METHOD FOR MANUFACTURING A PHOTONIC DEVICE PROVIDED WITH AT LEAST TWO PHOTONIC CHIPS AND PHOTONIC DEVICE - Patent application

Abstract

The invention relates to a method for manufacturing a device (100), comprising the steps of: a) providing a structure comprising a layer (300) on a final substrate (200), the layer (300) comprising a first guide (330) and a second guide (340) and a grating (341), the first and second waveguides being spaced apart from the coupling surface by a first distance D1 and a second distance D2, respectively, greater than D1; and b) providing a structure comprising a first photonic stack and a second photonic stack, respectively, on the coupling surface (320). and c) transferring at least one first block (510) and at least one second block (520) formed on the first and second blocks (510, 520); and c) forming a first component (610) and a second component (620) from the first block (510) and the second block (520), respectively, the first component (610) and the second component (620) being evanescently or adiabatically coupled to the first waveguide and coupled to the second waveguide via a grating, respectively.

Description

[Technical field]

[0001] The field of the invention is that of integrated photonic components. More particularly, the invention relates to the problem of optical coupling of photonic components in a photonic device. In particular, the invention proposes a method for co-integrating and optically coupling several photonic components on a device. In particular, the invention proposes a method that allows the integration of two photonic components in a device according to two different coupling modes. [Background technology]

[0002] The co-integration of photonic components with microelectronic devices has grown significantly over the past two decades, especially to meet new needs in the fields of communications and quantum optics.

[0003] In fact, these photonic components, generally made of III-V semiconductor materials, whose performance no longer needs to be proven, can be integrated directly on a silicon substrate or a support supporting a microelectronic device to form a monolithic device, in particular, their integration implementing proven techniques of the microelectronics industry such as bonding, polishing and even etching steps.

[0004] However, communication between photonic and microelectronic components of the same device requires the formation of optical coupling and / or guidance means for optical radiation that can be emitted or received by the photonic component.

[0005] In this regard, depending on the application in question or the nature of the photonic components, different types of optical coupling can be considered: among the latter, mention can be made of surface coupling, coupling by evanescent or adiabatic waves, and finally butt coupling.

[0006] Thus, FIG. 1 shows FIG. 2 of the non-patent document 1 of this specification, but of a surface bond (called the “bottom” bond) between a silicon waveguide GO1 and a photodetector PD1 made of III-V semiconductor materials.

[0007] In particular, in this FIG. 1, a waveguide GO1 encapsulated in an encapsulation layer CE1 (made of "BCB" resin) is terminated according to one of its ends by a grating coupler RC1.

[0008] The photodetector PD1 is mounted by its photosensitive surface on the encapsulation layer in alignment with the grating coupler RC1. Such an arrangement allows the radiation guided by the waveguide GO1, when it reaches the grating coupler RC1, to be transmitted to the photodetector PD1 by its photosensitive surface (or more generally by its coupling surface). Such a coupling mode allows to take into account media with different refractive indices. More specifically, the coupling surfaces of the grating coupler RC1 and the photodetector PD1 may be made of materials with different refractive indices.

[0009] Non-Patent Document 2 of this specification proposes a photonic device in which an avalanche photodiode (APD) is provided that is optically coupled to a waveguide made of silicon by evanescent or adiabatic waves (FIG. 2, which reproduces FIG. 2(a) of Non-Patent Document 2). For this purpose, the avalanche photodiode is positioned perpendicular to and close to the waveguide so as to enable effective coupling.

[0010] Finally, as described in Non-Patent Document 3 of this specification, butt coupling implements coupling on one side or outer surface SL3 of the photonic component PD3 in question. In particular, as shown in Figure 3 (Figure 2(a) of Non-Patent Document 3), the photonic component DP3 is configured to receive optical radiation guided by a waveguide G03.

[0011] No. 6,299,933, filed on Nov. 23, 2003, discloses a method for designing an adiabatic converter between two waveguides.

[0012] US Pat. No. 5,399,943 hereby proposes implementing optical coupling by means of a grating coupler between the waveguide and the sensor.

[0013] Therefore, each of the above mentioned couplings is implemented to meet the specific characteristics of the photonic component, more specifically its specificity regarding its shape and / or function, whereby the consideration of the integration of different types of photonic components may involve different optical coupling modes from one component to another.

[0014] However, each coupling mode meets very precise criteria. In particular, surface coupling generally requires a minimum distance of at least 200 nm between the grating coupler and the photonic component to avoid coupling by evanescent or adiabatic waves. Furthermore, the coupling surface generally has a non-zero reflection coefficient that is likely to limit the efficiency of the coupling between the waveguide and the photonic component. Indeed, radiation from the waveguide, coupled to the photonic component via the grating coupler, is likely to be at least partially reflected by the coupling surface and reinjected into the waveguide.

[0015] On the other hand, coupling by evanescent or adiabatic waves requires close proximity between the photonic component and the waveguide to which it is optically coupled, in particular a distance of 150 nm or less, and furthermore this coupling also implies that the refractive indices of the materials forming the waveguide and the photonic component are close.

[0016] In other words, taking into account surface coupling and evanescent or adiabatic wave coupling within a photonic device for two different photonic components makes the method of manufacturing said device more complicated, in particular this added complexity is characterized by an increase in the number of steps to form and / or transfer the components.

