7617. Domain period determination in CoCr films

Classified abstracts 7613-7622 deposited onto a thermal SiOz substrate, rapid thermal annealed in N 2 at 700-1050°C, and the phases formed examined using Auger electron spectroscopy, transmission electron microscopy, electron diffraction, and sheet resistance measurements. A CoSix film results where x is constant with depth and determined by the relative amounts of Co and Si deposited. With increasing x, phases identified are ~- and fl-Co containing dissolved Si, Co2Si, CoSi, and CoSi2. At high temperatures, the CoSi2 film agglomerates and thins the underlying oxide probably on account of excess Si in the silicide film. Furthermore, in an N2 atmosphere, the CoSi2 globules are converted into CoSi in accordance with the phase diagram. A E Morgan et al, J Appl Phys, 67, 1990, 6265~268. 34 7613. Reaction between SiC and W, Mo, and Ta at elevated temperatures The stability of W, Mo, and Ta in contact with single-crystal r-SiC at elevated temperatures has been investigated using Auger sputter profiling. All three metals were found to form a thin-mixed layer o f metal carbide and silicide upon metal deposition at room temperature. This layer is thought to be the result of surface defects which weaken the Si~C bonds and allow a low-temperature reaction to occur. Upon heating, the Ta readily reacts with the SiC substrate and forms a mixed layer of Ta carbide and silicide at annealing temperatures as low as 400°C, however, the W/SiC and Mo/SiC systems are stable and change very little after annealing at 850 and 800°C, respectively. K M Geib et al, J Appl Phys, 67, 1990, 2796-2800. 34 7614. A thermally activated solid state reaction process for fabricating ohmic contacts to semicondncting diamond Techniques have been developed to produce ohmic contacts to naturally occurring boron doped semiconducting diamond. Thin films o f Mo, Mo/Au, and Mo/Ni/Au deposited on diamond produced adherent ohmic contacts after annealing at 950°C. A thermally activated solid state reaction which produces a refractory carbide precipitate at the original diamond/metal interface is the principal factor in affecting the properties of the contacts. The interface reaction has been characterized using Auger electron spectroscopy, scanning electron microscopy, X-ray diffraction, metallography, and 1-V measurements. K L Moazed et al, J Appl Phys, 68, 1990, 2246-2254. 34 7615. The formation of Cu3Si : marker experiments Implanted rare gas markers, as well as a thin tungsten marker, show that the silicide Cu3Si, which is the first phase to form on the reaction of a copper film with a silicon substrate, grows by the motion of copper atoms. The same process seems to be at work in the formation o f the silicide by ion mixing, but the one result obtained in that case is not unambiguous since the observed disappearance at the surface of the implanted marker might be due as well to interface drag effects as to the specificity of the mobile atoms. The low temperature of formation of the silicide, about 200°C, is discussed in terms of what is known about point defects and diffusion in the very similar compound Cu3Sn. L Stolt and F M D'Heurle, Thin Solid Films, 189, 1990, 269-274. 34 7616. Crystallization kinetics of amorphous NiSi~ films In situ resistivity measurements have been used to determine the kinetics of crystal growth of co-evaporated NiSix films. Samples with various heat treatments have been examined with X-ray diffraction to determine the phases growing. It is found that all the films contain crystallites as deposited and that NiSi2 or Ni2Si grow in most of them. The variations in activation energy and 'mode of transformation' with composition are explained. R D Thompson et al, Thin Solid Films, 188, 1990, 259-265. 34 7617. Domain period determination in CoCr films Domain structures of two low coercivity (HclHk ~ 0.02) and one medium coercivity (Hc/Hk ,~ 0.05) films were observed by the colloid-scanning electron microscopy (SEM) method in dc magnetic fields applied normal to the surface. The dependence of the submicron domain period on ascending and descending fields was measured. Anhysteretic curves were obtained by the superposition of a slowly decreasing ac field on the given dc field. The field dependence of the anhysteretic domain period is compared with the theory of Kooy and Enz. In addition to the visual

measurement, the domain period was also determined by a two-dimensional Fourier analysis of the SEM photographs. J ~im~ov~ et al, Thin Solid Films, 188, 1990, 43-56. 34 7618. Observation of reactions between Ti/Permalloy bilayer thin films annealed at low temperatures The interdiffusion of Ti/Permalloy bilayer thin films annealed at 150~ 350°C is investigated. Preferential diffusion o f nickel atoms from the Permalloy layer into the titanium layer is measured by secondary-ion mass spectrometry. As a result o f the preferential diffusion, the coercivities of Permalloy films increase at above 225°C annealing and the electrical resistivities o f the bilayer thin films annealing at above 250°C also increase. An amorphous phase growth between the titanium and Permalloy thin films is observed by means of cross-sectional transmission electron microscopy. A part of the amorphous layer crystallizes by annealing at relatively higher temperatures. M Kitada et al, Thin Solid Films, 181, 1990, 35~41. 34 7619. Observation of random telegraph signals: anomalous nature of defects at the Si/SiO2 interface Current fluctuations with discrete levels, which are called random telegraph signals (RTSs), have been studied in small size metal-oxidesemiconductor field-effect transistors (MOSFETs) from both viewpoints of relative current change and o f correlated switchings. A large relative current change of as much as 30% has been observed, even at room temperature. It behaves similarly as normal small RTSs in terms of statistics and temperature dependence. RTSs have been found also in 20pm channel width MOSFETs. These results require another mechanism to explain RTSs in addition to simple Coulomb scattering or number fluctuation. It is emphasized that an interaction between defects at the Si/SiO2 interface is necessary to understand the correlated RTSs. The experimental results are reasonably reproduced by a model calculation assuming interacting defects. It is also pointed out that new RTSs generated by electrical stress might be a serious concern in lower submicron devices. A Ohata et al, J Appl Phys, 68, 1990, 20(~204. 34 7620. Rapid electron beam annealing of tantalum films on silicon The reaction of tantalum with silicon to form tantalum silicide has been studied using rapid electron beam annealing which gives well controlled time-temperature conditions. Tantalum layers were deposited on single crystal silicon substrates, and annealed at temperatures between 750 and 1100°C for times ranging between 0. l and 90 s. The films were studied using sheet resistance measurements, Auger electron spectroscopy depth profiling, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The diffusion of silicon into the tantalum film, and subsequent formation of a stable silicide, was investigated as a function of temperature and time of anneal. It was observed that at a peak temperature o f 900°C, lasting for a time of 0.1 s, only partial silicidation of the deposited tantalum layer had taken place. These conditions establish the minimum thermal processing requirement which must be met for complete silicide formation. F Mahmood et al, J Vac Sci Technol, B8, 1990, 63~634. 34 7621. CO2 laser treatment of A s - S chalcogenide thin films The changes of the refractive index o f As2S3 and As2S5 films deposited on glass substrates upon COz laser irradiation have been studied. The possibility of writing with the COz laser a waveguiding channel in As2S3 is demonstrated. A M Andriesch et al, J Appl Phys, 67, 1990, 7536-7541.

35. ION A N D PLASMA E T C H I N G 35 7622. Dry etching of III-V semiconductors: influence of substrate temperature on the anisotropy and induced damage During reactive ion etching (RIE) of GaAs and InP with SIC14, many different parameters will influence the etched profile. Among these process parameters, the substrate temperature is frequently neglected, but plays a very important role. While etching InP, not only the profile, but also the surface roughness is influenced. Beside geometrical effects, the optical and electrical damage for p- and n-type GaAs, induced during RIE, is 687