AFM tips for 58 nm and smaller node applications

The direct depth measurement of structures with aspect ratios between 1 and 4 in the arrays of memory cells represents a major challenge for inline metrology. For 75 nm and larger technology nodes these measurements are carried out using inline AFM using 50±5nm diameter cylindrical AFM probes. However, for 58 nm and smaller technology nodes these AFM probes are not capable anymore, because the tip diameter is comparable to the diameter of the trench structures themselves. Here we report about the development of 30 nm diameter cylindrical AFM probes suitable for direct depth measurements of 58 nm ground rule (GR) structures. The focus of the development was on tip lifetime, gage capability and throughput in a high volume environment. For the tests two different tip materials - silicon (Si) and electron beam deposited (EBD) carbon were investigated. Both tip types proved to be fully gage capable, and showed no throughput losses in comparison to larger node measurements. T he tip lifetime under production conditions however needs further improvement