Re: about fuse?
Hi shrbht!
Poly fuses work like a PROM. The user can fuse (literally burn) poly connections and thereby store information. Poly fuses can be programmed once.
Metal fuses- also called laser fuses- are metal connections that can be fused by cutting the metal line using laser light.
Poly and laser fuses are quite complicated "devices". Poly fuses are heavily technology dependant, as the required current to burn the poly varies. Laser fuses are complicated because the alignment of the laser can be tricky and the oxide on top of the fuses has to have special properties, as the metal will be evaporated by the laser light. LF also impose risks due to potential holes in the passivation. Moisture can get into the chip and cause corrosion. A lot of precautions have to be taken in order to make LF a safe way of fine tuning a circuit.
Hope that helps.
Regards,
Christian