Spatial Probing of Traps in nMOSFET with ALD HfO2/SiO2 Stacks Using Low Frequency Noise Characteristics

Low frequency (LF) noise is studied in n-type metal-oxide-semiconductor field-effect-transistors (nMOSFETs) with various HfO₂ or interfacial layer (IL) thicknesses and is found to be dominated by 1/f noise in the frequency range 1 Hz lesfles 1.6 kHz. LF noise magnitude increases with HfO₂ thickness and decreases with IL SiO₂ thickness. Traps at the channel and dielectric interface do not contribute to the 1/f noise or cannot be resolved from thermal noise. The LF noise correlates well with the hysteresis or V_th instability observed during DC measurements. The volume trap density calculated from 1/f noise analysis is more than one order of magnitude higher in 7 nm HfO₂ than in 3 nm HfO₂ devices. Qualitative trap spatial profiles can be obtained from the LF spectra, and the stress induced redistribution of trap distribution is discussed