Formation of Doping Profiles in Float Zone Silicon by Helium Implantation and Plasma Hydrogenation
- PDF / 99,297 Bytes
- 6 Pages / 595.22 x 842 pts (A4) Page_size
- 54 Downloads / 183 Views
1108-A12-03
Formation of Doping Profiles in Float-Zone Silicon by Helium Implantation and Plasma Hydrogenation R. Job 1), F.-J. Niedernostheide 2), H.-J. Schulze 2), H. Schulze 3) 1) 2)
University of Hagen, Dept. of Mathematics & Computer Science, D-58084 Hagen, Germany Infineon Technologies AG, D-81726 Munich, Germany 3) Infineon Technologies Austria AG, A-9500 Villach, Austria ABSTRACT By means of two-point-probe Spreading Resistance (SR) analyses, the formation and evolution of hydrogen-related and vacancy-related donor and acceptor states were studied in helium implanted and subsequently hydrogen plasma-treated n-type Float-Zone (FZ) silicon wafers. He+-implantation was carried out at 3.75 MeV and 11 MeV, applying fluences of 1⋅1014 cm-2 and 2⋅1013 cm-2. After 15-min post-implantation H-plasma exposures at substrate temperatures between 350 °C and 500 °C, distinct surplus doping profiles were observed in the subsurface layers of the treated FZ Si samples. Also acceptor-like states occurred, at least partially compensating for the initial n-type doping, so that even buried p-type layers could be created under appropriate process conditions. The nature of the involved defect complexes will be discussed. INTRODUCTION By applying light-ion irradiation – H+, He+ – the properties of semiconductors can be distinctly modified under controllable conditions [1]. Hence, implantation with light ions is a powerful tool in semiconductor device technology, and is widely used for device optimization – especially for silicon devices. Implantations with H+ or He+ can penetrate a wide range of depths within the Si wafers, spanning four orders of magnitude between about 100 nm and 1 mm. Therefore, such substrate modifications can follow rather deep profiles if desired. On the other hand, at moderate temperatures up to 500 °C, hydrogen-plasma treatments cause n-type doping in Si wafers under appropriate conditions. This doping can be related to hydrogen-supported thermal-donor formation – classical oxygen donors – or to hydrogen-related shallow donor complexes [2-5]. Those processes can even be used for simple device fabrication [6-8]. With this background, it is interesting to study the impact of successive light-ion implantation and H-plasma treatments in silicon. Hence, we recently investigated n-type FZ Si wafers treated by H+-implantation and subsequent H-plasma exposure at moderate temperatures. We observed that in the wafers’ subsurface regions down to the projected ion range of the implanted H+-ions, distinct surplus n-type doping occurred after 15-min H-plasma exposure at temperatures between 350 °C and 500 °C, which can be attributed to hydrogenated vacancy defect complexes [9]. In addition, acceptor-like defect complexes were observed close to the surface; they might be attributed to hydrogenated vacancy complexes, e. g. V2-H2 [10], or multi-vacancy-oxygen complexes, such as Vn-Om. Longer Hplasma treatments (60 min) resulted in a complete recovery of the initial n-type doping conditions based on phosphorous doping, i. e
Data Loading...
