Heterogenous integration technology using wafer-to-wafer transfer

The integration of heterogeneous components and materials is a powerful method to create more functional, higherperformance and/or smaller devices. A typical example is the integration of a frequency control device with a CMOS (complementary metal oxide semiconductor) integrated circuit (IC). This paper introduces three kinds of integration methods based on wafer-to-wafer transfer technology and their applications. 1) A functional film such as ferroelectric films was transferred from a Si wafer to a CMOS wafer by adhesive wafer bonding. PZT (lead zirconate titanate), B-doped diamond and BST (barium strontium titanate) were once deposited on Si wafers at high temperature, and then transferred to CMOS wafers to fabricate a piezoelectric microswitch, an electrochemical biosensor array and a tunable power amplifier, respectively. 2) A one-chip bandwidth-tunable filter for TV white space cognitive wireless LAN was made by the monolithic integration of SAW (surface acoustic wave) resonators and BST varactors. The BST film was transferred from a sapphire wafer to a LiTaO₃ wafer by laser-assisted peeling and Au-Au bonding. 3) Laser-assisted selective die transfer technology for the wafer-level integration and packaging of different sizes of dies has been developed. It was applied to a 2 GHz one-chip film bulk acoustic wave oscillator for timing applications.