Radio frequency MEMS switch and preparation method thereof

Abstract

The invention provides a radio frequency MEMS switch and a preparation method thereof, and relates to the technical field of radio frequency MEMS switches. A substrate of the radio frequency MEMS switch comprises a first surface and a second surface which are opposite to each other, a Peltier refrigeration module is embedded in the substrate, the Peltier refrigeration module comprises a refrigeration end and a heat dissipation end, and the refrigeration end is closer to the first surface compared with the heat dissipation end. The driving electrode is arranged on the first surface, and the first electrode and the second electrode are also arranged on the first surface. The cantilever beam is electrically connected with the first electrode, the cantilever beam is arranged on the side, away from the substrate, of the driving electrode, and the cantilever beam is configured to be electrically connected with the second electrode under driving of the driving electrode. The orthographic projection of the joint of the cantilever beam and the first electrode on the substrate is overlapped with the area where the Peltier refrigeration module is located, and / or the orthographic projection of the joint of the cantilever beam and the second electrode on the substrate is overlapped with the area where the Peltier refrigeration module is located, in-situ active cooling can be carried out, and thermal creep aggravation is restrained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radio frequency micro-electro-mechanical system (RF MEMS) switches, and in particular to a RF MEMS switch and a preparation method thereof. BACKGROUND

[0002] As a core actuator for microwave signals, the RF MEMS switch has the advantages of simple structure, low power consumption, high operating frequency, small insertion loss, high isolation, and good linearity. The switch can be turned on or turned off by the mechanical displacement of a movable cantilever beam or a movable thin film. However, the long-term reciprocating motion of the movable cantilever beam or the movable thin film can easily induce a creep effect due to thermal-mechanical coupling, which affects the reliability and service life of the switch. At present, the reliability and service life are mainly improved by researching new anti-creep materials. However, due to the long innovation cycle of the material system and poor process compatibility, it is difficult to achieve a fundamental breakthrough. SUMMARY

[0003] The present application provides a RF MEMS switch and a preparation method thereof, which aims to realize dynamic temperature drop of the cantilever beam by integrating a Peltier cooling module, greatly reduce the thermal creep rate, and improve the reliability and service life.

[0004] To achieve the above-mentioned purpose, the embodiments of the present application provide the following technical solutions:

[0005] In a first aspect, a RF MEMS switch is provided, which includes a substrate, a Peltier cooling module, a driving electrode, a first electrode and a second electrode, and a cantilever beam. The substrate includes opposite first and second surfaces, and the Peltier cooling module is embedded in the substrate. The Peltier cooling module includes a cooling end and a heat dissipation end, and the cooling end is closer to the first surface than the heat dissipation end. The driving electrode is disposed on the first surface, and the first and second electrodes are also disposed on the first surface. The cantilever beam is electrically connected to the first electrode, and is disposed on the side of the driving electrode away from the substrate. The cantilever beam is configured to be electrically connected to the second electrode under the driving of the driving electrode. The projection of the connection between the cantilever beam and the first electrode on the substrate overlaps the area where the Peltier cooling module is located. And / or, the projection of the connection between the cantilever beam and the second electrode on the substrate overlaps the area where the Peltier cooling module is located.

[0006] In some embodiments, the first and second electrodes are spaced apart along a first direction, and the first direction is parallel to the first surface. The cantilever beam includes an anchor portion and a suspended portion arranged along the first direction. The anchor portion is electrically connected to the first electrode, and the projection of the suspended portion on the substrate at least partially overlaps the projection of the driving electrode on the substrate. The connection between the anchor portion and the suspended portion has a chamfer.

[0007] In some embodiments, the chamfer is one of a circular chamfer, a straight-line chamfer, or an elliptical chamfer.

[0008] In some embodiments, the overhang includes a first sub-portion and a second sub-portion, the first sub-portion is connected with the anchor portion, and the first sub-portion extends along a first direction. The second sub-portion is arranged on opposite sides of the first sub-portion along a second direction, the second direction is parallel to the first surface, and intersects the first direction. A projection of the second sub-portion on the substrate is located within a projection of the driving electrode.

[0009] In some embodiments, the Peltier cooling module further includes a plurality of first thermoelectric legs and a plurality of second thermoelectric legs, the plurality of first thermoelectric legs and the plurality of second thermoelectric legs are arranged alternately between the cooling end and the heat-dissipating end. One first thermoelectric leg is electrically connected with one adjacent second thermoelectric leg at the cooling end, and electrically connected with another adjacent second thermoelectric leg at the heat-dissipating end.

[0010] In some embodiments, the first electrode includes a first PAD region and a first contact region, a thickness of the first PAD region is greater than a thickness of the first contact region along a direction perpendicular to the substrate, and the cantilever beam is electrically connected with the first contact region. The second electrode includes a second PAD region and a second contact region, a thickness of the second PAD region is greater than a thickness of the second contact region along the direction perpendicular to the substrate, and the cantilever beam is configured to be electrically connected with the second contact region under the driving of the driving electrode.

[0011] In some embodiments, the first electrode and the second electrode are arranged spaced apart along a first direction, the first direction is parallel to the first surface. The radio frequency MEMS switch further includes two coplanar waveguide transmission lines, the two coplanar waveguide transmission lines are located on the first surface, and the first electrode and the second electrode are both located between the two coplanar waveguide transmission lines along a second direction, the second direction is parallel to the first surface, and intersects the first direction.

[0012] In a second aspect, the present application further provides a preparation method of a radio frequency MEMS switch, including steps S10-S40 as follows:

[0013] Step S10: embedding a Peltier cooling module in a substrate, the substrate includes opposite first and second surfaces, the Peltier cooling module includes a cooling end and a heat-dissipating end, and the cooling end is closer to the first surface than the heat-dissipating end.

