Selective Silicon Etching via Sulfide Protection
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Solution Overview
Problem
Halogen gas chemistries exhibit higher etch selectivity for germanium over silicon, making it difficult to selectively etch high-silicon content materials from high-germanium content materials and separate germanium layers from silicon or silicon-germanium layers, which is a challenge in nanowire channel finFET fabrication.
Innovation Solution
A method involving a sulfurization process to form a sulfide layer on exposed germanium-rich surfaces, protecting them during a subsequent silicon etch process that removes silicon-rich materials, thereby achieving selective etching of silicon-rich materials over germanium-rich materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If halogen gas chemistries are used for etching, then etch selectivity for germanium over silicon is improved, but the ability to selectively etch silicon-rich materials from germanium-rich materials deteriorates
Solution Approach 1:
A sulfurization process is performed before the etch process to form a sulfide layer on the germanium-rich material surfaces. This preliminary protective layer prevents the germanium-rich material from being etched by halogen gas chemistries, enabling subsequent selective removal of silicon-rich materials without affecting the germanium-rich layers.
Solution Approach 2:
A sulfide layer acts as an intermediary protective layer between the halogen gas chemistry and the germanium-rich material. This intermediate layer selectively protects germanium-rich surfaces during the etch process, allowing silicon-rich materials to be removed while preserving the germanium-rich structures.
2Productivity
If halogen gas chemistries are used for etching, then etching speed for germanium is improved, but the separation of germanium layers from silicon or silicon-germanium layers deteriorates
Solution Approach 1:
The sulfurization process is performed in advance to deposit a protective sulfide layer on all germanium-containing surfaces. This preliminary protection enables high-speed halogen gas etching of silicon-rich materials while preventing unwanted etching of germanium layers, thus achieving both high productivity and precise layer separation.
Solution Approach 2:
The sulfide layer serves as a protective intermediary that allows rapid halogen gas etching to proceed without damaging germanium layers. This intermediary layer enables the use of aggressive etch chemistries for high-speed silicon removal while maintaining precise control over germanium layer integrity and separation.
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 allows for the selective removal of silicon-rich materials while preserving germanium-rich materials, enabling the formation of germanium-rich nanowire channels in finFETs, which is crucial for advanced nanowire-based devices.
Implementation Method 1
A method includes performing a sulfurization process to form a sulfide layer on exposed germanium-rich surfaces
Implementation Method 2
forming a protective layer on a germanium-rich material of the stack
Implementation Method 3
performing an etch process to remove the silicon-rich material from the stack
Data Source
AI summary
The present disclosure describes a method which can selectively etch silicon from silicon/silicon-germanium stacks or silicon-germanium from silicon-germanium/germanium stacks to form germanium-rich channel nanowires. For example, a method can include a multilayer stack formed with alternating layers of a silicon-rich material and a germanium-rich material. A first thin chalcogenide layer is concurrently formed on the silicon-rich material, and a second thick chalcogenide layer is formed on the germanium-rich material. The first chalcogenide layer and the second chalcogenide layer are etched until the first chalcogenide layer is removed from the silicon-rich material. The silicon-rich material and the second chalcogenide layer are etched with different etch rates.