Temperature calibration method for silicon carbide epitaxial equipment

Abstract

The present application provides a temperature calibration method for a silicon carbide epitaxial device, which comprises: heating a reaction cavity to a target temperature, and performing silicon carbide homoepitaxy doping growth on the surface of a silicon carbide epitaxial wafer to obtain a silicon carbide temperature calibration wafer; and calibrating the measured temperature of an infrared temperature measuring device based on the corresponding relationship between the doping concentration of the silicon carbide temperature calibration wafer and the silicon carbide homoepitaxy doping growth temperature. By performing homoepitaxy doping growth on the surface of the silicon carbide epitaxial wafer, the actual growth temperature of the reaction cavity can be obtained based on the influence of the growth temperature on the doping concentration and the relationship between the doping concentration and the growth temperature, and the temperature calibration of the infrared temperature measuring device can be realized. By using the silicon carbide epitaxial wafer for temperature calibration, the epitaxial temperature can be increased to the silicon carbide epitaxial process temperature range, thereby improving the temperature calibration temperature. Based on the relationship between the doping concentration and the doping growth temperature, the use of phosphorus atom diffusion is avoided, the sensitivity is high, and the temperature calibration accuracy is improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide epitaxial technology, and more particularly to a temperature calibration method for silicon carbide epitaxial equipment. Background Technology

[0002] Silicon carbide epitaxy requires a sealed quartz cavity under low pressure. Therefore, silicon carbide epitaxy equipment typically employs non-contact infrared thermography to monitor and control the process temperature. Infrared thermography is primarily based on blackbody radiation, meaning the intensity and wavelength of infrared radiation from the same object differ at different temperatures. In practical applications, the surface temperature of the measured point is calculated by collecting the infrared radiation intensity at the monitoring point (usually graphite). Infrared thermography has several limitations, leading to a deviation between the measured temperature and the actual temperature of the object; therefore, temperature calibration is necessary.

[0003] Currently used temperature calibration methods include: Method 1, using the melting point of silicon to calibrate the temperature. For example, a small piece of silicon is placed in the silicon carbide epitaxial equipment, and the temperature of the epitaxial equipment is raised to about the melting point of silicon (1400℃). The temperature measurement of the equipment is calibrated by observing the melting of the silicon. This method is simple and easy to implement. However, its disadvantage is that it can only calibrate a single temperature point. Moreover, the melting point of silicon is relatively low, which is far from the silicon carbide epitaxial process temperature range (1500℃-1700℃), so it cannot accurately calibrate the silicon carbide epitaxial process temperature range. Method 2, using phosphorus atoms implanted on the surface of the silicon wafer as a calibration plate, calibrating the temperature measurement of the equipment by observing the effect of the epitaxial annealing temperature on the diffusion of phosphorus atoms. This method has two drawbacks: firstly, the calibration temperature is limited by the melting point of the silicon wafer, resulting in a low calibration temperature; secondly, the diffusion rate of phosphorus atoms in silicon carbide is low, making it less sensitive to temperature changes, resulting in a larger calibration error. Summary of the Invention

[0004] This invention provides a temperature calibration method for silicon carbide epitaxial equipment to solve the problems of low calibration temperature and large calibration error in existing silicon wafer-based temperature calibration methods.

[0005] In a first aspect, embodiments of the present invention provide a temperature calibration method for a silicon carbide epitaxial device. The silicon carbide epitaxial device controls the temperature inside its reaction chamber based on an infrared thermometer. The method includes: heating the reaction chamber to a target temperature and performing homoepitaxial doping growth of silicon carbide on the surface of a silicon carbide epitaxial wafer to obtain a silicon carbide temperature calibration wafer. Based on the correspondence between the doping concentration of the silicon carbide temperature calibration wafer and the homoepitaxial doping growth temperature, the measurement temperature of the infrared thermometer is calibrated.

[0006] In one possible implementation, calibrating the infrared temperature measuring device based on the correspondence between the doping concentration of the silicon carbide temperature calibration sheet and the homoepitaxial doping growth temperature of silicon carbide includes: fabricating an ohmic contact electrode on the surface of the silicon carbide temperature calibration sheet and measuring the sheet resistance of the silicon carbide temperature calibration sheet, wherein the sheet resistance of the silicon carbide temperature calibration sheet is used to represent the corresponding doping concentration. Based on the correspondence between the sheet resistance of the silicon carbide temperature calibration sheet and the homoepitaxial doping growth temperature of silicon carbide, the actual temperature of the reaction chamber after heating is obtained. Based on the actual temperature, the measuring temperature of the infrared temperature measuring device is calibrated.

