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Superconducting Ohmic Contact

IP.com Disclosure Number: IPCOM000036942D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Delage, SL: AUTHOR [+3]

Abstract

Ohmic contacts constitute a major issue in the performance of high- speed integrated circuits. This is in fact more so in bipolar technology where high current densities are used. Present ohmic contact technology uses tunneling ohmic contacts which result when very high doping levels are employed at the metal/silicon interface. The contact resistance is very sensitive to the doping level at the silicon surface, and is a major detractor from circuit performance. The problem exacerbates at low temperatures due to possible carrier freeze-out. As devices scale, the problem is made severe because of the low-temperature processing employed, which in many cases does not fully activate the dopant in the silicon. Furthermore, when deep donors or acceptors are used (such as Ga, In, etc.) good ohmic contacts are almost impossible.

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Superconducting Ohmic Contact

Ohmic contacts constitute a major issue in the performance of high- speed integrated circuits. This is in fact more so in bipolar technology where high current densities are used. Present ohmic contact technology uses tunneling ohmic contacts which result when very high doping levels are employed at the metal/silicon interface. The contact resistance is very sensitive to the doping level at the silicon surface, and is a major detractor from circuit performance. The problem exacerbates at low temperatures due to possible carrier freeze-out. As devices scale, the problem is made severe because of the low-temperature processing employed, which in many cases does not fully activate the dopant in the silicon. Furthermore, when deep donors or acceptors are used (such as Ga, In, etc.) good ohmic contacts are almost impossible. In III-Vs, ohmic contacts are a far more serious problem on account of the inability to obtain high doping levels and compatible metallurgies.

In this article we show a method to obtain good ohmic contact using superconducting oxides with high transition temperatures. A simple metal does not generally exist with a low-enough work function to yield a low barrier. The essence of this invention lies in recognizing the intrinsic low work function exhibited by the constituents of the superconducting oxides, for example:

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Y2O3 - 2 eV

BaO - 1.6 eV

CuO - 4.1 eV.

Usually combinations of materials with differing work functions gi...