Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/8806—Specially adapted optical and illumination features
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P72/00—Handling or holding of wafers, substrates or devices during manufacture or treatment thereof
  • H10P72/04—Apparatus for manufacture or treatment
  • H10P72/0431—Apparatus for thermal treatment
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P72/00—Handling or holding of wafers, substrates or devices during manufacture or treatment thereof
  • H10P72/06—Apparatus for monitoring, sorting, marking, testing or measuring
  • H10P72/0604—Process monitoring, e.g. flow or thickness monitoring
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P74/00—Testing or measuring during manufacture or treatment of wafers, substrates or devices
  • H10P74/20—Testing or measuring during manufacture or treatment of wafers, substrates or devices characterised by the properties tested or measured, e.g. structural or electrical properties
  • H10P74/203—Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P90/00—Preparation of wafers not covered by a single main group of this subclass, e.g. wafer reinforcement
  • H10P90/19—Preparing inhomogeneous wafers
  • H10P90/1904—Preparing vertically inhomogeneous wafers
  • H10P90/1906—Preparing SOI wafers
  • H10P90/1914—Preparing SOI wafers using bonding
  • H10P90/1916—Preparing SOI wafers using bonding with separation or delamination along an ion implanted layer, e.g. Smart-cut
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/121—Correction signals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2201/00—Features of devices classified in G01N21/00
  • G01N2201/12—Circuits of general importance; Signal processing
  • G01N2201/127—Calibration; base line adjustment; drift compensation
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P10/00—Bonding of wafers, substrates or parts of devices
  • H10P10/12—Bonding of semiconductor wafers or semiconductor substrates to semiconductor wafers or semiconductor substrates

Definitions

• the invention relates to the field of the manufacture of microelectronics and optoelectronics structures and in particular that of the transfer of semiconductor layers capable of being used in the context of such manufacture.
• the invention thus more particularly relates to a method for monitoring embrittlement of an interface between a substrate and a layer, a method for embrittlement of such an interface, a device allowing the monitoring of embrittlement of this same interface and a system for fracturing an interface between a substrate and a layer.
• CutTM comprising an implantation step in the donor substrate to create a buried fragile interface delimiting the semiconductor layer to be transferred.
• Such a transfer requires, after the donor substrate/layer assembly has been bonded to the host substrate by said layer, fracturing between the donor substrate and the layer to be transferred at the level of the buried fragile interface.
• This fracturing is generally carried out by embrittlement annealing allowing the growth and coalescence of micro-cavities formed at said interface.
• FIG. 1 illustrates the variation in roughness along the layer after fracturing
• This variation in roughness is in particular the consequence of the differences in size of the cracks when the fracturing occurs at the scale of the wafer. It can have different sources and in particular the inhomogeneity of the implantation or of the embrittlement annealing or else the stress variations in the stack. Therefore, it would be advantageous to be able to monitor the embrittlement of the interface between the donor substrate and the layer to be transferred during the embrittlement annealing.
• tracking can be obtained by infrared microscopy. If such imaging makes it possible to obtain an image of the micro-cavities and therefore to quantify the characteristics of their population and their evolution, it is not really suitable for in-situ measurements in a fracturing furnace, in particular when the latter is of the type industrial.
• the IR radiation emitted by the plates and the oven can interfere with the IR signal used for visualization and therefore requires very powerful sources to illuminate the wafers.
• the invention aims to remedy the above drawback and thus has as its object the supply of a method for monitoring embrittlement which is compatible with the constraints of a fracturing furnace, in particular industrial, and which does not require, in particular, the installation of a lens at a short distance from the substrate/layer assembly whose interface must be monitored and from particularly powerful radiation sources.
• the invention relates for this purpose to a method for monitoring embrittlement of an interface between a layer and a substrate during embrittlement annealing of said interface, the substrate/layer assembly having at least a first and a second face, the method comprising the following steps:
• the inventors have identified that the intensity of the light scattered at a given angle with respect to the first direction is characteristic of the size of the micro-cavities and of the distance between them. Therefore, by following the variation of this intensity during an embrittlement annealing, it is possible to follow the embrittlement of the interface between the layer and the substrate.
