CN112289645A

CN112289645A - Single-pole four-throw integrated switch chip for realizing electrostatic driving of injected charges

Info

Publication number: CN112289645A
Application number: CN202011246666.7A
Authority: CN
Inventors: 汤玉生; 汤易天
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-11-10
Filing date: 2020-11-10
Publication date: 2021-01-29

Abstract

The invention relates to a single-pole four-throw integrated switch chip for realizing injection charge electrostatic driving, which comprises four groups of single-pole four-throw switches, wherein the switch chip is formed by bonding a fixed plate and a movable plate, two groups of driving unit arrays drive a suspended square plate to move towards the fixed plate or leave the fixed plate through real-time control of charge shielding, so that the single-pole four-throw switches are in a switch-on state or a switch-off state, and the switch-on action and the switch-off action of the single-pole four-throw switches are completed. The single-pole four-throw integrated switch chip for realizing the electrostatic drive of the injected charge applies a new electrostatic drive principle of the injected charge, the whole switch process control is completed by an IC system power supply, a higher drive power supply is not needed, the inherent defect that the capacitive type electrostatic drive needs high voltage drive is completely overcome, and the electrostatic drive tends to be more perfect. Therefore, the RF MEMS switch designed by the invention has more practicability, better isolation and better reliability.

Description

Single-pole four-throw integrated switch chip for realizing electrostatic driving of injected charges

Technical Field

The invention relates to the field of micro-electromechanical systems, in particular to the field of contact type RF MEMS switch chips, and specifically relates to a single-pole four-throw integrated switch chip for realizing injection charge electrostatic driving.

Background

Capacitive electrostatic actuation is mostly used in the current application of RF MEMS switches. The most outstanding advantages of the capacitive electrostatic driving principle are low power consumption, simple structure, easy compatibility with IC process and suitability for mass production. However, the biggest disadvantage is that the driving voltage is high (20V-80V), and the necessary charge pump component needs to be added in the system to complete the raising of the power supply voltage (for example, ADI ADGM1304 device packages the charge pump chip at the same time), which severely limits the application of the device in the RF MEMS switch. And more serious problems result from series reliability problems with the use of high voltages. The electrostatic force of the capacitive electrostatic drive is from the mutual attraction force generated by the different charges accumulated on the two parallel polar plates after the capacitor is charged; and the restoring force between the plates comes from the elastic force generated by the cantilever suspending the plates. When the plates start moving from the balance position, the distance between the capacitor plates is the largest, the capacitance is the smallest, the charged amount on the plates is the smallest (Q is CV) under the same driving voltage, and the generated electrostatic force is the smallest. At this time, the driving voltage is merely increased to increase the electrostatic force. However, under the driving of high voltage, in the process of the two polar plates approaching each other, the distance is reduced, the capacitance is increased, and the charge amount charged on the polar plates is increased sharply (or, the electrostatic force and the distance x between the polar plates are 1/x)²Relationship), the electrostatic force increases rapidly. This causes the two pole plates to collide with each other strongly, thereby generating the risk of sticking the two pole plates or/and increasing the reliability risk of the pole plates, such as cracking, and the like. To reduce these risks and increase the restoring force, the spring force needs to be increased; but in turn requires an increased drive voltage to initiate plate movement. It can be seen that the requirements of the two are contradictory. Moreover, at higher driving voltage, breakdown of the dielectric is easily caused; and effective driving of electrostatic force is affected by accumulation of charges trapped in the medium due to strong field excitation over time under repeated action of high voltage. Furthermore, for RF MEMS switches, the isolation requires that the plate spacing at the equilibrium point be large enough; but a reduction in the driving voltage requires that the pitch be small. This contradiction in the performance requirements has caused designers to deal with this only at the expense of one party, and the severity of the designPerformance of the RF MEMS switch is severely limited. As can be seen from the above, all the mentioned drawbacks of the capacitive electrostatic driving come from the principle of the capacitive electrostatic driving itself, which is an inherent drawback. If it is desired to overcome these inherent disadvantages fundamentally, it is necessary to start with changing the driving principle itself. This is the problem that the present invention mainly aims to solve.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a single-pole four-throw integrated switch chip which has the advantages of good practicability, high isolation and good reliability and realizes the electrostatic drive of injected charges.

