A novel low temperature integration of hybrid CMOS devices on flexible substrates

In this work we demonstrate a novel integration approach to fabricate CMOS circuits on plastic substrates (poly-ethylene naphthalate, PEN). We use pentacene and amorphous silicon (a-Si:H) thin-film transistors (TFTs) as p-channel and n-channel devices, respectively. The maximum processing temperature for n-channel TFTs is 180 °C and 120 °C for the p-channel TFTs. CMOS circuits demonstrated in this work include inverters, NAND, and NOR gates. Carrier mobilities for nMOS and pMOS after the CMOS integration process flow are 0.75 and 0.05 cm²/V s, respectively. Threshold voltages (V_t) are 1.14 V for nMOS and -1.89 V for pMOS. The voltage transfer curve of the CMOS inverter showed a gain of 16. Correct logic operation of integrated flexible NAND and NOR CMOS gates is also demonstrated. In addition, we show that the pMOS gate dielectric is likely failing after electrical stress.