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Silicon Diode

IP.com Disclosure Number: IPCOM000095593D
Original Publication Date: 1964-Mar-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Castrucci, PP: AUTHOR [+3]

Abstract

This silicon diode has junctions which have very low leakage current, The diode has forward characteristics which are comparable to normal diffused N-P silicon junctions.

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Silicon Diode

This silicon diode has junctions which have very low leakage current, The diode has forward characteristics which are comparable to normal diffused N-P silicon junctions.

A 0.4 ohm centimeter P-type wafer 20 is thermally oxidized at 970 degrees C for fifteen minutes in oxygen and then placed in a steam atmosphere for ninety minutes. A silicon dioxide coating 22 is formed on the surface of wafer 20. Openings 24 are established in the oxide coating by photoresist etching techniques. The silicon surface is exposed in opening 24. Aluminum metal is evaporated, sputtered or the like on the surface of the silicon dioxide in opening 24 to a thickness of the order of 500 Angstroms.

The aluminum is coated with a film of silver to a thickness of the order of 6000 Angstroms by deposition techniques. The aluminum-silver coated wafer is fired at 1000 degrees C for approximately five minutes. The aluminum alloys flat and parallel to the (1:1:1) crystal planes and the silver is carried as a dopant. The silver diffuses out from the molten interface and converts the P-type bulk silicon to N-type, thus establishing an N-P junction. As the molten alloy is cooled, the dissolved silicon crystallizes.

Capacitance versus reverse bias measurements indicate a linear graded, diffused junction. Low temperature measurements made of the forward characteristic of the silver-aluminum diode indicate high resistivity at approximately 78 degrees K.The high resistivity indicates the d...