Plasma-Enhanced Chemical Vapor Deposition is used to deposit thin films at lower temperatures compared to CVD at a pressure around 0.5-2Torr. 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 (375 KHz) which can be applied to the top electrode one at a time or simultaneously. 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 350°C. Gas molecules from a shower head inlet are ionized by the oscillating 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. Thin films deposited with PECVD generally have good uniformity, adhesion, step coverage and low pinhole density.

Process gases available:

• Materials allowed: Si, Al, III-V, quartz. For other materials, check with instrument responsible.
• Materials not allowed: Any metal (Ti, Au, Pt, Cu, etc.), ZnS or similar.
• Process gases: N₂, SiH₂, Ar, NH₃, He, H₂, N₂O, C₄F₈, O₂.
• RF source: 13.56 MHz; 0 – 3000 W
• LF source: 375 KHz; 0 – 1235 W
• Operating remperature: 20°C to 350°C
• Typical applications: SiO_x, SiN_x and amorphous Si (a-Si) .