Ceramic substrate, ceramic circuit board, semiconductor device, method for manufacturing ceramic substrate, and method for manufacturing divided ceramic substrate

Abstract

To provide a ceramic substrate excellent in cost performance by efficiently manufacturing a small substrate from a high-strength, thin, large ceramic substrate having both heat dissipation and electrical insulation properties.SOLUTION: A ceramic substrate according to an embodiment has two or more peaks in the range of 98 eV to 106 eV in the spectrum obtained by measuring the laser irradiation area of the laser-processed surface by XPS. and there are also provided a ceramic circuit board and a semiconductor device including the ceramic substrate, and a method for manufacturing the ceramic circuit board and a divided ceramic substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments generally relate to a ceramic substrate, a ceramic circuit board, a semiconductor device, a method for manufacturing a ceramic substrate, and a method for manufacturing divided ceramic substrates. [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. 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).

[0003] One method for dividing a silicon nitride substrate, which is a ceramic substrate manufactured in large size to reduce manufacturing costs, into the product size to be used is to use a method of dividing the substrate into multiple pieces using 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 multiple pieces can be carried out easily and at low cost.

[0004] On the other hand, as the substrate before separation has become larger and thinner, issues have become apparent when laser processing ceramic substrates, which have high strength and toughness. For example, because ceramic 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 ceramic substrate's thickness. However, forming such a deep scribe line in the thickness direction requires a large amount of energy. When the laser energy is converted into scribing energy, a portion of it is converted into thermal energy. If the conversion rate to thermal energy is high, the thermal effect becomes significant. Therefore, this thermal effect often leads to the oxidation of silicon compounds.

[0005] When measuring laser-processed surfaces with XPS (X-ray Photoelectron Spectroscopy) up until now, two or more peaks between 528 eV and 536 eV were not observed at any location. As a result, some areas were prone to splitting and others were not, which could cause problems with splitting during transportation or cleaning. [Prior art documents] [Patent documents]

[0006] [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]

[0007] In recent years, rising junction temperatures in power semiconductor chips have led to demand for higher reliability in ceramic 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.

[0008] 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]

[0009] The ceramic substrate according to the embodiment is characterized in that, in a ceramic substrate having a scribe line, a laser-processed surface including the scribe line is formed by irradiating with a laser, and the spectrum obtained by measuring the laser-irradiated area of the laser-processed surface by XPS (X-ray Photoelectron Spectroscopy) has two or more peaks in the range of 98 eV or more and 106 eV or less. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a top view showing an example of a ceramic substrate according to an embodiment. [Figure 2] FIG. 2 is a diagram schematically showing an example of the results of measuring the ceramic substrate according to the embodiment by XPS. [Figure 3] FIG. 2 is a diagram schematically illustrating an example of a scribe line on the substrate of FIG. 1 as viewed obliquely from above. [Figure 4] FIG. 3 is a top view showing another example of a ceramic substrate according to an embodiment. [Figure 5] FIG. 2 is a top view showing an example of a circular ceramic substrate according to an embodiment. [Figure 6] FIG. 1 is a side view showing an example of a ceramic circuit substrate according to an embodiment. [Figure 7] 1A to 1C are diagrams showing an example of a laser processing method according to an embodiment. [Figure 8] FIG. 3 is a top view showing another example of a ceramic substrate according to an embodiment. [Figure 9] FIG. 3 is a top view showing another example of a ceramic substrate according to an embodiment. [Figure 10]FIG. 3 is a top view showing another example of a ceramic substrate according to an embodiment. [Figure 11] FIG. 4 is an enlarged top view showing another example of a ceramic substrate according to an embodiment. [Figure 12] FIG. 3 is a cross-sectional view showing an example of a portion cut along a break line in a divided ceramic substrate according to an embodiment. [Figure 13] FIG. 3 is a cross-sectional view showing an example of a portion cut along a bric-a-brac line in a divided ceramic substrate according to an embodiment. [Figure 14] FIG. 2 is a flowchart illustrating an example of a method for manufacturing a ceramic substrate according to an embodiment. [Figure 15] FIG. 2 is a flowchart illustrating an example of a method for manufacturing a ceramic substrate according to an embodiment. [Figure 16] FIG. 2 is a flowchart illustrating an example of a method for manufacturing a ceramic substrate according to an embodiment. [Figure 17] FIG. 4 is an enlarged top view showing an example of misalignment of a ceramic substrate according to an embodiment. [Figure 18] FIG. 4 is an enlarged top view showing an example of a defect in dividing the ceramic substrate according to the embodiment. [Figure 19] FIG. 3 is a top view showing another example of a ceramic substrate according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The scribe lines according to the embodiments refer to the scribe lines before dividing a ceramic laser-scribed substrate into divided ceramic substrates, and the scribe line marks after dividing the divided ceramic substrates (hereinafter referred to as "scribe lines"). The ceramic substrate having scribe lines according to the embodiments is characterized in that the scribe lines are formed by laser irradiation, and in that a spectrum obtained by measuring with X-ray photoelectron spectroscopy (XPS) shows two or more peaks in the range of 98 eV to 106 eV. "Two or more peaks within this range" means that more than two peaks, such as three or four peaks, may be observed. Note that "division" of a ceramic laser-scribed substrate is also referred to as "breaking" of the ceramic laser-scribed substrate.

[0012] Figure 1 shows a plan view of an example of a ceramic substrate according to an embodiment. Reference numeral 1 denotes a ceramic laser scribed substrate, reference numeral 2 denotes a multi-piece ceramic substrate, reference numeral 3 denotes scribe lines which are non-through holes, reference numeral 4 denotes individual divided ceramic substrates which will become products, reference numeral 5 denotes a peripheral portion not used as a product, reference numeral 7 denotes a through hole, reference numeral 71 denotes a through hole which is an example of a through hole 7, and reference numeral 72 denotes a notch which is an example of a through hole 7. The ceramic laser scribed substrate 1 is broadly composed of a multi-piece ceramic substrate 2 and a peripheral portion 5. In this specification, the term "ceramic substrate" refers to the ceramic laser scribed substrate 1, the multi-piece ceramic substrate 2, or the divided ceramic substrate 4.

[0013] Furthermore, the laser processing of the present invention can be used to process any shape. This shape can be a scribe line 3 as described above, a notch 72 suitable for screw fastening, or even a hole drilling. The notch 7 is formed by overlapping multiple laser dots on the sintered substrate. By observing two or more peaks in the range of 98 eV to 106 eV in every observation region, for example, in the case of a screw fastening portion, this leads to reduced strength unevenness on the processed surface and increased torque. Similarly, when a scribe line is formed, it will not break during transportation and can also suppress the occurrence of defects during separation.

