Seed crystal substrate with adhesive layer and seed crystal unit

Abstract

To strike a balance between improvement in adhesive strength between a principal surface of a seed crystal substrate and an adhesive layer and suppression of cracks in the seed crystal substrate.SOLUTION: A seed crystal substrate 60 (seed crystal substrate with adhesive layer) includes: a principal surface 60A; and an adhesive layer 65 formed on the principal surface 60A, where the adhesive layer 65 is constituted of an adhesive agent containing phenol, the adhesive layer 65 has a thickness of 3 μm or more, and the principal surface 60A has roughness of 10 nm or less.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a seed crystal substrate with an adhesive layer and a seed crystal unit, and relates to a technique that is effective when applied to a seed crystal substrate with an adhesive layer and a seed crystal unit for growing a single crystal by a solution growth method, for example. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2015-30659 (Patent Document 1) describes a technique for improving adhesive strength by roughening the adhesive surface of a seed crystal substrate made of silicon carbide by electric discharge machining (roughness: Ra>500 nm). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-30659 A Summary of the Invention [Problem to be solved by the invention]

[0004] For example, to grow a single crystal by a solution growth method, a seed crystal unit that provides a nucleus for growth is used. This seed crystal unit includes, for example, a seed crystal substrate having a main surface, a sheet-like member that is bonded to the main surface of the seed crystal substrate via an adhesive layer, and a jig that is bonded to the sheet-like member. At this time, the seed crystal substrate and the sheet-like member are bonded to each other by an adhesive layer, and the roughness of the main surface of the seed crystal substrate is increased (Ra>30 nm) in order to improve the adhesive strength between the main surface of the seed crystal substrate and the adhesive layer.

[0005] However, when the seed crystal substrate and the sheet-like member are bonded via the adhesive layer, heating is performed, and the present inventor has newly discovered that the heating process causes the seed crystal substrate to crack. Therefore, based on the new knowledge found by the present inventor, it is necessary to improve the adhesive strength between the main surface of the seed crystal substrate and the adhesive layer, while it is desirable to suppress cracking of the seed crystal substrate. In other words, it is desirable to simultaneously improve the adhesive strength between the main surface of the seed crystal substrate and the adhesive layer and suppress cracking of the seed crystal substrate. [Means for solving the problem]

[0006] In one embodiment, the seed crystal substrate with an adhesive layer includes a main surface and an adhesive layer formed on the main surface, where the adhesive layer is made of an adhesive containing a phenol, the thickness of the adhesive layer is 3 μm or more, and the roughness of the main surface is 10 nm or less.

[0007] In one embodiment, the seed crystal unit includes a seed crystal substrate having a main surface, a sheet-like member bonded to the main surface of the seed crystal substrate via an adhesive layer, and a jig bonded to the sheet-like member, wherein the adhesive layer is made of an adhesive containing phenol, the thickness of the adhesive layer is 3 μm or more, and the roughness of the main surface is 10 nm or less. Effect of the Invention

[0008] According to one embodiment, it is possible to simultaneously improve the adhesive strength between the main surface of the seed crystal substrate and the adhesive layer and suppress cracking of the seed crystal substrate. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration of a single crystal manufacturing apparatus according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing a configuration of a seed crystal unit. [Diagram 3] FIG. 2 is a cross-sectional view showing a seed crystal unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In all the drawings for explaining the embodiments, the same members are generally designated by the same reference numerals, and the repeated explanations thereof will be omitted. In addition, hatching may be applied even to plan views in order to make the drawings easier to understand.

[0011] <Configuration of single crystal manufacturing equipment> FIG. 1 is a diagram showing the configuration of a single crystal manufacturing apparatus 100 according to the present embodiment.

[0012] In Fig. 1, a single crystal manufacturing apparatus 100 has a container 10. The internal space of this container 10 is filled with, for example, argon gas. A heat insulating member 13c is provided inside the container 10, and a pedestal 11 that can rotate in the horizontal direction is disposed inside the heat insulating member 13c. The container 10 is made of, for example, an iron-based material such as SUS.

