MEMS sensor comprising a deformation-free back electrode
An MEMS sensor constructed on a base chip and having a capacitive mode of operation is disclosed. The MEMS sensor has a patterned layer construction applied on the base chip. A cutout is produced in the layer construction, the moveable electrode, for example a membrane, being arranged in said cutout. The cutout is spanned by a covering layer, which bears on the layer construction around the cutout and comprises the back electrode.
1. An MEMS sensor having a capacitive mode of operation, comprising:
a base chip;
a patterned layer construction applied on a surface of the base chip;
a cutout in the layer construction, said cutout being surrounded by an edge region of the layer construction;
a moveable electrode, which is arranged in the cutout and is connected to the layer construction; and
a covering layer, which comprises a back electrode, bears on the layer construction around the cutout and spans the cutout;
wherein the covering layer or a partial layer of the covering layer comprises a portion extending to the base chip and surrounding the cutout within the layer construction.
2. The MEMS sensor as claimed in claim 1 ,
wherein the covering layer comprises an electrically conductive partial layer in the region of the cutout.
3. The MEMS sensor as claimed in claim 2 ,
wherein the covering layer comprises a partial layer composed of polysilicon.
4. The MEMS sensor as claimed in claim 1 , wherein
a top side of the covering layer in the region of the cutout and the edge region surrounding the cutout lies at the same level above the surface of the base chip.
5. The MEMS sensor as claimed in claim 2 , wherein
the electrically conductive partial layer of the covering layer is formed from polysilicon.
6. The MEMS sensor as claimed in claim 1 , wherein
the covering layer has a pattern of openings (OE) in the region of the cutout.
7. The MEMS sensor as claimed in claim 1 , wherein
the covering layer comprises a silicon nitride layer.
8. The MEMS sensor as claimed in claim 7 , wherein
the covering layer comprises two silicon nitride layers between which a polysilicon layer (PS) is arranged.
9. The MEMS sensor as claimed in claim 1 , wherein
the moveable electrode is formed as a membrane and the covering layer or the partial layer of the covering layer, in the edge region but within the cutout, has protuberances in the direction of the base chip which reach as far as directly over the membrane.
10. The MEMS sensor as claimed in claim 1 , wherein
a membrane is arranged above a perforation leading through the entire thickness of the base chip.