Monolithic integration of light sensor readout system for multi-functional LED wafer-level packaging based on BICMOS process

Monolithic integration of light sensor readout system for multi-functional LED wafer-level packaging based on BICMOS process

Ma, T.

Zhang, G.Q. (mentor)
Van Zeijl, H. (mentor)

Electrical Engineering, Mathematics and Computer Science

Department of Microelectronics

Electronic Engineering

2014-11-24

LED-based lighting is becoming increasingly popular in recent year, but LED development especially for lighting application now seems unavoidable. The various benefits of LEDs and the continuous increase in their performance allied to the decrease of the manufacturing costs makes it quite attractive. It is widely believed that LEDs would be a reliable alternative to conventional fluorescent and incandescent lamps which dominate the lighting applications in the last century. Integration and packaging is one of the critical issues that enable efficient and reliable solution to fulfill modern lighting requirements. Wafer Level Packaging (WLP) is a promising method for having lower costs, higher reliability and superior yields. In order to further improvement of the functionality and controlling capabilities of LED lighting system, various sensors and other electronics can be monolithically integrated with LED package on the wafer level. 7-mask BICMOS process was invented and developed by DIMES in Delft University of Technology. Just as its name implies, this process only requires 7 masks to fabricate fully functional CMOS transistors, sensors, passive electronics and even integrated circuits. Based on this process, the monolithic integration of light sensor readout circuit on a novel LED wafer level package is presented in this thesis. A blue selective stripe-shape photodiode is utilized as the light sensor to sense the light intensity of the blue LED in every 10 ?s. In this case, the BXCD4545 blue power die with nominal forward current of 350 mA was selected. Subsequent to the fabrication of silicon package, blue LEDs are glued and mounted in the package. The analogue output of the senor will be firstly amplified and then, synchronously converted to the digital code by a 4-bit analogue to digital converter (ADC). Each sample signal is encoded to a 4-bit digital string that is corresponding to 16 different light intensity levels. Afterwards, the code can be fed to an off-chip microprocessor which enable further control and adding more smart functions for different application to the system. Excluding the microprocessor, all the other components such as light sensor, amplifier, ADC and other passive electronics are monolithically integrated on the LED wafer level package. Since the 7-mask BICMOS process is an easily feasible and cheap process, it has the potential to enlarge the integration scale and have more functions embedded in a single system. The present system offers a promising solution for the further research and development of smart LED package on the wafer level. The use of WLP not only makes it possible to apply the highly-developed and batch-production methods of integrated circuits to the LED packaging, but also makes it achievable to combine sensors and integrated circuits on one single chip with LED.

http://resolver.tudelft.nl/uuid:c7cad366-8cf1-43a2-a178-352dcd6c347e

Student theses

master thesis

(c) 2014 Ma, T.