The move of EUV into semiconductor manufacturing has created new challenges to continued scaling with an increasing importance of metrology & inspection. There are limitations for current in-line metrology technologies that require new approaches. Dan Hutcheson has a conversation about this with Peter Jenkins, from Infinitesima, where he’s President & CEO.
Semiconductor devices — with tolerances at atomic levels — now have 3D problems due to use of atomic processes such as ALD and ALE, or Atomic Layer Deposition and Atomic Layer Etch. High NA EUV in development will only make matters worse. The challenge in scaling is moving to atomic level precision needs. Or to paraphrase Intel fellow Mark Philips from his SPIE keynote last year, ‘we are entering a Golden Age for metrology because when yield is limited by EPE better metrology has a compelling ROI.’ ICs sensitive to part per trillion failure rates there is a growing technical challenge for this undervalued sector of the equipment industry. Optical metrology lacks the resolution needed to capture local device information. This creates an opportunity for alterative techniques a leading candidate of which is Atomic Force Microscopy or AFM which brings true surface information. AFMs rely on detecting the atomic force interactions between a probe and the surface enabling sub nano-meter measurement of surfaces in 3D. Used in Semiconductor labs for many years they have been restricted for in-line applications due to their speed and probe lifetimes/cost. One approach to address the limitations of e-beam and optical techniques is hybrid metrology combining the strengths of the different techniques. Infinitesima developed an alternative approach to AFM they call Rapid Probe Metrology or RPM. Like traditional AFMs it uses atomic force interactions to detect the surface of a wafer. However, the system probes the surface in a completely different way measuring each pixel separately to avoid probe damage and can operate at extremely high bandwidth due to a different activation technique and measuring with the pico-meter accuracy of an integrated interferometer. Importantly, they designed RPM to be modular allowing integration into other equipment for hybrid applications. It’s been integrated for mask repair verification by Zeiss and is currently being tested in a leading Defect Review SEM for wafer applications. The ability of RPM to operate at much higher speed than classical AFMs and address the operating cost issue of the probe also opens up the opportunity in the future for standalone applications. Furthermore, Infinitesima’s optical implementation of probe actuation and measurement brings an opportunity for parallelisation for further future productivity scaling.