Low temperature nitrogen incorporation method for enhanced electrical properties in hafnia based gate dielectrics

Abstract

A low temperature method (∼400°C) for nitrogen incorporation in hafnia based dielectrics has been developed for future gate dielectric applications. Hf metal films were deposited on Si substrates in ammonia ambient and were subsequently oxidized under ultraviolet illumination. Using this method, an interfacial layer comprising Hf–Si–O–N bonding was formed at the hafnia-Si interface, which led to a substantial enhancement in the overall dielectric properties of the film. An equivalent oxide thickness of 11.5Å and leakage current densities lower than 10−4A∕cm2 at a gate bias of −1V were achieved by this approach.

Study of interface degradation of Hf-silicate gate dielectrics during thermal nitridation process

“…An increase in nitrogen incorporation with the increase in the nitridation temperature has been reported earlier. 5 The densification of film and IL can be attributed to the presence of a larger amount of nitrogen. The increase in thickness of IL is due to higher diffusivity of oxygen and nitrogen at higher temperatures.…”

“…Previous reports have already revealed that engineering IL by nitrogen incorporation improved the electrical properties of metal-oxidesemiconductor ͑MOS͒ device. 5 However, all the above mentioned results were qualitative studies. There are only a few quantitative reports for interface properties especially interface roughness change with respect to the nitridation process.…”

“…[1][2][3][4][5][6][7] However, hafnium-silicate film still has issues such as hafnium interdiffusion, low-k interface layer formation, and phase separation between hafnium oxide and silicon oxide. Nitrogen incorporation in the hafnium-silicate film was explored to overcome some of these issues.…”

High efficiency nitrogen incorporation technique using ultraviolet assisted low temperature process for hafnia gate dielectric

“…27 However, additional IL degradation ͑IL growth and high interface state; D it ͒ may not be avoidable in case of high temperature nitridation method. 5,27 In conclusion, the UV assisted low temperature nitrogen doping technique for hafnia gate dielectric film was investigated. The incorporation efficiency of UV assisted low temperature method was comparable to the high temperature ͑ϳ650°C͒ thermal nitridation process.…”

“…͓DOI: 10.1063/1.2892040͔ Hafnium silicate has been extensively studied as an alternative gate dielectric material in advanced metal oxide field effect transistors due to high crystallization temperature, thermodynamic stability with Si, high permittivity, and relatively large band gap ͑5.68 eV͒. [1][2][3][4][5][6][7] However, hafnium silicate film still has issues such as hafnium inter diffusion, lowk interface layer ͑IL͒ formation, and phase separation between hafnium and silicon oxides. Nitrogen incorporation in hafnium silicate was explored to enhance the resistance to thermal degradation.…”