ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Alloying is widely used in semiconductor device manufacture to form both ohmic contacts to, and p-n junctions in, the semiconductor body. Most of the literature on alloying deals with devices in which the alloyed area is small, while the present work refers to junction diameters of 19 to 25 mm. In the alloying process investigated, a metal foil preform is held in contact with the surface of a silicon disc during a thermal cycle, while arrangements are made to measure the temperature gradient across the slice and relate this to the metallography of the junction. It is shown that the initial formation and spreading of the liquid phase in a uniform manner is dependent on the achievement of a number of specific conditions. In particular, the temperature of the liquid should be higher than that of the solid during both heating and cooling stages. Jigs must therefore be designed as much for their thermal properties as for component location. Assemblies containing two metal/silicon alloy systems that have experienced the same thermal cycle, but opposite thermal gradient, illustrate how re-growth layer structure is affected by such gradients, and enable the effects of different dopants and amounts of dopant to be compared. Measured depths of alloying into silicon agree with those calculated from phase diagrams, except where support plate material is involved in the process.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00585477
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