Shielded probe for testing a device under test

• US 7,482,823 B2
• Filed: 10/24/2007
• Issued: 01/27/2009
• Est. Priority Date: 05/23/2002
• Status: Expired due to Fees

• Current Assignee: FormFactor Beaverton, Inc. (FormFactor Incorporated)
• Original Assignee: Cascade Microtech Incorporated (FormFactor Incorporated)
• Inventors: Safwat, Amr M. E., Gleason, K. Reed, Andrews, Mike, Martin, John, Lesher, Tim, Dunklee, John, Hayden, Leonard, Strid, Eric W.
• Primary Examiner(s): Nguyen; Vinh P
• Application Number:
  US11/977,282
• Publication Number:
  US 20080054923A1
• Time in Patent Office: 461 Days
• Field of Search: None
• US Class Current: 324/750.26
• CPC Class Codes: G01R 1/06711 Probe needles; Cantilever beams; "Bump" contacts; Replaceable probe pins
• CPC Class Codes: G01R 1/06755 Material aspects
• CPC Class Codes: G01R 1/06772 High frequency probes
• CPC Class Codes: G01R 1/06777 High voltage probes

Abstract

A probe for measuring the electrical characteristics of integrated circuits or other microelectronic devices at high frequencies may include a dielectric substrate that supports a signal path interconnecting test instrumentation and a probe tip and a ground path that shields both the signal path and the probe tip.

Claims

1. A probe comprising:

(a) a dielectric substrate;

(b) an elongate conductor suitable to be electrically interconnected to a test signal supported by said substrate;

(c) a conductive member suitable to be electrically interconnected to a ground signal supported by said substrate;

(d) a contact electrically interconnected to said elongate conductor for testing a device under test;

(e) wherein said elongate conductor and said conductive member form a controlled impedance structure;

(f) wherein said substrate has a thickness of less than 40 microns with a dielectric constant of less than 7.

2. The probe of claim 1 wherein said controlled impedance structure is a microstrip structure.

3. The probe of claim 1 wherein said elongate conductor is supported on a first side of said substrate and wherein said conductive member is supported on a second side of said substrate.

4. The probe of claim 1 further comprising a conductive path electrically connected to said elongate conductor that extends between a first side of said substrate and a second side of said substrate and said conductive path free from electrical interconnection with said conductive member.

5. The probe of claim 4 wherein said conductive path between said first side and said second side is in a manner free from an air gap between the conductive path and the end of said substrate for at least a majority of the thickness of said substrate.

6. The probe of claim 4 wherein said contact is in the form of a bump.

7. The probe of claim 1 wherein said elongate conductor is electrically interconnected to a central conductor of a coaxial cable.

8. The probe of claim 7 wherein said conductive member is electrically connected to a conductor surrounding said central conductor of said coaxial cable.

9. The probe of claim 8 wherein said substrate is supported by said coaxial cable.

10. The probe of claim 9 wherein said substrate is supported by a shelf of said coaxial cable.

11. The probe of claim 1 wherein said conductive member is substantially planar.

12. The probe of claim 1 wherein said dielectric substrate is semi-flexible.

13. The probe of claim 1 wherein said dielectric substrate has a dielectric constant less than 5.

14. The probe of claim 1 wherein said dielectric substrate has a dielectric constant less than 4.

15. The probe of claim 1 wherein said dielectric substrate has a dielectric constant less than 2.

16. The probe of claim 1 wherein said conductive member covers greater than 50% of a side of said substrate.

17. The probe of claim 1 wherein said conductive member covers greater than 60% of a side of said substrate.

18. The probe of claim 1 wherein said conductive member covers greater than 70% of a side of said substrate.

19. The probe of claim 1 wherein said conductive member covers greater than 80% of a side of said substrate.

20. The probe of claim 1 wherein said conductive member covers greater than 90% of a side of said substrate.

21. The probe of claim 1 wherein said contact comprises a via through said substrate.

22. The probe of claim 1 wherein said conductive member laterally surrounds at least 50% of said contact.

23. The probe of claim 1 wherein said conductive member laterally surrounds at least 75% of said contact.

24. The probe of claim 1 wherein said conductive member laterally surrounds at least 100% of said contact.

25. The probe of claim 1 wherein said contact is in the form of a conductive finger.

26. The probe of claim 1 wherein said substrate has a thickness less than 30 microns.

27. The probe of claim 1 wherein said substrate has a thickness less than 20 microns.

28. A probe comprising:

(a) a dielectric substrate supporting an elongate conductor on said substrate and a conductive member supported on said substrate;

(b) a contact electrically interconnected to said elongate conductor for testing a device under test;

(c) wherein said elongate conductor and said substrate form a controlled impedance structure;

(d) wherein said contact has a height relative to the adjoining surface of said dielectric substrate of less than 150 microns.

29. The probe of claim 28 wherein said contact has a height relative to the adjoining surface of said dielectric substrate of less than 100 microns.

30. The probe of claim 28 wherein said contact has a height relative to the adjoining surface of said dielectric substrate of less than 75 microns.

31. The probe of claim 28 wherein said contact has a height relative to the adjoining surface of said dielectric substrate of less than 55 microns.

32. The probe of claim 28 further comprising a co-axial cable interconnected to said dielectric substrate, wherein said co-axial cable is maintained in a tensioned state when said contact is free from being engaged with said device under test.

33. The probe of claim 28 herein said substrate has a thickness of less than 40 microns with a dielectric constant of less than 7.