Voltage Contrast for Gate-Leak Failures Detected by Electron Beam Inspection

Abstract

We examine a technique for enhancing the voltage contrast (VC) of a failure analysis (FA) tool, defect review scanning electron microscope (DR-SEM). For an SRAM, we demonstrate a dependence of gate-leak VC on the relative angle (RA) between the direction of beam scanning by the FA tool and the lengthwise direction of the gate electrode. Experimental results show that better VC results are obtained when RA is zero, in other words, a beam's scan-line is parallel with the SRAM gate. We propose a simple qualitative resistor-capacitor model to explain this phenomenon. With the help of this VC enhancement technique of the FA tool, we could tune the electron beam inspection (EBI) recipe to an appropriate condition quicker. The cycle time of EBI recipe tuning was shortened from five to two days. As a result, correct EBI evaluation results of countermeasure experiments led us to a yield enhancement solution within a shorter period of time.Index Terms-Dielectric breakdown, electron beams, failure analysis (FA), inspection, integrated circuit (IC) manufacture, leak detection, logic devices, SRAM chips, voltage measurement.

Analysis of Junction Leakage Current Failure of Nickel Silicide Abnormal Growth Using Advanced Transmission Electron Microscopy

“…The junction leakage current failure over 1 times 10 to the power of 5 pA/μm occurs in some transistors randomly. For the first step of failure analysis, to localized fault transistor, voltage contrast (VC) inspection by using scanning electron microscopy (SEM) was performed [17]. And then, in order to reveal the failure cause, we performed failure analysis using advanced TEM techniques.…”

Contact inspection and resistance–capacitance measurement of Si nanowire with SEM voltage contrast

“…VC-based inspection is already established for local contact, gate-leak, and dynamic random access memory capacitor. [4][5][6][7] Failure mode classification was demonstrated by changing the scan direction of EB, considering the device circuit. 8 The VC method should be applicable to NW-SD contact inspection, although there is no experimental verification yet.…”

“…Qualitatively, the impact of changing the scan direction of EB was discussed with an RC model. 7,8 It is already reported that rough estimation of parasitic resistance is only possible by evaluating VC. 10 Pulsed irradiation of EB by a special apparatus has been applied to analyze the charging dynamics, which gives information on both resistance and capacitance.…”

Application of conductive atomic force microscopy to study the in-line electrical defects

“…Electron beam inspection (EBI) methodology, implemented through the use of VC to differentiate the failing site, is widely used in industry for in-line electrical defect monitoring [1][2][3]. It provides timely information on the factors for yield detractors so that proper steps can be taken to rectify the problems promptly.…”