Wet Processing Nozzle Drip Prevention via Image Monitoring
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Solution Overview
Problem
In wet processing systems for semiconductor and LCD substrate manufacturing, the issue of resist solution dripping from nozzles during movement leads to irregular resist film thickness and reduced spin chuck attraction, causing unsatisfactory exposure and increased defect rates, especially when multiple nozzles are used, complicating the process and increasing the risk of solution dripping.
Innovation Solution
A wet processing system that includes a nozzle bath, a nozzle carrying mechanism, image pickup means for capturing nozzle tip images, a decision means to identify drippy or dripping states, and a control means to execute drip prevention operations, such as returning nozzles to the bath or performing dummy pouring, to prevent solution from reaching unintended areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple nozzles are used to increase processing throughput, then productivity is improved, but the risk of resist solution dripping increases
Solution Approach 1:
The system divides the monitoring task into individual nozzle-level detection by segmenting the image pickup field to capture each nozzle tip separately, allowing independent monitoring and control of drip prevention for each nozzle while maintaining multi-nozzle operation
Solution Approach 2:
The system implements real-time feedback by continuously monitoring nozzle tip images, detecting drip states, and automatically adjusting nozzle positioning or resist solution supply based on the detected state, creating a closed-loop control system that maintains reliability with multiple nozzles
2Speed
If the nozzle is moved to the pouring position immediately after filling, then response speed is improved, but resist solution may drip during movement
Solution Approach 1:
The system performs preliminary detection of the drip state by capturing images of the nozzle tip before movement begins, allowing the control system to prepare appropriate countermeasures such as adjusting nozzle position or resist solution supply timing to prevent dripping during the subsequent rapid movement
Solution Approach 2:
When no drip is detected, the system rapidly moves the nozzle from the home position to the pouring position without intermediate stopping, achieving high-speed operation. When dripping is detected, the system skips the rapid movement and instead executes drip prevention procedures first
3Reliability
If the suck-back valve vacuum chamber is expanded to create stronger vacuum, then drip prevention is improved, but bubbles may form and force the resist solution to advance
Solution Approach 1:
The system monitors the nozzle tip state and resist solution flow characteristics in real-time, detecting when bubble formation occurs due to excessive vacuum. Based on this feedback, the control system adjusts the suck-back valve operation or nozzle positioning to prevent bubbles from forcing resist solution advancement while maintaining effective drip prevention
Solution Approach 2:
The system dynamically adjusts the vacuum chamber expansion parameters based on detected conditions, modifying the vacuum strength or duration to achieve optimal drip prevention without causing bubble formation that would disrupt resist solution uniformity
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 system effectively prevents resist solution from dripping onto undesired areas, reducing defects and improving yield by allowing for real-time monitoring and corrective actions during the wet processing operation, even when multiple nozzles are used, thereby ensuring consistent film thickness and maintaining spin chuck attraction.
Implementation Method 1
an image pickup means for taking a picture of tips of the process solution pouring nozzles while the process solution pouring nozzles are being carried by the nozzle carrying mechanism
Implementation Method 2
The vacuum chamber of the suck-back valve is expanded to create a vacuum to retract the end surface of the resist solution in the nozzle
Data Source
AI summary
A wet processing system detects a globule of a process solution in a drippy or dripping state from the tip of any one of process solution pouring nozzles being moved to a pouring position for pouring the process solution onto a substrate by obtaining image data on the process solution pouring nozzle, and takes proper measures to prevent the process solution from dripping. A wet processing system 1 pours a process solution, such as a resist solution, through one of process solution pouring nozzles 10 onto a surface of a substrate, such as a wafer W, held substantially horizontally by a substrate holding device 41 surrounded by a cup 5 to process the surface by a wet process. A nozzle carrying mechanism 10a carries the process solution pouring nozzles 10 between a home position on a nozzle bath 14 and a pouring position above the substrate held by the substrate holding device 41. An optical image of the tips of the process solution pouring nozzles 10 is obtained by an image pickup means, such as a camera 17. Predetermined measures are taken according to the level of a drippy or dripping state of a globule of the process solution.