[0017] Therefore, one object of the invention is to propose a method for manufacturing a photonic device implementing evanescent wave coupling or adiabatic wave coupling and surface coupling with a first photonic component and a second photonic component, respectively.

[0018] Another object of the invention is also to propose a method for improving surface bonding. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] European Patent Application Publication No. 3764136 [Patent Document 2] US Patent Application Publication No. 2004 / 081399 [Non-patent literature]

[0020] [Non-Patent Document 1] G. Roelkens, J. Brouckaert, D. Taillaert, P. Dumon, W. Bogaerts, D. Van Thourhout, R. Baets, R. Notzel, and M. Smit, “Integration of InP / InGaAsP photodetectors onto silicon-on-insulator waveguide circuits”, Opt. Express 13, 10102-10108 (2005) [Non-Patent Document 2] Zhihong Huang, Cheng Li, Di Liang, Kunzhi Yu, Charles Santori, Marco Fiorentino, Wayne Sorin, Samuel Palermo, and Raymond G. Beausoleil, “25 Gbps low-voltage waveguide Si-Ge avalanche photodiode”, Optica 3, 793-798 (2016) [Non-Patent Document 3] L.Vivien, et al., “Zero-bias 40Gbit / s germanium waveguide photodetector on Silicon”, Optics Express, vol.20.(2), Nov.2011 [Non-Patent Document 4] Liu, J.-J., et al., “The Fabrication and Characterization of InAlAs / InGaAs APDs Based on Mesa-Structure with Polyimide Passivation”, Sensors 2019, 19, 3399 Summary of the Invention

[0021] The object of the present invention is achieved, at least in part, by a method for manufacturing a photonic device, the method comprising the following successive steps: a) providing a support structure comprising a bonding layer provided with a bonding surface and an assembly surface opposite the bonding surface, the bonding layer being placed by its assembly surface on a main surface of the final substrate, the bonding layer comprising at least one first waveguide and at least one second waveguide, the at least one second waveguide being terminated at one of its ends by a first grating coupler, the first waveguide comprising a monocrystalline material, the first and second waveguides being respectively spaced from the bonding surface by a first distance D1 and a second distance D2 greater than the first distance D1, advantageously the first distance D1 being less than 150 nm and the second distance D2 being greater than 200 nm, the provision of the support structure comprising forming the bonding layer from a semiconductor-on-insulator substrate and then transferring the bonding layer onto the main surface of the final substrate; b) transferring at least a first block and at least one second block made from a first photonic stack and a second photonic stack, respectively, onto the bonding surface; c) forming a first photonic component and a second photonic component from the first block and the second block, respectively, wherein the first photonic component and the second photonic component are optically coupled, evanescently or adiabatically, to at least one first waveguide and via a first grating coupler to at least one second waveguide, respectively.

[0022] According to one embodiment, the semiconductor-on-insulator substrate comprises, from the back surface towards the front surface, an initial substrate, a buried oxide layer and a semiconductor layer, the buried oxide layer forming part of the bonding layer and advantageously having a thickness equal to the first distance D1.

[0023] According to one embodiment, the formation of the bonding layer comprises a substep a1) of partially etching the semiconductor layer so as to form at least one first waveguide.

[0024] According to one embodiment, the formation of the bonding layer comprises a substep a2) of forming a first sheath layer, advantageously made of silicon dioxide, overlapping the front surface of the semiconductor-on-insulator substrate and intended to encapsulate the first waveguide.

[0025] According to one embodiment, the formation of the coupling layer comprises a substep a3) of forming a second waveguide and a first grating coupler on the first sheath layer, advantageously the thickness of the first sheath layer being adjusted so that the second waveguide and the first grating coupler are at a distance equal to a second distance D2 from the interface formed between the initial substrate and the buried oxide layer.

[0026] According to one embodiment, the formation of the bonding layer comprises a substep a4) of forming a second sheath layer, advantageously made of silicon dioxide, overlapping the first sheath layer and intended to encapsulate the second waveguide and the first grating coupler.

[0027] According to one embodiment, the transfer of the bonding layer comprises assembly of the assembly surface with a main surface of the final substrate and then removal of the initial substrate to transfer the bonding layer onto the main surface, the removal of the initial substrate advantageously comprising mechanical thinning.

[0028] According to one embodiment, step b) comprises the following sub-steps: b11) forming a first photonic stack by epitaxy on one face, called the seed face, of a first seed substrate; b12) cutting to form first areas, each of the first areas comprising a first portion of a first seed substrate on which a first piece formed from the first photonic stack is to be placed; b13) assembling the first piece onto the mating surface; b14) removing the first portion at the end of step c13) so as to transfer the first piece onto the bonding surface.

[0029] Similarly, the formation of the second stack on the bonding surface comprises the following steps: c21) forming a second photonic stack by epitaxy on one face, called the seed face, of a second seed substrate; c22) cutting to form second areas, each of the second areas comprising a second portion of a second seed substrate on which a second piece formed from the second photonic stack is to be placed; c23) assembling a second piece onto the mating surface; and c24) removing the second portion at the end of step c23) so as to transfer the second piece onto the bonding surface.

