Optical Liquid Dispense Control for Full Substrate Coverage
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Solution Overview
Problem
In semiconductor manufacturing, existing methods for dispensing liquids on rotating substrates often result in incomplete coverage due to non-uniform spreading, leading to excess material usage and waste, as the progression of the liquid across the substrate is not accurately monitored, especially for thin films that are transparent or have jagged edges.
Innovation Solution
A method and system that utilize a laser beam to monitor scattered and reflected light from the substrate's edge to determine the actual coating time of a liquid, allowing for real-time adjustments in the dispense operation, such as altering the volume of liquid or substrate rotation speed, to ensure complete coverage with minimal excess material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid is dispensed on a rotating substrate without real-time monitoring, then the coating process is simple and fast, but the liquid coverage is non-uniform and incomplete
Solution Approach 1:
The patent replaces complex mechanical monitoring systems with optical detection. A laser beam and photodetector system are used to detect the liquid front position optically, eliminating the need for mechanical sensors or complex feedback mechanisms while achieving precise coverage monitoring
Solution Approach 2:
The patent introduces light as an intermediary to detect liquid coverage. The laser beam serves as a mediator that interacts with the liquid front, and the photodetector converts this optical interaction into an electrical signal for control, enabling non-contact monitoring
2Reliability
If excess liquid is dispensed to ensure complete coverage, then coverage completeness is improved, but material waste increases
Solution Approach 1:
The patent implements real-time feedback control where the photodetector continuously monitors the liquid front position and feeds this information back to the controller. The controller adjusts the dispense valve based on this feedback, ensuring liquid is dispensed only until complete coverage is achieved, eliminating excess material
Solution Approach 2:
The patent makes the dispense system dynamic and adaptive. Instead of using a fixed dispense amount, the system continuously adjusts the liquid flow rate and dispense duration based on real-time detection of the liquid front position, optimizing material usage for each coating event
3Loss of time
If liquid progression is not monitored in real-time, then the dispensing process is simpler, but coating time control is inaccurate
Solution Approach 1:
The patent replaces mechanical timing mechanisms with optical detection for time measurement. The photodetector's detection of the liquid front position provides direct temporal information about coating progress, eliminating the need for complex mechanical timers or sensors
Solution Approach 2:
The patent maintains continuous monitoring of the liquid front position throughout the coating process. The photodetector continuously detects the liquid progression, providing uninterrupted temporal information that enables precise control of coating duration without interrupting the coating process
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 enables precise control over the dispensing process, reducing waste by up to 50% and ensuring full substrate coverage without the need for excessive safety stock, thereby improving efficiency and reducing tool downtime.
Implementation Method 1
monitoring scattered light from the laser beam
Implementation Method 2
monitoring reflected light from the laser beam
Implementation Method 3
the resist solution spreads radially across the substrate due to centrifugal forces imposed by the substrate rotation
Data Source
AI summary
Light can be used to monitor coating a liquid on a substrate. By directing the light to a spot on the substrate, when the liquid passes through the spot, some light will be reflected, while some light will be scattered. Monitoring this behavior can indicate whether a substrate has been successfully coated with the liquid, as well as identifying defects. Further, coating times can be monitored to make process adjustments.