EUV Mask Capping Layers for Carbon-Resistant Reflectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Carbon contamination on EUV masks during manufacturing processes affects critical dimension uniformity and increases exposure energy requirements, leading to higher costs and longer exposure times due to the absorption of EUV wavelengths by carbon deposits.
Innovation Solution
Employing a capping feature with materials having low solid carbon solubility and amorphous structure, such as Rh, Ir, Pt, Au, Zr, or alloys thereof, to reduce carbon buildup and protect the underlying reflective multilayer stack from oxidants, using single or multilayered capping layers to maintain EUV transmission and resist etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional capping layers are used on EUV masks, then the reflective multilayer stack is protected from oxidants, but carbon contamination builds up on the capping layer surface, affecting critical dimension uniformity and increasing exposure energy requirements
Solution Approach 1:
The capping layer is divided into multiple functional layers: a first capping layer (e.g., Ru, Rh, Ir, Pt, Pd, Au, or alloy) that provides carbon contamination resistance, and a second capping layer (e.g., Mo, W, Hf, Ta, or alloy) that provides oxidation resistance. This segmentation allows each layer to specialize in one protective function, preventing carbon buildup while protecting the underlying reflective multilayer stack without interference between functions.
Solution Approach 2:
The first capping layer acts as an intermediary between the environment and the second capping layer, specifically resisting carbon contamination that would otherwise deposit on the second capping layer. This intermediary layer prevents carbon from reaching and contaminating the oxidation-resistant second layer, maintaining both carbon resistance and oxidation protection simultaneously.
2Productivity
If carbon contamination is allowed to accumulate on the mask, then manufacturing costs and exposure times increase, but adding protective layers may reduce EUV transmission
Solution Approach 1:
The thickness of each capping layer is precisely controlled within specific ranges (first capping layer: 0.1-5 nm, second capping layer: 0.1-3 nm) to maintain optimal EUV transmission. By adjusting these thickness parameters, the patent achieves sufficient carbon and oxidation protection while minimizing impact on EUV light transmission, thus maintaining manufacturing efficiency without excessive energy loss.
3Device complexity
If a single-layer capping structure is used, then the structure is simpler and EUV transmission is maintained, but it cannot simultaneously resist both carbon contamination and oxidation effectively
Solution Approach 1:
The patent uses a composite capping structure with two distinct material layers: the first capping layer made from carbon-resistant materials (Ru, Rh, Ir, Pt, Pd, Au or alloy) and the second capping layer made from oxidation-resistant materials (Mo, W, Hf, Ta or alloy). This composite structure combines the beneficial properties of different materials to simultaneously achieve carbon contamination resistance and oxidation resistance, which a single material cannot provide alone.
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 capping feature effectively reduces carbon contamination, maintaining critical dimension uniformity and reducing the need for increased exposure energy, thereby optimizing manufacturing efficiency and cost-effectiveness.
Implementation Method 1
a first capping layer including material having an amorphous structure... a material including an element having a solid carbon solubility, at an eutectic point of a system containing the element and carbon, that is less than 3 atomic %
Implementation Method 2
a first capping layer including material having an amorphous structure... resists etching
Implementation Method 3
protect the underlying reflective multilayer stack from oxidants
Implementation Method 4
carbon contamination on EUV masks during manufacturing processes affects critical dimension uniformity and increases exposure energy requirements, leading to higher costs and longer exposure times due to the absorption of EUV wavelengths by carbon deposits
Data Source
AI summary
An extreme ultraviolet (EUV) mask includes a substrate, a reflective multilayer stack on the substrate, and a single layer or multi-layer capping feature on the reflective multilayer stack. The capping feature includes a capping layer or capping layers including a material having an amorphous structure. Other described embodiments include capping layer(s) that contain element(s) having a first solid carbon solubility less than about 3. In multilayer capping feature embodiments, element(s) of the respective capping layers have different solid carbon solubility properties.