JP2013098491A - Heat sink, method of manufacturing heat sink, semiconductor device and semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sink which enables a metal/diamond complex to present heat conductivity close to its original heat conductivity.SOLUTION: A heat sink 11 includes a mounting plane 11a for mounting a device thereon and comprises a metal region 15 which is provided on a principal surface 13a of a base 13. The principal surface 13a includes projections 23a-23c formed from diamond particles 17 and recesses 25a-25c which are positioned between the projections 23a-23c and differently from a solder material, the recesses 25a-25d are filled by the metal region 15 comprised of a metal of which the fusion point is higher than that of the solder material, and the mounting plane 11a is reconfigured into roughness smaller than roughness comprised of the projections 23a-23c and the recesses 25a-25d. Therefore, an effective contact area between a mounting plane of the device and the surface 11a of the heat sink 11 can be made closer to an area of the mounting plane of the device.

Description

  The present invention relates to a heat sink, a method for manufacturing a heat sink, a semiconductor device, and a semiconductor module.

  Patent Document 1 discloses a heat sink made of a metal / diamond composite material in which diamond particles and a metal are combined. Patent Document 2 discloses a package for housing a semiconductor element.

JP-A-9-312362 JP 2004-146413 A

  Since a green laser diode formed on semipolar {20-21} plane GaN using a group III nitride semiconductor requires high input power, it is very important to ensure its heat dissipation. A mounting component such as a submount for mounting such a laser diode is required.

  The metal / diamond composite has excellent thermal conductivity and is one of the candidates for mounting components. This material is applied to a heat sink as described in Patent Document 1 and applied to a package as described in Patent Document 2. However, according to the knowledge of the inventors, for example, in the mounting of a laser diode, a heat sink made of a metal / diamond composite has a high thermal conductivity, but its original thermal conductivity (550 W / (m · K). ) Is not shown.

  Among the metal / diamond composites, for example, a copper / diamond composite has a value close to the thermal expansion coefficient of the group III nitride semiconductor, and from this point of view, it can provide high reliability to the nitride semiconductor device. there is a possibility.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a heat sink that enables a metal / diamond composite to exhibit a thermal conductivity close to its original thermal conductivity. It is another object of the present invention to provide a method for manufacturing the heat sink, to provide a semiconductor device including the heat sink, and to provide a semiconductor module including the semiconductor device.

  A heat sink for mounting a device according to the present invention comprises (a) a base comprising a metal / diamond composite in which diamond particles and a metal are combined, and having a main surface on which the diamond particles and the metal appear; And a metal region including a metal layer provided so as to cover the main surface of the base and having a mounting surface for mounting the device. Unlike the solder material, the metal layer is made of a metal having a melting point higher than that of the solder material, and the main surface of the base includes a protrusion formed by the diamond particles and a recess positioned between the protrusion, and the metal region Fills the depression, and the mounting surface has a roughness smaller than that of the protrusion and the depression.

  In a heat sink including a base made of a metal / diamond composite, diamond and metal having different hardness appear on the surface of the metal / diamond composite, and therefore the surface of the metal / diamond composite has roughness. When a metal / diamond composite is polished to improve the flatness of the heat sink surface, the metal scraping and the diamond scraping are different from each other. As a result, a certain degree of roughness remains on the polished surface of the metal / diamond composite. When a device is mounted on this polished surface, the effective mounting area between the device mounting surface and the heat sink polishing surface is smaller than the area of the device mounting surface.

  Further, when metallizing is performed on the surface of the heat sink, the metallized layer is formed in accordance with the shape of the surface of the heat sink. As a result, the same level of roughness as the polished surface of the metal / diamond composite remains on the surface of the metallized metal layer.

  On the other hand, this heat sink has a mounting surface for mounting a device and includes a metal region provided on the main surface of the base. The base main surface includes a protrusion formed by diamond particles and a recess positioned between the protrusions, the metal region fills the recess, and the surface of the metal region has a roughness smaller than the roughness due to the protrusion and the recess. . Therefore, the effective contact area between the mounting surface of the device and the surface of the heat sink can be brought close to the area of the mounting surface of the semiconductor device.

  In the heat sink according to the present invention, the surface roughness of the main surface of the base is preferably greater than 3 μm, and the surface roughness of the mounting surface of the metal region is preferably 3 μm or less.

  According to this heat sink, this degree of surface roughness on the mounting surface is smaller than the surface roughness of the metal / diamond composite. When measuring the surface roughness of available metal-diamond composites using a laser microscope, the surface roughness is greater than 3 μm.

  In the heat sink according to the present invention, the thickness of the metal region is preferably greater than 3 μm at the depression.

  According to this heat sink, therefore, it is possible to avoid a decrease in contact area (effective contact area between the mounting surface of the semiconductor device and the surface of the heat sink) due to the roughness of the surface of the heat sink.

  In the heat sink according to the present invention, the surface roughness of the metal region is preferably 1 μm or less.

  According to this heat sink, an improvement in effective contact area corresponding to a reduction in surface roughness is provided.

  In the heat sink according to the present invention, the surface roughness of the metal region is preferably 0.15 μm or less.

  According to this heat sink, due to the improvement of the effective contact area according to the reduction of the surface roughness, the heat conduction characteristic of the heat sink becomes a value very close to the value of the material of the metal / diamond composite itself.

  In the heat sink according to the present invention, the surface roughness of the metal region is preferably 0.1 μm or less.

  According to this heat sink, the heat conduction characteristic of the heat sink can be made very close to the value of the material of the metal / diamond composite by improving the effective contact area according to the reduction of the surface roughness.

  In the heat sink according to the present invention, the main surface of the metal / diamond composite has a first surface roughness (rms), and the mounting surface of the metal region has a second surface roughness (rms), The first surface roughness and the second surface roughness are measured with a laser microscope and are defined by an area within a range of 50 μm square to 100 μm square, and the second surface roughness is smaller than the first surface roughness. .

  According to this heat sink, the laser microscope makes it possible to accurately measure the surface roughness of the metal surface and the metal / diamond composite as compared with the measurement using a surface roughness meter.

  In the heat sink according to the present invention, the metal layer may be made of a metal including at least one of Cu, Al, Ag, Au, and Ni.

  According to this heat sink, the surface of the diamond particles appearing on the surface of the metal / diamond composite can be covered.

  In the heat sink according to the present invention, the metal of the metal / diamond composite is a binder metal that binds the diamond grains, and the binder metal is made of Cu, Al, Ag, Au, W, Ni, Co, or Mn. One or more metals can be included as a main component.

  According to this heat sink, these binder metals allow the metal-diamond composite to have various thermal conductivities and thermal expansivities.

  In the heat sink according to the present invention, the binder metal may be different from the material of the metal region.

  According to this heat sink, the material of the metal region can be different from that of the binder metal, and the degree of freedom in film formation can be expanded.

  In the heat sink according to the present invention, the metal / diamond composite may include diamond grains having an average particle diameter of 1 to 200 μm.

  According to this heat sink, the surface roughness of the surface of the metal / diamond composite can be reduced when the metal / diamond composite includes diamond grains having an average particle diameter in this range.

In the heat sink according to the present invention, the metal / diamond composite may have a thermal expansion coefficient in a range of 2.5 × 10 ⁻⁶ / K to 6.5 × 10 ⁻⁶ / K.

  According to this heat sink, the thermal expansion property close to the thermal expansion coefficient of the metal / diamond composite can be provided to the heat sink.

  The method for producing a heat sink according to the present invention includes: (a) a step of preparing a metal / diamond composite for the base of the heat sink; and (b) a metal provided on the main surface of the metal / diamond composite. Forming a composite product including a region and the metal / diamond composite; and (c) separating the composite product by processing to form a heat sink having a mounting surface for mounting a semiconductor device. And a step of performing. The step of forming a composite product includes a step of forming a metal film so as to cover the main surface of the metal / diamond composite, and the metal region is provided to cover the main surface of the base. The metal film is made of a metal different from the solder material, and the metal / diamond composite is a composite of diamond particles and metal, and the main surface of the metal / diamond composite is The metal region includes a protrusion formed by the diamond particles and a recess positioned between the protrusions, the metal region fills the recess, and the mounting surface has a roughness smaller than that of the protrusion and the recess.

According to a method of manufacturing a heat sink (hereinafter referred to as “manufacturing method”), a composite product including a metal / diamond composite and a metal region provided on the main surface of the metal / diamond composite is formed. In the metal / diamond composite main surface including the projections formed by the diamond particles and the depressions located between the projections, the metal region can fill the depressions and provide a roughness smaller than the roughness caused by the projections and depressions on the mounting surface of the heat sink. .
In the main surface of the metal / diamond composite including the depressions caused by chipping due to diamond particle polishing and the projections located between these depressions, the metal region fills the depressions, and the heat sink has a roughness smaller than the roughness caused by the projections and depressions. Can be provided on the mounting surface.

  The base for the heat sink includes a surface of a metal / diamond composite, and diamond and metal appear on the surface of the metal / diamond composite, the metal and diamond have different hardnesses, and the hardness of the metal is Less than the hardness of diamond. Therefore, roughness is formed on the surface of the metal / diamond composite. When a metal / diamond composite is polished to improve the flatness of the heat sink surface, the metal scraping and the diamond scraping are different from each other. As a result, a certain degree of roughness remains on the polished surface of the metal / diamond composite. When metallizing the polished surface, the metallized metal layer is formed in accordance with the surface shape of the polished surface. As a result, the same level of roughness as the polished surface of the metal / diamond composite remains on the surface of the metallized metal layer. Therefore, when a device is mounted on the metallized surface, the effective mounting area between the mounting surface of the semiconductor device and the polished surface of the heat sink is smaller than the area of the mounting surface of the semiconductor device.

