M. Chvatal

Noise in Submicron Metal–Oxide–Semiconductor Field Effect Transistors: Lateral Electron Density Distribution and Active Trap Position

Experiments were carried out for the n-channel devices, processed in a 0.3 µm spacer less complementary metal–oxide–semiconductor technology. Random-telegraph-signal measurements were performed for the constant gate voltage. It is supposed that electron concentration in the channel decreases from the source to the drain contact. Lateral component of the electric field is inhomogeneous in the channel and it has a minimum value near the source and reaching the maximum value near the drain electrode. Drain current is given by two components – diffusion and drift ones. Diffusion current component is independent on the x-coordinate and it is equal to the drift current component for the low electric field. The model explaining the experimentally observed capture time constant dependence on the lateral electric field and the trap position is given. From the dependence of the capture time constant τc on the drain current could be calculated longitudinal coordinate of the trap position.

Noise in amperometric NO2 sensor

Nitrogen dioxide (NO2) is a highly toxic gas harmful to the environment, which can be threat to human health even at low concentrations. To overcome limitations of standard solid NO2 sensors based on inorganic materials, a new sensor with solid polymer electrolytes (SPE) was developed. Our study deals with investigation of fluctuation phenomena in the electrochemical NO2 sensor, which is based on three-electrode topology and solid polymer electrolyte. Experimental result shows that generation-recombination (G-R) noise seems to be main components of current fluctuations in this sensor. The concentration of detected matter affects noise spectral density of sensor. As the concentration increases, G-R noise rises and is supposed to be connected with chemical processes on active layer of sensor. The shift of G-R component is supposed to be caused by increased flux density between active layer and environment.

Tantalum and Niobium oxide capacitors: Field crystallization, leakage current kinetics and reliability

The study of the charge carrier transport in Ta and NbO capacitors was performed to analyze the leakage current kinetics at high temperature and high electric field for MnO2 and Conducting Polymer (CP) cathode. Leakage current of Ta and NbO capacitors at the room temperature is driven by the Ohmic and Poole-Frenkel mechanism at the rated voltage. It was found that these capacitors are very stable for temperature below 100°C. High temperature and high voltage applications are considered to be limited by the field crystallization mechanisms and ions diffusion. The leakage current changes in high electric field and at the elevated temperature T = 400 K could be divided into three time intervals: (i) Leakage current is stable (in some samples is slightly decreasing or increasing) during a period of 1 to 10 days. (ii) Leakage current increases with the slope 5 to100 pA/s for time interval about 10 days. (iii) Leakage current is stable or slightly increases with the slope less than 1 pA/s. Activation energy decreases during the ageing period from 0.55 to 0.45 eV. Leakage current variations are partly reversible. Irreversible changes of leakage current appear on about 1% of samples after ageing. Further investigation in this field can lead to the enhancement of reliability and performance of these capacitors.

RTS noise amplitude and electron concentration in MOSFETs

Random Telegraph Signal (RTS) noise was measured in submicron MOSFETs under various biasing conditions from sub threshold to inversion region and dependence of amplitude and mean time of capture and emission on electric field and electron concentration analyzed. Numerical model of charge carrier transport in the channel was used to estimate trap position between the source and drain electrodes from experimental characteristics.

Noise analysis of infrared detectors

Pyroelectric infrared detectors convert the changes in incoming infrared light to electric signals. Pyroelectric materials are characterized by having spontaneous electric polarization, which is altered by temperature changes as infrared light illuminates the elements. Since our sensor series uses this effect they can be used at ambient temperature even in the presence of thermal noise. By choosing appropriate infrared receiving electrodes, they serve a wide range of applications. Sometimes pyroelectric infrared detectors generate a false alarm. They include thermal resistor and FET device which can be a source of random signals. This paper deals with the measurement of output and transfer characteristics and voltage low noise spectral density. By the help these characteristics we can evaluate detectors and reduce false alarms.

