CN114808142A - Current heating device for conductive silicon carbide wafer - Google Patents

Abstract

The invention discloses a current heating device for a conductive silicon carbide wafer, which comprises a power supply control module, a temperature measuring unit, a first electrode, a second electrode and a tray structure, wherein the tray structure is provided with a containing groove, the first electrode and the second electrode are respectively arranged corresponding to the center and the edge of the tray structure, the first electrode and the second electrode are respectively electrically connected with the anode and the cathode of the power supply control module, the temperature measuring unit is arranged above the tray structure and is electrically connected with the power supply control module, when the silicon carbide wafer is contained in the containing groove, the silicon carbide wafer enables the first electrode and the second electrode to be conducted so as to form a heating circuit, the internal resistance heating of the conductive silicon carbide wafer is utilized to realize thermal annealing, and the voltage applied between the first electrode and the second electrode is controlled according to the detection result of the temperature measuring unit so as to adjust the heating temperature, the temperature rising and falling rates of the current heating device are far faster than those of the existing furnace chamber heating device, when the conductive silicon carbide wafer is processed in small batches, the advantages of large time cost and energy consumption cost are achieved.

Description

Current heating device for conductive silicon carbide wafer

Technical Field

The invention relates to the technical field of crystal synthesis, in particular to a heating device suitable for a silicon carbide wafer in high-temperature annealing processes before and after an epitaxial layer is grown by a chemical vapor deposition method.

Background

The silicon carbide semiconductor material has the advantages of high thermal conductivity, high breakdown field, high saturated electron drift rate, high bonding energy and the like, and can well meet the application requirements of modern electronic technology on severe conditions such as high temperature, high power, high voltage, high frequency, high radiation and the like.

Various silicon carbide power electronic devices must be manufactured on high-quality epitaxial wafers, and the batch production of the high-quality silicon carbide epitaxial wafers needs to go through necessary matching procedures such as pretreatment, grinding and polishing, cleaning and the like besides the growth of the epitaxial layers. For some ten-kilovolt epitaxial wafers (the thickness of the epitaxial layer is more than 100 mu m), minority carrier lifetime regulating and controlling procedures such as carbon ion implantation, hydrogen annealing and the like are required to be added so as to ensure that the carriers have enough diffusion distance to deal with the increase of the thickness. These associated processes often involve heat treatment of silicon carbide substrates or epitaxial wafers, and the conventional treatment is high temperature annealing in a furnace chamber heating device such as an epitaxial growth furnace or a special annealing furnace.

The existing mode of annealing treatment by using an epitaxial furnace greatly occupies the production capacity of epitaxial wafers. Although the dedicated annealing furnace can process epitaxial wafers in batch by using a jig, the time for raising and lowering the temperature is long due to the huge chamber, and therefore, the disadvantages of time per wafer and energy consumption cost are amplified when a small number of wafers are processed in a customized production process. The cost problem is one of the main factors for restricting the silicon carbide power electronic device to replace the traditional silicon power electronic device on a large scale at present.

Therefore, it is necessary to provide a heating apparatus capable of rapidly heating and annealing silicon carbide wafers, so as to improve efficiency and provide energy saving advantages compared to the conventional heating apparatus when processing silicon carbide wafers in small batches.

Disclosure of Invention

The invention aims to provide a current heating device for a conductive silicon carbide wafer, which can improve the efficiency and has the energy-saving advantage when the silicon carbide wafer is processed in small batches.

In order to achieve the purpose, the technical scheme of the invention is as follows: the current heating device for the conductive silicon carbide wafer comprises a power supply control module, a temperature measuring unit, a first electrode, a second electrode and a tray structure, wherein a containing groove is arranged on the tray structure, one of the first electrode and the second electrode is arranged corresponding to the center of the tray structure, the other of the first electrode and the second electrode is arranged at the edge of the tray structure, the first electrode and the second electrode are respectively and electrically connected with the anode and the cathode of the power supply control module, the temperature measuring unit is arranged above the tray structure and is electrically connected with the power supply control module, when the silicon carbide wafer is contained in the containing groove, the silicon carbide wafer enables the first electrode and the second electrode to be conducted to form a heating circuit, and the temperature measuring unit is used for detecting the surface temperature of the silicon carbide wafer in the containing groove, the power supply control module is used for adjusting the voltage applied between the first electrode and the second electrode according to the temperature detected by the temperature measuring unit.

Preferably, one of the first electrode and the second electrode is provided with one and is installed corresponding to the center of the tray structure, and the other of the first electrode and the second electrode is provided with a plurality of and is evenly installed at the edge of the tray structure.

