JP2003033810A - Wiredrawing method of metal fine wire for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiredrawing method of metal fine wire for a semiconductor device which improves longevity of a die while keeping surface smoothness of metal fine wire. SOLUTION: A desired diameter of metal fine wire 1' is produced by arranging plural number of dies 2a-2h and also capstans 3, 3' to draw a wire rod 1 which sequentially passes each die. In order to perform a wiredrawing by a single crystal diamond die after the wiredrawing is performed by a polycrystalline diamond die, a single crystal diamond die is arranged after the required number of the polycrystalline diamond dies. The wiredrawing process by the polycrystalline diamond dies is to be finished at the stage when a drawn mark on the surface of the wire rod 1 generated by wiredrawing is minute.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for drawing a fine metal wire used in a semiconductor device. More specifically, a plurality of dice are arranged, and in the dice arrangement, a polycrystalline diamond die and a single crystal diamond die are mixed. In addition, by specifying the arrangement of the polycrystal diamond die and the single crystal diamond die, the polycrystal diamond die is frequently used, but the surface smoothness is excellent, and it is possible to produce a fine metal wire suitable for use in a semiconductor device. Regarding the method.

[0002]

2. Description of the Related Art Currently, metal thin wires for semiconductor devices are Au,
20 to 100 in diameter by including trace elements in Al, Cu, etc.
After being drawn to 0 μm, it is heat-treated and surface-treated, and then wound on a spool at a predetermined length selected from a length of 100 to 5000 m and used as a material for connecting semiconductor element electrodes.

Since these metal thin wires have a diameter of 1 mm or less and require a long wire drawing work,
Using a wire drawing machine equipped with multiple dies and a capstan that pulls out wire rods that have passed through these dies, a method of continuously drawing between multiple dies is used. A diamond die with excellent properties is used.

Further, as the diamond dies used in this seed wire drawing method, single crystal diamond dies and polycrystalline diamond dies are known. Here, the single crystal diamond die is used by processing the single crystal as it is with natural diamond or artificial diamond as a block. On the other hand, the polycrystalline diamond die is used by mixing, pressing and sintering diamond powder, and has a polycrystalline structure inside.

[0005]

Conventionally, when drawing a fine metal wire to a diameter of 1.0 mm or less, a single crystal diamond die with a low die unit price has been used. 10 dies for drawing wire
As the number of dies increases, the degree of die wear has become a major problem. That is, in order to secure the surface property of the thin metal wires for semiconductor elements, die replacement due to wear of the dies has been frequently required.

Therefore, when a polycrystalline diamond die having excellent wear resistance was used, a certain result was obtained in improving the life of the entire die, but the smoothness of the surface of the thin metal wire after wire drawing was deteriorated. The problem has arisen.
Here, the smoothness of the surface of the thin metal wire can be effectively used as an index for displaying a microscopic state of surface scratches of the thin metal wire. Further, since an expensive diamond die is used, further improvement of die life is required.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to improve the die life while maintaining the smoothness of the surface of the fine metal wire. It is to provide a method for drawing a fine metal wire for use.

[0008]

In order to achieve the above object, the present invention arranges a plurality of dies, and arranges a capstan for pulling out the wire so that the wire passes sequentially through the dies. In the method of drawing a thin metal wire for a semiconductor device to obtain a thin metal wire having a desired diameter, a single crystal diamond die is drawn after the wire is drawn with a polycrystalline diamond die. It is characterized in that a single crystal diamond die is arranged later.

Further, the present invention is characterized by having one or a plurality of the above-mentioned single crystal diamond dies, and making the number of the single crystal diamond dies half or less of the total number of dies.

Further, the present invention is characterized in that the wire drawing step using a polycrystalline diamond die is terminated at a minute stage where scratches generated on the surface of the wire to be drawn are minute.

As described above, in the thin metal wire drawn by using the single crystal diamond die, the surface smoothness is satisfactory, but a large flaw is likely to occur in a short drawing time. On the other hand, when a polycrystalline diamond die is used, fine scratches are generated on the surface of the thin metal wire in a short drawing time, and surface smoothness cannot be obtained, but the degree of surface scratches is small even if the wire is drawn for a long time. It is something. The present invention, if within the limit of a minute surface scratch, by drawing with a single crystal diamond die subsequent to the drawing step with a polycrystalline diamond die, there is no surface scratch, and the surface smoothness is satisfactory. This was done based on the finding that a thin metal wire can be obtained. In the wire drawing using the polycrystalline diamond die, since the drawing time that can maintain the degree of the surface scratch of the fine metal wire in a minute range is long, the die array according to the present invention which uses the polycrystalline diamond die in many cases is used. As a result, it is possible to achieve the object of the present invention that the die life is improved while maintaining the surface smoothness of the metal fine wire.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The thin metal wire for a semiconductor device according to the present invention includes a thin metal wire for forming bumps, in addition to a thin metal wire used for wiring such as ball bonding and wedge bonding used for connecting semiconductor elements. Further, as the seed metal wire, for example, Au, Al, Cu, Pt
A base metal containing Ca, Be, a rare earth element, or the like as an additional element as needed is used, but the composition is not particularly limited in the present invention.
Among these, the gold wire (gold alloy wire) is most preferably used. The wire diameter of the metal thin wire is preferably 10 to 100 μm. Among these, the diameter of 10 to 50 μm is most preferably used. In the wire drawing method of the present invention, the fine metal wire subjected to the final wire drawing is coated with a lubricant on the surface thereof, wound on a spool for a predetermined length, and cross-multilayered to be used for connecting semiconductor elements.

