EUV Lithography Pupil Phase Modulator for Low Pattern Density

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Solution Overview

Problem

Extreme ultraviolet lithography (EUVL) faces challenges with low throughput and energy loss due to the high absorption of materials used in reflective optics and the low reflectance of EUV masks, particularly in achieving high resolution for low pattern density features.

Innovation Solution

A binary phase mask (BPM) with two phase states and a pupil filter are used in conjunction with an off-axis illumination mode to enhance EUV light intensity and reduce energy loss, achieving improved reflectivity and pattern density by filtering out non-diffracted light components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If reflective optics are used for EUV lithography, then the system can achieve the necessary resolution, but energy loss increases due to low reflectance of EUV mask materials

Engineering Contradiction:

ImproveresolutionVSAvoidenergy loss

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent changes the optical parameters by transitioning from reflective optics to refractive optics using zone plates. This parameter change allows the system to achieve the necessary resolution while significantly reducing energy loss, as refractive optics can focus EUV light more efficiently without the high absorption losses inherent in reflective mask configurations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical/optical reflection-based system with a refraction-based zone plate system. This substitution eliminates the need for highly reflective mask layers and enables more efficient EUV light transmission and focusing, thereby reducing energy loss while maintaining resolution capabilities.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If binary intensity masks are employed in EUVL, then the mask structure is simple, but throughput decreases due to low transmittance through via layers

Engineering Contradiction:

Improvemask structureVSAvoidthroughput

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent changes the mask operating parameters by using zone plates with specific focal lengths and zone configurations. This allows the system to achieve high throughput by efficiently transmitting EUV light through via layers while maintaining the simplicity of the mask structure through the use of standardized zone plate designs.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If EUV energy is substantially lost on the optical path, then the reflectance of EUV mask is low, but the EUV energy reaching the wafer is much less

Engineering Contradiction:

Improveenergy lossVSAvoidEUV energy reaching wafer

Core Design Contradiction:

Loss of energyVSIllumination intensity

Solution Approach 1:

The patent replaces the reflective optical path with a refractive zone plate system that focuses EUV light directly onto the wafer. This substitution eliminates the intermediate reflection steps that cause significant energy loss, thereby delivering higher EUV energy intensity to the wafer while reducing overall energy loss in the optical path.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enhances exposure intensity, reduces mask error enhancement factor, and increases throughput, especially for low pattern density features, while minimizing energy loss and improving printability.

Implementation Method 1

a binary phase mask (BPM) with two phase states and a pupil filter are used in conjunction with an off-axis illumination mode to enhance EUV light intensity and reduce energy loss, achieving improved reflectivity and pattern density by filtering out non-diffracted light components

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

filtering out non-diffracted light components

Methodology Applied

Scientific EffectAbsorption: Absorption (EM radiation)

Implementation Method 3

reflective optics rather than refractive optics is used. A reflective mask is used. However, the reflectance of EUV mask is very low. The EUV energy is substantially lost on the optical path

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS10976655B2Extreme ultraviolet lithography system, device, and method for printing low pattern density features

Publication Date: 2021.04.13 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A lithography system includes a radiation source configured to generate an extreme ultraviolet (EUV) light. The lithography system includes a mask that defines one or more features of an integrated circuit (IC). The lithography system includes an illuminator configured to direct the EUV light onto the mask. The mask diffracts the EUV light into a 0-th order ray and a plurality of higher order rays. The lithography system includes a wafer stage configured to secure a wafer that is to be patterned according to the one or more features defined by the mask. The lithography system includes a pupil phase modulator positioned in a pupil plane that is located between the mask and the wafer stage. The pupil phase modulator is configured to change a phase of the 0-th order ray.