Preferably, the first electrode is disposed corresponding to the center of the tray structure and is cylindrical, the plurality of second electrodes are uniformly arranged along the circumferential direction of the tray structure, each second electrode has a square contact portion, the contact portion protrudes into the accommodating groove, and the first electrode and the contact portion are both used for abutting against the silicon carbide wafer.

Preferably, the side length of the contact part is greater than or equal to the diameter of the first electrode.

Preferably, when the first electrode is electrically connected to the positive electrode of the power control module and the second electrode is electrically connected to the negative electrode of the power control module, the heating circuit is equivalently composed of a plurality of resistors R _i In this way, the silicon carbide wafer can be uniformly heated; when the first electrode is electrically connected to the negative electrode of the power control module and the second electrode is electrically connected to the positive electrode of the power control module, the heating circuit is equivalent to a plurality of resistors R _i And independent resistance heating circuits, in this way, controlled non-uniform heating annealing of a given area of the silicon carbide wafer can be carried out.

Preferably, when n second electrodes are provided, the resistance value R of the equivalent resistor corresponding to the ith second electrode is set to be n _i ＝ρ·r/l _i T, where ρ is the resistivity of the silicon carbide wafer, r is the radius of the silicon carbide wafer, t is the thickness of the silicon carbide wafer, l _i Is the minimum value of the width of the projection of the first electrode and the second electrode in the connecting direction of the first electrode and the ith second electrode; wherein n is a positive integer greater than or equal to 1, and i is a positive integer greater than or equal to 1 and less than or equal to n.

Preferably, the power control module is configured to control the power of the first electrode and the second electrode according to a voltage applied between the first electrode and the second electrode and a resistance value R of the equivalent resistor _i The equivalent resistance heating circuit current and resistance heating power can be calculated, and the voltage applied between the first electrode and the second electrode can be adjusted in real time according to the relation between the temperature detected by the temperature measuring unit and the resistance heating power so as to adjust the resistance heating power and further achieve the purpose of adjusting the heating temperature.

Preferably, the tray structure comprises a quartz glass substrate, the thickness of the quartz glass substrate is 1cm, and the silica content of the quartz glass substrate is more than 99.5%.

Preferably, the tray structure further comprises a zone-melting monocrystalline silicon layer adhered on the quartz glass substrate, and a diamond polycrystalline coating formed on the zone-melting monocrystalline silicon layer, wherein the thickness of the zone-melting monocrystalline silicon layer is 100-500 micrometers, the resistivity of the zone-melting monocrystalline silicon layer is greater than 5000 omega-cm, the thickness of the diamond polycrystalline coating is 10-50 micrometers, and the diamond polycrystalline coating has insulating and excellent heat conducting properties, so that heat generated during electric heating can be rapidly and uniformly conducted to the whole crystal face of the silicon carbide wafer, and uniform distribution of the temperature of the silicon carbide wafer is facilitated.

Preferably, the diameter of the containing groove is 1520mm, and the depth is 0.3 mm.

Preferably, the temperature measuring units are arranged above the accommodating groove at intervals and used for detecting the surface temperature of different areas of the silicon carbide wafer, and the temperature measuring units of different types can be arranged according to different annealing temperature ranges.

More preferably, the temperature measuring unit adopts an infrared thermometer, a monochromatic thermometer when the annealing temperature is between 25 ℃ and 450 ℃, and a radiation colorimetric thermometer when the annealing temperature is between 450 ℃ and 1600 ℃.

Compared with the prior art, because the current heating device for the conductive silicon carbide wafer is provided with the first electrode and the second electrode respectively corresponding to the center of the tray structure and the edge of the tray structure, and the first electrode and the second electrode are respectively electrically connected with the anode and the cathode of the power control module, when the silicon carbide wafer is accommodated in the accommodating groove of the tray structure, the silicon carbide wafer is contacted with the first electrode and the second electrode to conduct the two electrodes so as to form a heating circuit, firstly, the internal resistance heating of the conductive silicon carbide wafer is utilized to realize thermal annealing, the current heating device has the advantages that the temperature rising and reducing speed is far faster than that of the existing furnace chamber heating device, the current heating device has the advantages of higher time cost and energy consumption cost when the conductive silicon carbide wafer is processed in small batch, and can be used as a supplement scheme of the annealing process of the furnace chamber heating device in the mass production of the silicon carbide epitaxial wafer, secondly, the condition that complicated electric field distribution occurs in the conductive loop from the edge to the center of the circular wafer can be effectively avoided by adopting the conductive loop from the center to the edge, a two-dimensional electric field distribution model can be simplified into a one-dimensional simple circuit model, and the temperature of the silicon carbide wafer can be regulated and controlled by the power supply control module more easily.

