Manufacturing method of insulating circuit board

Abstract

To provide a method for manufacturing an insulating circuit board, capable of improving the reliability of joining with a joined layer.SOLUTION: The method for manufacturing the insulating circuit board comprises: a step of making a joined body; and at least one of a first chemical polishing step of chemically polishing the surface of a copper member, a first etching step of etching the copper member, a second etching step of etching a joined layer, a second chemical polishing step of chemically polishing the joined layer, and a rust prevention treatment step of executing rust prevention treatment for the copper member. A cleaning step is executed in at least one of after the first / second chemical polishing step, after the first / second etching step, and after the rust prevention treatment step. In the cleaning step, cleaning water is fed to the joined body through nozzles; a water quantity per nozzle is set within the range of 0.01 L / min / cm2-0.1 L / min / cm2; and when a nitrogen quantity on the surface of the copper member is XPS-analyzed, an average value among nitrogen quantities at three arbitrary places is set within the range of 0 at%-50 at%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The embodiments described below generally relate to a method for manufacturing an insulating circuit board. [Background technology]

[0002] There is an insulating circuit board in which an insulating substrate and a conductor are bonded. A ceramic copper circuit board, which is a type of insulating circuit board, is used in a circuit board on which semiconductor elements and the like are mounted. International Publication No. 2017 / 056360 (Patent Document 1) describes a bonded body in which a ceramic substrate and a copper plate are bonded via a bonding layer, and a ceramic copper circuit board in which the bonded body is improved. In Patent Document 1, a protruding portion is provided in which the bonding layer protrudes from the end of the copper plate. Temperature cycle test (TCT) characteristics are improved by controlling the size of such a protruding portion of the bonding layer. When a semiconductor element is mounted on a ceramic copper circuit board, a semiconductor device is obtained. A solder layer or silver paste is used to mount the semiconductor element. The solder layer or silver paste strengthens the bond between the ceramic copper circuit board and the semiconductor element. When a semiconductor element is mounted on the ceramic copper circuit board of Patent Document 1 via a solder layer, a phenomenon occurs in which the reliability of the solder layer bond is insufficient. When the cause of this was investigated, it was found to be due to the amount of nitrogen on the copper plate surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 056360 [Patent Document 2] International Publication No. 2019 / 054294 [Patent Document 3] JP 2007-81217 A [Patent Document 4] International Publication No. 2019 / 054291 [Patent Document 5] JP 2020-59228 A Summary of the Invention [Problem to be solved by the invention]

[0004] By imparting a circuit shape to the bonded body, an insulating circuit board (for example, a ceramic circuit board) is obtained. An etching process or a chemical polishing process is used as a process for imparting a circuit shape to the bonded body. For example, International Publication No. 2019 / 054294 (Patent Document 2) discloses a method combining a chemical polishing process and an etching process. In the chemical polishing process of Patent Document 2, chemical solutions such as hydrogen peroxide, hydrochloric acid, and sulfuric acid are used. In addition, in JP-A-2007-81217 (Patent Document 3), a rust prevention treatment is performed after chemical polishing of the copper plate surface. In Patent Document 3, a chemical solution such as benzotriazole is used for the rust prevention treatment of the copper plate. International Publication No. 2019 / 054291 (Patent Document 4) discloses ammonium peroxodisulfate and the like as a chemical solution used for etching active metal brazing materials containing silver, copper, and titanium. In JP 2020-59228 A (Patent Document 5), chemicals such as benzotriazole are used for anti-rust treatment of aluminum. Various chemicals are used in chemical polishing, etching, anti-rust treatment, etc. When a process using a chemical is performed, nitrogen residue is generated on the surface of the copper plate, which is the conductor. It has been found that this nitrogen causes a decrease in the bonding reliability of the solder layer. The present invention has been made to address such problems, and has an object to provide an insulating circuit board in which the amount of nitrogen on the surface of the conductor portion is reduced. [Means for solving the problem]

[0005] A method for producing an insulating circuit board according to an embodiment includes a step of preparing a bonded body including 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 elements selected from Ag, Cu, and Ti, and at least one of a first chemical polishing step of chemically polishing a 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 a rust-proofing step of applying a rust-proofing treatment to the copper member, wherein a cleaning step of cleaning the bonded body is performed at least in any one of the first chemical polishing step, the first etching step, the second chemical polishing step, the second etching step, and the rust-proofing treatment step, and in at least one of the cleaning steps, cleaning water is supplied to the bonded body using one or more nozzles, and the amount of water per nozzle is 0.01 L / min / cm. 2 More than 0.1L / min / cm 2 The insulating circuit board is characterized in that, when the nitrogen amount on the surface of the copper member in the manufactured insulating circuit board is analyzed by XPS, the average amount of nitrogen at any three points is within the range of 0 at % or more and 50 at % or less. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing an example of an insulating circuit board according to an embodiment. [Diagram 2] 1 is a schematic diagram showing an example of a semiconductor device according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] A method for producing an insulating circuit board according to an embodiment includes a step of preparing a bonded body including 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 elements selected from Ag, Cu, and Ti, and at least one of a first chemical polishing step of chemically polishing a 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 a rust-proofing step of applying a rust-proofing treatment to the copper member, wherein a cleaning step of cleaning the bonded body is performed at least in any one of the first chemical polishing step, the first etching step, the second chemical polishing step, the second etching step, and the rust-proofing treatment step, and in at least one of the cleaning steps, cleaning water is supplied to the bonded body using one or more nozzles, and the amount of water per nozzle is 0.01 L / min / cm. 2 More than 0.1L / min / cm 2 The insulating circuit board is characterized in that, when the nitrogen amount on the surface of the copper member in the manufactured insulating circuit board is analyzed by XPS, the average amount of nitrogen at any three points is within the range of 0 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 portion (front conductor portion), 4 is a conductor portion (rear conductor portion), and 5 is a bonding layer. In the insulating circuit board 1 illustrated in FIG. 1, a conductor portion 3 and a conductor portion 4 are arranged on both sides of an insulating substrate 2 via a bonding layer 5. In the structure shown in FIG. 1, a circuit shape is given to the conductor portion 3, and the conductor portion 4 is used as a heat sink. For convenience, the conductor portion 3 is called the front conductor portion, and the conductor portion 4 is called the rear conductor portion. In addition, two front conductor portions 3 are arranged. The insulating circuit board according to the embodiment is not limited to such a form, and one or three or more front conductor portions may be provided. A circuit shape may be given to the rear conductor portion 4. The insulating circuit board may not include the rear conductor portion 4, and may include only the front conductor portion 3. The insulating circuit board according to the embodiment is preferably a ceramic copper circuit board.

