%0 Journal Article %J Applied Physics Letters %D 2016 %T Improving positive and negative bias illumination stress stability in parylene passivated IGZO transistors %A Kiazadeh, A.a b %A Gomes, H.L.b c %A Barquinha, P.a %A Martins, J.a %A Rovisco, A.a %A Pinto, J.V.a %A Martins, R.a %A Fortunato, E.a %I American Institute of Physics Inc. %K Bias voltage %K Coatings %K Electrical performance %K Encapsulation layer %K Indium %K Indium gallium zinc oxides %K Neutralization process %K Operational stability %K Passivation %K Semi-conductor surfaces %K Stability %K Stretched exponential models %K Surface defects %K Thin film transistors %K Threshold voltage %K Threshold voltage shifts %K Transistors %K Zinc coatings %R 10.1063/1.4960200 %U https://www.scopus.com/inward/record.uri?eid=2-s2.0-84981155175&doi=10.1063%2f1.4960200&partnerID=40&md5=d3f5245134d17c2b45d10c6623cb25ef %V 109 %X The impact of a parylene top-coating layer on the illumination and bias stress instabilities of indium-gallium-zinc oxide thin-film transistors (TFTs) is presented and discussed. The parylene coating substantially reduces the threshold voltage shift caused by continuous application of a gate bias and light exposure. The operational stability improves by 75%, and the light induced instability is reduced by 35%. The operational stability is quantified by fitting the threshold voltage shift with a stretched exponential model. Storage time as long as 7 months does not cause any measurable degradation on the electrical performance. It is proposed that parylene plays not only the role of an encapsulation layer but also of a defect passivation on the top semiconductor surface. It is also reported that depletion-mode TFTs are less sensitive to light induced instabilities. This is attributed to a defect neutralization process in the presence of free electrons. © 2016 Author(s). %Z cited By 0