FORMATION OF ALUMINUM NITRIDE ON ALUMINUM SURFACES BY ECR NITROGEN PLASMAS

In order to overcome the difficulty in thermally nitriding aluminum, p lasma nitriding was attempted by means of electron cyclotron resonance (ECR) nitrogen plasma combined with negative bias to aluminum substra tes. Aluminum nitride (AlN) was formed on the substrate surface only w hen the vacuum chamber was evacuated to 2.3x10(-4) Pa or under, howeve r, the formation rate was as high as 15 mu m thick AlN layer was forme d in 900 s without any pretreatments. Vickers hardness (Hv) of AIN was about 1400. Also, this AIN layer showed an electrical conductivity. S canning electron microscopy (SEM) on the cross-section of AIN layer re vealed its bi-layer structure consisting of porous granular and dense columnar structure. It is speculated, from the SEM observations, that the AlN was formed through melting of the aluminum surface by ion bomb ardment.