An electron paramagnetic resonance study of electron injected oxides in metal-oxide-semiconductor capacitors

Abstract

Electron paramagnetic resonance, in conjuction with electrical measurements, has been used to study Si-SiO2 interface defects produced as a result of negative bias, high-field electron injection into the SiO2 layer of metal-oxide-semiconductor capacitors. In particular, a search was made for Pb centers, previously identified as a source of interface traps in unannealed SiO2 on Si, and for E′ centers, which have been associated with trapped holes in SiO2. The results of the EPR experiments show no change in the density of Pb centers following injection, despite the presence of interface traps as indicated by the electrical measurements. Further, no E′ centers are detected in samples for which an analysis of the current-voltage and capacitance-voltage data suggest the presence of 5×1012 cm−2 positively charged centers. We conclude that interface traps generated in the present samples are not of the same microscopic nature as those found in unannealed SiO2 on Si, and that positive charging under the present conditions is not due to trapped holes. It is suggested that the source of positive charge is the so-called ‘‘anomalous positive charge’’ (APC) center. The microscopic nature of the present defects has not been identified.

The impact of negative-bias-temperature-instability on the carrier generation lifetime of metal-oxynitride-silicon capacitors

“…Nevertheless, the possibility of interface trap generation where the defect atomic structure appears to be different from that of the P b -type center has been proposed by some researchers. 29,30 As far as nitrogen-containing dielectrics are concerned, EPR measurements have confirmed the existence of P b -type centres at Si-Si x N y and Si-SiO x N y interfaces. 31,32 Moreover, Fujieda et al 33 have inferred from a combination of conductance-frequency ͑G-͒, CV, and EPR measurements on a Si-SiO x N y interface undergoing NBTI that the P b -type centers are the dominant interface defects brought about by NBTI which was shown to occur mainly through the decomposition of P b -H pairs.…”

Evidence for two types of radiation-induced trapped positive charge

“…On the other hand, more recently Warren et al have compared ESR measurements with C-V measurements, and found the number of trapped charges present was greater than the number of spins detected [ 171. Furthermore, Trombetta et al have generated APC's and observed no measurable ESR signal [18]. It seems clear that some of the trapped charge is in E' centers.…”

Spectroscopic charge pumping investigation of the amphoteric nature of Si/SiO2 interface states

“…1-8 However, quantitative disagreements are common when comparing P b center data obtained from ESR and Si/ SiO 2 interface state data obtained from more conventional MOSFET electrical measurements. [9][10][11][12] For example, it's been argued that P b centers account for only a small fraction of electrically measured interface states with the remaining majority due to some unknown defect. 9,10 A potential source of the disagreements is the inability of most MOSFET electrical measurements to truly exclude the effects of noninterface defects, especially when dealing with samples of very poor quality.…”