JP3180419B2 - Bonding tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding tool used for mounting a semiconductor device such as an IC or LSI on a substrate or the like.

[0002]

2. Description of the Related Art A semiconductor device is mounted in a practical form,
In order to bring out the electrical characteristics, it is necessary to connect the electrodes formed on the semiconductor element to the leads of the package and to connect the leads to external terminals such as a printed wiring board.

The connection between the electrode of the semiconductor element and the lead of the package is made by a wire bonding method in which a thin metal wire made of gold or copper is used as a conducting wire (bonding wire) and connected one by one using a tool called a capillary. Has been done. Also, recently, a lead called a film carrier tape tin-plated on a patterned copper foil is used, and the patterned lead and all the electrodes of the semiconductor element are bonded using a bonding tool heated to a predetermined temperature. Wireless bonding, such as TAB (Tape Automated Bonding), in which connections are collectively and successively made one after another, is also widespread. On the other hand, the connection between the package lead and an external terminal such as a printed wiring board is performed by bonding an electrode such as solder formed on the printed wiring board by screen printing or the like and the lead using a bonding tool heated to a predetermined temperature. Are joined.

[0004] A bonding tool used for wireless bonding such as a TAB method or for connection to an external terminal includes M
o, Fe-Ni alloy, Ni alloy, Ti or Ti alloy, W
Alternatively, W alloys, Fe-Ni-Co alloys, and the like have been used. However, these bonding tools made of a single metal have disadvantages such as low flatness of the pressing surface at the tip, poor abrasion resistance, and short tool life. In addition, since the bonding tool is used in a state where it is heated to a predetermined temperature (for example, 400 ° C.), it is generally energized to perform resistance heating. Has a drawback that the temperature distribution is not good.

[0005] Recently, in order to improve the disadvantages of these metal-only bonding tools, a polycrystalline diamond, a diamond single crystal, a diamond sintered body, a cubic nitride and a polycrystalline diamond manufactured by a low-pressure gas phase synthesis method at a tip pressing surface portion. A bonding tool provided with a hard substance such as a boron sintered body (cBN) is often used. However, among the hard materials, polycrystalline diamond, diamond single crystal,
Since the cBN sintered body and the like have a high specific resistance and are difficult to conduct electricity, the metal shank to which these hard materials are joined is energized to generate heat by resistance heating, and the heat is transmitted through the joining surface to thereby make the pressing surface portion of the shank compact. The hard material is heated to a predetermined temperature. For this reason, there is a problem that the temperature responsiveness is poor, that is, the time required for heating and cooling is longer than that of a bonding tool made of a single metal, which hinders a reduction in mounting time.

Of course, it is possible to shorten the time required for the hard material on the pressing surface to reach a predetermined temperature by increasing the current flowing through the metal shank. Since the material is rapidly heated, damage to the shank material and the brazing material becomes large, and a new problem occurs in terms of tool life.

On the other hand, since a diamond sintered body is formed by bonding a large number of fine diamond particles using a ferrous metal such as Co as a binder, the resistivity is controlled by adjusting the content of the ferrous metal. It is possible. Therefore,
With a bonding tool with a diamond sintered body provided on the pressing surface, the diamond sintered body itself can be energized for resistance heating, and its thermal conductivity is higher than that of metal. There is no. However, since the binder metal in the diamond sintered body is alloyed with Sn, which is a plating material of the lead, and solder, etc., which are patterned on a printed circuit board, during use while being heated to a predetermined temperature. The surface was easily stained, requiring frequent cleaning. For this reason, the mounting work becomes complicated, and the mounting time is also greatly hindered.

[0008]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention is excellent in flatness, abrasion resistance, and temperature distribution of a pressing surface, is hardly contaminated with a pressing surface, and has a temperature response in heating and cooling. An object of the present invention is to provide a bonding tool having excellent performance.

[0009]

In order to achieve the above object, in a bonding tool used for mounting a semiconductor device according to the present invention, at least a pressing surface portion is made of conductive polycrystalline diamond containing boron, and a polycrystalline diamond is used.
Concentration of boron to carbon in the carbon is 0.1 to 50,000.
ppm, and the polycrystalline diamond is provided with a current-carrying terminal for resistance heating.