  However, according to the method of manufacturing the heat sink of the present invention, in forming a composite product including a metal / diamond composite and a metal region, a protrusion formed by diamond particles and a depression positioned between the protrusions are included. It is possible to provide a heat sink mounting surface in which the metal region fills the depression on the main surface of the metal / diamond composite, and the roughness caused by the protrusion and the depression is reduced.

  In the manufacturing method according to the present invention, the main surface of the metal / diamond composite has a first surface roughness. The step of forming a composite product includes: forming a metal coating including the metal film on the main surface of the metal / diamond composite; treating the metal coating; Providing the metal region with a metal surface having a small second surface roughness, wherein the first surface roughness and the second surface roughness are measured with a laser microscope and are also 50 μm square to 100 μm square. Can be specified in the range of

  According to this manufacturing method, the laser microscope can measure the surface roughness of the metal surface and the metal / diamond composite more accurately than the measurement using the surface roughness meter.

  In the manufacturing method according to the present invention, the metal film can be formed by at least one of a vapor deposition method and a plating method.

  According to this manufacturing method, for example, a vapor deposition method or a plating method can be used for forming the metal coating.

  In the manufacturing method according to the present invention, the treatment of the metal film may include polishing. According to this manufacturing method, when the surface of the metal film is insufficient for the desired surface roughness, the surface of the metal film can be polished as a treatment of the metal film.

  In the manufacturing method according to the present invention, the treatment of the metal film can be performed by at least one of a mechanical polishing method and a mechanical chemical polishing method. According to this manufacturing method, when metal polishing is performed as the treatment of the metal film, for example, a mechanical polishing method, a mechanical chemical polishing method, or the like can be performed.

  In the manufacturing method according to the present invention, the main surface of the metal / diamond composite has a first surface roughness, and the metal film may include a metal layer grown by an evaporation method. According to this production method, the main surface of the metal / diamond composite can be covered with the metal layer formed by vapor deposition.

  In the manufacturing method according to the present invention, the thickness of the metal layer may be twice or more the first surface roughness. According to this manufacturing method, when the thickness of the metal layer is twice or more the first surface roughness, the metal film has a thickness to which a planarization process can be applied.

  In the manufacturing method according to the present invention, the thickness of the metal layer may be three times or less of the first surface roughness. According to this manufacturing method, when the thickness of the metal layer is three times or more of the first surface roughness, the metal film has a sufficient thickness to which a planarization process can be applied.

  In the manufacturing method according to the present invention, the metal layer fills the recess in the main surface of the metal / diamond composite, and the metal layer may be 6 μm or more in the recess. According to this manufacturing method, the metal layer having the above-described thickness enables a flattening process after film formation.

  In the manufacturing method according to the present invention, the main surface of the metal / diamond composite has a first surface roughness, and the metal film may include a metal layer grown by a plating method.

  According to this manufacturing method, in the metal deposition by the plating method, the metal is first formed in the depression on the main surface of the metal / diamond composite, and the depression is slightly filled. Furthermore, when the metal deposition by the plating method is continued, the dent gradually fills. Therefore, the depression can be selectively and preferentially generated.

  In the manufacturing method according to the present invention, the thickness of the metal layer may be three times or more the first surface roughness.

  According to this manufacturing method, in the metal deposition by the plating method, when a metal layer having a thickness of three times or more of the first surface roughness is grown, the surface roughness of the metal film is the main one of the metal / diamond composite. It becomes smaller than the original first surface roughness on the surface.

  In the manufacturing method according to the present invention, the thickness of the metal layer may be 6 times or more the first surface roughness. According to this manufacturing method, in the metal deposition by the plating method, when a metal layer having a thickness of three times or more of the first surface roughness is grown, the surface roughness of the metal film is the main one of the metal / diamond composite. It can be made sufficiently smaller than the original first surface roughness on the surface.

  In the manufacturing method according to the present invention, the main surface of the metal / diamond composite includes a protrusion made of the diamond particles and a depression made of a metal surface, and the metal layer fills the depression, and the metal The layer may be 6 μm or more in the depression.

  According to this manufacturing method, in metal deposition by plating, when a metal layer is grown with a thickness of 6 μm or more, the surface roughness of the metal film is the original first surface roughness on the main surface of the metal / diamond composite. It can be smaller than this.

  In the manufacturing method according to the present invention, the metal layer may be 9 μm or more in the depression.

  According to this manufacturing method, in metal deposition by plating, when a metal layer is grown with a thickness of 9 μm or more, the surface roughness of the metal film is the original first surface roughness on the main surface of the metal / diamond composite. It can be made sufficiently smaller.

  In the manufacturing method according to the present invention, the surface roughness of the metal region can be less than 3 μm.

  According to this manufacturing method, in the metal deposition by the plating method, the depth of the depression in the main surface of the metal / diamond composite is reduced by the selective embedding action in the metal deposition, thereby reducing the surface roughness of the metal region. Can be reduced.

  In the manufacturing method according to the present invention, the surface roughness of the metal region may be 1 μm or less.

  According to this manufacturing method, the improvement of the effective contact area according to the reduction of the surface roughness is provided.

  In the manufacturing method according to the present invention, the surface roughness of the metal region may be 0.15 μm or less.

  According to this manufacturing method, the effective contact area is improved in accordance with the reduction of the surface roughness, so that the heat conduction characteristic of the heat sink becomes a value very close to the value of the material of the metal / diamond composite itself.

  In the manufacturing method according to the present invention, the surface roughness of the metal region may be 0.1 μm or less.

  According to this manufacturing method, by improving the effective contact area according to the reduction in surface roughness, the heat conduction characteristics of the heat sink can be made very close to the value of the material of the metal / diamond composite itself.

  In the production method according to the present invention, the metal / diamond composite may include diamond particles having an average particle diameter of 1 to 200 μm.

  According to this manufacturing method, when the metal / diamond composite includes diamond grains having an average particle diameter in this range, the surface roughness of the surface of the metal / diamond composite can be reduced.

  In the manufacturing method according to the present invention, the metal of the metal / diamond composite is a binder metal that binds the diamond grains, and the binder metal is Cu, Al, Ag, Au, W, Ni, Co, Mn. The metal which has as a main component one or more of these can be included.

  According to this fabrication method, these binder metals allow the metal / diamond composite to have various thermal conductivities and thermal expansivities.

  A method of manufacturing a heat sink according to the present invention includes: (a) preparing a metal / diamond composite having a first surface roughness main surface and a base of the heat sink; and (b) the metal / diamond. Forming a metal film on the main surface of the composite by plating to form a composite product including the metal film and the metal / diamond composite; and (c) processing the composite product. Forming a heat sink having a mounting surface for mounting the device. The metal film covers the protrusions by the diamond particles, and the main surface of the metal / diamond composite includes protrusions by the diamond particles and a recess made of a metal surface, and the metal film has the recesses. The mounting surface has a roughness smaller than the roughness due to the protrusion and the depression.

  According to the method of manufacturing the heat sink, the metal film is formed by the plating method. Therefore, the plating film first grows on the metal surface on the main surface of the metal / diamond composite. Therefore, the plating film grows while filling the recess. Further, the plating film grows along the diamond from the metal surface, covers the protrusions of the diamond particles, and finally forms an integral metal film. With such a growth mechanism, the mounting surface can be provided with a roughness smaller than the roughness caused by the protrusions and the depressions.

  In the manufacturing method according to the present invention, the surface of the metal film has a second surface roughness, the second surface roughness is smaller than the first surface roughness, and the first surface roughness and the second surface roughness. The thickness is measured with a laser microscope and can be defined by measurement in an area within the range of 50 μm square to 100 μm square.

  In the manufacturing method according to the present invention, the thickness of the metal film may be three times or more the first surface roughness.

  According to this manufacturing method, in the metal deposition by the plating method, when a metal layer having a thickness of three times or more of the first surface roughness is grown, the surface roughness of the metal film is the main one of the metal / diamond composite. It becomes smaller than the original first surface roughness on the surface.

  In the manufacturing method according to the present invention, the thickness of the metal film may be 6 times or more the first surface roughness.

  According to this manufacturing method, in the metal deposition by the plating method, when a metal layer having a thickness of three times or more of the first surface roughness is grown, the surface roughness of the metal film is the main one of the metal / diamond composite. It can be made sufficiently smaller than the original first surface roughness on the surface.

  In the manufacturing method according to the present invention, the main surface of the metal / diamond composite includes a protrusion formed by the diamond particles and a depression made of a metal surface, and the metal film fills the depression, and the metal The membrane may be 6 μm or more in the depression.

  According to this manufacturing method, in metal deposition by plating, when a metal layer is grown with a thickness of 6 μm or more, the surface roughness of the metal film is the original first surface roughness on the main surface of the metal / diamond composite. It can be smaller than this.

  In the manufacturing method according to the present invention, the metal film may be 9 μm or more in the depression.

  According to this manufacturing method, in metal deposition by plating, when a metal layer is grown with a thickness of 9 μm or more, the surface roughness of the metal film is the original first surface roughness on the main surface of the metal / diamond composite. It can be made sufficiently smaller.

  In the manufacturing method according to the present invention, the metal film has a thickness greater than or equal to the depth of the recess in the projection by the diamond particle, and the main surface of the metal / diamond composite has a projection by the diamond particle. And a depression made of a metal surface, the metal layer filling the depression, and the metal layer may have a thickness equal to or greater than the depth of the depression in the projection of the diamond particles.

