JPH09101326A - Probe structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accomplish a highly reliable test in an electrical test of a microscopic object to be inspected such as IC, especially in a burn-in test by maintaining a low and stable contact resistance to minimize degrading from an initial contact state even against the repetition of opening or closing in contact with the object to be inspected. SOLUTION: A contact part 2 is formed on one surface side 1a of an insulating substrate 1 and a conductive circuit 3 on the other surface side 1b of the insulating substrate 1. The contact part 2 and a conducting circuit 3 are made to conduct through a conduction path 5 formed in a through hole 4 across the thickness of the insulating substrate 1. The contact part 2 has a structure of laminating a deep layer 2c with a hardness of 100-700Hk, a middle layer 2b with a hardness of 10-300Hk and a surface layer 2a with a hardness of 700-1200Hk sequentially. The tensile stress of the surface layer 2a is below 50kg/mm<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a probe structure useful for measuring various electrical characteristics of a fine object to be inspected, burn-in test performed at high temperature, and the like. Concerning what is. As such an object to be inspected, a wafer before dicing on which a semiconductor element is formed or a bare die after dicing, and
A so-called chip size package in which a substrate of substantially the same size is integrated with these elements, and a plate-shaped or hemispherical solder ball or a bump electrode made of gold or the like formed on these pads are exemplified. .

[0002]

2. Description of the Related Art Conventionally, I.
It was done after packaging C. For example, in a burn-in test, which is a characteristic test under high temperature, a method of inserting an IC package into an IC socket arranged on a printed wiring board and conducting a test while applying a load voltage at high temperature has been adopted.

In recent years, the development of large-scale integrated circuits such as chip-on-board, multi-chip modules, etc., in which a large number of integrated circuits are combined at the stage of forming them on a wafer, has been rapidly expanded. The inspection of various characteristics is required to be performed in a bare state before packaging, that is, in an IC chip (die level) or at a wafer level stage before dicing.

As one method for performing a test at a die level, a plate-shaped or hemispherical solder bump is formed on a pad of a circuit-formed IC chip, and this is arranged on a printed wiring board. One method is to solder to the joint and test at high temperature while applying load voltage.

A probe card has been developed in order to inspect the electrical characteristics of such a minute object to be inspected. This has a contact portion (so-called bump) that abuts a contact target portion of a device under test on the surface of a flexible insulating substrate (Japanese Patent Laid-Open No. 62-1826).
72, etc.).

In such a probe card, the bumps must have low contact resistance and excellent corrosion resistance and abrasion resistance. For this reason, the outermost layer of the conventional bump has gold with low contact resistance and excellent corrosion resistance,
Alternatively, hard gold with about 0.1% nickel and cobalt added to gold to improve wear resistance has been used.

[0007]

However, when gold or hard gold is used for the outermost layer of the bumps, they are easily deformed by contact with the electrode pad of the object to be inspected, so that there is poor conduction or a change in contact resistance. Etc.
The reliability as a probe was low for use in repeated inspections. Further, when a base metal is used as the underlayer of the outermost layer, there is a problem that the gold of the outermost layer is crushed and the base metal is exposed, and the base metal is oxidized or corroded from that portion.

Further, when the object to be inspected is an IC, the material of the electrode pad is mainly aluminum, but when there is a heat history as in a burn-in test, aluminum is transferred and adhered to the gold on the bump surface and diffused. Then, there is a problem that the contact resistance becomes high. In addition, copper contained in soft gold,
A base metal such as nickel has a problem that it diffuses to the surface at a high temperature and is oxidized to increase the contact resistance.

Further, as described above, in the test method in which the plate-shaped or hemispherical solder bumps are formed on the pads of the IC chip to be used, after the test is finished, the temperature of the solder bumps is increased by heating the solder bumps. Since the IC chip is melted and removed, the bumps formed on the pads of the IC chip vary in size, volume, shape, etc., and it is necessary to form solder bumps again. Further, since the solder remains on the joint portion on the printed wiring board after the IC is peeled off, there is a problem that cleaning must be performed every time an inspection is performed.

Such a problem is pointed out not only in a bare chip wafer but also in a chip size package in which an IC chip is integrated with a substrate having the same size as the chip.

The present invention solves the above-mentioned conventional problems, and provides a low and stable contact in an electrical test of a fine inspection object such as a wafer, an IC, a semiconductor element, and a chip size package, particularly a burn-in test. The purpose is to maintain resistance. Further, in a test method in which solder bumps are formed on an object to be inspected, the solder component of the object to be inspected after inspection does not adhere to the contact portion of the probe structure, in other words, the object to be inspected. The purpose is to prevent the volume of solder bumps from decreasing. Further, it is an object of the present invention to perform a highly reliable test with little deterioration from the initial contact state even when the contact with the object to be inspected is repeated.

[0012]

The above object can be achieved by the probe structure of the present invention shown below. (1) A conductive contact portion is formed on one surface side of the insulating substrate, a conductive circuit is formed on the other surface side of the insulating substrate, and the contact portion and the conductive circuit are formed on the insulating substrate. Conductivity is established via a conduction path formed in the through hole in the thickness direction, and the contact portion has a hardness of 100 to 700 Hk (100 Hk or more and 700 Hk or more.
Hk or less, the same applies hereinafter) and a hardness of 10 to 3
A probe structure having a structure in which a middle layer of 00Hk and a surface layer having a hardness of 700 to 1200Hk are sequentially stacked. However, Hk is a unit of Knoop hardness number (Knoop hardness). (2) The surface layer of the contact portion is a rhodium layer, the middle layer is a gold layer,
The probe structure according to (1) above, wherein the deep layer is a nickel layer, a copper layer, or a laminated structure of a nickel layer and a copper layer. (3) The thickness of the middle layer in the contact portion is 0.01 to 3 μm,
The probe structure according to (1) or (2) above, wherein the surface layer has a thickness of 0.5 to 10 μm. (4) The tensile stress of the surface layer at the contact point is 50 kg /
The probe structure according to any one of (1) to (3) above, which has a size of mm ² or less. (5) At least one of the surface layer, the middle layer, and the deep layer in the contact portion is formed by plating.
(4) The probe structure according to any one of the above.

