Texas Instruments Corporation

Keith A Remack

John Anthony Rodriguez

Carl Z Zhou

Boku Katsushi

John Lane Gertas

Disclosed embodiments include a testing system that electrically connects to an integrated circuit (IC) having ferroelectric memory (FRAM) cells. The testing system programs the FRAM cells to a first data state and then iteratively reads the programmed cells at a plurality of reference voltages to identify a reference voltage limit that indicates a first occurrence at which at least one of the cells fails to return the first data state when read. Iteratively reading the cells includes reading each cell at an initial reference voltage at which all the cells return the first data state, and then reading each of the programmed cells at each of the remaining reference voltages by incrementally changing the initial reference voltage in one direction until the reference voltage limit is identified. The testing system sets the reference in the IC at an operating level based on the reference voltage limit.

Setting of reference voltage for data sensing in ferroelectric memories

A method of setting the reference voltage for sensing data states in integrated circuits including ferroelectric random access memory (FRAM) cells of the one-transistor-one capacitor (1T-1C) type. In an electrical test operation, some or all of the FRAM cells are programmed to a particular polarization state. A 'shmoo' of the reference voltage for sensing the data state is performed, at one or more worst case electrical or environmental conditions for that data state, to determine a reference voltage limit at which the weakest cell fails to return the correct data when read. A configuration register is then written with a reference voltage based on this reference voltage limit, for example at the limit plus/minus a tolerance.

A method () of identifying failing bits in a ferroelectric memory device including at least one ferroelectric capacitor includes () writing same state data to the first capacitor, and () baking the first capacitor for a first specified period of time at a first selected temperature. A same state read () is performed on the first capacitor after the baking. Based on the results from the same state read, it is determined whether an error occurred. The first specified period of time can be from 10 minutes to 2 hours and the first selected temperature can be in a range from 85&#xb0; C. to 150&#xb0; C. A repair can be performed () to corrected detected errors. A related method () can detect imprinted bits using a same state write (), followed by a relatively high temperature bake (), then a same state read (). An opposite state date write () is performed followed by a relatively low temperature bake (), and then an opposite state data read () to identify opposite state error or imprint.

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Richardson, TX, United States of America

Keith A Remack