FIB on Test Board

Abstract

This paper offers an alternative solution in dealing with Focused Ion Beam (FIB) circuit edit debug of RF products that often required soldering the device onto a test board to enable sensitive RF characterization. Performing FIB circuit edit while the device is soldered on a test board not only eliminates signal degradation and inconsistency caused by a socket; but also, it allows for adding additional FIB edits on the same device. The conventional way of RF product debug of devices in a wire bond package was to characterize the device in a socket, perform the FIB circuit edit, encapsulate the cavity to protect the device from physical & thermal damage, solder the device onto the test board, and then perform post-FIB characterization. This is a very long, one-way process and needs multiple devices for design debug. For RF products in flip chip package, this approach was extremely difficult to almost impossible, because thermal stress of soldering device would significantly deform thinned die. All characterization had to be done with a socket, which often introduced changes of the same magnitude of the parameters of interest as well as repeatability issues. The purpose of this paper is to outline steps to allow for the RF FIB and characterization cycle to be done in a way to decrease throughput time and increase measurement accuracy. True characterization of highly sensitive RF circuit modifications is achieved through: soldering the device to the test board, performing sample preparation, preforming pre-FIB characterization, preforming FIB, and finally preforming post FIB characterization. Elimination of the need to solder a thinned device to a test board allows for the edit location to remain open enabling additional FIB edits to be performed on the same device. This eliminates redundant steps in the device sample preparation and enables quicker throughput times.