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JP2018043261A - Bonding material to be bonded to electrode of semiconductor device - Google Patents

Bonding material to be bonded to electrode of semiconductor device Download PDF

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JP2018043261A
JP2018043261A JP2016178607A JP2016178607A JP2018043261A JP 2018043261 A JP2018043261 A JP 2018043261A JP 2016178607 A JP2016178607 A JP 2016178607A JP 2016178607 A JP2016178607 A JP 2016178607A JP 2018043261 A JP2018043261 A JP 2018043261A
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metal
bonding material
porous member
outer peripheral
semiconductor device
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JP6766542B2 (en
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真男 野口
Masao Noguchi
真男 野口
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Toyota Motor Corp
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Abstract

【課題】 接合材の外周部における応力を抑制する。【解決手段】 半導体装置の電極に接合される接合材であって、第１金属により構成されている多孔質部材と、前記第１金属よりも融点が低い第２金属により構成されており、前記多孔質部材の空孔内に配置されている低融点金属層を備えている。前記第１金属と前記第２金属が、加熱時に合金化する特性を備えている。前記第１金属のヤング率が、前記合金のヤング率よりも高い。前記第１金属の熱伝導率が、前記合金の熱伝導率よりも高い。前記接合材の中央部では、前記接合材の外周部よりも、前記多孔質部材の空孔率が低い。【選択図】図１PROBLEM TO BE SOLVED: To suppress stress in an outer peripheral portion of a joint material. SOLUTION: The bonding material is bonded to an electrode of a semiconductor device, and is composed of a porous member made of a first metal and a second metal having a melting point lower than that of the first metal. It includes a low melting point metal layer arranged in the pores of the porous member. The first metal and the second metal have a property of alloying when heated. The Young's modulus of the first metal is higher than the Young's modulus of the alloy. The thermal conductivity of the first metal is higher than the thermal conductivity of the alloy. In the central portion of the joining material, the porosity of the porous member is lower than that in the outer peripheral portion of the joining material. [Selection diagram] Fig. 1

Description

本明細書に開示の技術は、半導体装置の電極に接合される接合材に関する。   The technology disclosed in this specification relates to a bonding material bonded to an electrode of a semiconductor device.

特許文献１に、半導体装置の電極に接合される接合材が開示されている。この接合材は、銅、ニッケル、銀、鉄等によって構成されている多孔質部材と、多孔質部材の空孔内に配置されているはんだ層を備えている。接合材は、半導体装置の電極に接合される。接合材を介して、半導体装置の電極を外部の端子等に接続することができる。   Patent Document 1 discloses a bonding material bonded to an electrode of a semiconductor device. This bonding material includes a porous member made of copper, nickel, silver, iron, or the like, and a solder layer disposed in the pores of the porous member. The bonding material is bonded to the electrode of the semiconductor device. The electrode of the semiconductor device can be connected to an external terminal or the like through the bonding material.

特開２００４−２９８９６２号公報Japanese Patent Laid-Open No. 2004-29862

半導体装置の動作時に、半導体装置が発熱する。すると、半導体装置が熱膨張するとともに、半導体装置に接合されている接合材も熱膨張する。半導体装置と接合材との膨張率の差により、接合材の内部に応力が発生する。半導体装置と接合材は中央部から外周部に向かって膨張するので、応力は接合材の外周部で中央部よりも高くなる。接合材の外周部に繰り返し高い応力が加わると、その外周部で接合材にクラックが生じるおそれがある。したがって、本明細書では、接合材の外周部における応力を抑制する技術を提供する。   During operation of the semiconductor device, the semiconductor device generates heat. Then, the semiconductor device is thermally expanded, and the bonding material bonded to the semiconductor device is also thermally expanded. Stress is generated inside the bonding material due to a difference in expansion coefficient between the semiconductor device and the bonding material. Since the semiconductor device and the bonding material expand from the central portion toward the outer peripheral portion, the stress is higher at the outer peripheral portion of the bonding material than at the central portion. When a high stress is repeatedly applied to the outer peripheral portion of the bonding material, there is a risk that cracks may occur in the bonding material at the outer peripheral portion. Therefore, in this specification, the technique which suppresses the stress in the outer peripheral part of a joining material is provided.

