Insulating circuit board and method for manufacturing the same

Abstract

To provide an insulation circuit board that is reduced in carbon content on a surface of a conductor part, and a method of manufacturing the same.SOLUTION: An insulation circuit board comprises a ceramic substrate and a copper member which is joined to at least one surface of the ceramic substrate through a junction layer, and made of copper or copper alloy, and the junction layer includes one or more kinds selected out of Ag, Cu, and Ti, in which the carbon content of a surface of the copper member has an average value of three arbitrary places ranging from 0 to 70 at% through XPS analysis, and the oxygen content of the surface of the copper member has an average value of the three arbitrary places ranging from 3 to 50 at% through the XPS analysis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments described later generally relate to insulating circuit boards and methods for manufacturing the same. [Background technology]

[0002] Ceramic copper circuit boards, which are formed by bonding a ceramic substrate and a copper plate, are used as circuit boards for mounting semiconductor elements and the like. The ceramic copper circuit board described in International Publication No. 2017 / 056360 (Patent Document 1) is an improved version of the bonded structure in which the ceramic substrate and the copper plate are bonded via a bonding layer. In Patent Document 1, an overhang is provided where the bonding layer extends beyond the edge of the copper plate. By controlling the size of this overhang of the bonding layer, the TCT characteristics are improved. Semiconductor elements are mounted on the ceramic copper circuit board to form a semiconductor device. Lead frames are also bonded to the ceramic copper circuit board, and wire bonding is also performed. Lead-free solder is used for mounting semiconductor elements and the like. A plating film is applied to the surface of the copper plate to improve adhesion with the solder layer. Ni plating films and Au plating films are used as the plating films. Furthermore, with the increasing performance of semiconductor elements, it is expected that the junction temperature will rise. Accordingly, bonding using Ag nanoparticles is being considered for the mounting of semiconductor elements. When performing bonding using Ag nanoparticles, it has been considered to apply an Ag plating film to the surface of a copper plate. For example, International Publication No. 2018 / 225809 (Patent Document 2) controls the surface roughness of the Ag plating film. Patent Document 2 also improves the adhesion of the Ag plating film. For example, International Publication No. 2019 / 054294 (Patent Document 3) discloses a method that combines a chemical polishing step and an etching step. In the chemical polishing step of Patent Document 2, chemicals such as hydrogen peroxide, hydrochloric acid, and sulfuric acid are used. Furthermore, International Publication No. 2019 / 054291 (Patent Document 4) shows ammonium peroxodisulfate as a chemical used for etching activated metal brazing materials using silver, copper, and titanium. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2017 / 056360 [Patent Document 2] International Publication No. 2018 / 225809 [Patent Document 3] International Publication No. 2019 / 054294 [Patent Document 4] International Publication No. 2019 / 054291 [Overview of the project] [Problems that the invention aims to solve]

[0004] Plating films were used to improve bonding with semiconductor elements. However, when a plating film was applied to the conductive part (especially the copper plate) of an insulating circuit board, a phenomenon occurred where the adhesion between the plating film and the semiconductor element decreased. Upon investigation, it was found that the carbon present on the surface of the conductive part was the cause. The present invention aims to address these problems and provides an insulating circuit board with reduced carbon content on the surface of the conductor portion and a method for manufacturing the same. [Means for solving the problem]

[0005] The insulating circuit board according to the embodiment comprises a ceramic substrate and a copper member made of copper or a copper alloy, which is bonded to at least one surface of the ceramic substrate via a bonding layer, wherein the bonding layer contains one or more selected from Ag, Cu, and Ti, and when the carbon content on the surface of the copper member is analyzed by XPS, the average value of the carbon content at any three locations is in the range of 0 at% to 70 at%, and when the oxygen content on the surface of the copper member is analyzed by XPS, the average value of the oxygen content at the three locations is in the range of 3 at% to 50 at%. [Brief explanation of the drawing]

[0006] [Figure 1] Schematic diagram showing an example of an insulating circuit board according to an embodiment. [Figure 2] Schematic diagram showing an example of a semiconductor device according to an embodiment. [Figure 3] Schematic diagram showing another example of a semiconductor device according to an embodiment.

Mode for Carrying Out the Invention

[0007] The insulating circuit board according to the embodiment includes a ceramic substrate, and a copper member made of copper or a copper alloy, which is joined to at least one surface of the ceramic substrate via a joining layer. The joining layer contains one or more selected from Ag, Cu, and Ti. When the carbon amount on the surface of the copper member is analyzed by XPS, the average value of the carbon amount at any three locations is within the range of 0 at% or more and 70 at% or less. When the oxygen amount on the surface of the copper member is analyzed by XPS, the average value of the oxygen amount at the three locations is within the range of 3 at% or more and 50 at% or less. FIG. 1 is a schematic diagram showing an example of an insulating circuit board according to an embodiment. In FIG. 1, 1 is an insulating circuit board, 2 is an insulating substrate, 3 is a conductor part (front conductor part), 4 is a conductor part (back conductor part), and 5 is a joining layer. In the insulating circuit board 1 illustrated in FIG. 1, the conductor part 3 and the conductor part 4 are respectively arranged on both surfaces of the insulating substrate 2 via the joining layer 5. In the structure illustrated in FIG. 1, a circuit shape is given to the conductor part 3, and the conductor part 4 is used as a heat sink. For the sake of convenience, the conductor part 3 is called the front conductor part, and the conductor part 4 is called the back conductor part. Also, two conductor parts of the front conductor part 3 are arranged. The insulating circuit board according to the embodiment is not limited to such a form. One or three or more front conductor parts may be provided. A circuit shape may be given to the back conductor part 4. Also, only the front conductor part 3 may be provided without providing the back conductor part 4. FIG. 2 is a schematic diagram showing an example of a semiconductor device according to an embodiment. In the semiconductor device illustrated in FIG. 2, a plating film is provided on the surface of the conductor part used for joining with the semiconductor element among the front conductor part and the back conductor part. FIG. 3 is a schematic diagram showing another example of the semiconductor device according to the embodiment. FIG. 3 shows a structure in which plating films are provided on both surfaces of the front conductor portion and the back conductor portion. The semiconductor device according to the embodiment is not limited to such a form. A plating film may be provided for each front conductor portion, and semiconductor elements may be mounted for each plating film. The semiconductor elements may be mounted only on a part of the plurality of plating films. The plating film may be provided only on a part of the plurality of front conductor portions, and the semiconductor element may be mounted on the plating film. The plating film is provided on a part or all of the surface of the front conductor portion. The plating film may be provided not only on the surface of the front conductor portion but also on a part or all of the side surface. The plating film may be provided on the back conductor portion as needed. The form of the plating film provided on the front conductor portion may be the same as or different from the form of the plating film provided on the back conductor portion. For example, the area of the plating film provided on the front conductor portion may be the same as or different from the area of the plating film provided on the back conductor portion. For one of the front conductor portion and the back conductor portion, a plating film may be provided on the side surface, and for the other, a plating film may not be provided on the side surface. The component of the plating film provided on the front conductor portion may be the same as or different from the component of the plating film provided on the back conductor portion. Also, a plating film may be provided on the insulating circuit board shown in FIG. 1.

