MEMS device, MEMS device module and acoustic transducer
View Patent ↗A MEMS device includes a first insulating film formed on a semiconductor substrate, a vibrating film formed on the first insulating film, and a fixed film above the vibrating film with an air gap being interposed therebetween. The semiconductor substrate has a region containing N-type majority carriers. A concentration of N-type majority carriers in a portion of the semiconductor substrate where the semiconductor substrate contacts the first insulating film, is higher than a concentration of N-type majority carriers in the other portion of the semiconductor substrate.
1. A MEMS device comprising:
a semiconductor substrate;
a first insulating film formed between the semiconductor substrate and a first electrode;
a vibrating film formed on the first insulating film and having the first electrode;
a fixed film formed above the vibrating film with an air gap being interposed between the vibrating film and the fixed film, the fixed film having a second electrode; and
a second insulating film provided between the semiconductor substrate and a portion of the fixed film, the second insulating film having an opening that exposes a part of the first electrode,
wherein:
the semiconductor substrate has a region containing N-type majority carriers,
the semiconductor substrate contacts the first insulating film,
the region containing N-type majority carriers is provided in at least a portion of the semiconductor substrate where the semiconductor substrate contacts the first insulating film,
a concentration of N-type majority carriers in the portion of the semiconductor substrate where the semiconductor substrate contacts the first insulating film is higher than a concentration of N-type majority carriers in other portions of the semiconductor substrate, and
the portion of the semiconductor substrate which is in contact with the first insulating film is located in a region directly under the opening.
2. The MEMS device of claim 1 , wherein
the semiconductor substrate is a silicon substrate.
3. The MEMS device of claim 1 , wherein
the semiconductor substrate and the first insulating film are removed from a predetermined region, and the vibrating film is formed, covering the predetermined region.
4. The MEMS device of claim 1 , wherein
the region containing N-type majority carriers contains an N-type impurity.
5. The MEMS device of claim 4 , wherein
a concentration of the N-type impurity is 1×10 14 cm −3 or more and 1×10 21 cm −3 or less.
6. The MEMS device of claim 4 , wherein
the N-type impurity is a phosphorus atom or an arsenic atom.
7. The MEMS device of claim 1 , wherein
the semiconductor substrate is an N-type semiconductor substrate.
8. The MEMS device of claim 1 , wherein
the first insulating film is a silicon oxide film.
9. The MEMS device of claim 1 , wherein
the second insulating film is a silicon oxide film.
10. The MEMS device of claim 1 , wherein
a height of the air gap is substantially equal to a separation between the vibrating film and the fixed film.
11. A MEMS device module comprising:
the MEMS device of claim 1 ; and
a cover provided above the MEMS device and having an acoustic hole.
12. The MEMS device module of claim 11 , wherein
the acoustic hole is provided immediately above the MEMS device.
13. The MEMS device module of claim 11 , further comprising:
an amplifier electrically coupled to the MEMS device.