Drawings

Fig. 1 is a plan view of an electric current heating apparatus according to a first embodiment of the present invention.

Fig. 2 is a sectional view of fig. 1.

Fig. 3 is a sectional view of the current heating apparatus of fig. 1 in a use state.

Fig. 4 is a schematic diagram of the equivalent resistance of the current heating apparatus of fig. 3.

Fig. 5 is a schematic diagram of an equivalent circuit of the current heating apparatus of fig. 3.

Fig. 6 is a schematic block diagram of an electric current heating apparatus according to a first embodiment of the present invention.

Fig. 7 is a sectional view of an electric current heating apparatus according to a second embodiment of the present invention.

Fig. 8 is a sectional view of the medium current heating apparatus of fig. 7 in a use state.

Fig. 9 is a top view of the current heating apparatus of fig. 8.

Detailed Description

Embodiments of the present invention will now be described with reference to the drawings, wherein like element numerals represent like elements. It should be noted that the orientation descriptions of the present invention, such as the directions or positional relationships indicated above, below, left, right, front, rear, etc., are all based on the directions or positional relationships shown in the drawings, and are only for convenience of describing the technical solutions of the present application or simplifying the description, but do not indicate or imply that the devices or elements referred to must have specific orientations, be constructed in specific orientations, and operate, and therefore, should not be construed as limiting the present application. The description of first, second, etc. merely serves to distinguish technical features and should not be interpreted as indicating or implying a relative importance or implying a number of indicated technical features or implying a precedence relationship between indicated technical features.

First, referring to fig. 1 to 9, the current heating apparatus 100 for a conductive type silicon carbide wafer according to the present invention is mainly suitable for the thermal annealing of a conductive type silicon carbide single crystal substrate wafer and an epitaxial wafer, but is not limited thereto, and may also be used for the thermal annealing of other conductive type wafers, and for convenience of description, the silicon carbide wafer 200 is used to refer to all the conductive type wafers hereinafter.

Referring to fig. 1 to 9, a current heating apparatus 100 for a conductive type silicon carbide wafer according to the present invention includes a first electrode 110, a second electrode 120, a temperature measuring unit 130, a tray structure 140, and a power control module 150 (see fig. 5 to 6). Wherein, the tray structure 140 is provided with a containing groove 140a for containing the silicon carbide wafer 200, one of the first electrode 110 and the second electrode 120 is arranged corresponding to the center of the tray structure 140, the other of the first electrode 110 and the second electrode 120 is arranged at the edge of the tray structure 140, the first electrode 110 and the second electrode 120 are electrically connected to the positive electrode and the negative electrode of the power control module 150, respectively, the temperature measuring unit 130 is disposed above the tray structure 140 and electrically connected to the power control module 150, when the silicon carbide wafer 200 is received in the receiving groove 140a, the first electrode 110 and the second electrode 120 are in contact with the silicon carbide wafer 200 to conduct the two, therefore, the power control module 150, the first electrode 110, the silicon carbide wafer 200 and the second electrode 120 form a heating circuit, and the thermal annealing of the silicon carbide wafer 200 is realized by an electric heating mode; the temperature measuring unit 130 is used for detecting the surface temperature of the silicon carbide wafer 200 in the receiving groove 140a, and the power control module 150 is used for controlling and adjusting the voltage applied between the first electrode 110 and the second electrode 120 according to the temperature detected by the temperature measuring unit 130, so that the temperature of the silicon carbide wafer 200 is kept near the target value of the thermal annealing process.

In the present invention, one of the first and second electrodes 110 and 120 is provided and installed corresponding to the center of the tray structure 140, and the other of the first and second electrodes 110 and 120 is provided with a plurality of electrodes and evenly installed at the edge of the tray structure 140. In one embodiment, the first electrode 110 is disposed corresponding to the center of the tray structure 140 and has a cylindrical shape, the plurality of second electrodes 120 are uniformly arranged along the radial direction of the tray structure 140, and each second electrode 120 has a square contact portion 121, and the contact portion 121 protrudes into the accommodating groove 140a, as shown in fig. 2 and 5; when the silicon carbide wafer 200 is received in the receiving groove 140a, the first electrode 110 and the contact portion 121 may abut against the surface of the silicon carbide wafer 200, as shown in fig. 4 and 9.