The wire drawing method according to the present invention is a method of continuously drawing wire between a plurality of dies by using a wire drawing machine equipped with a plurality of dies and a capstan for pulling out a wire rod passing through the dies. Is intended for. An example of the wire drawing method using the plurality of dies and the capstan rolls will be described with reference to FIGS. 1 and 2.

In FIG. 1, reference numeral 1 is a metal wire rod, 2a to 2a.
h is a die, and 3 and 3'are straight type capstan rolls. The metal wire rod 1 is introduced in the direction of the arrow in the upper part of the figure, the wire drawing process is sequentially performed by the dies 2a to 2h of each stage, and the wire drawing process is continuously performed while changing the direction by the left and right capstan rolls 3 and 3 '. To go. Although FIG. 1 shows eight dice, the number of dice may be changed. Usually 2
It is selected from about 30 pieces. Finally, the thin metal wire 1'is led out in the direction of the arrow at the bottom of the drawing and wound by a winder (not shown).

FIG. 2 shows an example in which stepped rolls 4 and 4'are used as capstan rolls. Wire drawing is performed in the same manner as in FIG. 1 except that the shape of the capstan roll and the number of dies are changed.

The slip condition between the metal wire rod 1 and the capstan roll will be described. In the straight type capstan rolls 3 and 3'of FIG. 1, the peripheral speed of the capstan roll at the final stage of wire drawing (downward in FIG. 1). Is drawn about 2% faster than the linear velocity of the wire material, and the wire is drawn with a slight slip. At this time, in the initial stage of wire drawing (upper part in FIG. 1), a large speed difference corresponding to the total working rate occurs, which causes a large slip. On the other hand, in the case of the stepped rolls 4 and 4'of FIG. 2, the roll diameter of each stage can be set in consideration of the processing rate, so that wire drawing can be performed while slipping is set at each stage. In the present invention, either a straight type or a stepped type may be used as the capstan roll, but the stepped type is preferably used because the degree of slip can be controlled. In addition, the die and capstan can be set as one unit (one block), and the required number of the units can be arranged for continuous wire drawing.

In the present invention, the arrangement of the plurality of diamond dies is such that the necessary number of polycrystalline diamond dies are formed after the required number of polycrystalline diamond dies so that the drawing is performed by the single crystal diamond dies after the drawing step by the polycrystalline diamond dies. It is necessary to place a crystalline diamond die.

When a plurality of dies are used to draw a fine metal wire for a semiconductor device having a diameter of 1 mm or less, continuous drawing is performed using about 2 to 30 dies. Although the number of sheets is increasing due to the improvement of the wire drawing technique, it may be possible to use two dies depending on the required final wire diameter.

In the present invention, first, as a wire drawing step using a polycrystalline diamond die, a metal wire (element wire) having excellent surface smoothness is continuously drawn by a plurality of polycrystalline diamond dies. While the wire drawing time is short, surface scratches of the metal wire cannot be observed, but the surface smoothness deteriorates. Here, the surface scratches are observed by a magnifying glass with a magnification of 15 times, and the surface smoothness is an index showing the degree of unevenness of the microscopic surface. When the wire drawing with the polycrystalline diamond die is continued for a long time, minute scratches are generated on the surface of the metal wire, and the surface smoothness is still poor. In the present invention, continuous wire drawing is performed using a polycrystalline diamond die at the stage where the minute surface scratches are generated.

