Modeling electromagnetic fields for the excitation of microwave discharges used for materials processing

Low-pressure/high-density and moderate-pressure microwave plasma sources are finding increased use in a variety of materials processing applications. Several design variations have been developed using microwave excitation of the plasma discharges including permanent magnet and electromagnet ECR (electron cyclotron resonant) sources, resonant cavity sources, waveguide-excited sources, and surface wave sources. A central issue to understanding and modeling these sources is obtaining a self-consistent solution of the electromagnetic fields and plasma discharge behavior. A variety of numerical techniques have been applied to this problem by researchers including the finite difference time domain (FDTD) method, ray tracing calculations, finite element solutions of the wave equation, and other wave propagation-absorption solutions. In each of these solution methods, plasma parameters including electron density and electron collision frequencies must be known or solved self-consistent to determine the electromagnetic fields. This paper reviews the status and presents examples of electromagnetic field modeling solutions for microwave plasma sources used in materials processing

Microstripline applicators for creating microplasma discharges with microwave energy

A microwave plasma system based on microstripline technology is created and implemented for the experimental investigation of miniature size plasmas. Plasmas are generated across a wide range of input parameters, including pressure variation from below 1 Torr to 1 atm, microwave power at 2.45 GHz from 1 to 30W, and a variety of discharge sizes and shapes. Data are measured for the discharge power density as a function of discharge pressure, input power and size. The power densities for discharges of diameters in the range 2-0.45mm vary from 10 to 1000Wcm(-3). Basic characteristics of the plasmas such as the electron temperature, plasma density and gas temperature are measured using probe diagnostics and optical emission spectroscopy (OES). In the range of one to 10 Torr, the electron temperatures are 1.9-2.3 eV, gas temperatures range from 600-1200K and the plasma densities are in the range of 10(12)-10(15) cm(-3)

Progress on preferential etching and phosphorus doping of single crystal diamond

Phosphorus is incorporated into single crystal diamond during epitaxial growth at higher concentrations on the (111) crystallographic surface than on the (001) crystallographic surface. To form n+-type regions in diamond for semiconductor devices it is beneficial to deposit on the (111) surface. However, diamond deposition is faster and of higher quality on the (001) surface. A preferential etch method is described that forms inverted pyramids on the (001) surface of a substrate diamond crystal, which opens (111) faces for improved phosphorus incorporation. The preferential etching occurs on the surface in regions where a nickel film is deposited. The etching is performed in a microwave generated hydrogen plasma operating at 160 Torr with the substrate temperature in the range of 800-950 °C. The epitaxial growth of diamond with high phosphorus concentrations exceeding 1020 cm-3 is performed using a microwave plasma-assisted chemical vapor deposition process. Successful growth conditions were achieved with a feedgas mixture of 0.25% methane, 500 ppm phosphine and hydrogen at a pressure of 160 Torr and a substrate temperature of 950-1000°C. The room temperature resistivity of the phosphorus-doped diamond is 120-150 Ω-cm and the activation energy is 0.027 eV

Dopant uniformity and concentration in boron doped single crystal diamond films

High quality single crystal boron-doped diamond films are deposited in a microwave plasma-assisted CVD reactor with feedgas mixtures including hydrogen, methane, diborane, and carbon dioxide at reactor pressures of 160 Torr. The effect of diborane levels and other growth parameters on the incorporated boron levels are investigated, and the doping efficiency is calculated over a wide range of boron concentrations. The boron level is investigated using infrared absorption, and compared to SIMS measurements, and defects are shown to affect the doping uniformity

Deposition of thick boron-doped homoepitaxial single crystal diamond by microwave plasma chemical vapor deposition

The deposition of high quality single crystal boron-doped diamond is studied. The experimental conditions for the synthesis of 1-2 mm thick boron-doped diamond are investigated using a high power density microwave plasma-assisted chemical vapor deposition reactor. The boron-doped diamond is deposited at a rate of 8-11.5 m/h using 1 ppm diborane in the feed gas as the boron source, and the capability to overgrow defects is demonstrated. The experimental study also investigates the deposition of diamond with both 10 ppm diborane and 2.5-500 ppm of nitrogen added to the feedgas. Synthesized material properties are measured including the electrical conductivity using a four-point probe and the substitutional boron content using infrared absorption

Etude des couplages entre transport, chimie et transfert d'énergie dans les plasmas de décharge

Les problèmes de réactivité dans les plasmas froids sont au centre du développement d'un grand nombre de procédés et de dispositifs utilisant des décharges électriques. Nous pouvons citer par exemple les procédés de dépôt chimique assisté par plasma (PACVD), les procédés de gravure, les procédés de traitement de surface, les procédés de traitement d'effluents gazeux, la combustion assistée par plasma, le développement de laser à gaz et de nouvelles sources d'éclairage et enfin l'étude de la phase de rentrée de navettes spatiales dans l'atmosphère. Ces exemples correspondent à des conditions de décharge très différentes : pressions allant du mtorr à la pression atmosphérique, technique de couplage de type capacitive, inductive ou micro-onde... mais ont comme point commun d'utiliser des milieux faiblement ionisés et hors équilibre thermochimique : les plasmas de décharge. Dans cet article, nous nous intéressons tout particulièrement à la modélisation numérique des plasmas de décharge réactifs. Nous présentons les différentes approches et hypothèses simplificatrices pouvant être adoptées lorsque l'on s'intéresse à la description de la plupart des plasmas réactifs de laboratoire, à l'exception des plasmas magnétisés qui ne seront pas abordés ici