Etching method used in fabrications of microstructures

• US 7,027,200 B2
• Filed: 09/17/2003
• Issued: 04/11/2006
• Est. Priority Date: 03/22/2002
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Patel, Satyadev R., Huibers, Andrew G., Shi, Hongqin, Schaadt, Gregory P.
• Primary Examiner(s): Mack, Ricky L.
• Assistant Examiner(s): THOMAS, BRANDI N
• Application Number:
  US10/666,002
• Publication Number:
  US 20050020089A1
• Time in Patent Office: 937 Days
• Field of Search: 359/290, 359/291, 359/292, 359/293, 359/294, 359/295, 359/298
• US Class Current: 359/290
• CPC Class Codes: B81C 1/00595 Control etch selectivity
• CPC Class Codes: B81C 2201/0132 Dry etching, i.e. plasma etching, barrel etching, reactive ion etching [RIE], sputter etching or ion milling
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

The present invention discloses a method and apparatus for removing the sacrificial materials in fabrications of microstructures using a vapor phase etchant recipe having a spontaneous vapor phase chemical etchant. The vapor phase etchant recipe has a mean-free-path corresponding to the minimum thickness of the sacrificial layers between the structural layers of the microstructure. This method is of particular importance in removing the sacrificial layers underneath the structural layers of the microstructure.

Claims

1. A method for fabricating a micromirror, the method comprising:

preparing a substrate;

depositing one or more sacrificial layers;

forming a mirror plate and a hinge layer on the one or more sacrificial layers;

preparing a vapor phase etchant recipe such that a mean-free-path of the etchant recipe is equal to or less than a minimum thickness of the one or more sacrificial layers; and

removing the sacrificial layers using the prepared etchant recipe.

2. The method of claim 1, wherein the mean-free-path is equal to or less than 1.5 micrometer;

and wherein the minimum thickness of the sacrificial layer is around 1.5 micrometers or larger.

3. The method of claim 1, wherein the mean-free-path is equal to or less than 0.5 micrometers;

and wherein the minimum thickness of the sacrificial layer is around 0.5 micrometers or larger.

4. The method of claim 1, wherein the sacrificial material is amorphous silicon.

5. The method of claim 1, wherein the step of preparing the etchant recipe further comprises:

preparing the etchant recipe by mixing a spontaneous vapor phase chemical etchant with a diluent gas, wherein the chemical etchant is from a group comprising an interhalogen gas, a noble gas halide and HF.

6. The method of claim 5, wherein the interhalogen comprises bromine trifluoride;

and

wherein the noble gas halide comprises XeF₂.

7. The method of claim 1, wherein the diluent gas is selected from a group comprising He, N₂, Ar, Kr, Ne and Xe.

8. The method of claim 1, wherein the etchant recipe has a total pressure of from 1 to 700 torr.

9. The method of claim 1, wherein the etchant recipe has a total pressure higher than 2 atmospheres.

10. The method of claim 1, wherein the chemical etchant of the etchant recipe has a partial pressure from 1 to 15 torr.

11. The method of claim 1, wherein the diluent gas has a partial pressure of from 1 to 700 torr.

12. The method of claim 1, wherein a ratio of a partial pressure of the chemical etchant gas to a partial pressure of the diluent gas is from 1/1000 to 1/10.

13. The method of claim 1, wherein the ratio is from 6/100 to 4/200.

14. The method of claim 1, wherein the step of depositing one or more sacrificial layers further comprises:

depositing a first sacrificial layer between the substrate and the mirror plate and a second sacrificial layer between the mirror plate and the hinge layer.

15. The method of claim 14, wherein the second sacrificial layer has a thickness around 1.5 micrometers or less.

16. The method of claim 14, wherein the second sacrificial layer has a thickness around 0.5 micrometers or less.