Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1998-04-16
2001-06-05
Nguyen, Vinh P. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S761010
Reexamination Certificate
active
06242929
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a probe needle for a probe card and a fabrication method thereof. More particularly, the present invention relates to a probe needle for a vertical needle type probe card and a fabrication method thereof.
2. Description of the Background Art
Among the processes of fabricating an IC, an LSI and the like, a wafer test process is known to test whether each chip on a wafer is an acceptable product or not. In this wafer testing, a probe card is generally attached to a device called a prober. The test is carried out by placing the probe needle of the probe card on a predetermined pad (electrode) on the wafer chip (referred to as overdrive operation) with at least a predetermined pressure (referred to as stylus pressure) to form contact. More specifically, a probe card is developed to test the electrical characteristics of a semiconductor device in the fabrication process of a semiconductor device. This probe card includes the conventional vertical needle type probe card. Particularly, a cobra probe card developed by IBM has attracted a wide range of attention, and is now beginning to be used for practical usage.
FIG. 8
is a schematic diagram showing a conventional cobra probe card. Referring to
FIG. 8
, the upper end of a cobra type probe needle
101
is attached in a vertical manner to an upper guide plate
102
in this conventional probe card. Also, a lower guide plate
103
for positioning an electrode
109
that will form contact with probe needle
101
is located beneath upper guide plate
102
. A through hole
104
is provided in lower guide plate
103
to guide probe needle
101
. The upper end of probe needle
101
is connected to a terminal (not shown) arranged around upper guide plate
102
via a wiring (not shown). The leading end of probe needle
101
forms contact with electrode
106
provided at the surface of a semiconductor device that is the subject of testing. This probe card is used to test the electrical characteristics of a semiconductor device.
FIG. 9
is a schematic diagram for describing an operation of the probe needle of the cobra probe card shown in FIG.
8
. Referring to
FIG. 9
, an external force
105
is exerted to bring probe needle
101
in contact with electrode
109
. External force
105
is exerted onto this probe card in the direction indicated by the arrow in FIG.
9
. When leading end
107
of probe needle
101
is in contact with electrode
109
, a portion
108
fixed to upper guide plate
102
, a portion
106
guided by lower guide plate
103
, a bent portion
111
absorbing the stress, and leading end portion
107
of probe needle
101
in contact with electrode
109
are arranged as shown in FIG.
9
.
The above-described probe needle
101
of the conventional cobra type probe card has two problems set forth in the following.
The first problem is that a great deflection is generated at bending portion
111
when leading end
107
of probe needle
101
is brought into contact with electrode
109
since bending portion
111
is formed so as to absorb the stress at that one portion. When leading end
107
of probe needle
101
is brought into contact with electrode
109
, probe needle
101
will contact the side surface of through hole
104
in lower guide plate
103
. As a result, the side surface of through hole
104
is scraped to generate scraps. The scraps will block through hole
104
to degrade the passage of probe needle
101
. Furthermore, probe needle
101
will be caught at the side surface of through hole
104
due to the friction between probe needle
101
and through hole
104
. There is a possibility that probe needle
101
will be stuck in through hole
104
so as not to protrude therefrom. Therefore, the height level of each leading end
107
of each the plurality of probe needles
101
will differ to result in step-graded levels. This means that there is variation in the penetration pressure of probe needle
101
to project into an aluminum oxide film (not shown) formed on electrode
109
. The contact pressure between electrode
109
and leading end
107
of probe needle
101
will become improper, so that testing of the electrical characteristics cannot be carried out at high accuracy.
The second problem is that the stress is concentrated at one bending portion
111
of probe needle
101
when leading end
107
of probe needle
101
forms contact with electrode
109
since probe needle
101
is formed so that the stress is absorbed at only one bending portion
111
. Repetitive usage with the stress always concentrated at one location will cause metal fatigue due to the repetitive loading. Probe needle
101
was sometimes broken into two pieces or permanently bent. Thus, the lifetime of probe needle
101
becomes shorter. This was not cost effective since extra cost is required for the exchange.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a probe needle for a vertical needle type probe card that allows testing of electrical characteristics at higher accuracy.
Another object of the present invention is to provide a probe needle for a vertical needle type probe card that has high durability and that can reduce the exchange work and cost.
According to an aspect of the present invention, a probe needle for a vertical needle type probe card includes a bending portion. The bending portion includes a first bending portion that is bent towards a first lateral direction, and a second bending portion that is bent towards a second lateral direction that is opposite to the first lateral direction at approximately 180 degrees. By this structure, deflection is generated equally in the left and right directions in the probe needle of the present invention in contrast to a conventional cobra probe needle that has only one bending portion. The possibility of the leading end of the probe needle being within an axis identical to the initial one becomes higher. Furthermore, in contrast to the conventional cobra type probe needle having only one bending portion at which the stress exerted on the probe needle is absorbed, the probe needle of the present invention can have the exerted stress absorbed by at least two bending portions. Therefore, the resiliency of the entire probe needle increases. The probe needle of the present invention allows the contact pressure between the probe needle and the electrode to be substantially constant since deviation of the leading end portion is smaller than that of the conventional prove needle. Thus, a test result of higher accuracy can be obtained. Also, increase in the resiliency allows a greater stress to be absorbed. As a result, the possibility of being broken or permanently bent is reduced. The durability of the probe needle of the present invention is increased to result in a lower running cost.
According to the above-described structure, the radius of curvature of the first bending portion can be set greater than the radius of curvature of the second bending portion. This allows the rigidity to be increased than that of a probe needle having a bending portion of the same radius of curvature. The possibility of the probe needle being broken or bent becomes lower. Also, deviation of the leading end portion becomes smaller than that of a probe needle with first and second bending portion of the same radius of curvature.
Preferably, at least the first and second bending portions are formed of a sheet strip. This means that the portion absorbing the stress is sheet-like, and is bent in only one direction at the generation of a bending stress. By setting this bending direction so as to avoid an adjacent probe needle, the possibility of a bent probe needle contacting another adjacent probe needle is eliminated. Thus, accurate testing can be carried out.
Also, the first and second bending portions can have a bending shape of either substantially a S shape or a W shape. By providing a bending portion having a simple configuration of a S shape or a W shape, the probe needle of the present invent
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Vinh P.
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