Method for manufacturing a single-crystal layer of lno material and substrate for epitaxial growth of a single-crystal layer of lno material

Abstract

A method for producing a single crystal layer of LNO material, comprising transferring a single crystal seed layer of YSZ material to a carrier substrate of silicon material, followed by epitaxial growth of a single crystal layer of the LNO material.

Description

Technical Field

[0001] The present invention relates to a method for producing a single crystal layer of lithium niobate (LNO) material and a substrate for epitaxially growing such a single crystal layer of LNO material. Background Technology

[0002] Some materials are not currently available as single-crystal substrates in the form of large-diameter wafers. Furthermore, some materials can be obtained in large diameters, but lack certain characteristics or specifications in terms of quality, particularly regarding defect density or desired electrical or optical properties. Summary of the Invention

[0003] The object of this invention is to overcome these limitations of the prior art by providing a method for manufacturing a single-crystal layer of LNO material and a substrate for epitaxially growing such a single-crystal layer of LNO material. In this way, the size problem of currently available single-crystal substrates for LNO material can be solved.

[0004] The present invention relates to a method for producing a single crystal layer of LNO material, comprising transferring a single crystal seed layer of YSZ material to a carrier substrate of silicon material, and then epitaxially growing the single crystal layer of LNO material.

[0005] In an advantageous embodiment, the thickness of the single-crystal seed layer is less than 10 μm, preferably less than 2 μm, and more preferably less than 0.2 μm.

[0006] In an advantageous embodiment, transferring a single-crystal seed layer of YSZ material to a carrier substrate of silicon material includes the step of bonding the single-crystal substrate of YSZ material to the carrier substrate, followed by the step of thinning the single-crystal substrate of YSZ material.

[0007] In an advantageous embodiment, the thinning step includes forming a weakening region that defines a portion of the single-crystal substrate of YSZ material to be transferred to a carrier substrate of silicon material.

[0008] In an advantageous implementation, the weakened region is formed by implanting atomic and / or ionic substances.

[0009] In an advantageous embodiment, the thinning step includes separation at the weakened region, thereby transferring said portion of the YSZ material monocrystalline substrate to a silicon material carrier substrate. In particular, the separation includes applying thermal and / or mechanical stress.

[0010] In an advantageous embodiment, the bonding step is a molecular adhesion step.

[0011] In an advantageous embodiment, the single-crystal seed layer of YSZ material is in the form of multiple sheets, each transferred to a carrier substrate of silicon material.

[0012] In an advantageous embodiment, the silicon material carrier substrate includes a separable interface configured to be separated by means of laser ablation and / or chemical etching and / or by means of mechanical stress.

[0013] The present invention also relates to a substrate for epitaxial growth of a single crystal layer of LNO material, characterized in that it comprises a single crystal seed layer of YSZ material located on a silicon material carrier substrate.

[0014] In an advantageous embodiment, the single-crystal seed layer of the YSZ material is in the form of multiple sheets.

[0015] In an advantageous embodiment, the silicon material carrier substrate includes a separable interface configured to be separated by means of laser ablation and / or chemical etching and / or by means of mechanical stress.

[0016] The present invention also relates to a method for producing Li with lattice parameters close to those of LNO materials. x K y Na z Ti l Nb m A method for growing a single-crystal layer of O3 material, the method comprising transferring a single-crystal seed layer of YSZ material to a silicon carrier substrate, followed by epitaxial growth of Li. x K y Na z Ti l Nb m Single crystal layer of O3 material.

[0017] The present invention also relates to a method for producing Li with lattice parameters close to those of LNO materials. x K y Na z Ti l Nb m A method for creating a single-crystal layer of O3 material, the method comprising transferring a single-crystal seed layer of SrTiO3, CeO2, MgO, or Al2O3 material to a carrier substrate of silicon, sapphire, Ni, or Cu material, followed by epitaxial growth of Li. x K y Na z Ti l Nb m Single crystal layer of O3 material. Attached Figure Description

[0018] Other features and advantages of the invention will be better understood by reading the following detailed description with reference to the accompanying drawings, in which:

[0019] · Figure 1A method for producing a single crystal layer of LNO material according to an embodiment of the present invention and a substrate for epitaxially growing such a single crystal layer of LNO material according to the same embodiment of the present invention are shown.

