A flexible controllable thermal resistance radio frequency device based on liquid substrate and a preparation method thereof

Abstract

The application relates to a flexible controllable thermal resistance radio frequency device based on a liquid substrate and a preparation method thereof, and the preparation method comprises the following steps: S1, preparing an auxiliary peeling structure; S2, transferring the auxiliary peeling structure to the upper surface of a rigid substrate; S3, preparing an AlGaN / GaN HEMT structure on the upper surface of the auxiliary peeling structure to obtain a rigid radio frequency device; S4, preparing a modified liquid substrate solution; S5, destroying the auxiliary peeling structure of the rigid radio frequency device by using a rapid gradient cooling method to obtain a self-peeling state rigid radio frequency device; S6, placing the self-peeling state rigid radio frequency device in the modified liquid substrate solution to separate the AlGaN / GaN HEMT structure and the auxiliary peeling structure; and S7, solidifying the modified liquid substrate solution to form a flexible substrate on the lower surface of the AlGaN / GaN HEMT structure, thereby obtaining the flexible controllable thermal resistance radio frequency device based on the liquid substrate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of microelectronics technology, and particularly relates to a flexible controllable thermal resistance radio frequency device based on a liquid substrate and a preparation method thereof. BACKGROUND

[0002] In recent years, with the development of flexible electronics technology, flexible radio frequency devices have gradually emerged. Flexible radio frequency devices are mainly used in wearable wireless communication systems, conformal radars and other occasions. They can adapt to various shapes and sizes of application environments, providing flexibility that traditional rigid electronic devices do not have. AlGaN / GaN High Electron Mobility Transistor (HEMT) plays an important role in radio frequency (RF) technology due to its excellent electron mobility, breakdown voltage and power density. These characteristics make AlGaN / GaN HEMT perform well in high-frequency and high-power applications, and it is widely used in radar, communication systems and power amplifiers.

[0003] The main challenge in the preparation of flexible radio frequency devices is how to grow high-quality epitaxial layers on soft substrate materials, especially for materials such as GaN that require high-temperature processing. Existing technologies usually use methods such as laser lift-off and chemical etching to separate the rigid substrate, and then transfer the device structure to a flexible substrate to avoid damage to the flexible substrate caused by high temperature.

[0004] However, laser lift-off and chemical etching can cause a lot of damage to the device epitaxial layer structure, affecting the material quality of the device. Moreover, although flexible radio frequency devices have many advantages in theory, they still need to overcome problems such as heat dissipation difficulties in practical applications. AlGaN / GaN HEMT radio frequency devices are affected by material quality and thermal conductivity, and their application in flexible electronics technology is greatly limited. SUMMARY

[0005] In order to solve the above problems existing in the prior art, the present application provides a flexible controllable thermal resistance radio frequency device based on a liquid substrate and a preparation method thereof. The technical problem to be solved by the present application is solved by the following technical scheme:

[0006] The first aspect of the present application provides a preparation method of a flexible controllable thermal resistance radio frequency device based on a liquid substrate, comprising the following steps:

[0007] S1: preparing an auxiliary lift-off structure;

[0008] S2: transferring the auxiliary lift-off structure to the upper surface of the rigid substrate;

[0009] S3: preparing an AlGaN / GaN HEMT structure on the upper surface of the auxiliary lift-off structure to obtain a rigid radio frequency device.

[0010] S4: preparing a modified liquid substrate solution;

[0011] S5: destroying the auxiliary peeling structure of the rigid radio frequency device by using a rapid gradient cooling method to obtain a self-peeling rigid radio frequency device;

[0012] S6: placing the self-peeling rigid radio frequency device in the modified liquid substrate solution to separate the AlGaN / GaN HEMT structure and the auxiliary peeling structure;

[0013] S7: solidifying the modified liquid substrate solution to form a flexible substrate on the lower surface of the AlGaN / GaN HEMT structure to obtain a flexible controllable thermal resistance radio frequency device based on a liquid substrate.

[0014] In an implementable manner, step S1 comprises:

[0015] S101: obtaining a multi-layer h-BN film structure;

[0016] S102: performing wet etching on the multi-layer h-BN film structure to prepare a plurality of patterned structures on the multi-layer h-BN film to obtain an auxiliary peeling structure.

