Bidirectional temperature control thermoelectric chip for TEM or SEM

Abstract

The bidirectional temperature control thermoelectric chip comprises a substrate, a back cavity is arranged on the substrate, a supporting layer is arranged on the substrate, a slope structure is arranged on the periphery of the supporting layer, a temperature control area is arranged on the supporting layer, an observation window is arranged on the temperature control area, a thermoelectric unit is arranged on the periphery of the temperature control area, and the thermoelectric unit is connected with the back cavity. Two electrode pressure welding blocks are arranged on the substrate, and the thermoelectric units are connected with the electrode pressure welding blocks; heat dissipation structures corresponding to the thermoelectric units are arranged on the slope structure and the substrate on the periphery of the slope structure, and an isolation cavity is arranged between the thermoelectric units and the temperature control area. According to the invention, continuous and real-time dynamic imaging of the to-be-tested sample in a low-temperature to high-temperature environment can be realized, high-precision temperature control capability is realized, sample vibration can be effectively reduced, image quality can be improved, and repeatability and stability of an experiment can be remarkably improved.

Description

Technical Field

[0001] This invention relates to a bidirectional temperature-controlled thermoelectric chip for TEM or SEM, belonging to the field of temperature control chip technology. Background Technology

[0002] Transmission electron microscopy (TEM) / scanning electron microscopy (SEM), as important tools for high-resolution imaging and analysis, have wide applications in semiconductors, nanotechnology, materials science, and biology. In recent years, with the continuous development of in-situ electron microscopy technology, researchers have been able to observe the structural evolution of materials at the micrometer and nanometer scales in real time under various environmental variables (such as thermal, mechanical, electrical, liquid, and gas phases). Among these, temperature, as a crucial factor affecting material behavior, plays a central role in in-situ experiments.

[0003] At low temperatures, phenomena such as superconductivity, charge density waves, cryogenic catalysis, biomolecular stability, and suppression of electron beam irradiation effects exhibit significantly different mechanisms and kinetic behaviors compared to room temperature. The cryogenic environment not only helps in exploring the physical mechanisms of low temperatures and the performance of materials at low temperatures, but also effectively reduces thermal disturbances and improves sample stability.

[0004] Correspondingly, heating allows for direct observation of elemental diffusion, phase transitions, redox reactions, thin-film annealing, and thermal failure mechanisms in materials, providing crucial data for energy catalysis, thermal stability assessment of semiconductor devices, and research on high-temperature structural materials. However, high-temperature operation is often accompanied by thermal drift, electron beam diffraction artifacts, and thermal stress effects, placing higher demands on imaging accuracy and experimental controllability.

[0005] In existing TEM / SEM systems, low-temperature environments are mostly achieved using liquid nitrogen or liquid helium cold stages, while high-temperature environments typically rely on MEMS (microelectromechanical systems) heating chips based on the Joule heating principle. Currently, most researchers combine thermal chips with liquid nitrogen or liquid helium cold stages to achieve temperature switching, but this method generally has limitations, specifically:

[0006] (1) The combination of traditional cold stage and thermal chip makes it difficult to accurately control sample temperature.

[0007] (2) Traditional cold stages use an overall cooling method, which lacks the ability to precisely control the temperature of local areas of the sample.

[0008] (3) The evaporation of liquid nitrogen and liquid helium can easily cause splashing and vibration, which seriously affects the imaging stability and image resolution.

[0009] (4) Water vapor condensation is likely to occur during the cooling process, which will interfere with the experimental environment and affect the reliability of the data.

[0010] (5) Liquid nitrogen and liquid helium evaporate rapidly and their temperature fluctuates significantly, making it difficult to achieve a highly stable and finely adjustable temperature environment.

[0011] With the development of MEMS technology, miniature temperature control chips utilizing the thermoelectric effect have emerged, enabling bidirectional temperature control on a single chip. However, the reported thermoelectric chips still cannot meet the in-situ requirements of TEM / SEM, and the main bottlenecks include:

[0012] (1) The chip is too thick to fit into the narrow gap of the TEM sample holder.

[0013] (2) The chip does not have an electron beam transparent window, which hinders the imaging of the sample in TEM.

[0014] (3) The heat flow path is not designed properly, resulting in significant thermal crosstalk and making it difficult to maintain temperature stability between the cold end and the hot end.

[0015] Therefore, there is an urgent need to develop an in-situ MEMS temperature control chip that is compact, highly integrated, has precise local temperature control capabilities, and is suitable for TEM and SEM environments, in order to meet the needs of in-situ experiments in multiple temperature zones of TEM / SEM. Summary of the Invention

[0016] Objective: To overcome the technical bottlenecks in existing TEM or SEM experiments, such as low sample temperature control accuracy and poor imaging stability, this invention provides a bidirectional temperature-controlled thermoelectric chip for TEM or SEM, which can realize continuous, real-time dynamic imaging of the sample under test in low-temperature to high-temperature environments. It has high-precision temperature control capabilities, can effectively reduce sample vibration, improve image quality, and significantly improve the repeatability and stability of the experiment.

[0017] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0018] A bidirectional temperature-controlled thermoelectric chip for TEM or SEM includes a substrate, a back cavity on the substrate, a support layer on the substrate, a sloping structure around the periphery of the support layer, a temperature-controlled region on the support layer, an observation window on the temperature-controlled region, thermoelectric units around the temperature-controlled region, and two electrode bonding blocks on the substrate, with the thermoelectric units connected to the electrode bonding blocks. The sloping structure and the substrate surrounding the sloping structure have heat dissipation structures corresponding to the thermoelectric units, and an isolation cavity is provided between the thermoelectric units and the temperature-controlled region.

