Probe station
A probe station.
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This application is a continuation of U.S. patent application Ser. No. 10/759,481, filed Jan. 16, 2004, which is a continuation of U.S. patent application Ser. No. 10/285,135, filed Oct. 30, 2002, now U.S. Pat. No. 6,777,964, which claims the benefit of U.S. Provisional App. No. 60/351,844, filed Jan. 25, 2000.
BACKGROUND OF THE INVENTIONThe present invention relates to a probe station.
BRIEF SUMMARY OF THE INVENTIONProbe stations are designed to measure the characteristics of electrical devices such as silicon wafers. Probe stations typically include a chuck that supports the electrical device while it is being probed by needles or contacts on a membrane situated above the chuck. In order to provide a controlled environment to probe the electrical device, many of today's probe stations surround the chuck with an environmental enclosure so that temperature, humidity, etc. may be held within predetermined limits during testing. Environmental enclosures protect the device from spurious air currents that would otherwise affect measurements, and also facilitate thermal testing of electrical devices at other-than-ambient environmental conditions. Environmental conditions within the enclosure are principally controlled by a dry air ventilation system as well as a temperature element, usually located below the chuck, that heats or cools the electrical device being tested through thermal conduction.
Many probe stations also incorporate guarding and electromagnetic interference (EMI) shielding structures within or around the environmental enclosures in order to provide an electrically quiet environment, often essential during high frequency testing where electrical noise from external electromagnetic sources can hinder accurate measurement of the electrical device's characteristics. Guarding and EMI shielding structures are well known and discussed extensively in technical literature. See, for example, an article by William Knauer entitled “Fixturing for Low Current/Low Voltage Parametric Testing” appearing in Evaluation Engineering, November, 1990, pages 150-153.
Probe stations incorporating EMI shielding structures will usually at least partially surround the test signal with a guard signal that closely approximates the test signal, thus inhibiting electromagnetic current leakage from the test signal path to its immediately surrounding environment. Similarly, EMI shielding structures may provide a shield signal to the environmental enclosure surrounding much of the perimeter of the probe station. The environmental enclosure is typically connected to earth ground, instrumentation ground, or some other desired potential.
To provide guarding and shielding for systems of the type just described, existing probe stations may include a multistage chuck upon which the electrical device rests when being tested. The top stage of the chuck, which supports the electrical device, typically comprises a solid, electrically conductive metal plate through which the test signal may be routed. A middle stage and a bottom stage of the chuck similarly comprise solid electrically conductive plates through which a guard signal and a shield signal may be routed, respectively. In this fashion, an electrical device resting on such a multistage chuck may be both guarded and shielded from below.
To provide a substantially closed environment, the outer shield box 24 includes a sliding plate assembly 28 that defines a portion of the lower perimeter of the shield box 24. The sliding plate assembly 28 comprises a number of overlapping plate members. Each plate member defines a central opening 30 through which the positioner 22 may extend. Each successively higher plate member is smaller in size and also defines a smaller opening 30 through which the positioner 22 extends. The sliding plate assembly 28 is included to permit lateral movement of the positioner 22, and hence the chuck 12, while maintaining a substantially closed lower perimeter for the shield box 24.
Referring to
Referring to
What is desired, then, is a probe station that facilitates accurate alignment of electrical and optical probes.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
During testing, the end of the optical probes are typically aligned with the edge of the device under test while the electrical probes are typically aligned with the contacts on the upper surface of the device under test, with both the electrical probes and the optical probes being supported by the platen. In many cases, the entire platen is moved in the z-axis direction for selectively contacting the electrical probes on the device under test. Alternatively, the chuck is moved in a z-axis direction. The z-axis movement of the platen permits consistent simultaneous relative movement of all the electrical and optical probes. Each component of the device under test is successively moved in x and/or y lateral directions relative to the electrical probes using a chuck or other support to a location under the electrical probes.
The present inventors considered the z-axis movement of the platen or chuck to perform simultaneous probing and came to the realization that normal z-axis movement of the platen typically brings the probes into contact with the device under test with sufficient additional z-axis movement to result in lateral scrubbing of the contact surfaces to provide a good contact. This additional z-axis movement for the electrical probes, which may vary depending on the particular circuit being probed, different electronic components, the planarity of the devices, and differences in the height of the different contacts between devices, may result in inaccurate alignment of the optical probes which are likewise being moved in the z-axis direction together with the platen or chuck. The alignment of the optical inputs and outputs of the devices tends not to vary in the same manner as the contacts, if they vary significantly at all. In summary, the appropriate z-axis movement of the electrical probes varies depending on the particular device being tested; while the appropriate z-axis movement of the optical probes tends to be at a substantially fixed location with respect to the device under test, which may not be consistent with the z-axis movement provided for the electrical probes. Moreover, the relatively long optical device tends to expand and contract with temperature variations of the environment resulting in additional difficulty properly positioning the optical probe.
In light of the foregoing realizations the present inventors determined that the traditional probe station should be modified in some manner to facilitate at least partial independent movement or otherwise separation of the optical probes and electrical probes. Referring to
In the case that the device under test is moved in a direction perpendicular to the edge of the device under test 104 being tested, it may be observed that the optical probes 116 may not need to be repositioned for each device being tested. If realignment of the optical probes 116 are necessary, there is a good likelihood that minimal adjustment is necessary. In particular, there is a high likelihood that the elevation of the optical probe 116 is accurate (or nearly so) because the chuck 102 is moving within a horizontal plane for testing the device under test 104. It may be observed that optical probes 116 are effectively decoupled from the z-axis motion of the upper platen 106. Moreover movement of the upper platen 106 for bringing the electrical probes 110 into contact with the device under test 104 does not result in movement of the optical probe 116 with respect to the device under test 104. Similarly, it may be observed that movement of the optical probes 116 does not result in movement of the electrical probes 110.