• Such illumination and such a measurement can be carried out at a distance from the substrate/layer assembly and the method therefore has the advantage of being perfectly compatible with the constraints associated with the fracturing furnace, in particular of the industrial type.
• the method according to the invention makes it possible to carry out such monitoring from outside the enclosure of the fracturing furnace, since the light source and the detector can be arranged at a distance from the substrate assembly / layer and are compatible with the use of portholes.
• first direction corresponds to a direction of incidence of the monochromatic light beam while the second direction or directions correspond to one or more observation directions used for monitoring the fracturing.
• second direction corresponds to one or more observation directions used for monitoring the fracturing.
• the intensity can be measured along a plurality of second directions each presenting a non-zero angle with the first direction, and, preferably, at least two of said second directions can present distinct angles from each other with respect to the first direction.
• the diffusion peak linked to the cavities formed during the embrittlement of the interface can easily be identified and it is therefore easy to determine the state of embrittlement of the interface.
• the beam of light can be moved in at least two regions, or zones, of the first face.
• the monochromatic light beam may have a wavelength in the infrared wavelength range, preferably near infrared, said wavelength being even more advantageously between 1050 nm and 1550 nm.
• Such a wavelength is particularly suitable when the substrate and/or the layer is/are made of silicon, germanium or a silicon germanium alloy.
• the light beam may have a visible wavelength.
• Such an alternative is particularly suitable when the substrate and/or the layer is/are made of a wide-gap semiconductor such as galium nitride, aluminum nitride, an alloy of the two, or a silicon carbide.
• a wide-gap semiconductor such as galium nitride, aluminum nitride, an alloy of the two, or a silicon carbide.
• the invention further relates to a method for embrittlement of an interface between a layer and a substrate comprising a step of embrittlement annealing of the substrate/layer assembly in order to embrittle said interface, in which during said annealing step it is implemented an embrittlement monitoring method according to the invention.
• Such a method benefits from the advantages associated with the monitoring permitted by a monitoring method according to the invention. With such a method, it is thus easy to follow the maturation of the cavities present at the interface and to react if necessary.
• the oven heating profile can be modified in real time.
• the embrittlement annealing step can be stopped when a state of embrittlement of the interface measured by the embrittlement monitoring method reaches a given threshold, the state of embrittlement preferably corresponding to a fracturing of the interface, said fracturing then being detected by a variation in intensity along the at least one second direction and/or a displacement of the diffusion peak.
• the state of embrittlement can be chosen in such a way as to carry out the fracturing outside the furnace in which the embrittlement annealing is carried out. In this way, if the embrittlement process requires it, it will be possible to carry out billing outside the furnace.
• the annealing conditions used during the annealing step can be modified according to the embrittlement state of the interface determined during the implementation of the embrittlement monitoring method.
• the invention further relates to an interface embrittlement monitoring device for monitoring the embrittlement of an interface between a layer and a substrate during embrittlement annealing of said interface, the substrate/layer assembly having at least one first and a second face, comprising:
• an optical source capable of emitting a monochromatic light beam in the direction of the first face in a first direction
• an electromagnetic radiation detector capable of measuring an intensity of the light beam after scattering by the substrate/layer assembly, the electromagnetic radiation detector being arranged to measure said intensity of the light beam in a second direction having a non-zero angle with the first direction.
• Such a device is suitable for the implementation of a monitoring method according to the invention and therefore makes it possible to benefit from the advantages associated therewith.
• the electromagnetic radiation detector can be arranged to allow a measurement of the intensity of the light beam after scattering along a plurality of second directions each having a non-zero angle with the first direction and, preferably, at least two of said second directions have distinct angles from each other with respect to the first direction.
• such an arrangement of the electromagnetic radiation detector can be provided by the use of at least two electromagnetic radiation detection units each arranged to detect the intensity of the light beam after scattering along a respective second direction.
• the detector can thus for example take the form of a matrix of such units (or pixels) in order to allow a measurement along a plurality of second directions.
