S. Doering, R. Harzer, W. Werner, Qimonda Dresden GmbH & Co. OHG, Dresden, Germany

Summary: Our data confirms the effect of electron beam induced alteration of integrated devices. It could be shown that several parameters influence the investigated device like beam acceleration voltage and dose used for radiation. It is also shown that several device parameters are affected. Differences to the unexposed transistor are visible for IOFF, IL and ION as well as for the VTH. Whereas the device leakage currents increase with higher exposure, the ION values decrease. The VTH values shift to higher values. From our point of view the increase of the IL can be explained with trapped electrons at the interface between gate oxide and active area. Since charge carriers are available at the transistor channel the conductivity between the source drain regions is increased leading to a raised leakage current. The decreasing of ION currents might be explained by an increase of the resistance of the source drain regions whether to the underlying nwell or to the connecting source-drain contact. Diode characteristics of the source drain contacts to the nwell support this hypothesis. It is also shown that the electron beam irradiation leads to gate oxide degradation. In conclusion and as an answer to our initial questions it is possible to state that measurements with our available SEM based prober are possible, but under certain SEM parameters as low VACC and low doses. Only at those SEM parameters the electron beam influence on electrical device parameters is negligible. Our studies also show that it is from major importance to know the sample history before electrical device characterizations are carried out. This is due to the electron beam induced device parameter changes are nearly unaltered over a long period of time after the beam exposure.