Adhesive Protective Coating with Suppressed Reflectivity
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Solution Overview
Problem
High-power excimer lasers used in microlithographic systems degrade UV-curable adhesives due to stray DUV light, leading to premature failure of optical components, and existing solutions do not adequately address back-reflectance issues from dielectric coatings.
Innovation Solution
A thin film structure comprising a blocking layer and matching layers is applied to the optical element, where the blocking layer blocks wavelengths below 300 nm and the matching layers reduce internal reflectance, allowing transmission at 365 nm for UV curing while minimizing stray light transmission and reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blocking layer is applied to block below 300 nm light, then adhesive degradation from stray light is prevented, but internal reflectance from the blocking layer back into the substrate increases
Solution Approach 1:
An intermediate anti-reflective coating layer is introduced between the substrate and the blocking layer. This intermediate layer acts as a mediator that gradually transitions the optical impedance, reducing the abrupt refractive index mismatch that causes back-reflectance. The intermediate layer has optical properties that are intermediate between the substrate and blocking layer, enabling smoother light transmission and minimizing reflected light back into the substrate while preserving the blocking layer's protective function.
Solution Approach 2:
The coating structure employs composite materials with different optical properties arranged in specific layers. The combination of materials with varying refractive indices and absorption characteristics creates a composite coating system that simultaneously achieves light blocking, reflectance reduction, and adhesive protection. Each material in the composite structure contributes specific optical functions to resolve the contradiction.
2Use of energy by moving object
If the blocking layer is made thin to allow UV transmission for adhesive curing, then UV-curing capability is maintained, but blocking effectiveness against below 300 nm light is reduced
Solution Approach 1:
The coating structure applies different material properties and thicknesses to different layers to achieve localized functional optimization. The blocking layer uses materials with high absorption coefficients for below 300 nm light, allowing it to be relatively thin while maintaining effective blocking. The anti-reflective layers use materials optimized for their specific optical functions. This local quality differentiation enables the thin blocking layer to maintain both UV transmission capability and blocking effectiveness.
Solution Approach 2:
The multi-layer composite coating combines materials with complementary optical properties. Some layers are optimized for UV transmission to enable adhesive curing, while other layers are optimized for blocking below 300 nm light. The composite structure allows the thin blocking layer to achieve effective stray light blocking through the synergistic combination of multiple materials with different optical characteristics.
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
Significantly reduces the transmission of below 300 nm laser light into the adhesive and minimizes internal reflectance back into the substrate, enhancing the stability and longevity of optical components in laser systems.
Implementation Method 1
The blocking layer is made of a material that does not transmit light below 300 nm, but does transmit light at wavelengths above 300 nm, for example, at 365 nm to cure adhesives
Implementation Method 2
The matching structure consisting of 1-7 layers of a selected material. The matching layer(s) minimize internal reflectance of below 300 nm laser light from the blocking layer back into the substrate
Data Source
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AI summary
The disclosure is directed to a thin- film for use in below 300 nm laser systems that can be applied to a variety of substrate types. The thin film (57) consists of a blocking layer (54) of a selected material and a matching structure (56), the matching structure consisting of 1-7 layers of a selected material. The blocking layer serves to minimize or eliminate the transmission of below 300 nm laser light into an adhesive (60) that is used to bond the substrate (52) to a holder. The matching layer (s) minimize internal reflectance of below 300 nm laser light from the blocking layer (54) back into the substrate (52).