Abstract:
Next generation 3D/chiplet technology will require extremely high interconnect-density (>106/mm2) for die to wafer/wafer to wafer interconnection. Since the interconnect depends on metal to metal and dielectric to dielectric bonds, surface topography is critical for quality bonding. The hybrid bonding surface must reach atomic-scale smoothness for the entire 300 mm diameter wafer. The current tool of choice for metrology is atomic force microscopy (AFM) which measures a small local area at a time and is very slow. At RPI Physics department, using the matter wave property of electrons in quantum physics, we show for the first time the use of reflection high-energy electron diffraction (RHEED) where a glancing incident electron beam scatters over a large area of hybrid bonding surface. It measures quantitatively the atomic scale smoothness [1] of chemical mechanical polished wafer surface. This promising technique offers a large-area, fast real-time, high-resolution, and non-destructive, metrology solution for atomic scale surface roughness measurement [2]. It will improve yield in chiplet production.
[1] Jason Drotar, Toh-Ming Lu, and G.-C. Wang, J. Appl. Phys. 96, 7071 (2004). https://doi.org/10.1063/1.1811785
[2] Patent Reference: P202500264US01; Invention Reference: P202500264
Title: Electron beam glancing angle scattering for fast atomic scale roughness measurement over large semiconductor builds. Inventors: RPI - Weichang Lin, James Lu, Toh-Ming Lu, Gwo-Ching Wang. IBM - Roy Yu, Nicholas Alexander Polomoff, Katsuyuki Sakuma
Bio sketches: Dr. Gwo-Ching Wang, the Rensselaer Travelstead Institute Chair, was the head of the Physics Department at Rensselaer Polytechnic Institute (2000-2010). She was the Director of the NSF IGERT program (2005-2012), DOE GAANN program (2004-2008), and the NSF REU program (1991-2012) at RPI. She is Fellow of APS (1996), AVS 1(997), AAAS (2004), and MRS (2017). She is recipient of APS Davisson Germer Award (2025). Her recent research interests are optoelectronic properties of energy materials, wafer scale epitaxial monolayer TMDCs and multilayer TMDC on GAN and AlN heterostructures, phase transition, above room temperature Curie temperature magnetic van der Waals layer materials, ultrathin, thin films and nano lines for interconnects, and metrology for hybrid bonding wafer surface. She published three books, several US and international patents, and over 300 peer reviewed journal papers with former graduate and undergraduates.
