Ag alloy bonding wire for semiconductor device and semiconductor device

Abstract

Provided is an Ag alloy bonding wire for a semiconductor device, wherein even when a mold resin having a high S content is used, good bonding reliability can be exhibited in a high temperature environment and chip damage during ball bonding can be suppressed. The Ag alloy bonding wire contains at least one element (hereinafter referred to as "first element") selected from the group consisting of Pd and Pt, and at least one element (hereinafter referred to as "second element") selected from the group consisting of P, Cr, Zr, and Mo, with the remainder comprising Ag, wherein 0.05≤x1≤3.0 and 15≤x2≤700 are satisfied, where x1 is the total concentration [at. %] of the first element and x2 is the total concentration [at. ppm] of the second element.

Description

Technical Field

[0001] The present invention relates to an Ag alloy bonding wire for semiconductor devices. Furthermore, it relates to a semiconductor device including the Ag alloy bonding wire.

Background Art

[0002] In semiconductor devices, the electrodes formed on semiconductor elements are connected to the electrodes on lead frames or substrates by bonding wires. Gold (Au) has been the mainstream material for bonding wires. However, in recent years, against the backdrop of the soaring price of Au, the development of bonding wires using relatively inexpensive materials as an alternative to Au has been actively carried out. As a low-cost wire material to replace Au, for example, copper (Cu) has been studied, and reports have been made on Cu wires and Cu wires provided with a palladium (Pd) coating for suppressing oxidation on their surfaces.

[0003] Since Cu wires or Pd-coated Cu wires are harder than Au wires and tend to cause problems during connection to electrodes and the like, a material with lower hardness is desired. Silver (Ag) is expected as a wire material because it has electrical conductivity equal to or higher than that of Au and brings about lower hardness than Cu.

[0004] Regarding Ag wires, it has been found that their bonding reliability may be inferior to that of Au wires. As a technology to improve the bonding reliability, a technique of adding specific elements such as Pd, Pt, and Au to Ag wires and alloying them has been reported. For example, Patent Document 1 discloses an Ag alloy bonding wire containing a total of 0.1 to 10% by weight of one or more of Pd, Pt, Cu, Ru, Os, Rh, and Ir, with Pd being 10% by weight or less, Pt being 10% by weight or less, Cu being 5% by weight or less, Ru being 1% by weight or less, Os being 1% by weight or less, Rh being 1% by weight or less, and Ir being 1% by weight or less. Also, Patent Document 2 discloses a ternary alloy system bonding wire composed of Ag with a purity of 99.99% by mass or more, Au with a purity of 99.999% by mass or more, and Pd with a purity of 99.99% by mass or more, where Au is 4 to 10% by mass, Pd is 2 to 5% by mass, the oxidizing non-noble metal additive element is 15 to 70 ppm by mass, and the balance is Ag. The bonding wire is subjected to annealing heat treatment before continuous die drawing, quenching and tempering heat treatment after continuous die drawing, and is ball bonded in a nitrogen atmosphere. A semiconductor element Ag-Au-Pd ternary alloy system bonding wire is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In in - vehicle semiconductor devices, further improvement in bonding reliability is required. For example, it is required to provide good bonding reliability even in a high - temperature environment of 175°C or higher. Here, the molding resin (epoxy resin), which is the package of the semiconductor device, contains a silane coupling agent. In in - vehicle semiconductor devices where higher reliability at higher temperatures is required, a silane coupling agent with a high sulfur (S) content is added to provide high adhesiveness.

[0007] The S content in the molding resin has been increasing in recent years. Conventionally, commercially available epoxy resins containing S - containing silane coupling agents have been used. On the other hand, for the purpose of further improving the adhesiveness of the molding resin to the lead frame and the semiconductor chip, in recent epoxy resins, the S content has increased compared to the past. When attempting to apply an Ag wire to a system using such a molding resin with a high S content, it has been found that even in the case of an Ag alloy wire containing specific elements as described in Patent Documents 1 and 2, the bonding reliability of the connection part with the electrode, particularly the ball bonding part, may decrease in a high - temperature environment. Although the bonding reliability in a high - temperature environment is somewhat improved by further increasing the addition amount of the specific element, in that case, it has been found that damage to the semiconductor chip (hereinafter also referred to as "chip damage") occurs during ball bonding.

