Electrostatic discharge failure factor of LSIs and a new method for measuring it

Abstract

The electrostatic discharge (ESD) sensitivities of highly refined ULSIs should be evaluated by a test method based on the direct-charging charged device model (D-CDM) or the field-induced charged device model (F-CDM). The CDM features nanosecond transient response and high peak current, as compared with the human body model (HBM) and the machine model (MM). However, the MM and CDM failure factors have not been investigated sufficiently. Therefore, the MM and CDM withstand voltages could 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 first re-examine, the test results of the MM and show that the failure factors of PN junctions can be expressed by constant energy. Second, concerning F-CDM, we define and calculate the excessive mobile charge induced by the electrostatic charge. Third, we propose a new coulomb meter 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 actual manufacturing lines, we could easily measure the excessive mobile charge and the device capacitance. Those measurements were not possible until now, and thus the data we obtained is very important in order to carry out ESD controls. © 1998 Scripta Technica, Electron Comm Jpn Pt 2, 81(4): 38–49, 1998