Ceramic scribed substrate, ceramic substrate, method for manufacturing ceramic scribed substrate, method for manufacturing ceramic substrate, method for manufacturing ceramic circuit board, and method for manufacturing semiconductor element

Abstract

A ceramic scribe substrate according to an embodiment comprises, on the surface side of a scribe line for forming a ceramic substrate, a continuous groove in which a plurality of grooves are connected by irradiating with a fiber laser, wherein the depth of the continuous groove is more than 50 [μm], and falls within the range of 0.15 times to 0.55 times the thickness of the ceramic substrate.

Description

[Technical Field]

[0001] The embodiments generally relate to a ceramic scribe substrate, a ceramic substrate, a method for manufacturing a ceramic scribe substrate, a method for manufacturing a ceramic substrate, a method for manufacturing a ceramic circuit board, and a method for manufacturing a semiconductor element. [Background technology]

[0002] In recent years, with the development of semiconductor elements that require large currents, such as power electronics and next-generation power semiconductors, the demand for ceramic substrates that combine heat dissipation and electrical insulation has been increasing year by year. In particular, as elements generate more heat due to miniaturization and higher performance, the thickness of ceramic substrates tends to become thinner in order to dissipate heat more efficiently.

[0003] On the other hand, in order to reduce the manufacturing cost of ceramic substrates, they are being manufactured in larger shapes. For silicon nitride substrates, which have high strength, high toughness, and high heat dissipation properties among ceramic substrates, substrates measuring 220 mm × 220 mm × 0.32 mm have been disclosed (Patent Document 1).

[0004] To reduce manufacturing costs, large silicon nitride substrates are manufactured and then divided into the product size required. How to One method disclosed is a method of producing multiple pieces by utilizing scribe lines formed by laser processing (Patent Document 2). According to Patent Document 2, when dividing the substrate into multiple pieces by laser processing, no more microcracks than necessary occur in the silicon nitride substrate, and scribe line processing for producing multiple pieces can be carried out easily and at low cost.

[0005] On the other hand, because the substrate before separation has become larger and thinner, issues that arise when laser processing silicon nitride substrates, which have high strength and toughness, have become apparent. For example, because silicon nitride substrates are so strong, a large force is required to break them along the scribe line, so the laser must be inserted deep into the silicon nitride substrate's thickness. However, when silicon nitride substrates are thin, there is a greater chance that they will be split by the forces applied during processing or transportation after the scribe line is formed with the laser. Conversely, if the laser is inserted shallowly into the silicon nitride substrate's thickness, there is a lower chance of them being split during the process, but a large force must be applied when breaking, which increases the workload and can cause chips and cracks on the periphery.

[0006] In other words, it is possible to form scribe lines on ceramic substrates using laser processing, but it was found that controlling the scribe line processing method is necessary to improve work efficiency after the scribe line is formed and to prevent chipping and cracking. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6399252 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-176119 Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, rising junction temperatures in power semiconductor chips have led to demand for higher reliability in circuit boards. This has led to demand for high-strength, thin ceramic circuit boards that combine heat dissipation and electrical insulation without sacrificing high reliability.

[0009] The embodiments solve such problems and relate to a ceramic substrate with excellent cost performance that enables efficient production of small substrates from a high-strength, thin, large ceramic substrate that combines heat dissipation and electrical insulation properties. [Means for solving the problem]

[0010] The ceramic scribe substrate according to the embodiment has a continuous groove on the surface side of the scribe line for forming the ceramic substrate, in which multiple grooves are connected by irradiating with a fiber laser, and the depth of the continuous groove is greater than 50 μm and is within the range of 0.15 to 0.55 times the thickness of the ceramic substrate. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a top view showing an example of a ceramic scribed substrate according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a scribed cross section of a ceramic scribed substrate according to an embodiment. [Figure 3] FIG. 3 is an enlarged partial cross-sectional view of part A in FIG. 2. [Figure 4] 1A and 1B are diagrams showing an example of a ceramic circuit substrate according to an embodiment. [Figure 5] FIG. 2 is a side view showing an example of a ceramic circuit board integrated by a resin mold according to an embodiment. Embodiment

[0012] Hereinafter, embodiments of a ceramic scribe substrate, a ceramic substrate, a method for manufacturing a ceramic scribe substrate, a method for manufacturing a ceramic substrate, a method for manufacturing a ceramic circuit board, and a method for manufacturing a semiconductor element will be described in detail with reference to the drawings.

