Shielded probe with low contact resistance for testing a device under test

• US 7,436,194 B2
• Filed: 10/24/2007
• Issued: 10/14/2008
• Est. Priority Date: 05/23/2002
• Status: Expired due to Fees

• Current Assignee: FormFactor Incorporated
• Original Assignee: Cascade Microtech Incorporated (FormFactor Incorporated)
• Inventors: Gleason, K. Reed, Andrews, Mike, Martin, John, Lesher, Tim, Dunklee, John, Hayden, Leonard, Strid, Eric W., Safwat, Amr M. E.
• Primary Examiner(s): Nguyen; Vinh P
• Application Number:
  US11/977,324
• Publication Number:
  US 20080048692A1
• Time in Patent Office: 356 Days
• Field of Search: None
• US Class Current: 324/754.03
• 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 measurement system having low, stable contact resistance for measuring the electrical characteristics of integrated circuits or other microelectronic devices at high frequencies.

Claims

1. A probe comprising:

(a) a dielectric substrate supporting an elongate conductor on a first side of said substrate and supporting a conductive member on a second side of said substrate, said conductive member including a contact surface on a side of said conductive member distal of said dielectric substrate for contacting a device under test; and

(b) a contact electrically interconnected to said elongate conductor and protruding from said second side of said substrate for contacting said device under test;

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

(d) wherein said probe has a characteristic that its contact resistance when said contact is engaged with un-patterned aluminum of said device under test is generally less than 30 milliohms during any engagement of an initial 5000 engagements of said contact and said un-patterned aluminum.

2. The probe of claim 1 further comprising a resiliently flexible structure interconnected with said dielectric substrate, and a pre-loading mechanism that pre-loads said flexible structure by imparting a pre-load displacement of said structure when said contact is free from being engaged with said device under test in such a manner that when said probe is displaced with said contact in engagement with said device under test a force exerted on said device under test by said contact is greater than said force would be if said pre-load displacement had not been imparted to said flexible structure.

3. The probe of claim 1 further comprising a conductive path between said first side of said substrate and said second side of said substrate.

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

5. The probe of claim 2 wherein said flexible structure is a co-axial cable.

6. The probe of claim 1 herein said substrate has a thickness of less than 40 microns with a dielectric constant of less than 7.

7. The probe of claim 3 wherein said conductive path is in a region within the periphery of said substrate for at least a majority of the thickness of said substrate.

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

9. The probe of claim 1 wherein said conductive member is electrically connected to a conductor surrounding a central conductor of a coaxial cable.

10. The probe of claim 1 wherein said contact resistance generally varies less than 5 mΩ

over said initial 5000 engagements of said contact and said un-patterned aluminum.

11. A probe comprising:

(a) a dielectric substrate supporting an elongate conductor on a first side of said substrate and supporting a conductive member on a second side said substrate, said conductive member including a contact surface on a side of said member distal of said substrate for contacting a device under test; and

(b) a contact electrically interconnected to said elongate conductor and protruding from said second side of said substrate for contact with said device under test;

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

(d) wherein said probe has a characteristic that its contact resistance when said contact is engaged with un-patterned aluminum of said device under test is generally less than 35 milliohms throughout a 5 hour period of engagement of said contact and said un-patterned aluminum.

12. The probe of claim 11 wherein said contact resistance generally varies less than 10 milliohms throughout said 5 hour period of engagement of said contact and said un-patterned aluminum.

13. The probe of claim 11 further comprising a resiliently flexible structure interconnected with said dielectric substrate, and a pre-loading mechanism that pre-loads said flexible structure by imparting a pre-load displacement of said structure when said contact is free from being engaged with said device under test in such a manner that when said probe is displaced with said contact in engagement with said device under test a force exerted on said device under test by said contact is greater than said force would be if said pre-load displacement had not been imparted to said flexible structure.

14. The probe of claim 11 further comprising a conductive path between said first side of said substrate and said second side of said substrate.

15. The probe of claim 11 wherein said controlled impedance structure is a microstrip.

16. The probe of claim 13 wherein said flexible structure is a co-axial cable.

17. The probe of claim 11 herein said substrate has a thickness of less than 40 microns with a dielectric constant of less than 7.

18. The probe of claim 14 wherein said conductive path is in a region within the periphery of said substrate for at least a majority of the thickness of said substrate.

19. The probe of claim 11 wherein said elongate conductor is electrically interconnected to a central conductor of a coaxial cable.

20. The probe of claim 11 wherein said conductive member is electrically connected to a conductor surrounding a central conductor of a coaxial cable.