Method of manufacturing a composite structure including a rating step

Abstract

The invention relates to a method of manufacturing a composite structure comprising a thin film made of single-crystal silicon carbide, arranged on a carrier substrate made of polycrystalline silicon carbide, comprising the following steps: 1) providing at least one donor substrate made of single-crystal silicon carbide, said donor substrate having a front face and a back face, said front face potentially having defects, called primary defects; 2) checking the quality of said at least one donor substrate using a photoluminescence-like imaging technique to extract a map of the front face, called a first map, listing the primary defects, said primary defects being identified as micro-hole type, complex star stack defect type or point defect type; 3) transferring a thin film obtained from a surface layer of said at least one donor substrate onto a carrier substrate made of polycrystalline silicon carbide to obtain a composite structure and a remaining donor substrate; 4) checking the free surface of the thin film of the composite structure by means of a defect checking technique using ultraviolet laser beam scattering to extract a map of the free surface, called a second map, listing the defects, called secondary defects; 5) rating said composite structure, which comprises comparing said first map and said second map.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials, and in particular to composite structures comprising thin films (derived from donor substrates made of single-crystal silicon carbide) transferred onto a carrier substrate made of polycrystalline silicon carbide. The invention particularly relates to a method for manufacturing such composite structures, comprising a rating step based on a mapping map for inspecting the donor substrate and a mapping map for inspecting the thin film of the composite structure. Background Technology

[0002] Silicon carbide is a particularly interesting material for manufacturing power and radio frequency devices, or even devices that operate at very high temperatures.

[0003] Over the past decade, the quality of substrates made from single-crystal silicon carbide (c-SiC) has improved significantly, accompanied by increasingly precise recognition and detection of various types of crystal defects that may exist in this material. The JEITA (Japan Electronics and Information Technology Industries Association) standard includes four documents concerning the zoology of on-film / in-film defects generated on 4H-SiC substrates via homoepitaxial growth (EDR 4712 / 100) and non-destructive procedures for optical inspection of these defects (EDR 4712 / 200, / 300, / 400). In particular, a process for evaluating and referencing defects by combining optical inspection and photoluminescence imaging is provided.

[0004] Commercially available devices, particularly such as Lasertec’s SICA88, can be used to combine visible light Nomarski prism confocal microscopy with photoluminescence technology (as in T. Kimoto et al., "Fundamentas also f Silicon Carbide Technology Growth Characterization Devices and Applications", pg. 126, or in D. Baierhofer et al., "Materials Science in Semiconductor Processing", (2022) 106414), and are generally used to inspect c-SiC substrates before or after epitaxy.

[0005] As an example, Das et al.'s paper [3] ("Statistical analysis of killer and non-killer defects in SiC and the impact of device performance", Material Science Forum, ISSN 1662-9752, Vol. 1004, pp. 458-463 (2020), Trans Tech Publications Ltd) presents a statistical analysis of "killer" defects in devices generated on homoepitaxial films made of c-SiC, and shows optical and photoluminescence images of typical c-SiC defects.

[0006] Even with their rapid development, high-quality c-SiC substrates remain expensive and difficult to supply in large quantities. Therefore, film transfer methods are advantageous for fabricating composite structures, including thin films made of single-crystal SiC (derived from high-quality c-SiC donor substrates), on low-cost carrier substrates such as polycrystalline SiC (p-SiC), which also offer advantages in conductivity. A well-known thin film transfer solution is Smart Cut. TM The method is based on light ion implantation and direct bonding assembly between a donor substrate made of c-SiC and a carrier substrate at the bonding interface. Implantation creates a buried weak plane along which separation occurs, resulting in the transfer of a thin film made of c-SiC onto the carrier substrate to form a composite structure. This allows for the recovery and recycling of any remaining portion of the donor substrate, potentially enabling one or more further transfers of the film. Epitaxial growth can then be performed on the thin film of the composite structure, subsequently producing electronic devices.

[0007] To achieve an economically viable film transfer method, it is important to know how to inspect the quality of the donor substrate in order to avoid transferring films that will inevitably lead to the declassification of the composite structure, or films that will result in epitaxial films that are substandard in terms of "killing" defects. The taxonomy of defects in c-SiC is relatively well known, and many studies (some of which are cited above) tend to define the types and sizes of defects present in epitaxial films made of c-SiC that would be fatal to the part; however, the applicant has observed that the criteria used to classify defects in the donor substrate are not necessarily the same when epitaxial growth is performed on the donor substrate and when film transfer is performed from the donor substrate.

[0008] Therefore, it is crucial to detect and accurately classify crystal defects (called primary defects) present on the donor substrate in order to degrade those donor substrates that do not allow for the fabrication of thin films with the desired quality.

[0009] Furthermore, the detection and identification of defects (referred to as secondary defects) on and / or in the thin films (derived from the donor substrate) of composite structures whose carrier substrate is made of polycrystalline SiC (p-SiC) is complex because the p-SiC grains are visible beneath the film, especially when using equipment combining visible light Nomarski prism confocal microscopy and photoluminescence imaging. However, if secondary defects in the film could potentially result in substandard density killer defects in the homogeneous epitaxial film, reliable and efficient quality checks of the film are necessary to avoid continuing the epitaxial step (without requiring excessive inspection time per structure).

[0010] Given the increasing use of film transfer technology in the manufacturing chain of electronic devices on c-SiC, there is a key requirement for defining inspection steps that allow for reliable and rapid inspection of donor substrates at the beginning of the chain and composite structures in the middle of the chain, so as to assign ratings to donor substrates or composite structures as early as possible throughout the manufacturing chain and allow for the achievement of desired device specifications and yields.

