High-field Electron Injection Research Articles

Change in the Charge State of MOS Structures with a Radiation-Induced Charge under High-Field Injection of Electrons

Change in the Charge State of MOS Structures with a Radiation-Induced Charge under High-Field Injection of Electrons

Change in the Charge State of MOS Structures with a Radiation-Induced Charge under High-Field Injection of Electrons

Change in the Charge State of MOS Structures with a Radiation-Induced Charge under High-Field Injection of Electrons

Modeling of charge effects in dielectric films of radiation MOS sensors

We have modeled the charge effects in radiation metal-oxide-semiconductor (MOS) sensors functioning in a wide range of electric fields including high-field injection of electrons into the dielectric film. In order to study the charge effects taking place in MOS sensors, we use the extended model suggested by us previously. The extended model, besides the accumulation of positive charge in the dielectric and the generation of the surface states at the interface, takes into consideration the accumulation of negative charge in the bulk of dielectric film caused by the electron capturing on traps. We demonstrate that the accumulation of the negative and positive charges in the bulk of the gate dielectric under high fields can significantly influence on the redistribution of electric fields inside the dielectric and, as a sequence, on change of the charge state of MOS structure which describes the sensor characteristics. We have ascertained that in order to properly utilize MOS sensors under high-field injection of electrons it has been necessary to take into consideration the possible capturing of electrons in the bulk of gate dielectric and adjust results of measurements with the model suggested.

Use of High-Field Electron Injection into Dielectrics to Enhance Functional Capabilities of Radiation MOS Sensors

The paper suggests a design of radiation sensors based on metal-oxide-semiconductor (MOS) structures and p-channel radiation sensitive field effect transistors (RADFET) which are capable to function under conditions of high-field tunnel injection of electrons into the dielectric. We demonstrate that under these conditions, the dose sensitivity of the sensor can be significantly raised, and, besides, the intensity of radiation can be monitored in situ on the basis of determining the ionization current arising in the dielectric film. The paper proposes the model allowing to make a quantitative analysis of charge effects taking place in the radiation MOS sensors under concurrent influence of ionization radiation and high-field tunnel injection of electrons. Use of the model allows to properly interpret results of the radiation control. In order to test the designed sensors experimentally, we have utilized γ-rays, α-particle radiation, and proton beams. We have acquired experimental results verifying the enhancement of function capabilities of the radiation MOS sensors when these have been under high-field injection of electrons into the dielectric.

Use of MIS Sensors of Radiation in High-Field Electron Injection Modes

A model is proposed that describes the change in the charge state of metal-insulator-semiconductor (MIS) structures and sensors made from it under the conditions of the simultaneous effect of radiation ionization and high-field injection of electrons from a semiconductor. The proposed model takes into account the interaction of injected electrons with holes generated by radiation and high-field ionization and holes trapped at the interface of the SiO2 film with a semiconductor, as well as the generation of surface states during the annihilation of part of holes during their interaction with injected electrons. It is shown that the MIS sensor, where the high-field injection of electrons into the dielectric film takes place, can be used to control the intensity of radiation by determining the radiation ionization current from the time dependence of the voltage across the sensor using the proposed model. It has been established that in the high-field electron injection mode, a significant increase in the dose sensitivity of MIS sensors is possible, but at the same time, the operating time and dose range of the MIS sensor can be significantly reduced.

Charge Effects in the Dielectric Films of MIS Structures under the Concurrent Influence of Radiation and High-Field Electron Injection

Based on the obtained experimental data, a model is developed for the processes of a variation in the charge state of MIS (metal–insulator–semiconductor) structures under the concurrent influence of high-field tunneling electron injection and radiation. The model takes into account the interaction between injected electrons and charges appearing in the dielectric film due to radiation and high-field ionization. It is shown that some holes may be annihilated during the interaction between injected electrons and holes trapped in a SiO2 film, thus leading to the formation of surface states at the interface with silicon. The effect of the electric-field intensity and injection current density on the generation and annihilation of positive charge and the formation of surface states under radiation is studied. The effect of charge processes occurring in the insulator film of a MIS structure under the concurrent action of radiation and high-field electron injection on a change in the threshold voltage of MIS devices and radiation sensors based on them is considered.

Simulation of charge processes in dielectric films of MIS structures at simultaneous influence by ionization and high-field injection of electrons

The paper presents model of processes of charge state changing of gate dielectric of MIS structure under conditions of simultaneous influence of radiation and high-field injection of electrons. The model takes into account the generation of positive charge by both radiation and high-field ionization and, besides, it takes into consideration the interaction of injected electrons with charges taken place in the dielectric film because of concurrent influence by ionizing radiation and high fields. We model an influence of radiation on charge state of the dielectric films of MIS structures in a wide range of influences by radiation and high-field injection of electrons. We study an influence of electric field strength and intensity of radiation on processes of generation and annihilation of positive charge accumulated in the gate dielectric because of both radiation and high-field ionization. We make suggestions on use of radiation MIS sensors which are utilized under conditions of high-field injection of electrons into the gate dielectric.