[0014] FIG. 1 shows an example in which a total of eight divided ceramic substrates 4, two vertically and four horizontally, are obtained by laser scribing. The ceramic laser scribed substrate 1 is not limited to this shape. A single ceramic divided substrate 4 may be processed into the product shape using scribe lines 3, or multiple ceramic divided substrates 4 may be obtained in a number greater than two vertical and four horizontal. Furthermore, it is not necessary to form scribe lines 3 on all four sides of the ceramic divided substrate 4; one or more scribe lines 3 are sufficient. While the ceramic divided substrate 4 has a rectangular shape in the plan view of FIG. 1, it may also have a roughly polygonal shape, a roughly circular shape, or a roughly polygonal shape with rounded corners. The scribe lines 3 may also be formed on both the front and back of the ceramic laser scribed substrate 1. The scribe lines 3 may also be formed by combining a laser with another method. In addition, the laser processing of the present invention may use either continuous wave or pulsed wave oscillation, or a combination of both oscillation methods. Furthermore, the shape of the ceramic laser scribed substrate 1 may be circular, as shown in FIG. 5. Furthermore, the ceramic laser scribed substrate 1 may have a shape after breaking that has notches at the corners, as shown in FIG.

[0015] The ceramic substrates 1 and 2 and the ceramic divided substrate 4 portion of the ceramic circuit substrate 10 (shown in FIG. 6) are characterized in that two or more peaks are observed in the range of 98 eV to 106 eV in the spectrum obtained by XPS measurement.

[0016] When ceramic substrates 1, 2, and 4 are silicon nitride substrates, they can have a three-point bending strength of 600 MPa or more, or even 700 MPa or more. Furthermore, they have a thermal conductivity of 50 W / m·K or more, or even 80 W / m·K or more. An example of a substrate with a thermal conductivity of 80 W / m·K or more is approximately 130 W / m·K. When ceramic substrates 1, 2, and 4 are aluminum nitride substrates, they can have a high thermal conductivity of 170 W / m·K or more, or even 230 W / m·K or more. Furthermore, they can have a three-point bending strength of 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.

[0017] The ceramic substrates 1, 2, and 4 may be single plates or may have a three-dimensional structure such as a multilayer structure (ceramic-conductor-ceramic-conductor structure). Furthermore, the ceramic substrates 1, 2, and 4 are preferably silicon-containing ceramic substrates. Examples of silicon-containing ceramics include those containing one or more of sialon, silicon nitride, and silicon carbide as the main component. It is more preferable to use a silicon nitride substrate as the silicon-containing ceramic.

[0018] The scribe line 3 is processed using a laser. The laser used here is preferably selected from the group consisting of a semiconductor laser, fiber laser, excimer laser, femtosecond laser, YAG laser, YVO laser, CO2 laser, DDL laser, and blue laser. Furthermore, when using a YAG laser, a second, third, or fourth harmonic wave may be used as needed. It is particularly preferable to use a laser with a wavelength of 1200 nm. Lasers with wavelengths of 1200 nm or less include fiber lasers, excimer lasers, femtosecond lasers, YAG lasers, and YVO3 lasers. Among these laser types, fiber lasers are particularly preferable. When using such a laser, a focusing lens or mirror may be used as needed. Furthermore, when using a focusing lens, it is preferable to use the type and arrangement of the focusing lens under appropriate conditions depending on the position and thickness of the substrate. By optimizing the focusing lens conditions in this way, the depth of focus can be adjusted. As described above, when forming the scribe line 3, it is preferable to move the substrate (e.g., the sintered substrate after the sintering process) that will become the ceramic laser-scribed substrate 1 to form the groove shape. There are two methods for adjusting the laser beam to control the groove shape: adjusting the direction using a mirror, or adjusting the laser itself. However, with either method, there is a risk that positional accuracy may not be maintained depending on the length of the optical path. Furthermore, the irradiated energy may change depending on the length of the optical path, and because lasers are precision instruments, moving the laser itself repeatedly may cause the laser's oscillation energy to change over time. If such problems occur, there is a risk that the peaks obtained by XPS will not be controllable.

[0019] Therefore, it is preferable to place the sintered substrate itself on a stage and move the stage itself. When using a mirror, moving the mirror is also an option, but the longer the distance from the mirror to the workpiece, the worse the positioning accuracy may become. The fiber laser conforms to the definition in JIS Z 3001-5 (2013). The fiber laser may be a YAG crystal doped with Nd, Er, or Ho, or may use KLN, PPLN, sapphire, ruby, or other materials. The fiber diameter is preferably 100 μm or less. The diameter accuracy should preferably be within an error of 0.001 mm, and both parallelism and perpendicularity should preferably be controlled.

[0020] Furthermore, the above-mentioned lasers, including fiber lasers, may be used as second, third, or fourth harmonic waves, if necessary, using wavelength-convertible crystals such as BBO (beta-barium borite). Furthermore, when using fiber lasers, it is more preferable to use either a step index or a grating index as the index type. Here, a step index refers to a uniform refractive index within the core, while a grating index refers to a non-uniform refractive index within the core, resulting in a higher intensity distribution at the center. Therefore, for the same output, a grating index allows for deeper processing. The oscillation mode may be single mode or multimode, but single mode is more preferable. Here, the heat-affected zone (HAZ) is described. This heat-affected zone spreads out in a roughly concentric pattern.

[0021] An assist gas may also be used to form the scribe lines. The assist gas used in this case is preferably nitrogen or air. It is preferable that the assist gas be injected from the injection port before the laser beam is emitted from the laser irradiation port. This is because the speed of light is much faster than the speed of sound, and if the assist gas is injected simultaneously with the oscillation, air resistance will occur, and it will take time for the assist gas to reach the surface of the sintered substrate, resulting in a time lag. In such cases, there is a risk that the effect obtained by using the assist gas will be reduced.

[0022] In addition, it is preferable to collect dust regardless of whether or not an assist gas is used. By collecting dust, it is possible to remove high-temperature fine dust particles generated by laser irradiation. By collecting dust in this manner, it is possible to prevent the generation of bubbles that may occur when the generated fine dust particles are redeposited. Figure 7 is a schematic diagram of a dust collection method for laser processing. Reference numeral 1 denotes a ceramic laser scribed substrate, reference numeral 11 denotes a metal circuit, reference numeral 14 denotes a laser processing machine, reference numeral 15 denotes particles generated by laser irradiation, and reference numeral 16 denotes a dust collector. As shown in Figure 7, when a laser is irradiated from the laser processing machine 14 onto a ceramic laser scribed substrate 1 on which a metal circuit 11 has been formed, the particles 15 are simultaneously collected by the dust collector 16. This prevents the particles 15 from covering the laser outlet and destabilizing the laser output. Stabilizing the laser output in this way also prevents changes over time in the laser products in the laser irradiation area.