[0007] In one possible implementation, heating the reaction chamber to a target temperature and performing homoepitaxial doping growth of silicon carbide on the surface of a silicon carbide epitaxial wafer to obtain a silicon carbide temperature-calibrated wafer includes: heating the reaction chamber to the target temperature at a constant heating rate; introducing a carbon source, a silicon source, and a dopant source into the reaction chamber at the target temperature; and performing homoepitaxial doping growth of silicon carbide on the surface of the silicon carbide epitaxial wafer for a specified duration; and cooling the grown silicon carbide epitaxial wafer to obtain the silicon carbide temperature-calibrated wafer.

[0008] In one possible implementation, cooling the grown silicon carbide epitaxial wafer to obtain a silicon carbide temperature calibration wafer includes: introducing a silicon source into the reaction chamber to cool the grown silicon carbide epitaxial wafer and obtain a silicon carbide temperature calibration wafer.

[0009] In one possible implementation, the doping source includes a nitrogen source or an aluminum source.

[0010] In one possible implementation, the target temperature is greater than 1400°C.

[0011] In one possible implementation, fabricating an ohmic contact electrode on the surface of the silicon carbide temperature calibration sheet and measuring the sheet resistance of the silicon carbide temperature calibration sheet includes: fabricating an electrode on the surface of the silicon carbide temperature calibration sheet using photolithography and vapor deposition processes; annealing the silicon carbide temperature calibration sheet to form an ohmic contact; and measuring the sheet resistance of the annealed silicon carbide temperature calibration sheet.

[0012] In one possible implementation, the electrode is made of nickel or aluminum.

[0013] In one possible implementation, the annealing temperature range is 800 to 950°C, and the annealing pressure is <10. - 5 Torr, the annealing time ranges from 1 to 5 minutes.

[0014] In one possible implementation, the sheet resistance of the silicon carbide temperature calibration sheet is inversely proportional to the growth temperature of the silicon carbide homoepitaxial doping.

[0015] This invention provides a temperature calibration method for a silicon carbide epitaxial wafer. The silicon carbide epitaxial wafer controls the temperature inside its reaction chamber using an infrared thermometer. The method includes: heating the reaction chamber to a target temperature and performing homoepitaxial doping growth of silicon carbide on the surface of a silicon carbide epitaxial wafer to obtain a silicon carbide temperature calibration wafer. Based on the correspondence between the doping concentration of the silicon carbide temperature calibration wafer and the homoepitaxial doping growth temperature, the measurement temperature of the infrared thermometer is calibrated. This invention, by performing homoepitaxial doping growth on the surface of a silicon carbide epitaxial wafer within the reaction chamber of the silicon carbide epitaxial wafer, can obtain the actual growth temperature of the reaction chamber based on the influence of growth temperature on doping concentration and the relationship between doping concentration and growth temperature, thereby achieving temperature calibration of the infrared thermometer. Using a silicon carbide epitaxial wafer for temperature calibration allows the epitaxial temperature to be raised to the range of silicon carbide epitaxial process temperatures, improving the calibration temperature. Based on the relationship between doping concentration and doping growth temperature, the phosphorus atom diffusion method is avoided, resulting in high sensitivity and improved calibration accuracy. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is an application scenario diagram of the temperature calibration method for silicon carbide epitaxial equipment provided in the embodiments of the present invention; Figure 2 This is a flowchart illustrating the temperature calibration method for silicon carbide epitaxial equipment provided in this embodiment of the invention. Figure 3 This is a flowchart illustrating the calibration method implementation in step 202 of this embodiment of the invention. Figure 4 This is a schematic diagram of the sheet resistance measurement electrode distribution provided in an embodiment of the present invention; Figure 5 This is a schematic diagram showing the relationship between the sheet resistance of silicon carbide and temperature, provided in an embodiment of the present invention. Detailed Implementation

[0018] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0019] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0020] The implementation of the present invention will be described in detail below with reference to the accompanying drawings: Silicon carbide epitaxy requires a closed quartz cavity in a low-pressure, high-temperature environment. Therefore, silicon carbide epitaxy equipment typically employs non-contact infrared thermography to monitor and control the process temperature.

