Sequential Phosphoric Acid Etching for Silicon Nitride and Oxide Removal
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Solution Overview
Problem
The existing semiconductor production processes require multiple chambers for etching silicon oxide and silicon nitride films, leading to increased processing time and potential damage to gate electrodes due to the bumping phenomenon of phosphoric acid aqueous solutions when mixed with water, causing unstable spouting and improper film removal.
Innovation Solution
A substrate treatment method and apparatus that utilize sequential phosphoric acid treatment steps with varying concentrations to remove silicon oxide and silicon nitride films in a single chamber, adjusting the phosphoric acid concentration to optimize etching selectivity and prevent damage to the gate electrode, while also incorporating a nozzle design to manage gas generated during liquid mixing and stabilize the liquid mixture supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphoric acid aqueous solution and water are mixed together and supplied to a nozzle, then the etching process can be performed, but the mixture experiences bumping phenomenon and unstable spouting due to water vapor, causing substrate damage
Solution Approach 1:
The nozzle is divided into separate liquid supply channels and gas discharge channels. The liquid supply channel delivers phosphoric acid aqueous solution to the substrate, while the gas discharge channel separately removes water vapor generated during mixing. This segmentation prevents water vapor from causing bumping and unstable spouting, thereby maintaining substrate surface integrity while preserving etching efficiency.
2Manufacturing precision
If multiple chambers are used for etching silicon oxide and silicon nitride films, then each film can be treated with optimal etching liquid, but the processing time increases due to substrate transfer between chambers
Solution Approach 1:
The invention combines multiple etching functions into a single chamber by providing multiple nozzle assemblies, each capable of delivering different etching liquids (phosphoric acid aqueous solution and hydrofluoric acid aqueous solution). This allows sequential treatment of silicon nitride and silicon oxide films without substrate transfer, reducing processing time while maintaining etching quality through dedicated nozzle configurations.
Solution Approach 2:
The system employs periodic switching between different etching liquids supplied by different nozzle assemblies. The control unit alternates the operation of nozzles to first remove silicon nitride film with phosphoric acid, then remove silicon oxide film with hydrofluoric acid. This periodic action enables multi-step etching in a single chamber, eliminating transfer time while preserving film-specific etching optimization.
3Productivity
If phosphoric acid aqueous solution is supplied at high concentration, then silicon nitride film etching is effective, but silicon oxide film is also removed which is undesirable
Solution Approach 1:
The system applies different concentration qualities of phosphoric acid to different spatial locations and time periods. High concentration phosphoric acid is supplied to targeted areas for silicon nitride film removal, while lower concentration or controlled supply prevents excessive silicon oxide film removal. The nozzle design enables localized delivery, achieving high removal rate for silicon nitride while maintaining selective etching control.
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 reduces processing time by allowing simultaneous removal of both films in a single chamber without damaging the gate electrode, enhances etching efficiency, and stabilizes the liquid mixture supply to prevent substrate damage.
Implementation Method 1
a phosphoric acid aqueous solution is supplied to a substrate held by a spin chuck... for etching off the silicon nitride film
Implementation Method 2
a hydrofluoric acid aqueous solution is first supplied to the semiconductor wafer to remove the silicon oxide film
Data Source
AI summary
A substrate treatment method for treating a substrate including a first silicon nitride film provided on a front surface thereof and a silicon oxide film provided on the first silicon nitride film to remove the first silicon nitride film and the silicon oxide film from the substrate includes: a first phosphoric acid treatment step of supplying a phosphoric acid aqueous solution having a predetermined first concentration to the substrate held by a substrate holding unit to treat the substrate with the first concentration phosphoric acid aqueous solution for the removal of the first silicon nitride film; and a second phosphoric acid treatment step of supplying a phosphoric acid aqueous solution having a second concentration lower than the first concentration to the substrate to treat the substrate with the second concentration phosphoric acid aqueous solution for the removal of the silicon oxide film after the first phosphoric acid treatment step.