[0017] In an implementable manner, step S3 comprises:

[0018] S301: sequentially depositing an AlN nucleation layer, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer and a GaN cap layer on the upper surface of the auxiliary peeling structure from bottom to top;

[0019] S302: preparing a source electrode and a drain electrode on the upper surface of the GaN cap layer;

[0020] S303: preparing a SiN passivation layer on the upper surface of the GaN cap layer between the source electrode and the drain electrode;

[0021] S304: preparing a gate electrode penetrating through the SiN passivation layer between the source electrode and the drain electrode to obtain a rigid radio frequency device.

[0022] In an implementable manner, step S4 comprises:

[0023] S401: uniformly dispersing c-BN in a liquid polyimide to obtain a preliminary mixed solution;

[0024] S402: sequentially stirring and standing the preliminary mixed solution at a preset temperature to obtain a modified liquid substrate solution.

[0025] In an implementable manner, step S5 comprises:

[0026] S501: reducing the temperature from a first preset temperature to a second preset temperature within a first preset time;

[0027] S502: reducing the temperature from the second preset temperature to a third preset temperature within a second preset time, destroying the several layers of patterned structures, and obtaining a rigid radio frequency device in a self-stripping state.

[0028] In an implementable manner, the first preset time and the second preset time are both 1-2 min.

[0029] The first preset temperature is 850-900℃.

[0030] The second preset temperature is 500-550℃.

[0031] The third preset temperature is 100-150℃.

[0032] In an implementable manner, step S6 comprises:

[0033] S601: placing the rigid radio frequency device in a self-stripping state in the modified liquid substrate solution, separating the AlGaN / GaN HEMT structure and the auxiliary stripping structure.

[0034] S602: taking out the auxiliary stripping structure from the modified liquid substrate solution.

[0035] In an implementable manner, the material of the rigid substrate comprises sapphire.

[0036] A second aspect of the present application provides a flexible controllable thermal resistance radio frequency device based on a liquid substrate, which is prepared according to the preparation method provided in the first aspect of the present application, and comprises:

[0037] a flexible substrate and an AlGaN / GaN HEMT structure located on the upper surface of the flexible substrate.

[0038] In an implementable manner, the material of the flexible substrate is c-BN modified polyimide.

[0039] Compared with the prior art, the present application has the following beneficial effects:

[0040] The present invention discloses a method for preparing a flexible, controllable thermal resistance RF device based on a liquid substrate. This method uses a rapid gradient cooling method to destroy the auxiliary peeling structure. A modified liquid substrate solution is then used to assist in peeling, protecting the integrity of the structure. The modified liquid substrate solution is then solidified to directly form a flexible substrate, enabling the fabrication of a flexible RF device while avoiding the impact of traditional peeling methods on device material quality. Furthermore, by modifying polyimide to improve its thermal conductivity, the present invention achieves controllable thermal resistance, adapting to the heat dissipation requirements of transistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a step diagram of a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate provided by an embodiment of the present invention;

[0042] Figure 2 is a structural schematic diagram of an auxiliary peeling structure provided by an embodiment of the present invention;

[0043] Figure 3 is a schematic structural diagram of a rigid radio frequency device provided by an embodiment of the present invention;

[0044] Figure 4 is a structural diagram of another rigid radio frequency device provided by an embodiment of the present invention;

[0045] Figure 5 Schematic diagram of the structure of a flexible controllable thermal resistance radio frequency device based on a liquid substrate provided by an embodiment of the present invention;

[0046] Figure 6 This is a schematic structural diagram of another flexible controllable thermal resistance radio frequency device based on a liquid substrate provided by an embodiment of the present invention.

[0047] Reference numerals:

[0048] 1: Assisted peeling structure; 11: Multilayer h-BN thin film structure; 12: Several layers of patterned structure; 2: Rigid substrate; 3: AlGaN / GaN HEMT structure; 31: AlN nucleation layer; 32: GaN buffer layer; 33: GaN channel layer; 34: AlGaN barrier layer; 35: GaN cap layer; 36: Source; 37: Drain; 38: Gate; 39: SiN passivation layer; 4: Flexible substrate. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0050] Example 1

[0051] See Figure 1 , Figure 1This is a step diagram of a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate provided by an embodiment of the present invention.

[0052] This embodiment provides a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate, comprising the following steps:

[0053] S1: preparing an auxiliary peeling structure 1.

