Reliability aspects of epitaxial-planar-varactor structures

Numerous attempts have been made in recent years to improve the reliability of electronic components by taking corrective action at an early stage in the production cycle, and especially by controlling key fabrication processes. These efforts aim to correlate finished product parameters with manufacturing process steps. This paper describes some examples of high frequency Si devices whose parameter stability - one aspect of device processes. Complete diode structures and separate highly doped Si single crystal substrates with different epitaxial-, oxide-, diffusion-or ion implanted layers on them have been investigated by electron-probe and neutron-activation analysis, and by electrical tests. It has been shown that: • the precipitation of impurities, which is significantly enhanced by a code position mechanism in the presence of OH^-, Cl^-and S^-radicals, influences the stability of breakdown voltage in epitaxial planar varactor structures; • a pronounced difference exists between the electron-beam induced currents in reliable Si diodes and those with defective high-frequency performance, and this indicates the presence of microplasma sites; • ion drift in the oxide film is a further possible cause of parameter instability. Treatments which can be applied to eliminate these unwanted instabilities are briefly mentioned.