[0020] · Figure 2 A method for producing a single crystal layer of LNO material according to another embodiment of the present invention is shown, as well as a substrate for epitaxially growing such a single crystal layer of LNO material according to such another embodiment of the present invention.

[0021] · Figure 3 A method for producing a single crystal layer of LNO material according to another embodiment of the present invention is shown, as well as a substrate for epitaxially growing such a single crystal layer of LNO material according to such another embodiment of the present invention.

[0022] · Figure 4 A method for producing a single crystal layer of LNO material according to another embodiment of the present invention is shown, as well as a substrate for epitaxially growing such a single crystal layer of LNO material according to such another embodiment of the present invention.

[0023] · Figure 5 A method for producing a single crystal layer of LNO material according to another embodiment of the present invention is shown, as well as a substrate for epitaxially growing such a single crystal layer of LNO material according to such another embodiment of the present invention.

[0024] To improve readability of the accompanying drawings, the layers are not necessarily shown to scale. Detailed Implementation

[0025] Figure 1A silicon substrate 100 is shown, on which a single-crystal seed layer 200 of YSZ material is transferred. Other materials for the single-crystal seed layer 200, such as SrTiO3, CeO2, MgO, or Al2O3, are conceivable, as these materials have lattice parameters close to those of LNO materials. The silicon substrate 100 can also be replaced with a substrate 100 of sapphire, Ni, or Cu materials. The advantage of using silicon is that it not only opens up the application field of LNO material layers for large devices of the 300mm type, but also makes it compatible with the microelectronics industry, for which there are high acceptance requirements for foreign materials other than silicon, especially LNO, on the production line. The step of bonding the single-crystal seed layer 200 of YSZ material to the silicon substrate 100 is preferably carried out by a molecular adhesion step. This molecular adhesion step includes an adhesive step, preferably carried out at ambient temperature, followed by annealing to solidify the adhesive interface, which is typically carried out at high temperatures of up to 900°C or even 1100°C for several minutes to several hours. Regarding sapphire substrates, the step of bonding the single-crystal seed layer 1' to the substrate is preferably performed using a molecular adhesion step under typical conditions of the same order of magnitude as described above. Regarding Ni or Cu substrates, the step of bonding the single-crystal seed layer 1' to the substrate is replaced by a step of depositing Ni or Cu material on the single-crystal seed layer, for example, by electrodeposition (ECD) or electroplating. This technique typically involves the use of an adhesive layer and a peel-off, and is known in itself, and will not be described in detail here.

[0026] Figure 1 The steps of bonding a single-crystal substrate 20 of YSZ material to a carrier substrate 100 of silicon material are schematically shown. The next step is to thin the single-crystal substrate 20 of YSZ material 20 after it has been bonded to the carrier substrate 100 of silicon material 2'. Figure 1 The thinning step 2' is schematically shown, which can be implemented, for example, by chemical and / or mechanical etching (polishing, grinding, milling, etc.). Thus, a single-crystal seed layer 200 of YSZ material can be obtained, which will act as a... Figure 1The diagram schematically illustrates the step of epitaxially growing a single crystal layer 300 of 3'LNO material on a substrate for epitaxially growing a single crystal layer of LNO material 10. Those skilled in the art can adjust the parameters used for epitaxially growing a single crystal layer of LNO material on a bulk single crystal substrate, typically used for homoepitaxial or heteroepitaxial growth, to optimize the step of epitaxially growing a single crystal layer 300 of 3'LNO material on a substrate for epitaxially growing the single crystal layer of LNO material 10 of the present invention. The epitaxy of the LNO material is therefore performed by MOCVD at typical temperatures of 650°C to 850°C using precursors known to those skilled in the art. Incidentally, the present invention is not limited to the epitaxy of LNO material, but extends to Li₂ having lattice parameters close to those of LNO material. x K y Na z Ti l Nb m Some complexes with a trigonal crystal structure of type O3.