In order to achieve the above object, the single-pole four-throw integrated switch chip for implementing electrostatic driving by injecting charges of the invention is as follows:

the single-pole four-throw integrated switch chip for realizing the electrostatic driving by injecting charges is mainly characterized in that the switch chip comprises four groups of single-pole four-throw switches, the switch chip is formed by bonding a fixed plate and a movable plate, the movable plate and the fixed plate are respectively provided with a bonding frame with a symmetrical design, the movable plate further comprises a suspended square plate supported by symmetrical or windmill-shaped springs, two groups of driving unit arrays which are symmetrically distributed are arranged on the movable plate and the fixed plate, namely a first driving unit group and a second driving unit group, wherein different charges and the same charges are respectively pre-stored in the first driving unit group and the second driving unit group, electrostatic attraction force and electrostatic repulsion force are respectively generated, the two groups of driving unit arrays are used for driving the suspended square plate to move towards the fixed plate or leave the fixed plate to move through real-time control of charge shielding, so that the single-pole four-throw switches are in a connection state or, and completing the connection action and the disconnection action of the single-pole four-throw switch.

Preferably, the driving unit array includes a driving unit, the 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 disposed between the injection charge control electrode and the injection charge storage electrode, the charge injection window is disposed between the injection charge electrode and the injection charge storage electrode, and the injection charge electrode and the injection charge control electrode constitute a shield of the driving unit; the switch chip further comprises an MOS switch tube, the injection charge electrode and the injection charge control electrode are connected with one end of the corresponding MOS switch tube, and the other end of the MOS switch tube is grounded.

Preferably, the charge storage electrodes of the first and second driving unit groups are injected with different charges or the same charge in advance; two groups of staggered clock pulses are respectively acted on MOS switch tubes connected with the first group of driving units and the second group of driving units, charges of the charge storage electrode are respectively injected into the charge electrode to induce different charges or the same charges, electrostatic attraction or electrostatic repulsion is generated between the two electrode plates, the suspension square plate is driven to move towards the fixed plate or leave the fixed plate to move, and the single-pole four-throw switch is in a connection state or a disconnection state.

Preferably, the suspended square plate of the movable plate is provided with symmetrical driving units, namely a first driving unit and a third driving unit, the fixed plate is provided with symmetrical 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.

Preferably, the switch chip injects a predetermined charge type and a sufficient amount of charges into the driving unit through the charge injection window and the charge injection control window.

Preferably, four continuous contacts are arranged around the periphery of the suspended square plate of the movable plate, a contact area is arranged at the position of the fixed plate symmetrical to the continuous contacts of the movable plate, namely, an input contact, four output contacts and connecting lines of a switch signal are arranged on the fixed plate, and the single-pole four-throw switch consists of the continuous contacts on the movable plate and five contacts at symmetrical positions on the fixed plate; when the suspension square plate reciprocates, the continuous contact of the movable plate and the contact area of the fixed plate are mutually contacted or disconnected, so that the signals are distributed from the input contacts to the four output contacts, and the distributed output and the stop output of the signals are finished.

Preferably, the suspended square plate is provided with an array of small holes for releasing and reducing air damping generated when the suspended square plate moves, and the response speed of the switch is improved.

Preferably, the bonding frames of the movable plate and the fixed plate are provided with deposited low-temperature melting media which are adhesive bonding dielectric materials.

Preferably, the switch chip further comprises a bonding glass plate for sealing the cavity opening of the movable plate, so as to facilitate subsequent processing and reinforcement of the switch structure.

Preferably, the switch chip further includes a metal connection wire led out from the inside of the fixing plate to the back surface of the fixing plate.

The single-pole four-throw integrated switch chip for realizing the electrostatic drive of the injected charge applies a new electrostatic drive principle of the injected charge, the whole switch process control is completed by an IC system power supply, a higher drive power supply is not needed, the inherent defect that the capacitive type electrostatic drive needs high voltage drive is completely overcome, and the electrostatic drive tends to be more perfect. Therefore, the RF MEMS switch designed by the invention has more practicability, better isolation and better reliability.

Drawings

Fig. 1 is a schematic cross-sectional structure diagram of an RF MEMS switch of a single-pole four-throw integrated switch chip for implementing electrostatic driving by injecting charges according to the present invention.

FIG. 2 is a schematic diagram showing the relationship between the time t of the electrostatic force Fe and 5um stroke between the plates and the pre-injection charge density Qi.

FIG. 3 is a schematic cross-sectional view of the main process for processing a movable plate silicon wafer according to the present invention.

FIG. 4 is a schematic cross-sectional view of the main process for processing a fixed-plate silicon wafer according to the present invention.

