Transfer packaging method and packaging structure of graphene film

Abstract

The invention provides a transfer packaging method and packaging structure of a graphene wafer. The transfer packaging method comprises the steps that aluminum oxide is deposited on the surface of a graphene wafer directly growing on a substrate to serve as a transfer packaging layer, high-molecular polymer adhesive glue is spin-coated on the transfer packaging layer, and then a supporting layer is attached to the transfer packaging layer; separating the supporting layer / transfer packaging layer / graphene wafer from the substrate; the supporting layer / transfer packaging layer / graphene wafer composite structure is attached to a target substrate; and the supporting layer is separated from the transfer packaging layer through heat treatment. According to the transfer packaging method, aluminum oxide is adopted as the transfer packaging layer, doping and pollution of the graphene wafer in the transfer process are avoided, and the graphene wafer can be protected from being doped by water and oxygen in the environment after being transferred; and meanwhile, the aluminum oxide provides support for the graphene wafer, so that the problem that the graphene wafer is directly transferred on the uneven substrate with a suspended structure on the surface is solved.

Description

Technical Field

[0001] The invention belongs to the field of carbon materials, and in particular relates to a graphene film transfer packaging method and a packaging structure obtained by the method. Background Art

[0002] As a typical two-dimensional material, graphene has attracted widespread attention and research since its discovery in 2004. Its excellent electrical, chemical and mechanical properties enable graphene to play a great role in electronic devices, optical devices and other fields. The growth and transfer of graphene, these two important technologies, determine whether it can play its due application value as a high-end electronic material. Large-area, high-quality graphene single crystal wafers are prepared by direct growth on a metal substrate by chemical vapor deposition (CVD). In order to meet the needs of characterization, physical property measurement and application, it is often necessary to transfer graphene to important substrates such as SiO2 / Si and sapphire to seek the possibility of further semiconductor processing.

[0003] At present, most graphene transfer methods rely on polymers such as polymethyl methacrylate (PMMA) as transfer media, and based on this, a support layer is designed to assist in graphene transfer. In the process of transferring uneven substrates with suspended structures on the surface, these polymers have a strong interaction with graphene. During the removal process, the shear stress caused by the surface tension of the liquid will also cause graphene damage, which will cause the graphene to collapse in the substrate structure, greatly affecting the intrinsic structure of graphene and the physical properties of graphene devices. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a graphene wafer transfer packaging method and a packaging structure obtained by the method.

[0005] The invention provides a transfer packaging method for a graphene wafer, comprising: depositing aluminum oxide as a transfer packaging layer on the surface of a graphene wafer directly grown on a substrate, spin-coating a high molecular polymer adhesive on the transfer packaging layer, and then laminating a support layer to obtain a support layer / transfer packaging layer / graphene wafer / substrate composite structure; separating the support layer / transfer packaging layer / graphene wafer from the substrate to obtain a support layer / transfer packaging layer / graphene wafer composite structure; laminating the support layer / transfer packaging layer / graphene wafer composite structure to a target substrate to obtain a support layer / transfer packaging layer / graphene wafer / substrate composite structure; and performing heat treatment to separate the support layer from the transfer packaging layer to obtain a transfer packaging layer / graphene wafer / substrate composite structure.

[0006] According to one embodiment of the present invention, the transfer packaging layer is formed on the surface of the graphene wafer by atomic layer deposition, and the deposition condition is a chamber pressure of 4-8×10-1 mbar, the growth temperature is 100-200° C.; the thickness of the transfer encapsulation layer is greater than or equal to 3 nm, preferably, less than or equal to 20 μm.

[0007] According to another embodiment of the present invention, the adhesive is one or more of polyvinyl alcohol, polymethyl methacrylate, and polycarbonate, preferably polyvinyl alcohol; the supporting layer is a thermal release tape, a UV film, or a silicone film, preferably a thermal release tape.

[0008] According to another embodiment of the present invention, the spin-coated high molecular polymer adhesive is baked after spin-coating a solution containing the adhesive on the surface of the transfer packaging layer; the spin-coating speed is 500-8000rpm, and the spin-coating time is 30s-5min; the baking temperature is 50-200°C, and the baking time is 1-5min.