[0013] The scribe lines provided on the ceramic scribe substrate according to the embodiment are used to form the ceramic substrate and refer to the scribe lines before and after dividing the ceramic substrate (hereinafter referred to as "scribe lines"). The scribe lines on the ceramic scribe substrate according to the embodiment have a continuous groove on the surface side, in which multiple grooves are connected, formed by irradiation with a laser, for example, a fiber laser, and are characterized in that the depth of the continuous groove is greater than 50 μm and is 0.15 to 0.55 times the thickness of the ceramic substrate. Furthermore, it is preferable that the scribe line further includes a group of discontinuous grooves, in which multiple grooves are not connected by irradiation with a fiber laser, on the deeper side of the scribe line. The ceramic scribe substrate, ceramic substrate, method for manufacturing a ceramic scribe substrate, method for manufacturing a ceramic substrate, method for manufacturing a ceramic circuit substrate, and method for manufacturing a semiconductor element according to the embodiment will be described in detail below.

[0014] A top view of an example of a ceramic substrate according to an embodiment is shown in Figure 1. Reference numeral 1 denotes a ceramic scribe substrate, 2 denotes a ceramic multi-piece substrate, 3 denotes a scribe line, 4 denotes individual ceramic substrates that will become products, and 5 denotes a peripheral portion that will not be used as a product.

[0015] The ceramic scribe substrate 1 includes a multi-piece ceramic substrate 2 that can be divided to obtain multiple ceramic substrates, and a single-piece ceramic substrate (not shown) that can be divided to obtain a single ceramic substrate. FIG. 1 shows an example of a multi-piece ceramic substrate 2 that can be laser scribed to obtain four ceramic substrates 4 (two in each direction) along six scribe lines 3 (three in each direction). The ceramic scribe substrate 1 is not limited to this multi-piece ceramic substrate 2. It may be a single-piece ceramic substrate having scribe lines that can process a single ceramic substrate into a product shape, or a multi-piece ceramic substrate having scribe lines that can produce multiple ceramic substrates in a number greater than two in each direction. Furthermore, it is not necessary to form scribe lines 3 all around the periphery of the ceramic substrate 4; one or more scribe lines 3 will suffice. Although the ceramic scribe substrate 1 in FIG. 1 has a rectangular shape in plan view, it may also have a substantially polygonal shape.

[0016] When the ceramic scribe substrate 1 is a silicon nitride substrate, it can have a high three-point bending strength of 600 MPa or more, or even 700 MPa or more. Furthermore, the thermal conductivity can be 50 W / m·K or more, or even 80 W / m·K or more. When the ceramic scribe substrate 1 is an aluminum nitride substrate, it can have a high thermal conductivity of 170 W / m·K or more, or even 230 W / m·K or more. Furthermore, the three-point bending strength can be 350 MPa or more, or even 450 MPa or more. In particular, silicon nitride substrates and aluminum nitride substrates that combine both high strength and high thermal conductivity have become available in recent years. It goes without saying that when the ceramic scribe substrate 1 is a silicon nitride substrate, the ceramic substrate 4 is also a silicon nitride substrate, and the three-point bending strength of the ceramic scribe substrate 1 is synonymous with the three-point bending strength of the ceramic substrate 4. These ceramic scribe substrates 1 may be single plates or may have a three-dimensional structure such as a multi-layer structure.

[0017] Scribe line 3 is a laser scribe line processed with a fiber laser. The fiber laser complies with the definition of fiber laser in JIS-Z 3001-5 (2013).

[0018] 2 shows an example of a scribed cross section of a ceramic scribe substrate 1 according to an embodiment. Reference numeral 6 denotes a laser-irradiated surface (front surface) which is the surface on which laser irradiation is performed, 7 denotes a continuous groove in which multiple grooves are connected on the front surface side by laser irradiation, 8 denotes a group of discontinuous grooves (multiple recesses) in which multiple grooves are not connected on the deeper side by laser irradiation, and 9 denotes a non-laser-irradiated surface (back surface) which is the side on which laser irradiation is not performed and is the surface opposite to the laser-irradiated surface 6. Note that the continuous groove 7 may be provided in the ceramic scribe substrate 1 so that a continuous groove 7 is provided on the front surface side of the scribe lines 3 on at least one side of the scribe lines 3 on four sides of the ceramic substrate 4 formed by the ceramic scribe substrate 1.

[0019] Figure 3 is an enlarged cross section of part A in Figure 2. T is the thickness of the ceramic scribe substrate 1, D1 is the distance from the surface of the ceramic scribe substrate 1 to the deepest part of the continuous groove 7 (the depth of the continuous groove 7), and D2 is the distance from the deepest part of the continuous groove 7 to the deepest part of the discontinuous groove group 8 (the depth of the discontinuous groove group 8). The thickness of the ceramic scribe substrate 1 is synonymous with the thickness of the ceramic substrate 4.

