摘要:

We investigated the influence of electron temperature and rf bias on charge build‐up caused by electron shading in inductively‐coupled plasmas (ICP) at 2 to 40 mTorr in Ar. We used Si substrates covered with a 500‐nm‐thick SiO2film which had a line‐and‐space pattern. We measured the electron and ion currents going into the Si substrate through the dielectric structure. When the pattern size decreases, the electron current through the dielectric structure is suppressed and the floating potential increases. We also measured the change in the floating potential of the sample as the electron temperature was increased. As the electron temperature is increased from 2 eV to 4 eV by controlling the gas pressures, the floating potential difference increases between samples with different pattern sizes. To investigate the influence of rf bias (13.56 MHz) on charge build‐up, we measured differences in the dc self‐bias voltage between samples with different pattern sizes. dc self‐bias voltage differences increase with increasing rf bias voltage. This cannot be explained by the slight increase (3 eV to 5.5 eV) in the electron temperature near the rf electrode due to sheath oscillation heating. Therefore, the dc self‐bias voltage difference is mainly caused by a decrease in the ion flux impinging on the sidewall of the trench because of the increase in the ion energy. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363179

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have developed a computational model to optimize the design of a surface reflection neutralization source of hyperthermal neutrals for charge‐free processing. For the deployment of this technique to production (≥8 in. wafers) processing, a system design study has been completed. A Monte Carlo model is used to determine the energy and angular distributions of reflected hyperthermal neutrals at the surface of a wafer, as well as flux uniformity. A simple form for the plasma profile is chosen to allow simulation of various profiles reported in the literature. Neutrals are launched from the reflector consistent with the relative plasma density at each position on the reflector with angular and energy distributions consistent with experimental observations. These neutrals are then followed through interactions with thermal background atoms and the plasma. Charge exchange, ionization, and elastic scattering processes are considered for argon as the main feedstock gas. The results show the trade off between a high density plasma for substantial wafer neutral flux and losses of the neutral stream due to ionization and charge exchange in the plasma stream. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363180

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The elastic deformation of the surface of thin MgO films grown on Fe(001) induced by the presence of misfit dislocations at the Fe/MgO interface has been put into evidence using low‐energy electron diffraction. Satellite spots surrounding the fundamental Bragg reflections appear once the critical thickness is exceeded and undergo a shift in position as thickness of MgO increases, gradually blending in with the fundamental reflections. The evolution of the position of the spots is in good agreement with kinematical diffraction calculations in which the surface deformation is determined from the displacement field of a single misfit dislocation using both isotropic and anisotropic elasticity theory. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363181

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The evolution of surface morphologies of films prepared by ion‐based deposition techniques has been investigated by atomic force microscopy. Two deposition processes, filtered arc deposition (FAD) and ion‐beam‐assisted deposition, where low‐energy (<100 eV) ion irradiation and high‐energy (several tens of keV) ion‐beam bombardment concurrent with film growth were involved, respectively, have been employed to prepare TiN and Al films. Comparative studies on the effect of energetic ions on the development of topography have been performed between the low‐ion‐energy regime and high‐ion‐energy regime. In addition, the relationship between topography and mechanical properties of thin films has been revealed, by involving thin films prepared by thermal evaporation deposition (TED), where almost all depositing particles are neutral. In the images of the TED TiN and Al films, a large number of porous and deep boundaries between columnar grains was observed, suggesting a very rough and loose surface. In contrast, the FAD films exhibited much denser surface morphologies, although still columnar. The root‐mean‐square roughness of the FAD films was less than 1 A˚. Hardness test and optical parameter measurement indicated that the FAD films were much harder and, in the case of optical films, much more transparent than the TED films, which was considered to arise from the denser surface morphologies rather than crystallization of the films. The high density and super smoothness of the FAD films, and the resultant mechanical and optical properties superior to those of the TED films, were attributed to the enhancement of surface migration of the deposited adatoms in the FAD process, which could provide intensive low‐energy ion irradiation during film growth. As for topography modification by high‐energy ion‐beam bombardment concurrent with film growth, in addition to the increase of surface diffusion due to elastic collision and thermal spikes, physical sputtering must be considered while explaining the development of the film topography. Both surface migration enhancement and sputtering played important roles in the case of high‐energy heavy‐ion‐beam bombardment, under which condition surface morphology characterized by dense columns with larger dimension and deep clean boundaries was formed. However, under high‐energy light‐ion‐beam bombardment, the sputtering was dominant, and the variation of sputtering coefficient with position on the surface of growing film led to the formation of cones. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363182

