Physical quantity sensor having optical part and method for manufacturing the same

• US 20070069318A1
• Filed: 08/17/2006
• Published: 03/29/2007
• Est. Priority Date: 09/09/2005
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Takeuchi, Yukihiro, Oohara, Junji
• Granted Patent: US 7,540,192 B2
• Time in Patent Office: Days
• US Class Current: 257/432
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81C 1/00126 Static structures not provided for in groups B81C1/00031 - B81C1/00119
• CPC Class Codes: G01D 5/285 using a movable mirror
• CPC Class Codes: G02B 26/0816 by means of one or more reflecting elements

Abstract

A method for manufacturing a physical quantity sensor having a movable portion, a support portion and an optical part is provided. The method includes steps of: etching a silicon substrate so that a movable-portion-to-be-formed portion, a support-portion-to-be-formed portion, and an optical-part-to-be-formed portion having a plurality of columns and trenches are formed; oxidizing the optical-part-to-be-formed portion so that each column changes to a silicon oxide column and the trench is filled with a silicon oxide layer; and removing a part of the movable-portion-to-be-formed portion connecting to the silicon substrate so that the movable portion is separated from the silicon substrate.

Claims

1. A method for manufacturing a physical quantity sensor, which includes a movable portion, a support portion and an optical part, wherein the movable portion is movable in a predetermined direction in accordance with a physical quantity applied to the sensor, wherein the movable portion is movably supported on the support portion, wherein the optical part irradiates a light to the movable portion, the light emitted from an external light emitting device and entered into the optical part, and wherein the physical quantity is detected on the basis of detection of the light reflected on the movable portion, the detection performed by an external light detector, the method comprising steps of:

etching a silicon substrate so that a movable-portion-to-be-formed portion, a support-portion-to-be-formed portion, and an optical-part-to-be-formed portion are formed on the silicon substrate, wherein the movable-portion-to-be-formed portion provides the movable portion, the support-portion-to-be-formed portion provides the support portion, and the optical-part-to-be-formed portion provides the optical part, and wherein the optical-part-to-be-formed portion includes a plurality of columns, which are disposed in parallel each other and have a trench between two neighboring columns;

oxidizing the optical-part-to-be-formed portion so that each column changes to a silicon oxide column and the trench is filled with a silicon oxide layer; and

removing a part of the movable-portion-to-be-formed portion connecting to the silicon substrate so that the movable portion is separated from the silicon substrate and the movable portion is movably supported on the support portion.

2. The method according to claim 1, wherein

the silicon substrate is made of a SOI substrate.

3. The method according to claim 1, wherein

the support-portion-to-be-formed portion has a width larger than a width of the movable-portion-to-be-formed portion, and

the optical-part-to-be-formed portion has a width larger than the width of the movable-portion-to-be-formed portion.

4. The method according to claim 1, wherein

in the step of removing the part of the movable-portion-to-be-formed portion, a part of the support-portion-to-be-formed portion remains to integrally connect to the silicon substrate, and

in the step of removing the part of the movable-portion-to-be-formed portion, a part of the optical-part-to-be-formed portion remains to integrally connect to the silicon substrate.

5. The method according to claim 1, wherein

in the step of oxidizing the optical-part-to-be-formed portion, the silicon oxide layer and the silicon oxide column are integrated so that the silicon oxide layer and the silicon oxide column provide the optical part,

in the step of oxidizing the optical-part-to-be-formed portion, a silicon oxide film is formed on a surface of the silicon substrate, and

in the step of removing the part of the movable-portion-to-be-formed portion, the silicon oxide film on the silicon substrate is removed.

6. The method according to claim 1, wherein

in the step of removing the part of the movable-portion-to-be-formed portion, the part of the movable-portion-to-be-formed portion connecting to the silicon substrate is etched by using a XeF₂ gas.

7. The method according to claim 1, wherein, in the step of oxidizing the optical-part-to-be-formed portion, the trench is partially filled with the silicon oxide layer so that a groove remains between the silicon oxide columns, the method further comprising a step of:

depositing a silicon oxide film in the groove to fill the groove with the silicon oxide film.

