S. Alexandrova

R.F. plasma annealing of as-grown defects in the Si/SiO2 system

Abstract The annealing effect of an r.f. hydrogen plasma on the interface properties in Si/SiO2 systems was investigated. The fixed oxide charge is found to be sensitive to the low temperature plasma annealing. Annealing is more effective at higher temperatures and when applied to metallized structures. With bare oxides the generation of slow states is observed whose concentration depends on the substrate temperature. A final 450 °C hydrogen anneal gives very low fixed charge densities. Comments on the annealing mechanism are also given.

Capacitance–Voltage Characterization of LPCVD‐Silicon Oxynitride Films

LPCVD-silicon oxynitride films with different compositions were deposited on n-Si(111) substrates by reacting dichlorosilane (SiH 2 Cl 2 ) with nitrous oxide (N 2 O) and ammonia (NH 3 ) at a temperature of 860 °C varying the gas flow rate ratio of N 2 O and NH 3 . The electrical properties of the SiO x N y films were studied by analysis of the 1 MHz capacitance-voltage characteristics of the metal-SiO x N y -silicon capacitors. It has been found that with increasing amount of N 2 O in the deposition ambient the concentration of the dielectric charges in the SiO x N y /Si structures goes through a minimum, while the interface trap density gradually decreases. The nature of the defects is discussed.

Oxidation kinetics of hydrogen-enriched Si(100) and Si(111) surfaces

Abstract Hydrogen-enriched Si(100) and Si(111) wafers were thermally oxidized and the growth kinetics were studied by measuring the thickness and the refractive index of the oxide. The oxidation was performed in dry oxygen at temperatures of 800, 845 and 855 °C Prior to oxidation the Si surfaces were hydrogen-enriched by hydrogenation in hydrogen plasma in a planar r.f. unit. The substrates were kept at the lower electrode without heating or at a temperature of 100 °C. In the investigated thickness range of 40–200 A the growth was linear with time. The rate constant was smaller and the zero time thickness higher (as obtained from the fit of the experimental points) as compared with the case of the Si surface with wet RCA preoxidation clean only. A discussion on the role of the hydrogen in oxide growth mechanisms is included.

Charged defects in wet SiO2/Si structure modified by rf oxygen plasma treatment

In the present paper the influence of oxygen rf plasma treatment on the properties of both Si and SiO 2 sides of the wet thermal SiO 2 /Si interface was investigated. The defect concentrations of the oxide charge, dopant level and the interface trap density were obtained from capacitance-voltage (C-V) characterization. The amount of hydrogen trapped in the interfacial region was estimated from changes in the doping density of the silicon substrate. Generation and passivation of electrically active defect centers were found depending on the substrate temperature and the amount of hydrogen. Modification of the oxide and interface between Si and wet SiO 2 is inferred. Plasma promoted release from the oxide bulk of hydrogen species is suggested.

Interface defects introduced in Si/SiO2 structures by hydrogen implantation

The modification of the Si-SiO2 interface by hydrogen implantation with incident fluences of up to 1013 cm-3 was investigated. After a post-implantation anneal, negatively charged interface traps, energetically located in the upper half of the silicon band gap, were observed. A characteristic peak was found near the midgap in the interface trap distribution. A microscopic explanation of these defects is provided on the basis of existing models.

Defects in Si/SiO2 structures introduced by sputter metallization

Abstract A comparative study of MOS structures metallized in planar and cylindrical magnetron systems and in a conventional d.c. diode sputtering system was conducted. In all cases the influence of the discharge led to distortion and hysteresis in high frequency C-V curves owing to the generation of neutral traps spatially distributed in the oxide. The effective concentration of the traps was about 1.4 × 1012 eV−1cm−2 in the central part of the band gap. These defects can easily be removed by conventional low temperature annealing. The necessity of post-metallization annealing of MOS structures prepared in magnetron systems can be avoided if the substrates are isolated from ground and heated to 300 °C during the sputter deposition of the metal layer.

Sputter-metallization-induced electronic defects in thermal SiO2

The generation of interface states and oxide electron traps in thermal silicon dioxide (SiO 2 ) layers by sputtering metallization has been investigated. The dependence of the samples on electric field and temperature during the sputter process is observed. The interface state density spectra revealed narrow distributions indicating an increased density of band edge states. In the upper part of the Si band gap a peak was observed due to the generation of a particular interface defect site. Three bulk defect centers were found as identified by their capture cross sections of the order of 1 × 10 -16 , 3 × 10 -17 and 3 x 10 -18 cm 2 . The first one is associated with radiation induced neutral centers and is a feature of oxides metallized by sputtering. The other two traps are believed to be related to defects like SiOH and H 2 O. Post metallization annealing (PMA) resulted in a reduction of the density of the oxide and interface traps and a broadening of the interface trap spectra. A speculation on the defect formation process is included.

Mobile ions in thermal SiO2 on r.f. plasma annealing

Abstract The influence of hydrogen r.f. plasma exposure on the mobile ions in thermal SiO 2 layers was examined using the triangular voltage sweep method. The ion distribution was found to be different for bare oxide and metal/oxide/semiconductor capacitor samples treated in plasma. The sodium release and neutralization processes are discussed.