[0021] Figure 1 This is an application scenario diagram of the temperature calibration method for silicon carbide epitaxial equipment provided in this embodiment of the invention. (Refer to...) Figure 1 A silicon carbide epitaxial growth apparatus includes a reaction chamber and an infrared thermometer. The epitaxial wafer is placed inside the reaction chamber for epitaxial growth. The infrared thermometer measures the temperature inside the reaction chamber. Based on the measured temperature from the infrared thermometer, the silicon carbide epitaxial growth apparatus controls the heating device to heat the inside of the reaction chamber. For example, the reaction chamber can be controlled to be heated to a target temperature and maintained at that temperature for a certain period. The temperature obtained by the infrared thermometer deviates somewhat from the actual temperature of the object, therefore, temperature calibration is required. For example, the infrared thermometer system has two shortcomings: 1) The infrared intensity emitted by the actual measured object is not only related to temperature but also to the object's emissivity, surface condition, measurement angle, and other conditions. 2) Infrared thermometry has very high requirements for testing conditions; any obstruction, changes in gas pressure or composition within the chamber will cause changes in the collected infrared intensity.

[0022] Currently used temperature calibration methods include: Method 1, calibrating temperature using the melting point of silicon wafers. For example, a small silicon wafer is placed in a silicon carbide epitaxial wafer, and the temperature of the epitaxial wafer is raised to approximately the melting point of silicon (1400℃). The temperature measurement of the equipment is calibrated by observing the melting of the silicon wafer. This method is simple and easy to implement. However, its disadvantage is that it can only calibrate a single temperature point. Furthermore, the melting point of silicon wafers is relatively low, significantly different from the silicon carbide epitaxial process temperature range (1500℃-1700℃), making it unsuitable for accurately calibrating the entire silicon carbide epitaxial process temperature range.

[0023] Currently used temperature calibration methods also include: Method 2, which uses phosphorus atoms implanted into the silicon wafer surface as a calibration plate. The temperature measurement of the equipment is calibrated by measuring the effect of epitaxial annealing temperature on phosphorus atom diffusion. The working principle of this method is as follows: A certain amount of impurity phosphorus atoms are implanted into the surface of a high-purity silicon wafer using ion implantation. When the phosphorus atoms are implanted into the silicon wafer, they are in an electroactive, inactive state and do not cause a change in the silicon wafer's resistance. However, under the action of high-temperature annealing, the phosphorus atoms diffuse on the silicon wafer surface, and their electroactivity is activated, thus causing a decrease in the silicon wafer's resistance. Different annealing temperatures correspond to different resistivities. By measuring the sheet resistance (four-probe method) of the silicon calibration plate after annealing at a specified temperature in the epitaxial equipment, the precise annealing temperature of the calibration plate can be obtained, thereby calibrating the process temperature.

[0024] However, this method is limited by the melting point of silicon wafers and the low calibration temperature. The applicable temperature range for silicon calibration wafers is 1000℃-1400℃ (above 1400℃, the silicon wafer will melt), which is much lower than the process temperature range of 1500℃-1700℃ for silicon carbide epitaxy. Since the process temperature of silicon carbide epitaxy (>1500℃) is much higher than that of silicon epitaxy (1100℃), the calibration method for silicon epitaxy cannot be directly applied to the calibration process of silicon carbide epitaxy.

[0025] On the other hand, the inventors of this application have discovered that in order to solve the problem of silicon substrates being unable to withstand high temperatures, even if the silicon substrate in method 2 is directly replaced with a silicon carbide substrate, the sheet resistance will also change less due to the low diffusion rate of phosphorus atoms in silicon carbide and the low sensitivity of the diffusion degree to temperature changes, resulting in a large temperature calibration error.

[0026] This invention provides a temperature calibration method for silicon carbide epitaxial equipment, which uses the change in doping efficiency of homogeneous silicon carbide epitaxy to calibrate the temperature of the silicon carbide epitaxial equipment, thereby solving the problems of low calibration temperature and large calibration error in existing silicon wafer-based temperature calibration methods.

[0027] Figure 2 A flowchart illustrating the temperature calibration method for a silicon carbide epitaxial device provided in this embodiment of the invention. (Refer to...) Figure 2 The silicon carbide epitaxial device controls the temperature inside its reaction chamber based on an infrared thermometer. This method includes: In step 201, the reaction chamber is heated to the target temperature, and silicon carbide homoepitaxial doping growth is performed on the surface of the silicon carbide epitaxial wafer to obtain a silicon carbide temperature calibration wafer.