[0023] Furthermore, the scribe line 3 may be formed by multiple laser irradiations. When forming the scribe line 3 by multiple laser irradiations at the same location, it is preferable to leave an interval of 1 millisecond or more before the next laser processing. In other words, when performing laser processing on the same location, for example, the time interval between the nth (n: natural number) irradiation and the n+1th irradiation is 1 μsecond or more. Furthermore, the multiple time intervals that appear over time may be the same or different. For example, the interval between the nth irradiation and the n+1th irradiation may be the same or different from the interval between the n+1th irradiation and the n+2th irradiation. When irradiating multiple times, leaving a time interval between the irradiations allows the thermal energy remaining in the sintered substrate to be reduced before the next laser irradiation. It is more preferable that this interval be 3 minutes or less. This is because an interval longer than 3 minutes may take a long time to manufacture and may result in a decrease in yield. The laser oscillation may be either a continuous wave (CW) or a pulse wave (PW), or a combination of a continuous wave and a pulse wave. When a pulse wave is used, a short pulse width of the order of nanoseconds or less is preferable. If the pulse width is long, the influence of the laser irradiation becomes excessive, and oxidation progresses, which may result in the two or more peaks not being observed in the range of 98 eV to 106 eV.

[0024] The ceramic substrates 1, 2, and 4 are preferably Si-containing ceramics, and a scribe line 3 is formed by laser processing. The substrates are characterized in that, in the spectrum obtained by measuring the laser irradiation area, which is the laser-processed side, by XPS, two or more peaks are observed in the range of 98 eV to 10 eV. The upper limit of the number of peaks is not particularly limited, but is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less. If the peak intensity of the strongest peak between 98 eV and less than 101 eV is I2 and the peak intensity of the strongest peak between 101 eV and 106 eV is I3, the peak intensity ratio I3 / I2 is 0.4 to 12. Furthermore, I3 / I2 is preferably 0.6 to 4.5. More preferably, I3 / I2 is 0.9 to 4.1. Even more preferably, I3 / I2 is 0.9 to 1.7.

[0025] Here, we define peak intensity. Peak intensity is the peak height minus the baseline height. As shown in Figure 2, the baseline is a line connecting the two ends of a peak. This peak end is the point (minimum) where the spectral slope first becomes zero when viewed in one direction from the peak's strongest point. However, if a minimum exists between two maxima and is less than twice the half-width of one of the maxima, it is preferable to use the minimum that exceeds the other maxima. Furthermore, if it is difficult to measure such a minimum, the height of one of the ends is used as the baseline height. I2 here refers to the intensity of the Si-Si peak, and I3 refers to the intensity of the Si-O peak. Therefore, adjusting the intensity ratio of the Si-O and Si-Si peaks to 2.5 or less means reducing the oxidation of Si due to the thermal effects of laser processing.

[0026] To control the peak intensity, it is preferable to perform laser processing on a sintered substrate while collecting dust in an environment with a humidity of 30% to 80% and a temperature of 28°C or lower. A humidity of 35% to 75% is more preferable. Performing laser processing in an environment with a humidity of less than 30% is undesirable because static electricity may occur, causing microbubbles to form due to repulsion between charged particles. On the other hand, if the humidity exceeds 80%, water molecules in the air may absorb the laser energy, causing hydration of the silicon compound. Therefore, when hydrates are formed in this way, the absolute value of the Si-O peak may decrease. This is because the lone electron pair of oxygen is used to bond with hydrogen atoms rather than with Si. Furthermore, hydrates formed by absorbing laser energy form hydrogen bonds between molecules. Hydrogen bonds have weaker bond energy than covalent bonds.

[0027] Therefore, if a large amount of hydrate is produced, there is a risk that the strength of the side surface will decrease. Therefore, it is not desirable to produce a large amount of silicon hydrate. Here, humidity refers to the amount of water vapor in the atmosphere relative to the amount of saturated water vapor, and the amount of saturated water vapor increases with increasing temperature. Therefore, even at the same humidity, the higher the temperature, the greater the amount of water molecules present in the same volume. Therefore, if the temperature exceeds 28°C, the amount of saturated water vapor will increase, and there is a risk that the effect of controlling the humidity to 80% or less will not be fully obtained. Therefore, it is preferable that the temperature during laser processing be 28°C or less.

[0028] The timing of laser irradiation on the substrate that will become the ceramic laser scribed substrate 1 is not particularly limited, but is preferably after sintering. This is because a sintered substrate after sintering makes it easier to maintain the position of the scribe line, which changes little in size during subsequent processes. Furthermore, the conductor may be bonded after the scribe line is formed on the sintered substrate, or the scribe line may be formed after the conductor is bonded to the sintered substrate. Here, "after bonding the conductor" refers to either after the etching process or before the etching process, and does not necessarily require an etching process. An example of a method that does not require an etching process is a method of bonding a conductor that has already been given a circuit shape by punching or the like. Furthermore, the focusing distance is preferably 0.5 mm or more, and preferably 30 mm or less. If the distance between the irradiation port and the substrate is less than 0.5 mm, the emitted plume may adhere to the irradiation port, which may cause the laser processing energy to become unstable and may result in insufficient positional accuracy.

[0029] Furthermore, output instability may change the peaks observed by XPS. On the other hand, if the distance is greater than 30 mm, plume adhesion can be suppressed, but subtle differences in the angle between the laser and the ceramic substrates 1, 2, and 4 may significantly affect positional accuracy. Furthermore, a more preferable range for the focusing distance is 1 mm or more and 15 mm or less. The same molecular density results in the same amount of water molecules per distance. Therefore, the farther the distance from the irradiation port, the greater the influence of water molecules on the laser output energy. Furthermore, there is a risk that the influence of the laser processing environment, such as humidity and temperature, may become excessive. This may also change the peaks observed by XPS.

[0030] In this case, the XPS used was a Quantera SXM manufactured by PHI. Therefore, it is preferable to use a device with equal or better performance. The X-ray source used was a single crystal spectrometer AlKα ray. The X-ray output was 4.5 W. The analysis area had a diameter of 20 μm.

[0031] The absolute value (peak difference) of the peak intensity of the strongest peak in the irradiated region in the range of 528 eV to 536 eV minus the peak intensity of the strongest peak in the non-irradiated region (peak difference) is preferably 2500 or less, more preferably 1600 or less. More preferably, the peak difference is 1500 or less. Even more preferably, the peak difference is 800 or more and 1500 or less. Furthermore, the absolute value of the peak intensity of the strongest peak in the irradiated region in the range of 528 eV to 536 eV is preferably 1000 or more. A value of 1000 or more indicates a high laser energy density and suppresses the thermal impact on the non-irradiated region. As described above, increasing the energy density reduces the width of the scribed groove and improves the ratio of the area of the resulting ceramic divided substrate 4 to the overall size of the ceramic laser-scribed substrate 1. Furthermore, the absolute value of the peak intensity of the strongest peak in the irradiated region in the range of 528 eV to 536 eV is preferably 3500 or less. If it exceeds 3500, the oxidation number of the Si component increases too much, and the value of I3 / I2 may become uncontrollable.

