Selective Epitaxy for FinFET Gap Filling
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Solution Overview
Problem
The increasing aspect ratio of recesses in fin field-effect transistors poses a challenge in filling semiconductor material, leading to voids and seams due to difficulties in gap filling during the formation of semiconductor fins in integrated circuits.
Innovation Solution
A bottom-up gap-filling method is employed, where a semiconductor seed layer is deposited and selectively etched back to create a basin shape, followed by selective epitaxy to grow a semiconductor region from the seed layer, reducing the trench aspect ratio and preventing voids, and additional seed layers and epitaxy regions are formed to fully fill the trench.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional gap filling is used, then the process is simple, but voids and seams occur due to high aspect ratio
Solution Approach 1:
The gap filling process is segmented into multiple cycles, each consisting of seed layer deposition, selective etching, and epitaxial growth. This segmentation allows the high aspect ratio trench to be filled incrementally, preventing voids and seams that would occur with conventional single-step filling methods.
Solution Approach 2:
A seed layer is deposited and selectively etched to create a basin shape at the bottom of the trench before the actual gap filling begins. This preliminary action prepares the trench geometry to facilitate subsequent epitaxial growth from the bottom up, ensuring complete filling without defects.
2Reliability
If bottom-up gap filling is used, then voids are prevented, but multiple processing steps are required
Solution Approach 1:
The bottom-up gap filling process uses continuous epitaxial growth from the seed layer at the trench bottom, ensuring that material is deposited in a continuous manner that prevents void formation. This continuous action maintains filling integrity throughout the multi-cycle process.
Solution Approach 2:
The gap filling is performed through periodic cycles of seed layer deposition, selective etching, and epitaxial growth. Each cycle advances the filling process incrementally, and the periodic repetition of these steps ensures complete filling while maintaining reliability, even though multiple steps are involved.
3Manufacturing precision
If selective etching is applied, then basin shape is formed for controlled growth, but additional etching steps are needed
Solution Approach 1:
Selective etching is applied locally at the trench bottom to create a basin shape, while leaving the sidewalls and top regions unchanged. This localized modification of the trench geometry provides controlled growth initiation points without requiring extensive etching of the entire structure, thereby achieving growth control with minimal additional steps.
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 method effectively reduces the aspect ratio of the trench, preventing voids and ensuring complete filling of the semiconductor material, thereby improving the integrity of the semiconductor fins in FinFETs.
Implementation Method 1
a semiconductor seed layer is grown on a silicon substrate
Implementation Method 2
selective epitaxy to grow a semiconductor region from the seed layer
Data Source
AI summary
A method includes etching a portion of a semiconductor material between isolation regions to form a trench, forming a semiconductor seed layer extending on a bottom surface and sidewalls of the trench, etching-back the first semiconductor seed layer until a top surface of the semiconductor seed layer is lower than top surfaces of the isolation regions, performing a selective epitaxy to grow a semiconductor region from the semiconductor seed layer, and forming an additional semiconductor region over the semiconductor region to fill the trench.