A conductive atomic force microscope (AFM) tip based on B-implanted diamond has been developed for the determination of the spatial distribution of charge carriers in semiconducting structures. The characteristics of this tip have been determined by studying the current–voltage behavior as a function of substrate resistivity and tip load. From this work a model of the electrical properties of the microcontact is emerging. It includes an Ohmic contribution to the overall resistance, which is related to the plastically deformed area, and contributions from a barrier. The tip imprints have been imaged with AFM and their physical dimensions are seen to match the requirements of the model. From resistance measurements on uniformly doped silicon a calibration curve has been established which can be used as a standard to convert measured resistance into resistivity.

Thin SiGe-on-insulator (SGOI) substrates with Ge content varying between 42 and 93% were produced by the Ge condensation technique and full structural characterization was carried out. In a second step, the electrical properties of these substrates were analyzed by the pseudo metal-oxide semiconductor field-effect transistor technique which allowed determination of the carrier low-field mobilities, as well as the density of fixed charges in the buried oxide (BOX) and the density of interface traps at the BOX-SiGe film interface. Optimization of intermediate anneals in argon during the condensation process made the production of high crystalline quality and high-mobility substrates possible (up to 400cm2normalV−1normals−1 for a 93% SGOI). Opposite trends were observed for holes and electrons: while the hole mobility increases with increasing Ge content, the electron mobility decreases. In addition, the density of interface traps and also the density of oxide charges were found to increase with increasing Ge content. Possible causes for this increase are discussed.

Whereas the introduction of 3D-dimensional devices such as FINFET's may be a solution for next generation technologies, they do represent significant challenges with respect to the doping strategies and the junction characterization.Aiming at a conformal doping of the source/drain regions in a FINFET in order to induce a conformal under diffusion and homogenous device operation, one can quickly recognize that classical beam implants fail to fulfill these needs, in particular when considering closely spaced fin's. Indeed the effects of different implant angles (top vs bottom) and the concurrent variation in projected range, dose retention and sputtering as well as the effect of the wafer rotation when tilting is used, all lead to a non-conformal doping. Alternative processes such as vapor phase deposition (VPD) or plasma doping are presently being considered, as they hold the promise of conformality. Using VPD or Atomic Layer Doping dopant atoms are deposited on the surface through thermal decomposition of typical chemical vapor deposition precursors and are subsequently in diffused. Good conformality (~ 93 % for sidewall vs. top dose), defect free junctions and high activation levels are the positive points of this process. Plasma immersion doping is an alternative approach which is easier to integrate (similar to ion implantation) and suitable for p-and n-type doping. Whereas it holds the promise of conformality when implanting large macroscopic features, the latter is far less obvious when trying to dope microscopic feature conformally. In fact the formation of conformal junctions in FINFET's with plasma based processes is quite challenging and relies on secondary processes such as resputtering, deposition and in diffusion etc. Their optimization is compromised by concurrent artifacts, sputter erosion being the most important one. In support of these developments the measurement and identification of conformality adequate metrology is required. For this purpose we have extensively used Scanning Spreading Resistance Microscopy (SSRM) as a means to characterize the vertical/lateral junction depths, the concentration levels and the degree of conformality. Characterization of the (3D)-underdiffusion can be achieved by a dedicated SSRM experiment and/or the Tomographic Atomprobe. As a complement to the SSRM technique we also developed a concept based on resistance measurements of fin's which allows to map the sidewall doping across the wafers and provides fast feedback on conformality.

Articles you may be interested inCopper sample analyzed with an n-doped silicon tip using conducting probe atomic force microscopyThe determination of the spatial distribution of charge carriers in semiconducting structures with an atomic force microscope ͑AFM͒ is presented. This new technique is based on the measurement of the spreading resistance of a conducting AFM tip on a sample as the tip is scanned over the surface. The high spatial resolution of this method allows for its application on the cross section of a device providing one-dimensional ͑vertical͒ and two-dimensional ͑lateral͒ profile information. First, a detailed study is presented regarding the properties of the tip ͑tip material and preparation, lifetime͒ and the evolution of I -V characteristics with pressure on uniformly doped silicon. From this work a model for the electric properties of the microcontact is deduced. It includes an ohmic contribution to the overall resistance that is related to the plastically deformed area, and contributions from a barrier as well as from tunneling. Through the determination of a calibration curve, whereby the resistance was measured on homogeneously doped substrates with varying resistivities, the quantification properties of the method are determined. Finally, this method has been applied for junction delineation on the cross section of a device. The results show a 50 nm resolution and a sufficient sensitivity to encompass a dynamic range of concentrations between 10 14 and 10 19 cm Ϫ3 . These measurements were found to be in good agreement with those performed by the classical spreading resistance profiling technique and by secondary ion mass spectroscopy.