Amorphous (Mo, Ta, or W)-Si-N diffusion barriers for Al metallizations

Abstract

M-Si-N and M-Si (M=Mo, Ta, or W) thin films, reactively sputtered from M5Si3 and WSi2 targets, are examined as diffusion barriers for aluminum metallizations of silicon. Methods of analysis include electrical tests of shallow-junction diodes, 4He++ backscattering spectrometry, x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and secondary-ion-mass spectrometry. At the proper compositions, the M-Si-N films prevent Al overlayers from electrically degrading shallow-junction diodes after 10 min anneals above the melting point of aluminum. Secondary-ion-mass spectrometry indicates virtually no diffusivity of Al into the M-Si-N films during a 700 °C/10 h treatment. The stability can be partially attributed to a self-sealing 3-nm-thick AlN layer that grows at the M-Si-N/Al interface, as seen by transmission electron microscopy. © 1996 American Institute of Physics.