本明細書が開示する接合材は、半導体装置の電極に接合される。この接合材は、多孔質部材と低融点金属層を備えている。前記多孔質部材は、第１金属により構成されている。前記低融点金属層は、前記第１金属よりも融点が低い第２金属により構成されており、前記多孔質部材の空孔内に配置されている。前記第１金属と前記第２金属が、加熱時に合金化する特性を備えている。前記第１金属のヤング率が、前記合金のヤング率よりも高い。前記第１金属の熱伝導率が、前記合金の熱伝導率よりも高い。前記接合材の中央部では、前記接合材の外周部よりも、前記多孔質部材の空孔率が低い。   The bonding material disclosed in this specification is bonded to an electrode of a semiconductor device. This bonding material includes a porous member and a low melting point metal layer. The porous member is made of a first metal. The low melting point metal layer is made of a second metal having a melting point lower than that of the first metal, and is disposed in the pores of the porous member. The first metal and the second metal have a property of alloying when heated. The Young's modulus of the first metal is higher than the Young's modulus of the alloy. The thermal conductivity of the first metal is higher than the thermal conductivity of the alloy. The porosity of the porous member is lower in the central portion of the bonding material than in the outer peripheral portion of the bonding material.

なお、上記の「合金」は、金属間化合物であってもよいし、固溶体であってもよいが、金属間化合物であることが好ましい。   The above “alloy” may be an intermetallic compound or a solid solution, but is preferably an intermetallic compound.

接合材を半導体装置の電極に接合する際に、接合材が加熱される。すると、接合材の内部で第１金属と第２金属が合金化する。接合材の中央部では多孔質部材の空孔率が低いので、加熱後の接合材の中央部では合金に対する第１金属の割合が高くなる。第１金属の熱伝導率が高いので、加熱後の接合材の中央部の熱伝導率は高い。接合材の外周部では多孔質部材の空孔率が高いので、加熱後の接合材の外周部では第１金属に対する合金の割合が高くなる。合金のヤング率が低いので、加熱後の接合材の外周部のヤング率は低い。接合材の中央部は半導体装置の中央部に接合され、接合材の外周部は半導体装置の外周部に接合される。加熱後の接合材の中央部の熱伝導率が高いので、半導体装置の中央部から好適に放熱することができる。したがって、半導体装置の中央部の温度上昇を好適に抑制することができる。また、加熱後の接合材の外周部のヤング率が低いので、加熱後の接合材の外周部は柔軟性を有する。このため、加熱後の接合材の外周部に高い応力が生じることが抑制される。このように、この接合材によれば、半導体装置の中央部の温度上昇を抑制しながら、接合材の外周部における応力を抑制することができる。   When the bonding material is bonded to the electrode of the semiconductor device, the bonding material is heated. Then, the first metal and the second metal are alloyed inside the bonding material. Since the porosity of the porous member is low at the central portion of the bonding material, the ratio of the first metal to the alloy is high at the central portion of the bonding material after heating. Since the thermal conductivity of the first metal is high, the thermal conductivity of the central portion of the bonding material after heating is high. Since the porosity of the porous member is high at the outer peripheral portion of the bonding material, the ratio of the alloy to the first metal is high at the outer peripheral portion of the bonding material after heating. Since the Young's modulus of the alloy is low, the Young's modulus of the outer peripheral portion of the bonding material after heating is low. The central portion of the bonding material is bonded to the central portion of the semiconductor device, and the outer peripheral portion of the bonding material is bonded to the outer peripheral portion of the semiconductor device. Since the heat conductivity of the center part of the bonding material after heating is high, heat can be suitably radiated from the center part of the semiconductor device. Therefore, it is possible to suitably suppress the temperature rise in the central portion of the semiconductor device. Moreover, since the Young's modulus of the outer peripheral part of the bonding material after heating is low, the outer peripheral part of the bonding material after heating has flexibility. For this reason, it is suppressed that a high stress arises in the outer peripheral part of the joining material after a heating. Thus, according to this bonding material, it is possible to suppress the stress at the outer peripheral portion of the bonding material while suppressing the temperature rise in the central portion of the semiconductor device.

実施形態の接合材の断面図。Sectional drawing of the bonding | jointing material of embodiment. 接合材の製造方法の説明図。Explanatory drawing of the manufacturing method of a joining material. 接合材の製造方法の説明図。Explanatory drawing of the manufacturing method of a joining material. 接合材の製造方法の説明図。Explanatory drawing of the manufacturing method of a joining material. 接合材の製造方法の説明図。Explanatory drawing of the manufacturing method of a joining material. 接合材の使用方法の説明図。Explanatory drawing of the usage method of a joining material. 接合材の使用方法の説明図。Explanatory drawing of the usage method of a joining material.