8. The method according to claim 7, wherein

in the step of depositing the silicon oxide film, a supercritical fluid, in which a silicon oxide dissolves, is introduced into the groove to deposit the silicon oxide film on an inner wall of the groove.

9. The method according to claim 8, wherein

the supercritical fluid includes a main component made of carbon dioxide.

10. The method according to claim 8, wherein, in the step of oxidizing the optical-part-to-be-formed portion, the trench is partially filled with the silicon oxide layer so that a groove remains between the silicon oxide columns, the method further comprising a step of:

depositing a compound film on an inner wall of the groove to fill the groove with the compound film, wherein

in the step of depositing the compound film, a supercritical fluid, in which a compound dissolves, is introduced into the groove to deposit the compound film on the inner wall of the groove, and

the compound film has a refraction index, which is substantially equal to a refraction index of the silicon oxide column.

11. The method according to claim 1, wherein

in the step of etching the silicon substrate, each column has a thin plate shape with a longitudinal direction, which extends along with an optical axis of the optical part, and

the trench has a sidewall in parallel to the longitudinal direction of the column.

12. The method according to claim 1, wherein

in the step of etching the silicon substrate, a surface of the silicon substrate is etched by using an inductively coupled plasma so that the movable-portion-to-be-formed portion, the support-portion-to-be-formed portion, and the optical-part-to-be-formed portion are formed on the silicon substrate.

13. The method according to claim 1, wherein

the movable portion includes a beam for movably supporting the movable portion to the support portion,

in the step of etching the silicon substrate, a beam-to-be-formed portion is formed on the silicon substrate,

in the step of removing the part of the movable-portion-to-be-formed portion, a part of the beam-to-be-formed portion connecting to the silicon substrate is removed so that the beam is separated from the silicon substrate, and

the beam-to-be-formed portion provides the beam.

14. The method according to claim 13, wherein

the support-portion-to-be-formed portion has a width larger than a width of the movable-portion-to-be-formed portion and larger than a width of the beam-to-be-formed portion, and

the optical-part-to-be-formed portion has a width larger than the width of the movable-portion-to-be-formed portion and larger than the width of the beam-to-be-formed portion.

15. The method according to claim 13, wherein

in the step of removing the part of the movable-portion-to-be-formed portion, a part of the support-portion-to-be-formed portion remains to integrally connect to the silicon substrate, and

in the step of removing the part of the movable-portion-to-be-formed portion, a part of the optical-part-to-be-formed portion remains to integrally connect to the silicon substrate.

16. The method according to claim 13, wherein

in the step of oxidizing the optical-part-to-be-formed portion, the silicon oxide layer and the silicon oxide column are integrated so that the silicon oxide layer and the silicon oxide column provide the optical part,

in the step of oxidizing the optical-part-to-be-formed portion, a silicon oxide film is formed on a surface of the silicon substrate, and

in the step of removing the part of the movable-portion-to-be-formed portion, the silicon oxide film on the silicon substrate is removed.

17. The method according to claim 13, wherein

in the step of removing the part of the movable-portion-to-be-formed portion, the part of the movable-portion-to-be-formed portion connecting to the silicon substrate and the part of the beam-to-be-formed portion connecting to the silicon substrate are etched by using a XeF₂ gas.

18. The method according to claim 13, wherein, in the step of oxidizing the optical-part-to-be-formed portion, the trench is partially filled with the silicon oxide layer so that a groove remains between the silicon oxide columns, the method further comprising a step of:

depositing a silicon oxide film in the groove to fill the groove with the silicon oxide film.

19. The method according to claim 18, wherein

in the step of depositing the silicon oxide film, a supercritical fluid, in which a silicon oxide dissolves, is introduced into the groove to deposit the silicon oxide film on an inner wall of the groove.

20. The method according to claim 19, wherein

the supercritical fluid includes a main component made of carbon dioxide.

