FR3038393A1 - FIBER OF CRYSTALLINE MATERIAL AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

The invention relates to a method for manufacturing a fiber (12) comprising a core (9) made of a crystalline material, which is remarkable in that it comprises the following steps: a step of introduction of light species into a substrate monocrystalline (1), at a main face, to form a buried fragile plane (4) and delimit a surface layer (5); - A deposition step on the surface layer (5) of a liquid filament (6) of said material by a source (7), the surface layer (5) providing a seed for the crystallization of the filament (6); the liquid filament (6) of material being continuously deposited on a virgin deposition surface of the substrate (1). - A detachment step, at the buried fragile plane (4), the crystallized filament (6) and an underlying portion of the surface layer (5) to form the core (9) of crystalline material. The invention further relates to a fiber (12) comprising a core (9) of a crystalline material, characterized in that said material is monocrystalline.

Description

FIBER OF CRYSTALLINE MATERIAL AND METHOD OF MANUFACTURING THE SAME

FIELD OF 1 / INVENTION

The present invention relates to the field of son or fibers of crystalline material.

BACKGROUND OF THE INVENTION

Optical fibers, consisting of silica cores, are mainly used for "conventional" telecommunications applications. At the same time, increasing development efforts are being made to manufacture more specific optical fibers, leading to higher performance and more functionality. The specificity of these fibers comes in particular from the materials constituting their core ("core" according to the Anglo-Saxon terminology): metals, oxides, semiconductors, amorphous or crystalline.

Although still emerging, the field of optical fibers having a crystalline semiconductor core is attracting more and more interest. One of the motivations for the use of such fibers is the ability to manufacture optoelectronic structures and possibly to develop components at the semiconductor core so as to obtain an optical system integrated in the fiber itself. Furthermore, this new category of fibers, hitherto generally based on silicon or germanium cores, opens up fields of application in the field of nonlinear optical fibers and the transmission of large windows of wavelengths (from visible at far infrared).

For some applications, the best heart will be the one with the highest crystalline quality, even a single grain all along the fiber. By way of example, an optical fiber with a monocrystalline semiconductor core can make it possible to limit the interference phenomena on the grain boundaries and to improve the quality of signal transmission. The crystalline quality of the semiconductor core of the fiber is therefore an important criterion of quality and performance.

For example, see the article "Semiconductor optical fibers: progress and opportunities" by AC Peacock, JR Sparks and N. Healy, published in "Laser Photonics Review" (8, No. 1, 53-72). , 2014), which presents the evolution of fiber optic manufacturing techniques including a core made of semiconductor material and opportunities for applications.

There are several methods for developing a crystalline semiconductor core optical fiber. Among these, one can cite a first technique, based on the high-pressure chemical vapor deposition (HPCVD for "High Pressure Chemical Vapor Deposition") of the semiconductor material in an optical fiber. silica. It is a low temperature process for depositing amorphous or polycrystalline semiconductor materials. This technique nevertheless has two major drawbacks: it is not compatible with long fiber lengths, especially because of a low deposition rate; moreover, it is not suitable for the manufacture of high quality crystalline or even monocrystalline cores.

A second technique, called "molten-core drawing method" (MCD) according to English terminology, is based on the drawing of a fiber from a solid sample of semiconductor material inside a glass tube: the assembly is heated to the glass transition temperature, which is greater than the melting point of the semiconductor material, and pulled to form the fiber comprising a semiconductor core and a glass sheath. Although very well suited to drawing long fiber lengths, this technique has three main drawbacks: firstly, the very high temperature used generates a significant oxygen diffusion in the semiconductor material, which notably limits the diameter feasible minimum of the heart; the cores currently manufactured are of the order of 100 microns and more in diameter. On the other hand, the difference in coefficient of expansion between the semiconductor and the silica, again taking into account the high temperature of the process, can cause cracking of the fiber. Finally, this technique is also not suitable for the manufacture of semiconductor core with high crystalline or even monocrystalline quality.