[0028] In some embodiments, prior to step 201, the method further includes placing a silicon carbide epitaxial wafer inside the reaction chamber.

[0029] In some embodiments, the heating of the silicon carbide epitaxial device is controlled based on the real-time temperature inside the reaction chamber measured by the infrared thermometer, so as to raise the temperature of the reaction chamber to the target temperature.

[0030] After the reaction chamber is heated to the target temperature, the temperature of the silicon carbide epitaxial wafer is also raised to the target temperature accordingly.

[0031] In some embodiments, the target temperature is greater than 1400°C.

[0032] For example, the target temperature is less than 2700°C. The melting point of the silicon carbide substrate is 2700°C.

[0033] For example, the target temperature range is 1500°C to 1700°C.

[0034] In some embodiments, after heating the reaction chamber to a target temperature, silicon carbide homoepitaxial doping growth is initiated at the target temperature.

[0035] In some embodiments, silicon carbide homoepitaxial doping growth is the epitaxial growth of silicon carbide, while a doping source is introduced into the reaction chamber, and synchronous doping is performed during epitaxial growth.

[0036] The epitaxial layer obtained after homoepitaxial doping of silicon carbide is doped silicon carbide. During homoepitaxial doping of silicon carbide, the doping efficiency is affected by the epitaxial temperature. Since the epitaxial growth temperature is directly related to the doping efficiency of impurity atoms in the epitaxial layer, the higher the temperature, the faster the doping reaction rate; therefore, the higher the growth temperature, the higher the doping efficiency and the higher the doping concentration. Based on the relationship between impurity atom doping efficiency and temperature, the process temperature of the silicon carbide epitaxial furnace can be calibrated.

[0037] In step 202, the measurement temperature of the infrared thermometer is calibrated based on the correspondence between the doping concentration of the silicon carbide temperature calibration sheet and the growth temperature of silicon carbide homoepitaxial doping.

[0038] Silicon carbide temperature calibration sheets are obtained after homoepitaxial doping growth of silicon carbide. The doping concentration of the silicon carbide temperature calibration sheet is related to the homoepitaxial doping growth temperature of silicon carbide.

[0039] Before step 202, the method further includes pre-measuring the relationship between silicon carbide doping concentration and silicon carbide homoepitaxial doping growth temperature.

[0040] In some embodiments, silicon carbide epitaxial doping growth can be performed using a silicon carbide epitaxial device with calibrated temperature, and the doping concentration of silicon carbide at different epitaxial temperatures can be measured to obtain the correspondence between silicon carbide doping concentration and silicon carbide homoepitaxial doping growth temperature.

[0041] In some embodiments, in step 202, based on the doping concentration of the silicon carbide temperature calibration sheet and the pre-measured correspondence between the silicon carbide doping concentration and the silicon carbide homoepitaxial doping growth temperature, the actual epitaxial temperature of the silicon carbide temperature calibration sheet can be obtained, and then the measurement temperature of the infrared temperature measuring device can be calibrated based on the actual epitaxial temperature.

[0042] For example, the doping source used when the above correspondence is measured in advance is the same as the doping source used when doping growth is performed in step 201, the epitaxial growth pressure is the same, and the gas source flow rate is the same.

[0043] In some embodiments, after step 202, the method further includes: repeating step 201 based on different target temperatures to obtain multiple silicon carbide temperature calibration sheets. In step 202, the actual epitaxial temperature corresponding to each target temperature is obtained based on the silicon carbide temperature calibration sheets corresponding to each target temperature. The measurement temperature of the infrared thermometer is calibrated based on the multiple actual epitaxial temperatures.

[0044] For example, the target temperatures are set to 1550℃, 1600℃, 1650℃, and 1700℃ respectively, and step 201 is repeated to obtain data for four actual epitaxial temperature points. These four actual epitaxial temperature data are used to correct the relationship between the infrared measured temperature and the actual temperature obtained by infrared thermometry.

[0045] For example, the actual extrapolated temperature data points corresponding to the four measured temperatures of 1550℃, 1600℃, 1650℃, and 1700℃ are 1555℃, 1606℃, 1647℃, and 1693℃, respectively. These four actual extrapolated temperature data are used to correct the correspondence function between the infrared measured temperature and the actual temperature obtained from infrared thermography.

