TWI550924B - Piezoelectric sensing element and its making method - Google Patents

Description

Piezoelectric inductance measuring component and manufacturing method thereof

The invention relates to a method for manufacturing a sensing element and a sensing element, in particular to a method for manufacturing a lightweight piezoelectric sensing element and a piezoelectric sensing element obtained by the method.

A nanogenerator is a MEMS system that uses the environment to collect energy and generate current. It can be used to replace the general energy system. Therefore, it has received extensive attention. Piezoelectric materials have been widely used in self-powered nanosystems and piezoelectric field effect transistors because they have the characteristics of being subjected to pressure and being deformed by an applied electric field. Field-effect transistors) or different fields such as sensors. Among them, the application of a biosensor with a piezoelectric material is widely studied because it has the advantage of not requiring external power supply.

Zinc oxide (ZnO) piezoelectric materials are widely used because they have a direct bandgap of 3.37 eV and an exciton energy of 60 meV, which can be used to sense subtle changes. For example, Minbaek Lee et al. (Minbaek Lee, Chih-Yen Chen, Sihong Wang, Seung Nam Cha, Yong Jun Park, Jong Min Kim, Li-Jen Chou, and Zhong Lin Wang, A Hybrid Piezoelectric Structure for Wearable, Adv. Mater. 2012), published in 2012 a portable nanogenerator with zinc oxide nano columns, the structure of which is PS/PDMS/Electrode/ZnO Nanowire array/PVDF/Electrode A large-area zinc oxide nano-pillar array is formed on a support material made of a flexible polymer material to obtain a nano-generator having high performance and applicable to wearable electronic components.

However, in order to make the piezoelectric detector more suitable for sensing subtle changes in the human body, for example, the human body can feel the slight change of airflow to achieve the purpose of biodetection, and "lightweight" is such The main challenge of sensing components. Because the sensing element that senses the breathing of the human body as a sensing source is mainly a wind-driven bio-pressure sensing component, since the piezoelectric material can be generated by vibration or breathing of the human body. The airflow generates a current-current characteristic. Therefore, the change of the piezoelectric current can be used to detect the vital signs of the human body to achieve the purpose of biological sensing.

However, how to break the limitation of the volume and weight of the sensing component, the volume of the bio-pressure sensing component can be smaller and lighter, so as to improve the detection sensitivity of the bio-pressure sensing component, the technical field is An important key condition.

Therefore, an object of the present invention is to provide a method for fabricating a piezoelectric sensing element which is simple in process, can be effectively thinned, and reduces the volume of a component.

Thus, a method of fabricating a piezoelectric sensing component includes The next four steps.

(a) A substrate having a substrate, a sacrificial layer formed on one surface of the substrate, and a bottom electrode layer formed on a surface of the sacrificial layer.

(b) A plurality of nano-pillars composed of a piezoelectric material and having piezoelectric characteristics are formed on the surface of the bottom electrode layer.

(c) forming a polymer buffer layer in the gaps of the nano columns.

(d) removing the sacrificial layer and separating the bottom electrode layer from the substrate to obtain the piezoelectric sensing element.

Preferably, the piezoelectric sensing element manufacturing method is described, wherein the piezoelectric material is selected from the group consisting of zinc oxide, and the step (b) is a hydrothermal method, a gas-liquid-solid growth method, a chemical vapor deposition method, Electrochemical deposition method, wet chemical method, or template method, a plurality of nano columns made of zinc oxide are formed on the bottom electrode layer, and then annealed at 300 to 1000 ° C to obtain the piezoelectric properties. Zinc nano column.

Preferably, the method for fabricating the piezoelectric sensing element, wherein the step (c) is to fill a gap of the nano-pillars with a flexible polymer material by spin coating and cover the holes. The polymer buffer layer is formed on the surface of the column.

Preferably, the method for fabricating the piezoelectric sensing element, wherein the bottom electrode layer is selected from the group consisting of a metal, an alloy metal, a metal oxide, and a combination thereof.

Preferably, the method for fabricating the piezoelectric sensing element, wherein the polymer buffer layer is selected from the group consisting of acrylic resin, polyimide resin, epoxy Resin, and polyvinylidene fluoride.

Preferably, the method for fabricating the piezoelectric sensing element, wherein the sacrificial layer is selected from the group consisting of photoresist materials.

Preferably, the method for fabricating the piezoelectric sensing element, wherein the sacrificial layer is selected from a photoresist material having a heat resistant temperature of not less than 300 ° C.

Preferably, the method for fabricating the piezoelectric sensing element, wherein the step (d) is to remove the sacrificial layer by wet etching.