[0008] An object of the present invention is to provide an Ag alloy bonding wire that exhibits good bonding reliability in a high - temperature environment and can suppress chip damage during ball bonding even when using a molding resin with a high S content.

Means for Solving the Problems

[0009] As a result of intensive studies on the above problems, it has been found that the above problems can be solved by a bonding wire having the following configuration, and the present invention has been completed. That is, the present invention includes the following content. [1] One or more elements selected from the group consisting of Pd and Pt (hereinafter referred to as "the first element"), and one or more elements selected from the group consisting of P, Cr, Zr, and Mo (hereinafter referred to as "the second element"), and when the total concentration of the first element is x1 [at.%] and the total concentration of the second element is x2 [at.ppm], 0.05 ≤ x1 ≤ 3.0 15 ≤ x2 ≤ 700 An Ag alloy bonding wire for semiconductor devices, which satisfies the above conditions and the balance contains Ag. [2] The Ag alloy bonding wire according to [1], wherein the total concentration of In, Ga, Cd, and Sn is less than 0.05 at.%. [3] When the total concentration of the first element is x1 [at.%], the total concentration of the second element is x2 [at.%], and the concentration of Ag is x Ag [at.%, the Ag alloy bonding wire according to [1] or [2], wherein the total concentration of other elements determined by the following formula (1) is less than 0.05 at%. Formula (1): 100 - (x1 + x2 + x Ag ) [at.%] [4] The Ag alloy bonding wire according to any one of [1] to [3], wherein the balance consists of Ag and inevitable impurities. [5] The Ag alloy bonding wire according to any one of [1] to [4], wherein the concentration of each element is the concentration measured by ICP emission spectrometry or ICP mass spectrometry. [6] The Ag alloy bonding wire according to any one of [1] to [5], which does not have a coating mainly composed of a metal other than Ag. [7] A semiconductor device including the Ag alloy bonding wire according to any one of [1] to [6].

Advantages of the Invention

[0010] According to the present invention, even when a molding resin with a high S content is used, an Ag alloy bonding wire can be provided that exhibits good bonding reliability in a high-temperature environment and suppresses chip damage during ball bonding.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail according to its preferred embodiments.

[0012] [Ag alloy bonding wire for semiconductor devices] The Ag alloy bonding wire for semiconductor devices of the present invention (hereinafter, also simply referred to as "the wire of the present invention", "wire") contains one or more elements selected from the group consisting of Pd and Pt (hereinafter referred to as "the first element"), and one or more elements selected from the group consisting of P, Cr, Zr, and Mo (hereinafter referred to as "the second element"). When the total concentration of the first element is x1 [at.%] and the total concentration of the second element is x2 [at.ppm], it satisfies 0.05 ≤ x1 ≤ 3.0 and 15 ≤ x2 ≤ 700, and the balance contains Ag.

[0013] Techniques for improving the bonding reliability of Ag wires by adding the first elements such as Pd and Pt to Ag wires have been reported. However, as described above, in a semiconductor device using a mold resin with a high S content, even when an Ag wire containing such a first element is used, the inventors have found that in a high-temperature environment of 175°C or higher, the bonding reliability of the connection part with the electrode, particularly the ball bonding part, may decrease. S contained in the mold resin tends to be released in a high-temperature environment of 175°C or higher, and it is presumed that when the released S contacts the Ag wire, the corrosion of the Ag wire progresses and leads to a decrease in bonding reliability. Since the bonding reliability of the connection part with the electrode, particularly the ball bonding part, decreases, it is presumed that the intermetallic compound (e.g., Ag3Al) generated at the bonding interface by diffusion bonding between the Ag wire and the electrode material (e.g., Al) is easily corroded by the released S.