[0011] The subject of this invention

[0012] The present invention solves the aforementioned problem. The present invention relates to a method for manufacturing a composite structure comprising a thin film made of single-crystal silicon carbide transferred onto a carrier substrate made of polycrystalline silicon carbide. The manufacturing method includes initial, reliable, and rapid steps for grading the composite structure, combining initial inspection of the donor substrate with final inspection of the structure. Summary of the Invention

[0013] This invention relates to a method for manufacturing a composite structure comprising a thin film made of single-crystal silicon carbide disposed on a carrier substrate made of polycrystalline silicon carbide, the method comprising the following steps: 1) Provide at least one donor substrate made of single-crystal silicon carbide, the donor substrate having a front side and a back side, the front side potentially having a defect referred to as a primary defect; 2) Use photoluminescence imaging technology to inspect the quality of the at least one donor substrate to extract a front-side map, referred to as the first map, listing primary defects identified as microtubule type, complex star stack defect type or point defect type. 3) Transfer a thin film derived from the surface film of the at least one donor substrate onto a carrier substrate made of polycrystalline silicon carbide to obtain a composite structure and a remaining donor substrate; 4) Use a defect inspection technique that utilizes ultraviolet laser beam scattering to inspect the free surface of the thin film of the composite structure to extract a mapping map of the free surface, called a second mapping map, and list the defects referred to as secondary defects; 5) Rating the composite structure, including comparing the first mapping map and the second mapping map.

[0014] Other advantageous and non-limiting features according to the invention may be adopted individually or in any technically feasible combination: Step 2) includes the following sub-steps: i) Inspect the front side of the donor substrate to detect primary defects caused by local variations in the intensity of the photoluminescence signal emitted from the front side after excitation by the incident beam, and form a photoluminescence image of each primary defect; ii) By training an image recognition algorithm on various types of defects that may exist on the front side of a donor substrate made of single-crystal silicon carbide, such as micropipes, complex star-shaped stack defects and point defects particularly related to inclusions, defects of a certain similarity level are assigned to each detected primary defect, wherein the contrast level is associated with the photoluminescence image of each detected primary defect. iii) Classify each primary defect by applying the following criteria: - If the defect of the marked type is a microtubule, and if the similarity level is greater than the first level, then the primary defect is classified as a critical microtubule type defect; - If the defect of the marked type is a complex star-stacked defect, and if the similarity level is greater than the second level, then classify the primary defect as a critical defect of the complex star-stacked defect type; - If the defect of the marked type is a point defect, if the similarity level is greater than the third level, and if the contrast level is greater than a predetermined threshold, then the primary defect is classified as a critical defect of the point defect type. Otherwise, classify a defect as a non-critical defect.

[0015] Step i) The inspection is performed using an incident light beam with a wavelength of 313 nm, and the emitted photoluminescence signal is collected in the wavelength range of 700 nm to 1000 nm. Based on a study of the correlation between the contrast value of a primary defect detected on the front side of a test donor substrate and the presence of a secondary defect on a thin film obtained after the film is transferred from the test donor substrate to a carrier substrate, the predetermined threshold is empirically established for a type of donor substrate.

[0016] Upon completion of step 2), defects with a density greater than 1 defect / cm² will be... 2 Or even better, a defect rate greater than 0.25 / cm 2 The donor substrate is downgraded for a primary defect that is classified as a critical defect regardless of its type, and it is not used in step 3).

[0017] Step 5) includes coordination between the primary defects and the secondary defects that are classified as critical defects, wherein each primary defect that is classified as a critical defect and is not associated with a secondary defect is added to the defects in the second mapping map so that it can be considered in the rating decision.

[0018] The rating decision corresponds to a downgrade of the composite structure if the composite structure includes any of the following: - The density of secondary defects associated with critical primary defects, and the density of primary defects classified as critical defects and added to the second mapping map, are greater than 0.25 defects / cm². 2 ; - The density of secondary defects, which are unrelated to critical primary defects and are detected only on the second mapping map, is greater than 0.2 defects / cm². 2 .

[0019] Step 5) includes coordination between primary and secondary defects that are classified as critical defects, and step 5) includes additional inspection using a technique combining visible light optical microscopy and photoluminescence imaging to check for the presence of defects in the film at the location of the primary defects that are classified as critical defects.

[0020] Step 3) includes the following sub-steps: 3a) Implanting a light material into a donor substrate to form a buried weak plane that, together with the front side of the donor substrate, defines the surface film to be transferred; 3b) Assemble the carrier substrate made of polycrystalline silicon carbide together with the donor substrate implanted in step 3a); 3c) Separate along the buried weak plane to form an intermediate composite structure, which includes, on the one hand, the transferred surface film and carrier substrate, and on the other hand, the remaining part of the donor substrate, referred to as the remaining donor substrate; 3d) Apply one or more thermal, mechanical and / or chemical treatments to the free surface of the surface film to form a composite structure having a thin film made of single-crystal silicon carbide.

[0021] In this composite structure: the thin film includes a front surface corresponding to the donor substrate, a buried surface disposed opposite to the carrier substrate, and a free surface corresponding to the thin film, and another surface opposite to the front surface; and a mirror inversion is applied to the first mapping or the second mapping for comparison.

[0022] Step 3) includes the following sub-steps: 3i) Implanting a light material into a donor substrate to form a buried weak plane, the buried weak plane together with the front side of the donor substrate defining the surface film to be transferred; 3ii) Assemble the temporary substrate together with the donor substrate implanted in step 3i) via the first bonding interface; 3iii) Separate along the buried weak plane to form an intermediate assembly, which includes, on the one hand, the transferred surface film and temporary substrate, and on the other hand, the remaining portion of the donor substrate, referred to as the remaining donor substrate; 3iv) Apply one or more thermal, mechanical and / or chemical treatments to the free surface of the surface film to form a temporary structure, the temporary structure having a thin film made of single-crystal silicon carbide disposed on a temporary substrate; 3v) The carrier substrate made of polycrystalline silicon carbide is assembled together with the thin film of the temporary structure via the second bonding interface; 3vi) Dismantle along the first bonding interface to separate the temporary substrate from the composite structure having a thin film made of single-crystal silicon carbide.

[0023] The method includes step 6): recycling the remaining donor substrate to produce a recycled donor substrate, wherein: - In step 3), the recycled donor substrate is directly introduced as the donor substrate; and - In the next step 4), the resulting composite structure is rated using a first mapping established for the initial donor substrate from which the recycled donor substrate is obtained.

