JP5270467B2 - Cu bonding wire - Google Patents

Description

  The present invention relates to a Cu bonding wire used for connecting an electrode on a semiconductor element and an external electrode.

In general, the diameter of a bonding wire used for connection between an electrode of a semiconductor element and an external electrode is as very small as 15 to 75 μm. Also, from the viewpoint of chemical stability and ease of handling in the atmosphere, Au wire has been conventionally used. Has been used.
However, since the Au wire used for the bonding wire is a high-purity Au wire, it is very expensive, and the use of a cheaper Cu bonding wire is required to meet the demand for lowering the cost of semiconductor elements. It is desired.

  Also, Al or Al alloy is often used as the electrode material of the semiconductor element. However, an Au bonding wire or Cu bonding wire is bonded to the surface of the Al or Al alloy electrode, and the electrode is exposed to a high temperature environment. -When evaluating the bonding reliability of the bonding wire, it is known that the deterioration of the reliability of the bonding wire made of Cu is slower than the case of using the bonding wire made of Au. In order to improve the reliability of bonding with materials, there is an increasing expectation for Cu bonding wires. The reason for this reliability evaluation result is that the diffusion rate of Al atoms into Cu is much slower than the diffusion rate of Al atoms into Au, and the diffusion rate of Cu atoms into Al is also Au atoms. This is presumed to be slower than the diffusion rate.

  However, when the material used as the bonding wire is changed from Au to Cu, the greatest adverse effect is that the incidence of pad damage is higher when the Cu bonding wire is used than when the Au bonding wire is used. There is a problem. This is because the hardness of Cu is higher than that of Au.

In order to avoid this problem, it is necessary to reduce the hardness of the ball formed at the tip of the Cu bonding wire during ball bonding. For this purpose, oxygen-free copper (hereinafter referred to as oxygen-free copper) having a purity of 99.99% to 99.9999%, which is readily available industrially, and having an oxygen concentration of less than 10 ppm by oxygen concentration analysis by an inert gas melting method. (Denoted copper) is commonly used.
Patent Document 1 discloses a high-purity copper material having a purity of 99.999% or more obtained by refining electrolytic copper obtained by electrolytic refining several times and then purifying high-purity electrolytic copper by the zone melting method, That is, a method of reducing the incidence of pad damage using high-purity oxygen-free copper has been proposed.

In this way, the use of oxygen-free copper and the high purity of copper realizes softening of the formed ball, contributing to the significant reduction of damage to the aluminum electrode on the semiconductor element, so-called pad damage, for power ICs and transistors. Have been used for applications as copper bonding wires.
On the other hand, evaluations for the application of Cu bonding wires to semiconductor packages such as PBGA (Plastic Ball Grid Array package) or QFN (Quad Flat Non-lead package), whose production volume has increased rapidly in recent years, have started. Yes.

However, when PCT (Pressure Cooker Test), which is a high-temperature, high-pressure reliability test, was performed on these semiconductor packages, the ball joint was corroded and an electrical insulation was revealed.
More specifically, it was considered that the ball joint was corroded by Cl and the joint interface deteriorated. In other words, semiconductor packages such as PBGA and QFN are resin-sealed only on one side, and moisture can easily enter the package from the gap between the lead and the resin, so Al (electrode) is considered to corrode due to the presence of Cl. It was.

  For this reason, elemental qualitative analysis was performed by EPMA (Electron Probe X-ray Microanalyzer) on the Al electrode surface and the back surface of the ball where the ball was peeled off due to corrosion, and Cl was detected from any sample. From this, it has been found that Cl present in the Cu bonding wire is eluted from the Cu bonding wire due to the reaction with moisture, thereby corroding the ball joint and generating electrical insulation. Glow discharge mass spectrometry A Cu bonding wire made of oxygen-free copper having a chlorine content of 1 mass ppm or less detected by the method was found and disclosed in Patent Document 2.

  Although the occurrence of electrical insulation could be reduced by adopting the Cu bonding wire of Patent Document 2, ultrafine wires with a diameter (diameter) of 25 μm or 20 μm were used in response to recent high density and high integration. In such a case, a sufficient effect cannot always be obtained.

