EUV Reflective Photo Mask Structure Protecting Backside Conductive Layers
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Solution Overview
Problem
Existing EUV photo masks face challenges in preventing damage to the backside conductive layer, which is critical for maintaining the integrity and functionality of the mask during EUV lithography processes.
Innovation Solution
The development of an EUV reflective photo mask with a low reflective (high absorbing) absorber structure, including a substrate, a multilayer Mo/Si stack, a capping layer, an absorber layer, and a cover layer, along with a backside conductive layer made of tantalum boride, to enhance durability and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional EUV photo mask structure is used, then the mask can perform basic lithography functions, but the backside conductive layer is susceptible to damage during EUV lithography processes
Solution Approach 1:
A capping layer is introduced as an intermediary protective barrier between the EUV radiation and the backside conductive layer. This capping layer absorbs or blocks the harmful EUV radiation before it can reach and damage the conductive layer, thereby protecting the underlying structure while maintaining the overall functionality of the photo mask.
Solution Approach 2:
The photo mask employs a composite structure combining multiple materials with different properties: the substrate, multilayer Mo/Si stack for reflectivity, capping layer for protection, absorber layer for contrast, and backside conductive layer for electrical functionality. This composite approach allows each layer to perform its specific function while collectively protecting the conductive layer from EUV damage.
2Manufacturing precision
If the absorber layer is made with high absorption capability, then the contrast is improved, but the adhesion to underlying layers may be compromised
Solution Approach 1:
An intermediate layer is positioned between the capping layer and the absorber layer to serve as a bonding mediator. This intermediate layer is specifically selected to provide strong adhesion to both the capping layer above and the absorber layer below, ensuring mechanical strength while allowing the absorber layer to maintain its high absorption properties for improved contrast.
3Ease of manufacture
If hydrogen diffusion is not prevented, then the manufacturing process is simpler, but the durability and performance of the mask deteriorate
Solution Approach 1:
The capping layer acts as a diffusion barrier that mediates between the external environment and the internal conductive layer. It prevents hydrogen atoms from diffusing through the mask structure and reaching the conductive layer, thereby maintaining the electrical properties and durability of the mask without requiring complex additional manufacturing steps.
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 proposed structure effectively protects the backside conductive layer, ensuring the EUV photo mask's reliability and performance in extreme ultraviolet lithography by enhancing adhesion and resistance to hydrogen diffusion.
Implementation Method 1
a reflective mask including a substrate, a reflective multilayer disposed over the substrate
Implementation Method 2
an absorber layer disposed over the intermediate layer... a low reflective (high absorbing) absorber structure
Data Source
AI summary
A reflective mask includes a substrate, a reflective multilayer disposed over the substrate, a capping layer disposed over the reflective multilayer, an intermediate layer disposed over the capping layer, an absorber layer disposed over the intermediate layer, and a cover layer disposed over the absorber layer. The absorber layer includes one or more layers of an Ir based material, a Pt based material or a Ru based material.