摘要:

The role of fluid flow and heat transfer in determining the quality of the diamond films and the rate of their deposition in a hot‐filament chemical vapor deposition (HFCVD) reactor was investigated both experimentally and theoretically. The equations of conservation of mass, momentum, and enthalpy were solved numerically to calculate the temperature and fluid flow fields. Experiments were conducted with various flow configurations, and the deposition rates and the spatial variations of film thickness were examined in each case. The films were characterized by Raman spectroscopy, x‐ray, and scanning electron microscopy. The influences of free and forced convection, and diffusion due to concentration and temperature gradients (Soret effect) were examined. Comparison of the computed results with the experimental data revealed the importance of thermal diffusion in the HFCVD of diamond.

ISSN:0021-8979    

DOI:10.1063/1.346502

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A time‐of‐flight mass spectroscopy technique was developed that enables continuous monitoring of ion mass distribution in the output of a typical ionized cluster beam (ICB) source with minimum modification of the setup and negligible disturbance of film growth. The low mass resolution of this spectrometer is sufficient for cluster size determination and is counterbalanced by a number of advantages promising a more general applicability of the technique. This spectrometer has been used to study germanium cluster formation in a commercially available ICB source. No clusters larger than a few atoms were observed during several deposition runs, under conditions relevant to practical applications. It is difficult to reconcile these findings with the original hypothesis of homogeneous nucleation and growth of large clusters by free jet expansion of metal vapor. Since the precise temperature gradient in the crucible could not be controlled in this type of source, it cannot be excluded that large clusters may be formed under very particular conditions. If this is the case, vapor condensation on the nozzle’s walls must play the key role in the formation of clusters, of germanium at least, making ICB less attractive as a semiconductor thin film growth technique.

ISSN:0021-8979    

DOI:10.1063/1.346503

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An &egr;‐Ti2N film nearly free from any other phase of the Ti‐N compound was deposited and the temperature dependencies of the resistivity and the Hall coefficient of the film were measured. The resistivity data were analyzed in terms of the Bloch–Gru¨neisen equation. The characteristic temperature &thgr; of the film was 410.8 K, independent of the temperature ranging from 4.2 to 300 K. From a Hall measurement it was determined that the conduction carriers in the &egr;‐Ti2N were holelike over the temperature range from 77 to 300 K.

ISSN:0021-8979    

DOI:10.1063/1.347175

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The material and electrical properties of plasma‐enhanced chemical vapor deposition fluorinated silicon nitride were studied. These films were deposited using SiH4‐NF3‐NH3‐N2chemistry. The concentration of fluorine in the films increases as the flow rate of NF3increases during the deposition. The refractive index of the films was found to decrease as the concentration of the fluorine increases. The properties of the films, such as wet etch rates in various etching solutions, the reactive‐ion etch rate, and the stress were measured. The concentration of SiH and NH bonds were also measured. Most of the material properties of the films were found to be strongly dependent on the concentration of fluorine in the films. It was also found that the refractive index of the fluorinated silicon nitride is determined by the concentration of fluorine. As a result, the refractive index of the fluorinated silicon nitride, which can be readily measured using an ellipsometer, is a useful monitor for process and quality control of film preparation in manufacturing. High resistivity and a frequency‐independent dielectric constant were also observed from the fluorinated silicon nitride. The material and electrical properties of fluorinated silicon nitride with a refractive index in the range from 1.70 to 1.80, which shows promise for device applications, have been studied in detail.

ISSN:0021-8979    

DOI:10.1063/1.346504

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A monolithic integration between an active and an external passive waveguide in such a way they are directly butt‐jointed in a single epitaxial step is demonstrated in the InP system. The growth behavior during nonplanar metalorganic vapor‐phase epitaxy on a patterned InP substrate was investigated by using a periodic structure on GaInAs or InGaAsP/InP layers. A 1.5‐mm‐long ridge laser consisting of an active guide butt‐jointed to a transparent waveguide has exhibited lasing oscillation at 1.5 &mgr;m with a threshold current of 82 mA. A coupling coefficient of 60% has been experimentally measured.

ISSN:0021-8979    

DOI:10.1063/1.346505

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The dynamic behavior of a novel fast fuse opening switch has been analyzed theoretically. The outer cylinder of a resistive substrate, e.g., SiC, is uniformly coated with a thin film (∼10 &mgr;m) of aluminum fuse. The substrate provides mechanical stability and guards against voltage breakdown. The key aspects of the modeling are as follows: (1) time‐dependent ordinary differential equations for the fuse‐intensive variables which include coupling to circuit waveforms; (2) spatial dependence within the fuse is suppressed by assuming uniform expansion (linear velocity profile). Intimate contact between the fuse and substrate layer induces an additional inductive load voltage which the fuse must support due to the skin effect inside the substrate. The resulting overvoltage is not severe enough to cause fuse restrike before switching has completed. The fuse opening times are quite short (∼20–50 ns) and the voltage multiplication factors are high (∼10–30). These results raise the hope that a single‐stage fuse could ultimately be used in an inductive storage device intended for high‐current, high‐power pulsed diode applications.

