SiC crystal rough machining ingot cracking rate prediction device and method

Abstract

The invention discloses a SiC crystal rough machining ingot cracking rate prediction device which 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 prediction method can accurately predict the ingot cracking rate in the crystal rough machining process according to the difference value of the weights of part of the components in the insulation board 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 present invention relates to the field of semiconductor technology, and in particular to a device and method for predicting a SiC crystal rough machining ingot splitting rate. Background Art

[0002] It is pointed out in the relevant technology that in the growth of silicon carbide crystals by the PVT method, through induction heating, when the induction coil is loaded with medium-frequency alternating current, the graphite dry surface 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 adopts double-layer quartz water cooling, the cooling water is generally introduced from the bottom and then flows out from the top, taking away a large amount of heat, greatly reducing the temperature of the outer wall of the outer sleeve, and making its temperature relatively stable. Therefore, the temperature field in the reaction chamber is susceptible to external environmental disturbances, such as factory conditions, ambient temperature, and thermal field material properties. After a large amount of cooling water is introduced into the cavity, the temperature of the inner wall of the reaction chamber is lower than the temperature of the central area, forming a radial temperature gradient. When the crystal diameter is small, the radial temperature gradient will not have a significant effect on crystal growth, but as the crystal diameter increases, the radial temperature gradient will have an increasingly greater impact on crystal quality.

[0003] Among them, compared with the axial temperature gradient, in order to maintain the growth of large-sized single crystals, the radial temperature gradient is also more difficult to establish and control. It is very important to eliminate the growth stress or thermal stress in large-sized crystals and to achieve in-situ annealing of the crystals, which directly determines whether the crystals will crack. In addition, PVT usually bonds the seed crystals to the bottom of the graphite cover on the growth chamber. The bonding method is the key to achieving the fixation of the seed crystals and the growth of crystals. During the seed crystal fixation process, during the heating stage, due to the different expansion coefficients of the seed crystals and the graphite itself, they are easily affected by mechanical stress, resulting in crack formation or even separation. At the least, dislocations and macroscopic defects may occur. At worst, the mechanical stress between the two is also an important cause of crystal cracking.

[0004] In the diameter expansion process for the preparation of large-sized 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, the thermal field of large-sized single crystals has a large radial temperature gradient. Therefore, there is a large radial thermal stress during the growth process (the uneven distribution of temperature along the radial direction during crystal growth will produce thermal stress in the crystal). In theory, there are two sources of heat that produce thermal stress: ① Latent heat of crystallization: its value is related to the chemical reaction enthalpy and crystal growth rate during the crystallization process, and as the thickness of the crystal increases, the latent heat of crystallization is not easy to release; ② Heat radiated from the inner wall of the crucible, this part of heat is redundant for crystal growth, and it will cause a change in the temperature gradient on the surface of the seed crystal. The changing radial temperature gradient is the main cause of the formation of various defects, including microtubes.

[0005] The above-mentioned thermal stress caused by the existence of radial temperature gradient can be alleviated by a simple method: extend the cooling time, that is, design a suitable annealing process. The temperature control and corresponding time of the return section are particularly important. Its essence is to locally heat the crystal surface during the cooling process so that the crystal surface and the inside of the crystal are under a lower temperature gradient. However, the limitations of infrared temperature measurement during the annealing process also affect the accuracy of temperature measurement. Infrared pyrometer is a type of non-contact temperature measuring instrument that uses a balanced comparison method to measure the radiation energy of an object and converts it into a corresponding temperature value. However, due to the high temperature in the reaction chamber and the movement of gaseous substances, the infrared temperature measurement values ​​during the annealing process are only the relative temperature of the measured area. In addition, annealing only relieves the thermal stress after the end of crystal growth, and cannot completely prevent crystal cracking. Therefore, there is an urgent need for a method that can accurately predict the risk of cracking during crystal processing to avoid processing waste and reduce enterprise production costs. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a device for predicting the cracking rate of SiC crystal rough processing, which can accurately predict the risk of cracking during crystal processing to avoid processing waste.

[0007] The present invention also proposes a method for predicting the SiC crystal rough machining ingot splitting rate based on the above prediction device.

