Chamber material effects on actinometric measurements in rf glow discharges

The relative concentration of atomic fluroine was measured in a CF4 rf glow discharge using the actinometric technique. The dependence of fluorine concentration on power, pressure and flow are presented and shown to be dependent upon reactor wall material and electrode material.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70093/2/JAPIAU-69-5-2885-1.pd

A staggered-mesh finite-difference numerical method for solving the transport equations in low pressure rf glow discharges

A numerical model of a low pressure parallel plate rf glow discharge is presented based on a self-consistent formulation of the energy-momentum conservation equations for electrons, the continuity equations for both electrons and ions, and Poisson's equation. Various explicit finite-difference numerical methods are discussed in terms of stability and overshoot properties. Stability considerations for the numerical method that was implemented, including the initial and the boundary conditions, are examined. Results from a large-signal simulation of a low pressure argon rf glow discharge are presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27230/1/0000237.pd

Radial optical emission profiles of radio frequency glow discharges

Radial optical emission profiles are determined from Abel inverted emission spectroscopy of a parallel plate radio frequency system known as a GEC Reference Cell. These profiles in general show a nonuniform plasma, annular in shape. Etching results of silicon wafers also follow this annular pattern. This effect is explained by numerically computed large radial and axial electric fields near the edge of the electrodes, produced by the presence of the grounded dark shields.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71294/2/JAPIAU-74-5-3590-1.pd

Relative fluorine concentrations in radio frequency/electron cyclotron resonance hybrid glow discharges

The relative concentration of atomic fluorine was measured in a radio frequency (rf) glow discharge and a modified electron cyclotron resonance microwave/rf hybrid discharge in CF4 using an actinometric technique. The dependence of fluorine concentration on rf and microwave power, pressure, flow, and excitation source are presented. Anomalous behavior with rf power at constant microwave power was observed when using the Ar 750‐nm line as the actinometric species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70900/2/APPLAB-60-7-818-1.pd

High-temperature kinetic study for the reactive ion etching of InP in BCl 3 /Ar/O 2

The reactive ion etching kinetics of InP studied uses BCl 3 /Ar and BCl 3 /Ar/O 2 as etchants. High-temperature etching using BCl 3 and Ar increases the etch rate negligibly. However, the addition of 30% oxygen in the gas feed increases etch rates by a factor of 10,000 up to 1.5 micron/min at wafer temperatures of 250°C. X-ray photoelectron spectroscopy analysis reveals that oxygen removes the boron species adsorbing on the InP surface by scavenging the boron to form volatile boron oxides. To study the gas-phase chemistry, optical emission spectroscopy is used to monitor atomic chlorine intensity at different gas mixtures. The chlorine intensity shows a Gaussian-type dependence with oxygen addition, which is similar to the etch rate dependence. Two regimes of etching found are: at temperatures below 150°C, the etching is limited by the removal of indium chlorides; above 180°C, the etching is reaction-limited. The surface morphology shows that the etch profile becomes rougher as a result of increased chemical etching. At high power densities (0.21 W/cm 2 ) and intermediate temperatures (150°C), near vertical wall shapes are obtained. A kinetic model for the high-temperature etching is developed, as well as a rate law based on the InCl formation reaction. The rate law compares favorably with experimental etch rate results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37431/1/690410322_ftp.pd

The optimization of InxGa1-xAs and InP growth conditions by CBE

Minimization of the number of experiments needed to fully characterize and optimize the growth of epitaxial material is the first important step in realizing state of the art device structures. While widely used in some fields such as chemical engineering, response surface modeling (RSM) has been little used in crystal growth applications. Using RSM, input parameters such as substrate temperature hydride injector temperature and V/III ratio, were simultaneously adjusted to characterize the crystal growth process. This technique identified interactions among parameters, minimized the number of experiments necessary to understand and optimize the process, and minimized the variability of the growth process. RSM has been applied to the CBE growth of InGaAs and InP with the purpose of generating an operating point at which both good surface morphology and high mobility material can be produced. Although the best 77 K InP mobility was 70,000 cm2/V...s, in order to improve the surface quality the input parameters were changed so that the final mobility was 37,000 cm2/V...s. Although the quality of the InGaAs layers showed a dependence on the reactor history, there did not appear to be any sensitivity to variations made in the operating conditions. The best 77 K InGaAs mobility was 62,500 cm2/V...s.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29335/1/0000402.pd

The design of an ECR plasma system and its application to InP grown by CBE

An electron cyclotron resonance (ECR) plasma system has been designed for the purpose of using an excited beam of gases during CBE growth. The system was designed to use hydrogen, nitrogen and argon. An ECR plasma system has the ability to ignite a low pressure and low temperature plasma with very low ion energies, which should minimize any damage to the growing layer. The motivation behind using a plasma during growth is the ability of atomic hydrogen to remove contaminants from the growing layer and to enhance the decomposition of organometallic precursors at low substrate temperatures. InP grown with a hydrogen plasma showed an n-type background carrier concentration of 6.0X1016 cm-3, with a rough surface and a strong photoluminescence peak at 1.378 eV. A control sample grown with excess hydrogen but without the plasma had a background carrier concentration of 1.0X1015 cm-3, a 77 K mobility of 65,000 cm2/V[middle dot]s and a very weak photoluminescence peak at 1.378 eV. The most likely cause for the layer degradation during plasma growth is an intrinsic defect such as an antisite defect or a vacancy. The n-type nature of the layer and the relatively high carrier concentration would seem to exclude the possibility of carbon or any other unintentional impurities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29336/1/0000403.pd

The Gaseous Electronics Conference radio‐frequency reference cell: A defined parallel‐plate radio‐frequency system for experimental and theoretical studies of plasma‐processing discharges

A ‘‘reference cell’’ for generating radio‐frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self‐bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70394/2/RSINAK-65-1-140-1.pd

Erratum: ‘‘Large‐signal time‐domain modeling of low‐pressure rf glow discharges’’ [J. Appl. Phys. 61, 81 (1987)]

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69545/2/JAPIAU-61-9-4711-1.pd

Large‐signal time‐domain modeling of low‐pressure rf glow discharges

Large‐signal time‐domain modeling (simulation) of rf glow discharges is a very useful and potentially accurate tool for the study of low‐pressure (50–500‐mT) gaseous electronics at high frequencies. Unfortunately, the computational limitations imposed for stability, accuracy, and efficiency can often hinder the production of useful, cost‐effective results. This paper describes a self‐consistent argon rf glow‐discharge simulation at 13.56 MHz for equal‐ and unequal‐area parallel‐plate electrode geometries. Some of the numerical problems associated with this type of simulation are identified and the numerical methods used to overcome them are described. To illustrate the usefulness of this modeling scheme, the plasma potential and the cathode dc bias are examined as functions of electrode area ratio and rf power.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70493/2/JAPIAU-61-1-81-1.pd