[0014] Step S20: forming a driving electrode on the first surface.

[0015] Step S30: forming a first electrode and a second electrode on the first surface.

[0016] Step S40: forming a cantilever beam, the cantilever beam being electrically connected with the first electrode, the cantilever beam being disposed at a side of the driving electrode away from the substrate, the cantilever beam being configured to be electrically connected with the second electrode under the driving of the driving electrode. The normal projection of the connection between the cantilever beam and the first electrode on the substrate overlaps the area where the Peltier refrigeration module is located. And / or, the normal projection of the connection between the cantilever beam and the second electrode on the substrate overlaps the area where the Peltier refrigeration module is located.

[0017] In some embodiments, the forming of the cantilever beam comprises the following steps S41-S43:

[0018] Step S41: forming a sacrificial layer at a side of the first electrode and the second electrode away from the substrate, the sacrificial layer comprising a through hole.

[0019] Step S42: forming an anchor point part in the through hole, and forming a hanging part on the sacrificial layer, the connection between the anchor point part and the hanging part having a chamfer.

[0020] Step S43: removing the sacrificial layer.

[0021] In some embodiments, the embedding of the Peltier refrigeration module in the substrate comprises steps S11-S15:

[0022] Step S11: forming a trench on the first surface.

[0023] Step S12: forming a heat dissipation end in the trench, the heat dissipation end comprising a plurality of second interconnection structures.

[0024] Step S13: forming a plurality of first thermoelectric legs and a plurality of second thermoelectric legs, the plurality of first thermoelectric legs and the plurality of second thermoelectric legs being arranged alternately.

[0025] Step S14: forming a dielectric layer, the dielectric layer exposing the plurality of first thermoelectric legs and the plurality of second thermoelectric legs.

[0026] Step S15: forming a refrigeration end, the refrigeration end comprising a plurality of first interconnection structures, the first interconnection structures and the second interconnection structures being arranged alternately, so that one first thermoelectric leg and one adjacent second thermoelectric leg are electrically connected through a first interconnection structure at the refrigeration end, and another adjacent second thermoelectric leg is electrically connected through a second interconnection structure at the heat dissipation end.

[0027] In the present application, the cantilever beam is electrically connected with the first electrode, the cantilever beam is arranged on the side of the driving electrode away from the substrate, and the cantilever beam is configured to be electrically connected with the second electrode under the driving of the driving electrode, so as to realize the on and off functions of the radio frequency MEMS switch. Moreover, the Peltier refrigeration module is embedded in the substrate, the orthographic projection of the connection between the cantilever beam and the first electrode on the substrate overlaps the area where the Peltier refrigeration module is located. And / or, the orthographic projection of the connection between the cantilever beam and the second electrode on the substrate overlaps the area where the Peltier refrigeration module is located. The refrigeration end of the Peltier refrigeration module is closer to the first surface than the heat dissipation end. That is, by integrating the Peltier refrigeration module, the connection between the cantilever beam and the first electrode and / or the connection between the cantilever beam and the second electrode can be actively cooled in situ, the heat of the cantilever beam is conducted away, the temperature rise caused in the working process is avoided, the thermal creep aggravation effect can be effectively inhibited, and the reliability and service life of the switch can be significantly improved.

[0028] The preparation method has simple process, is easy to implement, has strong process compatibility, and is beneficial to improving production efficiency and reducing manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present application, the drawings needed to be used in some embodiments of the present application will be briefly introduced below. Obviously, the drawings in the following description are only the drawings of some embodiments of the present application, and other drawings can also be obtained by those skilled in the art according to these drawings. In addition, the drawings in the following description can be regarded as schematic diagrams, and are not the actual size of the product involved in the embodiments of the present application or the actual process of the method.

[0030] Figure 1 A top view structural schematic diagram of the radio frequency MEMS switch provided by the embodiments of the present application is shown;

[0031] Figure 2 A front view structural schematic diagram of the radio frequency MEMS switch provided by the embodiments of the present application is shown;

[0032] Figure 3 A structural schematic diagram of a first cantilever beam provided by the embodiments of the present application is shown;

[0033] Figure 4 A structural schematic diagram of a second cantilever beam provided by the embodiments of the present application is shown;

[0034] Figure 5 A structural schematic diagram of a third cantilever beam provided by the embodiments of the present application is shown;

[0035] Figure 6 A top view structural schematic diagram of a Peltier refrigeration module provided by the embodiments of the present application is shown;

[0036] Figure 7A partial enlarged view of the first electrode and the second electrode provided for the embodiment of the present application is shown in FIG. 1B.

[0037] Figure 8 A flow chart of a preparation method of a radio frequency MEMS switch provided for the embodiment of the present application is shown in FIG. 2.

[0038] Figures 9-20 For Figure 8 A diagram of each step of the preparation method is shown in FIG. 3. DETAILED DESCRIPTION

[0039] The technical solutions in some embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments provided by the present application, all other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

[0040] Unless otherwise required by the context, throughout the specification and claims, the term "comprising" is to be interpreted as open, inclusive, meaning "including, but not limited to".

[0041] Hereinafter, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0042] In describing some embodiments, the term "connected" and its derivatives can be used. The term "connected" should be interpreted broadly, for example, "connected" can be fixedly connected, or detachably connected, or integrated; can be directly connected, or indirectly connected through an intermediate medium. For example, in describing some embodiments, the term "connected" can be used to indicate that two or more components have direct physical or electrical contact with each other.

[0043] In addition, the use of "based on" means open and inclusive, because the process, step, calculation or other action "based on" one or more stated conditions or values can be based on additional conditions or values beyond those stated in practice.

[0044] It should be understood that when a layer or element is referred to as being on another layer or substrate, it can be that the layer or element is directly on the other layer or substrate, or there can be an intermediate layer between the layer or element and the other layer or substrate.