  According to this manufacturing method, in the metal deposition by the plating method, the depth of the depression in the main surface of the metal / diamond composite is reduced by the selective burying action in the metal deposition.

  A semiconductor device according to the present invention includes: (a) any of the heat sinks disclosed in the present case as according to the present invention; (b) a semiconductor device mounted on the mounting surface of the heat sink; A solder material for bonding the semiconductor device to the mounting surface of the heat sink.

  According to this semiconductor device, in a heat sink including a base made of a metal / diamond composite, the surface of the metal / diamond composite is made of diamond and metal having different hardnesses, but this heat sink is used for mounting a device. It has a mounting surface and a metal region provided on the main surface of the base. The main surface of the base includes a protrusion made of diamond particles and a recess located between the protrusions, the metal region fills the recess, and the mounting surface has a roughness smaller than the roughness due to the protrusion and the recess. Therefore, the effective mounting area between the mounting surface of the semiconductor device and the surface of the heat sink can be brought close to the area of the mounting surface of the semiconductor device. In this heat sink, when the semiconductor device is bonded to the mounting surface of the heat sink via the solder material, the solder material can fill the space between the underlying heat sink surface and the device mounting surface, and the mounting area is reduced to the device mounting surface. It helps to get closer to the area. Therefore, excellent heat dissipation characteristics can be provided to the semiconductor device.

  In the semiconductor device according to the present invention, the semiconductor device may include a semiconductor laser diode.

  According to this semiconductor device, the operating temperature of the semiconductor laser diode can be reduced.

  In the semiconductor device according to the present invention, the semiconductor laser diode includes an active layer that generates an oscillation wavelength in a wavelength range of 500 nm or more and 540 nm or less, a p-type cladding layer made of a group III nitride, and an n layer made of a group III nitride. The active layer may be provided between the p-type cladding layer and the n-type cladding layer.

  According to this semiconductor device, a semiconductor laser diode that generates an oscillation wavelength in the wavelength range of 500 nm or more and 540 nm or less generates relatively large heat during laser oscillation.

  In the semiconductor device according to the present invention, the semiconductor laser diode includes a substrate on which the n-type cladding layer, the active layer, and the p-type cladding layer are mounted, and the substrate includes a main surface made of a group III nitride. The main surface of the substrate may be inclined at an angle in the range of 10 degrees to 80 degrees or 100 degrees to 170 degrees with respect to a reference plane orthogonal to the c-axis of the group III nitride.

  According to this semiconductor device, the semiconductor laser diode using the semipolarity generates relatively large heat during laser oscillation.

  In the semiconductor device according to the present invention, the angle may be in a range of 63 degrees to 80 degrees or 100 degrees to 117 degrees.

  According to this semiconductor device, the semiconductor laser diode using the semipolarity generates very large heat during laser oscillation.

  A semiconductor module according to the present invention includes: (a) any one of the semiconductor devices disclosed in the present case as relating to the present invention; and (b) a package on which the semiconductor device is mounted.

  According to this semiconductor module, a semiconductor device having excellent heat dissipation characteristics can be mounted on the package, and heat generated in the semiconductor device propagates to the package via the heat sink.

  As described above, according to the present invention, it is possible to provide a heat sink that enables a metal / diamond composite to exhibit thermal conductivity close to its original thermal conductivity. Further, according to the present invention, a method for producing the heat sink can be provided. Furthermore, according to the present invention, a semiconductor device including the heat sink can be provided. Furthermore, according to the present invention, a semiconductor module including a semiconductor device can be provided.

FIG. 1 is a schematic view illustrating a heat sink and a semiconductor device according to the present invention. FIG. 2 is a drawing schematically showing a semiconductor module according to the present embodiment. FIG. 3 is a drawing showing main steps in a method for producing a heat sink according to the present invention. FIG. 4 is a drawing schematically showing main steps in a method for producing a heat sink according to the present invention. FIG. 5 is a drawing schematically showing the growth of a metal film by a vapor deposition method. FIG. 6 is a drawing schematically showing the growth of a metal film by a plating method. FIG. 7 is a drawing showing the surface of a gold metallization and the surface of a solder part provided on the surface of a copper / diamond composite. FIG. 8 is a drawing showing the surface of a gold metallization and the surface of a solder part provided on the surface of a copper / diamond composite. FIG. 9 is a drawing showing the appearance of a copper diamond composite submount whose surface roughness is not reduced. FIG. 10 is a view showing an appearance in which the laser diode is peeled off after the laser diode is mounted on the copper diamond composite submount whose surface roughness is not reduced. FIG. 11 is a diagram showing a frequency distribution of changes in thermal resistance depending on the submount. FIG. 12 is a drawing showing an example of the appearance of the copper diamond composite submount after the improvement and an example of the appearance of the copper diamond composite submount before the improvement.

  Subsequently, embodiments of the present invention relating to a heat sink, a method of manufacturing a heat sink, a semiconductor device, and a semiconductor module will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

The heat sink 11 has a mounting surface for mounting a device. The heat sink 11 includes a base 13 made of a metal / diamond composite 18 and a metal region 15 having a mounting surface for mounting a device. The metal / diamond composite 18 is a composite of diamond particles 17 and metal 19. The metal / diamond composite 18 may include diamond grains having an average particle diameter of 1 to 200 μm. When the metal / diamond composite 18 includes diamond grains having an average grain size in this range, the high thermal conductivity of diamond tends to be exhibited. The heat sink 11 can provide the heat sink with thermal conductivity close to that of the metal / diamond composite. The thermal expansion coefficient of the metal / diamond composite may be in the range of 2.5 × 10 ⁻⁶ / K to 6.5 × 10 ⁻⁶ / K. The value of this range in the thermal expansion coefficient is preferable because it is 3 × 10 ⁻⁶ / K or more and close to 6 × 10 ⁻⁶ / K, which is the thermal expansion coefficient of the semiconductor.

  The base 13 has a main surface 13a on which diamond particles 17 and a metal 19 appear. Metal region 15 includes a metal layer 21 provided to cover main surface 13a of base 13. Unlike the solder material, the metal layer 21 is made of a metal having a melting point higher than that of the solder material. Examples of the solder material include SnAg solder (melting point: 230 degrees Celsius). The main surface 13a of the base 13 includes projections 23a, 23b, 23c made of diamond particles 17 and depressions 25a, 25b, 25c, 25d located between the projections 23a, 23b, 23c. The metal region 15 fills the depressions 25a, 25b, 25c and 25d, and the mounting surface 11a has a roughness smaller than the roughness constituted by the protrusions 23a, 23b and 23c and the depressions 25a, 25b, 25c and 25d.

  In the heat sink 11 including the base 13 made of the metal / diamond composite 18, diamond and metal having different hardness appear on the surface 18a of the metal / diamond composite 18, and the hardness of the metal is lower than that of the diamond. Therefore, the surface 18a of the metal / diamond composite 18 has roughness. When a metal / diamond composite substrate is polished to improve the flatness of the heat sink surface 11a, the metal scraping and the diamond scraping are different from each other for a certain abrasive, and as a result, the metal / diamond composite polishing is performed. Some roughness remains on the surface. According to the knowledge of the inventors, when a device is mounted on this polishing surface, the effective mounting area between the device mounting surface and the heat sink polishing surface is smaller than the area of the device mounting surface.

  Further, when metallization is performed on the polished surface of the metal / diamond composite substrate, the metal film formed by metallization is formed in accordance with the shape of the metal / diamond composite substrate. As a result, roughness equal to the roughness of the polished surface of the metal / diamond composite substrate remains on the surface of the metallized metal film.

  On the other hand, the heat sink 11 has a mounting surface 11 a for mounting a semiconductor device and a metal region 15 provided on the main surface 13 a of the base 13. The main surface 13a of the base 13 includes the projections 23a to 23c formed by the diamond particles 17 and the depressions 25a to 25d located between the projections 23a to 23c, but the metal region 15 fills the depressions 25a to 25d, and the mounting surface 11a is formed so as to have a roughness smaller than the roughness constituted by the protrusions 23a to 23c and the depressions 25a to 25d. Therefore, the effective contact area between the mounting surface of the semiconductor device and the surface 11a of the heat sink 11 can be made close to the area of the mounting surface of the semiconductor device (for example, the area of the electrode).

  Furthermore, since the metal layer 21 is made of a metal having a melting point higher than that of the solder material, unlike the solder material, the metal is not melted by the process during device mounting, and the flatness of the mounting surface 11a is not lost. Here, an example of the solder material is SnAg solder (melting point: 230 degrees Celsius), for example.

  Although the surface 11a of the heat sink 11 shown in FIG. 1 is provided by the metal region 15, the surface 11a of the heat sink 11 is not limited thereto. The surface of the metal region 15 provides a surface roughness for allowing the metal / diamond composite to exhibit its original thermal conductivity, and the present embodiment provides such a desired surface. A customized heat sink can be produced by forming an additional film on the roughened metal surface by a conventional film forming method.

  According to the knowledge of the inventors, the surface roughness of the main surface 13a of the base 13 made of the available metal / diamond composite 18 is larger than 3 μm. When the metal is deposited on the surface of the metal / diamond composite 18 without taking into account the reduction of the surface roughness, the main surface 18a of the diamond composite 18 in such a surface roughness of the deposited metal. There is no improvement to the surface roughness.

