Device for predicting cracking risk of SiC crystal in rough machining

Abstract

The utility model discloses a device for predicting the cracking risk of SiC crystal rough machining. The device comprises a crucible assembly, a heat preservation assembly and a heat preservation plate. The crucible assembly comprises a crucible, a sealing piece and a porous graphite plate, the porous graphite plate is installed in the crucible, the upper portion of the crucible is sealed through a crucible cover, air holes are formed in the crucible cover, and the air holes are communicated with the interior of the crucible; the sealing element is mounted in the crucible, the sealing element and the porous graphite plate jointly define a crystal growth space, and the seed crystal is mounted on the inner wall of the top of the sealing element. The heat preservation assembly wraps the crucible assembly; the insulation board is arranged in the insulation assembly and located at the upper part of the crucible assembly. Based on the device, the ingot cracking rate in the crystal rough machining process can be accurately predicted according to the difference value of the weights of part of the components in the heat insulation plate and the crucible component before and after the process operation, and the crystal growth surface type parameters, so that the risk of crystal cracking is judged, the machining waste is avoided, and the production cost is reduced. And meanwhile, the effect of monitoring the abnormity of a certain process parameter can be achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a semiconductor technical field especially is related to a device for predicting SiC crystal rough machining cracking risk. BACKGROUND

[0002] In the related art, in the PVT method silicon carbide crystal growth, through induction heating, when the induction coil is loaded with intermediate frequency alternating current, the surface layer of the graphite crucible generates huge heat due to the skin effect. Among them, part of the heat is transferred to the inside of the graphite crucible through the heat conduction mechanism, and the other part of the heat is transferred to other areas of the reaction chamber through the heat radiation mechanism. If the equipment simultaneously adopts double-layer quartz water cooling, the cooling water is generally introduced from the bottom and flows out from the top, taking away a large amount of heat, greatly reducing the temperature of the outer sleeve pipe, and making the temperature relatively stable, therefore, the temperature field in the reaction cavity is easily disturbed by the external environment, such as factory conditions, environmental temperature and thermal field material properties, etc. After a large amount of cooling water is introduced into the cavity, the temperature of the inner wall of the reaction cavity is lower than that of the center area, forming a radial temperature gradient. When the crystal diameter is small, the radial temperature gradient will not have a significant impact on the crystal growth, but as the crystal diameter increases, the impact of the radial temperature gradient on the crystal quality will become greater and greater.

[0003] Among them, compared with the axial temperature gradient, it is more difficult to establish and control the radial temperature gradient in order to maintain the growth of large-size single crystals. It is very important to realize in-situ annealing of the crystal in order to eliminate the growth stress or thermal stress in the large-size crystal, which directly determines whether the crystal will crack. In addition, the PVT usually adheres the seed crystal to the bottom of the graphite cover on the growth cavity, and the sticking method is to fix the seed crystal and is also the key to crystal growth. During the seed crystal fixing process, due to the different expansion coefficients of the seed crystal and the graphite, the seed crystal is easily affected by mechanical stress during the heating stage, which leads to crack formation and even separation. Light may cause dislocation and macroscopic defects, and heavy mechanical stress between them is also an important reason for the cracking of the crystal.

[0004] In the process of expanding the diameter of large-size seed crystals, or in the growth process of 8-inch silicon carbide single crystals, in order to maintain the large radial driving force required for large-size growth, there is a large radial temperature gradient in the thermal field of large-size single crystals. Therefore, there is a large radial thermal stress in the growth process (the non-uniform distribution of temperature along the radial direction during crystal growth will produce thermal stress in the crystal). In theory, there are two parts of heat that produce thermal stress: ① crystallization latent heat: its value is related to the chemical reaction enthalpy and crystal growth rate during crystallization, and as the thickness of the crystal increases, the crystallization latent heat is not easy to release; ② heat radiated from the inner wall of the crucible, this part of heat is redundant for crystal growth, it will cause the change of temperature gradient on the surface of the seed crystal. The changing radial temperature gradient is the main reason for the formation of various defects including microtubules.

