Method for characterizing a donor substrate and / or an implantation device

Abstract

The invention relates to a method for characterizing a donor substrate for determining whether this donor substrate is liable to trigger the occurrence of defects in a layer that has been exfoliated by ion implantation. The characterization method comprises X-ray diffraction analysis of a region of the front face of the donor substrate, after the donor substrate has been implanted, to produce numerical angle-of-incidence / intensity data defining a diffraction pattern. The method also comprises a step of processing the diffraction pattern to provide an indicator quantifying the risk of triggering the occurrence of defects in an exfoliated layer of the donor substrate.

Description

[0001] DESCRIPTION

[0002] TITLE: METHOD FOR CHARACTERIZING A DONOR SUBSTRATE AND / OR IMPLANTATION EQUIPMENT

[0003] FIELD OF INVENTION

[0004] The field of the invention relates to substrates formed by means of a thin-film transfer process, and more particularly to a process comprising the exfoliation of the thin film from a so-called "donor" substrate by implantation of light species. This process can notably be used to form a piezoelectric-on-insulator (POI) structure. Such a structure finds application in the fields of microelectronics, microsystems, and photonics. It can be used to form radio frequency (RF) components or to construct such components, in particular filters or resonators based on elastic wave components, for example, surface elastic wave components.

[0005] TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0006] Document W02020200986A1 proposes a manufacturing process for such a POI substrate that preserves the single-domain nature of the thin film. This document describes transferring a layer taken from a donor substrate containing a piezoelectric material onto a support, via an implantation step of so-called "light" species (typically hydrogen and / or helium) according to the principles of Smart Cut™ technology. Following this transfer, the extracted layer is processed in a finishing sequence comprising a heat treatment followed by a polishing step. This finishing sequence results in the formation of the piezoelectric, single-crystal, single-domain thin film.

[0007] Document WO2023217845A1 relates to ion implantation equipment used to introduce light species into a donor substrate. In this document, the donor substrate consists of a thick layer of piezoelectric material deposited on a manipulator substrate. The advantages of such a donor substrate are presented in document US2020186117. The implantation equipment comprises an ion source and an implantation wheel. The wheel includes a main disk driven in rotation under an ion beam produced by the source, and a plurality of supports on which the donor substrates are deposited.The wheel includes a cooling circuit to cool the supports, each support having a receiving surface covered with a surface elastomer layer intended to receive a so-called "back" face of the donor substrate and to ensure satisfactory thermal conductivity with the cooled support.

[0008] The aim is generally to reduce the duration of the implantation step by increasing the ion beam current produced by the equipment, thereby increasing the power delivered to the donor substrates and consequently their temperature. The equipment proposed in document WO2023217845A1 is configured to prevent or delay the phenomenon of thermal runaway, which leads, through a progressive increase in the average temperature of the donor substrate, to deformation of the substrate and loss of intimate contact between its back face and the elastomer layer.

[0009] Application WO2024022723A1 reveals that defects can appear in the thin film after it has been transferred onto the POI substrate. These defects can, in particular, consist of "triangle defects," which take the form of ferroelectric domain inversion bars with triangular cross-sections ranging from 0.1 micron to 10 microns on each side. The bars emerge at the surface of the thin film and extend through its thickness, in some cases penetrating it. They are oriented in a direction antiparallel to the spontaneous polarization direction Ps of the piezoelectric thin film. These triangle defects can exhibit a density greater than 10 A 3 / cm 2 on the exposed surface of the thin layer.

[0010] These defects have a significant impact on the performance of devices, such as acoustic filters, formed on and within POI substrates. The physical phenomena leading to their formation are not fully understood, making it difficult to prevent or anticipate their development in the thin layer of the POI substrate. A final inspection plan is generally included in the manufacturing process of POI substrates, designed to detect and reject POI substrates exhibiting such defects or an excessive density of such defects.

[0011] SUBJECT OF THE INVENTION

[0012] In light of the current state of the art, it appears desirable to have a means of anticipating the appearance of defects, and in particular triangular defects, in the thin layer of the POI substrate during its manufacturing process. More generally, it appears desirable to have a means of characterizing a donor substrate and / or implantation equipment, this means aiming to determine whether the donor substrate or the implantation equipment is likely to trigger the appearance of defects in an exfoliated layer of the donor substrate. One object of the invention is to provide such a means.

