Charge coupled device, and method of manufacturing such a device

摘要

It is known in charge coupled devices to use a dual layer of silicon oxide and silicon nitride as the gate dielectric. Since silicon nitride is practically impermeable to hydrogen, the nitride layer is usually provided with openings through which hydrogen can penetrate up to the surface of the silicon body during the annealing step carried out for passivating the surface. The openings in the nitride layer are provided by a known method, with gates in a first poly layer serving as a mask, in that the nitride is removed from between these gates and an oxidation step is subsequently carried out. According to the invention, the openings in the nitride layer are formed by means of a separate mask (20), such that the edges of the openings (9) in the nitride layer (8) lie at some distance from the edges of the gates. It was found that the dark current can be substantially reduced by this method, and that in addition quantities such as the fixed pattern noise and the number of white spots can be advantageously reduced.