[0027] It should be noted that the coefficient of thermal expansion of the carrier substrate 100 dominates the thermal behavior of the substrate used for epitaxially growing the single crystal layer of LNO material 10 during the step of epitaxially growing the single crystal layer 300 of 3'LNO material. This is due to the low thickness (preferably less than 1 μm) of the single crystal seed layer 200 of YSZ material relative to the total thickness (about tens to hundreds of μm) of the substrate used for epitaxially growing the single crystal layer of LNO material 10. Incidentally, YSZ material is chosen to provide a single crystal seed layer having lattice parameters (preferably lattice parameters in the relaxed state) as close as possible to the lattice parameters selected for the single crystal layer 300 of LNO material, thereby generating as few defects as possible in the epitaxial growth of the single crystal layer 300 of LNO material. Incidentally, the material of the carrier substrate 100 advantageously has a coefficient of thermal expansion particularly close to that of the LNO material, for the same reason as reducing defects in the single crystal layer 300 obtained by epitaxy. Therefore, a carrier substrate 100 of sapphire material is preferably used in this invention.

[0028] Figure 2 An embodiment of a method for manufacturing a single-crystal layer of LNO material is schematically illustrated, which is combined with... Figure 1The difference in the described implementation lies in that the YSZ material single-crystal substrate 20' undergoes a step of implanting O" atoms and / or ions to form a weakened region defining a portion 200' of the YSZ material single-crystal substrate 20' to be transferred to the silicon material carrier substrate 100', and the thinning step 2" includes separation at this weakened region to transfer said portion 200' of the YSZ material single-crystal substrate 20' to the silicon material carrier substrate 100', specifically, this separation includes applying thermal and / or mechanical stress. Therefore, the advantage of this implementation is that the remaining portion 201 of the initial YSZ material single-crystal substrate 20' can be recovered and reused for the same process again, thus reducing costs. Figure 2 The substrate shown is used for epitaxial growth of a single crystal layer of LNO material 10' for bonding... Figure 1 The method described herein involves the step of growing a 3"LNO single crystal layer 300" of material. Typically, hydrogen ions are used for implantation step 0". An advantageous alternative well known to those skilled in the art involves replacing all or part of the hydrogen ions with helium ions. The hydrogen implantation dose is typically 6 × 10⁻⁶. 16 cm -2 and 1×10 17 cm -2 The implantation energy is typically between 50 and 170 keV. Therefore, separation is usually performed at temperatures between 300 and 600 °C. This yields a single-crystal seed layer thickness of approximately 200 nm to 1.5 μm. Immediately after the separation operation, additional technical steps are advantageously added to enhance the bonding interface or restore a good roughness level, or to correct any defects that may have occurred during the implantation step, or to prepare the surface of the seed layer for further epitaxy. These steps are, for example, polishing, (wet or dry) chemical etching, annealing, and chemical cleaning. They can be used individually or in combinations that can be adjusted by those skilled in the art.

