Study On Printed Silver Source And Drain Electrodes Based On IGZO-TFT

In recent years,inkjet printing technology had been widely used for the fabrication of patterned electrodes of thin film transistors?TFT?owing to its low cost,eco-friendly,high efficiency and direct writing.With the rapid development of high-density,large-size,flexible and low-power consumption electronic devices,higher requirements was put forward for the quality of printed electrodes.Therefore,studying different conditions of inkjet printing,optimizing the morphology of the printed electrode and improving the contact characteristics between the electrodes and the semiconductor layer are necessary for high performance of the thin film transistor.Firstly,a common silver nanoparticle ink?DGP 40TE-20C?was used as research object,printing different morphology of Ag electrodes by designing different pattern on the computer program connected to the printer,and different printing parameters were adjusted,including drop spacing and the substrate temperature for the morphology of Ag electrodes.The experimental results show that the drop spacing set at 25?m,the substrate temperature set at60?,the high performace Ag electrode can be printed with the resistivity of 4.2??·cm and the silver weight percentage was 78.3%.The a-IGZO TFT fabricated by printing silver nanoparticle ink source/drain electrodes based on a-IGZO,the device presents a mobility of0.15 cm2/V·s,on/off current ratio of 10⁴,and,and turn-on voltage of about 6.1V.The TEM and EElS measurements indicated that dispersant and other organics in silver nanoparticle ink were difficult to remove during the curing process,resulting in poor contact between the Ag electrodes and a-IGZO,and poor device performance.Secondly,another silver salt ink?TEC-IJ-010?without dispersant was used as research object,and optimized the printing process.When the drop spacing was 25?m and the substrate temperature was 60?,high performance silver electrodes could be obtainted.The silver weight percentage is 76.65%and the resistivity is 4.2??·cm.The same structure of a-IGZO TFT was fabricated by printing silver salt ink source/drain electrodes,the device presents a mobility of4.28 cm²/V·s,on/off current ratio of over 10⁶,and turn-on voltage close to zero.The TEM and EElS measurements show that the silver salt ink without dispersant can effectively eliminate the organic residue at the Ag electrodes and a-IGZO interface,improving the intercface characteristics,and greatly improve the devices performance.At last,the a-IGZO TFT array was fabricated by printing Ag electrodes with silver salt ink?TEC-IJ-010?,by regulating the Slew Rate and the pulse duration T in the piezoelectric waveform driving the printhead,we successfully overcome the problem of the common“satellite droplets”exist in the large area printing for high precision and patterned film,the uniform a-IGZO TFT array was obtained.The measurement results show that the size of device unit was 400?m×400?m,the channel length was 23?m,the mobility of 1.49 cm²V^-1s^-1,the on/off current ratio of about 10⁵,which exhibited a considerably electrical characteristic.