[0008] The insulating substrate is preferably a resin substrate or a ceramic substrate. Resin substrates are less expensive than ceramic substrates and are preferred when cost is a consideration. Examples of resin substrates include paper phenol substrates, paper epoxy substrates, glass epoxy substrates, composite substrate epoxy substrates, glass composite substrates, glass polyimide substrates, bismaleimide-triazine (BT) substrates, fluororesin substrates, polyphenylene oxide (PPO) substrates, etc. A ceramic substrate has superior heat dissipation and three-point bending strength compared to a resin substrate. The ceramic substrate preferably contains one or two main components selected from silicon nitride, aluminum nitride, sialon, alumina, and zirconia. The main component refers to a component contained in an amount of 50% by mass or more. Furthermore, the ceramic substrate is more preferably a silicon nitride substrate, an aluminum nitride substrate, or an alumina substrate. Alumina is a material containing alumina and zirconia in a total amount of 50% by mass or more. The thickness of the insulating substrate is preferably 0.1 mm or more and 1 mm or less. If the substrate thickness is less than 0.1 mm, the strength may be reduced. If the substrate thickness is greater than 1 mm, the insulating substrate itself may become a thermal resistor, which may reduce the heat dissipation of the insulating circuit board. The three-point bending strength of the silicon nitride substrate is preferably 600 MPa or more. The thermal conductivity of the silicon nitride substrate is preferably 80 W / m·K or more. By increasing the strength of the silicon nitride substrate, the substrate thickness can be reduced. Therefore, the three-point bending strength of the silicon nitride substrate is preferably 600 MPa or more, and more preferably 700 MPa or more. The thickness of the silicon nitride substrate can be reduced to 0.40 mm or less, and even 0.30 mm or less. The three-point bending strength of the aluminum nitride substrate is about 300 to 450 MPa. On the other hand, the thermal conductivity of the aluminum nitride substrate is 160 W / m·K or more. Since the strength of the aluminum nitride substrate is low, the substrate thickness is preferably 0.60 mm or more. The three-point bending strength of aluminum oxide substrates is about 300-450MPa, but aluminum oxide substrates are inexpensive among ceramic substrates. The three-point bending strength of aluminium oxide substrates is high at about 550MPa, but their thermal conductivity is about 30-50W / m K. Aluminium oxide substrates are substrates made of a sintered mixture of aluminium oxide and zirconium oxide.

[0009] The insulating substrate 2 is preferably a ceramic substrate. Among ceramic substrates, either a silicon nitride substrate or an aluminum nitride substrate is more preferable. The silicon nitride substrate and the aluminum nitride substrate are nitride-based ceramic substrates. The nitride-based ceramic reacts with an active brazing metal material containing Ti to form titanium nitride. The oxide-based ceramic reacts with an active brazing metal material containing Ti to form titanium oxide. The alumina substrate, the zirconia substrate, and the aluminium substrate are oxide-based ceramic substrates. The bonding strength between nitride ceramics and oxide ceramics and a conductor can be improved by using an active metal bonding method. The reaction layer that forms titanium nitride or titanium oxide is called a titanium reaction layer. The conductor part is preferably a copper member or an aluminum member. The copper member is a copper plate, a copper alloy plate, a member produced by imparting a circuit shape to a copper plate, or a member produced by imparting 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 produced by imparting a circuit shape to an aluminum plate, or a member produced by imparting a circuit shape to an aluminum alloy plate, and is made of aluminum or an aluminum alloy. Hereinafter, a member produced by imparting a circuit shape to a copper plate is called a copper circuit. A member produced by imparting a circuit shape to an aluminum plate is called an aluminum circuit. The conductor part may 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. The aluminum member is less expensive than the copper member. On the other hand, the copper member is preferable because it has excellent thermal conductivity compared to the aluminum member. The copper plate or copper circuit may be made of oxygen-free copper. Generally, the thermal conductivity of copper is high, about 400 W / m K. To improve heat dissipation, it is more preferable that the copper member is a copper plate or copper circuit made of oxygen-free copper. The thickness of the conductor 3 and the conductor 4 may be 0.3 mm or more, or even 0.6 mm or more. By making the conductor thicker, the heat dissipation of the bonded body can be improved. The thickness of the front conductor 3 may be the same as the thickness of the back conductor 4, or may be different from the thickness of the back conductor 4. As the conductor, a copper plate or a copper circuit is particularly preferable. For the copper plate or the copper circuit, oxygen-free copper is preferably used. As specified in JIS-H-3100, oxygen-free copper has a copper purity of 99.96 mass% or more.

[0010] The insulating circuit board according to the embodiment is characterized in that, when the nitrogen amount on the surface of the conductor portion is analyzed by XPS, the average value at any three points is within the range of 0 at% to 50 at%. The insulating circuit board according to the embodiment may include only one conductor portion, or may include multiple conductor portions. In other words, the number of conductor portions provided is not particularly limited. When the insulating circuit board includes multiple conductor portions, it is sufficient that the average value of the nitrogen amount at any three points on the surface of any conductor portion is within the range of 0 at% to 50 at%. More preferably, the average value of the nitrogen amount at any three points on the surface of any conductor portion is within the range of 0 at% to 50 at%. The surface of the conductor refers to the surface of at least one of the conductor parts, the front conductor part 3 or the back conductor part 4. The amount of nitrogen on the surface of the conductor part is analyzed by XPS. XPS analysis refers to analysis using X-ray photoelectron spectroscopy (XPS). XPS analysis is a method in which X-rays are irradiated onto the sample surface and the kinetic energy of photoelectrons emitted from the sample surface is measured. XPS analysis is used for qualitative and quantitative analysis of sample surfaces, as the penetration depth of X-rays is several μm. The XPS analysis equipment used is an X-probe made by SSI or an equipment equivalent to or greater than that. In the analysis, AlKα radiation (hν=1486.6 eV) is used, and the X-ray spot diameter is set to 1 mm. In addition to nitrogen and oxygen, the XPS analysis also measures the amount of each metal element used in the conductor and the amount of carbon. When a copper member is used as the conductor, nitrogen, oxygen, copper, and carbon are extracted from the measured components, and the total of these is taken as 100 at% to measure the amount of nitrogen.When the copper member contains a copper alloy, nitrogen, oxygen, copper, other alloy metals, and carbon are extracted from the measured components, and the total of these is taken as 100 at%. When an aluminum member is used as the conductor, nitrogen, oxygen, aluminum, and carbon are extracted from the measured components, and the total of these is taken as 100 at% to measure the amount of nitrogen.When an aluminum member contains an aluminum alloy, nitrogen, oxygen, aluminum, other alloy metals, and carbon are extracted from the measured components, and the total of these is taken as 100 at%.

[0011] In the embodiment described below, an example will be described in which a copper material is used for the conductor portion and a ceramic substrate is used for the insulating substrate. The following description is also applicable to cases in which a material other than a copper material is used for the conductor portion. When an aluminum material is used for the conductor portion, the "copper material" can be appropriately replaced with an "aluminum material" in the following description. Similarly, when a resin substrate other than a ceramic substrate is used for the insulating substrate, the "ceramic substrate" can be appropriately replaced with a resin substrate in the following description. In the embodiment, the nitrogen amount on the surface of the copper member is measured by XPS analysis. The nitrogen amount is the average value of three arbitrary points on the surface. The "surface" to be analyzed does not include the side surface of the copper member. The arbitrary three points are three points selected from the surface of one copper member. During measurement, three points are selected whose farthest points of the spot diameter are 500 μm or more apart from each other. It is preferable that the measurement points do not overlap each other. In addition, it is preferable that the measurement points are points where semiconductor elements are mounted. When the nitrogen amount on the copper member surface is within the range of 0 at% to 50 at%, the wettability between the copper member surface and the bonding layer can be improved. As the bonding layer, a solder layer or a layer mainly composed of silver (Ag nanoparticle layer) is used. The solder layer is, for example, lead-free solder defined in JIS-Z-3282. JIS-Z-3282 corresponds to "ISO DIS 9453 2005". An alloy containing Sn (tin) is mainly used for lead-free solder. Cu and Sn are components that easily react with each other. This can strengthen the bond between the copper member and the semiconductor element. On the other hand, nitrogen is a component that inhibits the reaction between Sn and Cu. For this reason, it is important that the nitrogen amount is 0 at% or more and 50 at% or less on the surface of the copper member that is the conductor. In particular, it is more preferable that the nitrogen amount is within the range of 0 at% or more and 50 at% or less regardless of where on the conductor surface is measured. As mentioned above, when the average value of three arbitrary points is calculated, there may be some parts of the surface where the nitrogen amount exceeds 50 at%. By making the nitrogen amount within the range of 0 at% or more and 50 at% or less regardless of where on the conductor surface is measured, the characteristics can be further improved.