[0013] As a filling structure for argon gas, for example, a structure can be adopted in which a quartz tube is passed between the insulating member 13c and the coil 14a and between the insulating member 13c and the coil 14b, and the upper and lower ends of the quartz tube are sealed with flanges to fill with argon gas.

[0014] Next, crucible 12 is placed on pedestal 11. This crucible 12 is made of, for example, graphite, and contains high-temperature solution 20 containing silicon (Si) inside. Specifically, crucible 12 includes a main body portion capable of containing solution 20 containing carbon and silicon, and heat transfer portion 12a protruding from the bottom of the main body portion.

[0015] In the crucible 12 thus configured, the heat transfer portion 12a also functions as a "foot portion," so that the heat transfer portion 12a can be said to have a secondary function of stably standing the crucible 12 upright. The heat transfer portion 12a is configured to be in contact with a pedestal 11 on which the crucible 12 can be placed. For example, as shown in FIG. 1, the pedestal 11 includes a first region R1 in contact with the heat transfer portion 12a, a second region R2 surrounded by the first region R1, and a third region R3 surrounding the first region R1, and a heat insulating member 13a is provided so as to be in contact with the second region R2, and a heat insulating member 13b is provided so as to be in contact with the third region R3.

[0016] The pedestal 11 is connected to a crucible holding shaft 18 that holds the pedestal 11. The crucible holding shaft 18 is configured to be movable in the vertical direction and to be able to rotate either clockwise or counterclockwise. This allows the pedestal 11 attached to the crucible holding shaft 18 and the crucible 12 placed on the pedestal 11 to be moved in the vertical direction and rotated in the horizontal direction by the crucible holding shaft 18. The crucible holding shaft 18 has a hollow structure inside, and is configured to allow a thermocouple or a radiation thermometer to be inserted therein for temperature measurement.

[0017] A coil through which a high-frequency current flows is provided on the outer periphery of the container 10 of the single crystal manufacturing apparatus 100, and the crucible 12 is heated by induction heating based on the high-frequency current flowing through the coil. Specifically, the single crystal manufacturing apparatus 100 has a heating unit 25a and a heating unit 25b. The heating unit 25a is configured to heat the crucible 12 by an induction heating phenomenon caused by passing a high-frequency current through the coil 14a provided at a position facing the side surface of the crucible 12. In other words, since the coil 14a functions as the heating unit 25a that heats the crucible 12, the heating unit 25a is also shown in FIG. 1 in addition to the coil 14a. On the other hand, the heating unit 25b is configured to heat the pedestal 11 by an induction heating phenomenon caused by passing a high-frequency current through the coil 14b provided at a position facing the pedestal 11 supporting the crucible 12. Then, the crucible 12 is heated by thermal conduction from the heated pedestal 11. In detail, heat is transferred from the pedestal 11 heated by the heating unit 25b to the heat transfer unit 12a, and then heat is transferred from the heat transfer unit 12a to the crucible 12 (main body) to heat the crucible 12. In this way, the heating unit 25b is configured to indirectly heat the crucible 12 via the pedestal 11 by an induction heating phenomenon caused by passing a high-frequency current through the coil 14b provided at a position opposite to the pedestal 11 supporting the crucible 12. For this reason, the coil 14b functions as the heating unit 25b that heats the crucible 12, and therefore the heating unit 25b is also shown in FIG. 1 in addition to the coil 14b. Although not shown in FIG. 1, the coil 14b and the coil 14a are configured to allow cooling water to flow inside.

[0018] In this way, in the single crystal manufacturing apparatus 100, the crucible 12 is configured so that not only the crucible 12 itself is heated by the heating section 25a, but also the crucible 12 is heated by thermal conduction from the pedestal 11 heated by the heating section 25b, and it can be said that the heat transfer section 12a of the crucible 12 has the function of thermally conducting the heat from the pedestal 11 heated by the heating section 25b to the main body section.

