Effects of strained layer near SiO2-Si interface on electrical characteristics of ultrathin gate oxides

ltrathin gate oxides formed by different process technologies are investiga ted in detail. The following important evidence is found: the discrepant re sult on the two time-dependent dielectric breakdown (TDDB) lifetime measure ments, the constant-current stress, and the constant-voltage stress. The di screpancy is due mainly to the difference in the oxide leakage characterist ics. Apparent changes in the activation energy and the defect generation ra te during the TDDB testing are also experimentally observed for the two oxi des formed by different process technologies. From the analysis based on th e x-ray photoelectron spectroscopy by means of the oxide etch by dilute HF and the Fourier-transform infrared attenuated total reflection method, we c onsider that the above phenomena are induced by the difference in the built -in compressive strain of the Si-O network near the SiO2 and Si interface. (C) 2000 American Institute of Physics. [S0021-8979(00)06904-8].