[0013]

As described above, in the probe structure of the present invention, the conductive contact portion has the three layers of the deep layer, the middle layer and the surface layer, and the action of each layer and the action of the entire structure are as follows.

Like the known bump contact, the deep layer serves as a conduction path for electric signals and serves as a base of the contact or a core at the center to support the strength of the contact. The middle layer absorbs and relaxes the stress generated in the contact portion due to the contact pressure applied to the surface layer. Further, it is more preferable because it has a function of closely adhering the surface layer and the deep layer as a base of the surface layer. The surface layer is a layer that is resistant to wear and damage. By having the corrosion resistance and the property of suppressing the transfer / diffusion of other metal from the inspection object, the contact resistance can be maintained in a low state, which is more preferable.

Further, in the test method in which the solder bumps are formed and used, the solder bumps of the object to be inspected are transferred and transferred to the contact portions with the bumps of the probe by imparting the touch resistance to the surface layer. The diffusion is suppressed, and the volume of the solder bumps of the inspection object after the inspection is hard to decrease, which is preferable. In addition, the combined structure of these three layers compensates for the defects of the materials of the respective layers to form a contact portion that is less deteriorated by repeated contact opening and closing.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The probe structure of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a sectional view showing an example of a probe structure of the present invention. As shown in the figure, the probe structure has one surface side 1 a of the insulating substrate 1.
A contact portion 2 is formed on the other surface side 1 of the insulating substrate 1.
The conductive circuit 3 is formed on the contact point b and the conductive circuit 3
Are through holes 4 provided in the thickness direction of the insulating substrate 1.
The contact portion 2 has a structure in which it conducts through a conduction path 5 formed inside, and the contact portion 2 has a deep layer 2c, a middle layer 2b, and a surface layer 2 whose hardness and properties are as described below.
a. However, this figure is a diagram showing an example in which the contact portion 2 and the conduction path 5 are integrally formed of the same material.

The material for the insulating substrate 1 is not particularly limited as long as it has an insulating property, but a material having insulating property and flexibility is preferable, and a polyester resin, an epoxy resin, a urethane resin, or polystyrene is used. Resin,
Polyethylene resin, polyamide resin, polyimide resin, acrylonitrile-butadiene-styrene (AB
Examples thereof include thermosetting resins and thermoplastic resins such as S) copolymer resins, polycarbonate resins, silicone resins, and fluorine resins. Of these, a polyimide resin is particularly preferably used because it is excellent in heat resistance and mechanical strength, and can be matched with the linear expansion coefficient of the test object.

The thickness of the insulating substrate 1 is not particularly limited, but in order to have sufficient mechanical strength and flexibility, it is 2-500 μm, preferably 5-150 μm, more preferably 8-150 μm, Most preferably 10-1
It is preferable to set it to 50 μm.

The conductive circuit 3 includes, in addition to the circuit pattern formed of a conductor / semiconductor, elements constituting a circuit such as a contact portion, a coil, a resistor and a capacitor. The material of the conductive circuit 3 is not particularly limited as long as it has conductivity regardless of conductor or semiconductor, but a known good conductor metal is preferable. For example, gold, silver, copper, platinum, lead,
Examples include single metals such as tin, nickel, cobalt, indium, rhodium, chromium, tungsten, and ruthenium, and various alloys containing these single metals as components, such as solder, nickel-tin, and gold-cobalt. The thickness of the conductive circuit 3 is not particularly limited, but is preferably 1 μm or more from the viewpoint of reducing the resistance value as an electric path, and preferably 200 μm or less from the viewpoint of workability by chemical etching or the like.
Within these ranges, it is particularly preferable to set the thickness to 5 to 50 μm.

As the method of forming the conductive circuit 3, a method of directly drawing and forming a target circuit pattern on the insulating substrate 1 (additive method) and a method of removing other conductor portions so as to leave the target circuit pattern. And a method of forming (subtractive method). Examples of the former method include drawing a circuit pattern using a film forming method such as sputtering, various vapor depositions, and various platings. As the latter method, a conductor layer is formed on the insulating substrate 1, a resist layer is formed on the conductor layer so as to cover only the desired circuit pattern shape, and then the exposed conductor layer is removed. There is a method of obtaining a desired circuit pattern by etching.

The through-holes 4 serve as conduction paths 5 between the contact portions 2 and the conductive circuits 3, and the diameters of the through-holes are made as large as possible and the pitch between the holes is made as small as possible within a range in which adjacent through-holes are not connected to each other. Therefore, it is preferable to increase the number of the through holes per unit area in order to reduce the electric resistance of the conductive path 5. The diameter of the through hole 4 is 5 to 200 μm, preferably about 8 to 50 μm. Examples of the method of forming the through holes 4 include mechanical punching methods such as punching, plasma processing, laser processing, photolithography processing, and chemical etching using a resist having a different chemical resistance from the insulating substrate 1. Further, the laser processing is a method capable of finely processing the through-holes 4 with an arbitrary hole diameter and a pitch between holes, and can cope with a fine pitch of the contact portions 2. Among them, drilling by irradiation with an excimer laser, a carbon dioxide gas laser, or a YAG laser whose pulse number or energy amount is controlled is preferable because of high accuracy.

The through hole 4 is formed not only perpendicularly to the surface of the insulating substrate 1 but also as shown in FIG.
Since the insulating substrate 1 is formed so as to form a predetermined angle with respect to the surface of the insulating substrate 1, the pressure applied to the object to be inspected is decomposed, and damage to the conductor portion of the object to be inspected can be prevented.

