CN101590999B - Micro cantilever beam driving member based on antiferroelectric thick film field induced phase transition strain effect - Google Patents

Abstract

The invention relates to a micro-actuator driving component, in particular to a micro-cantilever beam driving component based on the field-induced phase transition strain effect of an antiferroelectric thick film. The problems of slow response speed and small driving displacement of existing micro-actuator driving components are solved. Steps: ① prepare lead-based antiferroelectric material precursor sol and PbO sol; ② prepare lead-based Thick film of antiferroelectric material; ③ Spin-coat PbO sol on the thick film of lead-based antiferroelectric material, annealing treatment; ④ Sputter the metal layer as the upper electrode on the thick film of lead-based antiferroelectric material, and solder joints ; ⑤ corroding the back of the supporting base and reducing the thickness of the middle of the supporting base; etching the thick film of the lead-based antiferroelectric material and the front of the middle of the supporting base to form a peripheral base and a cantilever beam structure connected to the peripheral base at one end. The process and structure are simple, and the application of antiferroelectric materials in the field of micro-actuator drive components is realized, and a new idea is provided for the design and manufacture of micro-drive components with fast response and large displacement.

Description

Micro-cantilever driving component based on field-induced phase transition strain effect of antiferroelectric thick film

technical field

The invention relates to a driving component of a micro-actuator, in particular to a micro-cantilever beam driving component based on the field-induced phase transition strain effect of an antiferroelectric thick film.

Background technique

Micro-Electro-Mechanical Systems (MEMS) is a multi-disciplinary frontier research field developed by applying the latest achievements of modern information technology. The realization of highly intelligent and integrated MEMS must rely on new materials, new technologies, and new principles. , Innovative exploration and development of micro-components and micro-device systems with new effects. As the core movable part in MEMS, the micro-actuator mainly uses different energy conversion mechanisms to realize the action function of specific behaviors. It can not only constitute the power part of the micro-machine, but also become the operation or actuator of the micro-machine. The technical indicators such as the size of the range of motion, the level of motion efficiency, and the reliability of the motion determine the success or failure of the system.

At present, the types of microactuators mainly include micropumps and microvalves used in fluid control, adjustable micromirrors and optical switches in optomechanical systems, and micromotors, microdisplacers, microrelays, and microtweezers in the electromechanical field. The driving methods of micro-actuators mainly involve electrostatic, electromagnetic/magnetostrictive, piezoelectric/electrostrictive, and shape memory alloy diaphragms. Electrostatic actuators have the disadvantages of high driving voltage and small driving force, and require very precise design and processing to create a narrow gap to generate high driving force; There are considerable manufacturing process difficulties in the arrangement of conductive, insulating materials, etc.; shape memory alloys (TiNi, CuAlNi and CuZnAl alloys, etc.) have strong energy storage and transmission capabilities, making them suitable for use in micropumps, It can be used in micro-actuators such as micro-flowmeters and micro-tweezers, but its low response speed greatly affects the execution efficiency. Piezoelectric/electrostrictive driving is a kind of controllable strain realized by using the inverse piezoelectric effect of piezoelectric materials (PbZr _x Ti _1-x O ₃ , ZnO, etc.) at the moment of applying an electric field. drive mode. Piezoelectric/electrostrictive driving elements have attracted much attention for their unique advantages such as small size, high resolution, fast response, no heat generation, low energy consumption, no electromagnetic interference, and linear input/output, but low output displacement The widespread application of this type of driving method has been hindered.

In recent years, antiferroelectric functional materials have been favored by many researchers due to their unique phase transition behavior and potential application background. For antiferroelectric materials, there are abundant structural phases near the phase boundary where the antiferroelectric state (AFE) changes to the ferroelectric state (FE), and the AFE-FE phase transition can be induced under the action of an applied electric field Effect, because the cell volume of the ferroelectric phase material is larger than that of the antiferroelectric phase material, so when the phase transition occurs, the volume of the material changes, which causes the field-induced strain effect of the material. The strain produced by the field-induced strain effect of antiferroelectric materials can be as high as 0.8%, which is better than the inverse piezoelectric effect of piezoelectric materials to a large extent. For example, WYPan et al. are studying (Pb, La) (Zr , Sn, Ti)O ₃ AFE-FE phase transition of antiferroelectric ceramics, the measured strain is 0.85%. BMXu et al. reported that La or Nb doped optimized Pb(Zr, Sn, Ti)O ₃ antiferroelectric ceramics The phase change strain of ferroelectric thin film and thick film materials can reach 0.42% and 0.48%, respectively, while the strain of typical PZT relaxation ferroelectric ceramics caused by the inverse piezoelectric effect is generally only about 0.1%. At the same time, the phase transition behavior of antiferroelectric materials can be regulated by an external electric field. The polarization intensity change and longitudinal strain caused by the phase transition belong to the jump behavior. The phase transition strain effect has good switchable characteristics, and the switching response speed is fast. WYPan et al. showed that the phase transition switching time of (Pb, La)(Zr, Sn, Ti)O ₃ antiferroelectric ceramic bulk material is about 2 μs, while for (Pb, La)(Zr, Sn, Ti)O ₃ The response speed of the antiferroelectric thin film material is faster, which can reach within the order of 300ns. Therefore, how to apply antiferroelectric functional materials to the driving components of microactuators has become a key research topic for many researchers.

