TW201642279A - Bonding wire for semiconductor device - Google Patents

Abstract

Provided is a Cu bonding wire having a Pd coating layer on the surface thereof, the bonding wire being suitable for vehicle-mounted devices and having improved bonding reliability at ball joints in a high-temperature high-humidity environment. This bonding wire for semiconductor devices includes: a Cu alloy core material; and a Pd coating layer formed on the surface thereof. The bonding wire includes a total of from 0.1 to 100 ppm by mass of one or more types of elements among Ga, Ge, As, Te, Sn, Sb, Bi, and Se. Thus, the bonding life of ball joints in a high-temperature high-humidity environment is improved, and bonding reliability can be improved. When the Cu alloy core material further includes from 0.011 to 1.2 mass% of one or more of Ni, Zn, Rh, In, Ir, and Pt, ball joint reliability in a high-temperature environment of 170 DEG C or higher can be improved. Further, when an alloy skin layer including Au and Pd is formed on the surface of the Pd coating layer, wedge bondability is improved.

Description

Bonding wire for semiconductor device

The present invention relates to a bonding wire for a semiconductor device for connecting an electrode on a semiconductor element to a wiring of a circuit wiring board such as an external lead.

At present, as a bonding wire for a semiconductor device (hereinafter referred to as a "bonding wire") for bonding an electrode on a semiconductor element and an external lead, a thin wire having a wire diameter of about 15 to 50 μm is mainly used. The bonding method of the bonding wires is generally ultrasonic and is thermocompression bonding, and a universal bonding device, a capillary fixture for connecting the bonding wires through the inside thereof, and the like can be used. The bonding process of the bonding wires is performed by heating and melting the leading end of the wire by the arc heat input, forming a ball by the surface tension (FAB: Free Air Ball), and then the ball The crimp bonding (hereinafter referred to as "ball bonding") is performed on the electrode of the semiconductor element heated in the range of 150 to 300 ° C, and then the electrode is crimped to the external lead side (hereinafter referred to as "wedge" Join") wire section. The electrode on the semiconductor element to be bonded to the bonding wire is an electrode structure obtained by forming an alloy mainly composed of Al on the Si substrate, and an electrode obtained by performing Ag plating or Pd plating on the electrode on the external lead side. Construction, etc.

In the past, the material of the bonding wire was mainly in the form of Au, but Cu was gradually replaced by Cu in the LSI (Large Scale Integration) application. On the other hand, in recent years, in the context of the widespread use of electric vehicles or hybrid vehicles, the demand for Cu to replace Au in in-vehicle applications has also increased.

Regarding Cu-bonded wires, it has been proposed to use high-purity Cu (purity: 99.99% by mass) The above (for example, Patent Document 1). Cu has a disadvantage of being easily oxidized compared with Au, and has problems such as poor bonding reliability, spherical formability, and wedge bondability. As a method of preventing oxidation of the surface of the Cu-bonded wire, a structure in which the surface of the Cu core material is coated with a metal such as Au, Ag, Pt, Pd, Ni, Co, Cr, or Ti has been proposed (Patent Document 2). Further, a structure in which Pd is coated on the surface of the Cu core material and the surface is covered with Au, Ag, Cu, or the like is proposed (Patent Document 3).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 61-48543

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2005-167020

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2012-36490

The in-vehicle device requires a joint reliability in a severe high-temperature and high-humidity environment as compared with a conventional electronic device. In particular, the bonding life of the ball joint formed by joining the ball portion of the wire to the electrode is the biggest problem. There are several methods for evaluating the joint reliability in a high-temperature and high-humidity environment. As a representative evaluation method, there is a HAST (Highly Accelerated Temperature and Humidity Stress Test). When the joint reliability of the ball joint portion is evaluated by HAST, the ball joint portion for evaluation is exposed to a high temperature and high humidity environment having a temperature of 130 ° C and a relative humidity of 85%, and the resistance value of the joint portion is measured. The change in time or the change in the shear strength of the ball joint portion was measured, thereby evaluating the joint life of the ball joint portion. Recently, the joint life of 100 hours or more has been gradually required in HAST under such conditions.

Bonding with a pure Al electrode using a conventional Cu bonding wire having a Pd coating layer, the first bonding is a ball bonding, the second bonding is a wedge bonding, and after sealing with a molding resin, the evaluation under the HAST condition is performed. As a result, there is a joint life of the ball joint. In the case of 100 hours, it was found that the joint reliability required for the in-vehicle device was insufficient.

An object of the present invention is to provide a bonding wire suitable for an in-vehicle device in which a Cu bonding wire having a Pd coating layer on its surface is used to improve bonding reliability of a ball joint portion in a high-temperature and high-humidity environment.

That is, the gist of the present invention is as follows.

(1) A bonding wire for a semiconductor device comprising a Cu alloy core material and a Pd coating layer formed on a surface of the Cu alloy core material, wherein: The bonding wire includes at least one element selected from the group consisting of As, Te, Sn, Sb, Bi, and Se, and the total concentration of the element relative to the entire wire is 0.1 to 100 ppm by mass, and Sn ≦ 10 ppm by mass, Sb≦ 10 mass ppm, Bi≦1 mass ppm.

(2) The bonding wire for a semiconductor device according to the above aspect (1), wherein a concentration of at least one element selected from the group consisting of As, Te, Sn, Sb, Bi, and Se is 1 in total with respect to the total concentration of the wire. ~100 mass ppm.

(3) The bonding wire for a semiconductor device according to the above aspect (1), wherein the thickness of the Pd coating layer is 0.015 to 0.150 μm.

(4) The bonding wire for a semiconductor device according to any one of the above-mentioned (1), wherein the Pd coating layer further includes an alloy skin layer containing Au and Pd.

(5) The bonding wire for a semiconductor device according to the above (4), wherein the thickness of the alloy skin layer containing Au and Pd is 0.0005 to 0.050 μm.

(6) The bonding wire for a semiconductor device according to any one of the above aspects, wherein the bonding wire further comprises a material selected from the group consisting of Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge. At least one or more of the elements, the concentration of the element relative to the entire wire is 0.011 to 1.2% by mass.

(7) The bonding wire for a semiconductor device according to any one of the above aspects, wherein the Cu alloy core material contains Pd, and the concentration of Pd contained in the Cu alloy core material is It is 0.05 to 1.2% by mass.

(8) The bonding wire for a semiconductor device according to any one of the above aspects, wherein the bonding wire further includes at least one selected from the group consisting of B, P, Mg, Ca, and La. The element is such that the concentration of the above element relative to the entire wire is 1 to 100 ppm by mass.

The bonding wire for a semiconductor device according to any one of the above aspects of the present invention, characterized in that, in the measurement result of measuring the crystal orientation of the surface of the bonding wire, the length of the bonding wire is opposite to the length of the bonding wire The ratio of the crystal orientation <111> having an angular difference of 15 degrees or less is 30 to 100% in terms of area ratio.

The bonding wire for a semiconductor device according to any one of the above aspects of the present invention, wherein the bonding wire is provided on the outermost surface of the bonding wire.

According to the present invention, in the bonding wire for a semiconductor device having a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, the bonding wires contain a total of 0.1 to 100 ppm by mass selected from As, Te, and Sn. At least one or more of Sb, Bi, and Se can extend the bonding life of the ball joint portion in a high-temperature and high-humidity environment, thereby improving the joint reliability.