Fig. 5 is a process cross-sectional schematic view of a first bonding process scheme of the present invention.

Fig. 6 is a process cross-sectional schematic view of a second bonding process scheme of the present invention.

Fig. 7 is a simplified structural diagram of a single-pole four-throw integrated switch chip for implementing electrostatic driving by injecting charges according to the present invention.

Reference numerals:

11 fixed plate

12 Movable Board

4 bonded glass plate

21 first drive unit

22 second drive unit

23 third drive unit

24 fourth drive unit

211 injection charge control electrode

212 injection charge storage pole

213 injection charge pole

31. 32 windmill type spring

51. 52, 53 orifice array

61. 62, 63, 64 continuous contacts

71. 72, 73, 74 key frame

81. 82 low-temperature melting medium layer

91. 92 metal connecting wire

Detailed Description

In order to more clearly describe the technical contents of the present invention, the following further description is given in conjunction with specific embodiments.

The single-pole four-throw integrated switch chip for realizing the electrostatic driving by injecting the charges comprises four groups of single-pole four-throw switches, the switch chip is formed by bonding a fixed plate and a movable plate, the movable plate and the fixed plate are both provided with symmetrically designed bonding frames, the movable plate also comprises a suspension square plate supported by a symmetrical or windmill-shaped spring, two groups of driving unit arrays which are symmetrically distributed are arranged on the movable plate and the fixed plate, namely, the first driving unit group and the second driving unit group are respectively pre-stored with different charges and the same charges to respectively generate electrostatic attraction force and electrostatic repulsion force, the two groups of driving unit arrays drive the suspended square plate to move towards the fixed plate or leave the fixed polar plate through real-time control of charge shielding, so that the single-pole four-throw switch is in a switch-on state or a switch-off state, and the connection action and the switch-off action of the single-pole four-throw switch are completed.

As a preferred embodiment of the present invention, the driving unit array includes a driving unit, the driving unit includes an injected charge electrode, an injected charge control electrode, an injected charge storage electrode, a charge injection window, and a charge injection control window, the charge injection control window is disposed between the injected charge control electrode and the injected charge storage electrode, the charge injection window is disposed between the injected charge electrode and the injected charge storage electrode, and the injected charge electrode and the injected charge control electrode constitute a shield of the driving unit; the switch chip further comprises an MOS switch tube, the injection charge electrode and the injection charge control electrode are connected with one end of the corresponding MOS switch tube, and the other end of the MOS switch tube is grounded.

In a preferred embodiment of the present invention, the charge storage electrodes of the first and second driving unit groups are previously injected with different charges or the same charges; two groups of staggered clock pulses are respectively acted on MOS switch tubes connected with the first group of driving units and the second group of driving units, charges of the charge storage electrode are respectively injected into the charge electrode to induce different charges or the same charges, electrostatic attraction or electrostatic repulsion is generated between the two electrode plates, the suspension square plate is driven to move towards the fixed plate or leave the fixed plate to move, and the single-pole four-throw switch is in a connection state or a disconnection state.

In a preferred embodiment of the present invention, the suspended square plate of the movable plate is provided with symmetrical driving units, i.e., a first driving unit and a third driving unit, the fixed plate is provided with symmetrical driving units, i.e., a second driving unit and a 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.

As a preferred embodiment of the present invention, the switch chip injects a predetermined charge type and a sufficient amount of charges into the driving unit through the charge injection window and the charge injection control window.

As a preferred embodiment of the present invention, four continuous contacts are arranged around the periphery of the suspended square plate of the movable plate, a contact area, namely, an input contact and four output contacts of a switching signal and connecting lines thereof, is arranged at a position of the fixed plate symmetrical to the continuous contacts of the movable plate, and 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 square plate reciprocates, the continuous contact of the movable plate and the contact area of the fixed plate are mutually contacted or disconnected, so that the signals are distributed from the input contacts to the four output contacts, and the distributed output and the stop output of the signals are finished.

As a preferred embodiment of the invention, the suspended square plate is provided with an array of small holes for releasing and reducing air damping generated when the suspended square plate moves and improving the response speed of the switch.

In a preferred embodiment of the present invention, the bonding frames of the movable plate and the fixed plate have a low-temperature melting medium deposited thereon, and the low-temperature melting medium is a dielectric material bonded by adhesion.

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

As a preferred embodiment of the present invention, the switch chip further includes a metal wire, which is led out from the inside of the fixing plate to the back surface of the fixing plate.

