CN109554761B - Temperature control system and method for silicon carbide crystal resistance method annealing - Google Patents
Temperature control system and method for silicon carbide crystal resistance method annealing Download PDFInfo
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- CN109554761B CN109554761B CN201811419766.8A CN201811419766A CN109554761B CN 109554761 B CN109554761 B CN 109554761B CN 201811419766 A CN201811419766 A CN 201811419766A CN 109554761 B CN109554761 B CN 109554761B
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Abstract
The utility model provides a temperature control system is used in annealing of silicon carbide crystal resistance method, including the growth furnace body, the inside traversing of growth furnace body has the heat transfer pole, the delivery port sets up in the growth furnace body outside, the heat transfer pole right-hand member is provided with the water inlet, flow controller is installed in the water inlet left side, the heat transfer pole middle part is passed the base and is held in touch with base hole in close contact with, the base top holds in the palm with the crucible and is connected, the crucible bottom is provided with the seed crystal groove, the peripheral arrangement of crucible has the temperature thermocouple, install the heat preservation cover between growth furnace body and the crucible, and vacuum system is installed in growth furnace body below left side top. The system also comprises a control PC, wherein the control PC comprises control platform software, a control module and a signal transmission module.
Description
Technical Field
The invention relates to the technical field of silicon carbide crystal annealing, in particular to a temperature control system and method for silicon carbide crystal resistance method annealing.
Background
Silicon carbide crystals, an important technical crystal, have been widely used in many fields of scientific technology, national defense and civil industry, and electronic technology. Such as infrared-transmitting window materials, substrate substrates in the microelectronics field, laser substrates, optical components and other applications. In order to eliminate inclusions and color centers in the flaky silicon carbide crystal, annealing treatment of the grown crystal sample under different atmospheres is required. Various techniques for growing silicon carbide crystals are available, but these methods are basically carried out at high temperature, annealing defects frequently occur due to the nature of the crystals during annealing of the silicon carbide crystals to normal temperature, most often inclusions and color centers appear in the crystals, which greatly affect the application of the crystals.
In the prior art, a great deal of research is carried out on how to raise and maintain the temperature of the growth of the silicon carbide crystal, but the annealing process is not specially and finely controlled, the annealing process needs both speed and crystal safety, and if the annealing is carried out at a very slow speed, even if the annealing has no problem, the production efficiency is greatly reduced.
However, the prior art cannot provide a system and a method for a stable temperature control category, cannot ensure the quality of an annealing process, and has no way to ensure the safety of annealing and ask for efficiency.
Disclosure of Invention
The invention aims to provide a temperature control system and a method for silicon carbide crystal resistance method annealing, which aim to solve the technical problem that no special controllable annealing equipment exists in the prior art. Compared with the common annealing which only utilizes the common heating equipment of the common growing furnace, the technical scheme of the invention can carry out annealing very efficiently, save energy and safely, thereby achieving three purposes at a time.
In order to achieve the purpose, the invention provides the following technical scheme: the utility model provides a temperature control system is used in annealing of silicon carbide crystal resistance method, includes growth furnace body, heat preservation cover, crucible, heating device, its characterized in that: the temperature control system for annealing by the resistance method further comprises a flow controller, a water inlet, a flow control device, a thermometer, an air outlet pipe, a barometer, a heat transfer rod, a base, a crucible holder, a seed crystal groove, a vacuum system, a water outlet, a rack type temperature measuring thermocouple group and an air inlet pipe, wherein the heat transfer rod transversely penetrates through the interior of the growth furnace body, the water outlet is formed in the left end of the heat transfer rod, the water outlet is formed in the outer side of the growth furnace body, the water inlet is formed in the right end of the heat transfer rod, the flow controller is installed on the heat transfer rod on the left side of the water inlet, the middle of the heat transfer rod penetrates through the base and is tightly contacted with the inner surface of an inner hole of the base, the crucible holder is connected with the upper portion of the base, a crucible is embedded above the crucible holder, the seed crystal groove is formed in, and at least two sets of posture temperature thermocouple group with at least three heating device of group install in turn in Z axle direction, install the heat preservation cover between growth furnace body and the crucible, and growth furnace body below left side installs vacuum system, growth furnace body left side top and right side below are installed intake pipe and outlet duct respectively, and install flow control device, thermometer and barometer from the outside growth furnace body direction in proper order on intake pipe and the outlet duct. The control device comprises a heating device, a flow controller, a thermometer, a barometer, a vacuum system and a rack type temperature measuring thermocouple group, the control device is connected with the control module through control ports, the heating device, the flow controller, the thermometer, the barometer, the vacuum system and the rack type temperature measuring thermocouple group are connected with the signal transmission module through signal output ports, the control platform stores signals received by the signal transmission module, and the control platform stores the signals based on the signals and sends instructions through the control module according to preset rules.
