CN103552979B - A kind of heat-electrostatic reply type by force MEMS four-point supporting hanging beam structure - Google Patents

Abstract

The invention discloses a thermal-static strong recovery type MEMS four-point support suspension beam structure, which comprises a substrate, an electrostatic pull-down electrode coated on the top surface of the substrate, an anchor area, a suspension main beam and a bent support beam. The suspended main beam is suspended above the substrate through four anchorage areas and bending support beams; during the transition process of the suspended beam from the pull-down state ("down" state) to the suspended state ("up" state), through the bending The ohmic heating of the bending support beam makes the suspension main beam subject to tension, improves the effective stiffness of the suspension main beam, and strengthens the restoring force; The suspension main beam is more stable, and it is more conducive to the recovery of the suspension main beam from the "down" state to the "up" state after heating. The invention also discloses a specific working mode for enhancing the restoring force, and the method is simple, convenient and feasible.

Description

A thermal-static strong recovery type MEMS four-point support suspension beam structure

technical field

The invention relates to the field of reliability processing technology in the process of processing and using a micro-mechanical system (abbreviated as MEMS in the text). Specifically, it relates to a thermal-static strong recovery type MEMS four-point support suspension beam structure.

Background technique

MEMS is the abbreviation of Micro-Electro-Mechanical Systems (Micro-Electro-Mechanical Systems). MEMS mainly includes micro mechanisms, micro sensors, micro actuators and corresponding processing circuits. Many MEMS sensors and actuators include a movable structure, and use the movement of the movable structure to realize the conversion between electricity, heat, magnetism and machinery. Therefore, the kinematic performance of the movable structure is the key to the normal operation of MEMS devices.

Many MEMS movable structures are cantilever beams, fixed beams or their combination. For electrostatically actuated movable beam structures, the beam is usually switched between the "up" (suspension state) and "down" (pull-down) states by applying or releasing a voltage. In order to make the beam pull down to the "down" state smoothly, it is often hoped that the stiffness of the beam should not be too large during structural design, but it is often difficult for the beam with low stiffness to return to the "up" state after the voltage is released. Therefore, it is necessary to design a thermal-electrostatic strong recovery type MEMS four-point support suspension beam structure, so that the movable beam can be freely transformed between the pull-down "down" state and the spring-up "up" state.

Contents of the invention

The technical problem to be solved by the present invention is to provide a thermal-static strong recovery type MEMS four-point support suspension beam structure, which uses ohmic heating to cause thermal expansion of the beam to achieve the purpose of enhancing the recovery ability. Simultaneously, the invention also provides a specific working method for enhancing the restoring force, which is simple in structure, convenient and feasible in operation.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A thermal-electrostatic strong recovery type MEMS four-point support suspension beam structure, including a substrate, an anchor area, a suspension main beam suspended above the substrate, and a fixed connection on the top surface of the substrate and located in the middle of the suspension main beam. Electrostatic pull-down metal electrodes, the structure also includes two bent support beams, the bent support beam is composed of a beam connected vertically to the end of the main beam suspended and two sets of double beams connected to the beam and parallel to the main beam suspended The longitudinal beams are composed of longitudinal beams; the ends of the longitudinal beams are connected to the anchorage areas on both sides of the suspension main beam; the inner longitudinal beams of the bending support beams are wide beams of the same size, and the outer longitudinal beams are narrow beams of the same size . The design of the double wide and narrow beams side by side makes the suspension beam more stable, and it is more conducive to the recovery of the suspension beam from "down" to "up" state after heating; the electrostatic pull-down metal electrode is coated with anti-suspension beam Thin layer of dielectric that short-circuits when in contact with the pull-down electrode.

The above-mentioned thermal-static strong recovery type MEMS four-point support suspension beam structure, the working method of thermal-static strong recovery is as follows:

1) During work, when the suspension main beam is required to return from the "down" state to the "up" state, disconnect the electrostatic connection between the suspension main beam and the pull-down electrode, thereby releasing the electrostatic attraction between the pull-down electrode and the suspension main beam .

2) While releasing the electrostatic attraction, pass current to the bent support beams at both ends of the main beam. The longitudinal girder in the bending support beam is heated and expanded, so that the suspension main beam is subjected to a force stretched to both ends, which improves the effective stiffness of the suspension main beam and enhances the recovery force of the suspension main beam.

3) The longitudinal beams in the bending support are designed with wide and narrow beams, the inner beams are wide beams, and the outer beams are narrow beams. Due to the different cross-sectional areas of the wide and narrow beams, under the same voltage, the currents flowing are different, and the temperatures reached are also different. Here, wider beams are hotter than narrower beams and are capable of greater linear expansion. In this way, it is ensured that the crossbeam in the bending support is tight, which is more conducive to the recovery of the suspended main beam from the "down" state to the "up" state.

4) After the suspension main beam returns to the "up" state, disconnect the current on the bending beam and return to the normal state.

In the structure design of the MEMS movable beam, the present invention adopts a four-point support suspension beam structure, changes the effective stiffness of the bending support beam through ohmic heating, and satisfies the requirement of strong resilience. For the movable beam in many MEMS devices, it is common to switch back and forth between the "up" state and the "down" state during operation. The small stiffness of the beam is conducive to pulling down from the "up" state to the "down" state, but it often causes the movable beam to fail to return smoothly from the "down" state to the "up" state. If at this stage, ohmic heating is used to expand and tighten the beam to increase the effective stiffness of the beam, the recovery ability of the beam can be greatly improved. Therefore, the structure designed in the present invention and the corresponding working mode can not only satisfy the low stiffness in the pull-down stage, but also realize the high stiffness in the recovery stage. The operation of enhancing the restoring force of the structure is simple, and there is no additional requirement on the processing technology. Therefore, the structure and method provided by the present invention are feasible.