[0005] The thermal stress caused by the radial temperature gradient can be alleviated by a simple method: prolonging the cooling time, i.e. designing a suitable annealing process, and the temperature control and corresponding time of the annealing section are particularly important, and the essence is to locally heat the crystal surface during the cooling process, so that the crystal surface and the crystal interior are at a lower temperature gradient. However, the limitations of infrared temperature measurement during annealing also affect the accuracy of temperature measurement. The infrared pyrometer is a non-contact temperature measuring instrument, which uses the balance comparison method to measure the radiation energy of the object and converts it into the corresponding temperature value. However, due to the high temperature in the reaction cavity and the movement of gaseous substances, the infrared temperature measurement and measurement value during annealing is only the relative temperature of the measured area. In addition, annealing can only alleviate the thermal stress after the crystal growth is completed, and cannot completely avoid the cracking of the crystal. Therefore, there is an urgent need for a method that can accurately predict the cracking risk during crystal processing to avoid processing waste and reduce enterprise production costs. SUMMARY

[0006] The utility model aims at at least one of the prior art existing technical problems. For this purpose, the utility model provides a device for predicting SiC crystal rough machining cracking risk, which can accurately predict the risk of cracking during crystal processing to avoid processing waste.

[0007] The device for predicting SiC crystal rough machining cracking risk according to the utility model comprises a crucible assembly, a heat preservation assembly and a heat preservation plate. The crucible assembly comprises a crucible, a sealing element and a porous graphite plate. The porous graphite plate is installed inside the crucible, which divides the inside of the crucible into a growth zone and a raw material zone. The upper part of the crucible is sealed by a crucible cover. The crucible cover is provided with an air hole, which is in communication with the inside of the crucible. The sealing element is installed inside the crucible, and its top is in close contact with the inner wall of the crucible cover. The sealing element and the porous graphite plate jointly define a crystal growth space, and a seed crystal is installed on the inner wall of the top of the sealing element. The heat preservation assembly is wrapped outside the crucible assembly. The bottom wall and the side wall of the crucible assembly are in close contact with the side wall of the heat preservation assembly. The top of the crucible and the top of the heat preservation assembly have a set distance. The heat preservation plate is arranged inside the heat preservation assembly and located at the upper part of the crucible assembly. The side wall of the heat preservation plate is in close contact with the inner wall of the heat preservation assembly.

[0008] Compared with the prior art, the utility model discloses a sealing element and porous graphite board filter the impurity in silicon carbide gas, improve the growth quality of crystal, simultaneously, based on this prediction device accurate prediction crystal rough machining process's crack rate, according to crack rate selection whether adjust long crystal or rough machining process, thereby reduce the risk of crystal cracking in rough machining process, to avoid processing waste. In addition, the prediction result obtained by the prediction device of the utility model can also reflect whether the thermal field or the crystal growth process deviates, thereby causing abnormal crystal growth quality. Therefore, the utility model can also monitor abnormal process parameters, thereby allowing researchers to timely adjust the crystal growth process to save enterprise production cost. The utility model is especially suitable for predicting the cracking risk of large-size 4H-SiC crystal rough machining.

[0009] Additional aspects and advantages of the utility model will be partially given in the following description, partially will become obvious from the following description, or be understood by the practice of the utility model. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is the schematic diagram of the device for predicting the cracking risk of SiC crystal rough machining according to one embodiment of the utility model;

[0011] Figure 2 is the crucible assembly schematic diagram of the device for predicting the cracking risk of SiC crystal rough machining according to one embodiment of the utility model;

[0012] Figure 3 is the local schematic diagram of the crucible assembly of the device for predicting the cracking risk of SiC crystal rough machining according to one embodiment of the utility model;

[0013] Figure 4 is the crystal schematic diagram of the device for predicting the cracking risk of SiC crystal rough machining according to one embodiment of the utility model;

[0014] Figure 5 is the crystal cross-section schematic diagram of the device for predicting the cracking risk of SiC crystal rough machining according to one embodiment of the utility model;

[0015] Figure 6 is the crystal hoshi schematic diagram of the device for predicting the cracking risk of SiC crystal rough machining according to one embodiment of the utility model;

[0016] REFERENCE NUMERALS:

[0017] 100: device for predicting the cracking risk of SiC crystal rough machining;

[0018] 110: heat preservation assembly; 111: heat preservation cover; 1111: hollow structure; 112: heat preservation cylinder; 113: first heat preservation ring; 114: second heat preservation ring;

[0019] 120: crucible assembly; 121: crucible; 122: crucible cover; 1220: air hole; 123: porous graphite plate; 124: growth zone; 1241: crystal growth space; 1242: exhaust space; 125: raw material zone; 1250: silicon carbide powder; 126: sealing element;

[0020] 130: heat preservation plate;

[0021] 140: seed crystal; 141: graphite paper;

[0022] 150: crystal;

[0023] 160: electromagnetic induction coil. DETAILED DESCRIPTION

[0024] Embodiments of the present application are described in detail below with reference to the attached drawing figures, wherein like reference numerals refer to like elements or elements with similar functions throughout the description of the drawing figures. The embodiments described below are examples of the present application, which are intended to explain the present application and are not intended to limit the present application.

