Method and apparatus for transferring one or more layers of material from an initial substrate to a target substrate

Abstract

The present invention relates to a method and apparatus for transferring a layer of material from an initial substrate to a target substrate. The apparatus includes a container for holding an electrolyte solution, a substrate holding member disposed within the container, a voltage source connectable to the layer of material and / or the initial substrate, an actuator for moving the target substrate away from the initial substrate or vice versa, and a controller for controlling the actuator. The method includes the steps of: moving an edge of the target / initial substrate away from the initial / target substrate to form a separation space between the initial substrate and the layer of material, with a separation front at which the initial substrate and the layer of material begin to separate from each other; and, when the initial substrate with the layer of material and the target substrate are at least partially immersed in the electrolyte solution and a potential is applied to the layer of material and / or a surface of the initial substrate facing the layer of material, increasing the separation space and moving the separation front along the initial substrate, wherein the electrolyte diffuses between the initial substrate and the layer of material, and the actuator is controlled to provide a separation front progression equal to or less than the diffusion rate of the electrolyte.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for transferring one or more layers of material from an initial substrate to a target substrate, in particular the one or more layers of material comprising one or more single atomic layers, such as single-layer graphene or multi-layer graphene. [Background technology]

[0002] Such a method and apparatus are described, for example, in EP 2928700 B1. This patent publication describes a method for transferring graphene from a metal substrate on which it is formed to a second substrate. First, the second substrate is attached to the graphene. Next, the stack of the metal substrate on which the graphene is formed, the graphene, and the second substrate is immersed in a solution. Then, a mechanical pulling action is used to separate the graphene and the second substrate from the original metal substrate, using bubbles formed by electrolysis at the interface between the graphene and the metal, and to push the two layers apart. Summary of the Invention [Problem to be solved by the invention]

[0003] A drawback of known methods and devices is that bubbles formed by mechanical pulling and / or electrolysis can damage one or more graphene layers.

[0004] It is an object of the present invention to provide improved and / or alternative methods and apparatus for transferring one or more layers of material, such as graphene, from an initial substrate to a target substrate. In particular, the method at least substantially reduces, and preferably avoids, the occurrence of damage or loss of part of the one or more layers of material during transfer. [Means for solving the problem]

[0005] According to a first aspect, the present invention provides a method for transferring one or more layers of material from an initial substrate to a target substrate, the method comprising: - providing an initial substrate having one or more layers of material, the initial substrate contacting and supporting the one or more layers of material defining a first interface between the initial substrate and the one or more layers of material; - providing a target substrate and adhering the target substrate to a surface of the one or more layers of material opposite the first interface; - at least partially immersing an initial substrate having one or more layers of material and a target substrate in an electrolyte solution; - applying an electric potential to the surface of the initial substrate facing the first interface and / or to one or more layers of material; - before or during the step of applying the potential, moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate in order to provide a separation space between the initial substrate and the one or more layers of material, wherein a separation front is provided where the initial substrate and the one or more layers of material start to separate; - increasing the separation space and moving the separation front along the initial substrate by using an actuator for applying a separation force to the target substrate in a direction away from the initial substrate or for applying a separation force to the initial substrate in a direction away from the target substrate, wherein an electrolyte diffuses between the initial substrate and the one or more layers of material with a diffusion rate, and the actuator is controlled to provide a progression of the separation front that is equal to or less than the diffusion rate of the electrolyte; The present invention relates to a method, including:

[0006] The method of the present invention allows for controlled delamination of one or more layers of material from an initial substrate by applying cation / anion-induced delamination with controlled separation of the target substrate and the initial substrate. Meanwhile, controlling the actuator to provide a separation front progression equal to or less than the diffusion rate of the electrolyte ensures that the diffusion of the electrolyte, or in other words, the diffusion of the electrolyte's cations and / or anions and the resulting cation / anion-induced delamination, precedes the transfer of one or more layers of material from the initial substrate to the target substrate. As a result, the amount of force required to separate the target substrate with one or more layers of material from the initial substrate is very small, thereby at least substantially reducing and preferably avoiding damage or loss of a portion of the one or more layers of material during the transfer.

[0007] As described above, the actuator is controlled to provide a separation front progression that is equal to or less than the diffusion rate of the electrolyte. Here, the diffusion rate can be measured indirectly, for example, by observing the degree of separation of the interface between the initial substrate and one or more layers without applying a pulling force. This method involves ensuring that the separation force applied by the actuator is applied so that the separation front does not extend further into the interface between the initial substrate and one or more layers. Thus, the electrolyte diffusion rate can be measured or determined indirectly by observing the degree of separation of the interface. For example, it can be measured / determined optically, for example, by a camera positioned above a container holding the electrolyte and the substrate. The separation, and thus the degree of diffusion indirectly, can be observed as a line or outline using the camera. In this case, the force applied to separate the target substrate having one or more layers from the initial substrate can be controlled so that the separation front does not extend beyond the expected position of the line or outline indicating the degree of diffusion of material to the interface between the layer and the initial target.

[0008] According to this method, if at any point it is observed that diffusion is not progressing and / or has partially slowed or stopped, the application of the separation force can be withheld to allow diffusion to proceed. Once diffusion, and thus interfacial separation, is again progressing, the separation force can be reapplied. In some embodiments, this can be accomplished by a feedback loop.

[0009] The observation of diffusion rate (also called velocity of diffusion), separation front, and their relationship are explained in more detail below in the Overview section and in the Detailed Description.

[0010] It should be noted that the actuator includes a controllable actuator that can be controlled by a controller, such as a computer or PLC, to perform a desired movement on a substrate-holding member for holding an initial substrate or a target substrate. The actuator may include a mechanical device, such as a robot, that uses an electric motor, a pneumatic cylinder, or a hydraulic cylinder to provide the desired movement. Alternatively, the actuator may include a float that floats on the surface of the electrolyte and is connectable to the target substrate, and a level control system for controlling the height of the electrolyte in the container. Such a level control system may include a controllable valve connected to a drain for draining the container for holding the electrolyte solution for at least partially immersing the initial substrate and the target substrate with one or more layers of material to lower the liquid level in the container, and a pump unit for pumping electrolyte from a storage canister into the container to raise the liquid level in the container.

