CN201018426Y - Low-driving-voltage micro-grabbing actuator structure - Google Patents

Abstract

The utility model relates to a low-driving voltage micro-grab actuator structure, which comprises: an ultra-low resistance silicon substrate; an insulating layer deposited on the ultra-low resistance silicon substrate; at least one main structure layer deposited on the insulating layer; and one or more micro-bumps are made below the main structure layer to prevent the sticking effect. The utility model can significantly reduce the driving voltage of the micro-grab actuator element.

Description

Low driving voltage micro-snatch actuator structure

technical field

The utility model relates to a low driving voltage micro-snatch type actuator structure, which is applied to Surface Micromechaning Technology (Surface Micromechaning Technology) similar to semiconductor process technology, and has the characteristics of batch production, low cost and integration, to solve the problem of Disadvantages of traditional IC technology.

Background technique

In recent years, the micro fan (Micro Fan), which has been developed in the world, is a component made using Microelectromechanical Systems (MEMS) technology, and its size is only about 2mm×2mm. The structure of the micro fan consists of two parts, one is to make the micro fan blades by self-assembly technology (Self-assembly), and the other is to use the micro snatch actuator (Scratch Drive Actuator; SDA) as the rotor. Motor (Micro Motor), and the detailed manufacturing steps of the micro motor are based on the multi-user MEMS process (Multi-User MEMS Processes; MUMPs) developed by MEMSCAP.

Micro-snatch actuators are widely used and have many action modes. Many people have published research on micro-snatch actuators in international journals, such as:

The concept of the micro-snatch actuator first proposed by Junqi Zhu et al. is composed of polysilicon as its main structure. The actuation principle is to use the electrostatic force in the vertical direction to make the actuation plate (Plate) and the bushing (Bushing) rub against the insulating layer on the bottom surface. Horizontal actuation force, different arrangements of micro-snatch actuators can be composed of linear actuators or stepping rotary motors.

Terunobu Akiyama et al. observed the relationship between the displacement speed of the micro-snatch actuator and the frequency of the input voltage, the relationship between the peak value of the input voltage and the distance traveled by each step, and the relationship between the length of the actuated plate and the distance traveled by each step. The actuator is connected to a flexible rod, and the buckling of the flexible rod is used to measure the output force of the micro-snatch actuator, and the relationship between the peak value of the input voltage and the output force is obtained.

P.Langlet et al. used the micro-snatch actuator as the driver of the X/Y precision positioning platform, and applied this platform to the positioning of the fiber-optic coupling. Through the experimental results, different actuation plate geometries have different effects on the micro-snatch actuation. The influence of device pass rate.

Mita et al. used a special bonding technology (Boading) to fix multiple inverted micro-snatch actuators on a glass substrate to form an array to form a micro-snatch actuator conveyor belt.

Yamato Fukuta used Reshaping technology to use the micro-snatch actuator as a self-assembling (Self-assembling) device of three-dimensional structure.

Lin et al. used guide rails to introduce voltage into the micro-snatch actuator, and made it push the XYZ three-dimensional platform, mirror surface, and micro-Fresnel (Fresnel) lens to form a free-space (Free-space) micro-optical experiment table.

Ryan J. Linderman et al. formed an array of 188 micro-snatch actuators and connected the objects to be actuated through a special bonding technology (Boading), and then introduced voltage with a micro-chain. On the other hand, the micro-snatch actuator array is fixed on the ceramic plate by Flip chip bonding (flip chip) technology, and the optimal actuation plate length obtained by theoretical derivation is verified by experiments.

Paul E. Kladitis arranged the micro-snatch actuators in a circle to form a rotary motor with a diameter of 520 μm, and fixed the silicon blades on the motor, which can be applied to push microfluidics.

So far, none of the literature has been able to accurately measure the force and displacement that the micro-snatch actuator can output, the operational life and mode, and the allowable range of operating voltage. Due to the need to integrate a number of difficult key technologies, It is inferred that the reason is that the characteristics of the micro-snatch actuator have not been fully grasped, and the possible reasons are:

(1) Appropriate electrode layers and insulating layers are not easy to fabricate.

(2) The size design has not yet been optimized, including the aspect ratio, the shape of the beam (cantilever beam), and the size of the hole...etc.

(3) The driving voltage drops.

Each of the above-mentioned reasons is enough to affect the performance of the entire micro-snatch actuator. Changing any parameter is a challenge to the integration of the entire process. It is the current micro-snatch actuator to develop a complete process integration step for theoretical and experimental optimization. The most difficult bottleneck for the actuator to break through.

As shown in Figure 1, it is the principle of action of the micro-snatch type actuator. When the actuating plate 10 and the bushing 11 have a capacitive structure, an electrostatic force can be obtained on the actuating plate 10. When a periodic When the electrostatic force is applied to the actuating plate 10, it will cause the actuating plate 10 to form a stepping motion on the substrate 12, as shown in (b), (c) and (d) in the figure when the square wave is applied A stepping motion between the plate 10 and the substrate 12 is actuated.

