Physical quantity sensor having protrusion and method for manufacturing the same

• US 20040187592A1
• Filed: 03/09/2004
• Published: 09/30/2004
• Est. Priority Date: 03/28/2003
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Sugiura, Makiko
• Granted Patent: US 7,111,513 B2
• Time in Patent Office: Days
• US Class Current: 73/780
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A physical quantity sensor detects a physical quantity. The sensor includes a movable portion having a bottom and a protrusion disposed on the bottom of the movable portion. The protrusion is provided without adding a manufacturing process, so that a manufacturing cost is reduced. Preferably, the protrusion is provided by a remaining portion, which remains without being etched when the movable portion is prepared by etching.

Claims

1. A physical quantity sensor for detecting a physical quantity, the sensor comprising:

a movable portion having a bottom; and

a protrusion disposed on the bottom of the movable portion.

2. The sensor according to claim 1,

wherein the protrusion is provided by a remaining portion, which remains without being etched when the movable portion is prepared by etching.

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

a substrate for supporting the movable portion movably;

wherein the movable portion is disposed over the substrate at a predetermined distance therebetween,

wherein the protrusion protrudes toward the substrate so that the protrusion prevents the movable portion from adhering to the substrate,

wherein the movable portion includes a part, which has a wide width compared with other parts of the movable portion,

wherein the protrusion is disposed on the bottom of the part of the movable portion, and

wherein the protrusion is formed simultaneously together with the movable portion in a case where the movable portion is removed from the substrate by etching.

4. The sensor according to claim 3,

wherein the part of the movable portion remains in a case where the movable portion is formed by isotropically etching so that the protrusion is provided by a remaining portion of the part of the movable portion.

5. The sensor according to claim 1, further comprising:

a fixed electrode,

wherein the movable portion includes a movable electrode,

wherein the movable electrode faces the fixed electrode so that a capacitor having a capacitance is provided between the movable and fixed electrodes, and

wherein the physical quantity is detectable on the basis of the capacitance.

6. The sensor according to claim 1,

wherein the movable portion includes a spring,

wherein the spring is movable in accordance with an acceleration applied to the sensor, and

wherein the protrusion protrudes from the spring.

7. The sensor according to claim 6,

wherein the sensor is an acceleration sensor or an angular rate sensor.

8. The sensor according to claim 1,

wherein the movable portion includes a part, which has a wide width compared with other parts of the movable portion, and

wherein the protrusion is disposed on the bottom of the part of the movable portion.

9. The sensor according to claim 8,

wherein the part of the movable portion is provided by a convexity extending to a movable direction of the movable portion.

10. The sensor according to claim 9, further comprising:

a substrate,

wherein the movable portion is disposed over the substrate at a predetermined distance, and

wherein the protrusion protrudes from the movable portion toward the substrate for preventing the movable portion from adhering to the substrate.

11. The sensor according to claim 10, further comprising:

a fixed electrode,

wherein the movable portion includes a movable electrode,

wherein the movable electrode faces the fixed electrode,

wherein the fixed electrode is supported on the substrate,

wherein the movable portion is movably supported on the substrate, and

wherein the convexity protrudes from the movable electrode toward the fixed electrode for preventing the movable electrode from adhering to the fixed electrode.

12. A method for manufacturing a physical quantity sensor for detecting a physical quantity, the method comprising the steps of:

laminating a second substrate on a first substrate;

firstly etching the second substrate so that a groove is formed between a movable-portion-to-be-formed region and the second substrate, wherein the groove includes a part, which is narrow compared with other portions of the groove, so that the movable-portion-to-be-formed region includes a convexity; and

secondary etching the second substrate so that a movable portion with the convexity is separated from the first substrate and a protrusion is formed on a bottom of the convexity.

13. The method according to claim 12,

wherein the protrusion protrudes from the convexity of the movable portion toward the first substrate so that the protrusion prevents the movable portion from adhering to the first substrate, and

wherein the protrusion is provided by a remaining portion of the second substrate, which is remained in the step of secondary etching the second substrate.

14. The method according to claim 13,

wherein the first substrate supports the movable portion movably, and

wherein the movable portion is disposed over the first substrate at a predetermined distance.

15. The method according to claim 12,

wherein the step of firstly etching the second substrate is provided by anisotropically etching method, and

wherein the step of secondary etching the second substrate is provided by isotropically etching method.

16. The method according to claim 15,

wherein the step of firstly etching the second substrate is provided by an inductive coupled plasma etching method.

17. The method according to claim 12,

wherein the convexity protrudes in a movable direction of the movable portion.

18. The method according to claim 12,

wherein a fixed electrode is formed in the steps of firstly etching and secondary etching,

wherein the movable portion includes a movable electrode,

wherein the protrusion protrudes from the movable electrode,

wherein the movable electrode faces the fixed electrode so that a capacitor having a capacitance is provided between the movable and fixed electrodes, and

wherein the physical quantity is detectable on the basis of the capacitance.

19. The method according to claim 18,

wherein the fixed electrode is supported on the first substrate,

wherein the movable portion is movably supported on the first substrate, and

wherein the convexity protrudes from the movable electrode toward the fixed electrode for preventing the movable electrode from adhering to the fixed electrode.

20. The method according to claim 12,

wherein the movable portion includes a spring,

wherein the spring is movable in accordance with an acceleration applied to the sensor, and

wherein the protrusion protrudes from the spring.

21. The method according to claim 20,

wherein the sensor is an acceleration sensor or an angular rate sensor.