Fig. 4.3. Schematic Cross-section of a 2-tft Amoled Pixel Fabricated in This Work

deposition has been optimized for best quality at 250°C for the 250°C and 285°C processes, and at 200°C for the 200°C process [12] [13] [14]. Dry etching is used next to pattern the a-Si:H islands and open contact vias to the bottom metal. The top metal (Cr/Al based) is then thermally evaporated and patterned by wet etching. The n + a-Si:H is then cut at the backside of the a-Si:H channel by dry etching, and the samples are annealed at 180°C for 1 hour to repair the dry etching damage to the channel. The backplane is then passivated by a 250nm-thick layer of a-SiN x :H grown by PECVD at 125°C and dry-etching is used to open contact holes for ITO (OLED anode). Next, a 200nm-thick ITO layer is deposited at room temperature by DC-sputtering from an In 2 O 3 /SnO 2 target (with 90/10 weight ratio) in Ar/O 2 ambient and patterned by wet etching. A passivation layer is then deposited and patterned to cover the edges of ITO to avoid shorts between ITO and cathode in the OLED (evaporated subsequently). Dry etching is used next to open vias to the external pads in the passivation (not shown in the cross-section). Finally, the AMOLED structure is completed by the evaporation of small molecule green OLEDs through a pair of shadow masks for organic layers and cathode. The optical images of the arrays with 10μm and 20μm alignment tolerance prior to OLED evaporation are shown in Fig. 4.4 (a) and (b), respectively. OLED evaporation was initially performed in Princeton University to develop the AMOLED fabrication process and conduct the primary characterization of the pixels. OLEDs used for this purpose were standard bi-layer small-molecule OLEDs with TPD