Method for making a fuse structure for improved repaired yields on semiconductor memory devices

Abstract

This invention relates to a novel fuse structure and method for deleting redundant circuit elements on integrated circuits. This fuse structure is useful for increasing the repair yield on RAM chips by deleting defective rows of memory cells. The method involves forming a fuse area in a patterned electrically conducting layer also used to form interconnections. A relatively thin (0.4 um) insulating layer is deposited having a uniform thickness across the substrate. The next level of patterned interconnections is formed with a portion of the layer aligned over the fuse area to serve as an etch-stop layer. For example, the conducting layers can be the first and second poly-silicon layers on a RAM chip. The remaining multilevel of interconnections is then formed having a number of relatively thick interlevel dielectric (ILD) layers interposed which can have an accumulative large variation in thickness across the substrate. Fuse windows (openings) are then selectively etched in the ILD layers to the etch-stop layer and the etch-stop layer is selectively etched in the fuse window to the insulating layer over the fuse area. This process allows fuse structures to be built without overetching that can cause fuse damage. The uniform thick insulating layer allows repeatable and reliable laser abrading (evaporation) to open the desired fuses.