On-chip LDO voltage regulator failure analysis and yield improvement

Low dropout (LDO) voltage regulators are extensively used to provide a stable power supply voltage independent of load impedance, input voltage variations, temperature, and time. The increasing number of portable applications has led LDO circuit design into portable application chips which include embedded NOR type Flash, Mixed Signal/RF products, chip cardiac pacemaker and so on to maintain the system voltage independently of the state of battery charge. On-chip LDO voltage regulator function fail is one of major yield impact item and also reliability concern of portable system, but less FA article discussed, the electric FA and PFA in this paper. Two on-chip LDO circuit FA case analyzed by combining different failure analysis methods and tools. ILD CMP scratch and RPO etching damage confirmed by duplication on experimental wafers.