Die-Level Micrometers-Deep Subsurface Imaging for Fault Isolation Using Remote Bias Induced Electrostatic Force Microscopy
Evgheni Strelcov, Lin You, Yaw S. Obeng, Joseph J. Kopanski
In recent years, scanning probe microscopy (SPM) has drawn substantial attention for subsurface imaging, since the ultra-sharp AFM tip (≈10 nm in radius) can deliver and detect, mechanical and electrical signals right above the material's 3D volume with which it is directly interacting. Electrostatic force microscopy, or EFM, is one of the most common atomic force microscopy (AFM) variants for electrical property characterization. In this work, we demonstrate a method to significantly improve EFM's subsurface imaging capability. Unlike conventional EFM, where an AC bias is applied to the cantilever, we applied two out of phase AC biases to adjacent subsurface lines and image the resulting cantilever response at the surface. The resulting remote bias induced EFM (RB-EFM) amplitude shows decent contrast of metal lines with a 2.4 µm spacing buried up to 4 µm beneath the surface. This novel method may resolve lines with horizontal spacing of less than 130 nm at such depth and wider lines to at least 6 µm in depth. In addition, the results are compared with conventional EFM that detects subsurface structure with two independent DC biases. A COMSOL simulation model has been developed that reproduces the essential features of the measurement and explains the improvement of subsurface imaging with RB-EFM compared to other electrostatic force imaging techniques. We show, that by biasing independent lines at a small delta in frequency from the cantilever resonance, multiple line traces can be differentiated in the RB-EFM image.
Conference Proceedings of the 48th International Symposium for Testing and Failure Analysis (ISTFA 2022)
October 30-November 3, 2022
Pasadena, CA, US
International Symposium for Testing and Failure Analysis (ISTFA 2022)
, You, L.
, Obeng, Y.
and Kopanski, J.
Die-Level Micrometers-Deep Subsurface Imaging for Fault Isolation Using Remote Bias Induced Electrostatic Force Microscopy, Conference Proceedings of the 48th International Symposium for Testing and Failure Analysis (ISTFA 2022), Pasadena, CA, US, [online], https://doi.org/10.31399/asm.cp.istfa2022p0426, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935283
(Accessed December 9, 2023)