[0029] Figure 3 and combination Figure 1 and Figure 2The described implementation differs in that the substrate for epitaxially growing the single-crystal layer of LNO material (10, 10') includes a separable interface 40' configured to be separable. In the case of a silicon material carrier substrate 100, it can be a rough surface (e.g., silicon material) that is bonded to the single-crystal seed layer during the bonding step. Alternatively, a rough interface can be present within the silicon material carrier substrate 100, which is obtained, for example, by bonding two silicon wafers. Another implementation would involve introducing a porous silicon layer on the surface to be bonded to the single-crystal seed layer, which is easily separable during the application of mechanical and / or thermal stress, for example, by inserting a blade known to those skilled in the art at the edge of the wafer or by applying annealing. Clearly, this interface is chosen to withstand other mechanical and / or thermal stresses (e.g., separation, epitaxial growth, etc.) experienced during the method of the invention. In the case of a sapphire material carrier substrate, it can be a stack of silicon oxide, silicon nitride, and silicon oxide (so-called ONO-type structure) generated on the sapphire surface to be bonded to the single-crystal seed layer. When a laser is applied through the sapphire substrate (a "laser lift-off" type of separation or debonding), this stack readily undergoes separation at the silicon nitride layer. Those skilled in the art will be able to identify other processes used to create such separable interfaces. Therefore, these different separation configurations enable the transfer of epitaxial layers onto a final support incompatible with the growth parameters, or the fabrication of thick films of self-standing LNO materials.

[0030] Figure 4 The illustration schematically depicts one embodiment of a method for producing single-crystal layers of LNO material, which is combined with... Figure 1 , Figure 2 and Figure 3 The difference in the described implementation is that the single-crystal seed layer 2000' of the YSZ material is in the form of multiple sheets (2001', 2002', 2003'), each of which is transferred to a silicon material carrier substrate 100". Each sheet can take any shape (square, hexagonal, strip, etc.) and has a diameter ranging from several mm. 2 Up to cm 2 The varying sizes of the chips are also possible. The spacing between the chips can also vary significantly depending on whether the desired outcome is maximum coverage density (in which case, a spacing of less than 0.2 mm is preferred) or maximum dispersion of the chips within the substrate (in which case, the spacing can be several millimeters or even centimeters). For each chip, those skilled in the art will be able to apply their desired transfer, and are not limited to a particular process. Therefore, applications combining… Figure 1 The technical teachings illustrated in the diagram, or combined with the methods described, are technical teachings. Figure 2The method illustrated herein describes the technical teachings, or even a combination of both. Thus, a single-crystal substrate (2001, 2002, 2003) of YSZ material with a 1″′ dimension smaller than that of the carrier substrate 100″ can be bonded to generate single-crystal seed layers (2001′, 2002′, 2003′) for epitaxially growing a single-crystal layer (3001, 3002, 3003) of LNO material 3″′ on the respective wafers of the substrate for epitaxially growing a single-crystal layer (3001, 3002, 3003) of LNO material 10″ on the latter by thinning it by 2″′.

[0031] Therefore, combining Figures 1 to 4 The various embodiments described open up the possibility of co-integrating components fabricated in a single crystal layer of LNO material with components fabricated in a carrier substrate of silicon material. The latter can be simply a silicon substrate, but it can also be an SOI-type substrate including a silicon oxide layer separating the silicon substrate from a thin silicon layer. In combination Figures 1 to 4 In the described embodiments, access to the carrier substrate can be easily achieved using photolithography and etching techniques known to those skilled in the art. In combination with Figure 4 In the described implementation, it is also possible to select only the position of the sheets and their spacing.

[0032] Figure 5 An embodiment is schematically illustrated, which is combined with... Figure 4 The described implementation differs in that the carrier substrate 100″ and the substrate subsequently used for epitaxial growth of the single-crystal layer of LNO material 10″ include a separable interface 40, which is configured to be separable, for example, by laser lift-off techniques and / or chemical etching and / or by mechanical stress. This will allow a portion of the carrier substrate 100″ to be bonded as Figure 3 As already mentioned, it is removed. One example is the use of an SOI-type carrier substrate 100, which includes a silicon oxide layer separating the silicon substrate from a thin silicon layer. This oxide layer can be used as a separable interface 40 by selectively etching, for example, by immersion in a hydrofluoric acid (HF) bath. This option of separating the buried layer by chemical etching is particularly advantageous when processing multiple small substrates in combination. Specifically, the under-etched area is typically limited to a few centimeters or even millimeters if it is desirable to maintain industrially reasonable processing conditions and times. Processing multiple small substrates allows multiple chemical etching fronts to be initiated by potentially approaching the buried layer between the individual wafers rather than just at the extreme edges of the substrate (which can be up to 300 mm in diameter). Therefore, in the case of an SOI-type carrier substrate, the thin silicon layer between the wafers can be partially removed to allow the initiation of multiple etching fronts.

