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

Abstract

To provide a ceramic scribe substrate that enables efficient production of small substrates from a high-strength, thin, large ceramic substrate that combines heat dissipation and electrical insulation properties.SOLUTION: A ceramic scribe substrate 4 according to an embodiment includes a continuous groove 7 in which multiple grooves are connected by irradiating with a fiber laser from a laser irradiation surface 6 on the surface side of a scribe line for forming a ceramic substrate, 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.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The embodiments generally relate to a ceramic scribed substrate, a ceramic substrate, a method for manufacturing a ceramic scribed substrate, a method for manufacturing a ceramic substrate, a method for manufacturing a ceramic circuit substrate, 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 is increasing year by year. In particular, as the heat generated by elements increases with miniaturization and higher performance, there is a trend for the thickness of ceramic substrates 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 x 220 mm x 0.32 mm have been disclosed (Patent Document 1).

[0004] As one method for dividing a silicon nitride substrate, which has been manufactured large in order to reduce manufacturing costs, into the product size to be used, a method for dividing the substrate into multiple pieces using scribe lines formed by laser processing has been disclosed (Patent Document 2). According to Patent Document 2, when dividing the substrate into multiple pieces by laser processing, no more microcracks than necessary are generated in the silicon nitride substrate, and scribe line processing for dividing the substrate into multiple pieces can be performed easily and at low cost.

[0005] On the other hand, problems that arise when laser processing silicon nitride substrates, which have high strength and toughness, have become clear because the substrate before division has become large and thin. For example, because silicon nitride substrates have high strength, a large force is required to break along the scribe line, so the laser needs to be inserted deep in the thickness direction of the silicon nitride substrate. However, if the silicon nitride substrate is thin, there is a high possibility that it will be divided by the force applied during the processing process after the scribe line is formed by the laser or during transportation. Conversely, if the laser is inserted shallowly in the thickness direction of the silicon nitride substrate, the possibility of it being divided during the intermediate process is low, but it is necessary to apply a large force when breaking, which creates a burden on the work, and it was found that applying a large force causes chips and cracks on the outer periphery.

[0006] In other words, it is possible to form scribe lines on ceramic substrates by laser processing, but it was found that control of the scribe line processing method is necessary to improve work efficiency after the scribe line is formed and to prevent the occurrence of chips and cracks. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6399252 [Patent Document 2] JP 2002-176119 A Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, the rise in junction temperatures of power semiconductor chips has created a demand for highly reliable circuit boards, which in turn has led to a demand for thin, high-strength ceramic circuit boards that combine heat dissipation and electrical insulation without sacrificing high reliability.

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

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

[0011] [Figure 1] FIG. 2 is a top view showing an example of a ceramic scribed substrate according to the embodiment. [Diagram 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. [Diagram 3] FIG. 3 is an enlarged partial cross-sectional view of part A in FIG. 2. [Figure 4] FIG. 1 is a diagram showing an example of a ceramic circuit board according to an embodiment. [Diagram 5] FIG. 2 is a side view showing an example of a ceramic circuit board integrated by a resin mold according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of a ceramic scribed substrate, a ceramic substrate, a method for manufacturing a ceramic scribed substrate, a method for manufacturing a ceramic substrate, a method for manufacturing a ceramic circuit substrate, 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 for forming the ceramic substrate, and refer to the scribe lines before and after the ceramic substrate is divided (hereinafter referred to as "scribe lines"). The scribe lines of the ceramic scribe substrate according to the embodiment have a continuous groove on the surface side where a plurality of grooves are connected 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 deep side of the scribe line further includes a non-continuous groove group where a plurality of grooves are not connected by irradiation with a fiber laser. Hereinafter, the ceramic scribe substrate, ceramic substrate, manufacturing method of the ceramic scribe substrate, manufacturing method of the ceramic substrate, manufacturing method of the ceramic circuit substrate, and manufacturing method of the semiconductor element according to the embodiment will be described in detail.

