Patterned cracks in the buried oxide layer improve yield in device release from SOI wafers

Cracks patterned lithographically into the buried oxide (BOX) layer of silicon-on-insulator wafers were found to substantially improve yield in the release of ultrasoft silicon cantilevers. The BOX layer is useful as an etch stop and sacrificial layer in microfabrication. However, compressive stress in the BOX membrane can cause it to buckle and crack when released. These cracks can damage delicate structures in the device layer and reduce yield. Cracks were patterned into the BOX layer prior to avoid critical regions near or under devices; these patterned cracks reduced damage to devices from spontaneous cracks in the BOX layer and improved yield.