The invention relates generally to a fuse of a semiconductor device and a method for manufacturing the same and, more specifically, to technology for forming an island-type metal fuse in a region where a laser is irradiated so that laser energy may not be dispersed in a fuse blowing process, thereby improving repair efficiency.
In manufacturing semiconductor devices, if even a single fine cell of the device has a defect, the device does not serve as a memory, and is treated as a defective device.
However, it is inefficient to disuse the device as defective when a cell of the memory has a defect.
In some cases, a redundancy cell which is previously installed in the memory device is replaced with a defective cell to repair the entire memory, thereby improving yield.
The repair method using a redundancy cell includes replacing a normal word line having a defect or a normal bit line having a defect with a redundancy word line or a redundancy bit line which is disposed in each cell array.
When a defective cell is found through a test after processing a wafer, an internal circuit performs a program to replace an address corresponding to the defective cell with an address of a redundancy cell. As a result, in use an address signal corresponding to the defective cell is inputted to access data of the redundancy cell, which is replaced corresponding to the defective cell.
Generally, the program system includes burning and blowing a fuse with a laser beam to replace a path of an address. As a result, a common memory device includes a fuse unit configured to replace an address path by irradiating and blowing (opening) a fuse with a laser. A “fuse” refers to a line cut by irradiation of laser, and a “fuse box” refers to the cut site and its surrounding region.
The fuse unit has a plurality of fuse sets. One fuse set can replace an address path. The number of fuse sets in the fuse box corresponds to the number of redundancy word lines or redundancy bit lines in the memory device.
In general, a method for fabricating a semiconductor device includes forming and planarizing an interlayer insulating film over a fuse region of a semiconductor substrate, forming a plurality of fuses over the interlayer insulating film, and forming an insulating film over the semiconductor substrate to cover the fuses.
A partial thickness of the insulating film is etched to form a fuse open region so that the insulating film having a given thickness may remain on the fuse of a local blowing region. The fuse open region is then irradiated with laser, and a blowing process is performed to cut a given metal fuse.
The remaining insulating film generally has a thickness ranging from 1000 Å to 3000 Å over the fuse. However, laser energy is not absorbed in the insulating film but passed through the insulating film because the insulating film has a transparent property such as glass. As a result, most laser energy is absorbed by the fuse. The fuse is thermally expanded by the laser energy, and the insulating film surrounding the fuse is broken when the thermal expansion reaches a critical point. As a result, most of the residual fuse is vaporized.
The fuse is not formed by an additional process but by using an electrically conductive layer including a bit line, a word line, or a plate line of a capacitor. As the device is highly-integrated in 60 nm, a fuse is formed using a metal line formed on the plate line.
When the fuse is formed with a metal line, the fuse typically has a resistance smaller than that of the plate line by ten times, with excellent thermal conductivity. However, the excellent thermal conductivity disperses laser energy in the blowing process, so that the fuse may not be cut.