Germanium-Gas Etching for Selective Si Removal in GAA Fins
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the low etch selectivity and loss of germanium-containing nanosheets/nanowires during the etching process of silicon in GAA finFET devices, which affects device performance and process window control.
Innovation Solution
The use of a germanium-containing gas, such as germanium hydride, fluoride, or chloride, in combination with a primary etchant like hydrogen radicals or fluorine radicals, enhances etch selectivity by forming a passivation layer on silicon surfaces, inhibiting further etching and allowing selective removal of germanium-containing layers, thereby maintaining the integrity of the germanium nanosheets/nanowires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used to etch silicon in GAA finFET devices, then silicon can be removed, but germanium-containing nanosheets/nanowires are lost and etch selectivity is low
Solution Approach 1:
A germanium-containing gas is introduced as an intermediary substance during the etching process. This gas reacts with silicon to form a passivation layer that selectively protects germanium-containing materials while allowing silicon to be etched, thereby achieving high etch selectivity and preventing germanium loss
Solution Approach 2:
The etching process parameters are modified by introducing germanium-containing gases (such as germanium hydride, fluoride, or chloride) into the etching environment. This changes the chemical composition of the etching atmosphere, enabling selective etching of silicon while preserving germanium-containing nanosheets/nanowires
2Manufacturing precision
If etching process is performed without germanium-containing gas, then process is simpler, but etch selectivity is low and process window control is affected
Solution Approach 1:
The etching process parameters are modified by introducing germanium-containing gases (such as germanium hydride, fluoride, or chloride) into the etching environment. This changes the chemical composition of the etching atmosphere, enabling selective etching of silicon while preserving germanium-containing nanosheets/nanowires
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 increases etch selectivity from about 20 to 100, reducing SiGe and Ge loss, improving the etching profile, and enhancing the performance and process control of GAA finFET devices.
Implementation Method 1
The germanium-containing gas can increase surface adsorption of Ge-containing gas and Ge-containing byproducts on exposed surfaces of the first set of semiconductor layers, passivate the exposed surfaces
Data Source
AI summary
The present disclosure describes a method includes forming a fin structure including a fin bottom portion and a stacked fin portion on a substrate. The stacked fin portion includes a first semiconductor layer and a second semiconductor layer, in which the first semiconductor layer includes germanium. The method further includes etching the fin structure to form an opening, delivering a primary etchant and a germanium-containing gas to the fin structure through the opening, and etching a portion of the second semiconductor layer in the opening with the primary etchant and the germanium-containing gas.