A third technique, called "powder-in-tube" (PIT) according to the English terminology, is based on the incorporation of the semiconductor material in powder form into a silica tube. Vacuum evacuating the oxygen from the inside of the tube, and a high temperature heat treatment (for example 1600 ° C for silicon) allows the drawing of the fiber with semiconductor core. This time again, the major disadvantage comes from the irregularities related to the low crystalline quality of the core and the non-integral interface between the core and the sheath (taking into account the differences in thermal expansion between the respective materials of the core and the sheath). ).

OBJECT OF THE INVENTION

An object of the invention is therefore to propose a method of manufacturing fibers whose core is made of crystalline material, overcoming the drawbacks of the prior art. An object of the invention is notably to propose a method of manufacturing fibers whose core is made of material of good crystalline quality, of great length and of adaptable section.

BRIEF DESCRIPTION OF THE INVENTION The invention relates to a method for manufacturing a fiber comprising a core made of a crystalline material, which is remarkable in that it comprises the following steps:

A step of introducing light species into a monocrystalline substrate, at a main surface, to form a buried fragile plane and delimit a surface layer;

A deposition step on the surface layer of a liquid filament of said material by a source, the surface layer providing a seed for the crystallization of the filament; the liquid filament of material being continuously deposited on a virgin substrate deposition surface;

A detachment step, at the buried fragile plane, of the crystallized filament and an underlying portion of the surface layer to form the core of crystalline material.

The process for manufacturing a fiber according to the invention is based on the deposition of a liquid filament of the material constituting the core of the fiber, on a monocrystalline substrate providing the seed for the crystallization of the filament: it thus makes it possible to obtain fiber cores of good crystalline quality and in particular fiber cores of monocrystalline structure. It also makes it possible to manufacture fibers of great length, the entire surface of the substrate being able to serve as crystallization nucleus for the filament.

According to advantageous features of the invention, taken alone or in combination: the monocrystalline substrate consists of said material; the monocrystalline substrate is constituted by a semiconductor material, insulating or metallic; the introduction of light species consists of implantation of hydrogen and / or helium; a step of depositing a barrier layer on the main surface of the monocrystalline substrate and a step of locally removing said barrier layer in a band of a predetermined width are carried out prior to the step of introduction of light species; the liquid filament being intended to be deposited on the main face of the substrate at said strip; the barrier layer is an oxide layer; the source comprises a crucible in which is formed the melting of said material constituting the liquid filament the source releases the liquid filament through pressurization by injection of inert gas or reducing in the crucible; the source comprises a dispensing nozzle with a diameter of between 2.5 microns and 300 microns; the liquid filament has a diameter of between 2.5 microns and 300 microns; the source and the substrate move relative to each other during the filament deposition step; the detachment step takes place step by step, after crystallization of the deposited liquid filament; the detachment step takes place step by step, simultaneously with the crystallization of the deposited liquid filament; the detachment step is followed by a step of coating the core with a sheath; the coating step is carried out by spraying, depositing or spreading an organic or inorganic material constituting said sheath; the coating step is followed by a step of winding the fiber in a winder.

The method of manufacturing a fiber according to the invention allows the manufacture of fiber cores of adaptable diameter. Furthermore, the addition of the sheath around the core can be performed at low or medium temperature (typically between 20 ° and 1000 ° C), relative to the very high temperatures used in the techniques of the state of the art (> 1400 ° C), the stresses liable to damage the fiber are significantly reduced. The invention further relates to a fiber comprising a core of crystalline material, characterized in that said material is monocrystalline.