[0025] The disclosure below provides many different embodiments or examples for implementing different structures of the present application. For the purpose of simplicity, the elements and settings of the specific examples below are described in detail. Of course, they are merely examples and are intended to explain the present application, and should not be considered as limiting the present application. In addition, the present application can repeatedly refer to the same reference numerals and / or letters in different examples. Such repetition is for the purpose of simplicity and clarity, and does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides various specific examples of processes and materials, but those skilled in the art can realize the applicability of other processes and / or the use of other materials.

[0026] The following description is made with reference to the accompanying drawings, in which: Figures 1 to 3The utility model discloses a device 100 for predicting SiC crystal rough machining cracking risk, including crucible subassembly 120, heat preservation subassembly 110, heat preservation board 130 and electromagnetic induction coil 160, the crucible subassembly 120 is placed in the heat field system of heat preservation subassembly 110 constitution, and electromagnetic induction coil 160 is surrounded in the outside of heat preservation subassembly 110. Among them, the crucible subassembly 120 includes crucible 121, crucible cover 122, sealing element 126 and porous graphite board 123, the heat preservation subassembly 110 includes heat preservation cylinder 112 (graphite soft felt), heat preservation cover 111 (graphite hard felt), first heat preservation ring 113, second heat preservation ring 114. The heat preservation cylinder 112 and heat preservation board 130 of this embodiment are all made of graphite soft felt, and the first heat preservation ring 113, the second heat preservation ring 114 and the heat preservation cover 111 are made of graphite hard felt.

[0027] Specifically, the crucible subassembly 120 is placed in the heat preservation cylinder 112, the bottom thickness of the heat preservation cylinder 112 is relatively thick, the bottom thickness of the heat preservation cylinder in the embodiment can be 405-410mm, the side wall and the bottom wall of the crucible 121 are tightly attached to the inner wall of the heat preservation cylinder 112, the top of the crucible 121 has a certain distance from the top of the heat preservation cylinder 112, the first heat preservation ring 113 is coaxially arranged on the upper part of the heat preservation cylinder 112, the inner diameter of the first heat preservation ring 113 is smaller than the inner diameter of the heat preservation cylinder 112, the upper part of the second heat preservation ring 114 is coaxially arranged on the upper part of the first heat preservation ring 113, the inner diameter of the second heat preservation ring 114 is the same as the inner diameter of the heat preservation cylinder 112, the heat preservation board 130 is placed inside the first heat preservation ring 113 and is placed on the second heat preservation ring 114, the side wall of the heat preservation board 130 is in close contact with the side wall of the second heat preservation ring 114, the upper part of the second heat preservation ring 114 is sealed by the heat preservation cover 111, the inside of the heat preservation cover 111 has a hollow structure 1111, and the longitudinal sectional area of the hollow structure 1111 gradually decreases from top to bottom.

[0028] The porous plate graphite plate is arranged inside the crucible 121, which separates the raw material area 125 for containing silicon carbide powder 1250 and the growth area 124 for crystal 150 growth inside the crucible 121, and the top of the crucible 121 is sealed by the crucible cover 122. In order to maintain the circulation of the hot field atmosphere, the graphite cover is provided with air holes 1220 penetrating through the graphite cover, which are in communication with the inside of the crucible 121; the sealing element 126 is arranged inside the crucible 121, the top of which is in close contact with the inner wall of the crucible cover 122, and the sealing element 126 cooperates with the porous graphite plate 123 to define a crystal growth space 1241. Further, the inner side wall of the growth area 124 of the crucible 121 is provided with an annular groove, which is sealed by the sealing element 126. Specifically, the sealing element 126 is an annular sealing element 126 with an opening at the lower part, which is made of porous graphite. The inner wall of the annular sealing element 126 cooperates with the porous graphite plate 123 to define a crystal growth space 1241, and the outer side wall of the annular sealing element 126 cooperates with the inner wall of the annular groove to define an exhaust space 1242. The air holes 1220 on the crucible cover 122 are in communication with the exhaust space 1242, and the air holes 1220 are uniformly arranged on the crucible cover 122 at an interval of 30°, with a diameter of 2 mm, and are close to the edge of the crucible cover 122.

