An electron beam inspection system based on the projection imaging electron microscope was developed and the proof-of-concept system has been constructed and evaluated. The secondary electrons are projected through the projection imaging optics and imaged onto the image detection system. The projected secondary electron image is amplified by the microchannel plate and converted to an optical image by the fluorescent screen and detected by the 2048 element, eight-tap time delay and integration (TDI) image sensor. The stage is linearly moved in synchronism with the TDI signal output data rate, and then, the secondary electron image is continuously captured. The spatial resolution of around 0.1 μm has been obtained in this experiment. Several images obtained by the TDI imaging mode are also demonstrated.
Electron beam inspection system based on the projection imaging electron microscopeIn the semiconductor industry, the inspection technique using an electron beam is expected to play an important role because of its high spatial resolution. In comparison with conventional scanning techniques, direct imaging produced by projection optics offers both faster mapping rates due to parallel detection and higher resolution. An electron microscope based on the projection imaging optics has been designed and constructed. Secondary electrons emitted by the area exposure are projected through the projection optics consisting of fully electrostatic lenses, and then imaged onto the image detection system. A computational analysis indicates resolution of 0.27 m which can satisfy both adequate resolution and image grab time. An image of a 0.2 m design rule device is demonstrated.
We have developed a proof of concept system, utilizing a projection electron microscope for the next generation EB inspection system. In this POC system, the image quality of secondary electrons is quite sensitive to the homogeneity of wafer surface potential. In logic devices with a random pattern layout, both image distortion and inhomogeneous image contrast are serious problems. By homogenizing the wafer surface potential with negative charging of the semiconductor device, we could eliminate image distortion and inhomogeneous image contrast using a pretreatment dosage of 12 mC/cm 2 . Furthermore, by imaging the reflection electrons with 4000 V, a high image quality can be obtained, even with contact/via layers. By selecting the optimum energy of the imaging electrons, the imaging capability of this EB inspection system could be widely improved. We can also confirm the practicality of this technology for wafer inspection of ULSI devices.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.