図１に示す接合材１０は、多孔質部材２０と低融点金属層３０を有している。多孔質部材２０は、その内部に多数の空孔２２を有している。空孔２２は互いに繋がっている。低融点金属層３０は、空孔２２内に配置されている。各空孔２２は、低融点金属層３０によって満たされている。多孔質部材２０は、金属により構成されている。低融点金属層３０は、多孔質部材２０を構成する金属よりも融点が低い金属により構成されている。多孔質部材２０を構成する金属と低融点金属層３０を構成する金属は、加熱によって互いに合金化する組み合わせとされている。特に、本実施形態では、多孔質部材２０を構成する金属と低融点金属層３０を構成する金属は、加熱によって互いに反応して金属間化合物が生成される組み合わせとなっている。多孔質部材２０を構成する金属のヤング率は、加熱によって生成される金属間化合物のヤング率よりも高い。また、多孔質部材２０を構成する金属の熱伝導率は、加熱によって生成される金属間化合物の熱伝導率よりも高い。また、加熱によって生成される金属間化合物の融点は、低融点金属層３０を構成する金属の融点よりも高く、多孔質部材２０を構成する金属の融点よりも低い。上述した関係を満たす多孔質部材２０と低融点金属層３０との金属との組み合わせの例を、表１に示す。   The bonding material 10 shown in FIG. 1 has a porous member 20 and a low melting point metal layer 30. The porous member 20 has a large number of pores 22 therein. The holes 22 are connected to each other. The low melting point metal layer 30 is disposed in the holes 22. Each hole 22 is filled with a low melting point metal layer 30. The porous member 20 is made of metal. The low melting point metal layer 30 is made of a metal having a melting point lower than that of the metal constituting the porous member 20. The metal that constitutes the porous member 20 and the metal that constitutes the low melting point metal layer 30 are combined with each other by heating. In particular, in the present embodiment, the metal constituting the porous member 20 and the metal constituting the low melting point metal layer 30 are a combination in which an intermetallic compound is generated by reacting with each other by heating. The Young's modulus of the metal constituting the porous member 20 is higher than the Young's modulus of the intermetallic compound produced by heating. Moreover, the heat conductivity of the metal which comprises the porous member 20 is higher than the heat conductivity of the intermetallic compound produced | generated by heating. Further, the melting point of the intermetallic compound generated by heating is higher than the melting point of the metal constituting the low melting point metal layer 30 and lower than the melting point of the metal constituting the porous member 20. Table 1 shows examples of combinations of the porous member 20 and the metal of the low melting point metal layer 30 that satisfy the relationship described above.

Figure 2018043261
Figure 2018043261

接合材１０は、中央部１０ａと、中央部１０ａの周囲に配置された外周部１０ｂを有している。接合材１０の厚み方向に沿って見たときに、外周部１０ｂは中央部１０ａの周囲を一巡している。中央部１０ａでは、外周部１０ｂよりも、多孔質部材２０の空孔率が低い。すなわち、中央部１０ａでは、外周部１０ｂよりも、空孔２２の密度が低い。したがって、中央部１０ａでは外周部１０ｂよりも多孔質部材２０を構成する金属の体積比率が高く、外周部１０ｂでは中央部１０ａよりも低融点金属層３０を構成する金属の体積比率が高い。   The bonding material 10 has a central portion 10a and an outer peripheral portion 10b arranged around the central portion 10a. When viewed along the thickness direction of the bonding material 10, the outer peripheral portion 10b goes around the central portion 10a. In the central portion 10a, the porosity of the porous member 20 is lower than that of the outer peripheral portion 10b. That is, the density of the holes 22 is lower in the central portion 10a than in the outer peripheral portion 10b. Therefore, the volume ratio of the metal constituting the porous member 20 is higher in the central portion 10a than the outer peripheral portion 10b, and the volume ratio of the metal constituting the low melting point metal layer 30 is higher in the outer peripheral portion 10b than in the central portion 10a.