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A comparative study of the gettering efficiency of the twin grain boundaries &Sgr;=25, &Sgr;=13, and &Sgr;=9 has been carried out by means of electron‐beam‐induced current measurements performed on quenched silicon bicrystals precontaminated by Cu or Ni. The extent of the denuded zone appearing on both sides of each interface type has been considered as the ‘‘rating’’ of its gettering efficiency. For both contaminants, the same scaling of the gettering efficiencies of the boundaries has been observed and was found to be in the order &Sgr;=9≪&Sgr;=13<&Sgr;=25. To account for this ranking, we have correlated the gettering efficiency to the excess energy of the grain boundary with respect to the bulk energy, as theoretically calculated. The computational procedures have been performed by means of molecular‐dynamics simulations using several potentials. On the basis of the specific disorder affecting the &Sgr;=25 structure upon heat treatment, our calculations provided the same progression for the interfacial energies as that observed experimentally for the gettering efficiencies of the corresponding grain boundaries according to the extents of the appropriate denuded zones. Calculations of the strain fields developed by the three grain boundaries also support this view. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363183

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

This paper shows ion channeling images of the strain field produced by precipitate particles in a crystal matrix. Images have been produced by mapping the energy of 3 MeV protons transmitted through a thinned silicon crystal containing colonies of copper silicide particles, with the incident beam at or close to planar channeling directions of the lattice. Features of the precipitate contrast observed as a function of beam tilt angle away from channeling alignment are qualitatively explained using a model based on symmetrical plane rotation of the crystal lattice around the colonies. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363184

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Scanning force microscopy (SFM) is employed to study nm‐scale wear of single‐crystal calcite in an aqueous solution. When the SFM tip is drawn back and forth in a linear fashion across the edge of a preexisting single atomic layer etch pit, dissolution is strongly enhanced at the point where the tip crosses the step. The wear rate as a function of contact force is consistent with a thermally activated wear process, where the activation energy is locally reduced in the strain field of the SFM tip. The activation volume for the strain dependence is on the order of the average volume per ion in the CaCO3lattice. This study provides further support for strain enhanced nucleation of double kinks along preexisting steps. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363185

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A GaNp‐njunction structure was grown on a (0001) sapphire substrate by atmospheric pressure metalorganic chemical vapor deposition using a double buffer layer. The resulting light emitting diode (LED) was further exposed to a low‐energy electron beam source. The effect of e‐beam exposure on the room‐temperature electroluminescence spectra of the LED is reported. It is found that the electroluminescence spectral features change dramatically as a function of the electron‐beam exposure time and current density. This is attributed to changes in active Mg concentration. The origin of each electroluminescence band is discussed. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363131

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The nature of ion damage buildup and amorphization in GaAs–AlxGa1−xAs multilayers at liquid‐nitrogen temperature is investigated for a variety of compositions and structures using Rutherford backscattering‐channeling and cross‐sectional transmission electron microscopy techniques. In this multilayer system, damage accumulates preferentially in the GaAs layers; however, the presence of AlGaAs enhances the dynamic annealing process in adjacent GaAs regions and thus amorphization is retarded close to the GaAs–AlGaAs interfaces even when such regions suffer maximum collisional displacements. This dynamic annealing in AlGaAs and at GaAs–AlGaAs interfaces is more efficient with increasing Al content; however, the dynamic annealing process is not perfect and an amorphous phase may be formed at the interface above a critical defect level or ion dose. Once an amorphous phase is nucleated, amorphization proceeds rapidly into the adjacent AlGaAs. This is explained in terms of the interplay between defect migration and defect trapping at an amorphous–crystalline or GaAs–AlGaAs interface. In addition, enhanced recrystallization of the amorphous GaAs at the interface may occur during heating if an amorphous phase is not formed in the adjacent AlGaAs layer. This is most likely the result of mobile defects injected from the AlGaAs layer during heating. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363186

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Ion‐beam mixing of Fe‐Al and Mo‐Cr multilayers was studied by alternately sputtering with 5 keV Ar+and then analyzing with Auger electron spectroscopy. The target temperature was variously room temperature, 450, 525, or 600 K. The two systems were chosen on the basis of having heats of mixing (&Dgr;Hm) which were opposite in sign, namelyH1:1m=−0.25 eV for solid Fe‐Al and &Dgr;H1:1m=+0.075 eV for solid Mo‐Cr. (&Dgr;H1:1mapplies to a 1:1 composition.) With Fe‐Al a well‐defined peak broadening was observed as the profiling temperature increased, while with Mo‐Cr there was a slight narrowing of the peaks with increasing temperature. The results were analyzed in terms of numerical solutions of a diffusion equation which contained terms appropriate not only to ballistic motion but also to the motion of bombardment‐induced residual defects. The latter were assumed to be in part ‘‘chemically guided,’’ as quantified with the parameter ‘‘qp’’ (qp∼∝&Dgr;Hm). A major difference between Fe‐Al and Mo‐Cr was found. The peak changes with Fe‐Al scaled with what we have termed the effective diffusion coefficientDeff=Dt(1−qp/4). HereDtis the total diffusion coefficient, i.e., it describes the total diffusivity for all mixing processes. With Mo‐Cr, on the other hand, the peak changes scaled approximately with 1/qp. The mixing behavior of Fe‐Al, with negative &Dgr;Hm, could thus be said to be mainly kinetic (withDeffplaying a major role), while that of Mo‐Cr, with positive &Dgr;Hm, is more nearly thermodynamic (withqpplaying a major role). ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.363187

出版商:AIP    

年代:1996

数据来源: AIP