Selective batch transfer method based on phase change material, thermoelectric cell array and method of manufacturing the same

Abstract

The application discloses a selective batch transfer method based on a phase change material, which comprises the following steps: preparing a patterned bump array on a heat-conducting substrate, coating rosin on the surface of the patterned bump array; obtaining a donor substrate with a micro-element array on the surface, and corresponding bonding the patterned bump array coated with rosin and the micro-element array; controlling the temperature of the heat-conducting substrate to change the state of the rosin, so that the micro-element array is fixedly connected with the corresponding patterned bump array, and then picking up the micro-element array from the donor substrate; bonding the picked-up micro-element array with a receptor substrate surface, and changing the rosin from a solid state to a liquid state, so that the patterned bump array is separated from the corresponding micro-element array. By using the method, batch, selective and non-polluted transfer of non-planar or planar micro-elements can be realized. The application further discloses a thermoelectric element array and a preparation method thereof.

Description

Technical Field

[0001] This invention belongs to the field of micro-element transfer, specifically relating to a selective batch transfer method based on phase change materials, a thermoelectric element array and its fabrication method. Background Technology

[0002] As various microchips and related products develop towards high integration, arraying, and multifunctionality, the high-precision, high-efficiency, and high-yield selective batch transfer of arrayed micro-components has become a key technology that can be applied to many chip manufacturing and packaging fields.

[0003] For example, in the field of LED displays, it is necessary to transfer micro LED chips of different emitting colors in batches to the same substrate in a specific arrangement to form a pixel array; in the field of thermoelectric devices, it is necessary to transfer electronic and hole thermoelectric elements in batches and arrange them alternately into a high-density array, and then connect them through electrodes to form a high-performance thermoelectric device.

[0004] Current mass transfer technologies are mainly based on methods such as vacuum adsorption, elastic membranes, electromagnetic force, fluid assembly, fixtures, and adhesives.

[0005] Chinese patent CN114496744A discloses a diamond thin film transfer device and process, as well as a device and method for generating diamond thin film strain based on indirect pre-stretching. The transfer device includes a donor device and a receiver device. The device for generating diamond thin film strain based on indirect pre-stretching is the receiver device. In the diamond thin film transfer device, a transfer stamp adsorbs the diamond thin film located on the donor substrate through a photosensitive / thermal release adhesive film, and after transfer, releases the film to be transferred onto the receiver substrate via light / heat. In the device and method for generating diamond thin film strain based on indirect pre-stretching, the receiver substrate is opened by displacement / force / heat / electricity, causing the diamond thin film to stretch, thereby generating strain in the film. This patent enables rapid batch transfer of films to be transferred; it can also adapt to different spacings between films to be transferred, improving the versatility of the thin film transfer substrate, and fills the gap in the realization of batch diamond thin film stretching.

[0006] Chinese patent CN112366168A discloses a method and apparatus for mass transfer of micro-LED devices. The method includes: adhering multiple micro-LED devices to a carrier substrate; abutting the multiple micro-LED devices on the carrier substrate against a side of a buffer substrate coated with a second variable adhesive material, wherein the second variable adhesive material is an elastic material, and adjusting the adhesiveness of a portion of the first variable adhesive material to ensure the micro-LED devices on the carrier substrate adhere to the buffer substrate; and transferring the micro-LED devices on the buffer substrate to a receiving substrate at preset positions. This method and apparatus for mass transfer of micro-LED devices, by providing a carrier substrate, a buffer substrate, and a receiving substrate, utilizes the second variable adhesive material for efficient and selective batch transfer of micro-LEDs. The buffer substrate absorbs stress damage generated during the transfer process, reducing stress loss due to bonding, preventing breakage of the micro-LED devices during mass transfer, reducing transfer difficulty, and achieving good transfer results.

[0007] The aforementioned patent has the following drawbacks: a) The device is complex and costly; b) When picking up and releasing micro-components, the adhesion is poorly controlled, resulting in a low transfer yield; c) Due to limitations in the processing precision of the device, it can only transfer larger-sized micro-components; d) The transfer process can cause contamination to the micro-components; e) It is not suitable for transferring micro-components with non-planar surfaces. Summary of the Invention

[0008] This invention provides a selective batch transfer method based on phase change materials, which enables the batch, selective, and pollution-free transfer of non-planar or planar micro-components.

[0009] A selective batch transfer method based on phase change materials includes:

[0010] A patterned bump array is fabricated on a thermally conductive substrate, and rosin is coated on the surface of the patterned bump array.

