Naoto Kameda

Rapid Oxidation of Silicon Using UV-Light Irradiation in Low-Pressure, Highly Concentrated Ozone Gas below 300 °C

A low-temperature, damage-free process for growing ultrathin (<6 nm) silicon dioxide (SiO2) films was successfully developed. The excitation of low-pressure, highly concentrated O3 gas using photons with energies less than 5.6 eV led to rapid growth rates of 2 and 3 nm within 1 and 5 min, respectively, even when the process temperature was as low as 200 °C. The enhanced oxidation rate was due to an increased supply of O(1D) atoms at the Si surface. Transmission electron microscope images revealed that the SiO2 film formed with a uniform thickness and a smooth, distinct SiO2/Si interface. Capacitance–voltage and current–voltage measurements showed that 200 and 300 °C as-grown films had a satisfactorily low density of mobile ions and trap charges as well as ideal insulating properties.

Advantage of Highly Concentrated (≥90%) Ozone for Chemical Vapor Deposition SiO2 Grown under 200 °C Using Hexamethyldisilazane and Ultraviolet Light Excited Ozone

We have compared the UV-light-excited ozone chemical vapor deposition (CVD) process conditions and the film quality for the cases where either highly concentrated (≥90%: HC) or 7% ozone and either hexamethyldisilazane (HMDS) or tetraethoxysilane (TEOS) are used. The SiO2 film deposited using HMDS and UV-excited HC ozone with an optimized flow rate has the highest quality in terms of leakage current density, etching rate, and deposition rate which are comparable or superior to those of the conventional thermal TEOS SiO2 grown at 620 °C. These results lead to a conclusion that it is preferable to use HC ozone for UV-light-excited-ozone CVD to deposit the high quality SiO2 films at a practical rate at a temperature as low as 200 °C.

Photochemical Reaction of Ozone and 1,1,1,3,3,3-Hexamethyldisilazane: Analysis of the Gas Reaction between Precursors in a Photochemical Vapor Deposition Process

The photochemical reaction of 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and ozone (O3) in the gas phase was analyzed as the side reaction in the photochemical vapor deposition (photo-CVD) process irradiated by ultraviolet light: the analysis was conducted by Fourier-transform infrared absorption spectroscopy (FT-IR) and mass spectrometry (MS). The final products of this photochemical reaction between HMDS and O3 are CO2, N2, and H2O, although this reaction is initiated at the Si–N–Si bond of HMDS with O3 and ultraviolet (UV) light, thus producing, as a reaction intermediate, a compound with carbonyl and/or carboxylic group followed by Si–N–Si scission.

Nanoscale-order Homogeneous Structure of SiO2 Film on Poly-silicon Grown at Room Temperature using UV Light Excited Ozone.

1. Abstract We have grown SiO2 films on polycrystalline Si using excited ozone produced by ultra-violet light irradiation to ozone. An over-5 nm thick SiO2 film was grown in 30 min even at room temperature. The TEM image indicates that the spatial distribution of the SiO2 film thickness is 6.0 0.1 nm over an area of 100 nm square at the surface of poly-Si, where the grain sizes of poly-Si are less than 10 nm. This result suggests that the oxidation rate of silicon by excited ozone is independent of Si crystal orientation. The SiO2 film by the excited ozone is expected to be utilized for the buffer layer with good interface properties.