Investigation on Metal Pillar Defect in sub-micron CMOS Technology

We have investigated the metal pillar defect induced by tungsten (W)-plug missing inside contact hole sitting on the long W-plug LIL trench line in sub-micron CMOS technology. It is found that W-plug LIL trench line may have a seam due to high aspect ratio, resulting in W contact-plug missing caused by out-gassing from a seam inside the long trench LIL line. This missing W contact-plug can make defect like pillar shape after metal etch. The key process parameters for W contact-plug missing to cause metal pillar defect have been discussed. We reported the importance of process optimization on W-gap filling at LIL stage to avoid both W contact- plug missing and the metal pillar defect by proposing the methods to obtain better process margin.