A single-pole four-throw integrated switch chip that realizes electrostatic drive by injecting charge

Abstract

The present invention relates to a single-pole four-throw integrated switch chip that realizes electrostatic drive by injecting charge, including four groups of single-pole four-throw switches. The switch chip is formed by bonding a fixed plate and a movable plate. The two groups of drive unit arrays drive the suspended square plate to move towards or away from the fixed plate through real-time control of charge shielding, so that the single-pole four-throw switch is in the on state or the off state, completing the connection action and the turn-off action of the single-pole four-throw switch. By using the single-pole four-throw integrated switch chip that realizes electrostatic drive by injecting charge of the present invention, a new principle of electrostatic drive by injecting charge is applied. The entire switch process control is completed by the power supply of the IC system, without the need for a higher drive power supply, completely overcoming the inherent defect that capacitive electrostatic drive requires high-voltage drive, and making electrostatic drive tend to be more perfect. Therefore, the RF MEMS switch designed by the present invention is more practical, has better isolation and better reliability.

Description

Technical Field

[0001] The present invention relates to the field of micro-electromechanical systems, in particular to the field of contact-type RF MEMS switch chips, and specifically refers to a single-pole four-throw integrated switch chip that realizes charge injection electrostatic drive. Background Art

[0002] At present, most of the RF MEMS switches are driven by capacitive electrostatic drive. The most prominent advantages of the capacitive electrostatic drive principle are low power consumption, simple structure, easy compatibility with IC process, and suitable for mass production. However, its biggest disadvantage is the high driving voltage (20V~80V), which requires the addition of necessary charge pump components in the system to complete the power supply voltage increase (such as the ADGM1304 device of ADI Company, which also encapsulates the charge pump chip), which seriously limits its application in RF MEMS switches. The more serious problem comes from the series of reliability problems caused by the use of high voltage. The electrostatic force of capacitive electrostatic drive comes from the mutual attraction generated by the heterogeneous charges accumulated on the parallel plates after the capacitor is charged; and the restoring force between the plates comes from the elastic force generated by the cantilever of the suspended plates. When the plates start to move from the equilibrium position, the distance between the capacitor plates is the largest and the capacitance is the smallest. Under the same driving voltage, the amount of charge on the plates is the smallest (Q=CV), and the electrostatic force generated is the smallest. At this time, the only way to increase the electrostatic force is to increase the driving voltage. However, under high voltage driving, when the two plates are close to each other, the distance between them decreases, the capacitance increases, and the charge on the plates increases sharply (or, in other words, the electrostatic force is 1 / x the distance between the plates x). 2 relationship), the electrostatic force increases rapidly. This causes the two plates to collide with each other strongly, thereby generating the risk of adhesion of the two plates or\ and increasing the reliability risk of plate fragmentation. In order to reduce these risks and increase the restoring force, it is necessary to increase the spring force; but in turn, it is necessary to increase the driving voltage to start the movement of the plate. It can be seen that the requirements of the two are contradictory. Moreover, under a higher driving voltage, it is easy to cause the breakdown of the medium; and, under the repeated action of high voltage, the charges trapped in the medium due to the strong field excitation accumulate over time, affecting the effective driving of the electrostatic force. Furthermore, for the RF MEMS switch, its isolation requires that the plate spacing at its equilibrium state point be large enough; but the reduction of the driving voltage requires this spacing to be small. This contradiction in characteristic requirements forces the designer to deal with it at the expense of one side, which seriously limits the performance of the RF MEMS switch. As can be seen from the above, all the defects of the capacitive electrostatic drive mentioned above come from the capacitive electrostatic drive principle itself, which is its inherent defect. If you want to fundamentally overcome these inherent defects, you need to start with changing the driving principle itself. This is the main problem to be solved by the present invention. Summary of the invention

[0003] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a single-pole four-throw integrated switch chip that realizes injection charge electrostatic drive and has good practicability, high isolation degree, and good reliability.

[0004] In order to achieve the above object, the single-pole four-throw integrated switch chip that realizes injection charge electrostatic drive of the present invention is as follows:

[0005] The single-pole four-throw integrated switch chip that realizes injection charge electrostatic drive, its main feature is that the switch chip includes four groups of single-pole four-throw switches. The switch chip is formed by bonding a fixed plate and a movable plate. Both the movable plate and the fixed plate have symmetrically designed bonding frames. The movable plate further includes a suspended square plate supported by symmetric or windmill-shaped springs. There are two groups of drive unit arrays symmetrically distributed on the movable plate and the fixed plate, namely the first drive unit group and the second drive unit group, which are pre-stored with different kinds of charges and the same kind of charges respectively, and generate electrostatic attraction and electrostatic repulsion respectively. The two groups of drive unit arrays drive the suspended square plate to move towards the fixed plate or away from the fixed plate by real-time control of charge shielding, so that the single-pole four-throw switch is in the on state or the off state, and the connection action and disconnection action of the single-pole four-throw switch are completed.

