AMORPHOUS (MO, TA, OR W)-SI-N DIFFUSION-BARRIERS FOR AL METALLIZATIONS

M-Si-N and M-Si (M=Mo, Ta, or W) thin films, reactively sputtered from M(5)Si(3) and WSi2 targets, are examined as diffusion barriers for al uminum metallizations of silicon. Methods of analysis include electric al tests of shallow-junction diodes, He-4(++) backscattering spectrome try, x-ray diffraction, transmission electron microscopy, scanning ele ctron microscopy, and secondary-ion-mass spectrometry. At the proper c ompositions, the M-Si-N films prevent Al overlayers from electrically degrading shallow-junction diodes after 10 min anneals above the melti ng point of aluminum. Secondary-ion-mass spectrometry indicates virtua lly no diffusivity of Al into the M-Si-N films during a 700 degrees C/ 10 h treatment. The stability can be partially attributed to a self-se aling 3-nm-thick A1N layer that grows at the M-Si-N/AI interface, as s een by transmission electron microscopy. (C) 1996 American Institute o f Physics.