The conductive path 5 may be formed in the through hole 4 so as to connect the contact portion 2 and the conductive circuit 3 to each other,
Examples thereof include those obtained by filling the through hole 4 with a conductive substance, those obtained by forming a layer of a conductive substance on the entire circumference of the wall surface of the through hole 4 such as through hole plating, and the like. Examples of the method of forming the conductive path 5 include a method of mechanically fitting a conductive substance into the through hole 4, a film forming method such as a CVD method, a plating method such as electrolytic plating or electroless plating, and the like. A method by electrolytic plating using the circuit 3 as an electrode is simple and preferable.

The contact portion 2 makes electrical contact with the object to be inspected.
A conductor portion provided on the surface of the insulating substrate 1 for the purpose of connection. The aspect of the contact portion 2 as a whole is that of the insulating substrate 1.
Regardless of the presence or absence of protrusion from the surface, the shape of the contact surface on the upper surface of the contact portion 2 may be convex, planar, or concave depending on the projection state of the contacting partner. Therefore, the cross-sectional shape of the contact portion 2 when cut along a plane perpendicular or parallel to the surface of the substrate 1 is not limited, and all polygons, circles, ellipses, a part of these shapes, or a composite shape, etc. And the combination of these cross-sectional shapes,
The contact portion 2 can have any three-dimensional shape such as an end or a side surface of a polygonal column / cylinder, a cone (stand) / pyramid (stand), or a part of a sphere. As a result, the contact with the object to be inspected is point contact, line contact, surface contact, or the like.

The height of the contact portion 2 from the surface of the insulating substrate 1 is not particularly limited, but it may be about 0.1 μm to several hundreds μm for a fine inspection object such as an IC. preferable. Regarding the number of contacts per pad under test, 1
Alternatively, two or more can be provided and is not particularly limited.

The contact portion 2 includes a deep layer 2c, an intermediate layer 2b, and a surface layer 2a.
It has three layers. Further, the deep layer 2c and the conduction path 5 may be integrally formed of the same material. Deep 2c
The hardness is set to 100 to 700 Hk. Hardness 100
If the hardness is less than Hk, the contact portion 2 comes into contact with the contact object, and the contact portion 2 is likely to be deformed when pressure is applied, and if the hardness exceeds 700 Hk, cracks are likely to occur. Further, as the hardness increases, the electrical resistance increases and the electrical reliability decreases, so it is desirable to reduce the hardness as much as possible. A more preferable range of hardness of the deep layer 2c is 15
It is 0 to 600 Hk, and practically 150 to 250 Hk.

As a material which can obtain such hardness,
Although not particularly limited, an inexpensive good conductor metal used for known bumps is preferable, and copper, nickel, nickel-palladium alloy, etc. are exemplified.

In many cases, the deep layer 2c and the conductive path 5 are integrally formed of the same material and connected to the conductive circuit 3. In such a case, the material forming the deep layer 2c is preferably crystallographically consistent with the material forming the conductive circuit 3, has good adhesion, and is difficult to diffuse. For example, when the material of the conductive circuit 3 is copper,
On the other hand, the material of the deep layer 2c is preferably a combination of copper, nickel and nickel alloy. It is preferable to adjust the hardness by alloying or adding an organic substance from the viewpoint that the insulating substrate 1 is not damaged by heat.

The hardness of the middle layer 2b is set to 10 to 300 Hk. If the hardness is less than 10 Hk, it easily deforms, and 300 Hk
If it exceeds, the cushioning property will be poor. The preferable range of the hardness of the middle layer 2b is 50 to 200 Hk, particularly 50 to 150 Hk.
Hk, and further 50 to 100 Hk. Examples of materials having such hardness include gold, palladium,
Examples thereof include silver, indium and platinum. Also, deep layer 2
c, a metal having excellent adhesiveness with the surface layer 2a and having corrosion resistance even when exposed to the surface is more preferable. Particularly, when the deep layer is nickel and the surface layer 2a is rhodium, gold is most preferable for the intermediate layer 2b. Becomes

The thickness of the intermediate layer 2b is 0.01 to 3 μm, preferably 0.1 to 1 μm. If it is less than 0.01 μm, the cushioning effect is weak, and if it exceeds 3 μm, the amount of deformation when pressure is applied is large, so that the metal of the surface layer 2a is easily cracked.

The hardness of the surface layer 2a is 700 to 1200 Hk.
Set to. If the hardness is less than 700 Hk, the surface layer 2a is likely to be damaged when coming into contact with the conductor of the inspection object.
If it exceeds Hk, cracks are likely to occur. The preferable range of the hardness of the surface layer 2a is 800 to 1100 Hk,
Particularly preferably, it is 900 to 1000 Hk. The material that can obtain such hardness is not particularly limited, but examples thereof include hard metals such as rhodium, ruthenium, cobalt-tungsten alloy, chromium, iron-tungsten alloy, and chromium-molybdenum alloy. In particular, a material having corrosion resistance and a property as a barrier for preventing diffusion of a metal transferred from a contact object is more preferable, and a noble metal such as rhodium or ruthenium is exemplified.

When the above-mentioned noble metal is used for the surface layer 2a, the noble metal may be a single metal or an alloy, but the contact resistance increases due to the diffusion and oxidation of the base metal on the surface,
In order to suppress the increase of internal stress due to organic impurities and the generation of cracks, it is preferable that 99% or more is in the platinum group. In the case of an alloy, a combination of a noble metal having corrosion resistance and hard to diffuse is preferable, and a combination of rhodium and ruthenium is exemplified.

Aluminum of the pad portion of the inspection object, Sn
Even when rhodium or the like, which is difficult to diffuse, is used as a material for the surface layer 2a with respect to a metal such as Pb solder, it may be physically transferred when an electric resistance test such as a burn-in test is performed.
This is remarkable when the IC of the object to be inspected is replaced for each inspection and the test is repeated.

Since the transferred aluminum or solder forms an oxide film and has a high contact resistance, it is inferior in electrical reliability.
In order to stabilize the repeated electric resistance test, it is preferable that the aluminum or solder transferred to the contact portion 2 be selectively removed by etching after the end of one test. As the removal method, there are dry etching such as argon plasma, and wet etching in which the base metal is treated electrically and chemically with an etching solution that does not corrode the base metal. To prevent the base metal from being immersed, use an alkaline etching solution. preferable. A specific example of wet etching is shown below.