[0006] Preferably, the drive unit array includes drive units. Each drive unit includes an injection charge electrode, an injection charge control electrode, an injection charge storage electrode, a charge injection window, and a charge injection control window. The charge injection control window is arranged between the injection charge control electrode and the injection charge storage electrode, and the charge injection window is arranged between the injection charge electrode and the injection charge storage electrode. The injection charge electrode and the injection charge control electrode form the shielding body of the drive unit. The switch chip further includes MOS switch tubes. The injection charge electrode and the injection charge control electrode are connected to one end of the corresponding MOS switch tubes, and the other end of the MOS switch tubes is grounded.

[0007] Preferably, the charge storage electrodes of the first drive unit group and the second drive unit group are pre-injected with different kinds of charges or the same kind of charges respectively. When two groups of interleaved clock pulses act on the MOS switch tubes connected to the first group of drive units and the second group of drive units respectively, the charges on the charge storage electrodes respectively induce different kinds of charges or the same kind of charges on their injection charge electrodes, generating electrostatic attraction or electrostatic repulsion between the two electrodes, driving the suspended square plate to move towards the fixed plate or away from the fixed plate, so that the single-pole four-throw switch is in the on state or the off state.

[0008] Preferably, the hanging square plate of the movable plate is provided with symmetric driving units, namely a first driving unit and a third driving unit, and the fixed plate is provided with symmetric driving units, namely a second driving unit and a fourth driving unit. The first driving unit and the second driving unit form a first driving unit group, and the third driving unit and the fourth driving unit form a second driving unit group.

[0009] Preferably, the switching chip injects a preset charge type and a sufficient amount of charge into the driving unit through a charge injection window and a charge injection control window.

[0010] Preferably, four continuous contacts are arranged around the periphery of the hanging square plate of the movable plate. The fixed plate is provided with a contact area at a position symmetric to the continuous contacts of the movable plate, namely an input contact of the switching signal, four output contacts and their connections. The single-pole four-throw switch is composed of the continuous contacts on the movable plate and five contacts at symmetric positions on the fixed plate. When the hanging square plate reciprocates, the continuous contacts of the movable plate and the contact area of the fixed plate come into contact with or disconnect from each other, so as to realize the distribution of the signal from the input contact to the four output contacts and complete the distribution output and stop output of the signal.

[0011] Preferably, the hanging square plate is provided with a small hole array for releasing and reducing the air damping generated when the hanging square plate moves, and improving the response speed of the switch.

[0012] Preferably, a low-temperature molten medium is deposited on the bonding frames of the movable plate and the fixed plate, which is a medium material for adhesive bonding.

[0013] Preferably, the switching chip further includes a bonding glass plate for sealing the opening of the movable plate cavity, which is convenient for subsequent processing and strengthening of the switch structure.

[0014] Preferably, the switching chip further includes metal wirings led out from the inside of the fixed plate to the back of the fixed plate.

[0015] By adopting the single-pole four-throw integrated switching chip for realizing injection-charge electrostatic drive of the present invention, a new injection-charge electrostatic drive principle is applied. The control of the whole switching process is completed by the power supply of the IC system, and a higher driving power supply is not required, completely overcoming the inherent defect that the capacitive electrostatic drive requires a high voltage drive, and making the electrostatic drive tend to be more perfect. Therefore, the RF MEMS switch designed by the present invention is more practical, has better isolation and better reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a schematic cross-sectional structure diagram of an RF MEMS switch of a single-pole four-throw integrated switching chip for realizing injection-charge electrostatic drive of the present invention.

[0017] Figure 2 Schematic diagram of the relationship between the electrostatic force Fe between the plates, the time t taken for a 5-μm stroke, and the pre-injected charge density Qi of the present invention.

[0018] Figure 3 Schematic cross-sectional view of the main processing technology of the movable plate silicon wafer of the present invention.

[0019] Figure 4 Schematic cross-sectional view of the main processing technology of the fixed plate silicon wafer of the present invention.

[0020] Figure 5 Schematic cross-sectional view of the process of the first bonding process scheme of the present invention.

[0021] Figure 6 Schematic cross-sectional view of the process of the second bonding process scheme of the present invention.

[0022] Figure 7 Schematic diagram of the structure of a single-pole four-throw integrated switch chip that realizes electrostatic drive by injecting charge of the present invention.

