JP6430473B2 - Semiconductor device - Google Patents

Semiconductor device Download PDF

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JP6430473B2
JP6430473B2 JP2016252850A JP2016252850A JP6430473B2 JP 6430473 B2 JP6430473 B2 JP 6430473B2 JP 2016252850 A JP2016252850 A JP 2016252850A JP 2016252850 A JP2016252850 A JP 2016252850A JP 6430473 B2 JP6430473 B2 JP 6430473B2
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semiconductor
metal
intermetallic compound
alloy
metal particles
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JP2018022863A (en
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重信 関根
重信 関根
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有限会社 ナプラ
有限会社 ナプラ
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Description

  The present invention relates to a semiconductor device having a semiconductor element and a connection member connected to the semiconductor element.

In recent years, SiC semiconductor elements using SiC (silicon carbide) have been developed.
SiC semiconductor elements are attracting attention as power devices that control high power because they have higher breakdown field strength and wider band gaps than Si semiconductor elements. The SiC semiconductor element can operate even at a high temperature of 150 ° C. or higher, which exceeds the limit of the Si semiconductor element, and theoretically can operate even at 500 ° C. or higher (see Patent Document 1).
Such a power device is used in a harsh environment such that a high temperature operation state continues for a long time and a large temperature fluctuation occurs from a high temperature operation state to a low temperature stop state. Therefore, in a semiconductor device having a semiconductor element and a connecting member connected to the semiconductor element, high bonding strength is required for a long period of time and excellent heat resistance is required for a bonding portion that forms the bonding between the two.
However, conventionally known bonding materials are not necessarily capable of satisfying the above-described requirements.

  For example, the semiconductor junction structure disclosed in Patent Document 2 cannot satisfy the above-described requirements.

JP 2011-80796 A JP 2013-4894 A

  Accordingly, an object of the present invention is to provide a semiconductor device having a semiconductor element and a connection member connected to the semiconductor element, in which a bonding portion that forms a bond between the semiconductor element and the connection member has high heat resistance over a long period of time. Another object of the present invention is to provide a semiconductor device capable of maintaining bonding strength and mechanical strength.

  In order to solve the above-described problem, a semiconductor device according to the present invention includes a semiconductor element and a connection member connected to the semiconductor element, and forms a junction between the semiconductor element and the connection member. Has an intermetallic compound composed of Sn and Cu and a metal matrix containing an Sn alloy, the intermetallic compound is dispersed in the metal matrix, and at least a part of the intermetallic compound is composed of the Sn alloy and An epitaxial junction is formed.

The intermetallic compound preferably has a composition of Cu 6 Sn 5 .

  In the junction part in the semiconductor device according to the present invention, an intermetallic compound composed of Sn and Cu is dispersed in a metal matrix containing an Sn alloy, and at least a part of the intermetallic compound forms an epitaxial junction with the Sn alloy. By forming the epitaxial junction, it is possible to suppress the crack phenomenon due to Sn and / or Cu growing in one direction to form a long axis crystal. Moreover, a junction part has the high temperature heat resistance by an intermetallic compound, and the softness | flexibility by a metal matrix. For this reason, even when used in a harsh environment, such as when the high temperature operation state continues for a long time, or when it is used in a harsh environment such as a large temperature fluctuation from the high temperature operation state to the low temperature stop state, high heat resistance, Bonding strength and mechanical strength will be maintained.

  As described above, according to the present invention, in a semiconductor device having a semiconductor element and a connection member connected to the semiconductor element, a bonding portion that forms a bond between the semiconductor element and the connection member includes: A semiconductor device that can maintain high heat resistance, bonding strength, and mechanical strength over a long period of time can be provided.

It is a schematic cross section for demonstrating the structure of the junction part in this invention. 3 is an electron micrograph of a partial cross section of a joint 300. FIG. It is an enlarged view of the A section in FIG. It is an enlarged view of the B section in FIG. It is an electron micrograph of 8Cu · 92Sn metal particles. It is a figure for demonstrating an example of the manufacturing apparatus suitable for manufacture of a metal particle.