[0032] Furthermore, it is preferable that the absolute value (peak difference) of the value of the peak intensity of the strongest peak in the range of 395 eV to 400 eV in the irradiated region minus the value of the peak intensity of the strongest peak in the same range in the non-irradiated region is 2500 or less. More preferably, the peak difference is 2200 or less. Even more preferably, the peak difference is 300 to 2000. The peaks in this range are peaks derived from oxides. A peak difference of 300 or more indirectly indicates that the thermal effect on the non-irradiated area is small and the effect of the laser is limited to the irradiated area.

[0033] Furthermore, it is preferable that the absolute value (peak difference) of the value of the peak intensity of the strongest peak in the range of 282 eV to 288 eV in the irradiated region minus the value of the peak intensity of the strongest peak in the irradiated region in said range in the non-irradiated region is 2500 or less. It is more preferable that the peak difference is 1200 or less. The non-irradiated region is a region that is 0.05 mm or more away from the laser-processed surface, with the center of the measurement being the region. This peak indicates the presence of a carbon with a 1S orbital. The presence of a carbon with a 1S orbital means that the carbon has a bond, and the bond with the carbon is derived from a single bond.

[0034] Therefore, the small difference in the peak intensities of these three types of peaks indicates that the change in their contents is small with or without laser irradiation. Therefore, it is preferable that the peak difference between these three peak intensities is 2500 or less. Furthermore, it is even more preferable that the peak difference between the three peak intensities is 2000 or less. Furthermore, it is preferable that this peak difference is at a certain level. Therefore, it is more preferable that the peak difference is 1000 or less. Here, the peak difference is the absolute value of the value obtained by subtracting the peak intensity in that range in the laser irradiated region from the peak intensity in that range in the laser non-irradiated region.

[0035] Peak difference C in peak intensity in the range of E [eV] to F [eV] E-F is expressed by the following formula: C E-F = |(Peak intensity in the range of E [eV] to F [eV] in the irradiated area) - (Peak intensity in the range of E [eV] to F [eV] in the non-irradiated area) | The peak heights thus determined are compared, and the magnitude of the difference in peak height between the irradiated and non-irradiated regions is determined, thereby making it possible to indirectly determine the peak difference.

[0036] Furthermore, it is more preferable that the ceramic to be scribed has one or more of the following as its main component: alumina, zirconia, silicon nitride, sialon, and aluminum nitride. Here, "main component" means that it contains 50 wt% or more. It is more preferable that the ceramic to be scribed is a silicon-containing ceramic. It is more preferable that the type of ceramic has silicon nitride, sialon, or silicon carbide as its main component. It is even more preferable that the main component is silicon nitride.

[0037] Furthermore, the ceramic substrates 1, 2, and 4 are preferably Si-containing ceramics. The Si-containing ceramic is more preferably silicon nitride, silicon carbide, or sialon. The thickness of the ceramic substrates 1, 2, and 4 used here is not particularly limited, but is preferably 0.1 mm to 3.00 mm, and more preferably 0.2 mm to 2.5 mm. Substrates that are too thin, less than 0.1 mm, are prone to breakage during transportation after laser processing, which may adversely affect transportation. On the other hand, substrates that are thicker than 3 mm may be too oxidized during laser processing, making it impossible to observe two or more peaks on any laser-processed surface.

[0038] When the ceramic substrates 1, 2, and 4 are Si-containing ceramics, the XPS spectrum shows that the peak intensity of the strongest peak between 98 eV and 101 eV is I2, and the peak intensity of the strongest peak between 101 eV and 106 eV is I3. The peak intensity ratio, I3 / I2, is preferably 2.5 or less. I2 refers to the Si-Si peak intensity, and I3 refers to the Si-O peak intensity. Therefore, adjusting the intensity ratio of the Si-O and Si-Si peaks to 2.5 or less means that the increase in the oxidation state of Si due to the thermal effects of laser processing is reduced.

[0039] The peaks thus obtained are then subjected to waveform separation and their integral values are compared. Here, the integral value indicates the area of the peak. Therefore, this integral value depends on the peak intensity and half-width. The waveform separation method refers to the spectrum of the non-irradiated region and the main peak in the range of 98 eV to 106 eV.

[0040] If the peak integral value of the strongest peak between 98 eV or more and less than 101 eV is S2 and the peak integral value of the strongest peak between 101 eV or more and 106 eV or less is S3, the peak intensity ratio S3 / S2 is preferably 0.8 or more and 4.2 or less. By controlling the peak integral value in addition to the peak intensity in this way, it is possible to further control the generation ratio of compounds or simple substances capable of forming Si-Si bonds and compounds capable of forming Si-O bonds.

[0041] The depth of the scribe line 3 obtained by the laser may be changed as appropriate depending on the application. For example, the laser processing depth D (shown in FIG. 3) can be changed as appropriate by changing the energy density. As mentioned above, one method for changing the laser processing depth D is to change the moving (scanning) speed of the sintered substrate. An example of a method for changing the scanning speed is changing the speed at which the sintered substrate is moved. Furthermore, the scanning speed can be changed as appropriate as needed, but if it is too slow, there is a risk that the thermal effects of the laser energy will be excessive. Therefore, it is preferable to have a scanning speed above a certain level.

[0042] In the laser-processed surface 6 of the ceramic laser-scribed substrate 1 shown in FIG. 3, the opening end 81 and the opening end 82 are respectively two ends on the opening (laser irradiation side) of the laser recess 8, which are on a line perpendicular to the laser scanning direction L. In contrast, the minimum angle (angle θ) between the deepest portion at the laser-processed depth D of the laser recess 8 and the deepest portion consisting of the two opening ends 81 and 82 is preferably 3 degrees or more and less than 90 degrees. The angle θ is more preferably 5 degrees or more and less than 60 degrees. Furthermore, the angle θ is preferably 5 degrees or more and less than 45 degrees. An even more preferable range for the angle θ is 5 degrees or more and less than 30 degrees. As described above, controlling the angle θ reduces wasteful portions (edges) when dividing the ceramic laser-scribed substrate 1 along the scribe line 3 or when forming the notch 72, and also improves the positional accuracy during breaking (division) and separation. Furthermore, as mentioned above, not only is the positional accuracy during division or separation improved, but even if the angle θ becomes acute due to the presence of material layers with different strengths during division, division can be prevented when division is not desired. Furthermore, the laser-processed surface 6 of such a ceramic laser scribed substrate 1 may be provided with non-penetrating laser recesses 8 and / or partially penetrating laser recesses (not shown). In other words, one ceramic laser scribed substrate 1 may have both penetrating laser processing marks and non-penetrating areas.