ISSN:0021-8979    

DOI:10.1063/1.346506

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A new theory of polycrystalline silicon thin‐film transistors is proposed, based on a continuous trap state density. Three different regimes are predicted: subthreshold, transitional, and crystallinelike. Two characteristic voltages are identified: the threshold voltage, corresponding to the condition of equal trapped and free charge concentration at the oxide/semiconductor interface and the on‐voltage, corresponding to the condition of equal trapped and free charge in the whole space‐charge region. In the case of an exponential distribution of gap states, approximated analytical expressions can be deduced and a simple accurate fitting procedure is presented. A very good agreement with the experiment is obtained, confirming the importance of taking into account the detailed energy dependence of the trap distribution.

ISSN:0021-8979    

DOI:10.1063/1.346507

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of Si or Ge addition to NiInW ohmic contacts on their electrical behavior were studied, where the samples were prepared by evaporating Ni(Si) or Ni(Ge) pellets with In and W and annealed by a rapid thermal annealing method. An addition of Si affected the contact resistances of NiInW contacts: the resistances decreased with increasing the Si concentrations in the Ni(Si) pellets and the lowest value of ∼0.1 &OHgr; mm was obtained in the contact prepared with the Ni‐5 at. % Si pellets after annealing at temperatures around 800 °C. The contact resistances did not deteriorate during isothermal annealing at 400 °C for more than 100 h, far exceeding process requirements for self‐aligned GaAs metal‐semiconductor field‐effect‐transistor devices. In addition, the contacts were compatible with TiAlCu interconnects which have been widely used in the current Si process. Furthermore, the addition of Si to the NiInW contacts eliminated an annealing step for activation of implanted dopants and low resistance (∼0.2 &OHgr; mm) contacts were fabricated for the first time by a ‘‘one‐step’’ anneal. In contrast, an addition of Ge to the NiInW contacts did not significantly reduce the contact resistances.

ISSN:0021-8979    

DOI:10.1063/1.346508

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electrical properties and microstructure of InAs ohmic contacts ton‐type GaAs, prepared by sputter‐depositing a single target, were studied by measuring the contact resistance (Rc) by the transmission line method and analyzing the interfacial structure by x‐ray diffraction and cross‐sectional transmission electron microscopy. Current‐voltage measurement of an as‐deposited InAs/W contact showed Schottky behavior, where the W layer was used as a cap layer. The InAs layer had an amorphous structure and a uniform oxide layer was observed at the InAs/GaAs interface. Even after annealing at 800 °C, ohmic behavior was not obtained in this contact because the intervening oxide layer prevented the InAs and GaAs interaction. By adding Ni to the InAs/W contacts (where Ni was deposited by an evaporation method), the interaction between the InAs and the GaAs was enhanced. Nickel interacted with As in the InAs layer and formed NiAs phases after annealing at temperature above 600 °C. The excess In in the InAs layer reacted with the GaAs substrate, forming InxGa1−xAs phases which covered about 80% of the GaAs interface. TheRcvalues of ∼0.4 &OHgr; mm were obtained for InAs/Ni/W and Ni/InAs/Ni/W contacts at annealing temperatures in the range of 750–850 °C. These contacts contained only high melting point compounds and the contacts were stable during annealing at 400 °C for more than 100 h after ohmic contact formation.

ISSN:0021-8979    

DOI:10.1063/1.346509

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We compare the effectiveness of two types of SiC‐coated graphite susceptors in providing degradation‐free rapid thermal annealing of InP and GaAs. The first type of susceptor must be charged with the group‐V species prior to any annealing cycles. Under the optimum charging conditions, effective surface protection is provided for up to five sequential high‐temperature (900 °C, 10 s) anneals of GaAs, or only one anneal (750 °C, 10 s) of InP before recharging is necessary. The incorporation of small reservoirs into the susceptor allows for the provision of a constant group‐V partial pressure over the wafer, and it appears that for this type of susceptor many dozens of InP or GaAs wafers can be annealed without any apparent surface degradation. The relative merits of using InAs, GaAs, or InP as the group‐V source in the reservoirs have been compared, and it is found that the best protection is achieved when one uses the same semiconductor in the reservoirs as is being annealed.

ISSN:0021-8979    

DOI:10.1063/1.346510

出版商:AIP    

年代:1990

数据来源: AIP