[0011] It should be noted that the method is preferably used to transfer one or more layers of material from an initial substrate that is more rigid than the target substrate, or vice versa, and therefore the method preferably includes the step of separating an edge of the less rigid one of the initial substrate and the target substrate from the more rigid one of the initial substrate and the target substrate.

[0012] In one embodiment, the potential applied to the surface of the initial substrate facing the first interface is set to a voltage such that cations and / or anions of the electrolyte intercalate between one or more layers of material and the surface of the initial substrate facing the first interface, causing separation of one or more layers of material from the initial substrate into which the cations and anions of the electrolyte have intercalated. The advantage of using only a potential is that all electrochemically driven reactions, including gas evolution at the first interface, are prevented.

[0013] In some embodiments, the counter electrode is at least partially immersed in the electrolyte, and applying the potential comprises establishing a potential difference between the counter electrode and a surface of the initial substrate facing the first interface and / or between the counter electrode and one or more layers of material. Preferably, the potential difference is set to ensure that the first interface and / or one or more layers of material are substantially bubble-free. The absence of bubbles further reduces, and preferably avoids, damage or loss of portions of the one or more layers of material during transfer.

[0014] In some embodiments, the method further comprises detecting the extent of electrolyte diffusion between one or more layers of material and the initial substrate and controlling the actuator to provide movement of the separation front so that the separation front does not overtake the detected extent of diffusion. In some embodiments, the extent of diffusion is detected using an optical sensor, preferably a photodetector or camera, and the actuator is controlled to provide movement of the separation front so that the visible extent of diffusion is not overtaken by the separation front. For some materials, such as graphene, the extent of electrolyte diffusion between one or more layers of material and the initial substrate is visible by a change in color or contrast, which makes it possible to detect the extent of diffusion using an optical sensor, such as a photodetector or camera, and control the actuator to provide movement of the separation front so that the visible extent of diffusion is not overtaken by the separation front.

[0015] It should be noted that the optical sensor is particularly suitable for combination with a substantially optically transparent initial substrate and / or a substantially optically transparent target substrate, where the optical transparency does not necessarily have to be in the visible wavelength range, but may also be in the near-infrared or infrared wavelength range.

[0016] Additionally or alternatively, in some embodiments, the measured current flowing through the initial substrate and / or one or more layers of material to establish and / or maintain the potential or potential difference is used as a measure of the extent of electrolyte diffusion between the one or more layers of material and the initial substrate and / or as a measure of the surface area of ​​the one or more layers of material separated from the initial substrate. It should be noted that the measured current also depends on the geometry of the initial substrate, and the geometry of the initial substrate must be taken into account to establish a measure of the extent of diffusion. For example, if the first interface is substantially circular in shape, moving the separation front along the initial substrate will change the length of the separation front, which will result in a nonlinear relationship between the measured current and the extent of diffusion.

[0017] In some embodiments, the actuator is connected to the target substrate and configured to move an edge of the target substrate away from the initial substrate, to move the edge of the target substrate away from the initial substrate, and / or to increase the separation space and move the separation front along the initial substrate. Alternatively, in some embodiments, the actuator is connected to the initial substrate and configured to move an edge of the initial substrate away from the target substrate, to move the edge of the initial substrate away from the target substrate, and / or to increase the separation space and move the separation front along the initial substrate. An advantage of this embodiment is that the actuator can be positioned above the target substrate, in particular at least partially above and outside the container for holding the electrolyte solution, and therefore outside the electrolyte solution.

[0018] In one embodiment, a force sensor is disposed between the actuator and the target substrate, and the method further includes using the force sensor to measure the separation force when pulling the edge of the target substrate away from the initial substrate, and controlling the actuator to slow down the rate of pulling the edge of the target substrate when the measured separation force exceeds a threshold. Alternatively, in one embodiment, a force sensor is disposed between the actuator and the initial substrate, and the method further includes using the force sensor to measure the separation force when pulling the edge of the initial substrate away from the target substrate, and controlling the actuator to slow down the rate of pulling the edge of the initial substrate when the measured separation force exceeds a threshold. If the separation force exceeds the threshold, this indicates that the separation front has overtaken or is approaching the range of electrolyte diffusion. In one embodiment, the threshold measured separation force in Newtons (N) is less than or equal to 0.1 times the maximum length of the separation front in meters (m), preferably less than or equal to 0.05 times the maximum length of the separation front, and more preferably less than or equal to 0.01 times the maximum length of the separation front. For example, for a substantially circular initial substrate, such as a wafer, with a diameter of 100 mm, the maximum length of the separation front is 100 mm, and therefore the threshold is equal to or less than 0.1 x 100 mm = 10 millinewtons (mN), preferably equal to or less than 0.05 x 100 mm = 5 mN, and more preferably equal to or less than 0.01 x 100 mm = 1 mN.

[0019] It should be noted that the measured separation force may depend, among other things, on the bending stiffness of the substrate being peeled. If the substrate being peeled has significant bending stiffness, additional bending force is required to bend the substrate being peeled away from the other substrate. Thus, the force sensor measures at least a combination of the separation force and the bending force, and preferably, the portion of the measured force attributable to the bending force is at least partially subtracted from the force measured by the force sensor to obtain the measured separation force value. Alternatively, the maximum bending force of the particular substrate being peeled is added to the measured separation force threshold to obtain a threshold value for the combined separation force and bending force. This maximum bending force can be established experimentally before using this particular substrate in the method and apparatus of the present invention.

[0020] Additionally or alternatively, if the diffusion of electrolyte between one or more layers of a particular material and a particular type of initial substrate is known or established experimentally, one embodiment of the method further includes setting and / or timing the control of the actuator based on the known diffusion to provide a separation front progression that is no greater than the known diffusion rate of the electrolyte. For example, the rate of electrolyte diffusion can be established by using an optical sensor, preferably a photodetector or a camera, to detect the extent of diffusion and monitor it as a function of time. The use of a force sensor can also be used to establish a measure of the rate of electrolyte diffusion. This embodiment provides the possibility of controlling an apparatus or method for transferring one or more layers of material from an initial substrate to a target substrate in a simple manner by moving the target substrate at a speed that is no greater than the known diffusion rate of the electrolyte, substantially without the use of complex detection and feedback procedures.