次に、接合材１０の製造方法について説明する。まず、多孔質部材２０の材料金属により構成された金属粉末を有機溶媒（例えば、エチレングリコール等）に混合したペーストを作成する。金属粉末が有機溶媒中に均等に分散するように、十分にペーストを撹拌する。なお、ここでは、金属粉末の密度が高い第１のペーストと、金属粉末の密度が低い第２のペーストを準備する。次に、図２に示すように、グラファイトプレート５０上に作成したペーストを塗布する。つまり、図２に示すように、有機溶媒４２と金属粉末４０とが混合されたペーストをグラファイトプレート５０上に塗布する。ここでは、まず、金属粉末４０の密度が高い第１のペーストをグラファイトプレート５０上に塗布することで、中央部１０ａを作成する。次に、金属粉末４０の密度が低い第２のペーストを中央部１０ａの周囲を囲むようにグラファイトプレート５０上に塗布することで、外周部１０ｂを作成する。外周部１０ｂは、中央部１０ａに隣接するとともに中央部１０ａと略同じ厚さとなるように塗布する。ペーストの塗布には、ステンシルマスクを用いた塗布方法や、シリンジを用いた塗布方法を用いることができる。   Next, a method for manufacturing the bonding material 10 will be described. First, a paste is prepared by mixing a metal powder composed of a material metal of the porous member 20 in an organic solvent (for example, ethylene glycol). The paste is sufficiently stirred so that the metal powder is evenly dispersed in the organic solvent. Here, a first paste having a high density of metal powder and a second paste having a low density of metal powder are prepared. Next, as shown in FIG. 2, the prepared paste is applied on the graphite plate 50. That is, as shown in FIG. 2, a paste in which the organic solvent 42 and the metal powder 40 are mixed is applied on the graphite plate 50. Here, first, the central portion 10 a is created by applying a first paste having a high density of the metal powder 40 onto the graphite plate 50. Next, the outer peripheral part 10b is created by apply | coating the 2nd paste with the low density of the metal powder 40 on the graphite plate 50 so that the circumference | surroundings of the center part 10a may be enclosed. The outer peripheral part 10b is applied so as to be adjacent to the central part 10a and to have substantially the same thickness as the central part 10a. For applying the paste, an application method using a stencil mask or an application method using a syringe can be used.

次に、図３に示すように、ペーストを加熱しながら、加圧板５２によってペーストを上から加圧する。例えば、放電プラズマ焼結装置等によってこの工程を実施することができる。加熱によって、有機溶媒４２が揮発する。また、ペーストの加圧によって、金属粉末４０が圧縮されるとともに互いに密着する。金属粉末４０が圧縮された状態で加熱されることによって、金属粉末４０同士が互いに結合する。これによって、図４に示す多孔質部材２０が形成される。このように製造された多孔質部材２０は、空孔率が低い中央部１０ａと、中央部１０ａの周囲に配置されていると共に空孔率が高い外周部１０ｂを有する。   Next, as shown in FIG. 3, the paste is pressed from above by the pressure plate 52 while the paste is heated. For example, this step can be performed by a discharge plasma sintering apparatus or the like. The organic solvent 42 is volatilized by heating. Moreover, the metal powder 40 is compressed and adhered to each other by pressurizing the paste. By heating the metal powder 40 in a compressed state, the metal powders 40 are bonded to each other. Thereby, the porous member 20 shown in FIG. 4 is formed. The porous member 20 manufactured in this way has a central portion 10a having a low porosity and an outer peripheral portion 10b disposed around the central portion 10a and having a high porosity.

次に、図５に示すように、低融点金属層３０の材料金属を溶融させた溶融金属３０ａを容器内に準備し、溶融金属３０ａ内に多孔質部材２０を浸漬する。すると、多孔質部材２０の空孔２２内に溶融金属３０ａが流入し、空孔２２内に溶融金属３０ａが充填される。その後、容器内の溶融金属３０ａから多孔質部材２０を引き上げる。多孔質部材２０を引き上げると、空孔２２内の溶融金属３０ａが冷えて凝固する。これによって、空孔２２内に低融点金属層３０が形成される。すなわち、図１に示す接合材１０が完成する。なお、溶融金属３０ａ内に多孔質部材２０を浸漬するときに多孔質部材２０が加熱されるが、浸漬時間が短いので、多孔質部材２０と溶融金属３０ａはほとんど反応しない。すなわち、多孔質部材２０を構成する金属と溶融金属３０ａから金属間化合物が生成される反応はほとんど生じない。したがって、空孔２２内には低融点金属層３０が形成される。   Next, as shown in FIG. 5, a molten metal 30a obtained by melting the material metal of the low melting point metal layer 30 is prepared in a container, and the porous member 20 is immersed in the molten metal 30a. Then, the molten metal 30a flows into the pores 22 of the porous member 20, and the molten metal 30a is filled into the pores 22. Thereafter, the porous member 20 is pulled up from the molten metal 30a in the container. When the porous member 20 is pulled up, the molten metal 30a in the pores 22 is cooled and solidified. As a result, the low melting point metal layer 30 is formed in the holes 22. That is, the bonding material 10 shown in FIG. 1 is completed. In addition, although the porous member 20 is heated when the porous member 20 is immersed in the molten metal 30a, since the immersion time is short, the porous member 20 and the molten metal 30a hardly react. That is, a reaction in which an intermetallic compound is generated from the metal constituting the porous member 20 and the molten metal 30a hardly occurs. Therefore, the low melting point metal layer 30 is formed in the holes 22.