[0045] Exemplary embodiments are described herein with reference to cross-sectional illustrations that are idealized examples. In the drawings, the thickness of layers and regions are exaggerated for clarity. Accordingly, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, the exemplary embodiments should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etched region illustrated as a rectangle will typically have rounded or curved features. Thus, the regions illustrated in the drawings are schematic and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the exemplary embodiments.

[0046] Currently, RF MEMS switches have significant advantages in key indicators such as insertion loss (<0.3 dB@30 GHz), isolation (>30 dB@30 GHz), and linearity (IIP3>60 dBm) due to almost ideal ohmic contact characteristics, and have become the preferred solution for high-performance systems such as 5G millimeter wave communication, phased array radar, and satellite payloads.

[0047] However, for example, in the case of an electrostatically driven switch, the cantilever beam reciprocates to realize the conduction or disconnection of the switch. The RF MEMS switch generates heat due to high-frequency signal transmission, which causes the temperature of the cantilever beam to rise. Long-term thermal coupling will exacerbate the creep of the cantilever beam. Currently, the reliability and life of the cantilever beam are mainly improved by researching new anti-creep materials, but due to the bottleneck of long innovation cycle of material system and poor process compatibility, it is difficult to achieve a fundamental breakthrough.

[0048] Based on this, the present application provides a RF MEMS switch, as shown in Figures 1-2 Figure 1 A top view structural schematic diagram of the RF MEMS switch provided by the embodiment of the present application, Figure 2 A front view structural schematic diagram of the RF MEMS switch provided by the embodiment of the present application.

[0049] The RF MEMS switch includes a substrate 1, a Peltier refrigeration module 2, a driving electrode 3, a first electrode 4 and a second electrode 5, and a cantilever beam 6. The substrate 1 includes a first surface P1 and a second surface P2 opposite to each other, the Peltier refrigeration module 2 is embedded in the substrate 1, the Peltier refrigeration module 2 includes a refrigeration end 21 and a heat dissipation end 22, and the refrigeration end 21 is closer to the first surface P1 than the heat dissipation end 22. Exemplarily, after a directional driving current is applied, the Peltier refrigeration effect is generated on the side of the refrigeration end 21, realizing the cooling of the side of the first surface P1.

[0050] ​The driving electrode 3 is arranged on the first surface P1, and the first electrode 4 and the second electrode 5 are also arranged on the first surface P1. The cantilever beam 6 is arranged on the side of the driving electrode 3 away from the substrate 1, and the cantilever beam 6 is electrically connected with the first electrode 4. The cantilever beam 6 is configured to be electrically connected with the second electrode 5 under the driving of the driving electrode 3, that is, the driving electrode 3 controls the reciprocating movement of the cantilever beam 6, and the on-off function of the radio frequency MEMS switch can be realized.

[0051] In the working process of the radio frequency MEMS switch, the cantilever beam 6 reciprocates for a long time, and plastic deformation, that is, creep problem, is prone to occur. The creep of the cantilever beam 6 is not only related to the material properties of the cantilever beam 6 itself, but also related to the stress distribution and temperature. In the process of high-frequency signal transmission of the radio frequency MEMS switch, the connection between the cantilever beam 6 and the second electrode 5 generates a serious heating problem, and the heat will be conducted along the cantilever beam 6 to the connection between the cantilever beam 6 and the first electrode 4, so that the heat is accumulated at the connection between the cantilever beam 6 and the first electrode 4. In the related art, the heat cannot be conducted out, which will cause the overall temperature rise of the cantilever beam 6, and further aggravate the creep, causing the cantilever beam 6 to appear serious bending deformation, for example, deformation close to the driving electrode 3 and the second electrode 5, which seriously affects the characteristic parameters (such as pull-down voltage, isolation, etc.), and even causes the switch to be permanently closed, so that the switch is invalid.

[0052] In the embodiments of the present application, as shown in Figures 1-2 The normal projection of the connection between the cantilever beam 6 and the first electrode 4 on the substrate 1 overlaps the area where the Peltier refrigeration module 2 is located. Alternatively, the normal projection of the connection between the cantilever beam 6 and the second electrode 5 on the substrate 1 overlaps the area where the Peltier refrigeration module 2 is located. Alternatively, the normal projection of the connection between the cantilever beam 6 and the first electrode 4 on the substrate 1 overlaps the area where the Peltier refrigeration module 2 is located, and the normal projection of the connection between the cantilever beam 6 and the second electrode 5 on the substrate 1 overlaps the area where the Peltier refrigeration module 2 is located.

[0053] Taking the connection between the cantilever beam 6 and the first electrode 4 as an example, generally, the larger the normal projection area of the connection between the cantilever beam 6 and the first electrode 4, the larger the overlapping area with the Peltier refrigeration module 2, and the more conducive to realizing the in-situ active cooling of the cantilever beam 6. The refrigeration end 21 is close to the connection between the cantilever beam 6 and the first electrode 4, and the switch is actively cooled in-situ, which accelerates the heat conduction of the cantilever beam 6 to the substrate 1, realizes the dynamic temperature drop of the cantilever beam 6, greatly reduces the thermal creep rate, and is conducive to slowing down the bending deformation of the cantilever beam 6, thereby significantly improving the reliability and life of the switch.

[0054] The connection between the cantilever beam 6 and the second electrode 5 is the same, generally, the heat generation and temperature rise of the connection between the cantilever beam 6 and the second electrode 5 are more serious, and the cooling effect of the connection between the cantilever beam 6 and the second electrode 5 is better when the refrigeration end 21 is close to the connection between the cantilever beam 6 and the second electrode 5, which is more conducive to inhibiting the temperature rise of the cantilever beam 6 and slowing down the creep, thereby significantly improving the reliability and service life of the switch.