[0023] Reference numerals:

[0024] 11 Fixed plate

[0025] 12 Movable plate

[0026] 4 Bonding glass plate

[0027] 21 First driving unit

[0028] 22 Second driving unit

[0029] 23 Third driving unit

[0030] 24 Fourth driving unit

[0031] 211 Charge injection control electrode

[0032] 212 Charge injection storage electrode

[0033] 213 Charge injection electrode

[0034] 31, 32 Windmill-shaped springs

[0035] 51, 52, 53 Small hole arrays

[0036] 61, 62, 63, 64 Continuous contacts

[0037] 71, 72, 73, 74 Bonding frames

[0038] 81, 82 Low-temperature molten dielectric layers

[0039] 91, 92 Metal connections Detailed implementation manners

[0040] In order to more clearly describe the technical content of the present invention, the following will be further described in conjunction with specific embodiments.

[0041] The single-pole four-throw integrated switch chip of the present invention realizes injection charge electrostatic drive, which includes four groups of single-pole four-throw switches. The switch chip is formed by bonding a fixed plate and a movable plate. Both the movable plate and the fixed plate have symmetrically designed bonding frames. The movable plate further includes a suspended square plate supported by symmetric or windmill-shaped springs. The movable plate and the fixed plate are provided with two groups of driving unit arrays symmetrically distributed, namely the first driving unit group and the second driving unit group, which are pre-stored with different kinds of charges and the same kind of charges respectively, and generate electrostatic attraction and electrostatic repulsion respectively. The two groups of driving unit arrays drive the suspended square plate to move towards the fixed plate or away from the fixed plate by real-time control of charge shielding, so that the single-pole four-throw switch is in the on state or the off state, and the connection action and disconnection action of the single-pole four-throw switch are completed.

[0042] As a preferred embodiment of the present invention, the driving unit array includes driving units. Each driving unit includes an injection charge electrode, an injection charge control electrode, an injection charge storage electrode, a charge injection window and a charge injection control window. The charge injection control window is arranged between the injection charge control electrode and the injection charge storage electrode, and the charge injection window is arranged between the injection charge electrode and the injection charge storage electrode. The injection charge electrode and the injection charge control electrode form a shielding body of the driving unit. The switch chip further includes MOS switch tubes. The injection charge electrode and the injection charge control electrode are connected to one end of the corresponding MOS switch tubes, and the other end of the MOS switch tubes is grounded.

[0043] As a preferred embodiment of the present invention, the charge storage electrodes of the first driving unit group and the second driving unit group are pre-injected with different kinds of charges or the same kind of charges respectively. When two groups of interleaved clock pulses act on the MOS switch tubes connected to the first group of driving units and the second group of driving units respectively, the charges on the charge storage electrodes respectively induce different kinds of charges or the same kind of charges on their injection charge electrodes, generating electrostatic attraction or electrostatic repulsion between the two electrodes, driving the suspended square plate to move towards the fixed plate or away from the fixed plate, so that the single-pole four-throw switch is in the on state or the off state.

[0044] As a preferred embodiment of the present invention, the suspended square plate of the movable plate is provided with symmetric driving units, namely the first driving unit and the third driving unit. The fixed plate is provided with symmetric driving units, namely the second driving unit and the fourth driving unit. The first driving unit and the second driving unit form the first driving unit group, and the third driving unit and the fourth driving unit form the second driving unit group.

[0045] As a preferred embodiment of the present invention, the switching chip injects a preset type of charge and a sufficient amount of charge into the driving unit through a charge injection window and a charge injection control window.

[0046] As a preferred embodiment of the present invention, four continuous contacts are arranged around the periphery of the suspension quadrilateral plate of the movable plate. The fixed plate is provided with a contact area at a position symmetrical to the continuous contacts of the movable plate, that is, the input contact of the switching signal, four output contacts and their connections. The single-pole four-throw switch is composed of the continuous contacts on the movable plate and five contacts at symmetrical positions on the fixed plate. When the suspension quadrilateral plate reciprocates, the continuous contacts of the movable plate and the contact area of the fixed plate come into contact with or disconnect from each other, so as to realize the distribution of the signal from the input contact to the four output contacts, and complete the distribution output and stop output of the signal.

[0047] As a preferred embodiment of the present invention, the suspension quadrilateral plate is provided with a small hole array for releasing and reducing the air damping generated when the suspension quadrilateral plate moves, and improving the response speed of the switch.

[0048] As a preferred embodiment of the present invention, a low-temperature molten medium is deposited on the bonding frames of the movable plate and the fixed plate, which is a medium material for adhesive bonding.

[0049] As a preferred embodiment of the present invention, the switching chip further includes a bonding glass plate for sealing the opening of the movable plate cavity, facilitating subsequent processing and strengthening the switch structure.

[0050] As a preferred embodiment of the present invention, the switching chip further includes metal wirings led out from the inside of the fixed plate to the back surface of the fixed plate.

