JP6938966B2 - Manufacturing method of connection structure, connection structure and semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a connection structure, a connection structure, and a semiconductor device.

In a conventional power module, an electrode of a power device chip arranged on an insulating substrate in a module case and an external electrode of the module case are connected by wire bonding using an aluminum wire (see, for example, Patent Document 1). .. In such a semiconductor device, since the aluminum wire is directly bonded to the heat generating portion of the power device chip, thermal stress due to repeated on and off of the power device chip is applied to the aluminum wire, and this thermal stress is used as it is for fatigue life. Appears as.

For the purpose of reducing thermal stress on aluminum wires and improving reliability, wire bonding with thick copper wires of 200 μmΦ or more has been proposed for power devices instead of conventional bonding with aluminum wires (for example, non-bonding with aluminum wires). See Patent Document 1). In addition to wire bonding, a method of bonding with a metal wire such as aluminum, copper, or solder having a ribbon shape (for example, width 2 mm x thickness 0.3 mm) called ribbon bonding is also being studied.

Japanese Unexamined Patent Publication No. 2-260551

Copper Wire Bonding for Power Devices, Spring Lecture Meeting of the 26th Electronics Packaging Society, pp367-369

Compared with gold and aluminum, copper is more prone to work hardening. In order to join metal wires with sufficient strength, it is necessary to increase the pressing force or ultrasonic output at the time of joining, but such joining conditions tend to cause chip damage at the time of joining.

Even when joining ribbon-shaped metal wires, it is necessary to increase the pressing force or ultrasonic output at the time of joining in order to secure the joining strength, so there is a concern that chip damage may occur.

Therefore, the present invention relates to a method for manufacturing a connection structure capable of obtaining sufficient joint strength while reducing the influence on the members to be connected, and a member such as a thick wire metal wire or a ribbon-shaped metal wire is connected. It is an object of the present invention to provide a connection structure capable of having sufficient joint strength even when the case is used.

As a result of diligent studies by the present inventors in order to solve the above problems, a joint portion containing a specific sintered copper layer is provided on the semiconductor element, and a metal wire is bonded to this joint portion to form a semiconductor element. We have found that both damage suppression and good wire bonding can be achieved at the same time, and have completed the present invention.

That is, the present invention has a connection having a first member and a joint provided on the first member including a sintered copper layer having a copper content of 65% by volume or more and 95% by volume or less. Provided is a method for manufacturing a connecting structure, comprising a first step of preparing a working member and a second step of joining a second member to a joint portion, wherein the second member is a metal wire.

According to the method for manufacturing a connection structure of the present invention, it is possible to obtain a connection structure having sufficient joint strength while reducing the influence on the members to be connected. The reason why such an effect is exhibited is that the sintered copper layer having a copper content of 65% by volume or more and 95% by volume or less, that is, having appropriate voids, has sufficient strength but is a cushion layer. The present inventors consider that the impact on the first member could be sufficiently reduced by functioning as the first member.

The joint contains at least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver provided on the surface of the sintered copper layer opposite to the first member. It may further include a single layer or a multi-layer metal-containing layer. In this case, it becomes easier to obtain a connection structure having sufficient joint strength while reducing the influence on the members to be connected. The reason why such an effect is exhibited is that the sintered copper layer functions as a cushion layer and the conditions at the time of joining the second member by the specific metal-containing layer (for example, pressing force or ultrasonic waves). It is conceivable that the output etc.) can be relaxed.

The sintered copper layer has a structure derived from flake-shaped copper particles oriented substantially parallel to the surface of the first member in contact with the sintered copper layer, from the viewpoint of further reducing the impact on the first member. Is preferably included. For example, a second member, such as a thick wire metal wire or a ribbon-shaped metal wire, pressurizes the surface of the first member (for example, an aluminum film formed by sputtering on the surface of a Si chip) from almost perpendicular to the surface. When this is done, the effect of absorbing the impact can be easily obtained.

In the method for producing a connecting structure of the present invention, a copper paste layer containing flake-shaped copper particles is provided on a first member, and the copper paste layer is fired to form a sintered copper layer. can.

In the method for manufacturing a connection structure of the present invention, the first member and the above may be a semiconductor element.

Usually, an aluminum film is often formed on the surface of a semiconductor element such as a silicon (Si) chip, and in order to directly connect a metal wire to this aluminum film, a certain pressure or ultrasonic output is applied. There is a need. In particular, when the metal wire has a thick metal wire or a ribbon shape, a larger pressing force or ultrasonic output is required, and a problem that the Si chip is cracked after connection is likely to occur. On the Si chip, "electroless nickel plating film / electroless palladium plating film", "electroless nickel plating film / electroless palladium plating film / electroless gold plating film", or "electroless nickel plating film / electroless gold" A "plating film / electroless nickel plating film" may be formed, but if the pressing force at the time of connection or the ultrasonic output is too large, the Si chip will crack. Further, even if these coatings are thickened (for example, about 20 μm), the cushioning effect cannot be sufficiently obtained and the Si chip is cracked.

On the other hand, according to the present invention, the cracking of the Si chip can be suppressed. The reason for this is that even if the metal wire has a thick metal wire or a ribbon shape, the effect of absorbing impact can be obtained by the sintered metal layer. Further, when the joint portion further contains the metal-containing layer, sufficient bonding can be achieved even if the pressing force at the time of connection or the ultrasonic output is suppressed.

In the method for producing a connecting structure of the present invention, the metal wire may be at least one metal wire selected from the group consisting of an aluminum wire, a copper wire, a palladium-coated wire, a silver wire, and a gold wire. ..

Further, the metal-containing layer is viewed from the sintered copper layer side.
a) Nickel-containing layer and palladium-containing layer b) Nickel-containing layer and gold-containing layer c) Nickel-containing layer, palladium-containing layer and gold-containing layer d) Palladium-containing layer e) Palladium-containing layer or gold-containing layer You may.

In the method for producing a connection structure of the present invention, the metal-containing layer can be formed by electroless plating and / or sputtering. In the case of sputtering, even if there are holes of several μm level on the surface of the sintered copper layer, it is possible to prevent the holes from being blocked, and even in the case of electroless plating, the thickness of the plating film is adjusted appropriately. By doing so, even if there are holes on the surface of the sintered copper layer, it is possible to prevent the holes from being closed, and it is also possible to prevent the plating solution from remaining inside the holes. As a result, a metal-containing layer having irregularities on the surface of the sintered copper layer can be formed, and good connection reliability can be obtained even when a thick metal wire or a ribbon-shaped metal wire is joined. Is possible.

Further, from the viewpoint of forming a plating film on the surface inside the pores of the sintered copper layer, the metal-containing layer may be formed by electroless plating in which plating is deposited while applying ultrasonic waves. Especially in electroless nickel plating, the precipitation rate of plating is fast, and hydrogen gas is likely to be generated when hypophosphorous acid or the like is used as a reducing agent. Even in this case, by applying ultrasonic waves, it is possible to prevent the pores of the sintered copper layer from being blocked by hydrogen gas and allow the reaction to proceed, and the surface inside the pores can also be treated. It becomes easy to form a plating film.

The present invention also includes a first member, a joint including a sintered copper layer, and a second member in this order, and the sintered copper layer is provided on the first member and is made of copper. Provided is a connecting structure in which the content is 65% by volume or more and 95% by volume or less, and the second member is a metal wire, which is joined to the joint portion.

The connection structure of the present invention has the above-mentioned joint portion, and the first member and the metal wire which is the second member are joined through the joint portion, so that the damage to the first member is small. Moreover, it can have sufficient bonding strength. Further, the connection structure of the present invention can have sufficient bonding strength even when the metal wire is a thick metal wire or a ribbon-shaped metal wire, and is excellent in connection reliability.

The joint contains at least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver provided on the surface of the sintered copper layer opposite to the first member. A single-layer or multi-layer metal-containing layer may be further included, and the second member may be bonded to the metal-containing layer. In this case, the connection structure can be further excellent in connection reliability because the second member can be sufficiently joined even if the pressing force or the ultrasonic output at the time of connection is suppressed.

The joint may include a structure derived from flaky copper particles oriented substantially parallel to the surface in contact with the first member. In this case, a second member, such as a thick wire metal wire or a ribbon-shaped metal wire, is applied from substantially perpendicular to the surface of the first member (for example, an aluminum coating on a Si chip formed by sputtering). When pressed, the effect of absorbing the impact can be easily obtained.

The present invention also provides a semiconductor device including the connection structure according to the present invention, wherein the first member is a semiconductor element.

The semiconductor device of the present invention can be excellent in connection reliability by providing the connection structure according to the present invention.

According to the present invention, a method for manufacturing a connection structure capable of obtaining sufficient joint strength while reducing the influence on the members to be connected, and members such as a thick wire metal wire or a ribbon-shaped metal wire are connected. It is possible to provide a connection structure capable of having sufficient bonding strength even when the bonding structure is used.

It is a schematic cross-sectional view which shows an example of the connection structure of this embodiment. 6 is an SEM image showing a cross section of a structure derived from flake-shaped copper particles. It is a schematic cross-sectional view which shows an example of embodiment of a metal-containing layer. It is a schematic cross-sectional view which shows an example of the manufacturing method of the connection structure of this embodiment. It is a schematic cross-sectional view which shows an example of the manufacturing method of the connection structure of this embodiment. It is a schematic cross-sectional view which shows an example of the semiconductor device of this embodiment. It is a schematic cross-sectional view which shows an example of the manufacturing method of the connection structure of this embodiment. It is a schematic cross-sectional view which shows an example of the connection structure (semiconductor device) of this embodiment. It is a schematic cross-sectional view for demonstrating the fabrication of the connection structure in an Example. It is a schematic cross-sectional view for demonstrating the fabrication of the connection structure in an Example. It is a schematic cross-sectional view for demonstrating the fabrication of the connection structure in an Example.

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments.

Hereinafter, preferred embodiments will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

[Connection structure]
FIG. 1 is a schematic cross-sectional view showing an example of the connection structure of the present embodiment. The connection structure 100 shown in FIG. 1 includes a first member 10, a joint portion 15, and a second member 40 in this order, and the first member 10 and the second member 40 are joined together. It is connected via the unit 15. The joint portion 15 has a sintered copper layer 20 provided on the first member 10 and a metal-containing layer 30 provided on the sintered copper layer 20. In the present embodiment, the second member 40 is joined to the sintered copper layer 20 via the metal-containing layer 30.

<Members>
In the connection structure 100 of the present embodiment, the first member 10 is a semiconductor element and the second member 40 is a metal wire.

Examples of semiconductor elements include power modules including diodes, rectifiers, thyristors, MOS gate drivers, power switches, power MOSFETs, IGBTs, shotkey diodes, fast recovery diodes, transmitters, amplifiers, LED modules, and the like.

Examples of the metal wire include a copper wire, a ribbon-shaped aluminum, a metal wire such as copper or solder, and a ribbon-shaped copper wire coated with aluminum, solder or the like.

