Selective Epitaxy on Fin Crystal Planes to Prevent Layer Merging
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Solution Overview
Problem
In semiconductor fabrication, particularly for FinFET devices, the lateral growth of epitaxial layers on narrow fins and vertical sidewalls leads to merging of diamond-shaped epitaxial layers, causing voids and device defects due to increased aspect ratios and reduced distance between features.
Innovation Solution
Simultaneous epitaxial film growth and etching on specific crystal planes ({100} and {110} planes) within a process chamber using precursor gases like silane and germanium tetrachloride, where growth occurs on {100} planes while etching occurs on {110} planes, preventing lateral growth and merging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If epitaxial layers are grown on narrow fins with high aspect ratios, then the volume for contact is increased, but lateral growth on sidewalls causes merging of epitaxial layers and formation of voids
Solution Approach 1:
The patent applies local quality by making the epitaxial growth rate and etching rate dependent on the local crystallographic orientation of the fin surfaces. Different crystal planes ({100} vs {110}) exhibit different growth and etching rates, enabling selective modification of epitaxial layer morphology at different locations. This local differentiation prevents lateral merging while maintaining vertical growth for contact volume.
Solution Approach 2:
The patent changes physical and chemical parameters of the epitaxial growth process, specifically controlling temperature, pressure, and gas composition to achieve different growth rates on different crystal planes. By adjusting these parameters, the process enables preferential growth on vertical surfaces while suppressing lateral growth on sidewalls.
2Manufacturing precision
If sequential growth and etching processes are used, then manufacturing precision is improved, but productivity is reduced due to multiple process steps
Solution Approach 1:
The patent merges the epitaxial growth and etching processes into a single simultaneous operation. By introducing precursor gases that undergo both deposition and etching reactions in the same process chamber at the same time, the method eliminates the need for separate sequential steps, thereby improving productivity while maintaining precision through crystal-plane-selective reactions.
Solution Approach 2:
The patent implements continuous useful action by maintaining simultaneous growth and etching throughout the process. The precursor gases continuously react on different crystal planes, with growth occurring on vertical surfaces and etching on sidewalls, eliminating idle time between process steps and maximizing equipment utilization.
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 prevents the merging of epitaxial layers, reduces device defects, and enhances performance by allowing selective growth and etching, resulting in faster throughput and better process control compared to sequential processes.
Implementation Method 1
introducing precursor gases into the process chamber; growing an epitaxial layer on top surfaces of each of the one or more fins
Implementation Method 2
etching sidewall surfaces of each of the one or more fins; etching the {110} plane of each of the one or more fins
Implementation Method 3
growing an epitaxial layer on top surfaces of each of the one or more fins; growing an epitaxial layer on the {100} plane of each of the one or more fins
Data Source
AI summary
One or more embodiments described herein relate to selective methods for fabricating devices and structures. In these embodiments, the devices are exposed inside the process volume of a process chamber. Precursor gases are flowed in the process volume at certain flow ratios and at certain process conditions. The process conditions described herein result in selective epitaxial layer growth on the {100} planes of the crystal planes of the devices, which corresponds to the top of each of the fins. Additionally, the process conditions result in selective etching of the {110} plane of the crystal planes, which corresponds to the sidewalls of each of the fins. As such, the methods described herein provide a way to grow or etch epitaxial films at different crystal planes. Furthermore, the methods described herein allow for simultaneous epitaxial film growth and etch to occur on the different crystal planes.