Semiconductor Wafer Drying via Centrifugal Ozone Hydrophilization
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Solution Overview
Problem
Existing methods for cleaning and drying semiconductor wafers fail to effectively remove contaminants, leading to issues like inhomogeneous growth, polysilicon deposition, and the formation of 'watermarks' due to incomplete drying and rinsing processes.
Innovation Solution
A two-step process involving the application of a hydrogen fluoride solution to a rotating semiconductor wafer, followed by high-speed rotation in an ozone-containing atmosphere for simultaneous drying and hydrophilization, eliminating the need for separate rinsing and organic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor wafer is slowly withdrawn from a hydrofluoric acid bath into an ozone-containing atmosphere, then the wafer surface is hydrophilized and dried, but the process requires 10 minutes for a 300 mm wafer at 0.5 mm per second withdrawal speed
Solution Approach 1:
The patent replaces the slow mechanical withdrawal process with a combination of centrifugal force (mechanical rotation at high speed) and ozone treatment. The rapid rotation (1000-5000 rpm) generates centrifugal force that quickly removes liquid, while ozone in the atmosphere simultaneously hydrophilizes the surface, reducing the process from 10 minutes to a matter of seconds.
Solution Approach 2:
The patent changes the withdrawal speed parameter from slow (0.01-15 mm/s) to very fast (1000-5000 rpm rotation), and introduces ozone concentration as a new parameter to control surface hydrophilization. This parameter transformation enables rapid processing while maintaining quality.
2Manufacturing precision
If deionized water rinsing is performed after hydrofluoric acid cleaning, then contaminants are removed, but watermarks form on the wafer surface during subsequent drying
Solution Approach 1:
The patent extracts the rinsing step entirely from the process. Instead of using deionized water to rinse, the system relies on the ozone-containing atmosphere to provide the necessary cleaning and hydrophilization functions, eliminating the source of watermark formation.
Solution Approach 2:
Ozone, a strong oxidant, is used to clean and hydrophilize the wafer surface without leaving residual water that could form watermarks. The oxidative action of ozone removes contaminants while simultaneously creating a hydrophilic surface that prevents water accumulation.
3Reliability
If organic solvents like isopropanol are used during drying, then the liquid film flows away completely, but chemical consumption increases and environmental disposal costs arise
Solution Approach 1:
The system uses ozone from the atmosphere to perform the drying and hydrophilization functions that would otherwise require organic solvents. The ozone naturally present in the process atmosphere is utilized to complete the drying, eliminating the need for additional chemical substances.
Solution Approach 2:
The patent uses an ozone-containing atmosphere (inert environment) to achieve complete drying and hydrophilization without introducing organic solvents. This inert atmospheric approach eliminates chemical consumption and disposal issues while maintaining effective drying.
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 process significantly reduces contaminant concentration, avoids 'watermarks', and shortens the overall process duration while conserving chemicals and avoiding environmental disposal costs, resulting in a clean, hydrophilic, and dry wafer surface.
Implementation Method 1
the liquid aqueous solution containing hydrogen fluoride flowing away from the semiconductor wafer on account of the centrifugal force generated by the rotation
Implementation Method 2
the presence of an ozone-containing atmosphere, the liquid aqueous solution containing hydrogen fluoride flowing away from the semiconductor wafer
Implementation Method 3
the surface of the semiconductor wafer being hydrophilized by ozone
Data Source
AI summary
Semiconductor wafers are cleaned, dried, and hydrophilized the following steps in the order stated:a) treating the semiconductor wafer with a liquid aqueous solution containing hydrogen fluoride, the semiconductor wafer rotating about its center axis at least occasionally, andb) drying the semiconductor wafer by rotation of the semiconductor wafer about its center axis at a rotational speed of 1000 to 5000 revolutions per minute in an ozone-containing atmosphere, the liquid aqueous solution containing hydrogen fluoride flowing away from the semiconductor wafer on account of the centrifugal force generated by the rotation, and the surface of the semiconductor wafer being hydrophilized by ozone.