[0043] Furthermore, the ceramic laser scribe substrate 1 having the ceramic multi-piece substrate 2 can be used for other scribe lines as shown in FIGS. andThe substrate 4 includes at least two scribe lines 31 that extend outward from the intersection of the scribe lines 31 and 33 to the edges, a scribe line 32 between adjacent ceramic substrates 4, and other scribe lines 33 (shown only in FIGS. 8 and 9 among FIGS. 8 to 10). It is preferable that the scribe line 32 extends outward from the intersection of the scribe lines 31 and 33. For example, in FIG. 8, the two scribe lines 31 extend in the left-right direction of the paper, in FIG. 9, the two scribe lines 31 extend in the up-down direction of the paper, and in FIG. 10, the two scribe lines 31 extend in the left-right direction of the paper and the two scribe lines 31 extend in the up-down direction of the paper, for a total of four scribe lines 31. As mentioned above, if the scribe line 32 is designed to extend beyond the intersection with the scribe lines 31 and 33, this may lead to misalignment of the scribe dots (hereinafter simply referred to as "dots") 3A (as illustrated in FIG. 17) or to cracking defects U (shown in FIG. 18) caused by the dots 3A during breaking. On the other hand, as shown in FIG. 11, the ceramic laser scribed substrate 1 has a protruding width W2 of the scribe line 32 relative to the protruding width W1 of the scribe line 31, and it is more preferable that the width W2 is 0.1 mm or greater. Furthermore, it is preferable that the ratio of the protruding width W2 to the protruding width W1 (W2 / W1) is 1 / 2 or less. By keeping W2 / W1 1 / 2 or less as mentioned above, the ceramic laser scribed substrate 1 is prevented from being unintentionally split (broken) during transportation and the takt time can be shortened. It is even more preferable that the W2 / W1 ratio is 1 / 4 or less.

[0044] Furthermore, cutout shapes such as screw fastening portions may be formed by laser processing as a separate process from the laser processing for division. Also, only the formation of the cutout portions 72 may be performed without performing the laser processing for division. Therefore, the shape of the laser-processed surfaces 6 of the ceramic substrates 1, 2, and 4 is not particularly limited. Furthermore, the timing of the separation, such as separation, may be any. For example, such a separation process may be performed in two separate steps, with another process inserted between them.

[0045] The scanning speed of the sintered substrate may be freely changed, but in order to observe two or more peaks in the range of 98 eV to 106 eV regardless of the measurement range, it is preferable that the change in the scanning speed is greater than 0 and less than 1500 mm / s. On the other hand, there is a risk that it would be too costly to completely reduce the change in the scanning speed of the sintered substrate to zero. Therefore, the change in the scanning speed on the sintered substrate can be controlled to be as small as possible, so that it can exceed 0. This takes into account the possibility that it may take some time for the laser output to stabilize.

[0046] In laser processing of sintered substrates, fine powder called plume may be generated during processing. If the laser irradiation port is too close, this plume may adhere to the laser irradiation port, destabilizing the laser output and even blocking the injection port. In addition, dust collection is preferable to suppress the adhesion of these plumes, etc. Furthermore, an assist gas may be used as needed. Furthermore, it is preferable to use a dust collector or the like when performing this dust collection. Furthermore, it is preferable that the dust collector has a filter, etc. Furthermore, when using a dust collector with a filter structure as described above, it is preferable that fine powder, etc., adhering to the filter portion is removed as needed. By removing fine powder adhering to the filter portion in this way, it is possible to always maintain a certain level of dust collection power. Furthermore, dust collection also has the effect of suppressing the adhesion of fine powder, such as the generated plume, to the substrate. Although deposits produced by laser processing of the sintered substrate may be removed in a later process, if they remain on the surface of the ceramic laser scribe substrate 1, they may peel off. In addition, increasing the laser output without dust collection can increase the processing speed, but this will increase the damage to the laser-processed surface 6.

[0047] After laser processing of the sintered substrate, a conductor such as a metal plate can be joined to the ceramic laser scribed substrate 1 to form a circuit (for example, the metal circuit 11 shown in FIG. 6). Alternatively, a circuit shape may be imparted to the sintered substrate after the conductor is joined, and then laser processing may be performed. In these cases, the ceramic laser scribed substrate 1 is divided into ceramic circuit substrates 10 after the metal circuit 11 is formed (shown in FIGS. 14 and 15). Alternatively, the ceramic laser scribed substrate 1 may be divided into ceramic divided substrates 4, and then the metal circuit 11 may be formed to form the ceramic circuit substrates 10. Furthermore, another step may or may not be included between the laser processing step (step S2 shown in FIGS. 14 and 15) and the dividing step (step S8) along the scribe lines performed after laser processing.

[0048] Examples of metals used for the metal circuit 11 include copper (Cu), copper-based alloys, and aluminum (Al). When copper is used for the metal circuit 11, oxygen-free copper may be used. The metal circuit 11 may be formed by etching, or by joining a conductor portion that has a circuit shape in advance. An example of a method for forming the circuit shape in advance is a method called punching.

[0049] As shown in FIG. 6, the divided ceramic substrate (product portion) 4 and the metal circuit 11 are preferably bonded via a bonding layer (for example, a brazing material layer 13). Furthermore, when a metal heat sink 12 is bonded to the divided ceramic substrate 4, it is also preferable to bond them via a bonding layer (for example, a brazing material layer 13). Furthermore, it is preferable to provide an active metal brazing material containing an active metal such as Ti (titanium) as the brazing material layer 13 between the divided ceramic substrate 4 and the metal circuit 11. Examples of active metals other than Ti include Zr (zirconium), Nb (niobium), and Hf (hafnium). Therefore, other active metals may be used instead of Ti. Methods for providing such a bonding layer include a method using a brazing material paste and a method using an alloy foil.

[0050] Therefore, as long as a bonding layer can be formed, the method may use either foil or brazing paste. Examples of active metal brazing materials include mixtures primarily composed of either Ag (silver) or Cu in addition to Ti. Preferably, the Ti content is 0.1 wt% to 10 wt% and the Cu content is 5 wt% to 96 wt%. If necessary, one or more elements selected from the group consisting of In (indium), Sn (tin), Al, Si (silicon), C (carbon), Mg (magnesium), Mo (molybdenum), Mn (manganese), W (tungsten), Re (rhenium), and Os (osmium) may be added in a total amount of 1 wt% to 35 wt%. Ag is the remainder. Therefore, Ag is not necessarily included. The active metal bonding method using active metal brazing material involves applying an active metal brazing paste to the surface of the ceramic divided substrate 4 and then placing the metal circuit 11 on top of the active metal brazing paste. The materials are then heated to a temperature of 600°C to 900°C to bond them together. The bonding may be performed using a method requiring evacuation, or may be performed in an inert atmosphere. Examples of inert atmospheres include a nitrogen atmosphere (molar fraction of 80% or more, more preferably 85% or more) and a rare gas atmosphere (argon atmosphere, neon atmosphere). According to the active metal bonding method, the bonding strength between the ceramic divided substrate 4 and the metal circuit 11 can be made 16 kN / m or more.