[0030] According to one embodiment, step b) comprises the following sub-steps: b21) forming a second photonic stack by epitaxy on one face, called the seed face, of a second seed substrate; b22) cutting to form second areas, each of the second areas comprising a second portion of a second seed substrate on which a second piece formed from the second photonic stack is to be placed; b23) assembling a second piece to the mating surface; b24) removing the second portion at the end of step c23) so as to transfer the second piece onto the bonding surface.

[0031] According to one embodiment, the first photonic stack and the second photonic stack each comprise a stack of quantum wells sandwiched between a lower layer and an upper layer, the lower layer resting on a coupling layer.

[0032] According to one embodiment, the first photonic stack and the second photonic stack are formed by epitaxy before being transferred to the bonding surface.

[0033] According to one embodiment, the at least one first photonic component includes a laser.

[0034] According to one embodiment, the at least one second photonic component comprises an avalanche photodiode, and advantageously, the interface formed between the second photonic stack and the bonding layer is devoid of an anti-reflection layer.

[0035] According to one embodiment, a reflective element is formed in the coupling layer and arranged such that the first grating coupler is sandwiched between the reflective element and the at least one second photonic component.

[0036] According to one embodiment, the second waveguide is also terminated at its other end by a second grating coupler arranged to enable injection of optical radiation from the coupling surface into the second waveguide.

[0037] According to one embodiment, another reflective element is formed in the coupling layer and a second grating coupler is positioned to be sandwiched between the reflective element and the coupling surface.

[0038] The present invention also relates to a photonic device, the photonic device comprising: a final substrate provided with a main surface; a bonding layer comprising a bonding surface and an assembly surface opposite the bonding surface, the bonding layer being placed by its assembly surface on a main surface of a final substrate, the bonding layer comprising at least one first waveguide and at least one second waveguide, the at least one second waveguide being terminated at one of its ends by a first grating coupler, the first waveguide comprising a monocrystalline material, the first and second waveguides being respectively spaced apart from the bonding surface by a first distance D1 and a second distance D2 greater than the first distance D1, advantageously the first distance D1 being less than 150 nm and the second distance D2 being greater than 200 nm; and a first photonic component and a second photonic component formed from the first photonic stack and the second photonic stack, respectively, the first photonic component and the second photonic component being optically coupled, evanescently or adiabatically, to at least one first waveguide and to at least one second waveguide via a first grating coupler, respectively.

[0039] According to one embodiment, the second photonic component comprises an avalanche photodiode, advantageously the interface formed between the second photonic stack and the bonding layer is devoid of an anti-reflection layer.

[0040] According to one embodiment, the second waveguide is also terminated at its other end by a second grating coupler, the second grating coupler being arranged to enable injection of optical radiation from the coupling surface into the second waveguide.

[0041] According to one embodiment, the device further comprises a reflective element formed in the coupling layer, the first grating coupler being arranged such that it is sandwiched between the reflective element and the at least one second photonic component. [Brief description of the drawings]

[0042] Other features and advantages of the present invention will become apparent from the following detailed description of the invention which refers to the accompanying drawings. [Figure 1] FIG. 1 is a perspective view of surface coupling of a waveguide terminated by a first grating coupler and a photodetector, taken from the non-patent document 1 herein. [Diagram 2] FIG. 1 is a perspective view of evanescent wave coupling or adiabatic wave coupling between an avalanche photodiode and a waveguide, taken from Non-Patent Document 2 of this specification. [Diagram 3] 2(a) of the present specification, which in particular represents in a perspective view a butt coupling between a photonic device and a waveguide, as known from the prior art. [Figure 4] FIG. 2 is a schematic view along a section perpendicular to its main face of a support structure provided during step a) of the method according to the invention. [Diagram 5] 5 is a schematic representation of the support structure of FIG 4 according to another section perpendicular to its main face and including the elongation axis of the second waveguide. FIG 5 makes it possible in particular to show the grating couplers which terminate the second waveguide by each of its ends. [Figure 6] 1 is a schematic diagram of a semiconductor-on-insulator substrate that can be implemented for the formation of a bonding layer. [Figure 7] FIG. 7 is a schematic illustration of sub-step a1) of forming a first waveguide on the semiconductor-on-insulator substrate of FIG. 6. [Figure 8] FIG. 3 shows a schematic representation of substep a2) of forming a first layer intended to overlie the front side of the semiconductor-on-insulator substrate and encapsulate the first waveguide 330. [Figure 9]FIG. 13 is a schematic diagram of sub-step a3) of forming a second waveguide and a first grating coupler on the first sheath layer. [Figure 10a] FIG. 4 is a schematic illustration of substep a4) of forming a second layer overlapping the first sheath layer and intended to encapsulate the second waveguide and the first grating coupler. [Figure 10b] FIG. 2 is a schematic illustration of substep a4) of forming a second layer overlapping the first sheath layer and intended to encapsulate the second waveguide and the first grating coupler; step a4) in the context of this figure also includes the formation of two reflecting elements. [Figure 11] 1 is a schematic diagram showing the step of assembling the assembly surface of the bonding layer with a major surface of the final substrate. [Figure 12] FIG. 12 is a schematic diagram of the step of removing the initial substrate after carrying out the assembly shown in FIG. 11 so as to transfer a bonding layer onto the main surface of the final substrate. [Figure 13] FIG. 13 is a schematic diagram of a step of transferring a first block and a second block onto a bonding surface. [Figure 14] 1 is a photograph of a first block and a second block transferred onto a bonding surface, taken from the bonding surface. [Figure 15] FIG. 2 shows a schematic view along a cross section perpendicular to a main surface of a support structure on which a first photonic component and a second photonic component are formed at the end of the execution of step c). [Figure 16] FIG. 1 is a schematic diagram of a support structure on which a first photonic component and a second photonic component are formed, the first photonic component and the second photonic component being encapsulated by an encapsulation layer, along a cross section perpendicular to a main surface. [Figure 17] FIG. 2 is a schematic view taken along a cross section perpendicular to a major surface, showing electrical contacts that allow electrical control of the first and second photonic components. [Figure 18] FIG. 2 is a schematic diagram illustrating coupling between a second photonic component and a first grating coupler. [Figure 19]FIG. 2 is a schematic diagram of a first photonic component in adiabatic / evanescent coupling along a cross section parallel to the plane (0,y,z). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] The present invention relates to a method for manufacturing a photonic device. In particular, the method according to the invention makes it possible to consider the integration in the same photonic device of several photonic components coupled to said device in different ways.