  That is, it is generally required to perform wire bonding using a Cu bonding wire having a wire diameter of 25 μm and perform an HTB test (High Temperature Baking Test) on a package obtained by sealing with an epoxy resin. This is a new phenomenon in which conduction failure occurs without waiting for 1000 hours, which is the operation time.

  This is because wire bonding using a Cu bonding wire is performed by plasma discharge in a forming gas atmosphere of 5% hydrogen + 95% nitrogen to form a ball for ball bonding to the Al electrode on the semiconductor element side. This ball formation is performed by an ultra-high-speed operation of the bonding head that takes only 60 msec for wire bonding, a window clamper opening / closing operation for fixing the lead frame and the substrate, and a replacement operation of the magazine in which the lead frame and the substrate are inserted. Due to factors such as the movement of the generated air, the conductivity failure occurs.

  Also, in the opposed tube-shaped nozzle that is the mainstream in the assembly of power ICs, if the axes of both nozzles are not in a straight line, air is likely to be mixed into the forming gas flow after merging, and formed by the mixed air The surface of the ball is oxidized, oxygen is taken in between the aluminum electrode and the formed ball by ball bonding, and Cu is diffused to the Al electrode side by high temperature heating of about 150 ° C. in the HTB test. The cause is that the alloy layer is oxidized by this oxygen.

Also, when the formed ball is oxidized or the ball shape exhibits an elliptical shape extending to the bottom of the ball, the latest Low-k material (a material having a non-dielectric constant lower than SiO ₂ ) is used. It has also been found that pad damage is likely to occur in a semiconductor element in which a circuit is formed downward.

  Incidentally, there is a method of adding P in order to improve the oxidation resistance of a ball formed at the time of ball bonding. For example, there is a 3N purity Cu bonding wire to which P is added in an amount of 200 mass ppm or more. This Cu bonding wire is used for some power devices. For semiconductor elements that are not provided with wiring using a low-k material under a conventional aluminum electrode, ball bonding can be performed without pad damage using a Cu bonding wire to which P is added. However, when ball bonding is performed on a semiconductor element having an electrode structure using the latest Low-k material, the hardness of the ball formed at the time of bonding is high, and the electrode structure made of the Low-k material is damaged. There are so-called pad damages that cannot be used.

  To solve this problem, if the amount of P added is about 50 ppm, the oxidation of the ball can be suppressed, and even if it is used for ball bonding to a semiconductor device having an electrode structure using the latest Low-k material. Although it was confirmed that the pad can be used without any damage, the result of the PCT test conducted in an environment of a temperature of 125 ° C., an atmospheric pressure of 2.3 atm, and a humidity of 100% for 168 hours shows that corrosion occurs at the ball joint interface. As a result, there is a problem that poor conduction occurs.

  Furthermore, in assembling semiconductor devices, we have devised to maximize productivity from the viewpoint of cost minimum. For example, the cycle time of wire bonding is shortened, and the bonding head operates at an ultra-high speed to realize this, As a discharge condition at the time of ball formation, a large current and a short time discharge are mainly used. Further, in the semiconductor element using the latest Low-k material, a circuit is formed under the Al electrode for improving integration, and the area under the electrode is brittle and easily damaged.

  Then, air is mixed into the forming gas due to turbulent air flow due to ultra high-speed operation, the Cu ball surface is oxidized, oxygen is taken in between the Al electrode and the Cu ball, and high temperature heating of about 150 ° C. in the HTB test. For the problem that the alloy layer of Al and Cu generated by diffusion of Cu on the Al electrode side due to oxidation causes trouble, adjustment of the component composition of the Cu bonding wire, heat treatment conditions during the manufacturing process, etc. A response by adjusting is proposed.

  On the other hand, in one-side sealed packages such as PBGA and QFN, the bonding temperature is as low as 175 ° C. or lower, or the plating of the bonding part is hard palladium, so the bondability is basically poor, and the surface of the Cu bonding wire If the material oxidizes even a little, a defect that does not adhere to the stitch bonding performed after the ball bonding occurs and the bonding machine stops, or even if wire bonding is performed, sufficient bonding strength cannot be obtained. Has become prominent.

