Dual-Layer Light-Sensitive Bottom Anti-Reflective Coatings for 193-nm Lithography
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Solution Overview
Problem
High-NA lithography technologies face challenges with inadequate reflectance control, especially over topography, leading to increased standing waves, CD swing, and line edge roughness, which existing single-layer anti-reflective coatings fail to address effectively.
Innovation Solution
A dual-layer, light-sensitive, wet-developable bottom anti-reflective coating system is introduced, comprising two layers with distinct refractive indices and extinction coefficients, applied on a substrate to provide enhanced reflection control and improved exposure latitudes, depth of focus, and critical dimension control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If single-layer bottom anti-reflective coating is used, then manufacturing process is simple, but reflectance control is inadequate leading to increased CD swing and line edge roughness
Solution Approach 1:
The patent divides the single-layer anti-reflective coating into two distinct layers with different optical properties (refractive indices and extinction coefficients). The first layer has higher extinction coefficient to absorb light, while the second layer has lower extinction coefficient to reduce reflectance. This segmentation allows independent optimization of each layer's thickness and composition to achieve superior reflectance control and critical dimension uniformity across varying substrate topographies.
Solution Approach 2:
The patent employs composite material structure by combining two different anti-reflective coating materials with complementary optical characteristics. The first layer uses materials with high light absorption capability, while the second layer uses materials with lower absorption and appropriate refractive index matching. This composite approach creates a synergistic effect that provides broadband reflectance reduction and improved depth of focus compared to single-layer coatings.
2Measurement precision
If high-NA lithography is used, then resolution is improved, but reflectance increases causing standing waves and CD swing
Solution Approach 1:
The dual-layer anti-reflective coating acts as an intermediary layer between the photoresist and substrate. The first layer with high extinction coefficient absorbs incident light before it reaches the substrate, preventing strong reflections. The second layer with optimized optical properties further reduces reflectance and smooths out optical path variations. This intermediary structure effectively decouples the high-NA imaging performance from reflectance-induced defects, enabling standing wave suppression and CD uniformity.
3Object-affected harmful factors
If conventional bottom anti-reflective coating is used, then substrate reflectance is reduced, but exposure latitudes and depth of focus are not improved
Solution Approach 1:
The patent systematically varies key optical parameters including the refractive indices (n1, n2), extinction coefficients (k1, k2), and thicknesses (d1, d2) of the two layers to optimize performance across different exposure conditions. By adjusting these parameters, the coating maintains effective reflectance reduction while adapting to varying exposure latitudes, depths of focus, and numerical apertures. This parameter optimization enables the coating to perform consistently across a broader range of lithographic conditions compared to conventional single-layer coatings.
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 dual-layer coating system effectively reduces reflectance, achieves better critical dimension control, and enables printing of desired feature sizes within 10% of the target size, even at small feature sizes, by being developer-soluble and eliminating the need for dry etching.
Implementation Method 1
the first and second anti-reflective coating layers are both photosensitive and wet-developable
Implementation Method 2
the first and second anti-reflective coating layers are both photosensitive and wet-developable
Data Source
AI summary
The present invention provides methods of fabricating microelectronics structures and the resulting structures formed thereby using a dual-layer, light-sensitive, wet-developable bottom anti-reflective coating stack to reduce reflectance from the substrate during exposure. The invention provides dye-filled and dye-attached compositions for use in the anti-reflective coatings. The anti-reflective coatings are thermally crosslinkable and photochemically decrosslinkable. The bottom anti-reflective coating stack has gradient optical properties and develops at the same time as the photoresist. The method and structure are particularly suited to high-NA lithography processes.