Research Academics  

High TemperaturSiC Micro Hotplate for Gas Sensors


Contact Person : Dr.-Ing. Ha-Duong Ngo


In the last years some research on silicon fusion bonding was done.In this research some techniques for fusion bonding were evaluated. Different wafer pairs were investigated: without oxide layer, only one wafer with oxide layer and both wafers with oxide layers. The oxide layers had different thicknesses. Also the influence of the annealing time and temperature was examined.


Figure. 1: wafer pair before (left image) and after annealing (right image)


In Figure 1 a wafer pair before and after annealing is shown. The images were taken using an ultrasonic microscope. Dark areas represent good bonded interfaces. So the success of the annealing step is clearly visible: in the right image the wafer is bonded up to the edge, leaving only one small void (light spot at the right side). The wafer shown here was annealed at 1100°C for about 5h.


Figure 2: Results of pull tests done on fusion bonded wafers

With these wafers pull tests were done. For this test the wafers were diced into small chips (6×6 mm2) and glued onto aluminum pieces to install them into the pull tester. The results measured with this assembly achieved the practical limit, the stability of the glue. Compared with older measurements on anodic bonded glass/silicon wafer pairs the results gave an increased strength of the bonded interface. In comparison to a commercially available SOI-wafer also better results were obtained.