摘要:

The effects of a surface magnetic field on reactive ion etching are described. The surface magnetic field is formed by the construction of a surface‐multimagnetic mirror configuration (SURMAC) cage that consists of permanent magnets arranged inside the wall of a parallel plate rf discharge chamber. The experimental results of ion density, electron temperature, negative self‐bias of an rf‐generated N2plasma, and etching of Si and SiO2with a CF4plasma are obtained with and without the SURMAC cage (rf power 40–520 W, gas pressure 20–100 mTorr). The results show that a surface magnetic field increases the etch rates of Si and SiO2at high power (>250 W) and high pressure (100 mTorr), improves the Si to SiO2selectivity at low power (<200 W) and decreases the magnitude of negative self‐bias at all conditions.

ISSN:0021-8979    

DOI:10.1063/1.347682

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Results for room‐temperature oxidation of silicon using cesium ion bombardment and low oxygen exposure are presented. Bombardment with cesium ions is shown to allow oxidation at O2pressures orders of magnitude smaller than with noble gas ion bombardment. Oxide layers of up to 30 A˚ in thickness are grown with beam energies ranging from 20–2000 eV, O2pressures from 10−9to 10−6Torr, and total O2exposures of 100to 104L. Results are shown to be consistent with models indicating that initial oxidation of silicon is via dissociative chemisorption of O2, and that the low work function of the cesium‐ and oxygen‐coated silicon plays the primary role in promoting the oxidation process.

ISSN:0021-8979    

DOI:10.1063/1.347684

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

X‐ray photoelectron spectroscopy was used to study the reoxidation kinetics of both mechanically and chemically polished as well as freshly fractured SrTiO3surfaces. X‐ray take‐off angles were varied in order to resolve surface contributions from those further into the sample. Most surfaces were found to have Sr/Ti ratios that varied significantly from the stoichiometric ratio of 1. Only the oxygen peaks were found to be take‐off angle sensitive. We tentatively identify both adsorbed hydroxyl and carbonate O 1slevels as these angle sensitive peaks, indicating that hydroxyl adsorption occurs very rapidly.

ISSN:0021-8979    

DOI:10.1063/1.347685

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have measured normalized positive ion yields of more than 20 elements implanted into SiO2and compare them with positive ion yields of the same elements sputtered from Si by oxygen and argon ion bombardment. All measurements were made using similar instruments and similar primary ion beam conditions; thus, we compare secondary ion emission from an unoxygenated matrix (Si using argon ion bombardment), from a partially oxygenated matrix (Si using oxygen ion bombardment), and from a fully oxygenated matrix (SiO2). Plots of the logarithm of secondary ion yield or secondary ion mass spectrometry relative sensitivity factor (RSF) versus ionization potential of the sputtered impurity elements exhibit primary linear trends for these three conditions, the slopes of which decrease with increasing oxygenation. A trend line of opposite slope for impurity elements that have ionization potential greater than about 10.5 eV is observed in each case. This latter trend moves to lower values of yield (higher RSF) with increasing oxygenation, perhaps as the result of competition from electronegative elements with oxygen in forming element–Si bonds. These observed changes are primarily the result of increasing the oxygen content in the surface of the Si.

ISSN:0021-8979    

DOI:10.1063/1.347686

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have measured and plotted the dependence of secondary‐ion‐mass spectrometry (SIMS) relative sensitivity factor (RSF) on electron affinity and ionization potential of up to 74 elements implanted into 23 materials, measured using oxygen‐ion bombardment and positive SIMS, and cesium‐ion bombardment and negative SIMS. Reproducibility of ±60% in RSF has been demonstrated for many of these implanted standards over a period of 8 years in several Cameca magnetic sector instruments, especially in Si, GaAs, and HgCdTe matrices. More recently, reproducibilities of ±20%–30% have been achieved using more controlled experimental techniques. Similarities among plots of logRSF versus ionization potential or electron affinity have been found for a variety of semiconductor, metal, and insulator matrices. Universal patterns and trends are observed for oxygen bombardment and positive SIMS, and for cesium bombardment and negative SIMS. Four major regions are seen in the dependence of logRSF on ionization potential, one with possibly three branches with slightly differing slopes, that are characterized by elements from various groups of the periodic table. There are two major regions in the plots of RSF versus electron affinity, one of which is a region of constant RSF versus electron affinity, which includes the more electronegative elements, and meaning that the RSF is a constant for most of the elements commonly analyzed using negative (cesium) SIMS. This constant RSF has been measured for 20 matrices. We report the values of slope of logRSF versus ionization potential for the matrices studied and discuss the possible extension to other matrices. We tabulate the values of RSF for 74 elements in Si and for 69 elements in GaAs, as examples. Tentative explanations of the features of these dependencies are consistent with existing theories and models. We give generalized patterns of RSF (ion yield) versus ionization potential or electron affinity and an equation from which RSFs can be calculated for the matrices studied, and possibly others.

