Double Patterning lithography is very fascinating way of lithography which is capable of pushing down the k1 limit below 0.25. By using double patterning lithography, we can delineate the pattern beyond resolution capability. Target pattern is decomposed into patterns within resolution capability and decomposed patterns are combined together through twice lithography and twice etch processes. Two ways, negative and positive, of doing double patterning process are contrived and studied experimentally. In this paper, various issues in double patterning lithography such as pattern decomposition, resist process on patterned topography, process window of 1/4 pitch patterning, and overlay dependent CD variation are studied on positive and negative tone double patterning respectively. Among various issues about double patterning, only the overlay controllability and productivity seemed to be dominated as visible obstacles so far.

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It is the first time that the high-k/metal gate technology was used at peripheral transistors for fully integrated and functioning DRAM. For cost effective DRAM technology, capping nitride spacer was used on cell bit-line scheme, and single work function metal gate was employed without strain technology. The threshold voltage was controlled by using single TiN metal gate with La 2 O 3 and SiGe/Si epi technology. The optimized DRAM high-k/metal gate peripheral transistors showed current gains of 65%/55% and DIBL improvements of 52%/46% for nMOSFET and pMOSFET, respectively. The results in process yield, performance, and reliability characteristics of the technology on 4Gb DRAM have shown that the gate-first high-k/metal gate DRAM technology can be regarded as one of the major candidates for next-generation low power DRAM products.

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