Baking Unit Level Sensing for Photolithography Wafer Safety
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Solution Overview
Problem
Vibrations in photolithography equipment caused by transfer robots lead to loosening of baking unit components, resulting in uneven heating and potential wafer breakage, affecting the uniformity and quality of the photoresist layer and pattern development.
Innovation Solution
A sensing device with an optical sensor unit and reflecting/refracting element is mounted to the hot plate and cover of the baking unit to detect dislocations and particle presence, ensuring proper leveling and cleanliness before wafer loading, thus preventing sliding or breakage and ensuring uniform heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transfer robot operates at high speed to maximize yield, then productivity is improved, but vibrations are generated that loosen fasteners and displace the hot plate and cover
Solution Approach 1:
The patent employs level sensors that continuously monitor the horizontal orientation of the hot plate and cover. When displacement is detected, the system provides feedback to alert operators to tighten fasteners or adjust components, creating a closed-loop monitoring system that maintains reliability despite high-speed operation
Solution Approach 2:
The patent replaces manual inspection and adjustment of hot plate levelness with automated optical or electrostatic level sensors. This substitution of mechanical sensing with field-based sensing (optical/electrostatic) enables continuous monitoring without mechanical contact, preventing vibration-induced displacement from compromising measurement accuracy
2Ease of operation
If the hot plate becomes unbalanced due to loosened fasteners, then the upper surface becomes skewed, but this causes the wafer to slide and heat distribution becomes non-uniform
Solution Approach 1:
The patent implements preliminary level checking using sensors before wafer loading occurs. By detecting hot plate unbalance in advance, the system prevents wafer sliding and ensures uniform heat distribution from the start of the baking process, rather than attempting correction after problems arise
Solution Approach 2:
The level sensors provide continuous feedback on hot plate orientation, enabling real-time detection of unbalance conditions. This feedback mechanism allows operators to correct hot plate levelness before it affects wafer positioning or heat uniformity, maintaining manufacturing precision
3Temperature
If the cover is dislocated by vibrations, then heat leaks from the chamber, but this creates temperature variations across the wafer
Solution Approach 1:
The patent uses level sensors to detect cover dislocation before the baking process begins. By identifying cover position issues in advance, the system allows for corrective adjustment that prevents heat leakage and maintains uniform temperature distribution throughout the baking cycle
Solution Approach 2:
The sensing system provides feedback on cover orientation and position, enabling real-time monitoring of seal integrity. This feedback allows operators to ensure proper cover positioning that maintains thermal uniformity across the wafer surface
4Device complexity
If manual level checking is performed by eye, then no additional equipment is needed, but slight changes in attitude cannot be discerned and uniformity cannot be maintained
Solution Approach 1:
The patent replaces manual visual inspection with automated optical or electrostatic level sensors. These sensors detect subtle changes in hot plate and cover orientation that are imperceptible to the human eye, providing measurement precision far exceeding manual methods without requiring complex mechanical measurement devices
Solution Approach 2:
The sensing system enables the baking unit to self-monitor its own levelness and orientation automatically. The sensors continuously assess the horizontal orientation of components without requiring external inspection equipment or manual intervention, maintaining precision while minimizing added complexity
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
The solution prevents wafer sliding and breakage, ensures uniform heating, and maintains the desired Critical Dimension (CD) of the photoresist pattern, enhancing the reliability and yield of semiconductor devices by maintaining equipment cleanliness and operational efficiency.
Implementation Method 1
a light emitter and a light receiver spaced from one another
Implementation Method 2
The sensor unit includes a photo emitter that emits light and a photo detector that detects light of the type emitted by the photo emitter
Implementation Method 3
The optical element is positioned relative to the sensor unit such that the optical element receives light emitted from the photo emitter and transmits a predetermined quantity of the received light to the photo detector
Implementation Method 4
an optical (reflecting/refracting) element
Data Source
AI summary
A baking unit, for use in photolithography equipment, has a sensing device for sensing whether components of the baking unit are level and whether particles are present on inner surfaces of the baking. The sensing device has a sensor unit and an optical element. The sensor unit is preferably mounted to the hot plate of the baking unit and includes a light emitter and a light detector. The optical element is preferably mounted to a cover of the baking unit at a position at which the optical element reflects/refracts light emitted from the light emitter to the light detector when the hot plate and the cover are level, and as long as particles are not present on the optical element.