Investigation of ‘surface donors’ in Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructures: Correlation of electrical, structural, and chemical properties

III-N surface polarization compensating charge referred here to as ‘surface donors’ (SD) was analyzed in Al2O3/AlGaN/GaN metal-oxide-semiconductor (MOS) heterojunctions using scaled oxide films grown by metal-organic chemical vapor deposition at 600 °C. We systematically investigated impact of HCl pre-treatment prior to oxide deposition and post-deposition annealing (PDA) at 700 °C. SD density was reduced down to 1.9 × 1013 cm−2 by skipping HCl pre-treatment step as compared to 3.3 × 1013 cm−2 for structures with HCl pre-treatment followed by PDA. The nature and origin of SD was then analyzed based on the correlation between electrical, micro-structural, and chemical properties of the Al2O3/GaN interfaces with different SD density (NSD). From the comparison between distributions of interface traps of MOS heterojunction with different NSD, it is demonstrated that SD cannot be attributed to interface trapped charge. Instead, variation in the integrity of the GaOx interlayer confirmed by X-ray photoelectron spectroscopy is well correlated with NSD, indicating SD may be formed by border traps at the Al2O3/GaOx interface. © 2017 Elsevier B.V

Application of Ru-based gate materials for CMOS technology

\u3cp\u3eTogether with high-κ dielectric films, metal gate electrodes have to be employed in advanced CMOS technologies. The metal gate material should be carefully selected with respect to work function, stability of metal-dielectric stack and compatibility with the CMOS process. In our investigation, Ru, RuO\u3csub\u3e2\u3c/sub\u3e and SrRuO\u3csub\u3e3\u3c/sub\u3e gate electrodes grown on thermal SiO \u3csub\u3e2\u3c/sub\u3e, atomic-layer deposition Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e and HfO \u3csub\u3e2\u3c/sub\u3e dielectric films have been analyzed by means of high- and low-frequency capacitance-voltage measurement as well as current-voltage characteristics on MOS capacitors. Ru-based gate materials were prepared by metal-organic chemical vapor deposition at temperatures between 300 and 500°C. Work function of the investigated gate material, leakage current, density of effective defect charge as well as density of interface traps of the gate oxide film were extracted from the measurements. These properties are discussed with regard to application of Ru-based metal gates in CMOS technology.\u3c/p\u3

Ru and RuO\u3csub\u3e2\u3c/sub\u3e gate electrodes for advanced CMOS technology

\u3cp\u3eDue to the downscaling of device dimensions in CMOS technology, the introduction of metal gate electrodes and high-k dielectrics will be necessary in order to meet future performance requirements. In particular, deposition techniques such as chemical vapor deposition (CVD) and molecular beam epitaxy (MBE) have been identified as promising methods for growth of these materials. In this scope, we have analysed properties of Ru and RuO\u3csub\u3e2\u3c/sub\u3e gate electrodes in metal-oxide-semiconductor (MOS) gate stacks prepared on SiO \u3csub\u3e2\u3c/sub\u3e, atomic-layer chemical vapor deposition (ALCVD) Al \u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e and MBE Y\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e dielectric films. The Ru and RuO\u3csub\u3e2\u3c/sub\u3e films were grown by metal-organic chemical vapor deposition (MOCVD) at 250°C. The dielectric and metal gate electrode films were analysed by X-ray diffraction and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). The resistivity of the films at room temperature were 20 and 150μΩcm for the Ru and RuO\u3csub\u3e2\u3c/sub\u3e films, respectively. Thermal stability of the films in forming gas (10% H\u3csub\u3e2\u3c/sub\u3e + 90% N \u3csub\u3e2\u3c/sub\u3e), nitrogen and oxygen environments was investigated by applying low temperature (420°C, 30min) and rapid thermal (800°C) annealing. The results indicate good thermal behavior of the Ru films but limited thermal stability of the RuO\u3csub\u3e2\u3c/sub\u3e films. The Ru and RuO\u3csub\u3e2\u3c/sub\u3e gate electrode workfunctions were extracted from high-frequency capacitance-voltage measurements on MOS capacitors. The obtained results are discussed in connection with applications of Ru and RuO\u3csub\u3e2\u3c/sub\u3e films as gate electrodes in CMOS technology.\u3c/p\u3

Preparation of SrRuO\u3csub\u3e3\u3c/sub\u3e films for advanced CMOS metal gates

\u3cp\u3eWe report on the growth and properties of SrRuO\u3csub\u3e3\u3c/sub\u3e films for application as metal gates for CMOS devices. The films were grown at 500°C by metal-organic chemical vapour deposition on Si substrates with thermal SiO\u3csub\u3e2\u3c/sub\u3e, atomic-layer deposited Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e and HfO \u3csub\u3e2\u3c/sub\u3e dielectric films. The films exhibit room temperature resistivity below 1 mΩ cm. We have analysed the interface between the SrRuO \u3csub\u3e3\u3c/sub\u3e metal gate and the oxide film by Rutherford backscattering and secondary ion mass spectroscopy. Annealing in an oxygen atmosphere and forming gas (90% N\u3csub\u3e2\u3c/sub\u3e +10% H\u3csub\u3e2\u3c/sub\u3e) were employed for testing the stability of the SrRuO\u3csub\u3e3\u3c/sub\u3e metal gate. Finally, electrical characteristics of the metal gate stack were investigated by high-frequency capacitance-voltage measurements. The properties of metal-organic chemical vapour grown SrRuO\u3csub\u3e3\u3c/sub\u3e gate electrode are analysed with regards to integration in CMOS devices.\u3c/p\u3

Preparation of SrRuO\u3csub\u3e3\u3c/sub\u3e films for advanced CMOS metal gates

\u3cp\u3eWe report on the growth and properties of SrRuO\u3csub\u3e3\u3c/sub\u3e films for application as metal gates for CMOS devices. The films were grown at 500°C by metal-organic chemical vapour deposition on Si substrates with thermal SiO\u3csub\u3e2\u3c/sub\u3e, atomic-layer deposited Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e and HfO \u3csub\u3e2\u3c/sub\u3e dielectric films. The films exhibit room temperature resistivity below 1 mΩ cm. We have analysed the interface between the SrRuO \u3csub\u3e3\u3c/sub\u3e metal gate and the oxide film by Rutherford backscattering and secondary ion mass spectroscopy. Annealing in an oxygen atmosphere and forming gas (90% N\u3csub\u3e2\u3c/sub\u3e +10% H\u3csub\u3e2\u3c/sub\u3e) were employed for testing the stability of the SrRuO\u3csub\u3e3\u3c/sub\u3e metal gate. Finally, electrical characteristics of the metal gate stack were investigated by high-frequency capacitance-voltage measurements. The properties of metal-organic chemical vapour grown SrRuO\u3csub\u3e3\u3c/sub\u3e gate electrode are analysed with regards to integration in CMOS devices.\u3c/p\u3