[0020] The depth D1 of the continuous groove 7 and the depth D2 of the discontinuous groove group 8 can be determined from the cross section of the ceramic substrate 4. The cross section of the ceramic substrate 4 after being divided along the scribe lines 3 is photographed using a microscope or a scanning electron microscope (SEM). In the enlarged photograph, a line is drawn parallel to the surface of the ceramic substrate 4 at the deepest part of the continuous groove 7 (the mountain portion sandwiched between adjacent grooves in the discontinuous groove group 8), and the distance from the surface of the ceramic substrate 4 to this deepest part is measured as the depth D1. Similarly, in the enlarged photograph, a line is drawn parallel to the surface of the image showing the ceramic substrate 4 at the deepest part of the discontinuous groove group 8, and the distance from the deepest part of the continuous groove 7 to the deepest part of the discontinuous groove group 8 is measured as the depth D2. In this way, the depths D1 and D2 can be easily obtained. The depth D1 of the continuous groove 7 may be measured based on the position of one peak in the discontinuous groove group 8, or may be measured based on the positions of a plurality of equally spaced peaks, for example, ten peaks, in the discontinuous groove group 8 and then the arithmetic average is calculated. Furthermore, the depth D2 of the discontinuous groove group 8 may be measured based on the depth of one groove in the discontinuous groove group 8, or may be measured based on the arithmetic average of the depths of a plurality of equally spaced peaks, for example, ten grooves, in the discontinuous groove group 8 and then the arithmetic average is calculated.

[0021] The depth D1 of the continuous groove 7 from the laser irradiated surface 6 is greater than 50 μm. The continuous groove 7 is formed to smoothly divide the high-strength ceramic scribe substrate 1. By making the depth of the continuous groove 7 greater than 50 μm, it becomes unnecessary to apply a large force when dividing the ceramic scribe substrate 1. Furthermore, the depth of the continuous groove 7 is preferably greater than 75 μm, and more preferably greater than 100 μm.

[0022] On the other hand, the depth D1 of the continuous groove 7 is 0.15 to 0.55 times the thickness T of the ceramic scribe substrate 1. If the depth D1 is less than 0.15 times the thickness T of the ceramic scribe substrate 1, a large force is applied during division, which makes it easy for defects such as cracks and fissures to occur at the divided portions of the ceramic substrate 4 after division. Furthermore, if the depth D1 exceeds 0.55 times the thickness T of the ceramic scribe substrate 1, the ceramic substrate 4 will be divided even with a small force applied in a post-process or during transportation, making stable production impossible. Furthermore, the depth D1 of the continuous groove 7 is preferably 0.2 to 0.5 times the thickness T of the ceramic scribe substrate 1, and more preferably 0.25 to 0.45 times the thickness T of the ceramic scribe substrate 1.

[0023] The depth D2 of the discontinuous groove group 8 formed deeper than the continuous groove 7 is 0 to 0.45 times the thickness of the ceramic scribe substrate 1. If the depth D2 exceeds 0.45 times the thickness T of the ceramic scribe substrate 1, the ceramic scribe substrate 1 will be divided even if a small force is applied in a post-process or during transportation, making stable production impossible. Furthermore, the depth D2 of the discontinuous groove group 8 is preferably 0.05 to 0.4 times the thickness T of the ceramic scribe substrate 1, and more preferably 0.1 to 0.35 times.

[0024] In Fig. 3, W indicates the width of the opening of the discontinuous groove group 8 (hereinafter referred to as "groove opening width"), and P indicates the distance between adjacent grooves (hereinafter referred to as "groove distance") in the discontinuous groove group 8. Note that in Fig. 3, the groove distance P of the discontinuous groove group 8 is measured as the distance between the deepest parts of adjacent grooves, but it is also possible to measure the distance between the shallowest parts of adjacent grooves. The groove opening width W and groove distance P are determined by measuring the groove distance P and groove opening width W between adjacent grooves at, for example, 10 points where the depth D2 is measured, and calculating the arithmetic mean.

[0025] The groove distance P of the discontinuous groove group 8 is 10 μm or more and 100 μm or less. If the groove distance P is greater than 100 μm, a large force is applied during division, which makes it easy for defects such as chips and cracks to occur at the divided portions of the ceramic substrate 4 after division. Furthermore, if the groove distance P is less than 10 μm, the substrate may be divided even with a small force applied during post-processing or transportation, making stable manufacturing impossible. Furthermore, the groove distance P of the discontinuous groove group 8 is preferably 20 μm or more and 90 μm or less, and more preferably 30 μm or more and 80 μm or less.

[0026] The groove opening width W of the discontinuous groove group 8 is 5 μm or more and 50 μm or less. If the groove opening width W is greater than 50 μm, a large force is applied during division, which makes it easy for defects such as chips and cracks to occur at the divided portions of the ceramic substrate 4 after division. Furthermore, if the groove opening width W is less than 5 μm, the substrate may be divided even with a small force applied during post-processing or transportation, making stable manufacturing impossible. Furthermore, the groove opening width W of the discontinuous groove group 8 is preferably 10 μm or more and 45 μm or less, and more preferably 15 μm or more and 40 μm or less.

