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Redundancy with a Six Volt Switching Element

IP.com Disclosure Number: IPCOM000045083D
Original Publication Date: 1983-Jan-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Abbas, SA: AUTHOR [+3]

Abstract

The redundancy technique described hereinafter is based on a structure which is suitable for electrically programmable ROMs, PLAs, etc. The structure is a resistor which has a high electrical resistance which can be reduced by several orders of magnitude by applying an electrical pulse of about six volts.

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Redundancy with a Six Volt Switching Element

The redundancy technique described hereinafter is based on a structure which is suitable for electrically programmable ROMs, PLAs, etc. The structure is a resistor which has a high electrical resistance which can be reduced by several orders of magnitude by applying an electrical pulse of about six volts.

The resistor consists of three layers, as shown in Fig. 1. These layers can be built over single crystal or polycrystalline silicon substrate 10. Layer 11 consists of a material, such as a silicide (TaSi(2), WSi(2), PtSi, etc.), which is formed over the single crystal or polycrystalline silicon substrate 10. Alternatively, the layer 11 can consist of the silicon itself, without the silicide. Layer 12 is formed by the deposition of a semiconducting oxide, such as CrOx (probably Cr(2)O(3)). This can be done, for example, by reacting Cr with an Ar O(2) plasma (reactive sputtering). For the case of CrOx, Ar-O(2) (10%) is used at 300 watts to yield a 1,600 A film whose resistivity is about 10 /O/3/ ohm-cm. The CrOx layer can also be formed by reactive evaporation, that is, by evaporating Cr in a system with a controlled leak of water, air or oxygen to yield a continuous CrOx phase. Other semiconducting oxides which may be used include: Nb(2)0(3), Fe(3)0(4), V(2)0(5) and V(2)0(3), which have the highest conductivity at 293 degrees C. Layer 13 is the usual A1 or A1Cu metal film deposited over the layer 12.

Thicknesses of layers 12 and 13 are typically 150-170 nanometers and 800 nanometers, respectively, although the thicknesses are not critical in this application. The CrOx layer can be patterned by using lift-off or by any other suitable lithography means. The lift-off method is suitable with reactive evaporation of CrOx (increased CrOx concentration). If reactively sputtered CrOx, VOx, etc., are deposited, then RIE (reactive ion etching) or ion milling can be used. It may be desirable to phase the CrOx layer during growth, that is, H(2)O bleed Cr at interface between layers 11 and 12, and then increase H(2)O, or O(2), partial pressure to achieve a continuous CrOx layer at the layer 12 to layer 13 interface.

A TTL (transistor-transistor logic) type of decoder is used here for illustration of the type of redundancy circuits that can be designed with this novel element. The circuit itself has several novel and desirable features including compactness, low power, low extra circuit elements count for the redundancy, few additional pads, and avoidance of the high voltage pulse (about six volts) in the regular circuit path to eliminate reliability concerns.

Fig. 2 sho...