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Silicon Transistor Reach-Through Contact

IP.com Disclosure Number: IPCOM000062367D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Jackson, TN: AUTHOR [+4]

Abstract

A contact can be made in silicon at low temperatures by the phenomenon of pushing a dopant ahead of a silicide to silicon interface in the formation of a silicide layer. This phenomenon has become known in the art as dopant snowplow. It is shown in Fig. 1 for n-doping of silicon. In (A), a poly-Si layer with proper n doping is deposited on the silicon substrate, followed by a layer of metal capable of silicide formation, such as Pd. Upon thermal reaction induced by heating to 200- 250ŒC, a silicide interlayer grows between the poly-Si and metal layers, and part of the dopants in the poly-Si layer are pushed ahead of the moving silicide/poly-Si interface, as indicated in (B). Finally, this moving interface reaches the single crystal silicon substrate, pushing additional dopant atoms into the substrate.

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Silicon Transistor Reach-Through Contact

A contact can be made in silicon at low temperatures by the phenomenon of pushing a dopant ahead of a silicide to silicon interface in the formation of a silicide layer. This phenomenon has become known in the art as dopant snowplow. It is shown in Fig. 1 for n-doping of silicon. In (A), a poly-Si layer with proper n doping is deposited on the silicon substrate, followed by a layer of metal capable of silicide formation, such as Pd. Upon thermal reaction induced by heating to 200- 250OEC, a silicide interlayer grows between the poly-Si and metal layers, and part of the dopants in the poly-Si layer are pushed ahead of the moving silicide/poly-Si interface, as indicated in (B). Finally, this moving interface reaches the single crystal silicon substrate, pushing additional dopant atoms into the substrate. Depending on the amounts of metal and poly-Si deposited and the annealing treatment used, the new interface between silicide (which is metallic) and the single crystal silicon can be at or below the original surface of the substrate, while the metal can be partially or fully converted to silicide. This contact can be used to make reach-through contact to a buried region of a bipolar transistor, which will now be illustrated for the case of contacting the buried base region of a pnp bipolar transistor, as seen in Fig. 2. In this case the top surface is the p-type emitter layer of the device. The parameters of the silicide for...