Dry Etching Method for Vertical Profile Formation
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Solution Overview
Problem
Existing plasma etching techniques for high-aspect-ratio semiconductor structures, such as Fin FETs, face challenges in achieving vertical etching profiles due to difficulties in etchant penetration and the formation of tapered or footing profiles, which can lead to etching stoppages and reduced selectivity relative to masks.
Innovation Solution
A dry-etching method involving a two-step process: first, reactive gas etching to form a footing profile, followed by inert gas sputter-etching to convert this profile to a vertical one, using higher RF bias in the sputter-etching step to maintain mask selectivity and eliminate footing profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching conditions are adjusted to prevent etching stoppage by increasing process gas flow rate or adding fluorine-containing gas, then etching can proceed in high-aspect-ratio structures, but sidewall protection film cannot be formed and side-etching profile is generated
Solution Approach 1:
The etching process is divided into multiple steps with alternating reactive gas and oxygen plasma treatments. This segmentation allows the process to achieve both vertical profiling and sidewall protection by separating the functions of different etching steps.
Solution Approach 2:
The patent employs periodic alternation between reactive gas etching (which creates vertical profiles) and oxygen plasma treatment (which provides sidewall protection). This periodic action resolves the contradiction by cycling between the two opposing requirements.
2Reliability
If oxygen plasma is inserted in the middle of etching to protect sidewall and enable vertical etching, then sidewall protection is improved, but scallop profile is formed on the etching surface
Solution Approach 1:
The patent applies different plasma treatments to different regions and stages of the etching process. Oxygen plasma is selectively applied to protect sidewalls while controlling its exposure time and conditions to minimize scallop formation on the etching surface.
3Manufacturing precision
If RF bias output is increased to strengthen ion sputtering effect and form sidewall protection film, then etching progression in small spaces is improved, but mask selectivity is lowered and mask faceting occurs
Solution Approach 1:
The patent changes process parameters by using different gas compositions (reactive vs. inert) and controlling RF bias output at different stages. This allows achieving vertical profiles through controlled sputtering while maintaining mask selectivity by limiting high-power sputtering to inert gas steps where mask damage is minimized.
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 enables vertical plasma etching with maintained mask selectivity, preventing scallop profiles and mask faceting, while efficiently eliminating footing profiles to achieve the desired etching depth without compromising the etching process.
Implementation Method 1
a first process of etching a film to be etched with use of reactive gas to cause an etching profile of the film to be etched to be formed in a footing profile
Implementation Method 2
a second process of, after the first process, causing the footing profile to be formed in a vertical profile by means of sputtering etching
Data Source
AI summary
According to the present invention, a dry-etching method for performing plasma etching in a vertical profile while maintaining selectivity relative to a mask, includes: a first process of etching a film to be etched with use of reactive gas to cause an etching profile of the film to be etched to be formed in a footing profile; and a second process of, after the first process, causing the footing profile to be formed in a vertical profile by means of sputtering etching.