[0009] According to another embodiment of the present invention, the mass concentration of the binder in the solution is 0.1-10%, and the solvent of the solution is water or ethanol.

[0010] According to another embodiment of the present invention, the support layer / transfer packaging layer / graphene wafer is separated from the substrate by mechanical peeling, wherein the mechanical peeling is manual or mechanical device assisted peeling, and the peeling speed is 0.1-5 cm / s.

[0011] According to another embodiment of the present invention, the target substrate is a silicon wafer, sapphire or Nafion membrane, preferably a silicon wafer; the support layer / transfer packaging layer / graphene wafer composite structure is bonded to the target substrate by roller bonding or vacuum bonding.

[0012] According to another embodiment of the present invention, the support layer is detached by placing the support layer / transfer packaging layer / graphene wafer / target substrate composite structure into a vacuum drying oven for heating, the heating temperature is 100-200° C., and the time is 20-60 min.

[0013] According to another embodiment of the present invention, after removing the support layer, the transfer packaging layer / graphene wafer / target substrate composite structure is immersed in a solvent to remove residual organic molecular impurities, the solvent is water and / or ethanol, the immersion temperature is 20-80°C, and the time is 1-10min.

[0014] A packaging structure of the present invention comprises the aluminum oxide / graphene wafer / substrate composite structure obtained by the transfer packaging method described in any one of claims 1 to 9.

[0015] The transfer packaging method of the present invention adopts aluminum oxide (Al2O3) as a transfer packaging layer, which can not only avoid doping and contamination of the graphene wafer during the transfer process, but also protect the graphene wafer from being doped with water and oxygen in the environment after the transfer, and reduce the scattering effect of charged impurities on the graphene wafer on the carriers. At the same time, aluminum oxide provides support for the graphene wafer, which solves the problem of direct transfer of the graphene wafer on an uneven substrate with a suspended structure on the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic flow chart of a graphene wafer transfer packaging method according to one embodiment of the present invention.

[0017] Figure 2 These are physical photographs and optical photographs of the uneven target substrate with a suspended structure on the surface of Example 1 and the composite structure after transfer.

[0018] Figure 3 This is an optical microscope photograph of the graphene wafer of Example 1 before being transferred to an uneven target substrate composite structure with a suspended structure on the surface and then removed from the surface.

[0019] Figure 4 This is the Raman spectrum of the graphene wafer after transfer in Example 1. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with specific implementation modes.

[0021] like Figure 1 As shown, the transfer packaging method of the graphene wafer of the present invention comprises: depositing aluminum oxide as a transfer packaging layer on the surface of the graphene wafer directly grown on the substrate, spin coating a high molecular polymer adhesive on the transfer packaging layer, and then laminating a support layer to obtain a support layer / transfer packaging layer / graphene wafer / substrate composite structure; separating the support layer / transfer packaging layer / graphene wafer from the substrate to obtain a support layer / transfer packaging layer / graphene wafer composite structure; laminating the support layer / transfer packaging layer / graphene wafer composite structure to the target substrate to obtain a support layer / transfer packaging layer / graphene wafer / substrate composite structure; and heat treating the support layer and the transfer packaging layer to separate the transfer packaging layer to obtain a transfer packaging layer / graphene wafer / substrate composite structure. The present invention uses aluminum oxide as the transfer packaging layer, and aluminum oxide provides support for the graphene wafer to solve the problem of direct transfer of the graphene wafer on an uneven substrate with a suspended structure on the surface. At the same time, alumina is used as the transfer packaging layer, which can not only avoid doping and contamination of the graphene wafer during the transfer process, but also protect the graphene wafer from water and oxygen doping in the environment after transfer, and reduce the scattering effect of charged impurities in the substrate on the carriers of the graphene wafer.

