WO2014038850A1 - Bonding wire for semiconductor device and manufacturing method therefor - Google Patents

Abstract

The present invention relates to a bonding wire for a semiconductor device and a manufacturing method therefor and, more particularly, to a method for manufacturing a bonding wire for a semiconductor device, comprising the steps of: forming a first coating layer having a second metal as a main component on a core material having a first metal as a main component; wire-drawing the core material on which the first coating layer is formed; and forming a second coating layer having a third metal as a main component on the core material and the first coating layer for which the wire drawing has been completed. When a bonding wire and a manufacturing method therefor of the present invention are used, damage to a chip can be reduced while preventing the exposure of the core material, and the acid resistance and bonding properties of a second side can be improved.

Description

Bonding wire for semiconductor device and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding wire for semiconductor devices and a method for manufacturing the same. It is about.

Various structures exist in a package for mounting a semiconductor device, and bonding wires are still widely used to connect the substrate and the semiconductor device or to connect the semiconductor devices. As a bonding wire, gold bonding wires have been used a lot, but they are expensive and there is a demand for bonding wires that can replace them since the price has risen recently.

Many research efforts have been made to replace gold bonding wires, and there is a high interest in copper bonding wires. However, since a single layer copper bonding wire is easily surface oxidized in air, a problem may arise in the bonding property between the bonding pad and the lead. In order to improve this, a multilayer copper bonding wire has been proposed that coats the surface of a single layer copper bonding wire with another metal.

However, when forming a heterogeneous metal on a copper core material in order to manufacture a multilayer copper bonding wire and performing the drawing process several times, the heterogeneous metal may be peeled off and the copper core material may be exposed. As such, when the copper core is exposed, problems such as a single layer of copper bonding wire may occur, which may cause a defect when applied to a semiconductor device.

In addition, there is a demand for improving the bonding property of the multilayer copper bonding wire to the bonding pad or the lead.

The first technical problem to be achieved by the present invention is to provide a method of manufacturing a bonding wire for a semiconductor device that can reduce damage to the chip while preventing the exposure of the core material, and can improve the acid resistance and the bonding property of the second side.

The second technical problem to be achieved by the present invention is to provide a bonding wire for a semiconductor device which can reduce chip damage while preventing the exposure of the core material and can improve the acid resistance and the bonding property of the second side.

The present invention to achieve the first technical problem, the step of forming a first skin layer having a second metal as a main component on a core material having a first metal as a main component; Drawing the core material having a first skin layer formed thereon; And forming a second skin layer including a third metal as a main component on the core material and the first skin layer on which the drawing is completed.

Here, the first metal is copper, silver or an alloy thereof, the second metal is gold, silver, platinum, palladium, or an alloy thereof, and the third metal is gold, silver, platinum, palladium, or these Of alloys. The first metal and the second metal are different from each other in composition or composition.

In addition, after the forming of the second epidermal layer, the drawing process may be performed two times or less. Preferably, the drawing process is not performed after the forming of the second epidermal layer.

In addition, the method of manufacturing a bonding wire for a semiconductor device may further include roughening the second skin layer after the forming of the second skin layer. In this case, the roughening of the second epidermal layer may include a step of plasma treatment of the second epidermal layer. Roughness of the surface of the second epidermal layer may be about 1 nm to about 6 nm.

The present invention, in order to achieve the second technical problem, the core material having a first metal as a main component; A first epidermal layer formed on the surface of the core material and mainly comprising a second metal having a component or composition different from the first metal; And a second skin layer surrounding the core material and the first skin layer, the second skin layer being mainly composed of a third metal having a component or composition different from the second metal.

Here, the first metal is copper, silver or an alloy thereof, the second metal is gold, silver, platinum, palladium, or an alloy thereof, and the third metal is gold, silver, platinum, palladium, or these Of alloys. In addition, the surface of the second epidermal layer may have a surface roughness of about 1 nm to about 6 nm.

In this case, the sum of the thicknesses of the first epidermal layer and the second epidermal layer may be about 30 nm to about 100 nm. In addition, the thickness of the first epidermal layer may be about 25 nm to about 85 nm.