In the specific implementation mode of the invention, an integrated RF MEMS switch chip driven by adopting an injected charge electrostatic driving principle and integrating four groups of single poles and four throws is designed. The chip is formed by bonding the movable electrode plate and the fixed electrode plate. The movable polar plate is composed of a bonding frame and a square plate which is connected with the bonding frame and is supported by a symmetrical or windmill-shaped spring; the fixing plate is also designed with a symmetrical figure. Four groups of switch contact areas are respectively designed on the periphery of the square plate and on the symmetrical positions of the fixed plate: each group is provided with a continuous contact on the square plate of the movable polar plate; while the contact areas at symmetrical positions of the holding plate are designed with one input contact and four output contacts. Each group constitutes a single pole, four throw switch. The switch function is completed by adopting the principle of electrostatic driving by injecting charges, and the realized structure is as follows: two groups of driving unit arrays which are symmetrically distributed are designed in the inner side of the suspended square plate and at the corresponding positions of the fixed plate: a group of pre-stored heterogeneous charges which are set for generating electrostatic attraction force; and the other group is pre-stored with the same charge and is arranged for generating electrostatic repulsive force. The two groups of driving units realize the electrostatic driving of injected charges to complete the connection and disconnection actions of the switch by selecting shielding real-time control. In the drawings, fixed plate refers to a fixed plate, and movable plate refers to a movable plate.

The RF MEMS switch chip designed by the invention is shown in figure 1. Four sets of single pole, four throw RF MEMS switches are integrated within the switch chip. The chip is composed of a fixed plate 11 and a movable plate 12. The movable plate is formed of suspended square plates attached to the keyed frame, supported by symmetrical or windmill-type springs (e.g., 31 and 32). The fixed plate is designed with a figure which is completely symmetrical with the movable plate, but does not correspond to the movable part.

Four continuous contacts, such as 61 and 63, are arranged around the periphery of the suspended square plate attached to the movable plate; for each successive contact, there are arranged, in a corresponding symmetrical position of the fixed plate, an input contact and four output contacts (for example 62 and 64) of the switching signal and their corresponding connections. Thus, each successive contact on the movable plate and the five separate contacts at symmetrical positions on the corresponding stationary plate form a single pole, four throw switch. The design chip integrates four groups of single-pole four-throw switches which simultaneously make the same switch response along with the reciprocating motion of the square plate suspended on the movable plate. In practical application, the chip can realize single-pole, double-pole and four-pole multi-throw switches and the like through the change of the parallel number of the input and output ports.

An array of

apertures

51, 52 and 53 are also provided in the suspended square plate above the movable plate for release of the movable plate and to reduce air damping during movement of the suspended square plate, improving the response speed of the switch. However, there is no such corresponding pattern on the fixing plate, and only a corresponding space is left, so as to ensure symmetry of other patterns.

An array of drive units is also disposed within the interior of the square plate suspended from the movable plate. The driving unit array is composed of a plurality of injection charge driving units such as 21 and 23. Each of the driving units is composed of an injection charge control electrode 211, an injection charge storage electrode 212, and an injection charge electrode 213. The injection charge control electrode 211 and the injection charge electrode 213 constitute the shield of the present driving unit. A charge injection control window is designed between the charge injection control electrode and the charge injection storage electrode; a charge injection window is designed between the injection charge pole and the injection charge storage pole; the charge is pre-injected through an injection window using the principle of F-N tunneling (Fowler-Nordheim tunneling) and stored on an injection charge storage electrode. Likewise, symmetrical drive units, such as 22 and 24, are designed on the fastening plate.

The driving

units

21 and 22 are a pair, and different kinds of electric charges are stored in advance in their charge storage electrodes, respectively. The charge injection control electrode and the charge injection electrode of the group of driving units are respectively connected to the ground through two pairs of MOS switching tubes, and charges pre-stored on the storage electrodes in the groups of driving units are shielded; when the two pairs of switch tubes are switched off (controlled by a clock pulse T1), the charges pre-stored on the storage electrodes respectively induce different charges on the injection charge electrodes, so that electrostatic attraction is generated between the two electrode plates, the square plate suspended on the movable electrode plate is driven to move towards the fixed plate, the contacts on the two electrode plates are driven to be mutually contacted, and the RF MEMS switch is in a switched-on state.