[0021] An alternative embodiment for performing the steps of moving the edge of the target substrate away from the initial substrate and / or increasing the separation space and moving the separation front along the initial substrate further comprises inserting a wedge in a direction substantially parallel to the first interface to push the target substrate away from the initial substrate.

[0022] The method and apparatus of the present invention are particularly suitable for use with an initial substrate, including, but not limited to, a substantially rigid substrate, preferably a flat substantially rigid substrate, the surface of which facing the first interface is provided with a growth catalyst layer. In certain embodiments, the substantially rigid substrate comprises a silicon wafer or a sapphire plate, and / or the growth catalyst layer comprises a metal layer, preferably the metal layer comprises Cu and / or Ni. The use of a substantially rigid substrate, preferably a very flat rigid substrate, is highly advantageous for growing high-quality layers of, for example, graphene or hexagonal boron nitride, because the rigid substrate provides a stable support for very thin layers of these materials, which may even include layers having a thickness of a single atom, at least during their growth.

[0023] In some embodiments, one or more layers of material and / or metal layers are connected to a voltage source to apply a potential to the one or more layers of material and / or metal layers or to establish a potential difference between a counter electrode and the one or more layers of material and / or metal layers. Thus, the one or more layers of material and / or metal layers are used to drive or assist cation / anion-induced delamination in the electrolyte in combination with movement of the target substrate, as described above. To provide electrical connection to the one or more layers of material and / or metal layers, in some embodiments, the target substrate includes a cutout or is smaller than the initial substrate to provide an area for electrically connecting the metal layer and / or one or more layers of material to a voltage source.

[0024] In some embodiments, the target substrate is less rigid than the initial substrate. Preferably, the target substrate comprises a thermal release sheet, a thin silicon wafer, a sheet of glass, preferably borosilicate glass, and / or a sheet of plastic, preferably Plexiglas, polycarbonate, polyimide, or the like. Preferably, the target substrate is also rigid to provide a suitable carrier for a high-quality layer, for example, graphene or hexagonal boron nitride, but less rigid than the initial substrate to allow the target substrate to bend to separate its edges from the substantially imbendable initial substrate. On the other hand, when a stiffer target substrate is used, the bending radius of the target substrate becomes relatively large, thereby reducing the critical strain of one or more layers of material. On the other hand, a large bending radius results in a separation space with a small opening angle, which may prevent the diffusion of electrolyte from reaching the separation front. Therefore, a smaller bending radius and a larger opening angle may be advantageous for the diffusion of electrolyte to reach the separation front.

[0025] In some embodiments, the method further includes positioning a cylindrical roller above the target substrate, the cylindrical roller being disposed substantially above the separation front and / or separation space and preferably configured to move with the moving separation front. The cylindrical roller allows for control and adjustment of the movement of the target substrate so that the movement has a desired constant speed, allowing sufficient time for the cation / anion-induced delamination to perform its function and to prevent variations in the movement of the edge of the target substrate. Furthermore, the diameter of the cylindrical roller can also be used to define the bending radius of the target substrate, i.e., the bending radius is equal to or greater than the radius of the cylindrical roller.

[0026] The method and apparatus of the present invention are well suited to transferring one or more layers of material from an initial substrate to a target substrate, the one or more layers of material preferably comprising an atomically thick layer of material such as a layer of graphene or hexagonal boron nitride (h-BN).

[0027] According to a second aspect, the present invention provides an apparatus for transferring one or more layers of material from an initial substrate to a target substrate, the apparatus comprising: a container for holding an electrolyte solution and for at least partially immersing the initial substrate having one or more layers of material and the target substrate in the electrolyte solution; a substrate holding member disposed within the container, the substrate holding member configured to hold an initial substrate; a voltage source connectable to one or more layers of material and / or the initial substrate; an actuator configured to apply a separation force to the target substrate in a direction away from the initial substrate; A controller for controlling an actuator, - separating an edge of the target substrate from the initial substrate or separating an edge of the initial substrate from the target substrate to provide a separation space between the initial substrate and the one or more layers of material, wherein a separation front is provided where the initial substrate and the one or more layers of material start to separate; - increasing the separation space and moving the separation front along the initial substrate, in which the initial substrate having one or more layers of material and the target substrate are at least partially immersed in an electrolyte solution, an electric potential is applied to the surface of the initial substrate facing the one or more layers of material and / or to the one or more layers of material, the electrolyte diffuses between the initial substrate and the one or more layers of material, and the actuator is controlled to provide a progression of the separation front below the diffusion speed of the electrolyte; a controller for controlling the actuator to perform The present invention relates to an apparatus including:

[0028] In one embodiment, the actuator is connectable to the target substrate and is configured to separate an edge of the target substrate from the initial substrate, and the apparatus preferably includes a force sensor connected to the actuator and connectable to the target substrate. In an alternative embodiment, the actuator is connectable to the initial substrate and is configured to separate an edge of the initial substrate from the target substrate, and the apparatus preferably includes a force sensor connected to the actuator and connectable to the initial substrate.

[0029] In an embodiment, the container and / or the substrate holding member is movable in a direction having a component parallel to the first interface between the initial substrate and the one or more layers of material, and preferably the actuator is configured to pull the edge of the target substrate or the edge of the initial substrate in a direction having a component perpendicular to the first interface. This embodiment makes it possible to control the velocity of the container and / or the substrate holding member in the direction parallel to the first interface to be equal to the velocity of the pulling of the edge of the target substrate in the direction perpendicular to the first interface, so that the position of the separation front relative to the position of the actuator remains substantially the same.

[0030] In an embodiment, the actuator includes a wedge configured to be inserted between the initial substrate and the target substrate, preferably in a direction substantially parallel to the interface between the initial substrate and the target substrate, to push the target substrate, having one or more layers of material, away from the initial substrate.

[0031] In an embodiment, the apparatus further comprises an optical sensor, preferably a photodetector or camera, configured to detect diffusion of electrolyte between the one or more layers of material and the initial substrate, the optical sensor being connected to the controller to provide a measure of the diffusion of the electrolyte relative to the separation front.

[0032] In certain embodiments, the apparatus further includes a cylindrical roller disposed above the substrate holding member, the cylindrical roller configured to abut on the target substrate and to move along a surface of the target substrate opposite the initial substrate.