• each of these units can be provided with dedicated optics in order to allow measurement of the intensity of the light beam after scattering in the corresponding second direction.
• the embrittlement monitoring device may further comprise a processing unit configured to recover an intensity value of the light beam measured by the detector and to determine a state of embrittlement of the interface from said intensity value of the beam of light.
• Such a processing unit facilitates the use of the monitoring device according to the invention, the technician implementing the embrittlement annealing having direct access to a state of embrittlement of the interface.
• the processing unit can also be configured to, when determining the state of embrittlement of the interface, correct the measured intensity from a reference intensity determined before the embrittlement annealing.
• the invention further relates to an annealing furnace 40 capable of carrying out embrittlement annealing in order to embrittle an interface between a layer and a substrate, the furnace comprising an embrittlement monitoring device according to the invention.
• the annealing furnace may comprise a first location for the substrate/layer assembly and at least a second location for another substrate/layer assembly in order to allow simultaneous embrittlement annealing of the substrate/layer assembly and of the other assembly substrate/layer, the second location being arranged so that one face of the other substrate/layer assembly is illuminated by the light beam after the light beam has passed through the substrate/layer assembly, and the electromagnetic radiation detector also being capable of measuring an intensity of the light beam after scattering by the other substrate/layer assembly, the electromagnetic radiation detector being arranged to measure said intensity of the light beam in another second direction presenting an angle nonzero with the first direction.
• the electromagnetic radiation detector can comprise at least two detection units each dedicated to a corresponding location among the first and the second location.
• the annealing furnace can be configured so that, during the implementation of embrittlement annealing, annealing of the substrate/layer assembly is stopped when the embrittlement monitoring device determines that the state of embrittlement of the measured interface reaches a given threshold.
• the annealing furnace may comprise a control unit configured to communicate with the processing unit of the embrittlement monitoring device and to adjust the conditions of the embrittlement annealing according to the state of embrittlement provided by the embrittlement monitoring device.
• FIG. 1 illustrates a roughness map produced on a semiconductor layer after fracturing its interface with a donor substrate from which said semiconductor layer originates, a clear value corresponding to maximum roughness
• FIG. 2 illustrates an embrittlement furnace equipped with an embrittlement monitoring device according to the invention
• FIG. 3 graphically illustrates the variations in intensity of the beam scattered by a layer/substrate assembly as a function of the scattering angle obtained from the embrittlement monitoring device according to the invention measured respectively before and during embrittlement annealing;
• FIG. 4 graphically illustrates the intensity variation differential as a function of the diffusion angle calculated by subtracting the intensity measured during the embrittlement annealing from the intensity measured before the embrittlement annealing;
• FIG. 5 graphically compares the intensity of the scattered beam measured from a device according to the invention with a Fourier transform of a confocal microscopy image as implemented in the prior art.
• FIG. 2 illustrates an embrittlement furnace 40 in which an embrittlement annealing of an interface 13 is carried out between a donor substrate 11 and a layer 12, said embrittlement furnace 40 being equipped with an embrittlement monitoring device 30 according to the invention in order to allow monitoring of the weakening of said interface 13.
• the elements of the embrittlement monitoring device 30 are arranged outside the enclosure 40A of the embrittlement furnace 40, the enclosure 40A then being equipped with portholes, not illustrated, in order to allow monitoring of embrittlement by the embrittlement monitoring device 30 according to the invention.
• Such a usual configuration is in no way limiting and it is perfectly conceivable, without departing from the scope of the invention, that at least some of the elements of the embrittlement monitoring device 30 be at least partly arranged in enclosure 40A of embrittlement furnace 40.
• the substrate called the donor substrate
• the layer which is to be transferred are respectively a substrate and a layer of monocrystalline silicon Si. Therefore, the wavelengths, values, and other measurements given below and in the rest of this document are appropriate for such material.
• the invention is also particularly suitable in the context of an embrittlement of an interface between a layer and a substrate both made of germanium Ge, in a silicon-germanium alloy Si-Ge or even in a silicon carbide SiC , or even for a silicon Si substrate and a layer of silicon carbide SiC.
