Epitaxial film growth state detection method, and detection system

Abstract

Provided in the present application are an epitaxial film growth state detection method, and a detection system for executing the epitaxial film growth state detection method. In the epitaxial film growth state detection method of the present application, during the execution of an epitaxial process, an optical detection apparatus is controlled to emit light within a specific wavelength range onto an epitaxial film for optical detection, acquire light intensity information of the epitaxial film and send same to a main control apparatus, and the main control apparatus then performs calculation on the basis of the light intensity information of the epitaxial film, the specific wavelength range and crystal structure correspondence data that is pre-stored in the main control apparatus, such that the crystal structure on the surface of the film can be monitored and evaluated in real time during the growth of the epitaxial film.

Description

Methods and systems for detecting the growth status of epitaxial films

[0001] This application is based on and claims priority to Chinese Patent Application No. 202410907219.3, filed on July 8, 2024, entitled “Method and System for Detecting Epitaxial Film Growth State”, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This application relates to the field of semiconductor material growth technology, and in particular to methods and systems for detecting the growth state of epitaxial films. Background Technology

[0003] Some semiconductor materials, such as aluminum gallium nitride (AlGaN), are suitable for manufacturing high-temperature, high-power devices due to their wider bandgap, higher thermal conductivity, and dielectric constant. However, some of these semiconductor materials have very high bond energies, making it difficult to form high-quality substrates through crystal pulling or dicing processes.

[0004] Epitaxial growth is a technique for growing epitaxial films along a specific crystal orientation on a crystal-oriented substrate, with device fabrication continuing on the epitaxial film. The epitaxial film can be a homoepitaxial film, meaning the substrate and the epitaxial film are made of the same material, or a heteroepitaxial film, meaning the substrate and the epitaxial film are composed of different materials. Therefore, epitaxial growth can form high-quality heteroepitaxial films of high-bond-energy semiconductor materials on a substrate, which is beneficial for the fabrication of high-frequency, high-power devices.

[0005] However, for heteroepitaxial films, the mismatch in lattice and thermal expansion coefficients between the substrate material and the epitaxial film material makes the epitaxial film structure prone to high-density defects. Therefore, the requirements for heteroepitaxial processes are high, and it is necessary to monitor and evaluate the crystal structure of the epitaxial film surface in real time during the heteroepitaxial process. Summary of the Invention

[0006] This application provides a method for detecting the growth state of an epitaxial film and a detection system for performing the growth state detection method, so as to realize real-time monitoring and evaluation of the crystal structure of the film surface during the epitaxial film growth process.

[0007] The epitaxial film growth state detection method of this application includes at least the following steps:

[0008] S0: Provides a semiconductor growth device, an optical detection device, and a main control device. The semiconductor growth device carries a substrate. The optical detection device is disposed in the semiconductor growth device. The main control device is communicatively connected to the optical detection device. The main control device pre-stores data on the crystal form of semiconductor materials at different wavelengths and the corresponding absorption coefficients, and each absorption coefficient is different.

[0009] S1: Control the semiconductor growth equipment to perform an epitaxial process on the substrate, so that an epitaxial film composed of the semiconductor material is formed on the exposed surface of the substrate, and the material is different from that of the substrate;

[0010] S2: During the epitaxial process, the optical detection device is controlled to emit light of a specific wavelength range to the epitaxial film for optical detection, and the light intensity information of the epitaxial film is acquired and sent to the main control device.

[0011] S3: The main control device calculates the real-time crystal structure information of the epitaxial film surface based on the light intensity information of the epitaxial film, the specific wavelength and the corresponding data of the crystal structure.

[0012] The detection system described in this application is used to perform the epitaxial film growth state detection method. The detection system includes an optical detection device disposed on a semiconductor growth equipment and a main control device communicatively connected to the optical detection device. The semiconductor growth equipment is configured to perform an epitaxial process on a substrate to form an epitaxial film with a compositional material different from that of the substrate.

[0013] The beneficial effects of the epitaxial film growth state detection method and the detection system described in this application are as follows: during the epitaxial process, the optical detection device is controlled to emit light of a specific wavelength range to the epitaxial film for optical detection, and the light intensity information of the epitaxial film is acquired and sent to the main control device. The main control device calculates based on the light intensity information of the epitaxial film, the specific wavelength and the crystal form correspondence data, so that the crystal form of the film surface can be monitored and evaluated in real time during the epitaxial film growth process.

[0014] Optionally, the main control device also pre-stores empirical reflectivity correspondence data with the reflectivity, thickness, phase difference, absorption coefficient, and refractive index of the semiconductor material. In step S3, the step where the main control device performs calculations based on the light intensity information, the specific wavelength, and the crystal form correspondence data includes:

[0015] S31: The main control device obtains the real-time reflectance correspondence data between the real-time reflectance of the epitaxial film and the growth time based on the light intensity information of the epitaxial film;

[0016] S32: The main control device calculates the real-time absorption coefficient of the epitaxial film based on the real-time reflectivity correspondence data and the empirical reflectivity correspondence data, and obtains the real-time crystal structure information of the epitaxial film surface based on the real-time absorption coefficient, the specific wavelength and the crystal structure correspondence data.