[0019] Here, in order to facilitate heating of pedestal 11 by heating portion 25b, the thickness of pedestal 11 is increased so that the portion facing coil 14b is large. This pedestal 11 can be integrated with crucible 12, but considering the need to replace crucible 12 every time a silicon carbide single crystal is manufactured and the high manufacturing cost of the integrated product, it is desirable to configure pedestal 11 and crucible 12 as separate bodies. When pedestal 11 and crucible 12 are configured as separate bodies, the heat transfer portion 12a of crucible 12 may be simply disposed on pedestal 11, or pedestal 11 may be configured so that heat transfer portion 12a can be fitted into pedestal 11.

[0020] These heating units 25a and 25b are controlled by a control unit 50. That is, the single crystal manufacturing apparatus 100 has a control unit 50 that controls the power supplied to the heating units 25a and the power supplied to the heating units 25b. For example, the power supply that supplies power to the heating units 25a and the power supply that supplies power to the heating units 25b are separate power supplies, and the control unit 50 is configured to be able to control each of the heating units 25a and 25b, which have different power supplies.

[0021] The control unit 50 is configured to be able to alternate between a first operation of adjusting the power supplied to heating unit 25a and the power supplied to heating unit 25b so that the temperature of the solution 20 in contact with the side of the crucible 12 is higher than the temperature of the solution 20 in contact with the bottom of the crucible 12, and a second operation of adjusting the power supplied to heating unit 25a and the power supplied to heating unit 25b so that the temperature of the solution 20 in contact with the bottom of the crucible 12 is higher than the temperature of the solution 20 in contact with the side of the crucible 12.

[0022] The solution 20 contained in the crucible 12 heated by the heating parts 25a and 25b is at a high temperature, and the graphite (C) constituting the crucible 12 melts, so that the solution 20 contains carbon and silicon. The crucible lid 15 is attached to the crucible 12, and the crucible lid 15 has a cylindrical member 15a and a connecting member 15b connected to the cylindrical member 15a. The connecting member 15b has a function of fixing and supporting the cylindrical member 15a, and is configured to be able to come into contact with the crucible 12, for example.

[0023] Next, the single crystal manufacturing apparatus 100 is provided with a crystal holding shaft 16 that is movable in the vertical direction. This crystal holding shaft 16 may also be configured to be rotatable clockwise or counterclockwise, similar to the crucible holding shaft 18. In other words, the crystal holding shaft 16 and the crucible holding shaft 18 may or may not have a rotation mechanism.

[0024] A seed crystal unit 40 is attached to the tip of the crystal holding shaft 16. The crystal holding shaft 16 also has a fin structure 16a attached so as to intersect with the extension direction of the crystal holding shaft 16. Furthermore, the inside of the crystal holding shaft 16 has a hollow structure, and a thermocouple 17 for measuring the temperature in the vicinity of the seed crystal unit 40 is inserted into the inside of the crystal holding shaft 16. The temperature in the vicinity of the seed crystal unit 40 can also be measured by disposing a radiation thermometer having a measurement diameter smaller than the inner diameter of the crystal holding shaft 16 at the upper end of the crystal holding shaft 16, instead of inserting the thermocouple 17.

[0025] The control unit 50 of the single crystal manufacturing apparatus 100 is also configured to control the crystal holding shaft 16 having the fin structure 16a to move in the vertical direction. Specifically, the control unit 50 is configured to control the crystal holding shaft 16 so that the crystal holding shaft 16 having the fin structure 16a moves in the vertical direction through the inside of the cylindrical member 15a. The control unit 50 is configured to move the crystal holding shaft 16, to which the seed crystal unit 40 is attached at the tip, in the downward direction, so that the lower surface of the seed crystal unit 40 comes into contact with the surface of the solution 20 contained in the crucible 12, and to move the crystal holding shaft 16 in the upward direction after the lower surface of the seed crystal unit 40 comes into contact with the surface of the solution 20, so that a single crystal made of silicon carbide can be grown on the lower surface of the seed crystal unit 40. The seed crystal unit 40 may be brought into contact with the solution 20, but it is particularly preferable that the seed crystal unit 40 comes into contact with the surface of the solution 20.