• the embrittlement annealing follows a step bonding said layer on a host substrate 14, the substrate 11 being the donor substrate used in the context of the transfer of the layer 12 to the host substrate 14.
• the substrate assembly 10 11/ layer 12 includes substrate 11 and layer 12, in the typical application of the invention, assembly 10 also includes the host substrate as shown in Figure 2
• Such an embrittlement monitoring device 30 comprises:
• an optical source 31 capable of emitting a monochromatic light beam 25 in the direction of the first face 10A, the wavelength of said light beam 25 being chosen so that the layer 12 and the substrates 11 or 14 are substantially transparent to said wave length,
• an electromagnetic radiation detector 32 capable of measuring an intensity of the light beam 25 after diffusion by the substrate 11/layer 12 assembly, the electromagnetic radiation detector being arranged to measure said intensity of the light beam 25 in a second direction having a non-zero angle 20 with the first direction 25A.
• such a second direction 25B for detecting a light beam 25 diffused by the substrate 11/layer 12 assembly 10 crosses the first direction 25A, along which the light beam 25 is emitted, at the level of the element diffusing at the origin of said diffusion, that is to say the substrate 11/layer 12 assembly 10 (or more precisely the interface 13 between the layer 11 and the substrate 12).
• the second direction 25B can, as illustrated in FIG. 2, extend from the second face of the support while moving away from the latter.
• the second direction 25B can extend from the first face away from the latter.
• a processing unit 33 capable of controlling the optical source and the electromagnetic radiation detector 32 in order to calibrate from the intensity measured by the electromagnetic radiation detector 32 a weakened state of the interface 13.
• the optical source 31 is a light source able to supply/emit the light beam 25 with a wavelength adapted to the transparency of the material(s) of the substrate 11 and of the layer 12.
• the wavelength of the light beam can be an infrared wavelength, preferably near infrared.
• the light beam 25 may have a wavelength of between 1050 nm and 1550 nm. and be for example equal to 1.2 ⁇ m, 1.5 ⁇ m, or 1.3 ⁇ m.
• the optical source can be a laser source, such as a semiconductor laser, laser diode; or a light emitting diode.
• the optical source 31 may comprise a system for guiding the light beam 25, such as an optical fiber, advantageously comprising a collimation system (lenses, mirrors) to define the size and divergence of the light beam after its emission. .
• the first direction 25A is preferably perpendicular to the first surface.
• first direction 25A can be envisaged without departing from the scope of the invention.
• the electromagnetic radiation detector 32 is configured to receive electromagnetic radiation in a range of wavelengths including the wavelength of the light beam 25 emitted by the optical source 31 and to supply a signal representative of the intensity of the radiation received.
• the electromagnetic radiation detector may comprise a photodetector such as a photodiode or a plurality of photodiodes organized in a matrix.
• the electromagnetic radiation detector 32 may include a CMOS or CCD sensor whose spectral response is appropriate for the source used. In such a configuration, the different photodiodes or pixels form detection units
• the electromagnetic radiation detector 32 may comprise, in addition to such a photodetector, an objective in order to concentrate the part of the light beam 25 diffused in the second direction 25B on said photodetector.
• the electromagnetic radiation detector can be arranged to receive the part of the beam diffused in a second predetermined direction 25B and selectively image the light-emitting zone.
• the second direction is chosen to correspond to a direction of interest, that is to say presenting an angle 20 of interest with respect to the first direction 25A, corresponding to a predetermined state of weakening. interface 13.
• the radiation detector 32 can comprise a plurality of optical systems each dedicated to one or to a group of respective detection units. Said optical systems each being arranged to allow a measurement of the intensity of the light beam 25 diffused by the substrate 11/layer 12 assembly 10 in a second direction 25B which is respective thereto.
• a second direction having an angle 20 of between 5 and 15°, preferably between 8 and 12° and substantially equal to 10° corresponded to a state of embrittlement of the interface 13 adapted to provide optimized fracturing.