When the metal wire is a copper wire, the diameter is preferably 100 μm or more, more preferably 150 μm or more and 500 μm or less, still more preferably 200 μm or more and 400 μm or less, from the viewpoint of reducing thermal stress and improving reliability.

When the metal wire has a ribbon shape, the width is preferably 0.3 mm or more, more preferably 0.5 mm or more and 3 mm or less, and 0.7 mm or more and 2 mm from the viewpoint of reducing thermal stress and improving reliability. The following is more preferable. The thickness is preferably 0.05 mm or more, more preferably 0.08 mm or more and 0.5 mm or less, still more preferably 0.1 mm or more and 0.4 mm or less, from the viewpoint of reducing thermal stress and improving reliability. ..

<Sintered copper layer>
The copper content (volume ratio) in the sintered copper layer 20 is preferably 65% by volume or more and 95% by volume or less, more preferably 70% by volume or more and 90% by volume or less, based on the volume of the sintered copper layer. It is preferably 70% by volume or more and more preferably 80% by volume. By setting the copper content in the sintered copper layer within the above range, it can function as a cushion layer having excellent shock absorption as compared with the case where the copper content is 100% by volume, and the metal wire is a thick wire. The impact on the first member can be reduced even if the metal wire or ribbon shape of the above is used.

When the composition of the material constituting the sintered copper layer is known, for example, the copper content in the sintered copper layer can be determined by the following procedure. First, the sintered copper layer is cut into a rectangular body, the vertical and horizontal lengths of the sintered metal layer are measured with a caliper or an external shape measuring device, and the thickness is measured with a film thickness meter to measure the volume of the sintered copper layer. calculate. _{The apparent density M 1} (g / cm ³ ) is obtained from the volume of the cut out sintered copper layer and the weight of the sintered copper layer measured by a precision balance. Using the obtained M ₁ and the copper density of 8.96 g / cm ³ , the copper content (volume%) in the sintered copper layer can be determined from the following formula (A).
Copper content (volume%) in the sintered copper layer = [(M ₁ ) /8.96] × 100 ... (A)

In the sintered copper layer 20, the ratio of the copper element in the elements excluding the light element among the constituent elements may be 95% by mass or more, 97% by mass or more, or 98% by mass or more. It may be 100% by mass. When the above ratio of the copper element in the sintered copper layer is within the above range, the formation of an intermetallic compound or the precipitation of dissimilar elements at the metal copper crystal grain boundary can be suppressed, and the metallic copper constituting the sintered metal layer can be suppressed. The properties tend to be strong, and even better connection reliability is likely to be obtained.

Further, when the ratio of the copper element in the elements excluding the light element in the sintered copper layer 20 is 100% by mass, the volume ratio of the copper can be regarded as the density (%).

The sintered copper layer 20 may include a structure derived from flaky copper particles oriented substantially parallel to the bonding interface of the connector (for example, the bonding surface between the first member and the sintered copper layer). preferable. In this case, when the second member such as a thick wire metal wire or a ribbon-shaped metal wire is pressed from a direction substantially perpendicular to the surface of the first member, the effect of absorbing the impact can be easily obtained. .. The reason for this is that the joint surface of the second member (for example, a wire) and the sintered copper derived from the flake-shaped copper particles are substantially parallel, and the periphery of the sintered copper derived from the flake-shaped copper particles. It is conceivable that vacancies are likely to be formed in.

FIG. 2 is a schematic cross-sectional view showing an example of typical morphology of the sintered copper layer in the connection structure of the present embodiment. The sintered copper layer shown in FIG. 2 is a sintered copper 1 having a structure derived from flake-shaped copper particles (hereinafter, may be referred to as a “flake-shaped structure”) and a sintered copper derived from other copper particles. Includes copper 2 and vacancies 3.

The sintered copper layer having the above structure can be formed by sintering a bonding copper paste containing flake-shaped copper particles. The flake shape includes a flat plate shape such as a plate shape or a scale shape. As the flake-like structure, the ratio of the major axis to the thickness may be 5 or more. The number average diameter of the major axis of the flake-shaped structure may be 2 μm or more, 3 μm or more, or 4 μm or more. When the shape of the flake-like structure is within this range, the reinforcing effect of the flake-like structure contained in the sintered copper layer is improved, and the bonded body is further improved in joint strength and connection reliability.

The major axis and thickness of the flake-like structure can be obtained from, for example, an SEM image of the bonded body. The method of measuring the major axis and the thickness of the flake-like structure from the SEM image will be illustrated below. The conjugate is poured with epoxy cast resin so that the entire sample is filled and cured. Cut the cast sample near the cross section you want to observe, grind the cross section by polishing, and perform CP (cross section polisher) processing. The cross section of the sample is observed with an SEM device at a magnification of 5000. A cross-sectional image (for example, 5000 times) of the joint is acquired, and it is a dense continuous part, which is a linear, rectangular, or ellipsoidal part, and is the longest of the straight lines contained in this part. When the length of the major axis is the major axis and the one with the longest length of the straight lines included in this part orthogonal to the major axis is the thickness, the length of the major axis is 1 μm or more and the major axis / thickness ratio is 4 or more. Something is regarded as a flake-shaped structure, and the major axis and thickness of the flake-shaped structure can be measured by image processing software having a length measuring function. The average value thereof can be obtained by calculating the number average with 20 points or more randomly selected.

The thickness of the sintered copper layer 20 is preferably 10 μm or more and 300 μm or less, and more preferably 20 μm or more and 250 μm or less, from the viewpoint of buffering the pressing force or ultrasonic output at the time of connecting the metal wire and suppressing cracking of the Si chip or the like. , 50 μm or more and 200 μm or less is more preferable.

The sintered copper layer 20 may be provided on the joint surface in which the electroless nickel plating film and the electroless palladium plating film are formed in this order. In this case, an electroless nickel plating film and an electroless palladium plating film can be provided on the first member.

<Metal-containing layer>
The metal-containing layer 30 can be a single layer or a plurality of layers containing at least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver. In particular, nickel and palladium are highly effective in suppressing diffusion of the underlying sintered copper onto the surface. Further, by forming a gold-containing layer, when a thick wire metal wire or a ribbon-shaped metal wire is connected as a second member, a pressing force or an ultrasonic output can be obtained as compared with the case where there is no gold-containing layer. It can be made smaller and connected, and the influence on the first member can be further reduced.

The metal-containing layer 30 can be formed by sputtering or electroless plating. When the metal-containing layer is a multi-layer, sputtering and electroless plating may be used in combination. In this case, the metal-containing layer can cover a part or all of the surface (exposed surface) of the sintered copper layer.

As a method for forming the metal-containing layer by sputtering and a method for forming the metal-containing layer by electroless plating, known methods can be used and are not particularly limited.

The metal-containing layer 30 is viewed from the sintered copper layer 20 side.
a) Nickel-containing layer and palladium-containing layer b) Nickel-containing layer and gold-containing layer c) Nickel-containing layer, palladium-containing layer and gold-containing layer d) Palladium-containing layer e) Palladium-containing layer or gold-containing layer You may.

When the metal-containing layer 30 is formed by electroless plating,
a') Electroless nickel plating film and electroless palladium plating film b') Electroless nickel plating film and electroless gold plating film c') Electroless nickel plating film, electroless palladium plating film and electroless gold plating film d' ) Electroless palladium plating film e') It may be either an electroless palladium plating film or an electroless gold plating film.

The thickness of the nickel-containing layer is preferably 10 nm or more and 0.5 μm or less, more preferably 20 nm or more and 0.1 μm or less, and further preferably 20 nm or more and 50 nm or less. By setting the thickness of the nickel-containing layer to 10 nm or more, it is possible to sufficiently suppress the diffusion of copper to the surface of the nickel-containing layer opposite to the sintered copper layer. Further, the upper limit of the thickness is preferably 0.5 μm or less for economic reasons.

The thickness of the palladium-containing layer is preferably 10 nm or more and 0.5 μm or less, preferably 15 nm or more and 0.1 μm or less, and further preferably 20 nm or more and 50 nm or less. By setting the thickness of the palladium-containing layer to 10 nm or more, when a nickel-containing layer is provided on copper or a base, nickel is sufficiently suppressed from diffusing to the surface of the palladium-containing layer opposite to the sintered copper layer. can do. Further, the upper limit of the thickness is preferably 0.5 μm or less for economic reasons.

The thicker the gold-containing layer, the smaller the pressing force or ultrasonic output when connecting the thick metal wire or the ribbon-shaped metal wire. From the viewpoint of suppressing the influence on the first member, the thickness of the gold-containing layer is preferably large, but it is preferably 0.5 μm or less for economic reasons.

FIG. 3 is a schematic cross-sectional view showing an example of an embodiment of the metal-containing layer. The metal-containing layer 30 shown in FIG. 3 is composed of an electroless nickel plating film 34 and an electroless palladium plating film 36 provided on the sintered copper layer 20.

The purity (nickel content) of the electroless nickel plating film 34 is preferably 80% by mass or more. From the viewpoint of reliability, the purity of the electroless nickel plating film is preferably 85% by mass or more, preferably 90% by mass or more.

The element content in the electroless nickel plating film is obtained, for example, by cutting out a cross section of conductive particles by an ultramicrotome method, observing the particles at a magnification of 250,000 times using a TEM, and analyzing the components by the EDX attached to the TEM. be able to.

The electroless nickel plating film 34 preferably contains at least one selected from the group consisting of phosphorus and boron, and more preferably contains phosphorus. Such an electroless nickel plating film is formed as an electroless nickel plating film containing a nickel-phosphorus alloy by co-depositing phosphorus using, for example, a phosphorus-containing compound such as sodium hypophosphite as a reducing agent. can do. Further, an electroless nickel plating film containing a nickel-boron alloy is formed by co-depositing boron using a boron-containing compound such as dimethylamine borane, sodium borohydride, or potassium borohydride as a reducing agent. be able to.

The thickness of the electroless nickel plating film 34 is preferably 10 nm or more and 0.5 μm or less, more preferably 20 nm or more and 0.1 μm or less, and further preferably 20 nm or more and 50 nm or less. By setting the thickness of the electroless nickel plating film to 10 nm or more, it is possible to prevent copper from diffusing to the surface opposite to the sintered copper layer of the electroless nickel plating film. The upper limit of the thickness is preferably 0.5 μm or less from the viewpoint of preventing the coating film from blocking the outlet of the pores and leaving the plating solution inside the pores.

From the viewpoint of forming a plating film on the surface inside the pores of the sintered copper layer, it is preferable to deposit the plating film while applying ultrasonic waves. Especially in electroless nickel plating, the precipitation rate of plating is fast, and hydrogen gas is likely to be generated when hypophosphorous acid or the like is used as a reducing agent. Even in this case, by applying ultrasonic waves, it is possible to prevent the pores of the sintered copper layer from being blocked by hydrogen gas and allow the reaction to proceed, and the surface inside the pores can also be treated. It becomes easy to form a plating film.