[0019] Optionally, the thermoelectric unit includes: a primary thermoelectric unit, a secondary thermoelectric unit, and a conductive component. The primary thermoelectric unit, the secondary thermoelectric unit, and the conductive component are connected in series to form a thermoelectric circuit. The primary thermoelectric unit is fitted around the temperature control zone, and the secondary thermoelectric unit is fitted around the primary thermoelectric unit. The primary thermoelectric unit is provided with an isolation cavity, and the secondary thermoelectric unit is provided with an isolation cavity.

[0020] Optionally, the primary thermoelectric unit includes: a primary thermoelectric unit temperature control terminal, a primary thermoelectric unit opposite terminal, and a thermocouple. The thermocouple includes: an N-type thermocouple arm and a P-type thermocouple arm. The primary thermoelectric unit temperature control terminal and the primary thermoelectric unit opposite terminal are arranged opposite each other, and the alternately arranged N-type thermocouple arms and P-type thermocouple arms are connected in series through the primary thermoelectric unit temperature control terminal and the primary thermoelectric unit opposite terminal.

[0021] The secondary thermoelectric unit includes: a temperature control terminal of the secondary thermoelectric unit, a opposite terminal of the secondary thermoelectric unit, and a thermocouple. The thermocouple includes: an N-type thermocouple arm and a P-type thermocouple arm. The temperature control terminal of the secondary thermoelectric unit and the opposite terminal of the secondary thermoelectric unit are arranged opposite to each other, and the alternately arranged N-type thermocouple arms and P-type thermocouple arms are connected in series through the temperature control terminal of the secondary thermoelectric unit and the opposite terminal of the secondary thermoelectric unit.

[0022] The conductive components are connected to the opposite end of the primary thermoelectric unit and the temperature control end of the secondary thermoelectric unit, respectively.

[0023] Optionally, an isolation cavity is provided between the temperature control end of the primary thermoelectric unit and the opposite end of the primary thermoelectric unit.

[0024] Optionally, an isolation cavity is provided between the temperature control end of the secondary thermoelectric unit and the opposite end of the secondary thermoelectric unit.

[0025] Optionally, the isolation cavity is connected to the back cavity.

[0026] Optionally, the temperature control zone, conductive components, heat dissipation structure, temperature control terminal of the primary thermoelectric unit, opposite terminal of the primary thermoelectric unit, temperature control terminal of the secondary thermoelectric unit, and opposite terminal of the secondary thermoelectric unit shall have an electrical conductivity greater than 1×10⁻⁶. 7 Materials with a thermal conductivity greater than 90 W / mK (S / m).

[0027] Optionally, the thermocouple is made of bismuth telluride-based thermoelectric material.

[0028] Optionally, the support layer is made of PI material.

[0029] Beneficial Effects: This invention provides a bidirectional temperature-controlled thermoelectric chip for TEM or SEM, comprising an observation window, a temperature control zone, a ramp structure, and a heat dissipation structure. The observation window, serving as a sample-bearing area, is used to fix samples such as nanowires and nanofilms, and its shape is a circle, ellipse, rectangle, polygon, or irregular shape extending through the upper and lower surfaces of the chip. The temperature control zone and the underlying support layer have openings forming the observation window, which are thermally coupled to the chip's cold end. The sample temperature can be equivalent to the cold end temperature. This invention enables continuous and stable temperature control over a wide temperature range from approximately -52°C to approximately 850°C, effectively meeting the need for high-precision in-situ thermal regulation of micro-area samples in TEM / SEM.

[0030] This invention enables continuously adjustable temperature control from low to high temperatures within a single chip, making it suitable for in-situ TEM and SEM experiments. Compared to existing temperature control methods that rely on liquid nitrogen or liquid helium cold stages and heated chips, its advantages are as follows:

[0031] 1. This invention enables seamless switching from low to high temperatures without changing experimental equipment, while maintaining real-time controllability of the temperature change process, thereby achieving continuous and dynamic imaging and analysis of samples in different temperature zones. The chip structure is based on MEMS miniaturization design, with small thermal mass and fast response speed, significantly reducing vibration interference caused by heating / cooling transitions and liquid nitrogen evaporation, effectively improving the stability and resolution of electron microscope imaging.

[0032] 2. Local temperature control can avoid the thermal stress caused by overall temperature changes on the sample rod and surrounding structure, improve image quality and data reliability, and provide a more efficient and stable platform for the study of material structure evolution and performance in a wide temperature range.

[0033] 3. The chip of this invention is thin and compact, allowing for direct compatibility with existing TEM / SEM sample holders and environmental control accessories without additional modifications, significantly improving the compatibility and versatility of experimental equipment. The chip design incorporates an electron beam transparent window, maintaining high transmittance and low scattering during temperature control, ensuring imaging and spectral analysis quality. Optimized heat flow paths and thermal insulation structures effectively suppress thermal crosstalk, ensuring the stability and uniformity of temperature in local sample regions, thus providing a reliable guarantee for high-precision in-situ characterization. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the chip structure in an example of the present invention.

[0035] Figure 2 This is a cross-sectional view of the chip in an example of the present invention.

[0036] Figure 3 This is a schematic diagram of a chip-mounted sample in an example of the present invention.

[0037] Figure 4 This is a schematic diagram of the chip substrate in an example of the present invention.

[0038] Figure 5 This is a schematic diagram of the chip observation window and structural layers in an example of the present invention.

[0039] Figure 6 This is a schematic diagram of the chip ramp structure in an example of the present invention.

[0040] Figure 7 This is a schematic diagram of the chip substrate, observation window, and structural layers in an example of the present invention.

[0041] Figure 8 This is a schematic diagram of the temperature control zone, the temperature control terminals and opposite terminals of the first and second stage thermoelectric units, the heat dissipation structure, and the electrode bonding block, all fabricated using the same process steps in this invention example.

[0042] Figure 9 This is a simulation diagram of the chip cooling effect in an example of the present invention.

[0043] Figure 10 This is a simulation diagram of the chip heating effect in an example of the present invention.