[0008] According to the first aspect of the present invention, the device for predicting the ingot splitting rate of SiC crystal rough processing comprises a crucible assembly, an insulation assembly and an insulation plate; the crucible assembly comprises a crucible, a seal and a porous graphite plate, the porous graphite plate is installed inside the crucible, and the inside of the crucible is divided into a growth zone and a raw material zone, the upper part of the crucible is sealed by a crucible cover, and the crucible cover is provided with air holes, and the air holes are connected to the inside of the crucible; the seal is installed inside the crucible, and its top is in close contact with the inner wall of the crucible cover, the seal and the porous graphite plate jointly define a crystal growth space, and the seed crystal is installed on the inner wall of the top of the seal. The insulation assembly is wrapped around the outside of the crucible assembly, the bottom wall and the side wall of the crucible assembly are in close contact with the side wall of the insulation tube, and there is a set distance between the top of the crucible and the top of the insulation tube; the insulation plate is arranged inside the insulation assembly and located at the upper part of the crucible assembly, and the side wall of the insulation plate is in close contact with the inner wall of the insulation assembly.

[0009] The method for predicting the SiC crystal rough processing ingot splitting rate according to the second aspect of the present invention comprises the following steps:

[0010] S1, setting the reference thresholds of parameters m"1, m"2, m"3, m"4;

[0011] S2, record the initial weight m1 of the insulation board before the process is run, and the total weight m2 of the crucible cover, seal, seed crystal and graphite paper;

[0012] S3, recording the weight of the insulation board m'1 and the total weight of the crucible cover, seal, seed crystal and graphite paper m'2 after the process operation is completed;

[0013] S4. Obtain the parameters m"1 and m"2 by the following formula:

[0014] m"1 = m'1 - m1 (1)

[0015] m"2 = m'2 - m2 (2)

[0016] S5. Obtain the parameter m"3 by the following formula:

[0017] m"3 = m"1 + m"2 (3)

[0018] S6. Draw a cross-shaped measurement line along the surface of the grown crystal, and take 4 points symmetrically along the single cross-shaped line, take the center point to measure the center thickness of the crystal, take the average value of the highest thickness point + the lowest thickness point on the single cross-shaped line, subtract the center thickness, and obtain three sets of data. The average value is the growth surface parameter, recorded as parameter m";

[0019] S7. Compare the actual values ​​of parameters m"1, m"2, m"3, and m"4 with the reference thresholds. Parameters exceeding the reference thresholds are considered abnormal values, otherwise, they are normal values:

[0020] If the parameters m"1, m"2, m"3, and m"4 are all abnormal values, t = 0%;

[0021] If m"2 and m"4 are normal values, and any one of m"1 and m"3 is an abnormal value, t≤20%;

[0022] If parameter m"4 is a normal value, and only parameter m"2 is an abnormal value among other parameters, 20%<t<75%;

[0023] If parameter m"4 is a normal value, and any two of parameters m"1, m"2, and m"3 are abnormal values, t≥75%;

[0024] If parameter m"4 is a normal value, and parameters m"1, m"2, and m"3 are all abnormal values, t = 100%;

[0025] If the parameter m"4 is an abnormal value, t = 100%, it means that the thermal field or process has deviated and the crystal growth quality is abnormal.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1) The present invention uses seals and porous graphite plates to filter impurities in silicon carbide gas, thereby improving the growth quality of the crystal. At the same time, by calculating the weight difference m"1 of some components in the crucible assembly before and after the process, and the weight difference m"2 of the insulation plate, the parameter m"3 is obtained. Combined with the crystal growth surface parameter m"4, the above four parameters are compared with the benchmark thresholds of the four parameters, so as to accurately predict the ingot cracking rate of the crystal rough processing process, and choose whether to adjust the crystal growth or rough processing process according to the ingot cracking rate, so as to reduce the risk of crystal cracking during the rough processing process to avoid processing waste.

[0028] 2) In the prediction method of the present invention, if the growth surface parameter m"4 exceeds the reference threshold, it can reflect that the thermal field or crystal growth process has deviated and the crystal growth quality is abnormal. Therefore, the present invention can also play a role in monitoring the abnormality of a certain process parameter, so that the research and development personnel can adjust the crystal growth process in time to save the production cost of the enterprise. The present invention is particularly suitable for predicting the cracking rate of large-size 4H-SiC crystal rough processing.