Furthermore, inward-concave convection grooves which are parallel to each other are uniformly arranged on the outer surface of the heat-preservation cover; each heating device is an annular heating pipe, at least two heating devices are arranged in parallel in pairs and have different heights, and overlooking projection positions are overlapped; the annular heating pipe is formed by connecting two semicircular heating rings in parallel, each semicircular heating ring is a micro-spiral wire-drawing tungsten alloy wire, and positive and negative loads are respectively connected to 180-degree opposite positions opposite to each other through the circle center; the flow controller realizes flow control in a mode of automatically controlling the opening and closing of an anti-corrosion blocking piece vertical to the air outlet pipe or the air inlet pipe; the crucible support is made of high-temperature-resistant and high-toughness ceramic, and the crucible and the seed crystal groove are made of high-temperature-resistant ceramic; the thermometer is an induction thermocouple thermometer, and a thermocouple connected with the thermometer directly extends into the gas paths in the gas inlet pipe and the gas outlet pipe to be contacted with gas; the upper surface of the seed crystal groove is provided with 1 square or rectangular seed crystal inner groove which is provided with seed crystals and is sunken downwards for placing the seed crystals; the rack type temperature thermocouple groups are arranged on the annular rack in two groups, and each group of rack type temperature thermocouple groups is provided with four temperature thermocouples which are uniformly distributed on the annular rack; the heat transfer rod and the base are both made of high-temperature-resistant alloy; the vacuum system is connected with the inside of the heat-insulating cover in an openable and closable manner and is provided with an air extractor; the fluid in the heat transfer rod is purified water; the side surfaces of the growth furnace body and the heat preservation cover are provided with doors which can be opened and closed, and the top is provided with a seed crystal detection system which is inserted into the crucible just opposite to the central axis.
The temperature control method for the silicon carbide crystal resistance method annealing is implemented by utilizing the temperature control system for the silicon carbide crystal resistance method annealing, and is characterized by comprising the following steps of: 1) an annealing temperature step setting step: setting annealing temperature steps, setting initial temperature to be 1900 ℃, setting N-stage cooling intervals, setting the annealing temperature steps to be 50-70 ℃ for each stage, setting the final cooling temperature of the Nth stage to be TPn, setting the time required by each stage for cooling, setting the time required by the Nth stage from 1900 ℃ to the bottom to be Tn minutes, inputting and storing the setting in a control PC (personal computer) and calling the setting at any time when the annealing temperature steps are controlled; 2) an annealing heating load determining step: under the condition that silicon carbide is not placed or a replacement standard part similar to the shape and specific heat of the silicon carbide crystal is placed in a temperature control system for annealing by a silicon carbide crystal resistance method, a growth furnace body and a heat-preserving cover are sealed, the numerical value of the rack type temperature thermocouple group is monitored from 1900 ℃, the load voltage corresponding to each temperature step from 1900 ℃ is recorded, the load voltage at the temperature step to which the Nth level is finally cooled is Vn, and the load voltage at the temperature step of 1900 ℃ is recorded as V0; will Vn and V0All recorded in the control platform and input and stored in the control PC; 3) an annealing flow rate control determination step: on the premise that both V0 and Vn are determined in the steps, setting the flow speed of the fluid in the heat transfer rod to be VSn with a constant speed in each annealing temperature step, and recording the value of VSn in the cooling process of just taking Tn minutes to complete the whole temperature step according to repeated tests; VSn is recorded in a control platform, input and stored in a control PC; 4) and (3) correcting: in a temperature control system for silicon carbide crystal resistance method annealing, selecting self-growing silicon carbide or opening the silicon carbide from the side surface and putting the grown silicon carbide; the self-growing silicon carbide grows silicon carbide crystals upwards from the seed crystal groove by slowly lifting in the seed crystal detection system, and is heated in a preset temperature rise step by matching with the heating device; the grown silicon carbide is placed in the side opening mode, the side faces of the growing furnace body and the heat preservation cover are provided with openable and closable doors from the side faces, and the silicon carbide crystal at high temperature is placed in the side opening mode; under the automatic control of the control platform through the control module, the growth furnace is sealedA step of correcting and annealing the furnace body and the heat-insulating cover, wherein the load voltage of the heating device is adjusted to be Vn within the Tn time period of each temperature step, the flow rate of the fluid in the heat transfer rod is set to be VSn with a constant speed, and the difference value Qn between the actual temperature and the preset temperature target of the temperature step is recorded when the Tn time period of each temperature step is finished; when the absolute values of the Qn are less than or equal to S ℃, the step (5) is carried out, when the absolute value of any one Qn is greater than S ℃, the step (1) is returned, and the time required by each level of annealing temperature step and each level of cooling is reset; 5) and (3) annealing quality assurance step: under the automatic control of the control platform through the control module, under the premise that the absolute values of Qn in the step (4) are less than or equal to S ℃, selecting N sets of temperature control systems for silicon carbide crystal resistance annealing, placing grown silicon carbide with the same specification in the temperature control systems for silicon carbide crystal resistance annealing, sealing a growth furnace body and a heat preservation cover, respectively annealing from the 1 st stage to the N th stage according to preset temperature steps, adjusting the load voltage of a heating device to Vn within the corresponding Tn time period for each set of temperature control system, setting the flow velocity of fluid in a heat transfer rod to be VSn at a constant velocity, and after the annealing of the corresponding temperature steps is respectively carried out by the temperature control systems for N sets of silicon carbide crystal resistance annealing, reducing the silicon carbide crystals in the N sets of temperature control systems to room temperature at a sufficiently slow velocity; collecting high-resolution images of all silicon carbide crystals, storing the high-resolution images into a control PC, judging by using an image analysis part of a control platform, entering the step (6) if one or more silicon carbide crystals have inclusions or color centers, and entering the step (7) if any one or more silicon carbide crystals have no inclusions or color centers; 6) and (3) prolonging the annealing time: for one or more silicon carbide crystals with inclusions or color centers, prolonging the Tn value of the temperature step corresponding to the inclusions or the color centers by at least Pmin, and returning to the step (1); 7) and (3) annealing operation steps of the silicon carbide crystal: recording Tn, TPn, Vn and VSn values corresponding to each temperature step without annealing abnormal conditions, confirming the values in the control platform, sending a control command from the control platform through the control module, and repeatedly feeding the silicon carbide generated at high temperature by using a plurality of temperature control systems for silicon carbide crystal resistance annealingAnd (5) annealing.
