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Vertical Schottky Diode Memory Device

IP.com Disclosure Number: IPCOM000078277D
Original Publication Date: 1972-Dec-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Broom, RF: AUTHOR [+3]

Abstract

Schottky diodes with a contact distance between the Schottky contact and the adjacent ohmic contact or a second Schottky diode below 4 Vm, exhibit bistable switching and memory characteristics after undergoing a "forming process." Forming consists of driving the diode into reverse breakdown and increasing the current until switching into an ohmic state takes place. The forming process is difficult to perform in large memory arrays, because of the high voltages needed and the time consumed for forming each device individually. A method is, therefore, described by which forming may be brought under control or eliminated altogether.

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Vertical Schottky Diode Memory Device

Schottky diodes with a contact distance between the Schottky contact and the adjacent ohmic contact or a second Schottky diode below 4 Vm, exhibit bistable switching and memory characteristics after undergoing a "forming process." Forming consists of driving the diode into reverse breakdown and increasing the current until switching into an ohmic state takes place. The forming process is difficult to perform in large memory arrays, because of the high voltages needed and the time consumed for forming each device individually. A method is, therefore, described by which forming may be brought under control or eliminated altogether.

The method consists of implanting metal ions, e.g. Pt, Au or Ga through a metal mask or SiO(2) mask, or of using a focussed beam into an N-type silicon layer 1 or 2 mu m thick, deposited over a region of N+ silicon, as shown in drawing A. The metal mask may be the Schottky metal contact itself prior to subtractive etching, as shown in drawing B. If a focused beam is used the contact is made in a later metallization stage, as shown in drawing C. When the implanted ion density is sufficiently high so that this region shows metallic conduction. the Schottky diode is effectively extended towards the N+ region. By this method and structure, the breakdown voltage can be reduced substantially to the normal switching threshold of 1 to 5 volts. Any separate forming process which would require higher voltages...