Application of optical second harmonic generation in characterization of Si(100)/SiO2 interfacial microroughness

Current trends in the silicon microelectronics industry are driving metal-oxide-semiconductor (MOS) devices to deep sub-micron dimensions, and corresponding gate oxide layers to sub-50 Angstrom (A) thicknesses, thus tightening requirements for the control of Si(100)/SiO ₂ interfacial contamination and microroughness during device processing. Certain cleaning chemistries can roughen the silicon surface and roughening, even at the Angstrom level, can result in poor reliability for MOS devices. At the present time, few analytical techniques exist that can measure Angstrom-scale interface roughness in situ without removing the oxide. Optical techniques are attractive for this purpose because they are non-destructive and nonintrusive, and can measure through a thick transparent oxide overlayer. Optical surface second harmonic generation (SSHG), is interface-specific in centrosymmetric semiconductors. We present the first systematic SSHG studies of randomly oriented, angstrom-scale surface/interface microroughness at chemically cleaned Si(100)/SiO₂ interfaces