[0012] A nitrogen content of 0 at% (atomic %) indicates that the nitrogen content is below the detection limit of XPS analysis. Furthermore, if the nitrogen content exceeds 50 at%, the wettability between the copper member surface and the bonding layer decreases. In conventional insulating circuit boards, particularly ceramic copper circuit boards, there are some locations on the surface of the conductor at the location where the semiconductor element is bonded via the bonding layer where the nitrogen content is 60 at% or more. By setting the average nitrogen content at any three locations to 50 at% or less, the wettability between the conductor and the bonding layer can be improved. For this reason, the nitrogen content on the surface of the copper member is 0 at % or more and 50 at % or less. When no rust inhibitor is used, the nitrogen content is preferably 0 at % or more and 30 at % or less. When a rust inhibitor is used, the nitrogen content on the copper member surface may be 10 at % or more and 50 at % or less. A more preferable range of the nitrogen content when a rust inhibitor is used is 10 at % or more and 30 at % or less. The amount of nitrogen can be controlled by using a cleaning process described later. For this reason, it is preferable to control the amount of nitrogen depending on whether or not rust prevention treatment is performed. The smaller the nitrogen content on the copper member surface, the more preferable. On the other hand, as described below, by controlling the oxygen content on the copper member surface, the possibility of defects occurring can be reduced even if the nitrogen content is 10 at % or more.

[0013] When the oxygen amount on the copper member surface is analyzed by XPS, it is preferable that the average value at three locations is within the range of 3 at% to 50 at%. The method of XPS analysis is the same as the method of analyzing the nitrogen amount. The three locations used to measure the oxygen amount are the same as the three locations used to measure the nitrogen amount. In other words, both the nitrogen amount and the oxygen amount are measured in one XPS analysis. In other words, the amounts of nitrogen and oxygen present in the same measurement area are measured simultaneously.

[0014] If nitrogen is attached to the copper member surface, the bonding between the copper member and the bonding layer is hindered. Therefore, it is preferable that the amount of nitrogen is small. On the other hand, when oxygen is present on the copper member surface, it is possible to make it difficult for nitrogen to be attached to the copper member surface. The oxygen present on the copper member surface suppresses the attachment of nitrogen, thereby suppressing the inhibition of the bonding between the copper member and the bonding layer by nitrogen. Therefore, it is preferable that oxygen is present on the copper member surface. For example, when a chemical polishing process or an etching process is performed on the copper member surface, a part of the copper crystal particles is removed from the grain boundaries between the copper crystal particles of the copper member. Therefore, minute recesses are formed in the grain boundary portion of the copper member. Nitrogen is easily attached to the minute recesses in the grain boundary portion. This is because the use of a chemical solution containing nitrogen atoms makes it easier for the components of the chemical solution to remain in the recesses on the copper member surface, and nitrogen is attached to the copper member surface. For example, the chemical solution containing nitrogen atoms is a compound having an amino group. The presence of oxygen on the copper plate surface allows oxygen to be present in the recesses, which can suppress the attachment of nitrogen. In addition, there is also an effect of oxygen covering the nitrogen present in the recesses. Therefore, it is preferable that the amount of oxygen is within the above-mentioned range.