[0027] The groove opening width W of the discontinuous groove group 8 is 5 μm or more and 50 μm or less. If the groove opening width W is greater than 50 μm, a large force is applied during division, which makes it easy for defects such as cracks or fissures to occur at the divided portions of the ceramic substrate 4 after division. Furthermore, if the groove opening width W is less than 5 μm, the substrate may be divided even with a small force applied during post-processing or transportation, making stable manufacturing impossible. Furthermore, the groove opening width W of the discontinuous groove group 8 is preferably 10 μm or more and 45 μm or less, and more preferably 15 μm or more and 40 μm or less.

[0028] Furthermore, it is preferable that the difference in brightness between the laser irradiation marks of the continuous groove 7 and the surface brightness of the ceramic scribe substrate 1 (groove brightness difference) be 5 or less. If an assist gas is not used during laser processing, the surface of the continuous groove 7 will turn black due to laser processing residue. The laser residue may be removed in a later process, but if it remains on the surface, it may peel off. Furthermore, if the laser output is increased without using an assist gas, the processing speed can be increased, but damage to the surface of the continuous groove 7 will be greater. For this reason, the smaller the difference in brightness between the laser irradiation marks of the continuous groove 7 and the surface brightness of the ceramic scribe substrate 1, the less damage will be caused to the ceramic substrate. Furthermore, the difference in brightness between the laser irradiation marks of the continuous groove 7 and the surface brightness of the ceramic substrate is preferably 4 or less, and more preferably 3 or less. The brightness is based on the definition in JIS Z8721 (1993).

[0029] A ceramic circuit substrate can be formed by bonding a metal circuit such as a metal plate to the ceramic substrate 4 after it has been divided by laser processing. Fig. 4 shows an example of a ceramic circuit substrate 10 according to an embodiment. In Fig. 4, 4 is the ceramic substrate, 6 is the laser irradiated surface, 9 is the laser non-irradiated surface, 10 is the ceramic circuit substrate, 11 is the metal circuit, and 12 is the metal heat sink. The metal heat sink 12 is bonded to the laser irradiated surface 6 of the ceramic substrate 4. Meanwhile, the metal circuit 11 is bonded to the laser non-irradiated surface 9 of the ceramic substrate 4.

[0030] Examples of metal plates used for the metal circuit 11 include copper (Cu), copper-based alloys, and aluminum (Al). The ceramic substrate (product portion) 4 and the metal circuit 11 are preferably bonded via a bonding layer (not shown in the figure). Furthermore, when a metal heat sink is bonded, bonding via a bonding layer is also preferable. Furthermore, a bonding layer is preferably provided between the ceramic substrate 4 and the metal circuit 11 using an active metal brazing material containing an active metal such as Ti (titanium). Examples of active metals include Ti and zirconium (Zr). Examples of active metal brazing materials include a mixture containing either Ag (silver) or Cu as a main component in addition to Ti. Furthermore, Ti is 0.1 wt% to 10 wt%, Cu is 10 wt% to 60 wt%, and Ag is the balance. Furthermore, if necessary, one or more selected from In (indium), Sn (tin), Al, Si (silicon), C (carbon), and Mg (magnesium) may be added in an amount of 1 wt%. ] The active metal brazing method uses an active metal brazing material to apply an active metal brazing material paste to the surface of the ceramic substrate 4, and then place the metal circuit 11 on top of it. This is then heated to a temperature of 600°C to 900°C to bond the substrate. The active metal brazing method can achieve a bonding strength of 16 kN / m or more between the ceramic substrate 4 and the metal circuit 11, which is a copper circuit plate.

[0031] Furthermore, a metal thin film containing one selected from Ni (nickel), Ag (silver), and Au (gold) as a main component may be provided on the surface of the metal circuit 11. Examples of such a metal thin film include a plated film and a sputtered film. By providing a metal thin film, corrosion resistance and solder wettability can be improved.

[0032] In FIG. 4, the metal circuit 11 is formed on the non-laser irradiated surface (non-laser processed surface) 9 opposite the laser irradiated surface 6 on which the scribe line 3 is formed, but it is also possible to form the metal circuit 11 on the laser irradiated surface 6. This is because the laser scribing of the present invention reduces damage caused by laser scribing and can alleviate stress. When the metal circuit 11 is formed on the laser irradiated surface 6, it is easy to align the circuit formation using the scribe line 3. Conversely, when a metal heat sink 12 is formed on the laser irradiated surface 6, the adhesion to the resin of the resin mold 16 is improved.

[0033] Such a ceramic circuit board 10 is suitable for a semiconductor module 13, which is characterized by mounting a semiconductor element on a metal circuit 11 via a bonding layer.

