Immersion Lithography Liquid Confinement Bubble Deflection

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Solution Overview

Problem

In immersion lithographic apparatuses, bubbles can enter the projection beam during imaging, leading to imaging defects and potentially resulting in defective devices, especially if the bubbles are large enough to affect multiple imaged devices.

Innovation Solution

A lithographic apparatus with a liquid confinement system that includes an elongate liquid supply opening to create a region of high pressure in the immersion liquid, diverting bubbles away from the image field by directing liquid toward the substrate, and optionally using a gas supplying device to enhance bubble dissolution with gases of high solubility and diffusivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If immersion liquid is used in lithographic apparatus, then imaging resolution is improved, but bubbles may enter the projection beam causing imaging defects

Engineering Contradiction:

Improveimaging resolutionVSAvoidbubbles in projection beam

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of bubbles into a beneficial one by using the pressure gradient created by liquid flow to actively divert bubbles away from the image field. The same liquid that enables high-resolution imaging also creates a flow-driven pressure gradient that pushes bubbles away from critical areas, turning a potential defect source into a protective mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies hydraulic principles by using liquid flow to create a pressure gradient in the immersion liquid. The flowing liquid generates higher pressure in certain regions that acts on bubbles, forcing them to move away from the image field. This hydraulic approach provides active bubble management without mechanical components.

Inventive Principle:

Principle #29Pneumatics and hydraulics

2Reliability

If liquid confinement system is introduced to control bubbles, then bubble-related defects are reduced, but device complexity increases

Engineering Contradiction:

Improvedefect reductionVSAvoidliquid confinement system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The liquid confinement system serves multiple functions: it confines the immersion liquid to the necessary space, creates the pressure gradient for bubble diversion, and maintains liquid flow patterns that prevent bubble formation. By combining these functions into a single system, the patent avoids adding separate complex subsystems for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the immersion liquid itself to manage bubbles through the pressure gradient it creates during normal operation. The liquid flow that is essential for imaging also provides the bubble diversion mechanism, eliminating the need for separate active bubble control systems.

Inventive Principle:

Principle #25Self-service

3Productivity

If substrate scanning speed is increased for higher throughput, then productivity improves, but bubbles have less time to dissolve before reaching image field

Engineering Contradiction:

ImprovethroughputVSAvoidimaging quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent creates a pressure gradient and liquid flow patterns in advance that actively divert bubbles away from the image field before they can cause defects. This preliminary action of bubble diversion, combined with enhanced dissolution conditions, ensures that even at high scanning speeds, bubbles are removed or dissolved before reaching the exposure area.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces gas with high solubility and diffusivity as an intermediary substance that enhances bubble dissolution. This intermediary gas accelerates the dissolution process, allowing bubbles to dissolve quickly even at high scanning speeds where residence time in the liquid is reduced.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 prevents bubbles from entering the image field, reducing the risk of imaging defects and allowing for higher throughput and lower defectivity in device manufacturing by ensuring bubbles dissolve before reaching the image field.

Implementation Method 1

the liquid confinement system has an elongate liquid supply opening arranged to create a region of relatively high pressure in the body of liquid so as to direct bubbles of gas in the liquid away from the image

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 2

using a gas supplying device to enhance bubble dissolution with gases of high solubility and diffusivity

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS9618835B2Lithographic apparatus and a device manufacturing method involving an elongate liquid supply opening or an elongate region of relatively high pressure

Publication Date: 2017.04.11 ASML NETHERLANDS BV

AI summary

In a liquid confinement structure of an immersion lithographic apparatus an elongate continuous opening forms an outlet for supplying liquid to a space beneath the projection system. The elongate slit forms a region of high shear and pressure gradient that deflects bubbles away from the image field.