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

[0015] The ceramic scribed substrate 1 includes a ceramic multi-piece substrate 2 from which a plurality of ceramic substrates can be obtained by division, and a ceramic single-piece substrate (not shown) from which one ceramic substrate can be obtained by division. FIG. 1 shows an example of a ceramic multi-piece substrate 2 from which a total of four ceramic substrates 4, two in each direction, can be obtained by laser scribing along six scribe lines 3, three in each direction. The ceramic scribed substrate 1 is not limited to such a ceramic multi-piece substrate 2, but may be a ceramic single-piece substrate having scribe lines capable of processing one ceramic substrate into a product shape, or may be a ceramic multi-piece substrate having scribe lines capable of obtaining a number of substrates exceeding two in each direction. In addition, it is not necessary to form scribe lines 3 all around the periphery of the ceramic substrate 4, and it is sufficient that there is one or more scribe lines 3. In addition, the ceramic scribed substrate 1 has a rectangular shape in a plan view in FIG. 1, but may have a substantially polygonal shape.

[0016] When the ceramic scribe substrate 1 is a silicon nitride substrate, the three-point bending strength can be as high as 600 [MPa] or more, or even 700 [MPa] or more. In addition, the thermal conductivity can be as high as 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, the thermal conductivity can be as high as 170 [W / m·K] or more, or even 230 [W / m·K] or more. In addition, the three-point bending strength can be as high as 350 [MPa] or more, or even 450 [MPa] or more. In particular, in recent years, there are silicon nitride substrates and aluminum nitride substrates that have both high strength and high thermal conductivity. In addition, when the ceramic scribe substrate 1 is a silicon nitride substrate, it goes without saying that 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. The ceramic scribe substrate 1 may be a single plate, 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 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. 6 is a laser irradiated surface (front surface) which is the surface on which the laser is irradiated, 7 is a continuous groove in which a plurality of grooves are connected on the front surface side by laser irradiation, 8 is a discontinuous groove group (a plurality of recesses) in which a plurality of grooves are not connected on the deep side by laser irradiation, and 9 is a non-laser irradiated surface (rear surface) which is the side on which the laser is not irradiated and is the surface opposite to the laser irradiated surface 6. The continuous groove 7 may be provided in the ceramic scribe substrate 1 so that the 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 the four sides of the ceramic substrate 4 formed by the ceramic scribe substrate 1.

[0019] Fig. 3 is an enlarged cross section of part A in Fig. 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 obtained 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 part sandwiched between adjacent grooves in the discontinuous groove group 8), and the distance from the surface of the ceramic substrate 4 to the 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. This makes it possible to easily obtain the depths D1 and D2. 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 and the arithmetic average taken based on the positions of a plurality, for example 10 peaks, spaced at equal intervals in the discontinuous groove group 8. In addition, in the case of the depth D2 of the discontinuous groove group 8, the depth of one groove in the discontinuous groove group 8 may be measured, or may be measured and the arithmetic average taken of the depths of a plurality, for example 10 grooves, spaced at equal intervals in the discontinuous groove group 8.

[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 in order 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 times or more and 0.55 times or less the thickness T of the ceramic scribe substrate 1. If the depth D1 is smaller than 0.15 times the thickness T of the ceramic scribe substrate 1, a large force is applied during division, and defects such as cracks or fissures are likely to occur at the divided portions of the ceramic substrate 4 after division. In addition, 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 if only a small force is applied during a post-process or during transportation, and stable manufacturing cannot be performed. Furthermore, the depth D1 of the continuous groove 7 is preferably 0.2 times or more and 0.5 times or less the thickness T of the ceramic scribe substrate 1, and more preferably 0.25 times or more and 0.45 times or less.

[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 when a small force is applied during post-processing or 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 in the discontinuous groove group 8 (hereinafter referred to as "groove distance"). 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 for, for example, 10 points where the above-mentioned depth D2 is measured, and taking the arithmetic average.

