Study On The Effect Of O₂ Plasma Treatment For Improvement In The Wetting Characteristics Of Photoresist

With the increasing demand for complexity and packaging density of large-scale integrated circuits,the chip size is decreasing,and the electronic packaging is developing towards miniaturization and multi-function.The decrease in the size of the bump makes the defects of the preparation bump,such as holes,cracks,or even no full depositing bumps.In electroplating,the surrounding of the bump is a key basic material in the field of microelectronic technology--photoresist.The appearance of micro holes with fine pitch and high aspect ratio increases the coating properties of the photoresist.Photoresist,as an important material in the fine processing of electronic field,has a great influence on the further improvement of packaging technology.In this study,O₂ plasma treatment was performed on the negative UV photoresist at different power to modify the surface wetting characteristics for the micro-bumps electrodepositing.This method is simple and feasible,and can be large-scale applied in process of generation.What’s more,the performance can be obviously improved and easy to control.The aging effect on wetting characteristics of negative photoresist was also studied.Through different detection methods,contact angle measurement,surface microstructure and composition,we also discussed the mechanism of modification.Experiments show that O₂ plasma treatment of photoresist was adopted to enhance the wetting characteristics by measuring the contact angle between photoresist and liquid.Wetting characteristics were enhanced in varying degrees at different power.We have analyzed the changes in surface nanostructure and composition after O₂ plasma treatment.The appropriate surface roughness and nanostructure of the photoresist was obtained after the O₂ plasma treatment.Meanwhile,more hydroxyl groups were introduced on the surface of photoresist.The combination of surface composition and nanostructure makes the better wetting characteristics of photoresist.The wetting characteristics of photoresist gradually reduced with the increase of the time after O₂ plasma treatment.The surface microstructure of photoresist became sharper and the roughness gradually increased;and the number of hydrophilic groups decreased as time increased.The recovery of the structure and composition leads to a re-reduction of the wetting characteristics.The study of these treatment processes and the aging experiments after O₂ plasma treatment have important guiding significance for the practical application of miniaturized micro bump preparation.