次に、接合材１０の使用方法について説明する。接合材１０は、図６に示す半導体装置７０と基板６０との接続に用いられる。半導体装置７０は、半導体基板７０ａとその裏面に設けられた電極７０ｂを有する。半導体基板７０ａの主材料はＳｉＣ（炭化シリコン）であり、半導体装置７０は２５０℃程度の高温でも動作することが可能である。基板６０は、基板本体６０ｂとその表面に設けられたメッキ層６０ａ（金属層）を有する。接合材１０は、電極７０ｂとメッキ層６０ａとの接続に用いられる。   Next, a method for using the bonding material 10 will be described. The bonding material 10 is used to connect the semiconductor device 70 and the substrate 60 shown in FIG. The semiconductor device 70 includes a semiconductor substrate 70a and an electrode 70b provided on the back surface thereof. The main material of the semiconductor substrate 70 a is SiC (silicon carbide), and the semiconductor device 70 can operate even at a high temperature of about 250 ° C. The substrate 60 has a substrate body 60b and a plating layer 60a (metal layer) provided on the surface thereof. The bonding material 10 is used for connection between the electrode 70b and the plating layer 60a.

まず、図６に示すように、基板６０、接合材１０及び半導体装置７０を積層する。接合材１０を、電極７０ｂとメッキ層６０ａに接触させる。接合材１０の中央部１０ａが半導体装置７０の中央部に接触し、接合材１０の外周部１０ｂが半導体装置７０の外周部に接触する。次に、図６に示す積層体をリフロー炉に投入することで、積層体を加熱する。なお、基板６０、接合材１０及び半導体装置７０の酸化を防ぐために、水素などの還元雰囲気下で加熱することが好ましい。ここでは、ピーク温度が低融点金属層３０の融点よりも高い温度（例えば、低融点金属層３０がＳｎにより構成されている場合には、２３２℃以上の温度）となるように積層体を加熱する。すると、低融点金属層３０が溶融する。電極７０ｂ及びメッキ層６０ａは、低融点金属層３０に対して濡れ性が高い金属によって構成されている。したがって、溶融した低融点金属層３０は液相拡散反応によって電極７０ｂ及びメッキ層６０ａと反応し、金属間化合物が生成される。これによって、接合材１０が電極７０ｂ及びメッキ層６０ａに対して接合される。すなわち、電極７０ｂとメッキ層６０ａが、接合材１０を介して電気的に接続される。また、溶融した低融点金属層３０は、液相拡散反応によって多孔質部材２０と反応する。これによって、図７に示すように、金属間化合物３２が生成する。金属間化合物３２の融点は低融点金属層３０の融点よりも高いので、金属間化合物３２は生成される際に固化する。ここでは、図７に示すように、低融点金属層３０の略全体を金属間化合物３２に変化させる。多孔質部材２０は、大部分が元の純金属として残存する。その結果、図７に示すように、多孔質部材２０の空孔２２内が金属間化合物３２によって満たされている構造が得られる。   First, as shown in FIG. 6, the substrate 60, the bonding material 10, and the semiconductor device 70 are stacked. The bonding material 10 is brought into contact with the electrode 70b and the plating layer 60a. The central portion 10 a of the bonding material 10 contacts the central portion of the semiconductor device 70, and the outer peripheral portion 10 b of the bonding material 10 contacts the outer peripheral portion of the semiconductor device 70. Next, the laminate is heated by putting the laminate shown in FIG. 6 into a reflow furnace. In order to prevent oxidation of the substrate 60, the bonding material 10, and the semiconductor device 70, it is preferable to heat in a reducing atmosphere such as hydrogen. Here, the stacked body is heated so that the peak temperature is higher than the melting point of the low melting point metal layer 30 (for example, a temperature of 232 ° C. or more when the low melting point metal layer 30 is made of Sn). To do. Then, the low melting point metal layer 30 is melted. The electrode 70 b and the plating layer 60 a are made of a metal having high wettability with respect to the low melting point metal layer 30. Therefore, the molten low melting point metal layer 30 reacts with the electrode 70b and the plating layer 60a by a liquid phase diffusion reaction, and an intermetallic compound is generated. Thereby, the bonding material 10 is bonded to the electrode 70b and the plating layer 60a. In other words, the electrode 70 b and the plating layer 60 a are electrically connected via the bonding material 10. The molten low melting point metal layer 30 reacts with the porous member 20 by a liquid phase diffusion reaction. As a result, an intermetallic compound 32 is produced as shown in FIG. Since the melting point of the intermetallic compound 32 is higher than the melting point of the low melting point metal layer 30, the intermetallic compound 32 is solidified when it is generated. Here, as shown in FIG. 7, substantially the entire low melting point metal layer 30 is changed to an intermetallic compound 32. Most of the porous member 20 remains as the original pure metal. As a result, as shown in FIG. 7, a structure in which the pores 22 of the porous member 20 are filled with the intermetallic compound 32 is obtained.

