File:1D vs 2D SAQP.png

The 1D SAQP approach would require extra layers to bridge the interconnections with features aligned in perpendicular direction, and this also requires extra masks. Extra via layers (not shown) would also be needed as well. The 2D SAQP approach saves the extra layers and also does not need as many masks since the blocks/cuts are sparser. The minimum pitch for blocks/cuts is the minimum pitch resolvable by the immersion lithography (~72 nm).

In this drawn example, a 24 nm final minimum pitch is assumed.

Left: 1D SAQP with more than 5 numbered block/cut locations, each number corresponding to a separate mask. Center: 2D SAQP with 1 block/cut mask, reducing the cost, while already including the 1D SAQP pattern. The green features are short paths patterned by SAQP. A single block/cut mask (orange) is generally sufficient.Right: An alternative 2D SAQP, with longer paths, where the green features are patterned by SADP using the gray mandrels, and the red features are gaps between second spacers. No blocks or cuts are needed within this pattern area, but a trim using a cheaper patterning mask would be needed outside this pattern area.

References

• M. C. Smayling et al., Proc. SPIE vol. 8683, 868305 (2013).
• US Patent 8987008, assigned to TSMC.
• US Patent Application 20150021782, assigned to Kabushiki Kaisha Toshiba.