[0011] A donor substrate is obtained, the surface of which has a micro-element array, and a patterned bump array coated with rosin is correspondingly bonded to the micro-element array.

[0012] By controlling the temperature of the thermally conductive substrate, the rosin is changed from liquid to solid, so that the micro-element array and the corresponding patterned bump array are fixedly connected by the rosin, and then the micro-element array is picked up from the donor substrate.

[0013] The picked-up micro-element array is bonded to the surface of the host substrate, and the temperature of the thermally conductive substrate is controlled again to change the rosin from solid to liquid, so that the patterned bump array is separated from the corresponding micro-element array, thereby achieving the purpose of batch transferring the micro-element array to the host substrate.

[0014] Furthermore, the specific steps for changing the rosin from a liquid to a solid state by controlling the temperature of the thermally conductive substrate, thereby fixing the micro-element array and the corresponding multiple bumps together via the rosin, are as follows:

[0015] By heating the thermally conductive substrate to 110°C to 135°C, the rosin becomes liquid and viscous enough to wet the corresponding micro-element array. Then, the temperature of the thermally conductive substrate is lowered to below 110°C, and the rosin is transformed from a liquid to a solid state, thereby achieving a fixed connection between the patterned bump array and the corresponding micro-element array.

[0016] It is easy to achieve this by changing the temperature required for rosin to change from a liquid phase to a solid phase. Compared with existing technologies, it is possible to simply and efficiently fix the bumps to the corresponding micro-element array.

[0017] Furthermore, the specific steps of controlling the temperature of the thermally conductive substrate again to change the rosin from a solid to a liquid state, thereby detaching the patterned bump array from the corresponding micro-element array, are as follows:

[0018] The temperature of the thermally conductive substrate is reheated to 110℃~200℃, causing the rosin to change from a solid to a liquid state. Then, the patterned bump array is separated from the corresponding micro-element array.

[0019] Furthermore, the ratio of the surface area of ​​the bumps in the patterned bump array to the surface area of ​​the corresponding micro-element is 1:1 to 1:100.

[0020] During the process of detaching the micro-component from the substrate, by controlling the surface area of ​​the bumps and the temperature of the heated thermally conductive substrate, the liquid adhesion force between the bumps and the corresponding micro-component is made less than the adhesion force between the micro-component and the host substrate, thereby achieving the purpose of transferring the micro-component to the host substrate.

[0021] Furthermore, the present invention provides a method for coating rosin onto the surface of a patterned bump array. The coating process is as follows: the coating solution is a mixed solution obtained by dissolving rosin in ethanol, and then the ethanol is dried at a temperature of 50°C to 100°C.

[0022] Furthermore, preferably, the rosin in the mixed solution has a mass fraction of 10% to 40%.

[0023] Further, the specific steps for fabricating a patterned bump array on a thermally conductive substrate are as follows: depositing a thin film on the thermally conductive substrate, etching the thin film to obtain a patterned bump array, wherein the material of the thin film is a metal, a semiconductor, or a ceramic. More preferably, the metal is copper or aluminum, the semiconductor is silicon, and the ceramic is alumina.

[0024] Furthermore, the material of the donor substrate is PDMS or an adhesive film.

[0025] Furthermore, the material of the host substrate is PDMS or an adhesive film.

[0026] Furthermore, the material of the thermally conductive substrate is a metal, a metal nitride, a metal oxide, or an oxide of silicon. More preferably, the metal nitride is aluminum nitride, and the metal oxide is aluminum oxide.

[0027] Furthermore, the thin film on the etched thermally conductive substrate is used to obtain a patterned bump array, and the etching process is photolithography or laser scanning.

[0028] Furthermore, the positions of the bumps in the patterned bump array are matched with the positions of the micro-elements to be transferred in the donor substrate.

[0029] This invention provides a method for removing residual rosin from the surface of a micro-element array using ethanol after the micro-element array has been transferred in batches to a host substrate.

[0030] This invention also provides a method for fabricating a thermoelectric element array, comprising:

[0031] The selective batch transfer method based on phase change materials is used to transfer electronic thermoelectric element arrays in batches onto the host substrate.

[0032] The selective batch transfer method based on phase change materials is used again to transfer the hole-type thermoelectric element array in batches to the acceptor substrate of the transferred electronic-type thermoelectric element array, wherein the hole-type thermoelectric elements are located between the electronic-type thermoelectric elements.

