Changing the surface properties of the backside of a silicon wafer to repel oil and prevent particle binding

Wafers are thin semiconductor materials essential in the production of microchips, which are present in almost every electronic device. A semiconductor wafer chuck, a plate that holds wafers, is used in multiple semiconductor processes, including cleaning, etching, polishing, lithography, and deposition. Even though wafers are produced as silicon, the backside of the wafer can be oxidized by air or water vapor to create silanol (Si-OH). Silanol can easily bind to silica particles to cause leveling issues on the chuck. In addition, though the backside of the wafer has many Si-OH bonds, oil can stick to the nonpolar area of the wafer, causing wafer slip that can result in shattering. To address these issues, we coated the wafer backside using [acetoxy(polyethyleneoxy)propyl]triethoxysilane (APTS), which prevents particle binding and repels oil effectively. We hypothesized that the siloxane bond from APTS would block incoming silica particles and that the polyethylene glycol (PEG) group would repel oil because PEG is a polar group that does not attract oil. We used a contact angle goniometer to confirm that the hydrophobic part of the wafer became hydrophilic (contact angle < 90°) and found that the wafer repelled oils. Additionally, we exposed the backside of the wafer to silica particles to examine whether APTS prevented particles from binding onto the wafer. SEM data confirmed that the APTS-coated wafer effectively blocked silica from binding to the backside of the wafer. This approach can improve semiconductor wafer reliability and benefit other research needing contamination-resistant surfaces.