JP6386936B2 - Method of manufacturing electrode member for pressure contact type semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing an electrode member for a pressure contact type semiconductor device.

  In recent years, voltage-driven semiconductor switching elements represented by insulated gate bipolar transistors (IGBTs) have been used. A voltage-driven semiconductor switching element is often used by connecting a large number of semiconductor chips in order to increase the capacity. As such a pressure contact type semiconductor device in which a large number of semiconductor chips are connected, there is a pressure contact type semiconductor device in which a semiconductor chip and a plate-like electrode body are connected in pressure contact in order to electrically connect a large number of semiconductor chips. It is used. In order to make the driving state of a large number of semiconductor chips uniform, it is important to make the pressure contact state between the plate-like electrode body and the semiconductor chip as uniform as possible.

  For example, Patent Document 1 proposes a structure and a manufacturing method for making a pressure contact state between a plate-shaped electrode body and a semiconductor chip uniform in a pressure contact type semiconductor device. In Patent Document 1, a case is prepared in which a plate-like electrode body made of copper is fixed by brazing inside an annular insulating member made of ceramic, and a semiconductor chip is mounted on the surface of the electrode body of this housing. The semiconductor chip is pressed so as to be sandwiched between the housing (electrode body) and the lid body. In patent document 1, the distortion of the electrode body produced at the time of brazing by this pressing force is corrected.

JP, 2014-110298, A

  When using electrode members for pressure contact type semiconductor devices, the internal stress of the electrode body is released as the temperature of the electrode body rises during use, and the electrode body is deformed (strained) as the internal stress is released. There is. With the recent increase in the size of semiconductor switching elements and the increase in driving voltage, the temperature during use of the semiconductor switching elements tends to increase. For this reason, deformation of the electrode body that occurs as the temperature of the electrode body during use increases. The degree of (strain) tends to increase. As described above, with the recent increase in temperature during use, there has been a problem that the deformation of the electrode body during use cannot be sufficiently suppressed only by the method described in Patent Document 1. An object of the present invention is to provide a method for manufacturing an electrode member for a pressure contact type semiconductor device in which deformation of an electrode body during use is small.

  The present application is a method for manufacturing an electrode member for a pressure-contact type semiconductor device, and includes a step of cutting a columnar body containing copper as a main component into a plate shape, and a plate-like body obtained by the cutting step. A step of heat-treating in an atmosphere; a step of processing at least one main surface of the heat-treated plate-like body to form an electrode body; and an insulating ring surrounding the electrode body and the electrode body A pressure welding type semiconductor device, comprising: a step of brazing a body, wherein in the heat treatment step, the electrode body is heated at a temperature equal to a brazing temperature in the brazing step. A method for manufacturing an electrode member is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode member for press contact type semiconductor devices with a small deformation | transformation of the electrode body at the time of use can be manufactured.

An example of the electrode member for press-contact type semiconductor devices obtained using the manufacturing method of one Embodiment of this invention is shown, (a) is a top view, (b) is sectional drawing in the AA 'line of (a). It is. It is a flowchart figure of the manufacturing method of one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  1A and 1B show an example of an electrode member for a press contact type semiconductor device obtained by using the manufacturing method of the present embodiment, FIG. 1A is a plan view, and FIG. 1B is a cross section taken along line AA ′ in FIG. FIG. An electrode member 10 for a pressure-contact type semiconductor device shown in FIG. 1 includes an electrode body 1 mainly composed of copper and an insulating annular body 2 surrounding the electrode body 1. 1 and the annular body 2 are joined together via a brazing layer 4. In the present embodiment, the brazing layer 4 includes a metallized layer deposited on the surface of the annular body 2 and a brazing material layer joined to the metallized layer and the electrode body 1.