[0033] Because silicon thin layers have a predetermined thickness (which can vary between 5 nm and 600 nm, or even thicker depending on the intended application), they can be used to form microelectronic components, and thus allow for the co-integration of LNO-based components in a single substrate.

[0034] Therefore, after forming single-crystal layers (3001, 3002, 3003) via epitaxy, it is conceivable to bond this structure to a final substrate and separate a portion of the carrier substrate 100" at the separable interface 40. Thus, the final substrate can provide additional functionality, for example, that is incompatible with the parameters of the previously performed growth (e.g., a flexible plastic type final substrate or a final substrate including metal wires). Furthermore, and generally, the separable interface need not be located inside the carrier substrate, but can also be located at the interface with the seed layer of YSZ material bonded to this carrier substrate (e.g., a silicon nitride layer stacked between two silicon oxide layers allows for laser lift-off, particularly suitable for sapphire type carrier substrates), as already bonded. Figure 3 As mentioned above.

Claims

1. A method for producing a single-crystal layer (300, 300', 3001, 3002, 3003) of LNO material, comprising transferring a single-crystal seed layer (200, 200', 2000') of YSZ material to a carrier substrate (100, 100', 100") of silicon material, and subsequently epitaxially growing the single-crystal layer (300, 300', 3001, 3002, 3003) of said LNO material. in, The LNO is lithium niobate.

2. The method as described in claim 1, wherein, The thickness of the single crystal seed layer (200, 200', 2000') is less than 10 μm.

3. The method as described in claim 1, wherein, The thickness of the single crystal seed layer (200, 200', 2000') is less than 2 μm.

4. The method of claim 1, wherein, The thickness of the single crystal seed layer (200, 200', 2000') is less than 0.2 μm.

5. The method as described in any one of claims 1 to 4, wherein, Transferring a single-crystal seed layer (200, 200', 2000') of YSZ material to a carrier substrate (100, 100', 100'') of silicon material includes the steps of bonding (1', 1'', 1''') of a single-crystal substrate (20, 20', 2001, 2002, 2003) of YSZ material to the carrier substrate (100, 100', 100"), followed by the step of thinning (2', 2'', 2''') the single-crystal substrate (20, 20', 2001, 2002, 2003) of YSZ material.

6. The method of claim 5, wherein, The thinning step (2'') includes forming a weakening region that defines a portion (200') of the YSZ material single crystal substrate (20') to be transferred to the carrier substrate (100, 100', 100'') of the silicon material.

7. The method of claim 6, wherein, The weakened region is formed by injecting (0") atoms and / or ions.

8. The method of claim 6 or 7, wherein, The thinning step (2'') includes separation at the weakened region, thereby transferring the portion (200') of the single crystal substrate (20') of the YSZ material to the carrier substrate (100, 100', 100") of the silicon material.

9. The method of claim 8, wherein, The separation includes applying thermal and / or mechanical stress.

10. The method of claim 5, wherein, The bonding step (1', 1'', 1''') is a molecular adhesion step.

11. The method as claimed in any one of claims 1 to 4, wherein, The single-crystal seed layer (200, 200', 2000') of the YSZ material is in the form of multiple sheets (2001', 2002', 2003') each transferred to the carrier substrate (100, 100', 100") of the silicon material.

12. The method as claimed in any one of claims 1 to 4, wherein, The silicon material carrier substrate (100, 100', 100") includes separable interfaces (40, 40') configured to be separable by means of laser ablation and / or chemical etching and / or by means of mechanical stress.

Images