Direct channel length determination of sub-100 nm MOS devices using scanning capacitance microscopy

As MOSFET channel lengths are scaled to below 100 nm, the determination of the effective channel length, L/sub 0/ becomes increasingly important. We have studied cross-sectioned MOSFETs with gate lengths down to 90 nm using scanning capacitance microscopy (SCM), and show the first images of these state-of-the-art devices. Using a device simulator we have quantitatively established the relation between L/sub 0/ and the SCM response in the channel region, allowing us to determine L/sub 0/ from the SCM measurements. We have explored the ultimate resolution attainable using this technique; experimentally, using very sharp probe tips and with numerical simulations.