JP2000249721A - Probe card - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid degradation of a contact property caused by unevenness, reduction or the like of elasticity of springs for moving probe needles up and down, and to avoid increase of impedance caused by interposition of the springs. SOLUTION: This probe card 11 used for measuring electrical characteristics of chips formed in a semiconductor wafer has a substrate 12 functioning as a base; and plural probe needles 14 nearly vertically erected on the lower face side of the substrate 12 corresponding to a pad arrangement of the chip, each including a tip point 14a that is a contact part to a pad. A rear end side of the probe needle 14 is formed in a bifurcately opened, nearly V-shape. Both ends of bifurcate parts 14b, 14b of the probe needle 14 are fixed to the substrate 12 by use of solder 15 and are electrically connected to wiring 13 on the substrate 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a probe card suitable for use in measuring electrical characteristics of a chip (integrated circuit) formed on a semiconductor wafer.

[0002]

2. Description of the Related Art In general, an apparatus called a wafer probe is used to measure (inspection) the electrical characteristics of a chip formed on a semiconductor wafer. This wafer probe is, as shown in FIG. 6, a measuring device 1 having a test circuit for measuring electrical characteristics of chips T in a semiconductor wafer W.
And a probe card 2 connected to the measuring device 1 when the measuring device 1 measures the electrical characteristics of the chip T.

The probe card 2 is electrically connected to the measuring device 1 by a cable 3, and the measuring device 1 and the chip T
And a jig for exchanging signals (measurement signals) with the substrate 4. The substrate 4 serves as a base, a ceramic plate-shaped needle holding member 5 provided on the lower surface of the substrate 4, and a jig. A plurality of probe needles 6 held by a needle holding member 5. This probe card 2 is a vertical probe card capable of high-frequency measurement excellent in multi-pin measurement and multiple simultaneous measurement. As shown in FIG. The needle 6 is arranged.

The probe needle 6 is made of a conductive material such as metal, and is inserted into a circular cylindrical hole 7 formed in the needle holding member 5 as shown in FIGS. 8 (a) and 8 (b). Held vertically. The distal end of the probe needle 6 is disposed so as to protrude outside the hole 7, and a spring 8
Is connected. The probe needle 6 is formed in a substantially cylindrical shape as a whole, and is formed in a so-called tapered shape in which a tip side protruding outward from the hole 7 becomes smaller in diameter toward the tip.

On the other hand, the hole 7 is formed penetrating from the upper surface side to the lower surface side of the needle holding member 5. The above-mentioned spring 8 is incorporated in the upper part of the hole 7. The spring 8 is bent into a substantially U-shape, and has a structure capable of expanding and contracting by bending of the bent portion. The upper end of the spring 8 is pulled out through a small hole (not shown) formed in the substrate 4, and a wiring 10 is connected to the drawn-out portion via a solder 9.

[0006] The probe needle 6 is connected to the lower end of the extendable spring 8 as described above.
It is movably supported in the axial direction (depth direction) of the hole 7, and when it comes into contact with the pads P of the chip T, 50% from its initial position.
By being pushed about [mu] m to 100 [mu] m, an electrically and mechanically stable contact state can be obtained by the elasticity of the spring 8.

[0007]

FIG. 9 (a)
As shown in FIG. 9B, when the tip of the probe needle 6 is brought into contact with the pads P arranged in the chip T with the elasticity of the spring 8 as described above, as shown in FIG. , A contact mark (indentation) Pa of the probe needle 6 is attached. The contact mark Pa becomes a substantially circular point corresponding to the tip shape of the probe needle 6, and is aligned in advance at the start of use so that the position of the contact mark Pa is substantially at the center of the pad P.

However, in the conventional probe card 2, when the probe needle 6 is brought into contact with the pad P, the tip of the probe needle 6 is apt to slide laterally on the pad P due to the imbalance in the spring biasing force. Has become. Also, as the number of times the probe card 2 is used increases, the elasticity of the spring 8 decreases accordingly. If the elasticity falls below a predetermined level, the semiconductor wafer W is not measured after the chip T is measured.
When the probe card 2 is separated from the probe needle 2, the elasticity of the spring 8 is insufficient, and the posture of the probe needle 6 cannot be returned to the initial state. Then, as shown in FIG. 9C,
The probe needle 6 is held in an inclined state with respect to the needle holding member 5. As a result, the needle mark P with respect to the pad P
The position a gradually shifts from the initial position (the position indicated by the broken line in the figure) as shown in FIG. Then, an electrical connection state (conduction) cannot be obtained, and a circuit portion formed near the pad P may be damaged and broken.

Further, as the number of uses increases, the frictional resistance between the hole 7 of the needle holding member 5 and the probe needle 6 increases,
If the surface of the probe needle 6 is oxidized, the slip between the hole 7 and the probe needle 6 becomes dull (poor), and the contact property with the pad P deteriorates.

