SiGe Etching Sequence for Selectivity and Low Si Surface Roughness
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Solution Overview
Problem
Existing etching methods for silicon germanium (SiGe) films in semiconductor manufacturing struggle to selectively etch SiGe films without etching adjacent silicon (Si) films, while also minimizing surface roughness and germanium residues.
Innovation Solution
A two-stage etching method using different fluorine-containing gases, where a first etching gas (e.g., F2) is supplied for a longer duration to selectively etch the SiGe film, followed by a second etching gas (e.g., ClF3) for a shorter duration to purge the first gas and reduce roughness and residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single fluorine-containing etching gas is used to selectively etch SiGe film, then selectivity against Si film can be achieved, but surface roughness increases and germanium residues remain
Solution Approach 1:
The etching process is segmented into two distinct stages using two different fluorine-containing gases. The first gas (CF4/SF6 mixture) performs the primary selective etching of SiGe, while the second gas (NF3) performs a secondary cleaning step to remove residues and smooth the surface. This segmentation allows each gas to be optimized for its specific function, resolving the contradiction between selectivity and surface quality.
Solution Approach 2:
The etching process maintains continuous useful action by seamlessly transitioning from the first etching gas to the second etching gas without interrupting the overall etching flow. The second gas continues the action initiated by the first gas by removing residues and smoothing the surface, ensuring the useful action of achieving high-quality etched surfaces continues throughout the process.
2Manufacturing precision
If etching duration is extended to completely remove SiGe film, then etching completeness improves, but adjacent Si film begins to etch
Solution Approach 1:
The etching process is divided into two segmented stages with different gases and parameters. The first stage uses CF4/SF6 mixture for selective SiGe etching with controlled duration. The second stage uses NF3 to complete the removal of any remaining SiGe and clean the surface. This segmentation allows achieving complete etching without extending the duration of the first gas that could cause Si film etching.
Solution Approach 2:
The invention changes the chemical parameters by switching from CF4/SF6 mixture to NF3 gas between stages. This parameter change allows the process to transition from a selective etching mode to a cleaning and smoothing mode, enabling complete removal of SiGe film while preventing etching of the Si film through appropriate parameter selection for each stage.
3Manufacturing precision
If first etching gas is supplied for longer duration to ensure complete SiGe removal, then etching completeness improves, but surface roughness increases
Solution Approach 1:
The process segments the etching action into two phases: primary etching with CF4/SF6 mixture and secondary cleaning with NF3. The first phase ensures complete SiGe removal, while the second phase specifically addresses surface roughness and residue removal. This segmentation resolves the contradiction by assigning different functions to different gas stages.
Solution Approach 2:
The useful action of achieving complete etching with smooth surfaces is maintained continuously through the two-stage process. The second gas stage continues and complements the work of the first gas, ensuring that complete etching and surface smoothing are achieved as a continuous, integrated process rather than conflicting objectives.
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 effectively reduces the roughness of the Si film and minimizes germanium residues on the Si film surface, while maintaining selective etching of the SiGe film.
Implementation Method 1
supplying a first etching gas, which is a first fluorine-containing gas, to the substrate for a first duration; and after the supplying the first etching gas, supplying a second etching gas, which is a second fluorine-containing gas different from the first etching gas, to the substrate for a second duration
Data Source
AI summary
An etching method of etching a silicon germanium film formed on a substrate, includes: supplying a first etching gas, which is a first fluorine-containing gas, to the substrate for a first duration; and after the supplying the first etching gas, supplying a second etching gas, which is a second fluorine-containing gas different from the first etching gas, to the substrate for a second duration shorter than the first duration.