[0029] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of a device for predicting the ingot splitting rate of SiC crystal rough processing according to an embodiment of the present invention;

[0031] Figure 2 Schematic diagram of a crucible assembly of a device for predicting the ingot splitting rate of SiC crystal rough processing according to an embodiment of the present invention;

[0032] Figure 3 is a partial schematic diagram of a crucible assembly of a device for predicting the ingot splitting rate of SiC crystal rough processing according to an embodiment of the present invention;

[0033] Figure 4 Schematic diagram of a crystal according to a method for predicting the ingot splitting rate of SiC crystal rough processing according to an embodiment of the present invention;

[0034] Figure 5 is a schematic diagram of a crystal cross section of a method for predicting a SiC crystal rough machining ingot splitting rate according to an embodiment of the present invention;

[0035] Figure 6 : is a crystal cross-shaped diagram of a method for predicting the ingot splitting rate of SiC crystal rough processing according to an embodiment of the present invention;

[0036] Reference numerals:

[0037] 100: SiC crystal rough processing ingot cracking rate prediction device;

[0038] 110: insulation component; 111: insulation cover; 1111: hollow structure; 112: insulation cylinder; 113: first insulation ring; 114: second insulation ring;

[0039] 120: crucible assembly; 121: crucible; 122: crucible cover; 1220: air hole; 123: porous graphite plate; 124: growth area; 1241: crystal growth space; 1242: exhaust space; 125: raw material area; 1250: silicon carbide powder; 126: sealing element;

[0040] 130: Insulation board;

[0041] 140: seed crystal; 141: graphite paper;

[0042] 150: crystal;

[0043] 160: Electromagnetic induction coil. DETAILED DESCRIPTION

[0044] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0045] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific processes and examples of materials, but those of ordinary skill in the art can be aware of the applicability of other processes and / or the use of other materials.

[0046] Reference below Figures 1 to 3A device 100 for predicting the cracking rate of SiC crystal rough machining according to an embodiment of the present invention is described, comprising a crucible assembly 120, a heat preservation assembly 110, a heat preservation plate 130 and an electromagnetic induction coil 160, wherein the crucible assembly 120 is placed in a thermal field system formed by the heat preservation assembly 110, and the electromagnetic induction coil 160 surrounds the outside of the heat preservation assembly 110. The crucible assembly 120 comprises a crucible 121, a crucible cover 122, a seal 126 and a porous graphite plate 123; the heat preservation assembly 110 comprises a heat preservation tube 112 (graphite soft felt), a heat preservation cover 111 (graphite hard felt), a first heat preservation ring 113 and a second heat preservation ring 114. In this embodiment, the heat preservation tube 112 and the heat preservation plate 130 are 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.

[0047] Specifically, the crucible assembly 120 is placed in the insulation tube 112, the bottom thickness of the insulation tube 112 is relatively thick, and the bottom thickness of the insulation tube in this embodiment can be 405-410 mm, the side wall and the bottom wall of the crucible 121 are close to the inner wall of the insulation tube 112, and there is a certain distance between the top of the crucible 121 and the top of the insulation tube 112, the first insulation ring 113 is coaxially arranged on the upper part of the insulation tube 112, the inner diameter of the first insulation ring 113 is smaller than the inner diameter of the insulation tube 112, and the second insulation ring 114 is The upper part is coaxially arranged on the upper part of the first insulation ring 113, the second insulation ring 114 has the same inner diameter as the insulation tube 112, the insulation plate 130 is placed inside the first insulation ring 113, and is placed on the second insulation ring 114, and the side wall of the insulation plate 130 is in close contact with the side wall of the second insulation ring 114; the upper part of the second insulation ring 114 is sealed by the insulation cover 111, and the insulation cover 111 has a hollow structure 1111 inside, and the longitudinal cross-sectional area of ​​the hollow structure 1111 gradually decreases from top to bottom.

