Speaker
Description
With the continuous miniaturization and increasingly performance requirements of microelectronic devices, new materials have been integrated as the low-k SiOC:H dielectric, introduced in the interconnections. This low dielectric constant material was developed by introducing porosities, which reversely have negatively affected its mechanical properties. Thus, product reliability becomes a challenge for microelectronic industry. To understand the crack initiation and propagation in these materials, a microbending machine was designed to perform fracture tests under optical or scanning electron microscopy.
Double-torsion tests were performed on 775 µm-thick silicon wafers. Results confirmed that silicon is highly brittle and with no measurable subcritical crack growth. Even at $K_I$ approaching 98% of $K_{IC}$, crack rates were at least lower than $10^{-11}$ m/s. It was even possible to obtain relevant measurements of $K_{IC}$ on thinned substrate (200 µm), for loads lower than the newton. These results agreed with the literature and showed the potential of the method to accurately monitor crack propagation in very thin samples on which films can be deposited.
The same tests were done on a 0.7 µm-thick SiOC:H film deposited on the substrate. The crack initiates in the substrate rather than in the layer. Indeed, the low thickness of the coating, associated to its low stiffness compared to the silicon, lead to a crack propagation from the substrate. The same observations were done with a four-point bending configuration. Therefore, various sample preparations and pre-defect initiations are currently evaluated to contain the crack within the dielectric material.
This work brings insights on the double-torsion tool capability but also on the silicon fracture behavior at low thickness, which may be useful for microelectronics. It also highlights the difficulty to address the crack propagation in SiOC:H dielectric at submicron thicknesses.
| Speaker Country | France |
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