https://iopscience.iop.org/article/10.1016/S1468-6996(01)00150-4/pdf

Development of refractory ohmic contact materials for gallium arsenide compound semiconductors

The effect of a pulsed dc on the sintering of copper spheres to copper plates was investigated. It was shown that the current had a marked effect on neck growth between the spheres and the plates. The enhancement of sintering under the effect of the current was attributed to electromigration. Microstructural observations on fracture surfaces of necks formed under high currents showed considerable void formation. It was also observed that the current resulted in increased evaporation and the formation of bunched evaporation steps. Formation of these steps and their location relative to the neck were consistent with current density distributions. The results of this investigation provide direct evidence for the role of the current in the sintering in the pulse electric current sintering method.

/pdf/current-effects-on-neck-growth-in-the-sintering-of-copper-4g79k1fwcc.pdf

Current effects on neck growth in the sintering of copper spheres to copper plates by the pulsed electric current method

https://www.mri.psu.edu/sites/default/files/file_attach/200.pdf

Neck growth kinetics during microwave sintering of nickel powder

Congruent vaporization of GaAs(s) and stability of Ga(l) droplets at the GaAs(s) surface

Development of ohmic contact materials for GaAs integrated circuits

Spheres of nickel, and of nickel containing 0.5,1.0, 2.0, and 10.0 wt % aluminium, all of approximately 100μm diameter, were sintered under vacuum to nickel plates for various times within the temperature range 1000 to 1300° C. Neck growth was determined as a function of time. Values for the exponent of time in the neck growth equation,x/a = Atn of 0.19, 0.18, 0.15, and 0.16 were found for the above compositions, respectively. An activation energy of 33 kcal/mole was found for sintering nickel spheres to nickel plates. An activation energy of 69 kcal/mole was found for sintering Ni/1.0% Al spheres to nickel plates.

The sintering of nickel/aluminium spheres to nickel plates

Parameters influencing the interfacial interaction between liquid gallium and single crystalline gallium arsenide were investigated under vacuum by means of the sessile-drop technique over the temperature range ∼ 30 to 200° C. In addition to their dependence on the anisotropy of the {111} planes, contact angles in the Ga(I)/GaAs(s) system were found to be sensitive to the degree of misorientation and the direction of tilt of these planes. Furthermore, contact angles were found to be dependent on the size of the liquid drop and on the surface roughness of the substrate. In agreement with theoretical expectations the measured angles increased with increasing roughness of the GaAs surfaceS. However, these angles were found to be unaffected by the presence of N2, Ar, and He atmospheres, and by the nature and concentration of charge carriers in the substrate.

The influence of substrate characteristics on the contact angles between liquid gallium and gallium arsenide crystals

Contact angles between Au-Ge and Au-Sn alloys and {111} oriented gallium arsenide crystals were determined over the temperature ranges 360 to 450° C and 280 to 400° C, respectively. Three characteristic regions of the temperature dependence of these angles were observed. At the lower temperatures, contact angles,θ, decreased sharply with increasing temperature. This region was followed by another in which the values ofθ were essentially independent ofT and finally, at the higher temperatures,θ decreased again asT increased up to the highest limit indicated above. Based on microstructural and electron microprobe analyses these observations are explained in terms of diffusional processes at the interfacial regions between the gold alloys and GaAs crystals. Furthermore, from observations of the temperature dependence of contact angles between GaAs and pure tin, it is suggested that gold plays an important role in the observed interfacial phenomena.

Z. A. Munir

Papers

The sintering of nickel/aluminium spheres to nickel plates

The influence of substrate characteristics on the contact angles between liquid gallium and gallium arsenide crystals

Interfacial properties governing ohmic contacts between gold alloys and oriented gallium arsenide crystals