The bonding wire of the present invention is a bonding wire for a semiconductor device having a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, wherein the bonding wire contains a total of 0.1 to 100 mass ppm selected from As, At least one or more of Te, Sn, Sb, Bi, and Se. The bonding wire of the present invention having this specific configuration can improve the bonding reliability of the ball joint portion in the high temperature and high humidity environment required for the in-vehicle device.

The details will be explained below if the bonding wire of the present invention is used When the arc is formed to form a ball, an alloy layer having a Pd concentration higher than that inside the ball is formed on the surface of the ball during the melting and solidification of the bonding wire. When the ball is bonded to the Al electrode and the high-temperature and high-humidity test is performed, the Pd is concentrated in the joint interface. The concentrated layer formed by the concentration of Pd can suppress the diffusion of Cu and Al at the joint interface in the high-temperature and high-humidity test, reduce the growth rate of the corrosive compound, and significantly improve the bonding of the ball joint in the high-temperature and high-humidity environment. reliability.

Further, since the alloy layer having a high Pd concentration formed on the surface of the ball is excellent in oxidation resistance, it is possible to reduce defects such as a shift in the position at which the ball is formed at the time of ball formation with respect to the center of the bonding wire.

It is at least 1 selected from the group consisting of As, Te, Sn, Sb, Bi, and Se from the viewpoint of improving the bonding reliability of the ball joint portion in a high-temperature and high-humidity environment at a temperature of 130 ° C and a relative humidity of 85%. The total concentration of the above elements with respect to the entire bonding wire is 0.1 mass ppm or more, preferably 0.5 mass ppm or more, more preferably 1 mass ppm or more, further preferably 1.5 mass ppm or more, 2 mass ppm or more, 2.5 mass. More than ppm, or more than 3 ppm by mass.

A molding resin (epoxy resin) as an encapsulating material of a semiconductor device contains chlorine (Cl) in its molecular skeleton. Under a high-temperature and high-humidity environment of 130 ° C and a relative humidity of 85% as HAST evaluation conditions, Cl in the molecular skeleton is hydrolyzed and eluted as chloride ions (Cl ^- ). When a Cu bonding wire having no coating layer is bonded to an Al electrode, when the Cu/Al bonding interface is placed at a high temperature, Cu and Al are mutually diffused to form Cu ₉ Al ₄ as an intermetallic compound. Cu ₉ Al _{4 is} susceptible to corrosion by halogen, and corrosion is caused by chloride eluted from the molded resin, resulting in a decrease in bonding reliability. In the case where the Cu wire has a Pd coating layer, the bonding interface between the Pd-coated Cu wire and the Al electrode becomes a Cu/Pd-concentrated layer/Al structure, and thus the Cu ₉ Al ₄ metal is suppressed as compared with the Cu wire without the coating layer. The formation of the inter-compound is not sufficient in the high-temperature and high-humidity environment required for the in-vehicle device.

On the other hand, when the Pd-coated Cu-bonding wire contains a specific amount of at least one element selected from the group consisting of As, Te, Sn, Sb, Bi, and Se, it is considered that the formation of the joint portion is further suppressed. The tendency of Cu ₉ Al ₄ intermetallic compounds. It is estimated that when a certain amount of these elements are contained, the interfacial tension between the Cu of the core material and the Pd of the coating layer is lowered when the ball is formed, and the wettability of the interface is improved, so that the Pd concentration at the ball joint interface is more prominently exhibited. . Therefore, the mutual diffusion suppression effect of Cu and Al by the Pd-concentrated layer is further enhanced, and as a result, the amount of Cu ₉ Al ₄ which is easily corroded by the action of Cl is less, and the joint reliability in the high-humidity environment of the ball joint portion is low. Significantly improved.

In the present invention having a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, and optionally a skin alloy layer containing Au and Pd on the surface thereof, diffusion is performed as will be described later. In the heat treatment or the annealing heat treatment, Cu of the core material can be diffused in the coating layer or the skin alloy layer by grain boundary diffusion or the like, so that Cu reaches the outermost surface of the wire and Cu exists on the outermost surface. Therefore, in the present invention, there is a case where Cu is present on the outermost surface of the bonding wire.

When the Pd-coated Cu-bonding wire contains a specific amount of As, Te, Sn, Sb, Bi, or Se as in the present invention, if Cu is further present on the outermost surface of the bonding wire, the formation of Cu _{9 in the} joint portion is further suppressed. The tendency of Al ₄ intermetallic compounds. It is presumed that when the Pd-coated Cu bonding wire contains a specific amount of As, Te, Sn, Sb, Bi, or Se, if Cu is further present on the outermost surface of the bonding wire, the As, Te, and Sn included in the bonding wire are included. The interaction of Sb, Bi, Se and Cu promotes the Pd concentration on the surface of the FAB during FAB formation, and the Pd concentration at the ball joint interface is more prominent. Thereby, the interdiffusion suppression effect of Cu and Al by the Pd-concentrated layer is further enhanced, the amount of Cu ₉ Al ₄ which is easily corroded by the action of Cl is less, and the joint reliability in the high-humidity environment of the ball joint portion is obtained. Further improve.

When the surface of the bonding wire is measured by the Oujie electronic spectroscopic device, if Cu is detected on the surface, Cu can be present on the outermost surface, and the above effects can be exhibited. and then, When the Cu concentration of the metal element constituting the outermost surface of the bonding wire is 1 atom% or more, the effect of improving the bonding reliability of the ball joint portion in the high-temperature and high-humidity environment is improved, which is preferable. From the viewpoint of further improving the bonding reliability of the ball joint portion in a high-temperature and high-humidity environment, the Cu concentration of the metal element constituting the outermost surface of the bonding wire is preferably 1.5 atom% or more, and more preferably 2 atom% or more. 2.5 atom% or more, or 3 atom% or more. Moreover, the Cu concentration of the metal element constituting the outermost surface of the bonding wire is preferably 50 atom% or less from the viewpoint of suppressing the decrease in the oxidation resistance or the sulfidation resistance of the surface of the wire and suppressing the shortening of the service life of the bonding wire. It is more preferably 45 atom% or less, further preferably 40 atom% or less, 35 atom% or less, or 30 atom% or less.

Further, the above-described effect obtained by the presence of Cu on the surface is exhibited when the purity of Cu of the core material is low (for example, 3 N or less), and in particular, when the purity of Cu is 2 N or less, there is a tendency to exhibit more prominently.

The bonding reliability improving effect in a high-temperature and high-humidity environment by bonding a ball joint portion obtained by Cu on the outermost surface of the bonding wire is a bonding wire of the present invention containing a specific amount of As, Te, Sn, Sb, Bi, Se. Unique. If the ordinary Pd is not covered with the Cu-bonded wires, the bonding reliability in the high-temperature and high-humidity environment of the ball joint portion cannot be improved as in the present invention. Moreover, for a conventional Pd-coated Cu-bonded wire that does not contain such elements, the presence of Cu on the outermost surface of the bonded wire causes a decrease in oxidation resistance or sulfidation resistance of the wire surface, and the service life of the bonded wire is shortened. . In addition, the FAB has multiple eccentricities, and the shape of the ball is easily deteriorated. Further, it is seen that the wedge bondability tends to deteriorate.