なお、金属間化合物３２の融点は低融点金属層３０の融点よりも高い。また、多孔質部材２０の融点は金属間化合物３２の融点よりもさらに高い。例えば、多孔質部材２０がＣｕによって構成されており、低融点金属層３０がＳｎによって構成されている場合には、金属間化合物３２としてＣｕ６Ｓｎ５が生成される。金属間化合物３２（Ｃｕ６Ｓｎ５）の融点（約４１５℃）は、低融点金属層３０（Ｓｎ）の融点（約２３２℃）よりも高い。また、多孔質部材２０（Ｃｕ）の融点（約１０８５℃）は、金属間化合物３２（Ｃｕ６Ｓｎ５）の融点（約４１５℃）よりも高い。加熱後の接合材１０は、融点が高い金属間化合物３２と多孔質部材２０により構成されている。このため、加熱後の接合材１０は、高い耐熱性を有する。例えば、ＳｉＣを主材料とする半導体装置７０が動作可能な定格温度（約２５０℃）において、接合材１０は十分な耐熱性を有している。接合材１０によれば、はんだ等に比べて、より高い耐熱性を確保することができる。すなわち、接合材１０は、低融点金属層３０の融点の温度において接合することが可能である一方で、接合後は低融点金属層３０の融点よりも高い耐熱温度を有する。 Note that the melting point of the intermetallic compound 32 is higher than the melting point of the low melting point metal layer 30. Further, the melting point of the porous member 20 is higher than the melting point of the intermetallic compound 32. For example, when the porous member 20 is made of Cu and the low melting point metal layer 30 is made of Sn, Cu 6 Sn 5 is generated as the intermetallic compound 32. The melting point (about 415 ° C.) of the intermetallic compound 32 (Cu 6 Sn 5 ) is higher than the melting point (about 232 ° C.) of the low melting point metal layer 30 (Sn). Moreover, the melting point (about 1085 ° C.) of the porous member 20 (Cu) is higher than the melting point (about 415 ° C.) of the intermetallic compound 32 (Cu 6 Sn 5 ). The heated bonding material 10 includes an intermetallic compound 32 having a high melting point and a porous member 20. For this reason, the bonding material 10 after heating has high heat resistance. For example, the bonding material 10 has sufficient heat resistance at a rated temperature (about 250 ° C.) at which the semiconductor device 70 mainly composed of SiC can operate. According to the bonding material 10, higher heat resistance can be ensured compared to solder or the like. In other words, the bonding material 10 can be bonded at the temperature of the melting point of the low melting point metal layer 30, but has a heat resistance temperature higher than the melting point of the low melting point metal layer 30 after bonding.

