Foot (bottom corner) measurement of a structure with SPM

摘要

Foot (bottom corner) characterization of a trench or a line in semiconductor processing is of high interest to set and follow processes. The scanning probe microscopes (SPM) available at the present time are not capable of obtaining this measurement. Conventional atomic force microscopes (AFM) are not able to measure the shape of the foot of a trench or a line due to scanning algorithm and probe shape. Even CD-AFM performed with 2 dimensional servo code and boot shaped tips is limited in its ability to make this measurement if the corner is sharper than the radius of the corner of the boot tip used for measurement. We use an extra sharp probe (full cone angle 5 degrees or less) and a technique to tilt the sample to get at the foot of the structure to be measured. We are able to scan this corner of the structure and are able to characterize it by various techniques such as surface roughness. In addition, sidewall, line and line edge roughness can be addressed using the same technique. This characterization can be performed automatically and set as a production control.