EUV Reflective Mask Blank Phase Shift Film Etching Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of an Ir-based material for the phase shift film in reflective masks for EUV lithography results in low etching rates and poor etching selectivity between the phase shift film and the protection film, leading to potential damage to the multilayer reflective film during pattern formation.
Innovation Solution
A reflective mask blank is designed with a phase shift film made of an Ir-based material and a protection film made of a Rh-based material, enhancing the etching selectivity between the two films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If an Ir-based material is used for the phase shift film, then the film thickness can be reduced while maintaining desired phase difference, but the etching rate becomes low and etching selectivity against the protection film deteriorates
Solution Approach 1:
The patent changes the material composition parameters of the phase shift film by incorporating specific alloying elements (Ta, W, Mo, Re) in controlled amounts to adjust the etching rate while maintaining the low refractive index and high extinction coefficient properties of Ir. This allows optimization of both film thickness and etching selectivity through compositional parameter control.
Solution Approach 2:
The patent uses composite Ir-based alloy materials combining Ir with other metals (Ta, W, Mo, Re) to achieve a balance between optical properties and etching characteristics. The composite structure leverages the low refractive index of Ir while incorporating elements that improve etching rate and selectivity, resolving the contradiction between thin film requirement and manufacturability.
2Manufacturing precision
If the phase shift film is made thin to secure desired phase difference, then the optical performance is improved, but the multilayer reflective film may be etched during pattern formation
Solution Approach 1:
By adjusting the composition parameters of the Ir-based alloy (adding Ta, W, Mo, or Re), the patent modifies the etching rate parameter to ensure that even when the phase shift film is made thin for optimal phase difference, the etching selectivity remains sufficient to protect the multilayer reflective film during pattern formation.
Solution Approach 2:
The patent applies preliminary anti-action by selecting alloying elements that inherently provide etching resistance, creating a material composition that pre-defends against the harmful effect of excessive etching into the multilayer reflective film during the patterning process.
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 improved etching selectivity between the Ir-based phase shift film and the Rh-based protection film allows for more precise pattern formation in EUV lithography without damaging the multilayer reflective film.
Implementation Method 1
a multilayer reflective film that reflects EUV light
Implementation Method 2
a phase shift film that shifts a phase of the EUV light
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 are arranged in this order. The phase shift film is made of an Ir-based material containing Ir as a main component, and the protection film is made of a Rh-based material containing Rh as a main component.