
Plasma-Enhanced Chemical Vapor Deposition is used to deposit thinfilms at lower temperatures compared to CVD at a pressure around 0.5-2 Torr. The PECVD process chamber consists of two electrodes, a gas inlet and exhaust. The PECVD has two power supplies, one RF source (13.56 MHz) and one LF source (50 – 460 KHz) which can be applied to the top electrode one at a time or simultaniously. Sequential use of the two sources allows for stress control of deposited films. The sample stage (bottom electrode) which is grounded is heated to a maximum temperature of 700°C. Gas molecules from a shower head inlet are ionized by the oscilating electric field and plasma is struck. Electrons are absorbed at the bottom electrode creating a DC voltage of ~10-20V. Ionized gas and radicals react with the substrate and creates a deposition process. Because the reactive and energetic species are a product of collisions in the gas phase the temperature at the substrate is kept at a relatively low value. Thinfilms deposited with PECVD generally have good uniformity, adhesion, step coverage and low pinhole density.