[0014] Although increasing the addition amount of the first elements such as Pd and Pt can somewhat improve the bonding reliability in a high-temperature environment, in that case, problems such as the wire becoming hardened and causing chip damage or the specific resistance increasing will occur, and the excellent properties originally possessed by Ag cannot be enjoyed. Moreover, when the S concentration in the molding resin is high, it has been confirmed that it is difficult to avoid the decrease in bonding reliability in a high-temperature environment even by adjusting the addition amount of the first element.

[0015] On the other hand, the wire of the present invention containing a second element such as P, Cr, Zr, and Mo in addition to the above-mentioned first element can achieve good bonding reliability in a high-temperature environment even when using a molding resin with a high S content. When a FAB (Free Air Ball) was formed using the wire of the present invention containing a second element in addition to the first element, and the FAB was observed by SEM, it was confirmed that precipitates with a diameter of about several tens of nm occurred on the surface of the FAB. Further, when the generated precipitate was analyzed by energy dispersive X-ray spectroscopy (EDS), it was confirmed that the second element was concentrated. Although the detailed mechanism is unknown, it is presumed that such precipitates observed in the FAB are present at the bonding interface between the wire and the electrode in the ball bond, so that, for example, free S is trapped (compounded) by the precipitate before acting on the intermetallic compound at the bonding interface, thereby improving the bonding reliability of the ball bond in a high-temperature environment. Therefore, in a preferred embodiment, the wire of the present invention is characterized in that when a FAB is formed, precipitates in which the second element is concentrated occur on the surface of the FAB.

[0016] Furthermore, in the wire of the present invention containing a combination of a first element and a second element, the bonding reliability under a high-temperature environment can be improved without excessively increasing the addition amount of the first element, so that the occurrence of chip damage can also be suppressed. Thus, the present invention provides an Ag alloy bonding wire that suppresses the occurrence of chip damage and exhibits good bonding reliability under a high-temperature environment even when using a molding resin with a high S content, and significantly contributes to the practical application of Ag wires in in-vehicle semiconductor devices. The wire of the present invention, which can improve the bonding reliability under a high-temperature environment without excessively increasing the addition amount of the first element, is beneficial because it can also suppress the problem of increased specific resistance.

[0017] - First element - The wire of the present invention contains, as the first element, one or more elements selected from the group consisting of Pd and Pt in the range of 0.05 to 3.0 at.%. That is, when the total concentration of the first element in the wire is x1 [at. %], 0.05 ≤ x1 ≤ 3.0 is satisfied.

[0018] In combination with the second element described later, from the viewpoint of realizing good bonding reliability under a high-temperature environment even when using a molding resin with a high S content, the total concentration of the first element in the wire, that is, x1, is 0.05 at.% or more, preferably 0.1 at.% or more, 0.2 at.% or more, 0.3 at.% or more, 0.4 at.% or more, 0.5 at.% or more, 0.6 at.% or more, 0.8 at.% or more, or 1.0 at.% or more. In particular, when x1 exceeds 1.0 at.%, it is suitable because good bonding reliability can be achieved under a high-temperature environment even when using a molding resin with a high S content. Furthermore, when x1 exceeds 1.0 at.%, there is also an excellent effect that it is easy to control the crimping shape (the flattened shape of the ball) of the ball bonding portion to a shape close to a perfect circle. More preferably, x1 is 1.1 at.% or more, 1.2 at.% or more, 1.3 at.% or more, 1.4 at.% or more, or 1.5 at.% or more.

[0019] The upper limit of the total concentration x1 of the first element in the wire is 3.0 at.% or less, preferably 2.9 at.% or less, 2.8 at.% or less, 2.7 at.% or less, 2.6 at.% or less, or 2.5 at.% or less, from the viewpoint of suppressing hardening of the wire and suppressing chip damage. As described above, in the wire of the present invention containing the first element in combination with the second element, the bonding reliability in a high-temperature environment can be improved without excessively increasing the addition amount of the first element.