[0017] Optionally, the empirical reflectance correspondence data includes:

[0018] in:

[0019] R is the empirical reflectance, n i n is the refractive index of the reaction space medium located above the epitaxial film. j n is the refractive index of the semiconductor material. k γ is the refractive index of the substrate material, a is the absorption coefficient of a specific crystal plane of the semiconductor material at the specific wavelength, and γ is the phase difference. d is the optical thickness of the epitaxial film;

[0020] λ is the specific wavelength, i is the incident angle of light within the specific wavelength range incident from the reaction space medium onto the epitaxial film, j is the refraction angle of the emitted light emitted from the bottom surface of the epitaxial film, and k is the refraction angle of the emitted light emitted from the bottom surface of the substrate.

[0021] Optionally, the real-time reflectance correspondence data is the periodic oscillation curve data of the real-time reflectance of the epitaxial film versus the growth time.

[0022] Optionally, the real-time reflectivity of the epitaxial film decreases with the extension of the growth time.

[0023] Optionally, before performing step S1, the method further includes performing a step of acquiring the specific wavelength:

[0024] Obtain single-crystal samples of different crystal forms of the semiconductor material;

[0025] Optical tests and analyses were performed on each of the single crystal samples under light in different wavelength ranges to obtain absorption spectral data.

[0026] In the absorption spectral data set, the wavelengths corresponding to the highest absorption coefficient values ​​of each single crystal sample are obtained to form a wavelength data set, and the crystal form correspondence data are obtained;

[0027] Select any wavelength from the wavelength data set as the specific wavelength.

[0028] Optionally, the step of obtaining single-crystal samples of different crystal forms of the semiconductor material includes:

[0029] Obtain a single-crystal sample of the semiconductor material to be cut;

[0030] The single-crystal sample to be cut is subjected to crystal plane cutting to form each single-crystal sample.

[0031] Optionally, the semiconductor growth apparatus includes a support device to support the substrate;

[0032] The process of performing step S1 includes controlling the carrier device to drive the substrate to rotate;

[0033] The process of performing step S2 also includes controlling the optical detection device to emit light of the specific wavelength range to the carrier device, so as to obtain and send the received light intensity information of the carrier device to the main control device;

[0034] In step S3, the main control device performs subtraction processing based on the light intensity information of the epitaxial film and the light intensity information of the carrier device to subtract background information including thermal radiation information, and then performs calculations based on the obtained light intensity information, the specific wavelength and the crystal form correspondence data.

[0035] Optionally, after step S32 is completed, the following steps are further performed:

[0036] S33: The main control device calculates the real-time optical thickness increment of the epitaxial film based on the empirical reflectivity correspondence data, the real-time reflectivity correspondence data, and the real-time crystal form information;

[0037] S34: The main control device obtains the growth rate change data of the epitaxial film based on the real-time optical thickness increment.

[0038] Optionally, step S33 includes:

[0039] S331: The main control device obtains the reflectivity values ​​in the i-th period of the periodic oscillation curve, the empirical reflectivity correspondence data, and the real-time crystal form information, based on these values. i The real-time optical thickness increment Δd of the epitaxial film over the time period i ;

[0040] S332: The main control device obtains the real-time reflectivity values ​​in the (i+n)th period of the periodic oscillation curve, the empirical reflectivity correspondence data, and the real-time crystal form information, based on these values. (i+n) The real-time optical thickness increment Δd of the epitaxial film over the time period (i+n) ;

[0041] S333: Repeat step S332 until the epitaxial process is completed or until the condition is met.

[0042] in:

[0043] i is a positive integer greater than or equal to 1, and n is a positive integer greater than or equal to 1, taking values ​​in sequence.

[0044] Optionally, the energy of the light in the specific wavelength range is greater than the bandgap of the semiconductor material.

[0045] Optionally, the epitaxial film is an epitaxial doped film. Attached Figure Description

[0046] Figure 1 is a flowchart of the epitaxial film growth state detection method provided in an embodiment of the present invention;

[0047] Figure 2 is a schematic diagram of the working state of the detection device provided in an embodiment of the present invention;

[0048] Figure 3 is a schematic diagram of the detection device provided in an embodiment of the present invention;

[0049] Figure 4 is a schematic diagram of the optical path formed by light incident on a thin film on a substrate according to an embodiment of the present invention;

[0050] Figure 5 is a schematic diagram of the optical path formed by light incident on the homogeneous epitaxial film and substrate;

[0051] Figure 6 is a schematic diagram of the periodic oscillation of reflectivity with optical thickness provided in an embodiment of the present invention;

[0052] Figure 7 is a schematic diagram of the periodic decay oscillation of reflectivity with optical thickness provided by an embodiment of the present invention;

[0053] Figure 8 shows the relationship between the absorption coefficient and wavelength of different doped epitaxial films provided in the embodiments of the present invention.

