- September 2010 - August 2014
Silicon, laser, dicing, subsurface, three-dimensional micromachining
Semiconductor components are produced in large quantities on wafers. Individual dies are separated from these wafers by means of a dicing process. Commonly used dicing technologies are blade dicing using a diamond saw blade and laser ablation dicing. However, both methods generate significant amounts of contamination. This is especially problematic when cutting dies containing sensitive microelectromechanical systems (MEMS). During the ALISS project, an alternative laser-based dicing method that employs laser-induced subsurface modifications is studied. This method is a two-step process (see figure 1). First, short laser pulses are focused below the surface of the wafer to locally weaken the material. Secondly, an external force is applied to the wafer that causes the wafer to fracture along the planes with laser-induced subsurface modifications. Because the laser process is fully contained in the bulk of the material, subsurface laser dicing is a clean process. Additionally, since no material is removed, the width of the dicing streets can be minimized. An example of laser-induced subsurface modifications in silicon, as observed on the fracture plane after dicing, is shown in figure 2.
Figure 1 Schematic drawing of the subsurface wafer dicing process.
Figure 2 Side view of a die after dicing showing laser-induced subsurface modifications.
The goal of the research project is to study the laser-material interaction during the production of laser-induced subsurface modifications in the bulk of silicon wafers. For this purpose a combination of numerical modeling and experiments is used. Knowledge of the laser-material interaction allows for the selection of suitable processing parameters to create subsurface modifications of the desired dimensions. These parameters include the pulse duration and wavelength of the laser source and the properties of the focusing lens.
The project is funded by Point-One.