Preferably, the method for fabricating the piezoelectric sensing component further comprises a step (e) of forming a top electrode layer electrically connected to the nano columns on the surface of the nano column, and the top electrode layer is selected It consists of conductive materials such as metals, alloy metals, and metal oxides.

Moreover, the piezoelectric sensing component of the present invention comprises a substrate, a plurality of nano columns, and a polymer buffer layer.

The substrate is composed of a conductive material, the nano column extends upward from the surface of the substrate and has piezoelectric characteristics, and the polymer buffer layer covers the top surface of the nano columns and is filled in the nanometers. The gap between the meters.

The utility model has the advantages that the semi-finished product of the piezoelectric sensing component can be separated from the original supporting substrate by using the removable property of the sacrificial layer, and therefore, the obtained piezoelectric sensing component is not affected by the weight or volume of the original supporting substrate. The limitation can effectively reduce the weight and volume of the piezoelectric sensing component, and can improve the sensing sensitivity of the piezoelectric sensing component.

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31‧‧‧Substrate

32‧‧‧Zinc Oxide Nano Column

33‧‧‧ Polymer buffer layer

311‧‧‧Substrate

312‧‧‧ surface

313‧‧‧ Sacrifice layer

314‧‧‧ bottom electrode layer

Other features and effects of the present invention will be apparent from the embodiments of the drawings, in which: 1 is a text flow chart showing a preferred embodiment of the method for fabricating the piezoelectric sensing element of the present invention; FIG. 2 is a schematic flow chart for assisting the description of FIG. 1; FIG. 3 is a tidal volume-time relationship diagram illustrating The piezoelectric sensing component produced by the preferred embodiment simulates the normal person's breathing 12 times per minute, and the relationship between the tidal volume of the breath and the time; FIG. 4 is a current density-time relationship diagram illustrating the preferred embodiment. The obtained piezoelectric sensing element has a current density-time relationship measured by simulating a tidal volume of 500 ml and a gas flow rate of 2 m/s; FIG. 5 is a voltage-time relationship diagram illustrating the preferred embodiment. The piezoelectric sensing component is a voltage-time relationship measured by simulating a tidal volume of 500 ml and a gas flow rate of 2 m/s; and FIG. 6 is a current density-time relationship diagram illustrating the piezoelectric obtained by the preferred embodiment. The sensed current density-time relationship of the sensing element at a fixed tidal volume (500 ml) at different gas flow rates (0.5 to 5.0 m/s); Figure 7 is a voltage-time relationship diagram. The piezoelectric sensing component produced by the preferred embodiment is described in the fixed tidal volume (50 The measured voltage-time relationship at 0 ml) at different gas flow rates (0.5 to 5.0 m/s).

Referring to FIG. 1, the preferred embodiment of the method for fabricating a piezoelectric sensing component of the present invention comprises the following three steps.

First, in step 21, a substrate 31 having a substrate 311 and a layer formed on one surface 312 of the substrate 311 is prepared. The sacrificial layer 313 and a bottom electrode layer 314 formed on the surface of the sacrificial layer 313.

In detail, the substrate 311 may be selected from the group consisting of germanium, glass, metal, aluminum oxide, and a flexible polymer film. The sacrificial layer 313 is formed on the surface 312 of the substrate 311, and is selected from the group that can be removed by wet etching. The substrate 311 and the sacrificial layer 313 are selected from materials having a temperature resistance of more than 300 ° C. In this embodiment, the substrate 311 is selected. The sacrificial layer 313 is selected from the group consisting of a polymethyl glutarimide (PMGI) photoresist material and is formed on the surface 312 of the substrate 311 by screen printing to a thickness of about 2 to 3 μm.

The bottom electrode layer 314 is formed on the surface of the sacrificial layer 313 and is made of a conductive material such as a metal, an alloy metal, or a metal oxide. The formation of the bottom electrode layer 314 and related material selection are well known in the art. It is not the focus of the present invention, so the description will not be repeated. In this embodiment, a bottom electrode layer 314 made of gold/titanium alloy is deposited on the surface of the sacrificial layer 313 by sputtering.

Next, in step 22, a plurality of zinc oxide nano columns 32 having piezoelectric characteristics are formed on the surface of the substrate 31.

At present, methods for preparing zinc oxide nano column 32 include gas-liquid-solid (VLS) growth method, hydrothermal method, chemical vapor deposition (CVD), electrochemical deposition method, wet chemical method, membrane plate method, and the like. Since these methods can be used to prepare zinc oxide nano columns/wires and are known to those skilled in the art, they will not be described one by one. In the preferred embodiment of the present invention, a plurality of zinc oxide nano columns 32 are formed on the surface of the bottom electrode layer 314 by hydrothermal method to obtain half of the finished product, and then the semi-finished product is subjected to 300-1000 ° C / N ₂ . Annealing for 30 minutes gives a zinc oxide nanocolumn 32 having superior piezoelectric properties.

