摘要:

We describe nanometer‐scale feature definition in adsorbed hydrogen layers on Si(001) surfaces by exposure to low energy electrons from a scanning tunneling microscope tip. Feature sizes range from<5 to ≳40 nm as a function of bias voltage (5–30 V) and exposure dose (1–104μC/cm). We show that the cross section for electron stimulated desorption of hydrogen has a threshold at 6–8 eV and is nearly constant from 10 to 30 eV, so that above threshold the feature profiles are a direct reflection of the electron flux profile at the surface. Radial flux distributions are best fit by a simple exponential function, where the decay length is dependent primarily on the tip–sample separation. Low intensity tails at large radius are also observed for high bias emission. Comparison to field emission simulations shows that our tip has an ‘‘effective radius’’ of approximately 30 nm. Simulations demonstrate that tip geometry and tip–sample separation play the dominant role in defining the electron flux distribution, and that optimum beam diameter at the sample is obtained at small tip–sample separation (low bias) with sharp tips. We show that adsorbed hydrogen is a robust resist that can be used as a mask for selective area deposition of metals by chemical vapor deposition. Fe lines 10 nm wide are deposited by pyrolysis of Fe(CO)5in areas where H has been desorbed, with minimal nucleation in the H‐passivated areas.

ISSN:1071-1023    

DOI:10.1116/1.589204

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Transmission electron microscopy studies of localized Ge and GeSi surface nanostructures in the form of nanowires on a Si substrate were performed using a novel specimen preparation scheme assisted by a focused ion beam (FIB). The Ge nanowires/Si and GeSi nanowires/Si were fabricated in a lift‐off process using e‐beam lithography and a pulsed UV laser induced epitaxy process, respectively. By using a Pt/Au–Pd/C multilayer protection structure over the area of interest and a FIB marking technique, specimens of lattice imaging quality have been consistently obtained in which all features of interest were preserved. Multilayer protection structures of Pt/C and Pt/Au–Pd/spin‐on‐glass were also investigated. The versatile sample preparation procedure is applicable to a wide variety of surface structures other than the kind used in this work.

ISSN:1071-1023    

DOI:10.1116/1.589205

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

A systematic scanning tunneling microscopy (STM) study of the surface morphology of thin Sb layers deposited at room temperature on the Si(111)7×7 surface has been performed. Deposition of ≊0.25 monolayers (ML) of Sb results in a rough topography that consists mostly of two‐dimensional clusters. For greater Sb coverages, Sb forms three‐dimensional islands on the Si substrate. For a Sb thickness of ≊20 ML, a transition from an amorphous to a polycrystalline structure of the Sb overlayers is identified from the STM images.

ISSN:1071-1023    

DOI:10.1116/1.589206

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

High quality pseudomorphic Si1−yCyand Si1−x−yGexCylayers were grown on (100) Si between 530 and 650 °C by rapid thermal chemical vapor deposition in the SiH4/GeH4/SiH3CH3/H2system. These layers contained up to 30 at. % Ge and up to 2.2 at. % C. Strain engineering was achieved. The strain could be tailored continuously from compressive (up to 2.2% in Si1−xGex) to tensile (up to −0.8% in Si1−yCyand −0.35% in Si1−x−yGexCy). The relationship between the process parameters and the physical properties of the layers was investigated. A process window for growing high quality layers was defined in terms of the partial pressures of SiH4and SiH3CH3. It was found to be independent of Ge content, growth temperature, and growth rate. No carbon contamination was observed. No interference between Ge and C incorporation was observed. A model for the incorporation of substitutional C in the films which is based on the chemical reaction of SiH4and SiH3CH3on the surface is proposed.

ISSN:1071-1023    

DOI:10.1116/1.589207

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

During epitaxial lateral overgrowth of single‐crystal silicon over thermal SiO2, in the low‐pressure chemical vapor deposition reactor environment, thinning and even pinholes can occur in the underlying gate oxide of in dual‐gated silicon on insulator metal–oxide–semiconductor field‐effect transistors (MOSFETs). The epitaxial lateral overgrowth was grown using dichlorosilane (DCS), HCl, and H2at 970 °C and 40 Torr. Although the etch rate was very small, the thinning was large enough to change the bottom channel threshold voltage (Vt). Oxide thickness measurements, obtained by ellipsometry and by profilometer measurements, indicated an etch rate of about 0.1 nm/min, which was independently confirmed from MOSFET Vt shift measurements. The oxide etch rate decreased with increasing concentration of HCl and was less for oxides grown from heavily arsenic‐doped than from lightly doped boron silicon.