[0029] Specifically, the crucible 121, the porous graphite plate 123, the sealing element 126 and the crucible cover 122 are assembled together by threading, clamping or extrusion. Before assembly, the seed crystal 140 bonded by the adhesive method is first fixed and sintered on the inner wall of the top of the sealing element 126, and then the assembly of each component is carried out.

[0030] The method for predicting the cracking risk of SiC crystal based on the above device specifically includes the following steps:

[0031] S1, obtaining the reference threshold values of parameters m"1, m"2, m"3 and m"4;

[0032] S2, recording the initial weight m1 of the heat preservation plate 130 before the process is run, and the total weight m2 of the crucible cover 122, the sealing element 126, the seed crystal 140 and the graphite paper 141;

[0033] S3, recording the weight m'1 of the heat preservation plate 130 after the process is run, and the total weight m'2 of the crucible cover 122, the sealing element 126, the seed crystal 140 and the graphite paper 141; the above data is weighed by a general balance with a precision of 0.1 g;

[0034] S4, obtaining parameters m"1 and m"2 by the following formula:

[0035] m"1 = m'1 - m1 (1)

[0036] m"2 = m'2 - m2 (2)

[0037] S5, obtain the parameter m"3 by the following formula:

[0038] m"3 = m"1 + m"2 (3)

[0039] S6, draw a herringbone measuring line along the surface of the grown crystal 150, and accurately measure the crystal 150 face shape parameters with a precision of 0.01 mm thickness gauge. Referring to the figure, specifically, take 4 points symmetrically along a single herringbone line, take the center point to measure the center thickness of the crystal 150, take the average of the highest thickness point + the lowest thickness point on a single herringbone line, subtract the center thickness, obtain three groups of data, and obtain the average value m"4 through the three groups of data; Figure 6

[0040] S7, compare the actual values of the parameters m"1, m"2, m"3 and m"4 with the reference threshold value, and determine the abnormal value if the parameter exceeds the reference threshold value, otherwise, it is a normal value, and set the cracking risk, i.e. the cracking rate t;

[0041] If the parameters m"1, m"2, m"3 and m"4 are normal values, t = 0%;

[0042] If the parameters m"2 and m"4 are normal values, and any one of the parameters m"1 and m"3 is an abnormal value, t ≤ 20%, which means that the crystal 150 has little possibility of cracking in the rough machining process, and basically will not crack in the later machining process, and can be normally transferred to the rough machining process;

[0043] If the parameter m"4 is a normal value, and only the parameter m"2 is an abnormal value among the other parameters, 20% < t < 75%, which means that the crystal 150 has a certain cracking risk in the rough machining process, but the probability of cracking is not very large, and can be normally transferred to the rough machining process;

[0044] If the parameter m"4 is a normal value, and any two of the parameters m"1, m"2 and m"3 are abnormal values, t ≥ 75%, which means that the crystal 150 has a great risk of cracking in the rough machining process, and has a high probability of cracking, and such a crystal 150 needs to be marked, processed by special processing technology, and fed back to the crystal growing section to enable the crystal growing section to adjust the crystal growing process in time.

[0045] ​If parameter m"4 is a normal value, and parameters m"1, m"2, and m"3 are all abnormal values, t = 100%, it means that crystal 150 will basically crack during the roughing process. This type of crystal 150 also needs to be marked as special and should not be transferred. It should be directly fed back to the crystal growth section so that the crystal growth section can adjust the crystal growth process in time.

[0046] If parameter m"4 is an abnormal value, t=100%, it indicates that there is a deviation in the thermal field or process, the growth quality of crystal 150 is abnormal, and the crystal will definitely crack during the rough processing.

[0047] Table 1. Calculation of theoretical values ​​for large-size silicon carbide crystals (150).