Then, in step 23, a polymer buffer layer 33 is formed on the surface of the annealed zinc oxide nano columns 32.

In detail, the polymer buffer layer is 33 selected from an alkali-resistant etching developer such as potassium hydroxide (KOH), sodium hydroxide (NaOH), tetramethylammonium hydroxide (TMAH, (CH ₃ ) ₄ The polymer material of NOH) is filled in the gap between the zinc oxide nano columns 32 and covers the surface of the zinc oxide nano columns 32. The polymer buffer layer 33 can be stripped as a follow-up. The support substrate during the lift-off process can also be used to prevent the zinc oxide nano-pillars from contacting each other and affecting the piezoelectric current output of the subsequently produced piezoelectric sensing component. Preferably, the polymer material is a polymer material selected from the group consisting of acrylic resin, polyimide resin, epoxy resin, and polyvinylidene fluoride. In the present embodiment, the polymer material is exemplified by an epoxy resin.

Specifically, in the step 23, the polymer insulating material is applied to the gaps and the top surface of the zinc oxide nano columns 32 by spin coating to form the polymer buffer covering the zinc oxide nano columns 32. Layer 33, and a semi-finished product of a piezoelectric sensing component is produced.

Finally, in step 24, the sacrificial layer 313 is removed, and the bottom electrode layer 314 is separated from the substrate 311 to obtain the piezoelectric sensing element.

Specifically, the step 24 is to use a wet etching method. The sacrificial layer 313 is etched and removed. In this embodiment, the sacrificial layer 313 is removed by using an etchant containing tetramethylammonium hydroxide (TMAH), and the bottom electrode layer 314 is separated from the substrate 311. Pressure sensing component.

In addition, when the polymer buffer layer 33 formed in the step 23 does not cover the top surface of the zinc oxide nano-pillars 32, the piezoelectric sensing component of the present invention may be preceded by the step 24. A top electrode layer is formed on the top surface of the zinc oxide nano-pillars, so that a piezoelectric sensing element having a two-electrode sensing output can be obtained.

The invention utilizes the removable layer sacrificial property to separate the piezoelectric sensing component after the fabrication is completed from the substrate 311, thereby effectively reducing the weight and volume of the piezoelectric sensing component, and is more convenient to be applied in Portable or non-invasive biosensor.

Then, the piezoelectric sensing component obtained by using the preferred embodiment of the present invention is applied to a wind driven detection environment for sensing test.

Referring to Figures 3 to 5, Figures 3 to 5 are pressure sensing elements (length x width: 0.65 cm x 1.16 cm) obtained by using the breathing simulation device capable of simulating human respiratory airflow in accordance with the preferred embodiment of the present invention. As a result of measuring the current and voltage obtained as a sensor of the respiratory gas flow. Figure 3 is a graph showing the relationship between the tidal volume (spirometry) of breathing and the time when the normal person breathes 12 times per minute. Figure 4 shows the measurement under the condition of simulated tidal volume of 500 ml and air flow rate of 2 m/s. The closed-circuit current density is obtained. Figure 5 shows the open-circuit voltage measured under the condition of simulating tidal volume of 500 ml and air flow rate of 2 m/s. .

Specifically, the breathing simulation device has a hollow tubular column with a bilateral opening, and a respirator (Respironics Lifecare, PLV-100) connected to one of the openings of the hollow tubular string, the breathing device can simulate human exhalation And the process of inhaling, the airflow is sent into the hollow pipe column or the air intake flow is sucked from the hollow pipe column. In this experiment, the ventilator is used in the tidal volume (500 mL, air flow rate). 2m/s is used as an experiment to simulate the body's breathing and inhaling airflow; the piezoelectric sensing component is placed by directing the zinc oxide nanocolumn 32 of the piezoelectric sensing component toward the respirator, and is placed in the In the hollow tube column, the bottom electrode layer 314 of the piezoelectric sensing element is electrically connected to an external current detector to form a loop, so that the zinc oxide nano-pillars 32 are subjected to a bias current generated by an external force. The bottom electrode layer 314 can be outputted outward.

