Effect of nanometer-scale corrugation on densities of gap states and fixedcharges at the thermally grown SiO2/Si interface

Effect of nanometer-scale corrugation on gap state and fixed charge densiti es at the SiO2/Si interface in Si (001) metal-oxide-semiconductor (MOS) cap acitors has been studied by capacitance-voltage (C-V) and conductance-volta ge (G/omega -V) measurements. As the interface corrugation, a high density of Si protrusions, composed of a microscopic (001) plane at the top and hig h-index planes [typically (115) planes] at the sides, were formed by a micr oscopic selective oxidation technique developed by the authors. By changing the selective oxidation condition, the area ratio of the top and side plan es was varied. As a result, it was found that each of C-V and G/omega -V cu rves showed a mixture of two curves with different flatband voltages. This reflects that the interface fixed charge density at the side high-index pla nes is larger than that at the top (001) plane, similar to previous reports for classical MOS capacitors with a macroscopic flat interface. Furthermor e, it was found that the side high-index interface has a higher gap state d ensity than the top (001), also similar to the previous macroscopic results . Such orientation dependence of gap state and fixed charge densities in th e nanometer regime will play a significant role in electrical properties of ultrasmall Si devices, which accompany a relatively large area of curved i nterfaces. (C) 2001 American Institute of Physics.