[0022] In an optional embodiment, the aluminum oxide transfer encapsulation layer can be formed on the surface of the graphene wafer by atomic layer deposition (ALD). The aluminum oxide transfer encapsulation layer of atomic layer deposition can be in conformal contact with the graphene wafer, and the damage of the graphene wafer is avoided when it is transferred to an uneven substrate. At the same time, the aluminum oxide transfer encapsulation layer deposited by atomic layer deposition has a strong interaction force with the graphene wafer grown on a growth substrate such as a Cu wafer, and graphene can be directly mechanically peeled off from the growth substrate, and then transferred to a silicon substrate. After that, it can continue to be retained as an encapsulation layer to protect graphene. Graphene will not be damaged by pollution and the like throughout the process. At the same time, the method can greatly reduce the residual pollutants on the graphene surface because it does not use organic solvents between graphene and the encapsulation medium, and greatly improves the integrity and cleanliness of the graphene after transfer. It can be compatible with batch transfer of 2, 4, 6, 8, and 12-inch graphene wafers. The transfer method of the present invention is applicable to the growth substrate of any growth graphene wafer, including but not limited to copper / sapphire, copper-nickel alloy / sapphire, copper-cobalt alloy / sapphire, etc. The growth method of graphene wafers is not limited to chemical vapor deposition. The deposition conditions of atomic layer deposition are chamber pressure 4-8×10 -1 mbar, and the growth temperature is 100-200° C. The aluminum oxide transfer encapsulation layer obtained by atomic layer deposition has a thickness greater than or equal to 3 nm. Preferably, the thickness of the transfer encapsulation layer is less than or equal to 20 μm.

[0023] Subsequently, a high molecular polymer adhesive is spin-coated on the transfer encapsulation layer, and then the support layer is attached. In an optional embodiment, the adhesive may be one or more of polyvinyl alcohol, polymethyl methacrylate, and polycarbonate. Preferably, the adhesive is polyvinyl alcohol. The step of spin-coating the adhesive may be to spin-coat a solution containing the adhesive on the surface of the transfer encapsulation layer and then bake it. The mass concentration of the adhesive in the adhesive solution is 0.1-10%, and the solvent of the solution is water or ethanol. The spin coating speed is 500-8000rpm, and the spin coating time is 30s-5min; the baking temperature is 50-200℃, and the baking time is 1-5min.

[0024] In an optional embodiment, the support layer is a heat release tape, a UV film or a silicone film. Preferably, the support layer is a heat release tape. The lamination method can be roller lamination or vacuum lamination, which can reduce bubbles generated by lamination.

[0025] In an optional embodiment, the supporting layer / transfer packaging layer / graphene wafer is separated from the substrate by mechanical stripping. Mechanical stripping can be manual or mechanical device assisted stripping, and the stripping speed is 0.1-5cm / s. Slower speed can improve the integrity of graphene. Those skilled in the art can select appropriate stripping speed according to actual needs, such as but not limited to 0.1cm / s, 0.2cm / s, 0.3cm / s, 0.4cm / s, 0.5cm / s, 0.6cm / s, 0.7cm / s, 0.8cm / s, 0.9cm / s, 1cm / s, 2cm / s, 3cm / s, 4cm / s, 5cm / s etc.

[0026] The peeled support substrate / transfer packaging layer / graphene wafer composite structure is then bonded to the target substrate. The target substrate may be an uneven substrate with a suspended structure on the surface. Using the transfer method of the present invention, alumina plays a supporting role due to its large modulus to avoid graphene breakage. In an optional embodiment, the target substrate is a silicon wafer, sapphire or Nafion membrane. Preferably, the target substrate is a silicon wafer. The support layer / transfer packaging layer / graphene wafer composite structure may be bonded to the target substrate by roller bonding or vacuum bonding.

[0027] The support layer is then removed. In an optional embodiment, the support layer can be removed by heating. Specifically, the support layer can be removed by placing the support layer / transfer packaging layer / graphene wafer / target substrate composite structure into a vacuum drying oven for heating. The heating temperature is 100-200°C and the time is 20-60 minutes, so that the support layer loses its viscosity and is removed.

[0028] Finally, the residual adhesive is removed. In an optional embodiment, the adhesive can be removed by immersing the transfer packaging layer / graphene wafer / target substrate composite structure in a solvent after removing the support layer to remove residual organic molecular impurities. The solvent can be water and / or ethanol, and the immersion temperature is 20-80° C. and the time is 1-10 minutes.

[0029] The above transfer packaging method can obtain a packaging structure including an aluminum oxide / graphene wafer / substrate composite structure.