[0015] When the amount of oxygen on the surface of the copper member is 3 at% or more, defects due to nitrogen can be suppressed. When the amount of oxygen is less than 3 at%, the amount of oxygen is insufficient. When the amount of oxygen on the surface of the copper member is more than 50 at%, the oxygen itself reacts with the copper member to form copper oxide. Therefore, the thermal conductivity of the copper member may decrease. Therefore, the amount of oxygen on the surface of the copper member is preferably in the range of 3 at% to 50 at%. Furthermore, when the amount of oxygen on the surface of the copper member is in the range of 3 at% to 30 at%, the oxygen itself does not hinder the bonding between the copper member and the bonding layer. When the amount of oxygen is more than 30 at%, the oxygen itself may become a factor that hinders the bonding between the copper member and the bonding layer. Therefore, it is more preferable that the amount of oxygen on the surface of the copper member is in the range of 3 at% to 30 at%. In addition, the amount of oxygen (A OX ) relative to the amount of nitrogen (A N ) ratio (A N / A OXThe ratio (A) is preferably 0 or more and 5 or less. The nitrogen amount and oxygen amount used in calculating the ratio are the average values ​​of the above three places. N / A OX ) is 0 when the nitrogen content is 0 at%. N / A OX A ratio (A) of 5 or less indicates that the amount of nitrogen is 5 times or less than the amount of oxygen. N / A OX If the ratio (A) is greater than 5, the effect of suppressing the effect of nitrogen may be insufficient. N / A OX ) is preferably 0 or more and 5 or less. When no rust-proofing treatment was performed, the ratio (A N / A OX It is more preferable that the ratio (A ) is 0 to 4. On the other hand, when rust prevention treatment is performed, the ratio (A N / A OX It is more preferable that the ratio (A) is 0.5 or more and 4 or less. In other words, when the nitrogen amount on the surface of the copper member is not 0 at% due to the rust prevention treatment, N / A OX ) is preferably 0.5 or more and 4 or less. When performing rust prevention treatment, making the amount of nitrogen on the copper component surface 0 at% (below the detection limit) may increase the burden on the manufacturing process. Even if nitrogen remains, it is effective to reduce the impact. The amount of chloride ions present on the surface of an insulating circuit board is 40 cm 2 The amount of chloride ions is preferably 0 μg or more and 15 μg or less per 40 cm of surface area of ​​the insulating circuit board. 2 It is more preferable that the concentration is 0 μg or more and 3 μg or less per unit area. Sulfate ions (SO ) present on the surface of insulating circuit boards 4 ) amount is 40cm surface area of ​​insulating circuit board 2 The concentration of sulfate ions (SO 4 ) amount is 40cm surface area of ​​insulating circuit board 2It is more preferable that the concentration is 0 μg or more and 0.5 μg or less per unit area. Fluorine ions present on the surface of an insulating circuit board are 2 The amount of fluorine ions is preferably 0 μg or more and 2 μg or less per 40 cm of surface area of ​​the insulating circuit board. 2 It is more preferable that the concentration is 0 μg or more and 1 μg or less per unit area. Ammonium (NH4) ions present on the surface of an insulating circuit board are 2 The amount of ammonium ions is preferably 0 μg or more and 3 μg or less per 40 cm of the surface area of ​​the insulating circuit board. 2 It is more preferable that the concentration is 0 μg or more and 1 μg or less per unit area. The above-mentioned multiple ions tend to adhere more easily to the surface of a metal than to the surface of an insulating substrate. If the above-mentioned multiple ions are present on the surface of an insulating substrate, they may volatilize when the copper member and the semiconductor element are bonded, and may induce contamination of the copper member surface. If the copper member surface is contaminated, it may induce poor bonding between the copper member and the semiconductor element. Therefore, it is preferable to control the amount of the above-mentioned ions present on the entire surface of the insulating circuit board, including the areas where the copper member is not bonded. The surface area of ​​each insulating circuit board is 40 cm 2 If it is smaller, use multiple boards to make the total surface area of ​​the insulating circuit board 40 cm 2 The total surface area should be 40 cm or more. 2This is because, when the area of ​​the insulating circuit board surface is less than 100 mm, that is, when the area of ​​the insulating circuit board surface is extremely small, the influence of outliers or noise may be excessive when converting using a proportional relationship. The surface area measured here is the area of ​​the flat surface, not including the thickness component of the side surface. The flat surface refers to a surface that is approximately parallel to the joint surface with the conductor part of the insulating board when the insulating circuit board is viewed from above. For example, when the conductor part is provided so that it does not protrude from the end of the insulating board when viewed from above, the front surface (upper surface) and back surface (lower surface) of the insulating board can be considered as flat surfaces. Since the front and back surfaces of the insulating circuit board are the objects of calculation of the surface area, the surface area = the vertical dimension x horizontal dimension x 2 times of the insulating board. Also, when the conductor part protrudes from the end of the insulating board when viewed from above, the flat surface of the protruding conductor part is also counted in the surface area. In this way, the thickness components of the insulating board and the conductor part are not included in the calculation of the surface area. Here, the upward direction is defined as the direction perpendicular to a straight line connecting the ends of the insulating substrate. The area of ​​the flat surface is defined as the sum of the area when viewed from above and the area when viewed from below. Therefore, doubling the area when viewed from above is the surface area of ​​the insulating circuit substrate. In addition, there are only a few insulating circuit boards, and the total surface area of ​​the insulating circuit boards is less than 40 cm 2 If the impurity concentration is smaller than 100%, the amount of impurity obtained is calculated based on the surface area (cm 2 ) and then multiply by 40 to convert the surface area. The impurities are the above-mentioned chloride ions, sulfate ions, fluorine ions, and ammonium ions. If the surface area of ​​one insulating circuit board is 40 cm 2 If this is not the case, 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 perform conversion using the following formula. "40cm of copper material 2 "Amount of impurities per unit area" = "Amount of impurities obtained by measurement" x 40 ÷ "Total surface area of ​​insulating circuit boards (cm 2 )" The amounts of chloride ions, sulfate ions, fluoride ions, and ammonium ions are measured by ion chromatography. Chloride ions are likely to adhere to copper plates when etching is performed using chemicals such as iron chloride or copper chloride, and also when hydrochloric acid is used for cleaning. Sulfate ions are likely to adhere when an etching process or a chemical polishing process is performed on a layer containing Ag or Cu as a main component, using a chemical solution such as sodium thiosulfate, sulfuric acid, or ammonium peroxodisulfate. Fluorine ions are likely to adhere when an etching process of the Ti reaction layer is performed using a chemical solution such as ammonium fluoride. Ammonium ions are likely to adhere when a chemical solution such as ammonium fluoride or ammonium peroxodisulfate is used to perform an etching process for a Ti reaction layer, an etching process for a layer mainly composed of Ag or Cu, or a chemical polishing process. If ions such as chloride ions, sulfate ions, fluorine ions, and ammonium ions remain on the surface of an insulating circuit board (especially on the surface of copper components), the reliability of the bond between the copper components and semiconductor elements decreases. Furthermore, sulfate ions are divalent anions, while chloride ions and fluorine ions are monovalent anions. Ammonium ions are monovalent cations. The components described as ions here may be detected as ions during measurement, and may be present as compounds on the surface of the insulating circuit board.

[0016] Copper members are bonded to both sides of an insulating substrate such as a ceramic substrate or a resin substrate, and the amount of nitrogen on the surface of the copper members on both sides is preferably within a range of 0 at% to 50 at%. As described above, controlling the amount of nitrogen improves the bond with the bonding layer. Therefore, it is important to control the amount of nitrogen on the surface of the copper member on which the bonding layer is provided. The bonding layer is a solder layer or a layer mainly composed of silver. When copper members 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. A semiconductor element is mounted on the copper plate or copper circuit on the front side. The bonding layer is used when mounting a semiconductor element. The heat sink is used as a surface to be mounted on a heat sink or the like. Since grease or the like is used for mounting on a heat sink, the bonding layer may not be used. However, by controlling the amount of nitrogen on the surface of the copper members on both sides, both the front and back copper members can be used as mounting surfaces for semiconductor elements. In other words, an insulating circuit board that is easy to use can be provided.

[0017] The ceramic substrate and the copper member are preferably bonded via a bonding layer containing one or more selected from Ag, Cu, and Ti. A bonding method using a bonding brazing material containing Ti is called an active metal bonding method. The active metal bonding method can firmly bond the ceramic substrate and the copper member. The brazing material used in the active metal bonding method is called an active metal brazing material. The active metal brazing material contains 0% to 70% by mass of Ag (silver), 15% to 85% by mass of Cu (copper), Ti (titanium) or TiH 2 It is preferable that the active metal brazing material contains 1 mass % or more and 15 mass % or less of titanium hydride (titanium hydride). In addition, the active metal brazing material may contain Nb or Zr instead of Ti, or Nb or Zr may be added to Ti. However, the active metal brazing material is not limited to Ti (titanium) or TiH 2 It is preferable that the titanium hydride content is 1% by mass or more and 15% by mass or less. Ti and TiH 2When both of Ag and Cu are used, the total content of them is within the range of 1 mass % to 15 mass %. When both of Ag and Cu are used, the Ag content is preferably 20 mass % to 70 mass % and the Cu content is preferably 15 mass % to 65 mass %. If necessary, the brazing material may contain one or both of Sn (tin) and In (indium) in an amount of 1 mass% to 50 mass%. Ti or TiH 2 The content of is preferably 1 mass % or more and 15 mass % or less. If necessary, the brazing material may contain C (carbon) in an amount of 0.1 mass % or more and 2 mass % or less. The ratio of the active brazing material composition is calculated based on 100% by mass of the total of the mixed solid raw materials. The solid raw materials are preferably in powder form. For example, when the active brazing material is composed of three types of Ag, Cu, and Ti, Ag+Cu+Ti=100% by mass. Ag, Cu, TiH 2 When active metal brazing material is composed of four types of Ag, Cu, TiH, and In, 2 +In=100% by mass. When the active brazing metal is composed of five elements, Ag, Cu, Ti, Sn, and C, the formula is Ag+Cu+Ti+Sn+C=100% by mass. It is preferable to mix a solvent according to the composition of the powder raw material having the above composition. By mixing the solvent, the brazing material can be made into a paste.

[0018] Ag or Cu is a component that becomes the base material of the brazing material. Sn or In has the effect of lowering the melting point of the brazing material. C (carbon) has the effect of controlling the fluidity of the brazing material and controlling the structure of the joining layer by reacting with other components. For this reason, the components of the brazing material 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 addition, In may be used instead of Sn. Both Sn and In may be used.