  According to the knowledge of the inventors, the surface roughness of the mounting surface of the metal region 15 is preferably 3 μm or less. This level of surface roughness on the mounting surface is smaller than the surface roughness of the metal / diamond composite. When measuring the surface roughness of an available metal / diamond composite using a laser microscope, the surface roughness is greater than 3 μm. On the other hand, when measuring the surface roughness of this metal / diamond composite using a surface roughness meter, the surface roughness measured by the surface roughness meter is considerably smaller than the surface roughness measured by a laser microscope. It is in.

  Although it depends on the method of forming the metal region, the thickness TL (in the thick portion) of the metal region 15 is preferably larger than 3 μm. By embedding the roughness of the surface 13a of the base 13, it is possible to avoid a decrease in contact area (effective contact area between the mounting surface of the semiconductor device and the surface of the heat sink) due to the roughness of the surface 11a of the heat sink 11.

  In the heat sink 11, the main surface 18a of the metal / diamond composite 18 has a first surface roughness (rms) RMS1, and the main surface 15a of the metal region 15 has a second surface roughness (rms) RMS2. Have. The first surface roughness and the second surface roughness are measured with a laser microscope and are defined in any area within a range of 50 μm square to 100 μm square. Laser microscopes allow accurate surface roughness measurements of metal surfaces and metal / diamond composites as compared to measurements using surface roughness meters. In the measurement with the laser microscope, the second surface roughness RMS2 is smaller than the first surface roughness RMS1.

  The metal region 15 of the heat sink 11 can be composed of one or more metal layers. The lowermost metal layer (for example, the layer 21) can cover the surface of the diamond particles appearing on the surface of the metal / diamond composite. The metal layer 21 covering the main surface 18a in the heat sink 11 can be made of a metal containing at least one of Cu, Al, Ag, Au, and Ni.

  The metal 19 of the metal / diamond composite 18 is a binder metal that binds the diamond particles 17, and the binder metal mainly includes one or more of Cu, Al, Ag, Au, W, Ni, Co, and Mn. Metal can be included. These binder metals allow the metal / diamond composite to have various thermal conductivities and thermal expansivities. For example, from the viewpoint of thermal conductivity, the binder metal is preferably copper.

  When the binder metal is different from the material of the metal region, it is possible to control the surface reaction of the metal material, that is, there is an advantage that it can be designed in consideration of compatibility with the solder material and wire bonding.

  In addition, when the binder metal is the same as the material of the metal region, there is an advantage that the thermal and electrical potentials can be matched.

  The surface roughness of the metal region 15 of the heat sink 11 is preferably 1 μm or less. An increase in effective contact area corresponding to a reduction in surface roughness is provided.

  The surface roughness of the metal region 15 of the heat sink 11 is preferably 0.15 μm or less. By improving the effective contact area in accordance with the reduction in surface roughness, the heat conduction characteristics of the heat sink become values that are very close to those of the metal / diamond composite material itself.

  The surface roughness of the metal region 15 of the heat sink 11 is preferably 0.1 μm or less. By improving the effective contact area according to the reduction in surface roughness, the heat conduction characteristics of the heat sink can be made very close to the value of the metal / diamond composite material itself.

  Referring to FIG. 1, a semiconductor device 31 is shown. The semiconductor device 31 includes any one of the heat sinks 11 disclosed in the present case, a semiconductor device 33, and a solder material 35. The semiconductor device 33 is mounted on the mounting surface 11 a of the heat sink 11. The solder material 35 adheres the semiconductor device 33 to the mounting surface 11 a of the heat sink 11. For example, SnAg (melting point: 230 degrees) is applied to the solder material 35.

  According to the semiconductor device 31, in the heat sink 11 including the base 13 made of the metal / diamond composite 18, the diamond particles 17 and the metal 19 having different hardness appear on the surface 18 a of the metal / diamond composite 18. However, the heat sink 11 includes a metal region 15 provided on the main surface 13 a of the base 13, and the mounting surface 11 a mounts the semiconductor device 33. The metal region 15 fills the depressions 25a to 25d, and the mounting surface 11a has a roughness smaller than the roughness due to the protrusions 23a to 23c and the depressions 25a to 25d. Therefore, the effective contact area between the mounting surface 33 a of the semiconductor device 33 and the surface 11 a of the heat sink 11 can be brought close to the area of the mounting surface 33 a of the semiconductor device 33. When the semiconductor device 33 is bonded to the flat heat sink mounting surface 11a via the solder material 35, the solder material 35 can easily fill the space between the underlying flat heat sink surface 11a and the device mounting surface 33a. 31, 11) helps to bring the contact area of the semiconductor device 33 close to the area of the mounting surface 33 a. Therefore, excellent heat dissipation characteristics can be provided to the semiconductor device 31.

  In the semiconductor device 31, the semiconductor device 33 can include a semiconductor laser diode. Thereby, the operating temperature of the semiconductor laser diode can be reduced. The semiconductor laser diode can include a support made of, for example, a group III nitride semiconductor. In FIG. 12, for example, the semiconductor device 33 is mounted on the heat sink 11 in a so-called p-up configuration, but may be mounted in a p-down configuration.

  A semiconductor laser diode as an example of the semiconductor device 33 includes an n-type cladding layer 41, an n-side light guide layer 42, an active layer 43, a p-side light guide layer 44, a p-type cladding layer 45, and a p-type contact layer 46, for example. The substrate (eg, GaN) 40 may include a main surface 40a made of a group III nitride. An anode electrode 48 is provided on the p-type contact layer 46, and a cathode electrode 47 is provided on the back surface 40 b of the substrate 40. This main surface (hereinafter referred to as “semipolar main surface”) 40 has a range of 10 ° to 80 ° or 100 ° to 170 ° with respect to a reference plane perpendicular to the c-axis Cx of the group III nitride. It can be inclined at an inclination angle. A semiconductor laser diode using this semipolar main surface generates relatively large heat during laser oscillation. Furthermore, the inclination angle can be in the range of 63 degrees to 80 degrees or 100 degrees to 117 degrees. A semiconductor laser diode having a long wavelength emission that uses a semipolar main surface generates very large heat during laser oscillation.

  Further, the semiconductor laser diode can include an active layer 43 made of, for example, a group III nitride semiconductor. The active layer 43 may include a barrier layer (eg, GaN or InGaN) 43a and a well layer (eg, InGaN) 43b. Although a semiconductor laser diode that generates an oscillation wavelength in the wavelength range of 500 nm or more and 540 nm or less generates relatively large heat during laser oscillation, the heat sink 11 in this semiconductor device 31 is useful for lowering the operating temperature of the semiconductor laser diode. As an example, a semiconductor laser diode includes an active layer that generates an oscillation wavelength in a wavelength range of 500 nm or more and 540 nm or less, a p-type cladding layer made of group III nitride, and an n-type cladding layer made of group III nitride. including. The active layer can be provided between the p-type cladding layer and the n-type cladding layer.

An example of a method for producing the group III nitride semiconductor laser 11 according to this embodiment will be briefly described. On a {20-21} plane GaN substrate, an n-type InAlGaN cladding layer (In composition: 0.03, Al composition 0.14), an n-type GaN light guide layer, and an n-type InGaN light guide layer (In composition 0.03) ), Undoped InGaN light guide layer (In composition 0.03), InGaN active layer (In composition 0.30), undoped InGaN light guide layer (In composition 0.03), p-type GaN light guide layer, n-type InAlGaN cladding An epitaxial substrate is produced by growing a layer (In composition: 0.03, Al composition 0.14) and a p-type GaN contact layer. Next, after forming a SiO ₂ film having a stripe opening on the prepared epitaxial substrate, a Pd film for an ohmic electrode is grown. After forming a mask for the ohmic electrode, dry etching of the Pd film is performed to form a Pd electrode. On this, a pad electrode made of Au is formed by a lift-off method. Next, after polishing the substrate, a back electrode made of Ti / Au is formed. A substrate product is produced by these steps. The substrate product is scribed and pressed to produce a laser bar. An end face coat is formed on the laser end face. As the end face coating, for example, a SiO ₂ / TiO ₂ multilayer film or a SiO ₂ / Ta ₂ O ₅ multilayer film can be used. The number of repetitions of the multilayer film is, for example, 2 to 5 layers. Thereafter, individual semiconductor lasers are manufactured by separating the laser bars. The semiconductor laser is mounted on the submount in a p-up form to manufacture a semiconductor laser device. This semiconductor laser device is mounted on a can case to produce an optical module.

  The threading dislocations in the green laser diode on the semipolar plane are feared to grow in the active layer, and the growth is related to strain control. Control of the strain in this green laser diode is important compared to the blue-violet laser diode on c-plane GaN. When the green laser diode on the semipolar surface is mounted on the heat sink epi-down, the difference in thermal expansion coefficient between the heat sink and the semipolar GaN is important in reliability.

  FIG. 2 is a drawing schematically showing a semiconductor module according to the present embodiment. Referring to FIG. 2, a semiconductor laser module 71a is shown. The semiconductor laser device 61a is mounted on a pedestal (heat sink) 75 on the stem 73a. The group III nitride semiconductor laser 11 is firmly fixed to the submount 7 via the conductive adhesive 10b. A lens cap 73 b is provided on the stem 73 a, and the stem 73 a and the lens cap 73 b constitute a package 73. The stem 73a is made of, for example, iron, and the metal portion of the lens cap 73b is also made of iron. The base (heat sink) 11 is made of, for example, copper having excellent thermal conductivity. The stem 73a supports lead terminals 77a, 77b, and 77c. Lead terminal 77 a is connected to heat sink 11 through bonding wire 79 a and is connected to the anode electrode of group III nitride semiconductor laser 33 through the electrode layer of heat sink 11. The lead terminal 77b is connected to the electrode layer 7c on the mounting surface 7a of the submount 11 via a bonding wire 79b. The lead terminal 77c is connected to a metal stem 73. The heat sink 11 is firmly bonded to the anode electrode of the group III nitride semiconductor laser 33 via the conductive adhesive 10a.

