Differential signal probing system

• US 7,764,072 B2
• Filed: 02/22/2007
• Issued: 07/27/2010
• Est. Priority Date: 06/12/2006
• Status: Expired due to Fees

• Current Assignee: Cascade Microtech Incorporated (FormFactor Incorporated)
• Original Assignee: Cascade Microtech Incorporated (FormFactor Incorporated)
• Inventors: Campbell, Richard, Strid, Eric
• Primary Examiner(s): Nguyen; Ha Tran T
• Assistant Examiner(s): CAMPBELL, SHAUN M
• Application Number:
  US11/710,225
• Publication Number:
  US 20070285085A1
• Time in Patent Office: 1,251 Days
• Field of Search: 324/149, 324/754
• US Class Current: 324/755.01
• CPC Class Codes: G01R 1/06772 High frequency probes

Abstract

A probe measurement system comprises a probe with a linear array of probe tips enabling a single probe to be used when probing a test structure with a differential signal.

Claims

1. A probe for testing a differential test structure having a plurality of probe pads, said probe comprising:

(a) a first probe tip operable to conduct a first mode component of a first differential signal;

(b) a second probe tip proximate said first probe tip and operable to conduct a first mode component of a second differential signal;

(c) a third probe tip proximate said second probe tip;

(d) a fourth probe tip proximate said third probe tip and operable to conduct a second mode component of said second differential signal contemporaneous with conduction of said first mode component of said first differential signal by said first probe tip; and

(e) a fifth probe tip proximate said fourth probe tip and operable to conduct a second mode component of said first differential signal contemporaneous with conduction of said first mode component of said second differential signal by said second probe tip;

said first, said second, said fourth and said fifth probe tips being arranged in a substantially linear array and, with said third probe tip, contemporaneously co-locatable with respective probe pads of said test structure.

2. The probe of claim 1 wherein a source of said first differential signal comprises said respective probe pads of said test structure co-locatable with said first and said fifth probe tips.

3. The probe of claim 1 wherein a source of said second differential signal comprises said respective probe pads of said test structure co-locatable with said second and said fourth probe tips.

4. The probe of claim 1 wherein said third probe tip is interconnected to a source of a direct current.

5. The probe of claim 1 wherein said third probe tip is aligned substantially linearly with said linear array of said first, said second, said fourth and said fifth probe tips.

6. The probe of claim 5 further comprising:

(a) a sixth probe tip proximate said first probe tip; and

(b) a seventh probe tip proximate said fifth probe tip;

said sixth and said seventh probe tips being arrayed substantially linearly with said first, said second, said third, said fourth and said fifth probe tips;

interconnected to said third probe tip and co-locatable with respective probe pads of said test structure.

7. The probe of claim 6 wherein said third probe tip is interconnected to a source of a direct current.

8. A probe for testing a differential test structure having a plurality of probe pads, said probe comprising:

(a) a dielectric plate having a substantially planar first surface and a second surface;

(b) a first probe tip projecting from said first surface and operable to conduct a first mode component of a first differential signal;

(c) a second probe tip projecting from said first surface proximate said first probe tip and operable to conduct a first mode component of a second differential signal;

(d) a third probe tip projecting from said first surface proximate said second probe tip;

(e) a fourth probe tip projecting from said first surface proximate said third probe tip and operable to conduct a second mode component of said second differential signal contemporaneous with conduction of said first mode component of said first differential signal by said first probe tip; and

(f) a fifth probe tip projecting from said first surface proximate said fourth probe tip and operable to conduct a second mode component of said first differential signal contemporaneous with conduction of said first mode component of said second differential signal by said second probe tip;

said first, said second, said fourth and said fifth probe tips being arranged in a substantially linear array and contemporaneously co-locatable with respective probe pads of said test structure.

9. The probe of claim 8 wherein a source of said first differential signal comprises said respective probe pads of said test structure co-locatable with said first and said fifth probe tips.

10. The probe of claim 8 wherein a source of said second differential signal comprises said respective probe pads of said test structure co-locatable with said second and said fourth probe tips.

11. The probe of claim 8 wherein said third probe tip is interconnected to a source of a direct current.

12. The probe of claim 8 wherein said third probe tip is aligned substantially linearly with said linear array of said first, said second, said fourth and said fifth probe tips.

13. The probe of claim 12 further comprising:

(a) a sixth probe tip proximate said first probe tip; and

(b) a seventh probe tip proximate said fifth probe tip;

said sixth and said seventh probe tips being arrayed substantially linearly with said first, said second, said third, said fourth and said fifth probe tips;

interconnected to said third probe tip and co-locatable with respective probe pads of said test structure.

14. The probe of claim 8 further comprising:

(a) a first conductor overlaying an area of said first surface and electrically interconnected with said third probe tip;

(b) a second conductor extending from said first surface to said second surface of said dielectric plate and electrically interconnected with said first conductor; and

(c) a conductor of direct current electrically interconnected with said second conductor.

15. The probe of claim 14 further comprising:

(a) a sixth probe tip projecting from said first surface proximate said first probe tip; and

(b) a seventh probe tip projecting from said first surface proximate said fifth probe tip, said sixth and said seventh probe tips being electrically interconnected with said first conductor and arrayed substantially linearly with said first, said second, said third, said fourth and said fifth probe tips and respectively co-locatable with probe pads of said test structure.

