Jason P. Campbell

Disease Detection and Management via Single Nanopore-Based Sensors

Sensors Joseph E. Reiner,*,† Arvind Balijepalli,‡,§ Joseph W. F. Robertson,‡ Jason Campbell,‡ John Suehle,‡ and John J. Kasianowicz‡ †Department of Physics, Virginia Commonwealth University, 701 W. Grace Street, Richmond, Virginia 23284, United States ‡Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8120, United States Laboratory of Computational Biology, National Heart Lung and Blood Institute, Rockville, Maryland 20852, United States

Density of states of Pb1 Si/SiO2 interface trap centers

The electronic properties of the (100) Si/SiO2 interfacial defect called Pb1 are quite controversial. We present electron spin resonance measurements that demonstrate: (1) that the Pb1 defects have levels in the silicon band gap, (2) that the Pb1 correlation energy is significantly smaller than that of the Pb1 defect, and (3) that the Pb1 levels are skewed toward the lower part of the silicon band gap.

Atomic-Scale Defects Involved in the Negative-Bias Temperature Instability

This paper examines the atomic-scale defects involved in a metal-oxide-silicon field-effect-transistor reliability problem called the negative-bias temperature instability (NBTI). NBTI has become the most important reliability problem in modern complementary-metal-oxide-silicon technology. Despite 40 years of research, the defects involved in this instability were undetermined prior to this paper. We combine DC gate-controlled diode measurements of interface-state density with two very sensitive electrically detected magnetic-resonance measurements called spin-dependent recombination (SDR) and spin-dependent tunneling (SDT). An analysis of these measurements provides an identification of the dominating atomic-scale defects involved in NBTI in pure- and plasma-nitrided oxide (PNO)-based devices. We are also able to observe atomic-scale defects involved in HfO2-based devices (although a definitive identification of the dominating defects structure was not possible). Our results in pure- devices indicate an NBTI mechanism which is dominated by the generation of Pb0 and Pb1 interface-state defects. (Pb0 and Pb1 are both silicon dangling-bond defects, in which the central silicon is back-bonded to three other silicon atoms precisely at the interface). This observation is consistent with what most NBTI researchers have assumed. However, our observations in PNO devices contradict with what most NBTI researchers had previously assumed. We demonstrate that the dominating NBTI-induced defect in the plasma-nitrided devices is fundamentally different than those observed in pure-based devices. Our measurements indicate that the new plasma-nitrided NBTI-induced defects physical location extends into the gate dielectric. The defect participates in both SDR and SDT. Our SDR results strongly indicate that the plasma-nitrided defect has a density of states which is more narrowly peaked than that of centers and is near the middle of the band gap. The high sensitivity of our SDT measurements allow an identification of the physical and chemical nature of this defect through observations of hyperfine interactions. The defects are silicon dangling bonds, in which the central silicon is back-bonded to nitrogen atoms. We call these NBTI-induced defects centers because of the similarities to the centers observed in silicon nitride (the silicon-nitrided center is also a silicon dangling bond in which the silicon atom is back-bonded to nitrogen atoms). The defect identification in plasma-nitrided devices helps to explain the following phenomena: (1) NBTIs enhancement in plasma-nitrided devices; (2) conflicting reports of NBTI-induced interface states and/or bulk traps; and (3) fluorines ineffectiveness in reducing NBTI in plasma-nitrided devices. We also observe the atomic-scale defects involved in NBTI in HfO2-based devices and find that short- and long-term stressing generates different defects and that these defects are different than those observed in the SiO2 and plasma-nitrided devices. Our results also suggest that the NBTI-induced defects in these devices are physically located in the interfacial layer (not at the interface).

Direct observation of the structure of defect centers involved in the negative bias temperature instability

We utilize a very sensitive electron paramagnetic resonance technique called spin-dependent recombination to observe and identify defect centers generated by modest negative bias and moderately elevated temperatures in fully processed p-channel metal-oxide-silicon field-effect transistors. The defects include two Si∕SiO2 interface silicon dangling bond centers (Pb0 and Pb1) and may also include an oxide silicon dangling bond center (E′). Our observations strongly suggest that both Pb0 and Pb1 defects play major roles in the negative bias temperature instability.

A Simple Series Resistance Extraction Methodology for Advanced CMOS Devices

Series resistance has become a serious obstacle inhibiting the performance of advanced CMOS devices. However, series resistance quantification in these same advanced CMOS devices is becoming exceedingly difficult. In this letter, we demonstrate a very simple series resistance extraction procedure which is derived only from the ratio of two linear ID-VG measurements. This approach has a verifiable accuracy check and is successfully used to extract the series resistance from several advanced devices. Furthermore, the validity of the assumptions used in this series resistance extraction procedure is examined and shown to be justified. In an attempt to further test the validity of this technique, several known external resistors were inserted in series with the device under test. The series resistance extraction procedure faithfully reproduces these known external resistances to within ±10%.

