Wafer Cleaning with Merged Liquid Streams to Prevent Re-Deposition
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Solution Overview
Problem
Current wafer washing methods, such as spin washing, face challenges with contamination re-deposition and safety issues due to fast drying between process steps and the use of corrosive chemicals, leading to inefficient and unsafe multistep washing procedures.
Innovation Solution
A method and apparatus where different liquid streams are delivered simultaneously during a transition phase to merge into a single stream before impacting the rotating wafer, maintaining continuous wetness and minimizing splashing, using angled outlets to combine streams above the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spin washing is used to minimize contamination re-deposition, then washing effectiveness is improved, but the wafer dries too quickly between steps causing contaminant deposition
Solution Approach 1:
The patent applies continuity of useful action by overlapping the discharge of contiguous liquid streams during transition phases. The first liquid stream is discharged during a first time period, and a second liquid stream is discharged during a second time period that overlaps with the first time period. This ensures continuous wetness of the wafer surface, preventing premature drying and contaminant deposition while maintaining washing effectiveness.
2Reliability
If multiple liquid streams are discharged simultaneously onto rotating wafer surface, then continuous wetness is maintained, but waves are generated causing splashing and inhomogeneous treatment
Solution Approach 1:
The patent applies dimensionality change by positioning outlets at different heights above the wafer surface. The first outlet is positioned at a first height and the second outlet is positioned at a second height that is different from the first height. This vertical spatial arrangement allows liquid streams to merge smoothly without creating waves or splashing, maintaining both continuous wetness and treatment homogeneity.
Solution Approach 2:
The patent applies segmentation by using separate outlets positioned at different heights for different liquid streams. The first outlet discharges a first liquid stream and the second outlet discharges a second liquid stream. This segmented discharge approach allows controlled merging of streams without wave formation, solving the contradiction between continuous wetness and treatment homogeneity.
3Ease of operation
If tank washing with immersion is used, then simple implementation is achieved, but contaminants re-deposit onto the wafer from the washing tank
Solution Approach 1:
The patent applies the taking out principle by extracting the wafer from the washing tank and performing washing on the rotating wafer surface using directed liquid streams from overhead outlets. This eliminates contact with the tank interior and washing liquid reservoir, preventing contaminant re-deposition from the tank while maintaining washing effectiveness through controlled liquid application.
4Reliability
If corrosive chemicals are used for multistep washing, then thorough cleaning is achieved, but safety hazards increase
Solution Approach 1:
The patent applies the intermediary principle by using a controlled liquid delivery system with timed overlapping discharge of washing liquids. The system carefully manages the interaction between different chemicals through controlled timing and positioning, allowing thorough cleaning while minimizing safety hazards through precise control of chemical application and preventing uncontrolled reactions.
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 prevents contamination re-deposition, conserves high-purity washing liquids, ensures homogeneous treatment, and reduces safety hazards by maintaining continuous wetness and avoiding wave formation during the washing process.
Implementation Method 1
washing liquid is sprayed onto a rotating wafer, held on a rotary block, so that the washing liquid flows over the edge of the wafer by centrifugal force
Implementation Method 2
the liquid streams merge after exiting said outlets to form a merged liquid stream before impacting the rotating surface
Data Source
AI summary
The present invention relates to a method for treating the surface of a wafer with multiple liquids, comprising rotating the surface of the wafer and discharging different liquid streams onto the rotating surface in a sequence from separate outlets, wherein the discharge of liquid streams which are contiguous in the sequence overlaps during a transition phase, and wherein during the transition phase the liquid streams merge after exiting said outlets to form a merged liquid stream before impacting the rotating surface. The invention also provides a liquid dispensing device incorporating a housing holding two or more liquid delivery tubes, wherein the tubes' outlets are inwardly angled towards one another, such that in use liquid streams delivered from the outlets of the two or more liquid delivery tubes merge to form a merged liquid stream.