Research And Design Of A Vertical Current Regulator Diode

As compared with other traditional light-sources, LED is known as the most promising green lighting light source of 21 st century because of its quick-start, low energy consumption, long serving life, good direction, environmental and other advantages. It has been widely used in various types of indoor or outdoor display, all kinds of traffic lights, dashboard, tail lights of cars, electronic watches, mobile phones, computers and other displays, display of various kinds of electronic equipment. And driving circuit is the main reason of the failure problems when using LED, thus reasonable drive circuit design is the key of sustainable development and widely used for LED. A constant current diode structure is proposed in this thesis to apply in the LED driver circuit, including a kind of vertical CRD which is similar to depletion DMOS and a kind of vertical CRD with trench cathode based on double epitaxial layers which is similar to JFET. The device structures were optimized by TSUPREM4 and MEDICI, and studied the terminal device structure and process flow.The main content of this thesis are as follows:1、The development course of LED, LED drive circuit and CRD are briefly discussed.2、Design a kind of vertical CRD which is similar to depletion DMOS. Study the main working principles of CRD. I-V characteristics of CRD can be roughly divided into three regions, the linear region, the saturated region and the breakdown region. Also analyze how the effective channel length modulation effect impact on the saturated region characteristics. Good constant current characteristics, enough breakdown voltage and small pinch off voltage are essential when CRD is applied in the LED driver circuit. The thickness of epitaxial layer, the concentration of the epitaxial layer, the concentration of the channel is through simulation, the width of JFET zone, the thickness of oxide layer and the environment temperature will affect the performance of the devices. Therefore determine the optimal structure parameters and technological parameters of the device through simulation. Two kinds of extension structure are propose, and compared with the original structure, then provide reference for the follow-up work. The field limiting ring terminal which is suitable for the device structure is designed through the integrated analysis of theory and simulation. Combined with the actual situation of the process line, design the specific process of the device.3、 Design a kind of vertical CRD with trench cathode based on double epitaxial layers which is similar to JFET. The structure has good electrical properties because of the double epitaxial layers and trench cathode. Study how the groove depth, the first Nepitaxial layer thickness and concentration, the second N- epitaxial layer thickness and concentration and the diffusion time of Pwell affect the device through simulation. Then determine the process flow and layout structure. The experimental IV characteristics of the packaged different current level CRD are obtained. And the results are analyzed in many respects including time and temperature. Finally, the encapsulated product is used in LED driver circuit, and then test the application.