[0044] In particular, the invention allows for the integration within a photonic device of a first photonic component that is evanescently or adiabatically coupled to the device and a second photonic component that is coupled to the device by a grating coupler.

[0045] For this purpose, the method according to the invention comprises the following successive steps: a) providing a support structure comprising a bonding layer provided with a bonding surface and an assembly surface opposite the bonding surface, the bonding layer being placed by its assembly surface on a main surface of the final substrate, the bonding layer comprising at least one first waveguide and at least one second waveguide, the at least one second waveguide being terminated at one of its ends by a first grating coupler, the first waveguide and the grating coupler comprising a single crystal material, the first waveguide and the second waveguide being spaced from the bonding surface by a first distance D1 and a second distance D2 greater than the first distance D1, respectively, the providing of the support structure comprising forming the bonding layer from a semiconductor-on-insulator substrate and then transferring the bonding layer onto the main surface of the final substrate; b) transferring at least a first block and at least a second block made of a first photonic stack and a second photonic stack, respectively, onto the bonding surface; c) forming a first photonic component and a second photonic component from the first block and the second block, respectively, wherein the first photonic component and the second photonic component are optically coupled, respectively, evanescently or adiabatically to at least one first waveguide and to at least one second waveguide via a grating coupler.

[0046] FIG. 4 thus shows, in an orthonormal reference coordinate system (x,y,z), the support structure provided during the execution of step a).

[0047] In particular, the support structure comprises a final substrate 200 provided with a main surface 210, on which a bonding layer 300 is placed via its assembly surface 310. The bonding layer 300 also comprises a bonding surface 320 opposite the assembly surface 310.

[0048] In the description, unless stated otherwise, the surfaces and layers extend parallel to the plane (x,y) and are therefore perpendicular to the direction z.

[0049] The final substrate 200 may include any type of material. In particular, the final substrate 200 may include a semiconductor material. In this regard, the semiconductor material may include silicon, aluminum nitride, germanium, or a silicon germanium alloy.

[0050] Alternatively, the final substrate 200 may comprise an insulating material. For example, the insulating material may comprise glass.

[0051] The coupling layer 300 comprises at least a first waveguide 330 and at least a second waveguide 340. In particular, the first waveguide 330 is spaced a first distance D1 from the coupling surface 320. Similarly, the second waveguide 340 is spaced a second distance D2 from the coupling surface 320 that is greater than the first distance D1 (FIGS. 4 and 5).

[0052] It will be appreciated that the first waveguide 330 and the second waveguide 340 each extend in a plane parallel to the plane (x,y) and therefore remain at a constant distance from the coupling surface 320 .

[0053] It is also understood that the first waveguide 330 and the second waveguide 340 do not necessarily extend in the same direction.

[0054] The second waveguide 340 is terminated at one of its ends 340a by a first optical grating coupler 341 (FIG. 5). The first optical grating coupler 341 may be made of the same material as the first waveguide 340. It will also be understood that the first grating coupler 340 is also spaced a second distance D2 from the coupling surface 320, although this need not be specified.

[0055] Similarly, the second waveguide 340 may be terminated by a second optical grating coupler 342 at another of its ends 340b (FIG. 5). The second optical grating coupler 342 may be made of the same material as the second waveguide 340. It is understood that the second grating coupler 342 is also spaced a second distance D2 from the coupling surface 320, but this need not be specified. Alternatively, the second waveguide is terminated for the coupler by an edge surface at its other end. In the context of the present invention, the edge surface is defined as an outer contour connecting the assembly surface and the coupling surface.

[0056] Also, throughout this disclosure, a mere reference to the second waveguide 340 refers not only to that second waveguide, but also to the first grating coupler, and if the latter is considered, also to the second grating coupler.

[0057] The first waveguide 330 comprises a single crystal material, more specifically, single crystal silicon.

[0058] Advantageously, the second waveguide 340 may comprise silicon nitride, although the invention is not limited to implementation with only this material.

[0059] The step a) of providing a support structure comprises: forming a bonding layer 300 from a semiconductor-on-insulator substrate 400; - transferring the bonding layer 300 onto the main surface 210 of the final substrate 200.

