Laser writing deep inside silicon for 3D information Processing

Micromachining of silicon (Si) with lasers is being investigated since the 1970s [1]. So far, generation of controlled subsurface modification in the bulk of Si with high precision has not been achieved. This is highly desirable since successful integration of Si photonics and data transfer elements with conventional Si integrated circuits is proposed to lead to new generations of microprocessors [2,3]. Available techniques fabricate these optical and electronic elements on the top layer of the silicon-on-insulator platform. Despite the remarkable successes of conventional techniques, none of the available methods make use of the bulk of Si for positioning functional elements. Here, we report a method for photo-inducing deeply buried (down 1 mm) structures in Si wafers with pulsed infrared lasers. We demonstrate large aspect-ratio structures with 1-µm widths and long range order over millimetre scales. We further demonstrate multilevel spatial information encoding capabilities in subsurface barcodes.