Large area, production MOCVD rotating disk reactor development and characteristics

The compound semiconductor industry is poised for rapid market advances during the next several years and this is creating a need for development of economical and high yield production equipment. These development efforts increasingly rely on advanced modelling with experimental verification. We report here on the utilization of modeling to rapidly develop a large scale production Rotating Disk Reactor (RDR). The influence of the equipment design and deposition process parameters on flow and temperature uniformity and on process characteristics are analyzed in this payer. Three dimensional Navier-Stokes flow modelling has been used to study the effect of an asymmetric exhaust at the base of the reactor on the uniformity of the rotating disk boundary layer in a scaled RDR. Results show that the asymmetric exhaust port does not disrupt the symmetry of the flow above the rotating disk for typical operating conditions, and for hydrogen flow the convective heat transfer from the disk is quite uniform (2% variation) over most (80%) of the surface. Thermal modelling of the RDR, which includes heat transfer by radiation, convection and conductance, was used to improve the temperature uniformity. Use of the recently developed Rotating Wafer Thermal Mapping (RWTM) technique verified the temperature distribution across the wafer under operational conditions, with measured uniformities of 1.3 degrees C and 2.5 degrees C for 2" and 4" wafers, respectively. In-situ thermocouples were used to control substrate heating. The substrate temperature uniformity was found to depend strongly upon the process temperature, process pressure, gas composition, gas flow, and wafer carrier rotation speed. This in turn affects the properties of the sown Films. This new reactor has been used to produce multiple 4" GaAs/AlAs Bragg reflectors with < 1.0% variation in peak reflectivity wavelength, 4" GaAs Si doped epilayers with < 2.0% doping uniformity, and to simultaneously demonstrate multiple 2" InGaP films with better than +/- 0.75 nm photoluminescence wavelength uniformity.