[en] Spectroscopic ellipsometry, scanning electron microscopy, and transmission electron microscopy are all invaluable routine characterization techniques to determine the thickness of silicon nitrides during manufacturing of compound semiconductor devices. We describe in detail the accuracy and convenience of each technique. In addition to thickness, nitride composition is another process parameter that needs to be controlled in manufacturing. Therefore, we also discuss using UV Raman spectroscopy, Rutherford backscattering spectroscopy, and spectroscopic ellipsometry to measure composition. Finally, we discuss the correlation between electrical parameters (capacitance and breakdown voltage) and the stoichiometry of the silicon nitride used as a dielectric in a metal-insulator-metal capacitor