Thin-film tantalum nitride resistor technology for phosphide-based optoelectronics

The phosphide material system is an important material system for both microelectronics and optoelectronics, but integrated circuit technology on InP substrates is immature. In this work, thin-firm deposition techniques and resistor processing techniques to fabricate fine-line geometry resistors for InP-based electronics are reported. Deposition parameters for d.c. reactive sputtering of tantalum in an argon-nitrogen ambient to realize tantalum nitride thin films with 50 Omega/square sheet resistance are optimized. The dependence of electrical properties, including resistivity, Seebeck ratio and temperature coefficient of resistivity, are reported for a wide range of nitrogen flow. In common with other electronic material systems, Seebeck ratio characterization is implemented for process control monitoring of phosphide-based electronics fabrication. Material composition as a function of nitrogen flow is determined by Rutherford backscattering and elastic recoil detection. Techniques to fabricate low resistance contacts to the TaN are discussed. The processes are demonstrated with the fabrication of high-density, two-dimensional arrays of photoreceivers based on amplifiers using the tantalum nitride resistor technology.