Selective Silicon Oxide Etching via Boron Nitride Passivation
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in achieving high selectivity during the dry etch removal of silicon oxide relative to silicon nitride, which is critical for devices with small tolerances, such as self-aligned contacts.
Innovation Solution
A method involving exposing a substrate with both silicon oxide and silicon nitride films to specific gases, including boron or aluminum-containing gases and nitrogen-containing gases, to form nitride layers of varying thicknesses, where the thicker nitride layer on silicon nitride protects it from etching while allowing etching of the silicon oxide film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etching is used to remove silicon oxide, then etching speed is achieved, but selectivity relative to silicon nitride is insufficient causing material loss
Solution Approach 1:
The patent applies preliminary action by depositing a protective nitride layer on the silicon nitride film before the etching process. This is achieved by exposing the substrate to a first gas containing boron or aluminum that forms a first layer on both silicon oxide and silicon nitride, then exposing to a nitrogen-containing gas that reacts to form a second nitride layer preferentially thicker on silicon nitride. This pre-formed protective layer prevents silicon nitride loss during subsequent etching.
Solution Approach 2:
The patent implements local quality by creating a non-uniform nitride layer thickness where the second nitride layer is thicker on silicon nitride regions than on silicon oxide regions. This selective thickness distribution provides enhanced protection specifically where needed (on silicon nitride) while allowing adequate etching access to silicon oxide, thereby achieving high etch selectivity without excessive material loss.
2Manufacturing precision
If preferential passivation with carbon-based materials is used, then etch selectivity is improved, but process complexity and material compatibility issues arise
Solution Approach 1:
The patent applies parameter changes by switching from carbon-based passivation materials to boron or aluminum-based nitride forming gases. This material substitution simplifies the process by using gases that naturally form protective nitride layers through well-controlled chemical reactions with nitrogen-containing gases, avoiding the complexity of carbon-based deposition and passivation processes while maintaining high etch selectivity.
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 precise and selective etching of silicon oxide relative to silicon nitride, ensuring minimal loss of silicon nitride and achieving the required etch selectivity for advanced semiconductor devices.
Implementation Method 1
exposing the substrate to a first gas that forms a first layer on the silicon oxide film and a second layer on the silicon nitride film, where the first gas contains boron, aluminum, or both
Implementation Method 2
exposing the substrate to a nitrogen-containing gas that reacts with the first layer to form a first nitride layer on the silicon oxide film and reacts with the second layer to form a second nitride layer on the silicon nitride film
Implementation Method 3
exposing the substrate to an etching gas that etches the first nitride layer and the silicon oxide film, where the second nitride layer protects the silicon nitride film from etching by the etching gas
Implementation Method 4
exposing the substrate to a H2-containing gas that terminates the silicon oxide film with —OH surface species and terminates the silicon nitride film with —NHx surface species
Data Source
AI summary
A method for selective etching of silicon oxide relative to silicon nitride includes exposing a substrate to a first gas that forms a first layer on the silicon oxide film and a second layer on the silicon nitride film, where the first gas contains boron, aluminum, or both boron and aluminum, exposing the substrate to a nitrogen-containing gas that reacts with the first layer to form a first nitride layer on the silicon oxide film and reacts with the second layer to form a second nitride layer on the silicon nitride film, where a thickness of the second nitride layer is greater than a thickness of the first nitride layer. The method further includes exposing the substrate to an etching gas that etches the first nitride layer and silicon oxide film, where the second nitride layer protects the silicon nitride film from etching by the etching gas.