Flat spectral response of a CMOS photodiode using wedge structures in back-end SiO2.

CMOS photodiodes are used in many light sensing applications; however, the performance can be limited by oscillations in the spectral response caused by light interference from the back-end oxide. Gray-scale lithography has been used to fabricate wedge-like structures in the back-end oxide, which reduces the light interference and oscillations over the entire silicon sensitivity range. Dielectric filter stacks have been deposited on top of the structures, demonstrating an improved spectral response over photodiodes, with filters deposited directly on silicon. The present approach is suitable for mass production and fully compatible with CMOS.

Sub-10 nm nanoimprint lithography by wafer bowing.

We introduce the concept of wafer bowing to affect nanoimprinting. This approach allows a design that can fit the key imprinting mechanism into a compact module, which we have constructed and demonstrated with an overlay and resolution of <0.5 microm and <10 nm, respectively. In the short term, this wafer bowing approach makes nanoimprint lithography much more accessible to a broad range of researchers. More importantly, this approach eliminates machine movement other than wafer bowing and shortens the mechanical path; these will enable the achievement of excellent patterning and overlay at a much lower cost. In the long term, wafer bowing is extensible to step-and-repeat printing for volume manufacturing.