[0024] This invention relates to a method comprising the following steps: 1) Provide at least one donor substrate made of single-crystal silicon carbide, the donor substrate having a front side and a back side, the front side potentially having a defect referred to as a primary defect that extends through the back side and also exists on the back side; 2) Use photoluminescence imaging technology to examine the quality of the at least one donor substrate in order to extract a back-side mapping, referred to as the first mapping, listing primary defects identified as microtubule type, complex star stack defect type or point defect type. 3) Transfer a thin film derived from the surface film on the front side of the at least one donor substrate onto a carrier substrate made of polycrystalline silicon carbide to obtain a composite structure and a remaining donor substrate; 4) Use the defect inspection technique of ultraviolet laser beam scattering to inspect the free surface of the thin film of the composite structure to extract the mapping map of the free surface, called the second mapping map, and list the defects called secondary defects; 5) Rating the composite structure, including comparing the first mapping map and the second mapping map. Attached Figure Description

[0025] Other features and advantages of the invention will become apparent from the following detailed description of the invention, which is provided with reference to the accompanying drawings, in which: [ Figure 1 ] Figure 1 The donor substrate is shown, along with composite structures with and without epitaxial films; [ Figure 2a ] [ Figure 2b ] [ Figure 2c ] [ Figure 2d ] Figure 2a , Figure 2b , Figure 2c and Figure 2d An example of a study on the correlation between primary defects present on the front side of a donor substrate and related secondary defects present on the free surface of a thin film in a composite structure is shown, performed on a SICA88 instrument; the primary defects are imaged by photoluminescence microscopy; when they have a contrast value above a predetermined threshold, they lead to secondary defects; the secondary defects are imaged by Nomarski prism confocal optical microscopy. [ Figure 3a ] [ Figure 3b ] [ Figure 3c ] [ Figure 3d ] [ Figure 3e ] [ Figure 3f ] Figure 3a , Figure 3b , Figure 3c , Figure 3d , Figure 3e and Figure 3f The steps of a method for manufacturing a composite structure according to the present invention are shown; [ Figure 4 ] Figure 4 A mapping diagram (first mapping diagram) listing the primary defects of the donor substrate in step 2) of the method according to the invention is shown; [ Figure 5a ] [ Figure 5b ] Figure 5a and Figure 5b Two examples are shown of a mapping (second mapping) listing the secondary defects of the composite structure in step 4) of the method according to the invention (where the thin film originates from the donor substrate also shown in the first mapping); [ Figure 6a ] [ Figure 6b ] [ Figure 6c ] [ Figure 6d ] [ Figure 6e ] [ Figure 6e '] [ Figure 6e "] Figure 6a , Figure 6b , Figure 6c , Figure 6d , Figure 6e , Figure 6e 'and Figure 6e "The steps of an alternative embodiment of the method for manufacturing a composite structure according to the present invention are shown." Detailed Implementation

[0026] This invention relates to a method for manufacturing a composite structure 100, the composite structure 100 comprising a thin film 10 made of single-crystal silicon carbide disposed on a carrier substrate 20 made of polycrystalline silicon carbide. It should be understood that, although for ease of understanding this description relates only to the manufacturing of composite structure 100, the method is applicable to the manufacturing of multiple composite structures 100.

[0027] In the following description, "primary defect" generally refers to a defect present on and / or in the donor substrate 1 from which the thin film 10 originates, "secondary defect" generally refers to a defect present on and / or in the thin film of the composite structure 100, and "tertiary defect" generally refers to a defect present on and / or in the epitaxial film grown on the thin film 10.

[0028] In the principal plane (x, y), the donor substrate 1 and the composite structure 100 are preferably in the form of circular wafers with diameters of 100 mm, 150 mm, 200 mm, or even larger. However, they can take any other form that allows them to be subsequently processed to manufacture parts. The thickness of the substrate and structure is along... Figure 1 The z-axis extension in the diagram. The front surfaces 1a, 10a, and 150a of the substrate 1 and structure 100 are inspected and may have the aforementioned defects.

[0029] The manufacturing method includes a first step 1 of providing a donor substrate 1 made of single-crystal silicon carbide. The single-crystal SiC can be a 4H, 6H, or 3C polytype. The donor substrate 1 is preferably in the form of a wafer, with a diameter that is the same as or very similar to the diameter of the carrier substrate 20 to which it will subsequently be assembled, and its thickness is typically between 300 μm and 800 μm. It has a front side 1a and a back side 1b. Figure 3a The surface roughness of the front side 1a is advantageously selected to be less than 1 nm RMS, or even less than 0.5 nm RMS, as measured by atomic force microscopy (AFM) on a 20 μm × 20 μm scan. The doping type and resistivity of the donor substrate 1 are defined according to the application and target device. Preferably, the front side 1a is a "carbon" side [000-1] for providing a thin film 10 with a "silicon" type front side 10a

[0001] in the composite structure 100 after transfer.

[0030] Although step 1) describes providing a donor substrate 1, in an industrial setting, it is clear that multiple donor substrates 1 can be provided in this step.

[0031] The second step 2) of the method includes examining the quality of at least one donor substrate 1 using photoluminescence imaging to extract a mapping of the front side 1a, referred to as the first mapping, which lists primary defects identified as microtubular, complex star-shaped stacking, and point defects (e.g., defects related to inclusions in the material). In fact, the applicant has recognized that these types of defects can form critical defects that generate problematic secondary defects in the thin film 10 of the composite structure 100.

[0032] After excitation with an incident beam, a primary defect in the donor substrate 1 is revealed by photoluminescence imaging due to localized variations in the intensity of the photoluminescence (PL) signal emitted from the front side 1a. These localized variations in PL signal intensity reflect changes in material properties (stress, roughness, flatness, etc.) corresponding to the primary defect. These changes can appear as white or black dots on the generated PL image, depending on their characteristics.

