Acceleration sensor

• US 20060196270A1
• Filed: 12/20/2005
• Published: 09/07/2006
• Est. Priority Date: 12/20/2004
• Status: Active Grant

• Current Assignee: LAPIS Semiconductor Co., Ltd. (ROHM Co., Ltd.)
• Original Assignee: OKI Electric Industry Company Limited
• Inventors: Ino, Yoshihiko
• Granted Patent: US 7,650,787 B2
• Time in Patent Office: Days
• US Class Current: 73/514.16
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/49171 Fan-out arrangements
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/1461 MEMS

Abstract

An acceleration sensor has a semiconductor acceleration sensor chip and a case. The semiconductor acceleration sensor chip has a fixed portion, a plummet portion surrounding the fixed portion without contacting the fixed portion, and a beam portion connecting the fixed portion and the plummet portion, the thickness of the beam portion being thinner than the thickness of the fixed portion. The case has a cavity housing the semiconductor acceleration sensor chip, and a projection portion formed on the bottom face of the cavity, the bottom face of the fixed portion being fixed to the top face of the projection portion.

Claims

1. An acceleration sensor comprising:

a semiconductor acceleration sensor chip having

a fixed portion,

a plummet portion surrounding the fixed portion without contacting the fixed portion, and

a beam portion connecting the fixed portion and the plummet portion, the thickness of the beam portion being thinner than the thickness of the fixed portion; and

a case having

a cavity housing the semiconductor acceleration sensor chip, and

a projection portion formed on a bottom face of the cavity, a bottom face of the fixed portion being fixed to a top face of the projection portion.

2. The acceleration sensor according to claim 1, wherein

the shape of the plummet portion is an approximately square column which has a cavity for housing the fixed portion in the center thereof, and

the beam portion connects the plummet portion and the fixed portion on the diagonal line of the cavity of the plummet portion.

3. The acceleration sensor according to claim 2, further comprising:

first electrodes formed on the surface of the fixed portion at predetermined intervals.

4. The acceleration sensor according to claim 3, further comprising:

external wiring electrodes formed at one or more side faces of the case, the external wiring electrodes being electrically led to the exterior of the case; and

bonding wires electrically connecting the first electrodes and the external wiring electrodes.

5. The acceleration sensor according to claim 3, wherein

the bonding wire is a gold wire and bonded to the first electrode and the external wiring electrode by means of an ultrasonic concomitant thermocompression bonding method.

6. The acceleration sensor according to claim 4, wherein

the shape of the fixed portion is an approximately square column.

7. The acceleration sensor according to claim 6, wherein

the shape of the projection portion is an approximately square column.

8. The acceleration sensor according to claim 7, wherein

the case is comprised of a ceramic material, and

the projection portion is formed by attaching an approximately square green sheet to the surface of another green sheet which is to become the bottom face of the cavity of the case, and sintering the same.

9. The acceleration sensor according to claim 7, wherein

the case is comprised of a ceramic material, and

the projection portions are formed by attaching an approximately square resin film to the bottom face of the cavity of the case.

10. The acceleration sensor according to claim 4, wherein

the shape of the fixed portion is an approximately circular cylinder.

11. The acceleration sensor according to claim 10, wherein

the shape of the projection portion is an approximately circular cylinder.

12. The acceleration sensor according to claim 11, wherein

the case is comprised of a ceramic material, and

the projection portion is formed by attaching an approximately circular green sheet to the surface of another green sheet which is to become the bottom face of the cavity of the case, and sintering the same.

13. The acceleration sensor according to claim 11, wherein

the case is comprised of a ceramic material, and

the projection portion is formed by attaching an approximately circular resin film to the bottom face of the cavity of the case.

14. The acceleration sensor according to claim 1, further comprising:

an integrated circuit fixed on the bottom face of the cavity of the case, the integrated circuit connected with the semiconductor acceleration sensor chip.

15. The acceleration sensor according to claim 14, wherein

the shape of the plummet portion is an approximately square column which has a cavity for housing the fixed portion in the center thereof, and

the beam portion connects the plummet portion and the fixed portion on the diagonal line of the cavity of the plummet portion.

16. The acceleration sensor according to claim 15, further comprising:

first electrodes formed on the surface of the fixed portion at predetermined intervals.

17. The acceleration sensor according to claim 16, further comprising:

second electrodes formed on the surface of the integrated circuit at predetermined intervals.

18. The acceleration sensor according to claim 17, further comprising:

bonding wires electrically connecting the first electrodes and the second electrodes.

19. The acceleration sensor according to claim 18, wherein

the bonding wire is a gold wire and bonded to the first electrode and the second electrode by mean of an ultrasonic concomitant thermocompression bonding method.

20. The acceleration sensor according to claim 18, further comprising:

external wiring electrodes formed at one or more side faces of the case, the external wiring electrodes being electrically led to the exterior of the case; and

bonding wires that respectively electrically connect the first electrodes and the external wiring electrodes, and the second electrodes and the external wiring electrode.

21. The acceleration sensor according to claim 20, wherein

the bonding wire is a gold wire and bonded to the first electrode and the external wiring electrode by means of an ultrasonic concomitant thermocompression bonding method.

22. The acceleration sensor according to claim 20, wherein

the shape of the fixed portion is an approximately square column.

23. The acceleration sensor according to claim 22, wherein

the shape of the projection portion is an approximately square column.

24. The acceleration sensor according to claim 23, wherein

the case is comprised of a ceramic material, and

the projection portion is formed by attaching an approximately square green sheet to the surface of another green sheet which is to become the bottom face of the cavity of the case, and sintering the same.

25. The acceleration sensor according to claim 23, wherein

the case is comprised of a ceramic material, and

the projection portions are formed by attaching an approximately square resin film to the bottom face of the cavity of the case.

26. The acceleration sensor according to claim 20, wherein the shape of the fixed portion is an approximately circular cylinder.

27. The acceleration sensor according to claim 26, wherein the shape of the projection portion is an approximately circular cylinder.

28. The acceleration sensor according to claim 27, wherein

the case is comprised of a ceramic material, and

the projection portion is formed by attaching an approximately circular green sheet to the surface of another green sheet which is to become the bottom face of the cavity of the case, and sintering the same.

29. The acceleration sensor according to claim 27, wherein

the case is comprised of a ceramic material, and

the projection portion is formed by attaching an approximately circular resin film to the bottom face of the cavity of the case.