Physical quantity sensor
For a small sensor produced through a MEMS process, when an electrode pad, wiring, or a shield layer is formed in a final step, it is difficult to nondestructively investigate whether a structure for sensing a physical quantity has been processed satisfactorily. In the present invention, in a physical quantity sensor formed from an MEMS structure, in a structure in which a surface electrode having through wiring is formed on the surface of an electrode substrate and the periphery thereof is insulated, forming a shield layer comprising a metallic material on the surface of the electrode substrate in a planar view and providing a space for internal observation inside the shield layer makes it possible to check for internal defects.
1. A physical quantity sensor, comprising:
a lamination structure in which a first substrate and a second substrate are laminated;
an electrode pad and a wiring formed on a surface of the first substrate;
a sensing portion formed on the second substrate; and
a conductive film formed on a surface of the first substrate, electrically insulated with respect to the electrode and the wiring, and held at a constant potential, wherein
the conductive film includes a peep portion to observe the sensing portion,
the sensing portion comprises movable comb teeth and fixed comb teeth,
a fixed electrode is formed in the second substrate and is electrically connected to a through hole surface electrode that is formed on an electrode substrate via a first electrode,
a movable electrode is formed in the second substrate and is electrically connected to a through hole surface electrode that is formed in the electrode substrate via a second electrode,
a fixed electrode is electrically connected to the fixed comb teeth,
a movable electrode is electrically connected to the movable comb teeth,
a sensing space is defined in the second substrate as a sealed space by the first substrate and the electrode substrate, and
in the sensing space, a pressure ranges from 10000 Pa to 50000 Pa.
2. The physical quantity sensor according to claim 1 , wherein
a shield layer comprises the peep portion in an area where the fixed comb teeth and the movable comb teeth are projected with respect to the shield layer in a lamination direction.
3. The physical quantity sensor according to claim 1 , wherein the peep portion is a thin wall portion in which a thickness of the shield layer is thinner than other portions or a portion in which the shield layer is not provided.
4. The physical quantity sensor according to claim 3 , wherein all of a substrate material include a silicon material.
5. The physical quantity sensor according to claim 3 , wherein the first substrate and the peep portion transmit infrared rays.
6. The physical quantity sensor according to claim 3 , wherein the peep portion is polygonal.