The primary purpose of backside inspection is to determine if equipment chucks and pallets are creating contamination or damage and identify any defects to prevent them from being spread throughout the fab. It is critical that the backside of a wafer be free of defects prior to the photolithography process to prevent focus and exposure problems on the front-side of the wafer. It is ideal to implement backside wafer inspection prior to lithography in order to ensure backside defects do not create an un-flat exposure surface; after lithography to monitor photocell contamination; and throughout the FEOL and BEOL to monitor contamination, and prevent buildup of localized stress points and hot spots that cause wafer breakage or device failure further in the process.

Typical backside defects include:

• Surface particles
• Residues
• Contamination
• Scratches
• Damage
• Defect clusters