  The electrode body 1 includes, on one main surface side, a plurality of rectangular convex portions 1a arranged vertically and horizontally at intervals in a plan view across a groove-like portion formed in a lattice shape. A semiconductor element 3 (indicated by a broken line in FIG. 1) is disposed in contact with each top surface of the convex portion 1a. The semiconductor element 3 is a voltage-driven semiconductor element such as an insulated gate bipolar transistor (IGBT) or a thyristor (SCR). More specifically, the semiconductor element 3 is sandwiched between the electrode body 1 and a plate-like upper electrode structure (not shown), and is used in a state of being pressed by the upper electrode structure and the electrode body 1 with a strong pressure. .

  A high voltage is applied to the semiconductor element 3 during driving, and large heat is generated with driving. The electrode member 10 for a semiconductor device applies a voltage to the semiconductor element 3 and also functions as a heat radiating plate that radiates this heat. The degree of voltage application to the semiconductor element 3 and the degree of heat transfer from the semiconductor element 3 vary depending on the contact state between the semiconductor element 3 and the electrode body 1 and the degree of pressing force. In order to suppress variation in the voltage applied to the plurality of semiconductor elements 3 and also to suppress variation in the degree of heat release from the plurality of semiconductor elements 3, the deformation of the electrode body 1 is small even during use. Is important.

  The electrode body 1 contains copper as a main component. The electrode body 1 may be an alloy containing copper as a main component, but is preferably made of high-purity copper containing 99% by mass or more of copper such as oxygen-free copper, tough pitch copper, or phosphorus deoxidized copper. It is. When the electrode body 1 is made of high-purity copper, the heat conductivity of the electrode body 1 is relatively high, so that the heat generated by the semiconductor element 3 can be quickly released.

  The annular body 2 is made of, for example, a ceramic sintered body mainly composed of aluminum oxide, silicon carbide, silicon nitride, or aluminum nitride. When these ceramic sintered bodies are used, since the mechanical strength is high and the heat resistance is also high, the electrode member 10 for a pressure contact type semiconductor device can be used with a stable performance over a relatively long period.

  Although the material of the brazing material in the brazing layer 4 is not particularly limited, it is preferable to use, for example, a so-called silver-copper brazing or the like in view of high heat resistance and high bonding strength between the electrode body 1 and the annular body 2. For example, the electrode member 10 for a press contact type semiconductor device may be heated to about 200 ° C. to 500 ° C. during use (when the semiconductor element 3 is driven). The brazing material in the brazing layer 4 needs to have high heat resistance against such a high temperature, and the brazing temperature needs to be higher than 200 to 500 ° C. For example, as the silver-copper brazing, it is preferable to use a brazing material (so-called BAg-8 silver brazing) having a silver and copper ratio of 72 mass% and 28 mass%, respectively.

  In addition, a main component is a component which occupies 70 mass% or more with respect to the total 100 mass% of the component which comprises the member to which its attention is paid. When the member is made of metal, the content of each metal is determined using an ICP emission spectroscopic analyzer or a fluorescent X-ray analyzer, and 70% by mass or more with respect to the total of 100% by mass of the components constituting the member. Is the main component. Further, when the member is made of a ceramic sintered body, an ICP emission spectroscopic analysis apparatus or a fluorescent X-ray analysis apparatus is identified after identifying a compound constituting the ceramic sintered body using an X-ray diffractometer (XRD). What is necessary is just to obtain | require content of the metal which comprises a compound using, and to convert into the identified compound.

  In the embodiment shown in FIG. 1, the shape of the inner peripheral surface of the annular body 2 is circular in plan view, but the shape of the inner peripheral surface may be a polygonal shape such as a quadrangle or a hexagon. Further, the shape of the outer peripheral surface of the electrode body 1 may be a polygonal shape such as a quadrangle or a hexagon in a plan view. The shapes of the annular body 2 and the electrode body 1 are not particularly limited. Since the inner periphery of the annular body 2 and the outer periphery of the electrode body 1 are joined, the shape of the inner periphery of the annular body 2 and the shape of the outer periphery of the electrode body 1 are similar, and the outer periphery of the electrode body 1 is annular. If the brazing layer 4 is smaller than the inner circumference of the body 2, the inner circumference of the annular body 2, the outer circumference of the electrode body 1, and the thickness of the brazing layer 4 can be made uniform, and the deformation should be small. Can do.

