Development of atomic force microscopy combined with scanning electron microscopy for investigating electronic devices

Atomic force microscopy (AFM) was combined with scanning electron microscopy (SEM) to investigate electronic devices. In general, under observation using an optical microscope, it is difficult to position the cantilever at an arbitrary scan area of an electronic device with a microstructure. Thus, a method for positioning the cantilever is necessary to observe electronic devices. In this study, we developed an AFM/SEM system to evaluate an electronic device. The optical beam deflection (OBD) unit of the system was designed for a distance between the SEM objective lens and a sample surface to be 2 cm. A sample space large enough to place an actual device was created, using a scan unit fabricated with three tube scanners. The scanning ranges of the scan unit are 21.9 µm × 23.1 µm in the XY plane and of 2.5 µm for the Z axis. The noise density in the OBD unit was measured to be 0.29 pm/Hz0.5, which is comparable to noise density values reported for commercial AFM systems. Using the electron beam of SEM, the electron beam induced current (EBIC) is generated from a p–n junction of a semiconductor. Using the EBIC, the cantilever was positioned at the p–n-junction of a Si fast recovery diode (FRD). In addition, scanning capacitance force microscopy (SCFM) and Kelvin probe force microscopy (KFM) were combined with the AFM/SEM system. The SCFM and KFM signals were in qualitative agreement with the expected carrier density distribution of the p and n-regions of the Si-FRD.