The above-described effect obtained by the presence of Cu on the outermost surface of the bonding wire is similar to the case where the Pd coating layer is the outermost surface in the bonding wire of the present invention, and the case where the alloy skin layer containing Au and Pd is the outermost surface. .

Here, the outermost surface refers to a region obtained by measuring the surface of the bonding wire by an oujie electronic spectroscopic device in a state where sputtering or the like is not performed.

On the other hand, the viewpoint of obtaining a good FAB shape and thus good ball jointability The concentration of the above elements in the wire is 100 ppm by mass or less, preferably 95 ppm by mass or less, 90 ppm by mass or less, 85 ppm by mass or less, or 80 ppm by mass or less. In addition, when the concentration of Sn and Sb exceeds 10 ppm by mass or the concentration of Bi exceeds 1 ppm by mass, the FAB shape becomes poor. Therefore, it is set to Sn ≦ 10 ppm by mass, Sb ≦ 10 ppm by mass, and Bi ≦ 1 ppm by mass can further improve the shape of the FAB, and thus is preferable. Further, by setting the Se concentration to 4.9 ppm by mass or less, the FAB shape and the wedge bondability can be further improved, which is more preferable.

When As, Te, Sn, Sb, Bi, and Se are contained in the bonding wire, the above-described method can be utilized by a method in which the elements are contained in the Cu core material, and a method of coating the surface of the Cu core material or the wire. The effect of the invention. Since the addition amount of these components is a very small amount, the addition method is variable, and the effect is apparent as long as the component of the specified concentration range is contained, regardless of the method of addition.

In the bonding wire of the present invention, the thickness of the Pd coating layer is preferably 0.015 μm or more from the viewpoint of further improving the bonding reliability of the ball joint portion in the high-temperature and high-humidity environment required for the in-vehicle device, and more preferably 0.02 μm or more, more preferably 0.025 μm or more, 0.03 μm or more, 0.035 μm or more, 0.04 μm or more, 0.045 μm or more, or 0.05 μm or more. On the other hand, the thickness of the Pd coating layer is preferably 0.150 μm or less, more preferably 0.140 μm or less, 0.130 μm or less, 0.120 μm or less, 0.110 μm or less, or 0.100 μm or less from the viewpoint of obtaining a good FAB shape. .

The definition of the Cu alloy core material and the Pd coating layer of the above-mentioned bonding wire will be described. The boundary between the Cu alloy core material and the Pd coating layer is determined based on the Pd concentration. A region having a Pd concentration of 50 atom% was used as a boundary, and a region having a Pd concentration of 50 atom% or more was determined as a Pd coating layer, and a region having a Pd concentration of less than 50 atom% was determined as a Cu alloy core material. The reason for this is that if the Pd concentration in the Pd coating layer is 50 atom% or more, the effect of improving the properties can be obtained by the structure of the Pd coating layer. The Pd coating layer may also include a region of the Pd single layer, and a region where Pd and Cu have a concentration gradient in the depth direction of the wire. Formed in the Pd coating layer The reason for the region of the concentration gradient is that there is a case where atoms of Pd and Cu diffuse due to heat treatment or the like in the manufacturing step. In the present invention, the concentration gradient means that the degree of concentration change in the depth direction is 10 mol% or more per 0.1 μm. Further, the Pd coating layer may contain unavoidable impurities.

The bonding wire of the present invention may further have an alloy skin layer containing Au and Pd on the surface of the Pd coating layer. Thereby, the bonding wire of the present invention can further improve the joint reliability and can improve the wedge bondability.

The definition of the alloy skin layer containing Au and Pd of the above bonding wire will be described. The boundary between the alloy skin layer containing the Au and Pd and the Pd coating layer was determined based on the Au concentration. A region having an Au concentration of 10 at% was used as a boundary, and a region having an Au concentration of 10 at% or more was determined to be an alloy skin layer containing Au and Pd, and a region having less than 10 at% was determined as a Pd coating layer. In addition, even in the region where the Pd concentration is 50 atom% or more, if there is 10 atom% or more of Au, it is determined that the alloy skin layer of Au and Pd is contained. The basis for this is that if the Au concentration is within the above concentration range, the effect of improving the properties can be expected from the structure of the Au skin layer. The alloy skin layer Au-Pd alloy containing Au and Pd includes both a region containing Au and Pd having a concentration gradient in the depth direction of the wire, and a region not containing the concentration gradient. The alloy skin layer comprising Au and Pd preferably comprises the region having the concentration gradient. The reason why the region having the concentration gradient is formed in the alloy skin layer containing Au and Pd is that atoms of Au and Pd are diffused by heat treatment or the like in the production step. Further, the alloy skin layer containing Au and Pd may contain unavoidable impurities and Cu.

In the bonding wire of the present invention, the alloy skin layer containing Au and Pd can react with the Pd coating layer to improve the adhesion strength between the alloy skin layer including the Au and Pd, the Pd coating layer, and the Cu alloy core material, and suppress the wedge bonding. Peeling of the Pd coating layer or the alloy skin layer containing Au and Pd. Thereby, the bonding wire of the present invention can improve the wedge bondability. The thickness of the alloy skin layer comprising Au and Pd is preferably from the viewpoint of obtaining good wedge bondability. 0.0005 μm or more, more preferably 0.001 μm or more, 0.002 μm or more, or 0.003 μm or more. The thickness of the alloy skin layer containing Au and Pd is preferably 0.050 μm or less, more preferably 0.045 μm or less, 0.040 μm or less, 0.035 μm or less, or 0.030 μm from the viewpoint of suppressing the eccentricity and obtaining a good FAB shape. the following. Further, the alloy skin layer containing Au and Pd can be formed by the same method as the Pd coating layer.

A molding resin (epoxy resin) as a sealing material for a semiconductor device contains a decane coupling agent. The decane coupling agent has an effect of improving the adhesion between the organic substance (resin) and the inorganic substance (cerium or metal), so that the adhesion to the ruthenium substrate or the metal can be improved. Further, in the case where high-adhesiveness is required for a semiconductor-oriented semiconductor or the like which requires reliability at a higher temperature, a "sulfur-containing decane coupling agent" is added. The sulfur contained in the molding resin is not released under the temperature condition of HAST, that is, at about 130 ° C, but is used if it is used at 175 ° C or higher (for example, 175 ° C to 200 ° C). Further, if the free sulfur is brought into contact with Cu at a high temperature of 175 ° C or higher, the corrosion of Cu is aggravated to form a sulfide (Cu ₂ S) or an oxide (CuO). When Cu corrosion occurs in a semiconductor device using a Cu bonding wire, the bonding reliability of the ball bonding portion is particularly lowered.

As a method of evaluating the reliability of the ball joint portion in a high temperature environment of 170 ° C or higher, an HTS (High Temperature Storage Test) was employed. The evaluation sample was exposed to a high temperature environment, and the change in the resistance value of the ball joint portion was measured, or the change in shear strength of the ball joint portion was measured over time to evaluate the joint life of the ball joint portion. In recent years, for automotive semiconductor devices, the reliability of ball joints in HTS at 175 ° C to 200 ° C is required to be improved.

