Twinning rather than thinning: yields 100µm-thin wafers in minutes

February 27, 2018 // By Julien Happich
German wafering technology solutions provider Siltectra announced a breakthrough in wafer thinning, doing away with traditionally inefficient grinding methods.

The company has developed a laser-based technique called "Cold Split" which it says out-performs traditional grinding methods by thinning wafers to 100 microns and below in minutes instead of hours, cutting material loss by as much as 90 percent. The technique employs a chemical-physical process that uses thermal stress to generate a force that splits the material with exquisite precision along the desired plane.

The company had already proven its Cold Split wafer-thinning technique for substrate materials like silicon carbide (SiC), gallium nitride (GaN), silicon (Si) and sapphire. But now it managed to adapt the technique so that the removed substrate material can be reclaimed as a twin wafer, creating a second fully optimizable bonus wafer in the process. Previously, the removed material was just wasted during backside grinding.

Dubbed "Twinning", this Cold Split adaptation promises substantial benefits for manufacturers of SiC-based ICs like power electronics and RF devices. Twinning wafers means fewer process steps, potentially lower equipment costs, and together with the ultra-efficient use of substrate material, the new technique could reduce total device production costs by as much as 30 percent, anticipates Siltectra.

The company validated the process by producing a GaN on SiC high electron-mobility power transistor (HEMT) device on a split-off (or “twinned”) wafer at its new state-of-the-art facility in Dresden. The HEMT showed results that were superior to a non-Cold-Split-enabled HEMT when measured for CMP characterization, as well as GaN EPI, metal layer and gate layer outcomes. 

Leading integrated device manufacturers (IDMs) are now evaluating the technology. Until now, the traditional method to thin wafers to less than 20 percent of the original thickness was grinding, which involves the use of expensive diamond grinding wheels. What’s more, grinding is not a fast process, and the cost of consumables for the grinding wheels can be substantial. Finally, grinding generates material loss, and the process lowers overall yield, which further drives up cost.

The “twinning” breakthrough extends Cold Split’s capabilities.


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