[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, and defects such as chips and cracks are likely to occur at the divided portions of the ceramic substrate 4 after division. In addition, if the groove distance P is less than 10 μm, the ceramic substrate 4 will be divided by only a small force applied during post-processing or transportation, and stable manufacturing will not be possible. 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, and defects such as chips and cracks are likely to occur at the divided portions of the ceramic substrate 4 after division. In addition, if the groove opening width W is less than 5 μm, the ceramic substrate 4 will be divided even if only a small force is applied during post-processing or transportation, and stable manufacturing cannot be achieved. 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, and defects such as cracks or fissures are likely to occur at the division points of the ceramic substrate 4 after division. In addition, if the groove opening width W is less than 5 μm, the ceramic substrate 4 will be divided by only a small force applied during post-processing or transportation, and stable manufacturing will not be possible. 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 between the brightness of the laser irradiation mark of the continuous groove 7 and the brightness of the surface of the ceramic scribe substrate 1 (difference in groove brightness) is 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 the residue of the laser processing. The laser residue may be removed in a later process, but if it remains on the surface, it may peel off. In addition, if the laser output is increased without using an assist gas, the processing speed can be increased, but the damage to the surface of the continuous groove 7 will be greater. For this reason, the smaller the difference between the brightness of the laser irradiation mark of the continuous groove 7 and the brightness of the surface of the ceramic scribe substrate 1, the less damage will be caused to the ceramic substrate. Furthermore, the difference between the brightness of the laser irradiation mark of the continuous groove 7 and the brightness of the surface of the ceramic substrate is preferably 4 or less, more preferably 3 or less. The brightness is based on the definition in JIS Z8721 (1993).

[0029] A ceramic circuit board 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 board 10 according to an embodiment. In Fig. 4, 4 is a ceramic substrate, 6 is a laser irradiated surface, 9 is a laser non-irradiated surface, 10 is a ceramic circuit board, 11 is a metal circuit, and 12 is a metal heat sink. A metal heat sink 12 is bonded to the laser irradiated surface 6 of the ceramic substrate 4. Meanwhile, a metal circuit 11 is bonded to the laser non-irradiated surface 9 of the ceramic substrate 4.

[0030] Examples of the metal plate used for the metal circuit 11 include copper (Cu), copper-based alloy, and aluminum (Al). The ceramic substrate (product part) 4 and the metal circuit 11 are preferably bonded via a bonding layer (not shown in the figure). In addition, when a metal heat sink is bonded, it is also preferable to bond them via a bonding layer. In addition, it is preferable to provide a bonding layer between the ceramic substrate 4 and the metal circuit 11 using an active metal brazing material containing an active metal such as Ti (titanium). In addition to Ti, an example of the active metal is Zr (zirconium). In addition to Ti, an example of the active metal brazing material is a mixture containing either Ag (silver) or Cu as a main component. In addition, Ti is 0.1 [wt%] to 10 [wt%], Cu is 10 [wt%] to 60 [wt%], and Ag is the balance. If necessary, one or more selected from In (indium), Sn (tin), Al, Si (silicon), C (carbon), and Mg (magnesium) may be added at 1 [wt%] to 15 [wt%]. In the active metal bonding method using an active metal brazing material, an active metal brazing material paste is applied to the surface of the ceramic substrate 4, and the metal circuit 11 is placed on top of it. This is heated to 600 [°C] to 900 [°C] to bond them. According to the active metal bonding method, the bonding strength between the ceramic substrate 4 and the metal circuit 11, which is a copper circuit plate, can be 16 [kN / m] or more.

[0031] Also, a metal thin film mainly composed of one selected from Ni (nickel), Ag (silver), and Au (gold) 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 to 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 causes less damage during laser scribing and can alleviate stress. When the metal circuit 11 is formed on the laser irradiated surface 6, it is easy to use the scribe line 3 to align the circuit formation. 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 that is characterized in that a semiconductor element is mounted on the 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, wire bonding 14 and metal circuit 11 are bonded. 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 such a structure. For example, either the wire bonding 14 or the lead frame 17 may be provided. Also, 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. The solder is preferably lead-free. The solder has a melting point of 450°C or less. The brazing material has a melting point of more than 450°C. The material with a melting point of 500°C or more is called a high-temperature brazing material. The high-temperature brazing material may be 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 Fig. 4. This is because resin is unlikely to penetrate into the discontinuous groove group 8 created by laser scribing, and there is a possibility that voids will form. Since voids hinder heat dissipation, the scribe lines 3 are formed on the metal heat sink 12 side to prevent their formation.