Investigation of Injection- and Radiation-Thermal Processes in Thin Gate Dielectric Films of MIS Structures

In order to modify the gate dielectric of MIS structures we suggest to implement the injection-thermal treatment which consists in the high-field injection of electrons of set density into the thin dielectric film and the subsequent annealing of the structure. We investigate an influence of modes of the injection-thermal treatment onto the modification of MIS structures. We demonstrate that the processes of MIS structure modification taking place at the injection-thermal treatment in many respects are identical to the processes taking place at the radiation-thermal treatment. We study an influence of modes of the high-field electron injection into the gate dielectric of MIS structure onto densities of charge defects and the injection hardness of samples. Besides, we research an influence of doping of the silicone dioxide film by phosphorus onto the same characteristics.

Modification of MIS Devices by Irradiation and High-Field Electron Injection Treatments

Modification of MIS Devices by Irradiation and High-Field Electron Injection Treatments

Modification of MIS Devices by Irradiation and High-Field Electron Injection Treatments

Modification of MIS Devices by Irradiation and High-Field Electron Injection Treatments

Method of stress and measurement current levels for MIS structures researching and modifying under high-field injection of electrons

We developed new method of stress and measurement current levels to research and modify thin dielectric of MIS structures under high-field injection of electrons. This method allows to take into account processes of MIS structure capacity charging and trapping of charge in gate dielectric of MIS structure when injection mode. It is shown that when a high density of the injection current, a characteristics control of charge, which accumulates in gate dielectric, when realizing the method of stress and measurement current, is necessary to implement by monitoring of voltage change on MIS structure when amplitude of measurement injection current is lower than amplitude of stress current. In order to rise performance of the method and implement a possibility of researching of fast relaxation charges, which is accumulated in gate dielectric during the process of high-field stress influence, we suggest to realize charging and discharging of MIS structure in accelerated regime when higher density of measurement current takes place.

Modification of MIS structures by electron irradiation and high-field electron injection

The change in the charge state of metal–insulator–semiconductor (MIS) structures with a two-layer silicon-dioxide–phosphosilicate-glass gate insulator upon their modification under electron irradiation and high-field electron injection is studied. A thin glass film is formed by doping a thermal SiO2 film formed on the surface of a silicon wafer with phosphorus. It is found that the negative charge accumulated in a thin film of phosphosilicate glass during high-field tunneling electron injection or electron irradiation can be used to adjust the threshold voltage and to increase the charge stability and the breakdown voltage of MIS devices. It is shown that MIS structures need to be annealed at a temperature of approximately 200°C to obtain high thermal-field stability after modification of their charge state by the electron injection or electron irradiation. It is found that the use of a two-layer silicon-dioxide–phosphosilicate-glass gate dielectric increases the average value of the charge injected into the insulator to breakdown and decreases the amount of defect structures.

Charge characteristics of MOS structure with thermal SiO2 films doped with phosphorus under high-field electron injection

The processes of changing the charge state of metal–oxide–semiconductor (MOS) structures that contain a multilayer gate dielectric on the basis of a thermal SiO2 film doped with phosphorus under the influence of high-field electron injection are investigated. It is determined that a negative charge accumulating in a thin phosphosilicate glass (PSG) film of MOS structures containing a SiO2–PSG two-layer gate dielectric under high-field tunneling injection of electrons can be used for the correction of the threshold voltage, for the enhancement of the charge stability, and for an increase in the breakdown voltage of devices with MOS structure. It is shown that the density of electron traps increases with an increase in the thickness of the PSG film containing them, while their capture cross section remains unchanged. The method for the modification of the electrophysical characteristics of MOS structures by the high-field tunneling injection of electrons into a dielectric under a controlled current load is proposed. The method allows one to control changes in the parameters of MOS structures directly in the process of their modification. It is established that a MOS structure with a high thermal field stability can be obtained by its annealing at 200°C after the modification of its charge state by the electron injection.

Modification of thin oxide films of MOS structure by high-field injection and irradiation

We have investigated processes of modification and changing of the charge state of MOS structures having a multilayer gate dielectric based on a thermal SiO2 film doped with phosphorus under conditions of different modes of high-field electron injection and an electron irradiation. We have determined that negative charge, accumulating in the phosphosilicate glass (PSG) ultra thin film of the MOS structures having the two-layer gate dielectric SiO2-PSG under conditions of both high-field tunneling injection of electrons and electron beam, could be used for a modification of devices having the same structure (e.g. correction of threshold voltage, increase of charge stability and breakdown voltage of MOS structure). We have shown that when thickness of PSG film increased, a raising of the electron traps density occurred, but the value of the cross-section of electron traps was the same. It was established that in order to obtain MOS structures with high thermal stability, one has to anneal them at 200° C after performing irradiation treatment.