For this reason, the ball bonding reliability on the semiconductor element side is high, and the bonding reliability with the plated surface or the Pd plated surface is reduced even under the stitch bonding conditions where the external electrode side has poor bondability. There is a demand for a Cu bonding wire that is not allowed to occur.
As a method of improving the bondability of this stitch bonding, there is a method disclosed in Patent Documents 3 and 4 in which a surface of a Cu wire is coated with a noble metal with a Cu wire as a core.

  However, these methods require a process for forming a Pd film in addition to the normal bonding wire manufacturing process, but increase the manufacturing cost due to the addition of film forming equipment and additional work such as film thickness management. Is inevitable. Furthermore, in the case of noble metal film formation, if the film thickness is increased in order to increase the anti-oxidation effect on the surface of the Cu bonding wire, a concentrated layer of noble metal is formed in the vicinity of the formed ball surface. It becomes higher than the bare copper wire, and in the Al electrode structure using the latest Low-k material, there is a problem that pad damage occurs.

Furthermore, for the assembly of semiconductor devices that use Cu bonding wires, a gas atmosphere forming device for preventing oxidation and a discharge power supply device for forming balls are added to the conventional wire bonding device for Au wires. Installation and use of N ₂ gas containing 5% of H ₂ , that is, forming gas in general, increases the capital investment and running cost compared to Au bonding wires.

In addition, since H ₂ is a flammable gas, there is a disadvantage that a facility with sufficient safety considerations must be prepared, and development of a Cu bonding wire that can form a ball only with N ₂ gas is required. With a bonding wire in which the surface of the Cu wire is coated with Pd, it is possible to form a ball having a relatively good shape with only N ₂ gas by setting the coating thickness to 20 nm or more. Since a Cu—Pd alloy layer having a concentration is formed and the hardness of the alloy layer is high, the problem that pad damage is likely to occur has not been solved.

Japanese Patent Laid-Open No. 60-244054 JP 2008-153625 A Japanese Patent No. 4158828 Japanese Patent No. 4204359

In view of such a situation, the present invention can form a spherical ball in an atmosphere of only N ₂ gas, which is required for a Cu bonding wire in the assembly of a semiconductor device, and the formed ball surface hardness is determined as Pd-coated copper. It is to prevent the occurrence of pad damage by making it lower than the wire, and further to suppress the oxidation of the surface of the Cu bonding wire to prevent the occurrence of non-sticking at the time of stitch bonding, and the electric resistivity is comparable to Cu An object of the present invention is to provide a Cu bonding wire that is highly conductive and inexpensive.

The present invention is a bonding wire in which Cl is 2 mass ppm or less, Au is contained in an amount of 1 mass% or more, preferably 2 mass% or more and 7.5 mass% or less, and the balance is made of Cu and Cu inevitable impurities. Furthermore, it is a Cu bonding wire containing P in a proportion of 10 ppm to 40 ppm by mass.

  According to the Cu bonding wire of the present invention, the electrical resistivity is about 1.9 μΩcm or more and about 3.3 μΩcm or less because Au is contained in an amount of 1 to 7.5% by mass, and the purity is 99% Au bonding wire. It is a low resistance value less than or equal to the electrical resistivity.

In addition, by containing Au, the oxidation rate of the bonding wire surface is remarkably reduced, so that the non-stick failure at the time of stitch bonding can be eliminated. Further, even when the atmosphere at the time of ball formation is only N ₂ gas, the bonding wire surface and the formed ball It becomes possible to obtain a glossy ball having a very high sphericity with very little surface oxidation.

  The surface hardness of the formed ball is softer than that of the Pd-coated copper wire, and is free from occurrence of pad damage. Further, if the Cl content is 2 mass ppm or less, the reliability under high temperature and high humidity is improved, and if P is 10 mass ppm or more and 40 ppm or less, oxygen on the formed ball surface is completely removed, Even in high humidity, the amount of P leached into the moisture due to contact between the bonding wire and moisture is very small, and in the case of one-side resin-sealed package such as PBGA and QFN where moisture can easily enter when Cl is 1 ppm by mass or less However, the problem of corrosion of the ball joint due to the synergistic effect of P and Cl is completely solved.