Further, the annealing temperature step of each stage is 60 ℃, and the final temperature of annealing is 40 ℃; the numerical value of S ℃ is 3-5 ℃; the value of Pmin is 5-10 min. Preferably, air in the system is exhausted through the air outlet pipe, the furnace body is filled with He gas through the air inlet pipe, and the safety of the silicon carbide crystal can be further ensured by annealing under the He.
Compared with the prior art, the invention has the following beneficial effects: 1) compared with the common growth furnace which uses large-area heating plates, the heating furnace has the advantages that a plurality of heating rings can be sufficient for annealing without growing crystals, and compared with the common mode of arranging the left heating plate and the right heating plate, the heating furnace saves materials and energy, through test detection, more than three annular heaters can ensure the temperature around the crystals, the temperature is enough even at 1900 ℃, the materials are saved, and the thickness of the annular heating pipe can be increased under the condition of insufficient power so as to improve the power; 2) fine control, namely automatic fine control in the crystal annealing process is always a problem which is difficult to solve by direct cooling annealing in a common growth furnace, the automatic control of a certain degree is realized, and the efficiency can be greatly improved under the condition of ensuring safety through repeated experiments; 3) the risks of a specific temperature section can be found, the possible risks of each annealing temperature step can be visually found through the transverse comparison in the step 5, and the annealing time can be prolonged in a targeted manner, so that the annealing risks of the crystal can be effectively controlled; 4) the annealing time is effectively controlled, in the prior art, as to the possible annealing temperature risk, specific or targeted tests are not always carried out on the annealing speed, the safety is ensured, the annealing process is not infinitely prolonged, and the excessively time-consuming annealing process is effectively controlled by the method.
The temperature control system and method for silicon carbide crystal resistance method annealing show; a special system and a method which can provide a stable temperature control category are important guarantees for guaranteeing the quality of the annealing process. The heating means is the heating of the micro-spiral drawn tungsten alloy wire to ensure the heating, so the method is called as a resistance method.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic diagram of the structure of the present invention with a seed detection system inserted.
In the figure: 1. growth furnace body, 2, heat preservation cover, 3, crucible, 4, heating device, 5, flow controller, 6, water inlet, 7, flow control device, 8, thermometer, 9, outlet duct, 10, barometer, 11, heat transfer rod, 12, base, 13, crucible support, 14, seed crystal groove, 15, vacuum system, 16, delivery port, 17, temperature thermocouple, 18, intake pipe, 19, seed crystal detection system, 20, control PC.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Taking fig. 1 as an example, the following embodiments are specifically implemented: the utility model provides a temperature control system is used in annealing of silicon carbide crystal resistance method, includes growth furnace body 1, heat preservation cover 2, crucible 3, heating device 4, its characterized in that: the temperature control system for annealing by the resistance method further comprises a flow controller 5, a water inlet 6, a flow control device 7, a thermometer 8, an air outlet pipe 9, a barometer 10, a heat transfer rod 11, a base 12, a crucible support 13, a seed crystal groove 14, a vacuum system 15, a water outlet 16, a rack type temperature measuring thermocouple group 17 and an air inlet pipe 18, wherein the heat transfer rod 11 transversely penetrates through the interior of the growth furnace body 1, the water outlet 16 is arranged at the left end of the heat transfer rod 11, the water outlet 16 is arranged at the outer side of the growth furnace body 1, the water inlet 6 is arranged at the right end of the heat transfer rod 11, the flow controller 5 is arranged on the heat transfer rod 11 at the left side of the water inlet 6, the middle part of the heat transfer rod 11 penetrates through the base 12 and is in close contact with the inner surface of an inner hole of the base, the upper part of the base 12 is connected with the crucible support, and at least three groups of heating devices 4 are arranged on the periphery of the crucible 3, at least two groups of rack-type temperature thermocouple groups 17 are arranged on the periphery of the crucible 3, the at least two groups of rack-type temperature thermocouple groups 17 and the at least three groups of heating devices 4 are alternately arranged in the Z-axis direction, a heat preservation cover 2 is arranged between the growth furnace body 1 and the crucible 3, a vacuum system 15 is arranged on the left side below the growth furnace body 1, an air inlet pipe 18 and an air outlet pipe 9 are respectively arranged above the left side and below the right side of the growth furnace body 1, and a flow control device 7, a thermometer 8 and a barometer 10 are sequentially arranged on the air inlet pipe 18 and the air outlet pipe 9 from the outside to the growth furnace. Here three sets of heating means are already sufficient to heat up to 1900 c, and by increasing the thickness of the ring heater, its power can be increased to a level sufficient for use.
