Low-Cost GaN Plasma Enhanced Chemical Vapor Deposition System

Wide bandgap III/V nitrides, including GaN, InGaN and AlGaN, are emerging as important materials for solid-state lasers, high-electron-mobility transistors (HEMTs) and millimeter wave integrated circuits. These components serve critical functions inradar, sensors and communication systems used in ballistic missile defense. Nitride devices are grown epitaxially on sapphire or silicon carbide substrates by metalorganic chemical vapor deposition. Unfortunately, this process is expensive, requiringcopious amounts of ammonia to drive nitrogen into the semiconductor lattice. Moreover, ammonia decomposes at extremely high temperatures, where it is more difficult to control the film composition and dopant profiles. This proposal seeks funds todemonstrate that high-quality gallium nitride may be deposited by plasma-enhanced chemical vapor deposition with N2 feed gas. A novel Plasma Flow Source(TM) has been invented which produces a large flux of N atoms at low-temperature and pressures between10 and 1000 Torr. The N atoms should efficiently incorporate into the III/V nitride lattice and reduce gas costs by more than a hundredfold. In addition, lower growth temperatures will permit the fabrication of more advanced device structures withimproved process control and reliability. The project proposed herein will lead to a commercially viable plasma-enhanced chemical vapor deposition (PECVD) process for the fabrication of nitride semiconductor devices. This technology will lowertemperatures, reduce gas consumption, and enhance process yield and reliability. The nitride industry will benefit from having a low-cost method for manufacturing GaN devices. This will in turn benefit DoD's ballistic missile defense by making GaNelectronic components for radar and communications systems more affordable and more readily available. A second benefit of this project is to aid the development of a new, high-pressure plasma source for materials processing. This plasma has many advantages over competing technologies. It generates a uniform, high concentration of radical specieslarge areas (0.5 to 3.0 ft. in diameter), without ion bombardment, at temperatures below 120 C, and at pressures between 10 and 1000 Torr. This is the first commercially viable system for low-temperature processing of materials at ambient pressure. Theplasma source is low-cost and has many applications in semiconductor manufacturing, including photoresist stripping, PECVD of oxides and nitrides, copper etching and passivation, and wafer thinning. The potential benefit to the DoD Materials/ProcessesTechnology Area is substantial.