Semiconductor substrates in the form of wafers are diced to form singulated integrated devices or chips. As such semiconductor substrates become thinner for the production of thin semiconductor dice used in ever-smaller end-products, it has become increasingly challenging to cut thin semiconductor substrates, which are now manufactured in the order of 100 μm thickness or less.
Thin semiconductor substrates can be diced using a mechanical blade saw or by partially dicing a thicker semiconductor substrate with a mechanical blade saw, and then grinding the semiconductor substrate until the semiconductor dice are separated. However, it has been found that applying mechanical force with the saw blade leads to cracks in and/or breakage of the singulated semiconductor dice. The yield loss is typically more than 30% for semiconductor substrates that are of less than 100 μm thickness. This makes it an unattractive process for mass production. On the other hand, the two-step dice-before-grind approach is slow and is also not ideal for mass production.
Besides using mechanical blade saws, conventional laser dicing processes can also be carried out wherein a laser beam is projected onto a surface of the semiconductor substrate. This results in ablation of the material of the semiconductor substrate through melting and evaporation, until the integrated devices are separated.
When using conventional laser dicing to singulate a semiconductor substrate, a relatively high laser energy level is required to reach the point where melting and evaporation of the substrate material starts. A negative side-effect of such high laser intensity is that the heat damages the sides of the singulated integrated device. This heat damage results in significant reduction of die strength in the integrated devices, which is particularly problematic in the case of thin semiconductor substrates. While the die strength could in principle be recovered at least in part in a post-process etching step, the etching process requires aggressive chemicals that might damage active components on the semiconductor die, as well as the carrier (usually an adhesive tape) on which the semiconductor substrate is mounted.