Flexible controllable thermal resistance radio frequency device based on liquid substrate and preparation method thereof

Abstract

The invention relates to a flexible controllable thermal resistance radio frequency device based on a liquid substrate and a preparation method thereof. The preparation method comprises the following steps: S1, preparing an auxiliary stripping structure; s2, transferring the auxiliary stripping structure to the upper surface of the rigid substrate; s3, preparing an AlGaN / GaN HEMT structure on the upper surface of the auxiliary stripping structure to obtain a rigid radio frequency device; s4, preparing a modified liquid substrate solution; s5, destroying the auxiliary stripping structure of the rigid radio frequency device by using a rapid gradient cooling method to obtain the rigid radio frequency device in a self-stripping state; s6, the rigid radio frequency device in the self-stripping state is placed in the modified liquid substrate solution, and the AlGaN / GaN HEMT structure and the auxiliary stripping structure are separated; and S7, solidifying the modified liquid substrate solution, and forming a flexible substrate on the lower surface of the AlGaN / GaN HEMT structure to obtain the flexible controllable thermal resistance radio frequency device based on the liquid substrate.

Description

Technical Field

[0001] The present invention belongs to the field of microelectronic technology, and in particular relates to a flexible controllable thermal resistance radio frequency device based on a liquid substrate and a preparation method thereof. Background Art

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

[0003] The main challenge in the preparation of flexible RF 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 peel off the rigid substrate through methods such as laser lift-off and chemical etching, and then transfer the device structure to a flexible substrate to avoid damage to the flexible substrate caused by high temperature.

[0004] However, laser stripping and chemical etching can cause great damage to the epitaxial layer structure of the device, affecting the material quality of the device. In addition, although flexible RF devices have many advantages in theory, they still need to overcome problems such as heat dissipation difficulties in practical applications. The application of AlGaN / GaN HEMT RF devices in flexible electronic technology is greatly limited by the material quality and thermal conductivity. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention 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 invention is achieved by the following technical solutions:

[0006] A first aspect of the present invention provides a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate, comprising the following steps:

[0007] S1: preparing auxiliary peeling structure;

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

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

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

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

[0012] S6: placing the self-peeling rigid RF 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, thereby obtaining a flexible controllable thermal resistance radio frequency device based on a liquid substrate.

[0014] In one achievable manner, step S1 includes:

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

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

[0017] In one achievable manner, step S3 includes:

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

[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 and the drain;

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

[0022] In one achievable manner, step S4 includes:

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

[0024] S402: Stirring and standing the pre-mixed solution in sequence at a preset temperature to obtain a modified liquid substrate solution.

[0025] In one achievable manner, step S5 includes:

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

[0027] S502: Within the second preset time, the temperature is lowered from the second preset temperature to a third preset temperature to destroy the plurality of layers of patterned structures, thereby obtaining a rigid radio frequency device in a self-peeling state.

[0028] In an achievable manner, the first preset time and the second preset time are both 1 to 2 minutes;

[0029] The first preset temperature is 850-900°C;

[0030] The second preset temperature is 500-550°C;

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

[0032] In one achievable manner, step S6 includes:

[0033] S601: placing the rigid RF device in a self-peeling state in the modified liquid substrate solution to separate the AlGaN / GaN HEMT structure and the auxiliary peeling structure;

[0034] S602: taking the auxiliary peeling structure out of the modified liquid substrate solution.

[0035] In one achievable manner, the material of the rigid substrate includes sapphire.