[0020] - Second element - The wire of the present invention contains, as the second element, one or more elements selected from the group consisting of P, Cr, Zr, and Mo in the range of 15 to 700 at.ppm. That is, when the total concentration of the second element in the wire is x2 [at.ppm], 15 ≤ x2 ≤ 700 is satisfied.

[0021] Even when using a molding resin with a high S content, from the perspective of achieving good bonding reliability in a high-temperature environment, the total concentration of the second element in the wire, that is, x2, is 15 at.ppm or more, preferably 30 at.ppm or more, 40 at.ppm or more, 50 at.ppm or more, 60 at.ppm or more, 80 at.ppm or more, 100 at.ppm or more, 150 at.ppm or more, 200 at.ppm or more, 250 at.ppm or more, or 300 at.ppm or more. In addition, when x2 is within the above range, there is also an excellent effect that it is easy to control the crimping shape (the flattened shape of the ball) of the ball joint to a shape close to a perfect circle. Note that when the concentration x1 of the first element exceeds 2 at.% (for example, 2.03 at.% or more, 2.05 at.% or more, 2.1 at.% or more), even when using a molding resin with a high S content, even in an extremely low amount range where the total concentration x2 of the second element is less than 35 at.ppm (for example, 34.5 at.ppm or less, 34.3 at.ppm or less, 34 at.ppm or less), that is, 15 at.ppm or more and less than 35 at.ppm, it has been confirmed that it exhibits significantly excellent bonding reliability in a high-temperature environment and the crimping shape of the ball joint is also extremely good. For example, when the concentration x1 of the first element exceeds 2 at.% (such as 2.03 at.% or more, 2.05 at.% or more, 2.1 at.% or more), when using P alone as the second element, Cr alone, Zr alone, Mo alone, or a combination of two or more of P, Cr, Zr, and Mo, even when its concentration x2 is less than 35 at.ppm (for example, 34.5 at.ppm or less, 34.3 at.ppm or less, 34 at.ppm or less), that is, in an extremely low amount range of 15 at.ppm or more and less than 35 at.ppm, it has been confirmed that the above remarkable effects can be obtained.

[0022] The upper limit of the total concentration x2 of the second element in the wire is 700 at.ppm or less, preferably 650 at.ppm or less, 600 at.ppm or less, 550 at.ppm or less, or 500 at.ppm or less, from the viewpoint of realizing good initial bonding strength of the ball joint and thus good bonding reliability in a high-temperature environment. In particular, when x2 is 500 at.ppm or less, the initial bonding strength of the ball joint is remarkably high, and thus it is preferable because excellent bonding reliability can be realized in a high-temperature environment. In addition, when x2 is within the above range, excellent effects such as suppressing hardening of the wire and easily suppressing chip damage are also achieved.

[0023] The wire of the present invention contains the above-described first element and second element in combination, and the balance contains Ag. In the wire of the present invention, the concentration of Ag with respect to the entire wire is preferably 95 at.% or more, more preferably 96 at.% or more, 96.5 at.% or more, 96.6 at.% or more, 96.7 at.% or 96.8 at.% or more, from the viewpoint of more enjoying the effects of the present invention in the combination of the first element and the second element.

[0024] Within a range that does not inhibit the effects of the present invention, the wire of the present invention may further contain a dopant element other than the first element and the second element. The total concentration of such a dopant element in the wire is not particularly limited as long as it does not inhibit the effects of the present invention. The total concentration of the dopant element may be, for example, less than 0.05 at.% (less than 500 at.ppm). Therefore, when the total concentration of the first element is x1 [at.%], the total concentration of the second element is x2 [at.%], and the concentration of Ag is x Ag [at.%, the total concentration of other elements obtained by the following formula (1) may be less than 0.05 at.%. Formula (1): 100 - (x1 + x2 + x Ag ) [at.%]

