Developments in focused ion beam metrology

We present the ability of a Focused Ion Beam system (FIB) to perform as an effective metrology tool. This feature is a benefit in areas where FIB technology is or can be used, or where pre-measurement cross-sectioning is required, such as the case in Thin Film Head (TFH) trimming, Integrated Circuit (IC) inspection, and Micro-Electromechanical device (MEMS) development. The FIB is a proven tool for taking high-resolution images, performing mills and depositions, and cross-sectioning samples. We demonstrate the FIB's ability to perform these tasks in a repeatable manner and take accurate measurements independently of the operator. First, we find a quantitative method for analyzing the image quality in order to remove any operator discrepancy. We show that this task can be achieved by analyzing the FIB's Modulation Transfer Function (MTF). The MTF is a proven method for measuring the quality of light optics, but has never been used as a standard in FIB imaging because sub-100nm pitch resolution targets can not easily be fabricated; however, we demonstrate a new method for obtaining the MTF. By correlating changes in FIB parameters to changes in the MTF, we have a FIB image standard, as well as an image calibration tool that is transparent to the operator. Second, we describe how current FIB software can use an automated "measure tool" to take accurate measurements independently of the operator. We show that when using both these methods, the FIB is a repeatable metrology tool for a variety of applications.