In the present invention, one or more temperature measuring units 130 may be provided, the temperature measuring unit 130 is disposed above the accommodating groove 140a and is used for detecting the surface temperature of the silicon carbide wafer 200, and when a plurality of temperature measuring units 130 are provided, the plurality of temperature measuring units 130 are disposed at intervals and can respectively detect the surface temperature of different regions of the silicon carbide wafer 200. In addition, different types of temperature measuring units 130 can be set according to different annealing temperature ranges, as will be described in detail later.

Referring again to fig. 1-9, different embodiments of the current heating apparatus 100 for a conductive type silicon carbide wafer according to the present invention will be described.

Referring to fig. 1 to 4, in a first embodiment of the present invention, the tray structure 140 includes a quartz glass substrate 141, a zone-melting single crystal silicon layer 142 bonded on the quartz glass substrate 141, and a diamond polycrystalline coating 143 formed on the zone-melting single crystal silicon layer 142. Wherein, the thickness of the quartz glass substrate 141 is 1cm and the silicon dioxide content thereof is more than 99.5%, the thickness of the zone-melting monocrystalline silicon layer 142 is 100 μm-500 μm, the resistivity is more than 5000 Ω · cm, the diamond polycrystalline coating 143 is deposited on the zone-melting monocrystalline silicon layer 142 by using a direct current arc plasma jet chemical vapor deposition method, and the thickness of the diamond polycrystalline coating 143 is 10 μm-50 μm, of course, the diamond polycrystalline coating 143 can be formed by other methods, because the diamond polycrystalline coating 143 has insulating and excellent heat-conducting properties, the heat during electric heating can be rapidly and uniformly conducted to the whole crystal face of the silicon carbide wafer 200, and the uniform distribution of the temperature of the silicon carbide wafer 200 can be realized more favorably.

More specifically, the receiving groove 140a of the tray structure 140 is disposed above the diamond polycrystalline coating 143, that is, the diamond polycrystalline coating 143 forms the bottom surface of the receiving groove 140a, as shown in fig. 2. In the present embodiment, the diameter of the receiving groove 140a is preferably 1520mm, and the depth thereof is preferably 0.3mm, for receiving the silicon carbide wafer 200 having a diameter of 6 inches and a thickness of 350 μm. Understandably, the size of the receiving groove 140a is not limited thereto, and can be flexibly set according to different sizes of the silicon carbide wafer 200, so as to meet the requirements of heating silicon carbide wafers 200 with different sizes and models.

With continued reference to fig. 1-2, in the present embodiment, the current heating apparatus 100 for the conductive type silicon carbide wafer is provided with a first electrode 110 and a plurality of second electrodes 120, wherein the first electrode 110 is disposed corresponding to the center of the tray structure 140 and has a cylindrical shape, and the first electrode 110 is preferably tin-plated copper; a plurality of second electrodes 120 are uniformly arranged along the radial direction of the tray structure 140 and are grounded in parallel by a wire, each second electrode 120 has a contact portion 121 having a square shape, the contact portion 121 protrudes into the accommodating groove 140a for abutting against the silicon carbide wafer 200, and each second electrode 120 is also preferably tin-plated copper. After the conductive silicon carbide wafer 200 is placed in the receiving groove 140a, the first electrode 110 is in contact with the center of the silicon carbide wafer 200, the contact portion 121 is in contact with the edge of the silicon carbide wafer 200, and the silicon carbide wafer 200 is in contact with the first electrode 110 and the second electrode 120 to conduct the two.

In the present invention, the side length of the contact portion 121 is equal to or greater than the diameter of the first electrode 110, as shown in fig. 4. In the present embodiment, the diameter of the first electrode 110 and the side length of the contact portion 121 are preferably equal, and both are preferably 6mm, but the size is not limited to this value, and the size of both can be flexibly set according to specific needs.

With continued reference to fig. 1-2, in the present embodiment, the first electrode 110 is electrically connected to the power controlThe positive electrode of the module 150 and the second electrode 120 are electrically connected to the negative electrode of the power control module 150 and are grounded in parallel through a conducting wire, so that the heating circuit of the current heating apparatus 100 is equivalently composed of a plurality of resistors R _i In this manner, rapid and uniform heating of the silicon carbide wafer 200 can be achieved.

Referring to fig. 3 to 5, when n second electrodes 120 are provided, the heating circuit of the current heating apparatus 100 is equivalent to a resistance value R _i And (i-1, 2, … …, n), wherein n is a positive integer greater than or equal to 1. Resistance value R of the equivalent resistor corresponding to the ith second electrode 120 _i ＝ρ·r/l _i T, where ρ is the resistivity of the silicon carbide wafer 200, r is the radius of the silicon carbide wafer 200, t is the thickness of the silicon carbide wafer 200, l _i To minimize the width of the projection of the first electrode 110 and the second electrode 120 in the connection direction of the first electrode 110 and the ith second electrode 120, specifically, as shown in fig. 4, i is a positive integer greater than or equal to 1 and less than or equal to n.

