Semi-Automated Extraction of the Distribution of Single Defects for nMOS Transistors

Abstract

Miniaturization of metal-oxide-semiconductor field effect transistors (MOSFETs) is typically beneficial for their operating characteristics, such as switching speed and power consumption, but at the same time miniaturization also leads to increased variability among nominally identical devices. Adverse effects due to oxide traps in particular become a serious issue for device performance and reliability. While the average number of defects per device is lower for scaled devices, the impact of the oxide defects is significantly more pronounced than in large area transistors. This combination enables the investigation of charge transitions of single defects. In this study, we perform random telegraph noise (RTN) measurements on about 300 devices to statistically characterize oxide defects in a Si/SiO 2 technology. To extract the noise parameters from the measurements, we make use of the Canny edge detector. From the data, we obtain distributions of the step heights of defects, i.e., their impact on the threshold voltage of the devices. Detailed measurements of a subset of the defects further allow us to extract their vertical position in the oxide and their trap level using both analytical estimations and full numerical simulations. Contrary to published literature data, we observe a bimodal distribution of step heights, while the extracted distribution of trap levels agrees well with recent studies.

Random Telegraph Noise in Metal‐Oxide Memristors for True Random Number Generators: A Materials Study

“…[ 17 ] ii) The variability of the current within each level over time; lower variability is preferred because that will facilitate the recognition of each state using peripheral circuitry. [ 18 ] And iii) the duration of each current level, which in the field of memristors is often referred to as capture time (σ C ) and emission time (σ E ) because they refer to the emission and capture of electrical charges at the atomic defects [ 19 ] ; shorter times are preferred because that increases throughput of the device when used as entropy source in different circuits. [ 20 ] The acceptable current levels, current variability within a level, and capture and emission times of an RTN signal will depend on the application intended, which have been extensively discussed in the literature; [ 21,22 ] however, it is worth noting that in some cases no unanimous agreement among different research groups and/or companies has been reached, and in some cases values that are acceptable for one group/company are not acceptable for a different group/company.…”

Reliability of Miniaturized Transistors from the Perspective of Single-Defects

“…If the device is small enough discrete steps, which correspond to charge emission events of defects, can be observed. Afterwards, a step detection algorithm is applied to the measurement data in order to extract the charge transition events [ 68 , 69 ], which are then binned into a 2D histogram called spectral map, see Figure 7 (bottom). As can be seen, the charge emission transitions form a cluster in the spectral map, which is considered the fingerprint of the defect.…”