[0054] Explanation of reference numerals in the attached drawings: 1. 500 Substrate; 2. Thin film; 3. Dielectric; 100 Reaction chamber; 200 Main control device; 300 Detection device; 310 Light emitter; 320 Light emitter adjustment section; 330 Connecting seat; 340 Light propagation section; 400 Carrier device. Detailed Implementation

[0055] For semiconductor materials with high bond energies that are difficult to form high-quality substrates through crystal pulling or dicing, heteroepitaxial growth can be used to grow corresponding heteroepitaxial films on heterostructures. Since the substrates used in epitaxy have specific crystal orientation characteristics (determined by the requirements of semiconductor device manufacturing), the epitaxial process requires controlling the epitaxial film to grow along the crystal orientation characteristics of the substrate, thereby ensuring a high degree of crystal orientation consistency and high integrity of the crystal structure. However, due to the different compositional materials of the substrate and the epitaxial film, the mismatch in lattice and thermal expansion coefficients between them makes the epitaxial film structure prone to high-density defects. Therefore, it is necessary to monitor and evaluate the crystal structure of the epitaxial film surface in real time during the epitaxial process.

[0056] The technical solution provided in this application is not applicable to the detection of the thin film deposition process of homoepitaxial film. Referring to Figure 5, firstly, for homoepitaxial film, since the material composition of homoepitaxial film is the same as that of substrate, there is no optical interface between homoepitaxial film and substrate. After light is refracted by the medium and homoepitaxial film, it needs to pass through the substrate to reach the area between the substrate and the placement interface of the substrate. The reflected light is then refracted by the interface between homoepitaxial film and medium before exiting.

[0057] Secondly, the interference between emitted light from homogeneous epitaxial films is also affected by the substrate thickness. Furthermore, the high process temperature significantly interferes with the signal due to thermal radiation generated by the epitaxial film, easily weakening or even rendering the emitted light signal reflected from the substrate unmeasurable, thus failing to obtain the curve relationship shown in Figure 4. Moreover, under the conditions of thin film deposition processes in this field, which are typically carried out at high temperatures (e.g., the process temperature of Al(1-x)GaxAs epitaxy reaches 1100 degrees Celsius), significant thermal radiation is generated in the epitaxial film. Subsequent processes also involve transport after thin film deposition, requiring the substrate to have a certain thickness and strength to resist the adverse mechanical effects caused by thermal expansion and contraction. The thickness of substrates such as silicon wafers and quartz wafers is typically not less than 400 micrometers, which also affects the emitted light intensity within the substrate.

[0058] Therefore, even by increasing the light intensity, such as using a high-intensity laser to overcome signal weakening or even unmeasurability, the error obtained using the method of this application for homoepitaxial films is still significantly higher than that for heteroepitaxial films. In summary, the method provided in this application is mainly aimed at detecting the growth state of heteroepitaxial films.

[0059] This invention provides a method for detecting the growth state of an epitaxial film and a detection system for performing the growth detection method. This method uses a non-contact optical detection method to non-destructively, rapidly, and in real-time monitor and evaluate the lattice growth during the epitaxial film growth process. It also acquires information on the optical thickness and growth rate changes of the heteroepitaxial film. The detection system provided in this invention includes an optical detection device and a main control device that are communicatively connected to each other. The optical detection device is disposed in the semiconductor growth equipment.

[0060] The method for detecting the growth state of an epitaxial film according to an embodiment of the present invention, referring to Figure 1, includes:

[0061] S1: Control the semiconductor growth equipment to perform an epitaxial process on the substrate, so that an epitaxial film composed of the semiconductor material is formed on the exposed surface of the substrate, and the material is different from that of the substrate;

[0062] S2: During the epitaxial process, the optical detection device is controlled to emit light of a specific wavelength range to the epitaxial film for optical detection, and the received light intensity information of the epitaxial film is acquired and sent to the main control device.

[0063] S3: The main control device calculates the real-time crystal structure information of the epitaxial film surface based on the light intensity information, the specific wavelength and the crystal structure correspondence data.

[0064] The technical solutions of this application will be described in detail below with reference to the accompanying drawings in the embodiments of the present invention, through Embodiments 1 to 5. Those skilled in the art can understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0065] Example 1:

[0066] The semiconductor growth equipment provided in this embodiment for performing epitaxial processes is an MOCVD equipment. Referring to Figure 2, it includes a reaction chamber 100, which has a built-in support device 400. The top surface of the support device 400 supports a substrate 500. A gas injection device (not shown in the figure) is provided on the top of the reaction chamber 100 opposite to the top surface of the support device 400 to provide process gas toward the substrate 500.

[0067] In step S1, the semiconductor growth equipment is controlled to perform an epitaxial process on the substrate, so that an epitaxial film composed of the semiconductor material, but with a different composition from the substrate, is formed on the exposed surface of the substrate. Specifically:

[0068] In the semiconductor growth apparatus provided in this embodiment, a heating device is also provided below the support device 400 to regulate the temperature inside the reaction chamber 100. Specifically, the heating device transfers heat to the substrate 500 via the support device 400. The semiconductor growth apparatus provided in this embodiment also includes a pressure control system comprising a vacuum system and an exhaust system to regulate the pressure inside the process chamber. The specific implementation methods of the heating device and the pressure control system are conventional techniques used by those skilled in the art.

