Positive charge generation in metal-oxide-semiconductor capacitors

Abstract

Generation and relaxation phenomena of positive charge and interface trap in a metaloxidesemiconductor structurePositive charge and interface state generation in a thin gate oxide (30 nm) metaloxidesemiconductor capacitor J. Appl. Phys. 75, 1592 (1994; 10.1063/1.356396 Interface and bulk trap generation in metaloxidesemiconductor capacitorsThis work examines the electrical behavior of metal-oxide-semiconductor capacitors in which positive charge has been generated in the silicon dioxide layer using either avalanche hole injection, avalanche electron injection, or Fowler-Nordheim Tunneling injection. It is concluded on the basis of flatband voltage measurements made as a function of time following charge injection that two distinct species of positive charge are generated in the oxide layer, depending on the nature of charge generation. In particular, avalanche hole injection results in the generation of trapped holes, while avalanche electron injection and Fowler-Nordheim Tunneling result in so-called "slow-states'* or anomalous positive charge centers. The electrical behavior of these two species is discussed. In addition, interface trap density measurements following avalanche hole injection show that both a background level of interface traps and a peak at approximately 0.8 eV above the valence band edge build with time following injection. Further, the dependence of the interface trap density on injection fluence and time supports a model in which a neutral species is released from the bulk of the oxide during hole injection and subsequently generates an interface defect.

Influence of Ionizing Radiation and Hot Carrier Injection on Metal-Oxide-Semiconductor Transistors

“…ST may exchange charges with Si substrate during the measurement. The speed of ST depends on their distance from the Si -SiO 2 interface [24]. This indicates that all defects developed in the IR or HCI processes, which are located near this interface and are capable of exchanging charges with the substrate, become part of ST.…”

“…meaning that ∆N it (CP) ≡ ∆N fst ). SST (with density ∆N sst ) located in the oxide, near the Si -SiO 2 interface are frequently called slow states (SS) [21], anomalous positive charge (APC) [25], switching oxide traps (SOT) [26] or border traps (BT) [24]. Finally, it should be pointed out that during the measurement by the SMG technique, ST exchange charges during the measurement meaning that in case of an n-channel MOS transistor (NMOS) these centres capture charges from the channel but releases them when the measurement is finished.…”

“…MOS components annealing may be performed spontaneously (in air atmosphere, at room temperature, without polarization), or at lowered or elevated temperatures, or in the presence of various intensity and direction electric field. A number of experimental results [24,[74][75][76][77][78][79][80] have shown that the density of interface traps during annealing mainly does not change, while the density of trapped charge in the oxide decreases. Several models are proposed for the trapped charge annealing [75,77].…”

“…It has been observed that during annealing part of trapped charge is permanently burnt-in (neutralized), while the other part may only be compensated, which leads to the effect of "inverse burn-in" (apparent increase in the density of trapped charge during annealing at gate negative polarization), which is attributed, by a group of authors, to the existence of the so-called Switching Oxide Trap (SOT) centres [77,78]. Another group of authors attribute it to the existence of the so-called Anomalous Positive Charge (APC) centres [24,79,80]. Both groups explain inverse burn-in by the exchange of charge with substrate whereby such exchange, in case of SOT, is performed by electron tunnelling as the appropriate levels of these centres lay at the height of the substrate conductive zone [78], while APC are, similarly to interface traps, capable of performing direct exchange with the substrate as their energy levels are at the level of the forbidden zone [24,79,80].…”

“…Another group of authors attribute it to the existence of the so-called Anomalous Positive Charge (APC) centres [24,79,80]. Both groups explain inverse burn-in by the exchange of charge with substrate whereby such exchange, in case of SOT, is performed by electron tunnelling as the appropriate levels of these centres lay at the height of the substrate conductive zone [78], while APC are, similarly to interface traps, capable of performing direct exchange with the substrate as their energy levels are at the level of the forbidden zone [24,79,80]. Regardless of their different approaches, both groups have practically contributed to establishing the fact that SOT and APC are most probably the same centre, i.e.…”