Pressure transducer and method for fabricating same

A process for fabricating a pressure transducer, comprising;

• a first step of forming a support layer on a substrate,
• a second step of forming an inner layer on said support layer, and forming perforations in said inner layer by etching,
• a third step of forming a cavity in said support layer under said inner layer by etching through said perforations of said inner layers, and
• a fourth step of forming a cover layer on said inner layer to seal said cavity,
• wherein said support layer is made of a semiconductor material, and said inner layer comprises a first layer of an insulating material, and wherein said first step comprises a step of selectively doping said support layer so that said support layer has an undoped central region and a highly doped peripheral region surrounding said central region, and said third step is performed by etching away said central region of said support layer and leaving said highly doped peripheral region unetched.

A pressure transducer comprising:

• a substrate;
• a diaphragm layer;
• a support layer interposed between said substrate and said diaphragm layer, said support layer having an opening, both sides of which are closed by said substrate and said diaphragm layer to form a hermetically sealed internal cavity serving as a reference pressure chamber;
• said diaphragm layer comprising an inner layer, of a material different from that of said support layer, extending over said cavity of said support layer to constitute an interior surface of said cavity and having a plurality of perforations opening into said cavity, and a cover layer formed on said inner layer and closing said perforations to seal said cavity;
• and
• a capacitive type converting means for converting the displacement of said diaphragm into a change in capacitance between a lower electrode formed under said cavity and an upper electrode constituted by said cover layer of said diaphragm layer;
• said substrate comprising a silicon bulk layer of a first conductivity type, a highly doped diffusion region of a second conductivity type formed in said bulk layer and used as said lower electrode, and a lower insulating layer formed on said diffusion region and constituting a lower interior surface of said cavity.

A pressure transducer comprising;

• a substrate;
• a diaphragm layer comprising an inner layer extending over said cavity to form an interior surface of said cavity, said inner layer having a plurality of perforations opening into said cavity, and a cover layer formed on said inner layer and closing said perforations to seal said cavity;
• a support layer interposed between said substrate and said diaphragm layer, said support layer having an opening, both sides of which are closed by said substrate and said diaphragm layer to form a hermetically sealed internal cavity serving as a reference pressure chamber, said support layer formed of a material different from that of said inner layer;
• and
• piezoresistive means formed in said diaphragm layer for converting the displacement of said diaphragm layer into a change in resistance of said piezoresistive means.

A pressure transducer comprising:

• a substrate;
• a diaphragm layer;
• a support layer interposed between said substrate and said diaphragm layer, said support layer having an opening, both sides of which are closed by said substrate and said diaphragm layer to form a hermetically sealed internal cavity serving as a reference pressure chamber;
• said diaphragm layer comprising an inner layer, of a first layer of material different from that of said support layer, extending over said cavity, and having a plurality of perforations opening into said cavity, and a cover layer which is formed on said inner layer and closes said perforations to seal said cavity;
• said inner layer further comprising an interlying layer formed on said first layer and a second layer formed on said interlying layer, each perforations of said inner layer comprising a first perforation in said first layer, a second perforation in second layer at a displaced position right above said first perforation, and an intellying perforation formed in said interlying layer and connecting said first and second perforations;
• and
• means for converting a displacement of said diaphragm layer into an electric signal.