Hereinafter, the present invention will be described in more detail.
FIG. 1 is a schematic cross-sectional view for explaining the structure of the joint in the present invention.
In FIG. 1, a joining portion 300 joins metal / alloy bodies 101 and 501 (Cu electrodes in FIG. 1) formed on substrates 100 and 500 arranged to face each other. The joint portion 300 includes Cu 6 Sn 5 as an intermetallic compound (other Cu 3 Sn), includes an Sn alloy as a metal matrix, the intermetallic compound Cu 6 Sn 5 is dispersed in the metal matrix, and Cu 6 Sn 5 At least a part forms an epitaxial junction with the Sn alloy.

  The substrates 100 and 500 are substrates that include semiconductor elements and constitute electronic / electrical equipment such as power devices. The metal / alloy bodies 101 and 501 are electrodes, bumps, terminals, lead conductors, or the like. 500 is a connection member provided integrally with 500. In electronic / electric equipment such as power devices, the metal / alloy bodies 101, 501 are generally configured as Cu or an alloy thereof. However, the portion corresponding to the substrates 100 and 500 is not excluded from the case where the portion is made of a metal / alloy body.

  The term “epitaxial junction” as used in the present invention means a state in which crystals of different substances are joined at crystal planes.

FIG. 2 is an electron micrograph of a partial cross section of the joint 300. Cu 6 Sn 5 as an intermetallic compound and Sn alloy as a metal matrix are observed. 3 and 4 show enlarged views of the A part and the B part in FIG. 2, respectively.
From FIG. 3, since the crystals of Cu 6 Sn 5 and the Sn alloy are in a state where they are meshed with each other on the crystal plane, the intermetallic compound Cu 6 Sn 5 dispersed in the metal matrix is Sn alloy (for example, 4 mass% Cu and 96 It can be seen that an epitaxial junction is formed with an alloy including mass% Sn.
On the other hand, from FIG. 4, not all of the bonding surfaces of the intermetallic compound Cu 6 Sn 5 and the Sn alloy form an epitaxial bonding, and an amorphous layer (non-crystalline) may be interposed in a part of the bonding surface.

The epitaxial bonding as shown in FIG. 3 is preferably 30% or more, and more preferably 60% or more, assuming that the entire bonding surface between the intermetallic compound Cu 6 Sn 5 and the Sn alloy is 100%.
The proportion of the epitaxial junction can be calculated as follows, for example.
An electron micrograph of the cross section of the joint 300 is taken, and the joint surface between the intermetallic compound Cu 6 Sn 5 and the Sn alloy is arbitrarily sampled at 50 locations. Subsequently, image analysis is performed on the bonding surface, and it is examined how much epitaxial bonding as shown in FIG. 3 exists with respect to the sampled bonding surface.

Next, the method for forming the joint in the present invention will be described.
The joint can be formed of metal particles that combine Cu and Sn. Examples of the metal particles include metal particles having a composition of 8 mass% Cu and 92 mass% Sn (hereinafter referred to as 8Cu · 92Sn).
FIG. 5 shows an electron micrograph of the 8Cu · 92Sn metal particles. A part of the surface of the metal particles in FIG. 5 is thinly polished with a laser.
A part of the surface of the metal particles in FIG. 5 is polished to about 0.1 μm from the surface by a laser.
As can be understood from FIG. 5, the metal particles M of 8Cu · 92Sn are in the form of a mesh 121, a dot or film 122, etc., in an intermetallic compound CuxSny in a black metal matrix. The intermetallic compound CuxSny actually forms a three-dimensional structure. The size of the intermetallic compound CuxSny includes those of nm size (1 μm or less) in light of the scale display shown in FIG.
That is, the metal particle M has a large number of nano-sized intermetallic compounds that form a nanocomposite three-dimensional structure distributed in the metal matrix. Here, the nanocomposite three-dimensional structure refers to a three-dimensional structure made of a nanoscale size crystal of 1/10 or less of the metal particles M.
As can be understood from FIG. 5, the metal particles M of 8Cu · 92Sn have a network structure of the intermetallic compound Cu 6 Sn 5 in the vicinity of the surface thereof.

  Such metal particles are centrifuged in a centrifugal field forcibly formed by supplying molten metal having a composition of 8% by mass of Cu and 92% by mass of Sn on a dish-shaped disk that rotates at high speed, for example, in a nitrogen gas atmosphere. Molten metal dispersed as droplets by force or the like can be obtained by forcibly self-organizing in a rapid cooling and solidification process under controlled environmental conditions.