In the case of sputtering, it is difficult to deposit nickel on the inner wall of the pores, so that the copper of the sintered copper layer tends to diffuse to the surface of the nickel film formed by sputtering. On the other hand, according to electroless plating, it is possible to cover the inner wall of the pores, so that the sintered copper layer can be suppressed from diffusing to the upper part of the metal-containing layer, and the thick wire can be used as the second member. Even when connecting a metal wire or a ribbon-shaped metal wire, better connection reliability can be obtained.

The electroless palladium plating film 36 may be formed by using, for example, either a substitution type that does not use a reducing agent or a reduction type that uses a reducing agent. Examples of such an electroless palladium plating solution include MCA (manufactured by World Metal Co., Ltd., trade name) as a replacement type. Examples of the reduced type include APP (manufactured by Ishihara Pharmaceutical Co., Ltd., trade name). When the substituted type and the reduced type are compared, the reduced type is preferable from the viewpoint of having few voids and easily securing a covering area.

The source of palladium used in the electroless palladium plating solution is not particularly limited, and examples thereof include palladium compounds such as palladium chloride, sodium palladium chloride, ammonium palladium chloride, palladium sulfate, palladium nitrate, palladium acetate, and palladium oxide. .. Specifically, acidic palladium chloride "PdCl ₂ / HCl", tetraammine palladium nitrate "Pd (NH ₃ ) ₄ (NO ₃ ) ₂ ", dinitrodiammine palladium "Pd (NH ₃ ) ₂ (NO ₂ ) ₂ ", dicyano Diammine Palladium "Pd (CN) ₂ (NH ₃ ) ₂ ", Dichlorotetraammine Palladium "Pd (NH ₃ ) ₄ Cl ₂ ", Palladium Sulfamate "Pd (NH ₂ SO ₃ ) ₂ ", Diammine Palladium Sulfate "Pd (NH 3) 2" _{3) 2} SO ₄ ", oxalate tetraamminepalladium" _{Pd (NH 3) 4 C 2} O 4 ", may be used palladium sulfate" PdSO ₄ "or the like.

The reducing agent used in the electroless palladium plating solution is not particularly limited, but from the viewpoint of sufficiently increasing the palladium content in the obtained electroless palladium plating film and further suppressing the thickness variation of the electroless palladium plating film, a foric acid compound ( For example, sodium formate) is preferable.

The electroless palladium plating film 36 can contain at least one selected from the group consisting of phosphorus and boron. As the reducing agent used in the electroless palladium plating solution, for example, a phosphorus-containing compound such as hypophosphoric acid or phosphite; by using a boron-containing compound, an electroless palladium containing a palladium-phosphorus alloy or a palladium-boron alloy. A plating film can be obtained. In this case, it is preferable to adjust the concentration of the reducing agent, the pH, the temperature of the plating solution, and the like so that the palladium content in the electroless palladium plating film is within a desired range.

A complexing agent, a buffer, or the like can be added to the electroless palladium plating solution, if necessary. Examples of the complexing agent include ethylenediamine and tartaric acid. The type of buffer and the like is not particularly limited.

The palladium content in the electroless palladium plating film 36 is preferably 94% by mass or more, more preferably 97% by mass or more, still more preferably 99% by mass or more, based on the total amount of the electroless palladium plating film. The upper limit of the palladium content in the electroless palladium plating film is 100% by mass. When the palladium content in the electroless palladium plating film is in the above range, good connection reliability can be obtained even when a thick wire metal wire or a ribbon-shaped metal wire is connected as the second member.

The element content in the electroless palladium plating film is obtained, for example, by cutting out a cross section of conductive particles by an ultramicrotome method, observing the particles at a magnification of 250,000 times using a TEM, and analyzing the components with an EDX attached to the TEM. be able to.

The thickness of the electroless palladium plating film 36 is preferably 3 nm or more and 0.5 μm or less, more preferably 5 nm or more and 0.1 μm or less, and further preferably 10 nm or more and 50 nm or less. By setting the thickness of the electroless palladium plating film to 3 nm or more, it is possible to sufficiently suppress the diffusion of nickel to the surface opposite to the sintered copper layer of the electroless palladium plating film. Further, the upper limit of the thickness is preferably 0.5 μm or less for economic reasons.

An electroless gold plating film can be further formed on the surface of the electroless palladium plating film 36.

In this case, the purity of the electroless gold plating film is preferably 99% by mass or more, and more preferably 99.5% by mass or more. The electroless gold plating film may be formed by a replacement type gold plating solution, or a reduction type gold plating solution may be used after the replacement type gold plating solution to further thicken the gold plating film. Further, a substitution reduction type gold plating solution may be used. This is a replacement gold plating solution having a reducing agent in the plating solution, and can be thickened as compared with a normal replacement gold plating solution.

The thickness of the electroless gold plating film is preferably 10 nm or more and 0.5 μm or less, more preferably 20 nm or more and 0.4 μm or less, and further preferably 30 nm or more and 0.3 μm or less. The thicker the electroless gold-plated coating, the smaller the pressing force or ultrasonic output when connecting a thick wire metal wire or a ribbon-shaped metal wire. From the viewpoint of suppressing the influence on the first member, it is preferable that the thickness of the electroless gold plating film is large, but the reaction inside the pores tends to be more intense than that outside the pores. From the viewpoint of not blocking the outlet of the above, it is preferably 0.5 μm or less.

In the connection structure of the present embodiment, the sintered copper layer and the metal wire as the second member are connected via a metal-containing layer that covers a part or all of the surface of the sintered copper layer. .. By providing the above-mentioned sintered copper layer and metal-containing layer, the connection structure of the present embodiment can sufficiently reduce damage to the semiconductor element as the first member, and thus has excellent connection reliability. It can be a semiconductor device.

In the connection structure of the present embodiment, the metal-containing layer may have a form other than that formed by the above-mentioned plating or sputtering. In this case, a single-layer or multi-layer metal plate containing at least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver can be mentioned. By arranging such a metal plate on the sintered copper layer, a metal-containing layer can be provided.

Further, the joint portion may contain only a sintered copper layer. In this case as well, the metal wire, which is the second member, can be bonded to the sintered copper layer with sufficient bonding strength while sufficiently reducing the damage to the semiconductor element as the first member.

The wire pull strength between the first member and the second member, which is a metal wire, in the connection structure of the present embodiment may be 500 gf, 700 gf or more, or 1000 gf or more. It may be 1200 gf or more. The wire pull strength can be measured using a bond tester (manufactured by Dage, trade name: BT2400PC), a universal bond tester (4000 series, manufactured by Dage), or the like. The wire pull strength means the strength when the wire is pulled in a direction substantially perpendicular to the joint portion of the wire.

When the first member is a semiconductor element and the second member is a metal wire, the wire pull strength of these may be 500 gf or more, 700 gf or more, or 1000 gf or more. It may be 1200 gf or more. When the first member is a semiconductor element and the second member is a copper wire, the wire pull strength may be 500 gf or more, 700 gf or more, or 1000 gf or more. It may be 1200 gf or more.

In the connection structure according to the present embodiment, high connection reliability can be maintained even when the sintered copper layer is subjected to thermal stress generated by the difference in thermal expansion coefficient between the joined members. In addition, since this sintered copper layer is composed of a sufficient amount of metallic copper connected by metal bonds, it exhibits high thermal conductivity and can quickly dissipate heat when mounting a semiconductor device that generates a large amount of heat. be. Further, since the sintered copper layer is firmly bonded by metal bonding, it exhibits excellent bonding strength to a metal wire such as aluminum, copper or solder having a ribbon shape (for example, width 2 mm × thickness 0.3 mm). Can be done. As described above, the connection structure according to the present embodiment has a very effective property when applied to an electronic device having a large heat generation such as a power device, a logic circuit, and an amplifier. Such electronic devices can tolerate higher input power and can be operated at higher operating temperatures.

The connection structure according to the present invention is not limited to the above aspects and can be modified in various ways.

The first member is, for example, an IGBT, a diode, a Schottky barrier diode, a MOS-FET, a thyristor, a logic circuit, a sensor, an analog integrated circuit, an LED, a semiconductor laser, a semiconductor element such as a transmitter, a lead frame, and a metal plate attached. Ceramic substrates (for example, DBC), base materials for mounting semiconductor elements such as LED packages, metal wiring such as metal frames, block bodies having thermal conductivity and conductivity such as metal blocks, power supply members such as terminals, heat sinks, etc. It may be a water cooling plate or the like.

The above member may have a metal such as gold, silver, or nickel on the surface in contact with the sintered metal layer. When the member has electroless nickel plating, further forming electroless palladium plating on this plating greatly improves reliability.

Examples of the member containing metal on the surface in contact with the sintered metal layer include a member having various metal plating, a wire, a chip having metal plating, a heat spreader, a ceramic substrate to which a metal plate is attached, and a lead having various metal plating. Examples thereof include a frame or a lead frame made of various metals, a copper plate, and a copper foil.

[Manufacturing method of connection structure]
The method for manufacturing a connecting structure according to the present embodiment includes a first member and a sintered copper layer provided on the first member and having a copper content of 65% by volume or more and 95% by volume or less. It includes a first step of preparing a connecting member having a joint portion, and a second step of joining a second member to the joint portion. The second member is a metal wire.

In the present embodiment, the joint is at least selected from the group consisting of nickel, palladium, gold, platinum, and silver provided on the surface of the sintered copper layer opposite to the first member. A single or multi-layered metal-containing layer containing a kind of metal is further included, and a metal wire is bonded to the metal-containing layer or to the sintered copper layer via the metal-containing layer.

The sintered copper layer can be formed by using a bonding copper paste.

<Copper paste for joining>
The bonding copper paste of the present embodiment contains metal particles and a dispersion medium.

Examples of the metal particles according to the present embodiment include sub-micro copper particles, flake-shaped micro copper particles, copper particles other than these, and other metal particles. In the present specification, the sub-microcopper particles mean particles having a particle size or maximum diameter of 0.1 μm or more and less than 1.0 μm, and microcopper particles have a particle size or maximum diameter of 1.0 μm or more and 20 μm or less. Means particles.

(Sub-micro copper particles)
Examples of the sub-micro copper particles include copper particles having a particle size of 0.12 μm or more and 0.8 μm or less. For example, sub-micro copper particles having a volume average particle size of 0.12 μm or more and 0.8 μm or less are used. be able to. When the volume average particle size of the sub-micro copper particles is 0.12 μm or more, the effects of suppressing the synthesis cost of the sub-micro copper particles, good dispersibility, and suppressing the amount of the surface treatment agent used can be easily obtained. When the volume average particle size of the sub-micro copper particles is 0.8 μm or less, the effect of excellent sinterability of the sub-micro copper particles can be easily obtained. From the viewpoint of further exerting the above effect, the volume average particle size of the sub-micro copper particles may be 0.15 μm or more and 0.8 μm or less, 0.15 μm or more and 0.6 μm or less, and may be 0. It may be .2 μm or more and 0.5 μm or less, or 0.3 μm or more and 0.45 μm or less.

