EUV Photomask Capping Layer Repair Using Electron Beam Deposition

The patent converts the harmful effect of aggressive cleaning (which causes capping layer damage) into a beneficial repair process by using focused electron beam-induced deposition to selectively restore damaged regions. The cleaning process is allowed to be aggressive for thorough cleaning, and the damage is subsequently repaired through a controlled deposition process that targets only the affected areas, thereby converting the harm into an opportunity for localized reinforcement.

Instead of discarding photomasks that show signs of wear or damage, the patent implements a recovery process where damaged capping layers are repaired through focused electron beam deposition. This allows photomasks to be restored to their functional specifications and continue being used, thereby recovering value from what would otherwise be discarded components and reducing the frequency of replacement.

The repair process utilizes the photomask's own structure and properties to guide the repair. The focused electron beam automatically interacts with the damaged regions, and the deposition process is self-regulating based on the local conditions of the capping layer. This self-service approach maintains simplicity while achieving high precision, as the system adapts to the specific damage patterns without requiring complex external control mechanisms.