[0013] BRIEF DESCRIPTION OF THE INVENTION

[0014] To achieve this goal, the object of the invention proposes a characterization method for determining whether a donor substrate is likely to trigger the appearance of defects in a layer exfoliated by ion implantation, the characterization method comprising:

[0015] - A positioning step during which a rear face of the donor substrate is placed on a support of an implantation equipment; - an ion implantation step during which species are introduced into the donor substrate through a front face, then;

[0016] - a measurement step including an X-ray diffraction analysis of an area of ​​the front face of the donor substrate, the measurement step producing numerical angle of incidence-intensity data defining a diffraction diagram;

[0017] - a diffraction pattern processing step, the processing step providing an indicator quantifying the risk of triggering the appearance of defects in an exfoliated layer of the donor substrate.

[0018] According to other advantageous and non-limiting features of the invention, taken alone or in any technically feasible combination: the indicator is based on the relative position, in the diffraction pattern, of at least one secondary intensity peak with respect to a main intensity peak; the indicator results from the comparison between the relative position and a predetermined threshold; the indicator is a numerical value representative of the relative position; the diffraction pattern processing step includes determining the relative position of one of the secondary intensity peaks with the main intensity peak; the diffraction pattern processing step includes identifying the coordinates of the main intensity peak and the secondary intensity peak;A secondary peak intensity coordinate is representative of the difference between the angle of incidence corresponding to the secondary peak intensity and the angle of incidence corresponding to the main peak intensity; a secondary peak intensity coordinate corresponds to the intensity of the secondary peak intensity normalized by the intensity of the main peak intensity; the processing step is implemented by a classifier configured by learning; the positioning step includes the arrangement of a plurality of donor substrates on a plurality of supports of the implantation equipment, the ion implantation step includes the introduction of the species into the plurality of donor substrates, the measurement step includes the X-ray diffraction analysis of an area of ​​the front face of the donor substrates and the processing step includes the provision of a plurality of indicators respectively associated with the supports;The measurement step includes the symmetrical angular scanning of an area of ​​the front face of the donor substrate by an incident beam of monochromatic X-rays; the angular deflection of the symmetrical angular scanning is chosen to incorporate a primary intensity peak and a single secondary intensity peak in the dif fraction diagram; the area of ​​the front face of the donor substrate, irradiated by the X-rays, is not located at the center of the donor substrate; the donor substrate comprises a piezoelectric material; the defects likely to develop in the donor substrate are triangular defects.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features and advantages of the invention will become apparent from the detailed description of the invention which follows, with reference to the accompanying figures in which:

[0021] [Fig. 1] Figure 1 represents a POI substrate of the prior art;

[0022] [Fig. 2]

[0023] Figure 2 represents a manufacturing process for the POI substrate of Figure 1;

[0024] [Fig. 3]

[0025] Figure 3 illustrates an X-ray diffraction measurement installation;

[0026] [Fig. 4]

[0027] Figure 4 represents diffraction diagrams respectively obtained by X-ray diffraction measurements on a plurality of implanted donor substrates;

[0028] [Fig. 5]

[0029] Figure 5 represents the distribution of the abscissa coordinates of the first secondary intensity peak of the implanted donor substrate diffraction diagrams, depending on whether the final substrates obtained using these donor substrates have or are free of triangular defects;

[0030] [Fig. 6]

[0031] Figure 6 shows distributions similar to Figure 4 for, respectively, the x-coordinate of the second secondary intensity peak, the y-coordinate of the first secondary intensity peak, and the y-coordinate of the second secondary intensity peak. DETAILED DESCRIPTION OF THE INVENTION

[0032] We briefly recall first the manufacturing steps of a substrate of the "on insulation" type in accordance with the principles of Smart Cut® technology, taking as an example the manufacturing of a final substrate 1 of the piezoelectric on insulation type, represented in figure 1.

[0033] With reference to figures 1 and 2, this process generally involves transferring a first crystalline piezoelectric layer 8, exfoliated from a donor substrate 5, onto a support 2, via an intercalated dielectric layer 3.

