Monolithic Integration of Si3N4 Microring Filters With Bulk CMOS IC Through Post-Backend Process

An experimental demonstration of backend monolithic integration of Si
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microring filter with bulk complementary metal-oxide-semiconductor (CMOS) integrated circuit (IC) is accomplished using CMOS postbackend process. Si
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photonic layer is integrated on the top surface of CMOS IC die which is manufactured in commercial CMOS foundry. The Si
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microring filters in photonic layer are fabricated using CMOS postbackend process with only two additional lithography steps. The filters can be thermally tuned by microheaters integrated in CMOS circuits, which are controlled by transmission gates. A measured optical transmission spectrum and a dynamic characteristic of the integrated filter are provided.