Method and device for detecting silicon carbide epitaxial wafer

Abstract

The application relates to the field of semiconductor technology and discloses a silicon carbide epitaxial wafer detection method and device. The method comprises the following steps: an automatic conveying unit automatically transports an epitaxial wafer to a detection unit; the detection unit detects the film thickness and the carrier concentration of the epitaxial wafer and sends the detection result to a data acquisition and processing unit; the data acquisition and processing unit compares and analyzes the received data with preset target data; if the deviation is within the allowable range, no adjustment is made; if the deviation is not within the allowable range, the calculation result is fed back to an epitaxial growth control unit to adjust the process parameters of an epitaxial device. The method automatically takes and transports the epitaxial wafer by using the conveying unit, improves the production efficiency, and can improve the wafer consistency of the epitaxial wafer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a method and device for real-time detecting film thickness and carrier concentration of silicon carbide epitaxial wafer. BACKGROUND

[0002] The silicon carbide epitaxial wafer refers to a silicon carbide wafer with a single crystal thin film grown on a silicon carbide substrate. The quality determination parameters of the silicon carbide epitaxial wafer mainly include the epitaxial film thickness and the carrier concentration, which are directly related to the performance of the silicon carbide device and the yield, so it is very important to reduce the deviation and improve the uniformity. In the production process of the silicon carbide epitaxial wafer, the epitaxial film thickness and the carrier concentration in the epitaxial film are generally controlled by adjusting the flow rate of raw materials, the temperature of the reaction chamber and the reaction time. In practice, even if the process parameters are completely unchanged, due to the gradual changes of the cumulative conditions, temperature and gas flow in the reaction chamber, the indicators of the produced silicon carbide epitaxial wafer also drift, so it is necessary to conduct 100% full inspection on the epitaxial film thickness and the carrier concentration in the epitaxial film, and adjust the process parameters according to the detection results to ensure the stability of the wafer parameters.

[0003] At present, the common practice is that after the epitaxial device grows an epitaxial wafer, the epitaxial wafer is manually taken out and put into a detection device to detect the film thickness and the carrier concentration, and the process technician adjusts the process parameters according to the detection results. The epitaxial wafer is taken out from the epitaxial device and put into a wafer cassette, transported to a detection platform, taken out for detection, then taken back and put into the wafer cassette, and finally transported back to the wafer cassette in the device for unified storage. This method needs to consume a lot of time and labor, reduces the production efficiency, increases the labor cost, and different process technicians may also produce adjustment errors according to the same detection results, which reduces the wafer-to-wafer consistency of the epitaxial wafer. SUMMARY

[0004] In order to overcome the above-mentioned defects, the purpose of the present application is to provide a detection method and device for a silicon carbide epitaxial wafer, which can detect the film thickness and the carrier concentration of the silicon carbide epitaxial wafer in real time, so as to improve the production efficiency and the wafer-to-wafer consistency of the silicon carbide epitaxial wafer.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A detection method for a silicon carbide epitaxial wafer, comprising the following steps:

[0007] An automatic conveying unit automatically transports the epitaxial wafer to a detection unit,

[0008] The detection unit detects the film thickness and the carrier concentration of the epitaxial wafer and sends the detection results to a data acquisition and processing unit,

[0009] The data acquisition and processing unit receives and responds to the received data and compares it with preset target data,

[0010] If the deviation is within the preset range, no adjustment is made.

[0011] If the deviation is not within the preset range, the calculation result is fed back to the epitaxial growth control unit, which adjusts the process parameters of the epitaxial device. With such a design, there is no need for long-distance transportation between the epitaxial device and the detection platform, saving time, improving labor productivity, and achieving automatic operation, and improving the wafer-to-wafer consistency of the epitaxial wafer.

[0012] In a preferred embodiment, the detection unit is an online detection unit, and the automatic transportation unit takes out the epitaxial wafer from the epitaxial growth device and automatically transports it to the online detection platform for real-time detection.

[0013] In a preferred embodiment, the automatic transportation unit takes out the epitaxial wafer from the epitaxial device TM cavity wafer cassette and transports it to the detection platform for detection. The detection platform is installed in the epitaxial growth device PM cavity near the wafer cavity position, and the height is the same as the height of the mechanical hand in the TM cavity, facilitating wafer taking, placing, and transporting actions.

[0014] In a preferred embodiment, the automatic transportation unit includes an atmospheric robot located between the detection platform and the epitaxial device, facilitating close-range transportation and detection of the epitaxial wafer.

