EUV Mask Absorber Alloys for High-Aspect-Ratio Patterning
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Solution Overview
Problem
Current EUV lithography technologies face challenges in patterning chromium-based mask absorbers with sufficient control over cross-sectional shape and feature dimensions, limiting the achievable aspect ratio and minimum feature sizes due to issues with chromium etching.
Innovation Solution
The development of chromium or vanadium alloys with high extinction coefficient materials like silver, indium, cobalt, antimony, tin, or tellurium, which utilize a self-passivation mechanism for anisotropic patterning, allowing for thinner absorber layers and improved feature control through stoichiometry adjustments and low-temperature etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chromium-based mask absorbers are used in EUV lithography, then the extinction coefficient is sufficient, but the control over cross-sectional shape and feature dimensions is insufficient
Solution Approach 1:
The patent applies parameter changes by controlling the etching temperature to be below the dew point of water vapor, which fundamentally alters the etching chemistry and mechanism. This temperature parameter change enables the self-passivation effect to occur, where water vapor condenses on the chromium surface during etching, protecting sidewalls and enabling precise cross-sectional shape control that was not achievable at conventional etching temperatures
Solution Approach 2:
The patent employs composite materials by combining chromium absorber layers with mandrel layers made of different materials (silicon oxide, silicon nitride, or polymer resists). These composite structures enable complex patterning sequences where each material contributes its unique properties: chromium provides EUV absorption, while the mandrel materials provide etch selectivity and structural support during the patterning process
2Productivity
If conventional etching processes are used for chromium, then the etching speed is acceptable, but the aspect ratio and minimum feature sizes are limited
Solution Approach 1:
The patent changes the temperature parameter to below the dew point of water vapor, which transforms the etching mechanism from a conventional physical/chemical process to one dominated by self-passivation through water vapor condensation. This parameter change enables high aspect ratio features to be etched with precise sidewall control while maintaining practical etching speeds, resolving the contradiction between etching speed and aspect ratio achievement
Solution Approach 2:
The patent implements self-service through the self-passivation mechanism where water vapor automatically condenses on the chromium sidewalls during etching, forming a protective layer without requiring external intervention. This self-formed passivation layer protects the sidewalls from over-etching and enables high aspect ratio features to be created with precise dimensional control, eliminating the need for complex external protection mechanisms
3Reliability
If the absorber layer thickness is increased to improve extinction, then the EUV absorption is enhanced, but the patterning control and critical dimensions deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling etching temperature below the dew point, which enables precise patterning of thicker absorber layers. The self-passivation mechanism that results from this temperature control protects sidewalls during etching, allowing thicker chromium layers (which provide better EUV extinction) to be patterned with the same dimensional precision as thinner layers, thus resolving the contradiction between absorption enhancement and patterning control
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 enables precise control over feature profiles, achieving aspect ratios greater than 1 and allowing for the direct patterning of anisotropic or tapered sidewalls, thereby enabling the etching of smaller features with higher aspect ratios and improved critical dimensions.
Implementation Method 1
The material of the mask absorber attenuates the EUV radiation
Implementation Method 2
A EUV mask comprises a reflective multilayer mirror
Implementation Method 3
The sidewall passivation is available due to the ternary etch product formed in chromium or vanadium etching
Data Source
AI summary
This disclosure provides systems, methods, and apparatus related to extreme ultraviolet lithography. In one aspect, a method of fabricating a mask for extreme ultraviolet lithography includes providing a structure, depositing an absorber layer over the reflective layer, and patterning the absorber layer. The structure includes a substrate and a reflective layer disposed over the substrate. The absorber layer comprises A and B. A is chromium (Cr) or vanadium (V). B is silver (Ag), indium (In), cobalt (Co), antimony (Sb), tin (Sn), or tellurium (Te). Patterning the absorber layer includes etching the absorber layer to remove the absorber layer in a first region while leaving the absorber layer in a second region. The etching is performed at a temperature of about −80° C. to 0° C.