THERMAL NITRIDATION OF SILICON IN A CLUSTER TOOL

An integrated cluster tool process is described whereby stoichiometric Si3N4 films with less than 0.01 at % oxygen, hydrogen, and carbon are grown on <111> Si. The ultrahigh film purity is verified in situ with X-ray photoelectron spectroscopy and static secondary ion-mass spectrometry depth profiles. The two-step process consists of cleaning the surface in an electron cyclotron resonance excited H2 plasma, and passing in vacuum to a second chamber where it is exposed to NH3 for 2 min at 1070-degrees-C to promote nitridation. The films are approximately 5 nm thick with a refractive index of 2.01 at 633 nm. They are resistant to a dry O2 ambient for at least 6 h at 1050-degrees-C. The average breakdown field of Al/Si3N4/Si capacitors is around 9 MV/cm.