Lithographic Apparatus Substrate Table Cooling via Fluid Array

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Solution Overview

Problem

Conventional lithographic apparatuses face challenges with wafer heating due to high radiation dosages, leading to overlay errors and inefficient thermal conditioning, particularly due to the poor thermal conduction of wafer table materials and contact resistance.

Innovation Solution

A lithographic apparatus with a conditioning system that uses a dense array of holes in the substrate table to efficiently supply and remove a conditioning fluid, such as air or water, directly to and from the substrate, enhancing thermal conditioning and reducing wafer heating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional cooling techniques are used, then global wafer cooling is achieved, but local wafer heating cannot be effectively addressed due to poor thermal conduction of wafer table material

Engineering Contradiction:

Improvewafer temperatureVSAvoidoverlay accuracy

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent divides the cooling approach into global cooling (via wafer table) and local cooling (via direct fluid application to specific heated regions). This segmentation allows simultaneous addressal of both global and local thermal issues that cannot be effectively resolved by a single cooling method.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different cooling strategies to different regions of the wafer - global cooling through the wafer table for overall temperature control, and localized cooling through direct fluid application to specific hot spots. This local quality approach optimizes cooling efficiency for each region's specific thermal conditions.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If high radiation dosage is used to image smaller features, then imaging capability is improved, but wafer heating increases causing overlay errors

Engineering Contradiction:

Improvefeature size imaging capabilityVSAvoidwafer temperature

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The patent applies preliminary cooling measures before and during the exposure process to counteract the heating effect of high radiation dosage. By pre-cooling the wafer and maintaining cooling during exposure, the system prepares the wafer to withstand the thermal load of high-dose imaging without suffering overlay errors.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent converts the harmful thermal effect of high-radiation exposure into a manageable condition by implementing active cooling systems. The heat generated by high-dose imaging, which would normally cause overlay errors, is instead used as a controlled parameter that can be compensated for through precise thermal management, allowing the benefits of high-resolution imaging to be realized.

Inventive Principle:

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

3Manufacturing precision

If conventional lithographic apparatus operates at ultraviolet and shorter wavelengths, then imaging of smaller features is enabled, but wafer heating errors become a significant contributing factor to total overlay error

Engineering Contradiction:

Improvepattern imaging capabilityVSAvoidwafer heating errors

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements preliminary thermal conditioning of the wafer before exposure and maintains cooling during the process. This preliminary action ensures the wafer starts in an optimal thermal state and remains stable throughout high-energy exposure, preventing heating errors from degrading overlay accuracy at ultraviolet and shorter wavelengths.

Inventive Principle:

Principle #10Preliminary action

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 significantly reduces wafer heating, improving overlay performance and cooling efficiency without compromising the apparatus's performance or introducing vibrations, with air flow reducing global wafer temperature by a factor of 2 to 3 and water flow achieving a 4 to 10-fold reduction in global heating.

Implementation Method 1

a conditioning system constructed to directly condition a non-target portion of the substrate with a conditioning fluid

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a dense array of holes in the substrate table to efficiently supply and remove a conditioning fluid, such as air or water, directly to and from the substrate

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS8749762B2Lithographic apparatus and device manufacturing method

Publication Date: 2014.06.10 ASML NETHERLANDS BV

AI summary

A lithographic apparatus includes an illumination system to provide a beam of radiation, a support to support a patterning devices, the patterning devices configured to impart the beam with a pattern in its cross-section, a substrate table to hold a substrate, a projection system to project the patterned beam onto a target portion of the substrate, and a conditioning system to condition the substrate. The conditioning system conditions a non-target portion of the substrate with a conditioning fluid. A method of manufacturing a device includes conditioning a non-target portion of a substrate.