  According to the semiconductor module 71a, a semiconductor device having excellent heat dissipation characteristics can be mounted on the package, and heat generated in the semiconductor device propagates to the package via the heat sink 11.

  FIG. 3 is a drawing schematically showing main steps in the method of manufacturing the heat sink according to the present embodiment. In step S101, a metal / diamond composite substrate for the base of the heat sink is prepared. The size of the substrate can be greater than the area where multiple heat sinks can be made, rather than the area where a single heat sink can be made. The size of the substrate is preferably 2 inches, for example. An example of the size of the heat sink alone can be, for example, a height of 0.3 mm, a width of 0.8 mm, and a length of 1.0 mm.

The coefficient of thermal expansion of the metal / diamond composite may be in the range of 2.5 × 10 ⁻⁶ / K to 6.5 × 10 ⁻⁶ / K. In addition, the metal / diamond composite may include diamond grains having an average particle diameter of 1 to 200 μm. When the metal / diamond composite includes diamond grains having an average particle diameter in this range, the surface roughness of the surface of the metal / diamond composite on which the metal film is formed can be reduced. When the metal is copper, an example of the ratio of copper to diamond is shown below.
For a coefficient of thermal expansion of 2.5 × 10 ⁻⁶ / K (copper, diamond) = (0.04,096), mole percent. For the coefficient of thermal expansion of 6.5 × 10 ⁻⁶ / K (copper, diamond) = (0.30,070), mole percent.

  In step S102, a composite product is formed from a metal / diamond composite substrate (referred to by reference numeral 43 in FIG. 4). The composite product includes a metal / diamond composite substrate and a metal region provided on the main surface of the metal / diamond composite substrate.

  In step S103, as shown in part (a) of FIG. 4, a metal / diamond composite substrate 43 is placed in the film forming apparatus 10a. The main surface 43a of the metal / diamond composite substrate 43 includes protrusions 43a to 43c formed by the diamond particles 41 and depressions 45a to 45d mainly made of the metal 40 located between the protrusions 43a to 43c. The roughness surface 43a has a first surface roughness RMS1. This surface roughness (rms), and the surface roughness (rms) that appears in the following description, are measured with a laser microscope and can be defined in an area within the range of 50 μm square to 100 μm square. Laser microscopes allow more accurate measurement of the surface roughness of metal surfaces and metal / diamond composites as compared to measurements using surface roughness meters. In the measurement of the surface roughness (rms) in the examples, a laser microscope (apparatus: OLYMPUS OLS1200) is used.

  The metal 40 of the metal / diamond composite substrate 43 is a binder metal that binds the diamond particles 41, and the binder metal is mainly composed of one or more of Cu, Al, Ag, Au, W, Ni, Co, and Mn. It can contain a metal. These binder metals allow the metal / diamond composite to have various thermal conductivities and thermal expansivities. For example, from the viewpoint of thermal conductivity, the binder metal is preferably copper, for example.

  In step S104, as shown in part (b) of FIG. 4, a metal film 47 is formed on the main surface 43a of the metal / diamond composite substrate 43 in the film forming apparatus 10a. The metal film 47 included in the metal region is formed so as to cover the main surface of the metal / diamond composite substrate 43. The metal film 47 is made of a metal different from the solder material. In the film forming apparatus 10a, a growth method such as a vapor deposition method and a plating method can be used for film formation. As the vapor deposition method, for example, a resistance heating vapor deposition method or an electron beam method can be applied to the film formation, and as the plating method, for example, an electrolytic plating method, an electroless plating method, or the like can be applied to the film formation.

  In a preferred embodiment, when a suitable deposition method is selected, the metal film 47 fills the depressions 45a, 45b, 45c, 45d, and the surface 47a of the metal film 47 has projections 43a, 43b, 43c and depressions 45a, 45b, It is possible to have a roughness smaller than the roughness constituted by 45c and 45d (for example, the second surface roughness RMS2 below the desired roughness).

  In the case of polishing, the metal film before polishing may have a thickness of 1 or more times the surface roughness on the convex portion of the metal / diamond composite, and preferably about 3 times the surface roughness. For example, when the surface roughness is 3 μm, it may be 3 μm or more, and preferably 9 μm.

(Deposition by vapor deposition)
In one example of the present embodiment, the metal film 47 can include a metal layer grown by a vapor deposition method. The growth by the vapor deposition method enables the metal / diamond composite main surface having the first surface roughness to be covered by the vapor deposition method.

  As shown in part (a) of FIG. 5, in the film forming apparatus 10 c to which the vapor deposition method can be applied, the flux 49 from the vapor deposition source proceeds toward the main surface 43 a of the substrate 43. The flux 49 provides metal particles to the main surface 43a. The metal thin film 47b is deposited on the metal / diamond composite substrate main surface 43a by the adhesion of the metal particles of the flux 49 to the main surface 43a. The metal thin film 47b is deposited almost uniformly on the main surface 43a. At this time, the surface of the metal thin film 47b is substantially the same as the shape of the metal / diamond composite substrate main surface 43a.

  In the film forming apparatus 10c, as shown in part (b) of FIG. 5, the flux 49 from the vapor deposition source proceeds toward the main surface 43a of the substrate 43, so that the metal / diamond composite is gradually flattened. A metal thin film 47c is deposited on the substrate main surface 43a. Although the main surface 43a of the metal / diamond composite substrate 43 has a roughness due to a depression mainly made of the metal 40 located between the protrusions formed by the diamond particles 41, the metal particles supplied by the flux 49 are It accumulates in the hollow which is dented. Due to metal deposition, the surface roughness of the metal thin film 47c hardly changes due to protrusions and depressions.

  In the film forming apparatus 10c, as shown in FIG. 5C, a metal layer 47d having a desired thickness is grown. In the present embodiment, the metal film 47 includes a single metal layer 47d. If necessary, one or more metal films may be grown to a desired thickness. In this embodiment, the vapor deposition method is applied to the metal deposition. However, when a plurality of metal layers are grown, the second layer is formed for the subsequent film formation by the vapor deposition method and the plating method. Can be used.

  The thickness of the metal film 47 (on the metal) can be more than twice the first surface roughness RMS1. According to this manufacturing method, when the thickness of the metal film 47 is twice or more of the first surface roughness, the metal film 47 has a thickness that takes into account the reduction in planarization.

  Preferably, the thickness of the metal film 47 can be three times or less the first surface roughness RMS1. When the thickness of the metal film 47 is three times or more the first surface roughness RMS1, the metal film 47 has a sufficient thickness in consideration of flattening film reduction.

  The metal film 47 fills the depression of the main surface 43a of the metal / diamond composite substrate 43, and the metal film 47 can be 6 μm or more in the depression. The metal film 47 having the above thickness enables a flattening process after the film formation.

  The thickness of the deposited metal film may be about 2 to 3 times the depth (for example, about 3 μm) of the depression of the metal diamond composite (for example, about 6 to 9 μm from the bottom of the depression, The surface of the deposited metal film is planarized by polishing after growth of the deposited metal film.

(Deposition by plating method)
In another example of the present embodiment, the metal film 47 may include a metal layer grown by a plating method. The growth by the plating method makes it possible to cover the metal / diamond composite main surface having the first surface roughness with the metal layer by the plating method. In metal deposition by plating, metal is first formed in the depressions 45a to 45d in the main surface 43a of the metal / diamond composite substrate 43, and the depressions 45a to 45d are slightly filled. Furthermore, when the metal deposition by the plating method is continued, the recesses 45a to 45d are gradually filled and grow over the surface of the diamond particles. Finally, the main surface 43a is covered.

  The film forming apparatus 10d to which the plating method can be applied includes an electrolytic cell 50a, an electrode 50b, and a power source 50c, and the electrolytic solution 50d is filled in the electrolytic cell 50a. In the film forming apparatus 10d, as shown in part (a) of FIG. 6, the metal / diamond composite substrate 43 and the electrode 50b are immersed in the electrolytic solution 50d in the electrolytic bath 50a. A power source 50c is connected between the electrode 50b and the conductive portion of the metal / diamond composite substrate 43 to pass a current. The current from the power source 50c flows through the metal / diamond composite substrate 43 and the electrolytic solution 50d. This current flows through the metal 40 of the metal / diamond composite substrate 43. Due to this flow, the deposition by the plating method selectively occurs on the metal 40 of the main surface 43a of the metal / diamond composite substrate 43, and the metal thin film 47e grows on the metal / diamond composite substrate main surface 43a. To do. The metal thin film 47e is grown on the metal 40 increasingly. At this time, the surface roughness (roughness) of the intermediate surface composed of the metal thin film 47e and the metal / diamond composite substrate main surface 43a is smaller than the first surface roughness. Therefore, the surface of the metal thin film 47b has a flatness that is improved over the flatness of the metal / diamond composite substrate main surface 43a.

