ELECTROSTATIC DISCHARGE FAILURE FACTOR OF LSIS AND A NEW METHOD FOR MEASURING IT

The electrostatic discharge (ESD) sensitivities of highly refined ULSI s should be evaluated by a test method based on the direct-charging ch arged device model (D-CDM) or the field-induced charged device model ( F-CDM). The CDM features nanosecond transient response and high peak c urrent, as compared with the human body model (HBM) and the machine mo del (MM). However, the MM and CDM failure factors have not been invest igated sufficiently. Therefore, the MM and CDM withstand voltages coul d not be adopted as the criterion values to judge whether the electric potential of the charged objects containing LSIs damaged the LSIs or not. Concerning the F-CDM in particular, the mobile charge induced by the electrostatic charge has not been quantified. In this paper, we fi rst re-examine the test results of the MM and show that the failure fa ctors of PN junctions can be expressed by constant energy. Second, con cerning F-CDM, we define and calculate the excessive mobile charge ind uced by the electrostatic charge. Third, we propose a new coulomb mete r that allows measurement of the excessive mobile charge. The coulomb meter is also effective for the D-CDM and the MM. Applying the coulomb meter to the D-CDM test of LSIs, we found that the CDM failure factor of a logic MOS LSI was expressed by a constant charge. Moreover; in a ctual manufacturing lines, we could easily measure the excessive mobil e charge and the device capacitance. Those measurements were not possi ble until now, and thus the data we obtained is very important in orde r to carry out ESD controls. (C) 1998 Scripta Technica.