[0008] The insulating substrate is preferably a resin substrate or a ceramic substrate. Since the resin substrate is lower in cost than the ceramic substrate, it is preferable when cost is emphasized. The resin substrate is, for example, a paper phenol substrate, a paper epoxy substrate, a glass epoxy substrate, a composite base epoxy substrate, a glass composite substrate, a glass polyimide substrate, a bismaleimide - triazine (BT) substrate, a fluororesin substrate, a polyphenylene oxide (PPO) substrate, or the like. When heat dissipation, three - point bending strength, etc. are emphasized, the ceramic substrate is preferable. The ceramic substrate is preferably composed mainly of one or two of the following: silicon nitride, aluminum nitride, sialon, alumina (aluminum oxide), and zirconia (zirconium oxide). The main component refers to a component that is present in an amount of 50% by mass or more. The ceramic substrate is more preferably a silicon nitride substrate, an aluminum nitride substrate, or an algil substrate. Algil is a material that contains alumina and zirconia in a total amount of 50% by mass or more. The thickness of the insulating substrate is preferably between 0.1 mm and 1 mm. If the substrate thickness is less than 0.1 mm, the strength may be insufficient. Also, if the substrate thickness is greater than 1 mm, the insulating substrate itself may act as a thermal resistor, potentially reducing the heat dissipation performance of the insulating circuit board. For silicon nitride substrates, it is preferable that the three-point bending strength is 600 MPa or higher. The thermal conductivity is preferably 80 W / m·K or higher. Increasing the strength of the silicon nitride substrate allows for a thinner substrate. Therefore, the three-point bending strength of the silicon nitride substrate is preferably 600 MPa or higher, and more preferably 700 MPa or higher. The substrate thickness of the silicon nitride substrate can be reduced to 0.40 mm or less, and even further to 0.30 mm or less. The three-point bending strength of the aluminum nitride substrate is approximately 300-450 MPa. On the other hand, the thermal conductivity of the aluminum nitride substrate is 160 W / m·K or higher. Due to the low strength of the aluminum nitride substrate, a substrate thickness of 0.60 mm or more is preferable. The three-point bending strength of aluminum oxide substrates is approximately 300-450 MPa, and they are inexpensive. Argil substrates have a high three-point bending strength of approximately 550 MPa, but their thermal conductivity is only about 30-50 W / m·K. Argil substrates are substrates made from a sintered mixture of aluminum oxide and zirconium oxide. The conductive part is preferably a copper member or an aluminum member. The copper member is a copper plate, a copper alloy plate, a member made by applying a circuit shape to a copper plate, or a member made by applying a circuit shape to a copper alloy plate, and is made of copper or a copper alloy. The aluminum member is an aluminum plate, an aluminum alloy plate, a member made by applying a circuit shape to an aluminum plate, or a member made by applying a circuit shape to an aluminum alloy plate, and is made of aluminum or an aluminum alloy. Hereafter, a member made by applying a circuit shape to a copper plate will be called a copper circuit. A member made by applying a circuit shape to an aluminum plate will be called an aluminum circuit. The conductive part may also be a metallized layer or a conductive thin film other than a copper member or an aluminum member. The metallized layer is formed by firing a metal paste.

[0009] As the insulating substrate 2, a ceramic substrate is preferred. The ceramic substrate is preferably either a silicon nitride substrate or an aluminum nitride substrate. Silicon nitride substrates and aluminum nitride substrates are nitride-based ceramic substrates. Nitride-based ceramics react with an active metal brazing material containing Ti to form titanium nitride. Alumina substrates, zirconia substrates, and argil substrates are oxide-based ceramics. Oxide-based ceramics react with an active metal brazing material containing Ti to form titanium oxide. Nitride-based ceramics and oxide-based ceramics can have their bonding strength with the conductor improved by using an active metal bonding method. The layer in which titanium nitride or titanium oxide is formed by the reaction of ceramics with Ti is called the titanium reaction layer. The conductor is preferably made of copper or aluminum. Aluminum is less expensive than copper. Therefore, aluminum may be used for the conductor. On the other hand, copper components are preferred over aluminum components because they have superior thermal conductivity. Examples of copper plates or copper circuits include copper plates or copper circuits made of oxygen-free copper. Generally, copper has a high thermal conductivity of approximately 400 W / m·K. To improve heat dissipation, it is more preferable that the copper component be a copper plate or copper circuit made of oxygen-free copper. Here, the thickness of the conductor portion 3 and the conductor portion 4 may be 0.3 mm or more, and even 0.6 mm or more. By increasing the thickness of the conductor portion, the heat dissipation of the joint can be improved. The thickness of the front conductor portion 3 may be the same as or different from the thickness of the back conductor portion 4. Copper members are particularly preferred as the conductor portion. The copper member is preferably made of oxygen-free copper. Oxygen-free copper has a copper purity of 99.96% by mass or more, as indicated in JIS-H-3100.

[0010] The insulating circuit board according to the embodiment is characterized in that, when the carbon content on the surface of the conductor portion is analyzed by XPS, the average value at any three locations is within the range of 0 at% to 70 at%. The insulating circuit board according to the embodiment may have only one conductive part or may have multiple conductive parts. In other words, the number of conductive parts provided is not particularly limited. When the insulating circuit board has multiple conductive parts, it is sufficient that the average value of the carbon content at any three locations on the surface of any conductive part is within the range of 0 at% to 70 at%. More preferably, the average value of the carbon content at any three locations on the surface of any conductive part is within the range of 0 at% to 70 at%. The conductor surface refers to at least one of the conductor surfaces, either the front conductor 3 or the back conductor 4. The carbon content of the conductor surface will be analyzed using XPS. XPS analysis is a method of X-ray photoelectron spectroscopy. In XPS analysis, X-rays are irradiated onto the sample surface, and the kinetic energy of photoelectrons emitted from the sample surface is measured. Because the penetration depth of X-rays in XPS analysis is only a few micrometers, it is used for both qualitative and quantitative analysis of the sample surface. For XPS analysis, an SSI X-Probe or equivalent or superior instrument will be used. AlKα radiation (hν = 1486.6 eV) will be used, and the X-ray spot diameter will be set to 1 mm. In addition to carbon and oxygen, the XPS analysis will also measure the amounts of each metal element used in the conductive part, as well as the amount of nitrogen. When copper components are used as conductors, nitrogen, oxygen, copper, and carbon are extracted from the measured components. The total of these is set to 100 at%, and the carbon content is measured. When copper components contain copper alloys, nitrogen, oxygen, copper, other alloy metals, and carbon are extracted from the measured components, and the total of these is set to 100 at%. When an aluminum component is used as the conductive part, nitrogen, oxygen, aluminum, and carbon are extracted from the measured components. The total of these is set to 100 at%, and the carbon content is measured. When the aluminum component contains an aluminum alloy, nitrogen, oxygen, aluminum, other alloy metals, and carbon are extracted from the measured components, and the total of these is set to 100 at%.

[0011] The following embodiment describes an example in which a copper member is used for the conductor and a ceramic substrate is used for the insulating substrate. The following description can also be applied when a member other than copper is used for the conductor. When an aluminum member is used for the conductor, "copper member" can be appropriately replaced with "aluminum member" in the following description. Similarly, when a resin substrate other than a ceramic substrate is used for the insulating substrate, "ceramic substrate" can be appropriately replaced with a resin substrate in the following description. In this embodiment, the carbon content of the copper component surface is measured by XPS analysis. The average value of three arbitrary points on the surface is used as the carbon content. The "surface" to be analyzed does not include the sides of the copper component. The three arbitrary points are three locations selected from the surface of a single copper component. During measurement, three locations are selected where the furthest points of the spot diameters are separated by at least 500 μm from each other. Furthermore, it is preferable that the measurement locations are areas where semiconductor elements are mounted. By ensuring that the carbon content on the copper component surface is between 0 at% and 70 at%, the adhesion between the copper component and the plating film can be improved. The plating film can be made of Ni (nickel), Au (gold), Ag (silver), or alloys primarily composed of these elements. As an alloy, phosphonic nickel (NiP) can be used. Conventionally, carbon present on the copper component surface would precipitate onto the plating film surface. This carbon on the plating film surface caused void formation in the bonding layer used for joining semiconductor elements. Therefore, it hindered the adhesion between the plating film and the semiconductor element. The bonding layer can be a solder layer or a layer primarily composed of silver (Ag nanoparticle layer). The carbon content on the surface of the copper component is preferably 0 at% to 70 at%. More preferably, the carbon content on the surface of the copper component is 0 at% to 60 at%. Even more preferably, the carbon content on the surface of the copper component is 5 at% to 60 at%. The lower the carbon content, the better. On the other hand, reducing the carbon content on the surface of the copper component to less than 5 at% (including 0 at% (below the detection limit)) places a heavy burden on the manufacturing process. For example, Patent Document 1 describes how to impart a sloping shape to the copper plate side surface of a ceramic circuit board. It also describes how to adjust the shape of the overflow portion of the bonding layer. Etching and chemical polishing processes are used to prepare these shapes. International Publication No. 2019 / 054294 (Patent Document 3) discloses a method for manufacturing a ceramic circuit board using etching and chemical polishing processes. Etching or chemical polishing is effective for controlling the shape. Various chemicals are used in etching and chemical polishing processes. Furthermore, in order to perform etching or chemical polishing, it is necessary to apply a resist to the areas that should remain. Generally, resins are used as resists. Many resins contain carbon as a constituent element. Conventionally, if the resist was not sufficiently removed, carbon remained on the surface of the copper component. Also, trace amounts of hydrocarbons such as methane are present in the air. Hydrocarbons are easily adsorbed onto copper components. This also contributed to the presence of carbon on the copper component surface. Therefore, it is necessary to reduce the amount of carbon on the copper component surface to 70 at% or less. In particular, it is even more preferable that the carbon content is within the range of 0 at% to 70 at% regardless of where it is measured on the surface of the conductor. As mentioned above, when the average value of any three locations is calculated, there may be areas on the surface where the carbon content exceeds 70 at%. By ensuring that the carbon content is within the range of 0 at% to 70 at% regardless of where it is measured on the surface of the conductor, the characteristics can be further improved.