And the

drive units

23 and 24 are another pair, which have the same charge stored on their charge storage electrodes, respectively. Similarly, the charge injection control electrode and the charge injection electrode of the group of storage units are respectively connected to the ground through another two pairs of MOS switching tubes, and charges pre-stored on the storage electrodes in the storage units are shielded; when the two pairs of switching tubes are disconnected (controlled by a clock pulse T2; a pulse signal T2 can be an independent pulse source or generated by a T1 pulse adding reverser), the charges pre-stored on the storage electrodes respectively induce the same charges on the injection charge electrodes thereof, so that an electrostatic repulsive force is generated between the two electrode plates, the square plate suspended on the movable electrode plate is driven to move away from the fixed electrode plate, and the contacts on the two electrode plates are separated to generate enough separation, so that the RF MEMS switch is in an off state.

The clock pulses T1 and T2 are interlaced and associated with each other, thereby controlling the interlaced generation of electrostatic attraction and electrostatic repulsion between the plates, and causing the suspended square plate to reciprocate, thereby completing the corresponding functions of the integrated four groups of single-pole four-handle RF MEMS switches.

A key frame such as 71 and 73 is also designed on the movable plate; the key frames, e.g., 72 and 74, are also symmetrically designed on the mounting plate. Low temperature molten dielectric layers, such as 81 and 82, are deposited on the fixed plate bond frames for bonding the dielectric materials. The bonded glass plate 4 is used for sealing the opening of the cavity of the movable plate, and is convenient for subsequent processing and reinforcing the switch structure. The metal traces, e.g., 91 and 92, of the design chip system are all routed through the bulk silicon of the mounting plate to the back of the mounting plate. Thus, the final schematic structure shown in fig. 1, which is driven by the electrostatic driving principle of injected charges, and which integrates four groups of single-pole four-throw RF MEMS switches, has been systematically described.

In order to avoid wasting the silicon space of the movable plate, the cavity window of the movable plate can not be opened, so that the back of the movable plate can be used as the movable plate. If this design is chosen, the movable plate machining requires the movable part to be released in advance and then bonded to the fixed plate, with the final configuration shown in fig. 5 (d). Such a design can increase bonding difficulty and affect bonding yield, which requires appropriate consideration in selection.

The structure of the four-group single-pole four-throw RF MEMS switch is a movable plate and a fixed plate which are bonded together. Two groups of driving unit arrays which are symmetrically distributed in a staggered mode are respectively arranged on the two polar plates corresponding to the positions of the square plates which are fixed on the movable polar plate and suspended by the springs. The symmetrical driving unit array drives the suspended square pole plate to reciprocate through pre-injection of charges and selection of shielding in real time, and the connection and disconnection actions of the switch are continuously and repeatedly completed.

The driving unit is structurally 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; meanwhile, the injection electrode and the injection control electrode are shields of the driving unit; the injection electrode and the control electrode are led out and are respectively connected with one end of the corresponding MOS switch tube, and the other ends of the MOS switch tubes are connected with the ground.

And (3) electrostatic driving by injected charges: firstly, before leaving factory, a sufficient amount of different or same charges are injected to the storage electrodes of two groups of driving units in advance; then, two groups of staggered clock pulses act on the connected MOS switch tubes, whether different corresponding driving unit shields on the two polar plates are grounded or not is selected, and the extinction or generation of induction charges of the corresponding driving units on the two polar plates is controlled, so that electrostatic attraction or electrostatic repulsion is generated between the two polar plates to drive the two polar plates to reciprocate relatively.

The driving units are symmetrically distributed: two pairs of driving unit groups are symmetrically distributed on the two polar plates and are respectively used for pre-storing enough heterogeneous charges or the same charges; the groups of driving units are repeatedly distributed in set areas on the two plates to form a two-dimensional array of driving units so as to generate sufficient electrostatic attractive or repulsive forces.

Charge selective pre-injection: after the chip is processed, a charge injection electrode and a charge injection control electrode of each of two pairs of driving unit groups contained in the driving unit array are respectively led out, and a set charge type and sufficient charges are injected into a designated driving unit array region through a control window and an injection window in each driving unit by taking an F-N tunnel effect as an injection principle.

Selective masking of stored charge: 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 select and control the grounding and the disconnection of the shielding bodies of the two driving unit groups, and control the generation and the disappearance of different induced charges or the same induced charges on the two polar plates, thereby generating electrostatic attraction or electrostatic repulsion between the two polar plates and leading the two polar plates to generate reciprocating motion of mutually approaching and mutually departing.

