JP2005211976A - Tool for manufacturing diamond film coated semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tool for manufacturing a diamond film coated semiconductor which is a tool for working a lead wire of a semiconductor device etc., and which can suppress the damage due to the static electricity of the semiconductor device during working by preventing the electrostatic charge of the tool. <P>SOLUTION: The tool for manufacturing the diamond film coated semiconductor is coated with a diamond film on a base material surface. The base material is a cemented carbide or cermet. The diamond film is a conductive diamond film containing boron and hydrogen. The average surface roughness of the conductive diamond film is ≤0.2 μm in Ra. The average grain size of the diamond crystal particles on the surface of the conductive diamond film is ≤1.5 μm. The electric resistance of the outermost layer is preferably ≤1,000 Ωcm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a diamond film-coated semiconductor manufacturing tool used in fields where welding resistance and high processing accuracy are required, such as semiconductor manufacturing.

  Semiconductor devices incorporated in various electronic devices such as computers and control devices are manufactured through a molding process, a trimming process, and a forming process. The molding process is a resin sealing process for protecting the chip from the outside, and the trimming process is a process for individually taking out the package from the molded lead frame. The forming process is a process of cutting and molding a package lead wire or the like.

  The diamond film-coated semiconductor manufacturing tool used in these steps needs to have high resistance to welding and peeling. This is because the processing target of the diamond film-coated semiconductor manufacturing tool is a mold resin or a lead wire. The mold resin is not only easily welded to the diamond film-coated semiconductor manufacturing tool, but the silica and mica contained in the mold resin severely wear the tool. Silica and mica are added to increase the thermal conductivity of the mold resin and to lower the thermal expansion coefficient.

  When processing a lead wire, the lead wire is subjected to solder plating, and soldering is likely to occur. In recent years, the use of lead-free solder has become popular, and palladium contained therein wears the tool. In order to cut such lead wires, it is patented that the base material is coated with a high-hardness diamond thin film, the friction force generated between the tie bar cut punch and the tie bar is reduced, and the wear of the tie bar cut punch is prevented. It is described in Reference 1. Further, Patent Document 2 describes that an insulating diamond is used as a coating film for a lead bending punch. In the present invention, as a countermeasure against static electricity of the bending punch, it has been proposed to divide the diamond coating portion and the main body portion, to configure the main body portion with a conductor, and to integrally form the two.

JP-A-4-56258 JP 7-211842 A

  In recent years, the breakdown voltage of semiconductor devices has been lowered due to electrostatic discharge due to the reduction in the size of single elements and the reduction in thickness of oxide films. Protection circuits have been manufactured to protect internal circuits from static electricity, but this alone is not sufficient, and countermeasures against static electricity are taken in the mounting process.

  The diamond film-coated semiconductor manufacturing tool described in Patent Document 1 or the like is a tool that utilizes the welding resistance and wear resistance of a diamond film. The diamond film is usually an insulator and is charged with static electricity, which can destroy the package when the static electricity is discharged. For this reason, the measures described in Patent Document 2 and the like have been taken, but it is not sufficient, and when the product is processed, the chip or the like may be destroyed by discharging to a circuit in the package. That is, when the diamond film-coated semiconductor manufacturing tool charged with static electricity comes into contact with the product, electrostatic discharge occurs and the product is destroyed.

  On the other hand, since the miniaturization and high integration of packages and the like are advanced at the same time, the tools and parts used in these manufactures have particularly strict dimensional accuracy. For example, dimensional accuracy within ± 1 μm is required.

  In view of the above, an object of the present invention is to provide a diamond film-coated semiconductor manufacturing tool that is free from electrostatic breakdown due to static electricity, is excellent in welding resistance and peeling resistance, and has high dimensional accuracy.

  The present invention intends to remove static electricity from a package being processed by adding boron to form a conductive diamond film while maintaining the excellent performance of the diamond film.

  The present invention relates to a diamond film-coated semiconductor manufacturing tool in which a substrate surface is coated with a diamond film, the substrate is a cemented carbide or cermet, and the diamond film is a conductive diamond film containing boron and hydrogen. Provided is a diamond film-coated semiconductor manufacturing tool in which the average surface roughness of a conductive diamond film is 0.2 μm or less in terms of Ra, and the average particle diameter of crystal grains on the surface of the conductive diamond film is 1.5 μm or less. It is.

  In the present invention, a cemented carbide or cermet having both hardness and strength used for a cutting tool or the like is used for the base material.

  In addition, boron is contained in the diamond film to make the film conductive. By forming this conductive diamond film on a base material, the film and the base material can be electrically connected, and the charge charged on the tool can be eliminated.