• the inventors have in fact identified that such an angle value of 10° of the second direction 25B with respect to the first direction 25A corresponds to micro-cracks of 10 ⁇ m and to a maturity of the embrittlement of the interface 13 adapted for its fracturing.
• the electromagnetic radiation detector and its optics can be arranged to receive a part of the beam diffused in a plurality of second directions 25B, 25B′ each having a non-zero angle 20 with the first direction.
• This plurality of second directions can correspond to a range of angles 20 with the first direction corresponding to several states of embrittlement of the interface 13 of interest (thus including, for example 10° as mentioned above in the context of the first possibility).
• the electromagnetic radiation detector 32 can be arranged to be movable so as to allow a measurement of the intensity of the beam after its diffusion along a plurality of second directions 25B, 25B' each having an angle 20 not zero with the first direction.
• this plurality of second directions can correspond to an angle range 20 with the first direction corresponding to several states of weakening of the interface 13 of interest (thus including, for example 10° as mentioned above under the first possibility).
• the embrittlement tracking device 30 can be configured to move the light beam 25 into at least two locations, or regions, of the first face 10A , the detector then being arranged to allow measurement of the intensity of the light beam 25 diffused by the substrate 11/layer 12 assembly 10 in the at least one second direction 25B for said at least two regions.
• Such a possibility allows a mapping of the state of embrittlement of the interface 13 along the first face 10A.
• Such displacement of the light beam 25 can be obtained by a suitable configuration of the optical source 31, the latter being either arranged to be movable or comprising an optic, such as an optical fiber and/or an objective, that can be moved in order to allow a movement of the light beam 25.
• the electromagnetic radiation detector 31 is adapted to allow either by presenting an arrangement adapted to measure the intensity in the at least one second direction 25B for all of the measurement locations of the first face 10A, or by being movable to allow a measurement for each of these locations.
• the embrittlement furnace 40 accommodates a single substrate/layer assembly, it is perfectly possible for the embrittlement furnace 40 to be adapted to allow embrittlement annealing of a number of assemblies greater than or equal to two. According to this possibility, not illustrated, the embrittlement furnace 40 may include a first location for the substrate 11/layer 12 assembly and one or more second locations for one or more other substrate/layer assemblies in order to allow simultaneous embrittlement annealing of the the substrate 11/layer 12 assembly and the other substrate/layer assembly(ies).
• the said second location(s) are arranged so that one face of the other substrate/layer assembly(ies) is illuminated by the light beam after the latter has passed through the substrate 11/layer 12 assembly.
• electromagnetic radiation detector 32 is further able to measure an intensity of light beam 25 after scattering by the other substrate/layer assembly(ies), electromagnetic radiation detector 32 being arranged to measure said intensity of light beam 25 according to another second direction having a non-zero angle 20 with the first direction 25A.
• an electromagnetic radiation detector 32 comprising, for each location, at least one respective unit and a respective optical system dedicated to said unit.
• the embrittlement monitoring device 30 may comprise one or more other electromagnetic radiation detectors 32 in order to measure an intensity of the light beam 25 for one or more of the other substrate/layer assemblies.
• the embrittlement monitoring device 30 may further comprise a processing unit 33 configured to retrieve an intensity value of the light beam measured by the detector and to determine a state of embrittlement of the interface from said value of intensity of the light beam.
• This same processing unit can also be configured to, when determining the state of embrittlement of the interface, correct the intensity measured from a reference intensity determined before the embrittlement annealing.
• the processing unit is able to determine the state of embrittlement of the interface 13 from the intensity values measured according to the plurality of second directions 25B, 25B' and at different locations on the first face 10A.
• the optical source 31 is configured to allow movement of the light beam 25, and/or when the electromagnetic radiation detector 32 is configured to measure the intensity is in a plurality of second directions, controlling the optical source 31 and/or the electromagnetic radiation detector 32 in accordance with said possibility or possibilities.
• the processing unit can be configured to supply embrittlement furnace 40 with the state of embrittlement of interface 13 determined.