According to advantageous features of the invention, taken alone or in combination: the crystalline material constituting the core is a semiconductor or an insulator or a metal; a dimension of the core section is between 2.5 microns and 300 microns; the heart is surrounded by a sheath; the sheath is made of an organic material, such as a polymer, a resin, an adhesive; the sheath is made of a mineral material, for example based on silica; the sheath has a thickness of between 1 micron and 300 microns.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the invention will emerge from the detailed description of the invention which will follow with reference to the appended figures in which: FIG. 1 shows a first step in the process of manufacturing a compliant fiber to the invention; FIG. 2 presents a second step of the process for manufacturing a fiber according to the invention; FIGS. 3a and 3b show a third step of the process for manufacturing a fiber according to the invention; FIG. 4 shows other steps of the process for manufacturing a fiber according to the invention; FIG. 5 shows a variant of the process for manufacturing a fiber according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a first step of the process for manufacturing a fiber 12 comprising a core 9 made of crystalline material, according to the invention. This step comprises first of all the supply of a monocrystalline substrate 1. This substrate 1 may for example be in the form of a wafer, diameter 200, 300 or 450mm and thickness for example between 300 and 800 microns. This form makes it possible in particular to access standard microelectronic equipment for possible stages of cleaning, oxidation, etching, etc. Alternatively, this substrate 1 may have a rectangular or square shape.

The first step of the process for manufacturing the fiber 12 then consists of the introduction of light species 2 into the monocrystalline substrate 1, at its main face 3. By light species 2, it is understood in particular hydrogen ions, helium, argon or a combination of these species. They may in particular be introduced by an ion implantation technique: the ion acceleration energy determines the implantation depth of species 2, the dose of introduced ions determines the concentration of species 2 at this depth. Typically, the implantation energy will be chosen to introduce the species 2 to a depth of between 100 nm and 2000 nm. With reference to document FR2681472, these light species 2 will create, at the level of the implantation depth, a buried fragile plane 4 represented in FIG. 1. The main face 3 of the substrate 1 and this buried fragile plane 4 delimit a superficial layer 5.

According to one variant, a step of cleaning the substrate 1 is carried out prior to the step of introducing the light species 2; this cleaning makes it possible to remove at least partly the hydrocarbon, particulate and / or metal contaminations present on the substrate 1. It may for example consist of a standard sequence of the CARO + RCA type, well known in the field of microelectronics for the cleaning of silicon wafers for example.

According to another variant, a cleaning step of the substrate 1 can be carried out after the step of introducing the light species 2, with the aim of eliminating the contaminations brought by the implantation step as well as improving the quality of the next step (for example by eliminating a native oxide potential at the surface). The next step of the manufacturing process is presented in FIG. 2. It consists of a deposit on the main surface 3 of the substrate 1, and therefore on the surface layer 5, of a liquid filament 6 by a source 7. The liquid filament 6 is composed of the desired material to constitute the core 9 of the fiber 12. This material may be a semiconductor material, insulating or metallic. It may for example be chosen from silicon, silicon-germanium, germanium, copper, etc. It may also be doped or enriched in different species, depending on the desired characteristics of the core 9 of fiber 12.

The source 7 may comprise a crucible in which the melting of said material is performed. The crucible may consist of a conductive material (graphite ...) or insulator (Si02, Al203 ...) electrical, whose melting temperature is greater than that of the material constituting the liquid filament 6. The crucible is heated by heating means among electromagnetic induction, resistive, convective, radiative or gas combustion. For example, the crucible is made of graphite and the heating mode is electromagnetic induction.

The source 7 also comprises a dispensing nozzle 8, for releasing the liquid filament 6 by pressurizing said material in the crucible. The pressurization is carried out by injection of gas or mixture of inert gas (s) (Ar, He ...) or reducing agent (s) (H) in the crucible. Remember that for a liquid to flow from a nozzle, there must be a pressure difference between the internal and external environments: AP = 4σ / d where o is the surface tension of the liquid (~ 0.8 Nm for silicon liquid) and d is the diameter of the nozzle.

For example, in the case of silicon with a nozzle diameter of 50 μm, a pressure difference of 6.4 × 10 4 Pa is required to release the filament; with a lpm hole, the pressure difference must be 3.2 MPa.