上述したように、中央部１０ａでは、外周部１０ｂよりも、多孔質部材２０の空孔率が低い。上述したように空孔２２は金属間化合物３２で満たされているので、中央部１０ａでは、外周部１０ｂよりも、金属間化合物３２の体積比率が低い。すなわち、中央部１０ａでは、外周部１０ｂよりも、多孔質部材２０の体積比率が高い。多孔質部材２０のヤング率は、金属間化合物３２のヤング率よりも高い。また、多孔質部材２０の熱伝導率は、金属間化合物３２の熱伝導率よりも高い。中央部１０ａでは外周部１０ｂよりも多孔質部材２０の体積比率が高いので、中央部１０ａは外周部１０ｂよりも高いヤング率を有し、中央部１０ａは外周部１０ｂよりも高い熱伝導率を有する。   As described above, the porosity of the porous member 20 is lower in the central portion 10a than in the outer peripheral portion 10b. As described above, since the holes 22 are filled with the intermetallic compound 32, the volume ratio of the intermetallic compound 32 is lower in the central portion 10a than in the outer peripheral portion 10b. That is, the volume ratio of the porous member 20 is higher in the central portion 10a than in the outer peripheral portion 10b. The Young's modulus of the porous member 20 is higher than the Young's modulus of the intermetallic compound 32. Further, the thermal conductivity of the porous member 20 is higher than the thermal conductivity of the intermetallic compound 32. Since the volume ratio of the porous member 20 is higher in the central portion 10a than in the outer peripheral portion 10b, the central portion 10a has a higher Young's modulus than the outer peripheral portion 10b, and the central portion 10a has a higher thermal conductivity than the outer peripheral portion 10b. Have.

半導体装置７０は、動作時に発熱する。半導体装置７０の中央部（中央部１０ａの上側の部分）は、その周囲を半導体装置７０の外周部（外周部１０ｂの上側の部分）に囲まれている。このため、半導体装置７０の中央部で生じた熱は横方向に放熱され難い。しかしながら、本実施形態では、半導体装置７０の中央部が接合材１０の中央部１０ａに接合されている。中央部１０ａは高い熱伝導率を有するので、半導体装置７０の中央部で生じた熱が中央部１０ａを介して効率的に放熱される。したがって、半導体装置７０の中央部の温度上昇を抑制することができる。また、半導体装置７０の外周部は接合材１０の外周部１０ｂに接合されている。外周部１０ｂの熱伝導率は中央部１０ａよりも低い。このため、半導体装置７０の外周部では、接合材１０を介した放熱効率がそれほど高くはない。しかしながら、半導体装置７０の外周部では、半導体基板７０ａの外周面からも放熱される。このため、半導体装置７０の外周部でも温度上昇を抑制することができる。このように、半導体装置７０の中央部と外周部の何れでも、適切に温度上昇が抑制される。   The semiconductor device 70 generates heat during operation. The central portion of the semiconductor device 70 (the upper portion of the central portion 10a) is surrounded by the outer peripheral portion of the semiconductor device 70 (the upper portion of the outer peripheral portion 10b). For this reason, the heat generated in the central portion of the semiconductor device 70 is difficult to dissipate in the lateral direction. However, in the present embodiment, the central portion of the semiconductor device 70 is bonded to the central portion 10 a of the bonding material 10. Since the central portion 10a has a high thermal conductivity, heat generated at the central portion of the semiconductor device 70 is efficiently radiated through the central portion 10a. Therefore, the temperature rise at the center of the semiconductor device 70 can be suppressed. In addition, the outer peripheral portion of the semiconductor device 70 is bonded to the outer peripheral portion 10 b of the bonding material 10. The thermal conductivity of the outer peripheral part 10b is lower than that of the central part 10a. For this reason, in the outer peripheral part of the semiconductor device 70, the heat dissipation efficiency through the bonding material 10 is not so high. However, heat is also radiated from the outer peripheral surface of the semiconductor substrate 70a at the outer peripheral portion of the semiconductor device 70. For this reason, the temperature rise can be suppressed even in the outer peripheral portion of the semiconductor device 70. As described above, the temperature rise is appropriately suppressed in both the central portion and the outer peripheral portion of the semiconductor device 70.