  As shown in part (b) of FIG. 6, in the film forming apparatus 10d, the subsequent deposition proceeds using the metal thin film 47e on which the metal particles from the electrolytic solution are selectively grown as seeds. A metal thin film 47f is formed on the metal / diamond composite substrate main surface 43a by a plating method. The metal thin film 47f covers the metal / diamond composite substrate main surface 43a. As shown in part (b) of FIG. 6, the metal film thickness on the metal 40 in the metal / diamond composite substrate main surface 43a is larger than the metal film thickness on the diamond particles, and the plating film is first formed in a concave recess. Growing up. Due to the growth of the plating film, the surface roughness of the metal thin film 47f becomes smaller than the roughness due to the protrusions and depressions.

  In the film forming apparatus 10d, a metal layer 47g having a desired thickness is grown as shown in part (c) of FIG. In this embodiment, the metal film 47 includes a single metal layer 47g. If necessary, one or more metal films are grown so as to have a desired thickness. In this embodiment, the plating method is applied to the deposition. However, when a plurality of metal layers are grown, the second layer can be used for the subsequent deposition by the vapor deposition method and the plating method. .

  In the film formation by the plating method, the thickness of the metal layer 47g can be three times or more the first surface roughness. In the metal deposition by the plating method, when a metal layer having a thickness of three times or more the first surface roughness is grown, the surface roughness of the metal layer 47g is the original first in the metal / diamond composite substrate main surface 43a. Less than 1 surface roughness.

  The thickness of the metal layer 47g may be 6 times or more the first surface roughness RMS1. In the metal deposition by the plating method, when a metal layer having a thickness of three times or more of the first surface roughness RMS1 is grown, the surface roughness of the metal layer 47g is inherent to the metal / diamond composite substrate main surface 43a. The first surface roughness RMS1 can be made sufficiently smaller.

  The metal layer 47g fills the depression formed by the projections of the diamond particles 41 and the surface of the metal 40 on the metal / diamond composite substrate main surface 43a, and the metal layer 47g can be 6 μm or more in the depression. In metal deposition by plating, when a metal layer is grown with a thickness of 6 μm or more, the surface roughness of the metal layer 47g can be made smaller than the original first surface roughness RMS1 on the metal / diamond composite substrate main surface 43a. .

  The metal layer 47g can be 9 μm or more in the depression. In metal deposition by plating, when a metal layer is grown with a thickness of 9 μm or more, the surface roughness of the metal layer 47g can be sufficiently smaller than the original first surface roughness of the metal / diamond composite substrate main surface 43a. .

  The surface roughness of the metal layer 47g can be less than 3 μm. In metal deposition by the plating method, the depth of the depression in the main surface of the metal / diamond composite is reduced by the selective filling action in the metal deposition.

  When the thickness of the plated metal is 3 to 6 times the depth of the metal diamond recess (for example, 3 μm), after the recess is selectively plated, the plated portion is used as a seed for lateral plating. As a result, the surface of the plating film is flattened by itself. According to the inventor's experiment, it is possible to make the surface flatness (rms) less than 1 μm by growing a plating film having a thickness of 9 to 18 μm from the bottom of the recess. Polishing for planarization may not be performed after the growth of the plating film. The plating film may be 18 μm or more in the depression.

  The surface roughness of the metal film 47 formed by vapor deposition or plating can be 1 μm or less. An increase in effective contact area corresponding to a reduction in surface roughness is provided.

  Further, the surface roughness of the metal film 47 formed by vapor deposition or plating can be 0.15 μm or less. By improving the effective contact area in accordance with the reduction in surface roughness, the heat conduction characteristics of the heat sink become values that are very close to those of the metal / diamond composite material itself.

  Furthermore, the surface roughness of the metal film 47 formed by vapor deposition or plating can be 0.1 μm or less. By improving the effective contact area according to the reduction in surface roughness, the heat conduction characteristics of the heat sink can be made very close to the value of the metal / diamond composite material itself.

  Referring to part (c) of FIG. 4, when the surface of the deposited metal region 45 does not achieve the desired roughness, in step S104, the metal film 47 has a surface roughness for improving the surface roughness. Processing is performed by the processing apparatus 10b to provide a metal surface with a metal surface having a second surface roughness RMS2 smaller than the first surface roughness RMS1.

  The treatment of the metal film 47 can include polishing, for example. Specifically, when the surface 47a of the metal film 47 is insufficient to have a desired surface roughness, the metal film surface 47a can be polished as a treatment of the metal film 47. The metal film 47 can be polished by at least one of a mechanical polishing method and a mechanical chemical polishing method. According to this manufacturing method, when metal polishing is performed as the treatment of the metal film 47, for example, a polisher to which a mechanical polishing method, a mechanical chemical polishing method, or the like can be applied can be used.

The polishing method is performed as follows, for example. A metal diamond composite product (or metal diamond composite heat sink) is affixed to a surface plate with wax and placed on a buff of a polishing apparatus. By rotating the buff, the metal film of the metal diamond composite product (or metal diamond composite heat sink) is polished. In the preferred embodiment, the polish performs a primary polish and a secondary polish.
Primary polishing agent: Mixed liquid of an average particle size of 0.25 μm mainly composed of diamond and pure water.
Secondary polish agent: A mixture of an average particle size of 0.1 μm mainly composed of diamond and pure water.

  In step S106, after forming the composite product, the composite product is separated by processing to form one or a plurality of heat sinks 11 having a mounting surface for mounting a semiconductor device.

  According to the manufacturing method in the present embodiment, a composite product including the metal / diamond composite substrate 43 and the metal region 49 provided on the metal / diamond composite substrate main surface 43a is formed. In the metal / diamond composite substrate main surface 43a including the protrusions formed by the diamond particles 41 and the recesses located between the protrusions, the metal region 49 fills the recesses, and the heat sink mounting surface has a roughness smaller than the roughness caused by the protrusions and the recesses. Can be provided.

  In the heat sink produced from the metal / diamond composite substrate 43 (heat sink 11 in FIG. 1), diamond and metal appear on the metal / diamond composite substrate surface 43a, and these have different hardnesses. When the metal / diamond composite substrate surface 43a is polished in order to enhance the flatness of the heat sink surface, the metal scraping and the diamond scraping are different from each other. As a result, the polished surface of the polished metal / diamond composite substrate 43 Some roughness remains. Therefore, roughness is formed on the metal / diamond composite substrate surface 43a. When metallization is performed on the polished surface of the heat sink with solder or the like, the metalized metal is formed in accordance with the shape of the heat sink polished surface. As a result, a roughness comparable to that of the polished surface of the polished metal / diamond composite substrate 43 remains on the surface of the metallized metal layer. Therefore, when a semiconductor device is mounted on the metallized surface, the effective mounting area between the mounting surface of the semiconductor device and the polished surface of the heat sink is smaller than the area of the mounting surface of the semiconductor device.

  However, according to the method of manufacturing the heat sink of the present embodiment, when the composite product including the metal / diamond composite substrate 43 and the metal region 49 is formed, the diamond particles 41 are positioned between the protrusions. In the metal / diamond composite substrate main surface 43a including the recess, the metal region 47 fills the recess, thereby providing a heat sink mounting surface with reduced roughness due to the protrusion and the recess.

  With reference to FIG. 3 again, another embodiment will be described. In step S101, a metal / diamond composite 43 having a main surface with a first surface roughness RMS1 and for a heat sink base is prepared. In step S102, a composite product is formed from a metal / diamond composite substrate (referred to by reference numeral 43 in FIG. 4). The composite product includes a metal / diamond composite substrate and a metal film provided on the main surface of the metal / diamond composite substrate.

  In step S107, this metal film is formed by a plating method. The film formation by the plating method can be applied, for example, in the same manner as the embodiment described with reference to FIG. 6, but is not limited thereto. A metal / diamond composite substrate 43 is disposed in the film forming apparatus 10d. Next, a metal film 47 is formed on the main surface 43a of the metal / diamond composite substrate 43 by plating to form a composite product including the metal film 47 and the metal / diamond composite substrate 43. As a result, a plating film is grown on the metal / diamond composite substrate 43. In step S106, the composite product is separated by processing to form one or a plurality of heat sinks 11 having a mounting surface for mounting a semiconductor device.

  According to the method of manufacturing the heat sink, the metal film 47 is formed by the plating method. Therefore, the plating film first grows on the metal surface of the metal / diamond composite substrate main surface 43a. Therefore, the plating film grows while filling the recess. Further, the plating film grows along the diamond from the metal surface, covers the protrusions of the diamond particles 41, and finally forms an integral metal film 47. By such a growth mechanism, the metal / diamond composite substrate main surface 43a (mounting surface 11a of the heat sink 11) can be provided with a roughness smaller than the roughness caused by the protrusions and the depressions.

  The surface of the metal film 47 grown by plating, that is, without polishing, has a second surface roughness RMS2, and the second surface roughness RMS2 is smaller than the first surface roughness RMS1. As already explained, also in this embodiment, the first surface roughness RMS1 and the second surface roughness RMS2 are measured with a laser microscope and can be defined in any area within 50 μm to 100 squares. .

  The thickness of the metal film 47 grown by the plating method can be three times or more the first surface roughness RMS1. In the metal deposition by the plating method, when a metal layer having a thickness of three times or more the first surface roughness RMS1 is grown, the surface roughness of the metal film 47 is the original surface roughness of the metal / diamond composite substrate main surface 43a. It becomes smaller than the first surface roughness.

  The thickness of the metal film 47 grown by the plating method can be 6 times or more the first surface roughness RMS1. In the metal deposition by the plating method, when a metal layer having a thickness of three times or more the first surface roughness is grown, the surface roughness of the metal film 47 is the original first surface of the metal / diamond composite substrate main surface 43a. It can be made sufficiently smaller than one surface roughness RMS1.