[0033] According to a third aspect, the present invention provides an apparatus for transferring one or more layers of material from an initial substrate to a target substrate, the apparatus comprising: a container for holding an electrolyte solution and for at least partially immersing the initial substrate having one or more layers of material and the target substrate in the electrolyte solution; a substrate holding member disposed within the container, the substrate holding member configured to hold an initial substrate; a voltage source connectable to one or more layers of material and / or the initial substrate; an actuator configured to apply a separation force relative to the target substrate in a direction away from the initial substrate or relative to the initial substrate in a direction away from the target substrate, an actuator connectable to the target substrate or the initial substrate and configured to move an edge of the target substrate or the initial substrate away from the initial substrate, the device including a force sensor connected to the actuator and connectable to the target substrate or the initial substrate; a controller configured to use signals from the force sensor to control the actuator; The present invention relates to an apparatus including:

[0034] According to a fourth aspect, the present invention provides an apparatus for transferring one or more layers of material from an initial substrate to a target substrate, the apparatus comprising: a container for holding an electrolyte solution and for at least partially immersing the initial substrate having one or more layers of material and the target substrate in the electrolyte solution; a substrate holding member disposed within the container, the substrate holding member configured to hold an initial substrate; a voltage source connectable to one or more layers of material and / or the initial substrate; an actuator configured to apply a separation force relative to the target substrate away from the initial substrate or relative to the initial substrate away from the target substrate; an actuator connectable to the target substrate or initial substrate and configured to pull an edge of the target substrate or initial substrate away from the initial substrate, the container and / or substrate holding member being movable in a direction having a component parallel to a first interface between the initial substrate and the one or more layers of material, and the actuator configured to pull the edge of the target substrate or initial substrate in a direction having a component perpendicular to the first interface; a synchronization means or member for synchronizing movement of the container and / or substrate holding member along a direction parallel to the first interface with movement of the actuator along a direction perpendicular to the first interface; The present invention relates to an apparatus including:

[0035] According to a fifth aspect, the present invention provides an apparatus for transferring one or more layers of material from an initial substrate to a target substrate, the apparatus comprising: a container for holding an electrolyte solution and for at least partially immersing the initial substrate having one or more layers of material and the target substrate in the electrolyte solution; a substrate holding member disposed within the container, the substrate holding member configured to hold an initial substrate; a voltage source connectable to one or more layers of material and / or the initial substrate; an actuator configured to apply a separation force relative to the target substrate in a direction away from the initial substrate or relative to the initial substrate in a direction away from the target substrate; an optical sensor, preferably a photodetector or a camera, configured to detect diffusion of electrolyte between the one or more layers of material and the initial substrate, the optical sensor being connected to a controller to provide a measure of the diffusion of electrolyte relative to a separation front at which the initial substrate and the one or more layers of material begin to separate from one another, the controller being configured to control the actuator based on the measure of the diffusion of electrolyte relative to the separation front; The present invention relates to an apparatus including:

[0036] The various aspects and features described and illustrated in this specification may be applied individually to the extent possible, and these individual aspects, particularly those aspects and features recited in the accompanying dependent claims, may be the subject of divisional patent applications. [Brief explanation of the drawings]

[0037] The invention will be elucidated on the basis of exemplary embodiments shown in the accompanying drawings.

[0038] [Figure 1] 1 shows a schematic cross-sectional view of a first example of a device according to the invention; [Figure 2] 2 shows a schematic cross-sectional view of a second example of a part of an apparatus according to the invention; [Figure 3] 3 shows a schematic cross-sectional view of a third example of a device according to the invention; [Figure 4] 1 shows a schematic cross-sectional view of a fourth example of an apparatus according to the invention; [Figure 5] 1 shows schematically the steps of the method according to the invention;

[0039] It should be noted that in the accompanying figures, like features are designated with like reference numerals. DETAILED DESCRIPTION OF THE INVENTION

[0040] Examples of the present invention will now be described with reference to the accompanying drawings, in which: In the following description and drawings, identical or equivalent elements, or elements having identical or equivalent functionality, may be designated with identical or equivalent reference numerals.

[0041] 1 shows diagrammatically a cross-sectional view of a first example of an apparatus 1 according to the invention. The apparatus 1 is configured to transfer one or more layers 2 of material from an initial substrate to a target substrate 4.

[0042] One or more layers 3 of material, such as graphene of h-BN, are grown on a flat surface of an initial substrate 2. The present invention preferably uses a sapphire disk as the initial substrate 2, because sapphire disks can have a very flat surface and are readily available. The surface of the initial substrate 2 on which the one or more layers 3 of material are grown is provided with a growth catalyst layer 5, which is preferably a metal layer, more preferably a metal layer comprising copper (Cu) or nickel (Ni), or a combination of copper (Cu) and nickel (Ni). Other metals are also possible.

[0043] After the layer(s) of material 3 are provided on the growth catalyst layer 5, a thin polymer layer 6 is provided on the layer(s) of material 3. The thin polymer layer 6 is preferably a spin-coated layer comprising, for example, polymethyl methacrylate (PMMA), polycarbonate (PC), or polystyrene (PS), although many other polymers are possible. Preferably, a layer of PMMA is used for the thin polymer layer 6 because it can be relatively easily removed from the layer(s) of material 3.

[0044] Subsequently, a target substrate 4 is placed on top of the thin polymer layer 6. An example of such a stack comprises: sapphire / metal (preferably Cu and / or Ni) / one or more layers of material (e.g., graphene or h-BN) / PMMA / target substrate. The target substrate 4 may comprise a thermal release tape as known in the art, but preferably comprises a rigid substrate such as a thin sheet of borosilicate glass or a thin silicon wafer, with the target substrate 4 having a lower rigidity than the initial substrate 2. In the apparatus 1 of the present invention, the less rigid target substrate 4 is separated from the more rigid initial substrate 2.

[0045] It should be noted that in some examples, an additional adhesive layer is disposed between the polymer layer 6 and the target substrate 4. One example of such a stack includes: sapphire / metal (preferably Cu and / or Ni) / one or more layers of material (e.g., graphene or h-BN) / PMMA / adhesive / target substrate. One example of the additional adhesive can be BrewerScience's WaferBOND®, HT-10.11, or HT-10.12, although other adhesives can be used as well.

