摘要:

The oxidation of GaAs and AlxGa1−xAs targets by oxygen irradiation has been studied in detail. It was found that the oxidation process is characterized by the strong preferential oxidation of Al as compared to Ga, and of Ga as compared to As. This experimental observation, which has been accurately quantified by using x‐ray photoelectron spectroscopy, is connected to the different heats of formation of the corresponding oxides. The oxide grown by ion‐beam oxidation shows a strong depletion in As and relatively low oxidation of As as well. The depletion can be associated with the preferential sputtering of the As oxide in respect to other compounds whereas the low oxidation is due to the low heat of formation. In contrast Al is rapidly and fully oxidized, turning the outermost layer of the altered layer to a single Al2O3overlayer, as observed by transmission electron microscopy. The radiation enhanced diffusion of oxygen and aluminum in the altered layer explains the large thickness of these altered layers and the formation of Al oxides on top of the layers. For the case of ion‐beam oxidation of GaAs a simulation program has been developed which describes adequately the various growth mechanisms experimentally observed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358650

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The computation of director profiles and energy parameters in surface‐stabilized ferroelectric liquid crystal structures requires the evaluation of many terms accounting for different contributions to the general solution. This evaluation is usually performed using several simplifications and assumptions adapted to the specific phenomenon under study. In this work, a comprehensive expression including all possible terms not avoiding a computable solution is presented. The effect of every term on the general expression is analyzed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358651

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A set of experiments was conducted to determine the origin of residual stresses in amorphous Al2O3films formed by ion beam assisted deposition. Samples were deposited during bombardment by Ne, Ar, or Kr over a narrow range of energies,E, and a wide range of ion‐to‐atom arrival rate ratios,R. Films were characterized in terms of composition, thickness, density, crystallinity, microstructure, and residual stress. Film composition was independent of ion beam parameters and residual stress was independent of thickness over the range 200–1200 nm. Stress varied strongly with ion beam parameters and gas content. Residual stress and gas content saturated at a normalized energy of ∼20 eV/atom or anRof ∼0.05. Where residual stress varied linearly withRE1/2, results are consistent with an atom peening model, but saturation at highRorRE1/2is inconsistent with such a model. Stress due to gas pressure in existing voids explains neither the functional dependence on gas content nor the magnitude of the observed stress. A probable explanation for the behavior of stress is gas incorporation into the matrix, where the amount of incorporated gas is controlled by trapping. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358652

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A finite‐element method taking into account material nonlinearity was used to calculate the stress distribution in interconnecting lines and studs of a three‐dimensional multilevel metallization structure in a microelectronic device. A good correlation was obtained between the location of calculated stress concentration centers and the experimentally observed void sites in the stud. Accordingly, the failure mechanisms of the stress‐induced voiding in the stud and the crack formation in the underlying substrate were inferred to be associated with different stress components. Furthermore, the stress concentration centers were found to migrate as the temperature changes, which agrees with the experimental observations. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358653

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have investigated solid phase crystallization behavior of the molecular beam epitaxy grown amorphous Si1−xGex(x=0 to 0.53) alloy layers using x‐ray diffractometry and transmission electron microscopy (TEM). Our results show that the thermal budget for the full crystallization of the film is significantly reduced as the Ge concentration in the film is increased. In addition, we find that a pure amorphous Si film crystallizes with a strong (111) texture while that of the Si1−xGexalloy film crystallizes with a (311) texture suggesting that the solid phase crystallization mechanism is changed by the incorporation of Ge. TEM analysis of the crystallized film shows that the grain morphology of the pure Si is an elliptical and/or a dendrite shape with a high density of microtwins in the grains while that of the Si0.47Ge0.53alloy is more or less equiaxed shape with a much lower density of defects. From these results, we conclude that the crystallization mechanism changes from a twin‐assisted growth mode to a random growth mode as the Ge concentration in the film is increased. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358654

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Deposited oxides of silicon are used for a wide variety of purposes in integrated circuit technology; two of the most important being as interlevel dielectrics and for passivation purposes. It is important to characterize oxides deposited by newer techniques like electron cyclotron resonance (ECR), plasma enhanced (PE) chemical vapor deposition (CVD), and sputtering of quartz for these purposes. In this article, we studied ECR oxides and sputtered quartz oxides to correlate their mechanical behavior to the hydrogenous species concentration. Sputtered quartz oxides were chosen as they are not known to have hydrogenous species concentration, and hence would serve as a comparison tool for ECR oxides which are known to have significant H content. Si‐rich ECR oxides were found to have significant hydrogenous species content while near‐stoichiometric ECR oxides had low bulk H content (as seen from nuclear reaction analyses). The hydrogenous species was identified from Fourier transform infrared spectroscopy to be Si:H. In these oxides, the stress‐temperature behavior is directly related to the H content, with oxides high in hydrogenous species concentration ending up more tensile after thermal cycling. Realizing that these oxides are Si‐rich, the above observation indicates that these oxides have oxygen vacancies (as opposed to Si interstitials). In order to achieve stable stress‐temperature behavior (i.e., linear, and without hysteresis during thermal cycling), these oxides have to be annealed at temperatures greater than 700 °C. Sputtered quartz oxides exhibit stable stress‐temperature behavior up to 600 °C. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358655

