A Deep Level Transient Spectroscopy Comparison of the SiO 2 /Si and Al 2 O 3 /Si Interface States E. Simoen a , A. Rothschild a , B. Vermang a,b , J. Poortmans a,b and R. Mertens a,b a Imec, Kapeldreef 75, B-3001 Leuven, Belgium b Department Electrical Engineering, K.U. Leuven, Kasteelpark Arenberg 10, B-3001 Leuven, Belgium Deep Level Transient Spectroscopy (DLTS) has been applied to study the interface states of 5 nm Atomic Layer Deposited (ALD) Al 2 O 3 films on p-type Si. In addition, the passivation of the interface states by Forming Gas Anneal (FGA) and Firing has been explored. It is shown that the near mid-gap density of interface states (D it ) is successfully reduced by both treatments. From a comparison with 5 nm SiO 2 reference capacitors it can be concluded that similar interface defects are observed, suggesting that they are dominated by the thin interfacial SiO 2 layer formed during ALD. Introduction Since its introduction in 1974 (1), Deep Level Transient Spectroscopy (DLTS) has also been applied to the study of the Si-SiO 2 interface, using for example Metal-Oxide- Semiconductor (MOS) capacitors (2-8). Besides the classical temperature-scan DLTS, it has been shown that so-called isothermal DLTS, whereby the spectrum is formed by sweeping the pulse frequency at a fixed temperature, may yield the same information (9). A comparison with other frequently used interface-state characterization techniques demonstrates an overall good agreement (10-12). Some additional advantages are that one can make fairly easy a distinction between interface and bulk trap levels (13,14) and, secondly, it is relatively straightforward to determine the capture cross section as a function of the energy (15) or temperature (16), which is an important parameter in the modeling of the surface recombination velocity (15). This approach has recently also been applied to the Si/SiN x interface, SiN x being a popular passivation layer for among others crystalline silicon solar cells (17,18). Besides SiO 2 and SiN x , other, so-called high-k dielectrics are becoming more and more popular in microelectronics and solar cell applications (19). In present-day 45 and 32 nm node CMOS digital devices, SiO 2 is successfully replaced by an HfO 2 -based gate dielectric. At the same time, Al 2 O 3 has shown some interesting properties with respect to the field-induced passivation of p-type silicon (20-23). However, so far little DLTS results on the interface of these novel dielectrics with silicon have been reported: some studies have focused on HfO 2 (24,25), while one report mentions a peak with activation energy of 0.27 eV above the valence band in Al 2 O 3 /p-Si MIS capacitors (26). Therefore, the aim of the present work is to report on a detailed DLTS study of the deep-level states at the Al 2 O 3 /p-Si interface and to compare it with SiO 2 /p-Si references. It will be shown that very similar spectra have been obtained for 5 nm layers, which can be explained by ECS Transactions, 41 (4) 37-44 (2011) 10.1149/1.3628607 ©The Electrochemical Society 37 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 146.103.254.11 Downloaded on 2015-09-28 to IP