[0069] In this embodiment, the semiconductor growth equipment is controlled to perform an epitaxial process on the substrate. Specifically, the heating device is controlled to ensure that the reaction chamber 100 meets the process temperature requirements for the epitaxial process, and the pressure control system is controlled to ensure that the pressure within the reaction chamber 100 meets the process pressure requirements for the epitaxial process. Then, the carrier device 400 is controlled to rotate the substrate 500 around the axis of the reaction chamber 100 at a certain speed. The gas injection device is controlled to supply process gas for the epitaxial process to the top surface of the carrier device 400, so that the process gas grows an epitaxial film on the surface of the substrate 500, which is composed of semiconductor material and is different from the material of the substrate 500, i.e., a heteroepitaxial film. The rotation of the carrier device 400 ensures that the process gas above the top surface of the carrier device 400 is uniformly mixed, which is beneficial to improving the quality of the epitaxial film.

[0070] In some embodiments, the rotation of the support device 400 can be adjusted according to the requirements of the epitaxial process.

[0071] In some embodiments, the heteroepitaxial film is aluminum gallium nitride (Al₂O₃). (1 -x ) GaxAs) epitaxial film. The semiconductor growth equipment is an MOCVD system, with a graphite substrate 400 and a silicon substrate 500. Specifically, the growth temperature is controlled at 1100 degrees Celsius, the process pressure is controlled at 50 Torr, and the source gases used are trimethylaluminum, trimethylgallium, and ammonia. The specific epitaxial process is a conventional technique in this field.

[0072] In some embodiments, the epitaxial process includes any one of the epitaxial film preparation processes such as metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), or atomic layer deposition (ALD). As an example, the epitaxial film in this embodiment is obtained using metal-organic chemical vapor deposition (MOCVD).

[0073] To facilitate optical inspection of the epitaxial film formed on the substrate, referring to Figure 2, a transparent window (not shown in the figure) is provided at the top of the reaction chamber 100. The optical inspection device 300 is located above the transparent window and is electrically connected to the main control device 200 to transmit the light intensity information of the reflected light.

[0074] Furthermore, the specific arrangement of the transparent window and the optical detection device 300 is necessary to ensure that it does not affect the normal operation of the gas injection device or the pressure inside the reaction chamber 100.

[0075] An optical detection device 300 is located on top of the reaction chamber 100. During the epitaxial process, the optical detection device 300 emits light of a specific wavelength range into the area where the substrate is located in the reaction chamber 100, can receive the reflected light of the specific wavelength range, and transmits the acquired light intensity information to the main control device 200.

[0076] The main control unit 200 receives light intensity information from the optical detection unit 300 and processes this information to acquire real-time data on the growth status of the heteroepitaxial film within the reaction chamber 100, such as the surface crystal form, optical thickness, and growth rate changes of the epitaxial film. This information allows process engineers to promptly understand the epitaxial film's growth process, providing a reference for optimizing and adjusting the growth process. It also enables the immediate detection of anomalies during growth, such as abnormal crystal form, uneven thickness, or excessively fast or slow growth rates, allowing for timely adjustments to process parameters. This ensures the epitaxial film deposition quality meets requirements and helps reduce trial-and-error and waiting time in the epitaxial process, providing valuable reference for subsequent large-scale production.

[0077] In one embodiment, referring to FIG3, the detection device 300 includes at least:

[0078] Light extractor 310;

[0079] The light emitter adjustment unit 320 is connected to the light emitter 310 and is used to drive the light emitter 310 to move in order to adjust the position and direction of the light emitter 310.

[0080] The connector 330 is connected to the light emitter adjustment part 320. The connector 330 is provided with a light passage hole (not shown in the figure). The light passage hole is used for the light emitted by the light emitter 310 to pass through, and for the light reflected by the epitaxial film to pass through.

[0081] The light propagation unit 340 is located between the light emitter 310 and the light-transmitting aperture of the connector 330. It transmits and / or focuses the light emitted by the light emitter 310 onto the surface of the thin film under test, and receives light reflected from the epitaxial film and passing through the light-transmitting aperture. Furthermore, the light propagation unit 340 includes a photodetector that receives reflected light to acquire optical information and transmits the optical information to the main control device 200.

[0082] In step S2, during the epitaxial process, the optical detection device is controlled to emit light within a specific wavelength range onto the epitaxial film for optical detection, and the received light intensity information is acquired and sent to the main control device. Specifically:

[0083] The optical detection device 300 is mounted on the top of the transparent window of the reaction chamber 100 via a connector 330. Before detection, the light emitter adjustment unit 320 is adjusted so that the light emitted by the light emitter 310 is processed by the light propagation unit 340 and then incident on the substrate or epitaxial film through the light-transmitting hole of the connector 330 and the transparent window of the reaction chamber 100. Subsequently, the light is reflected back to the light propagation unit 340 of the detection device 300 after being reflected by the substrate or epitaxial film. The light propagation unit 340 processes the light into optical information and sends it to the main control device 200 for calculation and analysis.

[0084] In one embodiment, the main control device 200 pre-stores data on the crystal form of semiconductor materials at different wavelengths and the corresponding absorption coefficients.

[0085] In one embodiment, the main control device 200 pre-stores empirical reflectivity correspondence data between the reflectivity, thickness, phase difference, absorption coefficient and refractive index of the semiconductor material.

[0086] Example 2:

[0087] This embodiment provides a method for obtaining a specific wavelength λ.

[0088] In step S3, the main control device calculates the real-time crystal structure information of the epitaxial film surface based on the light intensity information, the specific wavelength, and the crystal structure correspondence data.

[0089] In this embodiment, step S3 includes:

[0090] S31: The main control device obtains the real-time reflectance correspondence data between the real-time reflectance of the epitaxial film and the growth time based on the light intensity information.