Example 1 Wet Etching on Aluminum Pad <Dip Type> Anhydrous Sodium Carbonate 23 g / L Sodium Phosphate 23 g / L Surfactant 2 g / L 70-80 ° C. <Electrolytic Type> Sodium Hydroxide 25 g / L Anhydrous Sodium Carbonate 25 g / L sodium gluconate 10 g / L EDTA 5 g / L 38 to 50 ° C., current density: 8 to 10 A / dm ^2.

Example 2 Wet etching of SnPb solder pad <immersion type> 30% hydrogen peroxide 40 ml / L hydrofluoric acid (HBF ₄ , tetrafluoroboric acid)
150 ml / L room temperature <electrolysis type> sodium hydroxide 65 g / L sodium gluconate 15 g / L 50-60 ° C., voltage: 2-4 v

The thickness of the surface layer 2a is 0.5 to 10 μm, preferably 1 to 5 μm, particularly preferably 2 to 3 μm.
If the thickness of the surface layer 2a is less than 0.5 μm, pinholes are likely to occur, and if it exceeds 10 μm, cracks are likely to occur.

A method of forming the contact portion 2, that is, each layer 2a, 2
The laminating method of b and 2c is, for example, a pressure welding method in which metal foils of the constituent metals of the respective layers 2a to 2c are brought into pressure contact with each other, a film forming method such as ion plating, ion sputtering, a CVD method, or plating such as electrolytic plating or electroless plating Law etc. are mentioned. Among these forming methods, the method of electroplating using the conductive path 5 as an electrode is particularly preferable because the metal purity, hardness, and external dimension can be controlled in terms of quality, and variation can be controlled to be small, which is preferable.

When the contact portion 2 is formed by a plating method, it is preferable to perform a wettability improving treatment such as methanol replacement or surface modification by plasma in order to surely fill the through hole 4 with the plating liquid. Further, when forming the metal of the core, by supplying a current linearly according to the surface area to be plated and maintaining a constant current density, the internal stress of the core can be made uniform and cracks can be prevented. . In particular, when the material of the surface layer 2a is the above-mentioned platinum group and is formed by plating, by swinging the object to be plated in the plating solution left and right, the flow direction and flow velocity of the plating solution with respect to the object to be plated become uniform. , The deposition efficiency of the surface layer 2a in each contact part 2 becomes uniform, and as a result, the surface layer 2a
The thickness of a becomes uniform. Further, in the case of forming by a plating method, particularly in rhodium plating, the tensile stress of the surface layer 2a is controlled to 50 k by controlling the composition of the plating solution and the operating conditions.
It is preferable to keep g / mm ² or less. 50 kg / mm
^When it exceeds ² , the plating film is apt to crack, which is not preferable.

It is preferable to keep the organic impurities in the composition of the plating solution at 50 mg / L or less by extraction with chloroform because the tensile stress can be kept at 50 kg / mm ² or less and cracks can be suppressed. However, 50 mg / L
Even if it exceeds the limit, it can be regenerated by removing the organic matter by treatment with activated carbon.

Depending on other inspected objects, a plurality of minute bumps 2 may be formed on the deep layer 2c, as schematically shown in FIG.
An example having d is given as an example of a preferable shape of the contact portion 2. Deep layer 2c on which the minute bumps 2d are formed
By sequentially forming the intermediate layer 2b and the surface layer 2a on the upper surface and making the surface of the contact portion 2 uneven, an oxide layer, a foreign substance, or the like formed on the conductor surface of the DUT during contact of the contact portion 2 The insulation layer is destroyed and contact reliability is improved.

As an example of the method of forming the minute bumps 2d, after forming the deep layer 2c, the metal powder 2e which becomes the nucleus of the minute bumps 2d is dispersed in a plating bath and electrolytic plating is performed. The particle diameter of the metal powder 2e is preferably 1/200 to 1/10 of the diameter of the deep layer 2c. Further, by using a magnetic metal powder 2e such as cobalt and applying a magnetic field of about 1 to 15 kilogauss in a plating bath to perform electrolytic plating, the metal powder 2e can be uniformly applied to the surface of the deep layer 2c.

There is also a method in which after forming the deep layer 2c, the crystal state is controlled by the plating condition to form the protrusion on the contact portion 2. This operation may be performed on any of the deep layer 2c, the intermediate layer 2b, and the surface layer 2a, but as shown in FIG. 4, if it is performed on the surface layer 2a, the projection 2 having a sharper tip.
f can be formed. The sharp protrusions can be formed by plating near the limit current density by operations such as increasing the current density, decreasing the metal concentration, and weakening the stirring. In addition, in order to adjust the crystal grain size, an operation of increasing or decreasing the addition amount of an organic or inorganic additive, a method of using a pulse or reversal current for current supply, and the like are adopted.

The shape of the fine protrusions on the surface layer 2a is not particularly limited, but when an oxide film having a thickness of about 100Å is formed on the aluminum layer of the pad portion of the inspection object, the tip is sharp. It is better to have The cross-sectional shape of the protrusion has a maximum value dimension of 0.1 to 2.0 μm at the bottom,
Triangles with a height of 0.1 to 0.8 μm are preferred. Base 0.
If it is less than 1 μm, the supporting strength will be weak, and the base is 2.0 μm.
If it is larger than m, the tip of the projection becomes an obtuse angle and it is difficult to break through the oxide film. If the height is smaller than 0.1 μm, the oxide film cannot be sufficiently removed to reach the metal layer under the oxide film, and the contact resistance becomes large. If the height is larger than 0.8 μm, the metal layer such as aluminum is pierced and the inspection is performed. Connection failure may occur during mounting of the device under test later, or electrical reliability after connection may deteriorate.