[0046] It should further be noted that in an alternative method, it is also possible to use a target substrate that is more rigid than the initial substrate. In this case, in the inventive apparatus 1, the less rigid initial substrate 2 is separated from the more rigid target substrate 4. The following examples relate to the combination of a more rigid initial substrate and a less rigid target substrate. However, the present apparatus and method can also be applied to transfer one or more layers of material from a less rigid initial substrate to a more rigid target substrate.

[0047] As further shown schematically in FIG. 1, the apparatus according to this first example comprises: a container 7 for holding an electrolyte solution 8 and for at least partially immersing the initial substrate 2 and the target substrate 4 with one or more layers 3 of material in the electrolyte solution 8; a substrate holding member 9 disposed inside the container 7, the substrate holding member 9 being configured to hold the substrate having the greater rigidity of the initial substrate 2 and the target substrate 4, in this example the initial substrate 2 being held by the substrate holding member 9; a voltage source 10 connected to a counter electrode 11 located within the vessel 7; an actuator 12 configured to apply a separation force to the less rigid one of the initial substrate 2 and the target substrate 4 in a direction away from the more rigid one of the initial substrate 2 and the target substrate 4, in this example the separation force is applied to the target substrate 4 in a direction away from the initial substrate 2; a controller 13 for controlling the device 1 and in particular the actuator 12; Includes:

[0048] The actuator 12 is mounted on a frame 19 which is connected to the vessel 7 .

[0049] In use, the initial substrate 2 with one or more layers 3 of material and the target substrate 4 are immersed in an electrolyte solution 8. The electrolyte solution 8 diffuses at least between the initial substrate 2 and the one or more layers 3 of material. In order to electrochemically exfoliate the one or more layers 3 of material from the growth catalyst layer 5 of the initial substrate 2, a potential difference is established between the counter electrode 11 and the surface of the initial substrate 2 facing the one or more layers 3 of material, in particular between the counter electrode 11 and the growth catalyst layer 5. The one or more layers 3 of material, in particular graphene, are exfoliated using the electrolyte solution 8 having cations and anions intercalatable between the one or more layers 3 of material and the growth catalyst layer 5.

[0050] Additionally, the actuator 12 is connected to the target substrate 4 via a connecting member 16 and is controlled by the controller 13 to lift an edge of the target substrate 4 away from the initial substrate 2 to provide a separation space 17 between the initial substrate 2 and the one or more layers of material 3. A separation front 18 is provided where the initial substrate 2 and the one or more layers of material 3 begin to separate. In particular, when the target substrate 4 comprises a semi-rigid substrate such as a thin sheet of borosilicate glass or a thin silicon wafer, the actuator 12 pulls the target substrate 4 such that the target substrate 4 bends slightly away from the initial substrate 2 to provide a larger diffusion path for the electrolyte solution 8 to diffuse into the separation space 17.

[0051] The present invention therefore utilizes a combination of moving the edge of the target substrate 4 by an actuator and using electrochemical delamination in a manner that precedes electrochemical delamination and reduces the mechanical stresses and / or forces exerted on the layer or layers 3 of material by the movement of the target substrate 4. That is, the actuator 12 is controlled to increase the separation space 17 and to move the separation front 18 along the initial substrate 2 in a manner that the progression of the separation front 18 is equal to or less than the diffusion rate of the electrolyte solution 8 between the initial substrate 2 and the layer or layers 3 of material.

[0052] There are several ways to ensure that diffusion and thereby electrochemical delamination precedes.

[0053] A first option is to use an optical sensor 15, preferably a photodetector or camera, to detect the extent of diffusion of the electrolyte solution 8 and / or intercalation of the cations and anions of the electrolyte solution 8 between the layer(s) of material 3 and the initial substrate 2. With some materials, for example in the case of graphene and when using a transparent polymer layer 6 and target substrate 4, the extent of diffusion of the electrolyte solution 8 and / or intercalation of the cations and anions of the electrolyte solution between the layer(s) of material 3 and the initial substrate 2 is visible by a change in color or contrast. The optical sensor 15 is connected to the controller 13 for transmitting data collected by the optical sensor 15 to the controller 13. A controller 13 is connected to the actuators 12 to control the actuators 12 based on data from the optical sensor 15 so that the progression of the separation front 18 does not approach or overtake the visible detection range of the diffusion of the electrolyte solution 8 and / or the intercalation of cations and anions of the electrolyte solution 8, thereby ensuring that diffusion and thereby electrochemical delamination is ahead in transferring one or more layers 3 of material from the initial substrate 2 to the target substrate 4.

[0054] It should be noted that the separation front 18, at which the initial substrate 2 and the one or more layers 3 of material begin to separate from each other, can also be detected by the optical sensor 15, which makes it possible to use the optical sensor 15 to detect both the separation front 18, on the one hand, and the extent of diffusion of the electrolyte solution 8 and / or intercalation of the cations and anions of the electrolyte solution 8, on the other hand.

[0055] A second option is to place a force sensor 14 between the actuator 12 and the target substrate 4. If the transfer of one or more layers 3 of material from the initial substrate 2 to the target substrate 4 is preceded by diffusion and therefore electrochemical delamination, the force F required to separate the target substrate 4 from the initial substrate 2 is small. Therefore, the force sensor 14 can be used to measure the separation force F when pulling the edge of the target substrate 4 away from the initial substrate 2. The force sensor 14 is connected to the controller 13 for transmitting data collected by the force sensor 14 to the controller 13. The controller 13 is connected to the actuator 12 for controlling the actuator 12 to slow down the pulling of the edge of the target substrate 4 by the actuator 12 based on the data from the force sensor 14 when the measured separation force F exceeds a threshold. If the separation force F exceeds the threshold, this indicates that the separation front 18 is approaching or has overtaken the range of diffusion of the electrolyte solution 8 and / or intercalation of cations and anions of the electrolyte solution 8. Experiments have shown that when transferring a graphene layer from a silicon wafer (initial substrate 2) with a copper layer (growth catalyst layer 5) to a thermal release tape (target substrate 4) and using a thin PMMA polymer layer 6, the separation force F is less than 10 mN when preceded by diffusion and thereby electrochemical delamination. Therefore, values ​​of the separation force F of 10 millinewtons (mN) or less can be used as a threshold value.

