Microfabricated miniature grids

• US 7,358,593 B2
• Filed: 05/06/2005
• Issued: 04/15/2008
• Est. Priority Date: 05/07/2004
• Status: Expired due to Fees

• Current Assignee: Stillwater Scientific Instruments, Inc., University of Toledo
• Original Assignee: Stillwater Scientific Instruments, Inc., The University Of Maine
• Inventors: Collins, Scott, LeGore, Lawrence J., Smith, Rosemary, Frederick, Brian G.
• Primary Examiner(s): Tran; Minhloan
• Assistant Examiner(s): Rodela; Eduardo A
• Application Number:
  US11/124,424
• Publication Number:
  US 20050258514A1
• Time in Patent Office: 1,075 Days
• Field of Search: 257/619
• US Class Current: 257/619
• CPC Class Codes: H01J 49/0018 Microminiaturised spectrometers, e.g. chip-integrated devices, Micro-Electro-Mechanical Systems [MEMS]
• CPC Class Codes: H01J 49/061 Ion deflecting means, e.g. ion gates
• CPC Class Codes: H01J 9/14 of non-emitting electrodes
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: Y10S 438/977 Thinning or removal of substrate

Abstract

A grid structure and method for manufacturing the same. The grid is used for gating a stream of charged particles in certain types of particle measurement instruments, such as ion mobility spectrometers and the like. The methods include various microfabrication techniques for etching and/or depositing grid structure materials on a silicon substrate.

Claims

1. A method of fabricating a micromachined grid for gating a beam of charged particles, comprising the steps of:

a) selecting a multilayered material consisting of a conductive layer bonded to an insulating layer;

b) patterning a photoresist onto the conductive layer to define a set of conductive elements;

c) micromachining the conductive layer to isolate the set of conductive elements;

d) patterning a photoresist onto the insulating layer to define a region where charged particles may pass through the grid; and

e) micromachining the substrate to open a hole through the grid while providing mechanical support to the ends of the conductive elements,

wherein the multilayered material is a silicon on insulator wafer.

2. A method as in claim 1, wherein at least one of the micromachining steps is performed using a process selected from deep reactive ion etching (DRIE) and reactive ion etching (RIB).

3. A method as in claim 1, wherein the conductive elements are formed of a metal.

4. A method as in any of claims 1 through 3, wherein the grid is used for gating a an electron particle beam in a time of flight spectrometer.

5. A method as in any of claims 1 through 3, wherein the grid is used for gating an ion particle beam in a time of flight mass spectrometer.

6. A method as in claim 1 wherein the step of patterning a photoresist on the conductive layer further defines a first and a second set of conductive elements to be applied to alternate potentials.

7. A method as in claim 6 wherein the step of patterning a photoresist on the conductive layer further defines one or more bus bars for providing connection to sources of alternate potentials.

8. A method as in claim 1 wherein the grid is arranged as a Bradbury-Nielson gate.

9. A method as in claim 1 wherein the step of micromachining the conductive layer to isolate the set of conductors is a DRIE process.

10. A method as in claim 1 wherein the step of micromachining the conductive layer to isolate the set of conductors is a wet etching process.

11. A method as in claim 1 additionally comprising a further step of electroplating the set of conductive elements.

12. A method as in claim 1 additionally comprising a further step of electroless plating of the set of conductive elements.

13. A method as in claim 1 wherein the step of micromachining to open a hole is selected from one of RIE or wet etching.

14. A method as in claim 1 wherein multiple grids are formed on the same substrate.

15. A method fabricating a unipotential grid for defining potential gradients in a charged particle optical system, comprising the steps of:

a) patterning a photoresist onto a semiconductive material layer;

b) micromachining the semiconductive material layer to define a width, depth and spacing of a set of conductive elements that comprise the grid;

c) patterning a photoresist onto an opposite side of the semiconductive material layer to define a hole where charged particles may pass through the grid; and

d) micromachining the opposite side to open a hole through the grid.

16. A method as in claim 15 wherein the semiconductive material is a single crystal.

17. A method as in claim 15 wherein at least one of the micromachining steps is performed using DRIE.

18. A method of fabricating a unipotential grid for defining potential gradients in a charged particle optical system, comprising the steps of:

a) patterning a photoresist onto a semiconductive material layer;

b) micromachining the semiconductive material layer to define a width, depth and spacing of a set of conductive elements that comprise the grid,

wherein the width of the conductive elements is less than about 10 micrometers (um).

19. A method of fabricating a unipotential grid for defining potential gradients in a charged particle optical system, comprising the steps of:

a) patterning a photoresist onto a semiconductive material layer;

b) micromachining the semiconductive material layer to define a width, depth and spacing of a set of conductive elements that comprise the grid,

wherein the conductive elements are disposed along two orthogonal axes and connected to one another.

20. A method as in claim 19 wherein the step of micromachining further defines a frame for supporting the ends of the conductive elements.

21. A method as in claim 19 additionally comprising the step of electroplating to further define the conductive elements.

22. A method as in claim 19 wherein the substrate is an insulator.

23. A method as in claim 19 wherein the substrate is a non-insulating material having an insulating layer on which the conductive elements defined.

24. A method of fabricating a unipotential and for defining potential gradients in a charged particle optical system, comprising the steps of:

a) patterning a photoresist onto a semiconductive material layer;

b) micromachining the semiconductive material layer to define a width, depth and spacing of a set of conductive elements that comprise the grid,

wherein the grid is used to define potential gradients in a reflectron ion mirror.