[0046] This invention, through homogeneous epitaxial doping growth on the surface of a silicon carbide epitaxial wafer within the reaction chamber of a silicon carbide epitaxial apparatus, allows for the determination of the actual growth temperature within the reaction chamber based on the influence of growth temperature on doping concentration and the relationship between doping concentration and growth temperature. This enables temperature calibration of the infrared thermometer. Using a silicon carbide epitaxial wafer for calibration allows the epitaxial temperature to be raised to the range of silicon carbide epitaxial process temperatures, thus improving the calibration temperature. By leveraging the relationship between doping concentration and doping growth temperature, the phosphorus atom diffusion method is avoided, resulting in high sensitivity and improved calibration accuracy.

[0047] Homoenomic growth of silicon carbide on a silicon carbide substrate is performed using CVD, allowing for the simultaneous introduction of dopant (e.g., nitrogen) to dope the epitaxial layer. Since the epitaxial growth temperature is directly related to the doping efficiency of impurity atoms in the epitaxial layer, higher temperatures result in faster diffusion and doping reactions, leading to higher doping efficiency and concentration. Higher doping concentration results in lower resistivity and sheet resistance of the epitaxial layer. Based on the relationship between impurity atom doping efficiency and temperature, the process temperature of the silicon carbide epitaxial furnace can be calibrated.

[0048] The calibration temperature in this invention can be matched with the silicon carbide process temperature, avoiding calibration errors caused by differences between the calibration temperature and the process temperature, resulting in high calibration accuracy. This method has no requirements regarding the structure, shape, or size of the epitaxial furnace and is applicable to various types of SiC epitaxial equipment. The silicon carbide substrate and doped atoms used in this method are the same as those used in the silicon carbide epitaxial process, preventing chamber contamination.

[0049] In one possible implementation, calibrating the infrared thermometer's measurement temperature based on the correlation between the doping concentration of the silicon carbide temperature calibration plate and the homoepitaxial doping growth temperature of silicon carbide involves: measuring the doping concentration of the silicon carbide temperature calibration plate; obtaining the actual temperature of the reaction chamber after heating based on the doping concentration of the silicon carbide temperature calibration plate and the correlation between silicon carbide doping concentration and the homoepitaxial doping growth temperature of silicon carbide; and calibrating the infrared thermometer's measurement temperature based on the actual temperature.

[0050] In this embodiment of the invention, the actual temperature can be calibrated by directly measuring the doping concentration based on the pre-obtained correspondence between silicon carbide doping concentration and silicon carbide homoepitaxial doping growth temperature.

[0051] Figure 3 This is a flowchart illustrating the calibration method implementation in step 202 of this embodiment of the invention. (Refer to...) Figure 3 In one possible implementation, the calibration of the infrared thermometer's measurement temperature, based on the correlation between the doping concentration of the silicon carbide temperature calibration plate and the growth temperature of the silicon carbide homoepitaxial doping, includes: In step 301, an ohmic contact electrode is prepared on the surface of the silicon carbide temperature calibration sheet, and the sheet resistance of the silicon carbide temperature calibration sheet is measured, wherein the sheet resistance of the silicon carbide temperature calibration sheet is used to represent the corresponding doping concentration.

[0052] In some embodiments, fabricating ohmic contact electrodes on the surface of a silicon carbide temperature calibration sheet and measuring the sheet resistance of the silicon carbide temperature calibration sheet includes: fabricating electrodes on the surface of the silicon carbide temperature calibration sheet using photolithography and vapor deposition processes; annealing the silicon carbide temperature calibration sheet to form ohmic contacts; and measuring the sheet resistance of the annealed silicon carbide temperature calibration sheet.

[0053] For example, fabricating electrodes on the surface of a silicon carbide temperature calibration sheet based on photolithography and vapor deposition processes includes: fabricating a photoresist mask on the surface of the silicon carbide temperature calibration sheet using photolithography; and depositing electrodes on the silicon carbide temperature calibration sheet using electron beam vapor deposition under the mask of the photoresist mask.

[0054] Figure 4 This is a schematic diagram of the sheet resistance measurement electrode distribution provided in an embodiment of the present invention. (Refer to...) Figure 4 For example, the electrodes on the surface of a silicon carbide temperature calibration sheet are four equally spaced matrix-distributed metal electrodes.