[0056] A third solution is to set and / or time the control of the actuator 12 to provide a progression of the separation front 18 that is equal to or less than a known rate of diffusion of the electrolyte solution 8 and / or intercalation of the cations and anions of the electrolyte solution 8 between the one or more layers 3 of material and the initial substrate 2, based on a known diffusion rate. This solution is convenient when the rate of diffusion of the electrolyte solution 8 and / or intercalation of the cations and anions of the electrolyte solution 8 between the one or more layers 3 of material and the initial substrate 2 is known or established by experiment. For example, the rate of electrolyte diffusion can be established by using an optical sensor 15, preferably a photodetector or camera, to detect the extent of diffusion and monitor it as a function of time. The use of a force sensor 14 can also be used to establish a measure of the rate of electrolyte diffusion.

[0057] It should be noted that when the present apparatus and method are used to transfer one or more layers of material from a less rigid initial substrate to a more rigid target substrate, the layered structure of the initial substrate 2 with one or more layers 3 of material and the target substrate 4 is placed in an upside down position on the substrate holding member 9. That is, the more rigid target substrate is attached to and held by the substrate holding member 9, and the connecting members 16 of the actuators 12 are connected to the edges of the initial substrate.

[0058] It is further noted that the actuator 12 comprises a controllable actuator that is controllable by a controller 13, such as a computer or PLC, to effect the desired movement of the connecting member 16 relative to the substrate holding member 9. The actuator 12 may comprise a mechanical device, such as a robot, that uses electric motors, pneumatic cylinders, or hydraulic cylinders to provide the desired movement.

[0059] As an alternative to using a connecting member 16 to connect the actuator 12 to the edge of the less rigid of the initial substrate 2 and the target substrate 4, a wedge 20 may be used to move the edge and / or increase the separation space between the initial substrate 1 and the target substrate 3 by inserting the wedge 20 in a direction substantially parallel to the surface of the growth catalyst layer 5 to push the target substrate 3 having one or more layers of material 2 away from the initial substrate 2, as shown schematically in FIG. 2 . The device including the wedge 20 may comprise an actuator connected to the wedge 20 and configured to push the wedge 20 with a force F′ in a direction substantially parallel to the surface of the growth catalyst layer 5. Additionally or alternatively, the device including the wedge 20 may comprise an actuator connected to the substrate holding member 9 and configured to move the substrate holding member 9 back and forth in a direction V′ substantially parallel to the surface of the growth catalyst layer 5, the wedge 20 remaining in a fixed position at least in the direction parallel to the surface of the growth catalyst layer 5 during edge lifting and / or increase of the separation space.

[0060] It should be noted that the size of the wedge 20 in Figure 2 has been greatly exaggerated to more clearly show the effect of inserting the wedge 20 between the growth catalyst layer 5 and the layer or layers of material 3. In practice, the angle of the wedge is preferably less than 45 degrees. Preferably, the wedge includes a tip 21 having a radius of curvature, the radius of curvature at the tip of the wedge being preferably less than 0.5 times the thickness of the polymer layer and adhesive layer (if present).

[0061] 3 shows a schematic cross-sectional view of a third example of a device according to the invention. In this example, the actuator or actuator assembly comprises: a floating body 30 that floats on the surface of the electrolyte solution 8 and is connectable to the target substrate 6; a level control system for controlling the height of the electrolyte solution 8 in the container 7, the level control system comprising a controllable valve 33 connected to an output port or drain of the container 7 for removing the electrolyte solution 8 from the container 7 and lowering the liquid level in the container 7, and a pump unit 36 ​​for pumping the electrolyte solution 8' from a storage canister 34 into the container 7 to raise the liquid level in the container 7; Includes:

[0062] In this example, the controllable valve 33 is disposed in an output tube 32 connecting the output port or drain of the container 7 to a storage canister 34. The electrolyte solution 8' from the storage canister 34 can be pumped into the container 7 by a pump unit 36 ​​disposed in the input tubes 35, 37 connecting the input port of the container 7 to the storage canister 34. Both the controllable valve 33 and the pump unit 36 ​​are connected to and controllable by the controller 13.

[0063] Furthermore, the float 30 may include a force sensor 31 disposed between the float 30 and the target substrate 4. The force sensor 31 is connected to the controller 13 for transmitting data collected by the force sensor 31 to the controller 13. The controller 13 is connected to a controllable valve 33 and a pump unit 36 ​​for controlling the height of the electrolyte solution 8 in the container 7 so as to slow down the pulling of the edge of the target substrate 4 by the float 30 by reducing the increase in the height of the electrolyte when the measured separation force F exceeds a threshold value based on the data from the force sensor 31.

[0064] Note that the device of the third example does not include a counter electrode. A voltage source 10 is connected to ground potential on one side and to the growth catalyst layer 5 on the other side so that a potential is applied to the growth catalyst layer 5 to allow intercalation of electrolyte cations / anions between the layer(s) of material 3 and the growth catalyst layer 5, resulting in cation / anion induced delamination of the layer(s) of material 3 from the growth catalyst layer 5.

[0065] It should be noted that the example of the device 1 of the present invention as shown in Figure 3 may also function with a counter electrode, as described above with reference to Figure 1. It should also be noted that the example of the device of the present invention as shown in Figure 1 may also function without a counter electrode 11, as described above with reference to Figure 3.

[0066] The apparatus may further include a cylindrical roller 40 disposed above the substrate holding member 9, which, in use, is configured to abut against the surface of the target substrate 4 opposite the initial substrate 2. As shown schematically in FIG. 3 , the cylindrical roller 40 is disposed substantially above the separation front 18 and / or the wedge-shaped separation space 17. Preferably, the cylindrical roller 40 is configured to move along with the moving separation front 18. The cylindrical roller 40 allows for control and adjustment of the movement of the target substrate 4 away from the initial substrate 2 such that the movement has a desired constant speed, allowing sufficient time for the electrochemical reaction to perform its function and preventing separation of the target substrate 4 from the initial substrate 2 or vice versa. Additionally or alternatively, the cylindrical roller 40 is configured to control and adjust the curvature of the upward bending of the semi-rigid target substrate 4. In the case of a flexible target substrate 4, the diameter of the cylindrical roller 40 can be used to define the bending radius of the target substrate 4, i.e., the bending radius is equal to or greater than the radius of the cylindrical roller 40.

