(Invited) Epitaxial III-Nitride Film Growth in a Single Wafer Rotating Disk MOCVD Reactor

Abstract

Epitaxy of GaN on large-size Si wafers can enable the adoption of AlGaN-based High Electron Mobility Transistors (HEMTs) in a broad range of applications ranging from consumer electronics, solar and wind power, power supplies, and automotive, to the potential integration with Si-based CMOS technologies. Device performance dictates stringent requirements for epitaxial film quality and uniformity, while wafer bow management during growth facilitates the use of larger diameter substrates. Uniform temperature profile and gas distribution in the MOCVD reactor become critical elements for film performance and, ultimately, technology adoption. In this work, we are reporting on the epitaxy of Al/Ga/N containing films on 200 mm Si wafers. The TurbodiscÒ, vertical, rotating disk reactor used for epitaxy encompasses the fundamental reaction and high velocity laminar flow characteristics of its predecessor batch systems, thus enabling stable, repeatable operation, long PM cycles, and direct, model-based process scale up. Moreover, it incorporates advanced features, which will be discussed, for alkyl/hydride flow distribution and temperature uniformity, which translate into excellent uniformity in epitaxial layer thickness, alloy composition, and doping profile across the wafer. Results on AlGaN/GaN heterostructures, thickness uniformity of GaN 0.48%, 1σ, and AlN 0.86%, 1σ, Al composition uniformity in AlGaN of 0.289%, 1σ, and 2DEG performance are presented. Uniform incorporation of dopant species (Mg and C) across the substrates is reported. The average Hall mobility is > 1700 cm2/V.s, with sheet carrier concentration at 9.5x1012/cm2, and sheet resistance 380 Ohm/sq for the 5 points across the wafer. Results on the repeatability of film quality, FWHM of GaN (002) and (102) showing < 1.5% 1σ over 20 runs, and average Al composition of AlGaN barrier, showing variation of 0.37 % 1σ over 16 runs, are presented. Wafer bow can be precisely engineered and controlled through the thickness and composition of the stress compliance structure.