Pulse Modifier with Adjustable Etendue for Lithography

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Lithographic apparatuses face issues with optical damage and degradation due to high-intensity pulses, which shorten the usable lifetime of lens elements, and existing pulse stretching units lack control over beam size and direction, leading to dynamic speckle and line width roughness.

Innovation Solution

A pulse modifier system using a beam splitter, divergence optical elements, and curved mirrors to increase the temporal pulse length and Etendue of the illumination beam, reducing speckle and optical damage by stretching pulses and adjusting beam parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If pulse energy is increased to improve illumination intensity, then productivity is improved, but optical damage and lens degradation increase

Engineering Contradiction:

Improveillumination intensityVSAvoidlens element lifetime

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The single high-intensity pulse is segmented into multiple lower-intensity pulses separated in time. The pulse stretcher divides the input pulse into multiple copies, each separated by an optical delay, thereby reducing the peak intensity of individual pulses while maintaining the total energy delivery for lithographic exposure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The pulse train creates periodic action by delivering multiple pulses in sequence rather than a single continuous high-intensity pulse. This periodic delivery allows the optical components to cool between pulses, reducing cumulative thermal damage while maintaining effective illumination for the lithographic process.

Inventive Principle:

Principle #19Periodic action

2Reliability

If pulse length is increased to reduce optical damage, then reliability is improved, but beam control capability deteriorates

Engineering Contradiction:

Improveoptical component lifetimeVSAvoidbeam size and direction control

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system dynamically controls beam parameters by using adjustable optical delay elements and variable Etendue control mechanisms. The pulse stretcher allows dynamic adjustment of pulse spacing and duration, while the Etendue control enables dynamic adjustment of beam size and divergence, maintaining operational flexibility despite pulse stretching.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If pulse duration is stretched to reduce speckle, then manufacturing precision is improved, but device complexity increases

Engineering Contradiction:

Improveline width uniformityVSAvoidpulse stretching unit structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The pulse stretching function is nested within the existing lithographic illumination system by integrating the pulse stretcher between the laser source and illumination optics. The Etendue control mechanism is nested within the beam delivery system, allowing both functions to be implemented without requiring completely separate systems.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The pulse stretcher and Etendue control unit serve multiple functions: they stretch pulse duration to reduce speckle, control beam Etendue to improve uniformity, and maintain beam delivery to the lithographic target. This multi-functionality reduces the need for separate dedicated systems for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 effectively extends the usable lifetime of lens elements, reduces speckle and line width roughness, and improves the uniformity of the illumination dose on the wafer by adjusting the pulse duration and beam Etendue.

Implementation Method 1

a beam splitter receives an input pulse of radiation and divides the input pulse into a first and a second pulse portion

Methodology Applied

Scientific EffectBeam splitting: Reflection

Implementation Method 2

a divergence optical element which diverts the first pulse portion by an angle resulting in a divergence wherein Etendue is increased

Methodology Applied

Scientific EffectOptical divergence: Refraction

Implementation Method 3

A first mirror and a second mirror, each with a radius of curvature, face each other with a predetermined separation and receive the diverted first pulse portion and redirect the first pulse portion along the diverted beam path

Methodology Applied

Scientific EffectOptical reflection: Reflection

Data Source

PatentUS8625199B2Pulse modifier with adjustable etendue

Publication Date: 2014.01.07 ASML NETHERLANDS BV

AI summary

A beam modifying unit increases both temporal pulse length and Etendue of an illumination beam. The pulse modifying unit receives an input pulse of radiation and emits one or more corresponding output pulses of radiation. A beam splitter divides the incoming pulse into a first and a second pulse portion, and directs the first pulse portion along a second optical path and the second portion along a first optical path as a portion of an output beam. The second optical path includes a divergence optical element. A first and a second mirror, each with a radius of curvature, are disposed facing each other with a predetermined separation, and receive the second pulse portion to redirect the second portion, such that the optical path of the second portion through the pulse modifier is longer than that of the first portion, and the separation is less than radius of curvature.