[0048] The porous graphite plate is arranged inside the crucible 121, and the inside of the crucible 121 is divided into a raw material area 125 and a growth area 124. The raw material area 125 is used to hold silicon carbide powder 1250, and the growth area 124 is used to grow crystals 150. The top of the crucible 121 is sealed by a crucible cover 122. In order to maintain the circulation of the hot field atmosphere, the graphite cover is provided with air holes 1220 that penetrate the graphite cover, and the air holes 1220 are connected to the inside of the crucible 121; the sealing member 126 is installed inside the crucible 121, and its top is in close contact with the inner wall of the crucible cover 122. The sealing member 126 and the porous graphite plate 123 jointly define a crystal growth space 1241. Furthermore, an annular groove is provided on the inner wall of the crucible 121 of the growth zone 124, and the annular groove is sealed by a seal 126. Specifically, the seal 126 is an annular seal 126 with an opening at the lower portion. The present embodiment is made of porous graphite. The inner wall of the annular seal 126 and the porous graphite plate 123 jointly define a crystal growth space 1241. The outer wall of the annular seal 126 and the inner wall of the annular groove jointly define an exhaust space 1242. The pores 1220 on the crucible cover 122 are connected to the exhaust space 1242. The pores 1220 are evenly provided on the crucible cover 122 at intervals of 30°. The pores 1220 have a diameter of 2 mm, and are close to the edge of the crucible cover 122.

[0049] Specifically, the crucible 121, the porous graphite plate 123, the seal 126 and the crucible cover 122 are assembled together by screw thread, slot or extrusion. Before assembly, the seed crystal 140 bonded by gluing is first fixed and sintered on the top inner wall of the seal 126, and then the components are assembled.

[0050] The method for predicting the SiC crystal rough processing ingot splitting rate based on the above device specifically comprises the following steps:

[0051] S1, obtain the reference thresholds of parameters m"1, m"2, m"3, m"4;

[0052] S2, recording the initial weight m1 of the insulation plate 130 before the process is run, and the total weight m2 of the crucible cover 122, the seal 126, the seed crystal 140 and the graphite paper 141;

[0053] S3, after the process is finished, record the weight m'1 of the insulation board 130 and the total weight m'2 of the crucible cover 122, the seal 126, the seed crystal 140 and the graphite paper 141; in this embodiment, an ordinary balance with an accuracy of 0.1g is used to weigh the above data;

[0054] S4. Obtain the parameters m"1 and m"2 by the following formula:

[0055] m"1 = m'1 - m1 (1)

[0056] m"2 = m'2 - m2 (2)

[0057] S5. Obtain the parameter m"3 by the following formula:

[0058] m"3 = m"1 + m"2 (3)

[0059] S6. Draw a cross-shaped measuring line along the surface of the grown crystal 150, and use a 0.01mm thickness gauge to accurately measure the surface parameters of the crystal 150. Figure 6 As shown, specifically, four points are taken symmetrically along a single cross line, and the central point is taken to measure the central thickness of the crystal 150. On the single cross line, the average value of the highest thickness point + the lowest thickness point is taken, and the central thickness is subtracted to obtain three sets of data, and the average value m"4 is obtained through the three sets of data;

[0060] S7, compare the actual values ​​of parameters m"1, m"2, m"3, and m"4 with the reference threshold, and determine the parameters exceeding the reference threshold as abnormal values, otherwise, as normal values, and set the ingot splitting rate as t;

[0061] If the parameters m"1, m"2, m"3, and m"4 are all normal values, t = 0%;

[0062] If m"2 and parameter m"4 are normal values, and any one of parameters m"1 and m"3 is an abnormal value, t≤20%, indicating that during the rough processing, the possibility of crystal 150 cracking is very small, and basically it will not crack during the later processing, and can be normally transferred to the rough processing process;

[0063] If parameter m"4 is a normal value, and only parameter m"2 is an abnormal value among other parameters, 20%<t<75%, which means that during the rough machining process, crystal 150 has a certain risk of cracking, but the probability of cracking is not very high, and it can be transferred to the rough machining process normally;

[0064] If parameter m"4 is a normal value, and any two of parameters m"1, m"2, and m"3 are abnormal values, t≥75%, it means that during the rough processing, the risk of crystal 150 cracking is very high and there is a high probability that it will crack. This type of crystal 150 needs to be marked and processed with a special processing technology. At the same time, it needs to be fed back to the crystal growth section so that the crystal growth section can adjust the crystal growth process in time.

