Sub-micrometre precision measurement method for wafer level assembly

We here present a novel measurement method for evaluating alignment accuracy in the assembly of optoelectronic components. The method has been designed and implemented to supply the sub-micrometer resolution required for optical single mode applications. The measurement method is applied to a technology platform for large chips carrying multiple optical waveguides. The chips are passively aligned utilising self-alignment through flip-chip soldering. Gold electrodes provide the possibility of realising active waveguide components via, e.g., electroabsorption or thermo-optic effects. Micromachined grooves are used for the alignment of fibre arrays (2/spl times/16 fibres). As no active alignment is require, this technology is inherently compatible with wafer level assembly (WLA). A hazardous risk, however, with WLA and optical assembly in general, is that the final yield can be unacceptably low if no simple means for verifying alignment accuracy are available before fibre attachment. This was the motivation behind this work.