Characterization of ultra-thin SiO2 by capacitance-voltage and charge pumping measurements

• Published in: Microelectronic engineering Vol. 81; no. 1; pp. 59 - 65
• Main Authors: MILITARU, L, PONCET, A, LEROUX, C
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Science 01-07-2005
• Subjects: Applied sciences; Compound structure devices; Electronics; Exact sciences and technology; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Transistors; Ultrathin films; Interface state; MOSFET; Density of states; Semiconductor insulator contact; Transistor gate; MOS structure; Quantum effect; Electrical measurement; Charge carrier trapping; Semiconductor device; Quantum effects; Gate oxide; Charge pumping; Gate dielectric; Surface potential; Voltage capacity curve; Ultra-thin SiO2
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2005.03.002

In this paper, we present results on electrical measurements of ultra thin SiO2 layers (from 3.5 nm down to 1.7 nm), used as gate dielectric in metal-oxide-semiconductors (MOS) devices. Capacitance-voltage (C-V) measurements and simulations on MOS capacitors have been used for extracting the electrical oxide thickness. The SiO2/Si interface and oxide quality have been analyzed by charge pumping (CP) measurements. The mean interface traps density is measured by 2-level CP, and the energy distribution within the semiconductor bandgap of these traps are investigated by 3-level charge pumping measurements. A comparison of the energy distribution of the SiO2/Si interface traps is made using classical and quantum simulations to extract the surface potential as a function of the gate signal. When the gate oxide thickness < 3.5 nm, we prove that it is mandatory to take into account the quantum effects to obtain a more accurate energy distribution of the SiO2/Si interface traps. We also explain the increase of the apparent interface traps density measured by 2-levels CP with the increase of the oxide thickness, for transistors made from the same technological process.