Temperature Control Method for Crystal Growth Using Bridgman Method

Abstract

The present invention relates to the technical field of crystal preparation, and specifically discloses a temperature control method for crystal growth using the Bridgman method, comprising: dividing the heating tube into a high temperature zone and a low temperature zone along the axial direction; evenly setting temperature collection points in the high temperature zone and the low temperature zone; evenly arranging the heating modules in the annular heating zone, and initializing and debugging the heating modules; turning on all heating modules to heat the heating tube, obtaining temperature data of each group of temperature collection points in the same temperature zone, and calculating the average temperature value of each group, and entering a detection adjustment mode when the deviation between the average temperature value and the set temperature value is less than a preset value; detection adjustment mode: obtaining temperature data corresponding to the temperature collection points of each group, and setting the rotation speed of the heating module corresponding to the temperature collection points of the group according to the maximum deviation value. The present invention can improve the temperature stability of crystals during crystallization.

Description

Technical Field

[0001] The invention relates to the technical field of crystal preparation, and in particular to a temperature control method for crystal growth using a Bridgman method. Background Art

[0002] The Bridgman method is also called directional crystallization, which is to keep the compound in a fully molten state under a specific temperature field, and then slowly crystallize from one end of the melt to the other. This method is mainly used to grow single crystals, and can also be used for a simple fractionation and purification. The Bridgman method single crystal growth methods are:

[0003] 1) The container system for the crystal does not move, while the entire heating furnace system moves slowly, and the single crystal is generated by moving the temperature gradient of the crystallization part;

[0004] 2) The heating furnace system does not move, and the container system containing the crystal moves slowly, so that the melt slowly passes through the specific temperature gradient part of the furnace and grows into a single crystal;

[0005] 3) Neither the heating furnace system nor the crystal container system moves, but the temperature field is slowly moved by cooling to generate a single crystal. This method is called gradient solidification.

[0006] The horizontal Bridgman method is mainly used to grow GaAs single crystals, and is also used to grow InAs, InSb or GaSb single crystals. The horizontal Bridgman furnace for growing GaAs single crystals is divided into: two-temperature zone furnace (2T-HB), three-temperature zone furnace (3T-HB) and gradient solidification furnace (GF).

[0007] The two-zone furnace is a typical method for growing GaAs single crystals by the HB method. The structure and temperature distribution of the 2T-HB furnace are shown in Figure 1 Gallium and arsenic are vacuum sealed in a quartz container. The high temperature zone is kept above the melting point of gallium arsenide (1245~1260*C), which can combine arsenic and gallium, or melt gallium arsenide ingots; the low temperature zone (610~620*C) can volatilize arsenic to the high temperature zone to combine with gallium, and keep the vapor pressure of arsenic at 0.1 MPa, which is balanced with the dissociation pressure of gallium arsenide (about 0.1 MPa). When the furnace moves to the right, the gallium arsenide melt can gradually crystallize along the seed crystal to form a single crystal in the temperature gradient zone between the high temperature zone and the low temperature zone. The temperature changes in the furnace are as follows: Figure 2 shown.

[0008] Therefore, the control of temperature is particularly important in the horizontal Bridgman method. In the prior art, in order to achieve the set temperature distribution, a multi-stage heating method is adopted. That is, each temperature zone is divided into multiple sections for independent heating, especially the high temperature zone is composed of 3 or more sections, so that the temperature of the crystallization site is more uniform. In the above method, although more refined operations can be achieved through multi-stage heating, thereby solving the problem of uneven heating temperature to a certain extent; however, there is a lack of integrity between the segments, especially at the intervals between the segments, which is prone to generate temperature gradients, thus affecting the heating effect. Summary of the invention

[0009] The purpose of the present invention is to provide a temperature control method for Bridgman crystal growth to solve the above technical problems.

[0010] The purpose of the present invention can be achieved through the following technical solutions:

[0011] The temperature control method for crystal growth by the Bridgman method comprises a high-temperature furnace, a low-temperature furnace and a heating module, and an annular heating zone arranged inside the high-temperature furnace and the low-temperature furnace, wherein a heating tube for a quartz boat to pass through is arranged in the annular heating zone, and comprises the following steps:

[0012] The heating tube is divided into a high temperature zone and a low temperature zone along the axial direction, and the high temperature zone and the low temperature zone correspond to the annular heating zones of the high temperature furnace and the low temperature furnace respectively; temperature collection points are evenly arranged in the high temperature zone and the low temperature zone; and the temperature collection points on the same vertical plane are set as the same group;

[0013] Evenly arrange the heating modules in the annular heating zone, and initialize and debug the heating modules;

[0014] Turn on all heating modules to heat the heating tube, obtain temperature data of each group of temperature collection points in the same temperature zone, and calculate the average temperature value of each group. When the deviation between the average temperature value and the set temperature value is less than a preset value, enter the detection adjustment mode;

[0015] Detection adjustment mode: obtain the temperature data corresponding to each group of temperature collection points, calculate the maximum deviation value Δt between each group of temperature data and the set temperature value, and set the rotation speed of the heating module corresponding to the group of temperature collection points according to the maximum deviation value until the maximum deviation value Δt is less than the preset adjustment value.