Identification of the atomic-scale defects involved in the negative bias temperature instability in plasma-nitrided p-channel metal-oxide-silicon field-effect transistors

We utilize a combination of DC gate-controlled diode recombination current measurements as well as two very sensitive electrically detected magnetic resonance techniques, spin-dependent recombination and spin-dependent tunneling, to identify atomic-scale defects involved in the negative bias temperature instability (NBTI) in 2.3nm plasma-nitrided SiO2-based p-channel metal-oxide-silicon field-effect transistors. We demonstrate that the dominating NBTI-induced defect in the plasma-nitrided devices is fundamentally different than those observed in pure SiO2-based devices. (In pure SiO2 devices, we observe NBTI-induced Pb0 and Pb1 defects.) Our measurements indicate that the NBTI-induced defect in the plasma-nitrided devices extends into the gate dielectric. The defect participates in both spin-dependent recombination and spin-dependent tunneling. The defect also has a density of states which is more narrowly peaked than that of Pb centers near the middle of the band gap. The high sensitivity of our spin-dep...

Large random telegraph noise in sub-threshold operation of nano-scale nMOSFETs

We utilize low-frequency noise measurements to examine the sub-threshold voltage (sub-VTH) operation of highly scaled devices. We find that the sub-VTH low-frequency noise is dominated by random telegraph noise (RTN). The RTN is exacerbated both by channel dimension scaling and reducing the gate overdrive into the sub-VTH regime. These large RTN fluctuations greatly impact circuit variability and represent a troubling obstacle that must be solved if sub-VTH operation is to become a viable solution for low-power applications.

A Model for NBTI in Nitrided Oxide MOSFETs Which Does Not Involve Hydrogen or Diffusion

The negative bias temperature instability (NBTI) is, arguably, the single most important reliability problem in present day metal-oxide-silicon field-effect transistor (MOSFET) technology. This paper presents a model for the NBTI which is radically different from the quite widely utilized reaction diffusion models which dominate the current day NBTI literature. The proposed model is relevant to technologically important nitrided oxide pMOSFETs. The model is clearly not, at least in its entirety, relevant to pure silicon dioxide gate pMOSFETs. The reaction diffusion models involve hydrogen/silicon bond breaking events at the silicon/silicon dioxide interface initiated by the presence of an interface hole, followed by the diffusion of a hydrogenic species from the interface as well as the potential rebonding of hydrogen and interface trap defect centers. This model does not invoke hydrogen in any form whatsoever but does simply account for the observed NBTI power law response with a reasonable, at least very plausible, assumption about defect distribution and provides a reasonably accurate value for this exponent. (Without making any assumption about defect distribution, the model still provides a time response semiquantitatively consistent with the observations, reasonable agreement considering the simplifying assumptions in the calculations.) The model also provides a reasonable explanation for the recovery which includes a simple explanation for the extremely rapid rate of recovery at short times. In addition, the model provides a very simple explanation why the introduction of nitrogen greatly enhances the NBTI. The model, as presented in this paper, should be viewed as a first-order approximation; it contains several simplifying assumptions. Finally, the model is consistent with recent electron paramagnetic resonance studies of NBTI defect chemistry in nitrided oxide pMOSFETs.

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

The amphoteric nature of Si/SiO2 interface states in submicron sized metal-oxide-silicon-field-effect-transistors is observed using an enhanced spectroscopic charge pumping method. The method’s simplicity and high sensitivity makes it a powerful tool for interrogating the true nature of electrically measured interface states in samples which exhibit extremely low defect densities. The spectroscopic results obtained clearly illustrate a signature “double peak” density of states consistent with amphoteric Pb center data obtained from electron spin resonance measurements. Since the method is a hybrid of the commonly used charge pumping methodology, it should find widespread use in electronic device characterization.

The Origins of Random Telegraph Noise in Highly Scaled SiON nMOSFETs

Random telegraph noise (RTN) has recently become an important issue in advanced circuit performance. It has also recently been used as a tool for gate dielectric defect profiling. In this work, we show that the widely accepted model thought to govern RTN behavior cannot be used to describe our experimental observations. The basis of this model (charge exchange between inversion layer and bulk oxide defects via tunneling) is inconsistent with our RTN observations on advanced SiON nMOSFETs with 1.4 nm physical gate oxide thickness. Alternatively, we show that RTN is qualitatively consistent with the capture and emission of inversion charge by interface states. Our results suggest that a large body of the low-frequency noise literature very likely needs to be re-interpreted.