Substrate and method of forming substrate for MEMS device with strain gage

• US 6,739,199 B1
• Filed: 03/10/2003
• Issued: 05/25/2004
• Est. Priority Date: 03/10/2003
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Nikkel, Eric Lee
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): MILLER, TAKISHA S
• Application Number:
  US10/384,887
• Time in Patent Office: 442 Days
• Field of Search: 737/20, 737/21, 737/19, 347/19, 438/50
• US Class Current: 73/777
• CPC Class Codes: B41J 2/14153 Structures including a sensor
• CPC Class Codes: B41J 2/14201 Structure of print heads with piezoelectric elements
• CPC Class Codes: G01L 1/2206 Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
• CPC Class Codes: G01L 1/2293 of the semi-conductor type semi-conductor devices controllable by variations of applied mechanical force H01L29/84

Abstract

A substrate for a MEMS device includes a base material having a first side, a poly silicon strain gage formed on the first side of the base material, a dielectric material disposed over the strain gage, and a conductive material in communication with the strain gage through the dielectric material, wherein the substrate is adapted to have at least one opening formed therethrough, and wherein the strain gage is adapted to be formed adjacent the at least one opening.

Claims

1. A substrate for a MEMS device, the substrate comprising:

a base material having a first side;

a strain gage formed on the first side of the base material, the strain gage including a poly silicon material;

a dielectric material disposed over the strain gage; and

a conductive material in communication with the strain gage through the dielectric material,

wherein the substrate is adapted to have at least one opening formed therethrough,

wherein the strain gage is adapted to be formed adjacent the at least one opening, and includes a first element oriented at a first angle relative to an edge of the at least one opening, a second element oriented at a second angle substantially perpendicular to the first angle, and a third element oriented at a third angle substantially bisecting the first angle and the second angle.

2. The substrate of claim 1, further comprising:

a dielectric layer formed on the first side of the base material,

wherein the strain gage is formed on the first side of the base material over the dielectric layer.

3. The substrate of claim 2, wherein the dielectric layer is one of grown and deposited on the first side of the base material.

4. The substrate of claim 2, wherein the base material includes silicon, and wherein the dielectric layer includes one of tetraethylorthosilicate, silane, silicon dioxide, silicon carbide, and silicon nitride.

5. The substrate of claim 1, wherein the poly silicon material of the strain gage is doped with a dopant material, and wherein the poly silicon material and the dopant material are annealed.

6. The substrate of claim 5, wherein the dopant material includes one of boron and phosphorus.

7. The substrate of claim 1, wherein the dielectric material includes one of phosphosilicate glass and tetraethylorthosilicate.

8. The substrate of claim 1, wherein the dielectric material has at least one opening formed therein to the strain gage, and wherein the conductive material is deposited within the at least one opening in the dielectric material.

9. The substrate of claim 1, wherein the strain gage is adapted to be formed at least one of at an end of the at least one opening through the substrate and along a side of the at least one opening through the substrate.

10. The substrate of claim 1, wherein the MEMS device comprises a fluid rejection device, and wherein the at least one opening through the substrate comprises a fluid passage through the substrate.

11. A method of forming a substrate for a MEMS device, the method comprising:

providing a base material having a first side;

forming a strain gage on the first side of the base material, the strain gage including a poly silicon material;

disposing a dielectric material over the strain gage; and

contacting a conductive material with the strain gage through the dielectric material,

wherein the substrate is adapted to have at least one opening formed therethrough,

wherein the strain gage is adapted to be formed adjacent the at least one opening and include a first element oriented at a first angle relative to an edge of the at least one opening, a second element oriented at a second angle substantially perpendicular to the first angle, and a third element oriented at a third angle substantially bisecting the first angle and the second angle.

12. The method of claim 11, further comprising:

forming a dielectric layer on the first side of the base material,

wherein forming the strain gage includes forming the strain gage on the first side of the base material over the dielectric layer.

13. The method of claim 12, wherein forming the dielectric layer includes one of growing and depositing the dielectric layer on the first side of the base material.