[0010]

In the bonding tool of the present invention, since at least the pressing surface portion is made of conductive polycrystalline diamond, the polycrystalline diamond can be heated directly by applying a current. In addition, compared to a single metal bonding tool or a conventional bonding tool in which a non-conductive diamond or the like is provided on the pressing surface of a metal shank, first, the heat capacity of a portion heated to a predetermined temperature is small, and second, heat conduction is reduced. Since the rate is as large as 10 W / cm · ° C. or higher, the temperature response is excellent, and heating and cooling can be performed in a shorter time as compared with the related art.

[0011] Such conductive polycrystalline diamond includes B, Al, P, Sb, Si, Li,
Metals such as S, Se, Cl, N, W, Ta, Re, Cr,
It is already known that it can be obtained by including one or two or more types of impurities among semimetals and nonmetallic elements. As a specific production method, in a known low-pressure gas-phase synthesis method for synthesizing polycrystalline diamond, a gas containing the impurity or a gas containing the impurity is used as a raw material gas of hydrogen and a carbon-containing gas such as methane. By adding an appropriate amount, it can be directly synthesized on a substrate. Further, impurities can also be added to polycrystalline diamond synthesized by a low-pressure vapor phase synthesis method using a known diffusion method or ion implantation method.

Although the degree of conductivity of the polycrystalline diamond to which impurities are added varies depending on the type of the added impurities, the conductivity increases as the content of the same impurity increases. However, the specific resistivity preferable as the conductive polycrystalline diamond used in the present invention is 10 ⁻⁵ to 10 ⁵ Ω ·
cm, more preferably from 10 ^-3 to 10 ³ Ω · cm. When the specific resistivity is larger than 10 ⁵ Ω · cm, it is difficult to directly heat and carry out resistance heating to a predetermined temperature. Conversely, when the specific resistance is smaller than 10 ^-5 Ω · cm, the current can be easily supplied. This is because, since the amount increases, the wear resistance at high temperatures and the flatness tend to decrease.

As for the impurities to be added, diamond has a lattice constant of 3.56562 ° and a very small interatomic distance, and therefore, it is preferable that diamond has a small atomic radius. Metal elements greatly affect the wear resistance and practical flatness of polycrystalline diamond.Because many of them have large atomic radii, they are difficult to enter as a diamond interstitial or substitutional type, and segregate at grain boundaries. Since the crystallinity is reduced, it is preferable that the amount of addition is small. From such a viewpoint, boron (B) is particularly preferable as an impurity added for imparting conductivity to polycrystalline diamond.

The concentration of the impurity added to the carbon of the polycrystalline diamond depends on the type of the impurity. However, while maintaining the crystallinity of the polycrystalline diamond and maintaining excellent abrasion resistance and flatness, the resistance is increased by energization. The range is set so that conductivity sufficient to be heated can be imparted. For example, when the concentration of boron with respect to carbon is less than 0.1 ppm, the specific resistance is too high and resistance heating by energization is impossible, and 50,000
If the content exceeds ppm, the crystallinity of diamond deteriorates, and in the case of low-pressure gas phase synthesis, graphite, amorphous carbon, etc. are simultaneously precipitated, and therefore, the wear resistance and flatness at high temperatures are extremely reduced. A range of ５０50,000 ppm is preferred.

The impurities added to impart conductivity as described above are contained in a form in which the impurities penetrate into the crystal lattice of the polycrystalline diamond or are substituted for a part of the lattice. Crystalline diamond retains the properties of a single diamond as a whole, and is different from a diamond sintered body in which a large number of fine diamond particles are bonded with a bonding metal. Therefore, the contained impurities do not alloy with the lead plating material Sn or the solder on the printed circuit board during mounting, and the pressing surface is not stained, so that the conventional bonding tool using a diamond sintered body is not used. The frequency of cleaning can be reduced.

The bonding tool of the present invention may be entirely composed of a single conductive polycrystalline diamond. However, from the viewpoint of economy and strength, a base or shank such as SiC or Si ₃ N ₄ is used. Alternatively, conductive polycrystalline diamond may be deposited on at least a portion of the pressing surface, or may be joined by brazing or the like.

[0017]

Example 1 A low-pressure gas-phase synthesis method using hydrogen, methane, and diborane (B ₂ H ₆ ) as raw material gases was performed at a total gas flow rate of 1000 SCCM, a B / C ratio of 1000 ppm, and a pressure of 40.
Under the condition of Torr, a polycrystalline diamond containing B as an impurity is deposited to a thickness of 1.5 mm on the Si base, and then the Si base is dissolved and removed with nitric hydrofluoric acid, and the pressing surface 2 shown in FIG. Is 1.3mm wide and 25mm long (L)
A bonding tool according to the present invention made of only the conductive polycrystalline diamond 1 was produced. This polycrystalline diamond is manufactured by SIMS (Secondary Ion Mass Spectrometry).
550 pp
m, and the specific resistivity was 10 ⁻¹ Ω · cm.

