An O/E measurement probe based on an optics-extended MCM-D motherboard technology

An ongoing trend in packaging technology is the introduction of optical interconnections to cope with the problems of increased data transmission speed and the raised interconnection density. Hence, improving packaging and interconnection technologies is only viable if the aspects of optical interfaces and O/E (opto-electronic) components are considered. In this paper, we will demonstrate an MCM-D (Multi Chip Module) technology with O/E features. We achieved to integrate high-precision V-grooves for alignment and fixation of the optical fibers into a standard MCM-D technology. The V-groove shape of the fiber fixation structures is a result of the anisotropic etching of (100) silicon by means of aqueous KOH. The technology aspects of this aggressive wet etching step are discussed as well as the optimisation results of a suitable KOH masking layer: a low-refractive-index PECVD (Plasma Enhanced Chemical Vapour Deposition) nitride. The extension of an MCM-D technology with V-grooves generates the possibility to integrate side-emitting lasers and fibers with the electronics on the same MCM-Si motherboard. This implies a more dense and compact motherboard with the potential of obtaining higher bandwidths due to the minimal distance between optics and electronics. Additionally, low coupling losses between laser and fiber are guaranteed as the accuracy of the V-grooves in silicon allows us to place the fibers with high precision. The feasibility of this optics-extended MCM-D technology will be shown in the example of O/E measurement probes. In the fabrication process of such O/E measurement probes, we will focus on the multilayer MCM-D motherboard extended with V-grooves, on the flip-chip (FC) mounting of the RF-amplifier chip and on the placement of both laserdiode and fiber.