[0091] Referring to Figure 4, a heterogeneous epitaxial film 2 is coated on the substrate 1. Light is incident from the dielectric onto the epitaxial film 2, undergoing one reflection and one refraction at the dielectric / epitaxy film interface. The first refracted light then undergoes a second reflection at the substrate / epitaxy film interface. It is understood that the technical solution provided in this application is applicable to thin film deposition processes where the substrate and epitaxial layer are made of different materials. If the technical solution of this application is used to detect homogeneous epitaxial films, it is difficult to obtain the significant periodic oscillation characteristics shown in Figure 4.

[0092] As mentioned earlier, one reason is that during the process of light incident on the epitaxial film and then emitted, the homoepitaxial film is also affected by the substrate thickness compared to the heteroepitaxial film.

[0093] On the other hand, the impact of high process temperature on the error of homoepitaxial film growth thickness testing is far greater than that of heteroepitaxial films. Specifically, high process temperature has a significant thermal expansion and contraction effect on both the film and the substrate. Even if the process temperature is controlled to a steady state, temperature fluctuations within a certain range will cause dynamic fluctuations in the interface height between the substrate and the film. Referring to Figure 4, since the two adjacent light sources at the film interface of a heteroepitaxial film are reflected from the interface between the film and the ambient medium, and refracted from the light path within the film, respectively. Unlike homoepitaxial films, heteroepitaxial films can flexibly select a suitable substrate to maximize or completely reflect the light entering the film. For heteroepitaxial films, the error of high process temperature on growth thickness testing only needs to consider the film thickness. However, compared to heteroepitaxial films, as can be seen from the comparison and analysis of Figures 4 and 5, homoepitaxial films not only need to consider the film thickness, but also the substrate thickness, which is much larger than the film thickness. The testing error caused by the substrate thickness alone far exceeds the testing error caused by the temperature effect on the film thickness itself. Taking the growth of a 5-micron thick film on a 500-micron thick substrate as an example, considering only linear thermal expansion and assuming a coefficient of thermal expansion of 1 × 10⁻⁵ nm / °C, the thickness change of the heteroepitaxial film is 5 μm × 1 × 10⁻⁵ nm / °C = 0.05 nm / °C. However, the thickness change of the substrate carrying the homoepitaxial film due to temperature changes can be as high as 500 μm × 1 × 10⁻⁵ nm / °C = 5 nm / °C. Therefore, the technical solution of this application is applicable to the detection of heteroepitaxial films where the substrate and the epitaxial film deposited on the substrate are of different materials.

[0094] After the epitaxial film growth begins, its reflectivity and refractive index change with increasing optical thickness. For example, under perpendicular incidence, the reflectivity exhibits a periodic oscillation characteristic as shown in Figure 6 with increasing optical thickness. The maximum and minimum values ​​of reflectivity occur when the film's optical thickness is an integer multiple of 1 / 4 of the incident wavelength. Therefore, the optical thickness of the film can be determined by judging the maximum and minimum values ​​of reflectivity. More importantly, the periodic oscillation characteristic of reflectivity with increasing optical thickness due to the increased film thickness during epitaxy is the theoretical basis for monitoring the real-time crystal structure information of the epitaxial film surface in this application.

[0095] However, due to the absorption of certain wavelengths of light by the epitaxial film, its reflectivity R will decrease over time. For example, Figure 7 shows the real-time reflectivity correspondence data of this embodiment, which is a periodic decay oscillation curve of the real-time reflectivity of the epitaxial film versus the growth time. If the incident wavelength is not properly selected, the significant decay of R makes its periodic change over time insignificant or even linear. Therefore, it is necessary to select a suitable light with a specific wavelength λ so that the real-time reflectivity correspondence data between the real-time reflectivity R and the growth time obtained by the main control device based on the light intensity information has a significant periodic change.

[0096] In some embodiments, the energy of a specific wavelength is greater than the bandgap of the semiconductor material. If the energy of a specific wavelength is lower than the bandgap, the incident light emitted to the epitaxial film will be completely absorbed by the semiconductor material or will be excited by fluorescence, thus preventing the optical detection device from detecting the corresponding reflected light.

[0097] In this embodiment, the step of obtaining the specific wavelength before executing step S1 includes:

[0098] S01: Obtain single-crystal samples of different crystal forms of the semiconductor material;

[0099] S02: Perform optical testing and analysis on each of the single crystal samples under light in different wavelength ranges to obtain absorption spectrum data;

[0100] S03: In the absorption spectrum data, the wavelength corresponding to the highest absorption coefficient of each single crystal sample is obtained to form a wavelength data set, and the crystal form correspondence data is obtained;

[0101] S04: Select any wavelength from the wavelength data group as the specific wavelength.

[0102] In step S01 of this embodiment, the epitaxial film is an epitaxial doped film with a corresponding composition of Al(1-x)GaxAs. Different values ​​of x correspond to different crystal forms of epitaxial films. After designing the required composition of the epitaxial film according to the functional requirements of the semiconductor device, the corresponding epitaxial process is selected. During the epitaxial process, the crystal form needs to be monitored to determine whether the composition of the epitaxial film meets the device requirements.

