**9. References**

452 Recent Advances in Nanofabrication Techniques and Applications

nearly zero. TIS 3 reported is from multiple fields (9 fields for all 1D targets, and 15 fields for the 2D targets); with *OVL*0 and *OVL*180 results averaged over 15 load/unload cycles respectively. By removing the contribution from dynamic variations for each loading angle,

All three types of standard 1D DBO targets have shown excellent performance with TMU <0.1nm and the 2D 1x1 target has a TMU ~0.2nm (not including tool matching). It is worth mentioning that the mDBO 2x2 target has better TMU, which is a good balance between measurement performance, target size, and measurement time. Similar performance is also

**Technology DYNP (nm) TIS Avg (nm) TIS 3 (nm) TMU\***

**Targets X X X X**

eDBO 1D 2x4 target 0.088 -0.006 0.029 0.092

mDBO 1D 2x2 target 0.050 -0.006 0.028 0.058 mDBO 1D 2x1 target 0.085 0.005 0.042 0.095

mDBO 2D 1x1 target 0.172 0.057 0.120 0.209

Table 6. Performance summary of eDBO and mDBO targets (\*TMU does not include tool

The multi-pad empirical diffraction-based overlay (eDBO) technique is capable of controlling the overlay in double patterning optical lithography processes (DPT). The usable range of LELE DPT eDBO is ±70nm. eDBO results agree well with traditional image-based overlay (IBO) results and with overlay calculated from CD-SEM data. While good correlation and linearity between DBO and IBO was observed, a significant systematic offset can occur that appears to originate in the IBO data. Reduction in the number of pads from

DBO measurements have near-zero TIS. TMU (including tool-to-tool matching) is less than 0.5nm for both the LELE and freeze process. The overlay errors determined by eDBO (4 pad measurement) agree well with modeled DBO (2 pad measurement) data. This ability to model the signal formation process allows model-generated spectra to be used to predict

Simultaneous model-based measurement of overlay in X&Y (2D mDBO), is possible with good results and also allows reduction in the overall target size. mDBO requires knowledge of the film stack, material optical properties and target layout and consequently more effort in creating recipes than eDBO but provides significant value in reducing measurement time

2x4 to 2x3 results in only a small deterioration in precision.

measurement precision with good success.

TIS 3 is very small (on the order of 0.01nm

observed for Y.

matching)

**7. Conclusion** 


**Other Lithographic Technologies: Scanning** 

**Probe, Nanosphere, Inkjet Printing, etc.** 

[17] B. Schultz, US Patent 7099010 "Two-dimensional structure for determining an overlay accuracy by means of scatterometry" **Part 5** 