Modification of MOS Devices by High-Field Electron Injection and Arc Plasma Jet Treatment

Modification of MOS Devices by High-Field Electron Injection and Arc Plasma Jet Treatment

Influence of high-field electron injection regimes on modification of dielectric films of MOS devices

The influence of high-field electron injection regimes on modification of metal-oxide-semiconductor (MOS) transistors with multilayered gate dielectric SiO2-PSG containing electron traps is studied. It is shown that the preferable regime for injection modification of MOS transistors is the regime of electron injection from the silicon substrate for which the maximum shift of the threshold voltage is higher and the gate dielectric breakdown probability is much lower as compared to injection from an aluminum electrode. The amplitude of current pulses used for charge injection into the gate dielectric should be chosen from the geometric size of the transistor and particular electrophysical characteristics of the dielectric film and should be in the range 10−7–10−4A/cm2. It is shown that, for obtaining MOS devices with high thermal field stability after modification of the charge state by electron injection, it is necessary to anneal devices at temperatures of about 200°C.

Impact of temperature on non-equilibrium Fowler-Nordheim EEPROM programming

High-field Fowler-Nordheim electron injection to the drain of EEPROM’s is studied using a specific time-resolved measurement technique. A transient injection regime is observed only in the case of moderately doped drain, but a non-equilibrium stationary injection regime is always evidenced, resulting, for a given temperature, in a current higher than expected for thermal equilibrium conditions. The magnitude of the phenomenon is shown to decrease with temperature and doping level. As a consequence, the memory cell programming window change with temperature, which is controlled by the total FN characteristics voltage shifts with temperature, should depend on drain doping and programming current.

Study of temperature dependence of positive charge generation in thin dielectric film of MOS structure under high-fields

In this work, the temperature effect on positive charge generation under high-field electron injection in MOS structures is studied using a new multilevel current stress technique. In our experiments, we used commercially made test MOS capacitors based on thermal silicon dioxide film with thickness in the range from 7 to 100 nm. Using the proposed multilevel current stress technique one can investigate the positive charge generation in MOS structure gate dioxide under high electric fields. The technique is different from the standard constant current stress technique, as it includes two levels of current: the stress current level, which provides the generation of positive charge, and the additional measuring current level, which allows to monitor the change of dielectric charge. Due to the additional measuring current level, it is possible to decrease significantly the error of positive charge density measurement in the dielectric. The latter error is caused by the positive charge trapped in the initial stage of electron injection while the steady-state of the stress mode is being reached. It was found that the rise of sample temperature leads to a decrease of the density of the positive charge generated in SiO 2 film under high-field injection of electrons from the silicon substrate. A model of the positive charge generation in MOS structures under high-field electron injection has been proposed. The new model of the positive charge generation in MOS structures takes into account the temperature effect and the subsequent phenomena of dielectric charge state change: the band-to-band impact ionization in SiO 2 with the creation of electron-hole pairs and the subsequent trapping of holes in traps in the oxide; the trapping of injected electrons by trapped holes as well as the thermal release of trapped holes from the traps.

Comparative Study of Charge Trapping in High-Dose Si and Ge-Implanted Al / SiO2 / Si Structures

We have studied the trapping of negative and positive charge in Si-implanted layers of -based devices during high-field electron injection from the Si substrate under conditions typically used for obtaining electroluminescence. The location, capture cross section, and concentration of negatively and positively charged traps are determined in dependence on the time of heat-treatment by rapid thermal annealing (RTA). A comparison between the results obtained from Si- and Ge-implanted oxide layers is made. It is shown that in the case of Si-rich oxides an increase in the RTA time leads to the formation of hole and electron traps of high concentration, both of which are located within the oxide. For Ge-rich oxide layers, however, the hole traps are found primarily in the vicinity of the interface while the electron traps are present within the oxide. The nature of these traps is discussed. © 2004 The Electrochemical Society. All rights reserved.

Screening of Si–H bonds during plasma processing

This work investigates the screening of Si–H bonds at the Si–SiO 2 interface in an n-channel MOSFET due to plasma charging damage. Since CMOS devices are subjected to high field electron injection during plasma processing, this condition was emulated by subjecting the devices to current stress (both gate injection and substrate injection). With the source and drain terminals reverse biased by a screening potential during stress, representing the impact from source and drain antenna, a decrease in stress-induced interface state density formation was noticed. Observed interface state density D it before and after the high field injection, therefore, demonstrates an effective screening of the source and the drain edges. During gate injection the Si–H bond concentration, estimated using a model based on a simple first order kinetic equation, is inversely proportional to measured D it at effective screening potentials. In substrate injection, however, the Si–H concentration does not relate to D it creation. Similar trends were observed for transistors with different antenna ratios. Subsequent hot carrier stress confirms that the screening is mainly due to protected drain edges. These results suggest that effective screening of Si–H bonds is possible during plasma processing.