[0034] The crystalline piezoelectric material can be, for example, lithium tantalate or lithium niobate. The piezoelectric material has any crystal direction, for example, between 30° and 60°RY. The donor substrate 5 can be a bulk substrate made entirely of the piezoelectric material, as shown in Figure 2, or it can be a composite substrate consisting of a bulk portion, for example, silicon, on which rests a thick layer of piezoelectric material from which the first layer 8 is taken. The thick layer can be assembled and retained to the bulk portion by any possible technique, for example, by molecular adhesion or via an adhesive layer, for example, a polymer adhesive. In some embodiments, the support 2 consists of a conductive or semiconductive bulk substrate.In other embodiments, the support 2 comprises a basic semiconductor substrate, generally exhibiting a high resistivity greater than 1000 ohms·cm, provided with a surface charge-trapping layer. This trapping layer is located on the side of the first face of the support 2, which is intended to receive the thin film 4. The trapping layer may be made of polycrystalline silicon. In these embodiments, the intercalated dielectric layer 3 is in contact with both the trapping layer and the thin film 4.

[0035] According to the transfer technique based on the implantation of light species, and with reference to Figure 2b, light species, typically hydrogen and / or helium in ionic form, are implanted in a front face 6 of the donor substrate 5 to form a buried weakening plane 7. The first layer 8 is thus defined between the weakening plane 7 and the first face 6 of the donor substrate 1.

[0036] As detailed in document WO2023217845A1 submitted in the introduction to this application, this implantation step involves positioning the donor substrate 5 within the implantation equipment. During this step, a rear face of the substrate 5 is placed on a support of the equipment. Typically, such equipment comprises a wheel on which are arranged a plurality of supports, each designed to receive a plurality of donor substrates 5 for collective processing. Each support is equipped with an elastomeric layer to ensure satisfactory thermal contact with the substrate and to allow the dissipation of any heat that may accumulate. The implantation equipment is then operated, and an ion beam with a determined energy and intensity is projected through the front face 6 of the donor substrates to introduce a specific dose of light species.

[0037] In a subsequent step, as shown in Figure 2c, this front face 6 of the donor substrate is joined to an exposed face 6' of the support 2, here via an intercalated dielectric layer 3. By way of example, the intercalated dielectric layer 3 may comprise or be made of silicon oxide, silicon oxynitride, or silicon nitride. It may be formed on either or both of the donor substrate and the support 2 prior to their assembly.

[0038] The donor substrate 5 is then fractured at the embrittlement plane 7, for example by means of moderate heat treatment and / or the application of mechanical stress. The first layer 8 of the donor substrate 5 is then released to expose a free face 9 of this first layer 8, the other face 6 being in direct contact with the intercalated dielectric layer 3 of the support 2.

[0039] A remaining portion 5' of the donor substrate 5, after the removal of the first layer 8, can be reconditioned in order to remove a new layer, in a removal cycle similar to that which has just been described.

[0040] It is generally necessary to plan the finishing of the first layer 8 transferred and placed on the support 2, to form a thin "useful" layer 4. These steps generally aim to improve the crystalline quality of the first layer 8 and its surface condition (for example its roughness) and, if necessary, adjust its thickness to a target thickness.

[0041] As reported in the introduction to this application, this finishing may include a heat treatment step of the first layer 8, followed by a thinning step of this layer 8 to form the single-domain thin layer 4.

[0042] The heat treatment step of the first layer 8 may consist of exposing the free face 9 of the first layer 8 to a neutral atmosphere or one containing oxygen, heated to a temperature between 300°C and the Curie temperature of the ferroelectric material composing the first layer 8, for a duration of between 30 minutes and 10 hours. The thinning step may be carried out by chemical polishing or dry etching. Following these manufacturing steps, the final substrate shown in Figure 1 is obtained.

[0043] In order to understand the origin of the defect in thin film 4, which was presented in the introduction, the applicant carried out numerous investigations. As part of this, it performed X-ray diffraction measurements on the donor substrate after the implantation step.