The dispensing nozzle 8 has a diameter of between a few microns and a few hundred microns. Advantageously, the diameter is between 2.5 and 300 microns. The adaptation of the diameter of the nozzle 8 allows the distribution of a filament 6 of adjustable diameter, which allows the manufacture of cores 9 of fiber 12 of different sections, for example between 2.5 microns and 300 microns.

The liquid filament 6, when it comes into contact with the main face 3 of the substrate 1, crystallizes by epitaxy in the liquid phase, taking up the crystalline orientation of the substrate 1: the surface layer 5 thus provides a monocrystalline seed for the crystallization of the filament 6. This makes it possible to obtain a core 9 of fiber 12, resulting from the crystallization of the deposited liquid filament 6, of monocrystalline quality throughout its length.

Advantageously, the surface of the surface layer 5 may be prepared prior to the deposition step of the filament 6, so as to confer on the surface particular hydrophilic or hydrophobic properties. For example, the strongly hydrophobic nature of the surface may allow the liquid filament 6 to maintain a more rounded shape in contact with the surface and to be less spreading on the surface. Treatment of the surface of the surface layer 5, for example by immersion in an HF solution in the case of a silicon substrate to provide the hydrophobic property, thus makes it possible to better control the shape of the section of the core 9 of the fiber 12.

During the deposition step of the filament 6, the source 7 and the substrate 1 move relative to each other, so that the liquid filament 6 is continuously deposited on a virgin substrate deposition surface 1. This relative movement can be generated by the displacement of the source 7 and / or the displacement of the substrate 1. For example, the source 7 may have a translational movement and the substrate 1 a rotational movement, so that the filament 6 is deposited according to a spiral strip.

According to a variant, the source 7 can move in translation from one edge to the other of the substrate 1, and then shift (for example by a distance of between 0.5mm to 3mm) in a direction perpendicular to the axis translation, and operate again the translational movement from one edge to the other of the substrate 1; the substrate remaining motionless. The liquid filament 6 will thus be deposited in a zig-zag band. Other variants of relative movement between the source 7 and the substrate 1 can be implemented without departing from the invention, the objective being that the filament 6 is continuously deposited on a surface of the surface layer 5, virgin deposit.

The thermal budget provided by the molten liquid filament 6, when it comes into contact with the main face 3 of the substrate 1, induces the formation and development of cavities in the buried fragile plane 4, until the separation of the layer The third step of the manufacturing method according to the invention thus consists in a detachment at the level of the buried fragile plane 4, of the assembly constituted by the crystallized filament 6 and a part of the surface layer 5. underlying the filament 6. This assembly forms the core 9 of the fiber 12. FIG. 3a illustrates this step of detaching the core 9 from the fiber 12. FIG. 3b shows a sectional view of the core 9 constituted by the filament 6 crystallized and part of the surface layer 5 of the substrate 1.

Under certain conditions, the detachment step of the core 9 of the fiber 12 at the level of the buried fragile plane 4 is carried out simultaneously with the crystallization of the filament 6. This is particularly the case where the thermal budget provided during the filing of the filament 6 in fusion corresponds to a fast regime of development kinetics of the cavities in the buried fragile plane 4. In other conditions, the detachment step of the core 9 of the fiber 12 at the buried fragile plane 4 is carried out after crystallization of the filament 6, typically between a few fractions of seconds and a few seconds later.

According to one variant, the detachment step may comprise an additional energy input with respect to the thermal budget provided during the deposition of the molten filament 6. It will be possible to mention in particular, a complementary thermal budget, making it possible to promote the development of the cavities in the buried fragile plane 4, or an external cooling to modify the kinetics of crystallization and development of the cavities, or a mechanical force to accompany or finalize the detachment at the level of the buried plane 4 weakened. The detachment step of the core 9 of the fiber 12 takes place step by step, as the liquid filament 6 is deposited and crystallized.

