Dummy Active Area Insertion

FIGURE 12.16 Schematic cross section of a wafer without optimization (above) and with dummy active area insertion optimization (below). 

Fig. 12.17). The additional mask required for OE is a reversed copy of the STI mask with reduced structure size. RIE then removes the oxide in the exposed areas, stopping on the nitride. After RIE of the oxide and resist removal, the remaining nonplanarity at the periphery of the active areas is easily removed with CMP. The planarity results are excellent (Fig. 12.18), and unlike in the case of dummy insertion, planarity improvement is achieved without a negative impact on performance. The main disadvantage of the technique is the increased process complexity due to the additional lithography and RIE steps. 

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