Beam Steering Assembly for Illumination Misalignment Compensation

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Solution Overview

Problem

Existing wafer inspection systems face challenges in compensating for illumination beam misalignment due to system jitter, which affects the capture rate of ever-shrinking semiconductor devices, with sources including air wiggle, light source instabilities, and mechanical vibrations.

Innovation Solution

A system and method that utilize a beam steering assembly and a beam monitoring assembly, coupled with a controller, to adjust the illumination beam by calculating differences between zero and offset parameters, and actuating motors to form a corrected beam, thereby compensating for misalignment in both x and y directions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional illumination systems are used without active compensation, then the system structure remains simple, but the beam alignment stability deteriorates due to system jitter

Engineering Contradiction:

Improvebeam alignment stabilityVSAvoidsystem structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements a feedback control system where a beam monitoring assembly continuously measures the position of the illumination beam, and a controller adjusts the beam steering assembly based on these measurements to maintain accurate alignment. This closed-loop feedback mechanism compensates for system jitter and maintains beam alignment stability.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces a beam steering assembly with movable mirrors as an intermediary component between the light source and the wafer. This intermediary allows dynamic adjustment of the beam path to compensate for alignment errors caused by system jitter without requiring changes to the fundamental illumination system architecture.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If higher inspection precision is required for ever-shrinking devices, then the capture rate improves, but the system becomes more sensitive to beam misalignment

Engineering Contradiction:

Improveinspection precisionVSAvoidbeam alignment stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent transitions from a static illumination system to a dynamic one by implementing real-time beam position monitoring and active compensation through the beam steering assembly. This allows the system to adapt to changing conditions and maintain alignment stability even as inspection precision requirements increase.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The continuous feedback loop monitors beam position and makes real-time adjustments to compensate for misalignment, ensuring that high inspection precision can be maintained without sacrificing beam alignment stability.

Inventive Principle:

Principle #23Feedback

3Reliability

If multiple jitter sources (air wiggle, light source instability, mechanical vibration) are present, then the system operates in realistic conditions, but the beam misalignment increases

Engineering Contradiction:

Improvebeam alignment stabilityVSAvoidsystem jitter

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful effect of system jitter into a measurable signal that triggers compensatory action. By monitoring beam position deviations caused by various jitter sources and actively correcting them, the system turns the problem of environmental disturbances into an opportunity for demonstrated compensation capability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The feedback control system continuously counteracts the effects of multiple jitter sources by measuring their impact on beam position and applying corrective adjustments through the beam steering assembly, maintaining alignment stability despite realistic operating conditions.

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

Significantly reduces system jitter by approximately 10 times, improving signal stability and capture rate in wafer inspection systems by accurately adjusting the illumination beam to compensate for misalignment.

Implementation Method 1

a beam steering assembly configured to adjust an incident beam to form a corrected beam

Methodology Applied

Scientific EffectLight reflection: Reflection

Data Source

PatentUS10495579B2System and method for compensation of illumination beam misalignment

Publication Date: 2019.12.03 KLA CORP

AI summary

A system includes a beam steering assembly configured to adjust an incident beam to form a corrected beam; a beam monitoring assembly configured to generate monitoring data for the corrected beam including one or more offset parameters of the corrected beam; and a controller configured to store one or more zero parameters of the corrected beam, calculate at least one difference between the one or more zero parameters and the one or more offset parameters of the corrected beam, determine one or more beam position adjustments of the incident beam based on the at least one difference between the one or more zero parameters and the one or more offset parameters of the corrected beam, and direct the beam steering assembly via one or more motor drivers to actuate one or more motors to adjust the incident beam to form the corrected beam.