  An example of a production apparatus suitable for producing metal particles will be described with reference to FIG. The granulation chamber 1 has a cylindrical shape at the top and a cone shape at the bottom, and has a lid 2 at the top. A nozzle 3 is inserted vertically in the center of the lid 2, and a dish-shaped rotating disk 4 is provided immediately below the nozzle 3. Reference numeral 5 denotes a mechanism for supporting the dish-shaped rotating disk 4 so as to be movable up and down. The generated particle discharge pipe 6 is connected to the lower end of the cone portion of the granulating chamber 1. The upper part of the nozzle 3 is connected to an electric furnace (high frequency furnace) 7 for melting the metal to be granulated. The atmospheric gas adjusted to a predetermined component in the mixed gas tank 8 is supplied to the inside of the granulating chamber 1 and the upper part of the electric furnace 7 through the pipe 9 and the pipe 10, respectively. The pressure in the granulating chamber 1 is controlled by the valve 11 and the exhaust device 12, and the pressure in the electric furnace 7 is controlled by the valve 13 and the exhaust device 14, respectively. The metal supplied from the nozzle 3 onto the dish-shaped rotating disk 4 becomes fine droplets due to the centrifugal force generated by the dish-shaped rotating disk 4 and the action in the parallel air flow environment centrifugal field created by the blowing airflow along the rotation axis. It is scattered and cooled to solid particles. The generated solid particles are supplied from the discharge pipe 6 to the automatic filter 15 and separated. Reference numeral 16 denotes a fine particle collecting apparatus.

  When the high-speed rotating body is disk-shaped or conical, if there is no centrifugal field, the centrifugal force applied to the molten metal varies greatly depending on the position of the molten metal supplied to the rotating body. Hard to get a body. However, when an inert gas is blown up from the lower part of the rotating shaft and filled into the lower part of the desk, a uniform air flow is created by centrifugal force, and a centrifugal field is created within the range of 2 m from the center of rotation to supply it on a dish-shaped disk that rotates at high speed It receives a uniform centrifugal force at the peripheral edge of the dish and is dispersed and scattered into small droplets with uniform grains. The scattered droplets are rapidly cooled in a centrifugal field gas, fall as solidified particles, and are collected.

  The molten metal is self-assembled during rapid cooling and solidification, and individual fine particles become metal particles having the nanocomposite structure.

  The higher the number of revolutions of the dish-shaped disk, the smaller the diameter of the obtained metal particles. When a dish-shaped disk having an inner diameter of 35 mm and a depth of 5 mm is used, in order to obtain particles having an average particle diameter of 100 μm or less, it is desirable that the rotation be 100,000 rotations or more per minute. As a result, the centrifugal force increases, intermetallic compounds lighter than Sn accumulate on the surface layer, and the nanocomposite structure is easily formed.

The temperature of the atmospheric gas supplied to the granulation chamber may be room temperature, but the oxygen concentration in the granulation chamber is on the order of 0 ppm or less, and the granulation chamber has an internal pressure of 10% or more with respect to atmospheric pressure. There is a need to. In the case of continuous operation for a long time, in order to maintain the rapid cooling effect of the molten metal droplets, it is desirable to control the air flow rate so that the granulation chamber temperature is 100 ° C. or less, preferably 40 ° C. or less. This rapid cooling step facilitates formation of the mesh basket structure.
The metal particles M have a diameter of 20 μm or less, for example.

When the 8Cu · 92Sn metal particles M are processed into a sheet or paste and melted and solidified between the two members to be joined, the intermetallic compound of the three-dimensional structure of the metal particles M is separated and recombined. Then, a new three-dimensional structure of the intermetallic compound is formed, and an epitaxial junction between at least a part of the intermetallic compound and the Sn alloy can be formed.
In order to obtain a preform sheet made of the metal particles M, the powder containing the metal particles M can be obtained by, for example, processing by metal-to-metal bonding using a cold welding method. Various metal-to-metal joints using the cold welding method are known. In the present invention, those known techniques can be applied. For example, the powder containing the metal particles M according to the present invention is supplied between a pair of pressure rollers that rotate in opposite directions, and pressure is applied to the powder from the pressure rollers to the metal particles M constituting the powder. Causes metal-to-metal bonding. In actual processing, it is desirable to apply heat of about 100 ° C. to the powder from the pressure roller. As a result, a preform sheet made of the metal particles M is obtained.