[0015] In a preferred embodiment, an FTIR Fourier infrared spectrum online detection instrument is used to detect the film thickness of the silicon carbide epitaxial wafer.

[0016] In a preferred embodiment, a mercury probe CV online detection instrument is used to detect the carrier concentration of the silicon carbide epitaxial wafer.

[0017] The present application provides a detection device for a silicon carbide epitaxial wafer, comprising:

[0018] An epitaxial growth control unit for real-time control of the entire growth cycle of the silicon carbide epitaxial wafer by adjusting parameters such as reaction gas flow and flow field, reaction temperature, and reaction time;

[0019] An automatic transportation unit for wafer taking, placing, and transporting;

[0020] A detection unit including a film thickness detection module and a carrier concentration detection module for detecting the film thickness and carrier concentration of the silicon carbide epitaxial wafer;

[0021] Data acquisition and processing unit: used for receiving detection data of the detection unit, comparing with target data preset by the system, judging whether the deviation is within the allowable range according to the comparison result, and calculating the process parameter data to be modified according to the corresponding formula if the deviation is not within the allowable range.

[0022] In a preferred embodiment, the automatic transmission unit comprises an atmospheric robot, which is located between the online detection unit and the PM cavity, facilitating the taking, placing and transmission of the silicon carbide epitaxial wafer.

[0023] In a preferred embodiment, the film thickness detection module in the detection unit is an infrared spectrum detection module, which comprises an infrared light source, an aperture, an interferometer, a sample chamber, a detector, a laser, a control circuit board and a power supply.

[0024] In a preferred embodiment, the carrier concentration detection module in the detection unit is a mercury probe detection module, which comprises a test bench, a motor, a pneumatic control unit, a measurement unit, an information processing unit and a capillary mercury probe.

[0025] Advantages:

[0026] The detection method for silicon carbide epitaxial wafers provided in the present application relies on the automatic transmission unit to take out, place and transmit the epitaxial wafer, without the need for long-distance transportation between the epitaxial equipment and the detection platform, saving time and improving labor productivity. Moreover, the method realizes automatic operation, reduces the dependence on manual labor, analyzes the results through the data acquisition and processing unit to regulate the process parameters of the epitaxial equipment, improves the wafer-to-wafer consistency of the epitaxial wafer, and also reduces the labor cost. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings are used to support the technical solutions of the present application, and constitute a part of the description, together with the embodiments of the present application, to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0028] Figure 1 The flowchart of the silicon carbide epitaxial wafer film thickness and carrier concentration detection method in the embodiments of the present application is shown in the following figure.

[0029] Figure 2 The actual detection flowchart of the silicon carbide epitaxial wafer film thickness and carrier concentration in the embodiments of the present application is shown in the following figure.

[0030] Figure 3 The linear graph of the relationship between the donor concentration and the N2 flow of the doped gas in the embodiments of the present application is shown in the following figure.

[0031] Figure 4 The detection device for silicon carbide epitaxial wafers in the embodiments of the present application is shown in the following figure. DETAILED DESCRIPTION

[0032] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The term “exemplary” as used herein means “serving as an example, embodiment, or illustration,” and any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0033] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0034] The applicant of this application discovered that in existing epitaxial wafer growth and inspection technologies, after an epitaxial wafer is grown, it is manually removed, placed in a wafer cassette, and transported to an inspection platform to measure the film thickness and carrier concentration. After inspection, the epitaxial wafer is placed back into the wafer cassette and then transported back to the equipment for unified storage. This process requires a significant amount of additional time, reduces production efficiency, and relies on manual labor, increasing labor costs. Furthermore, process engineers adjust the process parameters of the epitaxial equipment based on the inspection results, which may lead to adjustment errors by different process engineers, artificially reducing the consistency between epitaxial wafers.

[0035] Based on this, in one embodiment of this application provided by the applicant, after epitaxial growth is completed, the automatic transfer unit automatically transports the epitaxial wafer to the detection platform for film thickness and carrier concentration detection, and sends the detection results to the data acquisition and processing unit. Based on the calculation results, the epitaxial control system decides whether to adjust the process parameters of the epitaxial equipment, thereby improving the inter-wafer stability of epitaxial growth. The method provided in this embodiment saves time and improves production efficiency because it eliminates the need for placing and removing wafer cassettes and long-distance transmission between the epitaxial equipment and the detection platform; it also reduces reliance on manual labor and lowers labor costs; and by adjusting the process parameters of the epitaxial equipment based on the analysis results, it improves the inter-wafer consistency of the epitaxial wafers.

