Semiconductor device contg. redundancy circuits - where laser beam can be used to cut fuses, but is prevented from damaging device by laser absorbing layer of polycrystalline silicon

摘要

The device includes a semiconductor substrate (a), on which several semiconductor circuit elements are located, some of which being joined together by conductor paths which contain a fuse layer (c). Layer (c) can be cut by a laser beam to break the connection. The fuse layer (c) is sepd. from the substrate (a) by a laser blocking layer (b) which absorbs the laser beam, so the latter cannot damage other parts of the device. Layer (b) is pref. poly Si. The fuse layer (c) is pref. poly Si, and 0.1-1.0 microns thick. The conductor paths contg. a fuse pref. join a RAM cell to a redundancy circuit. The laser blocking layer (b) is pref. sepd. from the fuse layer (c) by a layer (b1) of insulation. Used esp. in a semiconductor memory store with a high capacity, where a faulty RAM cell of bit can be replaced by one of a number of redundancy cells, i.e. so a chip can be repaired.