Contents of the invention

In order to solve the technical bottleneck problems of high driving voltage, slow response speed, low response frequency, small driving displacement, complicated manufacturing process and low control precision in the driving components of the existing micro-actuator, the present invention provides a fast response and large Displacement characteristics of micro-cantilever driven components based on antiferroelectric thick film field-induced phase transition strain effect.

The present invention is realized by adopting the following technical scheme: the micro-cantilever driving component based on the field-induced phase transition strain effect of the antiferroelectric thick film is processed and manufactured according to the following process steps:

① Preparation of lead-based antiferroelectric material precursor sol with a concentration of 0.2mol/l to 0.6mol/l and PbO sol with a concentration of 0.2mol/l to 0.4mol/l by using sol-gel technology; the sol -gel technology is a known technology, how to prepare the lead-based antiferroelectric material sol and PbO sol of required concentration is known to those skilled in the art;

② The silicon base or Pt/TiO ₂ /SiO ₂ /Si coated with a Pt metal layer on the above surface is used as a supporting base, and the lead-based antiferroelectric material prepared in step ① is made into The precursor sol is spin-coated on the Pt metal layer of the supporting substrate, and the spinning time is 10s~30s; Heat treatment, after the heat treatment, take it out of the tube furnace, cool to room temperature, repeat the above steps of spinning glue and heat treatment until a thick film of lead-based antiferroelectric material with a thickness of 1 μm to 10 μm is obtained on the Pt metal layer of the supporting substrate;

③ Spin-coat the PbO sol prepared in step ① on the thick film of lead-based antiferroelectric material with a spin speed of 2000-4000r/min through a glue homogenizer, and the spin time is 10s-20s. Then, place the supporting substrate in a tube furnace for annealing treatment, the annealing temperature is 650°C-750°C, and the duration is 20min-40min. After the annealing treatment, it is taken out of the tube furnace and placed in air to cool to room temperature; spin coating The PbO sol on the lead-based antiferroelectric material thick film can regulate the Pb volatile components in the lead-based antiferroelectric material thick film, and reduce the volatilization of Pb components in the lead-based antiferroelectric material thick film.

④Use photolithography to define the pattern of micro-cantilever on the thick film of lead-based antiferroelectric material treated in step ③, and deposit a metal layer with a thickness of 100nm to 300nm by sputtering according to the pattern of micro-cantilever. layer as the upper electrode, and the Pt metal layer below the lead-based antiferroelectric material thick film as the lower electrode; The connected pads are sputter-deposited on the end surface of the supporting base to realize the connection of the lower electrode and the corresponding pads;

In step ④, the connection between the lower electrode and the corresponding pads is realized by sputtering and depositing a metal layer on the end surface of the supporting base, so that the pads of the lower electrode and the pads of the upper electrode are on the same plane, which is convenient for welding conductive metal Wire, to achieve a good connection with the external circuit.

⑤Using the back etching process to etch the back of the supporting substrate to reduce the thickness of the middle part of the supporting substrate to 10 μm to 50 μm; according to the micro-cantilever pattern defined by the photolithography process in step ④, use the front etching process to treat the lead-based anti-iron The thick film of electrical material and the middle part of the support base are etched to form a peripheral base and a cantilever beam structure connected to the peripheral base at one end.

For the microcantilever driving member of the present invention, when a bias DC voltage of 20V to 200V is applied between the upper and lower electrodes, the thick film of lead-based antiferroelectric material between the upper and lower electrodes will be induced by the electric field The phase transition of the antiferroelectric-ferroelectric structure causes the strain effect of the thick film of the lead-based antiferroelectric material, which makes the micro-cantilever structure move, thereby realizing the driving behavior of the micro-cantilever structure.