In this embodiment, eight second electrodes 120 are preferably provided, and the eight second electrodes 120 are sequentially and symmetrically distributed at 40 ° intervals on the edge of the tray structure 140, as shown in fig. 1 and 4. Therefore, the heating circuit in this embodiment can be equivalent to eight resistors R _i A resistance heating circuit formed by connecting silicon carbide resistors (i ═ 1, 2, … …, n) in parallel, as shown in fig. 5. For example, for one of the silicon carbide single crystal substrate sheets, the resistivity ρ is 0.02, the radius r is 7.1.2mm, and the wafer thickness t is 0.35 mm; for equivalent silicon carbide resistance R _i In other words, the equivalent silicon carbide resistance R between the first electrode 110 and any one of the second electrodes 120 _i Width l of _i Are all 6mm, as shown in FIG. 4, according to the above formula R _i ＝ρ·r/l _i T calculation to obtain each equivalent silicon carbide resistance R _i The resistance values of (1) are all 6.78 omega.

Referring again to FIGS. 1-5, in this example, the equivalent silicon carbide resistance R is calculated according to the above equation _i After the resistance value, the power supply controlsThe module 150 is configured to apply the equivalent silicon carbide resistance R according to its loading _i Upper voltage U and ohm's law to calculate equivalent silicon carbide resistance R _i According to the formula P ═ I ² R calculates the power of each equivalent resistive heating circuit. Then, according to the corresponding relationship between the power P and the annealing temperature, the voltage applied between the first electrode 110 and the second electrode 120 can be controlled or adjusted in real time, thereby achieving the adjustment of the annealing temperature.

Of particular note is the loading on the equivalent silicon carbide resistor R described above _i The voltage U on the silicon carbide wafer should take into account the maximum current density through the silicon carbide wafer to avoid damage to the silicon carbide lattice from excessive current densities. For example, reference may be made to the current density at power rating in silicon carbide Schottky barrier diode (SiC-SBD) or metal-oxide semiconductor field effect transistor (MOSFET) device applications, which are exemplified by a 600V, 6A SiC-SBD, which typically requires a die area of 2mm, and a current density at rated operating conditions of 1.5A/mm ² From the perspective of industrial experience, it is shown that the long-term stable use of the device can be ensured under the current density, and the problem of lattice damage does not exist. Therefore, at a maximum current density of 1.5A/mm ² For example, when the first and second electrodes 110 and 120 are brought into contact with the silicon carbide wafer 200 to conduct, the silicon carbide resistor R on the silicon carbide wafer 200 is equivalent _i Is equal to l _i ×t＝6mm×0.35mm＝2.1mm ² At a maximum current density of 1.5A/mm ² By calculation, the maximum current I is 2.1mm ² ×1.5A/mm ² From ohm's law, the resistance R loaded on each equivalent silicon carbide can be calculated _i The maximum voltage U of upper line is 3.15A × 6.78 Ω 21.357V. That is, adjusting the voltage applied between the first electrode 110 and the second electrode 120 within a range not exceeding 21.357V makes it possible to achieve adjustment of the annealing temperature without damaging the silicon carbide crystal lattice.

In one embodiment of the present invention, as shown in fig. 3-6, to avoid damage to the sic lattice due to excessive current density, one of the first electrode 110 and the second electrode 120 is selectedAdding a voltage of 20.3V (less than the maximum voltage 21.357V) to the substrate, and obtaining each equivalent silicon carbide resistor R according to ohm's law _i The current generated is I20.3V/6.78 Ω 3.0A, as described above, due to the current passing through the equivalent silicon carbide resistor R on the silicon carbide wafer 200 _i Is equal to _i ×t＝6mm×0.35mm＝2.1mm ² Therefore, it can be calculated that the current density through the cross section is about 1.4A/mm ² I.e. a current density of 1.5A/mm less than the rated operating condition ² . At this time, the power P per equivalent resistance heating circuit, i.e., P ═ I, can be calculated ² R＝(3.0A) ² X 6.78 Ω ═ 61w, and the total power of the electric heating apparatus 100 composed of eight resistance heating circuits was 61w × 8 ═ 488w, and it was possible to satisfy heating of the silicon carbide wafer 200 with an annealing target temperature of 600 ℃. And, in the specific heating process, the temperature measuring unit 130 is used to detect the surface temperature of the silicon carbide wafer 200 in real time and feed back the detected temperature to the power control module 150, and the power control module 150 calculates the voltage applied between the first electrode 110 and the second electrode 120 according to the corresponding relationship between the power P and the annealing temperature and through the above logic algorithm to control the temperature within the range of 600 ± 10 ℃.