[0051] In a specific embodiment of the present invention, an RF MEMS switch chip integrated with four single-pole four-throw switches and driven by the principle of injecting charge electrostatic drive is designed. The chip is formed by bonding a movable plate and a fixed plate. The movable plate is composed of a bonding frame and a square plate connected thereto and supported by symmetric or windmill-shaped springs; and a symmetric pattern is also designed on the fixed plate. Four groups of switch contact areas are respectively designed around the periphery of the square plate on the movable plate and at symmetric positions on the fixed plate: a continuous contact is designed on the square plate of the movable plate in each group; and an input contact and four output contacts are designed in the contact area at the symmetric position on the fixed plate. Each group constitutes a single-pole four-throw switch. The switch function is completed by the principle of injecting charge electrostatic drive, and the implemented structure is: two groups of driving unit arrays are symmetrically distributed inside the suspended square plate and at the corresponding positions on the fixed plate: one group stores different charges in advance for generating electrostatic attraction; and the other group stores the same charges in advance for generating electrostatic repulsion. The two groups of driving units complete the connection and disconnection actions of the switch by injecting charge electrostatic drive through selective shielding and real-time control. In the attached drawings of the specification, "fixed plate" refers to the fixed plate, and "movable plate" refers to the movable plate.

[0052] The RF MEMS switch chip designed by the present invention is as Figure 1 shown. The switch chip integrates four single-pole four-throw RF MEMS switches. The chip is composed of a fixed plate 11 and a movable plate 12. The movable plate is composed of a suspended square plate connected to the bonding frame and supported by symmetric or windmill-shaped springs (such as 31 and 32). And a pattern completely symmetric to the movable plate is designed on the fixed plate, but there is no corresponding movable part.

[0053] Four continuous contacts, such as 61 and 63, are arranged around the periphery of the suspended square plate connected to the movable plate; and for each continuous contact, an input contact and four output contacts (such as 62 and 64) of the switch signal and their corresponding connecting wires are arranged at the corresponding symmetric positions on the fixed plate. Therefore, each continuous contact on the movable plate and the five separate contacts at the symmetric positions on the corresponding fixed plate constitute a single-pole four-throw switch. And the designed chip integrates a total of four groups of single-pole four-throw switches, and they make the same switch response simultaneously with the reciprocating movement of the suspended square plate on the movable plate. In practical applications, the chip can realize switches of types such as single-pole, double-pole, and four-pole multi-throw by changing the number of parallel input and output ports.

[0054] An array of small holes 51, 52, and 53 is also arranged on the suspended square plate of the movable plate for releasing the movable plate and reducing the air damping generated during the movement of the suspended square plate, thereby improving the response speed of the switch. However, there is no such corresponding pattern on the fixed plate, and only the corresponding space is left to ensure the symmetry of other patterns.

[0055] Inside the square plate suspended on the movable plate, a driving unit array is also arranged. The driving unit array is composed of a plurality of charge injection driving units such as 21 and 23. Each driving unit is composed of a charge injection control electrode 211, a charge injection storage electrode 212, and a charge injection electrode 213. The charge injection control electrode 211 and the charge injection electrode 213 form the shielding body of this driving unit. And, a charge injection control window is designed between the charge injection control electrode and the charge injection storage electrode; and a charge injection window is designed between the charge injection electrode and the charge injection storage electrode; charges are pre-injected through the injection window using the principle of F-N tunneling (Fowler-Nordheim tunneling) and stored on the charge injection storage electrode. Similarly, symmetric driving units, such as 22 and 24, are designed on the fixed plate.

[0056] The driving units 21 and 22 are a pair, and different kinds of charges are pre-stored on their charge storage electrodes respectively. The charge injection control electrodes and the charge injection electrodes of this group of driving units are respectively connected to the ground through two pairs of MOS switching tubes, and the charges pre-stored on their internal storage electrodes are shielded; and when these two pairs of switching tubes are disconnected (controlled by the clock pulse T1), the charges pre-stored on the storage electrodes respectively induce different kinds of charges on their charge injection electrodes, thereby generating an electrostatic attraction force between the two plates, driving the square plate suspended on the movable plate towards the fixed plate, prompting the contacts on the two plates to contact each other, and making the RFMEMS switch in the on state.

[0057] The driving units 23 and 24 are another pair, and the same kind of charges are stored on their charge storage electrodes respectively. Similarly, the charge injection control electrodes and the charge injection electrodes of this group of storage units are respectively connected to the ground through another two pairs of MOS switching tubes, and the charges pre-stored on their internal storage electrodes are shielded; and when these two pairs of switching tubes are disconnected (controlled by the clock pulse T2; the pulse signal T2 can be an independent pulse source, or generated by the T1 pulse plus an inverter), the charges pre-stored on the storage electrodes respectively induce the same kind of charges on their charge injection electrodes, thereby generating an electrostatic repulsive force between the two plates, driving the square plate suspended on the movable plate to move away from the fixed plate, prompting the contacts on the two plates to separate and generating sufficient isolation, and making the RFMEMS switch in the off state.

