Directional accelerometer and its microlithographic fabrication process

A process for the fabrication of a monodirectional accelerometer used for measuring one component of an acceleration of a moving body, said component being parallel to a first direction, said accelerometer comprising a substrate having at least one recess, at least one parallelepipedic beam placed in the recess and having a first end which is integral with said substrate, said beam oriented to a second direction parallel to a surface of said substrate and perpendicular to said first direction being able to deform only in said first direction and having a thickness higher than its width, said thickness being oriented to a third direction perpendicular to said first and second directions and said width being oriented to said first direction, measuring means for measuring deformations of said beam in said first direction and electrical contacts formed on said substrate for connecting said measuring means with said beam, said process comprising the following stages:

• forming on said substrate a mask which defines the shape of said recess, said beam and in particular the width of said beam,
• etching mask-free substrate regions in said third direction in order to form said recess and beam, the thickness of said beam being defined by said etching,
• forming said measuring means,
• eliminating said mask and
• metallizing the etched substrate in order to produce said electrical connections and contacts.

A process for the fabrication of a monodirectional accelerometer used for measuring one component of an acceleration of a moving body, said component being parallel to a first direction, said accelerometer comprising a substrate having at least one recess, at least one parallelepipedic beam placed in the recess and having a first end which is integral with said substrate, said beam oriented to a second direction parallel to a surface of said substrate and perpendicular to said first direction being able to deform only in said first direction and having a thickness higher than its width, said thickness being oriented to a third direction perpendicular to said first and second directions and said width being oriented to said first direction, measuring means for measuring deformations of said beam in said first direction and electrical contacts formed on said substrate for connecting said measuring means with said beam, said process comprising the following stages:

• metallizing the substrate surface in order to produce said electrical connections and contacts,
• forming on said metallized substrate a mask which defines the shape of said recess, said beam and in particular the width of said beam,
• etching mask-free substrate regions in said third direction in order to form said recess and beam, the thickness of said beam being defined by said etching,
• forming said measuring means and
• eliminating said mask.

A process for the fabrication of a monodirectional accelerometer used for measuring one component of an acceleration of a moving body, said component being parallel to a first direction, said accelerometer comprising a substrate having at least one recess, at least one parallelepipedic beam placed in the recess and having a first end which is integral with said substrate, said beam oriented to a second direction parallel to a surface of said substrate and perpendicular to said first direction being able to deform only in said first direction and having a thickness higher than its width, said thickness being oriented to a third direction perpendicular to said first and second directions and said width being oriented to said first direction, measuring means for measuring deformations of said beam in said first direction and electrical contacts formed on said substrate for connecting said measuring means with said beam, said process comprising the following stages:

• forming on said substrate a conductive mask which defines the shape of said recess, said beam and in particular the width of said beam and which produces said electrical connections and contacts, said mask being shaped like a grid, of which bars have a limited spacing in the substrate regions which are to be free from said electrical connections,
• etching mask-free substrate regions in said third direction in order to form said recess and beam, the thickness of said beam being defined by said etching, and
• forming said measuring means.

A monodirectional accelerometer for measuring component of an acceleration of a moving body, comprising:

• a substrate formed of a material and having at least one recess;
• at least one parallelepipedic beam placed in the recess and having a first end which is integral with said substrate, said beam being formed of said material, being oriented in a first direction and being able to deform in a second direction in said recess and having a thickness higher than its width so that said beam is only deformable in said second direction, said second direction being parallel to the surface of said substrate and perpendicular to said first direction, said deformation in said second direction corresponding to said component of said acceleration to be measured;
• said beam having a second end which supports a block, said block being formed in said substrate and being able to move in said recess in the second direction, said block being connected to the substrate in the first direction with a spring which is formed in the substrate;
• means for measuring deformations of said beam in said second direction to determine the value of said component of said acceleration;
• and
• electrical contacts formed on said substrate for connecting said means for measuring with said beam.