[0044] It is worth recalling that XRD technology (for "X-Ray Diffraction" in the Anglo-Saxon terminology for "X-ray diffraction") is a widely used analytical technique for characterizing crystalline materials. Based on the interaction of X-rays with the atomic structure of crystals, this method makes it possible to determine the atomic arrangement, the dimensions of crystal lattices, the grain orientations, any structural deformations of a material, and other information about the internal structure of that material.

[0045] The foundation of X-ray diffraction rests on Bragg's law, which describes how incident X-rays are reflected by the atomic planes of crystals. When an X-ray beam strikes a material, a portion is coherently scattered by the atoms, producing a characteristic diffraction pattern. This pattern depends on the crystalline nature of the material, the position of the atoms within a unit cell of that material, and the spacing between the atomic planes. By measuring the angles and intensities of the diffracted rays, it is possible to reconstruct the crystal lattice parameters and identify the phase or structure of the analyzed material. A review of these principles and concrete examples of their application can be found in the document by Harrington, GF, Santiso, J. Back-to-Basics tutorial: X-ray diffraction of thin films. J Electroceram 47, 141-163 (2021).

[0046] As part of the investigations carried out by the Applicant, and as illustrated in Figure 3, the front face 6 of the donor substrate 5 (i.e., the implanted surface) is irradiated with a monochromatic X-ray beam produced by a source S, and a detector D measures the intensity of the diffracted rays as a function of the angle of incidence θ of the beam. The area irradiated by the beam is on the order of several mm A 2. The irradiated area of ​​the front face 6 of the substrate 5 can be located anywhere on this front face, although it appeared that the measurement seemed more reliable when this area was located on one side of this front face, rather than in its center.

[0047] The XRD analysis is implemented here using a 20 / œ scan, also known as symmetric or coupled-in-the-domain scanning. According to this approach, the angle œ (the angle of incidence between the source and the donor substrate surface) is maintained at half the angle 20 (the angle between the incident beam and the detector), as shown in Figure 3, during the angular scanning of the irradiated area. This collects numerical angle-intensity data, which constitute a diffraction pattern, this pattern forming a unique fingerprint of the material.

[0048] Figure 4 shows examples of diffraction patterns obtained by XRD measurement of a plurality of donor substrates 5 after they were implanted according to the manufacturing process described above, in the same production batch. The donor substrates were therefore placed on separate supports, but exposed to the same beam of light species, having a single energy and intensity, and received the same dose of light species.

[0049] Note that each diagram shows a principal intensity peak PI representing the most significant diffraction direction. This principal intensity peak PI corresponds to the nominal lattice parameter of the piezoelectric material that constitutes at least part of the donor substrate. By convention, the principal intensity peaks PI are all located on the 0-degree x-axis in the diagrams of Figure 4. Note that the intensity measurements taken during the XRD measurement were normalized by the intensity of the principal intensity peak PI as represented in Figure 4, thus controlling for emission variations from the source or detector of the XRD measurement equipment.

[0050] In the diffraction patterns shown in the figures, the coordinates of the points constituting these patterns are therefore formed by an abscissa representing the angular deviation from the angle at which the main intensity peak PI occurs, and an ordinate representing the intensity normalized to the intensity of this main PI peak. Naturally, any other representation of the numerical data collected during the XRD measurement is possible. The pattern also includes a flat area Zp for negative relative angles, and therefore to the left of the main intensity peak PI in the pattern shown in Figure 4.

[0051] Finally, for even more negative relative angles, and to the left of the flat area Zp on the diffraction diagrams, there is an oscillation zone Zo comprising a plurality of secondary intensity peaks. This oscillation zone Zo is delimited, on each diagram, by two secondary intensity peaks P2 and P3 at its extremities, a first secondary intensity peak P2 to the right of the oscillation zone Zo, and a second secondary intensity peak P3 to the left of the oscillation zone Zo.

[0052] Each intensity peak can be located by its coordinates (t,i) in the diffraction diagram. As an illustration, Figure 4 shows the coordinates of abscissa t2 and ordinate 12 of a first secondary intensity peak P2 from one of the diagrams.

[0053] The implanted donor substrates were then used to form a plurality of final substrates 1 according to the process described above. The free surfaces of these final substrates were inspected by scanning electron microscopy (SEM) or piezoresponse force microscopy (PEM) to detect the presence of triangular defects. The final substrates were then classified into two groups, depending on whether or not they exhibited triangular defects.