[0019] The side surface of the copper member preferably has an inclined shape. That is, the side surface of the copper member preferably is inclined with respect to the in-plane direction and the thickness direction. The in-plane direction is a direction parallel to the bonding surface of the ceramic substrate with the copper member. The thickness direction is a 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 a range of 10 μm to 60 μm. In addition, the insulating circuit board preferably has a shape in which the bonding layer protrudes from the side surface of the copper member. The protruding part of the bonding layer is called a bonding layer protruding part. The bonding layer protruding part preferably has a ratio (L / T) of the length L to the thickness T in a range of 0.5 to 3.0. The thickness of the bonding layer protruding part is the thickness of the thickest part of the bonding layer protruding part. The length of the bonding layer protruding part is the length of the longest part protruding from the side surface of the copper member. The thickness and length of the bonding layer protruding part are measured from an arbitrary cross section of the ceramic copper circuit board. By providing a sloped shape to the copper member and providing a bonding layer protruding part, the TCT characteristics of the ceramic copper circuit board can be improved. The maximum height Rz of the copper member surface is preferably 20 μm or less. The arithmetic mean roughness Ra of the copper member surface is preferably 5 μm or less. The arithmetic mean roughness Ra is more preferably 2 μm or less. The arithmetic mean roughness Ra is even more preferably 1 μm or less. By making the copper member surface flatter, the bonding with the solder layer or the layer mainly composed of silver can be strengthened. Ra and Rz are described 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 having a thickness of 0.4 mm or less, and the copper member is preferably 0.6 mm or more. A thin silicon nitride substrate having a thickness of 0.4 mm or less has the effect of lowering the thermal resistance of the ceramic substrate. A thick copper member having a thickness of 0.6 mm or more improves heat dissipation. Furthermore, a silicon nitride substrate having a three-point bending strength of 600 MPa or more is more likely to achieve the effect.

[0020] The above-mentioned ceramic copper circuit board is suitable for a semiconductor device in which a semiconductor element is mounted via a bonding layer. FIG. 2 is a schematic diagram showing an example of a semiconductor device according to an embodiment. In FIG. 2, 1 is an insulating circuit board, 6 is a semiconductor element, 7 is a solder layer, and 10 is a semiconductor device. FIG. 2 shows an example in which one semiconductor element 6 is mounted. Two semiconductor elements 6 may be mounted. A lead frame, wire bonding, or the like may be provided. Instead of the solder layer 7, a layer mainly composed of silver (Ag nanoparticle layer) may be used. In the semiconductor device 10 according to the embodiment, the amount of nitrogen on the surface of the conductor 3 is controlled, so that the bonding between the conductor 3, the solder layer 7, and the semiconductor element 6 can be strengthened. In recent years, the performance of semiconductor elements has been improved. Accordingly, the junction temperature of the semiconductor elements has reached 150° C. or higher, and even 170° C. or higher. According to the semiconductor device 10 according to the embodiment, even when a semiconductor element with a high junction temperature is mounted, peeling or cracking of the solder layer 7 can be suppressed, and bonding reliability can be improved.

[0021] A method for producing the ceramic copper circuit board according to the embodiment will be described. The method for producing the ceramic copper circuit board according to the embodiment is not particularly limited as long as it has the above-mentioned configuration. Here, a method for obtaining the ceramic copper circuit board with a high yield will be exemplified. First, a bonded body of a ceramic substrate and a copper plate is prepared. The specific configurations of the ceramic substrate and the copper plate are as described above.

[0022] The bonded bodies are bonded using an active metal bonding method. The active metal bonding method is a bonding method using an active metal brazing material containing an active metal such as Ti. The components of the active metal brazing material are as described above. An active metal brazing material paste is prepared and applied to the surface of the ceramic substrate. The thickness of the active metal brazing material paste applied is preferably within a range of 10 μm to 60 μm. A copper plate is placed on the active metal brazing material paste layer. The active metal brazing material paste may be applied on the copper plate, and the ceramic substrate may be placed on the copper plate. The length and width of the ceramic substrate may be the same as the length and width of the copper plate, or may be different from the length and width of the copper plate. When the thickness of the copper plate is 0.6 mm or more, it is preferable that the length and width of the ceramic substrate and the length and width of the copper plate are the same. It is also preferable to arrange the copper plates on both sides of the ceramic substrate. With such an arrangement, it becomes easier to reduce the warping of the bonded body. Any circuit shape can be formed on the copper plate by the etching process described later. A copper member previously processed into a circuit shape can also be bonded to the ceramic substrate. However, a dedicated mold is required to prepare the copper member previously processed into a circuit shape. Preparing a mold according to the circuit shape may lead to an increase in costs.

[0023] Next, a heat bonding step is performed. The heating temperature is preferably 600° C. or higher and 930° C. or lower. The heating atmosphere may be a vacuum or an inert atmosphere. A vacuum is defined as a pressure of 10 -3 Pa or less. The inert atmosphere is a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, a neon atmosphere, a xenon atmosphere, etc. In particular, in consideration of the cost, a nitrogen atmosphere and an argon atmosphere are more preferable. A nitrogen atmosphere is more preferable. A bonded body of a ceramic substrate and a copper plate can be manufactured by carrying out a heat bonding process. If necessary, a warping correction process may be carried out on the bonded body. Next, the bonded body is subjected to a chemical polishing process and an etching process. These processes are processes for imparting a circuit shape to the copper plate. In these processes, a sloping shape may be imparted to the side surface of the copper plate, or a bonding layer protruding portion may be formed by protruding the bonding layer from the side surface of the copper plate. In the active metal bonding method, an active metal brazing material containing Ti and mainly Ag or Cu is used. In a bonded body using the active metal bonding method, a Ti reaction layer is formed in the bonded layer. When a nitride ceramic substrate is used, the Ti reaction layer is a titanium nitride (TiN) layer. When an oxide ceramic substrate is used, the Ti reaction layer is a titanium oxide (TiO 2 The bonding layer of a bonded body manufactured by the active metal bonding method is formed of a layer mainly composed of Ag or Cu and a Ti reaction layer. The nitride ceramic substrate is a substrate made of sialon, silicon nitride, aluminum nitride, or the like. The oxide ceramic substrate is a substrate made of alumina, zirconia, or ardil (ceramics made of alumina and zirconia).

[0024] To give a circuit shape in the etching process, a copper plate etching process, an Ag or Cu-based layer etching process, and a Ti reaction layer etching process are required. Considering the etching efficiency, different chemicals are required for each of the three etching processes. In addition, resist must be applied to the areas that do not need to be etched. When the area to be etched changes, a resist removal process and a resist application process are required each time. It is necessary to perform multiple etching processes using different chemicals. For example, in the copper plate etching process, a chemical containing iron chloride or copper chloride is used. In the Ag or Cu-based layer etching process, a chemical containing hydrogen peroxide or ammonium peroxodisulfide is used. In the Ti reaction layer etching process, a chemical containing hydrogen peroxide or ammonium fluoride is used. In addition to these, various other chemicals are used. To increase the efficiency of the etching process, it is effective to use a chemical polishing process. The chemicals used in the etching process may oxidize the layer mainly composed of Ag or Cu. To remove the oxide layer, a chemical polishing process is effective. In the chemical polishing process, a chemical containing one or more selected from sulfuric acid, hydrochloric acid, and sodium thiosulfate is used. Various chemicals are also used in the etching process. If necessary, the copper plate is subjected to an anti-rust treatment. The anti-rust treatment is performed after etching of the brazing material. The anti-rust treatment is a treatment for preventing the occurrence of rust (i.e. oxidation) on the copper plate. Generally, plating is performed to prevent oxidation. On the other hand, when plating is not required, anti-rust treatment may be performed. For the anti-rust treatment, a chemical solution such as a benzotriazole-based compound containing benzotriazole is used. An example of a benzotriazole-based compound is carboxybenzotriazole. These benzotriazole compounds contain about 3 to 8 nitrogen atoms per molecule, and if these benzotriazole compounds remain on the surface of a copper member, they will be detected as nitrogen atoms in an XPS analysis.