The intelligent control system is characterized by further comprising a control PC20, wherein the control PC comprises control platform software, a control module and a signal transmission module, control ports of the heating device 4, the flow controller 5, the thermometer 8, the barometer 10, the vacuum system 15 and the rack type temperature measuring thermocouple group 17 are all connected into the control module, signal output ports of the heating device 4, the flow controller 5, the thermometer 8, the barometer 10, the vacuum system 15 and the rack type temperature measuring thermocouple group 17 are all connected into the signal transmission module, and the control platform software stores signals received by the signal transmission module and sends instructions through the control module according to preset rules based on the signals.
Because anneal after both can growing crystal in this application, consequently can be with furnace body and the heat preservation cover similar with ordinary growth stove to play same effect, if under the prerequisite that does not need growing crystal, the material of furnace body and heat preservation cover can be some simpler, also need not so good heat preservation effect.
Furthermore, the outer surface of the heat-insulating cover 2 is uniformly provided with inward-sunken convection grooves which are parallel to each other, so that the heat dissipation is more uniform due to the arrangement of the convection grooves; each heating device 4 is an annular heating pipe, at least two heating devices are arranged in parallel in pairs and have different heights, and overlooking projection positions are overlapped; generally, at least two thick heating plates are used in the crystal growth process, so that a constant temperature area around the crystal can be ensured to be larger as much as possible, the crystal growth effect can be further ensured, but for annealing, the arrangement is already sufficient, not only materials are saved, but also energy is saved, the temperature area condition is monitored by a far infrared camera, data are measured by a thermocouple, all parts of the crystal are kept at the temperature required by people, and the crystal is more uniform compared with plate type heating; the annular heating pipe is formed by connecting two semicircular heating rings in parallel, each semicircular heating ring is a micro-spiral wire-drawing tungsten alloy wire, and positive and negative loads are respectively connected to 180-degree opposite positions corresponding to the circle center, wherein the heating rings of each semicircle are in parallel connection and are considered when calculating the loads; the flow controller 5 realizes flow control by automatically controlling the opening and closing of an anti-corrosion blocking piece vertical to the air outlet pipe or the air inlet pipe, and the opening and closing of the anti-corrosion blocking piece can be automatic or manual; the material of the crucible support 13 is high-temperature-resistant and high-toughness ceramic, the material of the crucible 3 and the seed crystal groove 14 is high-temperature-resistant ceramic, and flanges and grooves can be reasonably arranged at the joint parts between the crucible support and the crucible and between the crucible and the seed crystal groove so as to be tightly embedded; the thermometer 8 is an induction thermocouple thermometer, and a thermocouple connected with the thermometer 8 directly extends into the gas path in the gas inlet pipe 18 and the gas outlet pipe 9 to be contacted with gas; the upper surface of the seed crystal groove 14 is provided with 1 square or rectangular seed crystal inner groove which is provided with seed crystals and is concave downwards for placing the seed crystals, and the seed crystal utilization mode is similar to that of the prior art; the two groups of the rack type temperature thermocouple groups 17 are arranged on the annular rack, four temperature thermocouples 17 are arranged on each group of the rack type temperature thermocouple groups 17, and the four temperature thermocouples 17 are uniformly distributed on the annular rack, so that under the arrangement, the temperature thermocouples 17 are just placed at the position of the heating blind area with the maximum possibility of the heating device, the temperature at the position meets the requirement, and the requirement is met at each part of the crystal; the heat transfer rod 11 and the base 12 are both made of high-temperature-resistant alloy; the vacuum system 15 is connected with the inside of the heat-insulating cover 2 in an openable and closable manner, is provided with an air extractor, and injects He gas into the system, wherein the system can be vacuumized firstly and then injects the He gas from an air inlet pipe; the fluid in the heat transfer rod 11 is pure water; the side surfaces of the growth furnace body 1 and the heat preservation cover 2 are provided with doors which can be opened and closed, the top is provided with a seed crystal detection system which is vertically inserted from the upper part and is opposite to the central axis of the crucible 3.
