摘要:

Scanning tunneling microscopy and related local probe methods have led to a novel perception of nanometer‐ and atomic‐scale structures and processes. Since the information is obtained directly in real space, the scanning probe techniques offer significant advantages for the investigation of nonperiodic structures at solid surfaces compared with diffraction techniques. Additionally, local probe methods allow the study of a large variety of physical properties of nanometer‐scale structures down to atomic resolution and even became useful for the fabrication of artificial nanometer‐scale structures. On the other hand, a large number of unresolved scientific and technological issues still remains. In this review, the focus is on two basic questions: what actually has been achieved and which fundamental physics issues need to be addressed further. The discussion will be restricted to topics in solid state physics.

ISSN:0734-211X    

DOI:10.1116/1.587032

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Low damage InGaAs/AlGaAs etching was realized by electron cyclotron resonance (ECR) plasma with a Cl2/He mixture for heterojunction bipolar transistors (HBTs) emitter mesa formation. By optimizing the etching pressure and the Cl2/He ratio,n‐InGaAs cap layer andn‐AlGaAs emitter layer are successively etched and the smooth surface morphology was obtained. An optical emission measurement reveals that the enhancement of the ionized Cl etching plays the essential role for etching of InGaAs. Raman scattering spectra and the base contact resistance measurements indicate that the etching induced damage is extremely low. Moreover, it was found that the etching rate ofp‐AlGaAs base layer decreased down to two‐thirds of that forn‐AlGaAs emitter layer under the optimized etching condition. These results demonstrate the potentiality of ECR plasma etching with Cl2/He discharge providing degradation‐free dry etching for AlGaAs/GaAs HBTs.

ISSN:0734-211X    

DOI:10.1116/1.587033

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The reactive ion etching of AlInGaP and GaAs with a gas mixture of SiCl4, CH4, and Ar is examined. Process parameters such as gas flow composition and radio‐frequency power input are varied. The CH4flow variation in particular has a substantial effect on the morphology of AlInGaP, while generally the effects on GaAs are less dramatic. The etch rates of AlInGaP and GaAs show similar trends. A suitable etching process was found and applied to an AlInGaP/InGaP index‐guided 675 nm laser structure.

ISSN:0734-211X    

DOI:10.1116/1.587034

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Electron cyclotron resonance plasma oxidation of InP was studied using both spectroscopic and single wavelength ellipsometry employed during the oxidation process. A two layer oxide was observed with the outer layer being In rich and the inner layer P rich as confirmed from x‐ray photoelectron spectroscopy and etch rate studies. Optical models and oxidation kinetics are analyzed. From positive substrate bias effects on oxidation rates, negative ion oxidant species were identified as dominant and oxide etching was observed at negative bias. Plasma oxidation, like thermal oxidation, yielded excess P near the semiconductor surface which would degrade electronic properties.

ISSN:0734-211X    

DOI:10.1116/1.587035

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Atomic hydrogen is commonly used to clean GaAs surfaces. The goals of this work are to optimize the cleaning process and to control surface reactions in order to avoid decomposition of GaAs. Chemically polished GaAs (001) surfaces have been cleaned by thermally generated atomic hydrogen and analyzed by surface sensitive techniques. We propose an optimal process involving two exposures. The first one at room temperature etches As oxides. The second one at 300 °C completes the reduction of Ga oxides. We demonstrate that the variations of the ionization energy, work function, and Fermi level are very sensitive to the completion of the cleaning reaction. These parameters can be used to monitor surface reactions on‐line in order to avoid excessive desorption of As and GaAs decomposition.

ISSN:0734-211X    

DOI:10.1116/1.587388

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A study of the surface of InyAl1−yAs, grown lattice matched on InP(100) by molecular beam epitaxy, protected by an As cap during storage in air and subsequently annealed in ultrahigh vacuum, is presented. The surface structure and stoichiometry of the layers are investigated by low energy electron diffraction and x‐ray photoemission spectroscopy. These investigations show that decapping may be achieved by annealing the sample at 390 °C to reveal an atomically clean, As‐stabilized surface, exhibiting a (3×1) symmetry. It is also shown that the relative population of In and Al on or near the surface is different from that of the underlying bulk InyAl1−yAs layer and that the overall surface symmetry and stoichiometry may be further adapted by annealing to higher temperatures.

