XPS Study of H-Terminated Silicon Surface under Inert Gas and UHV Annealing

Abstract

We have investigated the changes of chemical bonding states of an H-terminated silicon surface under inert gas (Ar,N 2 ) and ultrahigh vacuum ͑UHV͒ annealing using X-ray photoelectron spectroscopy ͑XPS͒ and thermal desorption spectroscopy ͑TDS͒. SiC is formed ͑corresponding to ϳ0.1 monolayer͒ under inert gas and UHV annealing at around 500°C, which is coincident with the temperature of the dangling bonds formation at the silicon surface by hydrogen desorption, whereas SiC is not formed under O 2 annealing. From the precise analysis using a combination of XPS and TDS, the SiC formation is related to the reaction between the silicon surface and the organic contamination that is unavoidably adsorbed during air exposure. We also studied the electrical properties of metal oxide semiconductor capacitors with a chemical vapor deposited silicon oxide gate insulator formed on Ar-and O 2 -annealed silicon surfaces. Ar preannealing increases the leakage current by approximately 10 Ϫ4 times compared with O 2 annealing.It is of great importance to obtain high reliability in less than 1.5 nm thick silicon oxide gate dielectrics for 65 nm metal oxide semiconductor ͑MOS͒ devices. Pyrogenic oxides have been frequently applied for the gate dielectrics up to the present. In a conventional furnace, an uncontrollable oxide layer is grown at low temperatures in the preannealing process because O 2 gas in the air unavoidably enters the furnace chamber simultaneously at the wafer loading step. 1 The growth of the uncontrollable oxide layer deteriorates the reliability of the gate dielectrics because the time-dependent dielectric breakdown ͑TDDB͒ characteristic of a MOS capacitor with silicon oxide film grown by dry O 2 at low temperature is inferior to that with a pyrogenic oxide film grown at high temperature. 1 A furnace equipped with a load lock chamber that can control residual O 2 is necessary to prevent the uncontrollable oxide layer formation. H-termination with HF treatment is also necessary to remove the chemical oxide layer formed by the RCA cleaning process and to deactivate the silicon surface. 2-7 Although the uncontrollable oxide or the chemical oxide layer is only about 1 nm thick, it is necessary to prevent the formation of these oxide layers to realize 1.5 nm thick, highly reliable gate dielectrics. Previously, it was reported that the TDDB characteristic for MOS capacitors degrades when using a load lock chamber after HF treatment. 8 It would be caused by remaining organic contamination or etching on the silicon surface by residual O 2 and H 2 O. 9,10 However, a microscopic mechanism for the TDDB degradation still remains unclear.In this paper, we investigate the influence of inert gas (Ar,N 2 ) and ultrahigh vacuum ͑UHV͒ annealing with a load lock chamber on the chemical bonding state and roughness of H-terminated silicon surfaces by X-ray photoelectron spectroscopy ͑XPS͒ and thermal desorption spectroscopy ͑TDS͒ analysis and atomic force microscopic ͑AFM͒ observation. The insulation characteristics of gate dielectric...

Metal Catalyst for Low-Temperature Growth of Controlled Zinc Oxide Nanowires on Arbitrary Substrates

“…4b, the binding energy (BE) scale was calibrated using the carbon peak (C-1s) at 285 eV as a reference3435. As these samples were exposed to ambient air prior to the XPS analysis, small amounts of carbonyl compounds (CO and CO 2 ) were observed, resulting in two additional peaks at 286.6 and 288.7 eV363738, respectively. Those peaks arising from carbonyl compounds were also used as a reference to identify the different O-related species present in the samples.…”

Hydrogen desorption from hydrogen fluoride and remote hydrogen plasma cleaned silicon carbide (0001) surfaces

“…6, the low temperature H 2 desorption observed from the 6H-SiC (0001) surface can be reasonably well reproduced using the Polanyi-Wigner equation and the previously determined b 1-3 kinetics for H 2 desorption from Si surfaces. 32,84 In particular, Kawase has shown a peak in CH 3 desorption at 450 C for organic contaminated Si (001) surfaces. This is consistent with a previous analysis of remote H-plasma treated Si (001) surfaces where additional desorption states were also needed to fully reproduce the H 2 TPD spectra from those surfaces.…”

A ultra-high-vacuum wafer-fusion-bonding system

“…The Si sample was then heated to 600 • C (the Si-H desorption temperature is 520 • C) for four hours to desorb the H from the surface. 17,24 Subsequent XPS measurements showed no increase in C or O contamination of the Si surface (H is not measurable with XPS). Atomic force microscopy (AFM) measurements showed no increase in the surface roughness of annealed samples (measured rms roughness ∼1 Å).…”

“…23 While some of the systems included x-ray photoelectron spectroscopy 19,22 (XPS) and Auger electron spectroscopy 20 (AES) systems for in situ surface analysis prior to bonding, additional surface preparation tools are necessary for manipulating the band alignment of wafer-fusion-bonded heterojunctions. Capabilities such as high-temperature annealing 17,24 and sputter deposition 14,15,25 provide important means for manipulating the surface chemistry of wafer surfaces prior to bonding to tune the magnitude of interface dipoles and adjust the band alignment.…”