[0054] See Figure 2 , Figure 2 Schematic diagram of the auxiliary peeling structure provided by an embodiment of the present invention. In this embodiment, step S1 includes:

[0055] S101: Obtain a multilayer hexagonal boron nitride (h-BN) thin film structure 11.

[0056] S102 : wet-etching the multilayer h-BN film structure 11 to prepare a plurality of layers of patterned structures 12 on the multilayer h-BN film 11 to obtain an auxiliary peeling structure 1 .

[0057] Furthermore, the multilayer h-BN thin film structure 11 is located on the copper foil and can be directly obtained. A 0.6 mol / L thionyl chloride etching solution is prepared, and the multilayer h-BN thin film structure 11 is patterned and etched using the thionyl chloride etching solution for 5 to 10 minutes. The etched layers in the multilayer h-BN thin film structure 11 form a plurality of layers of patterned structures 12. The multilayer h-BN thin film structure 11 and the plurality of layers of patterned structures 12 constitute the auxiliary peeling structure 1. The multilayer h-BN thin film structure 11 is 3 to 5 layers, and the plurality of layers of patterned structures 12 is 7 to 10 layers.

[0058] S2 : transferring the auxiliary release structure 1 to the upper surface of the rigid substrate 2 .

[0059] Specifically, the auxiliary peeling structure 1 is transferred from the copper foil surface to the upper surface of the rigid substrate 2 by PMMA / PDMS assisted wet transfer technology, wherein the multilayer h-BN thin film structure 11 faces downward and contacts the upper surface of the rigid substrate 2 .

[0060] In this embodiment, the specific steps of step S2 are:

[0061] A layer of PMMA is spin-coated on the upper surface of the auxiliary peeling structure 1 (i.e., the surface of the multiple layers of patterned structure 12). After the PMMA film solidifies, the PMMA surface is adsorbed onto the PDMS. The PDMS is then immersed in a 68g / L ammonium persulfate solution for 12 hours, with the PDMS facing upward. The copper foil is then removed, resulting in the auxiliary peeling structure 1 with the PDMS / PMMA layer. The auxiliary peeling structure 1 is then transferred to the upper surface of the rigid substrate 2 through the PDMS. The structure is then immersed in acetone and ethanol solutions, and air-dried to complete the transfer.

[0062] Further, the material of the rigid substrate 2 comprises sapphire. Exemplarily, the thickness of the rigid substrate 2 is 500 nm.

[0063] S3: preparing the AlGaN / GaN HEMT structure 3 on the upper surface of the auxiliary exfoliation structure 1, to obtain the rigid radio frequency device.

[0064] Referring to Figure 3 , Figure 3 is a structural schematic diagram of a rigid radio frequency device provided by an embodiment of the present application. In the embodiment, the AlGaN / GaN HEMT structure 3 is grown on the upper surface of the several-layer patterned structure 12, the AlGaN / GaN HEMT structure 3 comprises an epitaxial structure and an electrode structure, and the AlGaN / GaN HEMT structure 3, the auxiliary exfoliation structure 1 and the rigid substrate 2 form the rigid radio frequency device. Further, since the material of the auxiliary exfoliation structure 1 is h-BN, the auxiliary exfoliation structure 1 also has the function of an interlayer when the AlGaN / GaN HEMT structure 3 is grown, which can increase nucleation sites and improve interlayer stress through the N-rich surface, and improve the material quality of the AlGaN / GaN HEMT structure 3.

[0065] Referring to Figure 4 , Figure 4 is a structural schematic diagram of another rigid radio frequency device provided by an embodiment of the present application. In an implementable manner, step S3 comprises:

[0066] S301: sequentially depositing, from bottom to top, an AlN nucleation layer 31, a GaN buffer layer 32, a GaN channel layer 33, an AlGaN barrier layer 34 and a GaN cap layer 35 on the upper surface of the auxiliary exfoliation structure 1.

[0067] Specifically, 30 nm of the AlN nucleation layer 31 is deposited at 1200℃ and 75 Torr by MOCVD technology; 500 nm of the GaN buffer layer 32 is deposited at 1100℃ and 200 Torr; 120 nm of the GaN channel layer 33 is deposited at 1050℃ and 200 Torr; 20 nm of the AlGaN barrier layer 34 is deposited at 1010℃ and 200 Torr; and 3 nm of the GaN cap layer 35 is deposited at 950℃ and 200 Torr. 0.25 Ga 0.75 N barrier layer 34 is deposited on the upper surface of the GaN cap layer 35.

