REMOTE PLASMA-ENHANCED CVD OF FLUORINATED SILICON-NITRIDE FILMS

An investigation has been made of the effect of dilution of nitrogen w ith NF3 on the properties of silicon nitride deposited by remote plasm a-enhanced CVD (PECVD). For NF3/N-2 mixtures with < 1.5 % NF3, fluorin ated films with the structure of silicon nitride are formed but the to tal concentration of bonded hydrogen in the films decreases with incre asing NF3 flow rate, which leads to an improvement of the electrical p roperties of the films compared with unfluorinated films. Such films c ould be of interest for device applications. For NF3/N-2 mixtures with NF3 > 1.5 %, films with the structure of silicon dioxide are formed, but they do not contain enough oxygen to give typical SiO2 IR spectra. It is suggested that the silicon dioxide structure arises because of isoelectronic substitution of oxygen by NF.