EUV Reflective Mask Absorber Film Peeling Prevention
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Solution Overview
Problem
EUV lithography reflective masks experience peeling of the absorber pattern due to hydrogen gas exposure, leading to film stress and crack formation, which compromises the integrity of the mask during EUV exposure.
Innovation Solution
Incorporating boron in excess of 5 atomic % in the absorber film, along with hydrogen or deuterium, to form an amorphous structure that reduces film density and suppresses peeling by preventing hydrogen intrusion, and using a ruthenium-based protective film with high additive element content to enhance adhesion and prevent interface peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If hydrogen gas is introduced into the exposure atmosphere during EUV exposure, then exposure contamination is suppressed, but absorber pattern peeling occurs due to hydrogen intrusion and film stress
Solution Approach 1:
Hydrogen is incorporated into the absorber film during the film formation process itself, before exposure. This preliminary incorporation saturates the film's hydrogen capacity, preventing additional hydrogen intrusion during EUV exposure that would cause peeling. The absorber film is pre-conditioned with hydrogen content controlled within 0.1-30 at% to establish resistance against exposure-induced peeling while maintaining adhesion reliability
Solution Approach 2:
The hydrogen content in the absorber film is precisely controlled as a compositional parameter within 0.1-30 at%. This parameter optimization balances two competing requirements: sufficient hydrogen to suppress peeling by preventing further hydrogen intrusion, but not excessive hydrogen that would cause compressive stress and peeling. The specific range achieves optimal adhesion stability during EUV exposure in hydrogen-containing atmospheres
2Reliability
If the absorber film contains high hydrogen content to suppress peeling, then adhesion is improved, but compressive stress increases causing interface peeling
Solution Approach 1:
The hydrogen content is precisely controlled within 0.1-30 at% to optimize the balance between adhesion improvement and stress control. This parameter range provides sufficient hydrogen to suppress peeling by preventing further hydrogen intrusion, while avoiding excessive hydrogen that would generate compressive stress exceeding the adhesive strength at interfaces. The controlled hydrogen incorporation achieves adhesion enhancement without triggering stress-induced peeling
Solution Approach 2:
The absorber film is designed with an amorphous structure containing controlled voids and free volume that can accommodate hydrogen atoms. This porous-like amorphous structure allows hydrogen incorporation without significant lattice distortion, reducing compressive stress while maintaining adhesion. The amorphous phase provides a more tolerant structure for hydrogen content variation compared to crystalline phases
3Reliability
If boron content is increased to form amorphous structure and reduce film density, then peeling is suppressed, but manufacturing complexity increases
Solution Approach 1:
Boron content is controlled within 5-30 at% to ensure amorphous structure formation and optimal peeling resistance. This compositional parameter control achieves the desired amorphous phase while maintaining manufacturability. The specified range provides sufficient boron for amorphization and peeling suppression without excessive complexity in film formation processes
Solution Approach 2:
The absorber film is designed as a composite material containing multiple elements (Ta, B, N, H/D) in specific proportions. This composite structure leverages boron's amorphization capability, nitrogen's adhesion enhancement, and hydrogen/deuterium's peeling suppression. The multi-element composition achieves superior peeling resistance through synergistic effects while maintaining practical manufacturability
4Reliability
If deuterium is used instead of hydrogen in the absorber film, then peeling suppression is enhanced, but manufacturing cost increases
Solution Approach 1:
The additive element is selected from hydrogen or deuterium with content controlled at 0.1-30 at%. Deuterium provides slightly superior peeling suppression due to its lower diffusivity and stronger bonding, but hydrogen offers a more economical alternative with comparable performance. The patent allows either element, enabling cost-performance optimization based on specific application requirements and manufacturing capabilities
Solution Approach 2:
The choice between hydrogen and deuterium can be optimized locally based on specific mask requirements. For applications where maximum peeling suppression is critical and cost is secondary, deuterium is preferred. For cost-sensitive applications where adequate peeling suppression is sufficient, hydrogen provides an economical solution. This local optimization approach allows flexible manufacturing decisions
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 solution effectively suppresses peeling of the absorber pattern during EUV exposure in hydrogen-containing atmospheres, maintaining the structural integrity of the reflective mask and ensuring high-resolution pattern transfer in semiconductor manufacturing.
Implementation Method 1
an absorber film (4) that absorbs EUV light
Implementation Method 2
a multilayer reflective film (2) that reflects EUV light
Data Source
AI summary
Provided is a reflective mask blank for manufacturing a reflective mask capable of suppressing peeling of an absorber pattern when EUV exposure is performed in an atmosphere comprising a hydrogen gas.A reflective mask blank comprises: a substrate; a multilayer reflective film on the substrate; and an absorber film on the multilayer reflective film. The absorber film comprises an absorption layer and a reflectance adjustment layer. The absorption layer comprises tantalum (Ta), boron (B), nitrogen (N), and at least one additive element selected from hydrogen (H) and deuterium (D). A content of the boron (B) in the absorption layer is more than 5 atomic %. A content of the additive element in the absorption layer is 0.1 atomic % or more and 30 atomic % or less.