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I. INTRODUCTIONO N-FIELD operation of Flash memory arrays typically involves arbitrary time sequences of program/erase (P/E) cycles and idle periods, with the possibility for temperature to change within a wide range of values. The high electrical stress determined by P/E cycles on the cell tunnel oxide gives rise to charge trapping therein, impacting the array P/E performance [2]-[9] and determining threshold-voltage (V T ) instabilities when cells should instead keep their V T level, i.e., their datum, in time [7], [10]-[15]. V T instabilities come from Manuscript

This paper and the corresponding Part II [1] revisit charge trapping and detrapping in Flash memories considering some major features of the phenomenon which have been clearly detected on nanoscale technologies: charge discreteness, statistical charge capture and emission, statistical distribution of the threshold-voltage shift following a charge capture/emission event, and spectral distribution of the detrapping time constants over many decades of time. In this Part I, we address thresholdvoltage instabilities following charge detrapping from the cell tunnel oxide, highlighting their statistical properties and coming to a powerful formula for their quantitative analysis. These results pave the way to the development of a comprehensive statistical model able to deal with charge trapping/detrapping during whatever on-field array operation, representing the topic of Part II.

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In this work, we present a reliability investigation of T-RAM cells, considering their read failure, data retention and endurance. Experimental results on deca-nanometer devices reveal a successful cell operation solving the voltage trade-off for optimal performance on state-0 and state-1, whose origin is explained by clear pictures of the physical processes giving rise to read failure and limiting data retention. Moreover, endurance results appear very promising, with cell functionality preserved up to very high cycling doses.

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