[0103] In some embodiments, the step of obtaining single-crystal samples of different crystal forms of the semiconductor material includes: obtaining single-crystal samples of the semiconductor material to be cut; and performing crystal plane cutting on the single-crystal samples to form each single-crystal sample. This method requires that the single-crystal sample is suitable for crystal plane cleaving by crystal plane cutting, and requires the selection of a suitable crystal orientation angle to ensure that the cutting process does not damage the characteristics of the cut crystal plane as much as possible. For example, taking silicon carbide as an example, its (0001) and (11-20) oriented crystal planes are cut from a 4H-SiC single-crystal sample grown along (000-1)C, with a cutting angle of 4 degrees off the [11-20] crystal orientation. (11-22) and (11-2-2) oriented wafers are cut from 4H-SiC with the same orientation. The (11-22) oriented 4H-SiC crystal is cut from the (000-1)C crystal plane at an angle of 73° relative to the basal plane.

[0104] In step S02 of this embodiment, the optical testing and analysis uses a VERTEX 80 Fourier Transform Infrared (FTIR) spectrometer. The sample to be tested is placed on the instrument's measurement platform and analyzed at room temperature. Transmission and reflection measurements are performed at the same point on the sample, with the light incident angle chosen to be close to the normal of the corresponding sample. The probe beam is polarized by a linear polarizer, and the sample under study is rotated to change the angle between the optical axis of crystal c and the electric field vector of the incident electromagnetic wave e. The specific testing and analysis implementation method is a conventional operation for those skilled in the art.

[0105] In step S03 of this embodiment, the relationship between the absorption coefficient and wavelength of each single crystal sample, as shown in Figure 8, is obtained after step S02. As can be seen from Figure 8, the wavelengths corresponding to the maximum absorption coefficients of each single crystal sample all fall within a narrow range of 0.23 micrometers to 0.26 micrometers. This narrow range is the wavelength data set of light within this specific wavelength range, meaning that ultraviolet light can be used as the specific wavelength light.

[0106] Example 3:

[0107] This embodiment provides a step of subtracting background information, including thermal radiation information, using an optical detection device 300 during the epitaxial process to ensure accurate detection results.

[0108] Because the reaction space in the epitaxial process is filled with a thermal medium (thermal process gas atmosphere), such as Al ( 1-x ) The process temperature of GaxAs epitaxy reaches 1100 degrees Celsius. The epitaxial film itself will generate significant thermal radiation. This thermal radiation enters the optical detection device with the reflected light, so its radiation information is included in the light intensity information, and this part of the radiation information needs to be subtracted.

[0109] Since the carrier device drives the epitaxial film substrate to rotate synchronously, and the carrier device and the epitaxial film are in the same process environment and can be considered to have the same temperature, the execution of step S2 also includes controlling the optical detection device to emit light of the specific wavelength range towards the carrier device to obtain and send the light intensity information of the carrier device to the main control device. In this embodiment, the carrier device significantly absorbs most or even all of the specific wavelength range of light, and the real-time reflectivity of the carrier device remains basically unchanged with the growth time. The light intensity information of the carrier device is the information reflected to the optical detection device due to thermal radiation. Specifically, the constituent material of the carrier device in this embodiment is different from the epitaxial film material and is a light-absorbing material that absorbs light of the specific wavelength range, such as graphite. More specifically, the fixed-position optical detection device can collect the light intensity information of both the epitaxial film and the carrier device when detecting the rotating carrier device. The main control device can distinguish and process these two types of information using conventional techniques known to those skilled in the art.

[0110] In some embodiments, the carrier device reflects light within a specific wavelength range. The light intensity information of the carrier device includes not only thermal radiation information but also real-time reflection information. The main control device further deducts the real-time reflection information of the carrier device; the specific processing method is a conventional technique used by those skilled in the art.

[0111] Furthermore, in step S3, the main control device performs subtraction processing on the received light intensity information to subtract background information including thermal radiation information, and then performs calculations based on the obtained light intensity information, the specific wavelength, and the crystal form correspondence data.

[0112] Example 4:

[0113] This embodiment provides a method for obtaining the real-time crystal structure of an epitaxial film.

[0114] After step S31 of Example 2 is completed, step S32 is executed: the main control device calculates the real-time absorption coefficient of the epitaxial film based on the real-time reflectivity correspondence data and the empirical reflectivity correspondence data, and obtains the real-time crystal structure information of the epitaxial film surface based on the real-time absorption coefficient, the specific wavelength and the crystal structure correspondence data.

[0115] The main control device has pre-stored empirical reflectivity correspondence data related to the reflectivity, thickness, phase difference, absorption coefficient, and refractive index of the semiconductor material. The empirical reflectivity is R.

[0116] Specifically,

[0117] in:

[0118] n i n is the refractive index of the reaction space medium located above the epitaxial film. j n is the refractive index of the semiconductor material. k The refractive index of the substrate material is a constant that is pre-stored in the main control device.

[0119] α is the absorption coefficient of a specific crystal plane of the semiconductor material at the specific wavelength, and γ is the phase difference. d is the optical thickness of the epitaxial film, λ is the specific wavelength, i is the incident angle of the light in the specific wavelength range incident from the reaction space medium to the epitaxial film, j is the refraction angle of the outgoing light emitted from the bottom surface of the epitaxial film, and k is the refraction angle of the outgoing light emitted from the bottom surface of the substrate.

