Atmospheric Burning Research Articles

Recycling SiC Focus Rings for Reactive Ion Etching Equipment by Insertless Diffusion Bonding using Hot Isostatic Pressing

SiC focus rings are mount on the stage at the surround of wafer in the reactive ion etching chamber, in order to make the etching rate uniform. SiC is used for the material of focus ring because it has higher plasma resistance than Si. We investigated a new method to recycle SiC without using the chemical vapor deposition (CVD) method. The recycling process consists of grinding, dry cleaning, hot isostatic pressing (HIP), atmospheric burning, and aqueous solution cleaning. As a result, diffusion bonding with a tensile strength of 100 kg cm−2 or more was realized by reducing the surface roughness at the diffusion bonding surface to 0.1 μm or less. It was confirmed that the SiC surface was oxidized with thickness 135 nm by atmospheric burning in air ambience. It was also confirmed that the oxide layer at the SiC surface was completely removed by the aqueous solution cleaning. We have reduced the cost to 50% for SiC focus ring replacement by using the recycle method.

Anode-fall Voltages of Air Arcs Between Electrodes of Copper, Silver and Tungsten at Currents up to 1500 A

A method for estimating an anode-fall voltage of an arc discharge was developed. By using this method, the anode-fall voltages were evaluated for air arcs in atmosphere burning between the electrodes of copper, silver and tungsten. The anode-fall voltages Va of air arcs proved to be about 1.2, 4.5 and 1.2V for the copper, silver and tungsten electrodes respectively and were found to be almost independent of the ac half-wave current from 350 up to 1500Apeak. From the above results, the difference in the anode material seems to lead to the variation in the anode-fall voltage.

Anode-fall and cathode-fall voltages of air arc in atmosphere between silver electrodes

A method for estimating an anode-fall and a cathode-fall voltages of an arc discharge was proposed. By using this method, the separate estimation of the anode-fall and the cathode-fall voltages was performed for an air arc in atmosphere burning between silver electrodes. The derived anode-fall and cathode-fall voltages proved to be about 4.5 V and 14 V, respectively. It was also found that the anode-fall and the cathode-fall voltages were almost independent of an arc current in the range from 350 to 1200 A.

Combustion of magnesium particles in oxygen-inert atmospheres

The combustion mechanism of laser-ignited magnesium particles in the 100 ν-size range was studied by cinemicrography of burning particles and by scanning electron micrography of quenched samples. Burning was investigated in room-temperature, atmospheric-pressure, oxygen-argon atmospheres, with oxygen mass fractions ranging from 0.03 to unity. Certain observations also were made for burning in air, for burning at pressures between 1/5 and 2 atm, for burning at ambient temperatures up to roughly 500°C, for burning in atmospheres with water concentrations of roughly 2%, and for burning in carbon dioxide. Prompt and delayed types of ignition were identified. Combustion was found to involve an extended gas-phase reaction zone, surface accumulation of solid oxide, jetting, spinning, and fragmentation. Regular burning, with little accumulation of oxide within the particle, also was observed but only in dilute atmospheres. Except in very dilute atmospheres, buildup of surface oxide was found to produce extinction earlier than expected, either by enhancing the burning rate or by preventing combustion from going to completion. A number of different extinction modes were observed. Burning time was measured as a function of initial flame diameter. Ratios of flame to particle diameters also were estimated. A simplified theoretical model was developed for describing the quasi-steady combustion. Theory and experiment agree in most but not all respects. The theory suggests the occurrence of a homogenous magnesium-oxygen reaction followed later by condensation of the oxide. The fact that the oxide which condenses on the particle surface is solid rather than liquid, is reasoned to influence the combustion mechanism significantly.

Optical temperature measurements on metal-oxygen diffusion flames

An optical method was used to measure radial temperature profiles in low-pressure calcium-wire diffusion flames burning in atmospheres of 20% oxygen and 80% argon. The method is based on the solution of the equation of radiative transfer for a cylindrical, isotropically scattering medium in local thermodynamic equilibrium and is similar to the standard brightness-emissivity method. In order to complete the analysis, it was necessary to assume that the Rayleigh scattering law could be used to describe scattering and absorption. The most significant finding was the low maximum flame temperature (2550°K±10%) which was located approximately half-way between the wire and the edge of the flame. The maximum temperature is far below the adiabatic flame temperature (3200°K). The measured low temperatures and position of the maximum temperature are interpreted as indicative of a distributed reaction zone covering some finite portion of the flame. Temperature results were also compared with a flame model for low-pressure metal diffusion flames based on work conducted at Princeton. It was concluded that the temperature results were in complete agreement with the main features of the model, namely, a distributed reaction zone well inside the edge of the flame, thermal excitation of Ca-line and CaO-band emission, and significant homogeneous gas-phase reaction and condensation.