[0034] An example of a semiconductor module (semiconductor device) according to an embodiment is shown in Fig. 5. In Fig. 5, 10 is a ceramic circuit board, 13 is a semiconductor module, 14 is wire bonding, 15 is a semiconductor element, 16 is a resin mold, and 17 is a lead frame.

[0035] In FIG. 5, a semiconductor element 15 is bonded onto a metal circuit 11 of a ceramic circuit board 10 via a bonding layer (not shown). Similarly, a lead frame 17 is bonded via a bonding layer (not shown). Adjacent metal circuits 11 are electrically connected to each other via wire bonding 14. In FIG. 5, in addition to the semiconductor element 15, the wire bonding 14 is also bonded to the metal circuit 11. The ceramic circuit board 10 to which the wire bonding 14 is connected is integrated with a resin mold 16 to form a semiconductor module 13. The semiconductor module 13 is not limited to this structure. For example, either the wire bonding 14 or the lead frame 17 may be provided alone. Furthermore, a plurality of semiconductor elements 15, wire bonding 14, and lead frames 17 may be provided on the metal circuit 11.

[0036] The bonding layer for bonding the semiconductor element 15 and the lead frame 17 may be a solder or a brazing material. Lead-free solder is preferable. Solder refers to a material with a melting point of 450°C or less. Brazing material refers to a material with a melting point of more than 450°C. A material with a melting point of 500°C or more is called a high-temperature brazing material. An example of a high-temperature brazing material is one whose main component is Ag.

[0037] When sealing the entire ceramic circuit board 10 with resin mold 16, it is desirable that the scribed surface be on the opposite side to the metal circuit 11 (the heat sink side), as in the ceramic circuit board 10 shown in Figure 4. This is because resin does not easily penetrate into the discontinuous groove group 8 created by laser scribing, which may result in voids. Because voids hinder heat dissipation, the scribe lines 3 are formed on the metal heat sink 12 side to prevent their formation.

[0038] While semiconductor elements 15 continue to become smaller, the amount of heat generated by the chips continues to increase. Therefore, improving the heat dissipation performance of ceramic circuit substrates 10 on which semiconductor elements 15 are mounted is becoming increasingly important. Furthermore, to improve the performance of semiconductor modules 13, multiple semiconductor elements 15 are mounted on ceramic circuit substrates 10. If even a single semiconductor element 15 exceeds its intrinsic temperature, its resistance changes to a negative temperature coefficient. This can lead to thermal runaway, a phenomenon in which power flows intensively and can cause instantaneous breakdown. Therefore, improving heat dissipation performance is effective. Furthermore, semiconductor devices 13 can be used in PCUs, IGBTs, and IPM modules used in inverters for automobiles (including electric vehicles), electric railcars, industrial machinery, and air conditioners. Electric vehicles are becoming more common. Improving the reliability of semiconductor devices 13 directly contributes to the safety of automobiles. The same is true for electric railcars, industrial equipment, and other applications.

[0039] Next, we will explain the laser scribing method for a silicon nitride substrate, which is one of the ceramic scribe substrates 1 according to the embodiment. The manufacturing method for laser scribing a silicon nitride substrate is not particularly limited as long as it has the above-mentioned configuration, but the following methods can be mentioned as methods for obtaining a good yield.

[0040] First, a silicon nitride substrate is prepared. In particular, considering the heat dissipation properties of the entire ceramic circuit substrate 10 produced from the silicon nitride substrate, it is preferable that the silicon nitride substrate have a thermal conductivity of 50 [W / m K] or more and a three-point bending strength of 600 [MPa] or more.

[0041] Furthermore, when conducting electrical connection between the metal circuit 11 on the non-laser-irradiated surface 9 and the metal heat sink 12 on the laser-irradiated surface 6, a silicon nitride substrate with through holes is prepared. When providing through holes in the silicon nitride substrate, the through holes may be provided in advance at the stage of forming a molded body. Alternatively, a step of providing through holes in the silicon nitride sintered body may be performed. The step of providing through holes is performed by laser processing similar to laser scribing, cutting processing, or the like. Cutting processing is performed by drilling or the like.

[0042] The silicon nitride substrate is set on the precision processing table of a fiber laser processing machine. The silicon nitride substrate is irradiated with a fiber laser to form scribe lines 3 consisting of continuous grooves 7 and groups of discontinuous grooves 8. At this time, the continuous grooves 7 and groups of discontinuous grooves 8 of predetermined sizes are formed depending on the conditions of the fiber laser processing machine. In this case, after forming the continuous grooves 7 on the surface side of the silicon nitride substrate serving as the ceramic scribe substrate 1 with the fiber laser, the groups of discontinuous grooves 8 may be formed on the deeper side with the fiber laser.

[0043] Next, stress is applied to the silicon nitride substrate serving as the ceramic scribe substrate 1 to divide the ceramic scribe substrate 1 along the scribe lines 3, thereby producing one or more ceramic substrates 4.