[0068] S302: preparing a source electrode 36 and a drain electrode 37 on the upper surface of the GaN cap layer 35.

[0069] Specifically, the source electrode 36 and the drain electrode 37 are located at two ends of the upper surface of the GaN cap layer 35, and a gate electrode 38 is located between the source electrode 36 and the drain electrode 37.

[0070] Specifically, after the device obtained in S302 is cleaned by RCA and etched by inductively coupled plasma (ICP), an ohmic contact region with a line width of 1 μm is defined on both ends of the upper surface of the GaN cap layer 35 using a double-layer adhesion technology, and then the metalization and stabilization treatment is performed by annealing at 850°C in nitrogen for 35 seconds, thereby forming the source electrode 36 and the drain electrode 37. The metal used for the metalization is a Ti / Al / Ni / Au stacked metal.

[0071] S303: A SiN passivation layer 39 is prepared on the upper surface of the GaN cap layer 35 between the source electrode 36 and the drain electrode 37.

[0072] Specifically, a 120 nm thick SiN passivation layer 39 is deposited on the surface of the GaN cap layer 35 between the source electrode 36 and the drain electrode 37 by low-temperature plasma chemical vapor deposition (PECVD).

[0073] S304: A gate electrode 38 is prepared between the source electrode 36 and the drain electrode 37, which penetrates the SiN passivation layer 39, thereby obtaining a rigid radio frequency device.

[0074] Specifically, an electron beam lithography is used to define a gate region between the source electrode 36 and the drain electrode 37, and an inductively coupled plasma-reactive ion etching (ICP-RIE) is used to open a hole in the gate region, the depth of the hole being equal to the thickness of the SiN passivation layer 39, and Ni / Au is evaporated as a gate metal in the gate region, thereby obtaining the gate electrode 38. After the step S304 is completed, the rigid radio frequency device is obtained.

[0075] S4: A modified liquid substrate solution is prepared.

[0076] Specifically, the step S4 includes:

[0077] S401: The c-BN is uniformly dispersed in a liquid polyimide (PI) to obtain a preliminary mixed solution.

[0078] Specifically, the nanometer cubic boron nitride (c-BN) is uniformly dispersed in a liquid polyimide to prepare a preliminary mixed solution with a c-BN content of 5-20 mol / L.

[0079] S402: The preliminary mixed solution is sequentially stirred and rested at a preset temperature to obtain a modified liquid substrate solution.

[0080] Specifically, the primary mixed solution is placed in a blender, and stirring is continuously performed at 500 DEG C and 3000 revolutions per minute for 3-10 minutes. After the stirring is completed, the modified liquid substrate solution is obtained by standing at 500 DEG C for 10 minutes. The c-BN has high thermal conductivity, and the thermal conductivity of the polyimide can be improved by modifying the polyimide with the c-BN, so that the controllable thermal resistance is realized, and the heat dissipation requirement of the transistor is met.

[0081] S5: The auxiliary peeling structure 1 of the rigid radio frequency device is destroyed by using a rapid gradient cooling method, and the rigid radio frequency device in a self-peeling state is obtained.

[0082] Specifically, the step S5 comprises:

[0083] S501: The temperature is reduced from a first preset temperature to a second preset temperature within a first preset time.

[0084] S502: The temperature is reduced from the second preset temperature to a third preset temperature within a second preset time, and a plurality of layers of the patterned structure 12 are destroyed, and the rigid radio frequency device in a self-peeling state is obtained.

[0085] Further, the first preset time and the second preset time are both 1-2 minutes. The first preset temperature is 850-900 DEG C. The second preset temperature is 500-550 DEG C. The third preset temperature is 100-150 DEG C. The rapid gradient cooling method can introduce a downward compressive stress in the AlGaN / GaN HEMT structure 3, and the plurality of layers of the patterned structure 12 in the auxiliary peeling structure 1 will be destroyed under the action of the stress, and the connection between the multi-layer h-BN film structure 11 and the AlGaN / GaN HEMT structure 3 is disconnected, and the rigid radio frequency device in a self-peeling state is obtained.

[0086] S6: The rigid radio frequency device in a self-peeling state is placed in the modified liquid substrate solution, and the AlGaN / GaN HEMT structure 3 and the auxiliary peeling structure 1 are separated.