[0012] When the oxygen content of a copper component surface is analyzed using XPS, it is preferable that the average value of three points is within the range of 3 at% to 50 at%. The XPS analysis method is the same as the method for analyzing carbon content. The three points used to measure oxygen content are the same as the three points used to measure carbon content. In other words, both carbon content and oxygen content are measured in a single XPS analysis. To put it another way, the amount of carbon and oxygen present in the same measurement area is measured simultaneously. It is even more preferable that the oxygen content on the surface of the copper member be within the range of 3 at% to 30 at%. Furthermore, on the surface of the copper member, the oxygen content (A ox ) Carbon content (A C ) ratio (AC / A ox ) is preferably 0 or more and 20 or less. The amounts of carbon and oxygen used for calculating the ratio are the average values at the three locations described above. The ratio (A C / A OX ) being 0 is when the carbon amount is 0 at%. When oxygen is present on the surface of the copper member, defects caused by carbon can be suppressed. Carbon deposits on the surface of the plating film and causes defects. The presence of oxygen can suppress the deposition of carbon on the surface of the plating film. If the amount of oxygen on the surface of the copper member is less than 3 at%, the effect of the presence of oxygen may be insufficient. Also, if the amount of oxygen on the surface of the copper member is too much exceeding 50 at%, oxygen itself reacts with the copper member and copper oxide is formed on the surface of the copper member. Therefore, the thermal conductivity of the copper member may decrease. Thus, the amount of oxygen on the surface of the copper member is preferably in the range of 3 at% or more and 50 at% or less. Further, when the amount of oxygen on the surface of the copper member is in the range of 3 at% or more and 30 at% or less, it is possible to suppress oxygen itself from inhibiting the bonding between the copper member and the plating film or the bonding between the plating film and the solder layer. If the amount of oxygen is too much exceeding 30 at%, oxygen itself may inhibit the adhesion between the plating film and the solder layer. Similarly, when the ratio (A C / A ox ) on the surface of the copper member is 0 or more and 20 or less, the influence of carbon can be reduced. The ratio (A C / A ox ) on the surface of the copper member is more preferably 0.3 or more and 16 or less. As described above, reducing the amount of carbon on the surface of the copper member to less than 5 at% (including below the detection limit) places a large burden on the manufacturing process. Therefore, when controlling the ratio of the amount of oxygen to the amount of carbon, the amount of carbon may be 5 atomic% or more. When the amount of carbon is 5 at% or more and 60 at% or less, it is more preferable that the ratio (A C / A ox ) is in the range of 0.3 or more and 16 or less. The amount of chlorine ions present on the surface of the insulating circuit board is preferably 0 μg or more and 15 μg or less per 40 cm 2 of the surface area of the insulating circuit board. The amount of chlorine ions is per 40 cm 2It is even more preferable that the amount per unit be between 0 μg and 3 μg. The amount of sulfate ions (SO4) present on the surface of an insulating circuit board is calculated based on the surface area of ​​the insulating circuit board (40 cm²). 2 It is preferable that the amount is between 0 μg and 5 μg per unit area. Furthermore, the amount of sulfate ions (SO4) is such that the surface area of ​​the insulating circuit board is 40 cm². 2 It is even more preferable that the amount per unit be between 0 μg and 0.5 μg. The amount of fluoride ions present on the surface of an insulating circuit board is calculated based on the surface area of ​​the insulating circuit board (40 cm²). 2 It is preferable that the amount is between 0 μg and 2 μg per unit area. Furthermore, the amount of fluoride ions is determined by the surface area of ​​the insulating circuit board (40 cm²). 2 It is even more preferable that the amount per unit be between 0 μg and 1 μg. Ammonium (NH4) ions present on the surface of an insulating circuit board can reach a surface area of ​​40 cm². 2 It is preferable that the amount is between 0 μg and 3 μg per unit. Furthermore, the amount of ammonium ions (NH4) is such that the surface area of ​​the insulating circuit board is 40 cm². 2 It is even more preferable that the amount per unit be between 0 μg and 1 μg. The aforementioned ions tend to adhere more easily to the surface of copper components than to the surface of insulating substrates. If these ions are present on the surface of the insulating substrate, they may volatilize during bonding, potentially inducing contamination of the copper component surface. Contamination of the copper component can lead to poor bonding between the copper component and the semiconductor element. Therefore, it is preferable to control the amount of these ions present across the entire surface of the insulating circuit board, including areas where copper components are not bonded. The surface area of ​​each insulating circuit board is 40 cm². 2 If it is smaller than that, use multiple insulating circuit boards and the total surface area of ​​them should be 40 cm². 2 It is preferable to have a total surface area of ​​40 cm² or more. 2This is because, if the surface area of ​​the insulating circuit board is extremely small, the effects of outliers and noise may become excessive when converted using a proportional relationship. The surface area measured here is the area of ​​the flat surface, excluding the thickness component of the sides. The flat surface refers to the surface that is approximately parallel to the bonding surface between the insulating circuit board and the conductor when viewed from above. For example, if the conductor is provided so that it does not protrude from the edge of the insulating board when viewed from above, the front (top) and back (bottom) surfaces of the insulating board can be considered flat surfaces. Since the front and back surfaces of the insulating circuit board are included in the surface area calculation, the surface area = length dimension of the insulating board × width dimension × 2. Also, if the conductor protrudes from the edge of the insulating board when viewed from above, the flat surface of the protruding conductor is also counted in the surface area. Thus, the thickness components of the insulating board and the conductor are not included in the surface area calculation. Here, "upward" is defined as the direction perpendicular to a straight line connecting the edges of the insulating substrate. The area of ​​a flat surface is defined as the sum of the area viewed from above and the area viewed from below. Therefore, twice the area viewed from above is the surface area of ​​the insulating circuit board. Furthermore, there was only a small amount of insulating circuit board, and the total surface area of ​​these boards was 40 cm². 2 If the amount of impurities obtained is smaller, the surface area (cm²) 2 Alternatively, you can convert the surface area by dividing by ) and then multiplying by 40. Impurities refer to the chloride ions, sulfate ions, fluoride ions, and ammonium ions mentioned above. The surface area of ​​one insulating circuit board is 40 cm². 2 Otherwise, since there is a proportional relationship between the surface area of ​​the insulating circuit board and the amount of impurities, this relationship can be used to convert using the following formula. "40cm of copper material" 2 "Amount of impurities per unit" = "Amount of impurities obtained by measurement" × 40 ÷ "Total surface area of ​​insulating circuit boards (cm²)" 2 )" The amounts of chloride ions, sulfate ions, fluoride ions, and ammonium ions are measured using an ion chromatograph. Chloride ions are easily deposited when etching copper components using chemicals such as iron chloride or copper chloride. They are also easily deposited when hydrochloric acid is used during cleaning. Sulfate ions readily adhere to layers primarily composed of Ag or Cu during etching or chemical polishing processes using chemicals such as sodium thiosulfate, sulfuric acid, or ammonium peroxodisulfate. Fluoride ions are easily deposited during the etching process of the Ti reaction layer using chemicals such as ammonium fluoride. Ammonium ions readily adhere to layers when etching the Ti reaction layer, etching layers mainly composed of Ag or Cu, or chemical polishing processes using chemicals such as ammonium fluoride or ammonium peroxodisulfate. If ions such as chloride ions, sulfate ions, fluoride ions, and ammonium ions remain on the surface of an insulating circuit board (especially on the surface of copper components), the reliability of the junction between the conductive part (especially copper components) and the plating film, and the reliability of the junction between the plating film and the semiconductor element will decrease. Furthermore, if these ions are present in areas other than the copper component, they may vaporize, potentially reducing the reliability of the junction between the conductive part (especially the copper component) and the plating film, as well as the reliability of the junction between the plating film and the semiconductor element. Therefore, it is preferable to control the amount of these ions across the entire surface of the insulating circuit board. The components referred to as ions here only need to be detected as ions during measurement; they may also exist as compounds on the surface of the insulating circuit board. Sulfate ions are divalent anions, while chloride and fluoride ions are monovalent anions. Ammonium ions are monovalent cations. The reliability of the bond between the copper component and the plating film is maintained by controlling the amount of these ions on the surface of the insulating circuit board before the plating process. Therefore, it is preferable to measure the amount of each ion before the plating process. Furthermore, it is preferable that the amount of each ion remains within the range described above even on the surface after the plating process. Even on the surface after the plating film has formed, the reliability of the bond between the plating film and the semiconductor device can be ensured by keeping the amount of each ion within the above range. This is because the aforementioned ions can also adhere when chemical solutions such as sulfuric acid or ammonia are used during the plating process.

