EUV Reflective Mask Ruthenium Capping Layer Ashing
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Solution Overview
Problem
The manufacturing of reflective masks for EUV lithography using ruthenium capping layers faces issues with changes in optical characteristics during dry ashing processing, regardless of the gas type used, leading to inconsistent reflectance and refractive index changes.
Innovation Solution
The use of a mixed gas of ammonia and nitrogen, or solely ammonia gas, for dry ashing processing to remove resist masks, which helps maintain the optical characteristics of the ruthenium capping layer by setting the ammonia proportion to 50 vol% or higher, thereby improving the ashing rate and minimizing refractive index and extinction coefficient changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dry ashing processing is performed using oxygen plasma or sulfuric acid to remove the resist mask, then the resist mask is effectively removed, but the optical characteristics of the ruthenium capping layer change
Solution Approach 1:
The patent changes the chemical composition parameters of the ashing gas from conventional oxygen plasma or sulfuric acid to a mixed gas containing ammonia (5-50 vol%) and nitrogen (50-95 vol%). This parameter change in gas composition resolves the contradiction by providing effective resist removal while preventing degradation of the ruthenium capping layer's optical characteristics.
Solution Approach 2:
The patent uses nitrogen as the primary gas component (50-95 vol%) to create an inert atmosphere during ashing processing. This inert environment protects the ruthenium capping layer from chemical reactions that would otherwise alter its optical characteristics, while ammonia provides the necessary ashing capability.
2Ease of manufacture
If conventional ashing gases are used to remove resist mask, then the processing is simple and fast, but the reflectance and refractive index of the capping layer become inconsistent
Solution Approach 1:
The patent optimizes the ammonia concentration parameter (5-50 vol%) to achieve a balance between effective resist removal and maintaining optical characteristic consistency. This specific parameter range ensures both ease of manufacture through straightforward gas mixing and stability of the ruthenium capping layer's optical properties.
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 approach effectively suppresses changes in the optical characteristics of the ruthenium capping layer, improving the ashing rate and maintaining the reflectance of the capping layer, thus ensuring consistent performance in the manufacturing of reflective masks.
Implementation Method 1
performing dry ashing processing using a mixed gas of ammonia gas and nitrogen gas or only ammonia gas
Data Source
AI summary
According to one embodiment, a method for manufacturing a reflective mask includes: forming a reflection layer on a major surface of a substrate; forming a capping layer containing ruthenium on the reflection layer; forming an absorption layer on the capping layer; forming a pattern region in the absorption layer; removing a first resist mask used in forming the pattern region; and forming a light blocking region surrounding the pattern region in the absorption layer, the capping layer, and the reflection layer. The removing the first resist mask used in forming the pattern region includes: performing dry ashing processing using a mixed gas of ammonia gas and nitrogen gas or only ammonia gas.