Introduction of Si/SiO{sub 2} interface states by annealing Ge-implanted films

• Published in: Journal of applied physics Vol. 96; no. 8
• Main Authors: Marstein, E.S., Gunnaes, A.E., Olsen, A., Finstad, T.G., Turan, R., Serincan, U., Department of Physics, Middle East Technical University, 06531 Ankara
• Format: Journal Article
• Language: English
• Published: United States 15.10.2004
• Subjects: ANNEALING; CAPACITANCE; CAPACITORS; ELECTRONIC EQUIPMENT; ELECTRONIC STRUCTURE; FABRICATION; GERMANIUM IONS; INTERFACES; ION IMPLANTATION; ION MICROPROBE ANALYSIS; MASS SPECTROSCOPY; MATERIALS SCIENCE; NANOSTRUCTURES; RUTHERFORD BACKSCATTERING SPECTROSCOPY; SEMICONDUCTOR MATERIALS; SILICON; SILICON OXIDES; THIN FILMS; TRANSMISSION ELECTRON MICROSCOPY; VACUUM COATING; X RADIATION
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1790579

Nanocrystals embedded in SiO{sub 2} films are the subject of a number of recent works, mainly because of their potential usefulness in the fabrication of optoelectronic devices and nanocrystal memory structures. One interesting method for the fabrication of such nanocrystals is the ion implantation of segregating species into SiO{sub 2} films followed by heat treatment in order to induce nanocrystal formation. This method is both relatively simple and also compatible with the current MOS (metal-oxide-semiconductor) device technology. An unintentional effect can occur during the fabrication of nanocrystals using this method, namely a significant diffusion of the implanted species during annealing, away from the regions with the highest concentration. The Si/SiO{sub 2} interface can be exposed to this diffusion flux. This can result in an altered interface and have a significant influence on electronic devices. Here, we report on ion implantation of Ge into SiO{sub 2} on Si followed by annealing under conditions, resulting in Ge accumulation at the Si/SiO{sub 2} interface as determined by secondary-ion mass spectroscopy analysis, transmission electron microscopy with energy dispersive analysis of x-rays, and Rutherford backscattering spectrometry. The accumulation of Ge at the Si/SiO{sub 2} interface has also been reported before. The resulting effect on the electronic structure of the interface is a priori unknown. We have fabricated MOS capacitors on the sample structures and their capacitance-voltage characteristics were measured and analyzed. We measure an interface state density around 1x10{sup 12} cm{sup -2}, which is high compared to standard Si MOS devices. We discuss the results in terms of the previous electrical measurements on Ge-oxide interfaces and SiGe interfaces, which also can yield a high interface state density. The specific conditions we report result in a sufficiently low Ge concentration that nanocrystals are not segregated in the SiO{sub 2} film, while Ge still accumulates at the Si/SiO{sub 2} interface after annealing.