Novel Integration Technologies for Infrared Focal Plane Array Application

Alphacore is developing a new methodology and novel techniques for heterogeneous integration of infrared photodetector arrays into complete infrared focal plane arrays (IRFPAs). The approach involves three-dimensional (3D) hybridization of infrared (IR) photodetector arrays with CMOS-based readout integrated circuits (ROIC), which should improve performance, reliability, and manufacturability of IRFPAs, and bring significant cost savings for IRFPA fabrication. These benefits will not only provide the Army with a distinct advantage in electronic warfare arenas, they will also minimize cost to the Army for initial deployment and life-cycle sustainment.  It is an accepted fact that the currently used indium bump technologies have problems with uniformity, robustness and costs; the work we propose is to optimize a Direct Bond Interconnect (DBI) process for advanced MWIR and LWIR FPA integration. There has been work on SWIR detector integration via a DBI process, but a MWIR and LWIR applications are still commonly using indium bump technologies.  Alphacore is teaming up with NHanced Semiconductors, a global leader in DBI technology, a technology that enables high-density (pitch as low as 1um) true 3D stack bonding. 3D integration drastically lowers the parasitics of the interconnect wiring. NHanced’s DBI bonds typically have only 2-3 fF of capacitance and less than 3 ohms of resistance. In sensor applications, using DBI rather than micro-bumps has been shown to reduce noise and improve signal gain by 30% or more.  In Phase I, Alphacore and NHanced evaluated and analyzed the existing DBI Hybrid Bonding integration technology in the context of IRFPA fabrication: i.e. detector array to ROIC hybridization. Based upon the results of this analysis, Alphacore and NHanced devised a plan to develop, implement and demonstrate 3D integration technology in an IRFPA product that is relevant to Army requirements.  In Phase II, Alphacore will evaluate, develop, and demonstrate the novel application of emerging, advanced 3D-IC bonding technique, that is, DBI technology, to improve the hybridization of IR photodetector arrays built of III-V materials with corresponding ROICs built of Si-based CMOS technologies; design and develop a 3D integration process that is compatible with a relevant IRFPA product based upon analysis and planning of Phase I; implement, demonstrate, test, and evaluate the resulting process, in hardware, in a relevant IRFPA product, that is, a full FPA camera’ Deliver the new 3D hybrid integration technology to Army and make it available to the DoD community.