[0120] Prepare Al by performing epitaxial process (1-x) Ga x During the epitaxial film formation process, the optical detection device emits light perpendicularly to the epitaxial film, making the values ​​of cos i, cos j, and cos k approximately 1. The main control device obtains the periodic oscillation decay curve of real-time reflectivity versus growth time, as shown in Figure 7, based on the light intensity information of the epitaxial film acquired and transmitted by the optical detection device. The real-time reflectivity corresponding to adjacent sampling growth times (d) on the curve is obtained as R1 and R2, respectively. The real-time absorption coefficient a can be calculated by solving the following equation. Then, referring to Figure 8, Al is obtained based on the absorption coefficient a. (1-x) Ga x The value of x in As can be used to obtain the value of Al. (1-x) Ga x The crystal form corresponding to the As composition.

[0121] Example 5:

[0122] This embodiment provides a method for obtaining real-time optical thickness and growth rate variation data of epitaxial films.

[0123] After S32 in Example 5 is completed, S33 is executed: The main control device calculates the real-time optical thickness of the epitaxial film based on the empirical reflectivity correspondence data, the real-time reflectivity correspondence data, and the real-time crystal form information. Specifically:

[0124] S331: The main control device obtains the reflection rate at Δt based on the adjacent real-time reflectance values ​​within the i-th period of the periodic oscillation curve, the empirical reflectance correspondence data, and the real-time crystal form information. i Real-time optical thickness d of the epitaxial film over a time period i .

[0125] Specifically, since the duration of one cycle is very short, the absorption coefficient 'a' can be the value determined in step S32. Referring to Figure 7, within the Δt1 time interval (the first cycle) from t1 to t2, the absorption coefficient 'a' can be calculated at adjacent time nodes as described above. This is based on the adjacent real-time reflectivity peak values ​​R. max1 and R max2 The optical thickness increment Δd1 = d2 - d1 within the time interval Δt1 is calculated as follows:

[0126] After step S331 is completed, step S332 is executed: the main control device obtains the value of the adjacent real-time reflectance in the (i+n)th period of the periodic oscillation curve, the theoretical reflectance correspondence data, and the real-time crystal form information, based on the adjacent real-time reflectance values, the theoretical reflectance correspondence data, and the real-time crystal form information, at Δt (i+n) The real-time optical thickness increment Δd of the epitaxial film over the time period (i+n) .

[0127] Specifically, referring to Figure 7, within the Δt2 time period (the second cycle) from t2 to t3, based on the adjacent real-time reflectivity peak values ​​R... max3 and R max4 The average optical thickness increment Δd2 = d3 - d4 over the time interval Δt2 is calculated as follows:

[0128] Similarly, in step S333, the average optical thickness increment Δd3 within the Δt3 time interval of the next cycle can be calculated based on the adjacent real-time reflectivity peak values. This process is repeated for each of the n cycles to obtain the average optical thickness increments Δd1, Δd2, ..., Δd... n Until the epitaxial process is completed, or until the real-time reflectivity meets the requirements. exist In this case, it is shown that the decay oscillation trend of real-time reflectivity R with growth time has become linear.

[0129] Furthermore, based on the average optical thickness increments Δd1, Δd2, ..., Δd within each of the n periods... n And the corresponding time periods Δt1, Δt2, ..., Δt n Through this, one can obtain The changes in the growth rate of the epitaxial film in each cycle were calculated.

[0130] In some embodiments, the corresponding optical thickness increment can also be calculated based on the values ​​of adjacent real-time reflectivity troughs within the period.

[0131] The technical solution provided in this application is particularly applicable to an online optical detection method for heteroepitaxial film growth. It can not only measure the changes in growth rate and optical thickness over time, but also evaluate the crystal characteristics of the epitaxial film. Under the guidance of real-time detection data of heteroepitaxial growth, the epitaxial process can be further adjusted to precisely control the growth parameters of the epitaxial layer, which is of great significance for manufacturing semiconductor devices with excellent performance.

[0132] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A method for detecting the growth state of an epitaxial film, characterized in that, At least the following steps are included: S0: Provides a semiconductor growth device, an optical detection device, and a main control device. The semiconductor growth device carries a substrate. The optical detection device is disposed in the semiconductor growth device. The main control device is communicatively connected to the optical detection device. The main control device pre-stores data on the crystal form of semiconductor materials at different wavelengths and the corresponding absorption coefficients, and each absorption coefficient is different. S1: Control the semiconductor growth equipment to perform an epitaxial process on the substrate, so that an epitaxial film composed of the semiconductor material is formed on the exposed surface of the substrate, and the material is different from that of the substrate; S2: During the epitaxial process, the optical detection device is controlled to emit light of a specific wavelength range to the epitaxial film for optical detection, and the light intensity information of the epitaxial film is acquired and sent to the main control device. S3: The main control device calculates the real-time crystal structure information of the epitaxial film surface based on the light intensity information of the epitaxial film, the specific wavelength and the corresponding data of the crystal structure.