Four sets of single pole, four throw integrated RF MEMS switches: each side of the periphery of the suspension square plate is respectively provided with a contact area (continuous contact), when the suspension square plate reciprocates, the suspension square plate is mutually contacted with or disconnected from the contact areas (an input contact and four output contacts) at symmetrical positions on the fixed polar plate, so that signals are distributed from the input contacts to the four output contacts, and distribution output (mutual contact) and stop output (mutual disconnection) of the signals are completed.

The processing and manufacturing process of the RF MEMS switch chip designed by the invention comprises three sections: firstly, processing a movable plate silicon wafer; secondly, processing a silicon wafer of a fixed plate; and thirdly, bonding processing and lead layout of the processed movable plate silicon chip and the processed fixed plate silicon chip.

The cross section of the main process for processing the movable plate silicon wafer is shown in FIG. 3. Firstly, selecting a double-sided polished monocrystalline silicon wafer with low resistance (<0.1ohm.cm) 100; thermal oxidation of about 5000A to 10000A + LTO (10000A to 20000A) + densification treatment, as shown in FIG. a. Depositing a thick polysilicon layer (5000-10000A); the movable plate structure is lithographically illustrated in FIG. (b). A bonding frame and a square flat plate supported by a symmetrical cantilever or a windmill type cantilever are processed on the movable plate; and a driving unit array, a contact and a damping reducing hole array such as MP-1 are processed on the square flat plate. And (c) combining the CMP technology, respectively depositing three layers of polysilicon (the thickness of each layer is 1500A-5000A), and mainly performing photoetching on each layer of polysilicon to form a two-dimensional array MP-2 of the electrostatic driving unit for injecting charges, as shown in the figure (c). In each cell of the 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 fabricated. A charge injection control window (wherein the thickness of the isolation thermal oxidation layer is 100-300A) is processed between the charge injection control electrode and the charge storage electrode; and a charge injection window (wherein the thickness of the isolation thermal oxidation layer is 60A-150A) is arranged between the charge storage electrode and the charge injection electrode. Then, photolithography is performed to define the structure of the movable member, as shown in (d). To separate the movable parts, silicon nitride is deposited by LPCVD to a thickness of 1500A to 3000A, as shown in FIG. (e). Depositing metal AL or/and Au, and forming contacts such as MP-3/1 and MP-3/2 by photoetching; and extraction electrodes, such as MP-4/1 and MP-4/2, as shown in (f). A cavity cushion high layer (forming a bond frame) LTO is deposited with a thickness of 10000A-30000A, and the LTO is lithographically formed into cavity structures on the movable plate, such as MP-5/1 and MP-5/2, as shown in FIG. (g). Silicon nitride is deposited by PECVD to a thickness of 1500A-3000A, a high layer of protective spacers and the movable part release window is opened by photolithography, as shown in figure (h). Finally, the movable part is released by damping the hole array using gas phase HF, as shown in figure (i). Thus, the movable plate silicon wafer is processed.

The cross section of the main process for processing a fixed plate silicon wafer is shown in fig. 4. Similarly, a double-sided polished monocrystalline silicon wafer with low resistance (<0.1ohm.cm) 100 is selected; thermal oxidation is about 5000A-10000A + LTO (10000A-20000A } + densification treatment, as shown in figure a). And (3) respectively depositing three layers of polysilicon (the thickness of each layer is 1500A-5000A) by combining a CMP technology, and mainly performing photoetching on each layer of polysilicon to form a two-dimensional array FP-1 of the electrostatic driving unit for injecting charges, as shown in the figure (b). An injection charge control pole FP-1/1, a charge storage pole FP-1/2 and a charge injection pole FP-1/3 are machined into each cell in the array. A charge injection control window (wherein the thickness of the isolation thermal oxidation layer is 100-300A) is processed between the injection charge control electrode and the charge storage electrode; and a charge injection window (wherein the thickness of the isolation thermal oxidation layer is 60-150A) is processed between the charge storage electrode and the charge injection electrode. To protect the processed pattern on the fixed plate, silicon nitride was deposited by LPCVD to a thickness of 1500A-3000A, as shown in FIG. (c). Depositing metal AL or/and Au, and forming contacts such as FP-2/1 and FP-2/2 by photoetching; and an extraction electrode as shown in (d). Depositing a cavity cushion high layer LTO (forming a bonding frame), with a thickness of 10000A-30000A, and depositing glass frit (glass frit), and photolithographically forming cavity structures of LTO and frit on a movable plate, such as FP-3/1 and FP-3/2, as shown in (e). The backside via holes are lithographically etched using a double-sided lithography technique, as shown in (f). Thus, the fixed plate silicon wafer processing is completed.

