Oxygen and carbon content of silicon wafers

Measurement of the Oxygen and Carbon Content of Silicon Wafers by Fourier Transform IR Spectrophotometry... 

The silicon raw material can be analyzed by FT-IR spectroscopy. The oxygen and carbon content is determined by comparing the ratios of the oxygen and carbon bands with those of the characteristic phonon absorptions of the silicon lattice (see Fig. 5.1-9 Zachmann, 1987). The measurements are calibrated by a reference wafer of similar thickness and surface condition in order to avoid complicated correction calculations. In a special manufacturing process for integrated circuits. Si wafers are coated with very thin films... 

The carbon and oxygen content of silicon wafers can be determined at room temperature.53 The procedure is to record the spectrum of the sample wafer and ratio it against a background (empty cell) spectrum. The resulting absorbance spectrim is stored on the spectrometer data system. A similar absorbance spectrum of a pure wafer is recorded. A spectral subtraction is performed between the two spectra and only the impurity bands of the sample wafer remain. The peak height can be correlated to impurity concentration. This process can detect oxygen and carbon down to a few parts per million. This method has been shown to be very reliable and can be... 

---