[0060] 6, the semiconductor-on-insulator substrate 400 comprises, from the rear surface 410 to the front surface 420, an initial substrate 430, a buried oxide layer 440, and a semiconductor layer 450. The semiconductor layer comprises a single crystal material.

[0061] It will become apparent below that buried oxide layer 440 is intended to form, at least in part, bonding layer 300 .

[0062] Furthermore, the buried oxide layer 440 may advantageously have a thickness equal to the first distance D1.

[0063] The initial substrate 430 may include a semiconducting material, an insulating material, or a conducting material.

[0064] In particular, the initial substrate 430 may include silicon.

[0065] The buried oxide layer 440 may include silicon dioxide.

[0066] The semiconductor layer 450 may include silicon.

[0067] However, the invention should not be limited to only these materials, and one skilled in the art may implement any other materials that may be suitable depending on the intended application.

[0068] The formation of the bonding layer 300 from the semiconductor-on-insulator substrate 400 comprises the following sub-steps: a substep a1) of partially etching the semiconductor layer 450 so as to form at least one first waveguide 330 (FIG. 7), a substep a2) (FIG. 8) of forming a first sheath layer 360 by overlapping it on the front surface 420 of the semiconductor-on-insulator substrate 400 and intended to encapsulate the first waveguide 330, the first sheath layer for example comprising SiO2; a substep a3) (FIG. 9) of forming the second waveguide 340 and the first grating coupler 341 (and the second grating coupler 342, if considered) on the first sheath layer 360; - Substep a4) (Fig. 10a) of forming a second sheath layer 370 overlapping the first sheath layer 360 and intended to encapsulate the second waveguide 330 and the first grating coupler 340. The second sheath layer 370 may, for example, comprise SiO2.

[0069] Sub-step a1) may implement a combination of photolithography and etching steps, in particular a photolithography step making it possible to define a pattern, more particularly a pattern associated with the first waveguide 330, on the semiconductor layer 450, and an etching step making it possible to form said first waveguide 330 from the pattern defined during the photolithography step. These aspects are well known to the person skilled in the art and will not be detailed in the present invention.

[0070] The formation of the first sheath layer 360 during the execution of sub-step a2) can implement a technique for depositing layers. In particular, the first sheath layer 360 can be deposited by a chemical vapor deposition ("CVD") technique, more particularly a low-pressure chemical vapor deposition ("LPVCD") technique, or a plasma-enhanced chemical vapor deposition ("PEVCD") technique. Alternatively, the first sheath layer 360 can be deposited by a physical vapor deposition (PVD) technique.

[0071] Finally, this substep a2) can also implement a polishing (in particular a chemical-mechanical polishing) aimed at adjusting the thickness of the first sheath layer 360.

[0072] The first sheath layer 360 may include silicon dioxide.

[0073] The formation of the second waveguide 340 during sub-step a3) may implement a combination of layer deposition, photolithography and etching steps.

[0074] In particular, the formation of the second waveguide 340 may first include the formation of a guiding layer overlying the first sheath layer 360. The guiding layer may be deposited by an evaporation technique, more particularly a low pressure evaporation technique or a plasma activated gas phase deposition technique. Alternatively, the guiding layer may be deposited by a physical vapor deposition technique. The guiding layer advantageously comprises silicon nitride.

[0075] A photolithography step is then performed in order to define a pattern, more specifically that of the second waveguide 340, on the guiding layer. Finally, the implementation of an etching step makes it possible to form the second waveguide 340 from the pattern defined during the photolithography step. These aspects are well known to those skilled in the art and will not be detailed in the present invention.

[0076] It is understood that the execution of sub-step a3) also results in the formation of the first grating coupler 341 and the second grating coupler 342 from the guide layer. In other words, the second waveguide 340, the first grating coupler 341 and the second grating coupler 342 are mounted on the first sheath layer 360 and are made of the same material.

[0077] Finally, the formation of the second sheath layer 370 during the execution of sub-step a4) can implement a technique for depositing layers. In particular, the second sheath layer may be deposited by a deposition technique, more particularly a low pressure deposition technique, or a plasma activated vapor phase deposition technique. Alternatively, the second sheath layer 370 may be deposited by a physical vapor deposition technique.

[0078] Finally, this substep a4) can also implement a polishing (in particular a chemical-mechanical polishing) intended to adjust the thickness of the second sheath layer 370.

[0079] The second sheath layer 370 may include silicon dioxide.

[0080] Thereby, at the end of the execution of the sub-steps a1) to a4), a bonding layer 300 is obtained. The bonding layer 300 comprises, in particular, from its bonding surface to its assembly surface, a buried oxide layer 440, a first sheath layer 360 and a second sheath layer 370. The bonding layer 300 also comprises a first waveguide 330 and a second waveguide 340. In particular, the first waveguide 330 is sandwiched between the buried oxide layer 440 and the first sheath layer 360, while the second waveguide 340 is sandwiched between the first sheath layer 360 and the second sheath layer 370.

[0081] The thickness of the buried oxide layer 440 and the first sheath layer 360 allows adjusting the first distance D1 and the second distance D2.

[0082] This allows the bonding layer 300 on the initial substrate to be transferred onto the main surface 210 of the final substrate 200 .

[0083] This transfer in particular involves the assembly of an assembly surface of the bonding layer 300 with the main surface 210 of the final substrate 200 (FIG. 11). The assembly can in particular involve molecular bonding, without limiting the invention to this embodiment only.