[0026] In addition, the configuration in which a single crystal made of silicon carbide can be grown on the lower surface of the seed crystal unit 40 by moving the crystal holding shaft 16 upward is one example. For example, the single crystal made of silicon carbide may be grown on the lower surface of the seed crystal unit 40 while the crystal holding shaft 16 is stopped (maintained), or the single crystal made of silicon carbide may be grown on the lower surface of the seed crystal unit 40 by moving the crystal holding shaft 16 downward. This configuration takes into consideration, for example, that the surface of the solution 20 may drop due to evaporation of the solution 20. That is, when the surface of the solution 20 recedes due to evaporation of the solution 20, the single crystal can be reliably grown on the seed crystal unit 40 by growing the single crystal while moving the crystal holding shaft 16 downward.

[0027] The single crystal manufacturing apparatus 100 is configured as described above.

[0028] <Modification> In the single crystal manufacturing apparatus 100 shown in FIG. 1, the heating section 25b for heating the pedestal 11 is an example that utilizes the induction heating phenomenon caused by passing a high-frequency current through the coil 14b. However, the heating section 25b for heating the pedestal 11 is not limited to this and may be composed of, for example, a resistance heater provided below the pedestal 11.

[0029] However, when the heating unit 25b is made of a resistance heater, it is necessary to provide a "hole" in the heat insulating material in order to route a pair of wires used to energize the resistance heater. In particular, when the crucible 12 itself is configured to rotate, it is necessary to provide a circumferential opening in the heat insulating material in order to route the pair of wires. As a result, it may become difficult to ensure the high temperature retention characteristics of the crucible 12. Therefore, from the viewpoint of increasing the heat insulating effect of the heat insulating material and simplifying the configuration of the single crystal manufacturing apparatus 100, it is preferable that the heating unit 25b that heats the pedestal 11 is made of an induction heater that utilizes the induction heating phenomenon as shown in FIG. 1.

[0030] <Operation of single crystal manufacturing equipment (single crystal manufacturing method)> Next, the operation of the single crystal manufacturing apparatus 100 will be described.

[0031] First, the control unit 50 lowers the crystal holding shaft 16 having the seed crystal unit 40 attached to its tip. As a result, the seed crystal unit 40 attached to the crystal holding shaft 16 passes through the inside of the cylindrical member 15a provided on the crucible lid 15, and then comes into contact with the surface of the solution 20 containing carbon and silicon contained in the crucible 12. At this time, the fin structure 16a attached to the crystal holding shaft 16 is disposed in a position facing the inner wall of the cylindrical member 15a.

[0032] Next, the control unit 50 slowly raises the crystal holding shaft 16. As a result, a silicon carbide single crystal grows on the lower surface of the seed crystal unit 40 being pulled up. At this time, the fin structure 16a attached to the crystal holding shaft 16 moves while maintaining its facing against the inner wall of the cylindrical member 15a. Thereafter, if the crystal growth is to be continued, the pulling operation of the crystal holding shaft 16 is continued. On the other hand, if the crystal growth is to be ended, the control unit 50 further raises the crystal holding shaft 16 to separate the silicon carbide single crystal from the solution 20. This ends the growth of the silicon carbide single crystal. At this time, the fin structure 16a attached to the crystal holding shaft 16 is maintained in a state in which it is disposed at a position facing the inner wall of the cylindrical member 15a.

