XTEM sample preparation for failure analysis in semiconductor devices using high energy ion beam thinning

XTEM investigations are an important tool to characterize the geometry, structure and microchemical composition of semiconductor devices. Over the last 25 years, several thinning procedures have been used, based on Ar ions at about 5 kV. Common to all of them is that the thinning takes several hours, or the ion thinning has to be combined with awkward mechanical preparation steps, like dimpling. The technique described below uses Ar ions up to 15 keV and with a total ion current of up to 0.2 mA. A maximum sputtering rate of 25 mu m/h for Si is reached at an incidence angle of 6 degrees. A low energy thinning step at 3.5 keV is used at the end to reduce the amorphization and heating of the thinnest regions. The combination of this fast ion thinning with simpler mechanical steps requiring only a final lapping step, without the need for dimpling and polishing, results in a yield of nearly 100% and a preparation time of about 3h.