Further, since the spring 8 is interposed between the probe needle 6 and the wiring 10, the electrical resistance (Ω) between the probe needle 6 and the wiring 10 increases, and the reactance component increases. As a result, an alternating resistance component (impedance) particularly when handling a high-frequency signal increases. Then, the loss (attenuation) of the signal when the high-frequency signal flows increases, and the signal level input to the chip T decreases accordingly.

In such a probe card 2, since the probe needle 6 is moved up and down within the hole 7 of the needle holding member 5, the diameter of the probe needle 6 is increased as shown in FIGS. If (the diameter of the rear end located in the hole 7) is, for example, 80 μm, the inner diameter of the hole 7 in the needle holding member 5 needs to be set to 84 μm, which is larger than that. Then, in the arrangement direction of the probe needles 6, one probe needle 6 is 4 μm (84 μm-
An area as large as 80 μm) is used, and this area is one factor that limits the minimum dimension of the pad pitch of the chip T that can be supported by the current probe card 2.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is a probe card used for measuring electric characteristics of a chip formed on a semiconductor wafer. And a plurality of probe needles that are erected substantially vertically on the lower surface side of the substrate corresponding to the pad arrangement of the chips, and the tip ends of the probe needles serve as contact portions with the pads. The rear end side is formed so as to expand in a forked shape, and both ends of the forked portion are fixed to the substrate.

In this probe card, when the tip portion of the probe needle is brought into contact with the pad of the chip with a predetermined force, the same elasticity is applied to the contact portion from both the forked portion on the rear end side of the probe needle. Added. Thus, the sliding of the needle tip on the pad is suppressed, and the position of the needle mark of the probe needle does not shift even if the number of times of using the probe card increases. Further, since the probe needle itself has elasticity, there is no need to connect a spring to the probe needle. Further, in the arrangement direction of the probe needles corresponding to the pad arrangement, it is not necessary to secure a region for vertically moving the probe needles in the hole as in the related art.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 illustrates a probe card according to an embodiment of the present invention.
Is a schematic side view showing the entire structure, and FIG.
It is a part enlarged view. In the illustrated probe card 11, a wiring 13 is provided on a substrate 12 serving as a base. The wiring 13 is for transmitting a measurement signal for measuring the electrical characteristics of the chip, and is formed on the upper surface of the substrate 12 by, for example, a known patterning process.
A probe needle 14 is provided upright on the lower surface side of the substrate 12. The probe needle 14 is made of, for example, tungsten copper, and stands upright on the surface of the substrate 12.
Further, the probe needles 14 are linearly arranged in the depth direction of the drawing corresponding to the chip pad arrangement.

The tip side of the probe needle 14 is shown in FIG.
(B) as shown in FIG.
The tip 14a serves as a contact portion (contact portion) with the pad of the chip. On the other hand, the rear end side of the probe needle 14 is formed in a substantially V-shape (a substantially Y-shape as a whole needle) in a state of being expanded in a forked shape, and the forked portions 14b and 14 are formed.
The structure is such that b has an appropriate flexibility. Also,
The forked portions 14b, 14b of the probe needle 14 are formed so as to be inclined by the same angle θ with respect to the center axis of the probe needle 14. The inclination angle θ of the forked portions 14b, 14b is set to, for example, 6 ° to 60 ° so that a suitable elasticity can be obtained when a needle tip is pressed against a pad of a chip described later.
Is appropriately set within the range.

On the other hand, as shown in FIG. 3, the substrate 12 has through holes 12 corresponding to the mounting positions of the respective probe needles 14.
a is formed. The through hole 12a is provided at the end of the wiring 13 formed on the substrate 12, and a plating layer made of solder or copper is formed on the inner surface thereof. Further, two through holes 12 a are provided for each probe needle 14.

Both ends (only one side is shown in FIG. 3) of the forked portion 14b of the probe needle 14 are inserted into the through hole 12a of the substrate 12. Solder 15 is supplied onto substrate 12 so as to fill through hole 12a, and both ends of forked portions 14b, 14b of probe needle 14 are fixed to substrate 12 by this solder 15, respectively.
Further, a probe needle 14 is electrically connected to the wiring 13.

Further, on the lower surface of the substrate 12, a resin portion (elastomer or the like) 16 having rubber-like elasticity is formed in a layer with a predetermined thickness. The resin portion 16 has a rubber-like elasticity that does not hinder the bending deformation of the forked portions 14b, 14b of the probe needle 14. I have. The resin portion 16 is for preventing oxidation of metal at a connection portion (soldering portion) between the substrate 12 and the probe needle 14, and may be provided as necessary.