[0036] The second aspect of the present invention provides a flexible controllable thermal resistance radio frequency device based on a liquid substrate, which is prepared according to the preparation method provided by the first aspect of the present invention, comprising:

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

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

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

[0040] The present invention discloses a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate. The auxiliary peeling structure is destroyed by a rapid gradient cooling method, and the modified liquid substrate solution is used to assist peeling to protect the integrity of the structure. The modified liquid substrate solution is solidified to directly form a flexible substrate, thereby preparing a flexible radio frequency device and avoiding the traditional peeling method from affecting the material quality of the device. In addition, the present invention improves the thermal conductivity of polyimide by modifying the polyimide, thereby achieving controllable thermal resistance and meeting the heat dissipation requirements of transistors. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It 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 schematic structural 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 schematic structural diagram of another rigid radio frequency device provided by an embodiment of the present invention;

[0045] Figure 5 It is a schematic structural diagram of a flexible controllable thermal resistance radio frequency device based on a liquid substrate provided in an embodiment of the present invention;

[0046] Figure 6 It is a schematic structural diagram of another flexible controllable thermal resistance radio frequency device based on a liquid substrate provided in 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 is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0050] Embodiment 1

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

[0052] The present 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 also Figure 2 , Figure 2 is a schematic diagram of the structure of the auxiliary peeling structure provided in 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 , preparing a plurality of layers of patterned structures 12 on the multilayer h-BN film 11 , and obtaining 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. Several layers etched in the multilayer h-BN thin film structure 11 form several layers of patterned structures 12. The multilayer h-BN thin film structure 11 and the several layers of patterned structures 12 constitute an auxiliary peeling structure 1. The multilayer h-BN thin film structure 11 is 3 to 5 layers, and the several layers of patterned structures 12 are 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 several layers of patterned structure 12. After the PMMA film is cured, the PMMA surface is adsorbed on the PDMS. The PDMS is placed upward in a 68g / L ammonium persulfate solution and soaked for 12 hours, and the copper foil is removed to obtain an auxiliary peeling structure 1 with PDMS / PMMA. The auxiliary peeling structure 1 is transferred to the upper surface of the rigid substrate 2 through PDMS, and then soaked in acetone and ethanol solutions and dried naturally to complete the transfer of the auxiliary peeling structure 1.

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

[0063] S3: preparing an AlGaN / GaN HEMT structure 3 on the upper surface of the auxiliary lift-off structure 1 to obtain a rigid radio frequency device.

[0064] See also Figure 3 , Figure 3 : is a schematic diagram of the structure of a rigid RF device provided by an embodiment of the present invention. In this embodiment, an AlGaN / GaN HEMT structure 3 is grown on the upper surface of a plurality of layers of patterned structures 12, the AlGaN / GaN HEMT structure 3 includes an epitaxial structure and an electrode structure, and the AlGaN / GaN HEMT structure 3, the auxiliary peeling structure 1 and the rigid substrate 2 form a rigid RF device. Furthermore, since the material of the auxiliary peeling structure 1 is h-BN, when growing the AlGaN / GaN HEMT structure 3, the auxiliary peeling structure 1 also has the function of an insertion layer, which can increase the nucleation sites and improve the interlayer stress through the N-rich surface, thereby improving the material quality of the AlGaN / GaN HEMT structure 3.

[0065] See also Figure 4 , Figure 4 is a schematic diagram of the structure of another rigid radio frequency device provided by an embodiment of the present invention. In one achievable manner, step S3 includes:

[0066] S301 : 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 in sequence from bottom to top on the upper surface of the auxiliary lift-off structure 1 .

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

[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 the 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), a double-layer adhesion technique is used to define an ohmic contact region with a line width of 1 μm at both ends of the upper surface of the GaN cap layer 35, and then metallization and stabilization treatment are performed by annealing at 850° C. for 35 seconds in nitrogen to form a source 36 and a drain 37. The metal used for metallization is a Ti / Al / Ni / Au stacked metal.

[0071] S303 : forming 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 .

[0072] Specifically, a SiN passivation layer 39 with a thickness of 120 nm 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: preparing a gate 38 penetrating the SiN passivation layer 39 between the source 36 and the drain 37 to obtain a rigid radio frequency device.

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

[0075] S4: preparing a modified liquid substrate solution.

[0076] Specifically, step S4 includes:

[0077] S401: uniformly dispersing c-BN in liquid polyimide (PI) to obtain a primary mixed solution.