It is a scanning electron micrograph which shows the example of Cu ball | bowl with which grain boundary oxidation is recognized. It is a scanning electron micrograph which shows the example of Cu ball in which grain boundary oxidation is not recognized. It is a scanning electron micrograph which shows the example of the Cu ball | bowl which became the ellipsoid shape extended | stretched to the bottom part. It is a scanning electron micrograph which shows the example of the Cu ball | bowl which produced the hole (nest). It is a top view of the semiconductor package used for evaluation of Cu bonding wire concerning the present invention, and an explanatory view of electrical resistance measurement.

  The composition of the copper cast wire used in the present invention is such that Au is 2 mass% to 7.5 mass%, Cl is 2 ppm or less, P is further contained in a ratio of 10 mass ppm to 40 mass ppm, and the balance is copper. It is a copper cast wire consisting of inevitable impurities. The reason for this is as follows.

(1) Au content Since Cu wire is easy to oxidize, it is shipped with the winding length set as short as 500m so that it can be used up in a short period of time, or sealed with a plastic bag to prevent moisture absorption. If the device is stopped during use or left unopened after being opened, the surface will oxidize and the bondability in stitch bonding performed in the air will deteriorate.
Therefore, if Au is contained in an amount of 1% by mass or more, the oxidation rate of the surface of the Cu wire is reduced, and deterioration of stitch bonding bondability can be avoided. Further, when Au is contained in an amount of 2% by mass or more, even when forming a ball in a 100% N ₂ gas atmosphere, formation of an oxide film on the surface of the bonding wire immediately above the molten ball is suppressed. Is stable and a ball with high roundness is formed.

On the other hand, Au is sometimes is pointed to the ball parietal is less than 2 wt% occurs, will cause the pad damage during ball bonding, also because so oxidation were slightly observed, the ball only with N ₂ gas When forming, it is desirable to set it as 2 mass% or more. On the other hand, if it exceeds 7.5% by mass, the electrical resistivity exceeds the value of about 99% Au bonding wire with a purity of 99%. Therefore, the electrical resistivity is superior to Au bonding wire, which is an advantage of Cu bonding wire. I can't.
Furthermore, there is a method of adding Pt instead of adding Au, but since the surface hardness (Hv) of the ball exceeds 70, pad damage cannot be avoided, and the electrical resistivity is higher than when Au is added. Therefore, it is preferable to add Au.

(2) Cl content The reason for suppressing the Cl content to 2 mass ppm or less is to suppress the amount of Cl that oozes out to the bonding interface between the Cu ball and Al after wire bonding, and to prevent corrosion by Cl at the bonding interface. It is for suppressing. When Cl exudes, the atmosphere at the bonding interface becomes acidic and promotes the progress of corrosion of Al. Therefore, the smaller the amount of Cl, the better. However, the purpose is achieved by setting it to 2 ppm or less.

(3) P content P is added to prevent surface oxidation of the Cu ball when oxygen is adsorbed on the bonding wire surface or when a slight amount of oxygen remains in the bonding wire. If the P content is less than 10 mass ppm, the surface oxidation of the Cu balls cannot be prevented when oxygen is mixed in the ball forming atmosphere. Also, if the P content is high, P is oozed out of the bonding wire under high humidity, and the atmosphere at the bonding interface is shifted to the acidic side, which is not preferable.
In addition, in the present invention, even in one-side resin-encapsulated packages such as PBGA and QFN that easily enter moisture, the Cl content is reduced to 1 ppm or less, thereby causing a corrosion problem of the ball joint due to the synergistic effect of P and Cl. It will be resolved.

Hereinafter, the Cu bonding wire according to the present invention will be described.
Table 1 shows the component composition of the bonding wire for evaluation including the Cu bonding wire of the present invention. The amount of Au, Cl, and P contained in this bonding wire were determined by inserting a 25 μm diameter wire sample into an aluminum cap and flattening it using a 20-t press, and measuring it in the apparatus before measurement. Preliminary discharge was performed for about 1 hour, the surface of the sample was removed about several microns, and the removed surface was measured by glow discharge mass spectrometry.

