Substrate Pre-Wetting for Bubble-Free Ultrasonic Cleaning
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Solution Overview
Problem
The challenge in cleaning semiconductor substrates with ultra or mega sonic energy is the damage caused by bubble cavitation, particularly in patterned structures, due to violent bubble implosion, which is not effectively controlled by existing methods, leading to side wall loss and contamination issues during the cleaning process.
Innovation Solution
Implementing a bubble-less or bubble-free pre-wetting process before sonic cleaning, using a vacuum environment and pre-wetting chemical solutions or vaporized liquids to form a bubble-free layer on the substrate, preventing bubble attachment and subsequent implosion damage during the ultra/mega sonic cleaning process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ultra or mega sonic energy is applied to clean the substrate, then particle removal efficiency is improved, but bubble cavitation damages patterned structures
Solution Approach 1:
A pre-wetting process is performed before the sonic cleaning step to saturate the substrate surface and fill patterned structures with liquid. This preliminary action prevents bubble formation during subsequent sonic cleaning, eliminating cavitation damage while maintaining particle removal efficiency
Solution Approach 2:
A liquid medium (water or chemical solution) is introduced as an intermediary between the sonic energy source and the substrate surface. This liquid layer absorbs the sonic energy and prevents direct bubble formation on the substrate, mediating the interaction to avoid damage
2Manufacturing precision
If dilute chemicals or de-ionized water are used for wet cleaning, then side wall loss is reduced, but particle removal efficiency decreases
Solution Approach 1:
The patent combines wet cleaning with ultra/mega sonic cleaning in a unified process. The sonic energy provides mechanical force for particle removal while the liquid medium maintains moderate chemical concentration to minimize side wall loss, achieving both goals simultaneously
Solution Approach 2:
Ultra/mega sonic vibration is applied to provide mechanical force for particle removal. The high-frequency vibration creates controlled cavitation in the liquid medium that generates mechanical stress to dislodge particles without requiring aggressive chemicals, thus reducing side wall loss
3Object-affected harmful factors
If reduced sonic power is applied, then bubble implosion damage is minimized, but particle removal efficiency drops
Solution Approach 1:
The pre-wetting process is performed at reduced or zero sonic power to prepare the substrate surface. This preliminary saturation of the surface with liquid prevents bubble formation during the subsequent low-power sonic cleaning, enabling effective particle removal without the need for high power that would cause damage
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 effectively prevents bubble implosion damage to patterned structures, allowing for controlled cavitation and efficient particle removal without side wall loss, even at reduced sonic power levels, maintaining the integrity of fine features on the substrate.
Implementation Method 1
forming a vacuum environment in the chamber
Implementation Method 2
supplying the vaporized liquid molecules on the substrate to form a bubble less or bubble-free pre-wetting chemical liquid layer on the substrate
Implementation Method 3
implementing an ultra/mega sonic cleaning process for cleaning the substrate
Data Source
AI summary
The present invention provides a method for cleaning substrates comprising the steps of: placing a substrate on a substrate holder; implementing a bubble less or bubble-free pre-wetting process for the substrate; and implementing an ultra/mega sonic cleaning process for cleaning the substrate.