Wide Range Of Process Conditions Research Articles

In‐Source Al‐0.5%Cu Metallization for CMOS Devices

This study examines the use of radiation‐free RF induction‐source evaporated (In‐Source®) Al‐0.5%Cu as a viable metallization scheme for CMOS devices. The fact that it is radiation free offers ways of optimizing the thermal cycle so as to achieve desirable device and electromigration characteristics. Wafers fabricated with 3.5 μm design rules have shown no threshold shifts or changes in the transistor gain at sintering temperatures up to 450°C, in either or , for both N‐ and P‐channel devices, confirming the absence of deposition‐induced fixed interface charges. Wafers processed with 2.5 μm design rules have exhibited low and well‐behaved values of contact resistance to N+ and P+ diffusions, at sintering temperatures in the range 300°–400°C in either or , with no evidence of junction penetration. Electromigration measurements, gathered over a wide range of processing conditions, have yielded values of median time to failure (MTF) that were observed to improve with narrower linewidths, higher sintering temperatures, and in the presence of a plasma passivation coating. In typical device operation conditions of 80°C and , the extrapolated MTF value of , for 3.0 μm wide In‐Source Al‐0.5%Cu lines is found to exceed the value of reported for E‐Gun Al‐0.5%Cu.

Solidification morphologies in directionally solidified superalloys

the microstructures of several nickel-base superalloys directionally solidified using a wide range of processing conditions have been examined. The conditions required for plane front solidification are compatible with the concepts of constitutional supercooling. In the dendritic regime the variations in cell spacing λ 1 with temperature gradient G and solidification rate V are well described by the λ 1 ∞ G −1 2 V −1 4 relationship predicted by two recent theories; the observed magnitudes of λ 1 are in better agreement with the predictions of Hunt's theory. The implications of directional solidification processing conditions to the distribution of precipitates in nickel-base superalloys are also considered with particular reference to the occurrence of discontinuous γ′ precipitation and to the morphologies if Mc carbides.

Helical glassy alloy ribbons: Fabrication and Magnetic properties

Metallic glasses may be produced in continuous ribbon or tape form by flowing molten alloy onto a rapidly moving substrate surface. In the present investigation a variation of conventional chill block melt spinning is described. The process is used to fabricate samples with a helical appearance (constant in-plane curvature). Helical ribbon samples were cast using a wide range of process conditions and the dependence of sample cross section on process parameters was found to be well described by empirical equations already established for the fabrication of straight ribbons. Magnetic coercivity measurements of helical ribbons and of straight ribbons wound into toroids revealed a greater as-cast sample coercivity for the helical sample, while retesting after magnetic annealing showed that the helical sample had lower coercivity than toroids assembled using straight ribbon samples. This has been attributed to the increased quenched-in stress level resulting from the greater ribbon-substrate sticking distance to define the in-plane curvature of the helical ribbon. The coercivity of the straight ribbon tested in the form of toroids was found to be highly dependent on stresses induced during the preparation of the sample assembly for magnetic testing.

Modifications in optoelectronic behavior of plasma-deposited amorphous semiconductor alloys via impurity incorporation

We discuss electronic properties of plasma-deposited a-Si:H alloys as functions of oxygen and nitrogen impurities. Over a wide range of processing conditions, features displayed by the data include: i) “anomalous” behavior in photoconductivity versus temperature for films deficient in either, or both, impurities (peaks appear that are associated with thermal-quenching processes and supralinearity); and ii) modification to “classic” behavior in photoconductivity owing to synergistic effects of oxygen and nitrogen. Correlations with photoluminescence are presented. Optical emission spectroscopy is discussed within the context of an emerging spectroscopy for the detection of emitting reactive species in the plasma. The presence of impurities, particularly N 2, can be diagnosed.

On Redistribution of Boron during Thermal Oxidation of Silicon

Numerical and analytical methods for the calculation of redistribution of boron during thermal oxidation are reviewed. An approximate analytic two‐dimensional diffusion model is developed which is based on a modification of the approach used by Huang and Welliver. Accuracy of the analytic model in one dimension is examined over a wide range of processing conditions using exact numerical simulation as a benchmark. The new analytic model is effectively used to simulate the channel and channel stop profiles of an n‐MOS technology and measured results are shown.

A barrier model for ZnO varistors

A model of current transport in ZnO varistors is proposed. The model is a modification of an earlier one suggested by Levine, with the major difference being the inclusion of a thin (?10 Å) ’’disordered’’ layer which separates the single-crystal ZnO grains. The proposed model is shown to be consistent with electrical and microstructural observations and can satisfactorily account for α’s in excess of 60. A technique for extracting the surface-state density Ns(E) and doping profiles from C-V and I-V data is described. It is also shown from the theory that the maximum α is approximately proportional to the grain voltage, a result that is in agreement with measurements on varistors made under a wide range of processing conditions. By calculating the I-V characteristic for different Ns(E) profiles, it is shown that Ns(E) largely determines this characteristic and that certain profiles are to be favored over others when processing conditions are considered.