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Study On The Crucial Technologies Of OLED-on-silicon Microdisplay

Posted on:2014-01-05Degree:DoctorType:Dissertation
Country:ChinaCandidate:H G XuFull Text:PDF
GTID:1268330425483457Subject:Control theory and control engineering
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Micro-displays, an important sector of the wearable displays, have attractedintensive attention during the past decade due to their potential applications inmilitary and commercial productions. Compared with the currently dominatingLCoS (Liquid Crystal on Silicon) micro-displays, the OLED(organic light-emittingdiodes)-on-silicon micro-displays have the special features, such as self lightemitting, solid state display, fast response, wide temperature adaptation, lowconsumption, etc, which are of interest for the fabrication of the wearable displays.The OLED-on-silicon micro-displays integrate both the OLED manufacturingprocess and the CMOS (Complementary metal oxide semiconductor) process, is asubstantial branch for organic electron-on-silicon, especially molecular-on-silicon.The development of the OLED micro-display depends on achieving the successfulconvergence of several scientific and engineering developments, two of which arethe optoelectronic technology and microelectronic technology. In this dissertation,we predominantly focused on the fundamental researches such as OLEDmicro-displays structure, manufacture process, performance improvement, and someapplications to realizing OLED micro-displays. The results are listed as follows:(1) For OLED micro-display structure, we mainly focused on the performanceenhancement of the full color OLED micro-display, owing to the poor luminousintensity, inferior lifetime, and high cost in most conventional OLED micro-display.We investigated the novel full color structure based on RGB side by side. Thisstructure was employed direct-emission OLED without color filters (CFs), whichwill more efficient and cheaper than the conventional full color OLEDmicro-displays which use color filters. Moreover, we studied another new full colorstructure which based on white OLED+CFs on encapsulation cover glass. This separated structure of the OLED and CFs indicated potentially high yield and lowcost for commercial use if CFs are authorized outside processing.(2) Combined with standard CMOS process technology, we systematicallyinvestigated the overall processes technologies of the OLED micro-display. Based onthe investigation of the processes of conventional OLED micro-display, wesuggested novel low-cost overall processes and equipments, eliminating the need forthe lengthy technological flow and alternate wet/dry hybrid process in the traditionalprocesses. Furthermore, Hybrid encapsulation structures based on thin filmencapsulation (THE) and cover glass encapsulation were investigated, which willeffectively improve the stability of the devices.(3) In order to integrate both the OLED and the CMOS wafer, the surface andinterface properties (including optical, electrical and other physical characteristics)of the metals in the standard0.35um CMOS process, such as aluminium(Al),tungsten(W), titanium nitride (TiN), were investigated. In comparison withmolybdenum (Mo) which was used as the anode materials in conventional OLEDmicro-display, the work function of TiN (~5.0eV) is higher than that of Mo (~4.5eV), which suggested that the injection of holes could be improved by replacing theMo anode with a TiN one, leading to reduce the voltage and improve the luminousefficiency of the devices. Based on the standard0.35um CMOS process, wesuggested the one-time pattern process for the anode pixel on the silicon chip insteadof the traditional two-time pattern process, which indicated considerable savings andhigh production yield in manufacturing devices.(4) Due to the restriction maximum voltage (5.0V) in standard0.35umCMOS-based components, we mainly focused on low-voltage and high-efficientOLED device. The low-voltage high performance monochrome OLED devices (red,green, blue, and orange) were demonstrated. Moreover, we demonstratedsuperior-performance white OLED, which showed a maximum luminous efficiencyof17cd/A@5.5V, and the maximum luminance of5000cd/m~2@5.5V, which can be attributed to the efficient carrier injection and the optimization of device structure. Atlast, a white OLED with color filters was demonstrated.(5) Based on one-time pattern process, the passive matrix OLEDs on the siliconchip with Al and TiN as the anode metal were demonstrated, which showed highperformance. Furthermore, the OLED-on-silicon micro-displays with high definition(1920×3×1080) with Al and TiN as the anode metal were designed and fabricated bythe standard0.35um CMOS process.This dissertation systematically established the overall processes of the OLEDmicro-display, and found the way out of the current bottleneck of the traditionaldevice, which showed potentially high yield and low cost for commercial use.
Keywords/Search Tags:micro-display, organic light-emitting diodes (OLED), OLED-on-silicon, process technology, titanium nitride (TiN), organic electronics-on-silicon
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