Sample No. of the bonding wire for evaluation shown in Table 1 The production methods 1 to 14 are shown below.
First, sample no. In No. 1-12, high-purity electrolytic copper with a Cu purity of 99.995% or higher is placed in a high-purity carbon crucible with a purity of 99.99% or higher in a vacuum melting continuous casting furnace, and the degree of vacuum in the melting chamber is 1 × 10 ^−4. High-frequency melting is performed by holding at Pa or lower, and after sufficiently degassing at a molten metal temperature of 1150 ° C. or higher and a holding time of 10 minutes or longer, Au or Au and P weighed so as to have a predetermined content are put in the crucible. The melted chamber was returned to atmospheric pressure with an inert gas and cast into a diameter of 8 mm by continuous casting to obtain an oxygen-free copper cast wire.

Next, this oxygen-free copper cast wire is reduced to a diameter of 1 mm using a wire drawing die, and is divided into a case where acid cleaning is not performed and a case where it is not performed. Subsequently, the diameter is reduced to 25 μm and 5% H ₂ +95. Annealing is performed at a temperature at which the elongation becomes 11% in a forming gas atmosphere of% N ₂ . 1 to 12 Cu bonding wires were produced.
For cleaning, sample no. No. 5 was washed with hydrochloric acid at a temperature of about 60 ° C. after washing with hydrochloric acid at a diameter of 1 mm. 8 and sample no. No. 11 was washed thoroughly with tap water after hydrochloric acid washing with a diameter of 1 mm.

Sample No. No. 13, after melting and casting only high-purity electrolytic copper with a Cu purity of 99.995% or more, at a diameter of 1 mm, alkaline degreasing, water washing, electrolytic degreasing, water washing, acid activity, water washing, Pd strike plating, water washing, Pd plating, A Pd thin film is formed by sequentially performing washing with water and then with hot water, and after that, after reducing the diameter to 25 μm, annealing is performed at a temperature at which the elongation becomes 11% in a forming gas atmosphere of 5% H ₂ + 95% N _2. Pd-coated Cu copper bonding wire. The Pd plating thickness was adjusted to 80 nm when the wire was reduced to a diameter of 25 μm.

Furthermore, sample no. 14 is Sample No. As in 1 to 12, using a vacuum melting continuous casting furnace, high purity electrolytic copper with a Cu purity of 99.995% or higher is placed in a high purity carbon crucible with a purity of 99.99% or higher, and the melting chamber has a degree of vacuum of 1 After high-frequency melting while maintaining at ^10-4 Pa or less, and sufficiently degassing at a molten metal temperature of 1150 ° C or higher and a holding time of 10 minutes or longer, P weighed to have a predetermined content is an inert gas. The oxygen-free copper cast wire that was cast to a diameter of 8 mm by continuous casting was reduced to a diameter of 1 mm using a wire drawing die, and was not subjected to acid cleaning in the middle, and subsequently reduced to a diameter of 25 μm. A Cu bonding wire was manufactured by annealing at a temperature of 11% elongation in a forming gas atmosphere of 5% H ₂ + 95% N ₂ .

  Characteristics were evaluated using the samples shown in Table 1. 1 to 4 are scanning electron micrographs showing representative examples of samples at the time of evaluation.

[Bonding wire characteristics]
A: Presence / absence of oxide film during ball formation 5% H ₂ +95 used for normal Cu wire bonding to make the ball easy to oxidize using Shinkawa wire bonder UTC-1000 with fixed electric torch and discharge gas nozzle. % instead of N ₂ gas, if the ball diameter 75μm with 100% N ₂ gas in the atmosphere gas produced 50, to investigate the presence or absence of intergranular oxidation as shown in FIG. 1 by microscopic observation, it is observed oxidation 2 was determined to be defective, and the case where no oxidation at the grain boundary was observed as shown in FIG. 2 was determined to be normal, and the number of defects was determined.