[0044] Figure 11 This is a temperature curve diagram of the isothermal structure of the chip under different currents in an example of the present invention.

[0045] Figure 12 This is a cross-sectional view of the structure in the first step of the preparation method in this invention example.

[0046] Figure 13 This is a cross-sectional view of the structure in the second step of the preparation method in this invention example.

[0047] Figure 14 This is a structural cross-sectional view of the third step of the preparation method in this invention example.

[0048] Figure 15 This is a structural cross-sectional view of the fourth step of the preparation method in this invention example.

[0049] Figure 16 This is a cross-sectional view of the structure in the fifth step of the preparation method in this invention example.

[0050] Figure 17 This is a cross-sectional view of the structure in the sixth step of the preparation method in this invention example.

[0051] In the figure, 1. Temperature control zone; 2. Observation window; 3. Thermoelectric unit; 31. Primary thermoelectric unit; 311. Temperature control end of primary thermoelectric unit; 312. Opposite end of primary thermoelectric unit; 32. Secondary thermoelectric unit; 321. Temperature control end of secondary thermoelectric unit; 322. Opposite end of secondary thermoelectric unit; 33. Thermocouple; 331. N-type thermoelectric arm; 332. P-type thermoelectric arm; 4. Conductive component; 5. Structural layer; 51. Support layer; 52. Sloping structure; 53. Isolation cavity; 6. Substrate; 61. Substrate; 62. Back cavity; 7. Heat dissipation structure; 8. Electrode bonding block; 9. Sample; 91. Nanowire; 92. Nanofilm. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] Example 1:

[0055] This embodiment describes a bidirectional temperature-controlled thermoelectric chip for TEM or SEM, such as... Figure 1 and Figure 2 As shown, the system includes: a substrate 6, which includes a base 61, a back cavity 62 disposed on the base 61, and a structural layer 5 disposed on the base 61. The structural layer 5 includes: a support layer 51 disposed on the base 61, a sloped structure 52 around the support layer 51, a temperature control zone 1 disposed on the support layer 51, an observation window 2 disposed on the temperature control zone 1, and thermoelectric units 3 disposed around the temperature control zone 1. Two electrode bonding blocks 8 are disposed on the base 6, and the thermoelectric units 3 are connected to the electrode bonding blocks 8. A heat dissipation structure 7 corresponding to the thermoelectric units 3 is disposed on the sloped structure 52 and the base 61 surrounding the sloped structure 52. An isolation cavity 53 is disposed between the thermoelectric units 3 and the temperature control zone 1.

[0056] Furthermore, the isolation cavity 53 is connected to the back cavity 62.

[0057] Furthermore, the thermoelectric unit 3 includes: a primary thermoelectric unit 31, a secondary thermoelectric unit 32, and a conductive component 4. The primary thermoelectric unit 31, the secondary thermoelectric unit 32, and the conductive component 4 are connected in series to form a thermoelectric circuit. The primary thermoelectric unit 31 is sleeved around the temperature control zone 1, and the secondary thermoelectric unit 32 is sleeved around the primary thermoelectric unit 31. The primary thermoelectric unit 31 is provided with an isolation cavity 53, and the secondary thermoelectric unit 32 is provided with an isolation cavity 53.

[0058] Furthermore, the primary thermoelectric unit 31 includes: a primary thermoelectric unit temperature control terminal 311, a primary thermoelectric unit opposite terminal 312, and a thermocouple 33. The thermocouple 33 includes: an N-type thermoelectric arm 331 and a P-type thermoelectric arm 332. The primary thermoelectric unit temperature control terminal 311 and the primary thermoelectric unit opposite terminal 312 are arranged opposite to each other, and the alternately arranged N-type thermoelectric arms 331 and P-type thermoelectric arms 332 are connected in series through the primary thermoelectric unit temperature control terminal 311 and the primary thermoelectric unit opposite terminal 312.

[0059] The secondary thermoelectric unit 32 includes: a secondary thermoelectric unit temperature control terminal 321, a secondary thermoelectric unit opposite terminal 322, and a thermocouple 33. The thermocouple 33 includes: an N-type thermoelectric arm 331 and a P-type thermoelectric arm 332. The secondary thermoelectric unit temperature control terminal 321 and the secondary thermoelectric unit opposite terminal 322 are arranged opposite to each other, and the alternately arranged N-type thermoelectric arms 331 and P-type thermoelectric arms 332 are connected in series through the secondary thermoelectric unit temperature control terminal 321 and the secondary thermoelectric unit opposite terminal 322.

[0060] The conductive component 4 is connected to the opposite end 312 of the primary thermoelectric unit and the temperature control end 321 of the secondary thermoelectric unit, respectively.

[0061] Furthermore, an isolation cavity 53 is provided between the temperature control end 311 of the primary thermoelectric unit and the opposite end 312 of the primary thermoelectric unit.

[0062] Furthermore, an isolation cavity 53 is provided between the temperature control end 321 of the secondary thermoelectric unit and the opposite end 322 of the secondary thermoelectric unit.

[0063] Example 2:

[0064] This embodiment describes a specific example of a bidirectional temperature-controlled thermoelectric chip for TEM or SEM, including an observation window 2, a temperature control area 1, a ramp structure 52, and a heat dissipation structure 7. The primary thermoelectric unit 31 includes a primary thermoelectric unit temperature control end 311, a primary thermoelectric unit opposite end 312, and a thermocouple 33. The secondary thermoelectric unit 32 includes a secondary thermoelectric unit temperature control end 321, a secondary thermoelectric unit opposite end 322, and a thermocouple 33.

