RECENT INSIGHTS INTO THE PHYSICAL MODELING OF THE SPREADING RESISTANCE POINT-CONTACT

The generation of accurate electrically active dopant profiles from ra w spreading resistance probe (SRP) data requires a realistic physical description of the high-pressure point contact used. Comparisons betwe en SRP and secondary ion mass spectrometry for junction isolated struc tures have previously indicated a need to introduce, into the one-dime nsional Poisson calculations, rather high permittivity and band gap na rrowing values close to the contact. To clarify the situation, a syste matic survey of the literature has been made regarding the mechanical and electrical aspects of pressure contacts, including finite element calculations of the internal stress distributions and the characterist ics of the high-pressure phases of silicon. Furthermore correlation ha s been sought with current-voltage curves of the SRP point contact, na no-SRP low weight measurements, and atomic force microscopy and transm ission electron microscopy analysis of SRP probe imprints. The emergin g physical contact model is one dominated under the high-pressure cont act by a series of 20-50-nm-deep plastically deformed metallic beta-ti n Ohmic microcontacts embedded in an elastically deformed narrow band gap and high permittivity region several micrometers deep. On junction isolated structures the higher permittivity results in an enhanced re verse carrier spilling effect causing an apparent on-bevel junction sh ift larger than predicted by zero-field simulations. (C) 1996 American Vacuum Society.