[0033] In the manner described above, a silicon carbide single crystal can be manufactured by operating single crystal manufacturing apparatus 100. Although it has been described that crystal growth is terminated by further pulling up crystal holding shaft 16 to separate the silicon carbide single crystal from solution 20, the present invention is not limited to this, and for example, instead of pulling up crystal holding shaft 16, the crucible holding shaft 18 can be pulled down to separate the silicon carbide single crystal from solution 20 and terminate the crystal growth.

[0034] <Seed crystal unit configuration> Next, the configuration of the seed crystal unit 40 will be described.

[0035] Fig. 2 is a diagram showing the configuration of seed crystal unit 40. As shown in Fig. 2, seed crystal unit 40 is composed of a seed crystal substrate 60 formed of a silicon carbide single crystal, a carbon sheet 70 made of carbon, and a carbon jig 80 made of carbon. The seed crystal substrate 60 and the carbon sheet 70 are bonded together with an adhesive. Similarly, the carbon sheet 70 and the carbon jig 80 are bonded together with an adhesive.

[0036] The seed crystal substrate 60 is, for example, a wafer formed from a silicon carbide single crystal. The seed crystal substrate 60 has a main surface (upper surface) to be bonded to the carbon sheet 70, and a lower surface (rear surface) located opposite to the main surface. The lower surface of the seed crystal substrate 60 is brought into contact with the solution 20 shown in FIG. 1. This allows a silicon carbide single crystal to grow on the lower surface of the seed crystal substrate 60.

[0037] The carbon sheet 70 is a sheet-like member made of carbon, and is disposed so as to be interposed between the seed crystal substrate 60 and the carbon jig 80. This carbon sheet 70 is provided to relieve the stress acting between the seed crystal substrate 60 and the carbon jig 80. In other words, the carbon sheet 70 functions as a stress relief sheet that relieves the stress generated due to the difference in thermal expansion coefficient between the seed crystal substrate 60 and the carbon jig 80.

[0038] The carbon jig 80 has, for example, a screw hole (not shown) and is configured so that, for example, the crystal holding shaft 16 shown in Fig. 1 can be inserted therein. That is, the carbon jig 80 has a function of fixing the seed crystal unit 40 to the tip portion of the crystal holding shaft 16.

[0039] FIG. 3 is a cross-sectional view showing the seed crystal unit 40. As shown in FIG.

[0040] In FIG. 3, the seed crystal substrate 60 has a main surface 60A and a bottom surface 60B. The bottom surface 60B is the surface that is to be in contact with the solution 20 shown in FIG. 1. Meanwhile, an adhesive layer 65 is formed on the main surface 60A. Thus, the seed crystal substrate 60 includes the main surface 60A and the adhesive layer 65 formed on the main surface 60A. Then, a carbon sheet 70 is arranged so as to be adhered to the main surface 60A of the seed crystal substrate 60 via the adhesive layer 65. Furthermore, a carbon jig 80 is arranged so as to be adhered to the carbon sheet 70 via the adhesive layer 75.

[0041] Here, each of the adhesive layer 65 and the adhesive layer 75 is made of, for example, an adhesive containing phenol. The adhesive containing phenol is, for example, a photoresist.

[0042] Photoresist is usually used for patterning using photolithography technology, but in this embodiment, photoresist is used as an adhesive because photoresist has the following advantages: (1) it is easy to apply because of its low viscosity, and (2) the thickness of the adhesive layer can be accurately controlled because a method for controlling the thickness of the applied layer using a spin coater has been established.

[0043] In this manner, the seed crystal unit 40 is constructed.

[0044] <Consideration of improvements> In the above-mentioned seed crystal unit 40, it is necessary to ensure the adhesive strength between the seed crystal substrate 60 and the carbon sheet 70 via the adhesive layer 65. For this reason, the roughness of the main surface 60A of the seed crystal substrate 60 is increased. This is because, by increasing the roughness of the main surface 60A, the surface area of ​​the main surface 60A is increased, and as a result, the adhesive strength between the main surface 60A of the seed crystal substrate 60 and the adhesive layer 65 can be improved. That is, in the conventional technology, it is common to roughen the main surface 60A of the seed crystal substrate 60 constituting the seed crystal unit 40 from the viewpoint of ensuring the adhesive strength, as in Patent Document 1 described in the Background Art.

