CN102937607B - A kind of series-connection flexible vibration piezoelectric diaphragm type biosensor and preparation method thereof - Google Patents

Abstract

The invention relates to a serial flexible vibrating piezoelectric membrane biosensor and a preparation method thereof. It uses micromachining technology to prepare flexible vibrating piezoelectric diaphragms on SOI silicon wafer substrates. The Device layer of SOI silicon wafers is used as the supporting layer of the diaphragm, and the piezoelectric film is used as the driving layer for diaphragm vibration. The upper and lower electrodes are respectively located on the upper and lower sides of the piezoelectric layer. surface. In terms of principle and structural design, the sensor of the present invention skillfully avoids the high-cost and poor-effect piezoelectric layer patterning process, and at the same time, the existence of the reference unit greatly improves the detection accuracy of the sensor. In addition, compared with the QCM biosensor, the sensor of the present invention is more sensitive, has a high quality factor when used for liquid phase in-situ detection, and is convenient for miniaturization and batch manufacturing; compared with the flexible vibrating cantilever beam sensor, The sensor of the invention has firm structure and high quality factor when used for liquid phase in-situ detection.

Description

A series flexible vibration piezoelectric diaphragm biosensor and its preparation method

technical field

The invention belongs to the technical field of biosensors, and relates to a biosensor, in particular to a series flexible vibration piezoelectric diaphragm biosensor applied to biological detection and a preparation method thereof.

Background technique

Biosensors use certain biological or chemical immobilization techniques to immobilize biological recognition elements (enzymes, antibodies, antigens, proteins, nucleic acids, receptors, cells, microorganisms, animal and plant tissues, etc.) After the specific reaction between the substance and the biometric element, the resulting reaction result (formation of a complex or generation of sound, light, electricity, heat, etc.) This is to carry out qualitative and quantitative analysis of the substance to be tested, so as to achieve the purpose of detection and analysis. Piezoelectric biosensor is a new type of biosensor developed in recent years. This kind of sensor does not need any label, and has the advantages of simple instrument, convenient operation, sensitive response, good selectivity, and easy automation. Early piezoelectric biosensors mainly used the sensitivity of piezoelectric quartz resonators to mass, and detected the analyte by monitoring the resonant frequency change caused by the change of surface quality after the resonator undergoes an immune reaction. The piezoelectric biosensor used here The body is a quartz single crystal. However, as the system develops towards miniaturization, those skilled in the art are eager to use the piezoelectric body in the form of a thin film. Therefore, it is desirable for those skilled in the art to study piezoelectric sensors made of other piezoelectric materials that can be formed into films. Expected.

The present invention will introduce a series flexible vibration piezoelectric diaphragm biosensor and its preparation method. The preparation of the sensor adopts micro-machining technology and piezoelectric film preparation technology, and at the same time skillfully avoids the high-cost and poor-effect piezoelectric film patterning process from the principle and structural design. Another advantage of this sensor is that it provides a native reference unit, making the measurement results more accurate and reliable.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcoming of the prior art, provide a kind of series flexible vibrating piezoelectric diaphragm type biosensor and its preparation method, the preparation of this sensor adopts micromachining technology and piezoelectric thin film preparation technology, can be from principle and The structural design cleverly avoids the high-cost and poor-effect piezoelectric film patterning process; moreover, the sensor can provide a native reference unit to make the measurement results more accurate and reliable.

The purpose of the present invention is solved by the following technical solutions:

This series flexible vibration piezoelectric diaphragm type biosensor includes SOI silicon chip, wherein the bottom electrode adhesion layer and piezoelectric layer are arranged successively on the surface of the Device layer of SOI silicon chip; two piezoelectric layers are arranged on the piezoelectric layer. Adjacent flexible vibrating piezoelectric diaphragms: diaphragm one and diaphragm two; the upper and lower electrodes of the flexible vibrating piezoelectric diaphragm are arranged on the upper and lower surfaces of the piezoelectric layer respectively; Silicon thin film layer, wherein the Handle layer and the silicon nitride thin film layer of the SOI silicon wafer are provided with silicon cups at the positions corresponding to the first and second diaphragms; the first diaphragm is used as a detection unit, and biological probe molecule; the septum two serves as a reference unit.

Further, the above-mentioned flexible vibrating piezoelectric diaphragms are all square. The flexible vibrating piezoelectric diaphragms are all circular. The upper electrode of the flexible vibrating piezoelectric diaphragm is connected to an upper electrode pad through an upper electrode lead wire. The piezoelectric layer is a lead zirconate titanate film, strontium barium titanate film or bismuth sodium titanate film prepared by sol-gel method, magnetron sputtering or pulsed laser deposition process. The lower electrode of the flexible vibrating piezoelectric diaphragm is a platinum, aluminum or nickel metal film adhered to the bottom electrode adhesion layer (13).