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

[0079] S402: The initially mixed solution is stirred and allowed to stand in sequence at a preset temperature to obtain a modified liquid substrate solution.

[0080] Specifically, the initial mixed solution is placed in a mixer, and stirred for 3 to 10 minutes at a speed of 3000 rpm at 500°C. After stirring, the solution is allowed to stand at 500°C for 10 minutes to obtain a modified liquid substrate solution. c-BN has high thermal conductivity. Modifying polyimide with c-BN can improve the thermal conductivity of polyimide, achieve controllable thermal resistance, and meet the heat dissipation requirements of transistors.

[0081] S5: using a rapid gradient cooling method to destroy the auxiliary peeling structure 1 of the rigid radio frequency device, and obtaining a rigid radio frequency device in a self-peeling state.

[0082] Specifically, step S5 includes:

[0083] S501: Within a first preset time, lowering the temperature from a first preset temperature to a second preset temperature.

[0084] S502: Within the second preset time, the temperature is lowered from the second preset temperature to a third preset temperature, so as to destroy a plurality of layers of the patterned structure 12 and obtain a rigid radio frequency device in a self-peeling state.

[0085] Furthermore, the first preset time and the second preset time are both 1 to 2 minutes. The first preset temperature is 850 to 900°C. The second preset temperature is 500 to 550°C. The third preset temperature is 100 to 150°C. The rapid gradient cooling method can introduce downward compressive stress in the AlGaN / GaN HEMT structure 3, and several layers of patterned structures 12 in the auxiliary stripping structure 1 will be destroyed under the stress, and the connection between the multilayer h-BN film structure 11 and the AlGaN / GaN HEMT structure 3 is disconnected, presenting a self-stripping state.

[0086] S6: placing the self-peeling rigid RF device in a modified liquid substrate solution to separate the AlGaN / GaN HEMT structure 3 and the auxiliary peeling structure 1.

[0087] Specifically, step S6 includes:

[0088] S601: placing the rigid RF device in a self-peeling state in a modified liquid substrate solution to separate the AlGaN / GaN HEMT structure 3 and the auxiliary peeling structure 1.

[0089] Specifically, the modified liquid substrate solution obtained in step S4 is evenly placed in a clean culture dish, and the rigid RF device in the self-peeling state is quickly placed in the modified liquid substrate solution. Although the multilayer h-BN thin film structure 11 and the AlGaN / GaN HEMT structure 3 are in a self-peeling state, the AlGaN / GaN HEMT structure 3 is extremely thin and cannot be directly removed. Therefore, the rigid RF device in the self-peeling 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 peeling structure 1 under the action of the solution.

[0090] S602: taking out the auxiliary peeling structure 1 from the modified liquid substrate solution.

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

[0092] S7: solidifying the modified liquid substrate solution to form a flexible substrate 4 on the lower surface of the AlGaN / GaN HEMT structure 3, thereby obtaining a flexible controllable thermal resistance radio frequency device based on the liquid substrate.

[0093] Specifically, since the AlGaN / GaN HEMT structure 3 is very thin and can float on the modified liquid substrate solution, after the modified liquid substrate solution solidifies, a flexible substrate 4 can be formed on the lower surface of the AlGaN / GaN HEMT structure 3. The flexible substrate 4 is laser etched to form a flexible controllable thermal resistance RF device based on a liquid substrate. This embodiment helps to protect the integrity of the AlGaN / GaN HEMT structure 3 by stripping the device structure in a liquid environment, and uses polyimide to cure and bond the self-stripped AlGaN / GaN HEMT structure 3 to achieve the preparation of a flexible controllable thermal resistance RF device.