[0025] The copper plate on the front side is processed by the above-mentioned chemical polishing process, etching process, etc. For example, a circuit shape is given to the copper plate to form a copper circuit. Or, one copper plate is divided to form a plurality of copper plates. This results in a ceramic copper circuit board to which a copper member (copper circuit or copper plate) is bonded. As described above, various chemicals are used in the chemical polishing process, etching process, rust prevention process, etc. When a process using a chemical solution is performed, nitrogen adheres to the surface of the copper member. In order to control the amount of nitrogen on the surface of the copper member, it is effective to perform a cleaning process. In the cleaning process, one or two types selected from water cleaning, alkali cleaning, and alcohol cleaning are performed. In addition, when only water cleaning is performed, it is preferable that the following water cleaning process, which is a process other than immersion, is performed at least once. More preferably, the more times the cleaning process is the cleaning process described below when only water cleaning is used, the more preferable it is. In addition, a plurality of cleaning methods may be combined in one cleaning process. It is preferable that these cleanings are performed not only on the conductor portion but on the entire ceramic copper circuit board. In the water washing, the flow rate is preferably 1.3 L (liters) / min or more. If the flow rate is 1.3 L / min or more, the effect of washing away nitrogen attached to the copper member surface can be sufficiently obtained. If the flow rate is less than 1.3 L / min, the washing effect may be insufficient. For example, in a method in which the bonded body is immersed in a washing tank filled with water and left there, the flow rate is insufficient, and the effect of reducing the amount of nitrogen cannot be sufficiently obtained. The upper limit of the flow rate is not particularly limited, but is preferably 10 L / min or less. If the flow rate is greater than 10 L / min, the water pressure may be too high and the copper member surface may be deformed. For this reason, the flow rate of the water washing is preferably 1.3 L / min or more and 10 L / min or less. More preferably, the flow rate of the water washing is 1.5 L / min or more and 6 L / min or less. Methods for adjusting the flow rate include circulating the water stored in the cleaning tank and using a nozzle. The flow rate is preferably adjusted using a nozzle. Using a nozzle makes it easier to control the flow rate. When circulating the water stored in the cleaning tank, it may be difficult to control the flow rate if the amount of water is large. When using a nozzle, the flow rate of the water sprayed from the nozzle is set to 1.3 L / min or more. Ultrasonic waves may be applied to the water, or carbon dioxide or oxygen may be dissolved in the water. The distance between the nozzle and the ceramic copper circuit board is preferably within a range of 5 cm to 40 cm. More preferably, it is within a range of 5 cm to 20 cm. Within this range, it becomes easier to adjust the amount of water hitting the ceramic copper circuit board. The shape of the water sprayed from the nozzle can be various, such as a dot, a circle, an ellipse, a flattened shape, or a square shape. Various shapes such as a cone shape or a fan shape can be applied to the nozzle. When using a nozzle, multiple nozzles may be used per ceramic copper circuit board, and the front conductor part and the back conductor part may be washed simultaneously. The amount of water that hits the ceramic copper circuit board is 0.01 L / min / cm per nozzle. 2 More than 0.1L / min / cm 2 The amount of water that lands on the ceramic copper circuit board is called the impact water volume. The impact water volume is the volume of water that lands on the ceramic copper circuit board per 1 cm when viewed from above. 2The amount of water that lands on the ceramic copper circuit board can be adjusted by adjusting the amount of water from the nozzle, the nozzle type, the distance from the nozzle, and the like. Air can also be sprayed when spraying water from the nozzle. Ultrasonic waves may be applied in the cleaning process. It is also effective to perform the cleaning process while transporting the ceramic copper circuit board. In this case, the board may be tilted to improve cleaning efficiency (liquid recovery efficiency) and installation area efficiency. "Tilt" means that the direction of at least one side of the board is not parallel to a horizontal plane perpendicular to the direction of gravity. It is more preferable that the angle between the horizontal plane and the at least one side is 10 degrees or more and less than 90 degrees. The flow rate from the nozzle is 1.3 L / min or more, and the amount of water that lands on the ceramic copper circuit board is 0.01 L / min / cm per nozzle while transporting the ceramic copper circuit board. 2 More than 0.1L / min / cm 2 It is efficient to keep the value within the following range.

[0026] It is preferable that the water meets the quality requirements of JIS-K-0557 (1998). JIS-K-0557 specifies qualities of A1 to A4. For JIS-K-0557, ISO3696 is referred to.

[0027] Alkaline washing refers to the process of washing with an alkaline aqueous solution with a pH of 10 or higher. Examples of alkaline aqueous solutions with a pH of 10 or higher include aqueous solutions of organic alkali, metal hydroxides, and salts of metal hydroxides and weak acids. In particular, when metal hydroxides and their salts are used, the types of metals include lithium, potassium, sodium, barium, calcium, etc. bIf the base dissociation constant is too small, the amount of solute required increases, so the metal type of the metal hydroxide and its salt used is preferably selected from potassium, sodium, and lithium. In particular, taking cost into consideration, sodium hydroxide, sodium metasilicate, sodium carbonate, sodium phosphate, and sodium pyrophosphate are preferred, and an aqueous solution containing one or more selected from the above sodium compounds is preferred. An aqueous solution containing 0.5% by mass or more and 5% by mass or less of these components is more preferred. Alkaline washing has the effect of removing impurities from the surface of the copper member and cleaning it. It is preferable that the purity of these alkaline aqueous solutions is high. It is more preferable that the purity is 96% by mass or more. If the purity is less than 96% by mass, the impurities contained therein may adhere to the ceramic copper circuit board. The higher the purity, the fewer the impurities contained in the aqueous solution. Therefore, the higher the purity, the less impurities will adhere, which is preferable. Therefore, it is even more preferable that the purity is 98% by mass or more.

[0028] Benzotriazole compounds, which are often used in rust prevention treatments, have a lower polarity than water and dissolve in organic solvents. Therefore, alcohol cleaning may be used in the cleaning process after rust prevention treatment. Examples of alcohols include isopropanol, methanol, butanol, hexanol, and ethanol. For these alcohols, the purity of the benzotriazole-based compound excluding water and solvent components is preferably 99% by mass or more. If the purity of the alcohol used for alcohol cleaning excluding water and solvent components is less than 99% by mass, impurities contained therein may adhere to the ceramic copper circuit board. In addition, in the alcohol cleaning, two or more kinds of alcohols may be mixed. Furthermore, the alcohols may be mixed with water. When the alcohols are mixed with water, it is preferable that the quality of the water used meets JIS-K-0557 (1998). Benzene 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 the solvent, is 1 mass% or less. Here, taking into consideration the solubility and volatility of benzotriazole, ethanol or isopropanol is preferable. Isopropanol has a CAS registration number of 67-63-0 and an IUPAC name of 2-propanol. Isopropanol is also called IPA or isopropyl alcohol. Considering the cost, the cleaning method is preferably alkaline cleaning or water cleaning rather than alcohol cleaning, and a combination of multiple cleaning methods, such as alkaline cleaning followed by water cleaning, may be used.

