Sealed cavity semiconductor pressure transducers and method of producing the same

摘要

Sealed cavity structures suitable for use as pressure transducers are formed on a single surface of a semiconductor substrate (20) by, for example, deposit of a polycrystalline silicon layer (32) from silane gas over a relatively large silicon dioxide post (22) and smaller silicon dioxide ridges (27) leading outwardly from the post. The polysilicon layer is masked and etched to expose the outer edges of the ridges and the entire structure is then immersed in an etchant which etches the silicon dioxide forming the ridges and the post but not the substrate (20) or the deposited polysilicon layer (32). A cavity structure results in which channels (35) are left in place of the ridges and extend from communication with the atmosphere to the cavity (36) left in place of the post. The cavity (36) may be sealed off from the external atmosphere by a second vapor deposition of polysilicon or silicon nitride, which fills up and seals off the channels (35), or by exposing the substrate and the structure thereon to an oxidizing ambient which results in growth of silicon dioxide in the channels sufficient to seal off the channels. Deflection of the membrane spanning the cavity occurring as a result of pressure changes, may be detected, for example, by piezoresistive devices formed on the membrane.