Etching Solution Mixing Sequence for PPM Hydrofluoric Acid Dosing
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Solution Overview
Problem
Conventional liquid mixing supply apparatuses in semiconductor fabrication struggle with precision and reproducibility in adding extremely small quantities of chemicals, such as hydrofluoric acid, and generate heat due to chemical reactions during the mixing process.
Innovation Solution
A method involving a micro-amount supply unit that dilutes hydrofluoric acid with ultra pure water and supplies it first to the mixing tank, followed by sulfuric acid and hydrogen peroxide, using a flow rate control unit to set and maintain precise flow rates, ensuring equal finishing points and minimizing heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a typical flow rate control unit is used to supply liquid chemicals, then large quantities of ultra pure water, sulfuric acid, and hydrogen peroxide can be supplied in fixed quantities, but it is difficult to precisely supply extremely small quantities of hydrofluoric acid (89 ppm, 1.78 ml)
Solution Approach 1:
The supply system is divided into two independent units: a typical flow rate control unit for supplying large quantities of ultra pure water, sulfuric acid, and hydrogen peroxide, and a micro-amount supply unit for precisely supplying extremely small quantities of hydrofluoric acid (89 ppm). This segmentation allows each unit to be optimized for its specific supply range, resolving the contradiction between measurement precision and adaptability.
2Productivity
If sulfuric acid, hydrogen peroxide, and ultra pure water are supplied to the mixing tank simultaneously, then the mixing process is efficient, but heat is inevitably generated due to chemical reactions
Solution Approach 1:
The micro-amount supply unit supplies hydrofluoric acid to the mixing tank before the typical flow rate control unit supplies sulfuric acid, hydrogen peroxide, and ultra pure water. This preliminary action sequence is designed to control heat generation during the mixing process by establishing a specific mixing order that manages the exothermic reactions more effectively.
3Device complexity
If multiple liquid chemicals are mixed in a single tank, then the process is simplified, but precision and reproducibility are compromised when adding extremely small quantities of specific chemicals
Solution Approach 1:
The mixing system uses a single mixing tank but employs two independent supply units with different supply capabilities. The micro-amount supply unit is specifically designed for precise supply of extremely small quantities (ppm level), while the typical flow rate control unit handles bulk chemicals. This segmentation of supply functions maintains mixing process simplicity while achieving high precision for small quantity chemicals.
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 allows for precise and reproducible mixing of chemicals, including extremely small quantities like hydrofluoric acid, while reducing heat generation during the mixing process, thereby enhancing the precision and reliability of the semiconductor fabrication process.
Implementation Method 1
a micro-amount supply unit for supplying the hydrofluoric acid, wherein the micro-amount supply unit dilutes the hydrofluoric acid with a ultra pure water and supplies the diluted hydrofluoric acid solution to the mixing tank
Implementation Method 2
a flow rate control unit for controlling a flow rate of each of the liquid chemicals
Data Source
AI summary
There is provided a method for liquid mixing supply fabricating a mixed etching solution in which sulfuric acid, hydrogen peroxide, ultra pure water and hydrofluoric act are mixed together. The method includes: supplying a specific liquid chemical to a mixing tank such that it is mixed in ppm units; and supplying at least two liquid chemicals and a ultra pure water to the mixing tank at a predetermined ratio, and mixing them, wherein starting points of supplying the at least two liquid chemicals and the ultra pure water are different from each other. Since the starting points of supplying the sulfuric acid, the hydrogen peroxide, and the ultra pure water are different, it is possible to minimize the heat generation due to the reaction between the sulfuric acid with the hydrogen peroxide.