The probe card 11 configured as described above
In the case of measuring the electrical characteristics of the chip by using the probe needle 14, a predetermined pressing force F is applied from the upper surface side of the substrate 12 to the pad P of the chip T as shown in FIG.
(Contact). Then, the forked portions 14b, 14b of the probe needle 14 are bent and deformed in a bay shape by the pressing force F. As a result, the same elasticity f, f is applied in good balance from both the forked portions 14 b, 14 b of the probe needle 14 to the contact portion between the probe needle 14 and the pad P, so that the needle tip slides on the pad P. There is no contact, and a stable contact state is always obtained. Further, since a stable contact state can be obtained without using a spring as in the related art, it is possible to avoid variations in contact characteristics due to variations in spring characteristics.

Further, during use of the probe card 11, the probe needle 14 always comes into contact with the pad P in a well-balanced manner due to its own elasticity (bending deformation of the forked portions 14b, 14b). In this case, the position of the needle mark is not shifted on the pad P even if the number of times of use is increased, since the position is always kept perpendicular to the posture. Therefore, if the contact position of the probe needle 14 with respect to the pad P is aligned before the start of use, the position accuracy can be maintained for a long time. As a result, the probe tip of the probe needle 14 does not come into contact with a position deviated from the pad P, so that the circuit portion in the chip T can be reliably prevented from being damaged.

The forked part 14b of the probe needle 14
Since the wiring 13 is directly soldered (joined) to both ends of the wiring 14b, the electrical resistance (Ω) between the wiring 14 and the probe needle 14 becomes almost zero. Furthermore, since the reactance component does not increase due to the interposition of the spring, it is possible to minimize the loss (attenuation) of the signal particularly when handling a high-frequency signal.

In addition, the mounting direction of the probe needles 14 with respect to the substrate 12 is appropriately set (for example, the forked portions 14b, 14b are arranged in a direction substantially orthogonal to the arrangement direction of the probe needles 14). Accordingly, the probe needles 14 can be arranged closer to each other. As a result, it is possible to sufficiently cope with a chip T having a small pad pitch which cannot be coped with the conventional probe card.

Incidentally, the contact pressure of the probe needle 14 with respect to the pad P of the tip T can be arbitrarily adjusted by changing the inclination angle θ (FIG. 2) of the forked portions 14b, 14b on the rear end side of the probe needle 14. Can be.

In the above-described embodiment, the probe needle 14 has a rear end formed in a substantially V-shape. However, as shown in FIG.
May be formed in a substantially U-shaped (arched) rear end side. In the case of the probe needle 14 formed in a U-shape, the bifurcated portions 14b and 14c are always curved and have a structure that is easily bent. Higher resilience than the one (see FIG. 2) is obtained.

[0025]

As described above, according to the present invention, when the tip of the probe needle is brought into contact with the pad with a predetermined pressing force, the contact portion is bent by the forked portion of the probe needle from both sides. Because the same elasticity is applied, the tip of the probe can be prevented from slipping on the pad, and even if the number of times the probe card is used increases, the tip of the probe needle is always stably and reliably attached to the chip pad. Contact can be made. As a result, the tip of the probe needle does not come into contact with a position deviated from the pad, so that there is no danger of damaging the circuit portion in the chip. In addition, since the probe needle itself has elasticity, a spring is not required, so that it is possible to avoid a variation in contact due to the interposition of the spring and an increase in the reactance component. Furthermore, by appropriately setting the direction of the forked portion of the probe needle, each probe needle can be arranged closer to each other.
It is possible to respond sufficiently.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a probe card according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a structure of a probe needle in the embodiment.

FIG. 3 is a cross-sectional view showing a structure for attaching a probe needle to a substrate.

FIG. 4 is a diagram illustrating a state when the tip of a probe needle is brought into contact with a pad.

FIG. 5 is a view showing another example of the structure of the probe needle according to the present invention.

FIG. 6 is a schematic diagram showing a basic configuration of a wafer probe.

FIG. 7 is a perspective view showing a schematic configuration of a probe card.

FIG. 8 is a diagram showing a schematic configuration of a conventional probe card.

FIG. 9 is a diagram (part 1) for describing a conventional problem.

FIG. 10 is a diagram (part 2) for describing a conventional problem.

[Explanation of symbols]

11 probe card, 12 board, 13 wiring, 14
... probe needle, 14a ... tip (needle tip), 14b ... forked part, P ... pad, T ... chip, W ... semiconductor wafer

Claims (2)

[Claims] 1. A probe card used for measuring electrical characteristics of a chip formed on a semiconductor wafer, comprising: a substrate serving as a base; and a lower surface side of the substrate corresponding to a pad arrangement of the chip. A plurality of probe needles, each of which is provided substantially vertically, and whose tip serves as a contact portion with the pad, is formed in a state where the rear end of the probe needle is expanded in a bifurcated manner; A probe card having both ends fixed to the substrate. 2. The method according to claim 1, wherein the substrate has a wiring for transmitting a measurement signal for measuring an electrical characteristic of the chip, and both ends of a bifurcated portion of the probe needle are soldered to an end of the wiring. The probe card according to claim 1, wherein: