JP3838768B2 - Electrolytic plating method and probe pin manufacturing method using it - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrolytic plating method used in various industrial fields, and in particular, a probe pin for semiconductor measurement, or a probe for a micro microscope such as STM (scanning tunneling microscope) or AFM (atomic force microscope). Furthermore, the present invention relates to a method for performing electroplating with high accuracy on a minute region such as the tip of the adherend using an electrode having a sharp tip such as a needle electrode for a cathode for an electron microscope. The present invention also relates to a method for manufacturing the semiconductor measurement probe pin.
[0002]
[Prior art]
In the manufacturing process of a semiconductor integrated circuit or the like, generally, when a large number of chips are formed on a semiconductor wafer, the electrical characteristics of each chip are measured to determine whether the operating characteristics are good or bad. For this measurement, a probe card in which a large number of probe pins are implanted according to the electrode shape of the object to be inspected is used.
[0003]
As for the probe pins of the probe card, the number of pins has been increased and miniaturized along with the rapid miniaturization of semiconductor elements, and a conventional probe card is mounted on a substrate by bending a tungsten pin into a square shape. Has reached its limit, and a rod-shaped single crystal such as fine silicon is grown substantially vertically on a silicon substrate by a gas-liquid-solid phase method (VLS method), and conductivity is imparted to the rod-shaped single crystal. It has been devised that a metallized probe pin is used (JP-A-5-198638, JP-A-5-218156) and has been attracting attention.
[0004]
In order to use the rod-shaped single crystal as a probe pin, the metallization of the rod-shaped single crystal is generally electrolytic gold plated after applying electroless nickel. Gold is soft, has low electrical resistance, and is excellent in corrosion resistance. Therefore, gold is suitable as a metal rod metal of a fine rod-like single crystal, but is brought into contact with gold or aluminum electrodes (hereinafter referred to as probing). ) When the probing frequency is increased, the gold plating layer at the tip of the probe pin is deformed, and finally a rod-shaped single crystal silicon is exposed, and there is a problem that durability during probing is poor.
[0005]
The present inventors have studied to improve the durability, and invented and filed a technique for coating only the tip portion of the probe pin with a contact material (Japanese Patent Application No. 8-190417). As a method of providing the contact material only at the tip of the probe pin, for example, a portion where the contact material is not formed is masked with a resist or the like, and then a variety of film formation methods such as plating, vapor deposition, and sputtering are used. The contact material may be coated and then the masking material may be removed, but the plating method without using the masking material is easy and is a preferred method.
[0006]
[Problems to be solved by the invention]
The present inventors evaluated the characteristics of the probe pin provided with a contact material at the tip by the above plating method. Sometimes, there are probe pins that are insufficiently in contact with the electrode during probing. It has been found that there are problems such as that there are things that cause pin breakage. The present inventors have studied diligently about these causes and solved the above problem when the contact material is provided at a desired portion of the tip portion of the probe pin with high accuracy, uniform thickness and no variation between the probe pins. The present invention has been obtained with the knowledge that the
[0007]
That is, when a probe pin for a probe card is immersed in a plating solution in order to constitute a portion where the pin itself has a diameter of 10 to 150 μm and a pitch of 30 to 100 μm due to restrictions in use, In addition, the probe pin is difficult to be uniformly immersed in each probe pin, and even if the immersion state is substantially uniform, the probe pin concentration is uneven and the surface condition is not uniform. When comparing each other, it is not easy to perform uniform plating. In other words, the plating solution used conventionally is an aqueous solution containing a metal salt to be electrolyzed, a chelating agent, a PH buffer, and the like, and only the tip of the probe pin is plated without using a masking material using such an aqueous plating solution. Even if you try to do this, the amount of plating solution that crawls up the side of the probe pin will vary greatly depending on the probe pin diameter or pitch density, and the desired area should be plated with uniform thickness and less variation from probe pin to probe pin. I could not.
[0008]
As a method of plating the contact material on the tip of the probe pin, as disclosed in the specification of Japanese Patent Application No. 8-190417, the present inventors impregnate a brush with a plating solution, attach an electrode to the brush, There is a method in which the probe pin itself is used as another electrode to be brought into contact with the tip of the probe pin and subjected to electrolytic plating. According to this method, the tip of the probe pin can be brought into contact with the plating droplet while observing with a microscope or the like, and the above problem can be solved to some extent. However, it is not easy to plate a predetermined portion of the tip of a huge number of probe pins of 200 to 1000 with a predetermined thickness without variation for each probe pin, and requires a lot of labor. As a result, there is a problem that the probe card becomes expensive.
[0009]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a plating method for accurately depositing a plating layer having a uniform thickness on a predetermined region. It is an object of the present invention to provide a method for producing a probe pin at a low cost by plating the tip of a probe pin used for a probe card without variation for each probe pin and causing no problems such as contact failure or breakage to an electrode.
[0010]
[Means for Solving the Problems]
The present invention is an electrolytic plating method characterized in that a contact material is deposited on the tip of a needle-like object using a gel-like plating bath.
[0012]
The present invention also relates to a method of manufacturing a probe pin for semiconductor measurement, in which a contact material is provided at the tip, wherein the contact material is deposited on the tip by the electrolytic plating method. It is a manufacturing method.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
In order to solve the above problems, the present inventors have studied variously, so as not to cause a phenomenon that the plating solution crawls on the needle-shaped adherend, or even if it occurs, the degree thereof is reduced, It is only necessary to prevent variations in the plating conditions between the probe pins due to variations in the diameter and surface condition of each probe pin. As a specific method, the surface of the plating solution and the wettability are not affected. Examples include a method of providing a bad water-insoluble organic substance, or a method of using a water-insoluble plating solution having extremely small surface tension. The present inventors have found that the above-described object can be specifically achieved by reducing the fluidity and forming a gel-like plating bath, and have reached the present invention.
[0014]
The gel-like plating bath of the present invention refers to a liquid that has the same function as a conventionally known plating solution and has a non-flowable solid state. For example, when a solid such as a probe pin is applied to the surface. It is soft enough to be easily deformed, and contains at least a metal to be electrolyzed in order to achieve its function as a plating solution, and has conductivity under the conditions of electrolytic plating.
[0015]
The gel-like plating bath of the present invention can be easily obtained by adding a gelling agent to a conventionally known plating solution. In this case, conventionally known gelling agents such as a polymer compound having a carboxylic acid group and a nonionic polymer compound can be used as the gelling agent. However, the polymer compound having a carboxylic acid group generally has a difficulty in producing a uniform gel because the metal ion acts as a cross-linking agent. When the temperature during plating is high and the time is long, the surface of the gel However, it can be used for short-time plating. On the other hand, nonionic polymer compounds are preferred because they are not easily affected by ions in the plating solution and do not have the above-mentioned limitations.
[0016]
Among non-ionic polymer compounds, starch easily gels when dispersed in a plating solution and is heated, and also has a property of maintaining a stable gel state even at high temperatures. A suitable gelling agent. In addition, agarose (agar) has a feature that it can be easily washed after plating because it forms a sol at a high temperature while gelling the plating solution in a very small amount. Furthermore, agarose has excellent properties such as adding 0.5% by weight or more to the plating solution, heat-dissolving, and cooling to form a gel-like plating solution that can be plated at room temperature and has no stringiness. Have.
[0017]
Regarding the amount of the gelling agent added to the plating solution, there is no problem in plating even if 0.5 to 5% by weight of the total amount of the plating bath is added to the plating solution. When the addition amount exceeds 5% by weight, air bubbles may be involved in the plating bath when preparing the plating bath, or workability when plating using the plating bath may be reduced. 0.5-2% by weight is the most preferred range.
[0018]
In the present invention, as described above, a conventionally known plating solution can be used. For example, in palladium plating, Paradex 91GV, Paradex 110, Paradex HS, Paradex 91, Paradex MS, Paradex VIII, Paradex Strike, Decorex (all manufactured by Tanaka Kikinzoku), Platanex 31S (manufactured by Tanaka Kikinzoku) for platinum plating, and TSP-48 nickel (manufactured by Okuno Seiyaku) for nickel plating.
[0019]
In the present invention, a contact material is preferable to achieve the object of the present invention. The contact material referred to in the present invention is a metal having excellent durability, with little welding and movement of the contact portion when actually using the probe pin, excellent corrosion resistance, low consumption even in probing several hundred thousand times, for example, Metals such as Pd, Ir, Rh, and Ni, Pd alloys obtained by adding metals such as Ag, Cu, Pt, and Au to Pd, Ag alloys obtained by adding oxides such as Sn, In, Zn, and Cu to Ag, etc. Can be mentioned. Of these, Pd is preferable because it can be easily plated and has excellent durability.
[0020]
Since the plating bath of the present invention is in a gel form, it has a special effect that it can be handled as if part of a conventional electrode is formed. For example, a metal electrode plate is set inside a container encircling all sides of a resin such as an acrylic plate, covered with an acrylic plate with a small hole in one corner, fixed with a clip, and a gelling agent is added. The obtained plating solution is heated and dissolved, poured from a small hole, allowed to cool to room temperature, and then the lid is removed to obtain a gel-like plating bath having a mirror-like surface. Further, for example, by cutting a gel-like plating bath into a conical shape with a knife or the like and attaching it to the tip of the linear electrode, it is possible to plate only a minute predetermined position of the adherend.
[0021]
By using the plating bath of the present invention, it is possible to easily obtain a mirror surface that does not flow, and by using this, the tip of a rod-like or needle-like adherend is inserted into the plating bath, thereby plating with high dimensional accuracy. Can do. In particular, when the present invention is applied to a plurality of rod-like or needle-like adherends, there is no creeping phenomenon on the adherend surface of the plating solution that has occurred in the conventional plating solution. It can be controlled to be small.
[0022]
The present invention relates to a method of manufacturing a probe pin for semiconductor measurement in which a contact material is provided at the tip, and the probe material is manufactured by applying the contact material to the tip by the electrolytic plating method described above. Is the method. As a method for manufacturing a probe pin for semiconductor measurement, for example, a method of growing a needle-like single crystal on a single-crystal substrate such as silicon by a VLS method in a direction substantially perpendicular to the substrate, and making the needle-like single crystal conductive There is. In the present invention, the contact material is plated on the tip of the conductive needle-like single crystal using the gel-like plating bath.
[0023]
The area where the contact material is plated, that is, the tip of the needle-like object, need not be limited as long as it is selected depending on the application and purpose, but in the case of a probe pin, the bending of the probe pin itself that occurs during probing In general, when the entire length of the probe pin is 1600 μm, it is about 300 μm from the forefront. As a preferable range, it is preferable to cover from the tip of the probe pin up to 20 μm from the tip of the probe pin when it is small, and to cover up to 200 μm from the tip of the probe pin when there are many.
[0024]
Hereinafter, based on an Example, this invention is demonstrated still in detail.
[0025]
【Example】
<Production of probe pin>
Masking a desired position on the surface of the SOI wafer and etching the insulating layer, an electrode line having a desired shape was created. Next, an Au bump is formed at a predetermined position of the electrode line, a Si needle-shaped single crystal is formed at that position by the VLS method, and the tip of the needle-shaped single crystal is polished to a predetermined length. Aligned. Next, after providing a Ni layer with a thickness of 0.1 μm by electroless plating on the surface of the needle-like single crystal and the electrode line, an Au film is further formed thereon with a thickness of 2 μm by an electrolytic plating method. A substrate having the probe pins was obtained. As a result of the above operation, the probe pins provided on this substrate have a length of 1.4 mm, the tips of the probe pins are in the same plane, clustered in U-shaped rows, and each row has a pitch of 50 μm. 360, 80 at 120 μm pitch and 20 at 80 μm pitch.
