The AVIA 355-23-250 from Coherent was specifically designed to address silicon wafer scribing and dicing applications, but also appears to have interest in drilling via holes, in PCB’s as well as in silicon wafers.

Integrated circuits for logic and memory are fabricated as multiple chips on a wafer.  These must be then separated in a process called die singulation, before back-end packaging processes such as encapsulation can be performed.  Mechanical sawing technology has always been the tool of choice for these singulation applications.  But two important trends are making lasers increasingly attractive alternative tools: the use of low-? dielectrics for faster logic, and thinner silicon wafers for stacked memory applications.

 The use of low-dielectrics can address the problem of speed encountered by increasing feature miniaturization.  These materials, particularly those that are porous, are mechanically soft, compared to traditional dielectrics.  So they tend to crack, peel and suffer other damage when sawed.  The AVIA 355-23-250 is proving to be an excellent tool for scribing through these soft circuit layers.  These narrow cuts act as pre-processing crack-stops enabling fast mechanical saw cutting through the entire wafer thickness.  The high power and high pulse repetition rate of the AVIA 355-23-250 makes this laser an ideal choice for these low-? dicing applications.

With thinner wafers for stacked and embedded memory applications the main problem encountered with mechanical sawing is backside chipping, which reduces throughput and/or yield.  Specifically, to maintain high yields, the saw feed speed must slow dramatically and/or the saw must resort to multi-pass process recipes.  But with laser sawing, speed increases with decreasing wafer thickness and backside chipping problems are eliminated.  The AVIA 355-23-250 has been designed to achieve the twin goals of higher throughput and higher yield.

The advantage of the AVIA 355-23-250 is that it can do a good job of both scribing, using small energy pulses (using PulseEQ) at a high rep rate to scribe through 10 µm (typ.) top layer of circuitry.  The AVIA 355-23-250 can then quickly switch to much higher energy pulses to actually cut through the silicon (dicing).  Some technologies may claim an advantage at scribing (pico-regen) or at dicing (IR stealth dicing, hybrid laser/water, or mechanical saw), but the key advantage of the AVIA 355-23-250 is that many times it is the best choice at doing both applications, scribing and dicing.  The ability to scribe and dice in a single operation is often a big advantage.

In comparing the AVIA 355-23-250 to the standard AVIA 355-23 for the wafer singulation application, given that the two lasers are based on the same model but optimized for performance in different operating regions with AVIA 355-23-250 producing smaller pulse energies at higher repetition rates, we believe this new product may have an advantage of minimizing the possibility of micro-cracking the silicon substrate, especially in the case of brittle, low-dielectric materials.