Example 2
The temperature control method for the silicon carbide crystal resistance method annealing is implemented by utilizing the temperature control system for the silicon carbide crystal resistance method annealing, and is characterized by comprising the following steps of: 1) an annealing temperature step setting step: setting annealing temperature steps, setting initial temperature to be 1900 ℃, setting N-stage cooling intervals, setting 50 ℃ for each annealing temperature step, setting TPn (N is 1,2,3 … …) for the cooling final temperature of the Nth stage, setting time required for each cooling step, setting Tn minutes (N is 1,2,3 … …) for the cooling time of the Nth stage from 1900 ℃ to the bottom, setting 50 ℃ for the annealing final temperature, and inputting and storing the setting in a control platform in a control PC (personal computer) and calling the setting at any time when the annealing temperature steps are controlled; 2) an annealing heating load determining step: under the condition that silicon carbide is not placed or a replacement standard part similar to the shape and specific heat of the silicon carbide crystal is placed in a temperature control system for annealing by a silicon carbide crystal resistance method, a growth furnace body 1 and a heat preservation cover 2 are closed, the numerical value of a rack type temperature thermocouple group 17 is monitored from 1900 ℃, the load voltage corresponding to each temperature step from 1900 ℃ is recorded, the load voltage at the temperature step finally cooled to the Nth level is Vn (N is 1,2,3 … …), the Vn is gradually reduced along with the increase of N, all semi-circular rings of heating devices are connected in parallel to load, the load voltage at 1900 ℃ is calculated according to the load voltage, and the load voltage is recorded as V00(ii) a Will Vn and V0All recorded in the control platform and input and stored in the control PC; 3) an annealing flow rate control determination step: on the premise that both V0 and Vn are determined in step (2), for each stage of the annealing temperature step, the flow rate of the fluid in the heat transfer rod 11 is set to be VSn at a constant speed, and according to a trial and error, the value of VSn at the time of just taking Tn minutes to complete the cooling process of the entire temperature step is recorded, and VSn is determined based on Tn; VSn is recorded in a control platform, input and stored in a control PC; 4) and (3) correcting: is carried out by a control module on a control platformUnder automatic control, selecting self-growing silicon carbide in a temperature control system for silicon carbide crystal resistance method annealing; the self-growing silicon carbide grows upwards from a seed crystal groove (14) through slow lifting in a seed crystal detection system, the tops of a growth furnace body 1 and a heat preservation cover 2 are provided with central axes which are right opposite to a crucible 3, the seed crystal detection system is vertically inserted from the upper part, the seed crystal detection system is utilized to grow the silicon carbide crystal in a mode of slowly guiding and lifting and simultaneously guiding the growth of seed crystals in the seed crystal groove, and meanwhile, the heating device 4 is matched to heat the silicon carbide crystal in a preset temperature rising step; after the growth of the silicon carbide is finished, removing the seed crystal detection system, sealing the growth furnace body 1 and the heat-insulating cover 2 by using a cover plate made of the same material from the upper part, performing a correction annealing step, adjusting the load voltage of the heating device 4 to be Vn within the Tn time period of each temperature step, setting the flow rate of fluid in the heat transfer rod 11 to be VSn with uniform speed, and recording the difference Qn between the actual temperature and the preset temperature target of the temperature step at the end of the Tn time period of each temperature step; when the absolute values of the Qn are all less than or equal to 5 ℃, the step (5) is carried out, when the absolute value of any one Qn is more than 5 ℃, the step (1) is returned, and the time required by each level of annealing temperature step and each level of cooling is reset; 5) and (3) annealing quality assurance step: under the automatic control of the control platform through the control module, on the premise that the absolute value of Qn in the step (4) is less than or equal to 5 ℃, selecting 37 sets of temperature control systems for silicon carbide crystal resistance method annealing, placing grown silicon carbide with the same specification in the temperature control systems for silicon carbide crystal resistance method annealing, sealing the growth furnace body 1 and the heat preservation cover 2, respectively annealing from the 1 st stage to the 37 th stage according to preset temperature steps, adjusting the load voltage of the heating device (4) to Vn within the corresponding Tn time period for each set of temperature control systems, setting the flow rate of fluid in the heat transfer rod (11) to be VSn with constant speed, and after the annealing of the silicon crystal corresponding to the temperature steps is respectively completed by the temperature control systems for N sets of silicon carbide crystal resistance method annealing, reducing the silicon carbide therein to room temperature at sufficiently slow speed; collecting high-resolution images of all silicon carbide crystals, storing the images into a control PC, and judging by using an image analysis part of a control platform if one or more silicon carbide crystals are wrapped or coloredIf no inclusions or color centers appear in any one or more silicon carbide crystals, entering the step (6), and entering the step (7); 6) and (3) prolonging the annealing time: for one or more silicon carbide crystals with inclusions or color centers, prolonging the Tn value of the temperature steps corresponding to the inclusions or the color centers by at least 5min, and returning to the step (1); 7) and (3) annealing operation steps of the silicon carbide crystal: and recording Tn, TPn, Vn and VSn values corresponding to each temperature step without annealing abnormal conditions, confirming the Tn, TPn, Vn and VSn values in the control platform, sending a control command from the control platform through the control module according to the values, and repeatedly annealing the silicon carbide generated at high temperature by using a plurality of temperature control systems for silicon carbide crystal resistance annealing.
