EUV Reticle Absorber Layers via Electroless Deposition

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Solution Overview

Problem

Current EUV lithography reticles face limitations due to restricted material selection for absorber and phase shift layers, primarily because deposition and patterning processes must be conducted at low temperatures to prevent interdiffusion in alternating mirror layers, leading to suboptimal performance.

Innovation Solution

The use of an electroless deposition process allows for the formation of absorber and phase shift layers with materials having higher absorption coefficients and phase shifting characteristics, such as platinum group elements and transition metals, which are resistant to low-temperature anisotropic etching, enabling improved EUV reticle efficiency and resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional physical vapor deposition and reactive ion etching are used to form absorber layers, then the process can be implemented with existing equipment, but the material selection is limited to only a few practical materials (TaN or TaBN) due to low temperature constraints

Engineering Contradiction:

Improvematerial selectionVSAvoidprocess complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent changes the deposition temperature parameter from low temperature (conventional PVD) to high temperature (electroless deposition at 80-100°C), enabling the use of diverse materials such as platinum group elements, transition metals, and their alloys that have higher absorption coefficients and better phase shifting characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/physical vapor deposition process with an electroless chemical deposition process, and replaces reactive ion etching with electroless deposition, fundamentally changing the manufacturing mechanism to enable broader material selection while maintaining manufacturability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If absorber layers are formed with materials having higher absorption coefficients, then EUV reticle efficiency and resolution are improved, but the materials must be resistant to low-temperature anisotropic etching which limits material choices

Engineering Contradiction:

ImproveEUV reticle efficiencyVSAvoidmaterial selection

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of selecting materials that can be etched at low temperatures and then hoping they have good absorption properties, the patent inverts the approach by using electroless deposition to directly form absorber layers from materials selected based on their optimal optical properties, eliminating the etching step entirely

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If the thickness of absorber layers is reduced to improve resolution, then horizontal to vertical pattern bias is minimized, but the absorber layer must still provide sufficient absorption which is difficult with conventional materials

Engineering Contradiction:

Improvepattern resolutionVSAvoidabsorption coefficient

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent employs composite material systems including platinum group elements (Ru, Rh, Pd, Pt), transition metals (Ni, Co, Au), and their alloys, which provide superior absorption coefficients that enable thinner absorber layer thicknesses while maintaining sufficient EUV absorption and improving pattern resolution

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS11604406B2Method and apparatus for fabrication of very large scale integration pattern features via electroless deposition on extreme ultraviolet lithography photomasks

Publication Date: 2023.03.14 INTEL CORP

AI summary

Embodiments disclosed herein include EUV reticles and methods of forming such reticles. In an embodiment a method of forming an EUV reticle comprises providing a reticle, where the reticle comprises, a substrate, a mirror layer over the substrate, where the mirror layer comprises a plurality of first mirror layers and second mirror layers in an alternating pattern, and a capping layer over the mirror layer. In an embodiment, the method may further comprise disposing a first layer over the capping layer, patterning an opening in the first layer, and disposing a second layer in the opening, where the second layer is disposed with an electroless deposition process.