[0033] The beneficial effects of the above-mentioned method for fabricating thermoelectric element arrays provided by the present invention are as follows:

[0034] 1. A batch transfer device consisting of a thermally conductive substrate, a bump array, and a phase change material is used to pick up and release micro-components by utilizing the different connection strengths of the phase change material with the micro-components in different solid and liquid states, thereby achieving batch transfer.

[0035] 2. The state of the phase change material is controlled by adjusting the overall temperature of the thermally conductive substrate, enabling convenient and quick batch transfer.

[0036] 3. Selective batch transfer of micro-components is achieved through patterning of bump arrays.

[0037] 4. Achieve pollution-free transfer of micro-components by selecting easy-to-clean rosin materials.

[0038] The present invention also provides a thermoelectric element array, which is prepared by the method described above.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention utilizes the phase transition of rosin coated on the surface of a patterned bump array to selectively pick up and transfer micro-devices in batches. By impregnating the micro-devices with liquid rosin and then curing the rosin, the micro-devices can be strongly bonded to the bumps, enabling efficient pickup. Temperature control allows the rosin to transition from a solid to a liquid state, detaching the micro-devices from the bumps and achieving a high transfer yield. Since residual rosin can be easily and efficiently removed afterward, contamination of the micro-devices is avoided. Because the liquid rosin impregnates the micro-devices, this method is suitable for transferring micro-device arrays with non-planar surfaces. Attached Figure Description

[0041] Figure 1 This is a flowchart of the selective batch transfer method based on phase change materials provided in Embodiment 1 of the present invention;

[0042] Figure 2 This is a patterned bump array diagram prepared in Example 1 of the present invention;

[0043] Figure 3 This is a diagram of the micro-element array on the donor substrate prepared in Example 1 of the present invention;

[0044] Figure 4 The image shows the "BUAA" logo formed by the micro-sized copper film transferred to the host substrate as prepared in Example 1 of this invention.

[0045] Figure 5 This is a patterned bump array diagram prepared in Example 2 of the present invention;

[0046] Figure 6 This is a diagram of the electronic thermoelectric element array transferred onto the host substrate as prepared in Example 2 of the present invention;

[0047] Figure 7 This is a diagram of the array of electronic and hole thermoelectric elements transferred to the host substrate as prepared in Embodiment 2 of the present invention. Detailed Implementation

[0048] Based on long-term research and extensive practice, this invention proposes a specific technical solution. The technical solution will be clearly and completely described below, and a specific embodiment will be presented. It should be noted that the described embodiment is only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0049] Example 1

[0050] To selectively and in batches transfer the "BUAA" logo pattern constructed from micro-sized copper film, embodiments of the present invention provide a selective batch transfer method based on phase change materials. Figure 1 As shown, it includes:

[0051] (1) As Figure 1 As shown in (a), a raised dot stamp is prepared:

[0052] A thermally conductive substrate was obtained, the material of which is aluminum nitride, and a copper film with a thickness of 50 μm was coated on the surface of the substrate. The copper film was etched using femtosecond laser micro / nano technology to form... Figure 2 The patterned bump array shown is used to obtain a bump stamp, wherein the size of the bump is 100um × 100um, and the center distance between adjacent bumps is 500um. The bumps in the patterned bump array provided in this embodiment of the invention correspond to the micro-elements in the micro-element array on the donor substrate. The size of the bump is smaller than the size of the micro-element, and the position of the bump matches the position of the micro-element on the donor substrate.

[0053] (2) Figure 1 As shown in (b), a phase change material is coated on the surface of a patterned bump array. Rosin is dissolved in ethanol to prepare a mixed solution with a rosin mass fraction of 30%. The mixed solution is then dipped onto the surface of the patterned bump array and dried at 70°C to evaporate the ethanol, thereby coating the surface of the patterned bump array with rosin.

[0054] (3) Figure 1 As shown in (c), a patterned array of bumps coated with rosin is bonded to a micro-sized copper film on a donor substrate.

[0055] The specific fabrication steps of the donor substrate with a surface of micro-element array provided in this embodiment of the invention are as follows: a PDMS film is attached to a glass substrate, a copper film is then attached to the PDMS, and the copper film is cut into the shape shown in the figure using femtosecond laser processing. Figure 3 The micro-element array shown is a micro-sized copper film array. The size of the micro-sized copper film is 400um × 400um, and the center distance between the micro-sized copper films is 500um.

