Profile Measurement of micro-optics with steep sidewalls by using a long stroke atomic force microscope

In this research, a long stroke atomic force microscope (LS-AFM) is developed for surface profile measurement of micro-optics with steep sidewalls. An electrochemically polished tungsten probe with sharpened apex is employed as the AFM probe which provides the effective length of the probe tip more than 100 μm so that the accessibility to the valley part of a deep groove can be realized. The probe tip is vibrated by a tuning fork at their resonance frequency. The probe tapping the sample surface with constant force which is feedback controlled based on the constant frequency shift signal of the tuning fork. The trace of the probe tip in Z direction can be considered as the sample surface profile. Sectional profile measurement of a Fresnel lens is carried out by utilizing the LS-AFM and a commercial optical probe. The comparison of the measurement result demonstrates the effectiveness and the advantage of the developed LS-AFM in profile measurement of micro-optics with steep sidewalls.