Immersion Exposure Substrate Contact Angle Control
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Solution Overview
Problem
In immersion exposure processes for semiconductor manufacturing, the contamination of substrates due to impurities on the exposure stage is a significant issue, leading to defects in pattern formation and reduced yield, as immersion liquid can carry impurities from the stage to the substrate, compromising the quality and reliability of semiconductor devices.
Innovation Solution
The implementation of a method where the contact angle of the substrate's surface with the immersion liquid is set to be larger than that of the exposure stage's surface, using absorption and protection layers with specific contact angles to prevent impurities from being carried onto the substrate, and employing an auxiliary member with a smaller contact angle to manage the liquid flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact angle of the exposure stage surface with immersion liquid is set small (high hydrophilicity) to prevent liquid from moving toward the substrate, then the immersion liquid can be retained on the stage, but impurities on the stage are carried onto the substrate by the liquid flow, causing substrate contamination
Solution Approach 1:
The substrate surface is divided into a central exposure area and an outer peripheral area with different contact angle properties. The central area maintains smaller contact angles for proper exposure, while the outer peripheral area has larger contact angles to prevent impurity-laden liquid from reaching the substrate edge, thus locally differentiating surface properties to solve the contradiction
Solution Approach 2:
Instead of making the entire exposure stage highly hydrophilic to retain liquid, the invention inverts the approach by making the substrate's outer peripheral area hydrophobic (larger contact angle) relative to the stage, creating a contact angle gradient that reverses the natural flow direction of impurities away from the substrate surface
2Object-affected harmful factors
If the contact angle of the substrate surface with immersion liquid is set large (high water repellency) to prevent impurity movement, then substrate contamination is reduced, but the immersion liquid cannot be properly positioned for effective exposure
Solution Approach 1:
Different regions of the substrate are assigned different contact angle characteristics: the central exposure region maintains smaller contact angles to ensure proper liquid positioning and exposure accuracy, while the outer peripheral region has larger contact angles to prevent impurity migration, thus resolving the contradiction through spatial differentiation
Solution Approach 2:
The substrate surface is segmented into functional zones with distinct wetting properties, allowing independent optimization of each zone for its specific purpose (exposure accuracy vs. contamination prevention) without compromising the other
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 effectively prevents substrate contamination, reduces the occurrence of pattern defects, and enhances the yield and reliability of semiconductor devices by ensuring the immersion liquid does not carry impurities from the exposure stage to the substrate.
Implementation Method 1
making a large contact angle between the liquid and at least an outer peripheral portion of a main surface of the substrate when compared with a contact angle between the liquid and an area adjacent to the outer peripheral portion of the substrate
Data Source
AI summary
There is disclosed an immersion exposure method of carrying out an exposure process in a state that liquid is at least partly filled between a substrate to be exposed and a projection optical system of an exposure apparatus carrying out the exposure process, comprising carrying out a process of making large a contact angle to the liquid with at least outer peripheral portion of a main surface of the substrate compared with a contact angle to the liquid with an area adjacent to the outer peripheral portion of the substrate, which area is a part of a surface of a substrate supporting side of a substrate support member supporting the substrate included in the exposure apparatus, and carrying out the exposure process.