In addition, the percentage of the sum of the cross-sectional areas of the first skin layer and the second skin layer relative to the cross-sectional area of the bonding wire may be about 0.597% to about 1.97%. Optionally, the percentage of the sum of the cross-sectional areas of the first and second skin layers relative to the cross-sectional area of the bonding wire may be from about 0.993% to about 1.97%. Optionally, the percentage of the sum of the cross-sectional areas of the first and second skin layers relative to the cross-sectional area of the bonding wire may be from about 1.189% to about 1.581%.

In another aspect, the present invention is an alternative embodiment for achieving the second object, the core material having a first metal as a main component; And a skin layer formed on the surface of the core material, the skin layer mainly comprising a second metal having a component or composition different from the first metal, wherein the surface of the skin layer has a surface roughness of 1 nm to 6 nm. Provided is a bonding wire for a semiconductor device.

Here, the first metal is copper, silver or an alloy thereof, and the second metal is gold, silver, platinum, palladium, or an alloy thereof.

By using the bonding wire of the present invention and its manufacturing method, it is possible to reduce the damage of the chip while preventing the exposure of the core material, and there is an effect of improving the acid resistance and the bonding property of the second side.

1 and 2 are conceptual views showing a cross-section of the bonding wire according to an embodiment of the present invention.

3 is a flowchart illustrating a method of manufacturing a bonding wire according to an embodiment of the present invention in order.

Hereinafter, exemplary embodiments of the inventive concept will be described in detail with reference to the accompanying drawings. However, embodiments of the inventive concept may be modified in many different forms and should not be construed as limiting the scope of the inventive concept to the embodiments described below. Embodiments of the inventive concept are preferably interpreted as being provided to those skilled in the art to more fully describe the inventive concept. Like numbers refer to like elements all the time. Furthermore, various elements and regions in the drawings are schematically drawn. Accordingly, the inventive concept is not limited by the relative size or spacing drawn in the accompanying drawings.

Terms such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the inventive concept, the first component may be referred to as the second component, and vice versa, the second component may be referred to as the first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concepts. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the expression “comprises” or “having” is intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and that one or more other features It should be understood that it does not exclude in advance the possibility of the presence or addition of numbers, operations, components, parts or combinations thereof.

Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art, including technical terms and scientific terms. Also, as used in the prior art, terms as defined in advance should be construed to have a meaning consistent with what they mean in the context of the technology concerned, and in an overly formal sense unless explicitly defined herein. It will be understood that it should not be interpreted.

1 is a conceptual diagram illustrating a cross section of a bonding wire for a semiconductor device according to an embodiment of the present invention.

Referring to FIG. 1, the bonding wire 100 for a semiconductor device according to an embodiment of the present invention may include three layers. That is, the core material 110 having the first metal as a main component, the first skin layer 120 formed on the surface of the core material 110 and having the second metal as the main component, and the core material 110 and the first skin layer ( It may include a second skin layer 130 surrounding the 120 and the third metal as a main component.

Here, the "main component" means that the ratio of the concentration of the metal is 50 mol% or more.

The first metal may be copper (Cu), silver (Ag), or an alloy thereof. The second metal and the third metal may each independently be gold (Au), silver (Ag), platinum (Pt), palladium (Pd), or an alloy of two or more thereof. In addition, the first metal is different in component or composition from the second metal. The second metal may have the same composition as or different from that of the third metal. When the second metal has the same composition and composition as the third metal, the interface between the first skin layer 120 and the second skin layer 130 may not be identified. In this case, the first skin layer 120 and the first skin layer 120 may not be identified. The second epidermal layer 130 is bundled and referred to as the epidermal layer 140.

The first epidermal layer 120 may completely surround the core material 110, and a portion not surrounding the core material 110 may be partially present. 2 is a cross-sectional view showing an embodiment of the bonding wire 100a in which a portion of the first skin layer 120 that does not surround the core material 110 exists partially. Referring to FIG. 2, the first epidermal layer 120 does not cover the entire circumference of the core material 110 but is partially exposed to the outside of the first epidermal layer 120. However, since the exposed portion of the core material 110 is covered by the second skin layer 130, it is possible to prevent the core material 110 from being oxidized in the air to form an oxide film.