[0013] When copper components are bonded to both sides of a ceramic substrate, it is preferable that the carbon content on the surfaces of the copper components on both sides is within the range of 0 at% to 70 at%. As mentioned above, controlling the carbon content improves the bonding properties of the plating film. Therefore, it is important to control the carbon content on the surface of the copper component to which the plating film is applied. When copper components are provided on both sides of a ceramic substrate, a copper plate or copper circuit may be provided on the front side, and a copper plate may be provided on the back side as a heat sink. Semiconductor elements are mounted on the copper plate or copper circuit on the front side. When mounting semiconductor elements, a bonding layer such as a solder layer or a layer mainly composed of silver is provided via the plating film. The heat sink is used as the surface to be mounted on a heat sink, etc. Since grease is used for mounting to a heat sink, the plating film may not be used in some cases. However, by controlling the carbon content on the surfaces of the copper components on both sides, either the front or back copper component can be used as the mounting surface for semiconductor elements. In other words, it is possible to provide an insulating circuit board (for example, a ceramic copper circuit board) that is easy to use.

[0014] In the embodiment, it is preferable that the ceramic substrate and the copper member are joined via a bonding layer containing carbon. It is preferable that the ceramic substrate and the copper member are joined via a bonding layer containing titanium. In the active metal bonding method, an active metal brazing material containing Ti is used. The active metal brazing material contains silver or copper as the main component and also contains Ti. By incorporating carbon into the active metal brazing material, a bonding layer containing carbon can be formed. By incorporating carbon into the active metal brazing material, the fluidity of the brazing material can be improved. This can improve the bonding strength.

[0015] The activated metal brazing material preferably contains 0% to 70% by mass of Ag (silver), 15% to 85% by mass of Cu (copper), and 1% to 15% by mass of Ti (titanium) or TiH2 (titanium hydride). Alternatively, Nb or Zr may be used instead of Ti in the activated metal brazing material, or Nb or Zr may be added to Ti. However, it is preferable that the activated metal brazing material contains 1% to 15% by mass of Ti (titanium) or TiH2 (titanium hydride). When using both Ti and TiH2, their total content should be within the range of 1% by mass or more and 15% by mass or less. When using both Ag and Cu, it is preferable that the Ag content be between 20% by mass and 70% by mass or less, and the Cu content be between 15% by mass and 65% by mass or less. The brazing material may contain, as necessary, one or both of Sn (tin) or In (indium) in an amount of 1% to 50% by mass. The Ti or TiH2 content is preferably 1% to 15% by mass. The brazing material may also contain, as necessary, 0.1% to 2% by mass of C (carbon). The ratio of the active metal brazing alloy composition is calculated by considering the total amount of the mixed solid raw materials as 100% by mass. These solid raw materials are preferably in powder form. For example, when the active metal brazing alloy is composed of three types of materials: Ag, Cu, and Ti, Ag + Cu + Ti = 100% by mass. When the active metal brazing alloy is composed of four types of materials: Ag, Cu, TiH2, and In, Ag + Cu + TiH2 + In = 100% by mass. When the active metal brazing alloy is composed of five types of materials: Ag, Cu, Ti, Sn, and C, Ag + Cu + Ti + Sn + C = 100% by mass. It is preferable to mix the powder raw material having the above composition with a solvent appropriate to its composition. By mixing with a solvent, the wax material can be made into a paste.

[0016] Ag or Cu are the base material components of the brazing material. Sn or In have the effect of lowering the melting point of the brazing material. C (carbon) have the effect of controlling the fluidity of the brazing material and controlling the structure of the bonded layer by reacting with other components. For this reason, examples of brazing material components include Ag-Cu-Ti, Ag-Cu-Sn-Ti, Ag-Cu-Ti-C, Ag-Cu-Sn-Ti-C, Ag-Ti, Cu-Ti, Ag-Sn-Ti, Cu-Sn-Ti, Ag-Ti-C, Cu-Ti-C, Ag-Sn-Ti-C, and Cu-Sn-Ti-C. In may also be used instead of Sn. Both Sn and In may also be used.

[0017] The side surface of the copper member described above preferably has an inclined shape. That is, the side surface of the copper member is preferably inclined with respect to the in-plane direction and the thickness direction. The in-plane direction is the direction parallel to the bonding surface between the ceramic substrate and the copper member. The thickness direction is the direction connecting the ceramic substrate and the copper member and is perpendicular to the in-plane direction. The thickness of the bonding layer 5 is preferably within the range of 10 μm to 60 μm. Furthermore, the insulating circuit board preferably has a shape in which the bonding layer protrudes from the side surface of the copper member. A portion of the protruding bonding layer is called the bonding layer overhang. The ratio of the length L to the thickness T (L / T) of the bonding layer overhang is preferably within the range of 0.5 to 3.0. The thickness of the bonding layer overhang is the thickness of the thickest part of the bonding layer overhang. The length of the bonding layer overhang is the length of the longest part that protrudes from the side surface of the copper member. The thickness and length of the bonding layer overhang are measured from any cross-section of the ceramic copper circuit board. By providing a sloping shape to the copper member and providing a bonding layer overhang, the TCT characteristics of the ceramic copper circuit board can be improved. The maximum height Rz of the copper component surface is preferably 20 μm or less. Furthermore, the arithmetic mean roughness Ra of the copper component surface is preferably 5 μm or less. More preferably, the arithmetic mean roughness Ra is 2 μm or less. Even more preferably, the arithmetic mean roughness Ra is 1 μm or less. By making the copper component surface flatter, the adhesion between the copper component and the plating film, or the bonding between the plating film and the bonding layer, can be strengthened. Solder paste or silver paste can be used as the bonding layer for bonding the plating film. Ra and Rz are specified in JIS B 0601:2013. JIS B 0601:2013 corresponds to ISO 4287:1997 / AMENDMENT 1:2009(IDT). The ceramic substrate is preferably a silicon nitride substrate with a thickness of 0.4 mm or less, and the copper component is preferably 0.6 mm or thicker. A thin silicon nitride substrate with a thickness of 0.4 mm or less has the effect of lowering the thermal resistance of the ceramic substrate. On the other hand, a thick copper plate with a thickness of 0.6 mm or more improves heat dissipation. Furthermore, if the silicon nitride substrate has a three-point bending strength of 600 MPa or more, the effects are more easily obtained.