When a positive bias is applied, the actuating plate 10 is attracted by the substrate 12 due to electrostatic force, but the actuating plate 10 has a bushing 11 in front of it, so that the entire plate area will not be completely adsorbed on the insulating layer (insulator) 13 , so there will be charges temporarily stored on the actuating plate 10 , and then cause the actuating plate 10 to have elastic tension.

When the voltage drops, the elastic tension is released immediately, so that the actuating plate 10 returns to its original shape, and when the voltage is released, since the bushing 11 is always in contact with the insulating layer 13, a friction force is generated to allow the entire actuating plate 10 to advance .

When a negative bias voltage is applied, the actuating plate 10 will also be attracted by the substrate 12 to produce repeated actions, so that the actuating plate 10 moves continuously on the insulating layer 13 .

The action of the actuating plate 10 can be controlled by an external pulse, and the speed is proportional to the pulse frequency. The Δx value shown in the figure can be defined as the displacement caused by the applied voltage, and the Δx value is not only related to the voltage amplitude but also to the The length of the actuating plate 10 is related to the height of the bushing 11 .

Contents of the invention

The drive voltage is the key to the actuation of the micro-snatch actuator. Considering factors such as cost, process integration and process complexity, the main purpose of this utility model is to provide a low drive voltage micro-snatch actuator structure, which can overcome Machine limit, and use low-cost process steps to achieve high output and low driving voltage.

In order to achieve the above object, a low driving voltage micro-snatch actuator structure provided by the utility model is characterized in that it includes: an ultra-low resistance silicon substrate; an insulating layer deposited on the ultra-low resistance silicon substrate On top; at least one main structure layer is deposited on the insulating layer; more than one micro bumps are made under the main structure layer to prevent the sticking effect.

In the above-mentioned technical solution of the present invention, the resistance value of the ultra-low resistance silicon substrate is 0.001-0.004 Ω-cm.

In the above-mentioned technical solution of the present invention, the insulating layer is a low-stress silicon nitride film.

In the above-mentioned technical solution of the present invention, the main structure layer is a low-stress polysilicon film.

Since the traditional micro-snatch actuator uses a general resistance silicon substrate (20Ω-cm) as the lower electrode, the driving voltage is in the range of 70-120V, except that the silicon substrate material of the lower electrode will affect the driving voltage. The height and width of the liner and the thickness of the main structural layer polysilicon will also affect. Therefore, the utility model uses an ultra-low resistance silicon substrate (0.001～0.004Ω-cm) as the lower electrode material, and changes the process parameters of the micro-snatch actuator and the minimum line width of the adjustment element, and then the micro-snatch actuator The driving voltage of the actuator element is greatly reduced to between 5 and 25V. Therefore, this utility model is aimed at the integrated design and development of micro-motors. It uses ultra-low resistance silicon substrates to greatly reduce the driving voltage of micro-snatch actuators, and provides complete and stable manufacturing steps and methods. It can take into account both micro-fan chips and Possibility of integrating control circuits into a single chip.

Description of drawings

Fig. 1 is a schematic diagram of the stepping motion of the micro-snatch actuator with an external driving voltage;

Fig. 2 is the three-dimensional structural diagram of the micro-snatch type brake made by the utility model;

Fig. 3 is a schematic diagram of the process steps of the present invention;

Fig. 4 is the measurement curve of the bottom sticking voltage and the flexural voltage of the micro-snatch type actuator of the present invention;

Fig. 5 is the relationship diagram between the bottom sticking voltage and the shape of the actuating plate of the utility model micro-snatch type actuator;

Figure 6 is a comparison chart of the bonding voltage between the ultra-low resistance chip and the general chip.

Detailed ways

The utility model relates to a method and structure for making a low driving voltage micro-snatch type actuator with an ultra-low resistance silicon substrate. The ultra-low resistance silicon substrate material is matched with a complete and stable process step and method, which can reduce micro The driving voltage of the snatch actuator and the control of the bushing width not to exceed 1.5 μm, the following is a detailed description of the innovative process of the utility model with the help of the accompanying drawings:

As shown in FIG. 2 , the present invention at least includes an ultra-low resistance silicon substrate 20 , an insulating layer 21 , a main structure layer 30 , and upper and lower electrodes 41 and 42 .

In order to prevent the stiction effect (sticing effect), the utility model especially makes micro bumps (Dimple) 31 under the main structure layer 30 to prevent stiction. The detailed production process is shown in Figure 3:

(a) Deposit a low-stress silicon nitride film (Si3N4) as an insulating layer 21 on an ultra-low-resistance silicon substrate 20 by low-pressure chemical vapor deposition (LPCVD), and after the first lithography process, inductively couple Type plasma etcher (ICP) etch the insulating layer 21 to expose the predetermined position 25 of the lower electrode of the ultra-low resistance silicon substrate 20 .