  Next, an embodiment of the present invention will be described by taking as an example a method for manufacturing the electrode member 10 for a pressure contact type semiconductor device. FIG. 2 is a flow chart of a method for manufacturing the electrode member 10 for a pressure contact type semiconductor device. The manufacturing method of this embodiment includes a step of cutting a columnar body containing copper as a main component into a plate shape (step S102), and a step of heat-treating the plate-like body obtained in the cutting step in a non-oxidizing atmosphere. (Step S104), a step (Step S106) of forming the electrode body 1 by processing at least one main surface of the heat-treated plate-like body, and an insulating material surrounding the electrode body 1 and the electrode body 1 And brazing the annular body 2 (step S108), and in the heating process (step S104), heating is performed at the same temperature as the brazing temperature in the brazing process of the electrode body 1 (step S108). To do. Hereinafter, each step will be described.

  First, a columnar body mainly composed of copper is prepared, and the columnar body mainly composed of copper is cut into a plate shape (step S102). Specifically, for example, a cylindrical body having a diameter of about 125 to 135 mm and a height of about 450 to 550 mm is divided into a plurality of parts along the length direction using an apparatus such as a multi-wire saw, a band saw, or a dicing saw. By cutting in this way, for example, a plurality of plate-like bodies having a diameter of about 125 to 135 mm and a thickness (height) of 16 to 18 mm are obtained. The columnar body mainly composed of copper is formed in a cylindrical shape in the manufacturing process, but the magnitude of internal stress (initial residual tensile stress) depends on the molding process and subsequent temperature history. Vary partially, and the degree of variation is relatively large. The plate-like body obtained by cutting the columnar body also retains this initially residual tensile stress, and the degree of variation thereof is similarly large. Further, in this cutting step, residual compressive stress (processing residual compressive stress) accompanying processing is generated on both main surfaces of the plate-like body.

  Next, the plate-like body obtained in the cutting step is heat-treated in a non-oxidizing atmosphere (step S104). In the heat treatment step, heating is performed at the same temperature as the brazing temperature in the step (step S108) of brazing the electrode body 1 (the processed plate-like body) and the annular body 2 described later. The same temperature as the brazing temperature is not exactly the same temperature but a temperature range of the same degree, specifically, a brazing temperature and a temperature range of ± 50 ° C.

As described above, when so-called BAg-8 silver brazing is used as the brazing material in the brazing layer 4, the brazing temperature in the brazing material layer forming step (step S108 described later) is 820 ° C., for example. Therefore, this heating process (step S1
In 04), the plate-like body is heated to a temperature of 770 ° C. to 870 ° C. That is, in this heat treatment, the plate-like body is heat-treated prior to the main surface processing (step S106) to a temperature similar to the heating temperature in the brazing step (step S108). The heating temperature in the heat treatment step (step S104) may be set according to the brazing material to be used (in accordance with the brazing temperature of the brazing material to be used), and is not particularly limited.

  The atmosphere of the heat treatment is a non-oxidizing atmosphere, for example, a hydrogen, nitrogen or argon atmosphere. The holding time of the heating temperature is, for example, 3 minutes or more and 15 minutes or less, and particularly preferably 4 minutes or more and 10 minutes or less. In the present embodiment, before heating in the brazing step (S108), the plate-like body is heated to the same level as the brazing temperature in the brazing step (step S108), so that the cylinder before cutting. Prior to the brazing step (S108), the internal tensile stress (initial residual tensile stress) existing inside the body from the state can be reduced in advance and partial variations can be suppressed. . In addition, before the brazing step (S108), the compressive stress (processing residual compressive stress) on the surface of the plate-like body generated at the time of cutting in step S102 can also be reduced. By this heat treatment, a certain amount of tensile stress remains in the plate-like body, but its variation is small and the surface compressive stress is relatively small.

