Plasma Etching Selectivity for Germanium-Silicon Stacks
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Solution Overview
Problem
Conventional plasma etching techniques face challenges in selectively etching germanium-containing layers relative to silicon layers in semiconductor substrates, especially at low germanium concentrations, leading to poor selectivity and undesirable etching of silicon layers, which affects the formation of nanowires and nanosheets in 3D vertical structures.
Innovation Solution
A plasma etching method using a mixture of fluorine, nitrogen, and hydrogen agents is employed to selectively etch germanium-containing layers while forming a nitride passivation layer on silicon layers, inhibiting their etching and allowing for precise formation of indents in the germanium layers, thereby improving selectivity and etch profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional plasma etching techniques are used to etch germanium-containing layers, then etching of germanium layers can be achieved, but selectivity is poor and silicon layers are undesirably etched
Solution Approach 1:
The patent changes the chemical composition parameters of the plasma by introducing a multi-component gas mixture containing fluorocarbon compounds (for etching), nitrogen compounds (for passivation layer formation), and hydrogen compounds. This parameter change enables selective etching of germanium layers while protecting silicon layers through in-situ passivation layer formation.
Solution Approach 2:
The patent introduces a passivation layer as an intermediary substance that forms on the silicon layer surfaces during plasma exposure. This passivation layer acts as a protective barrier between the plasma and silicon layers, preventing undesirable etching of silicon while allowing germanium etching to proceed selectively.
2Manufacturing precision
If conventional plasma etching is used, then germanium layers can be etched, but surface roughness increases and corner rounding occurs
Solution Approach 1:
The patent optimizes plasma parameters including gas composition (fluorocarbon, nitrogen, hydrogen compounds), pressure (1-100 mTorr range), and power settings to achieve controlled etching. These parameter changes produce a smoother etch profile with reduced surface roughness and minimal corner rounding compared to conventional single-component plasma etching.
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
The method achieves high selectivity and improved etch profiles, reducing surface roughness and corner rounding, and is effective even at low germanium concentrations, enhancing the formation of nanowires for advanced semiconductor devices.
Implementation Method 1
selectively etching the first germanium-containing layer by exposing the film stack to a plasma that includes fluorine agents
Implementation Method 2
The plasma etches the first germanium-containing layer through chemical reactions with fluorine agents
Implementation Method 3
causes a passivation layer to be formed on exposed surfaces of the first silicon layer and the second silicon layer to inhibit etching
Implementation Method 4
The plasma causes a nitride passivation layer to be formed on exposed surfaces of the silicon layers
Data Source
AI summary
In certain embodiments, a method for processing a semiconductor substrate includes receiving a semiconductor substrate that includes a film stack. The film stack includes a first silicon layer, a second silicon layer, and a first germanium-containing layer positioned between the first silicon layer and the second silicon layer. The method further includes selectively etching the first germanium-containing layer by exposing the film stack to a plasma that includes fluorine agents, nitrogen agents, and hydrogen agents. The plasma etches the first germanium-containing layer and causes a passivation layer to be formed on exposed surfaces of the first silicon layer and the second silicon layer to inhibit etching of the first silicon layer and the second silicon layer during exposure of the film stack to the plasma.