Advanced Physical Failure Analysis Techniques Using 3D Rotation Imaging from Plane-View TEM Sample

Abstract

Dual beam focused ion beam (DB FIB) systems have been widely used for transmission electron microscopy (TEM) samples preparation in failure analysis for semiconductor device [1][2]. However, the sampling size of TEM sample is very limited, particularly for a cross-section and threedimensional (3D) sample. Therefore failure area by electrical test is usually too large to give accurate defect location. As a result, the failure site must be accurately located before FIB milling to prevent from missing target. FIB technique for dual-direction TEM analysis using both plane-view and crosssection samples from the same site previously has been reported because the plane-view sample has large area of inspection and therefore allows one easily capture the failure site [3]. However it would be difficult to prepare TEM sample since this technique needs attach and detach processes several times. It is also difficult to prepare samples for plane-view and 3D TEM observation which would be an effective method to resolve the physical failure analysis. This results in a less comprehensive understanding of failure structures. To address the above mentioned difficulties, we used the FIB/STEM system equipped with compatible sample rotation holder which allows fast and easy sample preparation [4][5].In this work, we newly developed FIB sample preparation techniques where both plane-view and cross-sectional sample are performed on a single STEM specimen using rotation holder. We also demonstrated advanced techniques of plane-view and 3D STEM sample from the same site. FIG. 1 and FIG.2 show schematic drawing of FIB sample preparation for cross-sectional and 3D sample from plane view sample, respectively. FIB sample preparation was used by Hitachi NB-5000 FIB equipped with compatible sample rotation holder which allows a 360-degree rotation of the sample both the FIB system and the TEM/STEM. The cross sectional and 3D STEM observations were performed with Hitachi HD2700 . FIG. 3 shows TEM image of (a) plane-view and 3D observation at different rotation angles with (b) 0, (c) 90, (d) 180 degrees prepared from plane-view sample. It has been confirmed that the failure is due to silicon substrate dislocations which could induce leakage current.