[0038] While the semiconductor element 15 is becoming smaller, the amount of heat generated from the chip is constantly increasing. Therefore, it is important to improve the heat dissipation of the ceramic circuit board 10 on which the semiconductor element 15 is mounted. In addition, in order to improve the performance of the semiconductor module 13, a plurality of semiconductor elements 15 are mounted on the ceramic circuit board 10. If even one semiconductor element 15 exceeds the intrinsic temperature of the element, the resistance changes to a negative temperature coefficient. As a result, a phenomenon occurs in which thermal runaway occurs in which power flows intensively and is instantly destroyed. Therefore, it is effective to improve the heat dissipation. In addition, the semiconductor device 13 can be used in PCUs, IGBTs, and IPM modules used in inverters for automobiles (including electric vehicles), electric railway vehicles, industrial machinery, and air conditioners. Automobiles are becoming more and more electric. Improving the reliability of the semiconductor device 13 directly leads to the safety of automobiles. The same is true for electric railways, industrial equipment, and the like.

[0039] Next, a method for laser scribing a silicon nitride substrate among the ceramic scribed substrates 1 according to the embodiment will be described. The method for laser scribing a silicon nitride substrate is not particularly limited as long as it has the above-mentioned configuration, but the following method can be mentioned as a method for obtaining a high yield.

[0040] First, a silicon nitride substrate is prepared. In particular, taking into consideration 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 has 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 between the metal circuit 11 on the laser non-irradiated surface 9 and the metal heat sink 12 on the laser irradiated surface 6, a silicon nitride substrate having through holes is prepared. When providing the through holes in the silicon nitride substrate, the through holes may be provided in advance at the stage of forming a molded body. Also, a step of providing the through holes in the silicon nitride sintered body may be performed. The step of providing the through holes is performed by laser processing similar to laser scribing, cutting processing, or the like. The cutting processing is performed by drilling with a drill or the like.

[0042] The silicon nitride substrate is set on the precision machining table of a fiber laser processing machine. The silicon nitride substrate is irradiated with a fiber laser to form scribe lines 3 consisting of a continuous groove 7 and a group of discontinuous grooves 8. At this time, the continuous groove 7 and the group of discontinuous grooves 8 of a predetermined size are formed according to the conditions of the fiber laser processing machine. At this time, the continuous groove 7 is formed on the surface side of the silicon nitride substrate as the ceramic scribe substrate 1 by the fiber laser, and then the group of discontinuous grooves 8 is formed on the deeper side by the fiber laser.

[0043] Next, a 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 a plurality of 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 mixed with an active metal such as Ti. The active metal brazing material may be a mixture of Ti, Ag, and Cu, for example, Ti is 0.1 wt% to 10 wt%, Cu is 10 wt% to 60 wt%, and Ag is the balance. If necessary, one or more 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 material is made into a paste. The paste is a mixture of brazing material components and organic matter, but the brazing material components must be mixed evenly. This is because if the brazing material components are not distributed evenly, brazing will be unstable and this can cause poor joints.

[0046] The active metal brazing paste is applied to the ceramic substrate 4. A copper plate is placed on top of the active metal brazing paste. Next, the process of bonding is performed by heating the substrate at a temperature between 600°C and 900°C. The heating process is performed in a vacuum or in a non-oxidizing atmosphere as necessary. When performing the heating process in a vacuum, the temperature is set at 1×10 -2 The pressure in the atmosphere is preferably not more than [Pa]. Examples of the non-oxidizing atmosphere include a nitrogen atmosphere and an argon atmosphere. By performing the bonding in a vacuum or in 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 processed into a pattern shape in advance for circuit formation, or a single plate that has not been patterned. If a single plate is used, it is etched after bonding to process it into a pattern shape. At this time, the metal circuit 11 is formed on the side opposite to the side on which the scribe lines 3 are formed. By this process, a silicon nitride metal circuit board can be manufactured as the ceramic circuit board 10.

[0048] Next, a process of bonding the semiconductor element 15 and the like is performed. A bonding layer is provided at the location where the semiconductor element 15 is to be bonded. The bonding layer is preferably a solder or brazing material. The bonding layer is provided, and the semiconductor element 15 is provided thereon. If necessary, the lead frame 17 is bonded via the bonding layer. If necessary, wire bonding 14 is 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 inside.