As illustrated in
Another feature that may be included is the capability of removing or otherwise moving the upper platen out of the way for in a controlled manner. The movement of the upper platen facilitates the adjustment and installation of the optical components thereunder. For example, a mechanical support mechanism may be included that supports the upper platen while the platen is moved with respect to the remainder of the probe station, and in particular the lower platen. For example, the upper platen may be displaced such that at least 20% (or at least 30% or at least 40% or at least 50%) of its surface area is laterally displaced beyond its original position on the supports. Alternatively, the upper platen may be tilted upwardly. For example, the upper platen may be tilted such that it is at least 5 degrees (or at least 10 degrees or at least 20 degrees or at least 45 degrees or at least 75 degrees) of its surface area is tiled with respect to its position when probing, such as horizontal.
Referring to
Referring to
Referring to
The probe station facilitates the testing of a photonics device that includes an optical test path, which is optimized based upon optical characteristics. In addition, the probe station facilitates the testing of a photonics device that includes an electrical test path, which is similarly optimized based upon electrical characteristics. Typically multiple electrical probes are supported and simultaneously brought into contact with the device under test. In this manner, the probe station includes a structure that brings together optimized electrical test paths and optimized optical test paths together on the device under test.
Referring to
Referring to
The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.
Claims
1. A method of probing a device under test comprising:
- (a) supporting said device under test on a first support;
- (b) supporting an electrical probe on a second support;
- (c) supporting an optical probe on a third support; and
- (d) moving said electrical probe relative to said device under test in a first direction relative to the surface of said device under test to sense electrical characteristics of said device under test while said optical probe remains substantially aligned with the edge of said device under test to sense optical characteristics of said device under test.
2. The method of claim 1 wherein said first support is a chuck.
3. The method of claim 2 wherein said chuck includes a substantially planar upper surface.
4. The method of claim 1 wherein said second support is a platen positioned above said device under test.
5. The method of claim 4 wherein said platen defines an opening therein though which a portion of said electrical probe extends.
6. The method of claim 1 wherein said first support is located between said second support and said third support.
7. The method of claim 1 wherein said second support and said third support remain stationary with respect to each other while said first support moves relative to said device under test while said moving.
8. The method of claim 1 wherein said first direction is a z-axis direction.
9. The method of claim 1 wherein said electrical probe may be moved independently of said optical probe.
10. A probe station for testing a device under test comprising:
- (a) a first platen supporting an electrical probe;
- (b) a chuck supporting said device under test;
- (c) a second platen supporting an optical probe;
- (d) said first platen and said second platen positioned at different elevations from one another and different elevations from said chuck;
- (e) said second platen movable relative to said chuck in a perpendicular direction, said first platen movable relative to said chuck in a perpendicular direction;
- (e) at least 70% of the top surface of said second platen terminating in free space when said optical probe is not supported thereon.
11. The probe station of claim 10 wherein said first platen and said second platen are movable in a perpendicular direction relative to one another.
12. The probe station of claim 10 wherein at least 80% of the top surface of said second platen terminating in free space when said optical probe is not supported thereon.
13. The probe station of claim 10 wherein at least 90% of the top surface of said second platen terminating in free space when said optical probe is not supported thereon.
14. The probe station of claim 10 wherein at least 95% of the top surface of said second platen terminating in free space when said optical probe is not supported thereon.
15. The probe station of claim 10 wherein said second platen has a greater top surface area than said first platen.
16. The probe station of claim 10 wherein said second platen has a smaller top surface area than said first platen.
17. The probe station of claim 10 wherein said first platen is maintained in position with respect to said second platen by gravity such that if said probe station were turned upside down said first platen would freely fall away from said second platen.
18. A probe station for testing a device under test comprising:
- (a) a first platen supporting an electrical probe;
- (b) a chuck supporting said device under test;
- (c) said first platen is positioned at a different elevation than said device under test;
- (d) a movement mechanism laterally displacing said first platen in a controlled manner such that at least 20% of the surface area of said first platen is laterally displaced to a spatial region not previously occupied by said first platen prior to said lateral displacement.
19. The probe station of claim 18 wherein said controlled manner is at least 30% of said surface area.
20. The probe station of claim 18 wherein said controlled manner is at least 40% of said surface area.
21. The probe station of claim 18 wherein said controlled manner is at least 50% of said surface area.
22. A probe station for testing a device under test comprising:
- (a) a first platen supporting an electrical probe;
- (b) a chuck supporting said device under test;
- (c) said first platen is positioned at a different elevation than said device under test;
- (d) a movement mechanism angularly displacing said first platen in a controlled manner such that said first platen is tilted at an angle of at least 5 degrees with respect to the angle of said first platen when probing said device under test.
23. The probe station of claim 22 wherein said controlled manner is at least 10 degrees.
24. The probe station of claim 22 wherein said controlled manner is at least 45 degrees.
25. The probe station of claim 22 wherein said controlled manner is at least 75 degrees.
Type: Application
Filed: Oct 19, 2007
Publication Date: Feb 21, 2008
Applicant:
Inventors: Peter Navratil (Tualatin, OR), Brad Froemke (Portland, OR), Craig Stewart (Bloxham), Anthony Lord (Banbury), Jeff Spencer (Vernonia, OR), Scott Runbaugh (Tigard, OR), Gavin Fisher (Chinnor), Pete McCann (Beaverton, OR), Rod Jones (Gaston, OR)
Application Number: 11/975,477
International Classification: G01R 31/02 (20060101);