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edfas.org ELECTRONIC DEV ICE FA I LURE ANALYSIS | VOLUME 24 NO . 2 12 NANOPROBING AT LOW BEAM ENERGY, ADDRESSING CURRENT AND FUTURE NODES Andreas Rummel and Andrew Jonathan Smith Kleindiek Nanotechnik, Reutlingen, Germany andrew.smith@kleindiek.com EDFAAO (2022) 2:12-15 1537-0755/$19.00 ©ASM International ® INTRODUCTION As the structures in semiconductor devices continue to shrink, analyzing individual transistors using nanoprobing techniques becomesmore andmore challenging. Inmany cases, the employed nanoprobing techniques are based on scanning electron microscopy (SEM). However, it has been shown that the incident electron beam can induce changes to a transistor’s behavior. [1] These effects could potentially mask the actual issue that is being explored. Therefore, there is now a requirement to go to very low electron beam acceleration voltages when imaging the devices to be tested. While SEM imagery is typically recorded using beam voltages of some keV (anywhere between 1 keV and 30 keV depending on the sample and application), now it is increasingly common to image samples at acceleration voltages of 100 eV or less. The image quality in an SΕM is governed by a number of factors including, but not limited to, the sample’s con- ductivity andmaterial composition, the cleanliness inside the SEM’s vacuum chamber, magnetic fields inside and outside of the vacuum chamber, as well as the electron beam’s current and acceleration voltage. As indicated above, the factor discussed here is the acceleration voltage. Luckily, modern SEMs are capable of producing high resolution images using electron beam acceleration voltages of less than 100 eV. However, the lower the acceleration voltage, the more susceptible the beam is to disturbances. The second major component in an SEM-based nano- probing configuration, besides the SEM itself, is a set of nanomanipulators that is used to place suitably sharp probe tips onto the transistors’ exposed contacts or onto metal lines used to perform adjacent analyses. These nanoprobing platforms are typically equipped with any- where between four and eight (sometimes even more) individual probers. Each prober can position the sharp probe tip with sub-nm precision. The nanomanipulators must exhibit very high stability (i.e., lowdrift) such that the probe tips remain at the desired positions for the desired length of time. When working at acceleration voltages of 1 keV and more, the (grounded) probe tips’ presence hardly affects the SEM’s image quality. This is because the fast-travelling electrons have large amounts of kinetic energy and inertia and thus are not affected by the additional electric fields Fig. 1 Left, SEM image showing the sample at lowmagnification aswell as eight probe tips arranged along the frame’s perimeter at an acceleration voltage of 1 keV. Right, the same frame at an acceleration voltage of 150 eV.