With the 14nm technology node becoming a reality at today's state-of-the-art semiconductor manufacturing plants and the 10nm node actively being planned for, device structures have shrunk well beyond the minimum conventional transmission electron microscope (TEM) sample thickness: 50-100nm. This paper addresses the challenges in TEM sample preparation of sub 22nm three-dimensional test structures. As semiconductor device technology continues to shrink and become more complicated with the addition of three-dimensional device integration, unique sample preparation challenges will continue to arise. This opens the door to novel solutions for these problems like the one presented in this paper: an issue that arose where TEM projection effects interfered with proper characterization of a finFET test structure.

Imaging tomography by transmission electron microscopy (TEM) is a technique which has been growing in popularity in recent years, yet it has not been widely applied to semiconductor defect studies and root cause determination [1- 3]. In part this is due to the complex equipment, computing needs, and microscope time required to generate the various images which ultimately compose the data set. However, the latest generation of TEMs—with their high level of stability and automation—are greatly reducing the resource needs to create high quality and informative movies of defects rotating about a central axis. One significant advance is the reduction in time required to fabricate a sample and perform the data acquisition by TEM. Today’s microscopes allow for sample fabrication to take place in a few hours or less and can acquire more than 100 images in about an hour at different sample tilt conditions with minimal analyst intervention. This paper describes using automated TEM sample preparation with dual beam focused ion beams (previously reported [4]) in conjunction with automated tomography software on a state-of-the-art TEM. By using an advanced tomography holder ±70° of tilt can be obtained. This is a powerful way to view defects as the failure can be viewed through more than 90° of rotation. Consequently a more complete understanding of the failure site can be obtained over a typical single projection TEM image. This can greatly facilitate root cause determination in a timely manner.

This paper deals primarily with the difficulties and solutions to STEM sample preparation. The dual beam focused ion beam (DBFIB) whole wafer platforms often come with scripting features which allow the tool to operate with a high level of automation. The main focus of the paper is on the variety of challenges which are encountered in trying to implement automated STEM and TEM sample fabrication with minimal operator input and the engineering solutions implemented to overcome the challenges. The paper demonstrates that the challenges with making STEM and TEM samples in a highly automated fashion by DBFIB, while difficult, are not insurmountable. It has highlighted a mechanical issue with the ion aperture motor mechanism, which required extensive troubleshooting to fully diagnose and correct. A long standing software routine had to be modified to fully enable script automation by extending the beam dwell time of the automatic brightness contrast routine.