[0058] The clock pulse T1 and the clock pulse T2 are interlaced and correlated with each other. Thus, it controls the alternating generation of the electrostatic attraction force and the electrostatic repulsive force between the plates, prompting the suspended square plate to perform reciprocating motion. Thereby, the corresponding functions of the integrated four groups of single-pole four-throw RFMEMS switches are completed.

[0059] The movable plate is also designed with bonding frames, such as 71 and 73; and the fixed plate is also symmetrically designed with bonding frames, such as 72 and 74. The low-temperature melting dielectric layer deposited on the fixed plate bonding frame, such as 81 and 82, is used to bond the dielectric material. The bonding glass plate 4 is used to seal the opening of the movable plate cavity to facilitate subsequent processing and reinforcement of the switch structure. The metal wiring of the chip system, such as 91 and 92, is all led out to the back of the fixed plate through the fixed plate silicon. So far, a systematic introduction has been made to the following aspects: Figure 1 The final schematic structure shown is a switch driven by the charge injection electrostatic driving principle and integrating four sets of single-pole four-throw RF MEMS switches.

[0060] In order not to waste the space of the movable plate silicon body, the movable plate cavity window can be left open, so that the back of the movable plate can be used for other purposes. If this design is selected, then the movable plate processing requires pre-release of the movable parts, and then bonding with the fixed plate. The final structure is as follows Figure 5 (d) This design will increase the bonding difficulty and affect the bonding yield, which needs to be properly considered when selecting.

[0061] The structure of the four-group single-pole four-throw RF MEMS switch of the present invention is a movable plate and a fixed plate bonded together. On the two plates, corresponding to the positions of the square plates fixed on the movable plate and suspended by springs, two groups of drive unit arrays with staggered and symmetrical distribution are respectively arranged. It is characterized in that the symmetrical drive unit array drives the suspended square plate to reciprocate through pre-charge injection and selective shielding real-time control, and continuously and repeatedly completes the connection and disconnection actions of the switch.

[0062] The structure of the driving unit is composed of a charge injection electrode, a charge injection window, a charge storage electrode, a charge injection control window and a charge injection control electrode; at the same time, the injection electrode and the injection control electrode are also the shielding body of the driving unit; the injection electrode and the control electrode are led out and connected to one end of the corresponding MOS switch tube respectively, and the other end of these MOS switch tubes is connected to the ground.

[0063] Charge injection electrostatic drive: First, before leaving the factory, a sufficient amount of heterogeneous or homogeneous charges are pre-selected and injected into the storage poles of the two sets of drive units; then, two sets of staggered clock pulses act on the connected MOS switch tubes, and the grounding of the shielding bodies of the different corresponding drive units on the two plates is selected to control the disappearance or generation of the induced charges of the corresponding drive units on the two plates, thereby generating an electrostatic attraction or electrostatic repulsion between the two plates, driving the two plates to move back and forth relative to each other.

[0064] Symmetrical distribution of drive units: On two electrodes, two pairs of drive unit groups are symmetrically distributed, which are respectively used to pre-store sufficient amounts of opposite charges or like charges; the drive unit groups are repeatedly distributed in the set areas on the two electrodes to form a two-dimensional array of drive units, so as to generate sufficient electrostatic attraction or electrostatic repulsion.

[0065] Pre-injection of selected charges: After the chip is processed, it is necessary to lead out the charge injection electrodes and charge injection control electrodes from each of the two pairs of drive unit groups contained in the drive unit array respectively. Taking the F-N tunneling effect as the injection principle, through the control window and injection window in each drive unit, the specified charge type and sufficient amount of charges are injected into the specified drive unit array area.

[0066] Selection and shielding of stored charges: When the RF MEMS switch operates, two groups of clock pulses alternately control the on and off of two groups of MOS switch transistors, respectively controlling the grounding and disconnection of the shields of the two drive unit groups, and controlling the generation and disappearance of opposite induced charges or like induced charges on the two electrodes. Thus, electrostatic attraction or electrostatic repulsion is generated between the two electrodes, causing the two electrodes to reciprocate closer and farther away from each other.

[0067] Integration of four single-pole four-throw RF MEMS switches: Contact areas (continuous contacts) are respectively arranged on each side around the suspended square plate. When the suspended square plate reciprocates, it contacts or disconnects from the contact areas (one input contact and four output contacts) at symmetric positions on the fixed electrode plate, realizing the distribution of signals from the input contact to the four output contacts, and completing the distribution output (when in contact with each other) and stop output (when disconnected from each other) of the signals.

[0068] The manufacturing process of the RF MEMS switch chip designed by the present invention is divided into three stages: one is the processing of the movable plate silicon wafer; the second is the processing of the fixed plate silicon wafer; the third is the bonding process and lead layout of the processed movable plate silicon wafer and fixed plate silicon wafer.