Example 3
The temperature control method for the silicon carbide crystal resistance method annealing is implemented by utilizing the temperature control system for the silicon carbide crystal resistance method annealing, and is characterized by comprising the following steps of: 1) an annealing temperature step setting step: setting annealing temperature steps, setting initial temperature to be 1900 ℃, setting N-stage cooling intervals, setting the annealing temperature steps to be 60 ℃, setting the cooling final temperature of the Nth stage to be TPn (N is 1,2,3 … …), setting the time required by each stage of cooling, setting the time required by the Nth stage from 1900 ℃ to be Tn minutes (N is 1,2,3 … …), setting the annealing final temperature to be 40 ℃, and setting 31 annealing temperature steps in total, wherein the setting is input into a control platform, stored in the control PC and can be called at any time when the annealing temperature steps are controlled; 2) an annealing heating load determining step: under the condition that silicon carbide is not placed or a replacement standard part similar to the shape and specific heat of the silicon carbide crystal is placed in a temperature control system for annealing by a silicon carbide crystal resistance method, a growth furnace body 1 and a heat preservation cover 2 are closed, the numerical value of a rack type temperature thermocouple group 17 is monitored from 1900 ℃, the load voltage corresponding to each temperature step from 1900 ℃ is recorded, the load voltage at the temperature step finally cooled to the Nth level is Vn (N is 1,2,3 … …), the Vn is gradually reduced along with the increase of N, all semi-circular rings of heating devices are connected in parallel to load, the load voltage at 1900 ℃ is calculated according to the load voltage, and the load voltage is recorded as V00(ii) a Will Vn and V0All records are input and coexist in the control platformStored in the control PC; 3) an annealing flow rate control determination step: at V0And Vn is determined in step (2), setting the flow rate of the fluid in the heat transfer rod 11 to be VSn with a constant speed in each annealing temperature step, and recording the value of VSn in the process of just taking Tn minutes to complete the temperature reduction of the whole temperature step according to a repeated test, wherein VSn is determined on the basis of Tn; VSn is recorded in a control platform, input and stored in a control PC; 4) and (3) correcting: under the automatic control of the control platform through the control module, in the temperature control system for annealing of the silicon carbide crystal by the resistance method, the grown silicon carbide is selected to be placed in the temperature control system from the side; the silicon carbide after growth is placed by opening from the side surface, the side surfaces of the growing furnace body and the heat-insulating cover are provided with openable and closable doors from the side surface, the prepared silicon carbide crystal at high temperature is placed, the correction annealing step is carried out, the load voltage of the heating device 4 is adjusted to be Vn within the Tn time period of each temperature step, the flow rate of the fluid in the heat transfer rod 11 is set to be VSn at a constant speed, and the difference value Qn between the actual temperature and the preset temperature target of the temperature step when the Tn time period of each temperature step is finished is recorded; when the absolute values of the Qn are all less than or equal to 3 ℃, the step (5) is carried out, when the absolute value of any one Qn is more than 3 ℃, the step (1) is returned, and the time required by each level of annealing temperature step and each level of cooling is reset; 5) and (3) annealing quality assurance step: under the automatic control of the control platform through the control module, on the premise that the absolute value of Qn in the step (4) is less than or equal to 3 ℃, selecting 31 sets of temperature control systems for silicon carbide crystal resistance method annealing, placing grown silicon carbide with the same specification in the temperature control systems for silicon carbide crystal resistance method annealing, sealing the growth furnace body 1 and the heat preservation cover 2, respectively annealing from the 1 st stage to the 31 st stage according to preset temperature steps, adjusting the load voltage of the heating device (4) to Vn within the corresponding Tn time period for each set of temperature control systems, setting the flow rate of the fluid in the heat transfer rod (11) to be VSn at a constant speed, and after the annealing of the corresponding temperature steps is respectively completed by the temperature control systems for 31 sets of silicon carbide crystal resistance method annealing, reducing the silicon carbide therein to room temperature at a sufficiently slow speed; capturing high resolution images of all silicon carbide crystals and co-minglingStoring the control PC, judging by using an image analysis part of the control platform, entering the step (6) if one or more silicon carbide crystals have inclusions or color centers, and entering the step (7) if any one or more silicon carbide crystals have no inclusions or color centers; 6) and (3) prolonging the annealing time: for one or more silicon carbide crystals with inclusions or color centers, prolonging the Tn value of the temperature steps corresponding to the inclusions or the color centers by at least 10min, and returning to the step (1); 7) and (3) annealing operation steps of the silicon carbide crystal: and recording Tn, TPn, Vn and VSn values corresponding to each temperature step without annealing abnormal conditions, confirming the Tn, TPn, Vn and VSn values in the control platform, sending a control command from the control platform through the control module according to the values, and repeatedly annealing the silicon carbide generated at high temperature by using a plurality of temperature control systems for silicon carbide crystal resistance annealing.
Example 4
The annealing of the silicon carbide generated at a high temperature in the step (7) may specifically include the following steps:
A. in order to eliminate inclusions and color centers in the flaky silicon carbide crystal, annealing the grown crystal sample in different atmospheres, and preparing experimental equipment;
B. annealing the tail sample containing the inclusion in a 1900 ℃ He gas, and cooling at the speed of 60 ℃/h, wherein each temperature step is 1h, and the total time is 31 h; .
