Eccentric Substrate Cleaning via Gas Nozzle
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Solution Overview
Problem
Conventional substrate cleaning methods, particularly for hydrophobic surfaces with high water-repellency (static contact angle of 85 degrees or more), struggle to effectively remove water droplets and particles, leading to development faults and reduced yield rates due to the high water-repellency of the surfaces, which causes issues in immersion exposure processes.
Innovation Solution
A substrate cleaning method involving a cleaning liquid and gas nozzle system where the cleaning liquid is discharged from a central point and moved eccentrically while an inert gas forms a dried area, allowing the cleaning liquid to spread and remove residues efficiently, with the gas nozzle positioned to control the dried area's formation and movement, ensuring thorough cleaning without leaving residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cleaning liquid is supplied to a central part of the wafer and spread by centrifugal force (spin cleaning method), then the cleaning process can be performed, but the dissolved matters cannot be fully eliminated and the cleaning time becomes excessively long (up to 60 seconds)
Solution Approach 1:
The patent introduces an inert gas (intermediary substance) between the cleaning liquid and the wafer surface. The gas flows along the liquid film to remove dissolved matters more effectively, acting as a mediator that enhances the cleaning action without requiring prolonged spin cleaning time
Solution Approach 2:
The patent utilizes pneumatic flow by supplying inert gas along the cleaning liquid film. This pneumatic action helps to sweep away dissolved matters from the wafer surface, improving cleaning effectiveness while reducing the required cleaning time compared to traditional spin cleaning methods
2Area of stationary object
If the cleaning-liquid nozzle is moved outward while discharging cleaning liquid, then the cleaning liquid can cover more area, but the cleaning liquid may be caught up with the spreading dried area and reduce cleaning effectiveness
Solution Approach 1:
The patent employs dynamic control of the nozzle movement speed, adjusting it to be slower than the dried area spreading speed. This dynamic adjustment ensures that the cleaning liquid is continuously supplied to areas not yet reached by the dried front, maintaining effective cleaning coverage without being overtaken by the drying process
Solution Approach 2:
The patent implements feedback control by monitoring the position of the dried area front and adjusting the nozzle movement accordingly. The nozzle speed is controlled to maintain an optimal distance from the dried area boundary, ensuring continuous effective cleaning while preventing the nozzle from entering the already-dried region
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 method achieves a high cleaning effect in a shorter time, significantly reducing development faults and improving yield rates by effectively managing the spread and removal of cleaning liquids on highly water-repellent surfaces, even in areas away from the central point.
Implementation Method 1
a cleaning liquid is discharged from a cleaning-liquid nozzle to a central part of the substrate and is spread over all the surface of the substrate by a centrifugal force
Implementation Method 2
a gas is discharged from a gas nozzle to the central part of the substrate so as to form a dried area of the cleaning liquid
Data Source
AI summary
A substrate cleaning method that includes: a step in which, while a substrate holder is being continuously rotated, a to-be-discharged position of the cleaning liquid on the substrate is changed to an eccentric position deviated from the central part of the substrate, and a gas is discharged from a gas nozzle to the central part of the substrate so as to form a dried area of the cleaning liquid under a condition in which a shortest distance between an edge of a cleaning liquid flow output from the cleaning-liquid nozzle and an edge of a gas flow output from the gas nozzle is set between 9 mm and 15 mm.