FORMATION OF HIGH-QUALITY SILICON DIOXIDE FILMS BY ELECTRON-CYCLOTRON-RESONANCE PLASMA OXIDATION AND PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION

High-duality silicon dioxide films have been deposited by plasma-enhan ced chemical vapour deposition and plasma oxidation using a single mag net electron cyclotron resonance plasma generator with both oxygen and nitrous oxide as the oxygen source. Langmuir probe measurements were used to characterise both molecular oxygen and nitrous oxide discharge s. Low electron temperatures, resulting in low sheath potential drops, coupled with the shape of the field lines results in low sputtering f rom the chamber walls between the source region and substrate. The res ulting buildup of an insulating layer of oxide on the chamber walls re sults in a very clean process. In situ thermal desorption and ellipsom etry measurements coupled with X-ray photoelectron spectroscopy have a llowed us to characterise the quality of the silicon surface prior to deposition and just after initiation of the plasma. Plasma oxidation d ominates over chemical vapour deposition during the early stages of ox ide film growth using either oxygen or nitrous oxide as the oxygen sou rce gas. Extensive ex-situ spectroscopic ellipsometry (SE) indicates t hat the bulk properties of the films are comparable to those of high-t emperature thermal oxides. There is no interface layer measurable by S E for any of the films produced by plasma oxidation or chemical vapour deposition with silane using either molecular oxygen or nitrous oxide as the oxygen source gas even though the fatter results in approximat ely a monolayer of nitrogen at the Si/SiO2 interface. Chemical analysi s by the total reflected X-ray fluorescence technique and by vapour-ph ase deposition coupled with graphite furnace atomic absorption spectro scopy found no impurities in the films made with silane and molecular oxygen. The high quality of the Si/SiO2 interface made with these two gases was confirmed by capacitance-voltage measurements on Al-gate cap acitors. After a 1 min anneal at 950 degrees C interface state densiti es below 3 x 10(10) eV(-1) cm(-2) were obtained.