[0067] It should be noted that the example of the device 1 of the present invention as shown in FIG. 3 can function without the cylindrical roller 40, and that such a cylindrical roller 40 can also be applied to the example of the device 1 of the present invention as shown in FIG.

[0068] FIG. 4 shows a schematic cross-sectional view of a fourth example of the apparatus 1 according to the present invention. The apparatus 1 of this fourth example is substantially the same as the first example, with the addition that the container 7 and the substrate holding member 9 are movable in a direction V substantially parallel to the first interface between the initial substrate 2 and the one or more layers of material 3. In this example, the movement of the container 7 and the substrate holding member 9 is provided by a conveyor having rollers 51, 52 rotatably connected to a conveyor frame 53. Furthermore, the actuator 12 and the optical sensor 15 are not directly connected to the container 7 but are connected to the conveyor frame 53, and are preferably stationary relative to the conveyor frame 53 and do not move with the container 7. Therefore, the apparatus 1 of this fourth example makes it possible to correct a horizontal deviation of the position at which the connecting member 16 is connected to the target substrate 4, which is caused by the target substrate 4 bending upward. By moving the container 7 and the substrate holding member 9 using the conveyors 51, 52, the horizontal deviation can be corrected.

[0069] Preferably, the apparatus 1 includes a synchronization means or member for synchronizing the movement of the container 7 and the substrate holding member 9 along a direction parallel to the first interface with the movement of the actuator 12 along a direction perpendicular to the first interface. The synchronization means may be provided by the controller 13, which is configured to control the velocity of the container 7 and the substrate holding member 9 in the direction V parallel to the first interface to be equal to the pulling velocity of the edge of the target substrate 4 in the direction perpendicular to the first interface. Alternatively, the synchronization member may include a mechanical coupling between the actuator 12 and the conveyors 51, 52 such that the actuator 12 and the conveyors 51, 52 move synchronously, such that when the actuator 12 moves the connecting member 16 upward, the same actuator 12 moves the conveyor to the right via a mechanical coupling (not shown). Preferably, the synchronization means is configured so that the relative position of the separation front 18 to the position of the actuator 12 remains substantially the same.

[0070] It should be noted that the example of the device of the present invention as shown in FIG. 4 can also function without the counter electrode 11, as described above with reference to FIG.

[0071] Figure 5 shows in a simplified manner the steps of the method according to the invention. In particular, the method starts at 51, which comprises: 52: Providing an initial substrate having one or more layers of material, the initial substrate contacting and supporting the one or more layers of material defining a first interface between the initial substrate and the one or more layers of material; 53: Providing a target substrate and adhering the target substrate to a surface of the one or more layers of material opposite the first interface; 54: At least partially immersing the initial substrate with one or more layers of material and the target substrate in an electrolyte solution with a counter electrode; 55: Establishing a potential difference between the counter electrode and the surface of the initial substrate facing the first interface; 56: Before or during the step of establishing the potential difference, moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate to provide a wedge-shaped separation space between the initial substrate and the one or more layers of material, wherein a separation front is provided where the initial substrate and the one or more layers of material start to separate; 57: Increasing the separation space and moving the separation front along the initial substrate by using an actuator for applying a separation force to the target substrate in a direction away from the initial substrate or for applying a separation force to the initial substrate in a direction away from the target substrate, wherein an electrolyte diffuses between the initial substrate and the one or more layers of material; 58: Controlling the actuator to provide a progression of the separation front below the diffusion rate of the electrolyte until the complete target substrate with one or more layers of material is separated from the initial substrate; and the method ends at 59.

[0072] It should be understood that the above description is included to illustrate the operation of the preferred embodiment and is not intended to limit the scope of the invention. Many variations within the scope of the invention will become apparent to those skilled in the art from the above description.

[0073] In summary, the present invention relates to a method and apparatus for transferring a layer of material from an initial substrate to a target substrate, the apparatus comprising a container for holding an electrolyte solution, a substrate holding member disposed within the container, a voltage source connectable to the layer of material and / or the initial substrate, an actuator for moving the target substrate away from the initial substrate and vice versa, and a controller for controlling the actuator. - moving an edge of the target / initial substrate away from the initial / target substrate to provide a separation space between the initial substrate and the layer of material with a separation front where the initial substrate and the layer of material start to separate from each other; an initial substrate having a layer of material and a target substrate are at least partially immersed in an electrolyte solution, and an electric potential is applied to the layer of material and / or to a surface of the initial substrate facing the layer of material, increasing the separation space and moving the separation front along the initial substrate, wherein the electrolyte diffuses between the initial substrate and the layer of material and the actuator is controlled to provide a progression of the separation front below the diffusion rate of the electrolyte; Includes:

Claims

1. 1. A method for transferring one or more layers of material from an initial substrate to a target substrate, the method comprising: providing the initial substrate having the one or more layers of material, the initial substrate contacting and supporting the one or more layers of material defining a first interface between the initial substrate and the one or more layers of material; providing a target substrate and adhering the target substrate to a surface of the one or more layers of the material opposite the first interface; at least partially immersing the initial substrate having the one or more layers of the material and the target substrate in an electrolyte solution; applying an electric potential to a surface of the initial substrate facing the first interface and / or to the one or more layers of the material; - before or during the step of applying the potential, moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate to provide a separation space between the initial substrate and the one or more layers of material, wherein a separation front is provided where the initial substrate and the one or more layers of material start to separate; increasing the separation space and moving the separation front along the initial substrate by using an actuator for applying a separation force to the target substrate in a direction away from the initial substrate or for applying a separation force to the initial substrate in a direction away from the target substrate, wherein the electrolyte diffuses between the initial substrate and the one or more layers of material and the actuator is controlled to provide a progression of the separation front at or below a diffusion rate of the electrolyte; A method comprising:

2. 2. The method of claim 1, further comprising detecting an extent of diffusion of the electrolyte between the one or more layers of material and the initial substrate, and controlling the actuator to provide movement of the separation front such that the separation front does not overtake the detected extent of diffusion.

3. 3. The method of claim 2, wherein the extent of the diffusion is detected by using an optical sensor, preferably a photodetector or a camera, and the actuator is controlled to provide for advancement of the separation front such that the visible extent of the diffusion is not overtaken by the separation front.

