Nanoelectrical Fault Isolation with Multi-Modulations by Atomic Force Microscopy

It is widely acknowledged that Atomic force microscopy (AFM) methods such as conductive probe AFM (CAFM) and Scanning Capacitance Microscopy (SCM) are valuable tools for semiconductor failure analysis. One of the main advantages of these techniques is the ability to provide localized, die-level fault isolation over an area of several microns much faster than conventional nanoprobing methods. SCM, has advantages over CAFM in that it is not limited to bulk technologies and can be utilized for fault isolation on SOI-based technologies. Herein, we present a case-study of SCM die-level fault isolation on SOI-based FinFET technology at the 14nm node.

Atomic force microscopy (AFM) methods have provided a wealth of knowledge into the topographic, electrical, mechanical, magnetic, and electrochemical properties of surfaces and materials at the micro- and nanoscale over the last several decades. More specifically, the application of conductive AFM (CAFM) techniques for failure analysis can provide a simultaneous view of the conductivity and topographic properties of the patterned features. As CMOS technology progresses to smaller and smaller devices, the benefits of CAFM techniques have become apparent [1-3]. Herein, we review several cases in which CAFM has been utilized as a fault-isolation technique to detect middle of line (MOL) and front end of line (FEOL) buried defects in 20nm technologies and beyond.

It has been long recognized that SRAM memory is an ideal vehicle for defect monitoring and yield improvement during process development because of its highly structured architecture and simplified approach using memory bitmapping. However, the success rate of defect detection, especially for soft single-column failures, which is one of the most complex failure modes of an SRAM failure, is decreasing when using traditional physical failure analysis (PFA) with only the bitmap available for guidance due to a variety of invisible or undetectable defects that cause a leakage behavior in the device. In order to understand the leakage behavior in advanced high voltage (HV) processes, conductive atomic force microscope (C-AFM) [1-5] is introduced to perform junction-level fault isolation prior to attempting PFA. In this study, the quantified data extracted using the C-AFM can also be used to establish a connection between the failure mechanism discovered and the soft single column failure mode.