THE POTENTIAL OF THE SCANNING PROBE MICROSCOPY FOR THIN-FILM CHARACTERIZATION

Since the invention of the scanning tunneling microscopy (STM) by Binn ig and Rohrer in 1982 various scanning probe microscopy (SPM) techniqu es have been employed to investigate sample properties with the highes t lateral-in particular cases atomic-resolution. The most versatile te chnique is scanning force microscopy (SFM) where a cantilever probe is scanned above the sample surface. The local interaction force between probe and sample is measured to investigate the topography as well as sample properties. Up to now SFM probes are fabricated in most cases of silicon, silicon nitride or silicon oxide cantilevers where a sharp tip of the same material is attached to the very cantilever. Neverthe less, for novel applications of SFM sensors, e.g. investigation of opt ical, magneto-optical, or thermal sample properties, testing of electr onic microwave devices or nanolithography applications etc., the mater ial choice as well as the standard SFM probe design are no longer suff icient. Therefore we concentrate in this contribution on the developme nt and application of novel probes where the design and the probe mate rial are the key parameters for new applications. To employ SFM probes simultaneously in scanning near-held optical microscopy (SNOM) an ape rture probe was developed. It has been used to sample the intensity di stribution in the near-field of an illuminated sample and it overcomes the diffraction limits of classical optical microscopy. Another appro ach for combined SFM/SNOM employs miniaturized optical photodetectors. In this case Schottky diodes are fabricated on top of GaAs or Si tips . Illuminating the tip by light emitted from a sample surface generate s an electrical current of photocarriers which is a measure of the lig ht intensity. Thermocouple probes have been used in scanning thermal m icroscopy (STM) to investigate thermal properties of thin films. The t ime constant of these probes is limited by the thermal diffusivity of cantilever and tip material. Therefore cantilevers and tips made of di amond have been developed which work as a heat sink due to the high th ermal diffusivity of diamond. For the electronic characterization of m icrowave devices a coplanar wave guide structure was integrated on a c antilever. The probe allows to sample the electrical force between the tip and the device under investigation and thus the electrical field distribution of the device. An operation bandwidth of about 10-40 GHz is feasible. (C) 1997 Elsevier Science S.A.