T.L. Lin

Simulation study of carbon nanotube field emission display with under-gate and planar-gate structures

Recently, two new CNTs-based triode structures, i.e., under-gate and planar-gate structures, for field emission display were proposed and exhibited good characteristics. In this paper, we will investigate how the current density distributed on anode plate and how the display’s resolution affected by the bias conditions of the emitter and the gate electrode via computer simulation. Our simulation results exhibit that the gate voltage has a strong effect on display’s resolution. For the planar triode structure, the good resolution is achieved when the gate voltage is adjusted to converge the electron beams on an anode plate. For the under-gate structure, the display has a good resolution provided that the gate voltage is not too large to pull the electrons striking on other pixels. In general, the under-gate structure has a wider gate-biased operating condition, but the planar triode structure has a higher light efficiency under the same resolution. Due to the lack of field effect in the y-direction, the spot size of the current density on anode plate looks like strips instead of points. And the resolution of the display will be affected by this factor.

Simulation study of junction effect on field emission from one-dimensional nanostructure grown on silicon substrate

Field emission properties of the one-dimensional nanostructure grown on doped silicon substrate are studied via computer simulation. The classical transport equation is used to describe the carrier transportation in the material and is solved coupled with the Poissons equation. The field emission process between emitter and vacuum interface is modeled by the Fowler-Nordheim equation. For studying the space-charge screening effect, the carriers are allowed to move in the vacuum region, and the space-charge fields of the carriers are also solved self-consistently through the Poissons equation. After the simulation, the F-N plot, the carrier distribution and the band structures are figured out. The simulation results of the anode current as a function of the applied voltage for single SiCN grown on n- and p-type doped silicon substrates are shown. The simulation results exhibit that the p-type substrate will limit the emission currents of the narrow- and wide-band-gap nanostructure at the high-field region. And the space-charge screening effect will further saturate the emission current.

Simulation studies of self-focusing carbon nanotube field emitter

A design for a self-focusing carbon nanotube co-planar field emitter without the focusing gate is proposed. Simulations were carried out for different gate voltages to study the effects on the emission current and beam divergence

Measurement of time varying RF impedance of a pulsed inductively coupled plasma

Summary form only given. Pulsed high density plasmas have been widely employed to enhance process results in advanced semiconductor fabrication, such as reducing the notch effect and increase the selectivity in the etch process and improving the properties of plasma deposited films. A RF plasma impedance meter has been developed to measure the time varying impedance during the power on the period of an inductively-coupled pulsed plasma, where a shape adjustable coil and conventional 13.56 MHz RF power were used. A capacitive voltage divider and a Rogowski coil were used to sense the RF voltage and current on the transmission line connected to the ICP coil, respectively. After passing through a low pass filter to eliminate high order harmonics, the voltage and current signals were sent into an analog electronic circuitry to extract their RMS values and relative phase. The circuitry was cold tested using a function generator to show that, for the 13.56 MHz signal frequency, little distortion was observed for modulation frequency up to 50 kHz. A digital oscilloscope was used to record the temporal behavior of the RMS values of RF voltage and current, as well as phase and the data was passed to a personal computer through a GPIP interface for further analysis to deduce the complex impedance observed into the ICP coil and the net input RF power.

Implement the PIC-MCC simulation of ECR plasma source on PC cluster with DRBL, an effective approach to integrate PC cluster

A parallel 2d3v PIC-MCC (particle-in-cell plasma simulations and Monte Carlo collisions) code is developed with message passing language PVM to simulate the electron cyclotron resonance plasma source in this research. This code has been run on a PC cluster with a cluster system we developed called diskless remote boot in Linux (DRBL), which is a centralized boot and management environment. By using DRBL, its easier for us to integrate some PCs to a cluster system. Once we have some computing power, with the grid technology, we can harvest more by sharing the computing resources with others. This is a new approach to harvest more computing power. With the PIC-MCC simulation of ECR plasma source, the results and benchmark for different cluster architectures arc given and discussed.

Simulation study of vircators with field emission cathode

Virtual cathode oscillators (vircators) are pulsed, high-power microwave generation devices with the advantages of configuration simplicity and wide frequency-tuning ability. The ability of electron beam pre-modulation in field emission cathode makes us to use it as electron source in vircators. Some current density models for the field emission had been proposed like Fowler-Nordheim equation for microscopic flat plate diode and relativistic Child-Langmuir equation for diode with the space charge limited effect. In this paper we investigate the characteristics of the vircators with field emission cathode via computer simulation. The particle-in-cell simulation code MAGIC was used in this study.

