Yoshikazu Kojima

Composition and Growth Mechanisms of a Boron Layer Formed Using the Molecular Layer Doping Process

A new doping process, molecular layer doping (MLD), allows for formation of extremely shallow junctions. We have studied the composition and growth mechanisms of boron layers formed on a Si substrate through the MLD process using diborane as the boron feed gas. At temperatures below 600°C, a pure boron layer is formed through the deposit of boron generated through thermal decomposition of diborane. At temperatures over 700°C, the boron layer contained silicon. At 800°C, a boron silicide layer is formed through reaction of boron with the silicon in the substrate. The growth rate of a boron silicide layer depends on the orientation of the Si substrate. However, that of a pure boron layer does not depend on the orientation. The composition of the layer after annealing at 900°C was analyzed using the RBS method and was found to be SiB6. Results of MLD processes on several kinds of underlying layers (e.g., SiO2, Si3N4, poly-Si) are also presented.

Oxide‐semiconductor interface roughness and electrical properties of polycrystalline silicon thin‐film transistors

Polycrystalline silicon thin‐film transistors (TFTs) have been fabricated with a smooth oxide‐semiconductor interface. Device characteristics are found to be improved with the interface smoothness. The channel mobility is especially improved to about 2 times larger than that of conventional poly‐Si TFTs. The topography of the oxide‐semiconductor interface was analyzed using nanometer resolution atomic force microscopy. The roughness of the oxide‐semiconductor interface and the electrical properties of poly‐Si TFTs are found to have a strong relationship.l

A stacked dielectric film for a silicon microstrip detector

Abstract Stacked dielectric films have been developed so as to be applied to a silicon microstrip detector (SSD). We expected that these stacked films would have superior properties for an integrated capacitor in terms of a high dielectric breakdown characteristic, reliability, a large capacitance and radiation hardness. We measured the capacitance and leakage current for test capacitors with single-layered silicon dioxide (SiO 2 ), single-layered silicon nitride (Si 3 N 4 ), NO (Si 3 N 4 SiO 2 ), ON (SiO 2 Si 3 N 4 ) and ONO (SiO 2 Si 3 N 4 SiO 2 ).

Characterization of an ONO-stacked insulator film for a silicon micro-strip detector

Abstract A semi-empirical model for an ONO-stacked insulator film is presented together with its implications. The model covers ONO, ON, and NO films as well as single-layered SiO 2 and Si 3 N 4 . We eventually present an assessment for estimating the lifetime of an ONO-stacked insulator film for a given configuration.