In addition to the method of forming protrusions by plating and stacking, a method of polishing a metal layer once formed by wet or dry etching, a method of pressing using a mold having fine irregularities, and a nozzle of the same mold are used. There is also a method of mechanically deforming the metal by applying pressure spotwise with a bonder or the like. This mechanical deformation is not preferable because it causes cracks when it is performed on the surface layer 2a. Therefore, it is preferable that the mechanical deformation is performed on the middle layer 2b or on the deep layer 2c having a relatively low hardness because molding is easy and cracks do not occur.

Although the probe structure of the present invention alone has a function as a probe, as shown below, a highly functional probe card is constructed by joining with a multilayer wiring board. FIG. 5 is a diagram schematically showing an example of the structure of the probe card. As shown in the figure, the probe card is formed by mechanically and electrically joining the probe structure A of the present invention and the multilayer wiring board B. The probe structure A is formed on the multilayer wiring board B. To the multilayer wiring board B via an elastic body 6 so that a stroke operation can be performed.
The conductive circuit 3 of the probe structure A and the conductive circuit 7 of the multilayer wiring board B are joined so as not to interfere with the stroke operation.

In the figure, the conductive circuit 3 and the conductive circuit 7 are connected such that the conductive circuit 3 is extended and protrudes from the end of the insulating substrate 1 and is gently bent to the surface of the multilayer wiring board B. , And is joined to the terminal 8 provided on the surface of the multilayer wiring board B. The terminal 8 has a probe structure A
With the structure similar to that of the conductive path, the conductive circuit 7 provided in the lower layer of the multilayer wiring board B is electrically connected and connected to an external connecting device or the like.

The multilayer wiring board B includes a conductive circuit 7 and an insulating layer 9.
Are alternately laminated, and circuits in different layers are connected by a structure similar to the conducting path of the probe structure of the present invention. The multilayer wiring board B can be manufactured by applying the technology of a multi-chip module (MCM) substrate, and the types thereof mainly include three types of MCM-D, C, and L.

By inserting a resistor (not shown) in series in the conductive circuit 7 of the multilayer wiring board B, a load voltage can be applied to the object to be inspected and an overcurrent due to a short circuit of the circuit of the object to be inspected. Can be prevented. Further, noise can be reduced by connecting a capacitor (not shown) in parallel with the resistor.

The elastic body 6 may be any one as long as it can absorb an error in the distance between the probe structure and the object to be inspected when the probe structure is brought into contact with the object to be inspected. Silicone rubber, fluororubber, Polymer elastic bodies such as urethane rubber are preferably used.

Examples of the method of forming the elastic body 6 on the multilayer wiring board B include a method of cutting and sticking the sheet-like elastic body 6, a method of directly forming by a screen printing method, a photolithography method, or the like.

The thickness of the elastic body 6 is equal to that of the conductor portion of the inspection object when absorbing a fine conductor portion such as an IC pad by absorbing the variation in the height of the terminal of the inspection object. In order to make the electrical connection with the contact portion 2 of the probe structure more reliable, 5-1000 μm, preferably 20-50
0 μm is preferable.

The external connection equipment is not limited to an independent inspection device such as a tester, but is connected to, for example, a device used for impedance matching between an object to be inspected and circuit wiring, or a product in a subsequent process. Other I like
It may be C.

By integrating the probe structure of the present invention with the rigid substrate, the flexible structure becomes solid and easier to handle. 6 and 7 are cross-sectional views showing an example of a probe structure in which a rigid substrate is integrated. The probe structure shown in FIG. 6 is basically the same as that shown in FIG.
Is similar to the probe structure shown in FIG.
The rigid substrate 10 is formed on the outer peripheral portion of the contact portion 2 side. Further, in the probe structure shown in FIG. 7, the conductive circuit 3 is covered with the insulating layer 11 made of polyimide or the like, and the insulating layer 11 excluding the area in the vicinity of the contact portion 2 is removed.
The rigid substrate 10 is formed on the top. As described above, the rigid substrate 10 may be any one as long as it can be integrally formed on the outer peripheral edge portion of the flexible probe structure, and may have any outer shape in actual use.

Examples of the material of the rigid substrate 10 include a glass epoxy substrate, a resin substrate such as BT resin, ceramics such as alumina and silicon nitride, and an inorganic substrate containing alloys such as 42 alloy. In particular, the latter inorganic substrate is preferably used for the purpose of suppressing the linear expansion coefficient to be low. For example, the inorganic substrate is attached to the entire surface of the insulating layer 11 of the probe structure, or, as shown in FIG. 7, in a region excluding only the vicinity of the contact portion 2, or the outer peripheral edge of the probe structure. Only the rigid board 1
0 is integrated, and in the integrated state, shrinkage stress is intentionally generated in the probe structure by heating or the like. In such a probe structure, it is possible to set such that tension in the substrate expansion direction (outward direction) is always generated in the temperature range in the burn-in cycle process, and the apparent linear expansion coefficient can be reduced.

In the case of the probe structure shown in FIG. 7, the rigid substrate 10 may be formed by adhering the rigid substrate 10 to the entire surface of the insulating layer 11 and then removing the portion near the contact portion 2 by etching or the like. By forming the opening in the vicinity of the contact portion 2 of the substrate in this manner, an appropriate cushioning property is exhibited at the time of pressurization, and the contact reliability is improved.

The coefficient of linear expansion of the rigid substrate 10 is
Depending on the purpose, it may be set to a value equal to or different from the linear expansion coefficient of the inspection object. Further, by using a rigid substrate 10 having a linear expansion coefficient of 1 to 8 ppm and integrating it with the probe structure, the obtained probe structure can have a low linear expansion. According to such a probe structure, problems such as alignment failure and electrode damage due to a mismatch in linear expansion coefficient between the probe structure and a bare die or wafer as an object to be inspected can be avoided, and reliability is significantly improved.