  Moreover, by setting the average surface roughness of the diamond film surface to 0.2 μm or less in Ra, welding to a tool such as solder can be prevented, and the processing accuracy of the lead wire can be kept high. The average surface roughness is measured with an AFM (atomic force microscope). This is because a general stylus type surface roughness meter has an average surface roughness that is so small that it cannot be measured.

  Furthermore, it is necessary that the average particle size of the crystal particles on the diamond film surface be 1.5 μm or less. By setting this range, high welding resistance can be obtained. This particle size is measured with a scanning electron microscope.

  The electric resistance of the surface of the conductive diamond film is desirably 1000 Ω · cm or less. In order to efficiently remove static electricity generated during semiconductor manufacturing, the conductive film in the above range is desirable. This electrical resistance may be measured between two points on the surface of the film, for example, by preparing a tool coated with a diamond film.

The boron content of the conductive diamond film is preferably 1.0 × 10 ^{18 to} 5.0 × 10 ²² atoms / cm ³ (number of boron atoms per unit volume). This value is a preferable boron content in order to provide conductivity for sufficiently eliminating static electricity. Within this range, it is easy to control a trace amount of boron during production, and a high adhesion of the diamond film can be obtained. In the present invention, the content of boron or hydrogen described later is measured in the direction of the thickness of the sample by SIMS (Secondary Ion Mass Spectroscopy) analysis. A more preferable range of the boron content is 5.0 × 10 ^{19 to} 1.5 × 10 ²¹ atoms / cm ³ (the number of boron atoms per unit volume).

The amount of hydrogen contained in the conductive diamond film is desirably 8.0 × 10 ^{20 to} 3.0 × 10 ²² atoms / cm ³ (number of hydrogen atoms per unit volume). A more preferable range is 1.0 × 10 ^{21 to} 3.0 × 10 ²² atoms / cm ³ . The hydrogen content in the diamond film is closely related to the adhesion between the substrate and the diamond film. As the hydrogen content increases, the thermal expansion coefficient of the diamond film increases and the difference in thermal expansion coefficient from the substrate can be reduced. As a result, the peel resistance between the substrate and the film can be increased. By containing hydrogen in the above range, a diamond film with a low crystallinity maintaining a fine structure can be obtained, and the thermal expansion coefficient can be increased to improve the peel resistance from the substrate.

  Further, it is desirable that this conductive diamond film contains substantially the same amount of hydrogen in the thickness direction. By making the hydrogen content in the conductive diamond film substantially uniform, uneven distribution of residual stress can be suppressed, and a diamond film having high adhesion to the substrate can be obtained.

  As for the cross-sectional structure of the conductive diamond film, it is desirable that fine diamonds are elongated and arranged in the growth direction of the diamond film, and the minor axis thereof is 0.001 μm or more and 0.1 μm or less. Since the cross-section has a fine structure, the strength of the diamond film itself can be improved, and cracking and progress due to processing can be prevented. Further, with such a structure, diamond crystal growth can be suppressed, and a diamond film having a small surface roughness can be formed. As a result, a highly accurate tool surface can be obtained without polishing. In addition, by having a high hydrogen content in the microstructure, the thermal expansion coefficient of the film can be increased to the limit, which is the most desirable state from the viewpoint of film adhesion.

  It is desirable that the aspect ratio of fine diamond in the cross-sectional structure of the conductive diamond film is 2 or more and 20 or less. By doing so, the strength of the diamond film is improved and the surface roughness is reduced.

  It is desirable that the conductive diamond film is a diamond film that has been vapor-phase synthesized. Since the surface roughness of the as-synthesized diamond film is small and the dimensional accuracy of the diamond film-coated tool is high, it can be used as it is without being polished. In the method of adjusting the thickness of the diamond film, the film thickness can be measured during the film formation, the film thickness to be added can be determined, and the subsequent growth time can be determined. At that time, a boundary layer is formed at the thickness where the formation of the diamond film is stopped, but it can be said to be substantially one film.

  At this time, since the surface roughness of the base material affects the surface roughness of the conductive diamond film, it is desirable to use a base material suitable for the purpose. In order to obtain a tool having a small surface roughness, a method of using a ground substrate and a ground substrate having a relatively large surface roughness can be considered.

  The diamond film-coated semiconductor manufacturing tool of the present invention is coated with a thin conductive diamond film. Therefore, the tool is not charged, and even if the package of the semiconductor device is charged, the static electricity of the package is removed by contact with the tool, and the discharge breakdown of the package can be prevented. Moreover, the conductive diamond film can improve the welding resistance by specifying the average surface roughness and the diamond crystal grain size.