[0065] The structure is fabricated using MEMS (Microelectromechanical systems) technology. The overall structure includes a substrate 61, a support layer 51, a primary thermoelectric unit 31, a secondary thermoelectric unit 32, a temperature control area 1, an observation window 2, and an electrode bonding pad 8. The electrode bonding pad 8 is located at the chip edge and is used to connect an external power supply to the bidirectional temperature-controlled thermoelectric chip to provide operating voltage / current. The cooling or heating mode of the temperature control area is achieved by switching the current direction. One end of the electrode bonding pad 8 is electrically connected to the thermoelectric unit 3, which consists of a primary thermoelectric unit 31 and a secondary thermoelectric unit 32 from the inside out. Each thermoelectric unit includes a temperature control end, a counter-end, and a thermocouple 33, which includes an N-type thermoelectric arm 331 and a P-type thermoelectric arm 332. Each thermoelectric unit has an internal isolation cavity 53. The primary thermoelectric unit 31 and the secondary thermoelectric unit 32 are electrically connected and thermally coupled through a conductive component 4. The two ends of the conductive component 4 are respectively connected to the thermocouples 33 of the primary thermoelectric unit 31 and the secondary thermoelectric unit 32. A temperature control area 1 is provided on the support layer 51 inside the temperature control terminal 311 of the primary thermoelectric unit of the thermoelectric chip. The temperature control area 1 is electrically insulated from the temperature control terminal 311 of the primary thermoelectric unit. A window is opened on the back side of the substrate 61 and etched to form a back cavity 62. The back cavity 62 is arranged in the areas corresponding to the temperature control area 1, the thermocouples 33 of the primary thermoelectric unit 31 and the secondary thermoelectric unit 321, so that the above areas are located above the support layer 51. The substrate 61 is left below the opposite end 322 of the secondary thermoelectric unit to provide mechanical support and heat diffusion channels. Thus, the chip thermoelectric unit 3 is set on the support layer 51, and the back cavity 62 is a partial substrate 61 removal structure formed by the process. The support layer 51 is preferably made of PI (polyimide) material, whose low thermal conductivity helps to reduce parasitic heat flow and improve temperature control efficiency.

[0066] The substrate 6 is composed of a substrate 61 and a back cavity 62, such as Figure 4As shown. The primary thermoelectric unit 31 and the secondary thermoelectric unit 32 are connected via the conductive component 4. Each pair of thermocouples 33 consists of an N-type thermoelectric arm 331 and a P-type thermoelectric arm 332. The temperature-controlled end and the opposite end employ a structure of several spaced-apart metal layers. The alternately arranged N-type thermoelectric arms 331 and P-type thermoelectric arms 332 are connected in series through the metal layers of the oppositely arranged temperature-controlled end and the opposite end. The temperature-controlled end and the opposite end are the functional areas of the thermocouple 33, not independent heating / cooling elements. The same-stage thermoelectric arms are electrically connected through metal layers, forming π-type thermocouples 33 connected in series to achieve voltage / current output. An insulating gap is provided between the opposite end 312 of the primary thermoelectric unit and the temperature-controlled end 321 of the secondary thermoelectric unit to prevent electrical short circuits. Simultaneously, the conductive component 4 also employs a metal layer structure to provide electrical connection and thermal coupling. The temperature-controlled area 1 is the metal layer within the temperature-controlled end 311 of the primary thermoelectric unit. When the circuit is in cooling mode, temperature control zone 1 is the cold end and the opposite end is the hot end; when the circuit is in heating mode, temperature control zone 1 is the hot end and the opposite end is the cold end.

[0067] like Figure 1 , Figure 2 and Figure 5 As shown, in this embodiment, both the primary thermoelectric unit 31 and the secondary thermoelectric unit 32 are provided with an isolation cavity 53. The isolation cavity 53 is located inside the primary thermoelectric unit 31 and the secondary thermoelectric unit 32, specifically in the area between the temperature control end and the opposite end of that stage, excluding the thermocouple 33, and is formed by removing the support layer 51 in this area. The isolation cavity 53 is used to block non-primary heat transfer paths between the temperature control end and the opposite end other than the thermocouple 33, thereby effectively suppressing parasitic heat flow and heat loss caused by structures such as the support layer 51. This structure constrains heat transfer and mainly proceeds along the preset direction of the thermocouple 33, which helps to increase the temperature difference between the temperature control end and the opposite end of each stage of the thermoelectric unit and improve the thermoelectric conversion efficiency. At the same time, the back cavity 62 further reduces the heat loss generated by heat transfer.

[0068] In this embodiment, thermocouple 33 uses a bismuth telluride-based thermoelectric material, suitable for the low-temperature region (200-300K) and exhibiting good thermoelectric performance. The conductive component 4 is made of a material with high electrical conductivity (greater than 1×10⁻⁶). 7 The support layer 51 is made of a metallic material with high thermal conductivity (greater than 90 W / (m·K)) and can be selected from any one or more combinations of copper, gold, silver, aluminum, chromium, and nickel. Because the support layer 51 has low thermal conductivity, it will create significant thermal resistance between the opposite end 312 of the first-stage thermoelectric unit and the temperature control end 321 of the second-stage thermoelectric unit, hindering effective heat transfer between stages. To solve this problem, this embodiment connects the opposite end 312 of the first-stage thermoelectric unit and the temperature control end 321 of the second-stage thermoelectric unit through a conductive component 4, such as... Figure 1 , Figure 2 and Figure 8As shown. The conductive component 4 utilizes excellent thermal conductivity to establish an efficient heat flow channel between stages, ensuring smooth heat transfer and significantly improving the device's temperature control performance. Simultaneously, to prevent electrical short circuits between the primary thermoelectric unit 31 and the secondary thermoelectric unit 32, a dielectric isolation structure (such as a gap) is provided at the interface between the opposite end 312 of the primary thermoelectric unit and the temperature control end 321 of the secondary thermoelectric unit, forming electrical insulation. Furthermore, to address the potential for localized temperature unevenness due to poor thermal conductivity of the support layer 51, a temperature control region 1 is provided on the surface of the temperature control end 311 of the primary thermoelectric unit. This temperature control region 1 has good thermal conductivity, promoting the homogenization of the temperature field at the temperature control end, thereby improving the overall temperature control performance and stability of the device. The temperature control region 1 and the temperature control end 311 of the primary thermoelectric unit are insulated to avoid electrical short circuits. In terms of structural design, both the primary thermoelectric unit 31 and the secondary thermoelectric unit 32 use large-area metal layers as their temperature control end and the opposite end, respectively, and maintain a small gap between the temperature control end and the opposite end inside each stage. This design helps to concentrate the heat flow path and improve the heat pumping rate of the thermocouple 33.