(b) Deposit a phosphosilicate glass film (PSG-0) on the insulating layer 20 by plasma-assisted chemical vapor deposition (PECVD) as the first layer of low-stress sacrificial layer 22, and use the second lithography process. A low-stress sacrificial layer 22 is etched by an inductively coupled plasma etcher (ICP) to simultaneously define three patterns of anchors, predetermined positions of micro bumps 23 and bushings.

(c) Deposit a phosphosilicate glass film (PSG-1) on the first low-stress sacrificial layer 22 by plasma-assisted chemical vapor deposition (PECVD) as the second low-stress sacrificial layer 24, and deposit the second low-stress sacrificial layer The main purpose of the sacrificial layer 24 is to correct the bushing width, because the minimum resolution of the line width of the exposure machine is 2 μm, but the matching component must have a minimum line width of 1.5 μm, so there is no way to use this step to shrink the machine The minimum line width limit reached.

(d) The third lithography process, using an inductively coupled plasma etcher (ICP) to etch the pattern defining the predetermined position 25 of the anchor and the bottom electrode.

(e) Deposit a low-stress polysilicon film (Poly-Si) as the main structure layer 30 on the second low-stress sacrificial layer 24 by low-pressure chemical vapor deposition (LPCVD), and place the chip into a horizontal furnace tube for phosphorus diffusion and High temperature annealing process.

(f) The fourth lithography process, using inductively coupled plasma etching (ICP) to etch to define the pattern of the main structure layer 30 .

(g) Evaporate chromium/gold with an electron beam evaporation machine, and define the patterns of the upper electrode 41 and the lower electrode 42 by wet etching in the fifth lithography process.

(h) Put the component in buffered hydrofluoric acid (BOE) for wet etching, and etch the first and second low-stress sacrificial layers 22 and 24 to release the main structure layer 30 .

If the element structure of the micro-snatch actuator is photographed with a scanning electron microscope (Scanning Electron Microscope; SEM), the suspended structure of the element after release can be seen, because the low-stress polysilicon film is used as the main structural layer to ensure the flatness of the element. Fairly good, no component failure due to film stress mismatch.

As shown in Figure 4, after the dynamic characteristic test of the micro-snatch actuator element of the present invention, it is found that its snap voltage (snap voltage) and the flexural voltage (priming voltage) present a linear relationship, and it is consistent with the prediction of foreign simulations. The results are consistent with the results simulated by the internationally renowned R&D team, but the driving voltage of the micro-snatch actuator element of the utility model is obviously much lower than that of the existing international micro-snatch actuator elements.

As shown in Figure 5 again, if the relationship between the shapes of various actuating plates designed by the utility model and the driving voltage is discussed, the test results find that:

When the actuating plate is a triangle (Triangle), its driving voltage is about 1-2V higher than that of a rectangular plate, but the triangular plate has the important advantage of not shortening its life due to accumulated charges, and the triangular plate also has a shorter drive delay time. On the other hand, if an appropriate etching hole design can be added to the end of the rectangular plate, not only can the accumulated charge be reduced, but the driving voltage can also be reduced.

As shown in Figure 6, if you compare the bottoming voltage of ultra-low resistance chips and ordinary chips, you can clearly find that:

To reduce the driving voltage, the material of the lower electrode (substrate) of the component can be corrected. In the process integration of the utility model, two batches of substrates with different resistance values are used as the lower electrodes. After the same process steps, it is found that:

The low-resistance substrate will obtain a driving voltage lower than that of the common substrate by about 5-6V, and this result is completely consistent with the prediction of the inventors. In the future, if it is combined with the adjustment of the metal material of the upper electrode, it is estimated that the driving voltage can be reduced by about 10V to a voltage level below 10V, which will be very conducive to the application of micro-snatch actuators in various mass-produced products in the future. .

To sum up, the utility model has indeed possessed the above advantages, and compared with the conventional structure, it also has significantly improved efficacy.

The above is only a preferred implementation form of the utility model, and all equivalent structural changes made by using the specification, claims or drawings of the utility model shall be included in the patent protection scope of the utility model.

Claims (4)

1. low driving voltage micro-holding type actuator structure is characterized in that comprising:

One ultralow resistance silicon substrate;

One insulating barrier is deposited on the ultralow resistance silicon substrate;

At least one main structure layer is deposited on the insulating barrier;

Main structure layer below is manufactured with more than one miniature prominent point, to prevent viscid effect.

2. low driving voltage micro-holding type actuator structure according to claim 1, it is characterized in that: the resistance of described ultralow resistance silicon substrate is 0.001～0.004 Ω-cm.

3. low driving voltage micro-holding type actuator structure according to claim 1, it is characterized in that: described insulating barrier is the low stress nitride silicon thin film.

4. low driving voltage micro-holding type actuator structure according to claim 1, it is characterized in that: described main structure layer is the low stress polysilicon membrane.

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