[0055] For example, the metal electrode is a square electrode. The square electrode has dimensions of 300 μm x 300 μm. The spacing between the metal electrodes is 500 μm.

[0056] For example, the material of the metal electrode is nickel or aluminum.

[0057] For example, annealing a silicon carbide temperature calibration sheet to form an ohmic contact includes: annealing the silicon carbide temperature calibration sheet using a rapid annealing furnace to form an ohmic contact.

[0058] For example, the annealing temperature range is 800 to 950°C, and the annealing pressure is <10. -5 Torr, the annealing time ranges from 1 to 5 minutes.

[0059] In some embodiments, measuring the sheet resistance of the silicon carbide temperature calibration sheet includes using a four-probe method to measure the ohmic contact electrode to obtain the sheet resistance of the silicon carbide temperature calibration sheet.

[0060] The contact between silicon carbide and the metal is a Schottky contact. Directly using a four-probe method to measure the sheet resistance of silicon carbide results in excessively high contact resistance between the metal probe and the silicon carbide, making accurate sheet resistance measurement impossible. After annealing, the Schottky contact of SiC-Ni can be transformed into an ohmic contact of SiC-NiC. Based on the four electrodes of the ohmic contact, a four-probe method can be used to contact each of the four electrodes separately to measure the sheet resistance of the temperature calibration plate.

[0061] The sheet resistance (SRT) of a silicon carbide temperature calibration sheet is related to its doping concentration. Higher doping concentration results in lower SRT, while lower doping concentration results in higher SRT. Therefore, the SRT of a silicon carbide temperature calibration sheet is used to represent the corresponding doping concentration.

[0062] Sheet resistance varies significantly with doping growth temperature, and can cover the temperature range involved in silicon carbide epitaxial processes, rather than just measuring a single temperature point.

[0063] In step 302, the actual temperature of the reaction chamber after heating is obtained based on the correspondence between the sheet resistance of the silicon carbide temperature calibration sheet and the growth temperature of silicon carbide homoepitaxial doping.

[0064] In some embodiments, before step 302, the method further includes: pre-measuring the correspondence between the silicon carbide sheet resistance and the silicon carbide homoepitaxial doping growth temperature.

[0065] Figure 5 This is a schematic diagram illustrating the relationship between the sheet resistance of silicon carbide and temperature, provided in an embodiment of the present invention. (Refer to...) Figure 5 The horizontal axis represents the growth temperature of homoepitaxial doping of silicon carbide, in °C. The vertical axis represents the sheet resistance of silicon carbide after doping growth, in Ω / □.

[0066] In some embodiments, silicon carbide epitaxial doping growth can be performed using a silicon carbide epitaxial apparatus with calibrated temperature, and the sheet resistance of silicon carbide at different epitaxial temperatures can be measured to represent the doping concentration at different epitaxial temperatures. This establishes the correspondence between silicon carbide sheet resistance and the homogeneous silicon carbide epitaxial doping growth temperature.

[0067] For example, the higher the growth temperature and the higher the doping concentration, the lower the sheet resistance. Conversely, the lower the growth temperature and the lower the doping concentration, the higher the sheet resistance.

[0068] In some embodiments, the actual temperature of the reaction chamber after heating is obtained based on the sheet resistance of the silicon carbide temperature calibration sheet, the correspondence between the sheet resistance of silicon carbide and the growth temperature of silicon carbide homoepitaxial doping.

[0069] In step 303, the measurement temperature of the infrared thermometer is calibrated based on the actual temperature.

[0070] This invention provides a method for preparing ohmic contacts on silicon carbide temperature calibration sheets and measuring sheet resistance. The relationship between sheet resistance and growth temperature is used to express the relationship between doping concentration and growth temperature. The method is simple, easy to implement, and highly accurate.

[0071] The inventors of this application also discovered that directly replacing the silicon substrate with a silicon carbide substrate in method 2 is problematic because measuring sheet resistance requires the preparation of ohmic contacts. During the high-temperature annealing process for preparing ohmic contacts, the annealing temperature also causes the diffusion of phosphorus atoms, resulting in errors in the sheet resistance measurement results. This leads to changes in the distribution of phosphorus atoms after epitaxial annealing, and the final sheet resistance measurement cannot fully reflect the epitaxial annealing temperature.