[0033] This inspection step can be performed on known equipment, such as the SICA88 (manufactured by Lasertec), the "Photoluminescence scanner" (manufactured by Intego), or the "MiPlato SiC" (manufactured by EtaMax). This equipment typically uses a combination of visible light optical microscopic images and photoluminescence images of the same defect to specify size (size, surface area) and intensity (contrast) criteria based on the measured optical microscopic and photoluminescence signals; for example, it can also assign type criteria (predefined defect categories) to each primary defect based on a learning algorithm. These predefined categories typically correspond to microtubule-type defects, complex star-shaped stacked defects, point defects (especially those associated with inclusions), scratches, particles, etc.

[0034] Advantageously, step 2) includes the three sub-steps described below: i) Inspect the front side 1a of donor substrate 1: The purpose of this step is to detect primary defects caused by localized variations in the intensity of the photoluminescence signal emitted from the front side 1a after excitation by the incident beam, and to form a photoluminescence image of each primary defect. In the SICA88 device, which will be preferred throughout this specification, the incident excitation beam has a wavelength of 313 nm, and the emitted photoluminescence signal is collected in the wavelength range of 700 nm to 1,000 nm.

[0035] ii) Assign the defect type of the marker to each detected defect: Various types of defects are provided and trained on an image recognition algorithm based on, for example, an SSD (Single Shot Detector) type model used for object detection. These defects may exist on the front side 1a of a donor substrate 1 made of single-crystal silicon carbide, such as micropipes, complex star-shaped stacked defects, and point defects (marker-type defects) particularly associated with inclusions. Therefore, the device can assign a marker-type defect with a certain level of similarity to each detected primary defect. The contrast level is also associated with the photoluminescence image of each detected primary defect.

[0036] iii) Classify each primary defect by applying the following criteria: - If the defect type is microtubule, and the similarity level is greater than the first level, then the primary defect is classified as a critical microtubule type defect; - If the marked defect type is a complex star-stacked defect, and if the similarity level is greater than the second level, then classify the primary defect as a critical defect of the complex star-stacked defect type. - If the marked defect type is a point defect, if the similarity level is greater than the third level, and if the contrast level is greater than a predetermined threshold, then the primary defect is classified as a critical defect of the point defect type. Otherwise, classify a defect as a non-critical defect.

[0037] The similarity of the first, second, and third levels can differ from each other because they depend on the type of defect and the number of defects of each type used to train the image recognition algorithm.

[0038] For a given type of donor substrate 1 (supplier, crystal structure, front surface roughness, manufacturing technology, etc.), a predetermined contrast threshold can be empirically established based on a study of the correlation between the contrast value of a primary defect detected on the front surface 1a of one (or preferably multiple) test donor substrates and the presence of a secondary defect on one (or preferably multiple) thin films 10, which originate from one or more test donor substrates transferred onto a carrier substrate 20.

[0039] Figure 2a The table in the table shows the critical primary defects on donor substrate 1. Figure 2a (a) and secondary defects caused in the thin film 10 obtained from the substrate 1. Figure 2a The observable correlation between (b) and (b)

[0040] Figure 2b , 2c As shown in Table 2d, not all primary defects detected on the donor substrate 1 generate secondary defects in the transferred thin film 10. Therefore, it is necessary to define criteria for correctly classifying these primary defects as critical or non-critical defects. In addition to the similarity level applied to each primary defect associated with the marked defect type, the contrast level of the photoluminescence image is an important criterion, particularly for determining the criticality of point defects, as these defects can exhibit a wide range of contrast from low to high. For this reason, a predetermined contrast threshold is used to distinguish critical from non-critical defects. Figure 2b In the example shown, the predetermined contrast threshold is set to 600 au. This threshold obviously depends on the parameters of the formulation and the characteristics of the carrier substrate 1 (roughness, doping, residual stress, manufacturing method, etc.), and a universal value can never be proposed.

[0041] For defects in microtubules or complex star-shaped stacks, a similarity level is often sufficient because these defects possess very specific characteristics and high correlated contrast. Photoluminescence images can also be correlated with optical microscopic images of these defects to further refine their classification.

[0042] As a reminder, the contrast in a photoluminescence image can be defined as the normalized difference between the photoluminescence signal intensity on a primary defect and the surrounding intensity in a field smaller than or equal to the microscope's field size. Other calculations of the contrast value will produce different numerical results and different predetermined contrast thresholds, but will have a similar meaning.

[0043] exist Figure 4 An example of the first mapping is provided: it lists the critical defects detected on donor substrate 1 and classified as critical defects (specifically, critical defects of the following types: complex star-shaped stacking defects, microtubes, or point defects of specific inclusion types); Figure 4 The top left corner shows another defect that was classified as non-critical.

[0044] According to an advantageous embodiment, in step 2) of the method according to the invention, upon completion of step 2), the defects having a density greater than 1 defect / cm² are... 2 or even greater than 0.25 defects / cm 2 The donor substrate 1 with a primary defect (which is classified as a critical defect regardless of type) is declassified, and the donor substrate 1 is not used in subsequent steps, step 3).

[0045] Then, the manufacturing method includes a third step 3): transferring the thin film 10 obtained from the surface film 10' of the donor substrate 1 onto a carrier substrate 20 made of polycrystalline silicon carbide, in order to obtain a composite structure 100 and the remaining donor substrate 1' without the surface film 10'. In the composite structure 100, the front side 1a of the donor substrate 1 is thus arranged opposite the front side 20a of the carrier substrate 20 and corresponds to the buried surface of the thin film 10, which is inaccessible for surface inspection; the other side 10a of the thin film 10 opposite the buried surface (front side 1a) is free and will be inspected in the next step.