[0055] That is, the embodiment of the present application integrates a miniature Peltier refrigeration module 2 in the substrate 1, uses the Peltier refrigeration module 2 to conduct heat away from the connection between the cantilever beam 6 and the first electrode 4, and / or conducts heat away from the connection between the cantilever beam 6 and the second electrode 5, thereby avoiding the overall temperature rise of the cantilever beam 6, without affecting the radio frequency performance of the switch, and achieving active in-situ heat dissipation with a simple structure and strong process compatibility, thereby achieving the improvement of reliability and the extension of service life at a lower cost.

[0056] In some embodiments, as shown in Figures 1-2 The first electrode 4 and the second electrode 5 are arranged at intervals along a first direction X, and the first direction X is parallel to the first surface P1. The cantilever beam 6 includes an anchor point part 61 and a suspended part 62 arranged along the first direction X, and the anchor point part 61 is electrically connected to the first electrode 4. The orthogonal projection of the suspended part 62 on the substrate 1 at least partially overlaps the orthogonal projection of the driving electrode 3 on the substrate 1, and the cantilever beam 6 is configured to be electrically connected to the second electrode 5 under the driving of the driving electrode 3.

[0057] That is, after a pull-down voltage is applied to the driving electrode 3, an electrostatic force is generated between the driving electrode 3 and the cantilever beam 6, and when the electrostatic force is greater than the elastic restoring force of the cantilever beam 6, the cantilever beam 6 bends in the direction of the first surface P1, until the suspended part 62 contacts the second electrode 5, thereby realizing the conduction of the switch. The size of the electrostatic force is related to the size of the applied pull-down voltage, the distance between the driving electrode 3 and the cantilever beam 6, and the overlapping area therebetween, and the elastic restoring force of the cantilever beam 6 is related to its material properties, shape and size, and thickness.

[0058] The orthogonal projection of the suspended part 62 on the substrate 1 at least partially overlaps the orthogonal projection of the driving electrode 3 on the substrate 1, and the greater the overlapping area, the greater the electrostatic force received by the suspended part 62 under the same conditions, and the easier it is to realize the conduction of the switch. Similarly, the greater the overlapping area, the more conducive it is to reducing the pull-down voltage in the working state under the same conditions.

[0059] The thickness of the cantilever beam 6 not only affects the switching sensitivity, but also affects the parameter characteristics of the switch. When the thickness of the cantilever beam 6 is small, although it is conducive to reducing the pull-down voltage in the working state, it will greatly reduce the peak value of the pull-down voltage that the switch can withstand, and easily cause secondary pull-down problems (that is, in the conduction state, the excessive electrostatic force further causes the bending deformation of the cantilever beam 6), thereby exacerbating the switch.

[0060] Based on this, for example, in some embodiments, the material of the cantilever beam 6 includes an AuNi alloy with a thickness of 5μm to 8μm, such as 5μm, 6μm, 7μm or 8μm, which can ensure that the suspended part 62 has both good elastic switching performance and stable performance, and improve the switch's tolerance.

[0061] Furthermore, in order to optimize the force distribution during the reciprocating motion of the cantilever beam 6, the connection between the anchor point 61 and the suspended part 62 has a chamfer.

[0062] For example, the chamfer can be one of a rounded chamfer, a straight chamfer, or an elliptical chamfer.

[0063] like Figures 3-5 As shown, Figure 3 This is a schematic diagram of the structure of the first type of cantilever beam provided in the embodiments of this application. Figure 4 This is a schematic diagram of the structure of the second type of cantilever beam provided in the embodiments of this application. Figure 5 This is a schematic diagram of the third type of cantilever beam provided in an embodiment of this application. Figure 3 The corresponding case is a rounded chamfer. Figure 4 The corresponding case is a straight chamfer. Figure 5 This corresponds to the case where the chamfer is an elliptical chamfer.

[0064] As explained in the switching principle above, one end (fixed end) of the suspended portion 62 is fixedly electrically connected to the first electrode 4 via the anchor point 61, while the other end reciprocates. To enhance the anchoring and support effect of the anchor point 61 and improve the switching performance of the suspended portion 62, the size of the anchor point 61 is larger than the size of the suspended portion 62 along the second direction Y. During the reciprocating motion of the cantilever beam 6, stress concentration occurs at the fixed end of the suspended portion 62, making it prone to deformation, which in turn affects the reliability of the switch.

[0065] In this embodiment, by setting a chamfer at the connection between the anchor point 61 and the suspended part 62, it is beneficial to improve the stress distribution during operation. By using a circular arc chamfer, a straight line chamfer, or an elliptical chamfer, the connection between the anchor point 61 and the suspended part 62 becomes smoother, and the stress is evenly distributed along the chamfer, which helps to avoid deformation caused by stress concentration, and further alleviates creep problems and improves the reliability and lifespan of the switch.

[0066] In some embodiments, such as Figure 1 and Figures 3-5 As shown, the suspended portion 62 includes a first sub-portion 621 and a second sub-portion 622. The first sub-portion 621 is connected to the anchor point portion 61 and extends along a first direction X. The second sub-portion 622 is disposed on opposite sides of the first sub-portion 621 along a second direction Y. The second direction Y is parallel to the first surface P1 and intersects the first direction X.

[0067] In combination with the switch conduction principle in the foregoing, the size of the electrostatic force is related to the overlapping area between the driving electrode 3 and the cantilever beam 6. In the embodiment of the present application, the overhanging part 62 further includes a second sub-part 622, and the orthogonal projection of the second sub-part 622 on the substrate 1 is located within the orthogonal projection range of the driving electrode 3, that is, the force receiving area of the cantilever beam 6 is increased, and the electrostatic force received by the overhanging part 62 is increased. Under the same conditions, the size of the pull-down voltage is reduced to achieve the target of switch conduction.