The processing design of the bonding process has two schemes: firstly, a structure of a closed cavity is formed after bonding; and the other is a structure forming an open cavity after bonding.

The first scheme is as follows: and an RF MEMS switch structure forming a closed cavity after bonding:

the method is characterized in that: the structure is firm, the occupied space is small, but the movable part is difficult to release, and the bonding yield is low due to the possibility of damage of the movable part, so that the bonding yield needs to be improved in the aspect of being suitable for mass production.

The process cross-section of the first bonding process scheme is shown in fig. 4. After the movable part is released, the movable plate silicon chip is bonded with the processed fixed plate silicon chip through pattern alignment. The low-temperature melting property of the glass powder layer is utilized to fuse and join the cavity frame part and seal the movable part in the cavity, as shown in the figure (a). Then, etching through the fixed plate silicon wafer along the contact hole window by using the DRIE technology from the back of the fixed plate silicon wafer by using the technology similar to TSV (through silicon via), as shown in a figure (b); continuing to dry etch away the exposed SiO2 until the metal is touched, as shown in FIG. (c); metal is deposited and the pad pattern is lithographically patterned as shown in figure (d). Thus, the packaging process is completed.

The second scheme is as follows: RF switch structure forming an open cavity after bonding:

the method is characterized in that: the bonding is easy, the movable part is easy to release due to the back opening cavity, and the bonding processing yield is high; but the structure needs to be reinforced and the movable plate silicon back surface is not available.

The second bonding process scheme is shown in cross-section in fig. 5. The movable plate silicon wafer is only processed until PECVD deposited silicon nitride is processed, release photoetching and gas-phase HF release are not carried out, but back cavity window photoetching is added, and the movable plate silicon wafer is processed. And then bonded with the processed fixed plate silicon wafer through pattern alignment. The low-temperature melting property of the glass powder layer is utilized to fuse and join the cavity frame part, as shown in figure (a). Then, the cavity is opened from the back surface of the silicon wafer of the movable plate by using the DRIE technique along the cavity window opened from the back surface of the silicon wafer of the movable plate, and the movable part is exposed, as shown in fig. (b). The exposed SiO2 was etched away using vapor phase HF to expose the silicon nitride as shown in figure (c). The silicon nitride film exposed on the movable plate is etched away by dry etching, and the movable member release is completed, as shown in fig. (d). The back sealing of the back of the movable plate is made of a thin glass plate, which serves both for structural reinforcement and for advantageous subsequent processing, as shown in fig. (e). And finally, etching through the fixed plate silicon wafer along the contact hole window by applying a TSV (through silicon Via) technology and using a DRIE technology from the back side of the fixed plate silicon wafer, as shown in a diagram (f). The dry etch is continued to remove the exposed SiO2 until the metal is encountered, as shown in figure (g). Metal is deposited and the pad pattern is lithographically patterned as shown in figure (h). At this point, the packaging is completed.

After the packaging is finished, the chips are diced into single chips, and the chips are subjected to pre-injection of charges (the pre-injection amount of the charges required by a customer can be determined according to the application requirement of the customer so as to adjust the performance of the RF switch) and necessary tests, so that the final product which is driven by adopting an injection charge driving principle and integrates four groups of single-pole four-throw RF MEMS switch chips is obtained.

The processing technology is based on batch production, and aims to enable the chip designed by the invention to have a good product with low cost and wide popularization and application.

The charge pre-injection adopts the F-N tunneling effect injection principle. Fig. 2 is an approximate analytical equation estimate derived from a designed RF switch architecture. The horizontal axis is the pre-injection charge density, and the left vertical axis is the electrostatic force which can be generated correspondingly; while the right vertical axis is the time it takes to hang the square plate for a 5um stroke. As can be seen from fig. 2, the larger the pre-injection charge density, the larger the electrostatic force that can be generated, and the shorter the time required to make a 5um stroke, which can be on the order of microseconds. It can be seen that the switching frequency can be adjusted by the pre-injection charge density. This is one of the advantages of the electrostatic driving principle of injected charges. Compared with capacitive electrostatic drive, electrostatic drive with injected charges has better performance, and the performance comparison is shown in table 1. As can be seen from table 1, the electrostatic driving principle of injected charges completely overcomes the inherent defects of the capacitive electrostatic driving principle; at the same time, all the advantages of the capacitive electrostatic drive principle are substantially retained. Therefore, the electrostatic driving with injected charges in MEMS will be developed as a more sophisticated driving method, which can make RF MEMS switch have better performance.

