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ELECTRICAL, HIGH TEMPERATURE TEST
PROBE WITH CONDUCTIVE DRIVEN
GUARD
CROSS-REFERENCE TO RELATED
APPLICATION
This patent application claims priority to U.S. Provisional Patent Application Ser. No. 60/458,467, filed on Mar. 28, 2003, and is related to U.S. patent application Ser. No. 09/730,130, filed Dec. 4,2000, now U.S. Pat. No. 6,586,954, entitled "PROBE TILE FOR PROBING SEMICONDUCTOR WAFER"; U.S. Provisional Patent Application Ser. No. 60/392,394, filed Jun. 28, 2002, entitled "SHIELDED PROBE APPARATUS FOR PROBING SEMICONDUCTOR WAFER"; and U.S. patent application Ser. No. 10/383, 079, filed Mar. 6, 2003, entitled "APPARATUS AND METHOD FOR TERMINATING PROBE APPARATUS OF SEMICONDUCTOR WAFER"; the subject matter of which are incorporated herewith by reference.
FIELD OF THE INVENTION
The present invention relates generally to semiconductor test equipment, and more particularly, to a probe apparatus used in semiconductor test equipment for electrically probing devices on a semiconductor wafer.
BACKGROUND OF THE INVENTION
The semiconductor industry has a need to access many electronic devices on a semiconductor wafer. As the semiconductor industry grows and devices become more complex, many electrical devices, most commonly semiconductor devices, must be electrically tested, for example, for leakage currents and extremely low operating currents. These currents are often below 100 fA. In addition, the currents and device characteristics are often required to be evaluated over a wide temperature range to understand how temperature affects a device. Also, because of materials characteristics of dielectrics, it is often difficult to test characteristics of semiconductor devices in a wide operating temperature range.
To effectively measure at currents below 100 fA (Femto Ampere), a measurement signal must be isolated from external electrical interference, leakage currents through the dielectric material, parasitic capacitance, triboelectric noise, piezoelectric noise, and dielectric absorption, etc.
Accordingly, there is a need for improved semiconductor test equipment for electrically probing semiconductor devices at low currents over a wide temperature range.
SUMMARY OF THE INVENTION
To solve the above and the other problems, the present invention provides a probe needle apparatus and method including a driven guard having the same potential as a probe needle for reducing signal noise in low current measurements. The probe needle apparatus includes a central conductive probe needle covered with alternating layers of dielectric and conductive materials.
In one embodiment, the probe needle apparatus comprises a central conductive probe needle surrounded by a high temperature dielectric layer of material. A conductive layer is deposited around the dielectric layer to provide a driven guard. The initial layer of dielectric material provides a thin and continuous barrier to prevent the conductive driven
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guard from contacting electrically to the probe needle. In one embodiment, a subsequent protective layer is applied over the driven guard.
In one embodiment of the present invention, the probe
5 needle can be a probe needle disclosed in U.S. Provisional Patent Application Ser. No. 60/392,394, filed Jun. 28, 2002, entitled "SHIELDED PROBE APPARATUS FOR PROBING SEMICONDUCTOR WAFER". Also, in one embodiment, the probe needle is masked at the distal and proximate
10 ends to allow continuity. The masked probe needle is then coated with a flexible high temperature dielectric, prior to being coated with a conductive layer, such as gold, for the driven guard. An optional top layer can be applied by a method, such as dipping and spinning, or depositing by other
15 means to protect the outer conductive layer.
In one embodiment of the probe needle, an initial dielectric layer is applied by dipping and spinning. After thermally curing the dielectric layer, the conductive layer for the driven guard is applied.
20 Additionally in one embodiment of the present invention, the probe needle may be coated with an initial dielectric layer of Si02. A thin conductive layer of the driven guard may be strengthened by over-plating.
These and other features of the present invention will
25 become apparent to those skilled in the art from the following detailed description, wherein it is shown and described illustrative embodiments of the invention, including best modes contemplated for carrying out the invention. As it will be realized, the invention is capable of modifications in
30 various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.
35 BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of one embodiment of a shielded probe apparatus in accordance with the principles of the present invention. 40 FIG. 2 is a masking technique for masking a shielded probe in accordance with the principles of the present invention.
FIG. 3 is a rotational technique for applying one or more conformal coatings on the shielded probe in accordance with 45 the principles of the present invention.
FIG. 4 is a cross sectional view of another embodiment of a shielded probe apparatus in accordance with the principles of the present invention.
FIG. 5 is a perspective view of one embodiment of a probe 50 apparatus having a co-axial shielded probe terminating with a co-axial signal cable at a terminating device, in accordance with the principles of the present invention.
FIG. 6 is a perspective view of one embodiment of a probe apparatus having a tri-axial shielded probe terminating with 55 a tri-axial signal cable at a terminating device, in accordance with the principles of the present invention.
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS
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In the following description of a preferred embodiment, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention 65 may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.