[0048] Diameter (mm) 160 180 200 210 215 Wafer area (cm 2 ) 200.96 254.34 314.00 342.90 362.87 Volume (cm 3 )]]> 358.8 454.2 560.7 600.6 647.9 Center thickness (mm) 17.86 17.86 17.86 17.86 17.86 Weight (g) 1148.3 1453.3 1794.2 1922.0 2073.6

[0049] Table 1 shows the theoretical values ​​calculated for large-size silicon carbide single crystals. The reference thresholds for parameters m"1, m"2, and m"3 were obtained using the following methods:

[0050] S1.1 Assume that silicon carbide crystal 150 reaches its theoretical optimal state after growth, refer to... Figure 4 and Figure 5 As shown, the growth interface of crystal 150 always maintains a near-flat, slightly convex state. At this point, crystal 150 can be considered an ideal cylinder, and the density of silicon carbide crystal 150 is 3.2 g / cm³. 3 The thickness of the silicon carbide crystal 150 is determined by the thermal insulation properties (which decrease under prolonged high temperatures) and the amount of silicon carbide powder 1250. Therefore, based on the actual thermal field conditions of this invention (the center thickness of the crystal 150 is approximately 18 mm) and the diameter of the crystal 150, the volume of crystals 150 with different diameters can be calculated, thereby calculating the theoretical weight of the crystal 150, which is the lower limit of m².

[0051] S1.2 To obtain the upper limit of parameter m"1, during the first single crystal debugging in the new hot zone, a higher power, such as 12-13 kW, is set according to the same charge weight and other conditions as normal crystal 150 growth, so that the carbonization rate of silicon carbide powder 1250 exceeds 70%, and the upper limit of parameter m"1 is obtained through formula (1). At the same time, the total weight of crucible cover 122, sealing part 126, seed crystal 140 and graphite paper 141 when the carbonization rate of silicon carbide powder 1250 exceeds 70% is recorded, and the upper limit of parameter m"2 is obtained through formula (2).

[0052] S1.3 In the second furnace single crystal debugging, the power is controlled according to the same idea as step S1.2, so that the total weight of the crucible cover 122, the sealing element 126, the seed crystal 140 and the graphite paper 141 increases by m, m = m"2 lower limit value ± 0.5, at this time, the weight m'1 of the heat preservation plate 130 is weighed, and the initial weight m1 of the crystal 150 before growth is subtracted, that is, the lower limit value of the parameter m"1 is obtained by formula (1);

[0053] S1.4 Based on the upper and lower limit values of the parameters m"1 and m"2, the upper and lower limit values of the parameter m"3 are obtained by formula (3);

[0054] Based on the above steps, the reference threshold values of the parameters m"1, m"2 and m"3 are obtained, and the reference threshold values of the parameters m"1, m"2 and m"3 are obtained by using the above invention idea combined with the actual data of the heat field of the utility model, as shown in Table 2.

[0055] Table 2 Reference threshold values of the parameters m"1, m"2 and m"3 of the large size silicon carbide crystal

[0056] Diameter (mm) Parameter m"1 parameter m"2 ​ 160 287.55～405.1 1148.3～1759.7 1435.8～2164.8 180 331.8～405.1 1453.3～1759.7 1785.1～2164.8 200 410.8～470.4 1794.2～2043.3 2205.0～2513.7 210 425.3～488.6 1859.6～2043.3 2284.9～2531.9 215 445.6～495.8 1925.1～2158.5 2370.7～2627.1

[0057] The reference threshold value of the parameter m"4 in this embodiment is obtained by the following method:

[0058] Suppose that the silicon carbide crystal reaches the theoretical best state after growth, and a plurality of groups of silicon carbide crystals in ideal best state are selected, and the following operations are performed on each group of silicon carbide crystals: draw a rice-shaped measuring line along the surface of the grown crystal, and symmetrically take 4 points along a single rice-shaped line, take the center point to measure the center thickness of the crystal, take the average of the highest point and the lowest point on a single rice-shaped line, and subtract the center thickness to obtain three groups of data, and obtain the average value through the three groups of data, which is the growth surface type parameter, denoted as parameter m"4; the reference threshold value of the parameter m"4 obtained based on a plurality of groups of silicon carbide crystals in ideal best state is 0-0.25.