[0030] The present invention is further described below by specific examples. However, these examples are merely exemplary and do not constitute any limitation to the scope of the present invention. In the following examples and comparative examples, the reagents, materials and instruments used are all commercially available unless otherwise specified.

[0031] Example 1

[0032] Aluminum oxide (Al2O3) was deposited on the surface of 4-inch graphene wafer / copper / sapphire wafer by atomic layer deposition (ALD). The deposition condition was a chamber pressure of about 6×10 -1 mbar, and the growth temperature is 120°C. Then spin-coat a polyvinyl alcohol solution (5% by mass, water as the solvent) at a speed of 4000 rpm for 60 seconds. After spin coating, place it on a hot plate and bake it at 80°C for 3 minutes. Then use a roller to bond the thermal release tape (TRT) to the surface of the polyvinyl alcohol to form a thermal release tape / polyvinyl alcohol / aluminum oxide / graphene / copper / sapphire composite structure. It is then fixed on a carrier, and a mechanical stripping device is used to slowly peel the thermal release tape / polyvinyl alcohol / aluminum oxide / graphene from the copper surface at a stripping speed of 0.5 cm / s. The copper / sapphire growth substrate is cleaned with deionized water and ethanol, and then dried with nitrogen and placed in a wafer box for recovery. Afterwards, the thermal release tape / polyvinyl alcohol / aluminum oxide / graphene composite structure is cut to a size that can cover the uneven substrate with a suspended structure on the surface, and bonded using a roller press. Then, the obtained composite structure of thermal release tape / polyvinyl alcohol / aluminum oxide / graphene / uneven substrate with suspended structures on the surface was placed in an oven, heated at 120°C for 30 minutes, and then the edge of the silicon wafer was fixed with a clamp to peel off the transfer support layer. The composite structure of aluminum oxide / graphene / uneven substrate with suspended structures on the surface was immersed in deionized water for 30 minutes to remove the residual polyvinyl alcohol adhesive, the surface was washed with deionized water, and dried with nitrogen to finally obtain a graphene device transferred to the uneven substrate with suspended structures on the surface.

[0033] Comparative Example 1

[0034] The same graphene wafer / copper / sapphire wafer structure as in Example 1 is used. Use a glue spreader to spin-coat PMMA solution (950PMMA A4) on the surface of the graphene wafer at a speed of 5000rpm for 60s. After spin coating, place it on a hot stage and bake at a temperature of 130°C for 3min. Then use a roller press to adhere thermal release tape (TRT) to the PMMA surface to form a TRT / PMMA / graphene / copper / sapphire composite structure. It is then fixed on a carrier and immersed in a sodium hydroxide solution with a concentration of 1mol / L. The negative pole of the DC power supply is connected to the copper part of the composite structure, and the positive pole is connected to a platinum sheet. During bubbling, the DC power supply applies a voltage of 6V for 5min. Subsequently, the TRT / PMMA / graphene wafer composite structure is peeled off from the copper / sapphire with a wafer clamp and put into deionized water for cleaning, washing 3 times, each time for 15min. The surface of the copper / sapphire growth substrate was cleaned with deionized water and ethanol, and then dried with nitrogen and placed in a wafer box for recovery. After the cleaned TRT / PMMA / graphene wafer composite structure was naturally dried for 3 hours, it was bonded to the uneven substrate with the same suspended structure as in Example 1 using a roller press. The obtained TRT / PMMA / graphene wafer / uneven substrate composite structure with a suspended structure on the surface was placed in an oven, heated at 120°C for 60 minutes to release the TRT and remove it. The obtained PMMA / graphene wafer / uneven substrate composite structure with a suspended structure on the surface was placed on a hot table and baked at 180°C for 3 hours. It was then placed in a mixed solution of acetone and isopropanol in a ratio of 3:2 for degumming, soaked 3 times, 10 minutes each time, and stirred with a magnet. Finally, it was dried with nitrogen to obtain a graphene wafer transferred to the uneven substrate composite structure with a suspended structure on the surface.