On the other hand, as a comparative example, a bonding tool made of Mo alone having the same dimensions and shape as the above-mentioned bonding tool, and the same Mo alone as a shank, as shown in FIG. Then, a bonding tool in which a cBN sintered body and a diamond sintered body were brazed as a hard substance 5 having a thickness of 1.5 mm was manufactured.

Electric current is applied between the terminal portions 3 of the respective bonding tools, and resistance heating is performed on the pressing surface portion having a small cross-sectional area, so that the heating time until the pressing surface 2 reaches 400 ° C. is measured. The temperature distribution of the pressing surface 2 is measured at 400 ° C., and then the pressing surface 2 is heated to 400 ° C. to 200 ° C. by air cooling.
The cooling time until the temperature reached was determined, and these results were shown in Table 1.
It was shown to. In addition, the temperature of the pressing surface 2 was measured using an infrared thermometer.

[0020]

Table 1 Cooling time (sec) from 400 ° C up to 400 ° C to 200 ° C to 400 ° C bonding tool heating time (sec) Temperature distribution (° C) Example of present invention 0.6 2.07 Mo unit 1.2 3.0 60 Mo shank + cBN sintered body 1.5 6.0 16 Mo shank + Tiamont sintered body 1.8 7.5 30 From the above Table 1, bonding made of polycrystalline diamond alone of the present invention example It can be seen that the tool is superior in both the temperature response and the temperature distribution of the pressing surface as compared with the conventional bonding tool.

[0021]

Embodiment 2 As shown in FIGS. 3 and 4, polycrystalline diamond containing B on the surface of the Si substrate 6 and one side to be the pressing surface 2 by the low-pressure gas phase synthesis method under the same conditions as in Embodiment 1. 1 was deposited to a thickness of 0.5 mm, and a pressing tool 2 having a width (W) of 2.0 mm and a length (L) of 30 mm was prepared as a bonding tool of the present invention. The B concentration and the specific resistivity to C of the polycrystalline diamond were the same as those in Example 1.

On the other hand, as a comparative example, a bonding tool made of Mo alone having the same dimensions and shape as the above-mentioned bonding tool, and this Mo alone was used as a shank. As shown in FIG. A bonding tool in which a cBN sintered body and a diamond sintered body were brazed as a hard substance 5 having a thickness of 1.5 mm on one side surface was prepared.

Electric current is applied between the terminals 3 of the respective bonding tools to perform resistance heating, and the heating time until the pressing surface 2 reaches 200 ° C. is measured in the same manner as in the first embodiment. The temperature distribution of the pressing surface 2 was measured, and then the cooling time until the pressing surface 2 reached 200 ° C. to 100 ° C. by air cooling was determined. The results are shown in Table 2.

[0024]

TABLE 2 Cooling time (seconds) Temperature distribution from 200 ° C. to 200 ° C. to 100 ° C. 200 ° C. bonding tool heating time in seconds (° C.) the onset bright example 0.3 4.7 5 Mo single body 0.6 9.0 50 Mo shank + cBN sintered body 0.8 12.0 10 Mo shank + Tiamont sintered body 0.9 13.5 18 From Table 2 above, polycrystalline diamond on Si shank of the present invention example It can be seen that the bonding tool provided with is superior in both the temperature responsiveness and the temperature distribution of the pressing surface as compared with the bonding tool of the conventional example.

[0025]

Example 3 By the same low-pressure gas phase synthesis method as in Example 1,
However, by changing the concentration of diborane to methane,
Concentration of B with respect to 0.01 ppm, 200 pp
m, 5000 ppm, and 80,000 ppm of polycrystalline diamond were deposited on Si substrates to a thickness of 1.5 mm. Thereafter, the Si base material was dissolved and removed with hydrofluoric nitric acid to produce a bonding tool made of a single polycrystalline diamond having the same dimensions as in Example 1.

For each of the obtained bonding tools,
The specific resistance was measured, and the heating time until the pressing surface 2 reached 400 ° C., 400 ° C. in the same manner as in Example 1.
The temperature distribution of the pressed surface 2 and the cooling time required for the pressed surface 2 to reach 200 ° C. from 400 ° C. were obtained. The results are shown in Table 3.