[0018] As described above, insulating substrates such as ceramic copper circuit boards are suitable for semiconductor devices in which semiconductor elements are mounted on the conductive portion via a plating film and a bonding layer. Figure 2 is a schematic diagram showing an example of a semiconductor device according to an embodiment. In Figure 2, 1 is an insulating circuit board, 6 is a semiconductor element, 7 is a plating film, 8 is a solder layer, and 10 is a semiconductor device. Figure 2 shows an example in which one semiconductor element 6 is mounted on one insulating circuit board. Two or more semiconductor elements 6 may be mounted on one insulating circuit board. The example shown in Figure 3 differs from the example shown in Figure 2 in that the plating film 7 is also provided on the back conductor portion. In embodiments of the present invention, as shown in Figure 3, a plating film may also be provided on the back conductor portion. The form of the plating film provided on the back conductor portion may differ from the form of the plating film provided on the front conductor portion. These plating films may be provided on the entire surface including the sides, or on only a part of the surface. The semiconductor device 10 may also be provided with a lead frame, wire bonding, etc. Instead of the solder layer 8, a layer mainly composed of silver (Ag nanoparticle layer) may be used. The solder layer is a bonding layer using solder paste. Lead-free solder is an example of a material for the solder layer. The layer mainly composed of silver is a bonding layer using silver paste. Silver paste is distinguished from lead-free solder containing Ag because it uses Ag nanoparticles.

[0019] In the semiconductor device 10 according to this embodiment, the amount of carbon on the surface of the conductive part 3 (for example, a copper member) is controlled, so that the deposition of carbon on the surface of the plating film 7 can be suppressed. When a solder layer 8 is provided on the surface of the plating film 7, if there is carbon on the surface of the plating film 7, voids are more likely to occur in the solder layer 8. If there are voids in the solder layer 8, the bonding performance with the semiconductor element 6 will decrease. The same is true when the solder layer 8 is replaced with an Ag nanoparticle bonding layer. In recent years, semiconductor devices have become increasingly high-performance. Consequently, the junction temperature of semiconductor devices has risen to 150°C or higher, and even 170°C or higher. The semiconductor device 10 can demonstrate reliable bonding between the plating film 7 and the semiconductor device 6, even when semiconductor devices with high junction temperatures are mounted on it. In other words, the insulating circuit board (e.g., a ceramic copper circuit board) according to this embodiment is suitable for a configuration in which a plating film is provided on the surface of the conductive part.

[0020] Next, a ceramic copper circuit board, which is an example of an insulating circuit board according to the embodiment, will be described in terms of its manufacturing method. The manufacturing method of the ceramic copper circuit board according to the embodiment is not particularly limited as long as it has the above configuration. Here, a method for obtaining a ceramic copper circuit board with good yield will be given as an example. First, a joint between the ceramic substrate and the copper plate is fabricated. The specific configuration of the ceramic substrate and copper plate is as described above.

[0021] The joined bodies are joined using an activated metal joining method. The activated metal joining method is a joining method that uses an activated metal brazing material containing an activated metal such as titanium. The components of the activated metal brazing material are as described above. An activated metal brazing paste is prepared and applied to the surface of the ceramic substrate. The thickness of the activated metal brazing paste application is preferably in the range of 10 μm to 60 μm. A copper plate is placed on top of the activated metal brazing paste layer. Alternatively, the activated metal brazing paste may be applied to the copper plate, and the ceramic substrate may be placed on top of the copper plate. The length and width dimensions of the ceramic substrate may be the same as or different from those of the copper plate. If the copper plate is 0.6 mm or thicker, it is preferable that the length and width dimensions of the ceramic substrate and the copper plate are the same. Furthermore, it is preferable to place copper plates on both sides of the ceramic substrate. This arrangement makes it easier to reduce warping of the bonded structure. Any circuit shape can be formed on the copper plate by the etching process described later. It is also possible to bond copper components that have been pre-processed into circuit shapes to the ceramic substrate. However, preparing copper components that have been pre-processed into circuit shapes requires a dedicated mold. Preparing molds according to the circuit shape may lead to increased costs.

[0022] Next, a heat bonding process is performed. The heating temperature is preferably between 600°C and 930°C. Examples of heating atmospheres include vacuum and inert atmosphere. Vacuum is defined as a pressure of 10⁻¹⁰ -3 This refers to a state below Pa. An inert atmosphere is a noble gas atmosphere or a nitrogen atmosphere. Examples of noble gas atmospheres include argon, helium, neon, and xenon atmospheres. In particular, considering cost, a nitrogen atmosphere or argon atmosphere is preferred. A nitrogen atmosphere is more preferable. By performing a heat bonding process, a bonded body of a ceramic substrate and a copper plate can be manufactured. If necessary, a warp correction process may be performed on the bonded body. Next, the bonded body is subjected to a chemical polishing process and an etching process. These processes are used to impart a circuit shape to the copper plate. In these processes, a sloping shape may be given to the side surface of the copper plate, or a bonded layer overhang may be formed where the bonded layer extends beyond the side surface of the copper plate. In the activated metal bonding method, an activated metal brazing material mainly composed of Ag or Cu and containing Ti is used. In a bonded body produced using the activated metal bonding method, a Ti reaction layer is formed in the bonded layer. When a nitride-based ceramic substrate is used, the Ti reaction layer becomes a titanium nitride (TiN) layer. When an oxide-based ceramic substrate is used, the Ti reaction layer becomes a titanium oxide (TiO2) layer. In a bonded body produced by the activated metal bonding method, a layer mainly composed of Ag or Cu and a Ti reaction layer are formed in the bonded layer. Carbon is distributed in the layer mainly composed of Ag or Cu. Nitride ceramic substrates are substrates made of materials such as SiAlON, silicon nitride, or aluminum nitride. Oxide ceramic substrates are substrates made of alumina, zirconia, or algil, among other materials.

[0023] To impart a circuit shape through etching, etching steps are required for the copper plate, the Ag or Cu-based layer, and the Ti reaction layer. Considering etching efficiency, different chemicals are needed for each of the three etching steps. In addition, resist must be applied to areas that do not want to be etched. If the area to be etched changes, a resist removal step and a resist application step are required each time. Multiple etching steps with different chemicals are necessary. For example, in the copper plate etching step, a chemical solution containing iron chloride or copper chloride is used. In the Ag or Cu-based layer etching step, a chemical solution containing hydrogen peroxide or ammonium peroxodisulfide is used. In the Ti reaction layer etching step, a chemical solution containing hydrogen peroxide or ammonium fluoride is used. Various other chemical solutions are also used. If necessary, a chemical polishing process can be used to improve the efficiency of the etching process. The chemicals used in the etching process may oxidize layers mainly composed of Ag or Cu. Chemical polishing is effective in removing this oxide layer. The chemical polishing process uses a solution containing one or more chemicals selected from sulfuric acid, hydrochloric acid, and sodium thiosulfate.

[0024] The copper plate on the front side is processed through the chemical polishing and etching processes described above. For example, a circuit shape is given to the copper plate, forming a copper circuit. Alternatively, one copper plate is divided to form multiple copper plates. This results in a ceramic copper circuit board in which copper components (copper circuits or copper plates) are joined together. Furthermore, as mentioned above, various chemicals are used in processes such as chemical polishing, etching, and rust prevention. Multiple processes are required to adjust the slope shape of the copper component's side surface and the shape of the bonded layer overflow. In each process, a resist is applied to areas that do not want to be removed. Generally, the resist is made of resin. Resins contain carbon. Chemicals are also used to remove the resist. If the resist is not removed sufficiently, the amount of carbon on the surface of the copper component increases. A cleaning process is effective in controlling the carbon content on the surface of copper components. In the cleaning process, water cleaning or alkaline cleaning is preferable.

