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 °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 °C. The average breakdown field of Al/Si3N4/Si capacitors is around 9 MV/cm.