Shadow step structures for the analysis of thin film conductors

A description is given of research on shadow step structures (3S), which are prepatterned, mesa-type geometries that are electrically self-isolating and self-aligning when overlaid with a conducting film. This basic mesa topography has been historically used as a disposable medium for lift-off metallization and other generic patterning forms. A modification of this technique has recently been useful in providing an analytic tool for the maskless evaluation of as-deposited thin-film conductors. On an experimental basis, 3S is being used as an intermediate means to verify the sheet resistivity and tempco of sichrome resistor films. Also, the formation of electromigration patterns is used as a simplified, nonintrusive alternative to the current fabrication method. The 3S technique is being evaluated for other QTAT analyses including the quantifying of physical film stress and Schottky diodes, together with other bulk silicon devices which evaluate metal-silicon interfaces.<>