[0025] Furthermore, when only water washing is performed, it is preferable that the following water washing process, which is not an immersion process, is performed at least once. More preferably, the more times the washing process using only water washing is the washing process described below, the better. In addition, multiple washing methods may be combined in a single washing process. It is preferable that these washings clean not only the conductive parts but the entire ceramic copper circuit board. In water washing, a flow rate of 1.3 L / min or more is preferable. A flow rate of 1.3 L / min or more is sufficient to effectively wash away carbon adhering to the surface of the copper component. A flow rate of less than 1.3 L / min may result in insufficient washing. For example, in a method where a ceramic copper circuit board is immersed in a washing tank filled with water and left to stand, the flow rate is insufficient, and therefore the effect of reducing the amount of carbon is not sufficiently obtained. There is no particular upper limit to the flow rate, but it is preferable to be 10 L / min or less. If the flow rate is greater than 10 L / min, the water pressure may be too high and the surface of the copper component may deform. For this reason, the flow rate for water washing is preferably 1.3 L / min or more and 10 L / min or less. More preferably, the flow rate for water washing is 1.5 L / min or more and 6 L / min or less. Methods for adjusting the flow rate include controlling the circulation of water stored in the cleaning tank and controlling it using a nozzle. Controlling the flow rate using a nozzle is preferable, as it makes flow control easier. With the method of circulating water stored in the cleaning tank, controlling the flow rate can become difficult if the amount of water increases. When using a nozzle, the flow rate of water sprayed from the nozzle should be set to 1.3 L / min or more. Furthermore, ultrasonic waves may be applied to this water, and carbon dioxide or oxygen may be dissolved in it. The distance between the nozzle and the ceramic copper circuit board is preferably within the range of 5 cm to 40 cm. It is even more preferable that the distance be within the range of 5 cm to 20 cm. Within this range, it becomes easier to adjust the amount of water that hits the ceramic copper circuit board. The shape of the water droplets ejected from the nozzle can be various, such as point-shaped, circular, elliptical, flattened, or square. Various nozzle shapes, such as cone-shaped or fan-shaped, can be applied. When using the nozzle, multiple nozzles may be used per ceramic copper circuit board, and the front and back conductor parts may be cleaned simultaneously. The amount of water hitting the ceramic copper circuit board is 0.01 L / min / cm³ per nozzle. 2 More than 0.1L / min / cm 2 The following range is preferable. The amount of water that lands on the ceramic copper circuit board is called the amount of water that lands. The amount of water that lands is measured when the ceramic copper circuit board is viewed from above, approximately 1 cm. 2This indicates the amount of water that hits the surface. The amount of water that hits the ceramic copper circuit board can be adjusted by the amount of water from the nozzle, the nozzle type, the distance from the nozzle, etc. Air jets can also be used in conjunction with the water jets from the nozzles. Ultrasonic waves may also be applied during the cleaning process. It is also effective to perform the cleaning process while transporting the ceramic copper circuit board. In this case, the ceramic copper circuit board may be tilted to improve cleaning efficiency (liquid recovery efficiency) and installation area efficiency. Tilting means that the orientation of at least one side of the board is not parallel to the horizontal plane perpendicular to the direction of gravity. It is even more preferable that the angle between the horizontal plane and the at least one side be between 10 degrees and less than 90 degrees. The flow rate from the nozzle should be 1.3 L / min or more, and the amount of water that hits the ceramic copper circuit board should be 0.01 L / min / cm per nozzle while transporting the ceramic copper circuit board. 2 More than 0.1L / min / cm 2 The following method is the most efficient.

[0026] The water should preferably meet the quality standards of JIS-K-0557 (1998). JIS-K-0557 specifies quality levels A1 to A4. ISO 3696 is referenced for JIS-K-0557.

[0027] Alkaline cleaning refers to a cleaning process using an alkaline aqueous solution with a pH of 10 or higher. Examples of alkaline aqueous solutions with a pH of 10 or higher include organic alkalis, metal hydroxides, and salts of metal hydroxides and weak acids. In particular, examples of weak acids in salts include carbonic acid, pyrophosphate, phosphoric acid, and metasilicic acid. When using metal hydroxides and their salts, examples of metals include lithium, potassium, sodium, barium, and calcium. bIf the base dissociation constant is too small, the required solubilization amount increases. Therefore, the metal hydroxide and its salt used should preferably be selected from potassium, sodium, and lithium. In particular, considering cost, sodium hydroxide, sodium metasilicate, sodium carbonate, sodium phosphate, and sodium pyrophosphate are preferred, and an aqueous solution containing one or more of the above sodium compounds is preferred. An aqueous solution containing 0.5% to 5% by mass of these components is even more preferred. Alkaline cleaning has the effect of removing impurities from the surface of copper members and cleaning them. The purity of these alkaline aqueous solutions is preferably high. A purity of 96% by mass or higher is more preferable. If the purity is lower than 96% by mass, the impurities contained therein may adhere to the ceramic copper circuit board. Higher purity means fewer impurities in the aqueous solution. Therefore, higher purity is preferable because it reduces the adhesion of impurities. For this reason, a purity of 98% by mass or higher is even more preferable.

[0028] Organic compounds are frequently used in resists. Because organic compounds have lower polarity than water, they are soluble in organic solvents. Therefore, when organic compounds are used in resists, cleaning with alcohol or ketones may be performed. Examples of alcohols include isopropanol, methanol, butanol, hexanol, and ethanol. Examples of ketones include acetone. Considering the solubility and volatility of organic compounds, ethanol or isopropanol are preferred. Isopropanol has CAS registry number 67-63-0 and IUPAC name 2-propanol. Isopropanol is sometimes called IPA or isopropyl alcohol. The purity of these alcohols, excluding water and solvent components, is preferably 99% by mass or higher. If the purity of the alcohols or ketones used for cleaning, excluding water and solvent components, is less than 99% by mass, impurities contained therein may adhere to the ceramic copper circuit board. Furthermore, two or more types of alcohol may be mixed and used for alcohol cleaning. In addition, alcohol cleaning may be mixed with water. When alcohols are mixed with water, it is preferable that the quality of the water used meets JIS-K-0557 (1998). Ketones such as acetone may be added to the alcohols as a solvent. In other words, it is preferable that the amount of impurities in the alcohols, excluding water or solvent, is 1% by mass or less. However, considering the cost, alkaline cleaning or water cleaning is preferable to alcohol cleaning as a cleaning method. Alternatively, multiple cleaning methods can be combined, such as performing alkaline cleaning followed by water cleaning.

[0029] By performing the cleaning process described above, the carbon content on the copper component surface can be reduced to 70 at% or less. Furthermore, it is preferable to perform the cleaning process after the resist removal process. If the resist removal process is performed multiple times, it is preferable to perform the cleaning process each time. The cleaning after the final resist removal step may be performed using the cleaning method described above, while cleaning after other resist removal steps may be done with ordinary water. In this case, it is preferable to set a longer time for the cleaning step after the final resist removal step. The cleaning process after the etching and chemical polishing steps may be ordinary water washing or water washing with controlled flow rate. Ordinary cleaning involves immersing the assembled parts in a water washing tank. Each cleaning step may be either batch-type or continuous-type. Batch-type cleaning involves placing multiple assembled parts in a cleaning basket and performing the cleaning process. Continuous-type cleaning involves transporting multiple assembled parts on a belt conveyor while performing the cleaning process. Ultrasonic waves may be applied during cleaning. Applying ultrasonic waves is expected to improve cleaning efficiency. One cleaning method involves using chlorine-based cleaning agents. However, chlorine-based cleaning agents may increase the amount of chlorine on the copper plate surface. Therefore, chlorine-based cleaning agents are less desirable than the cleaning methods described above. Furthermore, cleaning processes using steam or ozonated water are undesirable because they may oxidize the copper plate. For this reason, cleaning processes using water, alkaline, or alcohol are preferred. By following the above steps, a ceramic copper circuit board according to the embodiment can be manufactured.

