SOI Semiconductor Layer Transfer With Carbon Etch-Stop Control
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Solution Overview
Problem
Conventional silicon-on-insulator (SOI) CMOS devices face challenges such as boron diffusion during high temperature processes, which degrades device performance and requires effective methods to control etching processes for precise layer removal.
Innovation Solution
The implementation of a sacrificial substrate with a heavily doped epitaxial layer and an etch stop layer implanted with carbon atoms, followed by a series of controlled etching processes, allows for the precise removal of layers and prevents boron diffusion, thereby ensuring device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional SOI CMOS devices are used with thin silicon active layer on insulator, then device speed and packing density are improved, but boron diffusion during high temperature processes occurs which degrades device performance
Solution Approach 1:
An etch stop layer is introduced as an intermediary layer between the sacrificial substrate and the device layer. This etch stop layer contains carbon atoms that prevent boron diffusion during high temperature processes, thereby protecting the device performance while allowing the thin silicon active layer to maintain high speed operation
Solution Approach 2:
The etch stop layer is heavily doped with carbon atoms, changing the compositional parameter of the layer to create a boron diffusion barrier. This parameter change (adding carbon) fundamentally alters the material properties to prevent unwanted boron migration during thermal processing
2Manufacturing precision
If controlled etching processes are used to remove sacrificial substrate and epitaxial layer, then manufacturing precision is improved, but process complexity increases
Solution Approach 1:
The etch stop layer is prepared in advance with specific carbon doping and thickness parameters before the device layer is formed. This preliminary action establishes a predefined etching endpoint, allowing subsequent removal of the sacrificial substrate and epitaxial layer to proceed with high precision without requiring complex real-time control
Solution Approach 2:
The removal process is segmented into distinct stages: first removing the sacrificial substrate, then removing the epitaxial layer, with the etch stop layer serving as a clear boundary between these stages. This segmentation allows each etching step to be optimized and controlled independently, improving overall precision
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 effectively eliminates boron diffusion, ensures high uniformity and precision in layer thickness, and maintains device performance by using carbon-implanted etch stop layers and controlled etching processes.
Implementation Method 1
Carbon atoms are implanted into the etch stop layer
Implementation Method 2
prevents boron diffusion, thereby ensuring device performance
Implementation Method 3
followed by a series of controlled etching processes, allows for the precise removal of layers
Data Source
AI summary
A manufacturing method of a semiconductor device includes at least the following steps. A sacrificial substrate is provided. An etch stop layer is formed on the sacrificial substrate. A portion of the etch stop layer is oxidized to form an oxide layer between the sacrificial substrate and the remaining etch stop layer. A capping layer is formed on the remaining etch stop layer. A device layer is formed on the capping layer. A first etching process is performed to remove the sacrificial substrate. A second etching process is performed to remove the oxide layer. A third etching process is performed to remove the remaining etch stop layer. A power rail is formed on the capping layer opposite to the device layer.