[0058]

EXAMPLES Hereinafter, more specific examples of the probe structure of the present invention will be shown. Example 1 <Formation of Insulating Substrate and Conductive Circuit> A polyimide precursor solution having a thickness of 25 μm was dried on a copper foil having a thickness of 35 μm.
Was coated, dried and cured to prepare a two-layer film of a copper foil and a polyimide film as an insulating substrate. Next, after forming a resist layer in a circuit pattern shape on the surface of the copper foil, a photolithography process was used to form a conductive circuit having a desired circuit pattern. On this circuit pattern side, the thickness after drying the polyimide precursor solution is further 10
A cover coat was formed by coating, drying and curing so as to have a thickness of μm.

<Formation of Conduction Path and Deep Layer> Dry etching is performed by irradiating a position directly behind the conductive circuit of the above polyimide film with a KrF excimer laser beam having an oscillation wavelength of 248 nm through a mask in a direction perpendicular to the polyimide film surface. A φ60 μm fine through hole was formed in the polyimide film, and the conductive circuit was exposed in the through hole.

<Protection of resist on the conductive circuit side> A vinyl chloride-based resist is printed on 75 mesh and coated to form 170
It was dried at ℃ for 20 minutes.

<Pretreatment in Through Hole> In order to impart wettability, the through hole was irradiated with ultraviolet rays for 10 minutes. The following desmear treatment was performed in order to remove the polyimide decomposition products by the excimer laser [permanganate oxidizer,
Immersion at 75 ° C for 3 minutes, sulfuric acid reducing agent, 50 ° C for 1 minute, immersion]. In addition, a sodium persulfate-based soft etching solution is added to 25
The decomposition product on the copper in the through hole was removed by ultrasonic wave 40 kHz treatment at ℃ for 1 minute.

<Deep Layer Formation> Watt bath system nickel plating (composition: nickel sulfate 300 g / L, nickel chloride 65
g / L, boric acid 45 g / L) while changing the actual current according to the growing plating area, 60 ° C., 5 A /
It was treated with dm ² for 39 minutes to project 13 μm from the surface of the polyimide film (open end of the through hole) to form a deep layer. In addition, intermittent air agitation (stop for 5 minutes, drive for 20 seconds) was performed in the plating growth step. The hardness of the deep layer was 250 Hk.

<Formation of Middle Layer> Using cyan gold plating, the actual current was kept constant, and 67 ° C., 0.6 A / dm ² , 9
It was treated for 0 seconds, and a 0.5 μm middle layer was laminated on the deep layer. The vertical jet flow in the plating bath was 40 L / min, and the object to be plated was shaken at 3 m / min. The hardness of the middle layer is 100
It was Hk.

<Formation of surface layer> Sulfuric acid-based rhodium plating is used
And the actual current is constant, 50 ° C, 1.9 A / dm ^Two,
After the treatment for 6 minutes, a 2 μm surface layer was laminated on the middle layer. What
The liquid circulation in the plating bath is 2 L / min,
The swing was 1 m / min. The hardness of the surface layer is 850 Hk
Was. Also, the tensile stress in the surface spiral stress meter is
46 kg / mm^TwoMet.

<Removal of Resist on Conductive Circuit Side> The resist layer applied on the surface side of the conductive circuit was removed to obtain a probe whose contact portion was a mushroom type bump.

<Electrical Resistance Test> In order to investigate the contact resistance value of the obtained probe, an electric resistance test was conducted by passing a measurement current of 1 mA with a tester having an electric circuit. FIG.
Is a conceptual diagram of the measurement, in which the contact portion 2 of the probe structure 12 having a height of 15 ± 2 μm from the surface of the polyimide film 1 is brought into contact with the aluminum electrode of the IC 13 shown in FIG. The contact resistance between them was investigated. More specifically, as shown in the contact conceptual diagram of FIG. 10, the probe structure 12 is disposed in the carrier 14, and I
C13 is pressed through the pressing plate 15, and in order to make the contact between each contact part 2 and each electrode of the IC 13 uniform, the compliance material 15 is arranged on the pressing direction side of the contact part 2. There is.

The result of the contact resistance value due to the change of the load is as shown in the graph of FIG. 11, and although there was variation, it was 2000 mΩ or less in all cases. Furthermore, the load is 37 g / bump, 25 ° C for 30 minutes, -150 ° C,
As a result of performing the heat cycle test for 20 minutes 102 times, as shown in the graph in FIG. 12, the resistance value is 2000 mΩ.
A bump (contact point) that exceeds the limit was generated. However, after the heat cycle test, the surface rhodium did not show any scratches, cracks, or corrosion, nor did the aluminum of the IC be transferred or attached by diffusion. In addition, in FIG. 11, “c
h. "Indicates a specific bump for which the measurement was performed (the same applies hereinafter).

Comparative Example 1 In Example 1, the formation of the surface rhodium was omitted, and the same operation as the formation of the intermediate layer was performed for 6 minutes after the formation of the deep layer to obtain a gold probe in which a 2 μm gold layer was laminated on the nickel deep layer. . The hardness of the gold layer on the surface was 100 Hk. Example 1
Contact the aluminum electrode of the IC in the same way as
An electric resistance test was conducted by passing a measuring current of 100 mA with a tester. The test conditions are load 37 g / bump, 15
The measurement was performed for 1002 hours in an atmosphere of 0 ° C.

As a result, as shown in the graph of FIG. 13, the gold probe has a contact resistance value higher than that of the rhodium probe of Example 1 by about 150 mΩ, and aluminum transfer was observed on the surface of the gold probe. Was given.

Copper layer (35 μm) / Polyimide layer (25 μm
m) solder on the copper surface of the two-layer base material (Sn: Pb
= 6: 4) Each contact portion of the rhodium probe and the gold probe was brought into contact with the plated surface of 15 μm, and a measurement current of 100 mA was applied by a tester to conduct an electric resistance test. Initial probe load of 37g for both probes
/ Bump gave a resistance value of 1Ω. Furthermore, 25 ℃, 30
When a heat cycle test was performed at -150 ° C for 20 minutes, the solder was transferred to the surface for the second time with the gold probe, but with the rhodium probe, the solder did not transfer even after 50 times, and the resistance value was 1Ω. It was stable.