The characterization of the crystalline quality of the core 9 can be made by XRD (X-ray diffraction) or by Raman spectroscopy: this type of technique makes it possible to measure the mesh parameter and provides information on the distortion of the crystal lattice of a material. For example, Raman spectroscopy detection of a narrow peak, clearly defined and centered on the value 520cm_1 characteristic of silicon, shows the monocrystalline nature of the material obtained.

The process for manufacturing a fiber according to the invention may optionally include an additional step of etching the core 9. This etching step may be performed to adjust the dimensions of the core section 9 or to eliminate the peripheral layer of material, for example, can be contaminated. By way of example, this step may be carried out by wet or dry chemical method; in particular, a solution of TMAH may be used for the chemical etching of a silicon core 9.

The process for manufacturing a fiber according to the invention may also comprise one or more additional steps of f unctionalization of the core 9. By way of example, a step of doping the core 9, over a defined depth in its periphery and / or or a deposition step located on certain segments of the core 9 can easily be performed to achieve a single PN junction-type component in a silicon core.

The core 9 resting on the substrate 1 after detachment, it can be treated over its entire length by manipulation and treatment of the substrate 1.

The process for manufacturing a fiber 12 according to the invention may further comprise an additional step of coating the core 9 with a sheath 10, as shown in FIG. 4, occurring after the detachment step. The coating step can be carried out by a spraying device 11, by a deposition or spreading equipment, an organic material (for example a polymer, a resin, etc.) or a mineral material (for example SiO 2, SiON , SiN ...) constituting said sheath 10. The latter may have a thickness of between 1 micron and 300 microns. The sheath 10 can also be developed using a combination of the various techniques mentioned above. For example, the sheath 10 may consist of a first layer of 200nm deposited silicon oxide (or formed by thermal oxidation in the case of a silicon core 9), on which a second layer of 50 microns of polymer is sequentially deposited. The sheath 10 will in particular have a structural role (to ensure a better mechanical strength of the fiber 12) and a role of diffusion barrier. The key parameters for the choice of the material and the process for producing this sheath 10 are the good adhesion to the core 9 of fiber 12, the resistance to water, ultraviolet rays, etc., as well as the mechanical properties. In contrast to the techniques cited in the state of the art, the coating of the core 9 of the fiber 12 can be performed at low or medium temperatures, or even at room temperature, which prevents problems of damage to the core 9 and the sheath 10, related to the differential expansion of the two constituent materials.

The method of manufacturing a fiber according to the invention may also comprise an additional step of winding the fiber in a reel 13, occurring after the detachment step or after the coating step.

According to a first example of implementation of the invention, the monocrystalline substrate 1 is made of the same material as the material constituting the core 9 of the fiber 12. By way of example, the substrate 1 is a monocrystalline silicon substrate. It undergoes a standard RCA cleaning step prior to a step of implantation of hydrogen ions, at an energy of 70keV and a dose of 5.5e16 / cm2. The fragile buried plane 4 and the main face 3 thus define a surface layer 5, whose thickness is about 700 nm. The implanted substrate 1 also undergoes post-implantation cleaning and further comprising a surface deoxidation sequence (treatment with hydrofluoric acid) in order to remove the native oxide at the surface of the silicon substrate 1.

The source 7 of molten silicon (brought to a temperature greater than or equal to the melting point of silicon, 1414 ° C.) then deposits the liquid filament 6 on the main face 3 of the substrate 1. The very low viscosity of the silicon ( 0.75mPa / s) allows a small opening angle at the outlet of the nozzle 8, which allows better control of small diameters of filaments. For example, the dispensing nozzle 8 has a diameter for obtaining a filament of about 100 microns. In contact with the surface of the surface layer 5, the liquid filament 6 cools and crystallizes by liquid phase epitaxy on the superficial layer 5, which acts as a monocrystalline seed for the liquid filament 6. The thermal budget, provided by the filament 6 in melt, grows cavities at the buried fragile plane 4 and detachment occurs at said plane, thus separating the core 9 of the fiber 12, consisting of the crystallized filament 6 and an underlying part of the surface layer 5. The source 7 and the substrate 1 move relative to each other so as to form a spiral strip on the surface of the substrate 1. It is thus possible to form a core 9 of fiber 12 of great length and section substantially equal to 100 microns.