In the specification of the present application, the volume average particle diameter means a 50% volume average particle diameter. When determining the volume average particle size of copper particles, the particle size of the light scattering method is obtained by dispersing the copper particles as a raw material or dried copper particles obtained by removing volatile components from the bonding copper paste in a dispersion medium using a dispersant. It can be obtained by a method of measuring with a distribution measuring device (for example, Shimadzu nanoparticle size distribution measuring device (SALD-7500 nano, manufactured by Shimadzu Corporation)). When a light scattering particle size distribution measuring device is used, hexane, toluene, α-terpineol or the like can be used as the dispersion medium.

The sub-micro copper particles can contain 10% by mass or more of copper particles having a particle size of 0.12 μm or more and 0.8 μm or less. From the viewpoint of the sinterability of the copper paste for bonding, the sub-micro copper particles can contain 20% by mass or more of copper particles having a particle size of 0.12 μm or more and 0.8 μm or less, and can contain 30% by mass or more. , 100% by mass can be contained. When the content ratio of the copper particles having a particle size of 0.12 μm or more and 0.8 μm or less in the sub-micro copper particles is 20% by mass or more, the dispersibility of the copper particles is further improved, the viscosity is increased, and the paste concentration is decreased. It can be more suppressed.

The particle size of the copper particles can be determined by the following method. The particle size of the copper particles can be calculated from, for example, an SEM image. The powder of copper particles is placed on a carbon tape for SEM with a spatula to prepare a sample for SEM. This SEM sample is observed with an SEM device at a magnification of 5000. A quadrangle circumscribing the copper particles of this SEM image is drawn by image processing software, and one side thereof is used as the particle size of the particles.

The content of the sub-micro copper particles may be 20% by mass or more and 90% by mass or less, 30% by mass or more and 90% by mass or less, and 35% by mass or more, based on the total mass of the metal particles. It may be 85% by mass or less, and may be 40% by mass or more and 80% by mass or less. When the content of the sub-micro copper particles is within the above range, it becomes easy to form the sintered metal layer according to the above-described embodiment.

The content of the sub-micro copper particles may be 20% by mass or more and 90% by mass or less based on the total of the mass of the sub-micro copper particles and the mass of the flake-shaped micro copper particles. When the content of the sub-micro copper particles is 20% by mass or more, the space between the flake-shaped micro copper particles can be sufficiently filled, and the sintered metal layer according to the present embodiment described above can be easily formed. It becomes. When the content of the sub-micro copper particles is 90% by mass or less, the volume shrinkage when the bonding copper paste is sintered can be sufficiently suppressed, so that the sintered metal layer according to the present embodiment described above is formed. It becomes easy. From the viewpoint of further exerting the above effect, the content of the sub-micro copper particles is 30% by mass or more and 85% by mass or less based on the total of the mass of the sub-micro copper particles and the mass of the flake-shaped micro copper particles. It may be 35% by mass or more and 85% by mass or less, or 40% by mass or more and 80% by mass or less.

The shape of the sub-micro copper particles is not particularly limited. Examples of the shape of the sub-micro copper particles include a spherical shape, a lump shape, a needle shape, a flake shape, a substantially spherical shape, and an aggregate thereof. From the viewpoint of dispersibility and filling property, the shape of the sub-micro copper particles may be spherical, substantially spherical, or flake-shaped, and from the viewpoint of flammability, dispersibility, mixability with the flake-shaped micro-copper particles, and the like. It may be spherical or substantially spherical.

The sub-micro copper particles may have an aspect ratio of 5 or less or 3 or less from the viewpoint of dispersibility, filling property, and mixing property with the flake-shaped micro copper particles. As used herein, the "aspect ratio" refers to the long side / thickness of the particles. The measurement of the long side and the thickness of the particle can be obtained from, for example, an SEM image of the particle.

The submicro copper particles may be treated with a specific surface treatment agent. Specific surface treatment agents include, for example, organic acids having 8 to 16 carbon atoms. Examples of organic acids having 8 to 16 carbon atoms include capric acid, methylheptanic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid and ethyl. Octanoic acid, propylheptanic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, pentylheptanic acid, Tridecanoic acid, methyldodecanoic acid, ethylundecanoic acid, propyldecanoic acid, butylnonanoic acid, pentyloctanoic acid, myristic acid, methyltridecanoic acid, ethyldodecanoic acid, propylundecanoic acid, butyldecanoic acid, pentylnonanoic acid, hexyloctanoic acid, pentadecanoic acid , Methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecane Acids, heptylnonanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, nonylcyclohexanecarboxylic acid, etc. Saturated fatty acids in Aromas such as acid, pyromellitic acid, o-phenoxy benzoic acid, methyl benzoic acid, ethyl benzoic acid, propyl benzoic acid, butyl benzoic acid, pentyl benzoic acid, hexyl benzoic acid, heptyl benzoic acid, octyl benzoic acid, nonyl benzoic acid, etc. Group carboxylic acids include. One type of organic acid may be used alone, or two or more types may be used in combination. By combining such an organic acid with the above-mentioned sub-micro copper particles, there is a tendency that both the dispersibility of the sub-micro copper particles and the desorption of the organic acid at the time of sintering can be achieved at the same time.

The treatment amount of the surface treatment agent may be an amount that adheres to the surface of the sub-micro copper particles in a single-layer to a triple-layer. This amount is determined by the number of molecular layers (n) attached to the surface of the sub-micro copper particles, the specific surface area (A _p ) (unit: m ² / g) of the sub-micro copper particles, and the molecular weight (M _s ) of the surface treatment agent. the unit g / mol), the minimum coverage area of the surface treatment agent _(S S) (unit ^{m 2} / piece) can be calculated from Avogadro's number ^{_{(N a) (6.02 × 10}} 23 cells). Specifically, the processing amount of the surface treatment agent, the process amount of the surface treatment agent _{(wt%) = {(n · A} p · M s) / (S S · N A + n · A p · M s)} It is calculated according to the formula of × 100%.

The specific surface area of the sub-micro copper particles can be calculated by measuring the dried sub-micro copper particles by the BET specific surface area measurement method. Minimum coverage of the surface treatment agent, if the surface treatment agent is a straight-chain saturated fatty acids, is 2.05 × ¹⁰ -19 ^m 2/1 molecule. In the case of other surface treatment agents, for example, calculation from a molecular model or "Chemistry and Education" (Akihiro Ueda, Sumio Inafuku, Iwao Mori, 40 (2), 1992, p114-117). It can be measured by the method described. An example of a method for quantifying a surface treatment agent is shown. The surface treatment agent can be identified by a heat desorption gas / gas chromatograph mass spectrometer of the dry powder obtained by removing the dispersion medium from the bonding copper paste, whereby the carbon number and molecular weight of the surface treatment agent can be determined. The carbon content ratio of the surface treatment agent can be analyzed by carbon content analysis. Examples of the carbon content analysis method include a high-frequency induction heating furnace combustion / infrared absorption method. The amount of the surface treatment agent can be calculated from the carbon number, molecular weight and carbon content ratio of the identified surface treatment agent by the above formula.

The treatment amount of the surface treatment agent may be 0.07% by mass or more and 2.1% by mass or less, 0.10% by mass or more and 1.6% by mass or less, and 0.2% by mass. It may be 1.1% by mass or less.

As the submicro copper particles, commercially available ones can be used. Examples of commercially available sub-micro copper particles include CH-0200 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle diameter of 0.36 μm) and HT-14 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle diameter of 0. 41 μm), CT-500 (manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size 0.72 μm), Tn-Cu100 (manufactured by Taiyo Nisshi Co., Ltd., volume average particle size 0.12 μm).

(Flake-shaped micro copper particles)
Examples of the flake-shaped microcopper particles include copper particles having a maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of 4 or more. For example, an average maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of 4 are included. The above copper particles can be used. When the average maximum diameter and aspect ratio of the flake-shaped micro copper particles are within the above ranges, the volume shrinkage when the bonding copper paste is sintered can be sufficiently reduced, and the sintered metal layer according to the present embodiment described above can be used. It becomes easy to form. From the viewpoint of further exerting the above effect, the average maximum diameter of the flake-shaped microcopper particles may be 1 μm or more and 10 μm or less, or 3 μm or more and 10 μm or less. The measurement of the maximum diameter and the average maximum diameter of the flake-shaped microcopper particles can be obtained from, for example, an SEM image of the particles, and is obtained as the major axis X and the average value Xav of the major axis of the flake-shaped structure described later.

The flake-shaped micro copper particles can contain 50% by mass or more of copper particles having a maximum diameter of 1 μm or more and 20 μm or less. From the viewpoint of orientation in the connecting structure, reinforcing effect, and filling property of the bonding paste, the flake-shaped microcopper particles can contain 70% by mass or more of copper particles having a maximum diameter of 1 μm or more and 20 μm or less, and 80% by mass or more. It can contain, and can contain 100% by mass. From the viewpoint of suppressing bonding defects, the flake-shaped microcopper particles preferably do not contain particles having a size exceeding the bonding thickness, such as particles having a maximum diameter of more than 20 μm. The joint thickness means the thickness of the sintered copper layer in the direction perpendicular to the surface in contact with the first member.

An example is a method of calculating the major axis X of flake-shaped microcopper particles from an SEM image. The powder of flake-shaped microcopper particles is placed on a carbon tape for SEM with a spatula to prepare a sample for SEM. This SEM sample is observed with an SEM device at a magnification of 5000. A rectangle circumscribing the flake-shaped microcopper particles of the SEM image is drawn by image processing software, and the long side of the rectangle is defined as the major axis X of the particles. Using a plurality of SEM images, this measurement is performed on 50 or more flake-shaped microcopper particles, and the average value Xav of the major axis is calculated.

The flake-shaped microcopper particles may have an aspect ratio of 4 or more, or 6 or more. When the aspect ratio is within the above range, the flake-shaped microcopper particles in the bonding copper paste are oriented substantially parallel to the bonding surface, thereby causing volume shrinkage when the bonding copper paste is sintered. It can be suppressed, and it becomes easy to form the sintered metal layer according to the present embodiment described above.

The content of the flake-shaped microcopper particles may be 1% by mass or more and 90% by mass or less, 10% by mass or more and 70% by mass or less, or 20% by mass, based on the total mass of the metal particles. It may be 50% by mass or less. When the content of the flake-shaped microcopper particles is within the above range, it becomes easy to form the sintered metal layer according to the above-described embodiment.

The total content of the sub-micro copper particles and the content of the flake-shaped micro copper particles may be 80% by mass or more based on the total mass of the metal particles. When the total content of the sub-micro copper particles and the content of the micro copper particles is within the above range, it becomes easy to form the sintered metal layer according to the above-described embodiment. From the viewpoint of further exerting the above effect, the total content of the sub-micro copper particles and the content of the flake-shaped micro-copper particles may be 90% by mass or more based on the total mass of the metal particles. It may be 100% by mass or more, or 100% by mass.

