 
The kSA RateRat Pro is a deposition rate monitor and advanced process control system. This non-invasive, in-situ, optically based product makes thin-film deposition monitoring simple. By combining real-time calculations of deposition rate, layer thickness and optical constants with powerful advanced process control software, RateRat Pro makes monitoring even the most complex multi-layered materials easy and precise.
The kSA RateRat Pro detects and analyzes surface reflectance in real-time. The analysis is performed using sophisticated “Virtual Interface” algorithms, originally developed at Sandia National Laboratories, which allows RateRat Pro to determine deposition rate, layer thickness, and optical constants with as little as 350 Å of material. RateRat Pro provides real-time data analysis and output for feedback into process control software, and is ideal for input into CVD, MBE, sputtering, and evaporation control systems.
The RateRat Pro system uses a diode laser (either a 658 nm or 401 nm, depending on the deposition materials), high-speed photo detector (HSPD), high-speed 16-bit data acquisition board, and laser modulator to acquire reflectivity data during thin film deposition. The laser is modulated by inputting a user-selectable modulation frequency to the laser control module. Data is acquired from the HSPD by acquiring analog input blocks at high speed (typically 1 kHz) using the data acquisition board. This block analog input is then Fast-Fourier Transformed (FFT), and the peak frequency amplitude is extracted. In this way, signal-to-noise ratio is improved because only light signal modulated at our modulation frequency is analyzed, effectively throwing away all other ambient and stray signal. This peak frequency amplitude is then converted to an absolute reflectivity via a scaling factor, and the resultant reflectivity is plotted, stored, and fitted as a function of acquisition time. All data acquired during a deposition run may be stored and loaded at another time for post-acquisition analysis.
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