[0036] like Figure 1 As shown in the flowchart of one embodiment of this application, the method for detecting silicon carbide epitaxial wafers (film thickness and carrier concentration) includes the following steps:

[0037] S101: The epitaxial wafer has been grown in the epitaxial equipment.

[0038] S102: The automatic transfer unit automatically transports the epitaxial wafer to the detection unit for film thickness and carrier concentration detection, and sends the detection results to the data acquisition and processing unit.

[0039] S103: The data acquisition and processing unit compares and analyzes the received data with the preset target data, and determines whether the deviation is within the preset range / allowable range (the deviation is within 10%).

[0040] If the deviation is within the preset range / allowed range, the epitaxial device process parameters do not need to be adjusted (the current process parameters are maintained for epitaxial growth of the next batch), and step S105 is directly performed.

[0041] S104: In step S103, if the deviation is not within the allowed range, the epitaxial control system adjusts the epitaxial device process parameters according to the corrected process parameter data, so as to improve the stability between epitaxial wafers.

[0042] S105: Start growing the next epitaxial wafer.

[0043] During the growth of the epitaxial wafer, it is sometimes necessary to detect the performance indicators of the epitaxial wafer in real time, and to adjust the process parameters of the epitaxial growth device in real time according to the detection results, so as to improve the work efficiency and improve the wafer consistency.

[0044] In an embodiment of the present application, a real-time detection method for a silicon carbide epitaxial wafer is exemplified,

[0045] The detection platform is an online detection platform. As shown in Figure 2 The steps are as follows:

[0046] Step S201: After the PM reaction chamber initially completes the growth of the silicon carbide epitaxial wafer, the lower machine control system sends a wafer taking signal to the automatic transmission unit, informing that the epitaxial wafer growth has been completed and the wafer can be taken for detection.

[0047] Step S202: The PM reaction chamber is opened, and the atmospheric robot in the automatic transmission unit takes the wafer.

[0048] In a preferred embodiment, when the atmospheric robot completes wafer taking and moves to a safe area, it sends a wafer taking completion feedback signal to the PM chamber, and the PM chamber is closed, ready for the next cycle of epitaxial wafer growth.

[0049] Step S203: The atmospheric robot moves to the online detection platform and places the epitaxial wafer on the detection platform, then moves to a safe area and sends a detection signal to the online detection unit.

[0050] Step S204: The online detection unit performs real-time detection of the epitaxial layer film thickness and carrier concentration of the epitaxial wafer, and sends the detection results to the lower machine control system.

[0051] In a preferred embodiment, an FTIR Fourier infrared spectrum online detection instrument is used to detect the film thickness of the silicon carbide epitaxial wafer.

[0052] In a preferred embodiment, a mercury probe CV online detection instrument is used to detect the carrier concentration of the silicon carbide epitaxial wafer.

[0053] In a preferred embodiment, the film thickness detection is performed before the carrier concentration detection.

[0054] In a preferred embodiment, the on-line detection unit sends the detection data to the lower computer through ProfiNet network communication protocol.

[0055] In a preferred embodiment, after the lower computer sends the on-line detection data of the film thickness and carrier concentration of the silicon carbide epitaxial wafer to the upper computer, the method further comprises the following steps:

[0056] The on-line detection unit sends a wafer taking signal to the atmospheric robot;

[0057] After the atmospheric robot takes the wafer, it moves to the wafer box and sends a feedback signal to the on-line detection unit to inform it that the wafer taking action has been completed, so that the on-line detection unit is ready for the next wafer placing detection;

[0058] After the atmospheric robot places the wafer, it moves to the safety area and completes the detection cycle, ready for the next wafer taking detection.

[0059] Step S205: The lower computer sends the received on-line detection data to the upper computer through industrial Ethernet for further analysis and processing.

[0060] The analysis is based on the linear relationship between the source gas flow and / or the epitaxial reaction time and the film thickness, and the process doping nitrogen flow and the carrier concentration.

[0061] Step S206: The upper computer compares the received data with the target data preset by the system. If the deviation is within the allowable range, no adjustment is made to the epitaxial equipment process parameters, and the epitaxial equipment is ready for the next epitaxial wafer growth cycle.

[0062] If the deviation is not within the allowable range, the process parameter data to be modified is calculated according to the corresponding formula, and the modified process parameters are sent to the lower computer.