21. The method according to claim 19, wherein, in the step of oxidizing the optical-part-to-be-formed portion, the trench is partially filled with the silicon oxide layer so that a groove remains between the silicon oxide columns, the method further comprising a step of:

depositing a compound film on an inner wall of the groove to fill the groove with the compound film, wherein

in the step of depositing the compound film, a supercritical fluid, in which a compound dissolves, is introduced into the groove to deposit the compound film on the inner wall of the groove, and

the compound film has a refraction index, which is substantially equal to a refraction index of the silicon oxide column.

22. The method according to claim 13, wherein

in the step of etching the silicon substrate, each column has a thin plate shape with a longitudinal direction, which extends along with an optical axis of the optical part, and

the trench has a side wall in parallel to the longitudinal direction of the column.

23. The method according to claim 13, wherein

in the step of etching the silicon substrate, a surface of the silicon substrate is etched by using an inductively coupled plasma so that the movable-portion-to-be-formed portion, the support-portion-to-be-formed portion, the optical-part-to-be-formed portion and the beam-to-be-formed portion are formed on the silicon substrate.

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

a silicon substrate;

a light emitting element for emitting a light;

an optical part for irradiating the light from the light emitting element as an irradiation light;

a movable portion having a reflection surface, wherein the reflection surface reflects the irradiation light as a reflection light, and wherein the movable portion is movable in accordance with the physical quantity applied to the sensor so that an incident angle of the irradiation light with respect to the reflection surface is changed;

a support portion for movably supporting the movable portion on the silicon substrate; and

a detection element for detecting a change of the reflection light in order to detect the physical quantity, wherein

the optical part is made of silicon oxide, and integrated with the silicon substrate,

the support portion is made of silicon, and integrated with the silicon substrate,

the movable portion is made of silicon, and integrated with the silicon substrate through the support portion,

the optical part has a top surface opposite to the silicon substrate,

the movable portion has a top surface opposite to the silicon substrate, and

the top surface of the movable portion and the top surface of the optical part are disposed on almost a same plane.

25. The sensor according to claim 24, wherein

the optical part is one of a micro lens, an optical waveguide and a prism.

26. The sensor according to claim 25, wherein

the optical part is the micro lens.

27. The sensor according to claim 25, wherein

the optical part is the optical waveguide.

28. The sensor according to claim 25, wherein

the optical part is the prism.

29. The sensor according to claim 24, wherein

the optical part includes two of a micro lens, an optical waveguide and a prism.

30. The sensor according to claim 24, wherein

the optical part includes multiple pairs of two of a micro lens, an optical waveguide and a prism.

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

a silicon substrate;

a light emitting element for emitting a light;

an optical part for irradiating the light from the light emitting element as an irradiation light;

a movable portion having a reflection surface, wherein the reflection surface reflects the irradiation light as a reflection light, and wherein the movable portion is movable in accordance with the physical quantity applied to the sensor so that an incident angle of the irradiation light with respect to the reflection surface is changed;

a support portion for movably supporting the movable portion on the silicon substrate; and

a detection element for detecting a change of the reflection light in order to detect the physical quantity, wherein

the optical part is made of silicon oxide, and integrated with the silicon substrate,

the support portion is made of silicon, and integrated with the silicon substrate,

the movable portion other than the reflection surface is made of silicon, and integrated with the silicon substrate through the support portion, and

the reflection surface of the movable portion is made of silicon oxide.

32. The sensor according to claim 31, wherein

the optical part is one of a micro lens, an optical waveguide and a prism.

33. The sensor according to claim 32, wherein

the optical part is the micro lens.

34. The sensor according to claim 32, wherein

the optical part is the optical waveguide.

35. The sensor according to claim 32, wherein

the optical part is the prism.

36. The sensor according to claim 31, wherein

the optical part includes two of a micro lens, an optical waveguide and a prism.

37. The sensor according to claim 31, wherein

the optical part includes multiple pairs of two of a micro lens, an optical waveguide and a prism.