[0046] Advantageously, the surface film 10' is transferred using a thin-film transfer technique (e.g., Smart Cut). The first sub-step 3a) includes implanting a light material into the donor substrate 1 to form a buried weak plane 11, which, together with the front side 1a of the donor substrate 1, defines the surface film 10' to be transferred. Figure 3bThe light material is preferably hydrogen and / or helium, and is injected into the donor substrate 1 at a depth consistent with the thickness of the target thin film 10. This light material will form microcavities around the determined depth, distributed in a fine film parallel to a free surface 1a of the donor substrate 1, which is parallel to the plane (x, y) in the figure. For simplicity, this film is referred to as the buried weak plane 11. The injection energy of the light material is selected to achieve the given depth. For example, the injection energy level is between 10 keV and 250 keV, and the dose is between 5... E 16 / cm 2 and 1 E 17 / cm 2 Hydrogen ions are deposited between the hydrogen ions to define a thin film 10 with a thickness on the order of 100 nm to 1,500 nm. It should be noted that a protective film can be deposited on the front side 1a of the donor substrate 1 prior to the ion implantation step. For example, this protective film can be made of materials such as silicon oxide or silicon nitride. It can be removed before the following sub-step 3b). This sub-step corresponds to assembling the carrier substrate 20, made of polycrystalline silicon carbide on one side of its front side 20a, with the implanted donor substrate 1, also on one side of its front side 1a. Figure 3c The carrier substrate 20 corresponds to the mechanical support of the future composite structure 100. The lateral dimensions (specifically its diameter) in the principal plane (x, y) of the carrier substrate 20 are the same as the lateral dimensions of the composite structure 100. The thickness of the carrier substrate 20 is typically between about 50 μm and several hundred micrometers, for example, between 50 μm and 650 μm, or between 100 μm and 450 μm, or even between 200 μm and 350 μm.

[0047] Assembly is achieved through molecular adhesion via direct bonding along bonding interface 40. Optionally, an intermediate film may be formed on the front side 1a of the donor substrate 1 before or after the introduction of a light material, and in any case, before the assembly stage. This intermediate film may be made of a dielectric, semiconductor, or metallic material (e.g., silicon oxide, silicon, silicon carbide, tungsten, titanium, etc.). Optionally, an intermediate film may also be deposited on the assembly side 20a of the carrier substrate 20 before the assembly stage; it may be selected to have the same or different properties as the intermediate film mentioned for the donor substrate 1. Optionally, an intermediate film may be deposited on either of the two substrates 1, 20 to be assembled. The purpose of the one or more intermediate films is essentially to increase the binding energy (especially in the temperature range below 1,100°C) since covalent bonds are formed at lower temperatures than in the case of two directly assembled silicon carbide surfaces; another advantage of the one or more intermediate films may be improved vertical conductivity of the bonding interface 40. One or more intermediate membranes are intended to be embedded in the bonded component 50 after assembly, and ultimately embedded in the composite structure 100.

[0048] Direct bonding via molecular adhesion does not require adhesive materials because bonds are established at the atomic scale between the assembled surfaces. Several types of molecular adhesion bonding exist, which differ significantly in their temperature, pressure, or atmospheric conditions or the treatment prior to surface contact. Examples include room-temperature bonding with or without pre-plasma activation of the surfaces to be assembled, atomic diffusion bonding (ADB), surface-activated bonding (SAB), etc.

[0049] As a reminder, assembly step 3b) may include a conventional sequence of chemical cleaning (e.g., RCA cleaning), surface activation (e.g., by oxygen or nitrogen plasma), or other surface preparation (e.g., cleaning by brushing (wiping)) before bringing the surfaces 1a and 20a to be assembled into contact, which is conducive to improving the quality of the bonding interface 40 (low defects, high adhesion energy).

[0050] Sub-step 3c) below corresponds to separation along the buried weak plane 11 to form an intermediate composite structure 100', which includes, on one hand, the transferred thin film 10 and the carrier substrate 20, and on the other hand, the remaining portion 1' of the donor substrate. Figure 3dSeparation along the buried weak plane 11 is typically achieved by applying heat treatment in a temperature range between 800°C and 1,200°C. Such heat treatment results in the formation of cavities and microcracks in the buried weak plane 11, and causes them to be pressurized by a light material in gaseous form until the cracks propagate along the weak plane 11. Alternatively, or in combination, mechanical stress may be applied to the bonded assembly 50, particularly to the buried weak plane 11, to propagate or facilitate the mechanical propagation of cracks, leading to separation. Upon completion of this separation, an intermediate composite structure 100' is obtained on one hand, and the remaining portion 1' of the donor substrate is obtained on the other. The free surface 10'a of the surface film 10' is typically rough after separation: for example, it exhibits a roughness between 5 nm and 100 nm RMS.

[0051] Sub-step 3d) includes applying thermal, mechanical, and / or chemical treatment to the free surface 10'a of the surface film 10' to form a composite structure 100 having a thin film 10 made of single-crystal silicon carbide with a surface roughness less than or equal to 0.5 nm RMS, or even less than or equal to 0.1 nm RMS (10 × 10 μm). 2 Or 20 × 20 μm 2 AFM scan) Figure 3e Specifically, sub-step 3d) may include a chemical-mechanical smoothing treatment of the free surface 10'a of the surface film 10'. Removal in the range of 50 nm to 300 nm allows the surface finish of the film to be effectively restored. It may also include at least one heat treatment at a temperature of 1,200 °C to 1,800 °C. Such heat treatment removes residual light material from the film 10' and promotes its lattice rearrangement, thereby forming the film 10. It also allows the bonding interface 40 to be strengthened.

[0052] At this stage of the method, the thickness of the thin film 10 of the composite structure 100 is typically in the range of tens to hundreds of nm, for example, between 50 nm and 800 nm. The type and level of doping of the thin film 10 and the carrier substrate 20 are defined according to the intended application and device.

[0053] Further referring to the general description of the manufacturing method according to the invention, following step 3) of transferring the thin film 10 onto the carrier substrate 20 is a fourth step 4): inspecting the free surface 10a of the thin film 10 using a defect inspection technique based on dark-field and bright-field imaging combined with scanning the surface 10a with a DUV ("Deep UV", typically having wavelengths on the order of 200-280 nm) laser beam; the laser beam is scattered by defects in proportion to their size, which allows the defects to be located on the surface 10a and their size to be estimated. For example, a device such as the KLA SPA2 can be used. The DUV laser beam penetrates almost no thickness of the thin film 10, and therefore it is not contaminated by the presence of p-SiC grains in the carrier substrate 20. This technique allows the detection of secondary defects present on the surface of the thin film 10 and their association with known defects in a device database, such as voids, bubbles, scratches, particles, other point or aggregate defects, etc.