[0016] As a further solution of the present invention: the heating modules are arranged in a ring in the annular heating zone, and the heating modules in the same ring are set as the same zone, and a driving module is provided to control the heating modules in the zone to rotate along the axis of the heating tube.

[0017] As a further solution of the present invention: the initialization debugging includes a homogenization test and a synchronization test, wherein the homogenization test specifically includes the following steps:

[0018] According to the position information of each heating module, a temperature collection point corresponding to the heating module is obtained as a detection point;

[0019] A single heating module is started, and after a preset detection time t1, the temperature data of the detection point is obtained, and the temperature data is used as a data set to analyze the discreteness of the data set. When the preset conditions are met, it is determined that the homogenization test has passed.

[0020] As a further solution of the present invention: in the homogenization test, when the discreteness of the data set does not meet the preset conditions, the corresponding heating module is replaced and the homogenization test is performed again.

[0021] As a further solution of the present invention: after all the heating modules have completed the homogenization test, a synchronization test is performed, and the synchronization test specifically includes the following steps:

[0022] All heating modules are started at a preset power, and after a preset test time t2, the temperature data of each group of temperature collection points is obtained;

[0023] A plurality of data sets are obtained by using the temperature data corresponding to each group of temperature collection points, and the discreteness of the data sets is analyzed. When the preset conditions are met, it is determined that the synchronization test has been passed.

[0024] As a further solution of the present invention: in the synchronization test, when the discreteness of the data set does not meet the preset conditions, temperature data with a standard deviation exceeding a preset threshold is obtained as target data, the temperature collection points corresponding to the target data are obtained, and the heating module at the corresponding position is obtained according to the temperature collection points, the heating module is replaced and the homogenization test and synchronization test are performed again.

[0025] As a further solution of the present invention: setting the rotation speed of the heating module corresponding to the group of temperature collection points according to the maximum deviation value includes initial speed setting and secondary speed adjustment, wherein the initial speed setting specifically includes the following steps:

[0026] Obtain the temperature data of all groups of temperature collection points corresponding to the heating modules in the same zone;

[0027] Calculate the maximum deviation value Δt of each group respectively, and select the maximum value MAX (Δt);

[0028] When MAX(Δt)>t', the rotation speed of the heating module driven by the driving module in the zone is calculated to be V*(MAX(Δt)-t') / t, where t represents the set temperature, V represents the preset maximum rotation speed, and t' represents the preset adjustment value.

[0029] As a further solution of the present invention: after setting the initial speed, the speed is adjusted for a second time, and the specific steps are as follows;

[0030] Continue to obtain the maximum value MAX (Δt) of the heating module in this zone, and when the maximum value MAX (Δt) is greater than the preset adjustment value, increase the rotation speed until the maximum value MAX (Δt) is less than or equal to the preset adjustment value.

[0031] Beneficial effects of the present invention: Through the prior art, it is not difficult to understand that in the process of preparing crystals by the conventional horizontal Bridgman two-zone furnace method, there are three motion systems, and the fourth motion system is adopted in the present invention, in which the heating furnace system and the crystal container system are both moved; the movement mode of the heating furnace system is rotation, and the crystal container system adopts horizontal movement; the crystal is crystallized by the horizontal movement of the crystal container system, and the uniformity of the temperature zone is controlled by the rotation of the heating furnace system, and the two cooperate with each other to improve the quality of the crystal; and in the specific scheme, it is necessary to set the arrangement of the heating modules and select the corresponding temperature collection points in a preset manner, and complete the corresponding grouping and partitioning operations;

[0032] The temperature data corresponding to the temperature collection point is used as a sample data set for analysis, and the discrete index of the sample data set is used as a measurement standard to evaluate the performance of each heating module, thereby completing the initialization and debugging process. Common discrete indicators include deviation, variance, and standard deviation, which will not be described in detail here;

[0033] The initial rotation speed of the driving module is then set according to the deviation of each set of temperature data, so that the heating module is driven to rotate along the axis of the heating tube to eliminate the local heating unevenness, thereby improving the temperature stability during crystal crystallization. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings.

