structures to achieve proper height positioning for epitaxial layer growth without the harmful effects of uniform over-etching.
2Ease of manufacture
If fin-shaped structures are made lower than surrounding STI to accommodate epitaxial layer growth, then epitaxial layer can be formed, but the control over channel regions and current is reduced
Solution Approach 1:
By segmenting the STI into first and second types with different height levels, the invention enables the fin-shaped structures to maintain adequate height for reliable channel control while still providing sufficient space for epitaxial layer growth. The first STI (lower) provides growth space, while the second STI (higher) serves as a reference that prevents excessive fin structure removal.
Solution Approach 2:
The dual-STI structure acts as an intermediary reference system that mediates between the conflicting requirements of epitaxial layer growth space and fin structure height control. The second STI serves as a protective reference that prevents over-etching, while the first STI provides the necessary growth space, together enabling both epitaxial formation and reliable device performance.
Data Source
AI summary
A method for fabricating semiconductor device is disclosed. The method includes the steps of: providing a substrate having a plurality of fin-shaped structures thereon; forming a first shallow trench isolation (STI) between the fin-shaped structures and a second STI around the fin-shaped structures; removing part of the fin-shaped structures; and removing part of the first STI so that the top surfaces of the fin-shaped structures are higher than the top surface of the first STI and lower than the top surface of the second STI.