page_title: Multiple patterning
section_title: Spacer-is-dielectric (SID) SADP
hierarchical_section_title: Multiple patterning / Spacer-is-dielectric (SID) SADP
caption_attribution_description: Spacer-is-dielectric (SID) self-aligned double patterning (SADP) can effectively reduce the pitch 3x using only two masks. The second mask is already accepted for line cutting.
context_page_description: Multiple patterning is a class of technologies for manufacturing integrated circuits, developed for photolithography to enhance the feature density. It is expected to be necessary for the 10 nm and 7 nm node semiconductor processes and beyond. The premise is that a single lithographic exposure may not be enough to provide sufficient resolution. Hence additional exposures would be needed, or else positioning patterns using etched feature sidewalls would be necessary.
  Even with single exposure having sufficient resolution, extra masks have been implemented for better patterning quality such as by Intel for line-cutting at its 45nm node or TSMC at its 28nm node.
  Even for electron-beam lithography, single exposure appears insufficient at ~10 nm half-pitch, hence requiring double patterning.
  Pitch double-patterning was pioneered by Gurtej Singh Sandhu of Micron Technology during the 2000s, leading to the development of 30-nm class NAND flash memory. Multi-patterning has since been widely adopted by NAND flash and RAM memory manufacturers worldwide.
context_section_description: In self-aligned double patterning (SADP), the number of cut/block masks may be reduced or even eliminated in dense patches when the spacer is used to directly pattern inter-metal dielectric instead of metal features. The reason is the cut/block locations in the core/mandrel features are already patterned in the first mask. There are secondary features which emerge from the gaps between spacers after further patterning. The edge between a secondary feature and the spacer is self-aligned with the neighboring core feature.
caption: SID SADP has 3x the resolution with allowing the extra mask for line cutting.
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