The bonding wire of the present invention preferably further comprises at least one element selected from the group consisting of Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge, and the concentration of the element relative to the entire wire is 0.011 to 1.2 mass, respectively. %. According to the bonding wire of the present invention and the element, the bonding reliability in a high-temperature environment of the ball joint portion is improved in the HTS at 175 ° C or higher. Improves joint reliability in high temperature environments where ball joints are high (especially 175 ° C) The concentration of the above element with respect to the entire wire is preferably 0.011% by mass or more, more preferably 0.020% by mass or more, and further preferably 0.030% by mass or more and 0.050% by mass or more, from the viewpoint of the above-mentioned results in the HTS. 0.070% by mass or more, 0.090% by mass or more, 0.10% by mass or more, 0.15% by mass or more, or 0.20% by mass or more. The concentration of the element relative to the entire wire is preferably 1.2% by mass or less, and more preferably 1.1% by mass, from the viewpoint of obtaining a good FAB shape and suppressing the hardening of the bonding wire to suppress the decrease in the wedge bondability. the following. In the case where the bonding wire of the present invention comprises a plurality of elements selected from the group consisting of Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge, the total concentration of the elements relative to the entire wire is preferably 0.011 to 2.2. %. The total concentration of the above elements with respect to the entire wire is preferably 0.011% by mass or more, more preferably from the viewpoint of improving the bonding reliability in a high-temperature environment of the ball joint portion (especially in the HTS at 175 ° C or higher). 0.020% by mass or more, more preferably 0.030% by mass or more, 0.050% by mass or more, 0.070% by mass or more, 0.090% by mass or more, 0.10% by mass or more, 0.15% by mass or more, or 0.20% by mass or more. From the viewpoint of obtaining a good FAB shape and suppressing the hardening of the bonding wire and suppressing the decrease in the wedge bondability, the total concentration of the element with respect to the entire wire is preferably 2.0% by mass or less and 1.8% by mass or less, or 1.6% by mass or less.

Further, in the bonding wire of the present invention, it is preferable that the Cu alloy core material contains Pd and the concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2% by mass. Thereby, the same effects as those in the case of containing Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge described above can be obtained. In the bonding wire of the present invention, the concentration of Pd contained in the Cu alloy core material is improved in terms of improving the bonding reliability in a high-temperature environment of the ball joint portion (especially in the HTS at 175 ° C or higher). It is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass or more, or 0.5% by mass or more. In addition, the concentration of Pd contained in the Cu alloy core material is preferably 1.2% by mass or less, more preferably from the viewpoint of obtaining a good FAB shape, suppressing the hardening of the bonding wire, and suppressing the decrease in the wedge bondability. 1.1 Below mass%. The bonding wire of the present invention can improve the loop formation property by containing Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd in the above content range, that is, it can reduce the skewness which is problematic in high-density mounting. . The reason for this is that by including these elements in the bonding wires, the drop strength of the bonding wires is improved, and deformation of the bonding wires can be suppressed. In addition, as a method of determining the concentration of Pd contained in the Cu alloy core material by joining the lead wire products, for example, a method of exposing the cross section of the bonding wire and performing concentration analysis on the region of the Cu alloy core material; The surface of the self-bonding wire is cut toward the depth direction, and a method of concentration analysis is performed on the area of the Cu alloy core material. For example, in the case where the Cu alloy core material contains a region having a concentration gradient of Pd, as long as the profile of the bonding wire is subjected to line analysis, the region having a concentration gradient without Pd (that is, the degree of change in the concentration of Pd in the depth direction is The concentration analysis may be performed every 0.1 μm in a region of less than 10 mol%. The method of concentration analysis will be described below.

Moreover, by containing Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd in the above content range, the bonding wire of the present invention can further extend the temperature in a high temperature and high humidity environment at a temperature of 130 ° C and a relative humidity of 85%. The joint life of the ball joint. When the bonding wire of the present invention further contains a specific amount of Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, or Pd, it is considered that the Cu ₉ Al ₄ intermetallic compound is further suppressed from being formed in the joint portion. It is presumed that if these elements are further contained, the interfacial tension between the Cu of the core material and the Pd of the coating layer is further lowered, and the Pd concentration at the ball joint interface is more prominent. Therefore, the mutual diffusion suppressing effect of Cu and Al obtained from the Pd-concentrated layer is further enhanced, and as a result, the amount of Cu ₉ Al ₄ which is easily corroded by the action of Cl can be greatly reduced, and the high-humidity environment of the ball joint portion is high-temperature and high-humidity. The reliability is further improved.

The bonding wire of the present invention preferably further contains at least one element selected from the group consisting of B, P, Mg, Ca, and La, and the concentration of the element relative to the entire wire is 1 to 100 ppm by mass. Thereby, the collapsed shape of the ball joint portion required for high-density mounting can be improved, that is, the roundness of the shape of the ball joint portion can be improved. It can be considered as the reason: By adding the above elements, the crystal grain size of the ball can be made fine, and the deformation of the ball can be suppressed. The concentration of the element relative to the entire wire is preferably 1 ppm by mass or more, and more preferably 2 ppm by mass or more, from the viewpoint of improving the collapsed shape of the ball joint portion, that is, improving the roundness of the shape of the ball joint portion. 3 mass ppm or more, 4 mass ppm or more, or 5 mass ppm or more. The concentration of the above element with respect to the entire wire is preferably 100 ppm by mass or less, more preferably 95 ppm by mass or less, 90 ppm by mass or less, or 85, from the viewpoint of suppressing the hardening of the ball and suppressing wafer damage during ball bonding. The mass is ppm or less, or 80 ppm by mass or less. In the case where the bonding wire of the present invention contains a plurality of elements selected from the group consisting of B, P, Mg, Ca, and La, the total concentration of the elements relative to the entire wire is preferably from 1 to 100 ppm by mass. In view of improving the collapsed shape of the ball joint portion, that is, the roundness of the shape of the ball joint portion, the total concentration of the element with respect to the entire wire is preferably 1 ppm by mass or more, more preferably 2 ppm by mass or more. 3 mass ppm or more, 4 mass ppm or more, or 5 mass ppm or more. In addition, from the viewpoint of suppressing the hardening of the ball and suppressing wafer damage during ball bonding, the total concentration of the element with respect to the entire wire is preferably 90 ppm by mass or less, 80 ppm by mass or less, or 70 ppm by mass or less.

The concentration analysis of the Pd coating layer, the alloy skin layer containing Au and Pd, and the concentration analysis of Pd in the Cu alloy core material are effective in that the surface of the Pd coating layer is cut from the surface of the bonding wire to the depth direction by sputtering or the like. Or a method of exposing the cross section of the wire to perform line analysis, point analysis, or the like. The analysis device used for the concentration analysis may be an Oujie electronic spectroscopic analyzer, an energy dispersive X-ray analyzer, an electron beam microanalyzer, or the like attached to a scanning electron microscope or a transmission electron microscope. As a method of exposing the cross section of the wire, mechanical polishing, ion etching, or the like can be used. For the micro analysis of As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, B, P, Mg, Ca, La, etc. in the bonding wire, ICP can be used. (Inductively Coupled Plasma) emission spectroscopic analyzer or ICP mass spectrometer analyzes a solution obtained by dissolving a bonding wire in a strong acid to bond the elements contained in the entire wire The form of the concentration of the substance is detected.