[0065] If parameter m"4 is a normal value, and parameters m"1, m"2, and m"3 are all abnormal values, t=100%, indicating that during the rough processing, crystal 150 will basically crack. This crystal 150 also needs to be marked and cannot be circulated. 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.

[0066] If the parameter m"4 is an abnormal value, t = 100%, it means that the thermal field or process has deviated, the growth quality of the crystal 150 is abnormal, and the crystal will definitely crack during the rough processing.

[0067] Table 1 Theoretical value calculation of large size silicon carbide crystal 150

[0068]

[0069]

[0070] As shown in Table 1, the theoretical values ​​calculated for large-size silicon carbide single crystals, the benchmark thresholds of parameters m"1, m"2, and m"3 are obtained by the following method:

[0071] S1.1 Assume that the silicon carbide crystal 150 reaches the theoretical optimal state after growth, refer to Figure 4 and Figure 5 As shown, the growth interface of the crystal 150 always maintains a nearly flat and slightly convex state. At this time, the crystal 150 can be regarded as an ideal cylinder. The density of the silicon carbide crystal 150 is 3.2 g / cm 3 , and the thickness of the silicon carbide crystal 150 is determined by the thermal insulation of the thermal field (the thermal insulation decays under long-term high temperature conditions) and the amount of silicon carbide powder 1250. Therefore, according to the actual thermal field conditions of the present invention (the center thickness of the crystal 150 is about 18mm) and the diameter of the crystal 150, the volume of the crystal 150 with different diameters can be calculated, thereby calculating the theoretical weight of the crystal 150, which is the lower limit value of m"2;

[0072] S1.2 To obtain the upper limit of the parameter m"1, in the commissioning of the first single crystal furnace in the new heat field, a higher power, such as 12-13kw, is set according to the charging weight and other conditions that are exactly the same as those for the normal crystal 150 growth, so that the carbonization rate of the silicon carbide powder 1250 exceeds 70%, and the upper limit of the parameter m"1 is obtained by formula (1). At this time, the total weight of the crucible cover 122, the seal 126, the seed crystal 140 and the graphite paper 141 is recorded at the same time when the carbonization rate of the silicon carbide powder 1250 exceeds 70%, and the upper limit of the parameter m"2 is obtained by formula (2);

[0073] S1.3 According to the same idea as step S1.2, in the debugging of the second furnace single crystal, the power is controlled so that the total weight of the crucible cover 122, the seal 126, the seed crystal 140 and the graphite paper 141 increases by m, m = m"2 lower limit ± 0.5. At this time, the weight m'1 of the insulation board 130 is weighed and subtracted from the initial weight m1 of the crystal 150 before growth, that is, the lower limit of the parameter m"1 is obtained by formula (1);

[0074] S1.4 Based on the upper and lower limit values ​​of parameter m"1 and parameter m"2, the upper and lower limit values ​​of parameter m"3 are obtained by formula (3);

[0075] Based on the above steps, the benchmark thresholds of parameters m"1, m"2, and m"3 are obtained. Specifically, the above-mentioned inventive ideas are combined with multiple groups of actual data of the thermal field of the present invention to obtain the benchmark thresholds of parameters m"1, parameter m"2, and parameter m"3, as shown in Table 2.

[0076] Table 2 Benchmark thresholds for parameters m"1, m"2, and m"3 of large-size SiC crystals

[0077]

[0078]

[0079] The reference threshold of the parameter m4 in this embodiment is obtained by the following method:

[0080] Assuming that the silicon carbide crystal reaches a theoretical optimal state after growth, multiple groups of silicon carbide crystals in the ideal optimal state are selected, and the following operations are performed on each group of silicon carbide crystals: a cross-shaped measurement line is drawn along the surface of the grown crystal, and 4 points are symmetrically selected along the single cross-shaped line, and the central point is taken to measure the central thickness of the crystal. On the single cross-shaped line, the highest thickness point + the lowest thickness point are averaged, and the central thickness is subtracted to obtain three groups of data. The average value is obtained from the three groups of data. The average value is the growth surface parameter, recorded as parameter m"4; based on the multiple groups of silicon carbide crystals in the ideal optimal state, the benchmark threshold value of the parameter m"4 is 0 to 0.25.