[0029] By carrying out the above-mentioned cleaning process, the amount of nitrogen on the copper member surface can be reduced to 50 at % or less. The cleaning process is preferably carried out after each of the chemical polishing process, the etching process, and the rust-proofing process. The last cleaning process among the chemical polishing process, the etching process, and the rust-proofing process is carried out by the above-mentioned cleaning method, and cleaning after the other processes may be carried out by normal water cleaning. In this case, it is preferable to carry out the cleaning process after the last process for a longer time than the other cleaning processes. Each cleaning process may be either a batch type or a continuous type. The batch type is a method in which a cleaning process is carried out by storing a plurality of bonded bodies in a cleaning basket. The continuous type is a method in which a cleaning process is carried out while a plurality of bonded bodies are transported by a belt conveyer. As a cleaning method, a method using a chlorine-based cleaning agent may be used. The amount of chlorine on the copper plate surface may increase with a chlorine-based cleaning agent. Therefore, the chlorine-based cleaning agent is less preferable than the above-mentioned cleaning methods. Also, a cleaning process using water vapor or ozone water is not preferable because it may oxidize the copper plate. For this reason, one or more cleaning processes selected from water cleaning, alkali cleaning, and alcohol cleaning are preferable. By the above steps, a ceramic copper circuit board according to the embodiment in which the amount of nitrogen on the copper member surface is reduced can be manufactured.

[0030] Next, the drying process will be described. Examples of the drying process include treatment with a volatile solution, centrifugal force treatment, and air blowing treatment. A plurality of drying processes may be combined. The remaining water may be washed off from the ceramic copper circuit board after cleaning using a volatile solvent such as alcohols such as methanol, ethanol, and isopropanol, or ketones such as acetone. The purity of these solvents is preferably 99% by mass or more. If the purity is less than 99% by mass, the impurities contained therein may adhere to the ceramic copper circuit board. In this case, isopropanol is preferably used in consideration of safety aspects such as flammability. The remaining water droplets may be removed by rotating the ceramic copper circuit board after cleaning and using centrifugal force. The ceramic copper circuit board may be tilted. This tilt refers to a state in which, when any direction on a plane perpendicular to the direction of gravity is taken as the horizontal direction, the direction 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 taken as 90 degrees, it is more preferable that the angle between the horizontal direction and the direction of one or more sides of the board is 10 degrees or more and less than 90 degrees. It is more preferable that the diagonal line of the board is tilted. By tilting the board in this way, water droplets attached to the board are more likely to fall due to gravity. For example, a method of tilting the board may be to make the diagonal line of the board tilted. Dry air or nitrogen gas may be blown onto the ceramic copper circuit board that has been dried to some extent in this way to blow off any remaining water droplets. The method of blowing air, dry air, or nitrogen gas is sometimes called an air knife. This air knife is a type of air blower. In order to further ensure drying of the ceramic copper circuit board thus obtained, wind having a temperature of 10° C. or more and a humidity of 70% or less may be blown onto the ceramic copper circuit board at a wind speed of 20 m / s to 150 m / s. The drying process of blowing wind onto the ceramic copper circuit board in this manner is called air blowing. The preferred temperature of the wind in this air blowing process is 10° C. or more and 150° C. or less, more preferably 15° C. or more and less than 100° C. If the temperature exceeds this temperature, the surface of the conductor may be oxidized by heat. The preferred humidity in the air blowing process is 5% to 70%. If the humidity is more than 70%, the time required for the drying process may be longer. To reduce the humidity to less than 5%, the cost may increase. The wind speed is preferably 20 m / s to 150 m / s. The wind speed is more preferably 20 m / s to 100 m / s. If the wind speed is too low, it takes a long time to dry. If the wind speed is too high, it may have a negative effect on the transportation of the copper plate. When carrying out this drying process, by combining it with other drying processes, the drying time for applying hot air when using a hot air drying process can be shortened, and oxidation of the copper plate surface, which is the conductor, due to the heat of the hot air can be suppressed. For this reason, multiple drying processes may be combined.

[0031] (Example) (Examples 1 to 12, Comparative Examples 1 to 2) As an example of an insulating substrate, ceramic substrates (silicon nitride substrate and aluminum nitride substrate) were prepared. The silicon nitride substrates prepared had dimensions of 50 mm length x 40 mm width x 0.32 mm thickness. The thermal conductivity was 90 W / m K, and the three-point bending strength was 650 MPa. The aluminum nitride substrates prepared had dimensions of 50 mm length x 40 mm width x 0.635 mm thickness. The thermal conductivity was 170 W / m K, and the three-point bending strength was 400 MPa. A copper plate (oxygen-free copper plate) was prepared as an example of a conductor part. The size of the copper plate was 50 mm long x 40 mm wide. Next, the ceramic substrate and the copper plate were joined by an active metal joining method using an active metal brazing material containing Ti. 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 joining layer. By this process, joined bodies according to Examples 1 to 12 and Comparative Examples 1 and 2 were manufactured.

[0032] [Table 1]

[0033] Next, the bonded body was subjected to an etching process, a chemical polishing process, and a rust prevention process. As a result, a ceramic copper circuit board, which is an example of an insulating circuit board, was produced. The produced ceramic copper circuit board has a copper plate (copper circuit) with a circuit shape 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 each an example of a conductor part. An inclined shape was given to the side surfaces of the copper circuit and the copper plate. In addition, a bonding layer protruding part was provided in which the bonding layer protruded from the side surface of the copper plate. The ratio of the length to the thickness of the bonding layer protruding part was set to a range of 0.5 to 3.0. In addition, the surface roughness Ra of the copper circuit surface after etching was 1 μm or less. The etching and chemical polishing processes were carried out in the following order: copper plate etching process → chemical polishing process (first chemical polishing process) → etching process of the bonding layer mainly composed of Ag or Cu → chemical polishing process (second chemical polishing process) → etching process of the titanium nitride layer → rust prevention treatment process. The cleaning process after each process was carried out under the conditions shown in Table 2. In addition, in the cleaning process, in the case of water cleaning, the amount of water coming out of the nozzle was set to a 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 landing on the ceramic copper circuit board per nozzle was set to the amount of water shown in Table 2. In addition, the cleaning process in which the bonded body was immersed in a water cleaning tank was described as "immersion". When alkaline cleaning was used, it was described as "alkali". The drying process is as follows. In the drying process of the ceramic copper circuit board, in Examples 1 to 12 and Comparative Example 1, the drying process by air blowing was performed after the drying process by air knife. The temperature of the air knife and the air blowing was room temperature (near 25°C). Other conditions in the drying process were humidity of about 50% and wind speed of about 20 to 60 m / s. In Comparative Example 2, cleaning was performed under the same conditions as in Comparative Example 1, and then natural drying was performed. For examples in which rust prevention treatment was not performed, a "- (hyphen)" was entered in the column for cleaning after the rust prevention treatment process. In addition, the time required for drying was longer in Comparative Example 2 than in Comparative Example 1. It is considered that oxidation progressed because the time required for drying was long in this way.