The core 9 is then embedded in an organic material, for example a polymer, passing in the middle of spray jets 11 of this polymer, as shown in FIG. 4. The fiber 12 thus obtained, composed of the core 9 coated by the sheath 10, is then wound in a reel 13 for storage.

After detaching the desired length of fiber core, the substrate 1 can be recycled. The entire surface layer 5 should be removed and the surface condition restored for future use. Typically, techniques of chemical etching, chemical mechanical polishing and heat treatments may be applied to result in a recycled substrate 1, suitable for reuse for the manufacture of one or more new core (s) of fiber (s).

According to a second example of implementation of the invention, the monocrystalline substrate 1 consists of a material of a different nature from that of the material constituting the core 9 of the fiber 12. Advantageously, these two materials nevertheless have the same crystalline structure . For example, the substrate 1 is a substrate of germanium or silicon monocrystalline germanium and the filament 6 is silicon. It undergoes a standard RCA cleaning step prior to a step of implantation of hydrogen ions, at an energy of 32keV and a dose of 5e16 / cm2. The fragile buried plane 4 and the main face 3 thus define a superficial layer 5 whose thickness is about 230 nm. The implanted substrate 1 also undergoes post-implantation cleaning and further comprises a sequence for removing the native oxide at the surface.

The source 7 of molten silicon is then deposited the liquid filament 6 on the main face 3 of the substrate 1. For example, the dispensing nozzle 8 has a diameter to obtain a filament of about 70 microns . In contact with the surface of the surface layer 5, the liquid filament 6 cools and crystallizes by liquid phase epitaxy on the superficial layer 5. The surface layer 5 acts as a monocrystalline seed for the liquid filament 6. Because of the difference between the germanium or the silicon germanium and the deposited silicon, the material of the filament 6 will crystallize with a deformed mesh, in tension. This type of deformation of the crystal lattice induces an increase of the electronic mobility in the material: in the present case of the core 9 of a fiber 12, a beneficial effect of this deformation on the transmission properties of the fiber 12 can be expected.

The thermal budget provided by the molten filament 6 causes cavities to grow in the buried fragile plane 4 and the detachment takes place at said plane, thus separating the core 9 from the fiber, consisting of the crystallized filament 6 and a part of the surface layer 5 underlying the filament 6. The source 7 and the substrate 1 move relative to each other so as to form a spiral strip on the surface of the substrate 1. It is thus possible to form a fiber core 9 of great length and section substantially equal to 70 microns.

The core 9 is then embedded in an organic or inorganic material by spraying, spreading, deposition or thermal growth. The fiber 12 thus obtained, composed of the core 9 coated by the sheath 10, is then wound in a reel 13 for storage.

According to a third example of implementation of the invention, the monocrystalline substrate 1 is made of the same material as the material constituting the core of the fiber. For example, the substrate 1 is a monocrystalline silicon substrate. It undergoes a step of depositing a barrier layer 20 on its main face 3, prior to the step of introduction of light species 2. The barrier layer 20 may be selected from the group consisting of SiO 2, SiN, SiON. .. and may be developed by thermal oxidation or nitriding and / or deposition (LPCVD, PECVD ...). The thickness of the barrier layer 20 is typically between 200 and 600 nm, for example 500 nm.