Understandably, in the present invention, the number of the second electrodes 120 is not limited to eight, and in other embodiments, when a higher annealing temperature (for example, over 600 ℃) is required, the number of the second electrodes 120 can be increased, so as to increase the number of the equivalent resistance heating circuits, and thus the total heating power, to increase the annealing temperature.

Referring again to fig. 1 to 6, in this embodiment, only one temperature measuring unit 130 is provided, and the temperature measuring unit 130 preferably employs an infrared thermometer, and different types of infrared thermometers may be provided according to different annealing temperature ranges, for example, a monochromatic thermometer is employed when the annealing temperature is between 25 ℃ and 450 ℃, and a radiation colorimetric thermometer is employed when the annealing temperature is between 450 ℃ and 1600 ℃. Of course, the temperature measuring unit 130 may also be other temperature detecting devices.

Referring to fig. 1 and 4, when the current heating apparatus 100 of the present embodiment is used, a silicon carbide wafer 200 having a diameter of 6 inches and a thickness of 350 μm is placed in the receiving groove 140a of the tray structure 140, and the first electrode 110 is concentrically contacted and connected with the center of the surface of the silicon carbide wafer 200, the first electrode 110 is electrically connected to the positive electrode of the power control module 150, and the eight second electrodes 120 are symmetrically arranged at 40 ° intervals in sequence, the contact portion 121 of each second electrode 120 is contacted with the upper surface of the silicon carbide wafer 200, and each second electrode 120 is electrically connected to the negative electrode of the power control module and is grounded in parallel through a lead wire, as shown in fig. 6.

Then, the power control module 150 applies a voltage between the first electrode 110 and each second electrode 120, the conductive silicon carbide wafer 200 conducts the first electrode 110 and the second electrode 120, so as to achieve resistance heating inside the silicon carbide wafer 200, and further heat the silicon carbide wafer 200, and the arrangement of the eight second electrodes 120 is equivalent to generate eight parallel resistance heating circuits on the silicon carbide wafer 200, while the diamond polycrystalline coating 143 of the tray structure 140 plays an insulating role when contacting with the back of the silicon carbide wafer 200, and at the same time, the high thermal conductivity of the diamond polycrystalline coating helps heat to be more uniformly distributed in the transverse direction of the silicon carbide wafer 200, so that the heat generated by the eight resistance heating circuits can be rapidly and uniformly spread throughout the whole silicon carbide wafer 200, and is more beneficial to achieve uniform distribution of the temperature of the silicon carbide wafer 200.

In a second embodiment of the present invention, as shown in fig. 7-9, the main difference between the current heating apparatus 100 and the first embodiment is: the first electrode 110 and the second electrode 120 are electrically connected in different manners. In this embodiment, the first electrode 110 is electrically connected to the negative electrode of the power control module 150 and grounded, and the second electrode 120 is electrically connected to the positive electrode of the power control module 150, so that the heating circuit of the electric current heating apparatus 100 can be equivalent to a plurality of heating circuits with resistance R _i And the mutually independent resistance heating circuits are a plurality of independent resistance heating circuits, so that the controllable nonuniform heating and annealing can be carried out on the appointed area of the silicon carbide wafer 200A fire.

In this embodiment, the resistance value R of each equivalent silicon carbide resistor _i ＝ρ·r/l _i T, the equivalent and calculation manners are the same as those in the first embodiment described above, and the description will not be repeated, and therefore, the resistance value R of each equivalent silicon carbide resistor _i Are all 6.78 omega.

Referring to fig. 7-8, the eight second electrodes 120 are also disposed in this embodiment, so that the heating circuit of the current heating apparatus 100 is equivalent to eight heating circuits with resistance R _i And the voltage applied between the first electrode 110 and each of the second electrodes 120 is different and is a voltage V ₁ 、V ₂ ……V ₈ That is, the equivalent currents in the eight resistance heating circuits are different, and the resistance heating circuits generate different resistance heating values due to the different currents.

It is to be noted that, in this embodiment, it is not to be said that only different voltages can be applied to the eight equivalent resistance heating circuits, but it is needless to say that the same voltage can be applied to the eight equivalent resistance heating circuits as needed.