[0034] [Table 2]

[0035] The nitrogen and oxygen amounts on the copper member surface of the ceramic copper circuit board were measured for the examples and comparative examples. XPS analysis was used to measure the nitrogen and oxygen amounts. An X-probe manufactured by SSI was used as the XPS analyzer. In the XPS analysis, AlKα radiation (hν=1486.6 eV) was used, and the X-ray spot diameter was set to a diameter of 1 mm. In the XPS analysis, the amounts of nitrogen, oxygen, copper, and carbon were analyzed. The amount of each component was calculated assuming that the total of nitrogen, oxygen, copper, and carbon was 100 at%. The measurement results of the nitrogen and oxygen amounts are shown in Table 3.

[0036] [Table 3]

[0037] The amounts of chloride ions, ammonium ions, sulfate ions, and fluorine ions present on the surface of the ceramic copper circuit board were measured for the examples and comparative examples. Ion chromatography analysis was used to measure the amounts of chloride ions, ammonium ions, sulfate ions, and fluorine ions. DX500 manufactured by Nippon Dionex Co., Ltd. was used as the ion chromatography 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 thermostatic chamber at 80°C for 18 hours to extract the ion components. After that, the solution was left to cool for about an hour, washed, and then sampled in an autosampling tube. Next, the measurement methods for anions and cations are shown. For anions (fluoride ions, chloride ions, sulfate ions, etc.), Thermo Scientific's Dionex Anion Standard (product number: 056933) was used as a calibration curve standard sample after diluting it 10-fold. As for the column, 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 (ammonium ions, etc.), Thermo Scientific's Dionex Cation-II Standard (product number: 046070) was used as a calibration curve standard sample after diluting 100 times. As for the column, IonPac CS 12A was used as a separation column, and IonPac CG 12A was used as a guard column. 20 ml of methanesulfonic acid was used as the eluent. In the ion chromatography analysis, measurements were taken using two ceramic copper circuit boards. The amount of ions obtained was divided by 2 to determine the amount of ion impurities per ceramic copper circuit board. In this case, values ​​recorded as 0 were below the detection limit. The surface area of ​​one ceramic copper circuit board was 40 cm 2 It was. The results of measuring the amount of each ion in the examples and comparative examples are shown in Table 4.

[0038] [Table 4]

[0039] As can be seen from Table 4, the nitrogen and oxygen amounts on the copper circuit surface were within the desired ranges for the ceramic copper circuit boards in Examples 1 to 12. The nitrogen and oxygen amounts on the back copper plate surface were also comparable. In the case of Comparative Example 1, the cleaning process of immersing in a water cleaning tank alone resulted in a high nitrogen content of 62 at %. In the case of Comparative Example 2, when natural drying was performed without any special drying process, the drying took a long time and the amount of oxygen attached during that time increased.

[0040] Next, a solder layer, which is an example of a bonding layer, was formed on the ceramic copper circuit board according to the embodiment and the comparative example, and a semiconductor element was mounted thereon. In this way, a semiconductor device was manufactured. The solder layer was made of lead-free solder. The reliability of the bonding of the semiconductor element to the semiconductor device was evaluated. In order to check the reliability of the bonding, a TCT test was conducted on the semiconductor device. In the TCT test, 500 cycles were conducted, with -40℃ x 30 minutes → room temperature x 10 minutes → 170℃ x 30 minutes → room temperature x 10 minutes. The bonding strength of the semiconductor element before the test and the bonding strength of the semiconductor element after the test were measured. The bonding strength was measured by a peel test. A semiconductor device with a decrease rate of bonding strength after the test of 10% or less compared to the bonding strength before the test was determined as the best product (◎). A semiconductor device with a decrease rate of more than 10% and less than 15% was determined as a good product 1 (〇). A semiconductor device with a decrease rate of more than 15% and less than 20% was determined as a good product 2 (●). A semiconductor device with a decrease rate of more than 20% and less than 25% was determined as a defective product 1 (×). A semiconductor device with a decrease rate of more than 25% was determined as a defective product 2 (XX). In addition, two semiconductor elements were bonded on a copper plate via a solder layer. A peel test was conducted on one of the semiconductor elements before the test, and a peel test was conducted on the other one after the test. From these results, the rate of decrease was calculated, and the results are shown in Table 5.

[0041] [Table 5]

[0042] As can be seen from Table 5, the reliability of the joint via the solder layer was improved in the ceramic copper circuit board according to the embodiment. In contrast, in Comparative Example 1, the reliability was reduced due to the large amount of nitrogen on the copper circuit surface. For this reason, it was found that controlling the amount of nitrogen and oxygen on the copper circuit surface is effective in improving the reliability of the joint. It is particularly effective for semiconductor devices in which semiconductor elements are mounted using a lead-free solder layer.

[0043] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples 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, modifications, etc. can be made without departing from the gist of the invention. Modifications of these embodiments are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, the above-mentioned embodiments can be implemented in combination with each other. [Explanation of symbols]

[0044] 1...Insulating circuit board 2...Insulating substrate 3...Conductor part (surface conductor part) 4...Conductor part (back conductor part) 5...Joining layer 6...Semiconductor element 7...Solder layer 10...Semiconductor device

Claims

1. A step of preparing a bonded body including 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; At least one of a first chemical polishing step of chemically polishing a 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 a rust prevention treatment step of performing a rust prevention treatment on the copper member; A method for producing an insulating circuit board comprising: performing a cleaning step of cleaning the bonded body at least one of 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; In at least one of the cleaning steps, cleaning water is supplied to the assembly using one or more nozzles, and the amount of water per nozzle is 0.01 L / min / cm ２ More than 0.1L / min / cm ２ It is set within the following range:

13. A method for producing an insulating circuit board, wherein, when an amount of nitrogen on a surface of the copper member in the produced insulating circuit board is analyzed by XPS, an average amount of the nitrogen at any three points is within a range of 0 at % or more and 50 at % or less.

2. 2. The method for producing an insulating circuit board according to claim 1, wherein the distance between the one or more nozzles and the bonded body is within a range of 5 cm to 40 cm.

3. 3. The method for producing an insulating circuit board according to claim 1, further comprising the step of: after said cleaning step, performing a drying step of blowing air at a speed of 20 m / s to 150 m / s on said bonded body.

4. 4. The method for producing an insulating circuit board according to claim 1, wherein the average oxygen amount at the three points is within a range of 3 at % or more and 50 at % or less in the XPS analysis.

5. 5. The method for producing an insulating circuit board according to claim 4, wherein the average value of the oxygen content is within a range of 3 at % to 30 at %.

6. 6. The method for producing an insulating circuit board according to claim 1, wherein the average nitrogen content is within a range of 0 at % to 30 at %.

7. 7. The method for producing an insulating circuit board according to claim 1, wherein the ceramic substrate contains one of silicon nitride and aluminum nitride as a main component.

8. 8. The method for producing an insulating circuit board according to claim 1, wherein a maximum height Rz of the copper member in the produced insulating circuit board is 20 [mu]m or less.

9. 9. The method for producing an insulating circuit board according to claim 1, wherein the surface roughness Ra of the copper member in the produced insulating circuit board is 2 [mu]m or less.

10. The ceramic substrate is a silicon nitride substrate having a thickness of 0.4 mm or less, 10. The method for producing an insulating circuit board according to claim 1, wherein the copper member has a thickness of 0.6 mm or more.

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