Development of an electron optical system using EB projection optics in reflection mode for EB inspection

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.