We present a method to pattern masks for arbitrary nano- and microstructures on different, inclined planes of a sample. Our method allows standard CMOS fabrication techniques to be used in different inclined planes, thus yielding three-dimensional structures with a network topology. The method involves processing of the sample in a first plane, followed by mounting the prepared sample in a specially designed silicon holder wafer such that the second, inclined plane is exposed to continued processing. As a proof of principle we demonstrate the fabrication of a patterned chromium mask for three-dimensional photonic crystals in silicon. The mask is made on the 90 degree inclined plane of a silicon sample that already contains high-aspect ratio nanopores.The mask is carefully aligned with respect to these pores, with a high translational accuracy of <30 nm along the y-axis and a high rotational accuracy of 0.71 degrees around the z-axis of the crystal. Such high alignment precisions are crucial for nanophotonics and for sub-micrometer applications in general. Although we limit ourselves to processing on two planes of a sample, it is in principle possible to repeat the presented method on more planes. We foresee potential applications of this technique in, e.g., microfluidics, photonics, and three-dimensional silicon electronics.

http://dx.doi.org/10.1116/1.3662000

R. W. Tjerkstra, L.A. Woldering, J. M. van den Broek, F. Roozeboom, I.D. Setija, and W. L. Vos

2011

12/2011

J. Vac. Sci. Technol. B

29

061604: 1-8

10.1116/1.3662000

3D photonic crystals, 3D silicon photonics, nanofabrication, nanophotonics, nanotechnology, photonic crystals