[0044] Next, the metal circuit 11 is bonded to the silicon nitride substrate serving as the ceramic substrate 4 . The silicon nitride substrate and the metal circuit 11 are preferably bonded by an active metal bonding method. The active metal bonding method uses an active metal brazing material containing an active metal such as Ti. Examples of the active metal brazing material include a mixture of Ti, Ag, and Cu, with Ti at 0.1 wt% to 10 wt%, Cu at 10 wt% to 60 wt%, and Ag as the balance. If necessary, one or more elements selected from In, Sn, Al, Si, C, and Mg may be added in an amount of 1 wt% to 15 wt%.

[0045] The active metal brazing filler metal is made into a paste. The paste is a mixture of brazing filler metal components and organic matter, but the brazing filler metal components must be mixed evenly. This is because uneven distribution of the brazing filler metal components results in unstable brazing and poor joint performance.

[0046] Active metal brazing paste is applied to the ceramic substrate 4. A copper plate is placed on top of it. Next, the process of joining is performed by heating it at a temperature of 600°C to 900°C. The heating process is performed in a vacuum or a non-oxidizing atmosphere as necessary. When performing the heating process in a vacuum, the temperature is set to 1×10 -2 The pressure is preferably not more than [Pa]. Examples of the non-oxidizing atmosphere include a nitrogen atmosphere and an argon atmosphere. By using a vacuum or a non-oxidizing atmosphere, the bonding layer can be prevented from being oxidized, thereby improving the bonding strength.

[0047] The metal circuit 11 to be bonded may be either one that has been pre-patterned for circuit formation, or a single plate that has not been patterned. If a single plate is used, it is etched after bonding to form a pattern. In this case, the metal circuit 11 is formed on the side opposite to the side on which the scribe lines 3 are formed. This process allows the production of a silicon nitride metal circuit board as the ceramic circuit substrate 10.

[0048] Next, a process of bonding the semiconductor element 15 and the like is carried out. A bonding layer is provided at the location where the semiconductor element 15 is to be bonded. The bonding layer is preferably made of solder or brazing material. The bonding layer is provided, and the semiconductor element 15 is provided on top of it. If necessary, a lead frame 17 is bonded via the bonding layer. If necessary, wire bonding 14 is also provided. The required number of semiconductor elements 15, lead frames 17, and wire bonding 14 are provided. The silicon nitride circuit board with the semiconductor element 15, lead frame 17, and wire bonding 14 is integrated with a resin mold 16 to seal the interior.

[0049] In the above, it has been explained that the ceramic circuit substrate 10 is manufactured by bonding the metal circuit 11 and the like to the ceramic substrate 4 after separation from the ceramic scribe substrate 1, but the present invention is not limited to this case. For example, the ceramic circuit substrate 10 may be manufactured by bonding the metal circuit 11 and the like to the ceramic substrate 4 before separation within the ceramic scribe substrate, and then applying stress to the ceramic scribe substrate 1 with the bonded metal circuit 11 and the like to separate it along the scribe line 3 (results of Examples and Comparative Examples described later in Table 2). In other words, the order of the step of separating the ceramic scribe substrate 1 and the step of bonding the metal circuit 11 and the like does not matter.

[0050] A method for laser scribing an aluminum nitride substrate, one of the ceramic scribe substrates 1 according to the embodiment, will be described. First, an aluminum nitride substrate is prepared. In particular, considering the heat dissipation of the entire circuit board, it is preferable that the substrate have a thermal conductivity of 170 [W / m K] or more and a three-point bending strength of 350 [MPa] or more. There are no particular limitations on the manufacturing method for laser scribing an aluminum nitride substrate as long as it has the above-mentioned configuration, but to obtain a high yield, the same manufacturing process as for the silicon nitride substrate and silicon nitride circuit board described above will be used.

[0051] (Examples 1 to 32, Comparative Examples 1 to 20) The ceramic scribe substrates were silicon nitride substrates (thermal conductivity 90 W / m K, three-point bending strength 650 MPa) measuring 40 mm x 50 mm and with thicknesses of 0.32 mm and 0.50 mm, respectively.Also, aluminum nitride substrates (thermal conductivity 170 W / m K, three-point bending strength 400 MPa) measuring 40 mm x 50 mm and with thicknesses of 0.635 mm and 0.80 mm were prepared.

[0052] Next, as shown in Figure 1, a fiber laser was used to laser-process the surface side of the scribed ceramic substrate under each of the conditions of Examples 1 to 32 and Comparative Examples 1 to 20, with six laser lines per scribed ceramic substrate, for a total of 101 substrates. One of the scribed ceramic substrates after laser processing under each condition was divided, and the vicinity of the center of the cross section of the divided ceramic substrate (at a position approximately 10 mm from the edge) was observed and photographed using an SEM at 100x magnification. Lines were drawn on the surface of the ceramic substrate, at the deepest part of the continuous groove, and at the deepest part of the discontinuous groove group, and the depth D1 of the continuous groove and the depth D2 of the discontinuous groove group were determined.