[0084] Assembly can be followed by a step of removing the initial substrate 430 so as to transfer the bonding layer 300 onto the major surface 210 (FIG. 12). Removal of the initial substrate 430 can include mechanical thinning, chemical attack, or a combination of both.

[0085] The method according to the present invention also includes a step b) of transferring (by assembly, more specifically by bonding) onto the bonding surface at least one first block 510 and at least one second block 520 made from a first photonic stack and a second photonic stack, respectively (Figure 13).

[0086] "Photonic stack" is understood to mean a stack of layers of material, in particular layers of semiconductor material, which is capable of emitting optical radiation upon receiving an electrical signal or which emits an electrical signal upon absorbing optical radiation.

[0087] P is also understood according to the terminology of the present invention to mean that once the photonic stack has been transferred to the coupling surface, the layers of material forming it are stacked in the z-direction.

[0088] According to the invention, the first block 510 and the second block 520 form pieces that can be transferred by pick-and-place and bonding, respectively, as illustrated in FIG. 14 showing a piece (first block or second block).

[0089] The formation of the first block 510 and the second block 520 may involve an epitaxy step, in particular on a substrate called a seed substrate.

[0090] In particular, the formation of the first stack 510 on the bonding surface comprises the following steps: b11) forming a first photonic stack by epitaxy on one face, called the seed face, of a first seed substrate; b12) cutting to form first areas, each of the first areas comprising a first portion of a first seed substrate on which a first piece formed from the first photonic stack is to be placed; b13) assembling the first piece onto the mating surface; b14) removing the first portion at the end of step b13) so as to transfer the first piece onto the bonding surface.

[0091] Similarly, the formation of the second stack on the bonding surface comprises the following steps: b21) forming a second photonic stack by epitaxy on one face, called the seed face, of a second seed substrate; b22) cutting to form second sections, each of the second sections comprising a second portion of a second seed substrate on which a second piece formed from a second photonic stack is to be placed; b23) assembling a second piece to the mating surface; b24) removing the second portion at the end of step c23) so as to transfer the second piece onto the bonding surface.

[0092] The method according to the invention also comprises a step c) of forming a first photonic component 610 and a second photonic component 620 from the first block 510 and the second block 520, respectively. Step c) may in particular comprise a series of photolithography and etching steps intended to form the first photonic component and the second photonic component.

[0093] Thereby, at the end of step c), the first photonic component 610 is optically coupled with the first waveguide 330 according to an evanescent wave coupling mode or an adiabatic wave coupling mode (FIGS. 15, 19). In other words, the optical radiation guided by the first waveguide can be transferred to the first photonic component 610. Such optical coupling by evanescent or adiabatic waves is obtained as soon as the first photonic component is in the vicinity D1 of the first waveguide 330, it being understood that the waveguides have a similar refractive index. In other words, steps b) and c) of transferring the first block are performed such that the first optical component 610 is arranged perpendicularly to the area of ​​the first waveguide 330.

[0094] Similarly, at the end of step c), the second photonic component 620 is optically coupled to the second waveguide 340 via the first grating coupler 341 (FIGS. 15 and 18). In other words, the optical radiation guided by the second waveguide 340 can be transferred to the second photonic component 620 via the first grating coupler. Thereby, steps b) and c) of transferring the second block are performed such that the second optical component 620 is vertically arranged with the first grating coupler 330.

[0095] 18, optical radiation RI incident from the front surface and perpendicular to the second grating coupler 342 is transmitted to said second grating coupler 342 and then guided by the second waveguide from end 340b to end 340a until it reaches the first grating coupler 341. Once it reaches the first grating coupler 341, it is directed towards a surface, referred to as the lower surface, of the second optical component, which is in contact with the coupling surface 320.

[0096] Nevertheless, the lower surface may have a non-zero reflectivity coefficient, such that radiation directed at it is partially reflected by the lower surface.

[0097] Also, during interaction with the second grating coupler 342 , the optical radiation RI may partially pass through the second grating coupler without being guided towards the second waveguide 340 .

[0098] These undesirable effects directly affect the efficiency of the optical coupling.

[0099] However, considering anti-reflective layers to overcome these undesirable effects is neither desirable nor easy to implement.

[0100] Therefore, as shown in FIG. 18, it is possible to provide for the formation of two reflective elements 910 and 920 in order to improve the optical efficiency of the device.

[0101] In particular, the reflective element 910 is formed in the coupling layer 300 and positioned such that the first grating coupler is sandwiched between the reflective element 910 and the at least one second photonic component 620 .

[0102] Similarly, a reflective element 920 is formed in the coupling layer 300 and a second grating coupler is positioned between the reflective element 920 and the coupling surface.

[0103] The reflecting elements 910 and 920 may each comprise a Bragg mirror and may be formed during performance of sub-step a2).

[0104] This arrangement is particularly advantageous since it does not require the implementation of an anti-reflection layer overlying the optically active surface (lower surface) of the second photonic component. Indeed, in the example shown in Fig. 18, the reflector element 910 makes it possible to return to the lower surface of the second photonic component 620 the portion of the radiation reflected by said surface.

[0105] Similarly, optical radiation that partially passes through the second grating coupler 342 may be re-injected into the grating by being reflected on the reflective element 920 .

