Surface Position Detection for Non-Flat Substrate Alignment

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Solution Overview

Problem

In exposure apparatuses where a pattern is projected onto a photosensitive substrate, the shallow depth of focus of the projection optical system complicates accurate alignment of the substrate's surface relative to the image surface due to non-flat exposed surfaces.

Innovation Solution

A surface position detection device that uses a light transmission unit to radiate modulated detection lights obliquely onto the substrate surface, a light reception unit to receive and convert these lights, and a calculation unit to determine the substrate's position based on the photoelectric conversion signals, ensuring precise alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a projection optical system with shallow depth of focus is used to achieve high resolution patterning, then manufacturing precision is improved, but alignment accuracy of the substrate surface deteriorates due to non-flat exposed surfaces

Engineering Contradiction:

Improvepatterning resolutionVSAvoidsurface alignment accuracy

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent introduces an auxiliary optical system as an intermediary to measure substrate surface position and inclination independently from the main projection optical system. This separate measurement system uses light reception elements to detect reflected light from the substrate surface, providing accurate surface position data without being affected by the shallow depth of focus of the projection system, thereby resolving the contradiction between high-resolution patterning and accurate surface alignment

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical contact-based surface measurement methods with optical detection. By using light reflection and photoelectric conversion to measure substrate surface position and inclination, the system achieves non-contact, high-precision measurement that does not interfere with the exposure process or the shallow depth of focus requirements of the projection optical system

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If the substrate surface is made non-flat to accommodate process requirements, then manufacturing flexibility is improved, but position alignment accuracy relative to the image surface deteriorates

Engineering Contradiction:

Improveprocess adaptabilityVSAvoidsurface position alignment

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the auxiliary optical system continuously measures substrate surface position and inclination, and this measurement information is fed back to the control system. The control system then adjusts the substrate stage position and orientation in real-time to maintain accurate alignment with the image surface, allowing the system to accommodate non-flat surfaces while maintaining alignment precision through active compensation

Inventive Principle:

Principle #23Feedback

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

Enables accurate positioning of the substrate surface relative to the projection optical system, enhancing the exposure process's precision and effectiveness.

Implementation Method 1

a light reception unit that has a light detection portion having a light reception surface arranged at an optically conjugated position with respect to the detected surface, receives at a different position of each light reception surface, the plurality of detection lights reflected by a detection region

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

receives at a different position of each light reception surface, the plurality of detection lights reflected by a detection region of which a width in the first direction is a predetermined value in the irradiation region, and outputs each photoelectric conversion signal of the plurality of detection lights

Methodology Applied

Scientific EffectPhotoelectric conversion: Photoelectric Effect

Data Source

PatentUS20250279321A1Surface position detection device, exposure apparatus, substrate-processing system, and device-manufacturing method

Publication Date: 2025.09.04 NIKON CORP

AI summary

A surface position detection device that obtains position information of a detected surface along an axis that intersects the detected surface includes: a light transmission unit by which a plurality of detection lights having a smoothly modulated intensity in the detected surface in a first direction within the detected surface are radiated and superimposed onto the detected surface obliquely from a direction having a direction component in the first direction and which forms an irradiation region on the detected surface; a light reception unit that has a light detection portion having a light reception surface arranged at an optically conjugated position with respect to the detected surface, receives at a different position of each light reception surface, the plurality of detection lights reflected by a detection region of which a width in the first direction is a predetermined value in the irradiation region, and outputs each photoelectric conversion signal of the plurality of detection lights; and a calculation unit that calculates position information of the detected surface based on the photoelectric conversion signal of the plurality of detection lights output from the light reception unit.