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Browse Prior Art Database

Electrically Programmable Bipolar ROM Cell

IP.com Disclosure Number: IPCOM000052126D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Bergeron, DL: AUTHOR

Abstract

This structure is a bipolar electrically programmable ROM which uses ho carrier injection to electrically program the ROM and ultraviolet light to erase it.

This text was extracted from a PDF file.
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This is the abbreviated version, containing approximately 53% of the total text.

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Electrically Programmable Bipolar ROM Cell

This structure is a bipolar electrically programmable ROM which uses ho carrier injection to electrically program the ROM and ultraviolet light to erase it.

As shown in Fig. 1, this cell structure is formed by providing an opening in the oxide coating 10 overlying a formed n-type epitaxial layer 11 on a p-type semiconductor body 12.

Two Schottky barrier diode (SBD) contacts 13 and 14 are formed using known techniques at either end of the first opening, insuring a minimum separation between them. The contacts and the remaining exposed surface are passivated with sputtered SiO(2) 15, and a programming gate 16 is formed with second metal designed to overlap the two SBD contacts.

Programming the cell is done by selective hot hole injection into the quartz passivation layer between the two SBD devices. Figs. 2 and 3 outline the procedure for selectively programming a '1' and '0', respectively. In both cases the unit is biased to inject holes into the N epi layer 11, and the programming gate 16 is at a potential to insure deep inversion in the channel between the two SBD contacts 13 and 14. Such conditions will cause the injected holes to be accelerated through the depletion width, gaining sufficient energy to surmount the Si-SiO(2) interface barrier on the surface of the epi layer becoming trapped in the SiO(2).

In the case of programming a '1' the programming contact 14 (Fig. 2) is floating or slightly forward biased to insure that this device will not sink the injected holes, thus insuring that a high hole density is available for acceleration and subsequent trapping. This will in turn cause an increase in the positive oxide charge and hence the threshold between the select contact 13 and the programming contact 14.

On the other hand, to program a '0' the programming contact 14 is reverse biased to sink the majority of the injected holes, thus preventing uniform increase of positive oxide charge x in the channel between the select contact 13 and programming contact 14, thus no increase in threshold.

In both cases during read-out the programming contact 14 and epi region 11 are held at the intrinsic threshold voltage, i.e., the threshold...