Examples 2 and 3 The deep layer formation of Example 1 was replaced with the copper plating step and composition shown in Table 1 below to form mushroom bumps of a deep layer, and further Table 2 (Example 2) or Table 3 ( Copper plating was performed under the operating conditions of Example 3) to provide an uneven layer between the deep layer and the middle layer.

[0072]

[Table 1]

[0073]

[Table 2]

[0074]

[Table 3]

After substituting the deep layers of Example 1 with the steps and compositions shown in Tables 1 and 2, to form uneven deep layers, 0.5 μm of gold as an intermediate layer and 2 μm of rhodium as a surface layer were laminated in the same manner as in Example 1. Thus, a high current density uneven probe having spherical particles with a diameter of about 2 μm formed on the surface was obtained (Example 2). Further, the deep chloride formation in Example 1 was replaced with the steps and compositions in Tables 1 and 3, and a high chloride ion uneven probe having spherical particles with a diameter of about 0.5 μm formed on the surface was obtained by the same operation (implementation). Example 3).

The hardness of each layer in the high current density uneven probe of Example 2 was 190 Hk for the deep layer and 100 H for the middle layer.
k, the surface layer was 850 Hk, and the tensile stress of the surface layer measured by a spiral stress meter was 46 kg / mm ² . The hardness of each layer in the high chloride ion unevenness probe of Example 3 was 190 Hk for the deep layer and 10 for the intermediate layer, as in Example 2.
0 Hk, the surface layer was 850 Hk, and the tensile stress of the surface layer measured by a spiral stress meter was 46 kg / mm ² .
Using the above-mentioned two types of unevenness probe, the contact point of each unevenness probe was brought into contact with the aluminum electrode of the IC in the same manner as in Example 1, and a measurement current of 1 mA was applied by a tester to conduct an electrical resistance test.

The relationship between the load and the contact resistance value is shown in FIGS.
Shown in FIG. 14 shows the case where a high current density unevenness probe is used, and although there was variation at a load of 10 g / bump, 200 mΩ or less, and a minimum of 36 mΩ were obtained. FIG.
5 is the case of using a high chloride ion uneven probe,
It became 200 mΩ or more and 1600 mΩ or less at a load of 20 g / bump, and a resistance value slightly lower than that of the probe structure of Example 1 was obtained.

Example 4 In the same manner as in Example 2 or Example 3, after forming a deep layer of copper by the process of Table 1, a polyimide film having an uneven surface was brought into contact with a copper bump and pressed by a press. . As a result, the copper bump was deformed into a cylindrical shape, and at the same time, nine conical protrusions having a diameter of 10 μm and a height of 5 μm were formed on the surface of the copper bump. After performing the activation treatment by soft etching, in the same manner as in Example 1, 0.5 μm of gold in the middle layer and 2 μm of rhodium in the surface layer were laminated,
A press uneven probe was obtained.

The hardness of each layer in the press uneven probe was 190 Hk for the deep layer (copper layer), 100 Hk for the middle layer, and 850 Hk for the surface layer, and the tensile stress of the surface layer with a spiral stress meter was 46 kg / mm ² .

In the same manner as in Example 1, the contact portion (bump) of the pressed uneven probe was brought into contact with the aluminum electrode of the IC, and a measurement current of 1 mA was applied by a tester to conduct an electrical resistance test.

FIG. 16 shows the relationship between the load and the contact resistance value. With a load of 22.9 g / bump, a contact resistance value of 200 mΩ or less was stably obtained.

Example 5 In the deep layer forming step of Example 1, the nickel plating time was extended to 64 minutes, and in the surface layer forming step, the current density was changed from 1.9 A / dm ² to 3 A / dm ² to obtain polyimide. The height of the contact point from the film surface is 40 ± 5μ
m, and a probe composed of a 0.5 μm thick middle layer of gold and a 2 μm thick surface layer of rhodium having fine irregularities was obtained.

The hardness of each layer in this probe is 250 Hk in the deep layer, 100 Hk in the middle layer, and 850 Hk in the surface layer, and the tensile stress of the surface layer by the spiral stress meter is 4
It was 0 kg / mm ² .

In the same manner as in Example 1, the contact point (bump) of the probe was brought into contact with the aluminum electrode of the IC, and a measurement current of 1 mA was passed by a tester to conduct an electrical resistance test.

FIG. 17 shows the relationship between the load and the contact resistance value. Contact resistance values of 200 to 400 mΩ at a load of 11.4 g / bump and 100 to 200 mΩ at a load of 28.6 g / bump were obtained. After the test, there was no crack on the surface layer of rhodium, and there was no problem of breaking through the aluminum electrode. Also, although the fine irregularities on the surface are irregular,
When the vertical cross section of the unevenness was measured with a laser microscope, the height was 0.2 to 0.4 μm, and the upper tip of the base was 0.8 to 1.6 μm was a rounded triangular shape.

Example 6 In the same manner as in Example 5 except that the surface rhodium was formed at a current density of 1.9 A / dm ² for 6 minutes, the height of the contact portion from the polyimide film surface was 40 ± 5 μm, A probe composed of a deep nickel layer, a 0.5 μm gold middle layer, and a 2 μm rhodium surface layer was obtained.

The hardness of each layer in this probe is 250 Hk in the deep layer, 100 Hk in the middle layer, and 850 Hk in the surface layer, and the tensile stress of the surface layer by the spiral stress meter is 4
It was 6 kg / mm ² .

In the same manner as in Example 1, the contact points (bumps) of both probes were brought into contact with the aluminum electrodes of the IC, and a measurement current of 1 mA was applied by a tester to conduct an electrical resistance test.