[0068] The second sub-part 622 is symmetrically distributed on both sides of the first sub-part 621, so that the overhanging part 62 is balanced in force, which is conducive to ensuring the switch performance.

[0069] In some embodiments, the cantilever beam 6 further includes a contact 63, and the orthogonal projection of the contact 63 on the substrate 1 is located within the orthogonal projection range of the second electrode 5. The contact 63 protrudes to one side of the substrate 1, which reduces the distance between the cantilever beam 6 and the second electrode 5, so that the cantilever beam 6 can realize electrical connection with the second electrode 5 under smaller bending deformation, which is conducive to the stability and reliability of electrical connection.

[0070] In some embodiments, as shown in Figure 2 The Peltier refrigeration module 2 further includes a plurality of first thermoelectric legs 231 and a plurality of second thermoelectric legs 232. Exemplarily, the materials of the first thermoelectric legs 231 and the second thermoelectric legs 232 both include Bi2Te3 or Si or SnSe, and based on different ion doping, the first thermoelectric legs 231 are P-type thermoelectric legs, and the second thermoelectric legs 232 are N-type thermoelectric legs. The sizes of the first thermoelectric legs 231 and the second thermoelectric legs 232 are both in the order of hundreds of microns or less, which is conducive to embedding in the substrate 01 based on micro-electro-mechanical system related technology.

[0071] Between the refrigeration end 21 and the heat dissipation end 22, the plurality of first thermoelectric legs 231 and the plurality of second thermoelectric legs 232 are alternately arranged. One first thermoelectric leg 231 is electrically connected with one adjacent second thermoelectric leg 232 at the refrigeration end 21, and is electrically connected with another adjacent second thermoelectric leg 232 at the heat dissipation end 22.

[0072] Exemplarily, as shown in Figure 2 The refrigeration end 21 includes a plurality of first interconnection structures 210, and the heat dissipation end 22 includes a plurality of second interconnection structures 220. One first thermoelectric leg 231 is electrically connected with one adjacent second thermoelectric leg 232 through one first interconnection structure 210, and the other end of the first thermoelectric leg 231 is electrically connected with another adjacent second thermoelectric leg 232 through one second interconnection structure 220.

[0073] As shown in Figure 6 Figure 6 ​A top view structural schematic diagram of a Peltier refrigeration module is provided for the embodiments of the present application. For the convenience of understanding, Figure 6 Only the structural connection relationship is shown, and the size is not represented.

[0074] The plurality of first thermoelectric legs 231 and the plurality of second thermoelectric legs 232 are alternately connected in series. One second interconnection structure 220 is only electrically connected with one first thermoelectric leg 231, and another second interconnection structure 220 is only electrically connected with one second thermoelectric leg 232. The directional driving current is applied between the two second interconnection structures 220, and the carriers flow from the P-type thermoelectric leg to the N-type thermoelectric leg. The heat is absorbed from the crystal lattice at the refrigeration end 21, causing the side to cool down. The heat is released to the crystal lattice at the heat dissipation end 22, and finally dissipated through the second surface P2 of the substrate 1. Finally, the active cooling of the cantilever beam 6 is realized.

[0075] In some embodiments, as Figure 7 shown, Figure 7 A partial enlarged view of the first electrode and the second electrode is provided for the embodiments of the present application.

[0076] The first electrode 4 includes a first PAD region 41 and a first contact region 42. In combination Figure 2 , the thickness of the first PAD region 41 is greater than the thickness of the first contact region 42 in the direction perpendicular to the substrate 1. The first PAD region 41 is used for electrical connection with the external circuit to realize the input of the radio frequency signal, and the first contact region 42 is used for electrical connection with the cantilever beam 6.

[0077] The second electrode 5 includes a second PAD region 51 and a second contact region 52. The thickness of the second PAD region 51 is greater than the thickness of the second contact region 52 in the direction perpendicular to the substrate 1. The second PAD region 51 is used for electrical connection with the external circuit to realize the output of the radio frequency signal, and the second contact region 52 is used for electrical connection with the cantilever beam 6.

[0078] That is, the cantilever beam 6 is configured to be electrically connected with the second contact region 52 under the driving of the driving electrode 3.

[0079] The material of the first PAD region 41 and the first contact region 42 of the first electrode 4 both includes Cr and Au, the material Cr is located on the side of the material Au close to the substrate 1, and the thickness of the Au of the first PAD region 41 is greater than the thickness of the Au of the first contact region 42. The Cr as an adhesion layer can improve adhesion and avoid the material Au from falling off, the material Au has good conductivity, and thus the electrical connection of the first PAD region 41, the first contact region 42 and the cantilever beam 6 is realized, which is beneficial to reduce the switch resistance, reduce the input signal loss and improve the switch performance. For example, the first contact region 42 is formed by magnetron sputtering, the thickness of the material Au of the first contact region 42 is small and the surface roughness is low, the first PAD region 41 is formed by first controlling sputtering to form a thin layer of material Au and then locally electroplating a thick Au conductive layer, and thus for the first electrode 4, it is not only beneficial to save cost, but also can form a good contact surface and reduce the switch resistance. The second electrode 5 is the same, which will not be described here.

[0080] In some embodiments, as shown in FIG. 1, the first electrode 4 and the second electrode 5 are arranged along a first direction X, and the first direction X is parallel to the first surface P1. The radio frequency MEMS switch further includes two coplanar waveguide transmission lines 7 located on the first surface P1 and along a second direction Y, and the first electrode 4 and the second electrode 5 are both located between the two coplanar waveguide transmission lines 7, the second direction Y is parallel to the first surface P1 and intersects the first direction X. Figure 1

[0081] In the working process, the coplanar waveguide transmission line 7 can be used for grounding, can realize good electromagnetic field constraint, has the advantages of low radiation, low crosstalk and low loss, and is beneficial to improve the radio frequency performance. For example, the material of the coplanar waveguide transmission line 7 is the same as the material of the first electrode 4 and the second electrode 5, and can be prepared in the same process.

