Advanced Wafer Singulation Techniques for Miniaturized Metal-oxide (MOX) Micro-hotplates Based Gas Analyzer

A typical process flow for micro-hotplate sensors includes the fabrication of the sensor wafer followed by functionalization. Functionalization involves the local deposition of a sensing material, or several materials in the case of a multi-gas analyzer. Functionalization makes the analyzer sensitive to specific gases. Typically, functionalization is a wafer-level process, of which screen and inkjet printing, dispensing and direct atomic layer processing are good examples. Once the sensor wafer is fully processed and functionalized, it must be singulated onto individual sensor dies. After that the individual sensor die will be assembled. Various die singulation methods have been reported, but they can pose serious problems for the functionalized sensor wafer. The sensing materials used for functionalization are dominated by metal-oxides, which are sensitive to environmental factors, including thermal exposure, humidity uptake, etc. In this paper, we reviewed various die singulation techniques and methods, in function of their suitability for singulating fully functionalized metal-oxide (MOX) micro-hotplates sensor silicon wafers, including wafer sawing, laser ablation and dicing, scribe-and-break, stealth dicing, plasma dicing, dicing before grinding and others. Finally, we identified the most suitable wafer singulation method for the selected application and presented an outlook.