A local removal step of this barrier layer 20 is then performed, for example by lithography and etching, as is well known in the microelectronics field. The local removal of the barrier layer 20 is carried out according to a band 21 of a determined width, as illustrated in FIG. 5, on which the liquid filament will subsequently be deposited. By way of example, the band 21 has a width of 30 microns. This band 21, without a barrier layer 20, may take the form of a spiral or a zig-zag on the main surface 3 of the substrate 1. The introduction of light species 2 is then made, for example by co implantation of hydrogen and helium ions at an energy of 40keV and 20keV respectively and a dose of 2e16 / cm2 and le16 / cm2, respectively. At the level of the band 21 without a barrier layer 20, the buried fragile plane 4, formed by the implanted species 2, and the main face 3 define a surface layer 5, whose thickness is about 400 nm. In the regions comprising the barrier layer 20, the species 2 stop in the barrier layer and therefore do not form a brittle buried plane 4 in the substrate 1.

The implanted substrate 1 undergoes post-implantation cleaning and furthermore comprises a short wet or dry deoxidation sequence of the surface, making it possible to remove the native oxide on the surface of the silicon substrate 1 (ie that is to say at the level of the strip 21 devoid of a barrier layer 20). The hydrophobic nature of the surface of the substrate 1, at the level of the strip 21, will also limit the lateral spreading of the filament 6 and promote crystallization in a rounded shape.

The source 7 of molten silicon then deposits the liquid filament 6 on said strip 21 on the main face 3 of the substrate 1. For example, the dispensing nozzle 8 has a diameter enabling a filament to be obtained. about 30 microns. In contact with the surface of the superficial layer 5, the liquid filament 6 cools and crystallizes by liquid phase epitaxy on the superficial layer 5 which acts as a monocrystalline seed for the liquid filament 6. The thermal budget provided makes cavities grow at level of the buried fragile plane 4 and the detachment takes place at said plane, thus separating the core 9 of the fiber 12, consisting of the crystallized filament 6 and the underlying surface layer 5. The source 7 and the substrate 1 move relative to each other so as to deposit the filament 6 on the strip 21 devoid of barrier layer 20. It is thus possible to form a heart 9 of long fiber and of section substantially equal to 30 microns.

The definition of a band of controlled width, serving as crystal seed filament 6 advantageously allows sections and shapes of the core 9 of the fiber 12 smaller and more controlled.

The core 9 is then embedded in an organic material, for example a polymer, passing in the middle of spray jets 11 of this polymer. The fiber 12 thus obtained, composed of the core 9 coated by the sheath 10, is then wound in a reel 13 for storage.

According to a fourth example of implementation of the invention, the monocrystalline substrate 1 is made of the same material as the material constituting the core of the fiber. By way of example, the substrate 1 is a monocrystalline germanium substrate. It undergoes a step of implantation of hydrogen ions, at an energy of 70keV and a dose of 5e16 / cm2. The fragile buried plane 4 and the main face 3 thus define a superficial layer 5 whose thickness is about 500 nm. The implanted substrate 1 also undergoes post-implantation cleaning and further comprises a surface deoxidation sequence (by wet or dry etching) to remove the native oxide at the surface.

The molten germanium source (brought to a temperature greater than or equal to the germanium melting temperature, 938 ° C.) then deposits the liquid filament 6 on the main face 3 of the substrate 1. For example, the nozzle 8 has a diameter for obtaining a filament of about 150 microns. In contact with the surface of the surface layer 5, the liquid filament 6 cools and crystallizes by liquid phase epitaxy on the superficial layer 5, which acts as a monocrystalline seed. The thermal budget provided makes cavities grow at the level of the buried fragile plane 4 and the detachment takes place in a fraction of a second at said plane, thus separating the core 9 from the fiber 12, consisting of the crystallized filament 6 and the part underlying the superficial layer 5.

The source 7 and the substrate 1 move relative to each other so as to form a spiral strip on the surface of the substrate 1. It is thus possible to form a fiber core 9 of great length and section substantially equal to 150 microns.

The core 9 is then embedded in an organic material, for example a polymer or an adhesive, by passing in the middle of spray jets 11 of this polymer or this adhesive. The fiber 12 thus obtained, composed of the core 9 coated by the sheath 10, is then wound in a reel 13 for storage.