[0082] The above embodiments and the drawings do not limit the relative relationship of the driving electrode 3, the first electrode 4 and the second electrode 5 along the first direction X, and only need to meet the switch function. For example, in addition to the "first electrode 4 and second electrode 5 are respectively located on the two sides of the driving electrode 3" shown in FIG. 1, in some embodiments, the first electrode 4 and the driving electrode 3 are respectively located on the two sides of the second electrode 5, and the working principle is the same as the foregoing, which will not be described here. Figures 1-2

[0083] In addition, the application also provides a preparation method of a radio frequency MEMS switch, as shown in FIG. 2, Figure 8 Figure 8 A preparation method flow chart of a radio frequency MEMS switch provided by the embodiments of the application, Figures 9-20 Figures 9-20 The steps of the preparation method shown in FIG. 2.

[0084] ​​​​It can be understood that, Figures 9-20 The "positive projection of the connection between the cantilever beam 6 and the first electrode 4 on the substrate 1 overlaps the area where the Peltier refrigeration module 2 is located" is taken as an example for illustration. The scheme of "the positive projection of the connection between the cantilever beam 6 and the second electrode 5 on the substrate 1 overlaps the area where the Peltier refrigeration module 2 is located" can be prepared according to the process shown in Figure 8

[0085] As shown in Figures 9-14 The preparation method includes the following steps S10-S40:

[0086] Step S10: As shown in Figure 9 The Peltier refrigeration module 2 is embedded in the substrate 1, the substrate 1 includes opposite first surface P1 and second surface P2, the Peltier refrigeration module 2 includes refrigeration end 21 and heat dissipation end 22, and the refrigeration end 21 is closer to the first surface P1 than the heat dissipation end 22.

[0087] For example, the substrate 1 is a silicon substrate or a quartz substrate, and the thickness is in the range of 400 μm-600 μm.

[0088] The Peltier refrigeration module 2 is embedded in the substrate 1, including steps S11-S15:

[0089] Step S11: As shown in Figure 10 The groove T1 is formed on the first surface P1. For example, the groove T1 with a depth in the range of 20 μm-40 μm is formed by photolithography and deep reactive ion etching process.

[0090] Step S12: As shown in Figure 11 The heat dissipation end 22 is formed in the groove T1, and the heat dissipation end 22 includes a plurality of second interconnection structures 220. For example, the plurality of second interconnection structures 220 are arranged in an array to provide a basis for subsequent electrical connection of the thermoelectric legs. The material of the second interconnection structure 220 includes Cu or Au, which has low resistance and high thermal conductivity, and is beneficial to improve the heat dissipation effect.

[0091] Step S13: As shown in Figure 6 A plurality of first thermoelectric legs 231 and a plurality of second thermoelectric legs 232 are formed, and the plurality of first thermoelectric legs 231 and the plurality of second thermoelectric legs 232 are arranged alternately.

[0092] For example, the first thermoelectric leg 231 is a P-type thermoelectric leg, and the second thermoelectric leg 232 is an N-type thermoelectric leg. The material of the first thermoelectric leg 231 and the second thermoelectric leg 232 can include Bi2Te3 or Si or SnSe, and the plurality of first thermoelectric legs 231 and the plurality of second thermoelectric legs 232 are arranged alternately through deposition, ion implantation and etching process, as shown in Figure 11 the arrangement rule.​

[0093] Referring to Figure 12 , the plurality of first thermoelectric legs 231 and the plurality of second thermoelectric legs 232 are disposed on the second interconnection structure 220. For the plurality of second interconnection structures 220, one of them is disposed with a first thermoelectric leg 231, and another one is disposed with a second thermoelectric leg 232, and the rest are disposed with a first thermoelectric leg 231 and a second thermoelectric leg 232.

[0094] Step S14: as shown in Figure 13 , a dielectric layer 11 is formed, which exposes the plurality of first thermoelectric legs 231 and the plurality of second thermoelectric legs 232.

[0095] Exemplarily, the material of the dielectric layer 11 includes Si3N4, which is filled in the trench T1 to provide a flat surface for subsequent processes.

[0096] Step S15: as shown in Figure 6 , the cooling end 21 is formed, which includes a plurality of first interconnection structures 210. Exemplarily, the material of the first interconnection structure 210 includes Cu or Au, which has low resistance and high thermal conductivity, and good cooling effect, which is conducive to enhancing the in-situ active cooling capacity.

[0097] Referring to Figure 14 , the first interconnection structure 210 and the second interconnection structure 220 are arranged alternately, so that one first thermoelectric leg 231 and one adjacent second thermoelectric leg 232 are electrically connected through a first interconnection structure 210 at the cooling end 21, and another adjacent second thermoelectric leg 232 is electrically connected through a second interconnection structure 220 at the heat dissipation end 22.

[0098] Finally, the first thermoelectric leg 231 and the second thermoelectric leg 232 are connected in series alternately.

[0099] Then, as shown in Figure 15 , the dielectric layer 11 is formed again in the trench T1, and is polished by CMP technology to form a flat surface for subsequent processes.

[0100] Step S20: as shown in Figures 16-17 , a driving electrode 3 is formed on the first surface P1. Exemplarily, the material of the driving electrode 3 includes polysilicon.

[0101] Exemplarily, before forming the driving electrode 3, a buffer layer 12 is also formed, for example, the material of the buffer layer 12 includes SiO2, which is deposited by PECVD technology to a thickness of 0.5 μm-1 μm, which is conducive to reducing lattice mismatch, reducing dislocation density, and improving the performance and reliability of the device.

