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MATTHEW BANET, MICHAEL JOFFE, MICHAEL GOSTEIN, ALEX MAZNEV, ROBIN SACCO & FRANÇOISE QUEROMES,
Philips Analytical, Natick, MA, USA

ABSTRACT

The semiconductor industry is gradually replacing aluminium with copper as the metal of choice for interconnects in ICs. Copper interconnects are formed in a dual-Damascene structure that relies on chemical-mechanical polishing (CMP) to remove unwanted copper, leaving only a network of copper-filled Damascene trenches. Unfortunately, CMP of copper often leaves structures that have defects such as non-uniform thickness, rounding, dishing and erosion. To improve polishing performance on copper films and meet CMP’s metrology needs, Philips Analytical presents a cost-effective solution for copper CMP process control. This solution features a novel, opto-acoustic measurement technique, called “impulsive stimulated thermal scattering” (ISTS), that can be used to precisely and rapidly measure the thickness of metal films. This paper describes the ISTS technique and its use for characterising CMP of blanket copper films and CMP of copper Damascene structures.