Surface modification on hydrophilicity enhancement using NH4OH, NaOH, and KOH on fine-pitch low-temperature Cu/SiO2 Hybrid Bonding

A novel plasma-free hydrophilicity surface modification treatment on PECVD SiO
2
dielectric layer is proposed in this paper. Different alkaline chemicals such as ammonia (NH
4
OH), sodium hydroxide (NaOH), and potassium hydroxide (KOH) are used as pretreatment solutions. By using this pretreatment prior to the bonding process, we found the contact angle of water decreased significantly. Cu etching issue is further discussed while no serious variation in surface roughness of Cu after KOH and NaOH pretreatment. Cross-sectional HR TEM shows excellent bonding quality and no contamination signal of residual pretreatment solution detected by TEM-EDS. Low specific contact resistivity of 10
^-8
Ω/cm
²
was detected at kelvin structure.