[0053] In addition, the groove distance P and groove opening width W of the discontinuous groove group were measured by comparing adjacent discontinuous grooves at 10 consecutive points in the photograph. group The groove distance P and groove opening width W were measured and calculated as an arithmetic average. In Comparative Examples 7 and 16, processing was performed without using an assist gas. The measurement results for the examples and comparative examples are shown in Table 1 (in Table 1, silicon nitride substrates are represented as Si3N4 and aluminum nitride substrates are represented as AlN).

[0054] [Table 1] TIFF0007790836000001.tif246170TIFF0007790836000002.tif104170

[0055] As can be seen from Table 1, the values ​​of the continuous groove depth D1, discontinuous groove group depth D2, continuous groove depth / substrate thickness (D1 / T), discontinuous groove group depth / substrate thickness (D2 / T), groove spacing P, and groove opening width W of the ceramic scribe substrate were within the preferred ranges in Examples and Comparative Examples 16 to 20. On the other hand, in Comparative Examples 1 to 15, these values ​​were outside the preferred ranges.

[0056] Next, the surface of the ceramic scribed substrate and the continuous grooves were divided under each condition and observed by SEM photograph, and the difference in brightness was measured using a micro-surface spectrocolorimeter to determine the difference.

[0057] In addition, copper plates were bonded to both sides of the ceramic scribed substrates produced in the examples and comparative examples before separation using an active metal bonding method. The copper plates were oxygen-free copper plates measuring 40 mm long x 50 mm wide x 0.5 mm thick. The active metal brazing material used in the active metal bonding method was an active metal paste made by mixing 2 wt% Ti, 10 wt% Sn, 30 wt% Cu, and the remainder Ag with an organic component.

[0058] Using a semi-automatic screen printer, an active metal paste was printed on the scribed surface of the ceramic scribe substrate using a 320 x 320 mm, 250 mesh, stainless V screen mesh, and then dried. Subsequently, it was printed and dried on the non-laser irradiated surface. At this time, if the ceramic substrate was separated from the scribe line by the pressure of the printer's squeegee, it was counted as a printing defect and was not sent on to the subsequent process.

[0059] Copper plates were placed on both the top and bottom of the ceramic substrate on which the paste had been printed and dried. board The thermal bonding process was carried out by placing a weight on top of the jig and clamping the pieces. The bonding temperature was 810°C, the bonding time was 10 minutes, and the bonding was carried out in a vacuum (1 × 10 -2 The test was performed at 1000 kJ / s (below [Pa]).

[0060] After heat bonding, the copper plates were etched to form a circuit. The front copper plate had three circuit patterns, and the back copper plate was also etched to form a pull-back around the perimeter.

[0061] The etched ceramic substrate was scribed using an automatic substrate dividing machine to obtain a ceramic circuit substrate. That is, a metal circuit or the like was bonded to the ceramic substrate before division among the ceramic scribed substrates according to the examples and comparative examples, and stress was applied to the ceramic scribed substrate with the metal circuit or the like bonded to divide it along the scribe lines to produce a ceramic substrate circuit. The appearance of the ceramic circuit substrate was inspected, and any remaining cracks or chips or cracks occurring around the periphery of the substrate were counted as scribe defects and were not passed on to subsequent processes.

[0062] A semiconductor element was mounted on the central circuit portion of the ceramic circuit board manufactured from the ceramic scribed substrate according to the example and comparative example. Then, wire bonding was performed. After that, the substrate was integrated with a resin mold by a transfer molding method.

[0063] Next, for the ceramic circuit substrates manufactured from the ceramic scribed substrates according to the examples and comparative examples, the porosity between the resin and the ceramic circuit substrate was evaluated by ultrasonic testing (SAT) around the circuit side of the substrate where the semiconductor element was bonded. The porosity [%] was calculated as (total length of the part where the resin was not in close contact with the ceramic substrate and voids existed / perimeter length of the ceramic substrate) × 100, and a porosity of less than 95 [%] was considered to be a resin peeling defect.

[0064] The results obtained for the Examples and Comparative Examples are shown in Table 2. Note that the scribe defect rate [%] and resin peeling defect [%] exclude defects that occurred in the previous process, and were calculated as the defect rate per 100 products.

[0065] [Table 2] TIFF0007790836000003.tif245170TIFF0007790836000004.tif88170

[0066] As can be seen from Table 2, the difference in groove lightness and the orientation of the scribed surface of the ceramic circuit boards manufactured from the ceramic scribed substrates according to the example and comparative examples 1 to 15 were within the preferred ranges. On the other hand, the ceramic circuit boards manufactured from the ceramic scribed substrates according to comparative examples 16 to 18 were outside the preferred ranges.

