Heterogeneous Integration of AlN MEMS Contour-Mode Resonators and CMOS Circuits
Creators: name: Calayir, Enes
Publisher: name: Carnegie Mellon University
Year: 2017
Subjects: subject: Computer Engineering
subject: 90699 Electrical and Electronic Engineering not elsewhere classified
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: The increasing demand for high performance and miniature high frequency electronics has motivated the development of Micro-electro Mechanical Systems (MEMS) resonators, some of which have already become a commercial success for the making of filters, duplexers and oscillators used in radio frequency (RF) front-end systems for portable electronic devices. These MEMS components not only enable size, power and cost reduction with respect to their existing counterparts, but also open exciting opportunities for implementing new functionalities when used in large arrays. Almost all MEMS resonators require interfacing with one or more Complementary Metal Oxide Semiconductor (CMOS) integrated circuit components or modules in processing raw signals from individual MEMS devices. Hence, these devices should be integrated with CMOS circuits in an efficient and robust way in order to facilitate their deployment in large arrays with minimal parasitics, delay and power losses due to signal routing and CMOS-MEMS interconnects. Among the MEMS resonators developed to date, Aluminum Nitride (AlN) MEMS Contour-Mode Resonators (CMRs) offer high electro-mechanical coupling coefficient (𝑘𝑡2) and quality factor (Q), and a center frequency (f0) that can be set lithographically by varying the device in-plane dimensions. Also, AlN MEMS CMRs can be fabricated using state-of-the-art CMOS processes and micromachining techniques. These properties allow the synthesis of multi-frequency band-pass filters (BPFs) on a single chip with a low insertion loss and the capability of direct matching to 50 Ω systems. All these advantages, along with a sufficiently mature fabrication process, make AlN CMRs one of the ideal candidates for pursuing their integration with CMOS technology and implement high performance filters with programming capability. In this work we develop for the first time a three-dimensional (3D) heterogeneously integrated AlN MEMS-CMOS platform that enables the realization of such systems as self- healing filters for RF front-ends and programmable filter arrays for cognitive radios. We collaborated with the A*STAR, Institute of Microelectronics (IME), Singapore in the development of AlN MEMS platform on an 8" silicon (Si) wafer; on the other hand, CMOS chips were fabricated in 65 nm International Business Machines Corporation (IBM) and 28 nm Samsung processes. Solder bumps were placed on CMOS chips by Tag and Label Manufacturers Institute (TLMI) under the supervision of Metal Oxide Semiconductor Implementation Service (MOSIS). We demonstrated 3D integrated chip stacks with primary RF signal routing on MEMS and on CMOS for self-healing filters, and showcased the other system via wire-bonding to off-the-shelf CMOS components on a printed circuit board (PCB) because of the inability to continue to have access to the CMOS wafers and bumping processes over the last two years of the project.