In a preferred embodiment of the present invention, in the measurement result of measuring the crystal orientation of the surface of the bonding wire, the ratio of the crystal orientation <111> having an angular difference of 15 degrees or less with respect to the longitudinal direction of the bonding wire is measured by the area ratio. It is 30~100%. In this embodiment, the circuit formation property can be improved, that is, the linearity of the circuit required for high-density mounting can be improved, and the variation in the circuit height can be reduced. The reason for this is that if the crystal orientations of the surfaces are uniform, the resistance to the lateral deformation is enhanced, and the lateral deformation is suppressed, so that the skewness can be suppressed. The ratio of the crystal orientation <111> is more preferably 35% or more, more preferably 40% or more, 45% or more, 50% or more, or 55% or more, from the viewpoint of suppressing the skewness. .

(Production method)

Next, a method of manufacturing a bonded wire according to an embodiment of the present invention will be described. The bonding wire is obtained by, after manufacturing a Cu alloy for a core material, finely processing into a wire shape, forming a Pd coating layer, an Au layer, and performing heat treatment. There is also a case where the Pd coating layer and the Au layer are formed and then the drawing and heat treatment are performed again. A method for producing a Cu alloy core material, a Pd coating layer, a method for forming an alloy skin layer containing Au and Pd, and a heat treatment method will be described in detail.

The Cu alloy used for the core material is obtained by melting and solidifying Cu as a raw material together with an additive element. An arc furnace, a high frequency heating furnace, a resistance heating furnace, or the like can be used for melting. In order to prevent the incorporation of gases such as O ₂ and H ₂ from the atmosphere, it is preferred to carry out the melting in a vacuum atmosphere or an inert gas atmosphere such as Ar or N ₂ .

A method of forming a Pd coating layer or an Au layer on the surface of a Cu alloy core material includes a plating method, a vapor deposition method, a melting method, and the like. The plating method may be any one of electrolytic plating and electroless plating. For electroplating, which is called strike plating or flash plating, the plating speed is fast and the adhesion to the substrate is good. The solution used for electroless plating is divided into a replacement type and a reduction type. When the thickness is thin, only the replacement type plating is sufficient, and the thickness is relatively large. In the case of a thick case, it is effective to perform reduction plating after the displacement plating in stages.

As the vapor deposition method, chemical adsorption such as physical adsorption such as sputtering, ion plating, or vacuum vapor deposition, or chemical vapor deposition (CVD) can be used. These are dry types, and there is no need to wash after the formation of the Pd coating layer or the Au layer, and there is no concern such as surface contamination during washing.

After the Pd coating layer and the Au layer are formed and heat-treated, Pd of the Pd coating layer is diffused into the Au layer to form an alloy skin layer containing Au and Pd. Alternatively, the alloy skin layer containing Au and Pd may be formed by heat treatment after forming the Au layer, and the alloy skin layer containing Au and Pd may be coated from the beginning.

For the formation of a Pd coating layer, an alloy skin layer containing Au and Pd, a method of forming the layers after drawing to a final wire diameter, and forming the layers on a Cu alloy core material having a large diameter, and then performing a plurality of drawing The method until the target diameter is achieved is valid. When the Pd coating layer and the alloy skin layer of Au and Pd are formed in the state of the final diameter in the former state, it is easy to manufacture, quality control, and the like. In the case where the Pd coating layer and the alloy skin layer containing Au and Pd are combined with the wire drawing, the adhesion to the Cu alloy core material is improved. Specific examples of the respective formation methods include a method of forming a Pd coating layer and an alloy skin layer containing Au and Pd on a Cu alloy core material having a final wire diameter while continuously traversing a wire in an electrolytic plating solution. Or a method in which a thick Cu alloy core material is immersed in an electrolytic or electroless plating bath to form a Pd coating layer, an alloy skin layer containing Au and Pd, and then the wire is drawn to a final wire diameter.

After the Pd coating layer and the alloy skin layer containing Au and Pd are formed, there is a case where heat treatment is performed. By heat treatment, atomic diffusion between the alloy skin layer including the Au and Pd, the Pd coating layer, and the Cu alloy core material improves the adhesion strength, so that the alloy skin layer or the Pd coating layer containing Au and Pd during processing can be suppressed. The stripping is effective in terms of productivity improvement. In order to prevent the incorporation of O ₂ from the atmosphere, it is preferred to carry out heat treatment in a vacuum atmosphere or an inert gas atmosphere such as Ar or N ₂ .

As described above, by adjusting the conditions of the diffusion heat treatment or the annealing heat treatment applied to the bonding wires, Cu of the core material can be diffused in the Pd coating layer or the skin alloy layer containing Au and Pd by grain boundary diffusion or the like to cause Cu It reaches the outermost surface of the bonding wire so that Cu exists on the outermost surface. As the heat treatment for causing Cu to exist on the outermost surface, a heat treatment for forming an alloy skin layer containing Au and Pd as described above can be employed. When the heat treatment for forming the alloy skin layer is performed, Cu may be present on the outermost surface or Cu may be absent by selecting the heat treatment temperature and time. Further, the Cu concentration on the outermost surface may be adjusted to a specific range (for example, in the range of 1 to 50 atom%). It is also possible to diffuse Cu to the outermost surface by heat treatment other than when forming the alloy skin layer.

As described above, when As, Te, Sn, Sb, Bi, and Se are contained in the bonding wire, the method of including the elements in the Cu core material, and coating the surface of the Cu core material or the wire are used. The effects of the above invention can be exerted. The same applies to Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, B, P, Mg, Ca, and La.

As a method of adding the above components, the most convenient method is to add it to the starting material of the Cu alloy core material in advance. For example, after weighing high-purity copper and the above-mentioned component element raw materials as a starting material, the mixture is heated and melted under an atmosphere of high vacuum or nitrogen or argon gas to prepare a casting to which the above-mentioned components having a target concentration range are added. The ingot is used as a starting material for the above-mentioned constituent elements containing the target concentration. Therefore, in a preferred embodiment, the Cu alloy core material of the bonding wire of the present invention has a total concentration of the following elements with respect to the entire wire of 0.1 to 100 ppm by mass, and Sn ≦ 10 ppm by mass, Sb ≦ 10 ppm by mass, The Bi≦1 mass ppm includes at least one element selected from the group consisting of As, Te, Sn, Sb, Bi, and Se. The preferred range of values for the total concentration is as described above. In another preferred embodiment, the Cu alloy core material of the bonding wire of the present invention comprises a material selected from the group consisting of Ni, Zn, Rh, In, Ir, and the like, wherein the concentration of the element is 0.011 to 1.2% by mass, respectively. At least one or more of Pt, Ga, and Ge. The preferred range of values for this concentration is as described above. In a preferred embodiment, the Cu of the Cu alloy core material has a purity of 3 N or less (preferably It is 2N or less). Regarding the conventional Pd-coated Cu-bonded wire, a high-purity (4N or more) Cu core material is used from the viewpoint of bondability, and there is a tendency to avoid the use of a low-purity Cu core material. The bonding wire of the present invention containing a specific element is particularly suitable for the case of using a Cu alloy core material having a low Cu purity as described above, and achieving the joint reliability of the ball joint portion in a high temperature and high humidity environment required for an in-vehicle device. . In another preferred embodiment, the Cu alloy core material of the bonding wire of the present invention comprises a material selected from the group consisting of B, P, Mg, Ca, and La in such a manner that the concentration of the following elements is 1 to 100 ppm by mass with respect to the entire wire. At least one or more elements. The preferred range of values for this concentration is as described above.

