EUV Mask Pellicle Fabrication and Absorber Design

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Solution Overview

Problem

Conventional EUV lithography masks suffer from large aerial image shifts and pellicle membrane damage during fabrication, leading to poor lithography performance and usability issues.

Innovation Solution

The EUV mask incorporates an absorber layer with a specific refractive index and extinction coefficient range, and a pellicle membrane is bonded to a temporary layer with enhanced strength and a mesh-free structure to prevent damage, using materials like silicon carbide for the pellicle and Radium-based alloys for the absorber layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional EUV mask absorber layers are used, then the mask structure is simple, but large aerial image shifts occur leading to poor lithography performance

Engineering Contradiction:

Improveaerial image shiftVSAvoidabsorber layer structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent employs a composite absorber layer structure consisting of multiple materials with different optical properties. Specifically, it uses a first absorber material (e.g., TaBN) combined with a second absorber material (e.g., Ru) in specific thickness ratios to achieve the desired refractive index and extinction coefficient, thereby reducing aerial image shift while maintaining structural feasibility

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent systematically adjusts critical parameters including the refractive index (n) to 0.99-1.01 and extinction coefficient (k) to 0.40-0.55 by varying the thickness and composition of absorber layer materials. This parameter optimization directly reduces aerial image shift and improves lithography performance

Inventive Principle:

Principle #35Parameter changes

2Reliability

If conventional pellicle fabrication processes are used, then the process is simple, but the pellicle membrane becomes distorted, broken, or damaged

Engineering Contradiction:

Improvepellicle membrane integrityVSAvoidpellicle fabrication process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies a protective coating to the pellicle membrane before the fabrication process begins. This preliminary protective layer prevents the membrane from becoming distorted or broken during subsequent handling and processing steps, thereby improving reliability without significantly complicating the overall manufacturing process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a support structure or temporary carrier that cushions and supports the fragile pellicle membrane during fabrication. This beforehand cushioning prevents damage by distributing mechanical stresses and protecting the membrane from handling-induced distortion or breakage

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Object-generated harmful factors

If the pellicle membrane is made thinner to reduce interference, then the interference is minimized, but the membrane becomes more susceptible to damage

Engineering Contradiction:

Improvepellicle interferenceVSAvoidpellicle membrane strength

Core Design Contradiction:

Object-generated harmful factorsVSStrength

Solution Approach 1:

The patent uses composite material structures for the pellicle membrane, combining materials with different mechanical and optical properties. This allows the membrane to maintain sufficient strength and damage resistance while keeping the thickness optimized to minimize interference with the EUV lithography process

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent employs advanced thin film technology to create a pellicle membrane that achieves the desired thinness for minimal interference while incorporating structural features or material compositions that maintain adequate mechanical strength and damage resistance

Inventive Principle:

Principle #30Flexible shells and thin films

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 significantly reduces aerial image shifts, enhances pellicle membrane strength, and improves lithography performance by minimizing damage during processing and exposure.

Implementation Method 1

an absorber layer disposed over the capping layer. The absorber layer contains a material that has a refractive index in a range from about 0.95 to about 1.01 and an extinction coefficient greater than about 0.03

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

The EUV scanners use reflective rather than refractive optics, i.e., mirrors instead of lenses. EUV scanners provide the desired pattern on an absorption layer

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 3

reflective optics rather than refractive optics is used. A multi-layered (ML) structure is used as a EUV mask blank

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS10831094B2Pellicle for EUV mask and fabrication thereof

Publication Date: 2020.11.10 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The present disclosure provides a method in accordance with some embodiments. A wafer is grinded from a back side. The wafer is inserted into an opening defined by a frame holder. The frame holder is attached to a carrier through a temporary layer. A front side of the wafer is attached to the temporary layer. Thereafter, the wafer is etched from the back side until the wafer reaches a predetermined thickness. Thereafter, the frame holder and the wafer therein are separated from the temporary layer and the carrier.