EUV Absorber Layer with Embedded Particles for Shadowing Reduction
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Solution Overview
Problem
EUV photomasks with existing absorber layers, such as TaN or TaBN, suffer from shadowing, telecentricity errors, and contrast loss due to non-orthogonal illumination, and materials like Ni cannot be etched without damaging adjacent layers.
Innovation Solution
A method involving a Ta-based absorber layer with implanted nanoparticles of high EUV absorbing materials like Ni, Co, Ag, In, or Pt, forming a thinner, etchable, and highly absorbing layer, which maintains EUV reflectance and allows for precise patterning without line shadowing or pattern shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a thicker absorber layer (50-60 nm Ta) is used to achieve sufficient EUV absorption, then EUV absorption is improved, but the layer profile increases causing shadowing and telecentricity errors
Solution Approach 1:
The patent uses a composite absorber layer structure combining Ta-based material (etchable) with embedded high-absorption material particles (Ni, Co, Ag, In, or Pt). This composite approach achieves high EUV absorption with reduced thickness while maintaining etchability, as the dispersed particles provide absorption enhancement without requiring a thick continuous layer
Solution Approach 2:
The patent applies local quality by embedding discrete particles of high-absorption material throughout the Ta-based absorber layer. Rather than uniformly thickening the entire layer, the absorption enhancement is localized to specific regions where particles are embedded, achieving high overall absorption with a thinner average profile
2Length of moving object
If materials with high EUV absorption coefficients (Ni, Co, Ag) are used to thin the absorber layer, then absorber layer thickness is reduced, but etchability is lost and adjacent layers are damaged
Solution Approach 1:
The Ta-based material serves as an intermediary matrix that provides etchability while hosting the high-absorption particles. The Ta-based layer is etchable by standard processes, allowing selective removal of the absorber layer without damaging adjacent MLR stack layers, while the embedded particles maintain the high absorption capability
Solution Approach 2:
The composite structure combines the etchable Ta-based material with high-absorption particles, creating a material system that inherits the beneficial properties of both components: etchability from the Ta-based matrix and high absorption from the embedded particles
3Measurement precision
If non-orthogonal illumination is used in EUV lithography, then resolution is improved, but shadowing and pattern shift occur due to absorber layer thickness
Solution Approach 1:
By locally embedding particles throughout the absorber layer, the patent creates a three-dimensional absorption distribution that reduces the effective absorption path length at oblique angles, minimizing shadowing while maintaining resolution benefits of non-orthogonal illumination
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 solution achieves higher EUV absorption with reduced line shadowing and pattern shifting, ensuring etchability and maintaining image contrast, applicable in advanced IC fabrication nodes like 7 nm and beyond.
Implementation Method 1
implanting the first layer with particles of a second EUV absorbing material, wherein the first EUV absorbing material is etchable and has a lower EUV absorption coefficient than the second EUV absorbing material
Implementation Method 2
implanting the first layer with particles of a second EUV absorbing material
Data Source
AI summary
Methods for creating a EUV photolithography mask with a thinner highly EUV absorbing absorber layer and the resulting device are disclosed. Embodiments include forming a multilayer reflector (MLR); forming first and second layers of a first EUV absorbing material over the MLR, the second layer being between the first layer and the MLR; and implanting the first layer with particles of a second EUV absorbing material, wherein the first EUV absorbing material is etchable and has a lower EUV absorption coefficient than the second EUV absorbing material, and wherein the implanted particles are substantially separated from each other.