[0049] In the above, the ceramic circuit board 10 has been described as being manufactured by bonding the metal circuit 11, etc. 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 board 10 may be manufactured by bonding the metal circuit 11, etc. to the ceramic substrate 4 before separation in the ceramic scribe substrate, and applying stress to the ceramic scribe substrate 1 with the bonded metal circuit 11, etc., to separate it along the scribe line 3 (results of the 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, etc. does not matter.

[0050] A method for laser scribing an aluminum nitride substrate from among 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 substrate, it is preferable that the thermal conductivity is 170 [W / m·K] or more and the three-point bending strength is 350 [MPa] or more. The manufacturing method for laser scribing an aluminum nitride substrate is not particularly limited as long as it has the above-mentioned configuration, but in order to obtain a high yield, the same manufacturing process as that for the silicon nitride substrate and silicon nitride circuit substrate described above is adopted.

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

[0052] Next, as shown in Fig. 1, 101 ceramic scribed substrates were laser processed with six lines per substrate under each of the conditions of Examples 1 to 32 and Comparative Examples 1 to 20 using an assist gas with a fiber laser on the surface side of the ceramic scribed substrate. One of the ceramic scribed 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 about 10 mm from the end) was observed and photographed with a SEM at a magnification of 100 times. Lines were drawn on the surface of the ceramic substrate, the deepest part of the continuous groove, and 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] The groove distance P and groove opening width W of the discontinuous groove group were determined by measuring the groove distance P and groove opening width W of adjacent discontinuous groove groups at 10 consecutive points on the photograph and calculating the arithmetic average. In Comparative Example 7 and Comparative Example 16, processing was performed without using an assist gas. The measurement results of the examples and comparative examples are shown in Table 1 (in Table 1, the silicon nitride substrate is represented as Si3N4 and the aluminum nitride substrate is represented as AlN).

[0054] [Table 1] TIFF2025027018000003.tif100170

[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 distance 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 microsurface spectrophotometer to determine the difference.

[0057] In addition, copper plates were bonded to both sides of the ceramic scribed substrates before division produced in the examples and comparative examples by the active metal bonding method. The copper plates used were oxygen-free copper with a length of 40 [mm] × width of 50 [mm] × thickness of 0.5 [mm]. 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 of Ag with an organic component to form a paste.

[0058] Using a semi-automatic screen printer, an active metal paste was printed and dried on the scribed surface of the ceramic scribed substrate using a 320 x 320 mm, 250 mesh, stainless V screen mesh, and then printed and dried on the non-laser irradiated surface. At this time, any ceramic substrate that was separated from the scribe line by the pressure of the printer's squeegee was counted as a printing defect and was not sent 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, and then the substrate was sandwiched between a plate-shaped jig and a weight was placed on top to carry out the thermal bonding process. The thermal bonding was carried out at a bonding temperature of 810°C for 10 minutes in a vacuum (1×10 -2 The test was performed at 100 Pa (or less).

[0060] After heating and bonding, the copper plates were etched to create a circuit shape. The front copper plate had three circuit shapes, and the back copper plate was also etched to create pullbacks around the perimeter.

[0061] The etched ceramic substrate was scribed by 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 scribe substrates according to the examples and comparative examples, and the ceramic substrate circuit was manufactured by applying stress to the ceramic scribe substrate with the metal circuit or the like bonded thereto and dividing it along the scribe lines. The appearance of the ceramic circuit substrate was inspected, and remaining cracks, chips and cracks occurring around the substrate were counted as scribe defects and were not passed on to the subsequent process.

[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 embodiment and the 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 boards manufactured from the ceramic scribed substrates according to the examples and comparative examples, the porosity between the resin and the ceramic circuit board was evaluated by ultrasonic testing (SAT) for the substrate periphery on the circuit side 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 / periphery length of the ceramic substrate) x 100, and a porosity of less than 95 [%] was determined 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 [%] do not include defects that occurred in the previous process, but were calculated as the defect rate per 100 products.

