Effect of Compensatory Embedded Aluminum on the Electrical Characteristics of MIS Tunnel Diode with Ultrathin Oxide

In this thesis, we demonstrate the effect of compensatory embedded aluminum in metal-insulator-semiconductor (MIS) tunnel diodes on the reduction of lateral non-uniformity and sensitivity enhancements to charge trapping and illumination. In chapter 2, in order to reduce the degradation caused by lateral non-uniformity (LNU) of gate oxides in MIS devices, a method to ameliorate the lateral oxide uniformity was proposed. By adopting the anodic oxidation compensation technique to compensate the interface of oxide and embedded aluminum layer, significant uniformity improvements were found in capacitance per unit area-voltage and current density-voltage characteristics, and the percentage dispersions of capacitance per unit area and current density in accumulation regime also give the support to uniformity improvement. Besides, the outcomes of reliability tests also evidence that the LNU is reduced. Hence, with the advantages of superior oxide uniformity, the enhanced response in inversion capacitance was observed. At last, nitric acid solution is used for validating the effectiveness of anodic oxidation compensation, and the current density-voltage, capacitance-voltage reliability characteristics were compared to show that anodic oxidation compensation is necessary for fabricating reliable MIS-based devices. In chapter 3, because of high permittivity dielectric and electric field screening effect by the embedded aluminum, fringing field of the MIS tunnel diode is believed to be enhanced. The enhancement of fringing field leads to the broadening of depletion region at device edge, which intensified the amounts of electron trapping/de-trapping after negative/positive constant voltage stressing. For maintaining charge neutrality, more charge attenuation in silicon bulk due to charge trapping in oxide further modulates Schottky barrier height of majority carriers. As a result, more significant two-state saturation current behavior of the MIS tunnel diode with embedded aluminum was observed. In addition, enlarged photosensitivity was also detected in the MIS tunnel diode with embedded aluminum to serve as another evidence of fringing field enhancement. Finally, accurate TCAD simulations were employed, and the outcomes are consistent with the experimental results.