[0025] The total concentration of dopant elements other than the first element and the second element, that is, the above-mentioned "other elements", may be lower, for example, 0.045 at.% or less, 0.04 at.% or less, 0.035 at.% or less, 0.03 at.% or less, 0.025 at.% or less, 0.02 at.% or less, 0.015 at.% or less, less than 0.011 at.%, 0.01 at.% or less, 0.005 at.% or less, 0.003 at.% or less, 0.001 at.% or less, 0.0008 at.% or less, 0.0006 at.% or less, or 0.0005 at.% or less. The types of such dopant elements are not particularly limited as long as they do not inhibit the effects of the present invention, and examples include In, Ga, Cd, Sn, Cu, Zn, Fe, Ti, Mn, Mo, Ni, Au, etc. Therefore, for example, when using In, Ga, Cd, and Sn as such dopant elements, the total concentration of In, Ga, Cd, and Sn may be less than 0.05 at.%. The lower limit of the total concentration of such dopant elements is not particularly limited and may be 0 at.%.

[0026] In a preferred embodiment, the wire of the present invention contains a combination of the first element and the second element, and the balance consists of Ag and unavoidable impurities.

[0027] The concentrations of elements such as the first element, the second element, and other dopant elements contained in the wire of the present invention can be analyzed using an ICP emission spectrometer or an ICP mass spectrometer on a solution obtained by dissolving the wire in a strong acid, and detected as the concentrations of the elements contained in the entire wire. The concentrations of each element shown in the present invention are based on the concentrations measured by ICP emission spectroscopy or ICP mass spectrometry.

[0028] The wire of the present invention preferably does not have a coating mainly composed of a metal other than Ag. Therefore, in a preferred embodiment, the wire of the present invention does not have a coating mainly composed of a metal other than Ag. Here, the "coating mainly composed of a metal other than Ag" refers to a coating in which the content of a metal other than Ag is 50 at.% or more.

[0029] The diameter of the wire of the present invention is not particularly limited and may be appropriately determined according to specific purposes. Preferably, it can be 15 μm or more, 18 μm or more, or 20 μm or more, etc. The upper limit of the diameter is not particularly limited and can be, for example, 100 μm or less, 90 μm or less, or 80 μm or less, etc.

[0030] <Method for manufacturing wire> An example of the method for manufacturing an Ag alloy bonding wire for a semiconductor device of the present invention will be described.

[0031] Raw material Ag with a purity of 3N to 5N (99.9 to 99.999 mass%) is prepared. Then, after weighing raw material Ag and the raw materials of the first element, the second element, and other dopant elements (if any) so that the concentrations of the first element, the second element, and other dopant elements are within the above specific ranges, an Ag alloy is obtained by melting and mixing them. Alternatively, as the raw materials of the first element, the second element, and other dopant elements, master alloys containing these elements may be used. This Ag alloy is processed into a large diameter by continuous casting and then drawn into a thin wire to the final wire diameter.

[0032] The wire drawing process can be carried out using a continuous wire drawing apparatus capable of setting a plurality of diamond-coated dies. If necessary, heat treatment may be performed at an intermediate stage of the wire drawing process.

[0033] After the wire drawing process, final heat treatment is performed. As the temperature conditions for the final heat treatment, for example, while keeping the wire feeding speed constant, the elongation at break of the wire heat-treated by changing only the furnace temperature is confirmed, and the heat treatment temperature may be determined so that the elongation at break is within a predetermined range. The heat treatment temperature may be, for example, in the range of 200 to 600 °C. The heat treatment time is preferably set to 10 seconds or less (preferably 5 seconds or less, 4 seconds or less, or 3 seconds or less). As the atmosphere for the heat treatment, an inert gas such as nitrogen gas or argon gas, or a hydrogen-containing inert gas such as forming gas (5% H2-N2) may be used.