[0035] Figure 1 It is the structure of 2T-HB furnace and its temperature distribution diagram;

[0036] Figure 2 This is the temperature variation diagram of the 2T-HB furnace;

[0037] Figure 3 It is a schematic flow chart of the temperature control method for crystal growth by the Bridgman method of the present invention. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] See also Figure 1-3 As shown, the present invention is a temperature control method for crystal growth by the Bridgman method, comprising a high-temperature furnace, a low-temperature furnace and a heating module, and an annular heating zone arranged inside the high-temperature furnace and the low-temperature furnace, wherein a heating tube for a quartz boat to pass through is arranged in the annular heating zone, and comprises the following steps:

[0040] The heating tube is divided into a high temperature zone and a low temperature zone along the axial direction, and the high temperature zone and the low temperature zone correspond to the annular heating zones of the high temperature furnace and the low temperature furnace respectively; temperature collection points are evenly arranged in the high temperature zone and the low temperature zone; and the temperature collection points on the same vertical plane are set as the same group;

[0041] Evenly arrange the heating modules in the annular heating zone, and initialize and debug the heating modules;

[0042] Turn on all heating modules to heat the heating tube, obtain temperature data of each group of temperature collection points in the same temperature zone, and calculate the average temperature value of each group. When the deviation between the average temperature value and the set temperature value is less than a preset value, enter the detection adjustment mode;

[0043] Detection adjustment mode: obtain the temperature data corresponding to each group of temperature collection points, calculate the maximum deviation value Δt between each group of temperature data and the set temperature value, and set the rotation speed of the heating module corresponding to the group of temperature collection points according to the maximum deviation value until the maximum deviation value Δt is less than the preset adjustment value.

[0044] Through the prior art, it is not difficult for us to understand that in the process of preparing crystals by the conventional horizontal Bridgman two-zone furnace method, there are three motion systems, and the fourth motion system is adopted in the present invention, in which the heating furnace system and the crystal container system are both moved; the movement mode of the heating furnace system is rotation, and the crystal container system adopts horizontal movement; the crystal is crystallized by the horizontal movement of the crystal container system, and the uniformity of the temperature zone is controlled by the rotation of the heating furnace system, and the two cooperate with each other to improve the quality of the crystal; and in the specific scheme, it is necessary to set the arrangement of the heating modules and select the corresponding temperature collection points in a preset manner, and complete the corresponding grouping and partitioning operations;

[0045] The temperature data corresponding to the temperature collection point is used as a sample data set for analysis, and the discrete index of the sample data set is used as a measurement standard to evaluate the performance of each heating module, thereby completing the initialization and debugging process. Common discrete indicators include deviation, variance, and standard deviation, which will not be described in detail here;

[0046] The initial rotation speed of the driving module is then set according to the deviation of each set of temperature data, so that the heating module is driven to rotate along the axis of the heating tube to eliminate the local heating unevenness, thereby improving the temperature stability during crystal crystallization.

[0047] As a further solution of the present invention: the heating modules are arranged in a ring in the annular heating zone, and the heating modules in the same ring are set as the same zone, and a driving module is provided to control the heating modules in the zone to rotate along the axis of the heating tube.

[0048] As a further solution of the present invention: the initialization debugging includes a homogenization test and a synchronization test, wherein the homogenization test specifically includes the following steps:

[0049] According to the position information of each heating module, a temperature collection point corresponding to the heating module is obtained as a detection point;

[0050] A single heating module is started, and after a preset detection time t1, the temperature data of the detection point is obtained, and the temperature data is used as a data set to analyze the discreteness of the data set. When the preset conditions are met, it is determined that the homogenization test has passed.

[0051] As a further solution of the present invention: in the homogenization test, when the discreteness of the data set does not meet the preset conditions, the corresponding heating module is replaced and the homogenization test is performed again.

[0052] As a further solution of the present invention: after all the heating modules have completed the homogenization test, a synchronization test is performed, and the synchronization test specifically includes the following steps:

[0053] All heating modules are started at a preset power, and after a preset test time t2, the temperature data of each group of temperature collection points is obtained;

[0054] A plurality of data sets are obtained by using the temperature data corresponding to each group of temperature collection points, and the discreteness of the data sets is analyzed. When the preset conditions are met, it is determined that the synchronization test has been passed.

[0055] As a further solution of the present invention: in the synchronization test, when the discreteness of the data set does not meet the preset conditions, temperature data with a standard deviation exceeding a preset threshold is obtained as target data, the temperature collection points corresponding to the target data are obtained, and the heating module at the corresponding position is obtained according to the temperature collection points, the heating module is replaced and the homogenization test and synchronization test are performed again.

[0056] As a further solution of the present invention: setting the rotation speed of the heating module corresponding to the group of temperature collection points according to the maximum deviation value includes initial speed setting and secondary speed adjustment, wherein the initial speed setting specifically includes the following steps:

[0057] Obtain the temperature data of all groups of temperature collection points corresponding to the heating modules in the same zone;

[0058] Calculate the maximum deviation value Δt of each group respectively, and select the maximum value MAX (Δt);

[0059] When MAX(Δt)>t', the rotation speed of the heating module driven by the driving module in the zone is calculated to be V*(MAX(Δt)-t') / t, where t represents the set temperature, V represents the preset maximum rotation speed, and t' represents the preset adjustment value.

