AVS 46th International Symposium
    Electronic Materials and Processing Division Tuesday Sessions
       Session EM-TuM

Paper EM-TuM1
Structural Transition Layers at the Interface of SiO@sub 2@/Si(100) Fabricated by Ozone

Tuesday, October 26, 1999, 8:20 am, Room 608

Session: Si Surface Chemistry and Etching, Passivation, and Oxidation
Presenter: K. Nakamura, Electrotechnical Laboratory, Japan
Authors: K. Nakamura, Electrotechnical Laboratory, Japan
H. Itoh, Electrotechnical Laboratory, Japan
A. Kurokawa, Electrotechnical Laboratory, Japan
S. Ichimura, Electrotechnical Laboratory, Japan
K. Koike, Iwatani International Corporation, Japan
G. Inoue, Iwatani International Corporation, Japan
T. Fukuda, Iwatani International Corporation, Japan
Correspondent: Click to Email
A novel processing technique for oxidation with rapid growth kinetics at lower substrate temperature is strongly required to fabricate a much thinner silicon dioxide film <4nm for gate oxides in MOSFET in the near future. However, properties of the synthesized oxide must be maintained or upgraded simultaneously in comparison with those of a conventionally used thermally grown oxide. Especially, the interface of oxide and substrate is critical because the oxide reliability is expected to depend on the characteristics of the interface affected by strain, defects, roughness, P@sub b@ centers, etc. Using ozone as an alternative oxidant, we have found a distinguished feature in the structural transition layers at the interface. An ultrathin silicon dioxide film was fabricated on a Si(100) surface by concentrated ozone: The substrate temperature was between room temperature and 700 °C and the ozone pressure was at 8x10@super -4@Pa or atmospheric pressure. Structural transition layers in the SiO@sub 2@ ultrathin film by ozone was limited to a much thinner region than that of thermally grown oxide with > 1nm thickness. This was confirmed by a change of the etching rate of SiO@sub 2@ film with dilute hydrofluoric acid solution. Such thinner region of transition layers in the ozone-oxide was implemented either on clean Si(100)2x1 or on Si(100) with an already existing native oxide film at 300°C or more. However, exposure of ozone to Si(100) with an already existing thermally grown oxide film, for example at 350°C, caused no change in the distribution of transition layers in the oxide. This contrast indicates that the oxide growth by ozone or the further oxidation of lower oxidized silicon atoms in the native oxide by ozone formed transition layers with much less thickness, while highly oxidized silicon atoms in the thermally grown oxide film remained unreacted even by reactive ozone. Structural transition layers on the opposite side of the interface, i.e. in the substrate, will also be discussed.