• the embrittlement furnace 40 can be configured to stop the embrittlement annealing when the state of embrittlement of the interface 13 determined by the processing unit 33 reaches a given threshold.
• the processing unit can also be configured to detect the spontaneous fracturing of the assemblies at the end of annealing.
• this event is associated with a sudden variation in the intensity and the position of the diffusion intensity which can be detected by the embrittlement monitoring device 30 according to the invention.
• the given threshold of the state of embrittlement corresponds to a fracturing of the interface 13, said fracturing being detected by a sudden variation in intensity according to at least a second direction 25B and/or a peak displacement of diffusion.
• the furnace may include a control unit configured to communicate with the processing unit of the embrittlement monitoring device and to adjust the embrittlement annealing conditions according to the state of embrittlement provided by the embrittlement monitoring device. embrittlement.
• the weakening monitoring device 30 is able to allow the implementation of a weakening monitoring method 30 comprising the following steps:
• the wavelength of the light beam 25 being chosen so that the layer 12 and the substrate 13 are substantially transparent to said wavelength
• the method is compatible with these different possibilities.
• the method according to the invention can also comprise a preliminary calibration step carried out before the embrittlement annealing comprising the following sub-steps:
• a sub-step for correcting the intensity measured from the reference intensity is then provided.
• an embrittlement monitoring device 30 and the corresponding method can be used in production in the context of monitoring a fracturing step of an interface 13 between a layer and a support, it can also be used in more specific cases such as during a calibration of an embrittlement furnace 40 within the framework of an installation or a revision of said furnace.
• the embrittlement monitoring device 30 is not necessarily integrated into said embrittlement furnace 40 and can be installed in a removable manner in order to implement the calibration step. The embrittlement monitoring device 30 can thus perfectly be removed after completion of said calibration step.
• the entire embrittlement monitoring device 30 can be installed outside the enclosure 40A of the embrittlement furnace 40, said enclosure 40A then being provided with windows transparent to incident 25A and diffused 25B light. .
• the inventors measured the variation in intensity 102, 103 of the beam of light 25 scattered as a function of the angle 20 between the second direction 25B and the first direction 25A this during embrittlement annealing of a silicon layer 12 supported by a silicon substrate 11 for two different samples, the interface 13 between said layer and said substrate having been implanted beforehand to form micro-cavities at the level of said interface 13.
• the inventors have shown in this same figure the variation in intensity 101 of the beam of light 25 diffused as a function of the angle 0 between the second direction 25B and the first direction 25A obtained on a substrate 11/layer 12 assembly 10 before embrittlement annealing, such a measurement being able to form, as discussed below in connection with FIG. 4, a reference measurement.
• the scattered light is characteristic of the size and of the distribution of the cavities at the level of the interface 13 (such a characteristic being able to be formalized on the basis of a Fraunhofer approximation).
• FIG. 4 the inventors have shown in FIG. 4 the variation of the difference between the intensity of the light beam measured 102 during embrittlement annealing and that measured 101 before annealing as a function of the angle 20 between the second direction 25B and the first direction 25A. It can be seen that the intensity of scattered light linked to the embrittlement annealing is maximum around 9°, ie a size of micro-cavities of around 8 microns.
• the inventors used a confocal microscope to obtain an infrared image of this same interface 13 which was characterized by the embrittlement monitoring device during embrittlement annealing.
• the inventors performed a Fourier transform of this image and radially averaged the image thus obtained
• FIG. 5 graphically compares the result of this Fourier transform 111 with the intensity variation as a function of twice the angle between the second direction 25B and the first direction 25A. This comparison makes it possible to show that these two techniques make it possible to obtain similar results and therefore both make it possible to characterize the state of embrittlement of the interface 13.
• the method according to the invention presents, with respect to a such confocal imaging, the advantage of not requiring the placement of an objective close to the sample and therefore of being perfectly capable of equipping a large industrial embrittlement furnace.
• the state of embrittlement of the surface determined from the method according to the invention can be, for example, provided in the form of one of the following values:

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