[0069] like Figure 5 As shown, the bidirectional temperature-controlled thermoelectric chip of the present invention uses a PI film as a support layer 51. Located below the thermocouple 33, the support layer 51 utilizes its low thermal conductivity to significantly reduce parasitic heat flow and heat leakage within the thermoelectric unit from the temperature-controlled end to the opposite end, thereby effectively increasing the temperature difference between the temperature-controlled end and the opposite end, and ultimately achieving precise temperature control of the temperature control zone 1. Furthermore, the use of a PI film aligns with the requirements of MEMS microfabrication processes, facilitating mass production of the device. Moreover, the PI film material itself possesses good mechanical toughness, endowing the thermoelectric chip with excellent vibration and impact resistance, solving the problem of chip breakage during TEM and SEM applications.

[0070] The back side of substrate 61 is windowed and etched using microfabrication techniques to form a back cavity structure 62, such as... Figure 4 As shown. The position of the back cavity structure 62 is precisely designed to correspond to most of the area where the temperature control region 1, the primary thermoelectric unit 31, the temperature control end 321 of the secondary thermoelectric unit 32, and the thermocouple 33 of the secondary thermoelectric unit are located in the chip. A portion of the thermocouple at the end of the secondary thermoelectric unit near the chip edge remains on the substrate 6. By removing the substrate material in these areas, the aforementioned key functional areas are suspended above the back cavity 62 by the support layer 51, thereby greatly reducing parasitic heat conduction through the substrate 6 and ensuring the temperature difference between the temperature control region 1 and the substrate 6. The area below the opposite end 322 of the secondary thermoelectric unit 32 is retained on the substrate 6 without removal. This area provides necessary mechanical support for the chip and serves as a channel for the final outward diffusion of heat.

[0071] A polyimide film is formed on the upper surface of the substrate 61 by spin coating and thermosetting, serving as a support layer 51. The support layer 51 has good electrical insulation, mechanical toughness, and low thermal conductivity. Its thickness is preferably 2-8 μm, more preferably 3-5 μm. This low thermal conductivity characteristic can effectively suppress lateral parasitic heat flow from the temperature control end to the opposite end inside the thermoelectric unit.

[0072] like Figure 5 As shown, the support layer 51 is graphically processed, defining the distribution of the subsequent primary thermoelectric unit temperature control end 311, the primary thermoelectric unit opposite end 312, the secondary thermoelectric unit temperature control end 321, the secondary thermoelectric unit opposite end 322, and the thermocouple 33. Simultaneously, within the primary thermoelectric unit 31 and the secondary thermoelectric unit 32, in the area between the temperature control end and the opposite end, and outside the thermocouple 33, an isolation cavity 53 is designed. This isolation cavity 53 further blocks the non-primary heat transfer path formed by the support layer 51 itself between the cold and hot ends, confining the heat flow to the predetermined path of the thermocouple 33, thereby maximizing the temperature difference between the cold and hot ends and improving thermoelectric conversion efficiency.

[0073] like Figure 5 and Figure 6 As shown, the ramp structure 52 is an inclined structure in which the thickness of the support layer 51 gradually decreases as it extends from the opposite end 321 of the secondary thermoelectric unit toward the substrate 61, forming a continuous transition between the support layer 51 and the substrate 61, as shown. Figure 4 As shown, this avoids the film cracking or peeling caused by stress concentration in traditional stepped structures, while improving the quality of metal deposition in MEMS processing and enhancing the overall process compatibility and yield of the chip.

[0074] like Figure 1 , Figure 2 , Figure 6 and Figure 8 As shown, the heat dissipation structure 7 is located on the substrate 61 and surrounds the area around the ramp structure 52. The opposite ends 322 of the secondary thermoelectric units are connected to the heat dissipation structure 7 through the ramp structure 52. The presence of the heat dissipation structure 7 ensures that the primary thermoelectric unit 31 and the secondary thermoelectric unit 32 can quickly transfer heat to the substrate 61, avoiding heat retention that could lead to unstable temperature in the temperature control zone 1.

[0075] like Figure 8 As shown, a metal interconnect layer is fabricated on the patterned support layer 51 using photolithography, sputtering, and lift-off processes. This metal layer constitutes the electrical connections and part of the thermal conduction network of the chip, specifically including:

[0076] The temperature control end 311 and the opposite end 312 of the primary thermoelectric unit are two functional end faces of the primary thermoelectric unit 31, respectively, and are composed of a large metal layer to facilitate the uniform distribution and collection of heat.

[0077] The temperature control end 321 and the opposite end 322 of the secondary thermoelectric unit are the two functional end faces of the secondary thermoelectric unit 32, respectively, and are also composed of a large metal layer.

[0078] Conductive component 4: Located between the opposite end 312 of the primary thermoelectric unit and the temperature control end 321 of the secondary thermoelectric unit, connecting a pair of thermocouples 33 of the primary and secondary thermoelectric units. This component is made of a highly thermally conductive metal (such as copper, gold, silver, aluminum, or a combination thereof), and its function is to establish an efficient heat flow channel between the stages, ensuring effective heat transfer between the two stages. Simultaneously, at the connection interface between the opposite end 312 of the primary thermoelectric unit 31 and the temperature control end 321 of the secondary thermoelectric unit 32, a dielectric isolation structure with a small gap is used to achieve electrical insulation, maintaining only thermal conductivity and preventing short circuits between stages.

