Packaging Issues and Solutions for Ultra-Low Power, High Efficiency GaN micro-LEDs for a Battery Free, Sub-mm², Tetherless, Smart IoT System

Abstract

This paper discusses some design and implementation issues related to GaN micro-LED (µLED) incorporated into the heterogeneous packaging of IBM’s smart and secure sensor platform. For cost effective µLEDs, the sapphire substrate needs to be singulated reliably and with minimum kerf perimeter, be ultra-clean and smooth to allow back side emission without scattering, and high yielding front side flip chip bonding with 20µm C4s on 40µm pitch. The GaN µLEDs are design for low voltage/low power operation with an emission area of 20µm x 20µm with critical current density of ~10nA/µm2. Power and downlink data is delivered to the system via optical energy harvesting by on-silicon carrier photovoltaics and communication photodiode, respectively. Optical amplitude modulated uplink communication by heterogeneous packaging of the GaN µLED with a 14nm CMOS smart chip will be detailed and demonstrated in presentation.