Spatial Light Modulator Illumination System for Pupil Shaping

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Solution Overview

Problem

Conventional exposure apparatuses lack the flexibility to change the shape of the pupil intensity distribution and polarization state, limiting their ability to accurately transfer fine patterns onto a photosensitive substrate under optimal illumination conditions.

Innovation Solution

An illumination optical system incorporating a spatial light modulator with individually controlled optical elements and a polarization unit that can alter the polarization state of incident light beams, allowing for variable light intensity distributions and polarization changes in the illumination pupil.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If an aperture diaphragm with a wave plate is used to form a specific pupil intensity distribution and polarization state, then the illumination condition is optimized for pattern transfer, but the system lacks flexibility to change the shape of the pupil intensity distribution and polarization state without exchanging components

Engineering Contradiction:

Improveflexibility to change pupil intensity distribution shape and polarization stateVSAvoidsystem complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces the static aperture diaphragm with a wave plate with a dynamic spatial light modulator that can change the pupil intensity distribution shape and polarization state by controlling the tilt angles of its mirror elements, enabling flexible adaptation without component exchange

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The spatial light modulator changes the polarization state and intensity distribution by adjusting the tilt angles of its mirror elements, thereby dynamically modifying optical parameters to achieve different illumination conditions

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the aperture diaphragm equipped with the wave plate is exchanged to change the pupil intensity distribution shape and polarization state, then different illumination conditions can be achieved, but the operation time increases and productivity decreases

Engineering Contradiction:

Improveability to change illumination conditionsVSAvoidpattern transfer efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The spatial light modulator enables real-time dynamic adjustment of the pupil intensity distribution shape and polarization state by controlling mirror element tilt angles, eliminating the need for component exchange and improving productivity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent replaces the mechanical component exchange system with an optical control system using a spatial light modulator that adjusts illumination parameters through electronic control of mirror tilts, reducing operation time and increasing throughput

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration provides a high degree of freedom in shaping the pupil intensity distribution and polarization state, enabling precise and accurate transfer of fine patterns onto a photosensitive substrate with improved illumination conditions.

Implementation Method 1

a spatial light modulator (3) which includes a plurality of mirror elements (3a) arranged within a predetermined plane and controlled individually, and which forms a light intensity distribution in a variable manner in an illumination pupil

Methodology Applied

Scientific EffectOptical reflection: Reflection

Implementation Method 2

a polarization unit (5) which polarizes an incident light beam F1 into a first partial light beam F11 and a second partial light beam F12 different from the first partial light beam F11, coming into the polarization unit (5) such that the first partial light beam F11 and the second partial light beam F12 have polarization states different from each other

Methodology Applied

Scientific EffectPolarization: Polarisation

Data Source

PatentUS10691026B2Illumination optical system, exposure apparatus, device production method, and light polarization unit

Publication Date: 2020.06.23 NIKON CORP

AI summary

An illumination optical system which illuminates an illumination objective surface with a light from a light source. The illumination optical system includes a spatial light modulator which includes a plurality of optical elements arranged within a predetermined plane and controlled individually, and which forms a light intensity distribution in an illumination pupil of the illumination optical system; and a polarization unit which is arranged in a position optically conjugate with the predetermined plane, and which polarizes an incident light beam having a first and second partial light beams, coming into the polarization unit such that the first and second partial light beams have polarization states different from each other, and emits the polarized incident light beam as an outgoing light beam, wherein the polarization unit changes, in a cross section of the outgoing light beam, a ratio between a cross sectional areas of the first and second partial light beams.