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effects of low‐dose ion implants with Si+, Ne+, and F+on the transient enhanced diffusion of B in silicon after annealing at 900 °C for 30 min have been investigated. Processing conditions such as implant dose (3.5×1013cm−2) and energy (30–60 keV) were chosen to simulate the lightly doped drain implant in a 0.35 &mgr;m complementary metal‐oxide‐semiconductor technology. An epitaxially grown B‐doping superlattice is used to extract directly depth profiles of average Si self‐interstitial concentration after processing. For Si+the transient enhanced diffusion of B increases with the energy of the implanted ion. Ne+implanted with the same energy as Si+causes more transient enhanced diffusion, while Ne+implanted with the same range as Si+causes slightly less. Implantation of F+enhances the B diffusivity considerably less than Si or Ne implantation. These effects were modeled using simulations of defect diffusion in the presence of traps. A trap concentration of (2.4±0.5)×1016cm−3gave good agreement in all situations except F+implantation, where (6.6±0.6)×1016cm−3traps were necessary. It is proposed that this is caused by additional traps for Si interstitials that are related to F+. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358656

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The surface‐acoustic‐wave (SAW) propagation losses of two ceramics, a lead zirconate titanate composition and a modified lead titanate composition, are studied. Contrary to crystals, where only mechanical losses contribute, dielectric losses and scattering at the grain boundaries have to be taken into account. A first‐order perturbation theory is extended to include dielectric losses to calculate the surface attenuation. Based on the measurement of the mechanical and the dielectric losses of the two ceramics as a function of frequency, the frequency behavior of the SAW propagation losses of each material is theoretically calculated and values are compared to those obtained experimentally at 25 MHz. Both results show that the modified lead titanate ceramic has low SAW propagation losses, 0.22 dB/mm at 25 MHz, while the lead zirconate titanate has propagation losses of 2 dB/mm at 25 MHz. Using results published in literature, the effect of the scattering contribution is evaluated. Finally, other SAW properties of ceramics, i.e., the free‐surface‐wave velocity, the surface coupling coefficient, and the surface permittivity are measured and reported. All these results are discussed and the suitability of both materials for SAW applications is examined. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358657

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

B‐doped Si(001)2×1 films were grown on Si(001) substrates by gas‐source molecular beam epitaxy using Si2H6and B2H6. B concentrationsCB(5×1016–5×1019cm−3) were found to increase linearly with increasing flux ratioJB2H6/JSi2H6(9.3×10−5–2.5×10−2) at constant film growth temperatureTs(600–950 °C) and to decrease exponentially with 1/Tsat constantJB2H6/JSi2H6ratio. The B2H6reactive sticking probability ranged from &bartil;6.4×10−4atTs=600 °C to 1.4×10−3at 950 °C. The difference in the overall activation energies for B and Si incorporation atTs=600–950 °C is &bartil;0.34 eV. A comparison of quantitative secondary‐ion mass spectrometry (SIMS) and temperature‐dependent Hall‐effect measurements showed that B was incorporated into substitutional electrically active sites over the entire B concentration range investigated. SIMS B depth profiles from modulation‐doped samples were abrupt with no indication of surface segregation to within the instrumental resolution limit and initial &dgr;‐doping experiments were carried out. Structural analysis byinsitureflection high‐energy electron diffraction combined with post‐deposition high‐resolution plan‐view and cross‐sectional transmission electron microscopy showed that all films were high‐quality single crystals with no evidence of dislocations or other extended defects. Temperature‐dependent (20–300 K) hole carrier mobilities were equal to the best reported bulk Si:B values and in good agreement with theoretical maximum values. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358658

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The microstructures of metalorganic vapor‐phase epitaxy alloys of (In,Ga)P grown on GaAs substrates were examined using transmission electron microscopy. Alloys examined were grown at 600–775 °C on substrates at or near (001) or (113)Ausing growth rates of 0.69 and 0.17 nm/s. Two common semiconductor alloy phenomenon, ordering and phase separation, were studied over this range of growth conditions. The CuPt‐type ordering reflections are sharpest for growth at 675 °C and more diffuse at 600 and 725 °C due to higher densities of antiphase boundaries. Order can be eliminated by growth at 750 °C or above to obtain the highest band gaps and optical emission energies. Detailed investigation of the microstructure for growth at 675 °C indicates that ordered domains are platelets consisting of thin (1–2 nm) lamella on (001) planes that alternate between the two {111}Bordering variants, in agreement with a model proposed by others. We have formed ‘‘unicompositional’’ quantum wells with sharply defined ordered layers between disordered barrier layers by changing growth temperature, which demonstrates that ordering is determined to a great degree by the conditions during growth. Phase separation is seen for the entire range of growth parameters, independently of ordering; its contrast shows modulations with a variable spacing ranging from a few nanometers to ∼100 nm. Implications of the coexistence of phase separation and ordering for growth models describing these phenomena are discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358659

出版商:AIP    

年代:1995

数据来源: AIP