Thus, in the present invention, subsequent to the wire drawing step using the above-mentioned polycrystalline diamond die, wire drawing is performed using the single crystal diamond die. That is, at the stage where the above-mentioned minute surface scratches have occurred, in other words, the state in which the surface scratches exceed the minimum (medium scratch, large scratch).
Before that, by continuously drawing with a single crystal diamond die, surface scratches can no longer be observed, surface smoothness is greatly improved, and satisfactory metal thin wires for semiconductor devices can be obtained. You can

However, among those having fine surface scratches by drawing with a polycrystalline diamond die, the metal wire obtained through a longer drawing step of the polycrystalline diamond die has a plurality of single crystal diamond dies. It is preferable to repeatedly perform wire drawing work using a single crystal diamond die. In this way, after continuous drawing with the required number of polycrystalline diamond dies, by subsequently drawing with a single-crystal diamond die 1 to several times, the occurrence of surface scratches can be prevented, and a semiconductor with satisfactory surface smoothness. A thin metal wire for a device can be obtained.

As described above, continuous wire drawing with a polycrystalline diamond die is preferably terminated at a stage where surface scratches are minute. The life of the polycrystalline diamond die up to this stage is about 10 to 15 times as long as the life of the single crystal diamond die. Incidentally, when the final diameter of continuous wire drawing is 50 μm, it is about 10 times, and when it is 100 μm, it is about 15 times.

On the other hand, if continuous wire drawing with a polycrystalline diamond die is continued for a long time, the surface flaw of the metal wire material will exceed the minute limit and become moderate. With this as a material,
Even if you continue wire drawing with a single crystal diamond die,
It becomes impossible to obtain a surface smoothness. Therefore, when the surface flaw of the thin metal wire drawn by the polycrystalline diamond die is within the microscopic limit, the wire is drawn subsequently by using the single crystal diamond die to significantly improve the die life of the polycrystalline diamond die. It is possible to obtain a fine metal wire having satisfactory surface smoothness while using a large amount of.

In the plurality of dice arrangements according to the present invention, the number of single crystal diamond dies arranged after the polycrystalline diamond dies is one or more and 1/1 of the total number of dies.
When it is 2 or less, a fine metal wire having a long surface life of the fine metal wire can be obtained while using many polycrystalline diamond dies having a long life, which is preferable.

The wire drawing method according to the present invention is preferably applied to continuous wire drawing in which the diameter of the metal wire rod after wire drawing is from 1 mm to 50 μm. Here, the surface smoothness of the thin metal wire is made to be satisfactory each time one continuous wire drawing is completed, and the subsequent continuous wire drawing is similarly performed by using this as a material, so that finally there is no surface flaw and It is preferable because a fine metal wire having a satisfactory surface smoothness can be obtained.

[0026]

[Examples] Hereinafter, the tests conducted for confirming surface scratches and surface smoothness by the wire drawing method of the present invention will be described. In this test, a straight type capstan roll shown in FIG. 1 and a predetermined number of dies were used to perform wire drawing under the following conditions.

(Test A) A gold wire having a diameter of 100 μm, which has no surface scratches and has good surface smoothness, is used as an element wire and has a diameter of 60 μm.
Wires were drawn with 10 dies up to m. As the die, a single crystal diamond die or a polycrystalline diamond die was used. The wire-drawing time is determined by using a single-crystal diamond die to find the time limit at which surface scratches do not occur
Drawing was performed at multiple times of the reference time. Table 1 shows the types of dies and wire drawing time, and
Different types of wire drawing tests were performed. As a method for measuring the surface scratches of the obtained gold wire, the presence or absence of surface scratches was observed using a magnifying glass (magnification: 15 times) and the surface smoothness was visually observed. Regarding the observation of the presence or absence of surface scratches, those that could not be confirmed were displayed as “none”, those that could be recognized somehow were displayed as “small scratches”, and the degree of further scratches was displayed as “medium scratches” and “large scratches”. For the observation of the surface smoothness, a light beam was applied to perform a three-level evaluation of "best", "good" and "poor". The "poor" evaluation has a scratch width of 1 μm or more, the "best" evaluation has a value of about 1/10, and the "good" evaluation has a degree slightly worse than the "best" evaluation. Table 1 shows the presence or absence of surface scratches and the measurement results of surface smoothness.

[0028]

[Table 1]

(Test B) In Test A, there was no surface scratch and the best surface smoothness was obtained.
Using a gold wire having a diameter of 60 μm obtained in the tests of 3 to 8 as an element wire, wire drawing was performed to a diameter of 57 μm using one single crystal diamond die. As the single crystal diamond die, the one whose usage record is within the reference time is used. The wire used was subjected to six types of wire drawing tests for sample Nos. 9 to 14 as shown in Table 2. In the same manner as in Test A, Table 2 shows the results of measuring the presence or absence of surface scratches and the surface smoothness of the obtained gold wire.

[0030]

[Table 2]

(Test C) In Test B, there was no surface scratch and the best surface smoothness was obtained.
The gold wire having a diameter of 57 μm obtained in the tests of 9, 13, and 14 was used as an element wire, and drawn to a diameter of 55 μm using one single crystal diamond die. As the single crystal diamond die, the one whose usage record is within the reference time is used. The used wires are as shown in Table 3 and sample Nos. 15 to 17
3 types of wire drawing tests were performed. In the same manner as in Test A, Table 3 shows the results of measuring the presence or absence of surface flaws and the surface smoothness of the obtained gold wire.

