Stmicroelectronics S.r.l.

Sgs-thomson Microelectronics S.r.l.

Andrea Colognese

Simone Alba

Emilio Giambattista Ghio

Francedillaois Maugain

Giovanni Rivera

A method for assessing alterations in the dielectric properties of insulating layers on a wafer of semiconductor material induced by plasma treatments. The method includes forming cells of EEPROM type on a wafer with source, drain and control gate surface terminals (pads), subjecting the cells to UV radiation so as to erase them thereby fixing a reference threshold voltage, applying programming voltages of preset value to at least one of the cells and measuring the corresponding threshold voltages, and subjecting this cell to UV radiation so as to restore its threshold to the reference value. The wafer is then subjected to the plasma treatment to be assessed, and the threshold voltages of the cells are measured and compared with the reference threshold voltage so as to derive from the comparison information on the alterations induced on the dielectrics formed on the wafer and on the distribution of the plasma potential.

Method for assessing the effects of plasma treatments on wafers of

The process described requires the formation of floating-gate non-volatile memory cells entirely similar in structure to those produced by known processes. The process comprises an annealing treatment at relatively low temperature (430.degree. C.) to repair damage due to plasma treatments. To obtain threshold voltage values for the cells close to the theoretical values, especially for cells with particularly extended interconnections, the cells are subjected to ultraviolet radiation before the annealing treatment, in order to neutralize any electrical charges present in the floating-gate electrodes of the cells.

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Padua, Italy

Andrea Colognese