A. Malavé

Evaluating probes for “electrical” atomic force microscopy

The availability of very sharp, wear-proof, electrically conductive probes is one crucial issue for conductive atomic force microscopy (AFM) techniques such as scanning capacitance microscopy, scanning spreading resistance microscopy, and nanopotentiometry. The purpose of this systematic study is to give an overview of the existing probes and to evaluate their performance for the electrical techniques with emphasis on applications on Si at high contact forces. The suitability of the characterized probes has been demonstrated by applying conductive AFM techniques to test structures and state-of-the-art semiconductor devices. Two classes of probes were examined geometrically and electrically: Si sensors with a conductive coating and integrated pyramidal tips made of metal or diamond. Structural information about the conductive materials was obtained by electron microscopy and other analytical tools. Swift and nondestructive procedures to characterize the geometrical and electrical properties of the probes p...

Fabrication of integrated diamond cantilevers with tips for SPM applications

Abstract The fabrication of diamond cantilevers with diamond tips integrated on silicon wafers for scanning probe microscopy (SPM) applications is reported. Hot filament CVD diamond deposition and standard techniques of silicon micro-machining are employed. The deposition of well-developed tips depends critically on the pretreatment applied to enhance nucleation density. With an optimized process, well-shaped tips with a radius of curvature in the order of 30 nm are obtained. According to micro-Raman investigations they consist of high quality diamond. Another critical step is the definition of the cantilever area. It can be solved by proper process design. Preliminary performance tests show the cantilevers to possess high resonance frequencies.

Diamond cantilever with integrated tip for nanomachining

Atomic force microscopy was successfully applied for the reproducible nanomachining of in-plane gate transistors made from GaAs/AlGaAs heterostructures. Electronic devices with structures of less than 50 nm dimensions were realized by scribing with a pointed cantilever probe. This process demands tips made of an extreme hard material with sufficiently low abrasion. For this purpose all-diamond cantilever probes made of polycrystalline diamond films were proven to be ideally suited. The separate definition of the lateral and vertical probe geometry during diamond cantilever fabrication offers important advantages in comparison to conventionally moulded probes that will be discussed in some detail.

Tip-on-tip: a novel AFM tip configuration for the electrical characterization of semiconductor devices

A novel tip configuration for atomic force microscopy (AFM) called tip-on-tip is presented. In this concept a sharp, very small tip is created on top of a large truncated pyramid. The process scheme for the fabrication of tip-on-tip is presented. It is demonstrated that very sharp metal tips can be produced in this way. Advantages of tip-on-tip when applied in semiconductor device analysis are discussed. First results concerning the transfer of the developed technology to diamond are presented.

All-diamond cantilever probes for scanning probe microscopy applications realized by a proximity lithography process

All-diamond probes with an integrated tip were fabricated by means of a proximity lithography process and hot-filament chemical vapor deposition of polycrystalline diamond. Fabrication relies on the separate definition of the vertical and lateral cantilever probe geometries in two successive process steps. This process scheme offers the capability to adapt the mechanical properties of cantilever probes, e.g., the momentum of inertia of the cantilever beam, i.e., its compliance and resonance frequency, and the inclination angle of the tip with respect to the sample surface. Atomic force microscopy investigations of a SrTiO3 calibration sample demonstrate the application potential of these probes.

Fabrication of monolithic diamond probes for scanning probe microscopy applications

A process relying on the molding technique for the fabrication of diamond cantilevers with diamond tips integrated on silicon wafers for scanning probe microscopy applications is described. Either hot filament or microwave CVD diamond deposition and standard techniques of silicon micro-machining are employed. The deposition of well- developed tips depends critically on the pretreatment applied to enhance nucleation density; abrasive treatment with diamond powder as well as the bias-enhanced nucleation turned out to be successful. With optimized processes, well- shaped tips with a radius of curvature in the order of 30 nm can be obtained. They consist of high quality diamond according to micro-Raman spectroscopy. The definition of the cantilever area is another critical step which can be solved by proper process design. The fabrication of conductive tips/cantilevers is possible by boron doping. Finally, first performance tests of the diamond tips and cantilevers are presented.