Time-Domain Optical Metrology for Upper-Layer Semiconductor Inspection

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Solution Overview

Problem

Existing optical scatterometry techniques struggle to characterize semiconductor devices with both periodic and aperiodic patterned structures, as they are sensitive to all layers in the stack, making it difficult to separate and measure properties of upper and lower layers accurately.

Innovation Solution

The implementation of time-domain optical metrology systems that create a time-domain representation of wavelength-domain measurement data, allowing for the selection of an earlier-in-time portion that excludes a later-in-time portion, and using model-based processing to determine parameters of interest, specifically focusing on upper layers while excluding other layers, thereby reducing sensitivity to underlayers and improving measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If optical scatterometry measures light reflected by all layers of a semiconductor device, then comprehensive characterization data is obtained, but sensitivity to underlayers prevents accurate measurement of upper layer properties

Engineering Contradiction:

Improvemeasurement accuracy of upper layersVSAvoidsensitivity to underlayers

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent segments the time-domain representation of reflected light into multiple time windows, where each window corresponds to light reflected from different depth ranges. By selecting and analyzing only the time window corresponding to upper layers, the method separates the measurement of upper layers from the interfering signal from underlayers, thereby improving measurement precision while reducing sensitivity to irrelevant layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extracts the specific time window from the complete time-domain representation that contains information about upper layers only. This extraction process isolates the relevant signal component (upper layer reflection) from the harmful component (underlayer reflection), enabling accurate characterization of upper layers without interference from deeper structures.

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If optical scatterometry characterizes all patterned structures in a semiconductor device, then complete device characterization is achieved, but aperiodic structures make characterization difficult or impossible

Engineering Contradiction:

Improveability to characterize different structure typesVSAvoidcharacterization difficulty of aperiodic structures

Core Design Contradiction:

Adaptability or versatilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent transforms the measurement from the wavelength domain to the time domain, adding a temporal dimension to the analysis. This dimensional transformation enables the separation of signals from different depth ranges, allowing the method to handle both periodic and aperiodic structures effectively by analyzing only the relevant time window corresponding to the structure of interest.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Loss of information

If optical scatterometry analyzes the complete wavelength-domain measurement data, then all structural information is captured, but separation of upper and lower layer properties becomes difficult

Engineering Contradiction:

Improveinformation retention of all layersVSAvoidcomplexity of multi-layer characterization

Core Design Contradiction:

Loss of informationVSDevice complexity

Solution Approach 1:

The patent segments the complete wavelength-domain measurement data into multiple time windows after Fourier transformation, where each window contains information about a specific depth range. This segmentation allows selective analysis of upper layers by focusing on the appropriate time window, simplifying the characterization of multi-layer structures while retaining the ability to access information from all layers if needed.

Inventive Principle:

Principle #1Segmentation

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 enhances the ability to measure and inspect semiconductor devices by reducing sensitivity to irrelevant layers, improving parameter resolution, and enabling more accurate metrology on complex structures, including those with non-periodic underlayers, and facilitating in-die metrology.

Implementation Method 1

measuring light reflected by the various layers of a semiconductor device

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

creating a time-domain representation of wavelength-domain measurement data

Methodology Applied

Scientific EffectFourier transform:

Data Source

PatentUS20240085805A1Time-domain optical metrology and inspection of semiconductor devices

Publication Date: 2024.03.14 NOVA MEASURING INSTR LTD

AI summary

A semiconductor device metrology including creating a time-domain representation of wavelength-domain measurement data of light reflected by a patterned structure of a semiconductor device, selecting a relevant and irrelevant portion of the time-domain representation, and determining one or more measurements of one or more parameters of interest of the patterned structure by performing model-based processing using the relevant portion of the time-domain representation.