  If the heat treatment in step S104 is not performed, the tensile stress inside the electrode body 1 existing inside the cylindrical body before cutting in step S102 at the stage of heating in the brazing step in step S108. Both the (initial residual tensile stress) and the compressive stress (process residual compressive stress) on the surface of the electrode body 1 that has been further increased by the cutting in step S102 and the processing in step 106 described later are large, and both are partial. The variation is large. That is, in this case, at the stage of heating in the brazing process of step S108, both the internal tensile stress (initial residual tensile stress) of the plate-like body 1 and the surface compressive stress (working residual compressive stress) are relatively low. It is large and both of them remain unbalanced. For this reason, in this case, even if the stress is released by heating in the brazing process in step S108, the internal tensile stress (initial residual tensile stress) and the compressive stress (working residual compressive stress) are eliminated in an unbalanced manner, and partially In some cases, only one of the stresses remains strongly, and the electrode body 1 may be partially deformed by the partially remaining stress.

  Further, in the present embodiment, by performing the heat treatment before the step of forming the electrode body 1 by processing the plate body (step S106), the step of cutting the columnar body into a plate shape (step S102). The electrode body 1 is formed in a state where stress remaining in the plate-like body and variations in stress are reduced. Therefore, the electrode body 1 with high dimensional accuracy can be formed.

  Next, the electrode body 1 is formed by processing at least one main surface of the heat-treated plate-like body (step S106). In the present embodiment, the electrode body 1 is formed by processing both main surfaces of the plate-like body. First, by using a machining center apparatus or the like, mechanical processing is performed on one main surface of the plate-like body, and a plurality of groove portions are formed on the one main surface, whereby a plurality of convex portions 1a ( 1). In the present embodiment, for example, the depth of the groove (the height of the protrusion 1a, the height from the bottom of the groove to the top surface of the protrusion 1a) is, for example, 5 mm to 50 mm, and the length of each side of the top surface of the protrusion For example, 5 mm to 50 mm. Thereafter, both main surfaces of the one main surface and the other main surface on which the convex portion 1a is formed are ground to smooth both main surfaces. By grinding both main surfaces of the plate-like body, a certain amount of compressive stress is applied to the main surface, which is the outer surface of the plate-like body. Both main surfaces are smoothed, and the variation in processing residual compressive stress on both main surfaces is small.

That is, the plate-like body (electrode body 1) after undergoing the step of forming this electrode body has a certain amount of tensile stress (initial residual tensile stress) inside, but its variation is small,
In addition, the surface compressive stress (working residual compressive stress) remains to some extent, but the variation is small.

  Next, the electrode body 1 and the insulating annular body 2 surrounding the electrode body 1 are brazed (step S108). In the present embodiment, so-called BAg-8 silver brazing is used as the brazing material in the brazing layer 4, and the brazing temperature in the brazing layer 4 forming step (step S108 described later) is 820 ° C. .

  In addition, it is preferable to form a metallized layer on the inner peripheral surface of the annular body 2 prior to brazing in that the bonding strength between the electrode body 1 and the annular body 2 is further increased. For example, an intermediate layer containing molybdenum as a main component and containing manganese, and a first metal layer containing nickel as a main component and containing phosphorus or boron deposited on the surface of the intermediate layer are formed in advance on the inner peripheral surface of the annular body 2. It is preferable to keep it. Further, it is preferable that a second metal layer containing nickel as a main component and containing phosphorus or boron is formed in advance on the inner peripheral surface of the annular body 2. Specifically, in step S108, first, an intermediate layer containing molybdenum as a main component and containing manganese, and a first metal layer containing nickel as a main component and containing phosphorus or boron deposited on the surface of the intermediate layer are formed into an annular body 2. A second metal layer containing nickel as a main component and containing phosphorus or boron is formed on the inner peripheral surface of the annular body 2. Then, after weighing and mixing so that the ratios of the silver and copper powders are 72% by mass and 28% by mass, respectively, a resin or inorganic compound flux and an organic solvent are added and kneaded to form a paste-like wax After preparing a material and applying this brazing material to the surface of at least one of the first metal layer and the second metal layer by any method such as a screen printing method, a pressure printing method, and a brush coating method, 120 ° C. Dry at 150 ° C. or lower. Then, after the brazing material is dried, the brazing material is melted by heat treatment at a set temperature of 820 ° C., for example, and then the temperature is lowered to form the brazing layer 4 that joins the electrode body 1 and the annular body 2. In this embodiment, the electrode member 10 for pressure contact type semiconductor devices can be obtained in this way.

