Wafer carrier comprising a variable aperture shield

A wafer carrier, comprising:

• a variable aperture shield, the variable aperture shield further comprising:
• a cover plate,
• a fixed base plate, and
• a plurality of fins forming a variable aperture of the variable aperture shield, the plurality of fins mounted on the fixed base plate and disposed between the fixed base plate and the cover plate, wherein at least one of the plurality of fins is configured to move towards or away from a center of the variable aperture when the cover plate is moved such that at least one of the plurality of fins overlaps an adjacent fin and changes a diameter of the variable aperture.