摘要:

A novel remote plasma deposition technique has been used to deposit low hydrogen content silicon nitride at a temperature of 300 °C. This technique uses a remote noble gas discharge to excite nitrogen and silane species which are introduced downstream, out of the plasma region. Optical emission spectroscopy indicates that the downstream interaction creates excited molecular nitrogen with little evidence of atomic nitrogen. Infrared spectroscopy has been used to qualify the hydrogen content in these films. The etch rate in buffered HF of these films is as low as (1)/(20) that of thermal oxide. A surface reaction model for hydrogen removal is proposed. In that model the hydrogen incorporation is controlled by the arrival rate of SiHxspecies (i.e., the growth rate) and the desorption of NHxgroups from the film surface. Electrical results indicate that the fixed charge density in the nitride films is in the low 1011cm−2and the interface state density is in the upper 1011cm−2 eV−1range. The current–voltage characteristics under ramped bias show no ledges and sustain a current density of 4.6×10−4A cm−2at a field of 4.2 MV cm−1. Their analysis shows that conduction is through Poole–Frenkel transport (bulk‐trap limited) as in conventional chemical vapor deposited Si3N4. Furthermore, a trilayer oxide–nitride–oxide structure on silicon has been fabricated with no hysteresis observed on capacitance–voltage measurements and a (3–5)×1010cm−2 eV−1interface state density.

ISSN:0734-2101    

DOI:10.1116/1.575891

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Chemical vapor deposition of SiO2is often thought of as an innocuous process by which an insulating layer can be formed without affecting the underlying substrate. Here evidence is presented which indicates that asubcutaneousoxidation process takes place during remote plasma enhanced chemical vapor deposition of SiO2which oxidizes a few monolayers of the underlying substrate. This oxidation process is evidenced most directly by electrical measurements on metal–insulator semiconductor (MIS) structures fabricated on Ge and GaAs materials. These MIS structures utilize a thin Si interlayer between the semiconductor and the SiO2to form relatively low interface state density structures. Electrical measurements indicate that depositing SiO260 nm in thickness results in consumption of the 1 to 2 nm Si layer through oxidation. The performance of Si metal–oxide semiconductor structures fabricated using deposited oxides degrades as the thickness of the oxide is increased. The presence of a poor quality, highly strained, subcutaneous oxide formed at low temperature could lead to degraded device performance. Work has been carried out in a separate set of experiments to characterize the nature of oxides formed by direct exposure of Si, Ge, GaAs, and CdTe to remote plasma excited oxygen species.

ISSN:0734-2101    

DOI:10.1116/1.575892

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The removal of residual surface contaminants from chemically polished GaAs wafers has been examined with x‐ray photoelectron spectroscopy. AlKα‐excited As 2p3/2 and Ga 2p3/2 core level spectra with a shallow probing depth show complete desorption of As3+surface oxide after annealing in a stream of pure hydrogen at atmospheric pressure and 400 °C, whereas a temperature of 600 °C is required for entire removal of the Ga3+surface oxide. Carbonaceous surface impurities are also shown to be efficiently reduced by this hydrogen processing. The recorded core level peak intensities indicate formation of a fully stoichiometric substrate surface, with no depletion of arsenic. The chemical structure of the hydrogen processed surface compares favorably with that found for substrates annealed in an ultrahigh vacuum environment. In contrast, annealing at 600 °C in 1 atm of high‐purity inert gas (argon) is shown to promote formation of a thick Ga–oxide on the substrate surface, thus emphasizing the reactive nature of the ambient in this hydrogen processing.

ISSN:0734-2101    

DOI:10.1116/1.575893

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

A brief summary is given of recent work on five loosely connected topics within atomic collisions in solids: (i) preferential recoil implantation in multicomponent targets, (ii) pronounced nonlinear behavior of atomic collision sequences induced by keV heavy ions, (iii) linear and nonlinear effects induced by cluster bombardment, (iv) round robin computer simulation of ejection probability in sputtering, and (v) depth of origin and angular spectrum of sputtered atoms. A common theme is the mutual stimulation between a purely numerical approach and theoretical reasoning, the relative weight of the two approaches being different from item to item.

ISSN:0734-2101    

DOI:10.1116/1.575894

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

The growth of single‐crystal NiSi2and CoSi2thin films on silicon is briefly reviewed. Recent results concerning the growth of epitaxial CoSi2on Si(111) are also included. Various growth models to explain the observed epitaxial orientations based on reaction kinetics and interface energetics are examined. Present experimental data of the Schottky barrier heights and atomic structures of epitaxial silicide interfaces will be discussed and compared with results from recent calculations.