[0045] In regard to this point, the present inventors have newly discovered that roughening the main surface 60A of the seed crystal substrate 60 by performing a surface roughening treatment makes the seed crystal substrate 60 more susceptible to cracking. Specifically, when the roughness of the main surface 60A is made rough, the difference in roughness between the main surface 60A and the roughness (for example, about 1 nm) of the lower surface 60B that has not been subjected to the surface roughening treatment becomes large.

[0046] As a result, the present inventors speculate that the Twyman effect generates stress in the seed crystal substrate 60, and the heating performed when bonding the seed crystal substrate 60 and the carbon sheet 70 via the adhesive layer 65 causes cracks in the seed crystal substrate 60. That is, it is common knowledge among those skilled in the art that the main surface 60A of the seed crystal substrate 60 constituting the seed crystal unit 40 is roughened from the viewpoint of ensuring adhesive strength. However, the present inventors have newly discovered that this common knowledge increases the possibility of cracks occurring in the seed crystal substrate 60. That is, while roughening the main surface 60A is useful from the viewpoint of ensuring adhesive strength, there is room for improvement in that the side effect of cracks occurring in the seed crystal substrate 60 becomes apparent. Therefore, some ingenuity is required to simultaneously improve the adhesive strength between the main surface of the seed crystal substrate and the adhesive layer and suppress cracks in the seed crystal substrate.

[0047] In view of this, in the present embodiment, a technique is implemented to improve the adhesive strength between the main surface of the seed crystal substrate and the adhesive layer while suppressing cracking of the seed crystal substrate. The technical concept of this embodiment is described below.

[0048] <Basic Concept of the Embodiment> The basic idea of ​​this embodiment is to reduce the roughness of the main surface 60A of the seed crystal substrate 60 while increasing the thickness of the adhesive layer 65. As a result, the roughness of the main surface 60A is reduced, and the difference in roughness with the lower surface 60B is reduced, so that the occurrence of the Twyman effect, which causes stress, can be suppressed. Therefore, according to the basic idea, the occurrence of cracks in the seed crystal substrate 60 can be suppressed. However, in this case, the surface area of ​​the main surface 60A is reduced, so that the adhesive strength between the main surface 60A and the adhesive layer 65 may decrease. In this regard, the basic idea is to increase the thickness of the adhesive layer 65. As a result, the decrease in the adhesive strength between the main surface 60A and the adhesive layer 65 can be suppressed. That is, according to the basic idea, first, the roughness of the main surface 60A is reduced to suppress the occurrence of cracks in the seed crystal substrate 60, and the decrease in the adhesive strength between the main surface 60A and the adhesive layer 65, which becomes apparent when the roughness of the main surface 60A is reduced, is prevented by increasing the thickness of the adhesive layer 65. From the above, according to the basic concept, it is possible to simultaneously improve the adhesive strength between the main surface 60A of the seed crystal substrate 60 and the adhesive layer 65 and suppress cracking of the seed crystal substrate 60.

[0049] In this specification, roughness means "Ra". "Ra" is a height-direction parameter called "arithmetic mean roughness". "Ra" is obtained by extracting a portion of the roughness curve measured by a roughness meter over a reference length and expressing the unevenness of that section as an average value. Since "Ra" uses an average value, it is less susceptible to the influence of a single protruding scratch, and has the advantage of providing stable results in evaluating surface roughness.

[0050] <Embodiment> Hereinafter, an embodiment that embodies the above-mentioned basic concept will be described.

[0051] First, a brief description will be given of a method for manufacturing the seed crystal unit 40. For example, a description will be given of an example in which a seed crystal substrate 60 having a diameter of φ=150 mm is used.

