Characterization of Parylene as a Water Barrier via Buried-in Pentacene Moisture Sensors for Soaking Tests

We present a simple method to characterize parylene as a water barrier for soaking tests. The key component is the buried-in pentacene moisture sensor, which is a thin-film transistor sandwiched between two layers of parylene C. This pentacene thin-film transistor takes bottom contact configuration and uses parylene C as the gate dielectric material. Parylene films containing pentacene moisture sensors are soaked in saline at room temperature and the saturation drain current of pentacene thin film transistors is monitored. Hole mobility of pentacene is extracted via linearization of the square root of the drain current of the transistor versus gate voltages. We can determine the capability of parylene as a water permeation barrier by the changes of pentacene mobility.