The above components may be contained by coating the above components on the surface of the wire in the middle of the wire manufacturing step. In this case, it can be incorporated into somewhere in the wire manufacturing step, or it can be repeated multiple times. It can also be grouped into multiple steps. It may be added to the surface of the Cu before the Pd coating, or may be added to the surface of the Pd after the Pd coating, or may be added to the surface of the Au after the Au coating, and may be incorporated into each coating step. As a coating method, it can be applied from (1) aqueous solution dry It is selected from heat treatment, (2) plating method (wet type), and (3) vapor deposition method (dry type).

Coating with aqueous solution dry In the case of the heat treatment method, an aqueous solution of a suitable concentration is first prepared by using a water-soluble compound containing the above-mentioned constituent elements. Thereby, the above components can be taken into the wire material. It can be incorporated into somewhere in the wire manufacturing step, or it can be repeated multiple times. It can also be grouped into multiple steps. It may be added to the surface of the Cu before the Pd coating, or may be added to the surface of the Pd after the Pd coating, or may be added to the Au surface after the Au coating, or may be incorporated into each coating step.

In the case of using a plating method (wet type), the plating method may be applied to any of electrolytic plating method and electroless plating method. Regarding the electrolytic plating method, in addition to the usual electrolytic plating, a plating method in which the plating speed called flash paste plating is fast and the adhesion to the substrate is also good can be applied. The solution for electroless plating has a substitution type and a reduction type. Generally, displacement plating is applied when the plating thickness is thin, and reduction plating is applied in a thicker case, and any one may be applied, and the plating solution may be selected and adjusted according to the concentration to be added. concentrated Degree, time can be. Electrolytic plating and electroless plating can be incorporated into somewhere in the wire manufacturing step, or multiple times. It can also be grouped into multiple steps. It may be added to the surface of the Cu before the Pd coating, or may be added to the surface of the Pd after the Pd coating, or may be added to the Au surface after the Au coating, or may be incorporated into each coating step.

Among the vapor deposition methods (dry type), there are a sputtering method, an ion plating method, a vacuum evaporation method, a plasma CVD method, and the like. Since it is dry, it has the advantage of no post-treatment and no pollution concerns. In general, the vapor deposition method has a problem that the addition rate of the target element is slow, but since the concentration of the above-mentioned component elements is relatively low, it is one of the methods suitable for achieving the object of the present invention.

Each vapor deposition method can be incorporated into somewhere in the wire manufacturing step, or it can be repeated multiple times. It can also be grouped into multiple steps. It may be added to the surface of the Cu before the Pd coating, or may be added to the surface of the Pd after the Pd coating, or may be added to the Au surface after the Au coating, or may be incorporated into each coating step.

The method of determining the ratio of the crystal orientation <111> having an angular difference of 15 degrees or less with respect to the longitudinal direction of the bonding wire when the crystal orientation of the bonding wire is measured is 30 to 100% in terms of area ratio is as follows. In other words, by increasing the processing ratio after the formation of the Pd coating layer or the formation of the Pd coating layer and the Au skin layer, it is possible to grow the aggregate structure having a directionality on the surface of the wire (the aggregate structure in which the crystal orientation and the wire drawing direction coincide). . Specifically, when the Pd coating layer is formed or the Pd coating layer and the Au skin layer are formed to have a processing ratio of 90% or more, the crystal orientation of the surface of the bonding wire can be measured with respect to the longitudinal direction of the bonding wire. The ratio of the crystal orientation <111> having a difference of 15 degrees or less is 30% or more in terms of area ratio. Here, the "machining rate (%) = (the cross-sectional area of the wire before processing - the cross-sectional area of the wire after processing) / the cross-sectional area of the wire before processing × 100".

When measuring the crystal orientation of the surface of the wire, it is preferred to use an EBSD (Electron Backscattered Diffraction). The EBSD method has an observation of the crystal orientation of the observation surface and can show the angular difference of the crystal orientation between adjacent measurement points in the figure. The feature is that the crystal orientation can be observed relatively easily and accurately even in the case of a thin wire such as a bonding wire.

The present invention is not limited to the above embodiments, and can be appropriately changed within the scope of the gist of the invention.

[Examples]

The following is a detailed description of the bonding wires of the embodiment of the present invention.

(sample)

First, a method of producing a sample will be described. The Cu which is a core material is a purity of 99.99% by mass or more, and the rest is composed of unavoidable impurities. The purity of As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca, and La is 99% by mass or more and the rest Made up of unavoidable impurities. As a target composition of the wire or the core material, As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, which are added elements to the core material, are formulated. Pd, B, P, Mg, Ca, La. The addition of As, Te, Sn, Sb, Bi, Se, Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, Pd, B, P, Mg, Ca, and La may be formulated in a single form. In the case of a high melting point element or a very small amount in a monomer form, a Cu mother alloy containing an additive element may be prepared in advance and then formulated so as to be a target addition amount.

The Cu alloy of the core material is manufactured by filling the raw material into a diameter of In a cylindrical pot of 3 to 6 mm, a high-frequency furnace is used, and it is heated to 1090 to 1300 ° C in a vacuum or an inert gas atmosphere such as nitrogen or argon to be melted, and then furnace-cooled. For what is obtained 3~6mm alloy is drawn and processed to After 0.9 to 1.2 mm, the mold is continuously drawn using a mold, and the like. 300~600μm wire. A commercially available lubricating fluid is used for drawing, and the drawing speed is set to 20 to 150 m/min. In order to remove the oxide film on the surface of the wire and perform pickling treatment with hydrochloric acid, a Pd coating layer of 1 to 15 μm is formed so as to cover the entire surface of the Cu alloy of the core material. Further, a part of the wires was formed on the Pd coating layer to form an alloy skin layer containing Au and Pd of 0.05 to 1.5 μm. The Pd coating layer and the alloy skin layer containing Au and Pd are formed by electrolytic plating. As the plating liquid, a commercially available plating solution for a semiconductor is used. Thereafter, heat treatment and wire drawing were performed at 200 to 500 ° C, whereby the diameter was processed to 20 μm. After the processing, heat treatment is performed while flowing nitrogen gas or argon gas so that the final elongation at break becomes about 5 to 15%. The heat treatment method is carried out while continuously sweeping the wire while flowing nitrogen or argon while flowing. The wire transfer speed is set to 20 to 200 m/min, the heat treatment temperature is set to 200 to 600 ° C, and the heat treatment time is set to 0.2 to 1.0 second.

By adjusting the processing ratio after forming the Pd coating layer or forming the Pd coating layer and the alloy skin layer containing Au and Pd, the angle difference with respect to the longitudinal direction of the bonding wire when measuring the crystal orientation of the bonding wire surface can be measured. The ratio (area ratio) of the crystal orientation <111> of 15 degrees or less was adjusted.

Regarding the concentration analysis of the Pd coating layer and the alloy skin layer containing Au and Pd, the Auger electron spectroscopy was performed while cutting the surface of the bonding wire from the surface of the bonding wire by sputtering or the like. Based on the obtained concentration distribution in the depth direction, the thickness of the Pd coating layer and the thickness of the alloy skin layer containing Au and Pd were determined.

