EUV Mask Interstitial Absorber for Lower 3D Effects
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Solution Overview
Problem
Current tantalum-based absorber materials in EUV masks are limited in thickness, leading to significant mask 3D effects that cause feature-size dependent focus and pattern placement shifts, which worsen as technology nodes advance, and thinning below 50 nm reduces light absorption and image quality.
Innovation Solution
Employ interstitial type materials with high extinction coefficients, comprising a matrix metal and interstitial elements occupying interstitial sites, allowing for a thin absorber layer less than 50 nm to mitigate mask 3D effects and improve scanner throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tantalum-based absorber material thickness is reduced to mitigate mask 3D effects, then mask 3D effects and pattern placement shifts are reduced, but light absorption capability and image quality deteriorate
Solution Approach 1:
The patent changes the material composition parameters by introducing interstitial elements (B, C, N, Si, P) into the tantalum matrix, which fundamentally alters the optical properties. This enables the absorber layer to achieve both thin thickness (reducing 3D effects) and high light absorption (maintaining image quality) simultaneously, resolving the contradiction between pattern placement precision and light absorption capability
Solution Approach 2:
The patent creates composite materials by combining tantalum matrix with interstitial elements to form interstitial compounds (Ta-B, Ta-C, Ta-N, Ta-Si, Ta-P). These composite structures provide enhanced optical absorption per unit thickness, allowing thin absorber layers to maintain high light absorption capability while reducing mask 3D effects and improving pattern placement precision
2Illumination intensity
If absorber layer thickness is kept thick to maintain light absorption, then image quality is maintained, but mask 3D effects worsen causing feature-size dependent focus shifts
Solution Approach 1:
By changing the material composition to include interstitial elements, the optical absorption efficiency per unit thickness is dramatically improved. This allows the absorber layer to achieve sufficient light absorption with reduced thickness, thereby minimizing mask 3D effects and the associated feature-size dependent focus shifts while maintaining image quality
3Manufacturing precision
If absorber layer is thinned below 50 nm to reduce mask 3D effects, then pattern placement accuracy improves, but normalized image log-slope decreases
Solution Approach 1:
The patent modifies the material composition parameters by incorporating interstitial elements into the tantalum matrix, which fundamentally changes the optical absorption characteristics. This enables thin absorber layers (below 50 nm) to maintain high normalized image log-slope values, thereby preserving image quality and pattern placement accuracy simultaneously
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 use of interstitial type materials reduces mask 3D effects, enhances image quality by increasing normalized image log-slope, and improves scanner throughput.
Implementation Method 1
The absorber layer includes an interstitial type material having a high extinction coefficient
Data Source
AI summary
A method for lithographically patterning a photoresist is provided. The method includes receiving a wafer with the photoresist and exposing the photoresist using an extreme ultraviolet (EUV) radiation reflected by an EUV mask. The EUV mask includes a substrate, a reflective multilayer stack on the substrate, a capping layer on the reflective multilayer stack, a patterned absorber layer on the capping layer. The patterned absorber layer includes a matrix metal and an interstitial element occupying interstitial sites of the matrix metal, and a size ratio of the interstitial element to the matrix metal is from about 0.41 to about 0.59.