[0079] Temperature control zone 1: Located inside the temperature control terminal 311 of the primary thermoelectric unit and above the support layer 51. This structure is made of a layer of highly thermally conductive metal, which can quickly equalize the temperature of its covered area, eliminate local hot or cold spots, and ensure a highly uniform temperature field in the sample area. Temperature control zone 1 is electrically insulated from the temperature control terminal 311 of the primary thermoelectric unit through a tiny gap.

[0080] Electrode bonding pad 8: Located at the edge of the chip, it is a square (or other shape) metal layer, connected to a pair of thermocouples 33 of the secondary thermoelectric unit at the opposite end 322 of the secondary thermoelectric unit via metal leads. It is used to connect an external controllable power supply to the internal thermoelectric unit circuit of the chip, and to control the cooling or heating mode of the chip by switching the current direction.

[0081] In this embodiment, the material conductivity of the temperature control zone, conductive component 4, heat dissipation structure 7, primary thermoelectric unit 31, and secondary thermoelectric unit 32 at their temperature control ends and opposite ends is greater than 1×10⁻⁶. 7 S / m, thermal conductivity greater than 90 W / (mK). Since metallic materials meet the requirements and are widely used in MEMS fabrication processes, and in addition, metallic materials can also be used to fabricate electrode bonding blocks 8 in chips, metals or metal alloys are selected to fabricate these structures.

[0082] Copper is chosen as the metal material in this invention because of its high thermal conductivity, low cost, and stable processing. Furthermore, since copper and bismuth telluride-based thermoelectric materials are prone to elemental diffusion leading to interfacial alloying and a surge in contact resistance, this invention incorporates a Ni metal barrier layer between the thermoelectric material and copper to effectively suppress this phenomenon. Additionally, a Cr metal is placed between copper and the support layer 51 to increase adhesion, forming a Cr / Cu / Ni alloy.

[0083] like Figure 3 As shown, a hole is provided within the temperature control terminal 311 of the primary thermoelectric unit of the chip, penetrating the support layer 51 and the temperature control area 1 above it. The hole size and shape can be set to different dimensions and patterns, such as circular, elliptical, rectangular, polygonal, or irregular shapes, to meet different sample requirements. It can be used to hold samples such as nanowires 91 and nanofilms 92. When the chip of this invention is used in SEM experiments, the observation window 2 design can be omitted, and the sample can be placed directly on the surface of the temperature control area 1.

[0084] After the metal layer is prepared, thermocouples 33 are fabricated on the support layer 51 and the metal layer through photolithography, sputtering and lift-off processes. The thermoelectric unit 3 includes a primary thermoelectric unit 31 and a secondary thermoelectric unit 32, which are connected in series. Each stage contains multiple π-connected thermocouples 33.

[0085] Each thermocouple 33 consists of an N-type thermocouple arm 331 and a P-type thermocouple arm 332, with their two ends connected to the temperature control terminal and the opposite terminal formed by the metal layer, respectively. Specifically: in the first-stage thermocouple unit 31, one end of the N-type thermocouple arm 331 and the P-type thermocouple arm 332 are connected to the temperature control terminal 311 of that stage, and the other end is connected to the opposite terminal 312 of that stage. In the second-stage thermocouple unit 32, one end of the N-type thermocouple arm 331 and the P-type thermocouple arm 332 are connected to the temperature control terminal 321 of that stage, and the other end is connected to the opposite terminal 322 of that stage. The opposite terminal 312 of the first-stage thermocouple unit 31 and the temperature control terminal 321 of the second-stage thermocouple unit 32 are connected in series electrically through the conductive component 4, thereby forming a complete second-stage thermocouple circuit.

[0086] Thermocouple 33 is made of a material suitable for efficient thermoelectric conversion near room temperature, preferably bismuth telluride-based material, wherein the N-type thermocouple arm 331 can be Bi2Te. 2.7 Se 0.3 The P-type thermoelectric arm 332 can be a Bi 0.5 Sb 1.5 Te3. The thickness of the thermoelectric arm is preferably 1 μm to achieve a balance between performance and process feasibility.

[0087] The core working principle of the bidirectional temperature-controlled thermoelectric chip described in this invention is based on the Peltier effect. When an external direct current flows through the thermocouple 33, which is composed of an N-type thermoelectric arm 331 and a P-type thermoelectric arm 332, a reversible energy exchange occurs at both ends of the thermocouple 33: one end absorbs heat and becomes the cold end, while the other end releases heat and becomes the hot end. The allocation of the roles of the cold and hot ends is entirely determined by the direction of the current flowing through the thermocouple 33.

[0088] Example 3:

[0089] This invention utilizes a structured design with multi-stage thermoelectric units and optimized thermal circuits to efficiently cascade and amplify the Peltier effect. The specific working principle is as follows:

[0090] The chip employs multiple thermoelectric units (such as a primary thermoelectric unit 31 and a secondary thermoelectric unit 32) connected in series electrically. This design allows the temperature difference generated by the secondary thermoelectric unit 32 to act as a heat sink for the primary thermoelectric unit, thereby establishing a significant total temperature difference between the temperature control end and the opposite end of the chip.

[0091] The primary thermoelectric unit's opposite end 312 and the secondary thermoelectric unit's temperature control end 321 are thermally connected via a conductive component 4 made of a highly thermally conductive metal material. This conductive component 4 establishes a low thermal resistance channel between stages, ensuring that the heat pumped out by the primary thermoelectric unit 31 can be efficiently transferred to the secondary unit, and then pumped from the secondary unit to the final heat sink (i.e., the heat dissipation structure 7 and the substrate 61), thus achieving directional, relay-style heat transfer.

