EUV Photo Mask Backside Conductive Layer Damage Prevention
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Solution Overview
Problem
EUV photo masks face damage to their backside conductive layers during the manufacturing process, which affects their performance and longevity in extreme ultraviolet lithography (EUVL) systems.
Innovation Solution
The use of a reflective EUV photo mask design with a low reflective (high absorbing) absorber structure, comprising a multilayer Mo/Si stack, a capping layer, a protection layer, and two hard mask layers, along with a CrN-based absorber layer and a Ta-based backside conductive layer, which are carefully fabricated to prevent damage and enhance EUV absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional EUV photo mask design is used, then the manufacturing process is simpler, but the backside conductive layer suffers damage affecting performance and longevity
Solution Approach 1:
The mask is divided into distinct functional layers: a reflective multilayer (Mo/Si stack) for EUV reflection, a capping layer for protection, an absorber layer for pattern definition, and a backside conductive layer for charge management. This segmentation allows each layer to be optimized for its specific function while protecting the backside conductive layer from damage during manufacturing and operation.
Solution Approach 2:
The mask employs composite material structures, including a multilayer Mo/Si stack combining molybdenum and silicon layers for high EUV reflectivity, and a CrN-based absorber layer for high EUV absorption. These composite structures enhance both the reflective and absorptive properties while maintaining structural integrity to protect the backside conductive layer.
2Manufacturing precision
If the absorber layer has high EUV absorption, then the pattern profile and resolution improve, but the manufacturing precision requirements increase
Solution Approach 1:
A capping layer is introduced as an intermediary between the reflective multilayer and the absorber layer. This capping layer serves as a protective barrier during manufacturing processes and as a structural interface that facilitates the deposition and patterning of the absorber layer, thereby improving manufacturing precision while maintaining high EUV absorption properties.
Solution Approach 2:
The absorber layer is formulated with specific material compositions (CrN, CrON, CrCON) and thickness parameters optimized for high EUV absorption. By carefully controlling these parameters, the mask achieves improved pattern profile and resolution while managing the complexity of the fabrication process through standardized deposition techniques.
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 design effectively suppresses damage to the backside conductive layer, maintains high EUV absorption, and improves the pattern profile and resolution in EUVL, reducing three-dimensional effects and enhancing the overall performance and durability of the EUV photo masks.
Implementation Method 1
a reflective multilayer (Mo/Si stack) disposed on the substrate
Implementation Method 2
an absorber layer disposed on the capping layer, the absorber layer including a CrN layer
Data Source
AI summary
In a method of manufacturing a reflective mask, a photo resist layer is formed over a mask blank. The mask blank includes a substrate, a reflective multilayer on the substrate, a capping layer on the reflective multilayer, an absorber layer on the capping layer and a hard mask layer, and the absorber layer is made of Cr, CrO or CrON. The photo resist layer is patterned, the hard mask layer is patterned by using the patterned photo resist layer, the absorber layer is patterned by using the patterned hard mask layer, and an additional element is introduced into the patterned absorber layer to form a converted absorber layer.