New AFM imaging for an inline LSI process monitor

Abstract

New imaging technique in AFM has been developed to suppress bending of the sharpened probe during scanning. After analyzing the bending of probe, it is clear that the bending is caused by response of servo control and slipping of the probe on the slope. It is needed that we do not scan the probe under contact of it on a sample surface for friction- free and we approach it to the surface at a contact force of < 10nN for slip-free. The technique controls the probe such that approaching and gap-controlling are done without scanning after only one step xy-scanning is competed, and the xy-scanning is done without servo controlling after lifting the probe up from the sample surface. This technique permits to use very sharped and slim probe and to observe a steep structure such as a dry-etched groove and hole, and a photoresist pattern with a high aspect ratio faithfully. We can clarify that it is possible to apply this technique to monitoring the steep structures as an in-line process monitor in the LSI process without cracking the wafer.