Thin Film Thickness Measurement via Interference Signal Matching
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Solution Overview
Problem
Conventional white light interferometry methods fail to accurately measure the thickness of thin film layers with thin thicknesses due to interference between interference signal waveforms, making it impossible to determine the thickness by selecting maximum peaks.
Innovation Solution
A method using white light scanning interferometry that prepares simulation interference signals for various sample thin film layers, compares these with real interference signals, and determines the thickness by matching the simulation signals with the real signals, allowing for accurate measurement of thin film layers with interference between air and thin film layer interfaces and thin film and base layer interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If white light interferometry is used to measure thin film layer thickness, then measurement capability is provided, but for thin film layers with thin thickness, interference between waveforms makes it impossible to determine thickness by selecting maximum peaks
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing reference interference waveforms for various known thickness values before actual measurement. When measuring a thin film layer, the system compares the measured waveform against these pre-prepared references to determine thickness, avoiding the need to resolve complex interference patterns in real-time and enabling accurate measurement even when waveform interference occurs.
Solution Approach 2:
The patent uses copying by creating reference copies of interference waveforms for different thickness values. These reference waveforms are stored in a database, and the measured waveform is compared against these copies to identify the matching thickness. This approach transforms the measurement problem from resolving interference to pattern matching, solving the difficulty of detecting thickness amidst waveform interference.
2Measurement precision
If simulation interference signals are prepared and compared with real interference signals to determine thickness, then accurate measurement of thin film layers with interference is enabled, but system load and determination time increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing reference interference waveforms for various known thickness values before actual measurement. When measuring a thin film layer, the system compares the measured waveform against these pre-prepared references to determine thickness, avoiding the need to resolve complex interference patterns in real-time and enabling accurate measurement even when waveform interference occurs.
Solution Approach 2:
The patent applies partial action by comparing the measured waveform only against a selected subset of reference waveforms rather than all possible thickness values. The system identifies a range of plausible thickness values based on initial waveform characteristics and performs detailed comparison only within this range, reducing computational load while maintaining measurement accuracy.
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 measurement of thin film layer thickness and surface profile, even for layers where interference occurs, by reducing system load and time in determining the correct thickness, and provides comprehensive information about the thin film layer.
Implementation Method 1
there is interference between a first waveform 43 got from a first surface 21b and a second waveform 44 got from a second surface 11b
Data Source
AI summary
Disclosed is a method of measuring thickness or a surface profile of a thin film layer formed on a base layer through a white light scanning interferometry, the method including: preparing simulation interference signals corresponding to thicknesses by assuming a plurality of sample thin film layers different in thickness from one another and simulating interference signals with respect to the respective sample thin film layers; acquiring a real interference signal with respect to an optical-axis direction of entering the thin film layer by illuminating the thin film layer with white light; preparing a plurality of estimated thicknesses that the thin film layer may have on the basis of the real interference signal; comparing whether the simulation interference signal having thickness corresponding to the estimated thickness is substantially matched with the real interference signal; and determining the thickness of the simulation interference signal substantially matched with the real interference signal as the thickness of the thin film layer.