[0054] This inspection step is widely used in the semiconductor industry (especially silicon), making it compatible with industry standards and productivity requirements.

[0055] Secondary defects can arise from primary defects (crystal defects present on the donor substrate 1 that cause thin film 10), from particles or other surface contaminants that have not been completely eliminated before assembling the donor substrate 1 and the carrier substrate 20, or even from specific problems (scratches, deposited particles, peeling, etc.) during steps of the manufacturing process. Therefore, these can be crystal-originating defects or transfer-related defects, such as voids (local absence of thin film 10), bubbles (defects on the bonding interface 40 where thin film 10 is not bonded and forms bubbles), particles, scratches, etc.

[0056] Upon completion of step 4), a mapping map of the free surface 10a (referred to as the second mapping map) can be extracted, listing the identified secondary defects. Figure 5a An example of a second mapping showing secondary defects detected on a composite structure 100, the thin film 10 of which originates from a donor substrate 1 (first mapping), is shown. It should be noted that to compare the first and second mappings, a "mirror" inversion of the first mapping is required because the front side 1a of the donor substrate 1 is assembled onto the carrier substrate 20 and is therefore inverted. In this example, several primary defects classified as critical (visible in the first mapping) are also visible in the second mapping. Figure 5b Another example is shown: In this case, several primary defects that are classified as critical and visible on the first map are not visible on the second map.

[0057] The advantage of this inspection step 4) is that it is fast and therefore allows for a complete inspection of the composite structure on the production line. However, it may miss defects of crystal origin present in the thin film, as some of these defects do not cause UV laser beam scattering and remain hidden during this inspection.

[0058] Conversely, inspection techniques combining visible light optical microscopy and photoluminescence imaging can allow the detection of defects originating from these crystals, but the presence of underlying p-SiC grains can make inspection more difficult, and in particular, each structure requires a much longer processing time, which impacts high-volume production lines.

[0059] Therefore, the applicant has defined a reliable and effective fifth step (5) for rating the composite structure 100 based on a first mapping map (step 2) using the donor substrate 1 and a second mapping map (step 4) of the structure 100, wherein a thin film 10 of the composite structure 100 in question is obtained from the donor substrate 1. The purpose of this rating is to separate structures that meet the target specifications from those that have been downgraded.

[0060] Obviously, the second mapping map is compared with the first mapping map, while ensuring that the first mapping map is mirror-reversed, because the donor substrate 1 bonded to the carrier substrate 20 has an inverted front side 1a (the buried surface of the thin film 10). The rating of the composite structure 100 is determined based on this comparison.

[0061] Advantageously, step 5) includes coordination between primary defects classified as critical defects in the first mapping and secondary defects in the second mapping. This coordination is possible because the first and second mappings are established in the same orthogonal reference system and each point in either mapping is identified, for example, by a Cartesian or polar coordinate system. When a primary defect classified as critical cannot be associated with a secondary defect, because no defect is detected on the second mapping, an additional defect is added to the second mapping at the location of the primary defect so that it can be considered in the rating decision. Thus, primary defects identified as critical (i.e., defects that generate defects in the transferred film) are considered for evaluating the quality of the composite structure 100 without requiring a complex and ultimately time-consuming inspection of the composite structure 100.

[0062] According to one variant, step 5) includes coordination between primary and secondary defects classified as critical defects, and if not every primary defect classified as a critical defect is associated with a secondary defect, step 5) includes additional examination of the composite structure 100 in question using a technique combining visible light confocal microscopy and photoluminescence imaging, such that it is possible to examine whether a defect actually exists in the film 10 at the location of the critical primary defect.

[0063] The grading step 5 of the manufacturing method according to the invention allows for a reliable and effective decision on the rating to be assigned to the composite structure 100 by benefiting from precise inspection of the donor substrate 1 suitable for the field of film transfer, by rapid and ultimately standardized quality inspection of all composite structures 100, and by the teachings of combining these two inspections.

[0064] Specifically, if the composite structure 100 has the following characteristics, then the composite structure 100 can be downgraded: The density of secondary defects associated with critical primary defects, and the density of primary defects classified as critical defects and added to the second mapping map, are greater than 0.25 defects / cm². 2 ; and / or The density of secondary defects detected only on the second mapping map (i.e., those not related to critical primary defects) is greater than 0.2 defects / cm². 2 .

[0065] In subsequent steps, the epitaxial growth of SiC can be performed on the thin film 10 of the composite structure 100 (which has already passed the rating step 5) to increase its thickness and form an epitaxial film 150 thereon, on which devices will be fabricated ( Figure 3f The epitaxial growth step can be performed using techniques known in the prior art.

[0066] The manufacturing method may also include a sixth step 6): recycling the remaining donor substrate 1' to produce a recycled donor substrate. Step 6) may include mechanical and / or chemical treatments, similar to those applied to the composite structure 100, performed on the front side 1'a of the remaining donor substrate 1'.

[0067] The recycled donor substrate is then directly introduced into step 3) as a new donor substrate 1. In step 5), the rating of the resulting composite structure 100 is obtained using the first mapping map (step 2) established for the initial donor substrate 1, from which the recycled donor substrate is obtained.

[0068] Therefore, a first mapping reflecting the quality of the initial donor substrate 1 is used to classify each composite structure 100 obtained from the substrate 1 in its initial state and after multiple recycling steps. Although this inspection is time-consuming, it is industrially feasible because it is amortized over a very large number of composite structures 100 manufactured from the donor substrate 1.

[0069] The manufacturing method has been described in step 3), which involves transferring the thin film 10 onto the carrier substrate 20 without intermediate processing; this can be referred to as a single transfer.

[0070] According to another embodiment, step 3) may include a dual transfer, such as Figure 6a As shown in 6f, in this process, the thin film 10 first passes through the first bonding interface 60 ( Figure 6a , 6b (6c, 6d, 6e) are transferred from the donor substrate 1 to the temporary substrate 30, and then transferred a second time from the temporary substrate 30 to the carrier substrate 20 through the second bonding interface 40. Figure 6e ',6e").