[0034] The wire of the present invention can be used to connect a first electrode on a semiconductor element and a second electrode on a lead frame or a circuit board in the manufacture of a semiconductor device. The first connection (1st bonding) with the first electrode on the semiconductor element can be a ball bond, and the second connection (2nd bonding) with the electrode on the lead frame or the circuit board can be a wedge bond. In the ball bond, the tip of the wire is heated and melted by arc heat input, and after forming a ball (FAB: Free Air Ball) by surface tension, this ball portion is pressure-bonded onto the electrode of the heated semiconductor element. In the wedge bond, without forming a ball, the wire portion is pressure-bonded onto the electrode by applying heat, ultrasonic waves, and pressure. The wire of the present invention containing a second element such as P, Cr, Zr, and Mo in addition to a first element such as Pd and Pt can achieve good bonding reliability in a high-temperature environment even when a molding resin with a high S content is used in the sealing process after the 1st bonding and the 2nd bonding. Therefore, the wire of the present invention can be suitably used for semiconductor devices, and can be suitably used for semiconductor devices sealed (packaged) using a molding resin with a high S content.

[0035] [Method for manufacturing a semiconductor device] A semiconductor device can be manufactured by connecting an electrode on a semiconductor element and an electrode on a lead frame or a circuit board using the Ag alloy bonding wire for semiconductor devices of the present invention.

[0036] In one embodiment, the method for manufacturing a semiconductor device of the present invention (hereinafter, also simply referred to as "the method of the present invention") includes a step of connecting a first electrode on a semiconductor element and a second electrode on a lead frame or a circuit board with the wire of the present invention. The first connection between the first electrode and the wire of the present invention can be performed by ball bonding, and the second connection between the second electrode and the wire of the present invention can be performed by wedge bonding.

[0037] By using the wire of the present invention that combines the first element and the second element, even when a mold resin with a high S content is used in the encapsulation process, good bonding reliability can be achieved in a high-temperature environment. Therefore, in a preferred embodiment, the method of the present invention further includes a step of encapsulating with a mold resin having a high S content (for example, an S concentration of 5 mass ppm or more, 10 mass ppm or more, or 15 mass ppm or more) after bonding. By using the wire of the present invention, good bonding reliability in a high-temperature environment can be advantageously achieved regardless of the specifications of the mold resin including the S concentration.

[0038] [Semiconductor device] A semiconductor device can be manufactured by connecting an electrode on a semiconductor element and an electrode on a lead frame or a circuit board using the Ag alloy bonding wire for a semiconductor device of the present invention.

[0039] In one embodiment, the semiconductor device of the present invention includes a circuit board, a semiconductor element, and a bonding wire for electrically connecting the circuit board and the semiconductor element, and the bonding wire is the wire of the present invention.

[0040] In the semiconductor device of the present invention, the circuit board and the semiconductor element are not particularly limited, and known circuit boards and semiconductor elements that can be used to configure the semiconductor device may be used. Alternatively, a lead frame may be used instead of the circuit board. For example, it may be configured as a semiconductor device including a lead frame and a semiconductor element mounted on the lead frame, as described in Japanese Patent Application Laid-Open No. 2002-246542.

[0041] Examples of semiconductor devices include various semiconductor devices used in electrical products (for example, computers, mobile phones, digital cameras, televisions, air conditioners, solar power generation systems, etc.) and vehicles (for example, motorcycles, automobiles, trains, ships, airplanes, etc.). Among them, in-vehicle semiconductor devices that are required to provide good bonding reliability even in a high-temperature environment are preferred.

Examples

[0042] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples shown below.

[0043] (Sample) Ag used as a raw material had a purity of 99.9 at.% or more, and the balance was composed of unavoidable impurities. For the first elements (Pd and Pt), the second elements (P, Cr, Zr, and Mo), and other dopant elements (In, Cu, and Ga), those with a purity of 99.9 at.% or more and the balance composed of unavoidable impurities were used.

[0044] The Ag alloy used for the bonding wire was loaded with raw materials into a cylindrical carbon crucible, heated to 1080 - 1600 °C in a vacuum or an inert atmosphere such as N2 or Ar gas using a high-frequency furnace, melted, and then a wire with a diameter of φ4 - 6 mm was produced by continuous casting.