ISSN:1071-1023    

DOI:10.1116/1.589208

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Si1−xGexepitaxial layers were grown atT=525 °C using a commercially available, ultrahigh vacuum chemical vapor deposition reactor. Various techniques, including cross‐sectional transmission electron microscopy, Auger electron spectroscopy, secondary ion mass spectroscopy, double crystal x‐ray diffraction, and photoluminescence (PL) are used to characterize this material. For the first time, phonon resolved PL is used to map out the composition uniformity obtained with this high throughput, production‐ready technology. The composition variations along most of the wafer surface (except the flats) do not exceed ±0.15%. A discussion follows on the limitations of this technology, including the critical thickness for misfit strain relaxation, compared to other growth techniques such as molecular beam epitaxy and rapid thermal chemical vapor deposition. The material grown here exhibits characteristics that are very encouraging for the prospect of manufacturing high frequency devices and circuits.

ISSN:1071-1023    

DOI:10.1116/1.589209

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Nitridation studies of Si(100), Ge(100), and epitaxial strained Si1−xGexsurfaces in microwave ammonia plasma have been carried out by x‐ray photoelectron spectroscopy. A single crystalline Ge(100) surface is found to be totally inert in ammonia plasma, while Si(100) surface undergoes a nitridation reaction. In the case of a SiGe film, only selective nitridation of Si is observed. The selectivity in plasma nitridation has been discussed and the electrical properties of nitrided films have been studied by the characterization of metal–insulator–semiconductor capacitors fabricated using the grown films.

ISSN:1071-1023    

DOI:10.1116/1.589210

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Insitureal time single wavelength ellipsometry and spectroscopic ellipsometry were used to monitor electron cyclotron resonance plasma enhanced chemical vapor deposition of SiO2on Si and Ge at substrate temperatures from floating temperature (<50 °C) to 400 °C. Dielectric layers were evaluated by capacitance–voltage measurements. Single wavelength ellipsometry and x‐ray photoelectron spectroscopy results show that oxidation occurred along with SiO2deposition at the initial stage of plasma enhanced chemical vapor deposition. The real time oxidation analysis shows that the subcutaneous oxidation follows parabolic growth kinetics during SiO2deposition. The parabolic rate coefficient is proportional to the voltage drop across the subcutaneous oxide layer, and yields temperature activated transport. The subcutaneous oxidation of Ge yields a Ge rich oxide that degrades the electrical properties of metal–oxide capacitors. A thin Si layer deposited at room temperature before SiO2deposition protects the Ge surface from undesirable oxidation during SiO2deposition. The required thickness of Si layer is predicted. Electron cyclotron resonance plasma oxidation at 400 °C after SiO2deposition reduces the slow trap states. An Al/SiO2/Si/Ge structure shows improved electrical properties of metal–oxide Ge capacitors. Forc‐Si substrates, a rapid thermal anneal of the deposited SiO2in high vacuum can effectively eliminate the OH group incorporation, and thus reduces both interface trapped charge and slow trap states.

ISSN:1071-1023    

DOI:10.1116/1.589211

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

An ellipsometric method is demonstrated for the assessment of the amount of N in nitrided silicon oxides. The method utilizes the immersion of the film covered sample in a liquid that refractive index matches to the bulk film index. Thus, the overlayer is optically removed yielding greater measurement sensitivity to the interface region where the N is concentrated and is therefore optically distinct. A simple optical model is used and the ellipsometric results are compared with and found in concordance with secondary ion mass spectroscopy N profile measurements made on nitrided oxides that were prepared using N2O and NO. In addition, the interfacial roughness has been found to decrease with increasing N content also in agreement with a literature report. The new method called ‘‘spectroscopic immersion ellipsometry’’ is compared with conventional spectroscopic ellipsometry for the same samples and found to be superior.

ISSN:1071-1023    

DOI:10.1116/1.589212

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The use of Fourier transform infrared spectroscopy was investigated to analyze fluorine dopant levels in plasma‐enhanced chemical vapor deposited (PECVD) fluorinated silica glasses (FSG). The physical and electrical properties of FSG films are strongly dependent on the fluorine dopant concentrations in the film; however, peak overlaps and film thickness effects can reduce the reliability of fluorine dopant estimates. The relationships between peak positions, peak areas, FSG film thickness, physical properties, and fluorine dopant concentration levels were studied for a large number of PECVD FSG films deposited using a wide variety of process conditions. The position of the Si–F peak was found to be independent of dopant levels or film properties. Shifts of the Si–O peak to higher wave numbers were found to be dependent on the fluorine concentration in the film and on the film thickness. Peak deconvolution and curve fitting can be used to separate the effects of the two interfering peaks that make up the Si–O asymmetrical bond stretch peak. The peak area of the Si–F peak normalized to the peak area of the asymmetrical Si–O peak can give reliable quantitative estimates of fluorine dopant concentration when corrected for the effects of film thickness.

ISSN:1071-1023    

DOI:10.1116/1.589213

出版商:American Vacuum Society    

年代:1996

数据来源: AIP