Silicon Wafer Spin Cleaning to Prevent Water Marks and Particles
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Solution Overview
Problem
Conventional methods for cleaning silicon wafers using single-wafer-processing spin cleaning machines result in water marks and particle adhesion due to differences in oxide film formation rates and delayed hydrophilization, degrading wafer quality.
Innovation Solution
A method involving sequential steps: treating the silicon wafer with hydrofluoric acid at a first rotational rate, shaking off the acid without pure water at a second rotational rate, and then treating with ozone water at a third rotational rate faster than the second, to prevent water marks and particle adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If pure water is supplied onto the silicon wafer surface after hydrofluoric acid treatment, then the hydrofluoric acid is substituted, but water marks are generated on the wafer surface
Solution Approach 1:
The patent extracts the harmful substitution step by eliminating pure water supply after hydrofluoric acid treatment. Instead of substituting hydrofluoric acid with pure water, the method directly transitions to ozone water treatment, thereby removing the source of water mark generation while maintaining the acid removal function.
Solution Approach 2:
The patent introduces ozone water as an intermediary substance that performs dual functions: it substitutes hydrofluoric acid and simultaneously prevents water mark formation. The ozone water acts as a mediator between acid removal and surface cleaning, eliminating the need for pure water substitution.
2Manufacturing precision
If rotational rate is kept low during oxide film removal with hydrofluoric acid, then the oxide film is removed, but particles adhere to portions where hydrophilization is delayed
Solution Approach 1:
The patent applies dynamic rotational rate adjustment, transitioning from low speed during hydrofluoric acid treatment to high speed during ozone water treatment. This dynamic change optimizes each process stage: low speed ensures uniform oxide film removal, while high speed enhances hydrophilization and prevents particle adhesion.
Solution Approach 2:
The patent employs periodic action by dividing the cleaning process into distinct phases with different rotational rates. The first phase uses low rotational rate for controlled oxide film removal, then transitions to high rotational rate for rapid hydrophilization and particle prevention, creating a periodic cycle of speed variation.
3Productivity
If rotational rate is increased during ozone water treatment, then hydrophilization is accelerated, but the process requires higher rotational speed than acid removal
Solution Approach 1:
The patent changes the rotational rate parameter between different treatment stages. By setting the ozone water treatment rotational rate higher than the hydrofluoric acid treatment rate, the method optimizes hydrophilization efficiency while managing the complexity through defined parameter ranges.
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
Effectively removes oxide films while preventing water marks and particle adhesion, enhancing wafer quality by optimizing rotational rates for each step.
Implementation Method 1
an oxide film formed on the surface of a semiconductor wafer is generally removed with a cleaning liquid such as hydrofluoric acid (HF) from the semiconductor wafer
Implementation Method 2
perform a reoxidation treatment by performing a rinse treatment (pure water or ozone water)
Data Source
AI summary
A method for cleaning a silicon wafer includes the steps of: supplying hydrofluoric acid onto a surface of the silicon wafer to treat the silicon wafer while rotating at a first rotational rate, stopping the supply of the hydrofluoric acid and shaking off hydrofluoric acid on the surface of the silicon wafer without supplying pure water onto the surface of the silicon wafer while rotating the silicon wafer at a second rotational rate which is the same as or faster than the first rotational rate, and supplying ozone water onto the surface of the silicon wafer to treat the silicon wafer after shaking the hydrofluoric acid off the surface while rotating at a third rotational rate which is faster than the second rotational rate. This method for cleaning a silicon wafer is capable of suppressing adhesion of water marks and particles and enhancing the wafer quality.