4. the actuator is connected to the target substrate and configured to move the edge of the target substrate away from the initial substrate, to move the edge of the target substrate away from the initial substrate, and / or to increase the separation space and move the separation front along the initial substrate; or 4. The method of claim 1, wherein the actuator is connected to the initial substrate and configured to pull the edge of the initial substrate away from the target substrate, to move the edge of the initial substrate away from the target substrate, and / or to increase the separation space and move the separation front along the initial substrate.

5. a force sensor is disposed between the actuator and the target substrate, the method further comprising using the force sensor to measure a separation force when pulling the edge of the target substrate away from the initial substrate, and controlling the actuator to slow down the rate of pulling the edge of the target substrate when the measured separation force exceeds a threshold; or 5. The method of claim 4, wherein a force sensor is disposed between the actuator and the initial substrate, the method further comprising using the force sensor to measure a separation force when pulling the edge of the initial substrate away from the target substrate, and controlling the actuator to slow down the rate of pulling the edge of the initial substrate when the measured separation force exceeds a threshold.

6. 6. The method of claim 5, wherein the threshold value of the measured separation force (in Newtons) is less than or equal to 0.10 times the maximum length (in meters) of the separation front, preferably less than or equal to 0.05 times the maximum length of the separation front, more preferably less than or equal to 0.01 times the maximum length of the separation front.

7. 7. The method of claim 1, wherein the diffusion of the electrolyte between the one or more layers of a particular material and an initial substrate of a particular type is known or established by experiment or using the method steps of any one of claims 2 to 6, and wherein the method further comprises setting and / or timing the control of the actuator based on the known diffusion to provide a progression of the separation front at or below the known diffusion rate of the electrolyte.

8. 8. The method according to claim 1, wherein the step of moving an edge and / or the step of increasing the separation space and moving the separation front along the initial substrate further comprises the step of inserting a wedge in a direction substantially parallel to the first interface to push the target substrate away from the initial substrate.

9. 9. The method according to any one of claims 1 to 8, wherein the initial substrate comprises a substantially rigid substrate, preferably a flat substantially rigid substrate, the surface of the initial substrate facing the first interface being provided with a growth catalyst layer.

10. 10. The method of claim 9, wherein the substantially rigid substrate comprises a silicon wafer or a sapphire plate, and / or the growth catalyst layer comprises a metal layer, preferably the metal layer comprises Cu and / or Ni.

11. 11. The method of claim 10, wherein the metal layer is connected to a voltage source for applying a potential to the metal layer, and preferably the target substrate comprises a cutout or is smaller than the initial substrate to provide an area for electrically connecting the metal layer to the voltage source.

12. 12. The method according to any one of claims 1 to 11, wherein the method further comprises the step of positioning a cylindrical roller above the target substrate, the cylindrical roller being arranged substantially above the separation front and / or the separation space and configured to move together with the moving separation front.

13. 13. The method according to any one of claims 1 to 12, wherein the target substrate is less rigid than the initial substrate, preferably the target substrate comprises a thermal release sheet, a thin silicon wafer, a sheet of glass, preferably borosilicate glass, and / or a sheet of plastic, preferably a sheet of Plexiglas, polycarbonate, polyimide or the like.

14. 14. The method of any one of claims 1 to 13, wherein the one or more layers of materials comprise a layer of graphene or a layer of hexagonal boron nitride (h-BN).

15. 1. An apparatus for transferring one or more layers of material from an initial substrate to a target substrate, said apparatus comprising: a container for holding an electrolyte solution and for at least partially immersing the initial substrate having the one or more layers of the material and the target substrate in the electrolyte solution; a substrate holding member disposed within the vessel, the substrate holding member configured to hold the initial substrate or the target substrate; a voltage source connectable to the one or more layers of material and / or the initial substrate; an actuator configured to apply a separation force to the target substrate in a direction away from the initial substrate, or to apply a separation force to the initial substrate in a direction away from the target substrate; a controller for controlling the actuator, - moving an edge of the target substrate away from the initial substrate or moving an edge of the initial substrate away from the target substrate to provide a separation space between the initial substrate and the one or more layers of material, wherein a separation front is provided where the initial substrate and the one or more layers of material start to separate; increasing the separation space and moving the separation front along the initial substrate, wherein the initial substrate having the one or more layers of material and the target substrate are at least partially immersed in the electrolyte solution, an electric potential is applied to a surface of the initial substrate facing the one or more layers of material and / or to the one or more layers of material, the electrolyte diffuses between the initial substrate and the one or more layers of material, and the actuator is controlled to provide a progression of the separation front below a diffusion rate of the electrolyte; a controller for controlling the actuator to 1. An apparatus comprising:

16. the actuator is connectable to the target substrate and is configured to move the edge of the target substrate away from the initial substrate, the apparatus preferably including a force sensor connected to the actuator and connectable to the target substrate; or 16. The apparatus of claim 15, wherein the actuator is connectable to the initial substrate and configured to pull the edge of the initial substrate away from the target substrate, the apparatus preferably including a force sensor connected to the actuator and connectable to the initial substrate.

17. the container and / or the substrate holding member are movable in a direction having a component parallel to a first interface between the initial substrate and the one or more layers of material, preferably the actuator is configured to pull the edge of the target substrate in a direction having a component normal to the first interface; or The apparatus of claim 16 , wherein the actuator is configured to pull the edge of the initial substrate in a direction having a component perpendicular to the first interface.

18. 18. The apparatus of claim 15, 16 or 17, wherein the actuator comprises a wedge configured to be inserted between the initial substrate and the target substrate, preferably in a direction substantially parallel to an interface between the initial substrate and the target substrate, to push the target substrate having the one or more layers of material away from the initial substrate.

19. 19. Apparatus according to any one of claims 15 to 18, wherein the apparatus further comprises an optical sensor, preferably a photodetector or a camera, configured to detect diffusion of the electrolyte between the one or more layers of material and the initial substrate, the optical sensor being connected to the controller to provide a measure of the diffusion of the electrolyte relative to the separation front.

20. the apparatus further includes a cylindrical roller disposed above the substrate holding member; the cylindrical roller is configured to abut on the target substrate and move along a surface of the target substrate opposite the initial substrate; or 20. The apparatus of any one of claims 15 to 19, wherein the cylindrical roller is configured to abut on the initial substrate and to move along a surface of the initial substrate opposite the target substrate.

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