Laser link cutting for memory chip repair

Link processing with individual laser pulses has become an industry standard process in IC memory chip manufacturing. It is gaining wide acceptance in analog chip reprogramming and tuning as well. Traditional laser processing, using the standard output of Nd:YAG at 1.064-μm and Nd:YLF at 1.047-μm laser wavelengths, works well for polysilicon links but is not satisfactory for metal links. This paper describes the physics modeling and computer simulation of the laser link process and a new technique of using 1.3-μm laser wavelength for the process. While light absorption of link materials at 1.064-, 1.047-, and 1.3-μm wavelengths are relatively the same, the absorption of a Si substrate at 1.3 μm is considerably less. The improved absorption contrast between the link material and silicon substrate at 1.3-μm delivers a much wider laser process window. Both simulation and experimental results are given and discussed. A brief introduction of another new technique, which uses UV laser pulses for link processing, is given. This UV laser process delivers a laser beam spot size much smaller than 1.5 μm.