EUV Reticle Absorption Layer Shadowing Reduction
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Solution Overview
Problem
The semiconductor industry faces challenges in advancing lithography techniques to meet the demands of miniaturization, particularly in achieving high resolution and reducing the mask shadowing effect during extreme ultraviolet (EUV) lithography processes, which affects the complexity and precision of semiconductor manufacturing.
Innovation Solution
The development of an EUV reticle manufacturing process involving a reflective multilayer, capping layer, and absorption layer, with a sacrificial multilayer and adhesion layer, to enhance reflectivity, protect the multilayer, and improve pattern transfer accuracy, using materials like Mo/Si, Ru, and Ta-based materials, and deposition processes like PVD and CVD, to achieve high reflectivity and absorption efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick absorption layer is used to achieve high absorption efficiency, then absorption efficiency is improved, but mask shadowing effect increases and resolution deteriorates
Solution Approach 1:
The patent changes the material parameter (extinction coefficient) of the absorption layer from conventional Ta-based materials (k≈0.02) to high-extinction materials like Pt, Pd, Ir, or their nitrides/oxides (k≈0.08-0.12). This parameter change allows achieving the same absorption efficiency with a much thinner layer thickness, thereby reducing mask shadowing and improving resolution while maintaining absorption efficiency.
Solution Approach 2:
The patent employs composite material structures including: (1) combining high-extinction absorption materials with specific capping layer materials (Ru, Rh, Ir) to optimize both absorption and protection functions; (2) using multilayer composite structures with alternating high and low extinction coefficient layers to fine-tune absorption characteristics while minimizing shadowing effects.
2Manufacturing precision
If the absorption layer thickness is increased to improve pattern transfer accuracy, then pattern transfer accuracy is improved, but mask shadowing effect increases
Solution Approach 1:
By changing the extinction coefficient parameter from 0.02 (Ta-based) to 0.08-0.12 (Pt, Pd, Ir, or their compounds), the patent achieves the same pattern transfer accuracy with a thinner absorption layer, thereby eliminating mask shadowing while maintaining pattern transfer fidelity.
Solution Approach 2:
The patent converts the harmful mask shadowing effect into a benefit by using high-extinction materials that provide sufficient absorption in a thinner layer, allowing the light to pass through with minimal shadowing while still achieving accurate pattern transfer.
3Ease of manufacture
If conventional Ta-based materials are used for the absorption layer, then ease of manufacture is improved, but extinction coefficient is insufficient and mask shadowing increases
Solution Approach 1:
The patent changes from Ta-based materials (k≈0.02) to Pt, Pd, Ir, or their nitrides/oxides (k≈0.08-0.12), achieving a 4-6 fold increase in extinction coefficient. While these materials may be more expensive, the patent demonstrates that they can be deposited using standard PVD or CVD techniques, maintaining ease of manufacture while dramatically improving optical performance.
4Manufacturing precision
If the depth of focus is increased to improve manufacturing precision, then manufacturing precision is improved, but mask shadowing effect worsens
Solution Approach 1:
By increasing the extinction coefficient from 0.02 to 0.08-0.12, the patent enables using a thinner absorption layer that reduces mask shadowing, thereby increasing depth of focus and improving manufacturing precision simultaneously.
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 process improves the resolution and reduces the mask shadowing effect, enabling more precise pattern transfer and increased depth of focus, thus supporting the manufacturing of smaller and more complex semiconductor circuits.
Implementation Method 1
reflective multilayer (ML)... enhance reflectivity
Implementation Method 2
absorption layer... absorption patterns... absorption efficiency
Implementation Method 3
deposition processes like PVD
Implementation Method 4
deposition processes like CVD
Data Source
AI summary
A reticle and a method for manufacturing a reticle are provided. The method includes forming a reflective multilayer (ML) over a front-side surface of a mask substrate. The method further includes forming a capping layer over the reflective ML. The method further includes forming a sacrificial multilayer over the capping layer. The method further includes forming an opening in the sacrificial multilayer to expose the capping layer. The method further includes forming a first absorption layer over the sacrificial multilayer and covering the capping layer in the opening. The method further includes removing the first absorption layer outside the opening in the sacrificial multilayer to form a first absorption pattern on a portion of the capping layer.