[0094] This embodiment also provides a flexible controllable thermal resistance RF device based on a liquid substrate, see Figure 5 , Figure 5 Schematic diagram of the structure of a flexible controllable thermal resistance RF device based on a liquid substrate provided in an embodiment of the present invention. This embodiment also provides a flexible controllable thermal resistance RF device based on a liquid substrate, including: 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 AlGaN / GaN HEMT structure 3 in the flexible controllable thermal resistance RF device based on the liquid substrate provided in this embodiment is prepared on the rigid substrate 2 and the auxiliary peeling structure 1, and the AlGaN / GaN HEMT structure 3 is peeled off from the auxiliary peeling structure 1 by a rapid gradient cooling method combined with a modified liquid substrate solution to protect the integrity of the structure, and the modified liquid substrate solution is solidified and bonded to the AlGaN / GaN HEMT structure 3 to directly form a 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 the nucleation sites and improving the interlayer stress through the N-rich surface.

[0096] In another possible implementation, see Figure 6 , Figure 6 It is a structural schematic diagram of another flexible controllable thermal resistance RF device based on a liquid substrate provided by an embodiment of the present invention. The AlGaN / GaN HEMT structure 3 includes: 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 36, a drain 37, a gate 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 arranged in sequence from bottom to top, the source 36 and the drain 37 are located at both ends of the upper surface of the GaN cap layer 35, and the gate 38 is located on the upper surface of the GaN cap layer 35 between the source 36 and the drain 37. The SiN passivation layer 39 is located on the upper surface of the GaN cap layer 35 between the source 36, the drain 37 and the gate 38.

[0097] The method for preparing a flexible controllable thermal resistance RF device based on a liquid substrate provided in this embodiment destroys the auxiliary peeling structure by a rapid gradient cooling method, and assists peeling by a modified liquid substrate solution to protect the integrity of the structure, and solidifies the modified liquid substrate solution to directly form a flexible substrate, thereby preparing a flexible RF device. In addition, this embodiment modifies polyimide by using highly thermally conductive c-BN to improve the thermal conductivity of polyimide, achieve controllable thermal resistance, and meet the heat dissipation requirements of transistors.

[0098] Embodiment 2

[0099] On the basis of Example 1, this embodiment provides a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate. In this embodiment, the total number of layers of the auxiliary peeling structure 1 is 10 layers. The number of layers of the patterned structure 12 is controlled by controlling the etching time of the multilayer h-BN thin film structure 11. The c-BN content in the initial mixed solution is 5 to 20 mol / L. The initial mixed solution is placed in a mixer, and the speed is 3000 rpm at 500°C for 3 minutes. After the stirring is completed, it is allowed to stand for 10 minutes at 500°C to obtain a modified liquid substrate solution. In the rapid gradient cooling method, the first preset time and the second preset time are both 2 minutes. The first preset temperature is 850°C. The second preset temperature is 500°C. The third preset temperature is 100°C. The remaining steps are the same as in Example 1 and will not be repeated here.

[0100] Embodiment 3

[0101] On the basis of Example 1, this embodiment provides a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate. In this embodiment, the total number of layers of the auxiliary peeling structure 1 is 15 layers. The number of layers of the patterned structure 12 is controlled by controlling the etching time of the multilayer h-BN thin 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 at 500°C and a speed of 3000 rpm for 3 minutes. After stirring, let it stand at 500°C for 10 minutes to obtain a modified liquid substrate solution. In the rapid gradient cooling method, the first preset time and the second preset time are both 2 minutes. The first preset temperature is 900°C. The second preset temperature is 550°C. The third preset temperature is 150°C. The remaining steps are the same as in Example 1 and will not be repeated here.

[0102] Embodiment 4

[0103] On the basis of Example 1, this embodiment provides a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate. In this embodiment, the total number of layers of the auxiliary peeling structure 1 is 15 layers. The number of layers of the patterned structure 12 is controlled by controlling the etching time of the multilayer h-BN thin film structure 11. The c-BN content in the initial mixed solution is 10 mol / L. The initial mixed solution is placed in a mixer, and the speed is 3000 rpm at 500°C for 5 minutes. After the stirring is completed, it is allowed to stand at 500°C for 10 minutes to obtain a modified liquid substrate solution. In the rapid gradient cooling method, the first preset time and the second preset time are both 1min. The first preset temperature is 870°C. The second preset temperature is 530°C. The third preset temperature is 130°C. The remaining steps are the same as in Example 1 and will not be repeated here.

