The study and investigation of inline E-beam inspection for 28nm process development

Abstract

The research aims at the VC (voltage contrast) of contact-loop defects in 28nm processes. A new type defect, contact W (tungsten) missing, was found during process developments, and the designed inline E-beam inspection was used to detect those defects by their VC features. The mechanism of defects and the method of the enhancement of the detection were described. An extreme high signal E-beam scan recipe is required in corresponding to the unique defect wanted and, in doing so, the partial-opened W missing defects can be found. Since the defect can be detected instantly by E-beam inspection, and therefore an inline monitoring index can be set up. Compared to the end-of-line electrical test, this inline monitor is very much closer to the trouble process and shrinks the response time. The following process experiments and evaluation can be instantly verified and examined. Finally, the W missing defect was fixed by an optimization of CT Etch process and controlling of CT loop minienvironment. Instead to the debug method of failure analysis, E-beam inspection can speed up 8nm development.