After detaching the desired length of core 9 from the fiber, the substrate 1 can be recycled. The entire surface layer is removed and the surface condition restored for future use. Typically, techniques of chemical etching, chemical mechanical polishing and heat treatments may be applied to result in a recycled substrate 1, suitable for reuse for the manufacture of one or more new core (s) of fiber (s).

Of course, the invention is not limited to the embodiments described and variations can be made without departing from the scope of the invention as defined by the claims.

Claims (19)

1. A method of manufacturing a fiber (12) comprising a core (9) made of a crystalline material, characterized in that it comprises the following steps: • A step of introducing light species (2) into a substrate monocrystalline (1), at a main face (3), to form a buried fragile plane (4) and delimit a surface layer (5); A deposition step on the surface layer (5) of a liquid filament (6) of said material by a source (7), the surface layer (5) providing a seed for the crystallization of the filament (6); the liquid filament (6) of material being continuously deposited on a virgin deposition surface of the substrate (1). • A detachment step, at the buried fragile plane (4), the crystallized filament (6) and an underlying portion of the surface layer (5) to form the heart (9) of crystalline material. 2. A method of manufacturing a fiber (12) according to the preceding claim, wherein the monocrystalline substrate (1) is made of said material. 3. A method of manufacturing a fiber (12) according to one of the preceding claims, wherein the introduction of light species (2) consists of implantation of hydrogen and / or helium. 4. A method of manufacturing a fiber (12) according to one of the preceding claims, wherein a step of depositing a barrier layer (20) on the main face (3) of the single crystal substrate (1) and a step local removal of said barrier layer (20) in a band (21) of a predetermined width are carried out prior to the step of introduction of light species (2); the liquid filament (6) being intended to be deposited on the main face (3) of the substrate (2) at the level of said strip (21). 5. A method of manufacturing a fiber (12) according to the preceding claim, wherein the barrier layer (20) is an oxide layer. 6. A method of manufacturing a fiber (12) according to one of the preceding claims, wherein the liquid filament (6) has a diameter between 2.5 microns and 300 microns. 7. A method of manufacturing a fiber (12) according to one of the preceding claims, wherein the source (7) and the substrate (1) move relative to each other during the deposition step filament (6). 8. A method of manufacturing a fiber (12) according to one of the preceding claims, wherein the detachment step operates step by step, after crystallization of the liquid filament (6) deposited. 9. A method of manufacturing a fiber (12) according to one of claims 1 to 7, wherein the detachment step is carried out step by step, simultaneously with the crystallization of the liquid filament (6) deposited. 10. A method of manufacturing a fiber (12) according to one of the preceding claims, wherein the detachment step is followed by a step of coating the core (9) with a sheath (10). 11. A method of manufacturing a fiber (12) according to the preceding claim, wherein the coating step is carried out by spraying, depositing or spreading an organic or inorganic material constituting said sheath (10). 12. A method of manufacturing a fiber (12) according to one of the two preceding claims, wherein the coating step is followed by a step of winding the fiber (12) in a winder (13). . 13. Fiber (12) comprising a core (9) of a crystalline material, characterized in that said material is monocrystalline. 14. Fiber (12) according to the preceding claim, wherein the crystalline material constituting the core (9) is a semiconductor or an insulator or a metal. 15. Fiber (12) according to one of the two preceding claims, wherein a dimension of the core section (9) is between 2.5 microns and 300 microns. 16. Fiber (12) according to one of claims 13 to 15, wherein the core (9) is surrounded by a sheath (10). 17. Fiber (12) according to the preceding claim, wherein the sheath (10) is made of an organic material, such as a polymer, a resin or an adhesive. 18. Fiber (12) according to claim 16, wherein the sheath (10) is made of a mineral material, for example based on silica. 19. Fiber (12) according to one of claims 16 to 18, wherein the sheath (10) has a thickness between 1 micron and 300 microns.