Spectroscopic Film Thickness Measurement Classification
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Solution Overview
Problem
In-situ type spectroscopic film-thickness measuring apparatuses face challenges in accurately measuring film thickness on rotating substrates with varying structural elements, as the intensity of reflected light can vary due to structural features like devices and scribe lines, leading to inconsistent measurement results.
Innovation Solution
A method and apparatus that classify spectra into primary and secondary groups, using a classification model to determine film thicknesses from primary spectra and generate estimated spectra for secondary spectra through interpolation or extrapolation, ensuring accurate film thickness measurement across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an in-situ type spectroscopic film-thickness measuring apparatus is used to measure film thickness on a rotating substrate, then real-time film thickness measurement is achieved, but measurement precision deteriorates due to varying structural elements (devices and scribe lines) causing intensity variations in reflected light
Solution Approach 1:
The patent segments the measurement process by classifying measurement points into two groups: scribe line regions and device regions. This segmentation allows different analysis methods to be applied to each region type, thereby improving overall measurement precision while maintaining real-time measurement capability during substrate rotation
Solution Approach 2:
The patent changes the approach from direct intensity-based measurement to spectrum shape-based classification. By analyzing the shape characteristics of reflected light spectra rather than absolute intensity values, the system can accurately determine film thickness at scribe lines and devices simultaneously, resolving the precision issue while maintaining real-time measurement
2Area of stationary object
If the optical sensor head scans the substrate surface while the substrate rotates, then comprehensive surface coverage is achieved, but measurement consistency deteriorates due to non-fixed measurement point positions relative to structural elements
Solution Approach 1:
The patent creates a spectral fingerprint copy of the substrate surface structure by analyzing the shape of reflected light spectra. This spectral copying allows the system to identify and classify measurement points by their structural characteristics (scribe line vs. device) without requiring fixed positional reference, thereby maintaining measurement consistency across the rotating substrate surface
Solution Approach 2:
The patent performs preliminary classification of spectra into scribe line and device groups before conducting film thickness measurement. This preliminary action establishes a stable reference framework that enables consistent measurement interpretation regardless of the changing positions of measurement points during substrate rotation
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 enables precise film thickness determination on substrates with diverse structural elements, improving measurement accuracy and consistency across all measurement points.
Implementation Method 1
The spectrometer decomposes each reflected light from each measurement point according to wavelength and generates light intensity data. A spectrum generator of the spectroscopic film-thickness measuring apparatus generates a spectrum of the reflected light from the light intensity data.
Implementation Method 2
The optical sensor head irradiates multiple measurement points on the substrate with light while sweeping across the substrate, and receives the reflected lights from these measurement points.
Data Source
AI summary
A polishing method capable of measuring a film thickness of a substrate, such as a semiconductor wafer, having various structural elements on its surface with high accuracy is disclosed. The polishing method includes: generating spectra of reflected lights from measurement points on a substrate; classifying the spectra based on a shape of each spectrum into primary spectra belonging to a first group and a secondary spectrum belonging to a second group; determining film thicknesses of the substrate from the primary spectra; and determining a film thickness at a measurement point corresponding to the secondary spectrum using the primary spectra or the film thicknesses.