Since the zinc oxide nano columns 32 generate different phase currents under different pressure conditions, for example, when the zinc oxide nano column 32 is subjected to a tensile force, a positive phase current is generated; and when the zinc oxide nanometer is used, When the column 32 is compressed, a negative phase current is generated. When the respirator simulates exhalation of the human body, since the airflow is sent into the hollow tubular string, the zinc oxide nanocolumn 32 is subjected to the compression of the airflow to generate a negative phase of the current; When the human body is inhaled, since the gas is sucked from the hollow column, the zinc oxide nano-pillars 32 are smoothly drawn by the airflow to generate a positive current.

As can be seen from the results of FIG. 4 and FIG. 5, the piezoelectric sensing component of the present invention can generate distinct positive and negative phase current signals corresponding to exhalation and inhalation, respectively, and the measured closed loop current density (closed- Circuit The current density and the open-circuit voltage are 3.65 nA and 27.32 mV, respectively. That is to say, the electrical signal change of the piezoelectric sensing component of the present invention can measure a very slight airflow change, and can instantly observe the change of the respiratory state of the human body, so that it can be more suitable for biological sensing.

Referring to FIG. 6 and FIG. 7 , FIG. 6 to FIG. 7 are measured by using the piezoelectric inductance measuring component of the present invention under different air flow rates (0.5 to 5.0 m/s) under a fixed tidal volume (500 ml). Current density and voltage results.

It can be seen from the results of FIGS. 6-7 that the piezoelectric sensing component of the present invention can observe a significant change in output current and voltage as the airflow rate changes, showing the piezoelectric of the present invention under different breathing conditions. Good sensing results can be obtained for the sensing elements.

In summary, the present invention utilizes the removable layer sacrificial property to allow the piezoelectric sensing component semi-finished product to be separated from the substrate 311. Therefore, the finally fabricated piezoelectric sensing component is not affected by the original supporting substrate 311. The weight or volume limitation can effectively reduce the weight and volume of the piezoelectric sensing component, and can improve the sensing sensitivity of the piezoelectric sensing component, and is more convenient to be applied to a portable or non-invasive biosensor. .

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

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Claims (10)

A method for fabricating a piezoelectric sensing component, comprising: (a) providing a substrate having a substrate, a sacrificial layer formed on one surface of the substrate, and a bottom electrode formed on a surface of the sacrificial layer a layer; (b) forming a plurality of nano-pillars composed of a piezoelectric material and having piezoelectric characteristics on the surface of the bottom electrode layer; (c) forming a polymer buffer layer in the gaps of the nano-pillars; and (d) Removing the sacrificial layer to separate the bottom electrode layer from the substrate to produce the piezoelectric sensing component. The method of fabricating a piezoelectric sensing element according to claim 1, wherein the piezoelectric material is selected from the group consisting of zinc oxide, and the step (b) is a hydrothermal method, a gas-liquid-solid growth method, a chemical vapor deposition method. Method, electrochemical deposition method, wet chemical method, or template method, a plurality of nano columns made of zinc oxide are formed on the bottom electrode layer, and then annealed at 300 to 1000 ° C to obtain oxidation with piezoelectric characteristics. Zinc nano column. The method for fabricating a piezoelectric sensing component according to claim 1, wherein the step (c) is to fill a gap of the nano-pillars with a flexible polymer material by a spin coating method and cover the gap. The surface of the nano-pillars forms the polymer buffer layer. The method of fabricating a piezoelectric sensing element according to claim 1, wherein the bottom electrode layer is selected from the group consisting of a metal, an alloy metal, a metal oxide, and a combination thereof. The method for fabricating a piezoelectric sensing component according to claim 1, wherein The polymer buffer layer is selected from the group consisting of acrylic resin, polyimide resin, epoxy resin, and polyvinylidene fluoride. The method of fabricating a piezoelectric sensing element according to claim 1, wherein the sacrificial layer is selected from the group consisting of photoresist materials. The method of fabricating a piezoelectric sensing element according to claim 6, wherein the sacrificial layer is selected from a photoresist material having a heat-resistant temperature of not less than 300 °C. The method of fabricating a piezoelectric sensing element according to claim 6, wherein the step (d) is to remove the sacrificial layer by wet etching. The method for fabricating a piezoelectric sensing component according to claim 1, further comprising a step (e) of forming a top electrode layer electrically connected to the nano columns on the surface of the nano column, and the top electrode The layer is composed of a conductive material such as a metal, an alloy metal, or a metal oxide. A piezoelectric inductance measuring component prepared according to claim 1, comprising a substrate, a plurality of nano columns, and a polymer buffer layer, the substrate is composed of a conductive material, and the nano columns are from the base The surface of the material extends upward and has piezoelectric characteristics, and the polymer buffer layer covers the top surface of the nano-pillars and fills the gap between the nano-pillars.