A silicon wafer bonding process is described in which only thermally grown oxide is present between wafer pairs. Bonding occurs after insertion into an oxidizing ambient. It is proposed the wafers are drawn into intimate contact as a result of the gaseous oxygen between them being consumed by oxidation, thus producing a partial vacuum. The proposed bonding mechanism is polymerization of silanol bonds between wafer pairs. Silicon on insulator (SOI) is produced by etching away all but a few microns of one of the bonded pair. Capacitor measurements show a 27 μs minority‐carrier lifetime and no degradation of the SOI‐insulator interface. In addition, there is negligible charge at the bonding interface making the technique attractive for three‐dimensional as well as planar SOI applications.

Wafer bonding for silicon‐on‐insulator technologies

*† ‡ A particle and energy balance model of the plasma discharge in magnetic ring-cusp ion thrusters has been developed. The model follows the original work of Brophy in the development of global 0-D discharge models that utilize conservation of particles into and out of the thruster and conservation of energy into the discharge and out of the plasma in the form of charged particles to the walls and beam and plasma radiation. The present model is significantly expanded over Brophy’s original work by closing the set of equations with selfconsistently calculations of the internal neutral pressure, electron temperature, primary electron density, electrostatic ion confinement (due to the ring-cusp fields), plasma potential, discharge stability, and time dependent behavior during recycling. The model only requires information on the thruster geometry, ion optics performance and electrical inputs such as discharge voltage and currents, etc. to produce accurate performance curves of discharge loss versus mass utilization efficiency. The model has been benchmarked against NSTAR and NEXIS thrusters, and successfully predicts the thruster discharge loss as a function of mass utilization efficiency for a variety of thrusters. The discharge performance model will be described and results showing ion thruster performance and stability presented.

Analytical Ion Thruster Discharge Performance Model

Small ribbon‐shaped samples of spectroscopic grade graphite heated to between 500 and 1250 K have been exposed to atomic hydrogen produced by thermal dissociation of H2 on hot W and the rate of CH4 evolution has been measured mass spectrometrically. H2 pressures were between 1×10−6 and 5×10−5 Torr and arrival rates of H at the graphite surface ranged from 1×1014 to 5×1015 atoms cm−2 sec−1. When a well outgassed graphite surface is initially exposed to H atoms, the rate of CH4 evolution, NM, peaks and then decays to a steady‐state rate. A mechanism is proposed and examined which adequately explains the results observed. The mechanism involves the formation of a CH4‐producing surface complex by the reaction of an incident H atom with chemisorbed H atoms on the graphite surface. Additional chemisorbed H rapidly reacts with this complex and CH4 desorbs. The decay in NM to a steady‐state evolution rate is apparently caused by a surface reaction in which pairs of the surface complexes responsible for CH4 evolut...

Kinetics of CH4 formation from the reaction of H with graphite

A low pressure vapor phase growth apparatus is disclosed. The apparatus comprises a window made of a light-transmissive material, a gas feeder for feeding a reactive gas, an exhauster for pumping gases out after a chemical reaction, a lamp for effecting radiant heating of a substrate with a radiation emitted therefrom and transmitted through said light-transmissive window, and a cooling mechanism for forcibly cooling said light-transmissive window. The substrate and the light-transmissive window are maintained in no mutual contact with a gap therebetween having a width of at most the mean free path of a gas existing in the gap. The reactive gas fed through the gas feeder undergoes the chemical reaction on the obverse surface of the substrate to form a thin film thereon.

Low pressure vapor phase growth apparatus

A neglected parameter (water contamination) in sputtering of MoS2 films

Fundamentals of Vacuum Science and Technology

A method of determining length is described which reduces the measurement to a counting operation. The same technique is then applied to the measurement of flat areas and sections of the surface of a sphere. The limits of error are discussed and in particular the dependence of the error upon shape and the choice of a lattice is observed in the measurement of flat areas. Some possible applications are suggested.

Statistical Approach to Spatial Measurement

An experiment is described in which students of general science make many independent measurements of resistance and perform a statistical analysis on the accumulated data. The results are compared with the normal distribution curve. The values of various precision indices are determined and the significance of such statistical facts examined. Mention is made of the need for a similar kind of experiment that would use multifactorial analysis and correlation techniques.

Allan M. Russell

Papers

Fundamentals of Vacuum Science and Technology

Statistical Approach to Spatial Measurement

Statistical Experiment for a General Science Laboratory