Handbook of Silicon Based MEMS Materials and Technologies

7.4. Fabrication of Thick-Film BSOI by Mechanical Grinding and Polishing

The sequence of steps required to make thick-film SOI wafers by mechanical thinning of the device layer is illustrated in Figure 7.9. After wet cleaning and surface inspection, which form the last two process steps of silicon wafer manufacturing, a thermal oxide is formed on the wafers. This oxide later becomes the buried oxide of the SOI structure. The oxide thickness is defined by the requirements of the application, and it most commonly falls in the range from 400 nm to 2 μm (Figure 7.3). In direct bonding the wafers are aligned, keeping a narrow gap between them. In SOI wafer manufacturing the alignment is most commonly based on mechanical flat-to-flat or notch alignment. ...