AVS 45th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM2-WeA

Paper EM2-WeA2
Two-Dimensional Carrier Profiling of III-V Structures using Scanning Spreading Resistance Microscopy

Wednesday, November 4, 1998, 2:20 pm, Room 316

Session: Application of Scanning Probes to Electronic Materials
Presenter: W. Vandervorst, IMEC, Belgium
Authors: P. De Wolf, IMEC, Belgium
T. Hantschel, IMEC, Belgium
M. Geva, Bell Laboratories, Lucent Technologies
C.L. Reynolds, Bell Laboratories, Lucent Technologies
W. Vandervorst, IMEC, Belgium
F. Bylsma, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
Scanning Spreading Resistance Microscopy (SSRM) is a powerful tool originally developed for measuring two-dimensional (2D) carrier distributions in Si device structures with nm-spatial resolution.@footnote 1@ It is in essence based on an Atomic Force Microscope equipped with a conductive tip that is biased relative to the sample. From the current flowing through the tip one deduces the local spreading resistance value. The spreading resistance value is determined primarily by the resistivity of the material in the small semi-hemispherical volume at the surface region where the tip contacts it. The resistivity is closely related to the local carrier concentration (and mobility) in this surface region. The spatial resolution thus mainly depends on the tip radius and pressure. Since SSRM measures resistance, a material property that depends upon carrier concentration, rather than detecting the carriers directly, it is capable of producing images of both high spatial resolution and wide dynamic range of carrier concentration. We have demonstrated spatial resolution values as small as 20 nm, and dynamic ranges of 10@super 15@-10@super 20@ atoms/Cm@super -3@ in analyses of Si devices.@footnote 1@ Whereas its application has been explored in detail on Si structures,@footnote 1@ we report here for the first time on the application of SSRM for the analysis of III-V semiconductor structures, and in particular MOCVD-grown InP-based structures. We found that the application of SSRM to InP-based structures is much simpler than to Si. A minimal surface preparation is required in the cross sectioning process, much lower tip forces are needed, and metal tips instead of diamond tips can be used. When imaging complex multilayer epi-structures (containing p, n, and semi-insulating layers), close agreement between the SSRM profile and SIMS profiles can be obtained. More importantly is the capability of SSRM to image and determine 2D structures in actual devices, such as mesas and trenches common in semiconductor laser devices. SSRM also proved very valuable in characterizing with high spatial resolution 2D dopant and implant distributions. In this presentation we will present SSRM analysis of lateral Zn-diffusion into a semi-insulation layer in a mesa-like InP structure. @FootnoteText@ @footnote 1@P. De Wolf, T. Clarysse, W. Vandervorst, L. Hellemans, Ph. Niedermann, and W. Hänni, J. Vac. Sci. Technol. B16, 355 (1998).