[0045] For the obtained Ag alloy, wire drawing and other processes were performed using dies to produce a wire with a diameter of φ300 - 600 μm. Then, by repeating intermediate heat treatment at 200 - 700 °C and wire drawing, it was processed to a final wire diameter of φ20 μm. A commercially available lubricant was used for wire drawing, and the wire feeding speed during wire drawing was 20 - 600 m / min. The intermediate heat treatment was performed in an Ar gas atmosphere while continuously sweeping the wire. The wire feeding speed during the intermediate heat treatment was 20 - 100 m / min.

[0046] Finally, the wire after wire drawing was subjected to a final heat treatment so that the elongation at break was approximately 9 - 25%. The final heat treatment was performed in the same manner as the intermediate heat treatment. The wire feeding speed during the final heat treatment was 20 - 100 m / min, the same as that during the intermediate heat treatment. The final heat treatment temperature was 200 - 700 °C, and the heat treatment time was 0.2 - 1.0 seconds.

[0047] The concentrations of the first element, the second element, and other dopant elements in the bonding wire were detected as the concentrations of the elements contained in the entire bonding wire by analyzing the solution obtained by dissolving the bonding wire in strong acid using an ICP emission spectrometer and an ICP mass spectrometer.

[0048] (Test and Evaluation Method) The test and evaluation method will be described below.

[0049] [Evaluation of Bonding Reliability under High Temperature Environment] Samples for evaluating bonding reliability were prepared by forming a 1.0-μm-thick Al film on an electrode of a Si substrate on a general metal frame, performing ball bonding using a commercially available wire bonder, and encapsulating with an S-containing molding resin. Here, two types of epoxy resins with different S concentrations were used as the S-containing molding resin. As the low-concentration S-containing resin, one with an S concentration of 2 mass ppm was used, and as the high-concentration S-containing resin, one with an S concentration of 16 mass ppm was used. The S concentration in the epoxy resin was evaluated by pulverizing the resin, heating it at 200 °C for 10 hours in a nitrogen gas flow, collecting the outgas from the resin contained in the carrier nitrogen gas with hydrogen peroxide water, and performing ion chromatography. The ball was formed while flowing N2 + 5% H2 gas at a flow rate of 0.4 to 0.6 L / min, and the ball diameter was in the range of 1.5 to 1.6 times the wire diameter.

[0050] The bonding reliability under high temperature environment was evaluated by a high temperature storage life test (HTSL). Specifically, it was determined by the bonding life of the ball bonding part when exposed to an environment of 175 °C using a high temperature constant temperature machine. The bonding life of the ball bonding part was defined as the time when the share test of the ball bonding part was performed every 250 hours and the value of the share strength became 1 / 2 of the share strength obtained initially. The share test after the high temperature storage life test was performed after removing the resin by acid treatment to expose the ball bonding part.

[0051] For the shear test machine for HTSL evaluation, a test machine manufactured by DAGE was used. The shear strength value was the average of the measured values at 10 randomly selected ball joints. And the evaluation was carried out according to the following criteria.

[0052] Evaluation criteria: ◎◎: Bonding life of 3000 hours or more ◎ : Bonding life of more than 2000 hours and less than 3000 hours ○ : Bonding life of more than 1000 hours and less than 2000 hours × : Bonding life of less than 1000 hours

[0053] [Chip damage] The evaluation of chip damage was carried out by forming an Al film with a thickness of 1.0 μm on an electrode on an Si substrate, performing ball bonding using a commercially available wire bonder, dissolving the wire and the Al electrode in a chemical solution to expose the Si substrate, and observing the Si substrate directly under the ball joint with an optical microscope (evaluation number N = 100). When damage was found on the Si substrate, it was judged as defective. And the evaluation was carried out according to the following criteria.