[0072] The method provided in this invention allows for the fabrication of ohmic contacts on silicon carbide temperature calibration sheets without affecting the doping concentration. The resulting sheet resistance is closer to the epitaxial doping growth temperature, leading to more accurate temperature calibration.

[0073] In one possible implementation, heating the reaction chamber to a target temperature and performing homoepitaxial doping growth of silicon carbide on the surface of a silicon carbide epitaxial wafer to obtain a silicon carbide temperature-calibrated wafer includes: heating the reaction chamber to the target temperature at a constant heating rate; introducing a carbon source, a silicon source, and a dopant source into the reaction chamber at the target temperature; and performing homoepitaxial doping growth of silicon carbide on the surface of the silicon carbide epitaxial wafer for a specified duration; and cooling the grown silicon carbide epitaxial wafer to obtain the silicon carbide temperature-calibrated wafer.

[0074] For example, the temperature calibration plate is placed at the sample location of a silicon carbide epitaxial device. The silicon carbide epitaxial device is heated to the target temperature, i.e., the process temperature (1500℃-1700℃), at a certain constant heating rate and then held at that temperature. During the holding process, a specified amount of carbon source, silicon source, and nitrogen source are introduced into the chamber for epitaxy and doping for a specified duration. Subsequently, the temperature is lowered, and the temperature calibration plate is removed.

[0075] For example, after heating to the target temperature, silicon carbide homoepitaxial doping growth is performed for a specified duration. For example, the specified duration could be 10 minutes.

[0076] In one possible implementation, cooling the grown silicon carbide epitaxial wafer to obtain a silicon carbide temperature calibration wafer includes: introducing a silicon source into the reaction chamber to cool the grown silicon carbide epitaxial wafer and obtain a silicon carbide temperature calibration wafer.

[0077] The cooling process requires the introduction of a certain amount of silicon source into the chamber to prevent the SiC surface from carbonizing at high temperatures.

[0078] In one possible implementation, the doping source includes a nitrogen source or an aluminum source.

[0079] In one possible implementation, the target temperature ranges from 1500°C to 1700°C.

[0080] In one possible implementation, the electrode material includes nickel or aluminum.

[0081] In one possible implementation, the annealing temperature range is 800 to 950°C, and the annealing pressure is <10. -5 Torr, the annealing time ranges from 1 to 5 minutes.

[0082] In one possible implementation, the sheet resistance of the silicon carbide temperature calibration sheet is inversely proportional to the growth temperature of the silicon carbide homoepitaxial doping.

[0083] This invention provides embodiments to illustrate this solution: (1) Place the silicon carbide temperature calibration plate at the sample placement position on the silicon carbide epitaxial equipment. Use the infrared thermometer to be calibrated to heat the epitaxial system to the target temperature of 1600℃ for epitaxial growth and impurity doping. At this time, the infrared thermometer measures a temperature of 1600℃. Trichlorosilane, ethylene, and nitrogen are used as silicon, carbon, and nitrogen sources, respectively. The flow rates of the silicon, carbon, and nitrogen sources are 150 sccm, 70 sccm, and 10 sccm, respectively. Maintain the doping process for 10 minutes and then cool down.

[0084] (2) Using photolithography and electron beam evaporation, nickel metal electrodes with ohmic contact are formed on the surface of the annealed temperature calibration sheet and annealed in a rapid annealing furnace. The annealing conditions are: pressure 10 to 6 Torr, annealing temperature 900℃ (to form ohmic contact in the metal), and annealing time 2 min.

[0085] (3) The sheet resistance of the above temperature calibration plate was measured to be 965 W / □ using the four-probe method. Figure 5 The graph showing the relationship between the sheet resistance of silicon carbide and temperature indicates that the actual growth temperature was 1594℃, and the infrared test temperature deviated from the actual growth temperature by 6℃.

[0086] (4) Set the target temperatures to 1550℃, 1650℃ and 1700℃ respectively, and repeat (1)-(3) to obtain data for 4 actual temperature points. Use these 4 temperature data to correct the correspondence function between infrared measured temperature and actual temperature obtained by infrared temperature measurement.

[0087] Specifically, the actual temperature data points corresponding to the four measured temperatures of 1550℃, 1600℃, 1650℃, and 1700℃ are 1555℃, 1606℃, 1647℃, and 1693℃, respectively. These four temperature data are used to correct the infrared thermometry to obtain the correspondence function between the measured infrared temperature and the actual temperature.

