Production of silicon diaphragms by precision grinding

The application of precision grinding for silicon diaphragm formation is investigated. The test structures involved 6 mm diameter diaphragms with thickness in the range 25 micrometers - 150 micrometers . When grinding is performed without supporting the diaphragm, buckling occurs due to non-uniform removal of the silicon material over the diaphragm region. The magnitude of buckling depends on the final thickness of the diaphragm. Results obtained from using FEM analysis to determine deterioration in performance of the diaphragm performance due to buckling are presented. These results show a 10 percent reduction in performance for a 75 micrometers thick diaphragm with a buckling amplitude of 30 micrometers , but negligible reduction if the buckling is reduced to < 10 micrometers . It is shown that the use of a porous silicon support can significantly reduce the amount of buckling, by a factor of 4 in the case of 75 micrometers thick diaphragms. The use of SOI technology can also suppress or eliminate the buckling although this may be a less economical process.