The sum of the thicknesses of the first epidermal layer 120 and the second epidermal layer 130 at any point on the surface of the core material 110 may be about 30 nm to about 100 nm. If the sum of the thicknesses of the first epidermal layer 120 and the second epidermal layer 130 is too thin, the second side where the stitch bonding is performed may have poor adhesion. In addition, when the sum of the thicknesses of the first epidermal layer 120 and the second epidermal layer 130 is too thick, the ball bonded portion may be damaged. Here, the “second side” refers to a side of the two terminals to which the bonding wire is to be connected later, and is generally connected by a stitch bonding method.

In particular, the thickness of the first epidermal layer 120 may be about 25 nm to about 85 nm. When the thickness of the first epidermal layer 120 is not constant, the thickness of the thickest portion may be about 25 nm to about 85 nm. If the thickness of the first epidermal layer 120 is excessively thin, the first epidermal layer 120 may be peeled from the core material in the drawing process, and the second epidermal layer 130 formed later may be unstable. In addition, if the thickness of the first epidermal layer 120 is excessively thick, the ball bonded portion may be damaged.

The surface 132 of the second epidermal layer 130 may be roughened. In this way, roughening the surface 132 of the second skin layer 130 can improve the bonding property, especially on the second side. The surface roughness, that is, roughness, of the surface of the second epidermal layer 130 may be about 1 nm to about 6 nm. Or the roughness may be about 1 nm to about 4 nm. If the roughness is too small, the effect of improving the adhesion is insignificant, which is not preferable. On the contrary, if the roughness is too large, the second epidermal layer 130 may be damaged and the first epidermal layer 120 or the core material 110 may be exposed. Because it is not desirable.

As mentioned above, the core material 110 may be copper, silver, or an alloy thereof, and the properties of the bonding wire may be improved by additionally adding a small amount of alloying elements. For example, the core 110 is composed of zirconium (Zr), bismuth (Bi), phosphorus (P), boron (B), iridium (Ir), tin (Sn), molybdenum (Mo) and rare earth elements One or more elements selected from the group may comprise 0.002 to 0.05 mol% in total.

In the vicinity of the interface where the core material 110, the first skin layer 120, and the second skin layer 130 of the bonding wires 100 and 100 are in contact with each other, a region where a concentration gradient is formed by mutual diffusion of the corresponding components may be formed. Can be. Such diffusion layers with a concentration gradient can be produced by fresh or heat treatment. As mentioned above, "main component" means that the ratio of the concentration of the corresponding metal is 50 mol% or more, so that if the concentration of the first metal is 50 mol% or more even in the diffusion layer, it is regarded as belonging to the core region and the concentration of the second metal. Is 50 mol% or more, and is considered to belong to the first epidermal layer. If the concentration of the third metal is 50 mol% or more, it is considered to belong to the second epidermal layer.

Therefore, it is possible to determine which region of the core material 110, the first skin layer 120, and the second skin layer 130 belongs to any particular point of the cross section of the bonding wires 100 and 100a. To determine this, any method known in the art can be used to analyze the components and concentrations at that particular point. For example, the method of digging into the depth direction by sputtering from the surfaces of the bonding wires 100 and 100a, or the line analysis or point analysis in the wire cross section, etc. can be used.

The sputtering method is effective when the first epidermal layer 120 and the second epidermal layer 130 are thin, but the measurement time may be excessive when the thickness is thick. Line analysis or point analysis in the wire cross section is less accurate when the first epidermal layer 120 and the second epidermal layer 130 are thin, but when the first epidermal layer 120 and the second epidermal layer 130 are thick, There is an advantage that it is easy to confirm concentration distribution and reproducibility in various parts. As an analytical device used for concentration analysis, electron beam microanalysis (EPMA), energy dispersive X-ray analysis (EDX), Auger spectroscopy (AES), transmission electron microscope (TEM), and the like can be used. Auger spectroscopy, in particular, has high spatial resolution, making it suitable for concentration analysis of thinner regions on the outermost surface.