In the flake-shaped microcopper particles, the presence or absence of treatment with the surface treatment agent is not particularly limited. From the viewpoint of dispersion stability and oxidation resistance, the flake-shaped microcopper particles may be treated with a surface treatment agent. The surface treatment agent may be one that is removed at the time of joining. Examples of such surface treatment agents include aliphatic carboxylic acids such as palmitic acid, stearic acid, arachidic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; and cetyl alcohols. , Aliphatic alcohols such as stearyl alcohol, isobornylcyclohexanol, tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, stearylamine; Aliphatic nitriles; silane coupling agents such as alkylalkoxysilanes; polymer treatment agents such as polyethylene glycols, polyvinyl alcohols, polyvinylpyrrolidones, silicone oligomers and the like can be mentioned. As the surface treatment agent, one type may be used alone, or two or more types may be used in combination.

The amount of the surface treatment agent to be treated may be one or more molecular layers on the surface of the particles. The treatment amount of such a surface treatment agent varies depending on the specific surface area of the flake-shaped microcopper particles, the molecular weight of the surface treatment agent, and the minimum coating area of the surface treatment agent. The treatment amount of the surface treatment agent is usually 0.001% by mass or more. The specific surface area of the flake-shaped microcopper particles, the molecular weight of the surface treatment agent, and the minimum coating area of the surface treatment agent can be calculated by the above-mentioned method.

When the copper paste for bonding is prepared only from the above sub-micro copper particles, the volume shrinkage and the sintering shrinkage due to the drying of the dispersion medium are large, so that the copper paste for bonding is easily peeled off from the adherend surface at the time of sintering, and the semiconductor. It is difficult to obtain sufficient die shear strength and connection reliability when joining elements and the like. By using the sub-micro copper particles and the flake-shaped micro copper particles in combination, the volume shrinkage when the bonding copper paste is sintered is suppressed, and the sintered metal layer according to the present embodiment described above can be formed. It will be easy.

In the bonding copper paste of the present embodiment, the content of the micro copper particles having a maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of less than 2 contained in the metal particles is 1 μm or more and 20 μm or less. Based on the total amount of flake-shaped microcopper particles having an aspect ratio of 4 or more, 50% by mass or less is preferable, and 30% by mass or less is more preferable. By limiting the content of microcopper particles having an average maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of less than 2, the flake-shaped microcopper particles in the bonding copper paste are substantially parallel to the bonding surface. The orientation becomes easier, and the volume shrinkage when the bonding copper paste is sintered can be suppressed more effectively. This facilitates the formation of the sintered metal layer according to the present embodiment described above. In terms of making it easier to obtain such an effect, the content of microcopper particles having an average maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of less than 2 is such that the maximum diameter is 1 μm or more and 20 μm or less, and the aspect ratio. It may be 20% by mass or less, or 10% by mass or less, based on the total amount of flake-shaped microcopper particles having a value of 4 or more.

As the flake-shaped microcopper particles according to the present embodiment, commercially available ones can be used. Commercially available flake-shaped microcopper particles include, for example, MA-C025 (manufactured by Mitsui Mining & Smelting Co., Ltd., average maximum diameter 4.1 μm), 3L3 (manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., average maximum diameter 7.3 μm). ), 1110F (Mitsui Mining & Smelting Co., Ltd., average maximum diameter 5.8 μm), 2L3 (Fukuda Metal Foil Powder Industry Co., Ltd., average maximum diameter 9 μm).

In the bonding copper paste of the present embodiment, the micro copper particles to be blended include flake-shaped micro copper particles having a maximum diameter of 1 μm or more and 20 μm or less and an aspect ratio of 4 or more, and have a maximum diameter of 1 μm or more and 20 μm. Microcopper particles having an aspect ratio of less than 2 and having a content of microcopper particles of less than 50% by mass, preferably 30% by mass or less, based on the total amount of the flake-shaped microcopper particles can be used. .. When commercially available flake-shaped microcopper particles are used, the maximum diameter is 1 μm or more and 20 μm or less, the flake-shaped microcopper particles having an aspect ratio of 4 or more are included, and the maximum diameter is 1 μm or more and 20 μm or less. The content of the microcopper particles having a ratio of less than 2 may be selected to be 50% by mass or less, preferably 30% by mass or less, based on the total amount of the flake-shaped microcopper particles.

(Other metal particles other than copper particles)
The metal particles may include the above-mentioned sub-micro copper particles and other metal particles other than the micro-copper particles, and may include, for example, particles such as nickel, silver, gold, palladium, and platinum. The volume average particle diameter of the other metal particles may be 0.01 μm or more and 10 μm or less, 0.01 μm or more and 5 μm or less, or 0.05 μm or more and 3 μm or less. When other metal particles are contained, the content thereof may be less than 20% by mass and 10% by mass or less based on the total mass of the metal particles from the viewpoint of obtaining sufficient bondability. You may. Other metal particles may not be included. The shapes of the other metal particles are not particularly limited.

By including metal particles other than copper particles, it is possible to obtain a sintered metal layer in which a plurality of types of metals are solid-dissolved or dispersed, so that mechanical properties such as yield stress and fatigue strength of the sintered metal layer are improved. It is easy to improve the connection reliability. In addition, the sintered metal layer formed by adding a plurality of types of metal particles improves the bonding strength and connection reliability with respect to a specific adherend (for example, copper, silver, nickel and gold). It's easy to do.

(Dispersion medium)
The dispersion medium is not particularly limited and may be volatile. Examples of the volatile dispersion medium include monovalent and polyvalent and polyvalent such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, α-terpineol and isobornylcyclohexanol (MTPH). Valuable alcohols; ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol Butylmethyl ether, diethylene glycol isopropylmethyl ether, triethylene glycol dimethyl ether, triethylene glycol butylmethyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, di Ethers such as propylene glycol dimethyl ether, tripropylene glycol methyl ether, tripropylene glycol dimethyl ether; ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), lactic acid Ethers such as ethyl, butyl lactate, γ-butyrolactone, propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide; cyclohexane, octane, nonane, decane, Examples thereof include aliphatic hydrocarbons such as undecane; aromatic hydrocarbons such as benzene, toluene and xylene; mercaptans having an alkyl group having 1 to 18 carbon atoms; and mercaptans having a cycloalkyl group having 5 to 7 carbon atoms. Examples of mercaptans having an alkyl group having 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, and hexyl mercaptan. And dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group having 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan and cycloheptyl mercaptan.

The content of the dispersion medium may be 5 to 50 parts by mass, where 100 parts by mass is the total mass of the metal particles. When the content of the dispersion medium is within the above range, the bonding copper paste can be adjusted to a more appropriate viscosity, and the sintering of copper particles is less likely to be hindered.

(Additive)
Wetting improvers such as nonionic surfactants and fluorine-based surfactants; defoaming agents such as silicone oil; ion trapping agents such as inorganic ion exchangers, etc. are appropriately added to the bonding copper paste, if necessary. You may.

(Preparation of copper paste for bonding)
The copper paste for bonding may be prepared by mixing the above-mentioned sub-micro copper particles, micro copper particles, other metal particles and any additive with a dispersion medium. After mixing each component, stirring treatment may be performed. For the copper paste for bonding, the maximum particle size of the dispersion liquid may be adjusted by a classification operation.

The copper paste for bonding is prepared by mixing sub-micro copper particles, a surface treatment agent, and a dispersion medium in advance and performing dispersion treatment to prepare a dispersion liquid of sub-micro copper particles, and further micro copper particles, other metal particles, and optionally. Additives may be mixed and prepared. By performing such a procedure, the dispersibility of the sub-micro copper particles is improved, the mixing property with the micro copper particles is improved, and the performance of the copper paste for bonding is further improved. Agglomerates may be removed by classifying the dispersion of submicro copper particles.

A preferred embodiment of the connecting member including the sintered copper layer formed by using the bonding copper paste of the present embodiment will be described.

(Connecting member)
The connecting member 200 shown in FIG. 4 includes a third member 50, a first member 10, a sintered metal layer 52 for joining the third member 50 and the first member 10, and a first member. A sintered copper layer 20 is provided on the surface of the member 10 opposite to the side on which the sintered metal layer 52 is provided. The connecting member 200 can be obtained by the following method.

(1) A member including a third member 50, a first member 10, and a sintered metal layer 52 for joining the third member 50 and the first member 10 is prepared in advance. A method in which the copper paste for joining described above is provided on the surface of the first member 10 and then sintered to provide a sintered copper layer 20.
(2) A metal paste such as the above-mentioned copper paste for bonding is provided on the third member 50, the first member 10 is laminated on the metal paste, and the above-mentioned bonding is performed on the first member 10. A method in which a sintered metal layer 52 for joining a third member 50 and a first member 10 and a sintered copper layer 20 are simultaneously formed by providing a copper paste for use and then performing sintering.
(3) The above-mentioned bonding copper paste is provided on the surface of the first member 20 and sintered, and a member having the sintered copper layer 20 provided on the first member 20 is prepared. After that, a method in which a metal paste such as the above-mentioned copper paste for bonding is provided on the third member 50, and the above-mentioned member prepared in advance is laminated on the metal paste to perform sintering.

In the present embodiment, the metal paste can be fired under the weight of the member above the metal paste or a pressure of 0.01 MPa or less.

In the above (1), for example, the first member, the metal paste such as the copper paste for joining described above, and the third member are laminated in this order on the side in the direction in which the weight of the first member works. A body is prepared, and the metal paste can be obtained by sintering the metal paste under the weight of the first member or the weight of the first member and a pressure of 0.01 MPa or less.

In the same manner as in (2) and (3) above, a laminate is prepared, and the metal paste is obtained by firing under the weight of the member above it or a pressure of 0.01 MPa or less. Can be done.

As the metal paste, it is preferable to use the above-mentioned bonding copper paste. In this case, a sintered copper layer is formed as the sintered metal layer 52. The copper content in the sintered copper layer is preferably 65% by volume or more. When the copper content in the sintered copper layer is within the above range, it is possible to prevent the formation of large pores inside the sintered copper layer and the sparseness of the sintered copper connecting the flake-like structures. .. Therefore, if the copper content in the sintered copper layer is within the above range, sufficient thermal conductivity can be obtained, the bonding strength between the member and the sintered copper layer is improved, and the bonded body is excellent in connection reliability. It becomes a thing. The copper content in the sintered copper layer may be 67% by volume or more, or 70% by volume or more, based on the volume of the sintered copper layer. The copper content in the sintered copper layer may be 90% by volume or less based on the volume of the sintered copper layer from the viewpoint of easiness of the manufacturing process.

In the sintered metal layer 52, the ratio of the copper element in the elements excluding the light element among the constituent elements may be 95% by mass or more, 97% by mass or more, or 98% by mass or more. It may be 100% by mass. When the above ratio of the copper element in the sintered metal layer is within the above range, the formation of an intermetal compound or the precipitation of dissimilar elements at the metal copper crystal grain boundary can be suppressed, and the metallic copper constituting the sintered metal layer can be suppressed. The properties tend to be strong, and even better connection reliability is likely to be obtained.

The sintered metal layer 52 may include a structure derived from flaky copper particles oriented substantially parallel to the bonding interface of the connector (for example, the bonding surface between the third member and the sintered metal layer). preferable.

