Solid state transducer and method of making same

• US 4,144,516 A
• Filed: 07/21/1977
• Issued: 03/13/1979
• Est. Priority Date: 03/29/1976
• Status: Expired due to Term

• Current Assignee: Barry Block, Harry E. Aine
• Original Assignee: Harry E. Aine
• Inventors: Aine, Harry E.
• Primary Examiner(s): Dipalma, Victor A.
• Application Number:
  US05/817,556
• Time in Patent Office: 600 Days
• Field of Search: 29/610 SG, 29/576 R, 29/576 W, 29/580, 29/581, 29/582, 29/583, 29/592, 73/88.5 SD, 73/398 AR, 338/2, 338/4, 338/36, 338/41, 338/42, 338/5, 338/47, 156/662, 156/648, 357/26, 357/79
• US Class Current: 338/2
• CPC Class Codes: G01L 1/044 of leaf springs
• CPC Class Codes: G01L 1/148 using semiconductive material, e.g. silicon
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49103 Strain gauge making

Abstract

Solid state dual leaf spring transducers are fabricated by batch photolithographic etching techniques from a monocystalline nonmetallic material, such as silicon. Each leaf spring structure includes a leaf spring portion surrounded by a support structure defined by an intervening region of the wafer disposed between adjacent leaf spring structures etched into the wafer. A pair of such leaf spring structures with their respective surrounding support structures are joined together in mutually opposed relation to form a composite dual leaf spring transducer structure of the type wherein a pair of leaf spring structures are mechanically coupled together in axially spaced relation along an axis of sensitivity for equal displacement along said axis of sensitivity in response to displacement of either one of the spring structures relative to the support structure. In one embodiment, a third wafer is interposed between the first two opposed wafers, such third wafer having apertures formed therein so that the leaf spring structures are coupled together through the apertures in the third wafer. In another embodiment, conductive capacitive patterns are formed on the leaf spring structures so as to provide a capacitor structure for sensing displacement of the leaf spring structure.

Claims

1. In a method for fabricating a solid state transducer of the type having a leaf spring structure supported from a support structure in axially spaced relation along an axis of sensitivity, the steps of:

forming a leaf spring structure by recessing through a major face of first and second wafer portions in accordance with a predetermined leaf spring pattern to define first and second leaf spring structures having deflectable portions supported from respective first and second support structures which allow deflection of said deflectable portions of said leaf spring structures along an axis of sensitivity relative to said support structures in response to a force applied to said leaf spring structures; and

joining together said first and second leaf spring structures and said respective first and second support structures in spaced apart relation along an axis of sensitivity so that said first and second leaf spring structures are deflected along the axis of sensitivity by like amounts relative to said respective first and second support structures in response to deflection of either of said first and second spring structures along said axis of sensitivity.

2. The method of claim 1 including the step of, interposing a capacitive detector means between said deflectable portions of said first and second leaf spring portions in fixed relation relative to said first and second support structures for detecting displacement of said deflectable first and second leaf spring portions relative to said support structures.

3. The method of claim 1 wherein said first and second leaf spring patterns each include at least first and second coplanar E-shaped leaf spring portions each having a pair of outer leaf spring leg portions disposed on opposite sides of a central leaf spring leg portion all of said leg portions extending outwardly from said axis of sensitivity of the spring structure, said outer leg portions being fixedly connected to said central leg portions at their outer ends for deflection therewith, the inner legs of said outer leg portions being fixedly connected to said support structures and the inner ends of said central leg portions being connected together for deflection along the axis of sensitivity relative to said support structure;

and wherein the step of joining together individual ones of said leaf spring structures includes the step of joining together said central leg portions of said first and second leaf spring structures via projections extending outwardly from the plane of said respective first and second leaf spring structures and from said respective outer ends of said outer leg portions thereof into mutually opposed engaging relation one with the other.

4. The method of claim 3 wherein the step of joining together individual ones of said leaf spring structures includes the step of joining together said outer ends of respective outer leg portions of said first and second leaf spring structures via projections extending outwardly from the plane of said respective first and second leaf spring structures and from said respective outer ends of said outer leg portions thereof into mutually opposed engaging relation one with the other.

5. The method of claim 2 wherein said interposed capacitive detector means includes a third wafer portion and including the step of aperturing said third wafer portion through a major face thereof in alignment with the central portion of respective ones of said first and second leaf spring structures to be joined together, and wherein the step of joining said first and second leaf spring structures together includes the step of joining said first and second leaf spring structures together through said aperture in said apertured capacitive detector means.

6. The method of claim 4 interposing a capacitive detector means between said deflectable portions of said first and second leaf spring portions in fixed relation relative to said first and second support structures for detecting displacement of said deflectable first and second leaf spring portions relative to said support structures, and wherein said interposed capacitive detector means includes a third wafer portion and including the step of, aperturing said third wafer portion in alignment with said projections extending outwardly from the plane of said first and second leaf spring structure and from said respective outer ends of said outer leg portions thereof which are to be joined together, and wherein the step of joining said first and second leaf spring structures together includes the step of joining said projections together through said apertures in said apertured capacitive detector means.

7. The method of claim 2 including the step of laterally aligning said first and second leaf spring structures and said capacitive detector means in mutually opposed relation by mating mutually opposed aligning surfaces formed on said mutually opposed support structures and said interposed capacitive detector means.

8. The method of claim 2 including the step of aperturing at least one of said first and second leaf spring support structures in vertical registration with patterns of metallization on said capacitive detector means for making electrical contact to said pattern of metallization through said apertured one of said leaf spring support structures.

9. The method of claim 8 including the step of aperturing said capacitive detector means in vertical registration with a second pattern of metallization on said other one of said leaf spring support structure for making electrical contact to said second pattern of metallization through said apertured capacitive detector means.

10. The method of claim 1 wherein said recessed first and second wafer portions which define said first and second leaf spring structures are recessed from a common wafer, and including the step of subdividing the wafer after the step of forming the spring structures therein to obtain said first and second leaf spring structures prior to the step of mechanically coupling said first and second leaf spring structure together.

11. The product made by the method of claim 1.

12. The product made by the method of claim 3.

13. In a method for fabricating a solid state transducer of the type having a leaf spring structure supported from a support structure, the steps of:

forming the leaf spring structure by recessing through a major face of a wafer in accordance with a predetermined leaf spring pattern to define a leaf spring structure having a deflectable portion supported from a support structure, said leaf spring structure allowing deflection of said deflectable portion of said leaf spring structure along an axis of sensitivity relative to said support structure in response to a force applied to said leaf spring structure; and

forming a capacitive detector means between said deflectable portion of said leaf spring structure and a second structure fixed in relation relative to said support structure for detecting displacement of said deflectable portion of said leaf spring structure relative to said support structure.

14. The method of claim 13 wherein the step of forming a capacitive detector includes the step of interposing said deflectable portion of said leaf spring structure inbetween capacitive portions of said second structure which are fixed in relation to said support structure.

15. The product made by the method of claim 13.