Hole traps and trivalent silicon centers in metal/oxide/silicon devices

Abstract

Interaction of molecular hydrogen with trapped hole E' centers in irradiated and high field stressed metal/oxide/silicon oxides Dependence of radiationinduced interface traps on gate Al thickness in metal/SiO2/Si structures We report electron spin resonance (ESR) measurements of E' -center (a "trivalent silicon" center in SiOz) density as well as capacitance versus voltage (C-V) measurements on y-irradiated metal! oxide/silicon (MOS) structures. We also report a considerable refinement of earlier ESR measurements of the dependence of radiation-induced P b -center (a "trivalent silicon" center at the SiiSiO z interface) occupation as a function of the Fermi level at the SiiSiO z interface. These measurements indicate that the P b centers are neutral when the Fermi level is at mid-gap. Since the P b centers are largely responsible for the radiation-induced interface states, one may take L1 V mg Cox / e (where L1 V mg is the "mid-gap" C-V shift, Cox is the oxide capacitance, and e is the electronic charge) as the density of holes trapped in the oxide. We find that radiation-induced E' density equals L1 V mg Cox / e in oxides grown in both stream and dry oxygen. Etch-back experiments demonstrate that the E' centers are concentrated very near the SilSi0 2 interface (as are the trapped holes). Furthermore, we have subjected irradiated oxide structures to a sequence of isochronal anneals and find thatthe E ' density and L1 V mg annealing characteristics are virtually identical. We conclude that theE' centers are largely responsible for the deep hole traps in thermal Si0 2 on silicon. This observation coupled with observations regarding theP b center indicates that two intrinsic centers, both involving silicon atoms lacking one bond to an oxygen atom, are largely responsible for the two electrically significant aspects of radiation damage in MOS devices: charge buildup in the oxide and interface-state creation at the SiiSiO z interface.

Analysis of defect capture cross sections using non-radiative multiphonon-assisted trapping model

“…The total defect concentration is N T = 2.05 Â 10 12 cm À2 . These results are consistent with the considerations and quasi-static measurements [32,34].…”

“….Þ have been taken from measurement values based on scanning tunneling spectroscopy studies for single-defect Si dangling bonds [25]. The dynamics of other oxide traps (E c and E d [7,32]) are better described including metastable states [11,24]. However, EPR studies indicated that these defects relax almost immediately after the removal of the stress condition [9], and thus they have not been investigated in this study.…”

Properties of latent interface-trap buildup in irradiated metal–oxide–semiconductor transistors determined by switched bias isothermal annealing experiments

“…This is not very likely, since it has been established that the majority of the radiation-induced oxide-trap charge is from holes trapped at EЈ centers. 13 The data in Fig. 1 are in accordance with the so-called hydrogen cracking models, 1,4,5 as they assume as a first step diffusion to the Si/SiO 2 interface of radiolytic H 2 released in the gate oxide and/or adjacent structures ͑poly-Si gate, chemical-vapor-deposited oxide͒.…”

Radiation aging of stockpile and space-based microelectronics.

“…It is well known that ionizing radiation generally degrades the performance of Si microelectronic devices by creating interface traps and oxide-trapped charge [11,10]. The interface traps consist of Si atoms at the interface that failed to bond to the oxide [12]. Such traps act as recombination centers for electrons and holes, and this recombination leads to increased base current in bipolar transistors [10].…”