AL-REFLOW PROCESS WITH A CAP-CLAMP FOR SUBMICRON CONTACT HOLES

Abstract

The use of ''cap-clamp'' has been demonstrated for extending the process margin of Al-reflow process. To evaluate the process window of Al-reflow with and without the ''cap-clamp'', two major factors of in-situ annealing temperature and time were varied between 500-560 degrees C and 40-90 seconds, respectively. Sub-micron contact holes were completely filled by heating wafers at 500 degrees C or higher temperatures by adopting the ''cap-clamp'' to the conventional conduction heating system. The effect of the ''cap-clamp'' comes from the improved heating efficiency of the wafer by introducing hot Ar gas into the inner space of ''cap-clamp'', resulting in faster ramp-up as well as more effective heating of the front-side of the wafer. Al-reflow with the ''cap-clamp'' gives wider process window than that of the conventional heating method and realizes the contact planarization of 256 Mbit dynamic random access memory (DRAM) and beyond.