In the present invention examples 93 to 98 described in the following Tables 1-5, the core material was made of Cu having a purity of 99.99% by mass or more, and As, Te, Sn, and Sb were electrically deposited by the electroplating method in the middle of the wire manufacturing step. Bi, Se are coated on the surface of the wire to thereby contain the elements. Therefore, the "component addition method" column is provided in Table 1-5, and the present invention examples 99 to 109 are described as "cover layer". For example, in the column of "Component Addition Method" in Table 1-1 to Table 1-4 and "Core Material" in Table 1-5, As, Te, Sn, Sb, Bi, and Se are contained in the core material. in.

With respect to Invention Examples 99 to 109 and Comparative Examples 13 and 14 described in the following Tables 1-5, Cu was present on the outermost surface of the bonding wire. Therefore, in Table 1-5, "the surface of the wire is thick. In the column, the results obtained by measuring the surface of the bonding wire by the Auger electronic spectroscopic device are described. The outermost surface contains a specific concentration of Cu by selecting the heat treatment temperature and time of the bonding wires. For the examples in Table 1-1 to Table 1-4 and Table 1-5, the "Cu Concentration on the Conductor Surface" column is an empty column. The heat treatment condition is such that Cu is not present on the outermost surface, even if the Oujie electronic spectroscopic device is used. No Cu was detected.

The composition of each sample prepared in the above order is shown in Tables 1-1 to 1-5.

(evaluation method)

The surface of the wire was used as an observation surface to evaluate the crystal structure. As an evaluation method, an EBSD (Electron Backscattered Diffraction) method was used. The EBSD method has a feature of observing the crystal orientation of the observation surface and showing the angular difference of the crystal orientation between adjacent measurement points. Even if it is a thin wire such as a bonding wire, it can be observed relatively easily and accurately. Crystal orientation.

Note the following when implementing the EBSD method with a curved surface like a wire surface as an object. When a portion having a large curvature is measured, it is difficult to perform measurement with high precision. However, the measurement can be performed with high precision by fixing the bonding wire for measurement to a straight line in a plane and measuring the flat portion near the center of the bonding wire. Specifically, it is set as the measurement area as follows. The dimension in the circumferential direction is set to 50% or less of the wire diameter in the center of the longitudinal direction of the wire, and the dimension in the longitudinal direction of the wire is set to 100 μm or less. Preferably, the dimension in the circumferential direction is 40% or less of the wire diameter, and the dimension in the longitudinal direction of the wire is 40 μm or less. Thus, the measurement efficiency can be improved by shortening the measurement time. Further, in order to improve the accuracy, it is preferable to measure three or more places to obtain an average information in consideration of unevenness. The measurement site may be separated by 1 mm or more so as not to be close to each other.

The surface <111> azimuth ratio is obtained by using all the crystal orientations specified by a dedicated software (for example, OIM analysis manufactured by TSL Solutions, Inc.) as a parent group, and calculating the angular difference with respect to the length direction of the bonding wires. The ratio (area ratio) of the crystal orientation <111> of 15 degrees or less.

The joint reliability test was performed on the joint reliability of the ball joint portion in a high-temperature, high-humidity environment or a high-temperature environment, and the HAST and HTS evaluations were performed, and the joint life of the ball joint portion in each test was determined. For the sample for bonding reliability evaluation, an alloy of Al-1.0% Si-0.5% Cu having a thickness of 0.8 μm was formed on a Si substrate on a normal metal frame to form an electrode, and a commercially available wire bonding was used for the formed electrode. The machine was ball bonded and sealed by a commercially available epoxy resin to prepare a sample. The ball system is formed by flowing nitrogen gas + 5% hydrogen gas at a flow rate of 0.4 to 0.6 L/min, and the size is set to Range of 33~34μm.

With respect to the HAST evaluation, the prepared joint reliability evaluation sample was exposed to a high-temperature and high-humidity environment having a temperature of 130 ° C and a relative humidity of 85% using an unsaturated pressure cooker tester, and a bias voltage of 5 V was applied. Regarding the bonding life of the ball joint portion, the ball joint portion was subjected to a shear test every 48 hours, and the shear strength value was set to be 1/2 of the initial shear strength. The shear test after the high-temperature and high-humidity test was carried out by removing the resin by an acid treatment to expose the ball joint portion.

The shear tester evaluated by HAST used a test machine manufactured by DAGE Corporation. The value of the shear strength is the average of the measured values at 10 points on the randomly selected ball joint. In the above evaluation, if the bonding life is less than 96 hours, it is judged that there is a problem in practical use, and the symbol "X" is indicated. If it is 96 hours or more and less than 144 hours, it is judged to be practical but slightly problematic, and the symbol "△" is attached. "If it is 144 hours or more and it is less than 288 hours, it is judged that it is practically no problem and the symbol "○" is attached. If it is 288 hours or more and it is less than 384 hours, it is judged that it is excellent, and the symbol "◎" is attached, and if it is 384. When it is more than an hour, it is judged that it is particularly excellent, and the symbol "◎◎" is attached, and it is described in the "HAST" column of Table 1.

Regarding the HTS evaluation, the prepared joint reliability evaluation sample was exposed to a high temperature environment at a temperature of 200 ° C using a high temperature thermostat. Regarding the joint life of the ball joint portion, the ball joint portion was subjected to a shear test every 500 hours, and the shear strength value was set to be 1/2 of the shear strength obtained at the initial stage. The shear test after the high-temperature and high-humidity test was carried out by removing the resin by an acid treatment to expose the ball joint portion.

The shear test machine evaluated by HTS used a test machine manufactured by DAGE Corporation. The value of the shear strength is the average of the measured values at 10 points on the randomly selected ball joint. In the above evaluation, when the bonding life is 500 hours or more and less than 1000 hours, it is judged to be practical, but it is still necessary to be improved, and the symbol "△" is attached. If it is 1000 hours or more and less than 3000 hours, it is judged to be practically problem-free. Mark the mark "○", if it is more than 3000 hours, it is judged to be special Don't be excellent and mark it with "◎".

Regarding the evaluation of the ball formation property (FAB shape), the ball before the bonding was collected and observed, and it was determined whether or not the ball on the surface of the ball was deformed by the ball having the original spherical shape. The case where any of the above cases is caused is judged to be bad. The formation of the ball was carried out while blowing nitrogen gas at a flow rate of 0.5 L/min in order to suppress oxidation in the melting step. The size of the ball is set to 34 μm. 50 balls were observed under one condition. SEM was used for observation. In the evaluation of the ball formability, when five or more defects are caused, it is judged that there is a problem, and the symbol "X" is marked. When the defect is 3 to 4, it is judged to be practical but a problem is marked with the symbol "△". When the number of defects is 1 or 2, it is judged that there is no problem and the symbol "○" is attached. If no defect occurs, it is judged to be excellent, and the symbol "◎" is attached, and it is described in the "FAB shape" column of Table 1.

Regarding the evaluation of the wedge bondability of the wire bonding portion, 1000 lead wires were joined to the lead portion of the lead frame, and it was determined based on the frequency of occurrence of peeling of the joint portion. The lead frame used was a Fe-42 atom% Ni alloy lead frame treated with Ag to 1 to 3 μm. In this evaluation, it is assumed that the bonding conditions are more severe than usual, and the platform temperature is set to be 150 ° C lower than the general set temperature range. In the above evaluation, when 11 or more defects are caused, it is judged that there is a problem, and the symbol "X" is indicated. When the defect is 6 to 10, it is judged to be practical, but the problem is marked with "△", and the defect is In the case of 1 to 5, it is judged that there is no problem and the symbol "○" is attached. When no defect occurs, it is judged to be excellent, and the symbol "◎" is attached, and it is described in the "wedge bondability" column of Table 1.