The sintered copper layer having the above structure can be formed by sintering a bonding copper paste containing flake-shaped copper particles. The flake shape includes a flat plate shape such as a plate shape or a scale shape. As the flake-like structure, the ratio of the major axis to the thickness may be 5 or more. The number average diameter of the major axis of the flake-shaped structure may be 2 μm or more, 3 μm or more, or 4 μm or more. When the shape of the flake-like structure is within this range, the reinforcing effect of the flake-like structure contained in the sintered metal layer is improved, and the bonded body is further improved in joint strength and connection reliability.

The thickness of the sintered metal layer 52 is preferably 5 μm or more and 100 μm or less, more preferably 10 μm or more and 70 μm or less, and 15 μm or more and 60 μm or less from the viewpoint of maintaining good connection between the first member 10 and the third member 50. More preferred.

In the present embodiment, the bonding copper paste can be provided at a required portion of each member. A method of depositing copper paste for bonding can be used, for example, screen printing, transfer printing, offset printing, jet printing method, dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat. , Letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithograph, bar coat, applicator, particle deposition method, spray coater, spin coater, dip coater, electrodeposition coating and the like can be used. The thickness of the bonding copper paste may be 1 μm or more and 1000 μm or less, 10 μm or more and 500 μm or less, 50 μm or more and 200 μm or less, 10 μm or more and 3000 μm or less, and 15 μm or more. It may be 500 μm or less, 20 μm or more and 300 μm or less, 5 μm or more and 500 μm or less, 10 μm or more and 250 μm or less, or 15 μm or more and 150 μm or less.

The copper paste for joining provided on each member may be appropriately dried from the viewpoint of suppressing flow and generation of voids during sintering. The gas atmosphere at the time of drying may be in the atmosphere, in an oxygen-free atmosphere such as nitrogen or noble gas, or in a reducing atmosphere such as hydrogen or formic acid. The drying method may be drying by leaving at room temperature, heat drying, or vacuum drying. For heat drying or vacuum drying, for example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic wave. A heating device, a heater heating device, a steam heating furnace, a hot plate pressing device, or the like can be used. The drying temperature and time may be appropriately adjusted according to the type and amount of the dispersion medium used. As the drying temperature and time, for example, it may be dried at 50 ° C. or higher and 180 ° C. or lower for 1 minute or more and 120 minutes or less.

Examples of the method of arranging the members on the bonding copper paste include a chip mounter, a flip chip bonder, and a positioning jig made of carbon or ceramics. The above-mentioned drying step may be performed after the members are arranged.

Sintering can be done by heat treatment. For heat treatment, for example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, etc. A heater heating device, a steam heating furnace, or the like can be used.

The gas atmosphere at the time of sintering may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the sintered body and each member. The gas atmosphere at the time of sintering may be a reducing atmosphere from the viewpoint of removing surface oxides of copper particles of the copper paste for bonding. Examples of the anoxic atmosphere include the introduction of an oxygen-free gas such as nitrogen and a rare gas, or under vacuum. Examples of the reducing atmosphere include pure hydrogen gas, a mixed gas of hydrogen and nitrogen typified by a forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and rare gas, and a rare gas containing formic acid gas. Can be mentioned.

The maximum temperature reached during the heat treatment may be 250 ° C. or higher and 450 ° C. or lower, or 250 ° C. or higher and 400 ° C. or lower, from the viewpoint of reducing heat damage to each member and improving the yield. It may be 250 ° C. or higher and 350 ° C. or lower. When the maximum ultimate temperature is 200 ° C. or higher, sintering tends to proceed sufficiently when the maximum ultimate temperature holding time is 60 minutes or less. For the maximum temperature reached, it is preferable to measure the temperature of the member itself from the viewpoint of suppressing heat damage to each member.

The maximum temperature retention time may be 1 minute or more and 60 minutes or less, or 1 minute or more and less than 40 minutes, from the viewpoint of volatilizing all the dispersion medium and improving the yield. It may be more than 30 minutes.

The pressure at the time of joining can be set to a condition in which the copper content (deposition ratio) in the sintered metal layer is 65% by volume or more based on the sintered metal layer. For example, by using the copper paste for bonding according to the above-described embodiment, it is possible to form the sintered metal layer according to the above-described embodiment without applying pressure when sintering the laminate. In this case, sufficient bonding strength can be obtained only by the weight of the member laminated on the copper paste for bonding, or in a state where the pressure of 0.01 MPa or less, preferably 0.005 MPa or less is applied in addition to the weight of the member. .. When the pressure received at the time of sintering is within the above range, the reduction of voids, the joint strength and the connection reliability can be further improved without impairing the yield because a special pressurizing device is not required. Examples of the method in which the bonding copper paste receives a pressure of 0.01 MPa or less include a method in which a weight is placed on the member located at the top.

In the present embodiment, when a semiconductor element such as a Si chip is used as the first member 10, the bonding copper paste is provided on the surface of the Si chip or the like as described in (3) above, and then sintering is performed. A semiconductor device provided with a sintered copper layer can be obtained. Further, instead of the semiconductor element that has been fragmented, a layer of copper paste is provided on the entire surface or a part of the semiconductor wafer, and sintering is performed. After the sintered copper layer is provided, dicing is performed to fragment the semiconductor wafer. By doing so, a semiconductor device provided with a sintered copper layer can be obtained.

In the present embodiment, when the first member 10 is a semiconductor element, the third member 50 includes a lead frame, a metal plate-attached ceramic substrate (for example, DBC), a base material for mounting a semiconductor element such as an LED package, and the like. Examples thereof include metal wiring such as a metal frame, and a block body having thermal conductivity and conductivity such as a metal block.

The first member 10 and the third member 50 may have a metal such as gold, silver, or nickel on the surface in contact with the sintered metal layer 52. When the member has electroless nickel plating, further forming electroless palladium plating on this plating greatly improves reliability.

Examples of the member containing metal on the surface in contact with the sintered metal layer include a chip having metal plating, a heat spreader, a ceramic substrate to which a metal plate is attached, a lead frame having various metal plating, or a lead frame made of various metals. Examples include copper plates and copper foils.

The sintered metal layer may be used as it is as a joint portion, and a second member may be joined thereto. However, in the present embodiment, the joint portion is on the opposite side of the first member of the sintered copper layer. A single or multi-layered metal-containing layer containing at least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver provided on the surface is further included in the metal-containing layer, or A metal wire can be joined to the sintered copper layer via the metal-containing layer.

Examples of the method for forming the metal-containing layer include a method by plating or sputtering, a method of preparing a metal plate containing the metal, and arranging the metal plate on the sintered copper layer.

A single-layer or multi-layer metal-containing layer containing at least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver is provided to cover a part or all of the surface of the sintered copper layer. In this case, a method of electroless plating the connecting member 200 prepared above can be mentioned.

Like the connecting member 210 shown in FIG. 5A, for example, the surfaces of the third member 50 and the sintered copper layer 20 of the connecting member 200 are selectively electroless plated to eliminate the problem. A metal-containing layer 30 made of an electrolytic plating film can be provided. In this case, the connecting portion 15 having the sintered copper layer 20 and the metal-containing layer 30 is formed.

Further, as in the connecting member 220 shown in FIG. 5B, for example, a metal-containing layer 30 made of an electroless plating film may be provided only on the surface of the sintered copper layer 20 to form a joint portion 15. .. Such a joint can be formed by preparing a connecting member 200 and selectively performing electroless plating on the surface of the sintered copper layer 20. As another method, a member in which a sintered copper layer is formed on the first member and an electroless plating film is provided on the surface of the sintered copper layer is prepared, and the above (3) except that this member is used. ), The connecting member 220 can be obtained.

In FIGS. 1 and 5, the metal-containing layer 30 is provided on the exposed surface of the sintered copper layer 20, but it is one of the surfaces of the sintered copper layer 20 like the connecting member 230 shown in FIG. The metal-containing layer 32 may be provided in the portion.

Further, instead of electroless plating, a metal-containing layer may be provided by sputtering.

When the connecting member 230 shown in FIG. 6 is manufactured by sputtering, for example, a connecting member 200 can be prepared and only a predetermined portion can be selectively sputtered using a mask or the like. Further, the exposed surface of the sintered copper layer 20 may be sputtered like the connecting member 220, or only the upper surface of the sintered copper layer may be sputtered.

When a semiconductor element such as a Si chip is used as the first member, a bonding copper paste is provided on the surface of the Si chip or the like, and then sintering is performed to obtain a semiconductor element provided with a sintered copper layer. A metal-containing layer can be provided in a predetermined portion by sputtering using a mask. A connecting member 230 can be obtained in the same manner as in the above method (3) except that this member is used. Further, instead of the individualized semiconductor element, a copper paste layer is provided on the entire surface or a part of the semiconductor wafer, and the sintering is performed. After the sintered copper layer is provided, a predetermined portion is used with a mask. A metal-containing layer may be provided on the wafer by sputtering, and dicing may be performed to individualize the wafer.

In the present embodiment, the metal wire, which is the second member, can be joined to the metal-containing layer of the joint portion. The joining method and the conditions at the time of joining can be appropriately selected.

When the second member is a copper wire or the like, the pressing force at the time of joining or the ultrasonic output can be appropriately set for joining. As the pressing force at the time of joining, the load is preferably 150 gf or more and 350 gf or less, and more preferably 200 gf or more and 300 gf or less, from the viewpoint of achieving both the joining strength and low damage to the first member. It is preferable to reduce the ultrasonic output at the time of joining as much as possible from the viewpoint of achieving both the joining strength and low damage to the first member.

When the second member is a ribbon-shaped metal wire, it can be joined by a method such as a wire bonding machine.

Through the above steps, the connection structure shown in FIG. 1 or 7 can be obtained.

[Semiconductor device]
FIG. 8 is a schematic cross-sectional view showing an example of the semiconductor device according to the present invention. The semiconductor device 300 shown in FIG. 8 includes an insulating substrate 54 having a first electrode 56 and a second electrode 57, and a first member 10 joined to the first electrode 56 by a sintered metal layer 52. , A joint portion 15 composed of a sintered copper layer 20 provided on the first member 10 and a metal-containing layer 30 covering the surface of the sintered copper layer 20, and metal baking provided on the second electrode 57. The layer 8 is provided with a second member 42 having one end side bonded to the bonding portion 15 and the other end side bonded to the second electrode 57 via the metal sintered layer 8. In the semiconductor device 300, the first member 10 is a semiconductor element, the second member 42 is a metal wire, and the semiconductor element and the second electrode are electrically connected by the metal wire. Further, the semiconductor element is connected to the third electrode 59 via the wire 44. Further, the semiconductor device 300 includes a copper plate 58 provided on the side of the insulating substrate 54 opposite to the surface on which the electrodes and the like are mounted, and an insulator 60 for sealing the connection structure.

In the semiconductor device 300 of the present embodiment, at least the first member 10, the joint portion 15, and the second member 42 have the above-described connection structure according to the present embodiment or the method for manufacturing the same.

The semiconductor device 300 has one semiconductor element on the first electrode 56, but may have two or more. In this case, a sintered copper layer and a metal-containing layer covering the surface thereof can be provided on each of the plurality of semiconductor elements, and a metal wire bonded to the sintered copper layer via the metal-containing layer may be provided. can.