Compared with the prior art, the present invention uses MEMS micromachining technology to highly integrate the antiferroelectric material and the silicon-based semiconductor material, and uses the micro-cantilever beam structure as the mechanical component form, and utilizes the lead-based antiferroelectric material electric field to induce phase The driving behavior of the micro-cantilever beam driving member of the present invention is realized by changing the fast switching characteristics and the large field-induced strain effect. The advantages are: 1. As a basic structural unit widely used in micro-electromechanical systems, the micro-cantilever beam structure, especially mechanical drive components, is often used in MEMS sensors and actuators. The processing requirements of the driving component structure can ensure the stability of the micro-driving component processing and realize low-cost mass production; and the micro-cantilever has accurate movement and low power consumption, and the driving effect when used as a mechanical drive component is easy to observe. 2. Lead-based antiferroelectric materials have abundant structural phases near the phase boundary where the antiferroelectric state changes to the ferroelectric state. Under the action of an external electric field, the antiferroelectric-ferroelectric phase transition strain effect is induced, which is This kind of strain effect produced by the change of material phase structure is obviously better than the inverse piezoelectric effect of current piezoelectric materials, the strain amount is as high as 0.8%, and it has fast phase change switching characteristics, the response speed is on the order of hundreds of ns, and micro The large displacement and fast response characteristics of the cantilever beam driven member. 3. The lead-based antiferroelectric material is applied to the micro-cantilever driving member of the present invention with a thick film structure. For the thick film structure, it has better dielectric properties, greater driving force and more energy than the thin film structure. High compressive strength; and compared with the ceramic bulk structure, the thick film structure has an absolute advantage in the phase change driving threshold voltage, and is easier to combine with the silicon-based plane by the MEMS process. In order to realize the good integration of lead-based antiferroelectric materials and silicon-based semiconductor materials, the thick-film structure of lead-based antiferroelectric materials is realized by sol-gel process technology. The process temperature is low, and the equipment is simple and easy to operate.

The invention has simple process and structure, high reliability, easy realization of batch production, and realizes the application of antiferroelectric functional materials in the field of micro-actuator driving components, and provides for the design and manufacture of fast response and large displacement micro-driving components. A new way of thinking.

Description of drawings

Fig. 1 is the structural representation of micro-cantilever beam driving member of the present invention;

Fig. 2 is the A-A sectional view of Fig. 1;

In the figure: 1-pressure solder joint; 2-Pt metal layer; 3-lead-based antiferroelectric material thick film; 4-top electrode; 5-metal layer; 6-peripheral base; 7-cantilever beam structure; 8- Pressure solder joints.

Detailed ways

The microcantilever driving component based on the field-induced phase transition strain effect of the antiferroelectric thick film is processed and manufactured according to the following process steps:

①. Prepare lead-based antiferroelectric material precursor sol with a concentration of 0.2mol/l-0.6mol/l and PbO sol with a concentration of 0.2mol/l-0.4mol/l by sol-gel technology;

②. The silicon base or Pt/TiO ₂ /SiO ₂ /Si coated with a Pt metal layer on the above surface is used as a supporting base, and the lead-based antiferroelectric compound prepared in step ① is processed by a glue leveler at a spinning speed of 2000-4000r/min. The precursor sol of the material is spin-coated on the Pt metal layer 2 of the supporting substrate, and the spinning time is 10s to 30s; Heat treatment for 20 minutes, after heat treatment, take it out of the tube furnace, cool to room temperature, repeat the above process steps of spinning glue and heat treatment, until a lead-based antiferroelectric material with a thickness of 1 μm to 10 μm is obtained on the Pt metal layer 2 of the supporting substrate thick film 3;

③. Spin-coat the PbO sol prepared in step ① on the thick film 3 of lead-based antiferroelectric material through a glue leveler at a spinning speed of 2000-4000r/min. The spinning time is 10s-20s. Then, the supporting substrate Place it in a tube furnace for annealing treatment, the annealing temperature is 650°C-750°C, and the duration is 20min-40min. After annealing treatment, take it out of the tube furnace and place it in air to cool to room temperature;

④ Utilize the photolithography process to define the pattern of the micro-cantilever beam on the lead-based antiferroelectric material thick film 3 processed in step ③, and sputter and deposit a metal layer with a thickness of 100nm to 300nm according to the pattern of the micro-cantilever beam. The metal layer is used as the upper electrode 4, and the Pt metal layer 2 below the lead-based antiferroelectric material thick film 3 is used as the lower electrode; The bonding pads 1 and 8 connected to the upper and lower electrodes are sputter-deposited on the end surface of the support base side to realize the connection of the lower electrode and the corresponding bonding pads 8 with a metal layer 5;

⑤Using the back etching process to etch the back of the supporting substrate to reduce the thickness of the middle part of the supporting substrate to 10 μm to 50 μm; according to the micro-cantilever pattern defined by the photolithography process in step ④, use the front etching process to treat the lead-based anti-iron The thick film of electrical material 3 and the middle part of the supporting base are etched to form a peripheral base 6 and a cantilever beam structure 7 connected to the peripheral base at one end. As shown in Figure 1 and 2.

