Curved Silicon Electronics

Abstract

An electronic imaging system using a curved image sensor can use a faster lens, and cover a greater field of view, than an imaging system using a planar sensor. The simpler lens systems also weight less, a decisive advantage in portable applications.This paper describes a method to fabricate a curved silicon substrate from a flat wafer containing appropriate circuits. To curve the substrate, the processed wafer is diced, by dry-etching from the backside, into 1x1cm tiles. The tiles are separated by 0.5mm gaps, which are bridged, in turn, by a dense array of 45x100μm gold leads formed by electroplating using lithographically defined leads as seeds. Two methods were used to curve the wafer. In the first one, the wafer was bonded with epoxy to a PMMA disk, and then curved by heating the sandwich, under a load of ∼ 230gr, for 1.5 hrs at 130°C in a concave metal mold with a radius of curvature of 7.8cm. In the second method, the wafer was put into a curved metal mold, radius 14cm, loaded with 230gr, and heated to 290°C for 2 hrs. The normal and shear strains accommodated by the flexible interconnects were measured by analyzing their deformation. The experimentally measured strains are compared with a model that calculates the deformation required to deform a flat sheet into a spherical surface.

Shape Control of a Unimorph Deformable Mirror for Space Active Optics under Uncertainties

“…The variation in the morphing capability of a deformable mirror also occurs with the strain actuation with surface curvature, due to a slight modification in magnitudes and directions of piezoelectric forces, i.e., resulting in a change of in Equation ( 6 ). Note that the curvature can be made artificially as conic surfaces in the telescope optics, the techniques of moulding a thin-shell layer of a prescribed curvature are in development for the electronics industry [ 42 , 43 ]. At the same time, the surface curvature can be also uncontrollably generated due to manufacturing or release of residual stress, leading to a random initial shape, this is one of sources of deviated shape .…”