[0056] (4) Figure 1 As shown in (d), micro-sized copper films are batch-picked via liquid-solid phase transition of rosin:

[0057] The aluminum nitride substrate in the embossed stamp is heated to 130°C, causing the rosin on the surface of the embossed stamp to melt into a liquid state. After the molten rosin wets the surface of the micro-sized copper film, the temperature of the aluminum nitride substrate is reduced to 80°C, causing the rosin to solidify. At this point, a strong fixed connection is formed between the embossed stamp and the micro-sized copper film. The connection strength is greater than the adhesion force of PDMS to the micro-sized copper film, which can selectively pick up the micro-sized copper film under the embossed stamp.

[0058] (5) Figure 1 As shown in (e), the picked-up micro-sized copper film is bonded to the host substrate:

[0059] A receiver substrate is obtained, which is a glass substrate on which a PDMS film is attached, and a micro-sized copper film picked up by a dot stamp is attached to the receiver substrate.

[0060] (6) Figure 1 As shown in (f), micro-sized copper films are released using the liquid phase of rosin:

[0061] Heating the aluminum nitride substrate to 130°C melts the rosin on the bumps. At this point, the molten rosin's adhesion strength to the micro-copper film is less than the adhesion strength of the PDMS film on the host substrate to the micro-copper film. This allows the array of micro-copper films picked up from the bump stamp surface to be released in batches onto the host substrate. Then, ethanol is used to remove residual rosin from the surface of the micro-copper films. Figure 4 As shown, the final result is a "BUAA" logo made of micro-sized copper film.

[0062] Example 2

[0063] To obtain electron-type and hole-type thermoelectric element arrays through selective batch transfer, this embodiment provides a method for fabricating thermoelectric element arrays, including:

[0064] (1) Preparation of raised dot stamp:

[0065] A thermally conductive substrate was obtained, the material of which is aluminum nitride, and a copper film with a thickness of 50 μm was coated on the surface of the substrate. The copper film was etched using femtosecond laser micro / nano technology to form... Figure 5 The illustrated bump array forms a bump stamp, wherein the bump size is 50µm × 50µm, and the center distance between adjacent bumps is 250µm. In the patterned bump array provided in this embodiment of the invention, the bumps correspond to the micro-elements in the micro-element array on the donor substrate, the bump size is smaller than the micro-element size, and the position of the bump matches the position of the micro-elements on the donor substrate.

[0066] (2) Coating a phase change material onto the surface of the patterned bump array. Rosin is dissolved in ethanol to prepare a mixed solution with a rosin mass fraction of 30%. The mixed solution is then dipped onto the surface of the patterned bump array and dried at 70°C to evaporate the ethanol, thereby coating the surface of the patterned bump array with rosin.

[0067] (3) The patterned bump array coated with rosin is bonded to the micro-element array on the donor substrate.

[0068] The specific fabrication steps of the donor substrate with a surface of micro-element array provided in this embodiment of the invention are as follows: A PDMS film is attached to a glass substrate, then an electronic thermoelectric thin film is attached to the PDMS, and the electronic thermoelectric thin film is cut into the following shapes using femtosecond laser processing. Figure 3 The micro-element array shown is an electronic thermoelectric element array with dimensions of 200µm × 200µm and a center-to-center distance of 250µm between the electronic thermoelectric elements.

[0069] (4) Batch pickup of electron-type thermoelectric elements via liquid-solid phase conversion of rosin:

[0070] The aluminum nitride substrate in the raised stamp is heated to 130°C, causing the rosin on the surface of the raised stamp to melt into a liquid state. After the molten rosin wets the electronic thermoelectric element, the temperature of the aluminum nitride substrate is lowered to below 80°C, causing the rosin to solidify. At this point, a strong fixed connection is formed between the raised stamp and the electronic thermoelectric element. The connection strength is greater than the adhesion force of PDMS to the electronic thermoelectric element, which can selectively pick up the electronic thermoelectric element under the raised stamp.

[0071] (5) Attach the picked-up electronic thermoelectric element to the host substrate:

[0072] A receiver substrate is obtained, which is a glass substrate on which a PDMS film is attached, and an electronic thermoelectric element picked up by a dot stamp is attached to the receiver substrate.

[0073] (6) Utilizing rosin's liquid phase to release electrons in a thermoelectric element:

[0074] Heating the aluminum nitride substrate to 130°C melts the rosin on the bumps. At this point, the bond strength of the molten rosin to the electronic thermoelectric element is less than the adhesion force of the PDMS film on the host substrate to the electronic thermoelectric element. This allows for the batch release of the electronic thermoelectric element array picked up from the bump stamp surface onto the host substrate. Figure 6 As shown.