ISSN:0734-2101    

DOI:10.1116/1.575895

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Isoelectronic doping using antimony has been shown to reduce traps and improve material properties during epitaxial growth of Si doped GaAs(100) and AlGaAs(100). In this study, the effect of the antimony dopant on the optimal growth temperature is examined with the aim of producing high‐quality heterostructures at lower temperatures. High‐quality films of GaAs and AlGaAs have been grown by molecular‐beam epitaxy at the normal growth temperatures of 610 and 700 °C, respectively, and 50–100 °C below this temperature using varying small amounts of Sb as a dopant. Electrical properties of the films were then examined using Hall mobility measurements and deep‐level transient spectroscopy. Isoelectronic Sb doping of GaAs and AlGaAs allows the growth temperature for these materials to be reduced by up to 80 °C with trap densities and Hall mobilities at least comparable or better than those for films grown at optimal temperatures. It should therefore be possible to grow GaAs and AlGaAs heterostructures at one temperature without sacrificing the electrical properties of the individual materials.

ISSN:0734-2101    

DOI:10.1116/1.575896

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Large internal piezoelectric fields are generated when strained‐layer superlattices are grown from III–V zinc‐blende‐structure compound semiconductors. The orientation of these internal fields depends on the components of the strain tensor and, consequently, on the growth orientation of the superlattice. In the usual case of strained‐layer superlattices grown along the [001] axis, the piezoelectric fields vanish. However, the case of strained‐layer superlattices grown along the [111]axis is particularly interesting because the internal piezoelectric fields are parallel to the growth axis and their magnitude typically exceeds 100 kV/cm for lattice mismatches as small as 1%. Therefore, [111]‐oriented strained‐layer superlattices exhibit novel physical properties and present technological opportunities not afforded by commonly grown [001]‐oriented strained‐layer superlattices. The internal strain‐induced fields substantially modify the electronic structure and optical properties of [111]‐oriented strained‐layer superlattices. The presence of such large strain‐induced polarization fields in [111]‐oriented strained‐layer superlattices is a physically interesting and technologically significant feature because of the possibility of modulating these internal fields by the application of an external field. Examples of modulating fields include (i) screening by photogenerated free carriers, (ii) external electric bias, or (iii) applied uniaxial stress. As a consequence of these modulations, large nonlinear optic, electro‐optic and piezo‐optic effects result. These effects are illustrated by calculations performed for Ga1−xInxAs–Al1−yInyAs strained‐layer superlattices grown along the [111] axis.

ISSN:0734-2101    

DOI:10.1116/1.575897

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

(Zn,Cd)Te/CdTe strained layer superlattices have been grown by molecular‐beam epitaxy on CdTe(100), InSb(100), and GaAs(100) substrates and substrate/buffer layer combinations. Superlattice period thicknesses ranged from 90 to 330 Å; total superlattice thickness was 0.8 or 1.6 μm. The ratio in thickness between the (Zn,Cd)Te and CdTe layers was tailored to allow the in‐plane lattice parameter of a freestanding superlattice to match that of Hg0.8Cd0.2Te. A high degree of structural quality is indicated by the existence of multiple satellite peaks in the x‐ray diffraction spectra from these structures. Structural quality is found to depend on the substrate used.

ISSN:0734-2101    

DOI:10.1116/1.575898

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

Our previous studies found evidence for a selectivity loss mechanism that is initiated by desorption of tungsten subfluorides formed by the reaction of WF6with metallic tungsten surfaces. When a hot (≂600 °C) tungsten surface is exposed to WF6, a nonvolatile subfluoride, apparently WF4, will accumulate on a nearby SiO2surface held at ≂30 °C. Disproportionation of this tungsten subfluoride upon heating above 350 °C produces a reactive state of tungsten that induces rapid selectivity loss when exposed to chemical vapor deposition conditions. The net effect of this tungsten subfluoride desorption–disproportionation mechanism is the transport of tungsten from a tungsten surface to the silicon dioxide surface. Isolation of a higher tungsten subfluoride, apparently WF5, has been accomplished by cooling the SiO2surface to ≂−45 °C under otherwise similar experimental conditions. Preliminary Auger spectroscopic results yield a stochiometry of F/W=4.9±0.5 for this subfluoride, and temperature programmed desorption results are consistent with the behavior of tungsten pentafluoride. Upon heating WF5multilayers, most of the compound desorbs, but some reaction and disproportionation occurs leaving a reduced state of tungsten on the SiO2surface. It seems likely that tungsten pentafluoride is the key volatile species in a tungsten transport mechanism that can initiate selectivity loss.

ISSN:0734-2101    

DOI:10.1116/1.575854

出版商:American Vacuum Society    

年代:1989

数据来源: AIP

摘要:

We have studied the surface reactions of WF6/SiH4mixtures on Si(100) that are relevant to the chemical vapor deposition of tungsten using x‐ray photoemission and molecular‐beam reactive scattering. The overall reaction is found to be 3SiH4+2WF6→2W+3SiF4+6H2with very little production of HF. The reaction proceeds by repeating the cycle of tungsten deposition by the reaction of WF6with silicon, and the deposition of silicon by the reaction of SiH4with the fluorinated tungsten surface.

ISSN:0734-2101    

DOI:10.1116/1.575855

出版商:American Vacuum Society    

年代:1989

数据来源: AIP