As a result, the surface layer had no cracks and had a dull appearance with fine irregularities, but the bumps were smaller than the bumps of Example 5, and were irregular in shape. When a vertical cross section of unevenness was measured using a laser microscope, the height was 0.
The tip of the upper part having a diameter of 1 to 0.2 μm and a base of 0.4 to 0.6 μm was a rounded triangular shape.

FIG. 18 shows the relationship between the load and the contact resistance value. When the load is 11.4 g / bump, it is 500 to 4000 m.
It became a high resistance value of Ω.

The object to be inspected for contact / connection by the probe structure of the present invention is a semiconductor element, an assembly of semiconductor elements (a silicon wafer before dicing, a silicon chip after dicing, etc.), a device comprising a semiconductor element, A circuit board on which the device is mounted, a circuit board for an LCD, or the like having fine conductor portions, and solder (an alloy containing tin, lead, and a bimetal as a main component) or gold is attached to these conductor portions. Etc. have bumps.

The conductor portion of the object to be inspected means all the conductors that make up the circuit of the object to be inspected, such as various elements, their electrode portions, arbitrary locations on the circuit pattern, etc. The terminals, pads, lands, and the like, which the device under test has for the purpose of electrically contacting and connecting to other conductors, are important parts to be contacted.

[0093]

EFFECT OF THE INVENTION The probe structure of the present invention is characterized by a hard metal, particularly a hard noble metal, used for the surface layer of the contact portion.
It is possible to prevent the base metal such as aluminum used for the conductor portion of the object to be inspected from transferring and diffusing to the contact portion, resistant to corrosion, and maintaining low contact resistance. In addition, by using a hard and corrosion-resistant noble metal for the contact layer, it is possible to prevent the solder from being transferred to the contact portion and diffusing in the case of the solder bump of the DUT, maintaining a low resistance value. it can.

Further, the soft metal used for the intermediate layer serving as the surface underlayer adhesion layer alleviates the stress generated by the contact with the object to be inspected and suppresses the occurrence of damage such as cracks. Therefore, even if an electrical test is performed on a fine test object such as an IC or a semiconductor element, particularly repeated contact opening / closing with the test object in a burn-in test, deterioration from the initial contact state is small and high reliability is achieved. A stable electrical test can be done.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a probe structure of the present invention.

FIG. 2 is a cross-sectional view schematically showing an example of a mode of through holes in the probe structure of the present invention.

FIG. 3 is a cross-sectional view schematically showing an example of a mode of a contact portion in the probe structure of the present invention.

FIG. 4 is a sectional view schematically showing an example of a probe structure having sharp protrusions on the surface layer.

FIG. 5 is a diagram schematically showing an example of the structure of a probe card constituted by the probe structure of the present invention and a multilayer wiring board.

FIG. 6 is a cross-sectional view schematically showing a first example of a probe structure in which a rigid substrate is integrated.

FIG. 7 is a sectional view schematically showing a second example of a probe structure in which a rigid substrate is integrated.

FIG. 8 is a measurement conceptual diagram of an electric resistance test for examining a contact resistance value of a probe.

FIG. 9 is an enlarged sectional view schematically showing an example of an IC.

FIG. 10 is a conceptual diagram of contact between a bump and an IC in a carrier.

11 is a graph showing measurement results of load-contact resistance value in Example 1. FIG.

FIG. 12 is a graph showing the results of the heat cycle test of Example 1.

FIG. 13: Rhodium probe of Example 1 and Comparative Example 1
3 is a graph showing the contact resistance value of the gold probe of FIG.

14 is a graph showing the measurement results of load-contact resistance value in Example 2. FIG.

FIG. 15 is a graph showing measurement results of load-contact resistance value in Example 3.

16 is a graph showing measurement results of load-contact resistance value in Example 4. FIG.

FIG. 17 is a graph showing the measurement results of load-contact resistance value in Example 5.

FIG. 18 is a graph showing the measurement results of load-contact resistance value in Example 6;

[Explanation of symbols]

 1 Insulating Substrate 2 Contact Section 2a Surface Layer 2b Middle Layer 2c Deep Layer 3 Conductive Circuit 4 Through Hole 5 Conductive Path

Claims (6)

[Claims] 1. A conductive contact portion is formed on one surface side of an insulating substrate, a conductive circuit is formed on the other surface side of the insulating substrate, and the contact portion and the conductive circuit are insulated. Conduction is performed through a conduction path formed in the through hole in the thickness direction of the substrate,
The contact portion has a deep layer having a hardness of 100 Hk or more and less than 300 Hk, an intermediate layer having a hardness of 10 Hk or more and 300 Hk or less, and a hardness of 7
A probe structure having a structure in which a surface layer of 00 Hk or more and 1200 Hk or less is sequentially stacked. 2. The tensile stress of the surface layer at the contact portion is 5
The probe structure according to claim 1, which has a pressure of 0 kg / mm ² or less. 3. An electrically conductive contact portion is formed on one surface side of the insulating substrate, a conductive circuit is formed on the other surface side of the insulating substrate, and the contact portion and the conductive circuit are made of an insulating material. Conduction is performed through a conduction path formed in the through hole in the thickness direction of the substrate,
The contact portion has a deep layer having a hardness of 100 Hk or more and 700 Hk or less, an intermediate layer having a hardness of 10 Hk or more and 300 Hk or less, and a hardness of 7
A probe structure having a structure in which a surface layer of 00 Hk or more and 1200 Hk or less is sequentially laminated, and a tensile stress of the surface layer is 50 kg / mm ² or less. 4. The probe structure according to claim 1, wherein the surface layer of the contact portion is a rhodium layer, the middle layer is a gold layer, and the deep layer is a nickel layer or a copper layer or a laminated structure of a nickel layer and a copper layer. 5. The thickness of the intermediate layer at the contact portion is 0.01 μm.
m or more and 3 μm or less, and the thickness of the surface layer is 0.5 μm or more and 10 μm
The probe structure according to any one of claims 1 to 4, which is m or less. 6. The probe structure according to claim 1, wherein at least one of the surface layer, the intermediate layer and the deep layer in the contact portion is formed by plating.