A device for holding a substrate comprises upper and lower plates adapted to receive the substrate sandwiched in the interface between the plates. Each plate has at least one opening with a projecting rim surrounding the opening and directed away from the interface. The openings in the upper and lower plates are at least partially aligned in the sandwiched position of the plates. Each opening in the lower plate can be provided with a shielding member partially shielding the opening of the lower plate.