  The metal film 47 grown by the plating method can have a thickness of 6 μm or more in the depression in the metal / diamond composite substrate main surface 43a. In metal deposition by plating, when a metal layer is grown with a thickness of 6 μm or more, the surface roughness of the metal film 47 can be made smaller than the original first surface roughness RMS1 on the metal / diamond composite substrate main surface 43a. .

  The metal film 47 grown by the plating method can be 9 μm or more in the depression of the main surface 43a. In metal deposition by plating, when a metal layer is grown with a thickness of 9 μm or more, the surface roughness of the metal film 47 is sufficiently smaller than the original first surface roughness RMS1 on the main surface of the metal / diamond composite. it can.

  The metal film 47 grown by the plating method has a thickness that is equal to or greater than the depth of the depressions in the projections formed by the diamond particles 41. The metal-diamond composite substrate main surface 43a has projections and metal formed by the diamond particles. The metal film 47 fills the depression, and the metal film 47 can have a thickness greater than the depth of the depression in the projections of the diamond particles 41. In the metal deposition by the plating method, the depth of the recess in the metal / diamond composite substrate main surface 43a is reduced by the selective burying action in the metal deposition.

(Example)
FIG. 7 is a drawing showing the surface of a gold metallization and the surface of a solder part provided on the surface of a copper / diamond composite. Referring to FIG. 7, in addition to an image showing the surface of a copper / diamond composite, the change in surface roughness measured with a laser microscope is shown. In the image of FIG. 7, the left side of the image is a copper / diamond composite having Au deposited thereon, and the right side of the image is SnAg solder deposited on the composite.
In the image of FIG. 7, a line indicated by “Ref1” is shown, and numbers “1”, “2”, and “4” are drawn on the line Ref1.
In the change of the surface roughness, the values of the surface roughness at the positions indicated by the numbers “1”, “2” and “4” are as follows.
Position number, width, height, length.
Position 1: 14.796, 4.955, 15.604.
Position 2: 14.799, 3.106, 16.101.
Position 4: 7.273, 1.652, 7.458.
(Unit: micrometer).
In the measurement with a laser microscope, the surface roughness (the height described above) is about 3.1 μm to 5 μm in the gold metallized portion. The surface roughness at these positions is, for example, 0.1 micrometers as measured by a contact-type step gauge.

FIG. 8 is a drawing showing the surface of a gold metallization and the surface of a solder part provided on the surface of a copper / diamond composite. Referring to FIG. 8, in addition to an image showing the surface of a copper / diamond composite, the change in surface roughness measured with a laser microscope is shown. In the image of FIG. 8, the left side of the image is a copper / diamond composite with Au deposited, and the right side of the image is SnAg solder deposited on the composite.
In the image of FIG. 7, a line indicated by “Ref2” is shown, and numbers “1” and “2” are drawn on the line Ref2 in the solder portion.
In the change of the surface roughness, the values of the surface roughness at the positions indicated by the numbers “1” and “2” are as follows.
Position number, width, height, length.
Position 1: 22.319, 3.896, 22.657.
Position 2: 26.332, 3.898, 26.619.
(Unit: micrometer).
In the measurement with a laser microscope, the surface roughness (the height described above) is about 3.8 μm at the solder portion. The surface roughness at these positions is, for example, 0.1 micrometers as measured by a contact-type step gauge.

  In the present embodiment, the surface roughness of the metal composite diamond heat sink is examined from the viewpoint of improving the lifetime and reliability of the green laser diode.

  The inventors have found that since the input power of the green laser diode on the semipolar {20-21} plane is high, it is very important to improve its heat dissipation. From the viewpoint of thermal conductivity, it is preferable to use a material containing a copper diamond composite (thermal conductivity, for example, about 550 W / mK) for the submount in order to ensure the element lifetime of the green laser diode.

  However, according to the measurement by the inventors, the surface roughness of the available copper diamond composite is as shown in FIGS. 7 and 8, and the surface roughness of the copper diamond is severe, and the value is 3 μm. Over. In the evaluation using copper diamond having such a surface roughness as a submount, the copper diamond submount exhibits a heat radiation performance comparable to that of an AlN submount (thermal conductivity, for example, about 170 W / mK).

  FIG. 9 is a drawing showing the appearance of a copper diamond composite submount whose surface roughness is not reduced. Referring to part (a) of FIG. 9, this photomicrograph represents the surface roughness specific to the surface of the copper diamond composite. The surface roughness of the solder portion of the submount surface exceeds 3 μm as measured by a laser microscope, and copper appears in the recess when referring to the portion (b) of FIG.

FIG. 10 shows an appearance in which the laser diode is peeled off after mounting the laser diode on the copper diamond composite submount whose surface roughness is not reduced. Part (a) of FIG. 10 shows the appearance of the surface of the peeled submount. Part (b) of FIG. 10 shows the appearance of the electrode surface of the laser diode that has been peeled off. Referring to part (b) of FIG. 10, the large roughness of the copper diamond submount surface is directly transferred to the solder on the electrode surface of the laser diode chip. Further, the solder is not wet on the electrode surface of the laser diode chip. From these experimental results, the inventors believe that the physical properties of the copper diamond composite have not been drawn due to the surface roughness inherent in the copper diamond composite submount. The measurement of the shear strength shows the following values.
Copper diamond submount: 750 g.
AlN submount: 1000 g.
The adhesion in the copper diamond submount is worse than the adhesion in the AlN submount.

  In the conventional copper diamond, according to the examination by the inventors, the contact area between the electrode of the laser diode and the solder is smaller than expected because of the surface roughness exceeding 3 μm. For this reason, the heat sink of the copper diamond composite did not exhibit the original thermal conductivity (thermal conductivity, for example, about 550 W / mK) of the copper diamond composite.

  That is, it is desired to improve the surface roughness of the submount of the copper diamond composite. According to the study by the inventors, the copper diamond composite includes copper and diamond particles having different hardness, and the large surface roughness of the copper diamond composite is attributed to copper and diamond having different hardness. According to the observation by the inventors, it was found that the concave portion on the surface of the copper diamond composite was made of copper and the convex portion was made of diamond. The approach to improving this large surface roughness is to form a controlled surface roughness metal region on the surface of the copper diamond composite, and for this purpose an accurate surface roughness estimate is made. .

  In the experiment, a metal film having a thickness exceeding the roughness of the copper diamond composite surface (for example, a surface roughness exceeding 3 μm) is grown. It is preferable to deposit a metal having a thickness exceeding the roughness of the base (roughness of the surface of the copper diamond composite), for example, about 10 μm. The surface of the metal film is polished and polished to scrape the metal surface and provide a surface roughness (rms) of 0.1 μm or less to the metal surface of the submount surface. The surface roughness (rms) of the metal surface of the submount surface is preferably less than 0.1 μm, but even if it is 0.15 μm or less, it is sufficiently applicable. When the upper limit of the surface roughness (rms) is 1.0 μm or less, this submount can provide a sufficient effect. Further, when the upper limit of the surface roughness (rms) is 3.0 μm or less, the thermal conductivity of the submount can be brought close to the original value of the copper diamond composite. According to the study by the inventors, a surface roughness (rms) of about 10 nm can be formed in the metal surface of the submount surface. In the above surface roughness range, the original physical properties of copper diamond can be extracted, and as a result, the reliability of the green laser diode can be improved. Preferably, the surface roughness (rms) of the metal diamond heat sink containing copper is, for example, 10 nm or more and 1.0 μm, and more preferably, the surface roughness (rms) of the metal diamond heat sink containing copper is, for example, 10 nm or more. Yes, it is 0.1 μm. Further, a material having a hardness lower than that of diamond, such as aluminum, tungsten, and silver, can be applied instead of copper in the copper diamond composite.

  The inventors mount a green laser diode in a p-down form on several surface roughness submounts to produce a semiconductor device. The thermal resistance of these semiconductor devices is measured. FIG. 11 is a diagram showing a frequency distribution of changes in thermal resistance depending on the submount. Referring to FIG. 11, copper diamond composite submount before improvement (surface roughness: 5 micrometers for laser microscope, 0.1 micrometer for contact level meter) C1, copper diamond composite submount before improvement ( Surface roughness: 3 micrometer for laser microscope, 0.1 micrometer for contact level meter C2; improved copper diamond composite submount (surface roughness: 0.15 micrometer for laser microscope, contact level difference (The total is 0.1 micrometer) A1 and the relative value of the thermal resistance of the AlN submount. FIG. 12 (a) is a drawing showing an example of the appearance of the improved copper diamond composite submount, and FIG. 12 (b) is an example of the appearance of the copper diamond composite submount before improvement. It is drawing which shows.

  The thermal resistance of the copper diamond composite submount before improvement, when viewed as an average considering power, is + 7% higher than the AlN submount, while the thermal resistance of the copper diamond composite submount after improvement is When viewed as an average considering frequency, it is a value of -35 percent reduction of the AlN submount. The thermal conductivity of the copper diamond composite before and after the improvement is the same value.

  The present invention is not limited to the specific configuration disclosed in the present embodiment.

  As described above, according to the embodiment of the present invention, it is possible to provide a heat sink that enables a metal / diamond composite to exhibit its original thermal conductivity. Moreover, according to the embodiment of the present invention, a method for producing the heat sink can be provided. Furthermore, according to the embodiment of the present invention, a semiconductor device including the heat sink can be provided. Furthermore, according to the embodiment of the present invention, a semiconductor module including a semiconductor device can be provided.