[0067] Furthermore, ceramic circuit boards manufactured from the ceramic scribed substrates according to the examples either did not have paste printing defects or had a low defect rate. This is because laser scribes that could withstand the pressure applied to the surface of the ceramic scribed substrate during paste printing were formed. In contrast, many cracking defects occurred in the comparative examples. This is because the laser scribes were too large to withstand the pressure during paste printing.

[0068] Furthermore, ceramic circuit boards manufactured from the ceramic scribed substrates according to the examples did not experience any scribe defects or had a low defect rate. This is because laser scribes were formed that allowed the ceramic scribed substrate to be divided at a constant scribe load. In contrast, many scribe defects occurred in the comparative examples. This is because the laser scribes were not sufficiently formed, making it impossible to divide the substrate along the line at a constant scribe load, which resulted in chipping or cracking.

[0069] Furthermore, the ceramic circuit boards manufactured from the ceramic scribed substrates according to the examples either did not experience resin peeling defects or had a low defect rate. This is because there were no residues from laser processing by laser scribing or traces of continuous grooves and discontinuous groove groups in the resin-molded areas, so no non-bonding due to laser residues or voids due to traces of continuous grooves and discontinuous groove groups occurred. In contrast, many resin peeling defects occurred in the ceramic circuit boards manufactured from the ceramic scribed substrates according to the comparative examples. This is because non-bonding due to laser residues and voids due to continuous grooves and discontinuous groove groups were the causes of the peeling defects.

[0070] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other.

Claims

1. A continuous groove in which multiple grooves are connected by irradiating a fiber laser is provided on the surface side of the scribe line that forms the silicon nitride substrate as a ceramic substrate, A group of discontinuous grooves, each of which is not connected to the other, is formed by irradiating a fiber laser on the deep side of the scribe line, the depth of the continuous groove is greater than 50 μm and is in the range of more than 0.17 times and not more than 0.55 times the thickness of the silicon nitride substrate; the depth of the discontinuous groove group is in the range of more than 0 to 0.45 times the thickness of the silicon nitride substrate, the distance between adjacent grooves in the discontinuous groove group is in the range of 10 μm to 100 μm, the width of each groove of the discontinuous groove group is in the range of 5 μm to 50 μm, A ceramic scribe substrate having a three-point bending strength of 600 MPa or more.

2. 2. The ceramic scribe substrate according to claim 1, wherein the difference in brightness between the laser irradiation marks of the continuous groove and the surface of the silicon nitride substrate is 5 or less.

3. a continuous groove formed by irradiating a fiber laser on the surface side of the scribe line on at least one of the four sides; A group of discontinuous grooves, each of which is not connected to the other, is formed by irradiating a fiber laser on the deep side of the scribe line, the depth of the continuous groove is greater than 50 μm and is in the range of more than 0.17 times and not more than 0.55 times the thickness of the silicon nitride substrate serving as the ceramic substrate; the depth of the discontinuous groove group is in the range of more than 0 to 0.45 times the thickness of the silicon nitride substrate, the distance between adjacent grooves in the discontinuous groove group is in the range of 10 μm to 100 μm, the width of each groove of the discontinuous groove group is in the range of 5 μm to 50 μm, A ceramic substrate having a three-point bending strength of 600 MPa or more.

4. 3. A method for manufacturing a ceramic scribe substrate, characterized in that the ceramic scribe substrate according to claim 1 or 2 is manufactured by forming the continuous groove on the surface side with a fiber laser, and then forming the group of discontinuous grooves on the deeper side with a fiber laser.

5. 3. A method for manufacturing a ceramic substrate, comprising applying stress to the ceramic scribed substrate according to claim 1 to divide it along the scribe lines, thereby manufacturing the silicon nitride substrate.

6. The method for manufacturing the ceramic substrate according to claim 5, A method for producing a ceramic circuit board, characterized in that a ceramic circuit board is produced by joining a metal circuit to the silicon nitride substrate.

7. A metal circuit is bonded to the ceramic scribe substrate according to any one of claims 1 and 2, A method for manufacturing a ceramic circuit substrate, comprising applying stress to the ceramic scribe substrate to which the metal circuit is bonded, thereby dividing the ceramic circuit substrate along the scribe lines.

8. 8. The method for manufacturing a ceramic circuit board according to claim 6, wherein the metal circuit is bonded to a surface of the silicon nitride substrate opposite to a surface on which the scribe lines are formed.

9. The method for manufacturing a ceramic circuit board according to any one of claims 6 to 8, A method for manufacturing a semiconductor device, comprising mounting a semiconductor element on the ceramic circuit substrate.

10. 10. The method for manufacturing a semiconductor device according to claim 9, wherein the silicon nitride substrate, the metal circuit, and the semiconductor element are integrated by a resin mold.

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