[0106] As shown in FIG. 10b, the reflector elements 910 and 920 can be formed during step a4) of forming the second sheath layer 370. In particular, step a4) includes: forming a first section of a second sheath layer overlying the first sheath layer and the first waveguide; - forming two reflectors 910 and 920 on a first section of the second sheath layer; forming a second section of the second sheath layer overlapping the two reflectors and the first section of the second sheath layer.

[0107] As an example, the first photonic component may comprise a laser, in particular an InP-based laser. A photonic stack making it possible to form an InP-based laser comprises in particular a P-doped InP layer and an N-doped InP layer, between which a set of quantum wells is sandwiched.

[0108] Evanescent or adiabatic wave coupling in the vicinity of the first photonic component, for example made of monocrystalline silicon, is relatively effective. The closeness of the refractive indices in the wavelength range 1310 nm to 1550 nm between the monocrystalline silicon forming the first waveguide and the InP forming the first photonic component, as well as the closeness of these two elements (distance D1 ≦150 nm), makes the coupling by evanescent or adiabatic waves particularly effective.

[0109] The second photonic component may comprise an avalanche photodiode, which in particular may adopt the same terminology as the photodiode presented in the non-patent document 4 of this specification.

[0110] An encapsulation layer 700 may be formed overlying the first photonic component 610 and the second photonic component 620 (FIG. 16). The encapsulation layer 700 may comprise an insulating material, in particular silicon dioxide. The formation of the encapsulation layer 700 is within the purview of one skilled in the art and therefore will not be described herein.

[0111] Following the formation of the encapsulation layer 700, a first contact 810 associated with the first photonic component 610 and a second contact 820 associated with the second photonic component 620 may be formed (FIG. 17). The first contact 810 and the second contact 820 are intended in particular to enable electrical control of the first photonic component 610 and the second photonic component 620, respectively.

[0112] The formation of contacts 810 and 820 is within the purview of one skilled in the art and will not be described herein.

[0113] In particular, the method allows different waveguides to be embedded at different depths, as described above, which is particularly advantageous when optical components requiring different optical couplings have to be integrated in the same device.

[0114] Particularly advantageously, the coupling layer 300 is formed such that the first distance D1 is less than or equal to 150 nm (but not zero), such a distance making it possible to establish evanescent or adiabatic wave coupling between the first waveguide and the first optical component.

[0115] Also particularly advantageously, the coupling layer 300 is formed such that the second distance D2 is greater than 200 nm, such a distance making it possible to establish coupling between the second waveguide and the second photonic component via the grating coupler while limiting (or even preventing) coupling of evanescent or adiabatic waves.

[0116] The implementation of reflective elements 910 and 920 makes it possible, in particular, to improve the efficiency of optical coupling between the second waveguide and the second photonic component without the need to use an anti-reflective layer on the lower surface of the second photonic component.

[0117] Finally, the method according to the invention makes it possible to take into account a first waveguide made of monocrystalline semiconductor material at a distance D1 from the coupling plane that is smaller than the distance D2 at which the second waveguide is located.

[0118] The invention also relates to a photonic device comprising essentially the above mentioned characteristics.

[0119] In particular, photonic devices a final substrate provided with a main surface; a bonding layer comprising a bonding surface and an assembly surface opposite the bonding surface, the bonding layer being placed by its assembly surface on a main surface of the final substrate, the bonding layer comprising at least one first waveguide and at least one second waveguide, the at least one second waveguide being terminated at one of its ends by a first grating coupler, the first waveguide and the second waveguide being respectively spaced apart from the bonding surface by a first distance D1 and a second distance D2 greater than the first distance D1, the first waveguide and the first grating coupler comprising a monocrystalline material, advantageously the first distance D1 being less than 150 nm and the second distance D2 being greater than 200 nm; and a first photonic component and a second photonic component formed from the first photonic stack and the second photonic stack, respectively, the first photonic component and the second photonic component being optically coupled, evanescently or adiabatically, to at least one first waveguide and to at least one second waveguide via a first grating coupler, respectively.

[0120] Advantageously, the second photonic component comprises an avalanche photodiode, and advantageously, the interface formed between the second photonic stack and the bonding layer is devoid of an anti-reflection layer.

[0121] Advantageously, the second waveguide is also terminated at its other end by an edge facet with a second grating coupler or couplers, the second grating coupler being arranged to enable injection of optical radiation from the coupling facet into the second waveguide.

[0122] Also advantageously, the device further comprises a reflective element formed in the coupling layer and arranged such that the first grating coupler is sandwiched between the reflective element and the at least one second photonic component.

[0123] Naturally, the invention is not limited to the described embodiments and variants can be added thereto without departing from the scope of the invention as defined by the claims.