[0069] The cross-section of the main process for processing the movable plate silicon wafer is as Figure 3As shown below. First, select a low-resistance (<0.1 Ohm.cm) double-sided polished single-crystalline silicon wafer; thermal oxidation of approximately 5000A to 10000A + LTO (10000A to 20000A) + densification treatment, as shown in Figure a. Deposit a thick polysilicon layer (5000A to 10000A); lithography of the movable plate structure, as shown in Figure (b). A bonding frame and a square plate supported by symmetric cantilevers or windmill-shaped cantilevers are processed on the said movable plate; and on the square plate, a driving unit array, contacts, and a damping reduction hole array such as MP-1 are processed. Combining with CMP technology, deposit three layers of polysilicon (each layer with a thickness of 1500A to 5000A) respectively, mainly through lithography of each layer of polysilicon to form a two-dimensional array MP-2 of injection charge electrostatic driving units, as shown in Figure (c). In each unit of the said array, a charge injection control electrode MP-2 / 1, a charge storage electrode MP-2 / 2, and a charge injection electrode MP-2 / 3 are processed. A charge injection control window (where the thickness of the isolation thermal oxide layer is 100A to 300A) is processed between the charge injection control electrode and the charge storage electrode; and a charge injection window (where the thickness of the isolation thermal oxide layer is 60A to 150A) is set between the charge storage electrode and the charge injection electrode. Then, perform lithography for the definition of the movable component structure, as shown in Figure (d). To separate the movable components, deposit silicon nitride by LPCVD with a thickness of 1500A to 3000A, as shown in Figure (e). Deposit metal AL or / and Au, and perform lithography to form contacts such as MP-3 / 1 and MP-3 / 2; and lead-out electrodes such as MP-4 / 1 and MP-4 / 2, as shown in Figure (f). Deposit a cavity pad layer (forming a bonding frame) LTO with a thickness of 10000A to 30000A, and perform lithography on the LTO to form a cavity structure on the movable plate such as MP-5 / 1 and MP-5 / 2, as shown in Figure (g). Deposit silicon nitride by PECVD with a thickness of 1500A to 3000A to protect the pad layer, and perform lithography to open the movable component release window, as shown in Figure (h). Finally, use gaseous HF to release the movable components through the damping reduction hole array, as shown in Figure (i). Thus, the processing of the movable plate silicon wafer is completed.

[0070] The cross-section of the main process for processing the fixed plate silicon wafer is as Figure 4As shown. Similarly, a low-resistance (<0.1Ohm.cm) "100" double-sided polished single-crystal silicon wafer is selected; thermal oxidation is about 5000A~10000A+LTO (10000A~20000A}+densification treatment, as shown in Figure a). Combined with CMP technology, three layers of polysilicon (each layer is 1500A~5000A thick) are deposited respectively, mainly through each layer of polysilicon lithography, so as to form a two-dimensional array FP-1 of injection charge electrostatic drive units, as shown in Figure (b). In each unit of the array, an injection charge control electrode FP-1 / 1, a charge storage electrode FP-1 / 2 and a charge injection electrode FP-1 / 3 are processed. A charge injection control window is processed between the injection charge control electrode and the charge storage electrode (where the thickness of the isolation thermal oxide layer is 100A~300A); and a charge injection window is processed between the charge storage electrode and the charge injection electrode (where the thickness of the isolation thermal oxide layer is 60A~150A). To protect the processed patterns on the fixed plate, silicon nitride is deposited by LPCVD with a thickness of 1500A to 3000A, as shown in Figure (c). Metal AL and / or Au are deposited, and contacts are formed by photolithography, such as FP-2 / 1 and FP-2 / 2; and lead electrodes are formed, as shown in Figure (d). The cavity pad layer LTO (forming a bonding frame) is deposited with a thickness of 10000A to 30000A, and glass frit is deposited, and LTO and frit are photolithographically formed on the movable plate. The cavity structure, such as FP-3 / 1 and FP-3 / 2, is formed, as shown in Figure (e). Double-sided photolithography technology is used to photolithography the back lead holes, as shown in Figure (f). At this point, the fixed plate silicon wafer processing is completed.

[0071] There are two options for the processing design of the bonding process: one is to form a closed cavity structure after bonding; the other is to form an open cavity structure after bonding.

[0072] Solution 1: RF MEMS switch structure with a sealed cavity after bonding:

[0073] Features: Strong structure and small space occupation, but the movable parts are difficult to release, and the bonding yield is low because the movable parts may be damaged. The bonding yield needs to be improved for mass production.