[0051] 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 metal thin films include plated films and sputtered films. Providing a metal thin film can improve corrosion resistance and solder wettability. The film may be provided partially or may cover the entire conductor portion. Furthermore, the ceramic circuit board 10 is not limited to the metal plate-ceramic substrate-metal plate structure shown in FIG. 6, but may also have a five-layer structure such as metal plate-ceramic substrate-metal plate-ceramic substrate-metal plate. The metal plate referred to here may also have a circuit pattern or a grooved surface.

[0052] In the embodiment shown in Figure 6, the bonding area between the divided ceramic substrate 4 and the metal heat sink 12 is different from the bonding area between the divided ceramic substrate 4 and the metal circuit 11, but they may be the same. Furthermore, the thicknesses of these metals may be the same or different. Furthermore, the metal heat sink 12 and the divided ceramic substrate 4 may be bonded without the brazing material layer 13. Furthermore, a conductor other than the brazing material layer 13 may be provided between the metal heat sink 12 and the divided ceramic substrate 4.

[0053] Such a ceramic circuit board 10 is suitable for a semiconductor module characterized in that a semiconductor element is mounted on the metal circuit 11 via a bonding layer. Electronic components such as semiconductor elements may be mounted on the resulting ceramic circuit substrate 10. Furthermore, in addition to the semiconductor elements, wire bonding and a metal circuit 11 may be bonded. The wire-bonded ceramic circuit substrate 10 may be resin-molded to form a semiconductor module. The semiconductor module according to the embodiment is not limited in its structure. For example, either wire bonding or a lead frame may be used. Furthermore, multiple semiconductor elements, multiple wire bonding, and multiple lead frames may be provided on the metal circuit 11.

[0054] The bonding layer that bonds the semiconductor element and the lead frame can be made of solder or brazing filler metal. Lead-free solder is preferable. Solder refers to a material with a melting point of 450°C or less. Brazing filler metal refers to a material with a melting point of over 450°C. A material with a melting point of 500°C or more is called a high-temperature brazing filler metal. Examples of high-temperature brazing filler metals include those containing Ag as the main component. Brazing filler metals containing Ag as the main component include Ag paste with controlled particle size and Cu paste with copper as the main component.

[0055] When sealing the ceramic circuit board 10 with a resin mold, the laser scribed surface may be on the side opposite the metal circuit 11 (the metal heat sink 12 side). This is because resin does not easily penetrate into recesses created by laser scribing, which may result in voids. Because voids hinder heat dissipation, it is preferable to form the scribe line on the heat sink side to prevent their formation.

[0056] While semiconductor elements continue to become smaller, the amount of heat generated from the chips continues to increase. Therefore, improving heat dissipation is becoming increasingly important for ceramic circuit substrates 10 that mount semiconductor elements. Furthermore, to improve the performance of semiconductor devices (semiconductor modules), multiple semiconductor elements are now being mounted on ceramic circuit substrates 10. If even a single semiconductor element 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 is effective. Furthermore, semiconductor devices according to the embodiments can be used in PCUs (power control units), IGBTs (insulated gate bipolar transistors), and IPM (intelligent power 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 directly contributes to the safety of automobiles. The same is true for electric railcars, industrial equipment, and other applications.

[0057] Next, we will explain the laser scribing method for the silicon nitride substrate among the ceramic substrates 1, 2, and 4 according to the embodiments. The manufacturing method for the laser scribing of the 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.

[0058] First, a silicon nitride substrate is prepared. In particular, considering the heat dissipation properties of the entire ceramic circuit substrate 10, it is preferable that the substrate have a thermal conductivity of 50 W / m K or more and a three-point bending strength of 600 MPa or more. An example of a substrate with a thermal conductivity of 50 W / m K or more and a three-point bending strength of 600 MPa or more is one with a thermal conductivity of 130 W / m K and a three-point bending strength of 750 MPa.

[0059] Furthermore, when conducting the metal circuit 11 and the metal heat sink 12 of the ceramic circuit board 10 through through holes, a silicon nitride substrate having 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 (for example, through holes) 71 in the silicon nitride sintered body may be carried out. Examples of the step of providing through holes include laser processing similar to laser scribing and cutting processing. Examples of cutting processing include drilling using a drill or the like.

[0060] Furthermore, the scribe line 3 may be formed not by the continuous groove 3B shown in FIG. 13 but by a combination of dots 3A and shallow continuous grooves 3B (not shown), or may be formed only by dots 3A as shown in FIG. 12. Here, the dots 3A are composed of laser processing marks that are spaced apart without overlapping, while the continuous groove 3B is composed of laser processing marks that at least partially overlap. When the scribe line 3 is formed by dots 3A, the average value of the width W3 (shown in FIG. 12) between the points of maximum depth for each dot 3A is preferably 50 μm or more and 300 μm or less. More preferably, the average value of the width W3 is preferably 50 μm or more and 150 μm or less. Furthermore, it is preferable to control the width W4 (shown in FIG. 12) of the scribe marks of the dots 3A to be 20 μm or more and 100 μm or less. The depth of the dots 3A is preferably 1 / 6 to 2 / 3 of the substrate thickness. Furthermore, the depth of the dots 3A is preferably 50 μm to 300 μm. More preferably, the depth of the dots 3A is 150 μm or more and 250 μm or less. Furthermore, in the laser processing, in addition to the dots 3A (shown in FIG. 12) or continuous grooves 3B (shown in FIG. 13), it is preferable that auxiliary cut lines (auxiliary continuous grooves or dots) are formed by partially irradiating the periphery of the dots 3A or continuous grooves 3B multiple times. By forming the auxiliary cut lines in addition to the dots 3A or continuous grooves 3B to form the scribe lines 3 in step S2 shown in FIGS. 14 to 16, the defect rate during division can be further reduced.

[0061] It is preferable to include a step (step S1) of placing the substrate on a stage before the step (step S2) of providing scribe lines 3 on the ceramic substrates 1, 2, and 4, and to include a step (step S3) of cleaning the surface using honing or blasting after the step (step S2) of providing scribe lines 3. Furthermore, as shown in FIG. 16, a step (step S14) of cleaning the surface may be included after the step (step S13) of dividing the peripheral portion. Also, as shown in FIGS. 14 and 15, a step (step S8) of dividing into ceramic circuit substrates 10 may be performed after the step (step S5) of bonding the copper plates. It is more preferable to include a step (step S7) of cleaning the ceramic circuit substrates 10 after the step (step S8) of dividing into ceramic circuit substrates 10 as shown in FIG. 15, rather than a step (step S7) of cleaning the ceramic circuit substrates 10 before the step (step S8) of dividing into ceramic circuit substrates 10 as shown in FIG. 14. This is because there is a risk that minute powders generated during division may adhere to the wafer, and such powders should be washed away in step S7. Furthermore, the scribe lines 3 may be scribe lines for dividing only the peripheral edge portion, as shown in FIG.

