Manufacturing integrated circuits is a multi-step process from growing silicon boules to fabricating the circuits. To transform the boule into a substrate for printing circuits on, silicon wafer dicing is employed to create individual die from bulk material. Various methods of dicing have been developed over the years as demands for integrated circuits increase throughout society and industry.
Challenges of Wafer Dicing
Mechanical dicing methods using diamond blades require effective means of mounting wafers for precise cuts without damaging the substrate by chipping, cracking or contamination with silicon dust. Cooling is also necessary, as mechanical dicing produces heat via friction and thermal damage can ruin die, but liquid coolant can damage printed circuits. On top of quality control, new dicing processes need to be fast and feasible for producing high-quality chips from ultra-thin circuits, and damage to the cutting equipment should be minimized to extend its lifespan.
Improving Mechanical Dicing
Despite these obstacles, mechanical dicing is still an industry-standard thanks to improvements in die strength, equipment longevity and dimensional tolerances. One common technique is scribing shallow grooves between each die before performing a full cut. This makes it easier to cut the wafer without weakening or damaging it with mechanical stress. Another option is to aid cutting by using an ultrasonic blade horn, combining the rotary blade with radial vibration. The blade grit briefly contacts the substrate repeatedly, reducing the gradual wear on the blade while also improving the already-significant cutting power of diamond blades. This also produces less heat and stress, making it effective for thin, brittle wafers.
New Laser Dicing Methods
Laser cutting—done by heating the substrate at a focused point to evaporate it—is not new to wafer dicing, as the absence of mechanical stress mitigates chipping and cracking Still, this process is still risky with thinner or more delicate wafers; if the laser is too powerful, it’s difficult to keep the ablation localized to the desired cut, resulting in deformation. Stealth dicing circumvents this by using a low-power laser that the wafer is semi-transparent to. The beam is focused to a depth within the wafer, effectively cutting from the inside out by introducing localized defects. Expanding the carrier membrane that the wafer is mounted on then causes the die to separate along these defects. Not only do the results bear minimal thermal or mechanical damage, the kerf between die is negligible and no silicon dust is produced on the surface.
With more sophisticated dicing methods, integrated circuits can be fabricated with finer control and higher productivity. As a result, manufacturers can continue to meet the IT industry’s growing needs.