[0104] Embodiment 5

[0105] On the basis of Example 1, this embodiment provides a method for preparing a flexible controllable thermal resistance radio frequency device based on a liquid substrate. In this embodiment, the total number of layers of the auxiliary peeling structure 1 is 15 layers. The number of layers of the patterned structure 12 is controlled by controlling the etching time of the multilayer h-BN thin film structure 11. The c-BN content in the initial mixed solution is 15 mol / L. The initial mixed solution is placed in a mixer and stirred for 10 minutes at a speed of 3000 rpm at 500°C. After stirring, let it stand for 10 minutes at 500°C to obtain a modified liquid substrate solution. In the rapid gradient cooling method, the first preset time and the second preset time are both 1.5 min. The first preset temperature is 850°C. The second preset temperature is 500°C. The third preset temperature is 100°C. The remaining steps are the same as in Example 1 and will not be repeated here.

[0106] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A flexible controllable thermal resistance radio frequency device based on a liquid substrate, characterized in that: The following steps are involved: S1: preparing an auxiliary peeling structure (1); S2: transferring the auxiliary peeling structure (1) to the upper surface of the 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: using a rapid gradient cooling method to destroy the auxiliary peeling structure (1) of the rigid radio frequency device to obtain a rigid radio frequency device in a self-peeling state; S6: placing the self-peeling rigid RF 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), thereby obtaining a flexible controllable thermal resistance radio frequency device based on a liquid substrate.

2. A flexible controllable thermal resistance radio frequency device based on a liquid substrate according to claim 1, characterized in that: Step S1 includes: S101: Obtaining a multilayer h-BN film structure (11); S102: wet-etching the multilayer h-BN film structure (11), preparing a plurality of layers of patterned structures (12) on the multilayer h-BN film (11), and obtaining an auxiliary peeling structure (1).

3. The flexible controllable thermal resistance radio frequency device based on liquid substrate according to claim 1, characterized in that: Step S3 includes: S301: 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) in sequence from bottom to top on the upper surface of the auxiliary stripping structure (1); 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 (38) penetrating the SiN passivation layer (39) between the source (36) and the drain (37) to obtain a rigid radio frequency device.

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

5. The flexible controllable thermal resistance radio frequency device based on liquid substrate according to claim 2, characterized in that: Step S5 includes: S501: reducing the temperature from a first preset temperature to a second preset temperature within a first preset time; S502: Within the second preset time, the temperature is lowered from the second preset temperature to a third preset temperature, thereby destroying the plurality of layers of the patterned structure (12) and obtaining a rigid radio frequency device in a self-peeling state.

6. The flexible controllable thermal resistance radio frequency device based on liquid substrate according to claim 5, characterized in that: The first preset time and the second preset time are both 1 to 2 minutes; The first preset temperature is 850-900°C; The second preset temperature is 500-550°C; The third preset temperature is 100-150°C.

7. The flexible controllable thermal resistance radio frequency device based on liquid substrate according to claim 5, characterized in that: Step S6 includes: S601: placing the rigid radio frequency device in a self-peeling state in the modified liquid substrate solution to separate the AlGaN / GaN HEMT structure (3) and the auxiliary peeling structure (1); S602: taking out the auxiliary peeling structure (1) from the modified liquid substrate solution.

8. The flexible controllable thermal resistance radio frequency device based on liquid substrate according to claim 1, characterized in that: The material of the rigid substrate (2) includes sapphire.

9. A flexible controllable thermal resistance radio frequency device based on a liquid substrate, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 8, comprising: A flexible substrate (4) and an AlGaN / GaN HEMT structure (3) located on the upper surface of the flexible substrate (4).

10. The flexible controllable thermal resistance radio frequency device based on liquid substrate according to claim 9, characterized in that: The material of the flexible substrate (4) is c-BN-modified polyimide.

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