ISSN:0734-211X    

DOI:10.1116/1.587389

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Extensive theoretical and experimental investigation of the chlorine and argon chemically assisted ion beam etching process for the fabrication of vertical, ultrahigh quality facets in GaAs are reported. The dependence of etch rate and verticality of the etched profile on chlorine flow and ion flux have been studied and analytical expressions for the etch rate are presented. The analytical expressions are based on previously suggested surface‐reaction models as well as on a new model where the reactions are stimulated by the incident argon ions. Using this new surface‐reaction model together with ion trajectory simulations, computer programs were developed for the etch rate and etch profile which allow us to study the dependence on chlorine flow, argon ion current density, and argon ion energy. The dependence of the etch rate and the etch profile on the chlorine flow is explained by the combined effect of a saturation of the chlorine surface coverage and increased scattering of the high‐energetic argon ions with increasing chlorine flow. Furthermore, the importance of the etch‐mask profile as well as adequate heat sinking, for the verticality of the etched facets is demonstrated.

ISSN:0734-211X    

DOI:10.1116/1.587390

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The damage and contamination effects present in silicon substrates from both reactive ion etching and magnetron‐enhanced reactive ion etching of SiO2have been examined for various overetch percentages using spectroscopic ellipsometry (SE) and secondary ion mass spectroscopy (SIMS). The former method has shown that the thickness of the etch‐induced heavy damage layer in silicon decreases, but its damage density increases with magnetic field. In addition, a thinner fluorocarbon residue layer was detected by both SE and SIMS on the samples etched in the presence of a magnetic field. The high temperature annealing behavior of silicon surfaces after UV/O2removal of this polymer layer was also compared for samples etched with and without the presence of a magnetic field. Almost complete surface recovery was observed for the samples etched with the presence of a magnetic field as a result of a 15 min anneal at 600 °C.

ISSN:0734-211X    

DOI:10.1116/1.587391

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Hydrogen plasma produced by a microwave multipolar reactor has been used to clean a single crystal of silicon. The substrate is kept at room temperature and floating potential during the plasma treatment and then heated at 700 °C. The effect of atomic species created in the plasma on the silicon surface is studied byinsituanalysis (spectroscopic ellipsometry, low energy electron diffraction, and Auger electron spectroscopy) andexsituanalysis (atomic force microscopy). Quasi‐instantaneous removal of carbon is demonstrated, showing the high efficiency of hydrogen plasma to remove carbon of the silicon surface. This cleaning treatment allows the obtainability of silicon surfaces exempt of contaminants (carbon and oxygen) and roughness (very low perturbed thickness). The peaks values of the imaginary part of dielectric function of Si surface cleaned by hydrogen plasma exceed those previously reported (values of εiat 4.25 eV=48.25). This process seems to be compatible with very large scale integrated and ultra‐large scale integration technology.

ISSN:0734-211X    

DOI:10.1116/1.587392

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Silicon dioxide has been deposited from electron cyclotron resonance silane/oxygen plasmas at temperatures below 150 °C. Deposition rates over 4000 Å/min have been obtained. The refractive indexes in the measuring range of 1.5–4.5 eV were found to be almost insensitive to the different deposition rates and flux ratio regimes except in the near infrared region where small deviations from thermal oxide indexes were observed. Etch rates and refractive indexes were very close to the thermal oxide values for low silane/oxygen flow ratios 0.025, whereas the refractive index decreased and the etch rate increased for the largest flow ratios used (0.20). After a low temperature annealing, 500 °C in nitrogen ambient, the refractive indexes reached the best obtained values and were independent of the conditions under which the layers were deposited.

ISSN:0734-211X    

DOI:10.1116/1.587393

出版商:American Vacuum Society    

年代:1994

数据来源: AIP