Fabrication of high performance low temperature poly-silicon backplanes on metal foil for flexible active-matrix organic light emission diode displays

We have developed Low Temperature Poly-Silicon (LTPS) backplanes on metal for flexible 2.8-in. Active-Matrix Organic Light Emission Diode (AM-OLED) displays. The PMOS devices exhibit interesting characteristics such as field-effect mobility of 83 cm2/V.s, on/off current ratio of more than 107, a substhreshold slope of 0.47 V/dec, and a leakage current of 0.02 pA/μm at Vds = 0.1 V. Also, thin film transistors (TFT) characteristics were shown to be very homogeneous across the plates. These good performances are attributed to the possibility of developing an LTPS process on metal very close to the process existing on glass, thanks to the use of plasma enhanced chemical vapour deposition (PECVD) SiO2 as the thick insulator, which provides to maintain high temperature budget. The influence of the metal substrate as a back-gate was studied as a function of the insulator thickness. Based on simulation and measurements, it was evidenced that the metal potential can have a significant influence on the TFT operation. Overall, this self-aligned LTPS process on metal seems to be very promising for the manufacturing of high quality and high resolution flexible AM-OLED displays.