Further, the metal-containing layer may be formed by a metal plate arranged on the sintered copper layer. Further, in the semiconductor device 300, the bonding portion 15 may be composed of the sintered copper layer 20 without containing the metal-containing layer, and the metal wire as the second member may be directly bonded to the sintered copper layer 20. ..

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following examples.

[Preparation of copper paste A for bonding]
5.2 g of α-terpineol (manufactured by Wako Pure Chemical Industries, Ltd.) and 6.8 g of isobornylcyclohexanol (MTPH, manufactured by Nippon Terpen Chemical Co., Ltd.) as dispersion media, and CH0200 (Mitsui Metal Mining Co., Ltd.) as submicro copper particles. 52.8 g of copper particles having a particle size of 0.12 μm or more and 0.8 μm or less, manufactured by the same company, was mixed in a plastic bottle, and an ultrasonic homogenizer (US-600, manufactured by Nippon Seiki Co., Ltd.) was used. Treatment was performed at 19.6 kHz, 600 W for 1 minute to obtain a dispersion liquid. To this dispersion, 35.2 g of MA-C025 (manufactured by Mitsui Mining & Smelting Co., Ltd., content of copper particles having a maximum diameter of 1 μm or more and 20 μm or less, 100% by mass) was added as flake-shaped micro copper particles, and dried powder with a spatula. Stir until no more. The plastic bottle is tightly closed, and the copper paste A for joining is stirred at 2000 rpm for 2 minutes using a rotating and revolving stirrer (Planetry Vacuum Mixer ARV-310, manufactured by Shinky Co., Ltd.) and then stirred at 2000 rpm for 2 minutes under reduced pressure. Got

[Creation of connection structure]
(Example 1)
(Step a: Preparation of connecting member)
A stainless steel metal mask (thickness: 200 μm) having a square opening of 5 mm × 5 mm is placed on a copper plate (thickness: 3 mm) having a size of 19 mm × 25 mm, and a copper paste A for joining is printed by stencil printing using a metal squeegee. Was applied. A silicon chip in which an electroless nickel plating film having a thickness of 5 μm and an electroless palladium plating film having a thickness of 0.01 μm are formed in this order on one main surface S1 is prepared, and this silicon chip is placed on the opposite side of S1. It was placed so that the main surface was in contact with the applied copper paste, and lightly pressed with tweezers. This was set in a tube furnace (manufactured by ABC Co., Ltd.), and argon gas was flowed at 1 L / min to replace the air with argon gas. Then, the temperature was raised for 10 minutes while flowing hydrogen gas at 300 ml / min. After raising the temperature, sintering treatment is performed under the conditions of a maximum reaching temperature of 300 ° C. and a maximum reaching temperature holding time of 60 minutes. After sintering, the mixture is cooled to 200 ° C. in 30 minutes, and then the argon gas is changed to 0.3 L / min. After cooling, the sinter was taken out into the air at 50 ° C. or lower. In this way, as shown in FIG. 9, a connecting member 240 was produced in which the copper plate 71 and the silicon chip 73 were joined by a sintered copper layer 72 having a thickness of 100 μm.

(Step b: Formation of sintered copper layer)
A stainless steel metal mask having a 4 mm × 4 mm square opening on the surface of the silicon chip of the connecting member 240 obtained above provided with the electroless nickel plating film and the electroless palladium plating film (thickness:: 20 μm) was placed, and the bonding copper paste A was applied by stencil printing using a metal squeegee. This was set in a tube furnace (manufactured by ABC Co., Ltd.), and argon gas was flowed at 1 L / min to replace the air with argon gas. Then, a sintered copper layer having a thickness of 10 μm was formed on the silicon chip by sintering treatment under the conditions of a temperature rise of 10 minutes and 350 ° C. for 10 minutes while flowing hydrogen gas at 300 mL / min. Then, the argon gas was changed to 0.3 L / min and cooled, and the bonded body was taken out into the air at 50 ° C. or lower. In this way, as shown in FIG. 10, a connecting member 242 having a sintered copper layer 74 having a copper content of 80% by volume was produced.

(Step c: Formation of metal-containing layer)
Electroless nickel plating film with a thickness of 0.5 μm and electroless palladium plating with a thickness of 0.1 μm on the surface of the copper plate 71 of the connecting member 242 and the upper surface of the sintered copper layer 74 obtained above by the method shown below. An electroless gold-plated film having a thickness of 0.1 μm and a film were formed in this order to prepare a copper wire bonding connection member.

<Formation of electroless nickel plating film>
After immersing the connecting member in SA-100 (manufactured by Hitachi Kasei Co., Ltd., trade name), which is a plating activity treatment liquid at a liquid temperature of 25 ° C., while irradiating ultrasonic waves with a resonance frequency of 28 kHz and an output of 100 W. Washed with water for 2 minutes. Subsequently, the connecting member was irradiated to NIPS-100 (trade name, manufactured by Hitachi Kasei Co., Ltd.), which is an electroless nickel plating solution having a liquid temperature of 85 ° C., for 25 minutes while irradiating ultrasonic waves having a resonance frequency of 28 kHz and an output of 100 W. After the immersion, it was washed with water for 1 minute while irradiating ultrasonic waves having a resonance frequency of 28 kHz and an output of 100 W. The thickness of the formed electroless nickel plating film was 0.5 μm. The phosphorus concentration in the electroless nickel plating film was 7% by mass.

<Formation of electroless palladium plating film>
While irradiating the pallet (manufactured by Kojima Chemicals Co., Ltd., trade name), which is an electroless palladium plating solution with a liquid temperature of 55 ° C, ultrasonic waves with a resonance frequency of 28 kHz and an output of 100 W, the connecting members that have been electroless nickel plated are irradiated. After immersing for 9 seconds, it was washed with water for 1 minute while irradiating ultrasonic waves with a resonance frequency of 28 kHz and an output of 100 W. The thickness of the electroless palladium plating film formed was 0.1 μm. The palladium concentration in the electroless palladium coating was approximately 100% by mass.

<Formation of electroless gold plating film>
Immerse the connection member with electroless palladium plating in HGS-100 (Hitachi Kasei Co., Ltd., trade name), which is a replacement gold plating solution, for 10 minutes while irradiating ultrasonic waves with a resonance frequency of 28 kHz and an output of 100 W at 85 ° C. Then, the mixture was washed with water for 1 minute while irradiating ultrasonic waves having a resonance frequency of 28 kHz and an output of 100 W. The thickness of the formed electroless gold plating film was 0.1 μm.

(Step d: Copper wire bonding)
Wire bonding between the sintered copper layer on the silicon chip and the copper plate was performed using a copper wire "CHA" (manufactured by Tanaka Denshi Kogyo Co., Ltd., trade name) having a wire diameter of 300 μm. The wire bonding was carried out using a fully automatic ribbon bonder 3600plus type manufactured by Orthodyne Electronics Co. as a bonding apparatus at a frequency of 80 kHz with the ultrasonic output and load shown in Table 1. In this way, as shown in FIG. 11, a copper wire-bonded connection structure 244 in which the sintered copper layer 74 on the silicon chip and the copper plate 41 are connected by the copper wire 76 was obtained.

<Evaluation of copper wire bonded connection structure>
The copper wire-bonded connection structure obtained above was evaluated for wire pull strength, damage to silicon chips, and adhesiveness to a mold resin by the methods shown below.

(1) Measurement of wire pull strength A copper wire pull test is performed on a copper wire-bonded connection structure by using a bond tester (manufactured by Dage, trade name: BT2400PC) to pull the copper wire and measure the strength until it comes off from the terminal. went. From the average value of the wire pull strength at 20 terminals, the wire bonding connection reliability was evaluated based on the following criteria.
A: Average value of wire pull strength is 1000 g or more B: Average value of wire pull strength is 800 g or more and less than 1000 g C: Average value of wire pull strength is 500 g or more and less than 800 g D: Average value of wire pull strength is 200 g or more and less than 500 g E: Wire pull strength Average value is less than 200g

Further, a copper wire pull test was also performed on a copper wire-bonded connection structure that had been heat-treated at 150 ° C. for 3 hours before wire bonding in the same manner as described above.

(2) Evaluation of Damage to Silicon Chips The copper wire-bonded connection structure was cross-sectioned, and the copper wire bonding portion of the silicon chip was observed to confirm whether damage such as breakage or peeling had occurred. Fifty samples were evaluated and evaluated based on the following criteria.
A: No damage in 50 samples B: Damage in 1 to 2 samples C: Damage in 3 to 5 samples D: Damage in 6 to 10 samples E: Damage in 11 or more samples

(3) Adhesiveness evaluation with mold resin After applying an adhesiveness improving material (HIMAL, manufactured by Hitachi Kasei Co., Ltd.) on a copper wire-bonded connection structure and drying it, a solid encapsulant (CEL, Hitachi Kasei Co., Ltd.) It was sealed with (manufactured by the company) to obtain a test piece for adhesion evaluation.

Next, the test piece for adhesion evaluation was set in a temperature cycle tester (TSA-72SE-W, manufactured by ESPEC CORPORATION), and the low temperature side: -40 ° C, 15 minutes, room temperature: 2 minutes, high temperature side: 200 ° C. , 15 minutes, defrost cycle: automatic, number of cycles: 1000 cycles, temperature cycle connection reliability test was performed.

Temperature cycle connection For the test piece before the test and the test piece after the test, an ultrasonic flaw detector (Insight-300, manufactured by Insight Co., Ltd.) was used to SAT the interface between the copper plate and the solid encapsulant. An image was obtained and the presence or absence of peeling was examined. The peeled area was measured and evaluated based on the following criteria.
A: Peeling of less than 20 area% B: Peeling of 20 to less than 50 area% C: Peeling of 50 area% or more

(Example 2)
A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 3)
A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 4)
A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the thickness of the metal mask was changed in step b to form a sintered copper layer having a thickness of 20 μm on the silicon chip.

(Example 5)
A copper wire-bonded connection structure was produced in the same manner as in Example 4 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 6)
A copper wire-bonded connection structure was produced in the same manner as in Example 4 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 7)
A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the thickness of the metal mask was changed in step b to form a sintered copper layer having a thickness of 50 μm on the silicon chip.

(Example 8)
A copper wire-bonded connection structure was produced in the same manner as in Example 7 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 9)
A copper wire-bonded connection structure was produced in the same manner as in Example 7 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 10)
A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the thickness of the metal mask was changed in step b to form a sintered copper layer having a thickness of 100 μm on the silicon chip.

(Example 11)
A copper wire-bonded connection structure was produced in the same manner as in Example 10 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 12)
A copper wire-bonded connection structure was produced in the same manner as in Example 10 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 13)
A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 14)
A copper wire-bonded connection structure was produced in the same manner as in Example 2 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 15)
A copper wire-bonded connection structure was produced in the same manner as in Example 3 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 16)
A copper wire-bonded connection structure was produced in the same manner as in Example 4 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 17)
A copper wire-bonded connection structure was produced in the same manner as in Example 5 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 18)
A copper wire-bonded connection structure was produced in the same manner as in Example 6 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 19)
A copper wire-bonded connection structure was produced in the same manner as in Example 7 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 20)
A copper wire-bonded connection structure was produced in the same manner as in Example 8 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 21)
A copper wire-bonded connection structure was produced in the same manner as in Example 9 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 22)
A copper wire-bonded connection structure was produced in the same manner as in Example 10 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 23)
A copper wire-bonded connection structure was produced in the same manner as in Example 11 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 24)
A copper wire-bonded connection structure was produced in the same manner as in Example 12 except that the electroless gold plating film (0.1 μm) was not provided in step c.