[0052] 5 ml of photoresist is dropped onto the center of the seed crystal substrate 60. Then, the substrate is rotated in a spin coater under the conditions of (1) 600 rpm×20 seconds, and then (2) 1500 rpm×20 seconds to spread the photoresist. As a result, an adhesive layer 65 made of photoresist is formed on the main surface 60A of the seed crystal substrate 60. At this time, the thickness of the adhesive layer 65 is 3 μm to 4 μm.

[0053] Next, the main surface 60A of the seed crystal substrate 60 coated with the photoresist and the carbon sheet 70 are attached to each other, and heated on a hot plate to 200° C. or higher. This allows the seed crystal substrate 60 and the carbon sheet 70 to be bonded together via the adhesive layer 65.

[0054] Next, the carbon sheet 70 and the carbon jig 80 are bonded together via the adhesive layer 75. After that, the mixture is heated and sintered at 1000° C. or higher in an inert atmosphere. In this way, the seed crystal unit 40 can be manufactured.

[0055] Here, the characteristic features of the embodied embodiment are that the roughness of the main surface 60A of the seed crystal substrate 60 is 10 nm or less, and the thickness of the adhesive layer 65 bonding the seed crystal substrate 60 and the carbon sheet 70 is 3 μm or more and 30 μm or less.

[0056] As a result, firstly, the roughness of the main surface 60A of the seed crystal substrate 60 is 10 nm or less, and since the roughness of the main surface 60A is small, the difference in roughness with the lower surface 60B is small, so that the occurrence of the Twyman effect, which causes stress, can be suppressed. Therefore, according to the characteristic point of the embodied aspect, the occurrence of cracks in the seed crystal substrate 60 can be suppressed.

[0057] Here, the roughness Ra (arithmetic mean roughness) is calculated by evaluating the center of the seed crystal substrate 60 using a Bruker optical interference microscope (ContourGT-K) with a 50x lens and the VXI method (Vertical Scan Interferometry: high-resolution vertical scanning interferometry).

[0058] According to the feature of the embodied aspect, since the thickness of the adhesive layer 65 that bonds the seed crystal substrate 60 and the carbon sheet 70 is 3 μm or more and 30 μm or less, even if the roughness of the main surface 60A is small, the thick adhesive layer 65 can suppress a decrease in the adhesive strength between the main surface 60A and the adhesive layer 65. In this way, according to the feature, it is possible to improve the adhesive strength between the main surface 60A of the seed crystal substrate 60 and the adhesive layer 65 and suppress cracking of the seed crystal substrate 60 at the same time. As a result, according to the feature, it is possible to improve the adhesive strength between the seed crystal substrate 60 and the carbon sheet 70 and suppress cracking of the seed crystal substrate 60 at the same time.

[0059] As described above, the characteristic features of the embodied mode are that the roughness of the main surface 60A of the seed crystal substrate 60 is 10 nm or less and that the thickness of the adhesive layer 65 bonding the seed crystal substrate 60 and the carbon sheet 70 is 3 μm or more and 30 μm or less, but below, if the numerical ranges stipulated by these characteristic features are not met, cracking of the seed crystal substrate 60 or peeling of the carbon sheet 70 from the seed crystal substrate 60 may occur. An example of this will be described.

[0060] First, an example in which the seed crystal substrate was cracked as a result of high roughness will be described.

[0061] For example, a copper surface plate was used to process the main surface of a seed crystal substrate with diamond abrasive grains of 5s (3μm to 8μm) to a roughness of the main surface of Ra=33.5nm. Then, 5ml of photoresist was dropped onto the center of the seed crystal substrate, and the substrate was rotated under the conditions of (1) 600rpm×20 seconds, and then (2) 1500rpm×20 seconds to spread the photoresist. Then, the seed crystal substrate was bonded to a carbon sheet and prebaked, and cracks (cracks) occurred in the seed crystal substrate. This is thought to be because the roughness of the main surface was Ra=33.5nm, which was larger than Ra=10nm, and the cracks occurred in the seed crystal substrate.

