EUV Reticle Absorber with Diffuse Scattering Layers
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Solution Overview
Problem
Current EUV lithography technologies face challenges in maintaining printability and reducing defectivity at technology nodes smaller than 1x nm, particularly due to the H-V print difference and limitations of absorber layer thickness, which cannot be scaled effectively for smaller critical dimensions.
Innovation Solution
The implementation of a thin absorber with diffuse scattering layers and nano-particles, such as nickel, chromium, or tantalum, embedded or between absorber and diffuse scattering layers, to enhance scattering and reduce specular reflection, forming a stack with a high frequency roughened surface to increase the optical path and improve image contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of absorber layer is increased to compensate H-V print difference, then printability is improved, but manufacturing precision and defectivity worsen due to increased residual light reflection and process complexity
Solution Approach 1:
The patent applies composite materials by combining multiple layers with different optical properties: a thin absorber layer (2-20 nm) made of high-absorbing materials (TaN, TaNO, TaBO, Ni, Au, Ag, C, Pt, Pd, Te, or Cr) is combined with diffuse scattering layers (5-50 nm thick) made of materials such as Si, TiO2, or ZrO2. This composite structure achieves both high absorption and diffuse scattering to eliminate H-V print difference while maintaining low defectivity and reducing residual light reflection.
Solution Approach 2:
The patent changes the optical parameters of the mask structure by introducing diffuse scattering layers with specific roughness parameters (Rq of 0.5-5 nm) and controlling the thickness of each layer. By adjusting these parameters, the system transforms the optical interaction from specular reflection to diffuse scattering, fundamentally changing how EUV radiation interacts with the absorber structure to resolve H-V print differences.
2Reliability
If absorber layer is made thinner to improve manufacturing precision, then defectivity is reduced, but image contrast and process window deteriorate due to increased residual light reflection
Solution Approach 1:
The patent uses composite materials where a thin absorber layer (2-20 nm) is combined with diffuse scattering layers (5-50 nm) to achieve both low defectivity and high image contrast. The diffuse scattering layers scatter residual light that would otherwise be reflected specularly, maintaining image contrast even with thinner absorber layers while reducing defectivity from excessive absorption.
Solution Approach 2:
The diffuse scattering layer acts as an intermediary between the absorber layer and the reflective multilayer. It mediates the optical interaction by scattering residual light that passes through or reflects off the thin absorber layer, preventing this light from creating H-V print differences while maintaining the benefits of a thin absorber structure.
3Productivity
If offset angle is increased to improve productivity, then lithography efficiency is enhanced, but H-V print difference increases worsening manufacturing precision
Solution Approach 1:
The patent employs composite materials consisting of absorber layers and diffuse scattering layers that work together to eliminate H-V print difference even at increased offset angles (up to 10 degrees). The diffuse scattering layers scatter light in all directions, compensating for the angular effects that cause H-V print differences, thereby maintaining manufacturing precision while allowing higher offset angles for improved lithography efficiency.
Solution Approach 2:
The patent changes the optical scattering parameters by introducing diffuse scattering with controlled roughness (Rq of 0.5-5 nm) that redirects light paths. This parameter change in light scattering behavior compensates for the increased angular effects from higher offset angles, maintaining uniform printing performance across different feature orientations while enabling higher productivity through increased offset angles.
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 reduces the H-V print difference and enhances printability and defectivity at beyond 1x nm technology nodes, maintaining image quality and reducing residual light reflection issues.
Implementation Method 1
forming one or more diffuse scattering layers over the capping layer
Implementation Method 2
roughening a surface of each of the one or more diffuse scattering layers to a high frequency roughness
Implementation Method 3
etching the diffuse scattering layers to form a stack... forming an absorber layer over each diffuse scattering layer
Implementation Method 4
A reflective multilayer stack 101 on a substrate 103 reflects EUV radiation at unmasked portions by Bragg interference
Data Source
AI summary
A scattering enhanced thin absorber for a EUV reticle and a method of making thereof is disclosed. Embodiments include forming a multilayer on the upper surface of a substrate, forming a capping layer over the multilayer, forming one or more diffuse scattering layers over the capping layer, and etching the diffuse scattering layers to form a stack.