Lens Heating Aware Source Mask Optimization

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Solution Overview

Problem

Current lithographic processes face challenges in accurately compensating for lens heating effects, which lead to residual aberrations and reduced image quality, especially with off-axis illuminations and deep ultraviolet radiation, as existing correction methods are either experimentally driven and time-consuming or iterative and difficult to implement.

Innovation Solution

A computer-implemented method that computes a multi-variable cost function accounting for lens heating effects, adjusting design variables of the illumination source and design layout to optimize the lithographic process, thereby reconfiguring the characteristics until a predefined termination condition is satisfied, incorporating a lens-heating aware source mask optimization (SMO) to minimize aberrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If off-axis illumination and deep ultraviolet radiation are used to improve resolution, then imaging fidelity is improved, but lens heating effects increase causing residual aberrations

Engineering Contradiction:

Improveimaging fidelityVSAvoidlens heating effects

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by computing and applying lens heating compensation values before the actual lithography exposure. The system calculates expected lens heating effects based on the illumination source characteristics and design layout, then pre-determines compensation values that are applied to the illumination source configuration or mask design to counteract the anticipated heating-induced aberrations during exposure.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If experimental correction methods are used to compensate for lens heating, then aberration correction is achieved, but process time increases significantly

Engineering Contradiction:

Improveaberration correctionVSAvoidprocess time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent replaces experimental mechanical correction methods with a computational approach. Instead of physically adjusting optical elements through experimental trial-and-error procedures, the system uses computer algorithms to calculate lens heating effects and determine compensation values, which are then applied through software-controlled adjustments to the illumination source or mask design parameters.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If iterative correction methods are used to address lens heating, then image quality improves, but implementation complexity increases

Engineering Contradiction:

Improveimage qualityVSAvoidimplementation complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts the lens heating compensation calculation from the main lithography exposure process. The system separates the computation of lens heating effects and determination of compensation values as a distinct preliminary step, allowing the main exposure process to use the pre-calculated compensation values without requiring complex iterative adjustments during production.

Inventive Principle:

Principle #2Taking out (Extraction)

4Device complexity

If conventional source mask optimization is applied without lens heating awareness, then computational simplicity is maintained, but residual aberrations remain

Engineering Contradiction:

Improvecomputational simplicityVSAvoidresidual aberrations

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent modifies the optimization parameters by incorporating lens heating compensation values into the source mask optimization process. The system adjusts illumination source parameters or mask design parameters based on calculated lens heating effects, transforming the optimization problem to account for temperature-induced aberrations while maintaining a systematic computational approach.

Inventive Principle:

Principle #35Parameter changes

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 effectively reduces lens heating-induced aberrations, ensuring that more patterns meet specifications across the field, improving imaging fidelity and reducing printing defects, as demonstrated by comparisons between conventional and optimized methods.

Implementation Method 1

deep ultraviolet radiation

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Implementation Method 2

lens heating effects

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentUS9940427B2Lens heating aware source mask optimization for advanced lithography

Publication Date: 2018.04.10 ASML NETHERLANDS BV

AI summary

A computer-implemented method for improving a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus comprising an illumination source and projection optics, the method including computing a multi-variable cost function of a plurality of design variables that are characteristics of the lithographic process, at least some of the design variables being characteristics of the illumination source and the design layout, the computing of the multi-variable cost function accounting for lens heating effects; and reconfiguring the characteristics of the lithographic process by adjusting the design variables until a predefined termination condition is satisfied.