issues Multiple patterning entails the use of many processing steps to form a patterned layer, where conventionally only one lithographic exposure, one deposition sequence and one etch sequence would be sufficient. Consequently, there are more sources of variations and possible yield loss in multiple patterning. Where more than one exposure is involved, e.g., LELE or cut exposures for SAQP, the alignment between the exposures must be sufficiently tight. Current overlay capabilities are ≈0.6 nm for exposures of equal density (e.g., LELE) and ≈2.0 nm for dense lines vs. cuts/vias (e.g., SADP or SAQP) on dedicated or matched tools. In addition, each exposure must still meet specified width targets. Where spacers are involved, the width of the spacer is dependent on the initial deposition as well as the subsequent etching duration. Where more than one spacer is involved, each spacer may introduce its own width variation. Cut location overlay error can also distort line ends (leading to arcing) or infringe on an adjacent line. Mixed patterning methods Multiple patterning is evolving toward a combination of multiple exposures, spacer patterning, and/or EUV. Especially with tip-to-tip scaling being difficult in a single exposure on current EUV tools, a line-cutting approach may be necessary. IMEC reported that double patterning is becoming a requirement for EUV. Mixed patterning with overlay sensitivity: Mixed patterning with reduced overlay sensitivity: For line patterning, SADP/SAQP could have the advantage over the EUV exposure, due to cost and maturity of the former approach and stochastic missing or bridging feature issues of the latter. For grid location patterning, a single DUV exposure following grid formation also has the cost and maturity advantages (e.g., immersion lithography may not even be necessary for the spacer patterning in some cases) and no stochastic concerns associated with EUV. Grid location selection has an advantage over direct point cutting because the latter is sensitive to overlay and stochastic edge placement errors, which may distort the line ends. Self-aligned litho-etch-litho-etch (SALELE) is a hybrid SADP/LELE technique whose implementation has started in 7nm and continued use in 5nm. Industrial adoption The evolution of multiple patterning is being considered in parallel with the emergence of EUV lithography. While EUV lithography satisfies 10-20 nm resolution by basic optical considerations, the occurrence of stochastic defects as well as other infrastructure gaps and throughput considerations prevent its adoption currently. Consequently, 7nm tapeouts have largely proceeded without EUV. In other words, the multiple