[0075] (7) Repeat steps (2)-(6) to batch transfer the hole-type thermoelectric element array. During thermoelectric element release, a pick-up device is used to transfer the collected hole-type thermoelectric element array to the gaps between the electron-type thermoelectric elements on the host substrate, forming a high-density thermoelectric element array with alternating electron and hole-type thermoelectric elements, such as... Figure 7 As shown, the high-density thermoelectric element array with alternating electronic and hole thermoelectric elements can be welded to the electrode. Since rosin is a good flux, no cleaning is required, thus enabling the rapid construction of high-performance thermoelectric devices.

Claims

1. A selective batch transfer method based on phase change materials, characterized in that, include: A patterned bump array is fabricated on a thermally conductive substrate, and rosin is coated on the surface of the patterned bump array. A donor substrate is obtained, the surface of which has a micro-element array, and a patterned bump array coated with rosin is correspondingly bonded to the micro-element array. By controlling the temperature of the thermally conductive substrate, the rosin is changed from liquid to solid, so that the micro-element array and the corresponding patterned bump array are fixedly connected by the rosin, and then the micro-element array is picked up from the donor substrate. The picked-up micro-element array is bonded to the surface of the host substrate, and the temperature of the thermally conductive substrate is controlled again to change the rosin from solid to liquid, so that the patterned bump array is separated from the corresponding micro-element array, thereby achieving the purpose of batch transferring the micro-element array to the host substrate.

2. The selective batch transfer method based on phase change materials according to claim 1, characterized in that, The specific steps for changing rosin from liquid to solid by controlling the temperature of the thermally conductive substrate, thereby fixing the micro-element array and the corresponding patterned bump array together via rosin, are as follows: By heating the thermally conductive substrate to 110°C~200°C, the rosin becomes liquid and viscous enough to wet the corresponding micro-element array. Then, the temperature of the thermally conductive substrate is lowered to below 110°C, and the rosin is transformed from a liquid to a solid state, thereby achieving a fixed connection between the patterned bump array and the corresponding micro-element array.

3. The selective batch transfer method based on phase change materials according to claim 1, characterized in that, The specific steps for controlling the temperature of the thermally conductive substrate again to change the rosin from a solid to a liquid state, thereby detaching the patterned bump array from the corresponding micro-element array, are as follows: The temperature of the thermally conductive substrate is reheated to 110℃~200℃, causing the rosin to change from a solid to a liquid state. Then, the patterned bump array is separated from the corresponding micro-element array.

4. The selective batch transfer method based on phase change materials according to claim 1, characterized in that, The ratio of the surface area of ​​the bumps in the patterned bump array to the surface area of ​​the corresponding micro-element is 1:1 to 1:

100.

5. The selective batch transfer method based on phase change materials according to claim 1, characterized in that, The process of coating rosin onto the patterned bump array surface is as follows: the coating solution is a mixed solution obtained by dissolving rosin in ethanol, and then the ethanol is dried at a temperature of 50℃~100℃.

6. The selective batch transfer method based on phase change materials according to claim 5, characterized in that, In the mixed solution, the mass fraction of rosin is 10% to 40%.

7. The selective batch transfer method based on phase change materials according to claim 1, characterized in that, The specific steps for fabricating a patterned bump array on a thermally conductive substrate are as follows: depositing a thin film on the thermally conductive substrate and etching the thin film to obtain a patterned bump array, wherein the material of the thin film is metal, semiconductor or ceramic.

8. The selective batch transfer method based on phase change materials according to claim 1, characterized in that, After the micro-element arrays are transferred in batches to the host substrate, ethanol is used to remove residual rosin from the surface of the micro-element arrays.

9. A method for fabricating a thermoelectric element array, characterized in that, include: The selective batch transfer method based on phase change materials as described in any one of claims 1-8 is used to batch transfer electronic thermoelectric element arrays onto a host substrate. Again, the selective batch transfer method based on phase change materials as described in any one of claims 1-8 is used to transfer the hole-type thermoelectric element array in batches to the acceptor substrate of the transferred electronic-type thermoelectric element array, wherein the hole-type thermoelectric elements are located between the electronic-type thermoelectric elements.

10. A thermoelectric element array, characterized in that, It is prepared by the method described in claim 9 for the preparation of thermoelectric element array.

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