Method for Structuring a Device Layer of a Substrate

• US 20090303563A1
• Filed: 06/05/2009
• Published: 12/10/2009
• Est. Priority Date: 06/05/2008
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Drabe, Christian, Klose, Thomas
• Granted Patent: US 8,199,390 B2
• Time in Patent Office: Days
• US Class Current: 359/214.100
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81C 1/00682 Treatments for improving mechanical properties, not provided for in B81C1/00658 - B81C1/0065
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B

Abstract

Method for structuring a device layer of a substrate, wherein the substrate includes a carrier layer, the device layer and an intermediate layer disposed between the carrier layer and the device layer. Thereby, the intermediate layer is structured for exposing, at least in one portion, a first surface of the carrier layer facing the device layer. Starting from a second surface of the carrier layer opposing the first surface, the thickness of the device layer is reduced to a predetermined thickness at those positions where the intermediate layer is removed.

Claims

1. Method for structuring a device layer of a substrate, wherein the substrate comprises a carrier layer, the device layer and an intermediate layer disposed between the carrier layer and the device layer, and wherein the intermediate layer is structured for exposing, at least in one portion, a first surface of the carrier layer facing the device layer, wherein, starting from a second surface of the carrier layer opposing the first surface, the thickness of the device layer is reduced to a predetermined thickness at those positions where the intermediate layer is removed.

2. The method according to claim 1, wherein the reducing comprises etching.

3. The method according to claim 2, wherein the intermediate layer is implemented as an etch stop with regard to the materials of the carrier layer and the device layer.

4. The method according to claim 2, wherein the predetermined thickness of the device layer is adjusted by the duration of etching.

5. The method according to claim 2, wherein, during the step of reducing, the thickness of the device layer is monitored by optical end point control, wherein reducing is terminated when the predetermined thickness is reached.

6. The method according to claim 2, wherein the device layer comprises a stop layer integrated in the device layer or deposited on the device layer, which defines the predetermined thickness of the device layer.

7. The method according to claim 6, wherein the stop layer and the device layer comprise different dopant concentrations.

8. The method according to claim 6, wherein the dopant concentration between the device layer and the stop layer changes in steps or continuously, or wherein the different dopant concentrations are selected for defining a pn transition.

9. The method according to claim 6, wherein different electrical potentials are applied to the device layer and to the stop layer.

10. The method according to claim 6, wherein the stop layer comprises a different material than the device layer.

11. The method according to claim 6, wherein the stop layer arranged on the device layer comprises a different crystal structure or crystal orientation than the device layer.

12. The method according to claim 1, wherein removing the carrier layer is performed, in at least one portion, in one processing step with reducing the thickness of the device layer.

13. The method according to claim 1, wherein the device layer comprises, at least in one area opposing the first surface of the carrier layer, an additional layer which is effective as an etch stop with regard to the material of the carrier layer.

14. The method according to claim 13, wherein reducing comprises:

etching the carrier layer until the additional layer is exposed;

removing the additional layer on the surface of the device layer; and

etching the device layer to the predetermined thickness.

15. The method according to claim 1, wherein the substrate is a BSOI wafer.

16. A method for producing a micromechanical structure, comprising:

providing a substrate comprising a device layer, a carrier layer and an intermediate layer disposed between the device layer and the carrier layer, wherein the intermediate layer is structured for exposing, at least in one portion, a first surface of the carrier layer facing the device layer; and

generating a micromechanical structure in the device layer of the substrate, wherein generating the micromechanical structure comprises reducing the thickness of the device layer to a predetermined thickness in at least one area of the micromechanical structure according to a method for structuring a device layer of a substrate, wherein the substrate comprises a carrier layer, the device layer and an intermediate layer disposed between the carrier layer and the device layer, and wherein the intermediate layer is structured for exposing, at least in one portion, a first surface of the carrier layer facing the device layer, wherein, starting from a second surface of the carrier layer opposing the first surface, the thickness of the device layer is reduced to a predetermined thickness at those positions where the intermediate layer is removed.

17. Micromechanical structure, comprising:

a substrate comprising a device layer, a carrier layer and an intermediate layer disposed between the device layer and the carrier layer, wherein the intermediate layer is structured for exposing, at least in one portion, a first surface of the carrier layer facing the device layer; and

at least one portion in the area of the micromechanical structure, wherein the thickness of the device layer is reduced according to a method for structuring a device layer of a substrate, wherein the substrate comprises a carrier layer, the device layer and an intermediate layer disposed between the carrier layer and the device layer, and wherein the intermediate layer is structured for exposing, at least in one portion, a first surface of the carrier layer facing the device layer, wherein, starting from a second surface of the carrier layer opposing the first surface, the thickness of the device layer is reduced to a predetermined thickness at those positions where the intermediate layer is removed.

18. The micromechanical structure according to claim 17, wherein the thickness of the device layer is reduced in at least one portion for influencing the resonance frequency of the micromechanical structure.

19. The micromechanical structure according to claim 17, which is a two-dimensional scanner mirror and comprises at least one electrically conductive lead adjacent to a torsion spring of the scanner mirror, which is structured in or on a portion with reduced device layer thickness.

20. The micromechanical structure according to claim 17, which is a two-dimensional scanner mirror, wherein all torsion springs and potential leads as well as at least part of the mirrored areas are structured in a portion with reduced device layer thickness.

21. The micromechanical structure according to claim 17 for a microsystem for data acquisition, a microsystem for data output, a microsystem for optical path manipulation, a pressure, acceleration or viscosity sensor or a micromechanical gear element.