With manufacturers now capable of creating transistors in the 5-7 nm node range, the ability to isolate, inspect, and probe individual metal and via layers is of the utmost importance for defect inspection and design validation. These isolated layers can be inspected for defects via SEM, provide design validation, or tested with electrical probing for failure analysis. The work herein describes a functional workflow that enables manufacturers to perform this kind of sample preparation in an automated fashion using plasma focused ion beam (FIB) technology. The workflow is scalable and can be used in both lab and fabrication environments.

This paper presents a method for determining positional variation and offsets in high aspect ratio etches used in the production of 3D NAND devices. The method uses a 3D fiducial as a positional reference in the field-of-view, which not only allows for high precision tracking of features through the depth of the device, but also aids in the alignment of images when performing 3D reconstructions. The workflow is based on plasma dual beam diagonal milling, which allows users to characterize structures through the device stack at a much higher throughput/slice than conventional methods, enabling enhanced process monitoring and control.

In this paper, we describe automated FIB for TEM sample preparation using iFast software on a Helios 450HP dual-beam system. A robust iFast automation recipe needs to consider as many variables as possible in order to ensure consistent sample quality and high success rate. Variations mainly come from samples of different materials, structures, surface patterns, surface topography and surface charging. The recipe also needs to be user-friendly and provide high flexibility by allowing users to choose preferable working parameters for specific types of samples, such as: grounding, protective layer coating, milling steps, and final TEM lamella thickness/width. In addition to the iFast recipe, other practical factors affecting automation success rate are also discussed and highlighted.