The higher energy near-IR, approximately 14000-4000 cm -1 (0.8-2.5 μm wavelength) can excite overtone or harmonic vibrations. The infrared portion of the electromagnetic spectrum is usually divided into three regions the near-, mid- and far- infrared, named for their relation to the visible spectrum. A common laboratory instrument that uses this technique is a Fourier transform infrared (FTIR) spectrometer. As with all spectroscopic techniques, it can be used to identify and study chemicals. It covers a range of techniques, mostly based on absorption spectroscopy. Infrared spectroscopy (IR spectroscopy) is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. IMM Instrument Pages IMM Instrument Pages.Optical Spectroscopy Optical Spectroscopy.Analysis & Separation Analysis & Separation.The sensor reports the SiF 4 level remaining in the effluent from the chamber in real-time, allowing the user to rapidly detect the endpoint of the cleaning process and avoid over-etching of the chamber components that might lead to damage or other maintenance issues. For example, Process Sense™ monitors are used with fluorine-based chamber cleaning processes to monitor the by-product silicon tetrafluoride (SiF 4) from chambers employed for silicon-based deposition processes (including poly silicon, silicon dioxide, and silicon nitride). MKS' Process Sense™ endpoint sensor monitors the effluent from the chamber cleaning process in real-time using an NDIR method. Optimal cleaning times for different processes depend on a complex relationship between variables such as the thickness of the build-up, the interior temperature of the chamber components, deposition/sputter ratios, and the chemical composition of the materials to be removed. Semiconductor chemical-vapor deposition process chambers must be periodically cleaned to remove deposited build-up on the chamber walls and internal components. A well-designed FTIR instrument provides a very high unit-to-unit repeatability, eliminating the need for cumbersome and expensive individual unit calibration. An FTIR spectrometer normally uses a laser to control the position and velocity of the moving mirror and to trigger the collection of data points throughout the scan. Another advantage of the FTIR spectrometer is its wavelength precision and stability. This is important in quantitative analysis where SNR generally determines the sensitivity of the measurement. As a result, the spectra produced by FTIR spectrometers are generally much "sharper" than those produced by dispersive spectrometers under the same conditions. An FTIR does not use a slit to control the wavelength resolution of the instrument. Second, and perhaps most important, is the fact FTIR spectrometers have high optical throughput or etendue. With each scan, it covers the entire MIR wavelength region between approximately 2 µm and 16 µm, depending on the material of the optics and the type of photodetector employed in the instrument. A modern FTIR instrument such as the MKS MultiGas™ FTIR analyzer can perform a scan in as little as 200 ms. First, it provides fast measurements over a wide wavelength range. The FTIR spectrometer has several advantages over a traditional dispersive spectrometer.
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