The thicknesses of the first epidermal layer 120 and the second epidermal layer 130 may be measured using the methods described above. Furthermore, the cross-sectional area of each of the first skin layer 120 and the second skin layer 130 and the cross-sectional area of the entire bonding wire may be obtained using the measured thickness.

The percentage of the sum of the cross-sectional areas of the first and second skin layers 120 and 130 with respect to the total cross-sectional areas of the bonding wires 100 and 100a measured as described above may be about 0.597% to about 1.97%. In particular, the percentage of the sum of the cross-sectional areas of the first and second skin layers 120 and 130 with respect to the overall cross-sectional areas of the bonding wires 100 and 100a may be about 0.993% to about 1.97%. Alternatively, the percentage of the sum of the cross-sectional areas of the first and second skin layers 120 and 130 relative to the total cross-sectional areas of the bonding wires 100 and 100a may be about 1.189% to about 1.581%.

3 is a flowchart illustrating a method of manufacturing a bonding wire according to an embodiment of the present invention. Hereinafter, a method of manufacturing a bonding wire according to an embodiment of the present invention will be described with reference to FIG. 3. First, a core material mainly containing a first metal is provided. As described above, the first metal may be copper (Cu), silver (Ag), or an alloy thereof. The core material containing the first metal as a main component is drawn and / or heat treated, for example, to be processed to have a diameter of about 100 μm.

Then, a first skin layer having a second metal as a main component is formed on the core material having the first metal as a main component (S1). As a method of forming a 1st skin layer on a core material, a plating method, a vapor deposition method, a melting method, etc. can be used, for example. As the plating method, electrolytic plating may be used or electroless plating may be used. In electrolytic plating, strike plating or flash plating can be used especially. Electrolytic plating has a high plating speed and good adhesiveness with the underlying layer. The solution used for electroless plating may be classified into a substitution type and a reduction type. Substituting plating alone is sufficient when forming a thin film, but when forming a thick film, it is preferable to perform reduction plating after substitution plating.

As the vapor deposition method, a physical vapor deposition method such as sputtering method, ion plating method, vacuum deposition, or a chemical vapor deposition method such as plasma enhanced chemical vapor deposition can be used. If the vapor deposition method is used, cleaning is not necessary after film formation, and thus no problem of contamination due to cleaning occurs.

The melting method is a method of melting and injecting either the skin layer (the first skin layer and / or the second skin layer) or the core material by injecting the molten skin layer metal around the core material prepared in advance to form the skin layer. Alternatively, on the contrary, the core may be manufactured by injecting the core material into the center portion of the hollow cylinder of the skin layer prepared in advance.

Then, the core material in which the first epidermal layer 120 is formed is fresh (S2). The drawing may be carried out in several steps and may be drawn, for example, to a diameter of about 20 μm. If necessary, heat treatment may be performed during the drawing process. The heat treatment may be performed for about 0.001 seconds to about 5 seconds at a temperature of about 400 ℃ to about 600 ℃. In addition, the heat treatment may be performed only once, or may be performed two or more times.

By the heat treatment, but there is mutual diffusion at the interface between the core material 110 and the first skin layer 120 may be improved adhesion. In addition, when the heat treatment temperature is performed at a temperature higher than the recrystallization temperature of the core material 110 and lower than the recrystallization temperature of the first skin layer 120, physical properties of the bonding wire obtained may be improved.

Then, a second skin layer 130 is formed on the core material 110 and the first skin layer 120. As mentioned above, the composition and composition of the first epidermal layer 120 may be the same as or different from the composition and composition of the second epidermal layer 130. The thickness of the second epidermal layer 130 may be about 5 nm to about 25 nm. If the thickness of the second epidermal layer 130 is too thin, the peeling of the fresh portion of the first epidermal layer may be weakened, resulting in deterioration of the second bond. Also, since the ball formed by the bonding wire is deteriorated, eccentric balls may occur. Can be. In addition, if the thickness of the second skin layer 130 is too thick, the workability of the bonding wire may be deteriorated, and the true structure of the ball formed during ball bonding may be degraded.