[0065] [Table 2] TIFF2025027018000005.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 embodiment 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, the ceramic circuit boards manufactured from the ceramic scribed substrates according to the examples did not have any paste printing defects or had a low failure rate. This is because the laser scribes were formed to withstand the pressure applied to the surface of the ceramic scribed substrate during paste printing. 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, the ceramic circuit boards manufactured from the ceramic scribed substrates according to the examples did not have any scribe defects or had a low defect rate. This is because the laser scribes were formed so that the ceramic scribed substrate could 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 formed sufficiently, so the substrate could not be divided along the lines at a constant scribe load, which caused chipping defects and cracking defects.

[0069] In addition, the ceramic circuit boards manufactured from the ceramic scribed substrates according to the examples did not have resin peeling defects or had a low failure rate. This is because there were no residues from the laser processing by laser scribing or traces of the continuous grooves and discontinuous groove groups at the resin molded locations, so no non-bonding due to the laser residues or voids due to the traces of the 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 the laser residues and voids due to the continuous grooves and discontinuous groove groups were the causes of the peeling defects.

[0070] Although some 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. These embodiments and their modifications 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.

Claims

1. A continuous groove is formed on the surface of the scribe line that forms the ceramic substrate, with multiple grooves connected by fiber laser irradiation. A group of discontinuous grooves, in which a plurality of grooves are not connected, is provided on the deep side of the scribe line by irradiation with a fiber laser, The depth of the continuous groove is greater than 50 μm and is in the range of 0.15 to 0.55 times the thickness of the ceramic substrate; A ceramic scribe substrate having a three-point bending strength in the range of 350 MPa to 650 MPa.

2. 2. The ceramic scribe substrate according to claim 1, wherein the depth of the group of discontinuous grooves is greater than 0 and not more than 0.45 times the thickness of the ceramic substrate.

3. 3. The ceramic scribed substrate according to claim 1, wherein the distance between adjacent grooves in the group of discontinuous grooves is 10 [μm] or more and 100 [μm] or less.

4. 4. The ceramic scribed substrate according to claim 1, wherein the width of each groove in the non-continuous groove group is 5 [mu]m or more and 50 [mu]m or less.

5. 5. The ceramic scribed substrate according to claim 1, wherein a difference in brightness between the laser irradiation mark of the continuous groove and the surface of the ceramic substrate is 5 or less.

6. 6. The ceramic scribe substrate according to claim 1, wherein the ceramic substrate is a silicon nitride substrate or an aluminum nitride substrate.

7. A continuous groove is provided on the front surface side of the scribe line on at least one side of the four sides, in which a plurality of grooves are connected by irradiation with a fiber laser; A group of discontinuous grooves, in which a plurality of grooves are not connected, is provided on the deep side of the scribe line by irradiation with a fiber laser, The depth of the continuous groove is greater than 50 μm and is in the range of 0.15 to 0.55 times the thickness of the ceramic substrate; A ceramic substrate having a three-point bending strength in the range of 350 MPa to 650 MPa.

8. 7. A method for producing a ceramic substrate, comprising the steps of: applying stress to the ceramic scribed substrate according to claim 1 to divide the ceramic substrate along the scribe lines to produce a ceramic substrate.

9. The method for producing the ceramic substrate according to claim 8, A method for producing a ceramic circuit board, comprising bonding a metal circuit to the ceramic substrate to produce a ceramic circuit board.

10. A metal circuit is bonded to the ceramic scribe substrate according to any one of claims 1 to 6, A method for manufacturing a ceramic circuit board, comprising the steps of: applying stress to the ceramic scribed substrate to which the metal circuit is bonded, and dividing the substrate along the scribe lines to manufacture a ceramic circuit board.

11. 11. The method for manufacturing a ceramic circuit board according to claim 9, wherein the metal circuit is bonded to a surface of the ceramic board opposite to a surface on which the scribe lines are formed.

12. The method for producing a ceramic circuit board according to any one of claims 9 to 11, A method for manufacturing a semiconductor device, comprising the steps of: mounting a semiconductor element on the ceramic circuit board to manufacture the semiconductor device.

13. 13. The method for manufacturing a semiconductor device according to claim 12, wherein the ceramic substrate, the metal circuit, and the semiconductor element are integrated together by a resin mold.

Images