[0035] Figure 2 In the figure, abc are the actual photos of the uneven substrate with suspended structures on the surface before transfer, after transfer and after glue removal, respectively. a shows the macro structure of the target substrate, b shows the colored residual glue, and c shows the effective removal of the residual glue. Figure 2 Figure d is an optical microscope photograph of the graphene wafer of Example 1 transferred to an uneven substrate with a suspended structure on the surface. Figure 3 This is an optical microscope photo of the graphene wafer of Example 1 before removal of the adhesive after being transferred to the uneven substrate composite structure with suspended structures on the surface. Figure 2 and Figure 3 Through observation, it can be found that the integrity and cleanliness of the graphene in Example 1 are significantly higher than those in Comparative Example 1.

[0036] Figure 4 This is the Raman spectrum characterization result of the graphene on the uneven substrate with a suspended structure in Example 1. The G peak and 2D peak of the single-layer graphene can be seen in the figure, which can indicate that the graphene encapsulated by aluminum oxide is completely transferred to the substrate.

[0037] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A graphene wafer transfer packaging method, characterized in that: include: Aluminum oxide is deposited on the surface of a graphene wafer directly grown on a substrate as a transfer packaging layer, a high molecular polymer adhesive is spin-coated on the transfer packaging layer, and then a support layer is attached to obtain a support layer / transfer packaging layer / graphene wafer / substrate composite structure; Separating the support layer / transfer packaging layer / graphene wafer from the substrate to obtain a support layer / transfer packaging layer / graphene wafer composite structure; Laminating the support layer / transfer packaging layer / graphene wafer composite structure to a target substrate to obtain a support layer / transfer packaging layer / graphene wafer / substrate composite structure; The support layer is separated from the transfer packaging layer by heat treatment to obtain a transfer packaging layer / graphene wafer / substrate composite structure.

2. The transfer packaging method according to claim 1, characterized in that: The transfer packaging layer is formed on the surface of the graphene wafer by atomic layer deposition, and the deposition condition is a chamber pressure of 4-8×10 -1 mbar, the growth temperature is 100-200° C.; the thickness of the transfer encapsulation layer is greater than or equal to 3 nm, preferably, less than or equal to 20 μm.

3. The transfer packaging method according to claim 1, characterized in that: The adhesive is one or more of polyvinyl alcohol, polymethyl methacrylate, and polycarbonate, preferably polyvinyl alcohol; the support layer is a thermal release tape, a UV film, or a silicone film, preferably a thermal release tape.

4. The transfer packaging method according to claim 1, characterized in that: The spin-coated high molecular polymer adhesive is baked after the solution containing the adhesive is spin-coated on the surface of the transfer packaging layer; the spin-coating speed is 500-8000rpm, the spin-coating time is 30s-5min; the baking temperature is 50-200°C, and the baking time is 1-5min.

5. The transfer packaging method according to claim 4, characterized in that: The mass concentration of the binder in the solution is 0.1-10%, and the solvent of the solution is water or ethanol.

6. The transfer packaging method according to claim 1, characterized in that: The support layer / transfer packaging layer / graphene wafer is separated from the substrate by mechanical peeling, wherein the mechanical peeling is manual or mechanical device assisted peeling, and the peeling speed is 0.1-5 cm / s.

7. The transfer packaging method according to claim 1, characterized in that: The target substrate is a silicon wafer, sapphire or Nafion membrane, preferably a silicon wafer; the support layer / transfer packaging layer / graphene wafer composite structure is bonded to the target substrate by roller bonding or vacuum bonding.

8. The transfer packaging method according to claim 1, characterized in that: The support layer is separated by placing the support layer / transfer packaging layer / graphene wafer / target substrate composite structure into a vacuum drying oven for heating, wherein the heating temperature is 100-200° C. and the heating time is 20-60 minutes.

9. The transfer packaging method according to claim 8, characterized in that: After removing the support layer, the transfer packaging layer / graphene wafer / target substrate composite structure is immersed in a solvent to remove residual organic molecular impurities. The solvent is water and / or ethanol. The immersion temperature is 20-80° C. and the time is 1-10 minutes.

10. A packaging structure, characterized in that: It includes the alumina / graphene wafer / substrate composite structure obtained by the transfer packaging method according to any one of claims 1 to 9.

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