In this embodiment, the structures, mounting manners, and other parts not described of the first electrode 110 and the second electrode 120 are the same as those in the first embodiment, and the description thereof will not be repeated.

As shown in fig. 7 to 9, in this embodiment, the structure of the tray structure 140 is slightly different from that in the first embodiment, specifically, the tray structure 140 includes only the quartz glass substrate 141, and the thickness of the quartz glass substrate 141 is 1cm and the silica content of the quartz glass substrate 141 is 99.5% or more. Of course, the tray structure 140 can be formed using other high insulation and low thermal conductivity coating materials. In this embodiment, the diamond polycrystalline coating 143 is not provided, so that different heating values generated by eight equivalent resistance heating circuits of the current heating apparatus 100 cannot be quickly and uniformly conducted to the whole crystal plane of the silicon carbide wafer 200, and the temperature measurement unit 130 and the power control module 150 are matched to realize controllable non-uniform heating annealing of the specified region of the silicon carbide wafer 200. The manner of adjusting the heating power of each resistance heating circuit obtained by the specific equivalence is the same as that in the first embodiment described above, and the description will not be repeated.

With reference to fig. 7-8, in this embodiment, it is preferable to provide a plurality of temperature measurement units 130, wherein the temperature measurement units 130 are disposed above the receiving groove 140a at intervals and are disposed corresponding to the designated area of the sic wafer 200 for detecting the surface temperature of the designated area of the sic wafer 200, and the power control module 150 controls or adjusts the voltage between the first electrode 110 and the second electrode 120 of the corresponding area according to the detection results of different temperature measurement units 130, so as to make the voltages of the equivalent resistance heating circuits different, and realize the respective heating of different areas of the sic wafer 200.

It should be noted that the tray structure 140 in this embodiment is not limited to include only the quartz glass substrate 141, but may be provided as a three-layer structure in the first embodiment, which does not affect the equivalent heating of eight mutually independent resistance heating circuits.

Referring again to fig. 7 to 9, when the electric current heating apparatus 100 of the present embodiment is used, a silicon carbide wafer 200 having a diameter of 6 inches and a thickness of 350 μm is placed in the receiving groove 140a of the tray structure 140, and the first electrode 110 is concentrically contacted and connected with the center of the surface of the silicon carbide wafer 200, as shown in fig. 7 and 9, and the first electrode 110 is electrically connected to the negative electrode of the power control module 150 and is grounded, the eight second electrodes 120 are symmetrically disposed at 40 ° intervals, respectively, the contact portion 121 of each second electrode 120 is contacted with the upper surface of the silicon carbide wafer 200, and each second electrode 120 is electrically connected to the positive electrode of the power control module 150, as shown in fig. 7 to 9.

Then, the power control module 150 applies different voltages V to the eight second electrodes 120 respectively ₁ 、V ₂ 、……V ₈ Eight resistance heating circuits equivalent to the current heating apparatus 100 generate different heating values, and the tray structure 140 is not provided with the diamond polycrystalline coating 143, so that the eight resistance heating circuits generateDifferent generated heat values are respectively transmitted to the silicon carbide wafer 200, so that different areas of the silicon carbide wafer 200 can be respectively heated, and the voltage V can be respectively controlled and adjusted ₁ 、V ₂ 、……V ₈ Controlled non-uniform thermal annealing of a designated area of the silicon carbide wafer 200 is achieved.

In summary, since the current heating apparatus 100 for the conductive silicon carbide wafer according to the present invention is provided with the first electrode 110 and the second electrode 120 respectively corresponding to the center of the tray structure 140 and the edge of the tray structure 140, and the first electrode 110 and the second electrode 120 are respectively electrically connected to the positive and negative electrodes of the power control module 150, when the silicon carbide wafer 200 is accommodated in the accommodating groove 140a of the tray structure 140, the silicon carbide wafer 200 is in contact with the first electrode 110 and the second electrode 120 to be conducted to form a heating circuit, first, the internal resistance heating of the conductive silicon carbide wafer 200 is utilized to realize thermal annealing, which has the advantages of a faster temperature rising and lowering rate than the conventional furnace chamber heating apparatus, and has the advantages of higher time cost and energy consumption cost when processing the conductive silicon carbide wafer 200 in small batches, and can be used as a supplement to the annealing process of the furnace chamber heating apparatus in mass production of silicon carbide epitaxial wafers, secondly, the adoption of the conductive loop from the center to the edge can effectively avoid the situation that the complicated electric field distribution occurs in the conductive loop from the edge of the circular wafer to the edge, simplify a two-dimensional electric field distribution model into a one-dimensional simple circuit model, and more easily realize the temperature regulation and control of the power supply control module 150 on the silicon carbide wafer 200.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.