[0063] Step S207: The lower computer receives the modified process parameters sent by the upper computer and adjusts the actuators of the epitaxial equipment in real time.

[0064] By adjusting the source gas flow and / or the reaction time and the process doping nitrogen flow, the film thickness and the carrier concentration are ensured to be within the ideal index range, and the wafer-to-wafer consistency of epitaxial growth is improved.

[0065] Step S208: The epitaxial equipment process parameter modification is completed.

[0066] Step S209: Prepare to start the growth of the next epitaxial wafer.

[0067] In Figure 2In the embodiment of the application shown, the online detection platform is arranged at a position close to the wafer cavity of the epitaxial device PM cavity, and the automatic transmission unit is arranged between the epitaxial device PM cavity and the online detection platform. The automatic transmission unit comprises an atmospheric robot and a wafer box. The epitaxial wafer is picked up, stored and transmitted at a close distance by the atmospheric robot, and the process parameters of the epitaxial device are adjusted in real time by the lower computer. Thus, automatic detection and control can be realized, the labor productivity is improved, the labor cost is reduced, and the wafer-to-wafer consistency of the epitaxial wafer is improved.

[0068] In the embodiment, the epitaxial wafer does not need to be manually placed into and taken out of the wafer box, and does not need to be transported at a long distance between the epitaxial device and the detection unit. Each detection saves about 8 minutes of time. If the working time per shift is 8 hours, about 64 minutes is saved per shift. The actual working time per shift is about 420 minutes. Through calculation, it can be obtained that the efficiency is improved by about 15% per shift (64 / 420).

[0069] In some epitaxial growth processes, real-time detection of the epitaxial wafer is not required. The detection can be performed after a preset number of epitaxial wafers are grown or a preset time is grown. In an example embodiment, the epitaxial device PM cavity is connected to the TM cavity, and a mechanical hand is arranged in the TM cavity. After the epitaxial wafer is grown in the PM cavity, the mechanical hand in the TM cavity takes out the epitaxial wafer from the PM cavity and places it in the wafer box in the TM cavity. After a preset number of epitaxial wafers are grown or a preset time is grown, the atmospheric robot of the automatic transmission unit takes out the epitaxial wafer from the wafer box in the TM cavity, transports it to the detection platform for film thickness and carrier concentration detection, and takes it back to the wafer box for unified storage after the detection is completed. Preferably, the detection platform is installed at a position close to the wafer cavity of the epitaxial growth device PM cavity, and the height is the same as the height of the mechanical hand in the TM cavity. Thus, the epitaxial wafer can be conveniently picked up, placed and transmitted. This method can realize 100% full detection of the film thickness and carrier concentration of the epitaxial wafer.

[0070] In the embodiment of the application, a linear graph of the donor concentration and the N2 flow rate of the doping gas is shown. Referring to FIG. 6, the donor concentration is proportional to the N2 flow rate of the doping gas in a large range. Figure 3 .

[0071] The donor concentration is proportional to the N2 flow rate of the doping gas in a large range. The concentration is proportional to the source gas flow rate and time. The linear relationship can be determined by experiment for each device. Under a fixed growth temperature and pressure, the N2 flow rate is a key parameter for realizing large-range regulation of N doping.

[0072] The application is a silicon carbide epitaxial equipment equipped with a film thickness detection and carrier detection platform, after epitaxial growth is completed, it is transported to the detection platform for detection, a data acquisition and processing unit judges whether to adjust the epitaxial equipment process parameters according to the detection result, and an epitaxial growth control system adjusts the source gas flow (and / or reaction time) and process nitrogen flow according to the linear relationship between the source gas flow (and / or reaction time) and the film thickness and the process nitrogen flow and the carrier concentration, so that the epitaxial wafer film thickness and the carrier concentration are in the ideal range, and the wafer-to-wafer stability of the epitaxial wafer is improved.

[0073] The device embodiments provided by the application are described below.

[0074] As Figure 4 The detection device of the silicon carbide epitaxial wafer in an embodiment of the application is shown. The detection device comprises:

[0075] an epitaxial growth control unit 41,

[0076] an automatic transmission unit 42,

[0077] a detection unit 43,

[0078] a data acquisition and processing unit 44,

[0079] The epitaxial control unit 41 controls the core parameters such as reaction gas flow field, reaction temperature and reaction time to realize the control of the whole growth cycle of the silicon carbide epitaxial wafer.

