AVS 57th International Symposium & Exhibition
    Electronic Materials and Processing Wednesday Sessions
       Session EM+SS-WeA

Paper EM+SS-WeA11
Potential Profiles of III-V MOSCAPs with Kelvin Probe Force Microscopy In Situ

Wednesday, October 20, 2010, 5:20 pm, Room Dona Ana

Session: High-k Dielectrics for III-V Electronics
Presenter: W. Melitz, University of California at San Diego
Authors: W. Melitz, University of California at San Diego
J. Shen, University of California at San Diego
S. Lee, University of California at San Diego
J.S. Lee, University of California at San Diego
A.C. Kummel, University of California at San Diego
S. Bentley, University of Glasgow, UK
D. Macintyre, University of Glasgow, UK
M. Holland, University of Glasgow, UK
I. Thayne, University of Glasgow, UK
Correspondent: Click to Email
Cross-sectional scanning probe microscopy (SPM) is an imaging technique which can map the potentials inside an operational MOSCAP or MOSFET device. Kelvin probe force microscopy (KPFM) measures the contact potential difference (CPD) of a conductive cantilever and a sample surface with a precision of better than 10 meV. In cross-sectional KPFM, (X-KPFM) a fully functional MOSFET or MOSCAP is cleaved in UHV, and the potential inside the working device is measured in two-dimensions; UHV cleaving is critical to preserve an oxide-free surface so the unperturbed potentials can be measured. Cross-sectional KPFM can determine the effect of surface passivation of the gate oxide in operational devices, influence of the fixed charge in the gate oxide with semiconductor channel material, structural features and their effects on the potential distribution, and even work function offsets of the gate and semiconductor. The biggest challenges in imaging cleaved devices is obtaining good cleaves and finding the structure of interest while maintaining good tip conditions for high resolution. Using a comb structure for the electrodes increases the density of the devices on the cleave face to increase the number of working devices. The cleave edge of the sample drastically affects the stability of the cantilever. In order to increase the stability, the devices were embedded in a >300nm insulator; therefore, the device of interest in not located directly on the edge face. Using this capping technique, high spatial resolution in a UHV cleaved MOSCAP with KPFM shows the amount of band bending in the semiconductor channel caused by the fixed charge in the oxide. High resolution KPFM has also been demonstrated for a range of external gate biases, illustrating the flexibility of KPFM for investigating MOS devices. Current efforts focus on implementing KPFM into patterned scaled MOSCAP and MOSFET devices.