[0071] Therefore, step 3) may include the following sub-steps: 3i) Light material is implanted into the donor substrate 1 to form a buried weak plane 11, which together with the front side 1a of the donor substrate 1 defines the surface film 10' to be transferred; 3ii) The temporary substrate 30 is assembled with the donor substrate 1 implanted in step 3i) via the first bonding interface 60; 3iii) Separate along the buried weak plane 11 to form an intermediate assembly, which includes, on the one hand, the transferred surface film 10' and the carrier substrate 30, and on the other hand, the remaining portion 1' of the donor substrate, referred to as the remaining donor substrate 1'. 3iv) Apply one or more thermal, mechanical and / or chemical treatments to the free surface 10'a of the surface film 10' to form a temporary structure on which the film 10 is made of single-crystal silicon carbide and disposed on a temporary substrate 30. 3v) The carrier substrate 20 made of polycrystalline silicon carbide is assembled with the thin film 10 of the temporary structure through the second bonding interface 40; 3vi) Disassemble along the first bonding interface 60 to separate the temporary substrate 30 from the composite structure 100 on which the thin film 10 made of single-crystal silicon carbide is disposed.

[0072] The first bonding interface 60 can be based on molecular adhesion bonding, and the second interface 40 can also be based on molecular adhesion bonding. The temporary substrate 30 can be selected from any material compatible with direct bonding, particularly silicon, silicon carbide, etc. For example, the temporary substrate 30 can be removed by mechanical disassembly.

[0073] In this alternative embodiment, the composite structure 100 includes a thin film 10, the free surface 10b of which corresponds to the front side 1a of the donor substrate 1, taking into account the dual transfer.

[0074] Therefore, in step 5) of classifying the composite structure 100, the comparison of the first mapping map and the second mapping map can be performed without mirror reversal.

[0075] According to another specific implementation, where a single transfer is involved in step 3), the method may include the following steps: 1) Provide at least one donor substrate 1 made of single-crystal silicon carbide, the donor substrate 1 having a front side 1a and a back side 1b, the front side 1a potentially having a defect that extends through the back side 1b and is also present on the back side 1b, referred to as a primary defect; 2) Use photoluminescence imaging technology to examine the quality of the at least one donor substrate 1 in order to extract a mapping map of the back side 1b, referred to as the first mapping map, listing primary defects identified as microtubule type, complex star stack defect type or point defect type. 3) Transfer the thin film 10 onto a carrier substrate 20 made of polycrystalline silicon carbide to obtain a composite structure 100 and a remaining donor substrate 1', wherein the thin film 10 originates from a surface film 10' on the front side 1a of at least one donor substrate 1; 4) Using the defect inspection technique of ultraviolet laser beam scattering, inspect the free surface 10a of the thin film 10 of the composite structure 100 to extract a mapping map of the free surface 10a, called the second mapping map, and list the defects, called secondary defects. 5) Rating the composite structure 100, including comparing the first mapping map and the second mapping map.

[0076] According to this particular embodiment, considering that the critical primary defect is mainly a penetration defect, it can be detected on the back side 1b (e.g., on the front side 1a), and the quality of the donor substrate is checked on the back side 1b of the donor substrate 1. In step 5), the first and second mapping maps can be compared without mirror reversal.

[0077] It should be noted that, in the case of a single transfer, the general details of steps 1) to 5) set forth in this specification may be applied to this particular implementation as well as to alternative implementations based on dual transfers.

[0078] Of course, the present invention is not limited to the described embodiments and examples, and alternative embodiments may be used without departing from the scope of the invention as defined by the claims.

Claims

1. A method for manufacturing a composite structure (100), said composite structure (100) comprising a thin film (10) made of monocrystalline silicon carbide disposed on a carrier substrate (20) made of polycrystalline silicon carbide, said method comprising the following steps: 1) Provide at least one donor substrate (1) made of single-crystal silicon carbide, the donor substrate (1) having a front side (1a) and a back side (1b), the front side (1a) potentially having a defect referred to as a primary defect; 2) Use photoluminescence imaging technology to examine the quality of the at least one donor substrate (1) to extract a mapping map of the front side (1a), called the first mapping map, listing primary defects identified as microtubule type, complex star stack defect type or point defect type. 3) Transfer a thin film (10) from the surface film (10') of the at least one donor substrate (1) onto a carrier substrate (20) made of polycrystalline silicon carbide to obtain a composite structure (100) and a remaining donor substrate (1'); 4) Use a defect inspection technique that utilizes ultraviolet laser beam scattering to inspect the free surfaces (10a, 10b) of the thin film (10) of the composite structure (100) to extract a mapping map of the free surfaces (10a, 10b), called a second mapping map, and list the defects referred to as secondary defects. 5) Rating the composite structure (100) by comparing the first mapping map and the second mapping map.

2. The method for manufacturing a composite structure (100) according to claim 1, wherein, Step 2) includes the following sub-steps: i) Inspect the front side (1a) of the donor substrate (1) to detect primary defects caused by local changes in the intensity of the photoluminescence signal emitted from the front side (1a) after being excited by the incident beam, and form a photoluminescence image of each primary defect. ii) By training an image recognition algorithm on various types of defects that may exist on the front side (1a) of a donor substrate (1) made of single-crystal silicon carbide, such as micropipes, complex star-shaped stack defects and point defects particularly related to inclusions, defects of a certain similarity level are assigned to each detected primary defect, wherein the contrast level is associated with the photoluminescence image of each detected primary defect. iii) Classify each primary defect by applying the following criteria: - If the defect of the marked type is a microtubule, and if the similarity level is greater than the first level, then the primary defect is classified as a critical microtubule type defect; - If the defect of the marked type is a complex star-stacked defect, and if the similarity level is greater than the second level, then classify the primary defect as a critical defect of the complex star-stacked defect type; - If the defect of the marked type is a point defect, if the similarity level is greater than the third level, and if the contrast level is greater than a predetermined threshold, then the primary defect is classified as a critical defect of the point defect type. Otherwise, classify a defect as a non-critical defect.

3. The method for manufacturing the composite structure (100) according to claim 2, wherein, The inspection step i) is performed using an incident beam with a wavelength of 313 nm, and the emitted photoluminescence signal is collected in the wavelength range of 700 nm to 1000 nm.