Claims

1. A method for manufacturing a photonic device (100), the method comprising the following successive steps: a) providing a support structure comprising a bonding layer (300) provided with a bonding surface (320) and an assembly surface (310) opposite said bonding surface (320), said bonding layer (300) being placed by its assembly surface (310) on a main surface (210) of a final substrate (200), said bonding layer (300) comprising at least one first waveguide (330) and at least one second waveguide (340), said at least one second waveguide (340) being terminated at one of its ends by a first grating coupler (341); wherein the first waveguide comprises a single crystal material, the first waveguide (330) and the second waveguide (340) are respectively spaced from the bonding surface (320) by a first distance D1 and a second distance D2 greater than the first distance D1, advantageously the first distance D1 being less than 150 nm and the second distance D2 being greater than 200 nm, and the providing of the support structure comprises forming the bonding layer from a semiconductor-on-insulator substrate (400) and then transferring the bonding layer onto the main surface of the final substrate (200); b) transferring onto said coupling surface (320) at least a first block (510) and at least a second block (520) made of a first photonic stack and a second photonic stack, respectively; c) forming a first photonic component (610) and a second photonic component (620) from the first block (510) and from the second block (520), respectively, the first photonic component (610) and the second photonic component (620) being optically coupled evanescently or adiabatically with the at least one first waveguide (330) and with the at least one second waveguide (340) via the grating coupler (341), respectively; A manufacturing method comprising:

2. 2. The method of claim 1, wherein the semiconductor-on-insulator substrate (400) comprises, from a rear surface (410) towards a front surface (420), an initial substrate (430), a buried oxide layer (440), and a semiconductor layer (450), the buried oxide layer (440) forming part of the bonding layer (300) and advantageously having a thickness equal to the first distance D1.

3. The method of claim 2, wherein forming the bonding layer (300) comprises the sub-step a1) of partially etching the semiconductor layer (450) to form the at least one first waveguide (330).

4. 4. The method according to claim 3, wherein said forming of said bonding layer (300) comprises a sub-step a2) of forming a first sheath layer (360), advantageously made of silicon dioxide, overlapping said front surface of said semiconductor-on-insulator substrate and intended to encapsulate said first waveguide (330).

5. 5. The method of claim 4, wherein the formation of the coupling layer (300) comprises a sub-step a3) of forming the second waveguide (340) and the first grating coupler (341) on the first sheath layer (360), advantageously with a thickness of the first sheath layer (360) adjusted so that the second waveguide (340) and the first grating coupler (341) are at a distance equal to the second distance D2 from the interface formed between the initial substrate (430) and the buried oxide layer (440).

6. 6. The method according to claim 5, wherein said formation of said coupling layer (300) comprises sub-step a4) of forming a second sheath layer (370), advantageously made of silicon dioxide, overlapping said first sheath layer (360) and intended to encapsulate said second waveguide (340) and said first grating coupler (341).

7. The method according to any one of claims 1 to 6, wherein the first photonic stack and the second photonic stack are formed by epitaxy before being transferred to the coupling surface (320).

8. The method of any one of claims 1 to 7, wherein at least one said first photonic component comprises a laser.

9. The method according to any one of claims 1 to 8, wherein at least one said second photonic component comprises an avalanche photodiode, and advantageously the interface formed between said second photonic stack and said bonding layer (300) is devoid of an anti-reflection layer.

10. The method of any one of claims 1 to 9, wherein a reflective element (910) is formed in the coupling layer (300) and the first grating coupler (341) is arranged such that it is sandwiched between the reflective element (910) and the at least one second photonic component.

11. The method of any one of claims 1 to 10, wherein the second waveguide (340) is also terminated at its other end by a second grating coupler, the second grating coupler being arranged to enable injection of optical radiation from the coupling surface into the second waveguide (340).

12. A photonic device (100), comprising: a final substrate (200) provided with a main surface (210), a bonding layer (300) provided with a bonding surface (320) and an assembly surface (310) opposite said bonding surface (320), said bonding layer (300) being placed by its assembly surface (310) on said main surface (210) of said final substrate (200), said bonding layer (300) comprising at least one first waveguide (330) and at least one second waveguide (340), said at least one second waveguide (340) being connected to an end of said at least one first waveguide (330) and at least one second waveguide (340) a coupling layer (300) terminated at one end by a first grating coupler (341), the first waveguide comprising a semiconductor single crystal material, the first waveguide (330) and the second waveguide (340) being spaced apart from the coupling surface (320) by a first distance D1 and a second distance D2 greater than the first distance D1, respectively, and advantageously the first distance D1 being less than 150 nm and the second distance D2 being greater than 200 nm; a first photonic component (610) and a second photonic component (620) formed from a first photonic stack and a second photonic stack, respectively, the first photonic component (610) and the second photonic component (620) being optically coupled, evanescently or adiabatically, with the at least one first waveguide (330) and with the at least one second waveguide (340) via the first grating coupler (341), respectively; A photonic device (100).

13. 13. The photonic device of claim 12, wherein the second photonic component comprises an avalanche photodiode, and advantageously the interface formed between the second photonic stack and the bonding layer (300) is devoid of an anti-reflection layer.

14. 14. The photonic device of claim 12 or 13, wherein the second waveguide (340) is also terminated at its other end by a second coupling network (342), the second coupling network (342) being arranged to enable injection of optical radiation from the coupling surface into the second waveguide (340).

15. 14. The photonic device of claim 12 or 13, wherein the second waveguide (340) is also terminated at its other end by a coupler with an edge surface, the edge surface being the contour of the coupling layer connecting the coupling surface and the assembly surface.

16. The photonic device of any one of claims 12 to 15, further comprising a reflecting element (910) formed in the coupling layer (300), and the first grating coupler (341) is arranged to be sandwiched between the reflecting element (910) and at least one of the second photonic components (620).

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