The lead-based antiferroelectric material is selected from (Pb _1-3x/2 La _x )(Zr _{1-yz Snz} Ti _y )O ₃ antiferroelectric material, wherein, 0.01≤x≤0.04, 0.02≤y≤0.10, 0≤z≤0.40, hereinafter referred to as PLZST; to prepare PLZST sol with sol-gel process technology, for those skilled in the art, different compounds can be used as precursors to realize, in the present invention, when preparing PLZST sol, Use lead acetate (C ₄ H ₆ O ₄ Pb·3H2O), lanthanum acetate (C ₉ H ₉ LaO ₆ ), tin acetate (Sn(CH ₃ COO) ₂ ), zirconium isopropoxide (Zr(OCH ₂ CH ₂ CH ₃ ) ₄ ) and titanium propoxide (Ti[OCH(CH ₃ ) ₂ ] ₄ ) as precursor, acetic acid, ethylene glycol ethyl ether, acetylacetone and deionized water as solvent, lactic acid as stabilizer, ethylene glycol as dry As for how to formulate the control agent with sol-gel technology, it is well known to those skilled in the art.

The metal layer 5 deposited by sputtering on the end surface of the supporting base to realize the connection between the lower electrode and the corresponding pad 9, and the metal layer as the upper electrode 4 generally use metal Au or Pt;

In step ⑤, implement the back etching process on the back side of the support substrate with 30% (wt)～50% (wt) KOH, 5% (wt)～10% (wt) isopropanol solution; For the micro-cantilever pattern defined by the process, first, use an etching solution of V(HCl):V(HNO ₃ ):V(H ₂ O)=30～60:2～5:40～60 on the support substrate The thick film of lead-based antiferroelectric material is wet-etched, and then the middle part of the supporting substrate is continuously etched by a deep reactive ion etching process or a surface sacrificial layer technology to form a peripheral base and a single-end connection with the peripheral base cantilever beam structure.

According to the size requirements of the micro-cantilever beam driving component, when the micro-cantilever beam driving component is processed and manufactured according to the process steps of the present invention, the beam length is generally required to be 600 μm to 1000 μm, the beam width is 100 μm to 300 μm, and the beam thickness is 15 μm to 60 μm.

The process steps of the micro-cantilever beam driving component of the present invention are described in detail again with a specific processing process; the micro-cantilever beam driving component based on the antiferroelectric thick film field-induced phase transition strain effect is processed and manufactured according to the following process steps:

① Prepare 30ml, 0.3mol/l (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ antiferroelectric material precursor sol, and 0.4mol/l PbO sol; wherein, (Pb _0.97 La _0.02 ) The preparation process of (Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ antiferroelectric material precursor sol is as follows: According to the stoichiometric ratio of (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ , weigh 3.6713g C ₄ Put H ₆ O ₄ Pb·3H ₂ O, 0.0569g C ₉ H ₉ LaO ₆ , 0.4172g Sn(CH ₃ COO) ₄ in a beaker, add 15ml of acetic acid, heat and stir at 110°C for 30min, cool to room temperature, and then add 3.5799gZr(OCH ₂ CH ₂ CH ₃ ) ₄ , 0.0527gTi[OCH(CH ₃ ) ₂ ] ₄ , while adding a certain amount of deionized water (the molar ratio of water to lead is 30), and continue to stir at room temperature for 30min, In order to improve its stability, add a small amount of lactic acid and continue to stir for 20 minutes (the molar ratio to lead is 1); then add ethylene glycol with an equal lead molar amount and stir for 20 minutes at the same time; finally add an equal volume of acetic acid and ethylene glycol Dilute the colloid to 0.3 mol/l with ether, filter it in a drop bottle with medium-speed quantitative filter paper, and let it stand for 24 hours before use.