[0087] Specifically, the step S6 comprises:

[0088] S601: The rigid radio frequency device in a self-peeling state is placed in the modified liquid substrate solution, and the AlGaN / GaN HEMT structure 3 and the auxiliary peeling structure 1 are separated.

[0089] Specifically, the modified liquid substrate solution obtained in step S4 is uniformly placed in a clean culture dish, and the rigid radio frequency device in the self-stripped state is quickly placed in the modified liquid substrate solution. Although the multilayer h-BN film structure 11 and the AlGaN / GaN HEMT structure 3 are in the self-stripped state, the AlGaN / GaN HEMT structure 3 cannot be directly removed due to its extremely thin thickness. Therefore, the rigid radio frequency device in the self-stripped state is placed in the modified liquid substrate solution, and the AlGaN / GaN HEMT structure 3 is separated from the rigid substrate 2 and the auxiliary stripping structure 1 under the action of the solution.

[0090] S602: The auxiliary stripping structure 1 is taken out of the modified liquid substrate solution.

[0091] Specifically, the auxiliary stripping structure 1 and the rigid substrate 2 are separated from the AlGaN / GaN HEMT structure 3 as a whole, and the stripping structure 1 and the rigid substrate 2 are taken out by tweezers.

[0092] S7: The modified liquid substrate solution is solidified, a flexible substrate 4 is formed on the lower surface of the AlGaN / GaN HEMT structure 3, and a liquid-substrate-based flexible controllable thermal resistance radio frequency device is obtained.

[0093] Specifically, since the AlGaN / GaN HEMT structure 3 has a very thin thickness and can float on the modified liquid substrate solution, the flexible substrate 4 can be formed on the lower surface of the AlGaN / GaN HEMT structure 3 after the modified liquid substrate solution is solidified. The flexible controllable thermal resistance radio frequency device based on the liquid substrate is obtained by laser etching the flexible substrate 4. In this embodiment, the device structure stripping is performed in a liquid environment, which helps to protect the integrity of the AlGaN / GaN HEMT structure 3, and the self-stripped AlGaN / GaN HEMT structure 3 is bonded and solidified using polyimide, so as to realize the preparation of the flexible controllable thermal resistance radio frequency device.

[0094] This embodiment also provides a liquid-substrate-based flexible controllable thermal resistance radio frequency device, which will be described in detail below with reference to the accompanying drawings. Figure 5 , Figure 5 is a structural schematic diagram of the liquid-substrate-based flexible controllable thermal resistance radio frequency device provided in the embodiment of the present application. The liquid-substrate-based flexible controllable thermal resistance radio frequency device provided in this embodiment includes a flexible substrate 4 and an AlGaN / GaN HEMT structure 3 located on the upper surface of the flexible substrate 4. The material of the flexible substrate 4 is c-BN modified polyimide.

[0095] Specifically, the embodiment also provides the AlGaN / GaN HEMT structure 3 in the flexible controllable thermal resistance radio frequency device based on a liquid substrate, which is prepared on the rigid substrate 2 and the auxiliary peeling structure 1, and is peeled from the auxiliary peeling structure 1 by the rapid gradient cooling method combined with the modified liquid substrate solution auxiliary peeling, so as to protect the integrity of the structure, solidify the AlGaN / GaN HEMT structure 3 by the modified liquid substrate solution, and directly form the flexible substrate 4. Since the material of the auxiliary peeling structure 1 is h-BN, the material quality of the AlGaN / GaN HEMT structure 3 can be improved by increasing nucleation sites and improving interlayer stress through the N-rich surface.

[0096] In another implementable manner, referring to Figure 6 , Figure 6 is another structure diagram of the flexible controllable thermal resistance radio frequency device based on a liquid substrate provided by the embodiment of the present application. The AlGaN / GaN HEMT structure 3 comprises an AlN nucleation layer 31, a GaN buffer layer 32, a GaN channel layer 33, an AlGaN barrier layer 34, a GaN cap layer 35, a source electrode 36, a drain electrode 37, a gate electrode 38 and a SiN passivation layer 39. The AlN nucleation layer 31, the GaN buffer layer 32, the GaN channel layer 33, the AlGaN barrier layer 34 and the GaN cap layer 35 are sequentially arranged from bottom to top, the source electrode 36 and the drain electrode 37 are located at two ends of the upper surface of the GaN cap layer 35, and the gate electrode 38 is located on the upper surface of the GaN cap layer 35 between the source electrode 36 and the drain electrode 37. The SiN passivation layer 39 is located on the upper surface of the GaN cap layer 35 between the source electrode 36, the drain electrode 37 and the gate electrode 38.