[0054] Having completed this classification, the applicant discovered that the presence of triangular defects in a final substrate could be correlated with the diffraction pattern of the donor substrate used to form that final substrate. More specifically, the applicant realized that the presence or absence of triangular defects on a final substrate could be correlated with the position (i.e., the coordinates) of the first and second secondary intensity peaks of the diffraction pattern obtained on the donor substrate associated with that final substrate.

[0055] Thus, the results of this study are shown in Figure 5. On the left side of this figure, a boxplot illustrates the distribution of the x-coordinates of the first secondary peak of intensity P2 in the diffraction patterns of implanted donor substrates that led to the formation of final substrates free of triangular defects. On the right side of this figure, a second boxplot illustrates the distribution of the x-coordinates of the first secondary peak of intensity P2 in the diffraction patterns of implanted donor substrates that led to the formation of final substrates exhibiting triangular defects.

[0056] Recall that in a box plot, the box covers the data from the first quartile to the third quartile. The median line inside the box indicates the median of the data. The whiskers extend from the edges of the box to cover the rest of the data.

[0057] By comparing the two box plots in this figure, we observe that these distributions of the x-coordinates of the first secondary peak of intensity P2 are statistically distinct from one another. In particular, we can compare an x-coordinate t2 of the first secondary peak of intensity P2 in a diffraction pattern of a donor substrate with a threshold value Vs to determine whether this donor substrate, if used in the manufacturing process to form a final substrate, will statistically lead to a final substrate exhibiting (t2 > Vs) triangular defects or (t2 < Vs) without such defects.

[0058] These results obtained are not limited to the t2 coordinate of the abscissa of the first secondary peak of intensity P2. Thus, figure 6 represents distributions similar to figure 4 for, respectively, the abscissa of the second secondary peak of intensity, the ordinate of the first secondary peak of intensity and the ordinate of the second secondary peak of intensity.

[0059] It therefore emerges from these results that by comparing the relative position of a secondary intensity peak with respect to the main intensity peak in the diffraction diagram of a donor substrate implanted with a threshold position of this peak, one can develop an indicator aimed at determining whether this donor substrate is likely to trigger the appearance of defects in a layer exfoliated by ion implantation.

[0060] Other analyses carried out by the Applicant show first of all that the measurement by X-ray diffraction of a donor substrate is repeatable: very similar diffraction diagrams are produced when this measurement is repeated on the same substrate.

[0061] Furthermore, these additional analyses showed that donor substrates placed on the same implantation wheel support and implanted in successive implantation stages exhibited very similar diffraction patterns, whereas these patterns could be very different from one support to another. Analysis of the diffraction pattern therefore allows not only the characterization of the donor substrate, to determine whether it will produce a final substrate free of triangular defects, but also the characterization of the implantation equipment support.

[0062] When this equipment is fitted with several supports allowing the collective implantation of a plurality of substrates, it is then possible to order these supports, for example, according to the increasing value of the x-coordinates t2 of the first secondary peaks of intensity P2 in the diffraction patterns of the substrates respectively implanted on these supports. In this ordering, the supports are listed in ascending order of risk: the first supports are relatively unlikely, when used to implant a donor substrate, to generate defects in the final substrate. Conversely, the last supports are relatively very likely, when used to implant a donor substrate, to generate defects in the final substrate.

[0063] These additional analyses also showed that over time, the diffraction patterns obtained on donor substrates placed during the implantation stage on the same support tended to evolve, which encourages repeating the measurement regularly to identify these drifts.

[0064] The results just presented can be used to develop a treatment for the diffraction pattern, which results from an X-ray diffraction analysis of a portion of the leading face of the implanted donor substrate. This treatment step provides an indicator for quantifying the risk of triggering defects in an exfoliated layer of the donor substrate after creating a brittle plane embedded within it using implantation equipment.

[0065] This indicator can be used to characterize the implanted substrate itself or to characterize the implantation equipment, or a part thereof such as a support.