[0081] Table 3 Determination of the risk of cracking (ingot cracking rate) caused by growth stress of large-sized silicon carbide crystals 150

[0082] <![CDATA[Parameter m "1]]> <![CDATA[Parameter m"2]]> <![CDATA[Parameter m "3]]> <![CDATA[Parameter m "4]]> Predicted ingot breakage rate t Actual ingot breaking 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 normal 75％≤t≤100％ t＝100％ abnormal abnormal abnormal normal t＝100％ t＝100％ normal abnormal normal normal 20％＜t＜75％ t＝25％

[0083] As shown in Table 3, the ingot cracking trend in 100 sets of sample data after 8-inch 200mm diameter crystal 150 was grown. It can be seen from the table that:

[0084] When parameter m"4 is a normal value, and parameter m"1, parameter m"2, and parameter m"3 are all normal values, the crystal with such data will not crack during the rough processing, and the actual ingot cracking rate t=0%, which is consistent with the predicted result and will not crack.

[0085] When parameter m"4 is a normal value, and only parameter m"1 is an abnormal value among other parameters, the crystal with such data does not crack during the rough processing, and the ingot cracking rate t=0%, which is far less than 20%, is consistent with the predicted results, and the probability of cracking is very small.

[0086] When parameter m"4 is a normal value, and only parameter m"3 is an abnormal value among other parameters, 3% of the crystals with such data crack during the rough processing. The actual cracking rate t=3%, which is far less than 20%, is consistent with the predicted results and the cracking probability is very small.

[0087] When parameter m"4 is a normal value, and parameters m"1 and m"2 are abnormal values, 75% of the crystals with this data crack during the roughing process, and the cracking rate t = 75%, which is consistent with the prediction result. The probability of crystal cracking during the roughing process is very high;

[0088] When parameter m"4 is a normal value, and parameters m"1 and m"3 are abnormal values, 83% of the crystals with this data crack during the roughing process, and the cracking rate t=83%, which is consistent with the prediction result. The probability of crystal cracking during the roughing process is very high.

[0089] When parameter m"4 is a normal value, and parameter m"1, parameter m"2, and parameter m"3 are all abnormal values, the crystal with such data will crack during the rough machining process, and the cracking rate t=100%, which is consistent with the prediction result. The probability of the crystal cracking during the rough machining process is 100%;

[0090] When parameter m"4 is a normal value, and only parameter m"2 is an abnormal value among other parameters, 25% of the crystals with such data crack during the rough processing, and the actual cracking rate t=25%, which is consistent with the prediction result, and there is a risk of cracking. Therefore, it can be seen that the abnormal parameter m"2 has a relatively large impact on the cracking of crystal 150. Therefore, in the actual growth of crystal 150, parameter m"2 should be focused on controlling. In addition, the above consideration is that parameter m"4 is normal, that is, within the reference threshold (0~2.5). When parameter m"4 exceeds the reference threshold, it means that the thermal field or process has deviations, and the growth quality of crystal 150 is abnormal. In this case, there is no need to predict the cracking of crystal 150. Therefore, the order of importance for predicting whether crystal 150 has a risk of cracking should be parameter m"4 greater than parameter m"2 greater than others.

[0091] Table 4 and Table 5 are respectively the predicted and actual conditions of the first and second embodiments, taking the 8-inch 200 mm diameter silicon carbide crystal 150 as an example.

[0092] Table 4 Taking 8 inches 200mm diameter as an example, the predicted situation and actual situation of silicon carbide crystal 150 First embodiment

[0093]

[0094]

[0095] It can be seen from Table 4 that when the actual parameter m"4 is an abnormal value, the crystal will definitely crack during the rough processing process. The predicted cracking rate t = 100%, and the actual cracking is 100%, which is consistent with the predicted result.