The experimental result shows that the tail sample containing the inclusion is annealed in the air at 1900 ℃ and cooled at the speed of 60 ℃/h, so that the carbon inclusion in the crystal can be safely eliminated, and the crystal becomes colorless and transparent; through detection, a plurality of absorption peaks between 200nm and 300nm caused by the color center are eliminated. The annealing in the high-temperature He is an effective auxiliary method for eliminating the color center and the defects in the silicon carbide crystal grown by the guided mode method.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.
Claims (2)
1. A temperature control method for silicon carbide crystal resistance method annealing is used for implementing annealing of a silicon carbide crystal by using a temperature control system for silicon carbide crystal resistance method annealing, and is characterized in that:
temperature control system is used in annealing of silicon carbide crystal resistance method, including growth furnace body (1), heat preservation cover (2), crucible (3), heating device (4), its characterized in that: the temperature control system for annealing by the resistance method further comprises a flow controller (5), a water inlet (6), a flow control device (7), a thermometer (8), an air outlet pipe (9), a barometer (10), a heat transfer rod (11), a base (12), a crucible holder (13), a seed crystal groove (14), a vacuum system (15), a water outlet (16), a frame type temperature measuring thermocouple group (17) and an air inlet pipe (18), wherein the heat transfer rod (11) transversely penetrates through the inside of the growth furnace body (1), the water outlet (16) is formed in the left end of the heat transfer rod (11), the water outlet (16) is formed in the outer side of the growth furnace body (1), the water inlet (6) is formed in the right end of the heat transfer rod (11), the flow controller (5) is installed on the heat transfer rod (11) on the left side of the water inlet (6), the middle of the heat transfer rod (11) penetrates through the base (12) and is, the upper part of the base (12) is connected with a crucible support (13), a crucible (3) is embedded above the crucible support (13), and a seed crystal groove (14) is formed in the upper surface of the inner side of the crucible (3);
at least three groups of heating devices (4) are arranged on the periphery of the crucible (3), at least two groups of rack-type temperature thermocouple groups (17) are arranged on the periphery of the crucible (3), the at least two groups of rack-type temperature thermocouple groups (17) and the at least three groups of heating devices (4) are alternately arranged in the Z-axis direction, a heat-insulating cover (2) is arranged between the growth furnace body (1) and the crucible (3), a vacuum system (15) is arranged on the left side below the growth furnace body (1), an air inlet pipe (18) and an air outlet pipe (9) are respectively arranged on the upper left side and the lower right side of the growth furnace body (1), and a flow control device (7), a thermometer (8) and a barometer (10) are sequentially arranged on the air inlet pipe (18) and the air outlet pipe (9) from the outside to the growth furnace;
the distance between two adjacent groups of the at least three groups of heating devices (4) in the Z-axis direction is less than or equal to 10 cm;
the device is characterized by further comprising a control PC (20), wherein the control PC comprises control platform software, a control module and a signal transmission module, control ports of the heating device (4), the flow controller (5), the thermometer (8), the barometer (10), the vacuum system (15) and the rack type temperature thermocouple group (17) are all connected into the control module, signal output ports of the heating device (4), the flow controller (5), the thermometer (8), the barometer (10), the vacuum system (15) and the rack type temperature thermocouple group (17) are all connected into the signal transmission module, the control platform software stores signals received by the signal transmission module and sends instructions through the control module according to preset rules based on the signals;
the outer surface of the heat-insulating cover (2) is uniformly provided with inward-sunken convection grooves which are parallel to each other;
each heating device (4) is an annular heating pipe, at least two heating devices are arranged in parallel in pairs and have different heights, and overlooking projection positions are overlapped; the annular heating pipe is formed by connecting two semicircular heating rings in parallel, each semicircular heating ring is a micro-spiral wire-drawing tungsten alloy wire, and positive and negative loads are respectively connected to 180-degree opposite positions opposite to each other through the circle center;
the flow controller (5) realizes flow control in a mode of automatically controlling the opening and closing of an anti-corrosion blocking piece vertical to the air outlet pipe or the air inlet pipe;
the crucible holder (13) is made of high-temperature-resistant ceramic with high toughness, and the crucible (3) and the seed crystal groove (14) are made of high-temperature-resistant ceramic;
the thermometer (8) is an induction thermocouple thermometer, and a thermocouple connected with the thermometer (8) directly extends into the gas paths in the gas inlet pipe (18) and the gas outlet pipe (9) to be contacted with gas;
the upper surface of the seed crystal groove (14) is provided with 1 square or rectangular seed crystal inner groove which is provided with seed crystals and is sunken downwards for placing the seed crystals;
the rack type temperature thermocouple groups (17) are two groups arranged on the annular rack, four temperature thermocouples on each group of rack type temperature thermocouple groups (17) are arranged, and the four temperature thermocouples (17) are uniformly distributed on the annular rack;
the heat transfer rod (11) and the base (12) are both made of high-temperature-resistant alloy;
the vacuum system (15) is connected with the inside of the heat preservation cover (2) in an openable and closable way and is provided with an air extractor;