(Example 25)
In step b, the thickness of the metal mask was changed to form a sintered copper layer having a thickness of 50 μm on the silicon chip, and instead of step c, a palladium film having a thickness of 0.1 μm was formed on the upper surface of the sintered copper layer by sputtering. A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that a gold film having a thickness of 0.1 μm was formed in this order.

(Example 26)
A copper wire-bonded connection structure was produced in the same manner as in Example 25 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 27)
A copper wire-bonded connection structure was produced in the same manner as in Example 25 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 28)
A copper wire-bonded connection structure was produced in the same manner as in Example 25 except that the thickness of the metal mask was changed in step b to form a sintered copper layer having a thickness of 100 μm on the silicon chip.

(Example 29)
A copper wire-bonded connection structure was produced in the same manner as in Example 28 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 30)
A copper wire-bonded connection structure was produced in the same manner as in Example 28 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 31)
A copper wire-bonded connection structure was produced in the same manner as in Example 25 except that a gold film having a thickness of 0.1 μm was not provided.

(Example 32)
A copper wire-bonded connection structure was produced in the same manner as in Example 31 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 33)
A copper wire-bonded connection structure was produced in the same manner as in Example 31 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 34)
A copper wire-bonded connection structure was produced in the same manner as in Example 31 except that the thickness of the metal mask was changed in step b to form a sintered copper layer having a thickness of 100 μm on the silicon chip.

(Example 35)
A copper wire-bonded connection structure was produced in the same manner as in Example 31 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Example 36)
A copper wire-bonded connection structure was produced in the same manner as in Example 31 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Example 37)
A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the metal-containing layer was not formed in step c.

(Example 38)
A copper wire-bonded connection structure was produced in the same manner as in Example 37 except that the thickness of the metal mask was changed in step b to form a sintered copper layer having a thickness of 20 μm on the silicon chip.

(Example 39)
Except that in step b, a copper paste in which the amount of the dispersion medium was adjusted was prepared, the thickness of the metal mask was changed, and a sintered copper layer having a copper content of 60% by volume and a thickness of 50 μm was formed on the silicon chip. A copper wire-bonded connection structure was produced in the same manner as in Example 37.

(Example 40)
Except for the fact that in step b, a copper paste in which the amount of the dispersion medium was adjusted was prepared, the thickness of the metal mask was changed, and a sintered copper layer having a copper content of 70% by volume and a thickness of 50 μm was formed on the silicon chip. A copper wire-bonded connection structure was produced in the same manner as in Example 37.

(Example 41)
A copper wire-bonded connection structure is the same as in Example 37, except that the thickness of the metal mask is changed in step b to form a sintered copper layer having a copper content of 80% by volume and a thickness of 50 μm on the silicon chip. The body was made.

(Example 42)
Except that in step b, a copper paste in which the amount of the dispersion medium was adjusted was prepared, the thickness of the metal mask was changed, and a sintered copper layer having a copper content of 90% by volume and a thickness of 50 μm was formed on the silicon chip. A copper wire-bonded connection structure was produced in the same manner as in Example 37.

(Example 43)
A copper wire-bonded connection structure is the same as in Example 37, except that the thickness of the metal mask is changed in step b to form a sintered copper layer having a copper content of 80% by volume and a thickness of 100 μm on the silicon chip. The body was made.

(Comparative Example 1)
^{In step b, electrolytic copper plating is performed under the condition of a current density of 1 A / dm 2} using a commercially available electrolytic copper plating solution to obtain a connecting member having an electrolytic copper layer having a copper content of 100% by volume and a thickness of 10 μm. A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the metal-containing layer was not formed in step c.

(Comparative Example 2)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 1 except that an electrolytic copper layer having a copper content of 100% by volume and a thickness of 20 μm was formed on the silicon chip by changing the electrolytic copper plating time. bottom.

(Comparative Example 3)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 1 except that an electrolytic copper layer having a copper content of 100% by volume and a thickness of 50 μm was formed on the silicon chip by changing the electrolytic copper plating time. bottom.

(Comparative Example 4)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 1 except that an electrolytic copper layer having a copper content of 100% by volume and a thickness of 100 μm was formed on the silicon chip by changing the electrolytic copper plating time. bottom.

(Comparative Example 5)
^{In step b, electrolytic copper plating is performed under the condition of a current density of 1 A / dm 2} using a commercially available electrolytic copper plating solution to obtain a connecting member having an electrolytic copper layer having a copper content of 100% by volume and a thickness of 10 μm. A copper wire-bonded connection structure was produced in the same manner as in Example 1 except that the electroless nickel film was not formed in step c.

(Comparative Example 6)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 5 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Comparative Example 7)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 5 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Comparative Example 8)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 5 except that an electrolytic copper layer having a copper content of 100% by volume and a thickness of 20 μm was formed on the silicon chip by changing the electrolytic copper plating time. bottom.

(Comparative Example 9)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 8 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Comparative Example 10)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 8 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Comparative Example 11)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 5 except that an electrolytic copper layer having a copper content of 100% by volume and a thickness of 50 μm was formed on the silicon chip by changing the electrolytic copper plating time. bottom.

(Comparative Example 12)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 11 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Comparative Example 13)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 11 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

(Comparative Example 14)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 5 except that an electrolytic copper layer having a copper content of 100% by volume and a thickness of 100 μm was formed on the silicon chip by changing the electrolytic copper plating time. bottom.

(Comparative Example 15)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 14 except that the load in copper wire bonding was changed from 300 gf to 250 gf.

(Comparative Example 16)
A copper wire-bonded connection structure was produced in the same manner as in Comparative Example 14 except that the load in copper wire bonding was changed from 300 gf to 200 gf.

The connection structures of Examples 2 to 43 and Comparative Examples 1 to 16 were also evaluated in the same manner as in Example 1.

As shown in Tables 1 to 3, wire bonding of Examples 1 to 43 obtained by using a connecting member provided with a sintered copper layer having a copper content of 65% by volume or more and 95% by volume or less. It was confirmed that the connection structure can achieve both wire pull strength and low damage to the chip. Further, in the wire-bonded connection structures of Examples 1 to 36 obtained by using the connecting member provided with the metal-containing layer on the surface of the sintered copper layer, after the oxide film is formed on the sintered copper layer. Sufficient wire pull strength was obtained even when wire bonding was performed. Further, in Examples 13 to 24 and 31 to 36, since the outermost layer of the metal-containing layer was a palladium-containing layer, the adhesiveness with the mold resin was improved.

On the other hand, in Comparative Examples 1 to 4 using only the sintered copper layer having a copper content of 100% by volume, that is, a dense copper layer of 100%, even a connection condition of a load of 300 gf is sufficient. The wire pull strength was not obtained, and there was damage to the chip. Further, in Comparative Examples 7, 10, 13 and 16 in which a metal-containing layer was provided and wire-bonded under a connection condition of a load of 200 gf, damage to the chip was reduced, but sufficient wire pull strength could not be obtained.

1 ... structure derived from flake-shaped copper particles, 2 ... sintered copper derived from copper particles, 3 ... vacancies, 10 ... first member, 15 ... joint, 20 ... sintered copper layer, 30, 32 ... metal-containing layer, 34 ... electroless nickel plating film, 36 ... electroless palladium plating film, 40 ... second member (metal wire), 42 ... second member (metal wire), 44 ... wire, 50 ... th Three members, 52 ... sintered metal layer, 54 ... insulating substrate, 56 ... first electrode, 57 ... second electrode, 58 ... copper plate, 59 ... third electrode, 60 ... insulator, 100, 110 ... Connection structure, 200, 210, 220, 230 ... Connection member, 300 ... Semiconductor device.

Claims (12)

A connecting member having a first member and a joint portion provided on the first member and including a sintered copper layer having a copper content of 65% by volume or more and 95% by volume or less is prepared. The first step, and the second step of joining the second member to the joint,
With
It said second member Ri Ah with a metal wire,
A method for producing a connecting structure, comprising a structure derived from flake-shaped copper particles in which the sintered copper layer is oriented substantially parallel to a surface of the first member in contact with the sintered copper layer. A connecting member having a first member and a joint portion provided on the first member and including a sintered copper layer having a copper content of 65% by volume or more and 95% by volume or less is prepared. First step and
The second step of joining the second member to the joint portion,
With
The second member is a metal wire.
A method for producing a connecting structure, wherein a copper paste layer containing flake-shaped copper particles is provided on the first member, and the sintered copper layer is formed by firing the copper paste layer. The connection structure according to claim 2 , wherein the sintered copper layer includes a structure derived from flake-shaped copper particles oriented substantially parallel to the surface of the first member in contact with the sintered copper layer. Manufacturing method. At least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver, wherein the joint is provided on a surface of the sintered copper layer opposite to the first member. The method for producing a connecting structure according to any one of claims 1 to 3, further comprising a single layer or a multi-layered metal-containing layer containing the mixture. The method for manufacturing a connection structure according to any one of claims 1 to 4, wherein the first member is a semiconductor element. The connection according to any one of claims 1 to 5, wherein the metal wire is at least one metal wire selected from the group consisting of an aluminum wire, a copper wire, a palladium-coated wire, a silver wire, and a gold wire. Method of manufacturing the structure. The metal-containing layer is viewed from the sintered copper layer side.
a) Nickel-containing layer and palladium-containing layer b) Nickel-containing layer and gold-containing layer c) Nickel-containing layer, palladium-containing layer and gold-containing layer d) Palladium-containing layer e) Palladium-containing layer or gold-containing layer , The method for manufacturing a connection structure according to claim 4. The method for producing a connection structure according to claim 7, wherein the metal-containing layer is formed by electroless plating and / or sputtering. The method for producing a connection structure according to claim 7, wherein the metal-containing layer is formed by electroless plating in which plating is deposited while applying ultrasonic waves. The first member, the joint including the sintered copper layer, and the second member are provided in this order.
The sintered copper layer is provided on the first member, has a copper content of 65% by volume or more and 95% by volume or less, and is oriented substantially parallel to the surface in contact with the first member. Containing a structure derived from flaky copper particles
A connecting structure in which the second member is a metal wire and is joined to the joint portion. At least one metal selected from the group consisting of nickel, palladium, gold, platinum, and silver, wherein the joint is provided on a surface of the sintered copper layer opposite to the first member. Further including a single layer or a multi-layer metal-containing layer containing
The connection structure according to claim 10, wherein the second member is joined to the metal-containing layer. A semiconductor device comprising the connection structure according to claim 10 or 11 , wherein the first member is a semiconductor element.

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