2. The method for detecting the growth state of an epitaxial film according to claim 1, characterized in that, The main control device also pre-stores empirical reflectivity correspondence data with the reflectivity, thickness, phase difference, absorption coefficient, and refractive index of the semiconductor material. Step S3, in which the main control device performs calculations based on the light intensity information, the specific wavelength, and the crystal form correspondence data, includes: S31: The main control device obtains the real-time reflectance correspondence data between the real-time reflectance of the epitaxial film and the growth time based on the light intensity information of the epitaxial film; S32: The main control device calculates the real-time absorption coefficient of the epitaxial film based on the real-time reflectivity correspondence data and the empirical reflectivity correspondence data, and obtains the real-time crystal structure information of the epitaxial film surface based on the real-time absorption coefficient, the specific wavelength and the crystal structure correspondence data.

3. The method for detecting the growth state of an epitaxial film according to claim 2, characterized in that, The empirical reflectance correspondence data includes: in: R is the empirical reflectance, n i n is the refractive index of the reaction space medium located above the epitaxial film. j n is the refractive index of the semiconductor material. k γ is the refractive index of the substrate material, a is the absorption coefficient of a specific crystal plane of the semiconductor material at the specific wavelength, and γ is the phase difference. d is the optical thickness of the epitaxial film; λ is the specific wavelength, i is the incident angle of light within the specific wavelength range incident from the reaction space medium onto the epitaxial film, j is the refraction angle of the emitted light emitted from the bottom surface of the epitaxial film, and k is the refraction angle of the emitted light emitted from the bottom surface of the substrate.

4. The method for detecting the growth state of an epitaxial film according to claim 2, characterized in that, The real-time reflectance correspondence data is the periodic oscillation curve data of the real-time reflectance of the epitaxial film versus the growth time.

5. The method for detecting the growth state of an epitaxial film according to claim 4, characterized in that, The real-time reflectivity of the epitaxial film decreases with the extension of the growth time.

6. The method for detecting the growth state of an epitaxial film according to claim 5, characterized in that, Before performing step S1, the method further includes the step of obtaining the specific wavelength: Obtain single-crystal samples of different crystal forms of the semiconductor material; Optical tests and analyses were performed on each of the single crystal samples under light in different wavelength ranges to obtain absorption spectral data. In the absorption spectral data set, the wavelengths corresponding to the highest absorption coefficient values ​​of each single crystal sample are obtained to form a wavelength data set, and the crystal form correspondence data are obtained; Select any wavelength from the wavelength data set as the specific wavelength.

7. The method for detecting the growth state of an epitaxial film according to claim 6, characterized in that, The steps for obtaining single-crystal samples of different crystal forms of the semiconductor material include: Obtain a single-crystal sample of the semiconductor material to be cut; The single-crystal sample to be cut is subjected to crystal plane cutting to form each single-crystal sample.

8. The method for detecting the growth state of an epitaxial film according to claim 1, characterized in that, The semiconductor growth apparatus includes a support device for supporting the substrate; The process of performing step S1 includes controlling the carrier device to drive the substrate to rotate; The process of performing step S2 also includes controlling the optical detection device to emit light of the specific wavelength range to the carrier device, so as to obtain and send the received light intensity information of the carrier device to the main control device; In step S3, the main control device performs subtraction processing based on the light intensity information of the epitaxial film and the light intensity information of the carrier device to subtract background information including thermal radiation information, and then performs calculations based on the obtained light intensity information, the specific wavelength and the crystal form correspondence data.

9. The method for detecting the growth state of an epitaxial film according to claim 2, characterized in that, After step S32 is completed, the following steps are also performed: S33: The main control device calculates the real-time optical thickness increment of the epitaxial film based on the empirical reflectivity correspondence data, the real-time reflectivity correspondence data, and the real-time crystal form information; S34: The main control device obtains the growth rate change data of the epitaxial film based on the real-time optical thickness increment.

10. The method for detecting the growth state of an epitaxial film according to claim 9, characterized in that, Step S33 includes: S331: The main control device obtains the reflectivity value in the i-th period of the periodic oscillation curve, the empirical reflectivity correspondence data, and the real-time crystal form information, based on the real-time reflectivity value in the i-th period of the periodic oscillation curve. i The real-time optical thickness increment Δd of the epitaxial film over the time period i ; S332: The main control device obtains the real-time reflectivity values ​​in the (i+n)th period of the periodic oscillation curve, the empirical reflectivity correspondence data, and the real-time crystal form information, based on these values. (i+n) The real-time optical thickness increment Δd of the epitaxial film over the time period (i+n) ; S333: Repeat step S332 until the epitaxial process is completed or until the condition is met. in: i is a positive integer greater than or equal to 1, and n is a positive integer greater than or equal to 1, with values ​​taken in sequence.

11. The method for detecting the growth state of an epitaxial film according to claim 1, characterized in that, The energy of light in the specific wavelength range is greater than the bandgap of the semiconductor material.

12. The method for detecting the growth state of an epitaxial film according to claim 1, characterized in that, The epitaxial film is an epitaxial doped film.

13. A detection system, characterized in that, The method for detecting the growth state of an epitaxial film according to any one of claims 1-12, the detection system includes an optical detection device disposed on a semiconductor growth apparatus, and a main control device communicatively connected to the optical detection device, wherein the semiconductor growth apparatus is configured to perform an epitaxial process on a substrate to form an epitaxial film with a compositional material different from that of the substrate.

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