DESCRIPTION OF SYMBOLS 11 ... Heat sink, 13 ... Base, 15 ... Metal region, 18 ... Metal-diamond composite, 17 ... Diamond particle, 19 ... Metal, 23a, 23b, 23c ... Projection, 25a, 25b, 25c, 25d ... Depression, 31 ... Semiconductor device, 33... Semiconductor device, 35. Solder material.

Claims (45)

A heat sink for mounting a semiconductor device,
A base comprising a metal / diamond composite in which diamond particles and a metal are combined, and having a main surface on which the diamond particles and the metal appear;
A metal region including a metal layer provided to cover the main surface of the base, and having a mounting surface for mounting a device;
With
The metal layer is made of a metal different from the solder material,
The main surface of the base includes a projection formed by the diamond particles and a depression located between the projections,
The heat sink, wherein the metal region fills the depression, and the mounting surface has a roughness smaller than that of the protrusion and the depression.   2. The heat sink according to claim 1, wherein a surface roughness of the mounting surface of the metal region is 0.15 μm or less.   The heat sink according to claim 1 or 2, wherein the thickness of the metal region is larger than 3 µm in the depression.   The heat sink as described in any one of Claims 1-3 whose surface roughness of the said mounting surface of the said metal area | region is 0.1 micrometer or less. The surface roughness of the main surface of the base is greater than 3 μm,
The heat sink as described in any one of Claims 1-4 whose surface roughness of the said mounting surface of the said metal area | region is 3 micrometers or less.   The heat sink as described in any one of Claims 1-5 whose surface roughness of the said mounting surface of the said metal area | region is 1 micrometer or less. The main surface of the base has a first surface roughness (rms);
The mounting surface of the metal region has a second surface roughness (rms);
The first surface roughness and the second surface roughness are measured with a laser microscope and are defined in an area within a range of 50 μm square to 100 μm square;
The heat sink according to any one of claims 1 to 6, wherein the second surface roughness is smaller than the first surface roughness.   The heat sink according to claim 1, wherein the metal layer is made of a metal including at least one of Cu, Al, Ag, Au, and Ni. The metal of the metal-diamond composite is a binder metal that binds the diamond particles;
The heat sink according to any one of claims 1 to 8, wherein the binder metal includes a metal mainly composed of one or more of Cu, Al, Ag, Au, W, Ni, Co, and Mn. .   The heat sink according to any one of claims 1 to 9, wherein the binder metal is different from a material of the metal layer.   The heat sink according to any one of claims 1 to 10, wherein the metal / diamond composite includes diamond grains having an average particle diameter of 1 to 200 µm. The coefficient of thermal expansion of the metal / diamond composite is in a range of 2.5 × 10 ⁻⁶ / K or more and 6.5 × 10 ⁻⁶ / K or less, according to claim 1. The listed heat sink. A method of making a heat sink,
Preparing a metal-diamond composite for the base of the heat sink;
Forming a composite product comprising a metal region provided on a main surface of the metal / diamond composite and the metal / diamond composite;
Processing the composite product to form a heat sink having a mounting surface for mounting a semiconductor device; and
With
Said step of forming a composite product includes forming a metal film;
The metal film is made of a metal different from the solder material,
The metal region covers the main surface of the metal-diamond composite;
The metal / diamond composite is a composite of diamond particles and metal,
The main surface of the metal / diamond composite includes a protrusion formed by the diamond particles and a depression located between the protrusions,
The method for producing a heat sink, wherein the metal region fills the depression, and the mounting surface has a roughness smaller than that of the protrusion and the depression. The main surface of the metal / diamond composite has a first surface roughness;
Said step of forming a composite product comprises:
Forming the metal region on the main surface of the metal-diamond composite;
Providing the metal region with a metal surface having a second surface roughness less than the first surface roughness by treating the metal film;
14. The method of making a heat sink according to claim 13, wherein the first surface roughness and the second surface roughness are measured with a laser microscope and are defined in an area within a range of 50 [mu] m square to 100 [mu] m square. .   The method of making a heat sink according to claim 14, wherein the treatment of the metal film includes polishing.   The method for producing a heat sink according to claim 14 or 15, wherein the treatment of the metal film is performed by at least one of a mechanical polishing method and a mechanical chemical polishing method.   The method for producing a heat sink according to any one of claims 13 to 16, wherein the metal film is formed by a growth method of at least one of an evaporation method and a plating method. The main surface of the metal / diamond composite has a first surface roughness;
The method for producing a heat sink according to any one of claims 13 to 17, wherein the metal film includes a metal layer grown by an evaporation method.   The method of manufacturing a heat sink according to claim 18, wherein the thickness of the metal layer is twice or more the first surface roughness.   The method for producing a heat sink according to claim 18 or 19, wherein the thickness of the metal layer is three times or less of the first surface roughness. The metal layer fills the depression of the main surface of the metal / diamond composite,
The method for producing a heat sink according to any one of claims 18 to 20, wherein the metal layer has a thickness of 6 µm or more in the depression. The main surface of the metal / diamond composite has a first surface roughness;
The method for producing a heat sink according to claim 13, wherein the metal film includes a metal layer grown by a plating method.   The method for producing a heat sink according to claim 22, wherein the thickness of the metal layer is three times or more of the first surface roughness.   24. The method for producing a heat sink according to claim 22 or claim 23, wherein a thickness of the metal layer is six times or more of the first surface roughness. The main surface of the metal / diamond composite includes a protrusion made of the diamond particles and a depression made of a metal surface,
The metal layer fills the depression;
The method for producing a heat sink according to any one of claims 22 to 24, wherein the metal layer is 9 µm or more in the depression.   26. The method for producing a heat sink according to any one of claims 22 to 25, wherein the metal layer is 18 [mu] m or more in the depression.   27. A method for making a heat sink as claimed in any one of claims 22 to 26, wherein the surface roughness of the metal region is less than 3 [mu] m.   The method for producing a heat sink according to any one of claims 13 to 27, wherein the surface roughness of the metal region is 1 µm or less.   The method for producing a heat sink according to any one of claims 13 to 28, wherein a surface roughness of the metal region is 0.15 µm or less.   30. The method for producing a heat sink according to any one of claims 13 to 29, wherein a surface roughness of the metal region is 0.1 [mu] m or less.   The method for producing a heat sink according to any one of claims 13 to 30, wherein the metal / diamond composite includes diamond grains having an average particle diameter of 1 to 200 µm. The metal of the metal-diamond composite is a binder metal that binds the diamond particles,
The heat sink according to any one of claims 13 to 31, wherein the binder metal includes a metal mainly composed of one or more of Cu, Al, Ag, Au, W, Ni, Co, and Mn. How to make. A method of making a heat sink,
Providing a metal-diamond composite for a base of a heat sink having a first surface roughness major surface;
Forming a metal film on the main surface of the metal / diamond composite by plating to form a composite product including the metal film and the metal / diamond composite;
Processing the composite product to form a heat sink having a mounting surface for mounting the device; and
With
The metal / diamond composite is a composite of diamond particles and metal,
The metal film covers the protrusions of the diamond particles;
The main surface of the metal-diamond composite includes a protrusion formed by the diamond particles and a depression made of the surface of the metal,
The method for producing a heat sink, wherein the metal film fills the depression, and the mounting surface has a roughness smaller than that of the protrusion and the depression. The surface of the metal film has a second surface roughness;
The second surface roughness is less than the first surface roughness;
34. The method of making a heat sink according to claim 33, wherein the first surface roughness and the second surface roughness are measured with a laser microscope and are defined by 50 [mu] m square.   35. The method for producing a heat sink according to claim 33 or claim 34, wherein a thickness of the metal film is three times or more of the first surface roughness.   36. The method for producing a heat sink according to any one of claims 33 to 35, wherein a thickness of the metal film is six times or more of the first surface roughness. The metal film fills the depression,
37. The method for producing a heat sink according to any one of claims 33 to 36, wherein the metal film is 9 [mu] m or more in the depression.   The method for producing a heat sink according to any one of claims 33 to 37, wherein the metal film is 18 µm or more in the depression.   39. The method for producing a heat sink according to any one of claims 33 to 38, wherein the metal film has a thickness equal to or greater than a depth of the depression in the projection of the diamond particles. A heat sink according to any one of claims 1 to 12,
A semiconductor device mounted on the mounting surface of the heat sink;
A solder material for bonding the semiconductor device to the mounting surface of the heat sink;
A semiconductor device comprising:   41. The semiconductor device according to claim 40, wherein the semiconductor device includes a semiconductor laser diode. The semiconductor laser diode includes an active layer that generates an oscillation wavelength in a wavelength range of 500 nm or more and 540 nm or less, a p-type cladding layer made of group III nitride, and an n-type cladding layer made of group III nitride,
42. The semiconductor device according to claim 41, wherein the active layer is provided between the p-type cladding layer and the n-type cladding layer. The semiconductor laser diode includes a substrate on which the n-type cladding layer, the active layer, and the p-type cladding layer are mounted,
The substrate includes a main surface made of a group III nitride,
The main surface of the substrate is inclined at an angle in a range of 10 degrees to 80 degrees or 100 degrees to 170 degrees with respect to a reference plane orthogonal to the c-axis of the group III nitride. Item 43. The semiconductor device according to any one of Items 42.   44. The semiconductor device according to claim 43, wherein the angle of the main surface of the substrate is in a range of 63 degrees to 80 degrees or 100 degrees to 117 degrees. A semiconductor device according to any one of claims 40 to 44;
A package for mounting the semiconductor device;
A semiconductor module comprising: