JP2520971C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TAB bonding tool used in a semiconductor chip manufacturing process. [Prior Art] In recent years, the technical progress in the semiconductor field has been remarkable, and ICs, LSs,
The production of applied products using I and the like is increasing year by year. In order to bring out the electrical characteristics of these semiconductor elements, it is necessary to connect them to metal-plated leads or thin metal wires called bonding wires. Au is usually used for the connection metal because it is chemically stable and has high electrical conductivity.
Alternatively, an Au-Sn alloy is used, and as a connection method, a method of applying pressure by a heated bonding tool and thermocompression bonding is widely adopted. There are roughly two types of bonding tools used in the above-mentioned thermocompression bonding. [Problem] One of the methods is called a pulse heating method, in which a material such as nichrome, stainless steel, Inconel, or Mo is instantaneously energized and heated. In this method, as a problem of the material used, oxidation at a high temperature, seizure of a lead, deformation, and the like occur remarkably. Therefore, it is necessary to periodically clean the tip. The other one is a tool with a steady heating method, in which a polished diamond or ruby single crystal is embedded at the tip of a shank with a built-in cartridge heater. The one using a crystal has a long lifetime. Here, diamond is preferably used because remarkable thermal deterioration does not occur in the atmosphere up to about 900 ° C., and wettability with Au—Sn is poor and no reaction occurs. The surface state of the polished diamond single crystal is as good as 0.1 μm or less in Rmax and is high in hardness, so that the surface state hardly changes. Due to this characteristic,
Au-Sn melted at the time of press bonding is less likely to remain on the diamond surface. Furthermore, since diamond has the highest heat conducting portion among the existing materials, if it is used for a tool material of a steady heating method, the tool tip can be set to a desired position without excessively heating the heater, that is, without excessively heating the shank. It has the advantage that it can be heated to 500-600 ° C. However, a diamond single crystal is expensive, and it is a reality that a relatively inexpensive synthetic product having a size of several mm or more has not yet been obtained. In the future, it is considered that the process of thermocompression bonding a large number of terminals at once will increase, but in that case, a material shape of 10 mm or more is required. Therefore, it is an object of the present invention to provide a bonding tool having the above required characteristics. [Means for Solving the Problems] That is, a bonding tool according to the present invention includes a sintered body mainly composed of Si and Si ₃ N ₄ , a sintered body mainly composed of SiC, and a sintered body mainly composed of AlN. A substrate having a thickness of 0.5 to 5 mm, which is formed of a binder and / or a composite thereof, has a thickness of 5 to 3 mm by a gas phase synthesis method.
A tool coated with polycrystalline diamond having a thickness of 00 μm was used as a tool tip, and the purity of the polycrystalline diamond was such that the peak ratio (Y / X) of diamond carbon (X) to non-diamond carbon (Y) was 0 according to Raman spectroscopic analysis. 0.2 or less, and oriented in the thickness direction to the (100) plane and / or (110) plane, and the tool tip and the entire shank or a part of the joining side are made of Kovar or Invar alloy. And an alloy shank. [Operation] Hereinafter, the present invention will be described in detail along with the background of the invention. The present inventors first studied the use of a commercially available sintered diamond containing Co as a binder, which can produce a larger shape instead of a diamond single crystal, as a leading material of a tool for a steady heating method. After brazing to a stainless steel shank using a silver brazing material having a melting point of 750 ° C., the tip surface was polished and the shank was worked to produce a tool. The polished sintered diamond had a good surface condition with Rmax = 0.06 μm. When the tip of the tool was constantly heated to 570 ° C and the thermocompression bonding between the IC chip and the Au-Sn wire was repeated, irregularities gradually appeared on the polished tip surface, and the amount of the deposited Au-Sn alloy adhered. Was observed. The deformation of the tip surface is caused by the fact that the diamond sintered body is constantly heated,
It is considered that microcracks were generated based on the difference in thermal expansion between diamond and diamond, and the wear resistance was reduced due to the progress of graphitization of diamond. From the above, the commercially available sintered diamond using Co as a binder cannot satisfy the required characteristics of this kind of tool, a brazing filler metal having a higher melting point can be used, and it can withstand a long-time heating use. It turned out that a material with high heat resistance was necessary. A diamond sintered body having high heat resistance is disclosed in, for example, Japanese Patent Application Laid-Open No. 53-114589. However, since the sintered body is obtained by extracting an iron group metal binding material by an acid treatment, pores are not formed. The Au—Sn alloy is present and the surface state does not become good even after polishing, so that the Au—Sn alloy easily adheres during use. A heat-resistant diamond sintered body having no voids is disclosed in JP-A-59-161268 and JP-A-61-33865.
Since it is made of Si, SiC, an alloy of Si, or the like, and has a lower hardness than diamond, the surface state after polishing is still not sufficiently satisfactory. It is considered that a sintered body made of diamond alone without a binder is most desirable in all of heat resistance, hardness, thermal conductivity, and surface roughness. As an attempt, sintering only diamond powder under ultra-high pressure has been performed, but since the diamond particles themselves are not easily deformed, pressure is not transmitted to the gaps between the particles, so graphitization occurs, At present, only a diamond-graphite composite can be obtained. On the other hand, recently, a technique for producing a polycrystalline diamond containing no binder by a vapor phase synthesis method has made remarkable progress, and it has been considered effective to apply this technique. It is known that a diamond thin film is deposited on a substrate such as a cemented carbide or W by a gas phase synthesis method and is used as a cutting tool. Due to the low value, peeling and cracking of the coating film occurred during use, and good results were not obtained. The present inventors have intensively studied to obtain a more excellent bonding tool material, and further studied a tool configuration for utilizing this excellent material as a tool tip of a bonding tool. It was done. That is, a sintered body mainly composed of Si, Si ₃ N ₄ , a sintered body mainly composed of SiC, a sintered body mainly composed of AlN, and / or a composite of these having a thickness of 0
. A tool having a base of 5 to 5 mm coated with polycrystalline diamond having a thickness of 5 to 300 μm deposited by a vapor phase synthesis method is used as a tool tip. The diamond carbon (Y) has a peak ratio (Y / X) of 0.2 or less, and is oriented in the thickness direction on the (100) plane and / or the (110) plane; It has been found that an excellent bonding tool is obtained by being characterized in that the shank is entirely or partially joined to an alloy shank made of Kovar or an Invar alloy. In the practice of the present invention, in order to obtain an excellent bonding tool material, it is necessary to select a substrate having a coefficient of thermal expansion close to that of diamond and good adhesion to the coated diamond layer. When used as a tool manufacturing process and a tool, the temperature is 500 to 1000 ° C.
Since it is exposed to such a high temperature, it is necessary to have high heat resistance.
The present inventors have found that a sintered body mainly composed of Si, Si ₃ N ₄ , a sintered body mainly composed of SiC, and a sintered body mainly composed of AlN are effective as having these characteristics. I found something. After forming these substrates into required shapes, diamond is coated by a vapor phase synthesis method. The thickness of the base is selected in the range of 0.5 to 5 mm depending on the strength of the base material and the linear expansion coefficient of the shank material. As a means of the gas phase synthesis, any known method is possible, and a method of causing decomposition and excitation of the source gas using thermionic emission or plasma discharge, a film forming method using a combustion flame, and the like are effective. . As the raw material gas, for example, it is common to use a mixed gas containing, as main components, hydrocarbons such as methane, ethane, and propane; alcohols such as methanol and ethanol; organic carbon compounds such as esters; and hydrogen as main components. However, in addition to these, an inert gas such as argon, oxygen, carbon monoxide, water and the like may be contained in the raw material as long as the carbon synthesis reaction and its characteristics are not impaired. The coating thickness is preferably 5 to 300 μm. This is because if the film thickness is less than 5 μm, cracks tend to occur during polishing of the coated surface or during use as a tool. Further, in the current technology, it is not preferable to make the film thickness thicker than 300 μm because the deposition rate is low and it takes time, that is, costs. Also, in consideration of the fact that the upper surface of the coated polycrystalline diamond needs to be polished at the time of producing the tool, the (100) plane and / or (110) is preferably used in order to facilitate the workability. ) It is effective to synthesize so as to be oriented on the plane. The (111) plane has high hardness and poor workability. Further, for the same reason, it is desirable to synthesize the polycrystalline diamond so that the particle diameter of the upper surface of the coated polycrystalline diamond is 100 μm or less. Further, it is important for the purity of the polycrystalline diamond to be coated that the peak ratio (Y / X) of diamond carbon (X) to non-diamond carbon (Y) by Raman spectroscopy be 0.2 or less. If the purity is lower than this, the non-diamond carbon contained will increase, and when heated in the atmosphere when the tool is used, this non-diamond carbon will be selectively oxidized, reducing the surface roughness of the tool tip. Is not preferred. The tool material obtained by the above method can be further polished on the surface coated with diamond, and the surface state can be reduced to Rmax 0.05 μm or less, which is equivalent to that of single crystal diamond. The surface-polished tool material exhibits its performance as a bonding tool material by being joined to a tool base material by means such as brazing. As a joining method, a method using a brazing material having a melting point of 600 ° C. or more, and
A method of thermocompression bonding using gold is effective. In the former brazing method, as the brazing material, the periodic table Nos. IVa, Va, VIa, VIIa are used.
A method using an alloy containing 1 to 40% by weight of at least one kind of group element and the balance consisting of at least one kind of group VIII of the periodic table, Cu, Ag, Au, B, In, and Sn; A metal or alloy composed of at least one element from group IVa, Va, VIa, and VIIa of the periodic table, or a thin film composed of a compound of these elements, and a thin film composed of a compound of these elements, group VIII, Cu, Ag , And Au are coated in this order, and the tool tip can be joined to the shank by a brazing material having a melting point of 600 ° C. or more through the coating layer. Specific brazing materials usable in the method include Ag-Cu-Ti alloy, Ag-
Cu-In-Ti alloy, Cu-Ni-Zr alloy, Cu-Ni-Mn alloy, Au-
There is a Ni-Cr alloy or the like. In addition, in the method, for example, a thickness of several μm
It is effective to coat the following thin film Ti / Ni in this order, and then braze in an air or vacuum using an Ag-Cu alloy-based brazing material. By these methods, metals, alloys or compounds consisting of elements of Groups IVa, Va, VIa and VIIa of the Periodic Table generate carbides by reacting with polycrystalline diamond and have an effect of improving brazing strength. is there. In the latter method of gold crimping, the tool tip and / or the shank is formed on the joining surface from a metal or alloy composed of at least one element from Group IVa, Va, VIa, and VIIa of the periodic table, or a compound of these elements. A thin film of a metal or an alloy comprising at least one of Pt, Pd, W, Mo, Ta, and Ni as a diffusion preventing layer, and the diffusion preventing layer is coated on the outside. Is important to obtain high bonding strength. Kovar and Invar alloy correspond to the shank material. Further, if necessary, a method of interposing a soft metal such as Cu or Ni as a thermal stress relaxation layer in a part of the shank joint side is also effective. There are roughly three types of tool configurations using these shank materials.
The figure shows the conceptual diagram. That is, FIG. 1 shows the case where the above-mentioned material is used for the entire shank, and FIG. 2 shows the case where only the part (the shank (A)) near the tool tip is used. The configuration shown in FIG. 2 is particularly effective for a material having a high material cost or difficult to process. FIG. 3 shows that the above metal is interposed as a thermal stress relaxation layer between the shank main body and the tip of the tool. The soft metal is plastically deformed, thereby relaxing the thermal stress and joining strength. Can be prevented from decreasing. In any of the above configurations, the bonding strength shows a stable value of 10 kg / mm ² or more, and can be used as a bonding tool. Hereinafter, specific examples will be described. EXAMPLES Example 1 A substrate made of a SiC sintered body having a side of 15 mm and a thickness of 2 mm was fixed on a support made of quartz glass by a microwave plasma CVD method, and diamond was coated. The conditions were as follows, and a polycrystalline diamond having a thickness of 50 μm could be coated in 10 hours. Raw material gas (flow _{rate): H 2 200cc / min,} CH 4 4cc / min, Ar 50cc / min, pressure: 100 Torr microwave generator output: the particle size of the polycrystalline diamond is 800W coating layer is about 15 [mu] m, the surface roughness Is Rmax
Was 8.5 μm. When Mo was used as a substrate and treated under the same conditions,
Polycrystalline diamond having a film thickness of 45 μm, a particle diameter of 20 μm, and a surface roughness of Rmax of 10.5 μm could be coated. Each of these polycrystalline diamonds has a thickness direction (110
) Plane orientation. In addition, according to Raman spectroscopy, these polycrystalline diamonds had a peak ratio (Y / X) of diamond carbon (X) to non-diamond carbon (Y) of 0.05. These coated sintered bodies are polished with a diamond electrodeposition whetstone of mesh size □ 200.
The coated surface was polished. As a result, when the substrate was made of Mo, the film cracked during polishing, and the film was partially peeled off. However, when the substrate was made of a SiC sintered body, the Rmax was 0.03 μm without peeling. A good polished surface condition comparable to that of single crystal diamond was obtained. The polished surface was brazed to a Kovar shank with an Ag-Cu alloy brazing material at 850 ° C. in vacuum using a surface opposite to the polished surface as a brazing surface. As a pretreatment for brazing, the surface of the SiC sintered body to be brazed was preliminarily coated with Ti and Ni in a thickness of 2 μm by PVD. A bonded tool was produced by further polishing and finishing the joined body. When a durability test of this tool was carried out by mounting it on a bonding apparatus, it was able to withstand one million times of use similarly to a tool manufactured using a 3 mm square single crystal diamond. It has been clarified that the productivity can be increased about 5 times by increasing the dimension of the bonding surface. Example 2 By the same manufacturing method as in Example 1, the bonding tool materials shown in Table 1 were produced. Table 1 also shows materials other than the present invention for comparison. Coated surfaces of these materials and, as a comparison, commercially available sintered diamond containing 10% by volume of Co were polished. As a result, the thickness of the coating film was smaller than 5 μm.
Cracked during polishing. Further, the coating films of No. B and No. I using Mo and Ta respectively peeled off during polishing. Furthermore, A oriented to the (111) plane and No. H having a coarse upper surface particle diameter of the coated polycrystalline diamond of 150 μm were poor in workability and could not be entirely polished. Table 2 shows the surface roughness after polishing other than these. These materials were processed and brazed to a shank made of Invar alloy at 900 ° C. in vacuum using a brazing material having a weight ratio of Cu, Ni and Mn, respectively, of 7: 1: 2. . After bonding, processing was performed to produce a bonding tool having a tip angle of 10 mm. Table 2 also shows the results of the durability tests performed on these tools. The conditions of use were such that the tip temperature was 520 ° C., the pressure bonding time was 2 seconds, and ICs having 1000 pins were repeatedly bonded. As is clear from this table, the surface roughness of No. F whose non-diamond carbon content was higher than the standard of the present invention was observed by Raman spectroscopy, but the tool using the material of the present invention was not used. No significant deterioration was observed. Example 3 A straight tungsten filament having a diameter of 0.5 mm and a length of 20 mm was used as a thermionic emitting material, and a raw material gas composed of hydrogen, a carbon source and water vapor was decomposed and excited for 20 hours to form a 3 mm-thick SiC substrate. The polycrystalline diamond shown in Table 3 was synthesized. Table 3 shows the properties of the obtained polycrystalline diamond. Tools were manufactured with the configuration shown in Table 4 at the tip of these tools. Each of these endured 1 million times as a bonding tool. Table 4 shows the results of measuring the bonding strength (shear strength) using the used tool. As a comparison, SUS30 outside the present invention
4, when directly brazed, the value was as low as ² kg / mm ^2.
, P, and Q all show stable high bonding strength. [Effects of the Invention] As described above, according to the present invention, it is possible to obtain a bonding tool with further improved heat resistance, strength, and wear resistance.

[Brief description of the drawings]   1, 2 and 3 show the structure of the bonding tool of the present invention.   (number) 1: polycrystalline diamond 2: substrate 3: Brazing material or gold 4: Shank (A) 5: Shank (B) 6: Thermal stress relaxation layer 7: Shank (A)

Claims (1)

Claims: 1. A sintered body mainly composed of Si, Si ₃ N ₄ , a sintered body mainly composed of SiC, a sintered body mainly composed of AlN, and / or Composite thickness 0
. Polycrystalline diamond deposited on a 5 to 5 mm substrate by vapor phase synthesis with a thickness of 5 to 300 μm
The tip of the tool is coated with a diamond, and the purity of the polycrystalline diamond is
Peak ratio of diamond carbon (X) and non-diamond carbon (Y) by optical analysis (
(Y / X) is 0.2 or less, and (100) plane and / or (
110) Oriented to the plane, the tip of the tool and all or part of the shank
A bonding tool characterized by being joined to a shank made of Kovar or an alloy made of an Invar alloy . 2. As a shank material, Cu or Ni is partially relaxed on the joint side by thermal stress.
The bonding tool according to claim 1, wherein the bonding tool is interposed as a layer. 3. The joining between the tool tip and the shank is made of gold formed by thermocompression bonding.