[0062] A silicon nitride substrate is set on the precision processing table of a laser processing machine such as a fiber laser (step S1). A laser is irradiated onto the silicon nitride substrate to form laser processing marks such as scribe lines 3 consisting of dots 3A (shown in FIG. 12). At this time, dots 3A of a predetermined size are formed according to the conditions of the laser processing machine 14 (shown in FIG. 7). It is also preferable that the laser processing be performed by moving the precision processing table. This is because, during laser processing, controlling the processing by moving the laser or changing the orientation of a mirror can make it difficult to adjust the scanning speed.

[0063] A metal plate (metal circuit 11 and metal heat sink 12) is bonded to the silicon nitride substrate on which scribe lines 3 are formed, that is, the ceramic laser scribe substrate 1. The silicon nitride substrate and the metal plate are preferably joined using an active metal bonding method. This method uses an active metal brazing material containing an active metal such as Ti. Examples of active metal brazing materials include a mixture of Ti and Cu. Ag may also be added to this active metal brazing material as needed. If Ag is included, it is preferable that the Ag content be 99.5 wt% or less, and more preferably 95 wt% or less. Controlling the Ag content in this way is expected to reduce ion migration. It is known that ion migration occurs more easily with Ag than with Cu. On the other hand, a higher silver content improves the reliability of the bond at high temperatures. Therefore, it is more preferable to freely adjust the silver content within the range of 0 wt% to 95 wt% depending on the need and application. For example, Ti is 0.1 wt% to 10 wt%, Cu is 0.5 wt% to 60 wt%, and Ag is the remainder.

[0064] Therefore, Ag does not necessarily have to be present, and it may be present at about 95 wt%. If necessary, one or more elements selected from the group consisting of In, Sn, Al, Si, C, Mg, Mo (molybdenum), Mn (manganese), W (tungsten), Re (rhenium), and Os (osmium) may be added in a total amount of 1 wt% to 35 wt%. 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 uniformly mixed. This is because uneven distribution of the brazing filler metal components results in unstable brazing and poor joining.

[0065] Active metal brazing paste is applied to the ceramic laser scribe substrate 1. A copper plate is placed on top of it. Next, the process of heating and bonding is carried out at a temperature of 600°C to 900°C. The heating process is carried out in a vacuum or a non-oxidizing atmosphere as required. When carried out in a vacuum, the temperature is set to 1×10 -2The pressure is preferably 10 Pa or less. Examples of the non-oxidizing atmosphere include a nitrogen atmosphere, an argon atmosphere, a helium atmosphere, and a neon atmosphere. Here, the non-oxidizing atmosphere is not particularly limited, but refers to an atmosphere in which the oxygen partial pressure is 10% or less. By using a vacuum or a non-oxidizing atmosphere, the bonding layer can be prevented from being oxidized, thereby improving the bonding strength.

[0066] The conductor 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 may be formed on the side opposite to the side on which the scribe lines are formed. This process allows the production of a silicon nitride metal circuit substrate as the ceramic circuit substrate 10.

[0067] Next, a process is performed to bond a semiconductor element or the like to the silicon nitride metal circuit board. A bonding layer is provided at the location where the semiconductor element is to be bonded. The bonding layer may be solder or brazing material, or may be a silver layer using silver paste or the like. It may also be a copper layer using copper paste. The bonding layer is provided, and the semiconductor element is provided on top of it. If necessary, a lead frame is bonded via the bonding layer. If necessary, wire bonding is also provided. The required number of semiconductor elements, lead frames, and wire bonding are also provided. The silicon nitride circuit board to which the semiconductor elements, lead frames, and wire bonding have been applied is molded with resin to seal the interior.

[0068] A method for laser scribing a silicon carbide substrate, one of the ceramic substrates 1, 2, and 4 according to the embodiment, will be described. First, a silicon carbide substrate is prepared. In particular, considering the heat dissipation properties of the entire ceramic circuit substrate 10, it is preferable that the substrate have a thermal conductivity of 150 W / m·K or more and a three-point bending strength of 400 MPa or more. The method for laser scribing a silicon carbide substrate is not particularly limited as long as it has the above-mentioned configuration, but to obtain a high yield, the same manufacturing steps as those for the silicon nitride substrate and silicon nitride circuit substrate described above should be used.

[0069] (Examples 1 to 22, Comparative Examples 1 to 7) Ceramic substrates 1, 2, and 4 were prepared as silicon nitride substrates (thermal conductivity 90 W / m·K, three-point bending strength 650 MPa) measuring 200 mm long x 180 mm wide and 0.32 mm and 0.50 mm thick. Silicon carbide substrates (thermal conductivity 300 W / m·K, three-point bending strength 400 MPa) measuring 200 mm long x 180 mm wide and 0.635 mm and 0.80 mm thick were also prepared. Next, as shown in FIG. 1, dust was collected on one surface of a substrate (e.g., a sintered substrate) that would become the base for the ceramic laser scribed substrate using a fiber laser, and 200 substrates were laser processed, with eight lines per substrate, under each of the conditions of Examples 1 to 22 and Comparative Examples 1 to 7. The processed shapes are as shown in Table 2. Note that the scribe lines shown in Table 2 for Examples 2 to 4, 10 to 12, 18, and 21 and Comparative Examples 1 and 4 correspond to dots. Furthermore, cases that met both the temperature and humidity conditions are marked with a "○ (circle)" in the "Temperature and Humidity" column in Table 1, and cases that did not meet either condition are marked with an "× (cross)."

[0070] In addition, a "circle" in the "Laser conditions" column of Table 1 indicates that the pulse width was set to the order of nanoseconds or less and dust collection was performed. If the "focusing distance" met the conditions, a "circle" was written in the "focusing distance" column. In addition, no assist gas was used in the laser processing in the comparative examples. In addition, the ceramic substrates after laser processing under each condition were subjected to the following processes (called post-processes), such as transportation, under the same conditions. These processes are honing, cleaning, drying, and transportation. When this process was carried out, the number of pieces that were broken (divided) partially, along the scribe line, or deviated from the break line was shown in Table 2 as the percentage of pieces that were divided. The angle θ formed by the deepest part of the groove and the two opening ends (both ends) was also determined. The angle θ is shown in the "Laser processing angle" column in Table 2. The measurement results of the example and comparative example are shown in Tables 1 and 2. (In Table 1, silicon nitride (Si3N4) substrates are represented as "SiN" and silicon carbide substrates are represented as "SiC.")

