Beatrice Beyer
Figure 1. (OLED) microdisplay with a screen diagonal of 16 mm. Figure 2. CMOS cross section with OLED on top. Usually as small as fingernails, but of very high resolution Optical system necessary to enlarge the image Well known applications are beamers / projectors, head mounted displays in virtual or augmented reality use, electronic viewfinders Technologies Digital mirror devices (reflecting technology) Liquid crystal devices (transmitting technology) Liquid crystal on silicon (reflecting technology) OLED-based microdisplays (emissve technology) Integrated light source external drivers and controllers Beatrice Beyer (Fraunhofer FEP) 06/10/2016 2
Duration of 36 months (01.01.15 31.12.17) Budget of 4.1 million EUR Core objective: flexible, large area microdisplays at low cost Why? Novel functionalities offer new possibilities Many applications need to fit a high amount of information in a limited space Beatrice Beyer (Fraunhofer FEP) 06/10/2016 3
Assisted vision To increase visual capacity to a maximum level High brightness Monochrome (green) Virtual reality Very high information content demanded Conformable displays may enable wider field of view more easily Figure 4. Concept of assisted vision for visually impaired people. Figure 5. Conceptual design of glasses for virtual reality. Beatrice Beyer (Fraunhofer FEP) 06/10/2016 4
Beatrice Beyer (Fraunhofer FEP) 06/10/2016 5
8 partners after losing watch manufacturer (Slyde watch) in 2015 COM: CMOS design & OLED deposition LIM: Virtual reality glasses UOXF: Glasses for assisted vision ULEI: Transparent TFT materials XFAB: CMOS backplane manufacturing MOD: Microdisplay manufacturing CEA: Process development for flexible displays AMAN: Exploitation & dissemination Beatrice Beyer (Fraunhofer FEP) 06/10/2016 6
Fabrication of OLED microdisplays that: durable (operating lifetime > 15,000 hours at 1,500 cd/m 2 ) have an exceptionally large screen diagonal of 2.54 cm and high resolution of 2300 ppi address numerous application fields benefiting from the improvements such as: virtual reality due to the novel concept of the near-to-eye-optics assisted vision & are conformable (bending radius of 50 mm, thickness of <150 µm) can be produced with large areas and high yields (>60%) and thus at low cost (<100 /piece) Beatrice Beyer (Fraunhofer FEP) 06/10/2016 7
High yield CMOS-OLED interface Wafer thinning process development Extremely thin package Robust OLED before IC design Design tool kit Large area after Yield Äcost Information density (display area resolution) vs. particle density CMOS-OLED interface Wafer thinning Operating life time Bright, stable OLED and TFE Conformability (inorganic IC!) Beatrice Beyer (Fraunhofer FEP) 06/10/2016 8
Challenge Process optimisation to achieve high yields over large chip areas (à low cost) First results Test & qualification vehicle has been designed and fabricated Verification of anticipated improvements at CMOSlevel: New circuitry to improve dark level (>10,000:1 contrast) New circuitry for column decoder to reduce area and power consumption Figure 6. Left: test and qualification wafer, right: one of 1 st chips. Beatrice Beyer (Fraunhofer FEP) 06/10/2016 9
Challenge Optimisation of interface between CMOS and OLED to realize high yield and reliability Test & qualification vehicle For development purposes Screen diagonal of 2.54 cm First results Backplane top-metal interface is characterized by low angles and low roughness (< 5 nm) Beatrice Beyer (Fraunhofer FEP) 06/10/2016 10
CMOS wafer manufacturing OLED deposition with TFE Encapsulation including color filter Dicing Challenge PCB mounting Sufficient protection against mechanical stress First results Identification of coating material with appropriate wettability, adhesion & durability Without having any impact on OLED performance Figure 7. Evolution of Si/AlQ 3/Al 2O 3/HC under 85 C/85% relative humidity for 288 h. Figure 8. J-V (left) and L-V (right) curve of OLED with (blue) and without (red) hard coat. Densité de courant (ma/cm²) 1,0E+03 1,0E+02 1,0E+01 1,0E+00 1,0E-01 1,0E-02 1,0E-03 1,0E-04 1,0E-05 1,0E-06-3,0-2,0-1,0 0,0 1,0 2,0 3,0 4,0 5,0 6,0 7,0 8,0 1,0E-07 (V) Beatrice Beyer (Fraunhofer FEP) 06/10/2016 11
Challenge Keeping the OLED unharmed during thinning process Suitable stress resistance achieved First backplanes have successfully been thinned down After UV exposure 2 J/cm² 0,00 After UV exposure 5,5 J/cm² After UV exposure 9 J/cm² after development After After annealing annealing 90 C, 5 min 100 C, 5 min First results -4,00-8,00-12,00-16,00-20,00 Figure 9. Stress evolution(mpa) of the hard coat film versus the different steps of fabrication. Figure 10. Thinned and curved test vehicle Si/Alq 3/TFE/hard coat LETI2. Figure 11. Thinned vehicle OLED/TFE/ hard coat LETI2 fabricated by CEA LETI. Figure 12. Thinned CMOS/OLED/TFE/ hard coat (under development) using a microdisplay from Microoled. Beatrice Beyer (Fraunhofer FEP) 06/10/2016 12
Challenge High mobility at high transparency Optimization of material parameters of amorphous multi cation compound (MCC) zinc tin oxide (ZTO) multi anion compound (MAC) zinc oxynitride (ZnON) First ZTO-based MESFET Current on/off ratio of more than five orders of magnitude off-current below 1 na sub threshold slope is 0.27 V/dec y [cm] Figure 11. variation of cation ratio in ZTO thin film. 2 1 0-1 -2-2 -1 0 1 2 x [cm] Zn (Atom %) 54.5 First results 48.3 41.0 33.7 Figure 12. Mobility evolution over annealing time. Figure 13. Left: Schematic of TFT and its IV characteristic. Beatrice Beyer (Fraunhofer FEP) 06/10/2016 13
Information content increase Larger screen diagonal Higher resolution Weight and form factor reduction for glasses (compactness) Large-field-of-view optics Energy efficiency for wearables HTC LOMID Beatrice Beyer (Fraunhofer FEP) 06/10/2016 14
High resolution displays (WUXGA) will be accessible Large area (SD = 25.4 mm) High contrast (> 10,000:1) Conformable (r > 45 mm) Durable (t > 15,000 h) Transparent TFT materials with superior performance have been identified The work leading to these results has received funding from the European Union s Horizon 2020 research and innovation programme under grant agreement No 644101. www.lomid.eu Beatrice Beyer (Fraunhofer FEP) 06/10/2016 15