New atomic force microscopy imaging for an inline large scale integration process monitor

Abstract

New imaging techniques in atomic force microscopy have been developed to suppress bending of the sharpened probe during scanning. After analyzing the bending of the probe, it is clear that the bending is caused by response of servo control and slip of the probe on the slope. It is essential that we do not scan the probe under contact on a sample surface and we approach the surface at a contact force of <10 nN for slip-free operation. The technique controls the probe such that approaching and gap-controlling are done without scanning after the probe has been stepped from pixel to pixel, and the step movement is done after lifting the probe up from the sample surface without servo controlling. This technique permits us to use a very sharpened and slim probe so that we can observe a steep structure, such as a dry-etched groove and hole, and a photoresist pattern with a high aspect ratio faithfully. We clarify that it is possible to apply this technique to monitoring the steep structures with an inline process monitor in the large scale integration process without cracking the wafer.