16. The probe of claim 8 further comprising:

(a) a first conductor overlaying an area of said second surface; and

(b) a second conductor extending from said second surface of said dielectric plate and electrically interconnecting said first conductor with a ground potential.

17. The probe of claim 8 wherein said dielectric plate is rigid.

18. The probe of claim 8 wherein said dielectric plate is flexible.

19. A system for measuring a performance of a differential test structure having a plurality of probe pads, said system comprising:

(a) a source of a modulated differential signal comprising an even mode component and an odd mode component of approximately equal amplitude and opposite phase angle, said differential signal including a direct current component;

(b) a first bias tee interconnected with said source, said first bias tee separating said direct current component from one of said even mode component and said odd mode component of said modulated differential signal;

(c) a second bias tee interconnected with said source, said second bias tee separating said direct current component from the other of said even mode component and said odd mode component of said modulated differential signal;

(d) a probe comprising;

(i) a first probe tip interconnected to communicate one of said even mode component and said odd mode component of said modulated differential signal from one of said first bias tee and said second bias tee to a first probe pad of said test structure;

(ii) a second probe tip co-locatable with a second probe pad of said test structure;

(iii) a third probe tip interconnected with at least one of said first bias tee and said second bias tee to conduct said direct current component to a third probe pad of said test structure;

(iv) a fourth probe tip co-locatable with a fourth probe pad of said test structure;

(v) a fifth probe tip interconnected to communicate the other of said even mode component and said odd mode component of said modulated differential signal from the other of said first bias tee and said second bias tee to a fifth probe pad of said test structure, said first, said second, said third, said fourth and said fifth probe tips arranged to be contemporaneously co-locatable with said respective probe pads of said test structure and at least said first, said second, said fourth and said fifth probe tips being arranged in a substantially linear array; and

(e) a signal sink interconnected with said second probe tip and said fourth probe tip, said sink receiving a signal conducted from said second probe pad and said fourth probe pad of said test structure.

20. The system for measuring a performance of a differential test structure of claim 19 wherein said source of said modulated differential signal comprising an even mode component and an odd mode component of approximately equal amplitude and opposite phase angle comprises:

(a) a source of a single ended signal including a modulated signal component and a direct current component; and

(b) a first balun interconnecting said source and said first and said second bias tees, said first balun converting said single ended signal to a differential signal comprising an even mode component and an odd mode component of approximately equal amplitude and opposite phase angle.

21. The system for measuring a performance of a differential test structure of claim 20 further comprising a second balun interconnecting said second and said fourth probe tips and said sink, said second balun converting a differential signal transmitted from said second probe pad and said fourth probe pad to a single ended signal.

22. The system for measuring a performance of a differential test structure of claim 19 wherein:

(a) said second probe tip is proximate said first probe tip;

(b) said third probe tip is proximate said second probe tip;

(c) said fourth probe tip is proximate said third probe tip; and

(d) said fifth probe tip is proximate said fourth probe tip.

23. The system for measuring a performance of a differential test structure of claim 19 wherein:

(a) said second probe tip is proximate said first probe tip;

(b) said third probe tip is proximate said first probe tip;

(c) said fourth probe tip is proximate said fifth probe tip; and

(d) said fifth probe tip is proximate said third probe tip.

24. A system for measuring a characteristic of a differential gain cell having a first input terminal, a second input terminal, a first output terminal for transmitting a first output signal controllable by a signal at said first input terminal and a second output terminal for transmitting a second output signal controllable by a signal at said second input terminal, said system comprising:

(a) a source of a first differential signal having a first frequency of modulation, said first differential signal comprising a first mode component and a second mode component of approximately equal magnitude and opposite phase angle;

(b) an interconnection of said source and said first input terminal of said differential gain cell enabling communication of said first mode component of said first differential signal to said first input terminal;

(c) an interconnection of said source and said second input terminal of said differential gain cell enabling communication of said second mode component of said first differential signal to said second input terminal;

(d) a source of a second differential signal having a second frequency of modulation, said second differential signal comprising a first mode component and a second mode component of approximately equal magnitude and opposite phase angle;

(e) an interconnection of said first output terminal of said differential gain cell and said second source enabling conducting of a first combined signal comprising a combination of said first mode component of said second differential signal and a first mode component of an output signal of said differential gain cell;

(f) an interconnection of said second output terminal of said differential gain cell and said second source enabling conducting of a second combined signal comprising a combination of said second mode component of said second differential signal and a second mode component of an output signal of said differential gain cell;

(g) a first filter selectively permitting transmission of a portion of said first combined signal having a frequency approximately equal to a difference between said first frequency and said second frequency;

(h) a second filter selectively permitting transmission of a portion of said second combined signal having a frequency approximately equal to a difference between said first frequency and said second frequency; and

(i) a signal sink interconnected to said first filter and said second filter, said signal sink enabling analysis of said first and said second combined signals.

25. The system for measuring a characteristic of a differential test structure of claim 24 wherein said source of said first differential signal comprises:

(a) a source of a single ended signal; and

(b) a first balun interconnecting said source and said first and said input terminals of said differential gain cell.

26. The system for measuring a characteristic of a differential test structure of claim 24 wherein said source of said second differential signal comprises:

(a) a source of a single ended signal; and

(b) a balun interconnecting said source and said first and said output terminals of said differential gain cell.