[0096] Table 5 Taking 8 inches 200mm diameter as an example, the predicted situation and actual situation of silicon carbide crystal 150 Second embodiment

[0097]

[0098] It can be seen from the embodiment shown in Table 5 that when the parameter m"4 is an abnormal value, the predicted ingot splitting rate is 100%, and the actual crystal will also crack during the processing and cannot be circulated. It needs to be marked and fed back to the crystal growth section for defect analysis and process improvement, which speeds up the process improvement progress. Crystals with a predicted ingot splitting rate of less than or equal to 20% will basically not crack during the rough processing and can be normally transferred to the rough processing process; crystals with a predicted ingot splitting rate between 75% and 100% have a greater risk of cracking during the rough processing, but will not necessarily crack, so they can be normally transferred to the rough processing process.

[0099] In summary, there is a strong correlation between the four parameters. In addition, compared with the lower limit of the benchmark threshold, the upper limit of the benchmark threshold has a greater impact on the stress of crystal 150. 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 benchmark threshold, the actual risk of crystal 150 cracking is lower than the theoretical ingot cracking rate. At the same time, when each parameter exceeds or falls below a certain range of the benchmark threshold, about 50 to 80g, the actual ingot cracking risk is also much lower than the predicted ingot cracking rate. The prediction method of this embodiment combined with the device of the embodiment of the present invention plays a key guiding role in the growth process control of crystal 150 and whether it is circulated for processing.

[0100] Other components of the SiC crystal rough processing ingot splitting rate prediction device 100 and the prediction method according to the embodiment of the present invention, such as the crucible 121, the electromagnetic induction coil 160 and the heat preservation cylinder 112, etc., as well as the operation are well known to ordinary technicians in the field and will not be described in detail here.

[0101] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0102] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0103] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0104] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0105] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0106] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A device for predicting the cracking rate of SiC crystal rough processing, characterized in that: include A crucible assembly, the crucible assembly comprising a crucible, a sealing member and a porous graphite plate, the porous graphite plate being installed inside the crucible to separate the inside of the crucible into a growth zone and a raw material zone, the upper portion of the crucible being sealed by a crucible cover, the crucible cover being provided with pores which are connected to the inside of the crucible; the sealing member being installed inside the crucible, the top of the sealing member being in close contact with the inner wall of the crucible cover, the sealing member and the porous graphite plate jointly defining a crystal growth space, and the seed crystal being installed on the inner wall at the top of the sealing member. A heat preservation component, wherein the heat preservation component is wrapped around the outside of the crucible component, the bottom wall and the side wall of the crucible component are in close contact with the side wall of the heat preservation cylinder, and there is a set distance between the top of the crucible and the top of the heat preservation cylinder; The heat preservation plate is arranged inside the heat preservation component and located on the upper part of the crucible component, and the side wall of the heat preservation plate is in close contact with the inner wall of the heat preservation component.

2. The SiC crystal rough machining ingot splitting rate prediction device according to claim 1, characterized in that: An annular groove is provided on the side wall of the crucible in the growth zone, and the annular groove is sealed by the seal. The seal is an annular seal with an opening at the bottom. The outer wall of the annular seal and the inner wall of the annular groove jointly define an exhaust space, and the air hole on the crucible cover is connected to the exhaust space.

3. The device for predicting the SiC crystal rough machining ingot splitting rate according to claim 2, characterized in that: The air holes are evenly arranged on the crucible cover at intervals of 30 degrees, the diameter of the air holes is 2 mm, and the air holes are close to the edge of the crucible cover.

4. The device for predicting the SiC crystal rough machining ingot splitting rate according to any one of claims 1 to 3, characterized in that: The insulation component includes an insulation tube, a first insulation ring, a second insulation ring and an insulation cover. The first insulation ring is coaxially arranged on the upper part of the insulation tube, and its inner diameter is smaller than the inner diameter of the insulation tube. The second insulation ring is coaxially arranged on the upper part of the first insulation ring, and its inner diameter is the same as the inner diameter of the insulation tube. The insulation plate is placed inside the second insulation ring and overlapped on the second insulation ring. The side wall of the insulation plate is in close contact with the side wall of the second insulation ring.

5. The device for predicting the SiC crystal rough machining ingot splitting rate according to claim 4, characterized in that: The seed crystal is mounted on the top inner wall of the sealing member through graphite paper.