[0088] The temperature calibration method provided in this invention utilizes changes in doping efficiency to calibrate the temperature of silicon carbide epitaxial equipment. It obtains numerous accurate temperature points, covers a wide measurement range, and is cost-effective. It has no special requirements regarding the structure, shape, or size of the epitaxial furnace, exhibits strong compatibility with different furnace configurations, and simplifies testing conditions. It demonstrates good repeatability and stability, making it particularly suitable for comparing and aligning epitaxial temperatures between different silicon carbide epitaxial devices, thus facilitating standardized and regulated equipment management. The calibration sheet used is composed of commonly used silicon carbide substrates and common dopant ions, preventing impurity contamination of the epitaxial chamber. No special treatment is required after calibration, resulting in a pollution-free and simple-to-operate method.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A temperature calibration method for a silicon carbide epitaxial device, characterized in that, The silicon carbide epitaxial equipment uses an infrared thermometer to control the temperature inside its reaction chamber, and the silicon carbide epitaxy is performed using chemical vapor deposition; the method includes: The reaction chamber is heated to a target temperature at a constant heating rate; the target temperature is greater than 1400°C. At the target temperature, a carbon source, a silicon source, and a doping source are introduced into the reaction chamber to perform homoepitaxial doping growth of silicon carbide on the surface of a silicon carbide epitaxial wafer for a specified duration; the doping source includes a nitrogen source or an aluminum source; wherein, the epitaxial layer obtained after homoepitaxial doping growth of silicon carbide is doped silicon carbide. The grown silicon carbide epitaxial wafer is cooled to obtain a silicon carbide temperature calibration wafer; Based on the correspondence between the doping concentration of the silicon carbide temperature calibration sheet and the doping growth temperature of the silicon carbide homoepitaxial layer, the measurement temperature of the infrared temperature measuring device is calibrated; wherein, the doping concentration is the doping concentration of the epitaxial layer.

2. The temperature calibration method for silicon carbide epitaxial equipment as described in claim 1, characterized in that, The calibration of the infrared thermometer based on the relationship between the doping concentration of the silicon carbide temperature calibration sheet and the growth temperature of silicon carbide homoepitaxial doping includes: An ohmic contact electrode is fabricated on the surface of the silicon carbide temperature calibration sheet, and the sheet resistance of the silicon carbide temperature calibration sheet is measured, wherein the sheet resistance of the silicon carbide temperature calibration sheet is used to represent the corresponding doping concentration; Based on the relationship between the sheet resistance of the silicon carbide temperature calibration sheet and the growth temperature of silicon carbide homoepitaxial doping, the actual temperature of the reaction chamber after heating is obtained. Based on the actual temperature, calibrate the measurement temperature of the infrared thermometer.

3. The temperature calibration method for silicon carbide epitaxial equipment as described in claim 1, characterized in that, The step of cooling the grown silicon carbide epitaxial wafer to obtain a silicon carbide temperature calibration wafer includes: A silicon source is introduced into the reaction chamber to cool the grown silicon carbide epitaxial wafer, thereby obtaining a silicon carbide temperature calibration wafer.

4. The temperature calibration method for silicon carbide epitaxial equipment as described in claim 2, characterized in that, Fabricating an ohmic contact electrode on the surface of the silicon carbide temperature calibration sheet and measuring the sheet resistance of the silicon carbide temperature calibration sheet includes: Electrodes are fabricated on the surface of a silicon carbide temperature calibration sheet using photolithography and vapor deposition processes. The silicon carbide temperature calibration sheet is annealed to form an ohmic contact; The sheet resistance of the annealed silicon carbide temperature calibration plate was measured.

5. The temperature calibration method for silicon carbide epitaxial equipment as described in claim 4, characterized in that, The electrode is made of materials including nickel or aluminum.

6. The temperature calibration method for silicon carbide epitaxial equipment as described in claim 4, characterized in that, The annealing temperature range is 800 to 950°C, and the annealing pressure is <10. -5 Torr, the annealing time ranges from 1 to 5 minutes.

7. The temperature calibration method for silicon carbide epitaxial equipment as described in claim 2, characterized in that, The sheet resistance of the silicon carbide temperature calibration sheet is inversely proportional to the growth temperature of the silicon carbide homoepitaxial doping.

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