[0027]

[Table 3] Sample Specific resistivity B-concentration at 400 ° C from 400 ° C to 200 ° C 400 ° C Concentration (Ωcm) Heating time (second) Cooling time (second) Temperature distribution (° C) 0.01 ppm 10 ⁹ energized not energized not energized Call ^{200ppm 10 0 0.8 2.3 8.2 5000ppm 10} -2 0.6 2.0 7 80000ppm 10 -6 1.1 2.8 55 ( Note) Comparative examples as samples It is.

[0028]

Fourth Embodiment Polycrystalline diamond is deposited on a Si substrate by a normal low-pressure gas phase synthesis method using hydrogen and methane as raw material gases, and the Si substrate is dissolved and removed to obtain a bonding tool having the same shape and dimensions as in the first embodiment. Produced. Next, B and C were simultaneously ion-implanted from the surface of the polycrystalline diamond of the bonding tool using a known ion implantation method. The implantation conditions are as follows: acceleration energy 200 kV, B doping amount 1
0 ¹⁵ / cm ² and the C doping amount were 5 × 10 ¹⁵ / cm ² .

The obtained polycrystalline diamond was obtained by SIMS
The B concentration with respect to C measured by the method was 10 ppm, and the specific resistivity was 10 ² Ω · cm (resistance value about 50 kΩ). Further, with respect to the bonding tool consisting of a simple polycrystalline diamond containing B, the temperature responsiveness and the temperature distribution of the pressed surface were determined in the same manner as in Example 1.
The heating time until the pressing surface reaches 400 ° C is 0.7
Seconds, the cooling time for the pressing surface to reach 200 ° C from 400 ° C is 2.0 seconds, and the temperature distribution of the pressing surface at 400 ° C is 7 ° C, and both the temperature responsiveness and the temperature distribution are excellent. I understood.

[0030]

According to the present invention, a bonding tool is constituted by using polycrystalline diamond to which impurities are added to impart conductivity, and the polycrystalline diamond itself having a high thermal conductivity is supplied with electric current for resistance heating. As a result, the temperature responsiveness and the temperature distribution on the pressing surface can be significantly improved as compared with the conventional bonding tool.

Moreover, by using polycrystalline diamond, not only is the flatness and abrasion resistance of the pressing surface of the bonding tool excellent, but also the impurities contained in the polycrystalline diamond are different from the diamond sintered body in that the plating of the lead is performed. Since there is no alloying with the material or the solder on the printed circuit board, dirt hardly adheres to the pressing surface, and frequent cleaning is not required.

Therefore, by using the bonding tool of the present invention, the heating and cooling of the bonding tool itself can be performed quickly and the frequency of cleaning the pressing surface can be reduced, so that the time required for mounting the semiconductor element can be reduced. This is extremely effective in improving the efficiency and accuracy of the semiconductor element mounting process, in combination with the improvement in accuracy due to the improvement in the flatness of the pressing surface and the temperature distribution.

[Brief description of the drawings]

FIG. 1 is a front view showing a specific example of a bonding tool of the present invention made of only conductive polycrystalline diamond.

FIG. 2 is a front view showing a specific example of a conventional bonding tool in which a hard material is bonded to a metal shank.

FIG. 3 is a front view showing a specific example of the bonding tool of the present invention in which conductive polycrystalline diamond is provided on a substrate.

FIG. 4 is a side view of the bonding tool shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polycrystalline diamond 2 Pressing surface 3 Terminal part 4 Mo shank 5 Hard substance 6 Si base

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Akihiko Ikegaya 1-1-1, Koyo Kita, Itami-shi, Hyogo Sumitomo Electric Industries, Ltd. Itami Works (72) Inventor Naoji Fujimori 1-chome, Koyo-Kita, Itami-shi, Hyogo No. 1-1 In Itami Works, Sumitomo Electric Industries, Ltd. (56) References JP-A-1-280327 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/60

Claims (2)

(57) [Claims] In a bonding tool used for mounting a semiconductor element, at least a pressing surface portion is made of conductive polycrystalline diamond containing boron, and a polycrystalline diamond is formed.
Concentration of boron to carbon in the carbon is 0.1 to 50,000.
A bonding tool, characterized in that the polycrystalline diamond is provided with a current-carrying terminal for resistance heating. 2. The polycrystalline diamond has a specific resistivity of 1
0 ^-5 characterized in that it is a ~10 ⁵ Ω · cm, bonding tool of claim 1, wherein.