[0071] [Table 1]

[0072] [Table 2]

[0073] The laser processing conditions and the like of ceramic substrates 1, 2, and 4 according to Examples 1 to 17 were within the range of the preferred embodiment. On the other hand, the ceramic substrates according to Comparative Examples 1 to 7 were outside the range of the preferred embodiment. The cutout portion described in these examples refers to the cutout portion indicated by reference numeral 72 in FIG. 1.

[0074] Next, the specimens were divided under each condition, and the laser-processed surfaces of the divided sections were measured using XPS. The measurement results are shown in Tables 3 and 4. The equipment used for the measurements was a Quantera SXM manufactured by PHI. The X-ray source was a single crystal spectroscopic AlKα ray. The X-ray output was 4.5 W, the analysis area was φ20 μm, the geometry was 45 degrees, and the pass energy was −69.00 eV (0.125 eV / Step).

[0075] [Table 3]

[0076] [Table 4]

[0077] As can be seen from Tables 3 and 4, in all of the ceramic substrates 1, 2, and 4 according to Examples 1 to 22, the number of peaks measured by XPS at 98 eV or more and 106 eV or less was within a preferable range.

[0078] When comparing the Examples and Comparative Examples using Tables 1 to 4, the Comparative Examples had a high break rate of 4% or more in the post-processing regardless of the laser processing angle. On the other hand, the Examples, in which favorable peaks were observed in XPS, had a low break rate of less than 4%.

[0079] The observation of two or more peaks in the range of 98 eV to 106 eV indicates that the laser-processed surface is strengthened and no unnecessary breaks have occurred. The two or more peaks were observed on any laser-processed surface.

[0080] Furthermore, no defects (breaks, chips, cracks) were observed at the broken portions in the Examples, whereas these defects were observed in some of the Comparative Examples. These defects are thought to have been caused by instability of the output during laser processing (due to adhesion of the plume to the irradiation port, etc.).

[0081] Therefore, it was found that it was important to optimize various conditions in laser processing and control the obtained XPS spectrum.

[0082] 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. [Explanation of symbols]

[0083] 1...Ceramic substrate (for example, ceramic laser scribe substrate) 2...Ceramic substrate (for example, ceramic multi-cavity substrate) 3...Scribe line 4...Ceramic substrate (e.g., ceramic divided substrate (product part)) 5...Peripheral area (non-product area) 6...Laser processed surface 7...Through hole 71...Through hole (e.g., through hole) 72...Through hole (e.g., notch) 8...Laser recess 9...Non-laser irradiated surface (non-laser processed surface) 10...Ceramic circuit board 11...Metal circuit 12...Metal heat sink 13...Brazing layer 14...Laser processing machine 15...Particles generated by laser irradiation 16...Dust collector W1: Extrusion width of the periphery W2: Extrusion width of scribe line

Claims

1. The substrate is made of a silicon nitride substrate, and in the spectrum obtained by measuring the laser irradiation area of the laser processing surface by X-ray Photoelectron Spectroscopy (XPS), there are two or more peaks in the range of 98 eV to 106 eV, The silicon nitride substrate is a ceramic substrate characterized in that the minimum angle between the deepest part at the laser processing depth of the laser recess on the laser-processed surface and the deepest part formed by the opening edge is 3 degrees or more and less than 90 degrees.

2. 2. The ceramic substrate according to claim 1, wherein, in the spectrum obtained by measuring the laser irradiation area by the XPS, the peak intensity of the strongest peak at 98 eV or more and less than 101 eV is defined as I2, and the peak intensity of the strongest peak at 101 eV or more and 106 eV is defined as I3, and the peak intensity ratio I3 / I2 is 0.4 or more and 12 or less.

3. 2. The ceramic substrate according to claim 1, wherein, in the spectrum obtained by measuring the laser irradiation area by the XPS, the peak intensity of the strongest peak at 98 eV or more and less than 101 eV is defined as I2, and the peak intensity of the strongest peak at 101 eV or more and 106 eV is defined as I3, and the peak intensity ratio I3 / I2 is 0.6 or more and 4.5 or less.

4. 4. The ceramic substrate according to claim 1, wherein, in the spectra obtained by measuring the laser irradiated region and the laser non-irradiated region by the XPS, the absolute value of the value obtained by subtracting the value of the peak intensity of the strongest peak in the range of 528 eV to 536 eV in the irradiated region from the value of the peak intensity of the strongest peak in the non-irradiated region in the range is 1600 or less.

5. 4. The ceramic substrate according to claim 1, wherein, in the spectra obtained by measuring the laser irradiated region and the laser non-irradiated region by the XPS, the absolute value of the value obtained by subtracting the peak intensity of the strongest peak in the range of 395 eV to 400 eV in the irradiated region from the peak intensity of the strongest peak in the non-irradiated region in the range is 2500 or less.

6. 4. The ceramic substrate according to claim 1, wherein, in the spectra obtained by measuring the laser irradiation region and the laser non-irradiation region by the XPS, the absolute value of the value obtained by subtracting the peak intensity of the strongest peak in the range of 282 eV to 288 eV in the irradiated region from the peak intensity of the strongest peak in the non-irradiated region in the range is 2500 or less.

7. 2. A ceramic circuit board comprising the ceramic substrate according to claim 1, wherein a circuit portion is formed on the surface of the ceramic substrate.

8. 8. The ceramic circuit board according to claim 7, wherein a metal circuit is formed as the circuit portion on at least one of the surface irradiated with the laser and the surface opposite to the laser irradiated surface.

9. 8. The ceramic circuit board according to claim 7, wherein the circuit portion contains at least one material selected from the group consisting of aluminum, aluminum alloys, copper, and copper alloys.

10. 10. The ceramic circuit board according to claim 9, which is molded with resin.

11. A semiconductor device comprising the ceramic circuit board according to claim 7 and a semiconductor element mounted on the ceramic circuit board.

12. 2. A method for manufacturing a ceramic substrate according to claim 1, wherein a stage on which a sintered substrate is placed is moved and a laser is irradiated onto the sintered substrate to form a scribe line on the sintered substrate.

13. 10. A method for manufacturing a ceramic substrate, comprising forming a dot or continuous groove having a diameter of 100 μm or less on a part of at least one side of a sintered substrate using a step index type or grating index type fiber laser to form a scribe line, thereby manufacturing the ceramic substrate described in claim 1.

14. 2. A method for manufacturing a ceramic substrate according to claim 1, wherein the ceramic substrate is manufactured by irradiating a sintered substrate with a laser so that a focusing distance is 0.5 mm or more and 30 mm or less to form a scribe line on the sintered substrate.

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