The NNOS memory transistor has been observed to exhibit a negative shift of the threshold states and a loss of memory retention time after a large number of alternating polarity writing pulses. Oxide breakdown and the resulting creation of fast oxide surface states are correlated with the degradation of the memory performance of the device.

Annealed molybdenum Permalloy sheets of ⅛−1 mil thickness have been photoetched to form transfluxor-element memory arrays utilizing inhibited-flux storage. Operating characteristics are summarized for single elements switched in 21 nsec−3.2 μsec. Some findings are: one to zero information flux ratios of 5:1 to 16:1, one to disturb noise flux ratios greater than 30:1, and Sw values of 1.7 to 0.14 oe μsec. In addition, operation is possible over a temperature range of −70° to +150°C without drive-current compensation. Also, for a ⅛-mil thick element switched in times less than 0.1 μsec, Sw values less than 0.2 oe μsec are obtained, indicating that fast switching may occur partially by uniform flux rotation. Array photoetching is described. Arrays containing 128 and 1152 elements have been fabricated. The latter permit a storage density of 250 000 bits/cu in. to be attained. The arrays receive a stress-relief treatment which results in a signal uniformity of ±3%. Photofabrication of windings has been accomplished also. This process generates continuous windings linking the transfluxor apertures.

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