半導体装置７０が発熱すると、半導体装置７０と接合材１０が熱膨張する。半導体装置７０の線膨張係数は、接合材１０の線膨張係数よりも小さい。したがって、接合材１０は半導体装置７０よりも大きく膨張しようとする。しかしながら、半導体装置７０によって拘束されることで接合材１０の膨張が抑制される。その結果、接合材１０の内部に応力が生じる。接合材１０は中央部１０ａ（中央部）から外周部１０ｂ（外周部）に向かって膨張するので、接合材１０の中央部１０ａでは高い応力は生じないが、接合材１０の外周部１０ｂでは高い応力が生じやすい。しかしながら、外周部１０ｂはヤング率が低く、柔軟性を有する。したがって、外周部１０ｂの内部に応力が生じることが抑制される。また、中央部１０ａはヤング率が高いが、上述したように中央部１０ａでは高い応力が生じない。このように、接合材１０の中央部１０ａと外周部１０ｂのいずれでも、高い応力が生じることが抑制される。したがって、接合材１０は、繰り返しの温度変化に対して耐久性が高い。   When the semiconductor device 70 generates heat, the semiconductor device 70 and the bonding material 10 are thermally expanded. The linear expansion coefficient of the semiconductor device 70 is smaller than the linear expansion coefficient of the bonding material 10. Therefore, the bonding material 10 tends to expand more than the semiconductor device 70. However, the expansion of the bonding material 10 is suppressed by being restrained by the semiconductor device 70. As a result, stress is generated inside the bonding material 10. Since the bonding material 10 expands from the central portion 10a (central portion) toward the outer peripheral portion 10b (outer peripheral portion), high stress does not occur in the central portion 10a of the bonding material 10, but high in the outer peripheral portion 10b of the bonding material 10. Stress is likely to occur. However, the outer peripheral portion 10b has a low Young's modulus and has flexibility. Accordingly, the occurrence of stress in the outer peripheral portion 10b is suppressed. Further, although the central portion 10a has a high Young's modulus, as described above, no high stress is generated in the central portion 10a. Thus, high stress is suppressed from occurring in both the central portion 10a and the outer peripheral portion 10b of the bonding material 10. Therefore, the bonding material 10 has high durability against repeated temperature changes.

なお、上述した実施形態では、半導体基板７０ａがＳｉＣにより構成されていたが、Ｓｉ（シリコン）により構成されていてもよいし、他の化合物半導体により構成されていてもよい。また、上述した実施形態では、合金として金属間化合物が生成されたが、合金として金属の固溶体が生成されてもよい。   In the above-described embodiment, the semiconductor substrate 70a is made of SiC. However, the semiconductor substrate 70a may be made of Si (silicon) or another compound semiconductor. In the above-described embodiment, an intermetallic compound is generated as an alloy, but a metal solid solution may be generated as an alloy.

以上、本発明の具体例を詳細に説明したが、これらは例示にすぎず、特許請求の範囲を限定するものではない。特許請求の範囲に記載の技術には、以上に例示した具体例をさまざまに変形、変更したものが含まれる。本明細書または図面に説明した技術要素は、単独であるいは各種の組み合わせによって技術的有用性を発揮するものであり、出願時請求項記載の組み合わせに限定されるものではない。また、本明細書または図面に例示した技術は複数目的を同時に達成するものであり、そのうちの一つの目的を達成すること自体で技術的有用性を持つものである。   Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

１０ ：接合材
１０ａ ：中央部
１０ｂ ：外周部
２０ ：多孔質部材
２２ ：空孔
３０ ：低融点金属層
３２ ：金属間化合物
６０ ：基板
６０ａ ：メッキ層
６０ｂ ：基板本体
７０ ：半導体装置
７０ａ ：半導体基板
７０ｂ ：電極 DESCRIPTION OF SYMBOLS 10: Bonding material 10a: Center part 10b: Outer peripheral part 20: Porous member 22: Pore 30: Low melting metal layer 32: Intermetallic compound 60: Substrate 60a: Plating layer 60b: Substrate body 70: Semiconductor device 70a: Semiconductor Substrate 70b: Electrode

Claims (1)

半導体装置の電極に接合される接合材であって、
第１金属により構成されている多孔質部材と、
前記第１金属よりも融点が低い第２金属により構成されており、前記多孔質部材の空孔内に配置されている低融点金属層、
を備えており、
前記第１金属と前記第２金属が、加熱時に合金化する特性を備えており、
前記第１金属のヤング率が、前記合金のヤング率よりも高く、
前記第１金属の熱伝導率が、前記合金の熱伝導率よりも高く、
前記接合材の中央部では、前記接合材の外周部よりも、前記多孔質部材の空孔率が低い接合材。 A bonding material bonded to an electrode of a semiconductor device,
A porous member made of a first metal;
A low-melting-point metal layer made of a second metal having a melting point lower than that of the first metal and disposed in the pores of the porous member;
With
The first metal and the second metal have a property of alloying when heated,
The Young's modulus of the first metal is higher than the Young's modulus of the alloy;
The thermal conductivity of the first metal is higher than the thermal conductivity of the alloy;
The bonding material having a lower porosity of the porous member in the central portion of the bonding material than in the outer peripheral portion of the bonding material.
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