Microlithography Measuring Apparatus for Overlay Precision

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Solution Overview

Problem

Current microlithography projection exposure tools face challenges in efficiently measuring the lateral position of measurement structures on wafers and reticles, leading to position errors and reduced throughput due to high-speed and high-acceleration measurements, which result in vibration-induced errors and decreased overlay quality between exposure levels.

Innovation Solution

A measuring apparatus that simultaneously measures multiple measurement structures across a two-dimensional substrate surface, using interferometric methods with diffraction gratings and reflective elements to determine relative positions and adapt exposure parameters dynamically, thereby reducing measurement time and vibration transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high-speed and high-acceleration measurement is used to reduce measurement time, then productivity is improved, but measurement precision deteriorates due to vibration-induced errors

Engineering Contradiction:

Improvemeasurement speedVSAvoidposition measurement accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The measurement task is divided into multiple independent measurement channels, each measuring a specific lateral position component. By segmenting the measurement function across parallel channels rather than sequential scanning, the system achieves high throughput without requiring extreme speeds that cause vibrations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from one-dimensional sequential measurement to two-dimensional simultaneous measurement by introducing a second lateral direction measurement component. This dimensional expansion allows parallel measurement of multiple position components, reducing measurement time without compromising precision through high-speed motion.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If sequential measurement of adjustment marks is used, then measurement precision is maintained, but productivity deteriorates due to linear time increase

Engineering Contradiction:

Improveposition measurement accuracyVSAvoidwafer throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

Multiple measurement functions are merged into a single simultaneous measurement operation. The measuring apparatus measures adjustment marks in different lateral positions concurrently rather than sequentially, combining multiple measurement tasks into one operation to achieve parallel processing and improve throughput.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The measuring apparatus is designed with multi-functionality to measure multiple lateral position components and adjustment marks simultaneously using a single device and measurement operation, eliminating the need for separate measurement steps and improving overall productivity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Productivity

If high-acceleration wafer table movement is used to achieve fast measurement, then productivity is improved, but manufacturing precision deteriorates due to vibration transfer

Engineering Contradiction:

Improvemeasurement speedVSAvoidoverlay quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces high-speed mechanical table movement with a static or low-speed measurement system that uses optical interferometric methods to achieve fast measurement without mechanical acceleration. This substitution eliminates vibration transfer from the mechanical system while maintaining high measurement throughput through optical parallel measurement.

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 approach allows for faster and more accurate measurement of lateral positions, reducing vibration-induced errors and enhancing overlay quality between exposure levels, while also reducing the complexity and installation space required for the measuring apparatus.

Implementation Method 1

using interferometric methods with diffraction gratings and reflective elements to determine relative positions

Methodology Applied

Scientific EffectInterferometry: Interference

Implementation Method 2

using interferometric methods with diffraction gratings

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS9442393B2Projection exposure tool for microlithography and method for microlithographic imaging

Publication Date: 2016.09.13 CARL ZEISS SMT GMBH

AI summary

A projection exposure tool for microlithography for imaging mask structures of an image-providing substrate onto a substrate to be structured includes a measuring apparatus configured to determine a relative position of measurement structures disposed on a surface of one of the substrates in relation to one another in at least one lateral direction with respect to the substrate surface and to thereby simultaneously measure a number of measurement structures disposed laterally offset in relation to one another.