ISSN:0021-8979    

DOI:10.1063/1.347687

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Charge‐collection measurements on test structures were carried out for events induced by alphas, heavy ions, and proton‐induced nuclear reactions over a variety of bias values and for two doping levels. Analysis of charge‐collection pulse‐height spectra provides the shape and dimensions of the sensitive volume associated with the single‐event upset (SEU) sensitive junctions. The critical charge is determined by the circuit design. The critical charge and the dimensions of the sensitive volume are required by all the existing codes dealing with the calculation of SEU rates in natural space environments. The dimensions of the sensitive volume determined for some Rockwell GaAs test structures were used in simulations of charge collection by proton‐induced nuclear reactions using the Clemson University Proton Interactions in Devices codes. Comparison of the results with experimental data yields agreement.

ISSN:0021-8979    

DOI:10.1063/1.347688

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

High quality Te‐doped Al0.7Ga0.3As/Mg ‐doped In0.5Ga0.5P onp‐type GaAs substrate single‐heterostructure light‐emitting diodes have been reproducibly fabricated by liquid‐phase epitaxy using a supercooling technique. The growth conditions and properties of the undoped and Mg‐ and Zn‐doped In0.5Ga0.5P layers are described in detail. The strongest photoluminescence peak intensity occurs at a hole concentration of 1×1018cm−3of the Mg‐doped layer. Diodes fabricated from the heterostructure are characterized by electron‐beam‐induced current, current‐voltage measurement, electroluminescence, light output power, and external quantum efficiency. By appropriately controlling the hole concentration of the Mg‐doped In0.5Ga0.5P active layer and the electron concentration of the Te‐doped Al0.7Ga0.3As window layer, thep‐njunction can be precisely located at the metallurgical junction as measured by the electron‐beam‐induced current technique. A forward‐bias turn‐on voltage of 1.5 V with an ideality factor of 1.65 and a breakdown voltage as high as 20 V are obtained from the current‐voltage measurements. The emission peak wavelength and the full width at half maximum of electroluminescence spectra are around 6650 and 250 A˚ at 20 mA, respectively. The light output power of the uncoated diodes is as high as 150 &mgr;W at a dc current of 100 mA and an external quantum efficiency of 0.085%–0.10% is observed.

ISSN:0021-8979    

DOI:10.1063/1.347689

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Electron, ion, and x‐ray lithography are all being advocated as replacements for optical lithography at some time in the future for high‐volume production of integrated circuits. Of some concern is the potential for radiation damage to underlying circuit layers caused by these lithographies. In this paper we report results of an experiment designed specifically to compare damage to radiation‐hardened circuits arising from the three nonoptical lithographic technologies. We employ flood exposures of metal‐oxide‐semiconductor (MOS) capacitors by electrons, ions, and x rays to simulate lithographic exposures. We report results of characterizations by capacitance‐voltage analysis, radiation‐hardness testing, and bias‐stress testing. Degradation in radiation hardness is used as measure of residual damage caused by the simulated lithographic irradiations that is not annealed out at low temperatures. We find minimal damage to the oxide resulting from lithographic doses of ions. We measure voltage shifts due to oxide‐ and interface‐trap charge introduced by x rays and electrons and find that they can be removed by standard post‐metallization anneals. We find that the radiation tolerance of MOS capacitors so irradiated and annealed is nearly identical to that of devices that did not see irradiation and annealing. Moreover, in all cases, no bias‐temperature instabilities resulted from the exposure‐anneal sequences. We find that all three types of lithographic techniques are promising candidates for use in advanced, radiation‐hardened integrated circuit technologies.

ISSN:0021-8979    

DOI:10.1063/1.348909

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Depth‐resolved secondary‐ion mass spectrometry (SIMS) and high‐resolution transmission electron microscopy were used to study the composition and structure of the arsenic‐doped polycrystalline silicon (polysilicon)–single‐crystal silicon interface. This interface remains intact during an 880 °C anneal, with no alignment of the polysilicon occurring. When the interfacial oxide varies from a thin, discontinuous film, to a continuous layer, SIMS analysis is able to quantify differences in the interfacial oxygen content. This interfacial oxygen, expressed as oxygen atoms/cm2, is found to correlate to polysilicon emitter bipolar transistor device current gain.

ISSN:0021-8979    

DOI:10.1063/1.347690

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An x‐ray diffraction method for determining thicknesses of thin films grown on single‐crystal substrates is presented. The equations, based on the kinematical theory of x‐ray diffraction and the mosaic crystal model, were developed. The thickness of the thin film was computed from the absorption of the integrated diffracted x‐ray intensity from the single‐crystal substrate. Since the diffracted intensity from the film is not required, the film does not have to be single crystal in nature. Thus, thicknesses of less ordered, polycrystalline, or even amorphous films can be measured with high precision by this technique.

ISSN:0021-8979    

DOI:10.1063/1.347691

出版商:AIP    

年代:1991

数据来源: AIP