14. The method of claim 12, wherein the base material includes silicon, and wherein the dielectric layer includes one of tetraethylorthosilicate, silane, silicon dioxide, silicon carbide, and silicon nitride.

15. The method of claim 11, wherein forming the strain gage includes doping the poly silicon material with a dopant material and annealing the poly silicon material and the dopant material.

16. The method of claim 15, wherein the dopant material includes one of boron and phosphorus.

17. The method of claim 11, wherein the dielectric material includes one of phosphosilicate glass and tetraethylorthosilicate.

18. The method of claim 11, wherein contacting the conductive material with the strain gage includes forming at least one opening in the dielectric material to the strain gage and depositing the conductive material within the at least one opening.

19. The method of claim 11, wherein the strain gage is adapted to be formed at least one of at an end of the at least one opening through the substrate and along a side of the at least one opening through the substrate.

20. The method of claim 11, wherein the MEMS device comprises a fluid ejection device, and wherein the at least one opening through the substrate comprises a fluid passage through the substrate.

21. A method of measuring strain in a substrate of a MEMS device, the substrate having at least one opening formed therethrough, the method comprising:

integrating a poly silicon strain gags in the substrate, including forming the poly silicon strain gage in a layer of the substrate adjacent the least one opening, and orienting a first element of the poly silicon strain gage at a first angle relative to an edge of the at least one opening, orienting a second element of the poly silicon strain gage at a second angle substantially perpendicular to the first angle, and orienting a third element of the poly silicon strain gage at a third angle substantially bisecting the first angle and the second angle;

forming a strain measuring circuit with the poly silicon strain gage;

subjecting the substrate to a load;

measuring a change in resistance of the poly silicon strain gage with the strain measuring circuit in response to the load; and

equating the change in resistance of the poly silicon strain gage to strain in the substrate.

22. The method of claim 21, further comprising:

calibrating the poly silicon strain gage, including supporting a first end of the substrate, loading a second end of the substrate opposite the first end, recording a displacement of the second end of the substrate, and measuring a change in resistance of the strain gage in response to the displacement.

23. The method of claim 22, wherein measuring the change in resistance of the strain gage includes electrically coupling the poly silicon strain gage to a resistance measurement device.

24. The method of claim 21, wherein the first element, the second element, and the third element of the poly silicon strain gage each include a first terminal and a second terminal, and wherein forming the strain measuring circuit with the poly silicon strain gage includes electrically coupling the first terminal and the second terminal of each of the first element, the second element, and the third element in a full-bridge circuit.

25. The method of claim 21, wherein measuring the change in resistance of the poly silicon strain gage includes measuring resistance of the poly silicon strain gage at least one of while subjecting the substrate to the load and before and after subjecting the substrate to the load.

26. The method of claim 21, wherein the MEMS device comprises a fluid ejection device, and wherein the at least one opening comprises a fluid passage through the substrate.

27. A fluid ejection device, comprising:

a substrate having at least one opening formed therethrough;

a plurality of drop ejecting elements formed on the substrate; and

a strain gage formed in the substrate adjacent the at least one opening,

wherein the strain gage includes a first element oriented at a first angle relative to an edge of the at least one opening, a second element oriented at a angel substantially perpendicular to the first angle, and a third element oriented at a third angle substantially bisecting the first angle and the second angle.

28. The device of claim 27, wherein the strain gage includes a poly silicon material.

29. The device of claim 28, wherein the poly silicon material of the strain gage is doped with a dopant material, and wherein the poly silicon material and the dopant material are annealed.

30. The device of claim 27, wherein the substrate includes a dielectric material disposed over the strain gage and a conductive material in communication with the strain gage through the dielectric material.

31. The device of claim 30, wherein the substrate further includes a base material and a dielectric layer formed on a first side of the base material, and wherein the strain gage is formed on the first side of the base material over the dielectric layer.

32. The device of claim 27, wherein the at least one opening comprises a fluid passage through the substrate.

33. The device of claim 27, wherein the fluid ejection device includes an inkjet printhead.