The second skin layer 130 may also be performed by a method known in the art, such as a plating method, a deposition method, a melting method, and the like, and thus, a detailed description thereof will be omitted.

After the second skin layer 130 is formed, heat treatment may be further performed. The heat treatment may be performed to have an elongation of about 9%. To this end, heat treatment may be performed for about 0.001 seconds to about 5 seconds at a temperature of about 400 ℃ to about 600 ℃. Alternatively, the heat treatment time may be about 0.05 seconds to about 3 seconds.

In addition, after the second skin layer 130 is formed, the freshness may be further roughened as necessary. However, since the second epidermal layer 130 may be peeled off when the wire is subjected to a plurality of times, it is preferable that the second epidermal layer 130 be performed twice or less. It is more preferable not to draw after forming the second epidermal layer 130.

The surface of the second skin layer 130 formed as described above can be roughened. Roughness of the roughened second epidermal layer 130 may be about 1 nm to about 6 nm. Preferably, the roughness of the roughened second epidermal layer 130 may be about 1 nm to about 4 nm. The roughening treatment may be performed by, for example, atmospheric pressure plasma treatment. The atmospheric plasma treatment may be performed by applying 40 W to 60 W of power using, for example, Ar gas or Ar + H ₂ mixed gas.

The heat treatment and roughening treatment after forming the second skin layer 130 are not particularly limited in order, and any process may be performed first. Optionally, the heat treatment may be performed before or after the roughening treatment when a plurality of heat treatments are performed.

Hereinafter, the structure and effects of the present invention will be described in more detail with specific examples and comparative examples, but these examples are only intended to more clearly understand the present invention and are not intended to limit the scope of the present invention.

<Manufacture of Bonding Wire>

After preparing a core having a diameter of about 100 μm of copper or silver, a first metal was formed on the surface of the core by a plating method and a bonding wire having a diameter of 20 μm was obtained through a drawing process. Then, the second metal was formed on the surface by a plating method and heat-treated so that the elongation was 9%. The heat treatment conditions may be slightly different for each specific embodiment, and may be heat treated for 0.001 seconds to 5 seconds at a temperature of approximately 400 ℃ to 600 ℃. After the heat treatment was completed, the bonding wire surface was roughened by using an atmospheric pressure plasma. The power conditions of the atmospheric plasma were adjusted in the range of 40W to 60W to control the degree of roughening.

<Epidermal thickness analysis>

Auger spectroscopy (AES) was used to measure the skin layer thickness of the bonding wire surface by sputtering with Ar ions.

<Acid resistance>

The bonding wire was immersed in 30% nitric acid for 5 minutes, then taken out and washed with deionized water, and the mass change before and after immersion was within 10% of the original bonding wire mass (●), and from 10% to 25% was good (◐), If it exceeds 25%, it was judged as insufficient (○).

Bonding wire application test

Bonding of the ball bonding / stitch bonding method was performed by ultrasonic thermocompression method using K & S Maxum Ultra equipment using the manufactured bonding wire. A ball is formed at the end of the wire by arc discharge in a forming gas (N ₂ + 5% H ₂ ) atmosphere to first bond to a 1 μm aluminum pad on a silicon substrate, which is then extended to 2 μm Ag or Pd. Wedge bonding was performed on a plated 220 ° C. lead frame.

Second bonding and chip cratering tests were performed on the bonded wires thus bonded.

Chip cratering

As described above, after the aluminum pad was dissolved in an alkaline solution and removed from the bonded bonding wire, it was observed whether the silicon substrate at the position where the aluminum pad was present was damaged. If there was no damage, it was judged as good (●), and if there was damage, it was insufficient (○).

Second bonding

Pulling tests were performed using a Dage 4000 instrument for stitch bonding. The execution of the second bonding test was carried out for 15 places at each position with the same positions of up, down, left and right, and the error rate and the Cpk value were calculated based on the obtained values.

In each embodiment, the core material, the first skin layer, the metal component of the second skin layer, the measured surface roughness, the thickness of each skin layer and the area ratio thereof are summarized in Table 1 below.