[0097] The preparation method of the flexible controllable thermal resistance radio frequency device based on a liquid substrate provided by the embodiment can realize the preparation of the flexible radio frequency device by the rapid gradient cooling method, the destruction of the auxiliary peeling structure, the auxiliary peeling by the modified liquid substrate solution, the protection of the integrity of the structure, the solidification of the modified liquid substrate solution and the direct formation of the flexible substrate.

[0098] Embodiment two

[0099] Based on the embodiment one, the embodiment provides a preparation method of the flexible controllable thermal resistance radio frequency device based on the liquid substrate. In the embodiment, the total layer number of the auxiliary peeling structure 1 is 10. The layer number of the several layer patterned structure 12 is controlled by controlling the etching time of the multi-layer h-BN film structure 11. The c-BN content in the initial mixed solution is 5-20 mol / L. The initial mixed solution is placed in a blender. The stirring speed is 3000 revolutions / min at 500 DEG C. The stirring is continued for 3 minutes. After the stirring is completed, the modified liquid substrate solution is obtained by standing at 500 DEG C for 10 minutes. In the rapid gradient cooling method, the first preset time and the second preset time are both 2 min. The first preset temperature is 850 DEG C. The second preset temperature is 500 DEG C. The third preset temperature is 100 DEG C. The remaining steps are the same as those of the embodiment one, which will not be repeated here.

[0100] Embodiment three

[0101] Based on the embodiment one, the embodiment provides a preparation method of the flexible controllable thermal resistance radio frequency device based on the liquid substrate. In the embodiment, the total layer number of the auxiliary peeling structure 1 is 15. The layer number of the several layer patterned structure 12 is controlled by controlling the etching time of the multi-layer h-BN film structure 11. The c-BN content in the initial mixed solution is 5 mol / L. The initial mixed solution is placed in a blender. The stirring speed is 3000 revolutions / min at 500 DEG C. The stirring is continued for 3 minutes. After the stirring is completed, the modified liquid substrate solution is obtained by standing at 500 DEG C for 10 minutes. In the rapid gradient cooling method, the first preset time and the second preset time are both 2 min. The first preset temperature is 900 DEG C. The second preset temperature is 550 DEG C. The third preset temperature is 150 DEG C. The remaining steps are the same as those of the embodiment one, which will not be repeated here.

[0102] Embodiment four

[0103] Based on the embodiment one, the embodiment provides a preparation method of the flexible controllable thermal resistance radio frequency device based on the liquid substrate. In the embodiment, the total layer number of the auxiliary peeling structure 1 is 15. The layer number of the several layer patterned structure 12 is controlled by controlling the etching time of the multi-layer h-BN film structure 11. The c-BN content in the initial mixed solution is 10 mol / L. The initial mixed solution is placed in a blender. The stirring speed is 3000 revolutions / min at 500 DEG C. The stirring is continued for 5 minutes. After the stirring is completed, the modified liquid substrate solution is obtained by standing at 500 DEG C for 10 minutes. In the rapid gradient cooling method, the first preset time and the second preset time are both 1 min. The first preset temperature is 870 DEG C. The second preset temperature is 530 DEG C. The third preset temperature is 130 DEG C. The remaining steps are the same as those of the embodiment one, which will not be repeated here.

[0104] Embodiment five

[0105] Based on the embodiment one, the embodiment provides a preparation method of the flexible controllable thermal resistance radio frequency device based on the liquid substrate. In the embodiment, the total layer number of the auxiliary peeling structure 1 is 15. The layer number of the several layer patterned structures 12 is controlled by controlling the etching time of the multi-layer h-BN film structure 11. The c-BN content in the initial mixed solution is 15 mol / L. The initial mixed solution is placed in a blender. The stirring speed is 3000 revolutions per minute at 500 degrees Celsius. The stirring is continued for 10 minutes. After the stirring is completed, the modified liquid substrate solution is obtained by standing at 500 degrees Celsius for 10 minutes. In the rapid gradient cooling method, the first preset time and the second preset time are both 1.5 minutes. The first preset temperature is 850 degrees Celsius. The second preset temperature is 500 degrees Celsius. The third preset temperature is 100 degrees Celsius. The remaining steps are the same as those of the embodiment one, and are not described herein again.

