Engineering the nm-thick Interface Layer Formed Between a High-k Film and Silicon
- PDF / 1,130,692 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 87 Downloads / 186 Views
D3.11.1
Engineering the nm-thick Interface Layer Formed Between a High-k Film and Silicon J. Lu, J. -Y. Tewg, and Y. Kuo
Thin Film Nano and Microelectronics Research Laboratory, Texas A&M University, College Station, TX 77843 ABSTRACT The interface layer between thin sputter-deposited tantalum oxide (TaOx) high-k film and silicon substrate was engineered with the Hf doping method and the insertion of a thin 5Å TaNx interface. The following results have been obtained: 1) the Hf dopant in the TaOx film was involved in the interface formation process, e.g., forming a new, thinner high-k HfSixOy interface layer rather than the SiOx layer, 2) when the TaNx interface was inserted, the interface layer composition was even more complicated, e.g., including TaOxNy and HfSixOy structures. No hafnium nitride or oxynitride was detected, 3) the interface layer structure was changed, e.g., from single-zone to multi-zone with different compositions, 4) when a low concentration of Hf existed in the TaOx film, the high-k dielectric properties, such as the k value, fixed charge density, dielectric strength, were improved, and 5) when the thin TaNx interface layer was inserted, the above electric properties were further improved. However, the fixed charge density and interface states were increased due to the insertion of the TaNx interface layer. These results were contributed by factors such as the charge-trapping characteristics in the interface layer and the some damage repairing mechanisms. In summary, this research proved that the high-k film’s interface layer and bulk properties could be were improved with the doping process as well as the insertion of an ultra-thin TaNx interface film. INTRODUCTION Tantalum oxide (Ta2O5) is a promising high-k gate dielectric material with a high k value and has been successfully used in the high-density storage devices. However, Ta2O5 forms a SiOxlike interface layer when it is in direct contact with silicon after a high temperature process step [1]. The existence of the low-k interface layer will lower down the overall effective k value of the high-k film and limit its ultimate scalability. Nevertheless, if the interface is like the thermally grown SiO2, this can result in the improvement of device performance, such as the low interface state density and high mobility. Therefore, how to improve the ultra-thin interface layer between a high-k film and silicon substrate is one of most challenging issues in developing a practical high-k gate dielectric material for the next generation of CMOS technology. Previously the authors reported that when Ta2O5 was doped with Hf, several advantages were obtained, such as, increasing the amorphous-to-polycrystalline transition temperature, improving the interface layer quality, and enhancing the k value [2]. When a 5Å tantalum nitride (TaNx) is inserted between the Hf-doped TaOx and silicon, many the film’s dielectric properties can be further improved due to the change of the interfacial layer composition [3,4]. In this paper, the authors systematically
Data Loading...
