Tungsten Plug ETCH Process in IGBT Manufacturing

The most common method of forming tungsten (W) plug is to etchback (EB) a blanket layer of W film and leave only the plugs intact. Two major challenges are high selectivity to the underneath barrier layer, and W residue free on a step height of topography. This paper designed W plug EB process with high etch selectivity and endpoint control model in IGBT manufacturing. Especially, thick tungsten layer can be rapidly removed by SF6/CF4chemistry with high etch rate at the beginning of the process. The applicable O2gas ratio can increase etch selectivity of tungsten to titanium nitride (W/TiN), and we precisely trigger etch endpoint by optical emission spectrometer (OES) to avoid damage titanium nitride layer at over etch step. Finally, the results show that the metal residues localized stair high spacer had been completely removed, and TiN etch stop layer had no damage. Besides, we also achieved depth controllability of tungsten recess in contact holes.