Fabrication and characteristics of novel microelectronic structures fabricated by plasma-based techniques

A number of novel microelectronic structures have recently been produced using plasma-based techniques such as plasma immersion ion implantation (PIII) and this paper describes the recent progress made in this area in our laboratory. Conventional silicon-on-insulator (SOI) substrates utilizing a buried silicon dioxide layer suffer from self-heating effects as device dimensions shrink to the deep-submicrometer regime. Novel SOI structures using dielectric materials with higher thermal conductance such as aluminum nitride and diamond-like carbon have been produced. In the area of high-k (dielectric constant) thin films, plasma nitridation conducted on materials such as zirconium dioxide improves the recrystallization and interfacial properties. In the conventional Smart-Cut™ or ion-cut technique, high-energy hydrogen implantation is performed to effect layer transfer. Low-energy (several hundred eVs) plasma hydrogenation has recently been conducted in conjunction with damage engineering to produce wafer splitting for layer transfer. This new process allows more flexible control of the depth of hydrogen accumulation and the location of layer cleavage.     

Controlled density of vertically aligned carbon nanotubes in a triode plasma chemical vapor deposition system

We report on the growth mechanism and density control of vertically aligned carbon nanotubes using a triode plasma enhanced chemical vapor deposition system. The deposition reactor was designed in order to allow the intermediate mesh electrode to be biased independently from the ground and power electrodes. The CNTs grown with a mesh bias of + 300 V show a density of ∼ 1.5 μm^− 2 and a height of ∼ 5 μm. However, CNTs do not grow when the mesh electrode is biased to − 300 V. The growth of CNTs can be controlled by the mesh electrode bias which in turn controls the plasma density and ion flux on the sample.     

球墨铸铁Dg75阀体消失模近净型铸造

介绍消失模工艺生产Dg75闸阀阀体铸件的铸造工艺，生产过程中铸件重要装配尺寸精度的保证，铸件表面粗糙度、铸件表面碳夹杂缺陷及表面皱皮现象控制等试验情况。通过模具结构设计、成型工艺及参数的调整、浇注工艺的调整、陶瓷成型浇道的应用等措施，使铸件表面质量及尺寸精度符合客户验收标准。同时使铸件表面因轻微缺陷的返修率由试验初期的90％下降到10％以内，产品合格率达到99％。     

Two-dimensional full-electromagnetic Vlasov code with conservative scheme and its application to magnetic reconnection

A detailed procedure of full-electromagnetic Vlasov simulation technique is presented. Our new unsplitting conservative scheme exactly satisfies the continuity equation for charge. The implicit Finite Difference Time Domain method is also adopted for computation of electromagnetic fields, which is not restricted by the CFL condition for light. The Geospace Environment Modeling magnetic reconnection challenge problem is adopted as a benchmark test. The characteristics of the present Vlasov code are studied by varying the resolution in configuration space.     

Electromagnetic sources of nonuniformity in large area capacitive reactors

Theory and experiment show that two electromagnetic modes are necessary and sufficient to determine the field nonuniformity within a parallel-plate rf capacitive plasma reactor. These two modes give rise to the standing wave effect and the telegraph effect. The standing wave effect is associated with high frequencies in large reactors where the reactor size is larger than about a tenth of the vacuum wavelength of the rf excitation. The telegraph effect is associated with asymmetric electrode areas, which necessitates the redistribution of rf current along the plasma to maintain rf current continuity.     

The parallel implementation of the one-dimensional Fourier transformed Vlasov-Poisson system

A parallel implementation of an algorithm for solving the one-dimensional, Fourier transformed Vlasov-Poisson system of equations is documented, together with the code structure, file formats and settings to run the code. The properties of the Fourier transformed Vlasov-Poisson system is discussed in connection with the numerical solution of the system. The Fourier method in velocity space is used to treat numerical problems arising due the filamentation of the solution in velocity space. Outflow boundary conditions in the Fourier transformed velocity space removes the highest oscillations in velocity space. A fourth-order compact Padé scheme is used to calculate derivatives in the Fourier transformed velocity space, and spatial derivatives are calculated with a pseudo-spectral method. The parallel algorithms used are described in more detail, in particular the parallel solver of the tri-diagonal systems occurring in the Padé scheme.