[0066] The processing step includes identifying, in the diffraction pattern, a primary intensity peak and at least one secondary intensity peak. More specifically, the diffraction pattern processing step includes determining the relative position of one of the secondary intensity peaks P2, P3 with respect to the primary intensity peak PI.

[0067] In some cases, the processing step includes identifying the coordinates of the main peak of intensity PI and one of the secondary peaks of intensity P2,P3. One coordinate of the secondary peak of intensity P2,P3 may represent the difference between the angle of incidence corresponding to the secondary peak of intensity P2,P3 and the angle of incidence corresponding to the main peak of intensity PI. Another coordinate of the secondary peak of intensity P2,P3 may represent the intensity of the secondary peak of intensity P2,P3 normalized by the intensity of the main peak of intensity PI.

[0068] Regardless of how the relative position of one of the secondary peaks is expressed with respect to the main peak, this relative position can be used to form an indicator to discriminate whether the donor substrate and / or the implantation equipment is likely to trigger the appearance of defects in an exfoliated layer of that substrate.

[0069] The indicator can result from a comparison of this relative position to a predetermined threshold value. For example, at least one of the coordinates of the secondary intensity peaks in the diffraction pattern can form the indicator or be compared with a threshold value corresponding to a predetermined threshold position of that peak.

[0070] In this case, the indicator is binary in nature.

[0071] In other cases, the relative position of one of the secondary peaks with respect to the main peak (or a numerical value representing this relative position) in the diffraction pattern constitutes the indicator itself. This position may correspond to one of the coordinates of a secondary peak, for example, the relative abscissa of this secondary peak of intensity P2,P3 in the diffraction pattern. The value of this position with respect to the threshold value (which may be normalized, for example, between 0 and 1) quantifies the risk of triggering the appearance of defects in the exfoliated layer. The closer this indicator is to the threshold value at which defects are likely to appear, the greater the risk.

[0072] This approach is particularly useful for precisely characterizing the supports of an implanting system relative to one another, especially when that system has multiple supports, as previously noted. The characterization process then allows a distinct indicator to be associated with each support.

[0073] Although we have presented here a characterization method that analytically decomposes the diffraction pattern during the processing step to identify the position of certain secondary peaks, other approaches to exploiting the numerical data of the diffraction pattern are naturally conceivable. In particular, more comprehensive techniques can be used, for example, based on a pre-trained neural network or any other classifier configured through learning, to associate the donor substrate and / or the implant equipment with a risk indicator. The classifier can be trained using the data presented in the previous section, notably data similar to that shown in Figures 5 and 6. The indicator provided by such a classifier can be binary or continuous.

[0074] In all cases, and regardless of how the processing step is implemented, the characterization process includes a diffraction pattern processing step. This processing step provides an indicator to quantify the risk of triggering the appearance of defects in an exfoliated layer of the donor substrate. This indicator is based on the relative position, in the diffraction pattern, of a secondary peak with respect to the primary peak.

[0075] Similarly, the results presented in the previous section were obtained by symmetrical angular scanning of a region on the front face of the donor substrate with an incident beam of monochromatic X-rays. However, in some cases, other types of measurements obtained with an incident X-ray beam can be used, without necessarily employing symmetrical scanning, which nevertheless remains the preferred approach. To accelerate this symmetrical scanning measurement step, it is sufficient to choose the angular displacement to incorporate the main intensity peak and a single secondary intensity peak P2 into the diffraction pattern. Therefore, in this case, the angular displacement can be reduced without extending it to incorporate the second secondary intensity peak P3, thus shortening the acquisition time.

[0076] The characterization process can be exploited in multiple ways in a manufacturing process of a final substrate, a POI substrate in the example shown.

[0077] It is of course possible to sort the donor substrates at the end of the light species implantation stage based on the indicator provided by the characterization process, and to continue the manufacturing process only with the donor substrates which are not likely to trigger the appearance of triangle defects.

[0078] The indicator can also be used in a manufacturing process control plan. For example, final substrate inspections can be performed only on those derived from donor substrates whose indicator suggests a risk of defects. In this case, it is no longer necessary to systematically inspect all donor substrates. Alternatively, final substrate inspections can be performed on those derived from donor substrates implanted on supports exhibiting the highest risk indicators. By measuring only the substrates with the most unfavorable indicators within a batch of ion implantation, the chances of detecting triangular defects, if present, are significantly increased compared to random sampling.

