Carrier spilling revisited: On-bevel junction behavior of different electrical depth profiling techniques

It is well known that the electrical junction depth position measured along a beveled surface, as is routinely done in the spreading resistance probe (SRP) technique, is shallower than the, corresponding metallurgical junction as seen by secondary ion mass spectrometry. The amount of on bevel junction shift (i.e., the difference in electrical on bevel versus metallurgical junction depth) in SRP has previously been attributed to a combination of material removal during the beveling (i.e., one-dimensional zero-field Poisson model) and pressure enhanced carrier spilling (enhanced permittivity). Recently the interest in the application of two-dimensional electrical characterization techniques such as scanning capacitance microscopy, with virtually zero pressure, and scanning spreading resistance microscopy, with a much smaller contact, on beveled surfaces has emerged in order to meet the needed resolutions. The data from these techniques, however, indicate that our present understanding of the carrier-spilling phenomenon is incomplete. Based on a detailed intercomparison of the depth profiles on well-calibrated, junction isolated samples, the shapes of the calibration curves, current-voltage curves, and device simulations, an improved carrier spilling model is proposed that incorporates a uniform surface state density of 5 x 10(12)/eV/cm(2), with a neutral (Fermi-pinning) level of 0.28 eV above mid-band gap. (C) 2003 American Vacuum Society.