Abstract: A surface monitoring device is for monitoring a contact surface of a detected object. The surface monitoring device and the detected object are disposed on a substrate. The surface monitoring device includes a resonant mechanical part, having a contact tip adjacent to the contact surface by a preset gap in a static state. A driving circuit, applying an AC input signal to drive the resonant mechanical part to cause the contact tip to vibrate with respect to the contact surface at a plurality of sampling frequencies. The contact tip substantially hits the contact surface in a tapping bandwidth within the sampling frequencies. An analysis circuit to analyze a ratio of an output voltage to an input voltage of the input signal and determine the tapping bandwidth, wherein the ratio in the tapping bandwidth is jumping to a flatten phase.

Abstract: A surface monitoring device is for monitoring a contact surface of a detected object. The surface monitoring device and the detected object are disposed on a substrate. The surface monitoring device includes a resonant mechanical part, having a contact tip adjacent to the contact surface by a preset gap in a static state. A driving circuit, applying an AC input signal to drive the resonant mechanical part to cause the contact tip to vibrate with respect to the contact surface at a plurality of sampling frequencies. The contact tip substantially hits the contact surface in a tapping bandwidth within the sampling frequencies. An analysis circuit to analyze a ratio of an output voltage to an input voltage of the input signal and determine the tapping bandwidth, wherein the ratio in the tapping bandwidth is jumping to a flatten phase.