[0079] As also follows from the results presented in the previous section, the characterization process can also be used in a maintenance plan for implanting equipment. For example, preventive maintenance of the implanting equipment can be initiated based on the indicator. This maintenance might include, for instance, replacing the elastomer layer covering each support on the implanting wheel. The indicator can then be used to determine which support needs to be reconditioned in this way.

[0080] When the indicator results from comparing the position of a secondary intensity peak in the diffraction pattern with a threshold position of that peak, this threshold position may differ depending on the intended use of the indicator. In particular, different threshold positions may be used depending on whether the indicator is used for sorting donor substrates, during a final inspection, or for initiating maintenance of the implantation equipment.

[0081] Of course, the invention is not limited to the described embodiments, and alternative embodiments may be introduced without departing from the scope of the invention as defined by the claims. In particular, the implantation equipment is by no means limited to equipment comprising a wheel on which a support or a plurality of supports are arranged. It may be any type of equipment capable of introducing species into a substrate to form a buried, fragile layer, thereby causing exfoliation of a layer from that substrate.

Claims

DEMANDS 1. A characterization process for determining whether a donor substrate is likely to trigger the appearance of defects in a layer exfoliated by ion implantation, the characterization process comprising: - a positioning step during which a rear face of the donor substrate is placed on a support of an implantation equipment; - an ion implantation step during which species are introduced into the donor substrate through a front face, then; - a measurement step including an X-ray diffraction analysis of an area of ​​the front face of the donor substrate, the measurement step producing numerical angle of incidence-intensity data defining a diffraction diagram; - a diffraction pattern processing step, the processing step providing an indicator quantifying the risk of triggering the appearance of defects in an exfoliated layer of the donor substrate.

2. Characterization method according to the preceding claim in which the indicator is based on the relative position, in the diffraction diagram, of at least one secondary intensity peak (P2,P3) with respect to a main intensity peak (PI).

3. Characterization method according to claim 2 wherein the indicator results from the comparison between the relative position and a predetermined threshold.

4. Characterization method according to claim 2 wherein the indicator is a numerical value representative of the relative position.

5. A characterization method according to any one of the preceding claims, wherein the diffraction pattern processing step includes the identification of the coordinates of the main intensity peak (PI) and the secondary intensity peak (P2,P3).

6. Characterization method according to the preceding claim wherein a coordinate of the secondary intensity peak (P2,P3) is representative of the difference between the angle of incidence corresponding to the secondary intensity peak (P2,P3) and the angle of incidence corresponding to the main intensity peak (PI).

7. Characterization method according to one of the two preceding claims wherein a coordinate of the secondary intensity peak (P2,P3) corresponds to the intensity of the secondary intensity peak (P2,P3) normalized by the main intensity peak (PI).

8. A characterization method according to any one of the preceding claims, wherein the processing step is implemented by a classifier configured by learning.

9. A characterization method according to any one of the preceding claims, wherein the positioning step comprises the arrangement of a plurality of donor substrates on a plurality of supports of the implantation equipment, the ion implantation step includes the introduction of species into the plurality of donor substrates, the measurement step includes the X-ray diffraction analysis of an area of ​​the front face of the donor substrates and the processing step includes the provision of a plurality of indicators respectively associated with the supports.

10. A characterization method according to any one of the preceding claims, wherein the measurement step comprises the symmetrical angular scanning of an area of ​​the front face of the donor substrate by an incident beam of monochromatic X-rays.

11. Characterization method according to the preceding claim wherein the angular deflection of the symmetrical angular scan is chosen to incorporate a primary intensity peak (PI) and a single secondary intensity peak (P2) in the diffraction pattern.

12. A characterization method according to any one of the preceding claims in which the area of ​​the front face of the donor substrate, irradiated by X-rays, is not located at the center of the donor substrate.

13. A characterization method according to any one of the preceding claims, wherein the donor substrate comprises a piezoelectric material.

14. A characterization method according to any one of the preceding claims, wherein the defects likely to develop in the donor substrate are triangular defects.

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