Substrate Cleaning Methods for Fabricating OLEDs and Its Effect on Current Leakage Defect Formation

摘要

Various methods for cleaning the large glass substrates (300 times 400 mm) used in organic light-emitting diode (OLED) fabrication processes were investigated. Horizontal roller-bed cleaning methods using a shower-rinse with megasonic (MS)-irradiation, or brush-scrubbing, were investigated for use with anode sputtering processes. Substrates were contaminated with particulate contaminants (0.3-0.5 particles/cm2) generated from anode sputtering targets. Large particles ( ges 5 mum) were easily removed with the MS irradiation (efficiency ges 95% ). Small particles (<3 mum) were harder to remove. The brush-scrubbing cleaning removed them with 80 - 90% efficiency, while the MS-irradiation cleaning had an efficiency of 60%-70%. spin-rinse-dry cleaning methods using ozonized or electrolyzed cathode water were investigated for use with pre-organic deposition processes. Glass substrates were intentionally contaminated by exposing them to a clean room atmosphere for either 24 or 100 hours. The number of particles was reduced from around 0.4 to 0.03/cm2 and from around 1.7 to 0.08/cm2 by the MS-irradiation cleaning using de-ionized water alone, respectively. The effect of the ozonized water treatment was evident for the longer exposure substrates: it reduced the number of particles to 0.03. The electrolyzed-cathode water cleaning was successful in removing submicrometer size particles. We also investigated the effect of particulate contaminants on the current leakage defect formation.