Dual-Wavelength Pattern Exposure for Micromirror Diffraction Control

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Solution Overview

Problem

Existing pattern exposure devices using spatial light modulation elements like digital mirror devices (DMDs) suffer from degraded imaging states and reduced light intensity due to the action of diffraction gratings when projecting fine patterns, particularly when illuminated obliquely.

Innovation Solution

The pattern exposure device irradiates a spatial light modulation element with two types of illumination light, having different wavelengths, at specific incidence angles corresponding to twice the tilt angle of the ON-state micromirrors, to control the diffraction angles and ensure they fall within a predetermined range or are distributed around the optical axis, thereby optimizing the exposure process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If oblique illumination is used with a spatial light modulation element, then the device can project patterns without requiring a fixed mask substrate, but the diffraction grating effect degrades imaging quality and reduces light intensity

Engineering Contradiction:

Improvemask pattern flexibilityVSAvoidimaging quality

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent changes the wavelength parameter of illumination light from a single wavelength to multiple wavelengths (λ1 and λ2). By carefully selecting wavelengths where the diffraction angle difference falls within an allowable range, the system maintains acceptable imaging quality while preserving the flexibility of spatial light modulation. This parameter adjustment resolves the contradiction by finding optimal wavelengths that minimize diffraction grating effects.

Inventive Principle:

Principle #35Parameter changes

2Extent of automation

If oblique illumination is used with a spatial light modulation element, then the device can project patterns dynamically, but the diffraction grating effect reduces light intensity reaching the substrate

Engineering Contradiction:

Improvedynamic pattern projectionVSAvoidlight intensity

Core Design Contradiction:

Extent of automationVSIllumination intensity

Solution Approach 1:

The patent adjusts the wavelength parameter to compensate for intensity loss. By selecting specific wavelength pairs (λ1, λ2) where the diffraction angle difference is within an allowable range, the system maintains sufficient light intensity reaching the substrate while preserving dynamic pattern projection capabilities. The wavelength selection optimizes the balance between automation and illumination intensity.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a single wavelength is used for illumination, then the optical system is simpler, but the diffraction angle cannot be optimized for different pattern requirements

Engineering Contradiction:

Improveillumination system complexityVSAvoiddiffraction angle control

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent introduces multiple wavelengths (λ1 and λ2) to enable diffraction angle optimization for different pattern requirements. The wavelength difference is carefully controlled so that the resulting diffraction angle difference remains within an allowable range, preventing excessive system complexity while achieving adaptable diffraction control for various exposure needs.

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 enhances the imaging quality and light intensity of projected patterns by minimizing degradation caused by diffraction gratings, resulting in improved exposure performance.

Implementation Method 1

a diffraction angle of main diffraction light of an order j1, which is generated from the ON-state micromirror under the wavelength λ1

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

reflection light from a selected ON-state micromirror of the spatial light modulation element

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS20250306470A1Pattern exposure device and device manufacturing method

Publication Date: 2025.10.02 NIKON CORP

AI summary

An exposure device includes: a spatial light modulation element including micromirrors; an illumination unit that irradiates the spatial light modulation element with first light with a peak wavelength λ1 and second light with a peak wavelength λ2 (λ2≈λ1), so that the first light is diffracted by ON-state micromirrors of the spatial light modulation element as first diffraction light and the second light is diffracted by the ON-state micromirror as second diffraction light; and a projection unit, wherein the first diffraction light and the second diffraction light enter the projection unit, so that the first diffraction light and the second diffraction light are distributed with an optical axis of the projection unit interposed therebetween.