[0030] Next, the drying process will be described. Drying processes include treatment with volatile solutions, centrifugal force treatment, and blown air treatment. Multiple drying processes may be combined. After cleaning, the ceramic copper circuit board may be washed away with a volatile solvent such as methanol, ethanol, isopropanol, or ketones such as acetone to remove any remaining water. Alcohols and ketones may also be used in mixtures. In this case, isopropanol is preferable considering safety aspects such as flammability. Alternatively, the ceramic copper circuit board may be rotated after cleaning and centrifugal force may be used to remove any remaining water droplets. Furthermore, the ceramic copper circuit board may be angled. This angle refers to a state in which, when any orientation on a plane perpendicular to the direction of gravity is defined as the horizontal direction, the orientation of one or more sides of the board is not parallel to this horizontal direction. In this case, when the angle between the horizontal direction and the direction of gravity is defined as 90 degrees, it is even more preferable that the angle between the horizontal direction and the orientation of one or more sides of the board is 10 degrees or more and less than 90 degrees. Regarding the orientation of the board, it is even more preferable that the diagonals of the board are angled. By angling the board in this way, water droplets adhering to the board are more likely to fall off due to gravity. One way to angle the board is, for example, to make the diagonals of the board angled. It is preferable to blow dry air or nitrogen gas onto the ceramic copper circuit board, which has been dried to a certain extent in this manner, to blow away any remaining water droplets. This method of blowing air, dry air, or nitrogen gas is sometimes called an air knife. This air knife is a type of air blow. To further ensure thorough drying of the ceramic copper circuit board obtained in this manner, air with a temperature of 10°C or higher and a humidity of 70% or lower may be applied to the ceramic copper circuit board at a wind speed of 20 m / s to 150 m / s. This drying process of applying air to the ceramic copper circuit board is called air blowing. The preferred air temperature in this air blowing process is 10°C to 150°C, and more preferably 15°C to less than 100°C. Exceeding this temperature may cause oxidation of the conductive surface due to heat. The preferred humidity in the air blowing process is 5% to 70%. If the humidity is greater than 70%, the drying process may take longer. Lowering the humidity to less than 5% may increase costs. The preferred wind speed is 20 m / s to 150 m / s. A wind speed of 20 m / s to 100 m / s is even more preferred. If the wind speed is too low, drying will take a long time. If the wind speed is too high, it may negatively affect the transport of the copper plate. When performing this drying process, combining it with other drying processes can shorten the drying time using hot air, thereby suppressing oxidation of the copper plate surface, which is the conductive part, due to the heat of the hot air. For this reason, multiple drying processes may be combined.

[0031] After the circuit shape is formed on the copper plate, plating is performed as necessary. The plating film used is typically Ni (nickel), Au (gold), Ag (silver), or an alloy mainly composed of these elements. The plating can be either electroplating or electroless plating. Through the above steps, a ceramic copper circuit board according to the embodiment can be manufactured. Subsequently, semiconductor elements are mounted on the ceramic copper circuit board with a plated film to create a semiconductor device. In other words, a ceramic copper circuit board with a plated film is a type of ceramic copper circuit board.

[0032] (Examples) (Examples 1-12, Comparative Example 1) As examples of insulating substrates, ceramic substrates (silicon nitride substrate and aluminum nitride substrate) were prepared. The silicon nitride substrate measured 50 mm (length) x 40 mm (width) x 0.32 mm (thickness). Its thermal conductivity was 90 W / m·K, and its three-point bending strength was 650 MPa. The aluminum nitride substrate measured 50 mm (length) x 40 mm (width) x 0.635 mm (thickness). Its thermal conductivity was 170 W / m·K, and its three-point bending strength was 400 MPa. As an example of a conductive part, a copper plate (oxygen-free copper plate) was prepared. The size of the copper plate was 50 mm in length and 40 mm in width. Next, the ceramic substrate and the copper plate were joined using an activated metal bonding method with an activated metal brazing material containing silver, copper, carbon, and titanium. Copper plates were joined to both sides of the ceramic substrate. Table 1 shows the thickness of the copper plate and the thickness of the bonded layer. Through this process, the bonded bodies according to Examples 1 to 12 and Comparative Examples 1 and 2 were manufactured.

[0033] [Table 1]

[0034] Next, the bonded body was subjected to etching and chemical polishing processes to produce a ceramic copper circuit board, which is an example of an insulating circuit board. The produced ceramic copper circuit board has a copper plate with a circuit shape (copper circuit) on the front side and a copper plate as a heat sink on the back side. The copper circuit on the front side and the copper plate on the back side are examples of conductive parts. The sides of the copper circuit and copper plate were given a sloped shape. In addition, a bonding layer overhang was provided where the bonding layer protrudes from the side of the copper plate. For the bonding layer overhang, the ratio of length to thickness was set within the range of 0.5 to 3.0. The etching and chemical polishing processes were carried out in the following order: copper plate etching → resist removal → chemical polishing (first chemical polishing process) → etching of the bonding layer mainly composed of Ag or Cu → resist removal → chemical polishing (second chemical polishing process) → etching of the titanium reaction layer → resist removal. The cleaning process after each step was carried out under the conditions shown in Table 2. In the case of water cleaning, the amount of water discharged from the nozzle was set to within the range of 1.5 L / min to 6 L / min. The cleaning process was carried out while transporting the ceramic copper circuit board. As a result, the amount of water that landed on the ceramic copper circuit board per nozzle was set to the amount shown in Table 2. In addition, the cleaning process in which the bonded body was immersed in the water cleaning tank was described as "immersion". Furthermore, for the cleaning steps following the copper plate etching process, the first chemical polishing process, the etching process of the bonding layer mainly composed of Ag or Cu, the second chemical polishing process, and the etching process of the titanium nitride layer, the amount of water that hits the ceramic copper circuit board per nozzle is 0.02 L / min / cm². 2 It was standardized to this. When alkaline cleaning was used, it was indicated as "alkaline cleaning". In the drying process for ceramic copper circuit boards, Examples 1-12 and Comparative Example 1 involved a drying process using an air knife followed by a drying process using an air blower. The temperature of the air knife and air blower was room temperature (around 25°C). Other conditions in the drying process included a humidity of approximately 50% and an air velocity of approximately 20-60 m / s. In Comparative Example 2, the same conditions as in Comparative Example 1 were used up to the washing stage, followed by natural drying.

[0035] [Table 2]

[0036] For the examples and comparative examples, the carbon and oxygen content on the copper surface of ceramic copper circuit boards was measured. XPS analysis was used to measure the carbon and oxygen content. An SSI X-probe was used as the XPS analyzer. In the XPS analysis, AlKα rays (hν = 1486.6 eV) were used, and the X-ray spot diameter was set to 1 mm. The amounts of carbon, oxygen, copper, and nitrogen were analyzed in the XPS analysis. The amount of each component was calculated with the sum of carbon, oxygen, copper, and nitrogen being 100 at%. The measurement results for the carbon and oxygen content are shown in Table 3.

[0037] [Table 3]

[0038] Chloride ions, ammonium ions, sulfate ions, and fluoride ions present on the surface of ceramic copper circuit boards in the examples and comparative examples were measured. Ion chromatography was used to measure the amounts of chloride ions, ammonium ions, sulfate ions, and fluoride ions. A DX500 ion chromatograph manufactured by Nippon Dionex Co., Ltd. was used as the ion chromatograph analyzer. For ion extraction, two samples and 40 ml of ultrapure water were placed in a cleaned fluororesin container (Φ100 mm), the lid of the fluororesin container was closed, and the container was kept in a constant temperature bath at 80°C for 18 hours to extract the ionic components. Afterward, the samples were allowed to cool for about an hour, rinsed with water, and then sampled into an auto-sampling tube. Next, the measurement methods for anions and cations are described. For anions (fluoride ions, chloride ions, sulfate ions, etc.), Thermo SCIENTIFIC's Dionex Anion Standard (product number: 056933), diluted 10-fold, was used as the calibration curve standard sample. For the columns, IonPac AS 4A-SC was used as the separation column, and IonPac AG 4A-SC was used as the guard column. 30 ml of potassium hydroxide (KOH) was used as the eluent. For cations (such as ammonium ions), Thermo SCIENTIFIC's Dionex Cation-II Standard (product number: 046070), diluted 100-fold, was used as the calibration curve standard sample. For the columns, IonPac CS 12A was used as the separation column, and IonPac CG 12A was used as the guard column. 20 ml of methanesulfonic acid was used as the eluent. Ion chromatography analysis was performed using two ceramic copper circuit boards. Therefore, the amount of ions obtained was divided by two to obtain the amount of ionic impurities per ceramic copper circuit board. The surface area of ​​each ceramic copper circuit board was 40 cm². 2 That was the case. Table 4 shows the measurement results of each ion amount in the examples and comparative examples. Furthermore, after applying a plating film to the ceramic copper circuit board, ion chromatography analysis was performed in the same manner. In the ceramic copper circuit board described as an example, the amounts of chloride ions, ammonium ions, sulfate ions, and fluoride ions were all within a favorable range.

