Phosphoric Acid Etching Tank Flow Layout for Silica Concentration Control
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Solution Overview
Problem
The challenge in selectively etching silicon nitride films relative to silicon oxide films using phosphoric acid solutions is that low silica concentrations result in low selectivity, leading to erosion of the silicon oxide film, while high concentrations can cause silica precipitation, necessitating uniform silica concentration control in the etchant solution.
Innovation Solution
A substrate processing apparatus with a treatment tank, bubble discharge pipes, and a rectifying plate is used to create a uniform jet flow velocity distribution in the phosphoric acid solution, improving stirring efficiency and controlling silica concentration by recirculating and heating the solution with a circulation path and filter system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the concentration of silica in the phosphoric acid solution is increased to improve selectivity, then the selection ratio of silicon nitride film to silicon oxide film is improved, but silica may precipitate out of solution on the substrate
Solution Approach 1:
The patent implements a circulation system that continuously moves the phosphoric acid solution through the treatment tank, allowing dynamic control of silica concentration. The system can maintain high silica concentration for selectivity while preventing precipitation through continuous circulation and controlled exposure time
Solution Approach 2:
The circulation system enables monitoring and adjustment of silica concentration in real-time, allowing the process to maintain optimal conditions for high selectivity while preventing harmful precipitation effects
2Stability of the object's composition
If the phosphoric acid solution is made more uniform to control silica concentration, then silica precipitation is prevented, but the complexity of the processing system increases
Solution Approach 1:
The patent uses a circulation system with pumps and pipes to hydraulically move and distribute the phosphoric acid solution uniformly throughout the treatment tank, achieving concentration uniformity through fluid dynamics rather than complex mechanical mixing devices
Solution Approach 2:
The circulation system serves multiple functions: it distributes the etchant uniformly, controls silica concentration distribution, prevents precipitation, and enables temperature control, reducing the need for separate systems for each function
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 configuration enhances the selectivity of silicon nitride film etching over silicon oxide film and prevents silica precipitation, ensuring efficient and uniform etching processes by maintaining optimal silica concentration in the phosphoric acid solution.
Implementation Method 1
a bubble discharge pipe below the position of the holder for discharging a gas
Implementation Method 2
recirculating and heating the solution with a circulation path and filter system
Implementation Method 3
create a uniform jet flow velocity distribution in the phosphoric acid solution
Data Source
AI summary
According to one embodiment, a substrate processing apparatus has a treatment tank, a holder to hold the substrate while in the treatment tank, a chemical discharge pipe below a position of the holder for supplying a chemical solution to the treatment tank, a bubble discharge pipe below the position of the holder for discharging a gas. The first bubble discharge pipe is closer along a horizontal direction to a centerline of the treatment tank than is the chemical discharge pipe. A rectifying plate is disposed below the position of the holder and extends from a position above the chemical discharge pipe to a position above the first bubble discharge pipe at an incline with respect to the first direction horizontal.