6. A method for predicting the cracking rate of SiC crystal rough processing, characterized in that: The following steps are involved: S1. Set the benchmark thresholds of parameters m"1, m"2, m"3, and m"4: S2, record the initial weight m1 of the insulation board before the process is run, and the total weight m2 of the crucible cover, seal, seed crystal and graphite paper; S3, recording the weight of the insulation board m'1 and the total weight of the crucible cover, seal, seed crystal and graphite paper m'2 after the process operation is completed; S4. Obtain the parameters m"1 and m"2 by the following formula: m"1 = m'1 - m1 (1) m"2 = m'2 - m2 (2) S5. Obtain the parameter m"3 by the following formula: m"3 = m"1 + m"2 (3) S6, draw a cross-shaped measurement line along the surface of the grown crystal, and take 4 points symmetrically along the single cross-shaped line, take the center point to measure the center thickness of the crystal, take the average value of the highest thickness point + the lowest thickness point on the single cross-shaped line, subtract the center thickness, and obtain three groups of data. The average value is the growth surface parameter, recorded as parameter m"4; S7, compare the actual values ​​of parameters m"1, m"2, m"3, and m"4 with the reference threshold, and determine the parameters exceeding the reference threshold as abnormal values, otherwise, as normal values, and set the ingot splitting rate as t; If the parameters m"1, m"2, m"3, and m"4 are all normal values, t = 0%; If m"2 and m"4 are normal values, and any one of m"1 and m"3 is an abnormal value, t≤20%; If parameter m"4 is a normal value, and only parameter m"2 is an abnormal value among other parameters, 20%<t<75%; If parameter m"4 is a normal value, and any two of parameters m"1, m"2, and m"3 are abnormal values, t≥75%; If parameter m"4 is a normal value, and parameters m"1, m"2, and m"3 are all abnormal values, t = 100%; If the parameter m"4 is an abnormal value, t = 100%.

7. The method for predicting the SiC crystal rough machining ingot splitting rate according to claim 6, characterized in that: The reference thresholds of the parameters m"1, m"2, and m"3 in step S1 are obtained by the following method: S1.1 Assume that the silicon carbide crystal reaches the theoretical optimal state after growth. According to the diameter and center thickness of the crystal, the volume of crystals with different diameters is calculated, and thus the theoretical weight of the crystal is calculated. The theoretical weight is the lower limit value of the parameter m"2; S1.2 During the commissioning of the first single crystal furnace in the new heat field, a higher power is set according to the same charging weight and other conditions as those for normal crystal growth, so that the carbonization rate of silicon carbide powder exceeds 70%, and the upper limit value of parameter m"1 is obtained by formula (1); at this time, the total weight of the crucible cover, seal, seed crystal and graphite paper is recorded when the carbonization rate of silicon carbide powder exceeds 70%, and the upper limit value of parameter m"2 is obtained by formula (2); S1.3 According to the same idea as step S1.2, in the debugging of the second furnace single crystal, the power is controlled so that the total weight of the crucible cover, the seal, the seed crystal and the graphite paper increases to m, m = m"2 lower limit value ± 0.5, at this time, the weight m'1 of the insulation board is weighed, and the lower limit value of the parameter m"1 is obtained by formula (1); S1.4 Based on the upper and lower limit values ​​of parameter m"1 and parameter m"2, the upper and lower limit values ​​of parameter m"3 are obtained by formula (3).

8. The method for predicting the SiC crystal rough machining ingot splitting rate according to claim 7, characterized in that: The reference threshold of the parameter m4 in step S1 is obtained by the following method: Assuming that the silicon carbide crystal reaches the theoretical optimal state after growth, multiple groups of silicon carbide crystals in the ideal optimal state are selected, and the following operations are performed on each group of silicon carbide crystals: a cross-shaped measuring line is drawn along the surface of the grown crystal, and 4 points are symmetrically taken along the single cross-shaped line, and the central point is taken to measure the central thickness of the crystal. On the single cross-shaped line, the highest thickness point + the lowest thickness point are averaged, and the central thickness is subtracted to obtain three groups of data. The average value is obtained through the three groups of data. The average value is the growth surface parameter, recorded as parameter m"4; Based on multiple groups of silicon carbide crystals, the baseline threshold of the parameter m"4 is 0 to 0.25.

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