FinFET Fin Profile Control via Mandrel Template and Epitaxial Growth
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Solution Overview
Problem
Existing methods for fabricating multi-fin structures in advanced integrated circuits face challenges in fin height control, fin profile precision, and stress-induced distortion due to oxide quality and etch stability issues, leading to suboptimal device performance and increased fabrication costs.
Innovation Solution
A semiconductor structure and method involving shallow trench isolation (STI) features and epitaxial growth of fin features with controlled hard mask formation and chemical mechanical polishing (CMP) processes to achieve precise fin profiles and reduced capacitive coupling, allowing for enhanced fin feature geometry and electrical isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If oxide recess is used to define fin height, then fin height can be controlled, but fin height control becomes highly sensitive to oxide quality, etch stability and fin bottom oxide shape variations
Solution Approach 1:
The patent introduces a mandrel structure as an intermediary element that mediates the fin formation process. The mandrel serves as a physical template that directly defines fin dimensions through its geometry, eliminating the need for oxide recess to control fin height. This intermediary structure transfers the dimension control function from the oxide layer to the mandrel itself, which can be precisely formed and maintained throughout the process.
Solution Approach 2:
The mandrel is formed in advance before the fin structure is created. By preliminarily establishing the dimensional template (mandrel) with precise geometry, the subsequent fin formation process inherits this precision without being subject to variations in oxide quality or etch stability. The preliminary mandrel structure pre-determines the fin dimensions, making the process more robust.
2Reliability
If shallow trench isolation (STI) deposition and anneal are performed, then electrical isolation is achieved, but stress is induced causing fin distortion
Solution Approach 1:
The patent segments the isolation function from the fin structure by introducing separate mandrel-defined regions. The mandrel structures create distinct, isolated fin regions that are self-contained and electrically isolated by their geometric separation and the intervening dielectric material. This segmentation allows electrical isolation to be achieved through spatial separation rather than stress-induced STI, thereby preventing fin distortion.
3Ease of manufacture
If a single etch step is used to define fin profile, then fabrication complexity is reduced, but fin profile control becomes difficult resulting in taper shapes
Solution Approach 1:
The mandrel structure serves as an intermediary template that defines the desired fin profile geometry. By forming the mandrel with the target profile (e.g., rectangular cross-section), the subsequent fin formation process automatically replicates this profile through conformal deposition or direct copying. This intermediary template enables precise profile control without requiring complex multi-step etching sequences.
Solution Approach 2:
The fin structure is formed as a copy or replica of the mandrel geometry. The mandrel's shape, dimensions, and profile are directly transferred to the fin structure through the formation process. This copying mechanism ensures that the fin profile precisely matches the mandrel template, achieving accurate profile control (such as rectangular shapes with sharp corners) without the need for complex etching processes.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach enables improved fin profile control, reduced stress-induced distortion, and enhanced device performance while lowering fabrication costs by ensuring consistent and precise multi-fin structure formation.
Implementation Method 1
epitaxial growth of fin features
Implementation Method 2
chemical mechanical polishing (CMP) processes
Data Source
AI summary
A method of forming a fin field effect transistor (FinFET) structure including forming a plurality of shallow trench isolation (STI) features in a semiconductor substrate, thereby defining a plurality of bulk-semiconductor areas separated from each other by the STI features. The method then forms a first hard mask layer on the semiconductor substrate, the first hard mask layer being patterned to have a plurality of openings over one of the bulk-semiconductor areas. A second semiconductor material is then grown on the semiconductor substrate within the plurality of openings of the first hard mask layer, thereby forming a multi-fin active region having multiple fin features within the one of the bulk-semiconductor areas.