Ordered nanostructures in semiconductors are a prime platform to study basic nanophotonics and have many applications as photonic crystals. In addition these structures can function as chemical sensors, devices to alter the wetting of liquids on a surface, and capacitors in high-frequency electronics used in mobile phones.

Therefore, COPS has developed a novel CMOS compatible method to fabricate arrays of many deep nanopores in silicon. We have defined the structures with the aid of advanced deep UV lithography in collaboration with ASML.

We optimized the plasma etching method that is also used in industry, to obtain very deep nanopores with world-record depth to diameter aspect ratios. We found that the novel structures behave as high-quality photonic crystals with broad forbidden bands in the telecommunication ranges near 1300 and 1550 nm, see Figures below.

(A) Scanning electron micrograph of an array of pores made by deep UV lithography. The diameter of the holes in the pattern is 462 nm. The distance between the holes is 600 nm.
(B) A cross-section of deeply etched pores. These have a diameter of 423 nm and a high aspect ratio of 15.2. The apparent irregularity on the right side is due to cleaving of the sample.
(C) Optical reflectivity measurement of an array of nanopores that demonstrates photonic crystal behaviour. The peak at 1471 nm is the first order stop band. The scale bar size in (a) and (b) is 1 µm.