B: Ball outer shape at the time of ball formation An ellipsoidal ball extended to the bottom as shown in FIG. 3 or a ball with a “nest” as shown in FIG. The case was determined to be defective, and those that did not occur were determined to be normal, and the number of defects was determined.

C: Surface hardness The surface hardness of the formed Cu ball was determined by Vickers hardness. The load was 0.5 gf.

D: Electric resistivity As shown in FIG. 5, a semiconductor element 3 having an Al electrode 4 having a thickness of 0.8 μm, and a Ti layer having a thickness of 50 nm and a silicon oxide layer having a thickness of 50 nm between the Al electrode 4 and the silicon layer. The Al electrode 4 and the Ag plated lead 5 were subjected to ultrasonic thermocompression ball bonding and stitch bonding using the Cu bonding wires of Samples 1 to 13, and then Wheatstone using a wire having a diameter of 25.0 μm. The electrical resistance was calculated by measuring the electrical resistance using a bridge circuit.

[Bondability]
E: Pad damage during ball bonding A semiconductor element having an Al electrode 4 having a thickness of 0.8 μm and a Ti layer having a thickness of 50 nm and a silicon oxide layer having a thickness of 50 nm between the Al electrode 4 and the silicon layer shown in FIG. 3 and the lead 5 with Ag plating were subjected to ultrasonic thermocompression ball bonding and stitch bonding using the Cu bonding wires of Samples 1 to 13, and then Al together with the Cu balls with a potassium hydroxide solution. After washing, the pad damage under the Al electrode was observed, and even when damage such as cracking or chipping occurred in 1 out of 100, it was judged as defective. As a comparative example, a Pd-coated Cu wire in which a 99.99% pure Cu surface was coated with Pd at a thickness of 80 nm was also used. Ball formation was performed only with N ₂ gas.

F: Bondability of stitch bonding After the bonding wire wound on the spool is left at room temperature in the air in a clean room for two weeks, the Al electrode on the above semiconductor element having two Al electrodes connected to each other and leads The lead tip of a lead frame made of a copper alloy plated with Ag at the tip was ball and stitch bonded, and the ratio of stitch bonding non-sticking in 1200 locations was determined as a non-sticking rate (%).

G: Pressure cooker test (PCT)
Adjacent Al electrodes are connected by Al wiring. Using a semiconductor element with the same structure as the "Pad damage during ball bonding" measurement of E, ball bonding is performed on the Al electrode side, and the lead tip of the copper alloy lead frame is The Ag plating electrode is stitch-bonded to form a so-called daisy chain that continues with a wire, an Al electrode, a wire, an Ag plating, a wire, and an Al electrode, and is molded with a so-called green epoxy compound that does not contain Br or Sb. After conducting a so-called pressure cooker test (PCT) in which the semiconductor device is left in an environment of a temperature of 125 ° C., an atmospheric pressure of 2.3 atm, and a humidity of 100% for 168 hours, the electrical resistance has a high electrical resistance among 50 sets in an energization test. If even one pair that has become 20% or more before being left is generated, A set also as normal if not generated was determined the defective number.
Table 2 shows the evaluation results of characteristics A to G.

As is apparent from Table 2, Examples 1 to 6 (Sample Nos. 3 to 8) of Cu bonding wires having the component composition of the present invention are each in the 100% N ₂ gas which is an inert gas. All of the 50 samples have a glossy spherical shape, no pad damage was observed under all 50 aluminum electrodes on the semiconductor element, and in the 50% PCT test, the increase in electrical resistance was 20%. The electrical resistivity was 2.08 μΩcm in Example 1 (Sample No. 3) and 3.25 μΩcm in Example 5 (Sample No. 7), indicating a lower electrical resistivity than Au.

  On the other hand, both the contents of Cl and P are within the scope of the present invention, but the Au contents are as small as 1% by mass (sample No. 1) and 1.6% by mass (sample No. 2). The bonding property was good, but the ball surface was oxidized at the time of ball formation, and a true spherical shape was not obtained.