RTS noise in MOSFETs: Mean capture time and trap position

RTS noise in MOSFETs is given by drain current fluctuation due to charge carrier capture and emission by a single active trap. From the drain voltage dependence of the ratio of capture tauC and emission tauE times the longitudinal trap position in the channel can be calculated. According to the Shockley-Read-Hall statistic, tauC is inversely proportional to the concentration of charge carriers n and in most noise papers, drain current ID is commonly supposed to be proportional to n and used to express concentration. Then we should expect tauC to decrease with increasing current, however, opposite dependence is usually experimentally found. In order to explain this discrepancy, we present a model of non-uniform charge carrier density distribution in channel with concentration decreasing towards the drain electrode.

RTS in Submicron MOSFETs: Lateral Field Effect and Active Trap Position

Experiments were carried out for n‐channel devices, processed in a 0.3 μm spacerless CMOS technology. The investigated devices have a gate oxide thickness of 6 nm and the effective interface area is AG = 1.5 μm2. The RTS measurements were performed for constant gate voltage, where the drain current was changed by varying the drain voltage. The capture time constant increases with increasing drain current. The model explaining the experimentally observed capture time constant dependence on the lateral electric field and the trap position is given. From the dependence of the capture time constant τc on the drain current we can calculate x‐coordinate of the trap position. Electron concentration in the channel decreases linearly from the source to the drain contact. Diffusion current component is independent on the x‐coordinate and it is equal to the drift current component for the low electric field. Lateral component of the electric field intensity is inhomogeneous in the channel and it has a minimum value ...

Noise of Ta 2 O 5 and Nb 2 O 5 thin insulating films in the temperature range 10 K to 400 K

We have performed investigation of noise and transport mechanisms in insulating films of Ta2O5 and Nb2O5 from the point of view of their application as dielectric layers in capacitors, MOS devices, etc. These dielectric films show high relative permittivity, low leakage current density of the order of nA/cm2 in the electric field 1MV/cm, and high breakdown field of the order of 3–4 MV/cm. Analysis of I–V characteristics performed as a function of temperature allows the identification of dominant conduction mechanisms and corresponding noise sources. Ta2O5 films of the thickness about 28 nm and Nb2O5 thin films of the thickness about 150 nm were investigated. Tunneling current mechanism is dominant for the temperatures below 200 K. In this temperature range current noise spectral density is 1/f type. Poole-Frenkel and Schottky current transport mechanism is dominant for temperatures higher than 350 K. 1/f noise is pronounced in the frequency range bellow 20 Hz, while in the range 20 to 100 Hz GR noise is dominant for low current values. For the insulating layer thickness below 50 nm current noise spectral density is given by the superposition of at least two GR noise components with different time constants. This behavior is observed for the temperature higher than 200 K.

RTS Noise of CMOS Technology

Experiments were carried out for n-channel devices, processed in a 300 nm CMOS technology. The investigated devices have a gate oxide thickness of 6 nm and the effective interface area is AG = 1.5 m2. The RTS measurements were performed for constant gate voltage, where the drain current was changed by varying the drain voltage. The capture time constant increases with increasing drain current. The model explaining the experimentally observed capture time constant dependence on the lateral electric field and the trap position is given. From the dependence of the capture time constant c on the drain current we can calculate x-coordinate of the trap position. Electron concentration in the channel decreases linearly from the source to the drain contact. Diffusion current component is independent on the x-coordinate and it is equal to the drift current component for the low electric field. Lateral component of the electric field intensity is inhomogeneous in the channel and it has a minimum value near the source contact and increases with the distance from the source to the drain. It reaches maximum value near the drain electrode.

Development of a new technique for the study of a single trap in insulators for electronic components

This paper presents temperature measurement of electron density for electronic components. Our department has a cryogenic laboratory for measurement at the different temperature from 10 to 500 K. We perform experiments and calculations VA (volt-ampere) characteristics and RTS (Random Telegraph Signal) noise for submicron technology with a channel length less than 300 nm. The electron temperature is then higher than the lattice one and the field dependent electron mobility must be considered. The capture time constant increases with increasing drain current. From the dependence of the capture time constant τc on the drain current we can calculate x-coordinate of the trap position. Electron concentration in the channel decreases linearly from the source to the drain contact. Diffusion current component is independent on the x-coordinate and it is equal to the drift current component for the low electric field. Lateral component of the electric field intensity is inhomogeneous in the channel and it has a minimum value near the source contact and increases with the distance from the source to the drain. It reaches maximum value near the drain electrode.