[0032]

[Table 3]

According to the above-mentioned test results, the following is the result of wire drawing using a gold wire for a semiconductor element having a diameter of 100 μm, which has no surface scratch and has excellent surface smoothness as an element wire.

When a plurality of polycrystalline diamond dies were used for continuous wire drawing up to a diameter of 60 μm and the wire drawing time was within 10 times the reference time, the surface scratches of the obtained gold wire were within a minute range. It can be seen from Sample Nos. 4 to 7 in Table 1 that the surface smoothness is poor. Then, the sample No.
57 samples of 4-7 using a single crystal diamond die
When wire drawing was performed up to μm, the surface scratches of the wire sample Nos. 4 to 6 could not be observed with a loupe, and the surface smoothness had the best surface property. From ~ 12. It can be seen from Sample No. 13 in Table 2 that the wire sample No. 7 has a slightly inferior surface smoothness. Next, when the sample No. 13 was used as an element wire and was drawn to 55 μm using a single crystal diamond die, surface scratches could not be observed with a loupe, and the surface smoothness with the best surface smoothness was obtained. This can be understood from sample No. 16 in Table 3. From the above results, by arranging the single polycrystalline diamond die after the required number of polycrystalline diamond dies in the die arrangement, a metal thin wire having the best surface property is obtained while using a long life die called polycrystalline diamond die. It was confirmed that it was possible.

Continuous drawing is performed using a plurality of single crystal diamond dies up to a diameter of 60 μm, and surface scratches cannot be observed with a magnifying glass within the reference time and the surface smoothness is the best. Can be seen from sample Nos. 1 and 2 in Table 1. However, this method cannot obtain the effect of improving the life of the die.

When a plurality of single crystal or polycrystal diamond dies are used for continuous wire drawing up to a diameter of 60 μm and the wire drawing time exceeds its life, surface scratches are observed with a magnifying glass and have medium or large scratches. There is sample No. 3 in Table 1,
I understand from 8. Then, the sample Nos. 3 and 8 were drawn to a diameter of 57 μm using a single crystal diamond die, and the wire sample Nos. 3 and 8 had bad surface scratches and were bad. That is, sample No. 9 and 14 in Table 2
I understand from Then, when the sample Nos. 9 and 14 were used as an element wire and drawn to a thickness of 55 μm using a single crystal diamond die, the surface scratches remained unchanged and were bad. It can be understood from .15 and 17. From this, it is understood that the drawing time in the polycrystalline diamond die needs to be set within the life time of the polycrystalline diamond die.

[0037]

As described above, according to the present invention, in the wire drawing step in which the polycrystalline diamond die is frequently used, the wire drawing time for maintaining the degree of the surface scratch of the fine metal wire in a minute range becomes longer, By drawing using a single crystal diamond die following the process, it is possible to obtain a fine metal wire with no surface scratches and satisfactory surface smoothness, and by using a die array that uses a large number of polycrystalline diamond dies, The die life can be improved while maintaining the surface smoothness of the thin metal wire. Therefore, for example, it is extremely useful as a wire drawing method when manufacturing a metal thin wire for connecting a semiconductor element or forming a bump.

[Brief description of drawings]

FIG. 1 is a simplified diagram showing an example of an embodiment of a wire drawing method according to the present invention.

FIG. 2 is a simplified view showing another example of the embodiment of the wire drawing method according to the present invention.

[Explanation of symbols]

1: Metal wire rod (wire rod before wire drawing) 1 ': fine metal wire (wire material after wire drawing) 2a-2h: Dice 3,3 ', 4,4': Capstan

Claims (3)

[Claims] 1. A method for drawing a thin metal wire for a semiconductor device, in which a plurality of dies are arranged and a capstan for pulling out the wire is arranged at a proper position so that the wire sequentially passes through the dies to obtain a thin metal wire having a desired diameter. In, in order to be drawn by a single crystal diamond die after drawing by a polycrystalline diamond die, a metal for a semiconductor device characterized by arranging a single crystal diamond die after a required number of polycrystalline diamond dies How to draw a thin wire. 2. A single crystal diamond die or a plurality of the single crystal diamond dies, and the number of the single crystal diamond dies is ½ or less of the total number of dies.
A method for drawing a thin metal wire for a semiconductor device as described above. 3. The semiconductor device according to claim 1, wherein the wire drawing step with the polycrystalline diamond die is terminated at a minute stage where a scratch generated on the surface of the wire to be drawn is minute. Method for drawing fine metal wire.