(110) Oriented silicon wafer latch accelerometer and process for forming the same

• US 4,891,255 A
• Filed: 09/29/1988
• Issued: 01/02/1990
• Est. Priority Date: 09/29/1988
• Status: Expired due to Fees

• Current Assignee: United States Department of Energy
• Original Assignee: United States Department of Energy
• Inventors: Ciarlo, Dino R.
• Primary Examiner(s): Powell, William A.
• Application Number:
  US07/250,591
• Time in Patent Office: 460 Days
• Field of Search: 156/644, 156/647, 156/657, 156/659.1, 156/662, 428/131, 428/134, 428/137, 73/488, 73/510, 73/517 R, 73/726, 73/754, 357/26, 357/55, 357/60, 338/2, 338/4, 338/42, 338/47, 29/621.1
• US Class Current: 428/131
• CPC Class Codes: G01P 15/036 for indicating predetermined acceleration values
• CPC Class Codes: H01H 2001/0047 operable only by mechanical latching
• CPC Class Codes: H01L 21/30608 Anisotropic liquid etching H01L21/3063 takes precedence
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24322 Composite web or sheet

Abstract

A method for etching a (110) silicon wafer to produce latching cantilever beams, which bend parallel to the surface of the wafer. The resulting apparatus is also part of the invention.

Claims

1. An apparatus, comprising:

a (110) silicon wafer with a thickness, comprising;

a frame;

a first cantilever beam, with a first end attached to the frame and a second end, which is a free end which is not attached to the frame, and with a length dimension from the first end to the second end, and a thickness, wherein the length and the thickness are substantially parallel to the (110) plane, and a width substantially perpendicular to the (110) plane and substantially equal to the thickness of the wafer;

a second cantilever beam, with a first end attached to the frame and a second end, which is a free end which is not attached to the frame, and with a length dimension from the first end to the second end, and a thickness, wherein the length and the thickness are substantially parallel to the (110) plane, and a width substantially perpendicular to the (110) plane and substantially equal to the thickness of the wafer, and where the length of the first cantilever forms an angle with the length of the second cantilever, where the value of the angle is substantially 70.5°

or 109.5°

.

2. An apparatus as recited in claim 1, wherein the first cantilever further comprises at least one outer corner with a corner compensated peak.

3. An apparatus as recited in claim 2, wherein the second cantilever further comprises at least one outer corner with a corner compensated peak.

4. An apparatus as recited in claim 2, wherein the second end of the first cantilever is enlarged.

5. An apparatus as recited in claim 3, wherein the second end of the first cantilever is enlarged.

6. An apparatus as recited in claim 5, wherein the second end of the second cantilever is enlarged.

7. An apparatus as recited in claim 2, wherein the (110) silicon wafer is made of a plurality of silicon unit cells, and wherein each edge of the first cantilever, except for the corner compensated peaks is substantially along a plane that intersects only three corners of each unit cell through which the plane passes.

8. An apparatus as recited in claim 7, wherein each edge of the second cantilever, except for the corner compensated peaks is substantially along a plane that intersects only three corners of each unit cell through which the plane passes.

9. An apparatus as recited in claim 7, wherein the second end of the first cantilever is the closest part of the first cantilever to the second cantilever and the second end of the second cantilever is the closest part of the second cantilever to the first cantilever.

10. A method for manufacturing a frame and first and second silicon cantilevers, wherein the cantilevers have a first end which is attached to the frame and a second end not attached to the frame and wherein each cantilever has a length from the first end of the cantilever to the second end of the cantilever and wherein the length of the first cantilever is not parallel to the length of the second cantilever, and wherein the first and second cantilevers bend in the plane of the frame, comprising:

making a silicon wafer, which has first and second surfaces on opposite sides, and wherein the two surfaces are parallel to the (110) plane, and wherein the silicon wafer is made of a plurality of silicon unit cells;

masking the silicon wafer on the first surface so that there is a masked area, and an unmasked area of the silicon wafer and a border between the masked area and the unmasked area, wherein the masked area forms patterns for a frame and at least two cantilevers, wherein each border between the masked and the unmasked area is substantially along a plane that intersects only three corners of each unit cell through which the plane passes, and wherein each of the cantilever patterns each have a first end which is attached to the frame pattern and a second end, which is a free end which is not attached to the frame pattern and wherein each of the cantilever patterns has a length from the first end of the cantilever pattern to the second end of the cantilever pattern and wherein the length of the first cantilever pattern is not parallel to the length of the second cantilever pattern; and

exposing the silicon wafer to an anisotropic etchant.

11. A method as recited in claim 10, wherein the masked area forming the cantilever patterns also contains at least one masked area for corner compensation.

12. A method as recited in claim 10, further comprising the step of, masking the second surface, and wherein the silicon wafer is etched on the first and second surfaces.

13. A method as recited in claim 10, wherein the masking step applies a silicon nitride mask on the order of 400 angstroms.

14. A method as recited in claim 10, wherein the step of exposing the silicon wafer to an etchant uses KOH as the etchant.

15. A (110) silicon wafer latching apparatus, comprising:

frame

a first cantilever beam, with a first end attached to the frame and a second end, which is a free end which is not attached to the frame, and with a length dimension from the first end to the second end, and a thickness, wherein the length and the thickness are substantially parallel to the (110) plane, and a width substantially perpendicular to the (110) plane and substantially equal to the thickness of the wafer and which comprises at least one outer corner which has a corner compensated peak;

a second cantilever beam, with a first end attached to the frame and a second end, which is a free end which is not attached to the frame, and with a length dimension from the first end to the second end, and a thickness, wherein the length and the thickness are substantially parallel to the (110) plane, and a width substantially perpendicular to the (110) plane and substantially equal to the thickness of the wafer, and where the length of the first cantilever forms an angle with the length of the second cantilever, where the value of the angle is substantially 70.5°

or 109.5° and

which comprises at least on outer corner which has a corner compensated peak to allow the first cantilever to be latched to the second cantilever.

16. An apparatus as recited in claim 15, wherein the second end of the first cantilever is enlarged.

17. An apparatus as recited in claim 16, wherein the second end of the second cantilever is enlarged.

18. An apparatus as recited in claim 15, wherein the (110) silicon wafer is made of a plurality of silicon unit cells, and wherein each edge of the first cantilever, except for the corner compensated peaks, is substantially along a plane that intersects only three corners of each unit cell through which the plane passes.

19. An apparatus as recited in claim 18, wherein each edge of the second cantilever, except for the corner compensated peaks, is substantially along a plane that intersects only three corners of each unit cell through which the plane passes.

20. An apparatus as recited in claim 19, wherein the second end of the first cantilever is the closest part of the first cantilever to the second cantilever and the second end of the second cantilever is the closest part of the second cantilever to the first cantilever.