What Is an Infrared Microscope?
An infrared microscope, utilizing infrared microspectroscopy, analyzes microscopic samples by employing infrared light, which, despite its limited spatial resolution due to the diffraction limit, enables detailed spectral analysis. Modern infrared microscopes often integrate Fourier transform infrared spectroscopy (FTIR) and total internal reflection capabilities, enhancing their analytical potential.
Uses of Infrared Microscopes
Primarily used in failure analysis and materials science, infrared microscopes excel in examining microscopic samples, identifying foreign matter and defects through differential infrared absorption rates, and measuring semiconductor thickness with less impact from surface irregularities. Interferometry methods measure semiconductor thickness by analyzing the optical path difference of reflected light.
Principle of Infrared Microscopes
Infrared microscopes combine microscopic imaging and spectroscopic analysis. Samples are initially observed under visible light to locate the target area and then analyzed under infrared light for detailed spectral data.
Types of Infrared Microscopes
1. Infrared Spectrometer
This type uses infrared light to illuminate a sample, capturing the spectrum of transmitted or reflected light. Utilizing a Cassegrain optical system instead of refractive lenses, it achieves spatial resolutions limited to a few to several micrometers, with the infrared band between 2.5 and 25 micrometers revealing material-specific spectra.
2. Fourier Transform Type (FT-IR)
The FT-IR microscope characterizes samples using a continuous light beam, analyzing all wavelengths simultaneously through an interferometer. Its advantages include simultaneous multiple wavelength detection, high signal-to-noise ratios, improved wavelength resolution, and an extended measurement range. DTGS and MCT are two common detector types, with MCT requiring liquid nitrogen cooling for optimal performance.
Other Information on Infrared Microscopes
Measurement With a Two-Dimensional Array Detector
Advanced infrared microscopes using two-dimensional array detectors necessitate liquid nitrogen cooling to prevent damage from heat. While some models can operate without liquid nitrogen, cooling significantly affects measurement capabilities and accuracy.