静電気力顕微鏡のセンサにおける静電気力検出感度によるセンサ先端―測定面距離自動制御

抄録

An electrostatic force microscopy (EFM) is a highly effective system for a measurement of surface voltage distribution. We have been working on the development of the EFM which enables to measure surface voltage in the range from +/-0.1 V up to +/-2 kV with a high spatial resolution better than 10 µm in diameter under atmospheric environment. The EFM is able to scan a wide area larger than tens of mm. However, since the EFM employs a non-contacting measurement method and we expect a wide scanning range as well, the distance between a sensor tip (ST) and a sample under test (SUT) is always a very critical issue. We have successfully developed a new methodology with which we can always keep an equal distance d between ST and SUT automatically throughout a measurement process. Since the EFM also employs a field nullification technology for the electric field between ST and SUT, the EFM keeps monitoring the voltage difference between ST and SUT. This methodology utilizes the information of aforementioned voltage difference for controlling the distance to be always equal. We have confirmed that we can control the d with a resolution as good as 1 µm throughout a measurement.