Phosphoric Acid Etching Solution Siloxane Control
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Solution Overview
Problem
The existing etching processes using phosphoric acid solutions for selectively etching silicon nitride films face challenges in maintaining consistent etching characteristics due to the accumulation of siloxane, leading to fluctuations in etching rates and selection ratios, and require lengthy downtime or unstable additive solutions.
Innovation Solution
A substrate processing apparatus and method that incorporates an additive containing hexafluorosilicic acid and a trap agent with fluoroboric acid into the phosphoric acid solution, controlled for sequential input to maintain stable etching rates and prevent siloxane accumulation, using a concentration meter to adjust trap agent input based on siloxane levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an etching process is performed by using a phosphoric acid solution, then the silicon nitride film can be selectively etched, but siloxane accumulates in the etching solution causing etching characteristics to deteriorate over time
Solution Approach 1:
The patent implements a feedback control mechanism where a concentration meter continuously monitors siloxane concentration in the etching solution, and the control unit automatically adjusts the dosage of hexafluorosilicic acid additive based on the measured concentration to maintain stable etching characteristics
Solution Approach 2:
The patent changes the chemical parameters of the etching solution by adding hexafluorosilicic acid (H2SiF6) as an additive and fluoroboric acid (HBF4) as a trap agent, transforming the solution composition to prevent siloxane accumulation and maintain stable etching performance
2Manufacturing precision
If the concentration of siloxane in the etching solution is increased by seasoning, then the etching selection ratio improves, but the apparatus downtime becomes too long
Solution Approach 1:
The patent applies preliminary action by pre-adding hexafluorosilicic acid and fluoroboric acid to the etching solution before processing begins, establishing the proper chemical balance in advance to achieve stable etching characteristics without requiring lengthy seasoning periods
Solution Approach 2:
The patent enables continuous operation by implementing automatic control that maintains stable etching characteristics throughout the process, eliminating the need to stop the apparatus for seasonal adjustments and allowing continuous processing without downtime
3Manufacturing precision
If an additive containing siloxane is inputted into the phosphoric acid solution in advance, then the etching characteristics can be improved, but the etching characteristics become unstable due to decomposition or deterioration of the additive
Solution Approach 1:
The patent uses feedback control where the concentration meter continuously monitors siloxane concentration and the control unit adjusts additive dosage in real-time, ensuring stable etching characteristics by compensating for any decomposition or deterioration of the additive
Solution Approach 2:
The patent introduces fluoroboric acid as an intermediary substance that stabilizes the etching solution by preventing siloxane accumulation, which mediates between the hexafluorosilicic acid additive and the phosphoric acid solution to maintain consistent etching performance
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 maintains consistent etching characteristics of both silicon nitride and silicon oxide films over time, stabilizing etching rates and preventing siloxane buildup, thereby enhancing processing efficiency and reducing downtime.
Implementation Method 1
an additive containing a hexafluorosilicic acid is inputted into the phosphoric acid solution
Implementation Method 2
a trap agent containing a fluoroboric acid is inputted into the phosphoric acid solution
Data Source
AI summary
An additive containing a hexafluorosilicic acid solution (H2SiF6+H2O) is sequentially inputted into a phosphoric acid solution pooled in an immersion bath from an additive input mechanism. Further, a trap agent containing a fluoroboric acid solution (HBF4+H2O) is inputted into the phosphoric acid solution from a trap agent input mechanism. F− which accelerates etching of a silicon nitride film is added as appropriate by sequentially inputting the additive and siloxane which increases by the sequential input is etched with hydrofluoric acid generated by decomposition of the fluoroboric acid, to thereby suppress a significant increase in the concentration of siloxane. This makes it possible to maintain respective initial etching rates of the silicon nitride film and a silicon oxide film.