TABLE 1 comparison of capacitive and injected charge electrostatic drive characteristics

Note: electric field strength E ═ V/d: under the condition that the voltage V is kept constant, when the distance d between the polar plates approaches to 0, E approaches to infinity;

voltage V ═ Q/C and C ═ epsilon/d: under the condition that the charge Q is kept constant, when the distance d between the plates tends to 0, the capacitance C tends to infinity, and therefore the voltage V tends to 0;

there are methods like series capacitance, but other performance sacrifices can result;

spring parameter adjustment, charge injection volume control, and mask selection control expansion may be used.

In this specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. The utility model provides a realize injecting charge electrostatic drive's single-pole four throw integrated switch chip which characterized in that, the switch chip include four groups single-pole four throw switches, the switch chip constitute by fixed plate and movable plate bonding, movable plate and fixed plate all have the bonding frame of symmetry design, the movable plate still include through the suspension square plate of symmetry type or windmill type spring-supported, movable plate and fixed plate on have two sets of drive unit arrays of symmetric distribution, first drive unit group and second drive unit group, different form charge and the same kind charge of prestore respectively, produce electrostatic attraction and electrostatic repulsion respectively, two sets of drive unit arrays through real-time control charge shielding, the drive hangs the square plate and moves to the fixed plate or leave the fixed polar plate and move, make single-pole four throw switch be in the on-state or the off-state, and completing the connection action and the disconnection action of the single-pole four-throw switch.

2. The SCP implementing electrostatic driving by injecting charges according to claim 1, wherein the driving unit array comprises a driving unit, the driving unit comprises 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, the charge injection window is arranged between the injection charge electrode and the injection charge storage electrode, and the injection charge electrode and the injection charge control electrode form a shield of the driving unit; the switch chip further comprises an MOS switch tube, the injection charge electrode and the injection charge control electrode are connected with one end of the corresponding MOS switch tube, and the other end of the MOS switch tube is grounded.

3. The switch chip of claim 2, wherein the charge storage electrodes of the first and second driving unit groups are pre-charged with different charges or the same charge; two groups of staggered clock pulses are respectively acted on MOS switch tubes connected with the first group of driving units and the second group of driving units, charges of the charge storage electrode are respectively injected into the charge electrode to induce different charges or the same charges, electrostatic attraction or electrostatic repulsion is generated between the two electrode plates, the suspension square plate is driven to move towards the fixed plate or leave the fixed plate to move, and the single-pole four-throw switch is in a connection state or a disconnection state.

4. The switch chip of claim 1, wherein the suspended square plates of the movable plate are provided with symmetrical driving units, i.e. a first driving unit and a third driving unit, the fixed plate is provided with symmetrical driving units, i.e. 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.

5. The switch chip of claim 2, wherein the switch chip injects a predetermined charge type and a sufficient amount of charges into the driving unit through the charge injection window and the charge injection control window.

6. The integrated switch chip of claim 1, wherein four continuous contacts are disposed around the periphery of the suspended square plate of the movable plate, the fixed plate has contact areas, i.e. input contacts and four output contacts of switching signals and their connecting lines, at positions symmetrical to the continuous contacts of the movable plate, and 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 square plate reciprocates, the continuous contact of the movable plate and the contact area of the fixed plate are mutually contacted or disconnected, so that the signals are distributed from the input contacts to the four output contacts, and the distributed output and the stop output of the signals are finished.

7. The switch chip of claim 1, wherein the suspended square plate is configured with an array of small holes for releasing and reducing air damping generated during the motion of the suspended square plate, thereby improving the response speed of the switch.

8. The switch chip of claim 1, wherein the bonding frames of the movable and fixed plates have a low temperature melting medium deposited thereon, and the low temperature melting medium is a bonding medium material.

9. The integrated switch chip for electrostatic actuation with injected charge according to claim 1, further comprising a bonding glass plate for sealing the cavity opening of the movable plate for facilitating subsequent processing and switch structure reinforcement.

10. The switch chip of claim 1, further comprising a metal wire led out from the inside of the fixed board to the back side of the fixed board.