  In Comparative Example 3 (Sample No. 9) having a small Au content of 0.5% by mass, the effect of containing Au was not observed, the surface of the ball and the wire surface were oxidized, and the shape was also deformed into an elliptical shape. . Although no pad damage was observed, the stitch bondability in wire bonding after leaving in a clean room for 2 weeks deteriorated. There was no conduction failure in PCT.

  Although P is 10 mass ppm, in Comparative Example 4 (sample No. 10) with a small Au content of 0.5 mass%, no abnormality was observed in the appearance of the ball due to the effect of P. Because of the low content of, an elliptical ball shape was observed. Although no pad damage was observed, the stitch bondability in wire bonding after leaving for 2 weeks in a clean room deteriorated. There was no conduction failure in PCT.

  In Comparative Example 5 (Sample No. 11) containing an excessive amount of P and containing a large amount of Cl, no abnormality was observed in the appearance of the ball, but pad damage due to ball bonding was observed, and 2 weeks in a clean room. Stitch bondability in wire bonding after standing was deteriorated. Many conduction failures occurred in PCT.

  In Comparative Example 6 (Sample No. 12) containing 9 mass% of Au excessively, no abnormality was observed in the appearance of the ball, but pad damage such as cracking and chipping was observed in the ball bonding. Moreover, the electrical resistivity was 3.57 μΩcm, which was higher than that of a 99% pure gold wire.

  Although Pd-coated and contained Cl is 1.2 mass ppm within the scope of the present invention, Comparative Example 7 (sample No. 13) containing no Au showed no abnormality in the appearance of the initial ball. In ball bonding, pad damage such as cracking and chipping was observed. Moreover, the wire which shows a conduction defect generate | occur | produced in PCT.

  In Comparative Example 8 (sample No. 14) containing only 30 mass ppm of P without containing Au, the surface of the ball was oxidized and the shape was deformed into an elliptical shape. No pad damage was observed, but the stitch bondability in wire bonding after leaving in a clean room for 2 weeks deteriorated, and a wire showing poor conduction was generated in PCT.

Furthermore, sample no. Samples 1, 2 and 9 did not show good bonding wire properties in 100% N ₂ gas, ie inert gas (see Comparative Examples 1, 2 and 3), but in a reducing atmosphere under conventional bonding conditions When the ball was formed in a forming gas of 2% H ₂ + 98% N ₂ , which had less H ₂ than 5% H ₂ + 95% N ₂ gas, neither ball surface oxidation nor wire surface oxidation was observed. Was a glossy sphere. Table 3 shows the results of the same evaluation as described above using this 2% H ₂ + 98% N ₂ forming gas.

  Sample No. No. 1 using Sample No. 1 and Sample No. In Example 8 using No. 2, no pad damage due to ball bonding was observed, the stitch bondability was good even when left in a clean room for 2 weeks, and no poor conduction was seen even in PCT. However, sample no. In Comparative Example 9 using 9, the surface of the ball was oxidized, the shape was deformed into an ellipse, and the stitch bondability was also deteriorated. No conduction failure in PCT was measured.

DESCRIPTION OF SYMBOLS 1 Copper bonding wire 2 Ball 3 Semiconductor element 4 Aluminum electrode 5 Lead with silver plating 6 Epoxy sealing resin 7 Resistance measuring instrument

Claims (3)

A Cu bonding wire for ball bonding, in order that Ru enhanced roundness deterioration avoidance and ball stitch bonding bondability comprises 2.2 wt% or more 7.5 mass% of Au, containing Cl the amount is less than 2 mass ppm, Ri Do the balance Cu and inevitable impurities, Cu bonding wire, characterized in that the al used for wire bonding in an inert atmosphere. A Cu bonding wire for ball bonding, in order that Ru enhanced roundness deterioration avoidance and ball stitch bonding bondability comprises 2.2 wt% or more 7.5 mass% of Au, containing Cl the amount is not more than 2 mass ppm, include the following P least 10 mass ppm 40 mass ppm, Ri Do the balance Cu and inevitable impurities, Cu bonding, characterized in using et al is that the wire bonding in an inert atmosphere Wire. Using Cu bonding wire according to 請 Motomeko 1 or 2, wherein a is wire-bonded in an inert atmosphere.