[0102] Then, an amorphous silicon layer with a thickness of 0.2 μm to 0.5 μm is deposited by PECVD technology, and the amorphous silicon layer is converted into a polysilicon layer by B or P ion implantation and rapid thermal annealing, and the implanted B or P ions are activated, and then a mask layer is formed by photolithography to perform patterning, and finally the driving electrode 3 is formed.

[0103] Step S30: As shown in Figure 16 , the first electrode 4 and the second electrode 5 are formed on the first surface P1.

[0104] For example, as shown in Figure 1 , after the driving electrode 3 is formed, the insulating layer 13 is first formed, and the material of the insulating layer 13 includes Si3N4, which is used to protect and isolate the driving electrode 3. In order to facilitate the subsequent connection of the pull-down voltage on the driving electrode 3, the insulating layer 13 needs to be etched to form a silicon contact via hole that exposes the driving electrode 3, which is not shown here.

[0105] After that, the first electrode 4 and the second electrode 5 can also be formed synchronously during the process of forming the coplanar waveguide transmission line 7. As shown in Figure 17 , it can be seen that the position of the silicon contact via hole should avoid the two coplanar waveguide transmission lines 7 and the area therebetween.

[0106] As shown in Figure 1 , in combination with the topography shown in Figures 18-20 , first, a 20 nm thick Cr adhesion layer and a 200 nm thick Au seed layer are magnetron sputtered on the insulating layer 13, a photoresist is used to form an electroplating mask layer, and the opening topography of the electroplating mask layer corresponds to the topography of the coplanar waveguide transmission line 7, the first PAD area 41 and the second PAD area 51. After electroplating a conductive layer with a thickness of 2 μm to 3 μm, the electroplating mask layer is removed, and an etching mask layer is formed again, and the topography of the etching mask layer corresponds to the topography of the coplanar waveguide transmission line 7, the first electrode 4 and the second electrode 5. Under the shielding of the etching mask layer, the exposed adhesion layer and seed layer are etched and removed, thereby forming the first electrode 4 and the second electrode 5 arranged in a spaced manner, and the coplanar waveguide transmission lines 7 on both sides thereof. The thickness difference between the first PAD area 41 and the first contact area 42, and the thickness difference between the second PAD area 52 and the second contact area 52, is the thickness of the conductive layer. For example, the material of the conductive layer includes Au.

[0107] Step S40: As shown in Figure 18As shown, a cantilever beam 6 is formed, which is electrically connected to the first electrode 4. The cantilever beam 6 is disposed on the side of the driving electrode 3 away from the substrate 1, and is configured to be electrically connected to the second electrode 5 under the drive of the driving electrode 3. The orthographic projection of the connection point between the cantilever beam 6 and the first electrode 4 on the substrate 1 overlaps with the area where the Peltier cooling module 2 is located. And / or, the orthographic projection of the connection point between the cantilever beam 6 and the second electrode 5 on the substrate 1 overlaps with the area where the Peltier cooling module 2 is located.

[0108] For example, the material of the cantilever beam 6 includes an AuNi alloy.

[0109] The formation of cantilever beam 6 includes the following steps S41 to S43:

[0110] Step S41: As Figure 19 As shown, a sacrificial layer 14 is formed on the side of the first electrode 4 and the second electrode 5 away from the substrate 1. The sacrificial layer 14 includes a through-hole T2 that exposes the first contact area 42.

[0111] For example, the material of the sacrificial layer 14 includes SiO2, the thickness of the sacrificial layer 14 is in the range of 1μm to 3μm, and the sacrificial layer 14 also includes a groove T3, the orthographic projection of the groove T3 on the substrate 1 is located within the orthographic projection of the second contact area 52.

[0112] Step S42: As Figures 3-5 As shown, an anchor point 61 is formed inside the through hole, and a suspended portion 62 is formed on the sacrificial layer. The connection between the anchor point 61 and the suspended portion 62 has a chamfer. The type of chamfer can be referred to Figure 17 As shown. For example, a contact 63 is also formed in the groove T3 to reduce the distance between the cantilever beam 6 and the second electrode 5, which helps to improve the stability and reliability of the contact between the cantilever beam 6 and the second electrode 5.

[0113] For example, refer to Figure 20 The corresponding preparation method involves first sputtering a 150 nm thick Au seed layer, then electroplating a 5 μm to 8 μm thick AuNi alloy, and finally obtaining the cantilever beam 6 with the desired morphology after patterning.

[0114] Step S43: As Figure 1 As shown, the sacrificial layer 14 is removed. For example, the sacrificial layer 14 is released and dried using a buffered oxide etchant and a CO2 boundary dryer to prevent device failure due to surface tension, and finally obtains an RF MEMS switch.

[0115] The preparation method has simple process, is easy to implement, and is controllable in size and structure precision, and the size of a key structure can be controlled in a range from nanometer to micrometer, which is beneficial to the design and manufacture of high-precision micro-nano structures. In addition, the preparation method has strong process compatibility, adopts a relatively mature semiconductor process, is convenient to integrate with an existing MEMS or integrated circuit manufacturing process, improves production efficiency, and reduces manufacturing cost.

[0116] The radio frequency MEMS switch formed based on the preparation method avoids the overall temperature rise of the cantilever beam 6 by using the Peltier cooling module 2 to conduct heat away from the cantilever beam 6, does not affect the radio frequency performance of the switch, can realize active in-situ heat dissipation, has a simple structure and strong process compatibility, and realizes the improvement of reliability and the prolongation of service life at a low cost. In addition, by optimizing the design in the process, a chamfer is arranged at the connection between the anchor point 61 and the suspended part 62, which is also beneficial to avoiding deformation caused by stress concentration, and is beneficial to further relieving the creep problem, improving the reliability and service life of the switch.