[0092] By utilizing the support layer 51 with low thermal conductivity and combining it with the isolation cavity 53 set inside each thermoelectric unit, the lateral parasitic backflow of heat from the temperature control end to the opposite end is greatly suppressed, forcing the heat to be transferred mainly along the preset thermoelectric arm path, thereby maximizing the temperature difference between the hot and cold ends.

[0093] A substrate 61 is retained below the opposite end of the chip and a heat dissipation structure 7 is provided to provide an efficient diffusion path for the heat pumped out to the external environment (such as the sample rod).

[0094] Cooling mode: When a forward current is applied to the chip, the temperature control terminal 311 of the first-stage thermoelectric unit operates as the cold end, absorbing heat from the temperature control area 1 and the sample 9 above it. This heat is pumped to the opposite end 312 of the first-stage thermoelectric unit via the first-stage thermocouple, and then transferred to the temperature control terminal 321 of the second-stage thermoelectric unit through the conduction component 4. The second-stage thermoelectric unit then pumps this heat to the opposite end 322 of the second-stage thermoelectric unit, and finally dissipates it to the external environment through the heat dissipation structure 7 and the substrate 61, thereby achieving cooling of the sample area.

[0095] Heating Mode: When a reverse current is applied to the chip, the direction of the Peltier effect reverses. The temperature control end 311 of the primary thermoelectric unit becomes the hot end, releasing heat to the sample area; while the opposite end 322 of the secondary thermoelectric unit becomes the port for absorbing heat from the environment. Heat is pumped from the environment through the secondary unit, transferred to the primary thermoelectric unit via the conduction component 4, and finally concentrated and released at the temperature control end 311 of the primary thermoelectric unit, thus heating the sample.

[0096] Example 4:

[0097] This embodiment describes the usage process of a bidirectional temperature-controlled thermoelectric chip for TEM or SEM, specifically including:

[0098] Chip usage in TEM: First, the chip is placed on the TEM sample holder, aligning the electrode bonding pad 8 with the pins on the sample holder. Next, voltage or current is applied to the chip via the sample holder controller, at which point the thermocouple generates a temperature difference across its sides through the Peltier effect. Heat is transferred between each thermoelectric unit via the conductive component 4, creating a temperature difference between the temperature control zone 1 and the heat dissipation structure 7. Since the chip's heat dissipation structure 7 is thermally connected to the substrate 61, the heat transferred from the chip can be effectively transferred to the substrate. Furthermore, the substrate is in contact with the copper sample holder, allowing heat contained within the substrate to be transferred to the sample holder and the TEM chamber. For sensitive materials, the chip on the sample holder can be energized from the start of sample preparation, keeping it at a low temperature for an extended period, which is beneficial for in-situ studies of sensitive materials.

[0099] Chip usage in SEM: When chips are used in SEM, they are fixed to a customized sample stage and PCB board. Power is supplied to the PCB board through a power source, so that voltage or current passes through the chip to form an electrical circuit, thereby controlling the temperature of the sample.

[0100] The observation window 2 is set through the chip from top to bottom to enable electron beam transmission imaging in TEM experiments, ensuring that the sample still has high electron transmittance under in-situ temperature control conditions.

[0101] In this embodiment, observation window 1 is the sample-bearing area, such as Figure 3 As shown, the chip can be made into circular, elliptical, rectangular, polygonal, or irregular shapes according to different experimental needs, and can be used to carry samples such as nanowires 91 and nanofilms 92. When the chip of this invention is applied to SEM experiments, the design of the observation window 2 can be omitted, and the sample can be placed directly on the surface of the temperature control zone 1.

[0102] The primary thermoelectric unit's opposite end 312 and the secondary thermoelectric unit's control end 321 are connected via a conductive component 4. The conductive component 4 possesses excellent thermal and electrical conductivity, achieving low resistance loss and high heat transfer efficiency, thereby reducing the overall thermal resistance of the device and ensuring the temperature difference transfer efficiency of the two-stage thermoelectric structure. This connection method not only achieves physical thermal coupling but also forms an electrical closed loop, avoiding space occupation and heat loss caused by additional wiring.

[0103] The ramp structure 52 is an inclined structure in which the thickness of the support layer 51 gradually decreases from the hot end 321 of the secondary thermoelectric unit toward the substrate 61, forming a continuous transition between the support layer 51 and the substrate 61, such as... Figure 4 As shown, this avoids the film cracking or peeling caused by stress concentration in traditional stepped structures, while improving the quality of metal deposition in MEMS processing and enhancing the overall process compatibility and yield of the chip.

[0104] The heat dissipation structure 7 is located on the substrate 61 and surrounds the area around the ramp structure 52. The hot end 322 of the secondary thermoelectric unit is thermally connected to the heat dissipation structure 7 through the ramp structure 52. The presence of the heat dissipation structure 7 ensures that the heat pumped by the primary thermoelectric unit 31 and the secondary thermoelectric unit 32 can be quickly conducted to the substrate 61 and dissipated to the external environment through the substrate 61, avoiding heat retention that could lead to unstable cold end temperature control.

[0105] To verify the performance of the bidirectional temperature-controlled thermoelectric chip for TEM / SEM described in this invention, multiphysics coupling simulation of the chip was performed using finite element analysis software.

[0106] In the heat conduction physics field, all solid structures are considered, and the initial temperature is uniformly set to room temperature (20°C). Except for the bottom surface of substrate 61, the boundary conditions of the other surfaces in contact with the outside world are set to be adiabatic to simulate an ideal thermal insulation state. The bottom surface of substrate 61 is set as a constant temperature boundary, with the temperature fixed at 20°C.

[0107] During the simulation, multi-physics field coupling simulation was implemented, incorporating thermoelectric and electromagnetic thermal effects. Specifically, thermoelectric coupling effects were considered for the thermocouple structure; Joule heating effects were considered for thermocouple 33, conductive component 4, and the temperature control terminals 311, 312, 321, and 322 of the first-stage thermoelectric unit, as well as the temperature control terminals 321 and 322 of the second-stage thermoelectric unit. The multi-physics fields were solved by coupling the current physical field with the solid heat transfer physical field.