[0059] Table 3 Risk of cracking caused by growth stress of large size silicon carbide crystal 150 (crack rate) determination

[0060] Parameter m"1 ​ ​ Parameter m"4 Predicted crack rate t Actual crack rate t Normal Normal Normal Normal t＝0％ t＝0％ Abnormal Normal Normal Normal t≤20％ t＝0％ Normal Normal Abnormal Normal t≤20％ t＝3％ Abnormal Abnormal Normal Normal 75％≤t≤100％ t＝75％ Normal Abnormal Abnormal Normal 75％≤t≤100％ t＝83％ Abnormal Normal Abnormal Abnormal 75％≤t≤100％ t＝100％ Abnormal Normal Normal Abnormal t＝100％ t＝100％ Normal Normal ​ ​ 20％＜t＜75％ t＝25％

[0061] As shown in Table 3, the crack trend of 100 groups of sample data after 8 inch 200 mm diameter crystal 150 growth is shown in Table 3, and it can be seen from the table that:

[0062] When the parameter m"4 is a normal value, and the parameters m"1, m"2 and m"3 are normal values, the crystal with such data does not crack in the rough machining process, and the actual crack rate t = 0%, which is consistent with the prediction result, and will not crack.

[0063] When the parameter m"4 is normal, and only the parameter m"1 is abnormal in other parameters, the crystal with such data does not crack in the roughing process, the cracking rate t = 0%, which is far less than 20%, consistent with the prediction result, and the cracking probability is very small.

[0064] When the parameter m"4 is normal, and only the parameter m"3 is abnormal in other parameters, the crystal with such data has 3% of the crystals that appear cracking phenomenon in the roughing process, the actual cracking rate t = 3%, which is far less than 20%, consistent with the prediction result, and the cracking probability is very small.

[0065] When the parameter m"4 is normal, and the parameters m"1 and m"2 are abnormal in other parameters, the crystal with such data has 75% of the crystals that appear cracking phenomenon in the roughing process, the cracking rate t = 75%, consistent with the prediction result, and the probability of cracking of the crystal in the roughing process is very large;

[0066] When the parameter m"4 is normal, and the parameters m"1 and m"3 are abnormal in other parameters, the crystal with such data has 83% of the crystals that appear cracking phenomenon in the roughing process, the cracking rate t = 83%, consistent with the prediction result, and the probability of cracking of the crystal in the roughing process is very large;

[0067] When the parameter m"4 is normal, and the parameters m"1, m"2, and m"3 are all abnormal, the crystal with such data all appears cracking phenomenon in the roughing process, the cracking rate t = 100%, consistent with the prediction result, and the probability of cracking of the crystal in the roughing process is 100%;

[0068] When the parameter m"4 is normal, and only the parameter m"2 is abnormal in other parameters, the crystal with such data has 25% of the crystals that appear cracking phenomenon in the roughing process, the actual cracking rate t = 25%, consistent with the prediction result, and has the risk of cracking, therefore, it can be seen that the abnormal parameter m"2 has a greater impact on the cracking of the crystal 150, therefore, in the actual growth of the crystal 150, the parameter m"2 should be focused on. In addition, the above considers that the parameter m"4 is normal, that is, within the reference threshold (0-2.5). When the parameter m"4 exceeds the reference threshold, it indicates that the thermal field or the process deviates, and the quality of the crystal 150 growth is abnormal, then there is no need to predict the cracking of the crystal 150, therefore, the importance order of predicting whether the crystal 150 has the risk of cracking should be the parameter m"4 greater than the parameter m"2 greater than the others.

[0069] Tables 4 and 5 are respectively the prediction and actual situation of the first embodiment and the second embodiment of the silicon carbide crystal 150 with an 8-inch 200mm diameter as an example.

[0070] Table 4: Predicted and actual cases of 8-inch, 200mm-diameter SiC crystal 150, first embodiment

[0071]

[0072]

[0073] As can be seen from Table 4, when the actual parameter m"4 is an abnormal value, the crystal will certainly crack during rough machining, the predicted cracking rate t = 100%, and the actual cracking rate is also 100%, which is consistent with the predicted result.

[0074] Table 5: Predicted and actual cases of 8-inch, 200mm-diameter SiC crystal 150, second embodiment

[0075]

[0076]

[0077] As can be seen from the embodiment shown in Table 5, when the parameter m"4 is an abnormal value, the predicted cracking rate is 100%, and the actual crystal will also crack during machining, which cannot be transferred, needs to be marked and fed back to the crystal growth section for defect analysis and process improvement, which speeds up the process improvement schedule. The crystal with a predicted cracking rate less than 20% will not crack during rough machining, and can be normally transferred to the rough machining process; the crystal with a predicted cracking rate between 75% and 100% has a high risk of cracking during rough machining, but it may not crack, so it can be normally transferred to the rough machining process.