[0080] The automatic transmission unit 42 is located between the detection unit and the epitaxial growth control unit 41, and the automatic transmission unit comprises an atmospheric robot and a wafer box, the atmospheric robot takes, places and transmits the epitaxial wafer, and the wafer box is located on one side of the atmospheric robot and is used to store the epitaxial wafer after detection.

[0081] The detection unit 43 is close to the epitaxial growth equipment, comprises a film thickness detection module and a carrier concentration detection module, and is used to detect the film thickness and the carrier concentration of the epitaxial wafer. Preferably, the film thickness detection module is an infrared spectrum detection module, which comprises an infrared light source, an aperture, an interferometer, a sample chamber, a detector, a laser, a control circuit board and a power supply, and realizes film thickness detection. The carrier concentration detection module is a mercury probe detection module, which comprises a test table, a motor, a pneumatic control unit, a measurement unit, an information processing unit and a capillary mercury probe, and realizes carrier concentration detection.

[0082] The data acquisition processing unit 44 comprises a signal acquisition module, a communication module, an upper computer and a lower computer. The signal acquisition module receives data transmitted by the detection unit 43, and sends the data to the lower computer through the communication module. The lower computer sends the data to the upper computer through a network. The upper computer compares and analyzes the detection data with preset target data. If the deviation is within the allowable range, no adjustment is made. If the deviation is not within the allowable range, the process parameters to be modified are calculated through a corresponding formula, and the modified process parameters are sent to the lower computer to control the epitaxial growth control unit 41 to adjust the process parameters of the epitaxial equipment.

[0083] The above is only some embodiments of the application, and does not limit the application in any form. Any simple modification, equivalent change and modification of the above embodiments still belongs to the protection scope of the technical solutions of the application.

Claims

1. A method of detecting a silicon carbide epitaxial wafer, characterized by, The method comprises the following steps: The automatic conveying unit automatically transports the epitaxial wafer to the detection unit, The detection unit detects the film thickness and carrier concentration of the epitaxial wafer and sends the detection result to the data acquisition and processing unit, The data acquisition and processing unit receives and responds to the received data and compares it with the preset target data, If the deviation is within the preset range, no adjustment is made; If the deviation is not within the preset range, the calculation result is fed back to the epitaxial growth control unit, and the epitaxial growth control unit adjusts the process parameters of the epitaxial device; The detection unit is an online detection unit, and the automatic conveying unit takes out the epitaxial wafer from the epitaxial device and automatically transports it to the online detection platform for real-time detection; The film thickness of the silicon carbide epitaxial wafer is detected based on an FTIR Fourier infrared spectrum detection instrument, and the detected information is fed back to the data acquisition and processing unit; The carrier concentration of the silicon carbide epitaxial wafer is detected based on a mercury probe CV online detection instrument, and the detected information is fed back to the data acquisition and processing unit.

2. The method of claim 1, wherein The automatic conveying unit takes out the epitaxial wafer from the TM cavity wafer box of the epitaxial device and transports it to the detection platform for detection.

3. The method of claim 2, wherein The detection platform is installed on the side of the PM cavity of the epitaxial device close to the wafer cavity, and the height is the same as that of the mechanical hand in the TM cavity.

4. The method of claim 1, wherein The automatic conveying unit comprises an atmospheric robot located between the detection platform and the epitaxial device.

5. A device for detecting a silicon carbide epitaxial wafer, for use in a method as claimed in any one of claims 1-4, characterized in that It comprises: An epitaxial growth control unit for controlling the flow of reaction gas into the reaction cavity, the reaction temperature and the reaction time parameters based on instructions to control the real-time growth cycle of the epitaxial wafer; An automatic conveying unit arranged on the side of the reaction cavity for taking, placing and conveying the epitaxial wafer; A detection unit comprising a film thickness detection module and a carrier concentration detection module for detecting the film thickness and carrier concentration of the epitaxial wafer; A data acquisition and processing unit for receiving the detection data of the detection unit and comparing it with the target data preset by the system, and judging whether the deviation is within the allowable range according to the comparison result, and adjusting the process parameters according to the preset model if the deviation is outside the allowable range.

6. The device of claim 5, wherein The film thickness detection module in the detection unit is an infrared spectrum detection module, which comprises an infrared light source, an aperture, an interferometer, a sample chamber, a detector, a laser, a control circuit board and a power supply.

7. The apparatus of claim 5, wherein, The carrier concentration detection module in the detection unit is a mercury probe detection module, which comprises a test bench, a motor, a pneumatic control unit, a measurement unit, an information processing unit and a capillary mercury probe.

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