  As an example of a semiconductor manufacturing tool, the tool of the present invention will be described taking a lead frame bending and cutting tool as an example. FIG. 1 shows an example of processing the outer lead 6 covered with the solder 7 of the package 5 by using the bending die 8, the cut bend-punch 9 and the cut die 10. The bending die substrate 2, the cut / bend-punch substrate 3 and the cut die substrate 4 are each made of a cemented carbide, and the diamond film 1 is formed on the surface thereof. The diamond film 1 is formed on at least a part that slides on each other and a part that acts on processing.

  The semiconductor manufacturing tool in FIG. 1 has a configuration in which an outer lead is pushed and bent by a bending die 8 and a cut / bend-punch 9 and then cut by a cut die 10. In the bending die 8 of FIG. 1, diamond is coated from the protruding portion 11 in contact with the outer lead to the cutting sliding surface. FIG. 1A shows a state before processing, in which the package 5 is set on the bending die 8 and the outer lead 6 is placed on the protrusion 11. A cut bend-punch 9 is set above the bending die 8, and a cut die 10 is set beside it.

When processing, as shown in FIG. 1 (B), the cut / bend-punch 9 moves relatively in the direction of the arrow, and the outer lead 6 of the package 5 is pressed against the bending die 8, and the outer lead 6 Bend. Thereafter, as shown in FIG. 1C, the cut die 10 moves relatively in the direction of the arrow along the side surface of the bending die 8, and the outer lead 6 is cut at the corner. At this time, the right side surface of the cut bend-punch 9 serves as a cut punch.
Embodiments of the present invention will be described below.

  A tool shown in FIG. 1 for bending and cutting the outer lead of the package was produced. First, a cemented carbide of WC-8% Co was prepared as a base material for bending die 8, cut bend-punch 9 and cut die 10. Since high dimensional accuracy is required for the outer lead processing of the package, all the surfaces of these cemented carbides coated with diamond are polished with high accuracy.

  These base materials, that is, the die base material 2, the cut / bend-punch base material 3 and the cut die base material 4 were manufactured as one set, and each base material was subjected to carburizing treatment. Carburizing conditions were as follows: each substrate was set in a hot filament CVD apparatus, under a 1.5% by volume methane-hydrogen gas atmosphere, at a pressure of 15.0 kPa, and at a treatment temperature of 950 ° C. for 2 hours.

  The obtained base material was immersed in 8% nitric acid solution to remove the binder phase in the cemented carbide, and then washed and dried well. Next, ultrafine diamond was applied to the substrate. 0.02 g of polycrystalline diamond powder having a particle size of 4 to 6 nm was dispersed in 100 cc of isopropyl alcohol. The substrate was immersed in this liquid, and ultrasonic waves were applied for 10 minutes. The ultrafine diamond adhering to the substrate becomes a starting point for nucleation during diamond film formation.

  Next, a conductive diamond film having a thickness of 3 μm was produced under the conditions shown in Table 1. The film formation of the conductive diamond film was stopped when the film thickness was expected to reach 2.5 μm, the actual film thickness was measured, and the film was formed by adding the shortage. When the cross section of the diamond film was polished and etched, there was a trace that the growth was temporarily stopped.

Table 1 shows the manufacturing conditions of the conductive diamond film, and Table 2 shows the characteristics of the conductive diamond film. Sample numbers were common in Tables 1 and 2. The items in Table 1 will be described. The CH ₄ concentration indicates the amount of methane relative to hydrogen as a carrier in volume%. F temperature indicates the temperature of the filament.

  Next, the B flow rate will be described. Boron is added to make the diamond film conductive. As a method of adding boron to the diamond film, a method of supplying diborane or trimethylboron, which is usually a gas, directly to the reaction system is used. In addition, a method of bubbling argon gas or hydrogen gas to an organic solvent containing boric acid, triethyl borate, or trimethyl borate and supplying the reaction system is used. Although the method of bubbling trimethyl borate with argon gas was used this time, the same result can be obtained by any of the above methods. The B flow rate is the flow rate of Ar gas at that time in the standard state.

  The surface roughness of the conductive diamond film thus obtained, the average particle diameter of the diamond film surface, the content of boron (indicated as “B content” in Table 2), hydrogen (in Table 2, “H The content and the electrical resistance were examined and are shown in Table 2.

  The surface roughness in the table is a value of the average surface roughness Ra, and was measured with an AFM (atomic force microscope). Moreover, the average particle diameter was measured with SEM (scanning electron microscope). The electrical resistance was measured between two points on the surface of the diamond film-coated semiconductor manufacturing tool.

  The boron and hydrogen contents were measured by SIMS (Secondary Ion Mass Spectroscopy) analysis. The values listed in Table 2 are values for the surface portion of the conductive diamond film. The hydrogen content of the conductive diamond film was almost the same in the depth direction.