[0074] The process section of the first bonding process is as follows: Figure 4As shown. After the movable plate wafer releases the movable components, it is then bonded to the processed fixed plate wafer through pattern alignment. Utilizing the low-temperature melting property of the glass powder layer, the cavity frame part is melted and joined together, and the movable components are enclosed within the cavity, as shown in Figure (a). Then, applying a technology similar to TSV (Through-Silicon Via), from the back of the fixed plate wafer, using the DRIE technology, the fixed plate wafer is etched through along the contact hole window, as shown in Figure (b); continue to dry-etch the exposed SiO2 until the metal is encountered, as shown in Figure (c); deposit metal and lithograph the pad pattern, as shown in Figure (d). Thus, the packaging process is completed.

[0075] Second solution: The RF switch structure with an open cavity formed after bonding:

[0076] Features: Easy to bond, and the movable components are easily released through the cavity opened at the back, and the bonding processing yield will be relatively high; however, the structure needs to be strengthened, and the back of the movable plate wafer cannot be used for other purposes.

[0077] The cross-section of the second bonding process solution is as Figure 5 shown. The movable plate wafer is only processed up to the PECVD deposition of silicon nitride, without performing release lithography or gas-phase HF release, but adding back cavity window lithography. Thus, the processing of the movable plate wafer is completed. It is then bonded to the processed fixed plate wafer through pattern alignment. Utilizing the low-temperature melting property of the glass powder layer, the cavity frame part is melted and joined, as shown in Figure (a). Then, along the cavity window opened at the back of the movable plate wafer, using the DRIE technology, the cavity is opened from the back of the movable plate wafer to expose the movable components, as shown in Figure (b). Use gas-phase HF to etch away the exposed SiO2 to expose the silicon nitride, as shown in Figure (c). Use dry etching to etch away the exposed silicon nitride film of the movable plate, and the release of the movable components is completed, as shown in Figure (d). Use a thin glass plate to make the back seal of the back of the movable plate, which simultaneously plays a role in strengthening the structure and facilitating subsequent processing, as shown in Figure (e). Finally, applying the TSV (Through-Silicon Via) technology, from the back of the fixed plate wafer, using the DRIE technology, the fixed plate wafer is etched through along the contact hole window, as shown in Figure (f). Continue to dry-etch the exposed SiO2 until the metal is encountered, as shown in Figure (g). Deposit metal and lithograph the pad pattern, as shown in Figure (h). Thus, the packaging is completed.

[0078] After the packaging is completed, dicing is performed to form individual chips, and pre-injection of charges is carried out on the chips (customers can also decide the amount of charge pre-injection they need according to their own application requirements to adjust the performance of the RF switch) and necessary tests are conducted, and finally, an integrated four-group single-pole four-throw RF MEMS switch chip product driven by the injection charge drive principle is obtained.

[0079] The processing technology of the above design is based on mass production, aiming to make the chip designed by the present invention an excellent product with low cost and wide application.

[0080] The charge pre-injection of the present invention adopts the injection principle of F-N tunneling effect. Figure 2 It is estimated according to the approximate analytical equation derived from the designed RF switch structure. The horizontal axis is the pre-injected charge density, the left vertical axis is the electrostatic force that can be generated correspondingly; while the right vertical axis is the time required for the suspended square plate to travel a distance of 5um. Figure 2 It can be seen that the greater the pre-injected charge density, the greater the electrostatic force that can be generated, and the shorter the time required for a 5um travel, which can reach the microsecond level. It can be seen that the switching frequency can be adjusted by the pre-injected charge density. This is one of the advantages of the injection charge electrostatic drive principle. Compared with the capacitive electrostatic drive, the injection charge electrostatic drive has better performance, and the performance comparison is shown in Table 1. It can be seen from Table 1 that the injection charge electrostatic drive principle completely overcomes the inherent defects of the capacitive electrostatic drive principle; at the same time, it basically retains all the advantages of the capacitive electrostatic drive principle. Therefore, the injection charge electrostatic drive will be developed into a more perfect drive method in MEMS, which can make the RF MEMS switch have better performance.

[0081] Table 1 Comparison of the characteristics of capacitive and injection charge electrostatic drives

[0082]

[0083] Note: * Electric field strength E = V / d: Under the condition that the voltage V remains constant, when the plate spacing d approaches 0, then E tends to ∞;

[0084] ** Voltage V = Q / C and C = ε / d: Under the condition that the charge Q remains constant, when the plate spacing d approaches 0, then the capacitance C tends to ∞, and therefore, the voltage V tends to 0;

[0085] *** Such as the series capacitance method, but it will result in the sacrifice of other performances;

[0086] **** It can be expanded by adjusting the spring parameters, controlling the charge injection amount and selecting the shielding.