[0106] The above is a further detailed description of the present application in combination with specific preferred embodiments, and the specific implementation of the present application should not be limited to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present application, and all of them should be regarded as falling within the protection scope of the present application.

Claims

1. A method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate, characterized in that: The method comprises the following steps: S1: preparing an auxiliary peeling structure (1); S2: transferring the auxiliary peeling structure (1) to the upper surface of a rigid substrate (2); S3: preparing an AlGaN / GaN HEMT structure (3) on the upper surface of the auxiliary peeling structure (1) to obtain a rigid radio frequency device; S4: preparing a modified liquid substrate solution; S5: destroying the auxiliary peeling structure (1) of the rigid radio frequency device by using a rapid gradient cooling method to obtain a self-peeling rigid radio frequency device; S6: placing the self-peeling rigid radio frequency device in the modified liquid substrate solution to separate the AlGaN / GaN HEMT structure (3) and the auxiliary peeling structure (1); S7: solidifying the modified liquid substrate solution to form a flexible substrate (4) on the lower surface of the AlGaN / GaN HEMT structure (3) to obtain a flexible controllable thermal resistance radio frequency device based on a liquid substrate.

2. The method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate according to claim 1, characterized in that: Step S1 comprises: S101: obtaining a multi-layer h-BN film structure (11); S102: performing wet etching on the multi-layer h-BN film structure (11) to prepare a plurality of layer patterned structures (12) on the multi-layer h-BN film (11) to obtain an auxiliary peeling structure (1).

3. The method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate according to claim 1, characterized in that: Step S3 comprises: S301: sequentially depositing an AlN nucleation layer (31), a GaN buffer layer (32), a GaN channel layer (33), an AlGaN barrier layer (34) and a GaN cap layer (35) on the upper surface of the auxiliary peeling structure (1) from bottom to top; S302: preparing a source electrode (36) and a drain electrode (37) on the upper surface of the GaN cap layer (35); S303: preparing a SiN passivation layer (39) on the upper surface of the GaN cap layer (35) between the source electrode (36) and the drain electrode (37); S304: preparing a gate electrode (38) penetrating through the SiN passivation layer (39) between the source electrode (36) and the drain electrode (37) to obtain a rigid radio frequency device.

4. The method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate according to claim 1, characterized in that: Step S4 comprises: S401: uniformly dispersing c-BN in a liquid polyimide to obtain a primary mixed solution; S402: sequentially stirring and standing the primary mixed solution at a preset temperature to obtain a modified liquid substrate solution.

5. The method of claim 2, wherein the liquid substrate is a liquid metal. 5 Step S5 comprises: S501: reducing the temperature from a first preset temperature to a second preset temperature within a first preset time; S502: reducing the temperature from the second preset temperature to a third preset temperature within a second preset time to destroy the plurality of layer patterned structures (12) to obtain a self-peeling rigid radio frequency device.

6. The method of claim 5, wherein the liquid substrate is a liquid metal. 5 The first preset time and the second preset time are both 1-2 min; The first preset temperature is 850-900℃; The second preset temperature is 500-550℃; The third preset temperature is 100-150℃.

7. The method of claim 5, wherein the liquid substrate is a liquid metal. Step S6 comprises: ​ S601: placing the self-peeling rigid radio frequency device in the modified liquid substrate solution to separate the AlGaN / GaN HEMT structure (3) and the auxiliary peeling structure (1); S602: removing the auxiliary release structure (1) from the modified liquid substrate solution.

8. The method of claim 1, wherein the liquid substrate is a liquid metal. The material of the rigid substrate (2) comprises sapphire. ​ 9. A liquid-subsfrate-based flexible controllable thermal resistance radio frequency device, characterized in that, Prepared according to the preparation method of any one of claims 1-8, comprising: a flexible substrate (4) and an AlGaN / GaN HEMT structure (3) located on the upper surface of the flexible substrate (4).

10. A liquid-substrate-based flexible controllable thermal resistance RF device according to claim 9, wherein, The material of the flexible substrate (4) is c-BN modified polyimide.

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