[0039] [Table 4]

[0040] As can be seen from Table 4, the carbon and oxygen content in the ceramic copper circuit boards according to the examples was within the desirable range. The carbon and oxygen content on the surface of the back copper plate was also at similar values. Furthermore, the surface roughness Ra of the copper component surface in the obtained ceramic copper circuit board was 1 μm or less. Next, a plating process was carried out. A Ni plating film or an Ag plating film was used as the plating film. For the copper component on the front side, a plating film was applied to an area of ​​20 mm vertically x 20 mm horizontally. The adhesion of the plating film was evaluated. The adhesion evaluation was performed using a tape test. Tape was attached to the plating film, and the percentage of the plating film remaining after peeling off the tape was measured. The plating film remaining rate (%) was expressed as (plating film area after test / plating film area before test) × 100. The results are shown in Table 5.

[0041] [Table 5]

[0042] As can be seen from Table 5, the ceramic copper circuit board according to the example showed good adhesion between the copper component and the plating film. Good adhesion was observed even with a plating film covering a wide area of ​​20 mm x 20 mm. Next, semiconductor elements were mounted on ceramic copper circuit boards according to the examples and comparative examples. Semiconductor elements were mounted on a Ni plating film via lead-free solder. Semiconductor elements were also mounted on an Ag plating film via an Ag nanoparticle junction layer. A semiconductor device was manufactured as a result. The reliability of semiconductor element junctions was evaluated for semiconductor devices. To investigate the reliability of the bonding, a TCT test was performed on the semiconductor device. The TCT test consisted of 500 cycles, with one cycle being -40°C for 30 minutes → room temperature for 10 minutes → 170°C for 30 minutes → room temperature for 10 minutes. The bonding strength of the semiconductor device before and after the test was measured. Bonding strength was measured by a peel test. The rate of decrease compared to the bonding strength before the test was investigated. In this case, the rate of decrease was calculated as an integer, rounded to the first decimal place. Semiconductor devices with a bond strength reduction rate of 10% or less after testing were classified as the best product (◎). Semiconductor devices with a reduction rate of 11% to 19% were classified as good products (〇). Semiconductor devices with a reduction rate of 20% to less than 30% were classified as defective product 1 (×). Semiconductor devices with a reduction rate of 30% or more were classified as defective product 2 (××). In addition, two semiconductor elements were bonded to a copper plate via a solder layer. A peel test was performed on one element before the test, and a peel test was performed on the other element after the test. The reduction rate was measured from these results. The results are shown in Table 6.

[0043] [Table 6]

[0044] As can be seen from the table, the reliability of the plating film on the ceramic copper circuit boards in the examples was improved. Furthermore, the effect was confirmed for both Ni and Ag plating films. It was confirmed that the effect could be obtained even when the material of the plating film was changed. In contrast, in Comparative Examples 1 and 2, the reliability decreased due to the high carbon content on the surface of the copper components. Moreover, compared to Comparative Example 1, Comparative Example 2 had a higher oxygen content, resulting in an even greater decrease in reliability.

[0045] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Modifications of these embodiments are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Furthermore, the embodiments described above can be implemented in combination with each other. [Explanation of symbols]

[0046] 1…Insulating circuit board 2…Insulating substrate 3…Conductor part (front conductor part) 4…Conductor part (back conductor part) 5...Joining layer 6… Semiconductor elements 7…Plating film 8... Handa Formation 10… Semiconductor equipment

Claims

1. Ceramic substrate and An insulating circuit board comprising a copper member made of copper or a copper alloy, which is bonded to at least one surface of the ceramic substrate via a bonding layer, The bonding layer comprises one or more selected from Ag, Cu, and Ti. When the carbon content of the surface of the copper member is analyzed by XPS, the average value of the carbon content at any three locations is within the range of 0 at% to 70 at%. When the oxygen content on the surface of the copper member is analyzed by XPS, the average value of the oxygen content at the three locations is within the range of 3 at% to 50 at%. The arithmetic mean roughness Ra of the surface of the copper member is 1 μm or less. An insulating circuit board characterized in that the surface of the copper member includes portions on which a plating film made of Ag, Au, or Ni is provided.

2. The insulating circuit board according to claim 1, characterized in that the average value of the carbon content is within the range of 0 at% to 60 at%.

3. An insulating circuit board according to any one of claims 1 to 2, characterized in that the average value of the oxygen amount is within the range of 3 at% or more and 30 at% or less.

4. An insulating circuit board according to any one of claims 1 to 3, characterized in that the ratio of the average value of the carbon amount to the average value of the oxygen amount is 0 or more and 20 or less.

5. The insulating circuit board according to any one of claims 1 to 4, characterized in that the ceramic substrate mainly consists of silicon nitride or aluminum nitride.

6. A step of manufacturing a bonded body comprising a ceramic substrate made of insulating ceramics and a copper member made of copper or a copper alloy bonded to at least one surface of the ceramic substrate via a bonding layer containing one or more selected from Ag, Cu, and Ti, A first chemical polishing step of chemically polishing the surface of the copper member, a first etching step of etching the copper member, a second etching step of etching the bonding layer, a second chemical polishing step of chemically polishing the bonding layer, and at least one of the following steps: A method for manufacturing an insulating circuit board, comprising: After the first chemical polishing step, after the first etching step, after the second chemical polishing step, after the second etching step, and after the rust prevention treatment step, a cleaning step is performed to clean the joined body. In at least one of the cleaning steps, cleaning water is supplied to the assembly using one or more nozzles, with a water flow rate of 0.01 L / min / cm³ per nozzle. ２ More than 0.1L / min / cm ２ It is set within the following range: After the washing step, a drying step is performed in which air is blown onto the joint at a wind speed of 20 m / s to 150 m / s. A method for manufacturing an insulating circuit board, characterized in that when the carbon content on the surface of the copper member in the manufactured insulating circuit board is analyzed by XPS, the average value of the carbon content at any three locations is within the range of 0 at% to 70 at%.

7. The method for manufacturing an insulating circuit board according to claim 6, characterized in that the distance between one or more nozzles and the joining body is within the range of 5 cm to 40 cm.

8. A method for manufacturing an insulating circuit board according to any one of claims 6 to 7, characterized in that, in the XPS analysis, the average value of the oxygen content at the three locations is within the range of 3 at% to 50 at%.

9. The method for manufacturing an insulating circuit board according to claim 8, characterized in that the average value of the oxygen amount is within the range of 3 at% or more and 30 at% or less.

10. A method for manufacturing an insulating circuit board according to any one of claims 6 to 9, characterized in that the average value of the carbon content is within the range of 0 at% to 60 at%.

11. The method for manufacturing an insulating circuit board according to any one of claims 6 to 10, characterized in that the ceramic substrate mainly contains silicon nitride or aluminum nitride.

12. A method for manufacturing an insulating circuit board according to any one of claims 6 to 11, characterized in that the maximum height Rz of the surface of the copper member in the manufactured insulating circuit board is 20 μm or less.

13. A method for manufacturing an insulating circuit board according to any one of claims 6 to 12, characterized in that the arithmetic mean roughness Ra of the surface of the copper member in the manufactured insulating circuit board is 2 μm or less.

14. The ceramic substrate is a silicon nitride substrate with a thickness of 0.4 mm or less. A method for manufacturing an insulating circuit board according to any one of claims 6 to 13, characterized in that the thickness of the copper member is 0.6 mm or more.

15. A method for manufacturing an insulating circuit board, characterized by performing the method for manufacturing an insulating circuit board according to any one of claims 6 to 14, and providing a plating film on the surface of the copper member of the manufactured insulating circuit board.

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