[0108] To optimize device performance while considering the feasibility of MEMS micro / nano fabrication processes, a parametric scan was performed on the length, width, height, and applied current of the thermocouple structure. By comparing the temperature of the cold junction of the device under different parameter combinations, the influence of different structural dimensions and driving conditions on the device's cooling capacity was analyzed. Based on this, the key geometric parameters and operating current range of the semiconductor cooling device of this invention were determined to achieve an optimized balance between structural performance and fabrication process.

[0109] Simulation results show that bidirectional temperature control can be achieved in the same observation area by applying currents of different directions and magnitudes to the thermoelectric chip: when a positive current is applied, the cold junction of the chip can reach as low as -52°C. Figure 9 As shown; when a reverse current is applied, the chip can reach 854°C, as... Figure 10 As shown; the complete two-way temperature control curve is as follows: Figure 11 As shown.

[0110] Example 5:

[0111] This embodiment describes a method for fabricating a bidirectional temperature-controlled thermoelectric chip for TEM or SEM, such as... Figures 12 to 17 As shown, it includes the following steps:

[0112] The first step is to prepare a PI support layer 51 on the front side of the Si substrate 61 by spin coating and curing.

[0113] The second step is to control the photoresist thickness gradient in the slope region by controlling the photolithography parameters.

[0114] The third step involves fabricating the observation window 2, the ramp structure 52, and the isolation cavity 53 using reactive ion etching (RIE) technology.

[0115] The fourth step involves simultaneously fabricating the temperature control region 1, heat dissipation structure 7, electrode bonding block 8, conductive component 4, and the temperature control end and opposite end of the primary thermoelectric unit and the secondary thermoelectric unit on the surface of the support layer 51 by photolithography, thermal evaporation, or magnetron sputtering.

[0116] The fifth step involves sequentially fabricating the N-type thermoelectric arm 331 and the P-type thermoelectric arm 332 of the primary thermoelectric unit and the secondary thermoelectric unit using photolithography, magnetron sputtering, and lift-off methods, followed by annealing.

[0117] The sixth step involves fabricating the back cavity structure on the back side of the Si substrate 61 using processes such as photolithography and deep reactive ion etching (DRIE).

[0118] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM, characterized in that: The device includes a substrate, a back cavity on the substrate, a support layer on the substrate, a sloped structure around the support layer, a temperature control zone on the support layer, an observation window on the temperature control zone, thermoelectric units around the temperature control zone, two electrode bonding blocks on the substrate, and the thermoelectric units connected to the electrode bonding blocks; a heat dissipation structure corresponding to the thermoelectric units is provided on the sloped structure and the substrate around the sloped structure, and an isolation cavity is provided between the thermoelectric units and the temperature control zone.

2. The bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 1, characterized in that: The thermoelectric unit includes: a primary thermoelectric unit, a secondary thermoelectric unit, and a conductive component. The primary thermoelectric unit, the secondary thermoelectric unit, and the conductive component are connected in series to form a thermoelectric circuit. The primary thermoelectric unit is fitted around the temperature control zone, and the secondary thermoelectric unit is fitted around the primary thermoelectric unit. An isolation cavity is provided between the primary thermoelectric unit and the temperature control zone, and an isolation cavity is provided between the primary thermoelectric unit and the secondary thermoelectric unit.

3. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 2, characterized in that: The primary thermoelectric unit includes: a primary thermoelectric unit temperature control terminal, a primary thermoelectric unit opposite terminal, and a thermocouple. The thermocouple includes: an N-type thermocouple arm and a P-type thermocouple arm. The primary thermoelectric unit temperature control terminal and the primary thermoelectric unit opposite terminal are arranged opposite to each other, and the primary thermoelectric unit temperature control terminal and the primary thermoelectric unit opposite terminal are connected in series through alternately arranged N-type thermocouple arms and P-type thermocouple arms. The secondary thermoelectric unit includes: a temperature control terminal of the secondary thermoelectric unit, a opposite terminal of the secondary thermoelectric unit, and a thermocouple. The thermocouple includes: an N-type thermocouple arm and a P-type thermocouple arm. The temperature control terminal of the secondary thermoelectric unit and the opposite terminal of the secondary thermoelectric unit are arranged opposite to each other, and the temperature control terminal of the secondary thermoelectric unit and the opposite terminal of the secondary thermoelectric unit are connected in series through alternately arranged N-type thermocouple arms and P-type thermocouple arms. The conductive components are connected to the opposite end of the primary thermoelectric unit and the temperature control end of the secondary thermoelectric unit, respectively.

4. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 3, characterized in that: An isolation cavity is provided between the temperature control end of the primary thermoelectric unit and the opposite end of the primary thermoelectric unit.

5. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 3, characterized in that: An isolation cavity is provided between the temperature control end of the secondary thermoelectric unit and the opposite end of the secondary thermoelectric unit.

6. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to any one of claims 1 to 5, characterized in that: The isolation cavity is connected to the back cavity.

7. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 3, characterized in that: The conductive component, heat dissipation structure, temperature control terminal of the primary thermoelectric unit, opposite terminal of the primary thermoelectric unit, temperature control terminal of the secondary thermoelectric unit, and opposite terminal of the secondary thermoelectric unit all have an electrical conductivity greater than 1×10⁻⁶. 7 Materials with a thermal conductivity greater than 90 W / mK (S / m).

8. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 3, characterized in that: The thermocouple is made of bismuth telluride-based thermoelectric material.

9. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 1, characterized in that: The support layer is made of PI material.

10. A bidirectional temperature-controlled thermoelectric chip for TEM or SEM according to claim 1, characterized in that: The temperature control zone uses materials with a conductivity greater than 1×10⁻⁶. 7 Materials with a thermal conductivity greater than 90 W / mK (S / m).

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