A new method for measuring the coupling coefficient of a split-gate flash EEPROM without an additional test structure

A new method for measuring the actual coupling coefficient of a split-gate flash EEPROM whose floating gate voltage is controlled by the source voltage is presented, which uses no additional test structure or nonfloating gate TEG. In this method, the subthreshold current is measured twice as the source voltage is increased after the control gate transistor has turned on sufficiently. After the drain voltage is slightly altered (/spl Delta/V), the subthreshold curve is a/spl middot//spl Delta/V shifted from the previous one. The coefficient a obtained by this method agrees with the value obtained by the well known subthreshold slope method using a test structure.