[0078] In summary, the four parameters have a strong correlation, and in addition, the upper limit of the reference threshold value has a greater impact on the stress of the crystal 150 than the lower limit of the reference threshold value. It can be understood that when the actual data of the three parameters m"1, m"2 and m"3 are lower than the lower limit of the reference threshold value, the actual risk of cracking of the crystal 150 is lower than the theoretical cracking rate, i.e. the theoretical cracking risk, and when each parameter exceeds or is lower than the reference threshold value by a certain range, about 50-80g, the actual cracking risk is also much lower than the predicted cracking rate. The prediction method of the embodiment plays a key guiding significance in controlling the crystal 150 growth process and whether to transfer for machining in combination with the device of the embodiment of the utility model.

[0079] Other configurations of the device 100 for predicting the rough machining cracking risk of the SiC crystal according to the embodiment of the utility model, such as the crucible 121, the electromagnetic induction coil 160 and the insulation cylinder 112, etc. and the operation are known to those skilled in the art, and will not be described in detail here.

[0080] In the description of the utility model, it is understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the utility model.

[0081] In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "multiple" is two or more than two, unless otherwise specifically limited.

[0082] In the utility model, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrated; it can be mechanical connection, or electrical connection, or communication; it can be directly connected, or indirectly connected through intermediate medium, or the communication or interaction relationship between two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0083] In the utility model, unless otherwise specifically defined and limited, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be directly above or obliquely above the first feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be directly below or obliquely below the first feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0084] In the description of the present specification, the description referring to the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without mutual contradiction.

[0085] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. An apparatus for predicting the risk of cracking of a SiC crystal during roughing, characterized by, Comprising A crucible assembly, which comprises a crucible, a sealing element and a porous graphite plate, the porous graphite plate is installed inside the crucible, separating the inside of the crucible into a growth zone and a raw material zone, the upper part of the crucible is sealed by a crucible cover, a gas hole is opened on the crucible cover, which is in communication with the inside of the crucible; the sealing element is installed inside the crucible, and its top is in close contact with the inner wall of the crucible cover, the sealing element and the porous graphite plate jointly define a crystal growth space, and a seed crystal is installed on the inner wall of the top of the sealing element; A heat preservation assembly, which is wrapped outside the crucible assembly, the bottom wall and the side wall of the crucible are in close contact with the side wall of the heat preservation assembly, and there is a set distance between the top of the crucible and the top of the heat preservation assembly; A heat preservation plate, which is arranged inside the heat preservation assembly and located at the upper part of the crucible assembly, and the side wall of the heat preservation plate is in close contact with the inner wall of the heat preservation assembly.

2. The device for predicting SiC crystal roughing cracking risk according to claim 1, characterized in that, The side wall of the growth zone of the crucible is provided with an annular groove, which is sealed by the sealing element, and the sealing element is an annular sealing element with an opening at the bottom, and the outer side wall of the annular sealing element and the inner wall of the annular groove jointly define an exhaust space, and the gas hole on the crucible cover is in communication with the exhaust space.

3. The device for predicting the risk of cracking of a SiC crystal roughing according to claim 2, characterized in that, The gas holes are uniformly arranged on the crucible cover at an interval of 30°, the diameter of the gas holes is 2mm, and the gas holes are close to the edge of the crucible cover.

4. The device for predicting the risk of cracking of a SiC crystal roughing according to any one of claims 1 to 3, characterized in that, The heat preservation assembly comprises a heat preservation cylinder, a first heat preservation ring, a second heat preservation ring and a heat preservation cover, the first heat preservation ring is coaxially arranged on the upper part of the heat preservation cylinder, and its inner diameter is smaller than the inner diameter of the heat preservation cylinder, the second heat preservation ring is coaxially arranged on the upper part of the first heat preservation ring, and its inner diameter is the same as the inner diameter of the heat preservation cylinder, the heat preservation plate is arranged inside the second heat preservation ring and is clamped on the second heat preservation ring, and the side wall of the heat preservation plate is in close contact with the side wall of the second heat preservation ring.

5. The device for predicting the risk of cracking of a SiC crystal roughing according to claim 4, characterized in that, The seed crystal is installed on the inner wall of the top of the sealing element through graphite paper.

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