Atomic Layer Etching Using Boron and HF Gas
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Solution Overview
Problem
As semiconductor device feature sizes scale below 10 nm, accurately controlling etching of fine features becomes a significant challenge due to high variability in etching processes, necessitating advanced techniques like atomic layer etching (ALE) for precise material removal.
Innovation Solution
The method involves exposing a substrate to alternating cycles of hydrogen fluoride (HF) gas and boron-containing gases, such as boron hydrides or boron halides, to form and remove fluorinated surface layers on metal oxide films, allowing for low-temperature thermal ALE without plasma, thereby achieving precise etching control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching processes are used, then etching speed is maintained, but etching precision and control become poor at 10 nm and below nodes
Solution Approach 1:
The etching process is segmented into multiple sequential steps: first exposing the substrate to HF gas to form a fluorinated surface layer, then exposing to boron-containing gas to remove the fluorinated layer. This segmentation allows precise control of material removal at atomic scale while maintaining acceptable etching speed through repeated cycles
Solution Approach 2:
The patent employs periodic alternating exposure to HF gas and boron-containing gas in cyclic fashion. Each cycle consists of HF exposure followed by boron-containing gas exposure, repeated multiple times to achieve the desired etching depth. This periodic action enables precise control over total material removal while maintaining process speed
2Manufacturing precision
If atomic layer etching is used to achieve atomic scaled fidelity, then etching precision is improved, but process complexity increases
Solution Approach 1:
The patent utilizes parameter changes in the chemical reactions: HF gas exposure changes the surface chemistry by fluorinating the metal oxide, and subsequent boron-containing gas exposure changes the volatility of the surface species enabling removal. These parameter changes (chemical state, volatility) are controlled to achieve atomic-scale precision without overly complex process equipment
Solution Approach 2:
The fluorinated surface layer acts as an intermediary species that facilitates precise etching control. HF gas creates this intermediate fluorinated layer on the metal oxide surface, which then serves as the target for boron-containing gas removal. This intermediary layer enables controlled material removal at atomic scale while simplifying the overall process mechanism
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 enables atomic-scale etching fidelity and reduced process variability, improving device performance by efficiently removing material in a controlled, layer-by-layer manner, suitable for advanced semiconductor manufacturing.
Implementation Method 1
exposing the substrate to HF gas to form a fluorinated surface layer on the metal oxide film
Implementation Method 2
exposing the substrate to a boron-containing gas to remove the fluorinated surface layer from the metal oxide film
Data Source
AI summary
Embodiments of the invention provide a method for atomic layer etching (ALE) of a substrate. According to one embodiment, the method includes providing a substrate, and exposing the substrate to hydrogen fluoride (HF) gas and a boron-containing gas to etch the substrate. According to another embodiment, the method includes providing a substrate containing a metal oxide film, exposing the substrate to HF gas to form a fluorinated surface layer on the metal oxide film, and exposing the substrate to a boron-containing gas to remove the fluorinated surface layer from the metal oxide film. The exposures may be repeated at least once to further etch the metal oxide film.