New CMP Pad Conditioners with Increased Number of Diamond Tips for Longer Dressing Life

Abstract

With the relentless progression of Moore's Law toward sub-virus sized (e.g. 28 nm) node of interconnected circuitry (IC), and also the planned debut of 450 mm wafers for 2015, CMP reaches a bottleneck that the polishing of the delicate IC wafers must be achieved by effective deglazing of pad with the extended life of dressers (diamond disks). The conventional diamond disks are made by bonding individual diamond grits by either brazing or electroplating. Brazing can allow higher protrusion of diamond tips that facilitate the deglazing process, but the tips leveling cannot be controlled due to the melting of the braze powder at high temperature (e.g. 1000 C). On the other hand, electroplating may improve the leveling of diamond tips, but the protrusion is limited (e.g. 50 microns) so the deglazing of metal layers cannot be achieved efficiently. Moreover, all pad conditioners today used an array of diamond grid that was invented by Dr. James Sung back in 1997. Due to the alignment of the diamond tips, the pad dressing may not be uniform so the wafer polishing could not be uniform. Worse still, deep penetrating diamond tips may be chipped and cause scratches on expensive IC wafers. Here we introduce the world's first diamond disks that are brazed with amorphous alloy without using powder and binder. Amorphous alloy can allow uniform melting across the diamond disk surface and also avoid the presence of residue carbon from charring of binder. Additionally, we use concentric rings of diamond placement that avoids stress concentration on certain diamond tips. Due to the improved process design, we have demonstrated a significant increase of working diamond tips from conventional number of a few hundreds to over one thousand. This can be seen by indenting diamond disks on colored films spread on a flat platform. Our diamond disks have been tested on CMP process with high removal rate of IC wafers and we expect that the life time may be at least twice of conventional diamond disks. This can allow the dressing of large pad such as that for polishing future 450 mm IC wafers.