Regarding the evaluation of the collapsed shape of the ball joint portion, the joined ball joint portion was observed from the immediately upper side thereof, and was determined based on its roundness. The bonding target was an electrode obtained by forming an alloy of Al-0.5% Cu having a thickness of 1.0 μm on a Si substrate. The observation system was observed at 200 places under one condition using an optical microscope. It is judged that the elliptical shape having a large deviation from the perfect circle and the anisotropy of the deformation have a collapsed shape of the ball joint portion. In the above evaluation, when there are six or more cases of defects, it is judged that there is a problem, and the symbol "X" is marked, and the defect is 4 to 5 pieces. In the case of the case, it is judged to be practical but slightly problematic, and the symbol "△" is marked. When the defect is 1 to 3, it is judged that there is no problem and the symbol "○" is marked, and when it is good in roundness, it is judged to be special. The mark "◎" which is excellent and is marked in the "collapse shape" column of Table 1.

[skew]

100 wires were joined to the evaluation lead frame with a loop length of 5 mm and a loop height of 0.5 mm. As an evaluation method, the wire upright portion was observed from the horizontal direction of the wafer, and was evaluated by the interval (offset interval) at which the distance between the vertical line of the ball joint portion and the wire upright portion was the largest. When the skew interval is smaller than the wire diameter, it is judged that the skew is good, and when it is larger than the wire diameter, it is judged to be poorly skewed due to the inclination of the upright portion. The 100 bonded wires were observed with an optical microscope, and the number of skewed defects was counted. When there are 7 or more defects, it is judged that there is a problem and the symbol "X" is marked. If the defect is 4-6, it is judged to be practical, but the problem is marked with "△", and the defect is 1~3. In the case of the case, it is judged that there is no problem and the symbol "○" is attached. When there is no defect, it is judged to be excellent, and the symbol "◎" is attached, and it is described in the "skew" column of Table 1.

(Evaluation results)

The bonding wires of Inventive Examples 1 to 109 have a Cu alloy core material and a Pd coating layer formed on the surface of the Cu alloy core material, and the bonding wires include at least one selected from the group consisting of As, Te, Sn, Sb, Bi, and Se. In the above elements, the total concentration of the above elements with respect to the entire wire is 0.1 to 100 ppm by mass. It was confirmed that the bonding wires of Examples 1 to 109 of the present invention were obtained in a HAST test in a high-temperature and high-humidity environment at a temperature of 130 ° C and a relative humidity of 85%, and the ball joint reliability was obtained.

On the other hand, in Comparative Examples 1, 2, 4 to 6, and 11 to 14, the above element concentration exceeded the lower limit, and the ball joint reliability was not obtained in the HAST test. In Comparative Examples 3 and 7 to 10, the above element concentration exceeded the upper limit, and the FAB shape was poor. In Comparative Examples 1, 3, and 5 to 10, the area ratio of the <111> crystal orientation was out of the preferred range of the present invention, and the skew was "?".

In the example of the present invention which further has an alloy skin layer containing Au and Pd on the Pd coating layer, it has been confirmed that the layer thickness of the alloy skin layer containing Au and Pd is 0.0005 to 0.050 μm, whereby excellent wedge bondability can be obtained.

In the examples 27 to 92, 100, 102, and 104 to 109 of the present invention, at least one selected from the group consisting of Ni, Zn, Rh, In, Ir, Pt, Ga, Ge, and Pd is further included in the bonding wire. The concentration of the element other than Pd relative to the entire wire is 0.011 to 1.2% by mass, and the concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2% by mass, and the ball joint portion obtained by HTS evaluation is high in temperature. Good sex.

In one of the examples 28 to 92 of the present invention, at least one element selected from the group consisting of B, P, Mg, Ca, and La is further contained by the bonding wire, and the concentration of the element relative to the entire wire is 1 to 100, respectively. The mass ppm, the FAB shape is good, and the wedge bondability is good.

In the inventive examples 99 to 109, the wires contained As, Te, Sn, Sb, Bi, and Se, and Cu was present on the outermost surface of the wires. As a result, the HAST evaluation results of Examples 99, 101, 103, 105, 106, 108, and 109 of the present invention were ◎ ◎ or ◎, and the effect of Cu on the outermost surface was exhibited. In Examples 100, 102, 104, and 107 of the present invention, the purity of Cu of the wire was as low as 2 N or less, and the HAST evaluation results were all excellent. On the other hand, in the examples of the present invention, a slight decrease was observed with respect to the wedge bondability.

In Comparative Examples 13 and 14, the wires did not contain As, Te, Sn, Sb, Bi, and Se. On the other hand, Cu was present on the outermost surface of the wire, so that not only HAST evaluation but also HTS evaluation results were poor, FAB shape and collapse shape. Also bad, and the wedge bondability and deflection are also deteriorated.

Claims (10)

A bonding wire for a semiconductor device comprising a Cu alloy core material and a Pd coating layer formed on a surface of the Cu alloy core material, wherein the bonding wire comprises a component selected from the group consisting of As, Te, Sn, Sb, and Bi In the element of at least one of Se, the total concentration of the element relative to the entire wire is 0.1 to 100 ppm by mass, Sn ≦ 10 ppm by mass, Sb ≦ 10 ppm by mass, and Bi ≦ 1 ppm by mass. The bonding wire for a semiconductor device according to claim 1, wherein a concentration of at least one element selected from the group consisting of As, Te, Sn, Sb, Bi, and Se is 1 to 100 ppm by mass based on the total concentration of the wire. The bonding wire for a semiconductor device according to claim 1 or 2, wherein the thickness of the Pd coating layer is 0.015 to 0.150 μm. The bonding wire for a semiconductor device according to any one of claims 1 to 3, further comprising an alloy skin layer containing Au and Pd on the Pd coating layer. The bonding wire for a semiconductor device according to claim 4, wherein the thickness of the alloy skin layer containing Au and Pd is 0.0005 to 0.050 μm. The bonding wire for a semiconductor device according to any one of claims 1 to 5, wherein the bonding wire further includes at least one element selected from the group consisting of Ni, Zn, Rh, In, Ir, Pt, Ga, and Ge, The concentration of the element relative to the entire wire is 0.011 to 1.2% by mass, respectively. The bonding wire for a semiconductor device according to any one of claims 1 to 6, wherein the Cu alloy core material contains Pd, and the concentration of Pd contained in the Cu alloy core material is 0.05 to 1.2% by mass. The bonding wire for a semiconductor device according to any one of claims 1 to 7, wherein the bonding wire further comprises at least one element selected from the group consisting of B, P, Mg, Ca, and La, wherein the element is substantially the same as the wire The concentrations are respectively from 1 to 100 ppm by mass. The bonding wire for a semiconductor device according to any one of claims 1 to 8, wherein, in the measurement result of measuring the crystal orientation of the surface of the bonding wire, a crystal orientation of an angle difference of 15 degrees or less with respect to the longitudinal direction of the bonding wire The existence ratio of <111> is 30 to 100% in terms of area ratio. The bonding wire for a semiconductor device according to any one of claims 1 to 9, wherein Cu is present on the outermost surface of the bonding wire.