Solid state transducer and method of making same

• US 4,783,237 A
• Filed: 06/11/1986
• Issued: 11/08/1988
• Est. Priority Date: 12/01/1983
• Status: Expired due to Fees

• Current Assignee: Barry Block, Harry E. Aine
• Original Assignee: Barry Block, Harry E. Aine
• Inventors: Block, Barry, Aine, Harry E.
• Primary Examiner(s): Schor, Kenneth M.
• Application Number:
  US06/873,854
• Time in Patent Office: 881 Days
• Field of Search: 156/628, 156/644, 156/647, 156/648, 156/650, 156/651, 156/654, 156/657, 156/659.1, 156/662, 156/655, 156/345, 148/1.5, 148/171, 148/175, 29/580, 29/584, 29/586, 29/595, 29/610 SG, 338/2, 338/4, 338/42, 338/47, 73/510, 73/517 R, 73/726, 73/754, 361/283, 357/26
• US Class Current: 438/52
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: Y10S 438/97 Specified etch stop material

Abstract

Folded cantilever structures and solid state force transducers using same are made by chemical etching of a semiconductive wafer. In the chemical etching process, an etch stop layer is provided on a wafer of semiconductive material. The etch stop layer is opened in a certain pre-determined pattern and etchant is introduced through the opening in the etch stop layer to produce substantial undercut etching of portions of the etch stop layer. The opening is patterned to define a support structure (frame) for the folded cantilever portion which is undercut. The etch is terminated such that one end of the undercut folded cantilever structure is supported from the frame and the other end terminates on a structure such as a mass that is supported from the frame by means of the folded cantilever structure.

Claims

1. In a method for making flexible structures by chemical etching of a semiconductive wafer, the steps of;

providing a first etch stop layer (12) on a wafer (11) of semiconductive material;

opening said first etch stop layer in a predetermined pattern (18);

introducing an etchant through said patterned opening (18) in said first etch stop layer (12);

etching the semiconductive wafer (11) through said opening pattern (18) in said first etch stop layer (12) to undercut substantial portions (51) of said first etch stop layer (12);

said opening (18) being patterned to define a support structure (54) of said wafer (11) and a doubled back cantilever portion (51) of said first etch stop layer (12); and

terminating (50) the etch of wafer material such that one end of the undercut doubled back cantilever beam portion (51) is supported from the support structure (54) and the other end of the undercut doubled back cantilever beam portion terminates on a structure (55) which structure (55) is supported from and being movable relative to said support structure (54) by means of flexure of said undercut doubled back cantilever portion (51).

2. The method of claim 1 including the step of, forming a second etch stop layer portion underlaying said first etch stop layer portion and;

wherein

said step of etching the semiconductive wafer includes etching wafer material from inbetween said first and second etch stop layer portions.

3. The method of claim 2 wherein said opening pattern in said first etch stop layer is patterned so as to form when the etch is terminated a structural portion of the wafer substantially thicker than the cantilever beam portion and affixed to the end of the undercut doubled back cantilever portion remote from the support structure.

4. The method of claim 3 including the step of selectively etching said second etch stop layer to undercut said thicker structural portion affixed to the end of said undercut doubled back cantilever beam portion to free said thicker structural portion for movement with flexure of said doubled back cantilever beam portion.

5. The method of claim 3 including a step of providing a P+ type layer buried within said wafer in an N-type conductivity material and spaced from and underneath said thicker structural portion of said wafer, and including the step of selectively etching said wafer to undercut said thicker structural portion and to etch a spacer region inbetween said undercut structural portion of said P+ type layer to form a capacitive gap therebetween;

and making electrical contact to said P+ type layer for capacitively coupling to said thicker structural portion.

6. The method of claim 1 wherein said wafer material and said first etch stop layer are of single crystalline semiconductive material.

7. The method of claim 1 wherein the step of etching the wafer includes etching said wafer material completely through the thickness of the wafer.

8. In a method for making flexible structures by chemical etching of a semiconductive wafer, the steps of:

providing a first etch stop layer (12) on a wafer (11) of semiconductive material;

opening said first etch stop layer in a predetermined pattern (18);

introducing an etchant through said patterned opening (18) in said first etch stop layer (12);

etching the semiconductive wafer (11) through said opening pattern (18) in said first etch stop layer (12) to undercut substantial portions (51) of said first etch stop layer (12);

said opening (18) being patterned to define a support structure (54) of said wafer (11) and a doubled back cantilever portion (51) of said first etch stop layer (12);

terminating (50) the etch of wafer material such that one end of the undercut doubled back cantilever beam portion (51) is supported from the support structure (54) and the other end of the undercut doubled back cantilever beam portion terminates on a structure (55) which structure (55) is supported from and being moveable relative to said support structure (54) by means of flexure of said undercut doubled back cantilever portion (51); and

said pattern including central slot regions disposed intermediate the folded cantilever spring portions connecting said central portion (55) to said support structure (54), said central slot region terminating at one end on a (111) plane defining one side of said central support (55) for preventing the undercutting of structure (55) during etching.

9. The method of claim 8 including the step of forming a second etch stop layer portion underlaying said first etch stop layer portion and;

wherein said step of etching the semiconductive wafer includes etching wafer material from inbetween said first and second etch stop layer portions.

10. The method of claim 9 wherein said opening pattern in said first etch stop layer is patterned so as to form when the etch is terminated a structural portion of the wafer substantially thicker than the cantilever beam portion and affixed to the end of the undercut doubled back cantilever portion remote from the support structure.

11. The method of claim 10 including the step of selectively etching said second etch stop layer to undercut said thicker structural portion affixed to the end of said undercut doubled back cantilever beam portion to free said thicker structural portion for movement with flexure of said doubled back cantilever beam portion.

12. The method of claim 10 including a step of providing a P+ type layer buried within said wafer in an N type conductivity material and spaced from and beneath said thicker structural portion of said wafer, and including the step of selectively etching said wafer to undercut said thicker structural portion and to etch a spacer region inbetween said undercut structural portion and said P+ type layer to form a capacitive gap therebetween;

and making electrical contact to said P+ type layer for capacitively coupling to said thicker structural portion.