TABLE 1

In each comparative example, the core material, the first skin layer, the metal components of the second skin layer, the measured surface roughness, the thickness of each skin layer, and the area ratios thereof are summarized in the following Table 2.

TABLE 2

For each of the above examples and comparative examples, chip cratering, acid resistance, second bondability, and error rate were measured and summarized in Tables 3 and 4 below.

TABLE 3

TABLE 4

Looking at the results of the above Examples and Comparative Examples it can be seen that when the surface roughness of the bonding wire falls within the range of 1 nm to 6 nm, all of the chip cratering, acid resistance and second side bonding are excellent. In particular, when the percentage of the sum of the cross-sectional areas of the first skin layer and the second skin layer to the cross-sectional area of the entire bonding wire is within 0.597% to 1.97%, it was confirmed that the bonding property is more excellent.

Although described in detail with respect to preferred embodiments of the present invention as described above, those of ordinary skill in the art, without departing from the spirit and scope of the invention as defined in the appended claims Various modifications may be made to the invention. Therefore, changes in the future embodiments of the present invention will not be able to escape the technology of the present invention.

The present invention can be usefully used in the semiconductor industry.

Claims (14)

Core material based on the first metal; A first epidermal layer formed on the surface of the core material and mainly comprising a second metal having a component or composition different from the first metal; And A second skin layer surrounding the core material and the first skin layer and having a third metal having a component or composition different from that of the second metal; Including, The first metal is copper, silver or an alloy thereof, The second metal is gold, silver, platinum, palladium, or an alloy thereof; The third metal is gold, silver, platinum, palladium, or an alloy thereof; The surface of the said 2nd skin layer has the surface roughness of 1 nm-6 nm, The bonding wire for semiconductor devices. The method of claim 1, The sum of the thicknesses of the first skin layer and the second skin layer is 30 nm to 100 nm. The method of claim 2, Bonding wire for a semiconductor device, characterized in that the thickness of the first skin layer is 25 nm to 85 nm. The method of claim 1, And a percentage of the sum of the cross-sectional areas of the first and second skin layers with respect to the cross-sectional areas of the bonding wires is 0.597% to 1.97%. The method of claim 1, The percentage of the sum of the cross-sectional areas of the first and second skin layers relative to the cross-sectional area of the bonding wire is 0.993% to 1.97%. The method of claim 1, The percentage of the sum of the cross-sectional areas of the first and second skin layers relative to the cross-sectional areas of the bonding wires is 1.189% to 1.581%. Core material based on the first metal; And An epidermal layer formed on the surface of the core material and mainly composed of a second metal having a different component or composition than the first metal; Including, The first metal is copper, silver or an alloy thereof, The second metal is gold, silver, platinum, palladium, or an alloy thereof; The surface of the said skin layer has the surface roughness of 1 nm-6 nm, The bonding wire for semiconductor devices. As a manufacturing method of the bonding wire for semiconductor devices, Forming a first skin layer including a second metal as a main component on the core material containing the first metal as a main component; Drawing the core material having a first skin layer formed thereon; And Forming a second skin layer including a third metal as a main component on the core material and the first skin layer on which the drawing is completed; Including, The first metal is copper, silver or an alloy thereof, The second metal is gold, silver, platinum, palladium, or an alloy thereof; And said third metal is gold, silver, platinum, palladium, or an alloy thereof. The method of claim 8, A method for manufacturing a bonding wire for a semiconductor device, wherein the first metal and the second metal are different from each other. The method of claim 8, After the forming of the second skin layer, a drawing process is performed twice or less, characterized in that the manufacturing method of the bonding wire for a semiconductor device. The method of claim 8, And after the forming of the second skin layer, a drawing process is not performed. The method of claim 8, And roughening the second skin layer after the forming of the second skin layer. The method of claim 12, And roughening the second skin layer comprises plasma treating the second skin layer. The method of claim 12, The roughness of the surface of the said 2nd skin layer is 1 nm-6 nm, The manufacturing method of the bonding wire for semiconductor devices.

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