Segmented Polarizer for Optical Imaging Defect Detection

Solution Overview

Problem

Discriminating defect signals from background noise in optical imaging of unpatterned wafers is challenging due to light scattered off the wafer, which affects high-throughput defect inspection and review processes.

Innovation Solution

A system utilizing a segmented polarizer with multiple polarizer segments, each with distinct dimensions and polarization directions, is employed to enhance the signal-to-noise ratio (SNR) by minimizing background noise radiation and maximizing SNR when defects are present, combined with an optical mask to further optimize radiation passing through the polarizer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a linear polarizer is used to filter scattered light, then the system structure is simple, but the background noise radiation cannot be sufficiently minimized and the signal-to-noise ratio is limited

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidpolarizer structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The polarizer is divided into multiple segments (at least four) with different polarization directions arranged in a segmented polarizer structure. Each segment filters radiation with specific polarization characteristics, enabling differential suppression of background noise while preserving defect signals, thereby achieving higher signal-to-noise ratio without using a single complex polarizer design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the polarizer are assigned different polarization directions tailored to the local scattering characteristics. The polarization direction of each segment is optimized for the specific radiation pattern it needs to filter, creating local optimization that collectively minimizes background noise across the entire field of view

Inventive Principle:

Principle #3Local quality

2Measurement precision

If the polarization direction of the polarizer is optimized for maximum signal transmission, then the defect detection capability is enhanced, but the background noise from scattered light increases

Engineering Contradiction:

Improvedefect detection accuracyVSAvoidbackground noise radiation

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The polarizer is divided into multiple segments (at least four) with different polarization directions arranged in a segmented polarizer structure. Each segment filters radiation with specific polarization characteristics, enabling differential suppression of background noise while preserving defect signals, thereby achieving higher signal-to-noise ratio without using a single complex polarizer design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the polarizer are assigned different polarization directions tailored to the local scattering characteristics. The polarization direction of each segment is optimized for the specific radiation pattern it needs to filter, creating local optimization that collectively minimizes background noise across the entire field of view

Inventive Principle:

Principle #3Local quality

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 improves the discrimination of defect signatures from background noise, enhancing the accuracy of defect detection and correction in optical imaging systems for unpatterned wafers.

Implementation Method 1

The segmented polarizer includes at least four polarizer segments characterized by respective dimensions and polarization directions. The respective dimensions and polarization direction of each of the at least four polarizer segments are such that an overall power of background noise radiation, generated in the scattering of the incident light beam from the region and passed through all of the at least four polarizer segments, is decreased

Methodology Applied

Scientific EffectPolarization: Polarisation

Implementation Method 2

The relay optics is configured to collect and guide, radiation scattered off the unpatterned wafer, onto the segmented polarizer

Methodology Applied

Scientific EffectLight scattering: Scattering

Data Source

PatentUS11474437B2Increasing signal-to-noise ratio in optical imaging of defects on unpatterned wafers

Publication Date: 2022.10.18 APPL MATERIALS ISRAEL LTD

AI summary

Disclosed herein is a method for increasing signal-to-noise (SNR) in optical imaging of defects on unpatterned wafers. The method includes: (i) irradiating a region of an unpatterned wafer with a substantially polarized, incident light beam, and (ii) employing relay optics to collect and guide, radiation scattered off the region, onto a segmented polarizer comprising at least four polarizer segments characterized by respective dimensions and polarization directions. The respective dimensions and polarization direction of each of the at least four polarizer segments are such that an overall power of background noise radiation, generated in the scattering of the incident light beam from the region and passed through all of the at least four polarizer segments, is decreased as compared to utilizing a linear polarizer.