Simulation study of carbon nanotubes field emission display with triode structure

Owing to the high aspect ratios and small radii of curvature, carbon nanotubes (CNTs) exhibit excellent field emission characteristics, which is very advantageous for the field emission display (FED) applications. In FED design, the triode structures are more attractive for their lower driving voltage and higher light efficiency. Recently, a new CNT-based triode structure, i.e., planar triode structures, was proposed and exhibited good characteristics. In this design, the lateral gate electrode generates the transverse electric fields to pull out the electrons from the neighboring emitters. But how the display resolution affected by the bias conditions of the gate electrode and by the electron beams diverged in the y-direction is not clear yet. In this paper, these problems are investigated via computer simulation.

Real-time feedback control of ion energy flux in chlorine inductively coupled plasma for poly-silicon etch process

Summary form only given. Advanced semiconductor fabrication requires tighter process monitoring and control to improve production yield and reliability. Recently, advanced process control (APC), an in situ sensor based methodology, has been applied to achieve the desired process goals in operating individual process steps. For instance, in etching of polysilicon using chlorine discharges, in order to obtain a desired etch profile, the process often is operated at the ion-enhanced regime where the etch rate and etched profile are strongly dependent on the total ion energy flux incident on the wafer surface. Therefore, a better process control can be achieved if one can implement the real-time control of ion energy flux in etch processing. In this study, we have demonstrated experimentally the real-time multiple-input multiple-output (MIMO) control of both ion density and ion energy in etching of polysilicon using chlorine inductively coupled plasma. To measure relative positive ion density, the optical emission at 750.4 nm from trace amounts of Ar is used which is proportional to the total positive ion density. An RF voltage meter is adopted to measure the peak RF voltage on the electrostatic chuck which is linearly dependent on sheath voltage. One actuator is a 13.56 MHz RF generator having a maximum power of 5 kW to drive the inductive coil seated on a ceramic window, along with a L-type matching network to minimize the reflected power. The second actuator is also a 13.56 MHz RF generator to power the electrostatic chuck via a matching network. The two RF generator is locked in phase. The design of MIMO controller is applied by Quantitative Feedback Theory (QFT) to compensate process drift, process disturbance, and pilot wafer effect. The experiment results showed that the MIMO control system has a better reproducibility in etch rate as compared to current industrial practice.

Experimental characterization of a pulsed ICP discharge

Summary form only given. Pulsed low-pressure high-density plasmas attracted a great deal of attention recently owing to their applications in ULSI processing. It has been demonstrated that processing with pulsed plasma can reduce charge-induced damage, such as notching effect. It has been shown that this feature is related to the effect of a reduced electron temperature and an increase of negative ion density during the off period of the pulse. The purpose of this work is to characterize basic properties of a pulsed ICP discharge by employing various diagnostic tools, including a Langmuir probe, a 36 GHz interferometer, an ion energy analyzer, a plasma impedance probe, as well as a monochromator. These tools have been modified from existing ones to measure time-resolved signals associated with a pulsed discharge. Preliminary measurement results show that, in an Ar plasma, electron temperature drops much faster than plasma density. The plasma potential also decreases during the off period because the plasma becomes cooler. The result from the interferometer measurement exhibits a different time dependence of the plasma density from the Langmuir probe data. This is mainly because the former measures the line-averaged values while the latter extracts local properties. In a time-modulated plasma with a typical frequency around 10-100 kHz, there will be a time-delay on the plasma properties, such as density and temperature, at different location in a plasma chamber. As it is averaged spatially, the time dependence is smeared out and exhibits a totally different behavior from the local ones. Further study is being conducted to investigate this issue. Detailed experimental results will be presented.

Computer simulation of field emission devices with focusing structure

Summary form only given. Beam focusing is a crucial technique for promoting the resolution of the field-emission displays. Various focusing structures for the Spindt-type field emission device have been proposed and applied on previous works, e.g. coaxial-type focusing, coplanar-type focusing (Kesling et al., 1995), ridge-type focusing and mesh-electrode focusing. The diamond-film coating provides another possibility to design new types of field emission devices with inherently smaller beam size. The planar-type and concave-lens-type cathodes are examples. In this study, diamond-film-coated field emitters with different emitting shapes are proposed and simulated by the MAGIC particle-in-cell code (Goplen et al., 1997). The focusing effect inherent in the emitting shape will be characterized and analyzed. The traditional Spindt-type devices with various focusing structures are also studied for comparisons. The electron trajectories, the spot sizes of beams, and the I-V curves are investigated systematically for each device.