EUV Mask Absorber Layer Optimization for 3D Effect Reduction

Solution Overview

Problem

In extreme ultraviolet lithography, the reduction in size of semiconductor components poses challenges in maintaining efficient and stable generation of EUV radiation due to variations in target droplet size and arrival time, affecting the reproducibility and intensity of EUV radiation.

Innovation Solution

The use of a laser-produced plasma (LPP) EUV radiation source with a mechanism to generate EUV radiation, where target droplets are stabilized to arrive uniformly at the excitation zone, synchronized with the excitation laser pulse, and an absorber layer with optimized thickness and material properties to reduce the mask 3D effect and enhance lithographic performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If target droplet size and arrival time are reduced to enable smaller semiconductor components, then component size decreases, but EUV radiation stability and reproducibility deteriorate

Engineering Contradiction:

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent applies parameter changes by precisely controlling the physical and chemical parameters of the absorber layer, including thickness (30-50 nm), material composition (molybdenum, silicon, ruthenium), and optical properties (extinction coefficient, index of refraction). These parameter optimizations enable the absorber to effectively attenuate EUV radiation while minimizing mask 3D effects, thereby maintaining radiation stability despite reduced component sizes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite materials by using multi-layer absorber structures combining different materials (molybdenum, silicon, ruthenium) with complementary properties. This composite approach allows simultaneous optimization of radiation absorption, phase control, and mechanical stability, resolving the contradiction between miniaturization and radiation stability

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If absorber thickness is reduced to minimize mask 3D effect, then mask 3D effect decreases, but photolithographic performance deteriorates

Engineering Contradiction:

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The patent optimizes the absorber layer parameters by precisely controlling thickness (30-50 nm) and material composition to achieve the optimal balance. This parameter optimization ensures sufficient radiation attenuation while minimizing mask 3D effects, and the controlled index of refraction and extinction coefficient further enhance photolithographic performance by improving image log slope and reducing best focus shift

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The multi-layer composite absorber structure allows different materials to perform specialized functions: molybdenum and silicon layers provide radiation attenuation and phase control, while ruthenium capping layer protects the underlying layers. This division of labor enables simultaneous achievement of reduced mask 3D effect and enhanced photolithographic performance

Inventive Principle:

Principle #40Composite materials

3Reliability

If target droplets are stabilized to arrive uniformly at excitation zone, then EUV radiation reproducibility improves, but system complexity increases

Engineering Contradiction:

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements feedback control by monitoring target droplet characteristics and adjusting generation parameters in real-time. This feedback mechanism ensures uniform droplet arrival at the excitation zone, maintaining consistent EUV radiation output despite variations in operating conditions, while the automated control system manages the increased complexity

Inventive Principle:

Principle #23Feedback

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 improves the stability and efficiency of EUV radiation generation, leading to enhanced photolithographic performance with improved best focus shift, critical depth of focus, and reduced mask 3D effect, thereby supporting the miniaturization of semiconductor components.

Implementation Method 1

a laser-produced plasma (LPP) EUV radiation source with a mechanism to generate EUV radiation

Methodology Applied

Scientific EffectLaser-produced plasma: Plasma

Implementation Method 2

synchronized with the excitation laser pulse

Methodology Applied

Scientific EffectLaser excitation: Laser

Implementation Method 3

an absorber layer with optimized thickness and material properties to reduce the mask 3D effect

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Data Source

PatentUS20220350236A1Extreme ultraviolet mask and method of manufacturing the same

Publication Date: 2022.11.03

AI summary

An extreme ultraviolet mask, comprising an absorber having an index of refraction ranging from 0.87 to 1.02, an extinction coefficient ranging from 0.065 to 0.085, and a thickness ranging from 33.5 nm to 43.5 nm.