Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Self Differential Sensing of MNOS Memory Arrays

IP.com Disclosure Number: IPCOM000081405D
Original Publication Date: 1974-May-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Krick, PJ: AUTHOR

Abstract

Described is a sensing system which makes it possible to use much smaller device threshold windows than conventional sense schemes, and to provide increased memory retention time. It is known that switching characteristics of metal-nitride-oxide semiconductor (MNOS) and metal-alumina-oxide semiconductor (MAOS) memory devices are a very sensitive function of the thin SiO(2) layer thickness. Variations in this SiO(2) thickness occur over the area of an MNOS memory array, and hitherto have made it necessary to use relatively large threshold windows in the range of 5 to 10 volts. Using this new self-differential sense scheme, much smaller windows in the range of 1 to 2 volts can be used, because the device operation becomes independent of the variations in the device switching characteristics.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Self Differential Sensing of MNOS Memory Arrays

Described is a sensing system which makes it possible to use much smaller device threshold windows than conventional sense schemes, and to provide increased memory retention time. It is known that switching characteristics of metal-nitride-oxide semiconductor (MNOS) and metal-alumina-oxide semiconductor (MAOS) memory devices are a very sensitive function of the thin SiO(2) layer thickness. Variations in this SiO(2) thickness occur over the area of an MNOS memory array, and hitherto have made it necessary to use relatively large threshold windows in the range of 5 to 10 volts. Using this new self- differential sense scheme, much smaller windows in the range of 1 to 2 volts can be used, because the device operation becomes independent of the variations in the device switching characteristics.

Fig. 1 shows the voltage levels which would be used in the operation of a typical MNOS memory array with the conventional sensing scheme. In the conventional read schemes, the read voltage; V(Read); must be less than the MNOS's high-threshold state; V(T) (High) or the read output signal will give a false reading. This constraint that V(T) (High) must be greater than V(Read) determines the devices usable retention time, and also the number of cycles before device fatigue becomes unacceptable. With the new scheme, this constraint does not apply and it is possible to sense devices when the high- threshold state has drifted below the read voltage level, as illustrated in Fig. 2.

The array structure for the new scheme is shown in Fig. 3 for a 2 x...