FinFET Seed Layer Uniform Epitaxial Growth
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Solution Overview
Problem
The challenge in fabricating semiconductor devices is the abnormal growth of epitaxial layers on fin field effect transistors (FinFETs) due to differences in fin pitches and widths, leading to non-uniform shapes and crystal orientations, which complicates subsequent processing steps.
Innovation Solution
A method is developed where a seed layer is formed using directional deposition after partially removing the fin, and an epitaxial layer is grown on this seed layer, with the epitaxial layer having a higher concentration of stress material than the seed layer, to improve carrier mobility and prevent non-uniform growth by ensuring uniform crystal orientation across the fin structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If epitaxial layer is grown directly on fins with varying pitches and widths, then carrier mobility can be improved through stress application, but non-uniform growth and abnormal crystal orientation occur
Solution Approach 1:
A seed layer is formed on the fins before growing the epitaxial layer. This preliminary seed layer provides a uniform crystal orientation template that prevents abnormal growth during subsequent epitaxial layer formation, ensuring uniform growth despite variations in fin pitch and width.
Solution Approach 2:
The seed layer acts as an intermediary between the fin structure and the epitaxial layer. It mediates the crystal growth process by providing a controlled interface that ensures uniform epitaxial layer formation while maintaining the stress application needed for carrier mobility improvement.
2Reliability
If fin structure is used to reduce short channel effects, then transistor performance is improved, but subsequent processing becomes complicated due to varying fin pitches and widths
Solution Approach 1:
The seed layer serves multiple functions simultaneously: it provides crystal orientation control for uniform epitaxial growth, acts as a stress transmission layer for carrier mobility enhancement, and serves as a buffer that simplifies subsequent processing by creating a uniform surface regardless of fin geometry variations.
3Speed
If stress material is applied to improve carrier mobility, then transistor speed increases, but non-uniform stress distribution occurs due to fin geometry variations
Solution Approach 1:
The seed layer is formed with controlled local properties including graded composition and varying thickness to match the local fin geometry. This ensures uniform stress distribution across the epitaxial layer while maintaining the high carrier mobility needed for fast transistor operation.
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
This approach enhances the performance of FinFETs by maintaining uniform epitaxial layer growth and stress application, improving carrier mobility and reducing processing complexities associated with varying fin pitches and widths.
Implementation Method 1
A seed layer is formed by crystallizing amorphous material
Implementation Method 2
An epitaxial layer is formed on the seed layer
Data Source
AI summary
A semiconductor device is provided. At least two active fins protrude from a substrate. A gate pattern crosses the at least two active fins, covering part of each active fin. A seed layer is disposed on other part of the each active fin. The other part of the each active fin is not covered with the gate pattern. An epitaxial layer is disposed on the seed layer.