Program summary

Title of program:vlasovCatalogue identifier:ADVQProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVQProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandOperating system under which the program has been tested: Sun Solaris; HP-UX; Read Hat LinuxProgramming language used: FORTRAN 90 with Message Passing Interface (MPI)Computers: Sun Ultra Sparc; HP 9000/785; HP IPF (Itanium Processor Family) ia64 Cluster; PCs clusterNumber of lines in distributed program, including test data, etc.:3737Number of bytes in distributed program, including test data, etc.:18 772Distribution format: tar.gzNature of physical problem: Kinetic simulations of collisionless electron-ion plasmas.Method of solution: A Fourier method in velocity space, a pseudo-spectral method in space and a fourth-order Runge-Kutta scheme in time.Memory required to execute with typical data: Uses typically of the order 10⁵-10⁶ double precision numbers.Restriction on the complexity of the problem: The program uses periodic boundary conditions in space.Typical running time: Depends strongly on the problem size, typically few hours if only electron dynamics is considered and longer if both ion and electron dynamics is important.Unusual features of the program: No     

Synchronous plasma enhancement in RF-driven plasma source for ion implantation

We report an original method to increase periodically the plasma density in RF-driven plasma source for surface treatment of materials by ion implantation. The method consists of supplementary injection of ions, electrons and metastable atoms into the processing RF plasma using very short high voltage pulsed discharges applied on a separate electrode at the same repetition rate as the negative accelerating pulses applied on the target. Thus plasma density is periodically increased by an order of magnitude so that the synchronized negative pulses applied on the target for ion implantation find a background plasma about 10 times denser. The advantages of this new method were revealed by nitrogen implanted tests on copper and brass samples.     

Fluctuations of DC atmospheric double arc argon plasma jet

An original DC double anode plasma torch has been devised and tested, which generates a long-time and highly stable argon plasma jet at atmospheric pressure. The arc unsteadiness and dynamic behaviour are investigated through the fluctuations of electrical signals combined with the classical tools, such as the statistic method, fast Fourier transform (FFT) and correlation analysis. The current-voltage characteristics of the argon plasma jet show an increasing tendency. The takeover mode is identified as the typical fluctuation behaviour of the double arc argon plasma jet in our experiment. The FFT and correlation calculation results of electrical signals exhibit the only characteristic frequency of 150 Hz, whereas the high frequency fluctuations are totally disappeared. Such low frequency fluctuation (150 Hz) can be attributed to the inherent characteristic of the torch power source and is independent of any change in the operating parameters. These results indicate that the nature of fluctuation in an argon plasma jet is mainly induced by the undulation of tri-phase rectified power supply. In addition, both arcs are characterized as the one and only system, and each arc root attachment is rather evenly diffused than located at a fixed position on the anode surface. The time shift derived from the cross correlation between the arc voltage and current intensity can be used as an independent parameter to reflect the fluctuating behaviour in the plasma jet.     

Effect of surface alteration of hydride titanium washers on discharge characteristics of plasma gun

Several titanium (Ti) hydride washers containing different amounts of both TiN and an oxide compound (Ox) are tested for the source of hydrogen (H⁺) plasmas. According to the different-looking surfaces of the washers of Ti hydride, considerable change in the required discharge voltage is observed. Slightly larger probe currents are also measured from plasmas produced with the washers having the smallest amounts of TiN and Ox, which suggests the existence of more H⁺ ions in the formed plasmas. Once apparent grain coarsening appears on the surface of Ti hydride washers at the temperature around 950°C, no successful electric discharge occurred.     

The effect of glow discharge plasma on the surface properties of Poly (ethylene terephthalate) (PET) film

In the present work, Poly (ethylene terephthalate) films have been exposed to glow discharge air plasma to improve their surface properties for technical applications. Surface energy values have been estimated using contact angle value for different exposure times and different test liquids. Surface composition and morphology of the films were analyzed by XPS and AFM. Crystallinity of the plasma treated samples were studied by XRD analysis. The improvement in adhesive strength was studied by measuring T-peel strength and lap shear strength tests. It was found that the plasma treatment modified the surfaces both in chemical composition and morphology. Change of chemical composition made the polymer surfaces to be highly hydrophilic, which mainly depends on the increase in oxygen-containing groups. The AFM and XRD observation showed that the surface roughness and crystallinity of the PET film increased due to plasma treatment.