[0062] Next, an example will be described in which the carbon sheet peeled off from the seed crystal substrate as a result of the photoresist being too thin. For example, a Pla-Pad surface plate was used to process the main surface of the seed crystal substrate with diamond abrasive grains having a particle size of 5s (3 μm to 8 μm), and the roughness of the main surface was set to Ra=5.9 nm. Then, 5 ml of photoresist was dropped onto the center of the seed crystal substrate, and the substrate was rotated under the conditions of (1) 600 rpm×20 seconds, and then (2) 3000 rpm×20 seconds, so that the photoresist was spread. At this time, the thickness of the photoresist was less than 3 μm (about 2 μm). Then, the seed crystal substrate and the carbon sheet were bonded together and prebaked, and the carbon sheet peeled off from the seed crystal substrate. This is thought to be due to the fact that the thickness of the photoresist was about 2 μm, which is smaller than 3 μm, and the adhesive strength between the main surface of the seed crystal substrate and the adhesive layer was reduced, resulting in the peeling off of the carbon sheet.

[0063] For the above reasons, if the numerical range defined by the characteristic points in the embodiment is deviated from, there is a risk that the seed crystal substrate may crack or the carbon sheet may peel off from the seed crystal substrate. Therefore, in order to simultaneously improve the adhesive strength between the seed crystal substrate and the carbon sheet and suppress cracking of the seed crystal substrate, it is useful to realize the characteristic points in the embodiment.

[0064] The invention made by the inventor has been specifically described above based on the embodiment thereof. However, it goes without saying that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. [Explanation of symbols]

[0065] 10 containers 11 Pedestal 12 Crucible 12a Heat transfer section 13a Insulation materials 13b Insulation material 13c Insulation materials 14a Coil 14b Coil 15 Crucible lid 15a Cylindrical member 15b Connection member 16 Crystal holding shaft 16a Fin structure 17 Thermocouple 18 Crucible holding shaft 20 solution 25a Heating section 25b Heating section 40 Seed Crystal Unit 50 Control section 60 Seed crystal substrate 60A Main surface 60B Bottom 65 Adhesive layer 70 Carbon Sheet 75 Adhesive layer 80 Carbon jig 100 Single crystal manufacturing equipment R1 1st area R2 2nd area R3 3rd area

Claims

1. A main surface; an adhesive layer formed on the main surface; A seed crystal substrate with an adhesive layer comprising: The adhesive layer is made of a phenol-containing adhesive, The thickness of the adhesive layer is 3 μm or more, A seed crystal substrate with an adhesive layer, wherein the main surface has a roughness of 10 nm or less.

2. The seed crystal substrate with an adhesive layer according to claim 1 , The adhesive layer is made of a photoresist.

3. The seed crystal substrate with an adhesive layer according to claim 1 , The adhesive layer has a thickness of 30 μm or less.

4. The seed crystal substrate with an adhesive layer according to claim 1 , The seed crystal substrate with an adhesive layer is made of silicon carbide.

5. a seed crystal substrate having a main surface; a sheet-like member bonded to the main surface of the seed crystal substrate via an adhesive layer; A jig for adhering to the sheet-like member; A seed crystal unit comprising: The adhesive layer is made of a phenol-containing adhesive, The thickness of the adhesive layer is 3 μm or more, A seed crystal unit, wherein the roughness of the main surface is 10 nm or less.

6. The seed crystal unit according to claim 5 , The adhesive layer is made of a photoresist.

7. The seed crystal unit according to claim 5 , The adhesive layer has a thickness of 30 μm or less.

8. The seed crystal unit according to claim 5 , the seed crystal substrate is made of silicon carbide; the sheet-like member is a carbon sheet, The jig is a carbon jig.

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