4. The method for manufacturing the composite structure (100) according to any one of claims 2 and 3, wherein, Based on a study of the correlation between the contrast value of a primary defect detected on the front side (1a) of the test donor substrate (1) and the presence of a secondary defect on the thin film (10) obtained by transferring the test donor substrate to the carrier substrate (20), the predetermined threshold is empirically established for a type of donor substrate (1).

5. The method of manufacturing the composite structure (100) as described in any one of claims 2 to 4, wherein, Upon completion of step 2), defects with a density greater than 1 defect / cm² will be... 2 Or even better, a defect rate greater than 0.25 / cm 2 The donor substrate (1) that is classified as a critical defect regardless of type is downgraded and is not used in step 3).

6. The method for manufacturing a composite structure (100) according to any one of claims 2 to 5, wherein, Step 5) includes coordination between the primary defects and the secondary defects that are classified as critical defects, wherein each primary defect that is classified as a critical defect and is not associated with a secondary defect is added to the defects in the second mapping map so that it can be considered in the rating decision.

7. The method for manufacturing a composite structure (100) according to claim 6, wherein, The rating decision corresponds to a downgrade of the composite structure if the composite structure includes any of the following: - The density of secondary defects associated with critical primary defects, and the density of primary defects classified as critical defects and added to the second mapping map, are greater than 0.25 defects / cm². 2 ; - The density of secondary defects, which are unrelated to critical primary defects and are detected only on the second mapping map, is greater than 0.2 defects / cm². 2 .

8. The method for manufacturing a composite structure (100) according to any one of claims 2 to 5, wherein, Step 5) includes coordination between primary and secondary defects that are classified as critical defects, and step 5) includes additional inspection using a technique combining visible light optical microscopy and photoluminescence imaging to check for the presence of defects in the film (10) at the location of the primary defect that is classified as a critical defect.

9. A method for manufacturing a composite structure (100) according to any one of the preceding claims, wherein, Step 3) includes the following sub-steps: 3a) A light material is injected into the donor substrate (1) to form a buried weak plane (11), which together with the front side (1a) of the donor substrate (1) defines the surface film (10) to be transferred; 3b) Assemble the carrier substrate (20) made of polycrystalline silicon carbide together with the donor substrate (1) implanted in step 3a); 3c) Separate along the buried weak plane (11) to form an intermediate composite structure (100'), which includes, on the one hand, the transferred surface film (10') and the carrier substrate (20), and on the other hand, the remaining part (1') of the donor substrate, referred to as the remaining donor substrate (1'). 3d) Apply one or more thermal, mechanical and / or chemical treatments to the free surface (10'a) of the surface film (10') to form a composite structure (100) having a thin film (10) made of single-crystal silicon carbide.

10. A method for manufacturing a composite structure (100) according to any one of the preceding claims, wherein, In the composite structure (100): - The thin film (10) includes a front surface (1a) corresponding to the donor substrate (1), a buried surface disposed opposite to the carrier substrate (20), and a free surface (10a) corresponding to the thin film (10) and another surface opposite to the front surface (1a); - In step 5), a mirror inversion is applied to the first map or the second map so that they can be compared.

11. The method for manufacturing a composite structure (100) according to any one of claims 1 to 8, wherein, Step 3) includes the following sub-steps: 3i) A light material is injected into the donor substrate (1) to form a buried weak plane (11), which together with the front side (1a) of the donor substrate (1) defines the surface film (10) to be transferred. 3ii) The temporary substrate (30) is assembled together with the donor substrate (1) implanted in step 3i) via the first bonding interface (60); 3iii) Separate along the buried weak plane (11) to form an intermediate assembly, which on the one hand includes the transferred surface film (10') and temporary substrate (30), and on the other hand includes the remaining portion (1') of the donor substrate, referred to as the remaining donor substrate (1'); 3iv) Apply one or more thermal, mechanical and / or chemical treatments to the free surface (10'a) of the surface film (10') to form a temporary structure having a thin film (10) made of single-crystal silicon carbide and disposed on a temporary substrate (30); 3v) The carrier substrate (20) made of polycrystalline silicon carbide is assembled together with the thin film (10) of the temporary structure via the second bonding interface (40); 3vi) Disassemble along the first bonding interface (60) to separate the temporary substrate (30) from the composite structure (100) provided with a thin film (10) made of single-crystal silicon carbide.

12. A method for manufacturing a composite structure according to any one of the preceding claims, the method comprising step 6): recycling the remaining donor substrate (1') to produce a recycled donor substrate (1"), wherein: - In step 3), the recycled donor substrate (1") is directly introduced as the donor substrate (1); and - In the next step 4), the resulting composite structure (100) is rated using a first mapping established from the initial donor substrate (10) from which the recycled donor substrate (1") is obtained.

13. A method for manufacturing a composite structure (100), the composite structure (100) comprising a thin film (10) made of monocrystalline silicon carbide disposed on a carrier substrate (20) made of polycrystalline silicon carbide, the method comprising the steps of: 1) Provide at least one donor substrate (1) made of single-crystal silicon carbide, the donor substrate (1) having a front side (1a) and a back side (1b), the front side (1a) potentially having a defect referred to as a primary defect that extends through the back side (1b) and is also present on the back side (1b); 2) Use photoluminescence imaging technology to examine the quality of the at least one donor substrate (1) in order to extract a mapping map of the back side (1b), referred to as the first mapping map, listing primary defects identified as microtubule type, complex star stack defect type or point defect type. 3) A thin film (10) originating from the surface film (10') on the front (1a) side of the at least one donor substrate (1) is transferred onto a carrier substrate (20) made of polycrystalline silicon carbide to obtain a composite structure (100) and a remaining donor substrate (1'); 4) Use the defect inspection technique of using ultraviolet laser beam scattering to inspect the free surface (10a) of the thin film (10) of the composite structure (100) to extract a mapping map of the free surface (10a), called the second mapping map, and list the defects called secondary defects. 5) Rating the composite structure (100) by comparing the first mapping map and the second mapping map.

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