  When a preform sheet is obtained by performing an intermetallic joining process using a cold pressure welding method on the powder containing the metal particles M, inside the preform sheet, the metal particles M and other particles of the present invention are: Although the outer shape changes, the internal structure of the particles is almost intact. That is, the preform sheet has a nanocomposite structure including an nm-sized intermetallic compound composed of a plurality of metal components. Therefore, the molded body preserves the operational effects of the metal particles according to the present invention as they are.

Next, the preform sheet is interposed between the two members to be joined and baked (baking treatment) to form a joined portion. The baking process temperature is, for example, 250 ° C., and the baking process time is appropriately adjusted.
Alternatively, in order to efficiently form the joint using the metal particles M, for example, a conductive paste in which the metal particles M are mixed in an organic vehicle is formed.
Then, the conductive paste is applied to one surface of the two members to be joined, and baked (baking treatment) to form a joined portion. The baking process temperature is, for example, 250 ° C., and the baking process time is appropriately adjusted.

  In addition, the ratio of 3 volume% or more and 85 volume% or less is preferable with respect to the whole metal particle M, and the ratio of 10 volume% or more and 75 volume% or less is more preferable with respect to the metal particle M whole. According to such metal particles M, it is possible to obtain a highly reliable and high quality bonded portion further excellent in heat resistance.

  By the way, in the high temperature holding test (HTS) at 350 ° C., the shear strength increases from about 60 MPa to about 80 MPa from the start of the test to about 100 hours, and is stable at about 70 MPa in the time region exceeding 100 hours. Results were obtained.

  In addition, in the thermal cycle test (TCT) of (−40 to 200 ° C.), the test result that the shear strength is stabilized at about 50 MPa over the entire cycle (1000 cycles) from around about 200 cycles is obtained. It was.

  The present invention has been described in detail with reference to the accompanying drawings. However, the present invention is not limited to these, and various modifications can be made by those skilled in the art based on the basic technical idea and teachings. It is self-evident that you can think of it.

M metal particle 1 granulating chamber 2 lid 3 nozzle 4 rotating disk 5 rotating disk support mechanism 6 particle discharge pipe 7 electric furnace 8 mixed gas tank 9 pipe 10 pipe 11 valve 12 exhaust device 13 valve 14 exhaust device 15 automatic filter 16 particulate collection device 100,500 Substrate 101,501 Metal / alloy body 121,122 Intermetallic compound 300 Joint

Claims (2)

  1. A semiconductor device having a semiconductor element and a connection member connected to the semiconductor element,
    A joint portion that forms a joint between the semiconductor element and the connection member is:
    An intermetallic compound composed of Sn and Cu and a metal matrix containing an Sn alloy;
    The intermetallic compound is dispersed in the metal matrix;
    At least one part of the intermetallic compound forms an epitaxial junction in which the crystal plane is bonded to the Sn alloy.
    Semiconductor device.
  2. The semiconductor device according to claim 1, wherein the intermetallic compound has a composition of Cu 6 Sn 5 .
JP2016252850A 2016-07-21 2016-12-27 Semiconductor device Active JP6430473B2 (en)

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JP2016143224 2016-07-21

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Publication number Priority date Publication date Assignee Title
JP2006167735A (en) * 2004-12-14 2006-06-29 Hitachi Ltd Manufacturing method for equipment and structural material or the like
JP2010179336A (en) * 2009-02-05 2010-08-19 Toyota Central R&D Labs Inc Joint product, semiconductor module, and method for manufacturing the joint product
US20170232562A1 (en) * 2014-08-22 2017-08-17 Kabushiki Kaisha Toyota Jidoshokki Bonding structure, bonding material and bonding method
JP6398499B2 (en) * 2014-09-09 2018-10-03 富士通株式会社 Electronic device and method of manufacturing electronic device
JP2016128184A (en) * 2015-01-09 2016-07-14 カルソニックカンセイ株式会社 Solder joint method and power module

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