  As the brazing material, a so-called active brazing material in which 2 parts by mass or more and 5 parts by mass or less of titanium, hafnium, zirconium, niobium, or a hydride thereof is added to and mixed with 100 parts by mass of the silver and copper powders may be used. Good. In this case, high bonding strength can be obtained without forming a metallized layer on the inner peripheral surface of the annular body 2.

  Moreover, the melting point of the brazing material is lowered by adding 1 to 10 parts by mass of indium or tin to 100 parts by mass of the silver and copper powders, and the hardness of the brazing layer 4 is lowered. Can be.

  Also by this heat treatment during brazing, the internal tensile stress (initial residual tensile stress) and the surface compressive stress (working residual compressive stress) remaining inside the electrode body 1 after step S106 are released. .

  As described above, in this embodiment in which the annealing process (step S104) is performed at the same temperature as the brazing temperature before the brazing process of step S108 and the processing process of step S106, the brazing process of step S108 is performed. At the stage of performing the attaching process, the electrode body 1 has a certain amount of tensile stress (initial residual tensile stress) inside, but the variation is small, and the surface compressive stress (working residual compressive stress) is also to some extent. However, the variation is small. For this reason, the internal tensile stress (initial residual tensile stress) and the compressive stress (working residual compressive stress) are eliminated in a well-balanced manner by releasing the stress by heating in the brazing process of step S108. Therefore, it is suppressed that only one stress remains strongly, and thus the electrode body 1 is suppressed from being partially deformed by the remaining stress.

  The electrode member 10 for a pressure-contact type semiconductor device obtained by such a manufacturing method has little shape deformation in the brazing step (step S108), and has high shape accuracy. Further, the internal stress remaining in the electrode body 1 is small, and the partial variation in the magnitude of the internal stress is very small. For this reason, the deformation (strain) of the electrode body according to the release of the internal stress caused by the temperature rise of the electrode body or the annular body can be sufficiently suppressed. As described above, the electrode member 10 for a pressure contact type semiconductor device suppresses deformation of the electrode body 1 due to a temperature rise, and a variation in contact state and contact pressure between the semiconductor element 3 and the electrode body 1 is small. The degree of variation in the operating characteristics of the semiconductor element 3 can be suppressed.

  While the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples. It goes without saying that various improvements and modifications may be made to the present invention without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Electrode body 2 Ring body 3 Semiconductor element 4 Brazing layer 10 Electrode member for press-contact type semiconductor devices

Claims (3)

A manufacturing method of an electrode member for a pressure contact type semiconductor device,
Cutting the columnar body mainly composed of copper into a plate shape;
A step of heat-treating the plate-like body obtained in the cutting step in a non-oxidizing atmosphere;
A step of forming an electrode body by processing at least one main surface of the heat-treated plate-like body;
Brazing the electrode body and an insulating annular body surrounding the electrode body,
In the heat treatment step, the electrode member is heated at the same temperature as the brazing temperature in the brazing step.   2. The method for manufacturing an electrode member for a pressure contact type semiconductor device according to claim 1, wherein, in the heat treatment step, the plate-like body is heated to a temperature of 770 ° C. or more and 870 ° C. or less.   The method for manufacturing an electrode member for a pressure contact type semiconductor device according to claim 1, wherein the plate-like body is made of oxygen-free copper, tough pitch copper, or phosphorus deoxidized copper.

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