Interferometric Micropositioning in the Planar Chip Insertion Technique for Multichip Modules (MCMs)

Abstract

A novel planar insertion technique has been developed at the CNET, Grenoble. This technique, combining laser cutting and, in particular, micropositioning controlled by interferometric vision, allows chip‐to‐substrate interconnection using a microlithography process and also chip insertion into a substrate with no physical contact with the active surfaces. Holes in MCM substrates are made by moving the 15 micron spot of a YAG laser. The chip‐to‐substrate gap of 100 ?m is filled with UV curable epoxy resin in order to bind the chip to the substrate. Chip insertion into these holes is controlled by interferometric vision yielding a planar alignment better than 0.1 µm between the active surfaces (pads) of both chip and substrate; interferometric vision enables simultaneous measurements on many chosen pads of less than 100 µm square in one imaging zone. After epoxy resin curing, this planar alignment remains in the order of 1 µm. The micropositioning by interferometric vision described above has been demonstrated in the fabrication of HDTV modules with 19 chips; on each MCM, six different types of chips from 1 mm2 to 32 mm2 have been micropositioned using interferometric vision. The feasibility of micropositioning optical fibres is also shown.