[0087] The single-pole four-throw integrated switch chip that realizes the injection charge electrostatic drive by adopting the present invention uses the new injection charge electrostatic drive principle. The entire switching process control is completed by the IC system power supply, and no higher drive power supply is required, completely overcoming the inherent defect that the capacitive electrostatic drive requires high voltage drive, making the electrostatic drive tend to be more perfect. Therefore, the RF MEMS switch designed by the present invention is more practical, has better isolation and better reliability.

[0088] In this specification, the invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations can be made without departing from the spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive.

Claims

1. A single-pole four-throw integrated switch chip that realizes charge injection electrostatic drive, It is characterized in that The switch chip includes four groups of single-pole four-throw switches, and the switch chip is composed of a fixed plate and a movable plate bonded together. The movable plate and the fixed plate both have a symmetrically designed bonding frame. The movable plate also includes a suspended square plate supported by a symmetrical or windmill-type spring. The movable plate and the fixed plate have two symmetrically distributed drive unit arrays, namely a first drive unit group and a second drive unit group, which are respectively pre-stored with opposite charges and the same charges, and generate electrostatic attraction and electrostatic repulsion, respectively. The two drive unit arrays control the charge shielding in real time, drive the suspended square plate to move toward the fixed plate or away from the fixed plate, so that the single-pole four-throw switch is in an on state or an off state, and complete the connection action and the disconnection action of the single-pole four-throw switch; The driving unit array comprises a driving unit, the driving unit comprises a charge injection electrode, a charge injection control electrode, a charge injection storage electrode, a charge injection window and a charge injection control window, the charge injection control window is arranged between the charge injection control electrode and the charge injection storage electrode, the charge injection window is arranged between the charge injection electrode and the charge injection storage electrode, the charge injection electrode and the charge injection control electrode constitute a shielding body of the driving unit; the switch chip also comprises a MOS switch tube, the charge injection electrode and the charge injection control electrode are connected to one end of the corresponding MOS switch tube, and the other end of the MOS switch tube is grounded; The symmetrical drive unit array drives the suspended quadrilateral plates to reciprocate by pre-injecting charges and selectively shielding for real-time control, repeatedly completing the connection and disconnection of the switch. The charge storage electrodes of the first drive unit group and the second drive unit group are respectively injected with heterogeneous charges or homogeneous charges in advance; when two groups of staggered clock pulses act on the MOS switch tubes connected to the first drive unit group and the second drive unit group, the charges of the charge storage electrodes respectively induce heterogeneous charges or homogeneous charges at the charge injection electrodes, generating electrostatic attraction or electrostatic repulsion between the two plates, driving the suspended square plate to move toward the fixed plate or away from the fixed plate, so that the single-pole four-throw switch is in an on state or an off state; The hanging square plate is arranged with a small hole array for releasing and reducing the air damping generated when the hanging square plate moves, thereby improving the response speed of the switch.

2. The single-pole four-throw integrated switch chip for realizing charge injection electrostatic drive according to claim 1, It is characterized in that The suspended square plate of the movable plate is provided with symmetrical driving units, namely the first driving unit and the third driving unit, and the fixed plate is provided with symmetrical driving units, namely the second driving unit and the fourth driving unit. The first driving unit and the second driving unit constitute a first driving unit group, and the third driving unit and the fourth driving unit constitute a second driving unit group.

3. The single-pole four-throw integrated switch chip for realizing charge injection electrostatic drive according to claim 1, It is characterized in that The described switching chip injects a preset type of charge and a sufficient amount of charge into the driving unit through a charge injection window and a charge injection control window.

4. The single-pole four-throw integrated switching chip for realizing charge injection electrostatic drive according to claim 1, characterized in that, Four continuous contacts are arranged around the periphery of the suspended square plate of the movable plate, and a contact area is provided on the fixed plate at a position symmetrical to the continuous contacts of the movable plate, that is, the input contact of the switching signal and the four output contacts and their connections. The single-pole four-throw switch is composed of the continuous contacts on the movable plate and the five contacts at symmetrical positions on the fixed plate; when the suspended square plate reciprocates, the continuous contacts of the movable plate and the contact area of the fixed plate come into contact with or disconnect from each other, realizing the distribution of the signal from the input contact to the four output contacts, and completing the distribution output and stop output of the signal.

5. The single-pole four-throw integrated switching chip for realizing charge injection electrostatic drive according to claim 1, characterized in that, A low-temperature molten medium is deposited on the bonding frames of the movable plate and the fixed plate, which is a medium material for adhesive bonding.

6. The single-pole four-throw integrated switching chip for realizing charge injection electrostatic drive according to claim 1, characterized in that, The switching chip further includes a bonding glass plate for sealing the opening of the movable plate cavity, facilitating subsequent processing and strengthening of the switching structure.

7. The single-pole four-throw integrated switching chip for realizing charge injection electrostatic drive according to claim 1, characterized in that, The switching chip further includes metal wiring, which is led out from the inside of the fixed plate to the back of the fixed plate.

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