EUV Reflective Mask Phase Shift Film Composition
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Solution Overview
Problem
In EUV lithography, the phase shift film in reflective masks is prone to crystallization and hydrogen desorption when exposed to hydrogen gas, leading to reduced hydrogen resistance and image quality issues due to shadowing effects.
Innovation Solution
A reflective mask blank with a phase shift film containing at least one first element selected from ruthenium, iridium, platinum, palladium, and gold, and at least one second element selected from oxygen, boron, carbon, and nitrogen, where the chemical shift of the first element's peak observed by X-ray electron spectroscopy is less than 0.3 eV, suppressing crystallization and hydrogen desorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If ruthenium is used alone for the phase shift film to reduce film thickness, then the phase shift film can be made thin while ensuring phase difference, but the film is easily crystallized leading to increased sidewall roughness
Solution Approach 1:
The patent uses composite materials by combining ruthenium with at least one of nitrogen, oxygen, or carbon to form a phase shift film. This composite structure suppresses crystallization of ruthenium while maintaining low refractive index, thereby preventing etching along grain boundaries and reducing sidewall roughness while keeping the film thin
2Manufacturing precision
If nitrogen and oxygen are added to ruthenium to reduce crystallite size, then sidewall roughness is reduced, but non-metallic elements are desorbed when exposed to hydrogen gas, reducing hydrogen resistance
Solution Approach 1:
The patent optimizes the composition parameters by including carbon in addition to nitrogen and/or oxygen, creating a specific compositional range (Ru: 50-90 at%, N: 5-30 at%, O: 5-30 at%, C: 5-30 at%). This parameter optimization enhances hydrogen resistance while maintaining suppressed crystallization and low sidewall roughness
3Measurement precision
If the phase shift film is made thin to reduce shadowing effect, then image alignment accuracy is improved, but the film becomes more susceptible to crystallization and hydrogen desorption
Solution Approach 1:
The patent employs composite materials (ruthenium combined with nitrogen, oxygen, and carbon) to achieve a thin film structure that simultaneously provides low refractive index for phase shifting, suppressed crystallization, and enhanced hydrogen resistance, thereby maintaining image alignment accuracy while improving reliability
Solution Approach 2:
The patent optimizes compositional parameters within specific ranges to achieve the desired balance between film thickness, crystallization suppression, and hydrogen resistance, allowing the thin film to maintain structural integrity and chemical stability under EUV lithography conditions
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 crystallization of the phase shift film and improves its hydrogen resistance, reducing sidewall roughness and enhancing the transfer accuracy of the opening pattern in EUV lithography.
Implementation Method 1
a phase shift film that shifts a phase of the EUV light
Implementation Method 2
a multilayer reflective film that reflects EUV light
Implementation Method 3
a chemical shift of a peak of 3d5/2 or a peak of 4f7/2 of the first element X1 observed by X-ray electron spectroscopy
Data Source
AI summary
A reflective mask blank includes a substrate; a multilayer reflective film that reflects EUV light; a protection film that protects the multilayer reflective film; and a phase shift film that shifts a phase of the EUV light, the substrate, the multilayer reflective film, the protection film, and the phase shift film being arranged in this order. The phase shift film contains at least one first element X1 selected from the first group consisting of ruthenium (Ru), iridium (Ir), platinum (Pt), palladium (Pd), and gold (Au), and at least one second element X2 selected from the second group consisting of oxygen (O), boron (B), carbon (C), and nitrogen (N). In the phase shift film, a chemical shift of a peak of 3d5/2 or a peak of 4f7/2 of the first element X1 observed by X-ray electron spectroscopy is less than 0.3 eV.