[0054] Evaluation criteria: ◎: 0 defective parts ○: 1 defective part (no problem in practical use) ×: 2 or more defective parts

[0055] [Crimping shape] The evaluation of the crimping shape (the shape of the ball being flattened) of the ball joint was carried out by forming an Al film with a thickness of 1.0 μm on an electrode on an Si substrate, performing ball bonding using a commercially available wire bonder, and observing it with an optical microscope from directly above (evaluation number N = 100). The determination of the flattened shape of the ball was judged as good when the flattened shape was close to circular, and judged as defective if it was an elliptical or petal-shaped. And the evaluation was carried out according to the following criteria.

[0056] Evaluation criteria: ◎: No defect ○: 1 to 4 defective parts (no problem in practical use) ×: 5 or more defective parts

[0057] [Initial Bonding Strength] The initial bonding strength of the ball bonding part was evaluated by performing ball bonding on an electrode formed with an Al film having a thickness of 1.0 μm on an Si substrate using a commercially available wire bonder and conducting a shear test on the ball bonding part. A tester manufactured by DAGE was used as the shear tester. The value of the shear strength was evaluated according to the following criteria using the average value of the measured values at 20 randomly selected locations of the ball bonding part.

[0058] Evaluation Criteria: ◎: Average value of 16 gf or more ○: Average value of 10 gf or more and less than 16 gf ×: Average value less than 10 gf

[0059] The evaluation results of the examples and comparative examples are shown in Tables 1 and 2.

[0060]

Table 1

[0061]

Table 2

[0062] In all of Examples Nos. 1 to 19, even when using a molding resin with a high S content (high-concentration S-containing resin) where the contents of the first element and the second element are within the scope of the present invention, it was confirmed that good bonding reliability is exhibited in a high-temperature environment and chip damage during ball bonding can be suppressed. In addition, Examples Nos. 8 to 15 and 19 in which the content of the first element exceeds 1 at.% (particularly Examples Nos. 8 to 11, 13 to 15, and 19 in which the content of the second element is 500 at.ppm or less) exhibit remarkably excellent bonding reliability even when using a high-concentration S-containing resin in a high-temperature environment, and it was confirmed that the crimping shape of the ball bond is also particularly good. Further, when the content of the first element exceeds 2 at.%, even in an extremely low amount range where the total concentration of the second element is 15 at.ppm or more and less than 35 at.ppm, it exhibits remarkably excellent bonding reliability even when using a high-concentration S-containing resin in a high-temperature environment, and it was confirmed that the crimping shape of the ball bond is also particularly good (Examples Nos. 11 and 19). On the other hand, in Comparative Examples Nos. 1 to 12, the content of at least one of the first element and the second element is outside the scope of the present invention, and it was confirmed that the bonding reliability is poor in a high-temperature environment when using a high-concentration S-containing resin, or chip damage occurs during ball bonding.

Claims

1. It contains one or more elements selected from the group consisting of Pd and Pt (hereinafter referred to as "the first element") and one or more elements selected from the group consisting of P, Cr, Zr, and Mo (hereinafter referred to as "the second element"). When the total concentration of the first element is x1 [at. %] and the total concentration of the second element is x2 [at. ppm], 0.05 ≦ x1 ≦ 3.0 15 ≦ x2 ≦ 700 satisfying the total concentration of In, Ga, Cd, and Sn is less than 0.05 at. %, and the balance contains Ag, an Ag alloy bonding wire for semiconductor devices.

2. The Ag alloy bonding wire according to Claim 1, wherein the total concentration of elements not corresponding to any of the first element, the second element, and Ag is less than 0.05 at. %.

3. The Ag alloy bonding wire according to Claim 1 or 2, wherein the balance consists of Ag and inevitable impurities.

4. The Ag alloy bonding wire according to any one of Claims 1 to 3, wherein the concentration of each element is the concentration measured by ICP emission spectrometry or ICP mass spectrometry.

5. The Ag alloy bonding wire according to any one of Claims 1 to 4, which does not have a coating mainly composed of a metal other than Ag.

6. A semiconductor device including the Ag alloy bonding wire according to any one of Claims 1 to 5.

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