Reflective Mask Blank Stack for Fine EUV Patterns and Stable Reflectivity
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Solution Overview
Problem
Existing reflective mask blanks face challenges in forming fine absorber film patterns and often suffer from reflective property deterioration during the production of reflective masks.
Innovation Solution
A reflective mask blank comprising a substrate with a multilayer reflective film, a protective film containing Rh, Pd, or Ir, and a hard mask film made of Ru, with specific etching rate ratios and film thicknesses to facilitate fine pattern formation and minimize reflective property deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hard mask film containing chromium, nitrogen and hydrogen is used, then the absorber film can be etched with appropriate selectivity, but the reflective properties of the multilayer reflective film deteriorate during mask production
Solution Approach 1:
The invention changes the material composition parameters of the hard mask film by incorporating ruthenium (5-50 at%) along with chromium, nitrogen, and hydrogen. This parameter modification allows the hard mask film to maintain appropriate etching selectivity against the absorber film while simultaneously improving resistance to reflective property deterioration during mask production processes
Solution Approach 2:
The invention uses a composite hard mask film material consisting of chromium, nitrogen, hydrogen, and ruthenium. This composite structure combines the etching selectivity benefits of chromium-based materials with the oxidative stability and reflective property protection benefits of ruthenium, resolving the contradiction between pattern fineness and reflective stability
2Manufacturing precision
If the photoresist thickness is reduced to enable finer patterning, then the absorber film pattern fineness improves, but the photoresist becomes insufficient as a dry etching mask
Solution Approach 1:
The invention introduces a hard mask film as an intermediary layer between the thin photoresist and the absorber film. The photoresist (50-200 nm) forms the initial pattern, the hard mask film (5-20 nm) serves as the dry etching mask with appropriate selectivity, and together they enable fine absorber film patterning while maintaining manufacturing feasibility
Solution Approach 2:
The masking function is segmented into two distinct layers: the photoresist layer for pattern definition and the hard mask film layer for dry etching protection. This segmentation allows each layer to be optimized independently - the photoresist for fine patterning capability and the hard mask film for etching selectivity and durability
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 enables easy formation of fine mask patterns while maintaining the reflective properties of the multilayer reflective film, enhancing the production efficiency and quality of reflective masks.
Implementation Method 1
a multilayer reflective film provided on a substrate to reflect EUV light
Implementation Method 2
The reflective mask has a multilayer reflective film provided on a substrate to reflect EUV light
Implementation Method 3
a patterned absorber film provided on the multilayer reflective film to absorb EUV light
Implementation Method 4
a hard mask film... wherein the hard mask film comprises ruthenium... it is important to adjust the chemical resistance of a hard mask film and the dry etching ratio
Implementation Method 5
a protective film... wherein the protective film comprises more than 50 at % of at least one element selected from the group consisting of rhodium, palladium, iridium and platinum
Data Source
AI summary
Provided is a reflective mask blank capable of easily forming a fine mask pattern and less likely to cause reflective property deterioration of a multilayer reflective film during the production of a reflective mask. The reflective mask blank includes a substrate, a multilayer reflective film to reflect EUV light, a protective film, an absorber film and a hard mask film stacked in this order, wherein the protective film contains more than 50 at % of at least one element selected from the group consisting of rhodium, palladium, iridium and platinum, and wherein the hard mask film contains ruthenium.