the fluid in the heat transfer rod (11) is pure water;
the side surfaces of the growth furnace body (1) and the heat-preserving cover (2) are provided with doors which can be opened and closed, and the top is provided with a seed crystal detection system which is inserted into the crucible (3) just opposite to the central axis;
the temperature control method for annealing comprises the following steps:
1) an annealing temperature step setting step: setting annealing temperature steps, setting initial temperature to be 1900 ℃, setting N-stage cooling intervals, setting the annealing temperature steps to be 50-70 ℃ for each stage, setting the final cooling temperature of the Nth stage to be TPn, setting the time required by each stage for cooling, setting the time required by the Nth stage from 1900 ℃ to the bottom to be Tn minutes, inputting and storing the setting in a control PC (personal computer) and calling the setting at any time when the annealing temperature steps are controlled;
2) an annealing heating load determining step: under the condition that silicon carbide is not placed or a replacement standard part similar to the shape and specific heat of the silicon carbide crystal is placed in a temperature control system for annealing by a silicon carbide crystal resistance method, a growth furnace body (1) and a heat preservation cover (2) are sealed, the numerical value of the rack type temperature thermocouple group (17) is monitored from 1900 ℃, the load voltage corresponding to each temperature step from 1900 ℃ is recorded, the load voltage at the temperature step of the Nth final temperature reduction stage is Vn, and the load voltage at the temperature step of 1900 ℃ is recorded as V0(ii) a Will Vn and V0All recorded in the control platform and input and stored in the control PC;
3) an annealing flow rate control determination step: on the premise that both V0 and Vn are determined in the step 2), setting the flow rate of the fluid in the heat transfer rod (11) to be VSn with a constant speed in each annealing temperature step, and recording the value of VSn under the condition that the cooling process of the whole temperature step just takes Tn minutes according to repeated tests; VSn is recorded in a control platform, input and stored in a control PC;
4) and (3) correcting: in a temperature control system for silicon carbide crystal resistance method annealing, the grown silicon carbide is placed in the temperature control system from the side; the silicon carbide after growth is placed into the silicon carbide furnace body (1) through opening from the side surface, and the silicon carbide crystal at high temperature is placed into the silicon carbide furnace body through opening and closing the doors which can be opened and closed and are arranged on the side surfaces of the heat preservation cover (2) from the side surface;
under the automatic control of a control platform through a control module, a furnace body (1) of the closed growth furnace and a heat-preservation cover (2) are subjected to a correction annealing step, the load voltage of the heating device (4) is adjusted to be Vn within the Tn time period of each temperature step, the flow rate of fluid in the heat transfer rod (11) is set to be VSn with a constant speed, and the difference value Qn between the actual temperature and the temperature step preset temperature target at the end of the Tn time period of each temperature step is recorded; when the absolute values of Qn are less than or equal to S ℃, the step 5) is carried out, when the absolute value of any one Qn is greater than S ℃, the step 1) is carried out, and the time required by each level of annealing temperature step and each level of cooling is reset;
5) and (3) annealing quality assurance step: under the automatic control of a control platform through a control module, under the premise that the absolute values of Qn in the step 4) are less than or equal to S ℃, selecting N sets of temperature control systems for silicon carbide crystal resistance annealing, placing grown silicon carbide with the same specification in the temperature control systems for silicon carbide crystal resistance annealing, sealing a growth furnace body (1) and a heat preservation cover (2), respectively annealing from the 1 st stage to the N th stage according to preset temperature steps, adjusting the load voltage of a heating device (4) to Vn within the corresponding Tn time period for each set of temperature control system, setting the flow rate of fluid in a heat transfer rod (11) to be VSn with constant speed, and reducing the silicon carbide crystals in the N sets of temperature control systems to room temperature at sufficiently slow speed after the annealing of the corresponding temperature steps is respectively performed by the temperature control systems for silicon carbide crystal resistance annealing; collecting high-resolution images of all silicon carbide crystals, storing the high-resolution images into a control PC, judging by using an image analysis part of a control platform, and entering step 6) if one or more silicon carbide crystals have inclusions or color centers, or entering step 7) if any one or more silicon carbide crystals have no inclusions or color centers;
6) and (3) prolonging the annealing time: for one or more silicon carbide crystals with inclusions or color centers, prolonging the Tn value of the temperature step corresponding to the inclusions or the color centers by at least Pmin, and returning to the step 1);
7) and (3) annealing operation steps of the silicon carbide crystal: and recording Tn, TPn, Vn and VSn values corresponding to each temperature step without annealing abnormal conditions, confirming the Tn, TPn, Vn and VSn values in the control platform, sending a control command from the control platform through the control module according to the values, and repeatedly annealing the silicon carbide generated at high temperature by using a plurality of temperature control systems for silicon carbide crystal resistance annealing.
2. The method of claim 1, wherein the temperature control step comprises:
the annealing temperature step of each stage is 60 ℃, and the final annealing temperature is 40 ℃.
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