  As is clear from Table 2, the diamond film of sample number 1 is peeled off and is a comparative example. Sample No. 2 is a comparative example in which the average surface roughness exceeds 0.2 μm and the average particle size exceeds 1.5 μm. Further, the content of boron and hydrogen depends on various production conditions, but is related to the increase or decrease of the B flow rate or the hydrogen flow rate, which is a measure of the supply amount of each element.

  A cross section corresponding to the conductive diamond film of Sample No. 5 produced in Example 1 was observed by SEM, and FIG. 2 was obtained. The diamond film was cut together with the base material, the surface was polished, and then etched and observed in hydrogen plasma. It can be seen that fine diamonds are elongated in the direction of diamond growth, and the minor axis is mostly about 0.1 to 0.01 μm. It can also be seen that most of the aspect ratio is in the range of 2-20.

  Using these uncoated punches and dies, bending and cutting of the lead frame coated with lead-free solder was performed in the process shown in FIG. The maximum number of machining was 1 million. The evaluation items are shown in Table 3 by evaluating whether solder adheres to the diamond film and whether there is peeling of the film at 100,000 times, 500,000 times and 1 million times. The samples used in Example 1 were used, and the sample numbers in Table 3 are the same as those in Tables 1 and 2.

  The welding resistance was determined to be “X” because the size of the weld was slightly flat and welded to a size of about 10 μm or less, and if it exceeded that, the yield deteriorated. The peel resistance was evaluated by the size and number of peels, but the case where there was a peel of a size of about 5 μm or less was a single circle. Good semiconductor manufacturing tools were able to withstand 1 million uses. The results are shown in Table 3.

  Sample No. 1 cannot be used because it is peeled off. In Sample No. 2, the temperature of the base material during production was as high as 980 ° C., the surface roughness was large, and the welding resistance was poor. Sample Nos. 3 to 7 were able to obtain good results with respect to welding resistance and peeling resistance. Samples of sample number 8 and later could be used more than 500,000 times, which was within a practical range. Sample No. 8 is slightly inferior in conductivity, so there is a possibility that LSI or the like will be damaged by discharge depending on conditions.

  Since the tool of the present invention can prevent electrification, it is expected to be effectively used in the field of processing products such as semiconductor devices that need to avoid dielectric breakdown due to static electricity. In particular, it has high adhesion and can be used for cut dies and cut punches.

FIG. 1A is a schematic diagram showing a state in which a lead frame is bent and cut using the diamond film-coated semiconductor manufacturing tool of the present invention. FIG. 1A shows the arrangement of tool components, and FIG. B) shows a state of bending, and FIG. 1C shows a state of cutting. It is a cross-sectional microscope picture of the electroconductive diamond film obtained by this invention.

Explanation of symbols

1 Diamond film
2 Die base material
3 Cut bend-punch substrate
4 Cut die substrate
5 packages
6 Outer lead
7 Solder
8 Bending die
9 Cut bend-punch
10 Cut die
11 Protrusion

Claims (7)

A diamond film-coated semiconductor manufacturing tool having a substrate surface coated with a diamond film,
The substrate is a cemented carbide or cermet,
The diamond film is a conductive diamond film containing boron and hydrogen,
The conductive diamond film has an average surface roughness Ra of 0.2 μm or less,
A diamond film-coated semiconductor manufacturing tool, wherein an average particle diameter of diamond crystal particles on the surface of the conductive diamond film is 1.5 μm or less.   2. The diamond film-coated semiconductor manufacturing tool according to claim 1, wherein an electrical resistance of a surface of the conductive diamond film is 1000 Ω · cm or less. 3. The boron content in the conductive diamond film is 1.0 × 10 ^{18 to} 5.0 × 10 ²² atoms / cm ³ (the number of boron atoms per unit volume), The diamond film-coated semiconductor manufacturing tool described in 1. The conductive diamond film contains approximately the same amount of hydrogen in the thickness direction, and the hydrogen content is 8.0 × 10 ^{20 to} 3.0 × 10 ²² atoms / cm ³ (number of hydrogen atoms per unit volume) The diamond film-coated semiconductor manufacturing tool according to any one of claims 1 to 3, wherein   5. The cross-sectional structure of the conductive diamond film is characterized in that fine diamonds are elongated and arranged in the growth direction of the diamond film, and the minor axis thereof is 0.001 μm or more and 0.1 μm or less. The diamond film-coated semiconductor manufacturing tool as described.   6. The diamond film-coated semiconductor manufacturing tool according to claim 5, wherein an aspect ratio of fine diamond in a cross-sectional structure of the conductive diamond film is 2 or more and 20 or less.   7. The diamond film-covered semiconductor manufacturing tool according to claim 1, wherein the conductive diamond film is a diamond film that has been vapor-phase synthesized.

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