②Using Pt/TiO ₂ /SiO ₂ /Si as the supporting substrate, spin the (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ sol prepared in step ① through a homogenizer at a spinning speed of 3000r/min. Coated on the Pt metal layer of the support substrate, the spinning time is 20s; and after the glue is applied, the support substrate is placed in a tube furnace for 10 minutes of heat treatment at a temperature of 450 ° C, and after heat treatment, it is taken out from the tube furnace , cooled to room temperature, and repeating the above steps of spinning glue and heat treatment until a thick film of (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ with a thickness of 5 μm is obtained on the Pt metal layer of the supporting substrate;

③Spin-coat the 0.4mol/l PbO sol prepared in step ① on the (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ thick film at a speed of 3000r/min by a homogenizer, spin the gel The time is 15s, and then, the support substrate is placed in a tube furnace for annealing treatment, the annealing temperature is 700°C, and the duration is 30 minutes. After the annealing treatment, it is taken out of the tube furnace and placed in air to cool to room temperature;

④Use the photolithography process to define the pattern of the micro-cantilever on the (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ thick film treated in step ③: the length is 800 μm, the width is 200 μm, and according to the Pattern sputtering deposition of a cantilever beam with a thickness of 200nm Au metal layer as the upper electrode, (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ thick film below the Pt metal layer as the lower electrode; and On the (Pb _0.97 La _0.02 )(Zr _0.85 Sn _0.13 Ti _0.02 )O ₃ thick film treated in step ③, sputtering deposits pads for connecting the upper and lower electrodes respectively, sputtering on the end surface of the supporting base side Spray deposition is used to realize the metal layer connecting the lower electrode and the corresponding pad;

⑤ Implement a back etching process on the back of the support substrate with 35% (wt) KOH and 7.5% (wt) isopropanol solution, so that the thickness of the middle part of the support substrate is reduced to 25 μm; according to the microcantilever defined by the photolithography process in step ④ _{Beam pattern, firstly, (Pb 0.97 La 0.02 ) ( Zr 0.85} Sn _0.13 Ti _0.02 ) O ₃ thick film is wet-etched, and then, the middle part of the supporting substrate is continuously etched by a deep reactive ion etching process or a surface sacrificial layer technology to form a peripheral pedestal and a cantilever connected to the peripheral pedestal at a single end Beam structure, and the length of the cantilever beam is 800 μm, the width is 200 μm, and the thickness is 15 μm.

Claims (1)

1. micro cantilever beam driving member based on antiferroelectric thick film field induced phase transition strain effect is characterized in that according to following processing step processing and manufacturing:

1. be that lead base antiferroelectric materials precursor colloidal sol and the concentration of 0.2mol/l～0.6mol/l is the PbO colloidal sol of 0.2mol/l～0.4mol/l with sol-gel technology technology compound concentration;

2. be coated with the silica-based or Pt/TiO of Pt metal level with upper surface ₂/ SiO ₂/ Si is as support base, and the lead base antiferroelectric materials precursor colloidal sol of with the glue speed of revolving of 2000～4000r/min 1. step being prepared by sol evenning machine is spun on the Pt metal level (2) of support base, and revolving the glue time is 10s～30s; And after revolving glue, place tube furnace to carry out the heat treatment of 8～20min support base with 400 ℃～600 ℃ temperature, after the heat treatment, by taking out in the tube furnace, be cooled to room temperature, repeating above-mentioned glue, the Technology for Heating Processing step of revolving, is the lead base antiferroelectric materials thick film (3) of 1 μ m～10 μ m until going up acquisition thickness at the Pt of support base metal level (2);

3. the PbO colloidal sol of with the glue speed of revolving of 2000～4000r/min 1. step being prepared by sol evenning machine is spun on the lead base antiferroelectric materials thick film (3), revolving the glue time is 15s～20s, then, place tube furnace to carry out annealing in process support base, annealing temperature is 650 ℃～750 ℃, and duration 20min～40min is after the annealing in process, by taking out in the tube furnace, place air to be cooled to room temperature;

4. utilize the figure that defines micro-cantilever on the lead base antiferroelectric materials thick film (3) of photoetching process after 3. handling through step, and be the metal level of 100nm～300nm according to the figure sputtering sedimentation thickness of micro-cantilever, this metal level is as top electrode (4), and the Pt metal level (2) of lead base antiferroelectric materials thick film (3) below is as bottom electrode; And the last sputtering sedimentation of the lead base antiferroelectric materials thick film (3) after 3. handling through step is respectively applied for the pressure welding point (1,8) that is connected with upper and lower electrode, the metal level (5) that sputtering sedimentation realization bottom electrode is connected with corresponding bonding point (8) on the support base side end face;

5. utilize back-etching technology that the support base back side is corroded, make the support base interior thickness reduce to 10 μ m～50 μ m; 4. the micro-cantilever figure that utilizes photoetching process to define in according to step, with the front etching technics to lead base antiferroelectric materials thick film (3), and support base middle part carry out etching, form peripheral pedestal (6), and and the single-ended cantilever beam structure that links to each other of peripheral pedestal (7).

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