[0060] As a further solution of the present invention: after setting the initial speed, the speed is adjusted for a second time, and the specific steps are as follows;

[0061] Continue to obtain the maximum value MAX (Δt) of the heating module in this zone, and when the maximum value MAX (Δt) is greater than the preset adjustment value, increase the rotation speed until the maximum value MAX (Δt) is less than or equal to the preset adjustment value.

[0062] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A temperature control method for crystal growth by the Bridgman method, comprising a high temperature furnace, a low temperature furnace and a heating module, and an annular heating zone arranged inside the high temperature furnace and the low temperature furnace, wherein a heating tube for a quartz boat to pass through is arranged in the annular heating zone, characterized in that: The following steps are involved: Divide the heating tube into a high temperature zone and a low temperature zone along the axial direction, wherein the high temperature zone and the low temperature zone correspond to the annular heating zones of the high temperature furnace and the low temperature furnace respectively; The temperature collection points are evenly arranged in the high temperature zone and the low temperature zone; and the temperature collection points on the same vertical plane are set as the same group; Evenly arrange the heating modules in the annular heating zone, and initialize and debug the heating modules; Turn on all heating modules to heat the heating tube, obtain temperature data of each group of temperature collection points in the same temperature zone, and calculate the average temperature value of each group. When the deviation between the average temperature value and the set temperature value is less than a preset value, enter the detection adjustment mode; Detection adjustment mode: obtain the temperature data corresponding to each group of temperature collection points, calculate the maximum deviation value Δt between each group of temperature data and the set temperature value, and set the rotation speed of the heating module corresponding to the group of temperature collection points according to the maximum deviation value until the maximum deviation value Δt is less than the preset adjustment value; The heating modules are arranged in a ring in the annular heating zone, and the heating modules in the same ring are set as the same zone, and a driving module is set to control the heating modules in the zone to rotate along the axis of the heating tube; Setting the rotation speed of the heating module corresponding to the group of temperature collection points according to the maximum deviation value includes initial speed setting and secondary speed adjustment, wherein the initial speed setting specifically includes the following steps: Obtain the temperature data of all groups of temperature collection points corresponding to the heating modules in the same zone; Calculate the maximum deviation value Δt of each group respectively, and select the maximum value MAX (Δt); When MAX(Δt)>t', the rotation speed of the heating module driven by the driving module in the zone is calculated to be V*(MAX(Δt)-t') / t, where t represents the set temperature, V represents the preset maximum rotation speed, and t' represents the preset adjustment value; After setting the initial speed, perform secondary speed adjustment. The specific steps are as follows: Continue to obtain the maximum value MAX (Δt) of the heating module in this zone, and when the maximum value MAX (Δt) is greater than the preset adjustment value, increase the rotation speed until the maximum value MAX (Δt) is less than or equal to the preset adjustment value.

2. The temperature control method for Bridgman crystal growth according to claim 1, characterized in that: The initialization debugging includes a homogenization test and a synchronization test, wherein the homogenization test specifically includes the following steps: According to the position information of each heating module, a temperature collection point corresponding to the heating module is obtained as a detection point; A single heating module is started, and after a preset detection time t1, the temperature data of the detection point is obtained, and the temperature data is used as a data set to analyze the discreteness of the data set. When the preset conditions are met, it is determined that the homogenization test has passed.

3. The temperature control method for Bridgman crystal growth according to claim 2, characterized in that: In the homogenization test, when the discreteness of the data set does not meet the preset conditions, the corresponding heating module is replaced and the homogenization test is performed again.

4. The temperature control method for Bridgman crystal growth according to claim 2, characterized in that: After all the heating modules have completed the homogenization test, a synchronization test is performed. The synchronization test specifically includes the following steps: All heating modules are started at a preset power, and after a preset test time t2, the temperature data of each group of temperature collection points is obtained; A plurality of data sets are obtained by using the temperature data corresponding to each group of temperature collection points, and the discreteness of the data sets is analyzed. When the preset conditions are met, it is determined that the synchronization test has been passed.

5. The temperature control method for Bridgman crystal growth according to claim 4, characterized in that: In the synchronization test, when the degree of discreteness of the data set does not meet the preset conditions, temperature data with a standard deviation exceeding a preset threshold is obtained as target data, the temperature collection points corresponding to the target data are obtained, and the heating module at the corresponding position is obtained according to the temperature collection points. The heating module is replaced and the homogenization test and synchronization test are performed again.

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