[0026]
The following examples and comparative examples were performed using the substrate having the probe pins.
[0027]
〔Example〕
<Production of gel-like plating solution having a mirror surface>
An acrylic plate having a thickness of 5 mm cut through the center portion was fixed with an instantaneous adhesive on an electrode plate plated with gold on a copper plate to form a container. Next, a small hole was made in an acrylic plate having a thickness of 1.5 mm, and a lid was set so that the small hole became an end of the container, and clipped.
[0028]
10 g of palladium plating solution (Tanaka Kikinzoku Co., Ltd .: Paradex 110) is weighed in a glass beaker, 0.08 g of agarose (manufactured by Wako Pure Chemicals: purified agarose) is weighed and added, and heated to 95 ° C to agarose. Dissolved. After cooling to about 70 ° C., it was injected from the small hole of the container with a dropper. After leaving at room temperature of 23 ° C. for about 10 minutes, the lid was removed to prepare a gelled palladium plating bath having a mirror surface.
[0029]
<Electrolytic plating on tip of probe pin>
The palladium plating bath and the substrate were set in an apparatus in which the mirror surface and the probe pin of the substrate face each other, and the probe pin can be moved minutely, and the movement state can be controlled under microscope observation. Using this apparatus, the tip of the probe pin on the substrate was immersed in a gel plating bath in a region from the tip to 50 μm and electroplated for 90 seconds at a current of 0.5 μA per pin.
[0030]
After completion of the plating operation, the probe pin was removed from the gel plating bath, washed with hot water at about 95 ° C., and rinsed. About the probe pin of this board | substrate, the shape of the front-end | tip part was observed by SEM. As a result, in each probe pin, palladium plating was formed with a thickness of 1.8 μm in an area of about 50 μm from the tip. The variation in the 50 μm region from the tip was ± 2 μm.
[0031]
Furthermore, using this substrate, a probing test was performed 1 million times under the conditions of an overdrive amount of 40 μm, a cycle time of 175 msec, and a contact time of 125 msec. Defects such as breakage did not occur.
[0032]
[Comparative Example]
Except that agarose is not used, and therefore the plating solution is not gelled, the same operation as in the example was carried out, and the tip of the probe pin on the substrate was electroplated with palladium. A phenomenon that the plating solution crawls up was observed. Note that the plating distance from the tip (the creeping distance of the plating solution) is the shortest of the probe pins at both ends of the group of probe pins in a row, has a smooth trapezoidal shape with a long center, and has a small pitch. The difference between the end and the center of the probe pin array was the largest.
[0033]
As a result of SEM observation of the probe pins of the substrate obtained here, the thickness of the palladium plating film is thin with a long length plated from the probe pin tip, and the length plated from the probe pin tip is thin. The short one was thick and showed a matchstick shape. In addition, as a result of probing tests of 1 million times, there were two cases in which the match rod-shaped pin was permanently deformed and the probe pin itself was broken. In addition, in the pin having a thin plating thickness, the tip of the silicon single crystal inside was exposed.
[0034]
【The invention's effect】
Since the present invention uses a gel-like plating bath, it has been a problem in the past due to the crawl-up of the plating solution on the surface of the adherend such as the tip of a needle-like object. It is possible to solve the problem that the area cannot be controlled, which is industrially useful.
[0035]
According to the present invention, plating can be applied to the tip of a fine needle-like or rod-like object such as an STM short needle under controlled conditions, and only a very limited area of the adherend is plated. Therefore, its industrial value is high.
[0036]
Further, according to the present invention, there is obtained an effect that the tip of the probe pin of the semiconductor measurement probe card can be plated with a contact material with good controllability, and a probe card having a probe pin with excellent probing durability is provided. It can be provided stably and inexpensively.

Claims (2)

The contact material on the tip of the needle like object, using a gel-like bath, electrolytic plating you wherein the depositing. A method for manufacturing a probe pin for semiconductor measurement, wherein a contact material is provided at the tip, wherein the contact material is deposited on the tip by the electrolytic plating method according to claim 1. .