[0117] The single-pole single-throw switch is taken as an example for illustration and description, and it can be understood that the above scheme is also applicable to a single-pole double-throw switch or a single-pole multi-throw switch. For example, the single-pole double-throw switch includes a first switch and a second switch, the first switch is the single-pole single-throw switch shown in Figure 1 , the second switch is symmetrical to the switch shown in ​ along the Y-Z plane, and the first switch and the second switch share a first electrode 4.

[0118] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can think of changes or replacements within the technical range disclosed in the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A radio frequency MEMS switch, characterized by, The application relates to a radio frequency MEMS switch, comprising: a substrate comprising a first surface and a second surface opposite to each other; a Peltier cooling module embedded in the substrate, the Peltier cooling module comprising a cooling end and a heat dissipation end, the cooling end being closer to the first surface than the heat dissipation end; a driving electrode arranged on the first surface; a first electrode and a second electrode, both arranged on the first surface; a cantilever beam electrically connected with the first electrode, the cantilever beam being arranged on a side of the driving electrode away from the substrate, and the cantilever beam being configured to be electrically connected with the second electrode under the driving of the driving electrode; a projection of a connection between the cantilever beam and the first electrode on the substrate overlaps with an area where the Peltier cooling module is located; and / or a projection of a connection between the cantilever beam and the second electrode on the substrate overlaps with the area where the Peltier cooling module is located.

2. The RF MEMS switch of claim 1, wherein, The first electrode and the second electrode are arranged in a first direction parallel to the first surface; the cantilever beam comprises an anchor point part and a suspended part arranged in the first direction, the anchor point part being electrically connected with the first electrode, and a projection of the suspended part on the substrate at least partially overlaps with a projection of the driving electrode on the substrate; a connection between the anchor point part and the suspended part has a chamfer.

3. The RF MEMS switch of claim 2, wherein, The chamfer is one of a circular chamfer, a straight-line chamfer or an elliptical chamfer.

4. The RF MEMS switch of claim 2, wherein, The suspended part comprises a first subpart and a second subpart, the first subpart being connected with the anchor point part and extending in the first direction; the second subpart is arranged on opposite sides of the first subpart in a second direction parallel to the first surface and intersecting the first direction; a projection of the second subpart on the substrate is located within a projection of the driving electrode.

5. The RF MEMS switch of claim 1, wherein, The Peltier cooling module further comprises a plurality of first thermoelectric legs and a plurality of second thermoelectric legs arranged alternately between the cooling end and the heat dissipation end; one first thermoelectric leg is electrically connected with one adjacent second thermoelectric leg at the cooling end and with another adjacent second thermoelectric leg at the heat dissipation end.

6. The RF MEMS switch of claim 1, wherein, The first electrode comprises a first PAD area and a first contact area, a thickness of the first PAD area being greater than a thickness of the first contact area in a direction perpendicular to the substrate; the cantilever beam is electrically connected with the first contact area; The second electrode comprises a second PAD area and a second contact area, a thickness of the second PAD area being greater than a thickness of the second contact area in a direction perpendicular to the substrate; the cantilever beam is configured to be electrically connected with the second contact area under the driving of the driving electrode.

7. The RF MEMS switch of claim 1, wherein, The first electrode and the second electrode are arranged in a first direction parallel to the first surface; The radio frequency MEMS switch further comprises two coplanar waveguide transmission lines, the coplanar waveguide transmission lines being located on the first surface; In a second direction, both the first electrode and the second electrode are located between two coplanar waveguide transmission lines; the second direction is parallel to the first surface and intersects the first direction.

8. A method of fabricating a radio frequency MEMS switch, the method comprising: Comprising: Embedding a Peltier cooling module in a substrate, the substrate comprising a first surface and a second surface opposite to the first surface, the Peltier cooling module comprising a cooling end and a heat dissipation end, the cooling end being closer to the first surface than the heat dissipation end; Forming a driving electrode on the first surface; Forming a first electrode and a second electrode on the first surface; Forming a cantilever beam, the cantilever beam being electrically connected to the first electrode; the cantilever beam is disposed on a side of the driving electrode away from the substrate, and the cantilever beam is configured to be electrically connected to the second electrode under the driving of the driving electrode; the projection of the connection between the cantilever beam and the first electrode on the substrate overlaps the area where the Peltier cooling module is located; and / or, the projection of the connection between the cantilever beam and the second electrode on the substrate overlaps the area where the Peltier cooling module is located.

9. The production method according to claim 8, characterized by, The forming of the cantilever beam comprises: Forming a sacrificial layer on a side of the first electrode and the second electrode away from the substrate, the sacrificial layer comprising a through hole; Forming an anchor point part in the through hole and a suspended part on the sacrificial layer, the connection between the anchor point part and the suspended part having a chamfer; Removing the sacrificial layer.

10. The method of claim 8, wherein, The embedding of the Peltier cooling module in the substrate comprises: Forming a groove on the first surface; Forming the heat dissipation end in the groove, the heat dissipation end comprising a plurality of second interconnection structures; Forming a plurality of first thermoelectric legs and a plurality of second thermoelectric legs, the plurality of first thermoelectric legs and the plurality of second thermoelectric legs being arranged alternately; Forming a dielectric layer, the dielectric layer exposing the plurality of first thermoelectric legs and the plurality of second thermoelectric legs; Forming the cooling end, the cooling end comprising a plurality of first interconnection structures, the first interconnection structures being staggered with the second interconnection structures, so that one first thermoelectric leg and one adjacent second thermoelectric leg are electrically connected by a first interconnection structure in the cooling end, and another adjacent second thermoelectric leg is electrically connected by a second interconnection structure in the heat dissipation end.

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