Claims (10)

1. A current heating device for a conductive silicon carbide wafer is characterized by comprising a power supply control module, a temperature measuring unit, a first electrode, a second electrode and a tray structure, wherein a containing groove is arranged on the tray structure, one of the first electrode and the second electrode is arranged corresponding to the center of the tray structure, the other of the first electrode and the second electrode is arranged at the edge of the tray structure, the first electrode and the second electrode are respectively and electrically connected with the positive electrode and the negative electrode of the power supply control module, the temperature measuring unit is arranged above the tray structure and is electrically connected with the power supply control module, when the silicon carbide wafer is contained in the containing groove, the silicon carbide wafer enables the first electrode and the second electrode to be conducted to form a heating circuit, and the temperature measuring unit is used for detecting the surface temperature of the silicon carbide wafer in the containing groove, the power supply control module is used for adjusting the voltage applied between the first electrode and the second electrode according to the temperature detected by the temperature measuring unit.

2. The electric current heating apparatus for conductivity type silicon carbide wafer as claimed in claim 1, wherein one of said first electrode and said second electrode is provided with one and installed corresponding to the center of said tray structure, and the other of said first electrode and said second electrode is provided with a plurality of and evenly installed at the edge of said tray structure.

3. The electric current heating apparatus for conductivity type silicon carbide wafer according to claim 1 or 2, wherein the first electrode is provided corresponding to the center of the tray structure and has a cylindrical shape, a plurality of the second electrodes are uniformly arranged along the circumferential direction of the tray structure, and each of the second electrodes has a contact portion having a square shape, the contact portion protruding into the accommodation groove, and the first electrode, the contact portion are used to abut against the silicon carbide wafer.

4. The electric current heating apparatus for conductivity type silicon carbide wafer as claimed in claim 3, wherein the side length of said contact portion is equal to or larger than the diameter of said first electrode.

5. The silicon carbide crystal for conduction type according to claim 3The current heating device of the slice is characterized in that when the first electrode is electrically connected with the anode of the power supply control module and the second electrode is electrically connected with the cathode of the power supply control module, the heating circuit is equivalent to a plurality of heating circuits with the resistance value of R _i The resistance of the resistance heating circuit is connected in parallel; when the first electrode is electrically connected to the negative electrode of the power control module and the second electrode is electrically connected to the positive electrode of the power control module, the heating circuit is equivalent to a plurality of resistors R _i And mutually independent resistance heating circuits.

6. The electric current heating apparatus for conduction type silicon carbide wafer according to claim 5, wherein when n number of the second electrodes are provided, a resistance value R of an equivalent resistance corresponding to an ith one of the second electrodes _i ＝ρ·r/l _i T, where ρ is the resistivity of the silicon carbide wafer, r is the radius of the silicon carbide wafer, t is the thickness of the silicon carbide wafer, l _i Is the minimum value of the width of the projection of the first electrode and the second electrode in the connecting direction of the first electrode and the ith second electrode; wherein n is a positive integer greater than or equal to 1, and i is a positive integer greater than or equal to 1 and less than or equal to n.

7. The electric current heating apparatus for conduction type silicon carbide wafer according to claim 6, wherein the power control module is configured to control the resistance R according to the voltage applied between the first electrode and the second electrode and the equivalent resistance _i And calculating the current and the resistance heating power of the equivalent resistance heating circuit, and adjusting the voltage applied between the first electrode and the second electrode in real time according to the relationship between the temperature detected by the temperature measuring unit and the resistance heating power.

8. The current heating apparatus for conductivity type silicon carbide wafer according to claim 1, wherein the tray structure comprises a quartz glass substrate having a thickness of 1cm and a silica content of 99.5% or more.

9. The current heating apparatus for conductivity type silicon carbide wafer according to claim 8, wherein the tray structure further comprises a zone-melted single crystal silicon layer adhered on the quartz glass substrate, a diamond polycrystalline coating formed on the zone-melted single crystal silicon layer, wherein the zone-melted single crystal silicon layer has a thickness of 100 μm to 500 μm, a resistivity of more than 5000 Ω -cm, and the diamond polycrystalline coating has a thickness of 10 μm to 50 μm.

10. The electric current heating apparatus for silicon carbide wafers of conductive type according to claim 1 or 2, wherein a plurality of temperature measuring units are provided, and a plurality of temperature measuring units are provided above the container tank at intervals for detecting surface temperatures of different regions of the silicon carbide wafer.

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