Observation of deep holes using new technique

Abstract

We discovered the phenomena in scanning electron microscopy that the bottom of deep holes can be observed clearly when a high energy electron beam is irradiated. In order to utilize this phenomena, we developed a novel instrument that generates a scanning electron probe of 50 to 200 keVwith TV-scan rate that enables us to inspect maximum 8 inches diameter wafers.In the past, we could inspect deep holes by observing cross sectional view of a hole milled with a focused ion beam (FIB).1 Using the novel instrument, we can easily inspect such holes without destroying samples. This observation does not depend on the specimen conditions, such as aspect ratio of holes and specimen charging that often occurs in the case of observing insulators. This instrument enables us to observe inside structures of semiconductor devices. Irradiation damage on semiconductor devices, such as threshold voltage and sub-threshold coefficient deviation of MOS transistors can be recovered, except for the irradiated area by means of hydrogen annealing of 30 minutes with temperature of 450 degrees C.

Critical issues in scanning electron microscope metrology

“…17b). Mizuno et al [61] used high accelerating voltage to penetrate the photoresist in order to view the holes. Alternatively, Monahan et al [66] have shown that the backscattered electron signal can be used to image the bottom of the contact holes (Fig.…”

Effect of electron-beam parameters on critical-dimension measurements

“…As for the resist pattern thinning, judging from observations through the HM-2000 SEM, 3 we may also conclude that the electron beam induced resist contraction mainly causes resist patterns to thin. Figure 4 shows measured linewidths by the HM-2000 SEM to support the idea of the electron-beam induced resist contraction.…”