Description of drawings

Fig. 1 is the structural representation of the present invention.

Fig. 2 is a schematic diagram of the top surface of the substrate in the present invention.

In the figure, there are: substrate 1, pull-down electrode 2, anchor regions 31-34, suspension main beam 4, bending support beams 5 and 6 (bending support beams 5 and 6 are respectively in two dotted line frames).

Detailed ways

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figures 1 and 2, a thermal-static strong recovery type MEMS four-point support suspension beam structure of the present invention, the structure includes a substrate 1, a pull-down electrode 2 for electrostatic excitation, and anchor regions 31-34 , suspension main beam 4, bending support beam 5 and 6. The suspension main beam 4 is suspended above the substrate 1 through four anchor areas 31 , 32 , 33 , 34 and bending support beams 5 and 6 at both ends.

As shown in FIG. 1 and FIG. 2 , the bending support beam 5 is composed of a cross beam 51 and two sets of parallel longitudinal beams 52 , 53 and 54 , 55 . Among them, the longitudinal beam adopts wide and narrow beam design, 52 and 54 are narrow beams, and 53 and 55 are wide beams. The bending support beam 6 at the other end is structurally symmetrical with the bending support beam 5, 62 and 64 are narrow beams, and 63 and 55 are wide beams.

The substrate 1 in the suspension beam structure is made of single crystal silicon. The suspension main beam 4 , the bent support beam 5 and the bent support beam 6 are made of the same material, which can be doped polysilicon or single crystal silicon beams, or metal beams. The pull-down electrode 2 is made of metal material (gold or aluminum), and a thin dielectric layer is deposited on the metal surface, which can be SiO ₂ or SiN, to prevent short circuit when the suspension beam contacts the pull-down electrode.

A thermal-static strong recovery type MEMS four-point support suspension beam structure of the present invention can be completed by using general MEMS processing technology.

The above thermal-static strong recovery type MEMS four-point support suspension beam structure, the specific working method of the thermal-static strong recovery is as follows:

1) During work, apply a voltage between the suspension main beam 4 and the pull-down electrode 2, and the suspension main beam 4 will bend downward until the middle part contacts the pull-down electrode 2, so that the suspension main beam 4 changes from "up" to "up". down” state.

2) When the suspension main beam 4 is required to return from the "down" state to the "up" state, the electrostatic connection between the suspension main beam 4 and the pull-down electrode 2 is disconnected, and the electrostatic attraction between the pull-down electrode 2 and the suspension main beam 4 is released. combine. Simultaneously, a voltage of the same magnitude, about 10 V or more, is applied between the anchor regions 31 and 33 and between the anchor regions 32 and 34, respectively. In this way, the bending support beams 5 and 6 at both ends of the main beam pass through the same magnitude of current.

3) The current flowing through the bending support beams 5 and 6 causes the longitudinal beams 52, 53 and 54, 55 and the longitudinal beams 62, 63 and 64, 65 to be heated and linearly expand, and elongate to both ends respectively. The suspension main beam 4 is subjected to a force stretched toward both ends, which improves the effective stiffness of the suspension main beam and enhances the restoring force of the suspension main beam.

4) The longitudinal beams in the bending support beams are designed with double side-by-side wide and narrow beams. Since the cross-sectional areas of the wide and narrow beams are different, under the same voltage, the currents flowing are different and the temperatures reached are also different. Here, wider beams are hotter than narrower beams and are capable of greater linear expansion. Therefore, the wide beams 53, 55 in the bending support beam 5 are stretched longer than the narrow beams 52, 54. Similarly, the wide beams 63, 65 are also stretched longer than the narrow beams 62, 64. Thus, heating stretches the longitudinal beams 52, 53, 54, 55 and 62, 63, 64, 65 while also tensioning the cross beams 51 and 61.

5) The stretching of the above-mentioned longitudinal beam gives the main suspension beam 4 a stretching force to both ends through the cross beams 51 and 61 in the tense state, so that the suspension main beam 4 returns strongly to the "up" state.

6) After the suspension main beam returns to the "up" state, disconnect the current on the bending beam and return to the normal state.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (1)

1. heat-electrostatic reply type by force MEMS four-point supporting hanging beam structure, comprise substrate (1), anchor district, be suspended on the suspension girder (4) of types of flexure, be fixedly connected on the end face of substrate (1) and be positioned at the drop-down metal electrode of electrostatic (2) hanging middle part immediately below girder (4), it is characterized in that: also comprise two bending brace summers (5, 6), two described bending brace summers (5, 6) crossbeam (51 be connected with suspension girder (4) ending vertical by respectively, 61) and with this crossbeam be connected and be parallel to two groups of double joints hanging girder (4) longeron (52 arranged side by side, 53, 54, 55, 62, 63, 64, 65) form, inner side rail is measure-alike wide beam, outer side rail is measure-alike narrow beam, the end of described longeron be connected to be positioned at hang girder (4) both sides anchor district (31,32,33,34) on, the drop-down metal electrode of described electrostatic (2) is coated with the dielectric layer be short-circuited when preventing hanging beam from contacting with pull-down electrode.