A microfabricated platform for three-dimensional microsystems

Abstract

This work presents a manually assembled three-dimensional (3-D) silicon platform structure that fully houses a microsystem containing sensors and the necessary system electronics including the power supply. The unique design of this platform provides a supporting package in a 3-D form factor, as well as routing capabilities with orthogonal mechanical and electrical connections between the assembled internal sides. An example platform is fabricated to realize an autonomous data-logging inertial measurement unit (IMU). The IMU consists of a programmable microcontroller, Flash memory, a three-axis accelerometer and a three-axis gyroscope. Double-sided polished, 250 µm-thick silicon wafers are processed using standard microfabrication techniques to produce the individual platform pieces. Sensor data, at a rate of 100Hz, is collected via a microcontroller and stored in the on-board Flash memory. Reliable and repeatable inertial data are collected with maximum power consumption of ∼16 mW, and the duration of data-logging capability of ∼48 hours. It is envisioned that extensions of this 3-D platform, combined with standard microfabrication techniques, will enable the integration of a variety of heterogeneous materials and devices with a form factor that reduces planar footprint and expands 3-D design space. Through-wafer vias can be used to integrate more functionality per surface area by increasing the interconnect density and allowing both the front and backside of the wafers to be populated with either fabricated or mounted devices.