The present invention also proposes a method for preparing a series flexible vibration piezoelectric diaphragm type biosensor, comprising the following steps:

1) Take the SOI silicon substrate, specify that the side of the Device layer is the front side, and the side of the Handle layer is the back side;

2) On the front side of the SOI silicon substrate, a titanium dioxide film is deposited by radio frequency magnetron sputtering as the bottom electrode adhesion layer, and then a metal film is deposited on the bottom electrode adhesion layer as the lower electrode of the flexible vibrating piezoelectric diaphragm; the bottom electrode adhesion Both the attached layer and the lower electrode of the flexible vibrating piezoelectric diaphragm are deposited in a radio frequency magnetron sputtering apparatus;

3) On the front side of the SOI silicon substrate, a piezoelectric thin film is deposited on the lower electrode of the flexible vibrating piezoelectric diaphragm as a piezoelectric layer, and the thickness of the deposited piezoelectric thin film is 0.1-10 μm;

4) Deposit silicon nitride film on the front side by LPCVD method, the thickness of silicon nitride film is 80~200nm;

5) On the front side, the silicon nitride film is patterned using photolithography and dry etching processes to expose the piezoelectric layer that performs the flexible vibration diaphragm;

6) On the front side, the Ti/Au upper electrode and its leads and pads are prepared by photolithography and radio frequency magnetron sputtering combined with the lift-off process; the Ti/Au in contact with the piezoelectric layer is the upper electrode, and the upper electrode is connected to Ti/Au on the silicon nitride film next to it, which is convenient for bonding wires, is called wires and pads; the thickness of the Ti layer is 10~20nm, and the thickness of the Au layer is 100~500nm;

7) On the reverse side, the silicon nitride film is deposited by LPCVD method, and the thickness of the silicon nitride film is 80~200nm;

8) On the reverse side, use photolithography and dry etching processes to pattern the silicon nitride film to expose the silicon etching window of the Handle layer corresponding to the upper electrode;

9) On the reverse side, use silicon anisotropic wet etching or dry etching to remove the silicon in the silicon etching window area of the Handle layer, form a silicon cup, and release the flexible vibration diaphragm; the etching solution is potassium hydroxide solution or tetramethyl hydrogen Ammonium oxide solution; the corrosion stop layer is the buried layer SiO ₂ between the Device layer and the Handle layer of the SOI substrate;

10) On the front side, the silicon nitride film on the surface is removed by dry etching;

11) Two adjacent diaphragms form a series flexible vibration piezoelectric diaphragm biosensor;

12) Polarize the piezoelectric layer in the diaphragm region of the biosensor; then functionalize the surface of one diaphragm in the series as a detection unit; the other diaphragm in the series as a reference unit.

Further, in the above step 1), the thickness of the Device layer of the SOI silicon substrate is 0.5-10 μm, and the orientation is (100) or (110) or (111); the thickness of the buried layer SiO ₂ of the SOI silicon substrate is 0.1-10 μm. 1μm; the thickness of the Handle layer of the SOI silicon substrate is 200~900μm, and the orientation is (100).

Further, in the above step 2), the thickness of the titanium dioxide film used as the adhesion layer of the bottom electrode is 10-20nm; the thickness of the metal film of the bottom electrode of the flexible vibrating piezoelectric diaphragm is 100-500nm; the bottom electrode is distributed on the entire substrate. continuous film.

Compared with the prior art, the present invention has the following beneficial effects:

1. The upper electrodes of the two adjacent diaphragms of the present invention and their leads and pads are used to apply the AC excitation signal to the sensor and measure the frequency response of the sensor, while the series connection of the two adjacent diaphragms passes through the connected bottom Electrode realization (the bottom electrode is a continuous metal film distributed on the entire substrate, so the piezoelectric layer patterning process with high cost and poor effect is effectively avoided in the manufacturing process. No patterning of the piezoelectric layer and bottom electrode shortens the The manufacturing time is reduced, the manufacturing cost is reduced, and the processing yield is improved.

2. Due to the existence of the reference unit of the present invention, the influence of external factors such as non-specific adsorption and temperature drift on the detection results of the sensor is reduced, thereby greatly improving the detection accuracy of the sensor.

3. Because the present invention adopts the micromachining process, compared with the quartz microbalance (QCM) biosensor, the sensor of the present invention not only has high sensitivity, but also is convenient for miniaturization and mass production, and can be prepared on a silicon chip. Hundreds of sensors (the specific number depends on the size of a single sensor), and it is possible to further integrate related driving and detection circuits on silicon chips.

4. Compared with the flexible vibrating cantilever sensor and the QCM biosensor, the sensor of the present invention has a higher quality factor when detecting in the liquid phase.

5. Compared with QCM, film bulk acoustic resonator (FBAR) and surface acoustic wave device (SAW), the sensor of the present invention has a lower resonance frequency, which is beneficial to the design of related driving and detection circuits.

6. Compared with the flexible vibrating cantilever beam sensor, the sensor of the present invention has higher structural strength.

Description of drawings

Figure 1 is a schematic three-view diagram of the structure of a series flexible vibration piezoelectric diaphragm biosensor; where (a) is a top view, (b) is the A-A' sectional view of (a); (c) is B of (b) -B' section view;

Fig. 2 is another schematic three views of the structure of another flexible vibration piezoelectric diaphragm biosensor in series; where (a) is a top view, (b) is the A-A' sectional view of (a); (c) is (b) BB' section view;

In Figure 1 and Figure 2: 1 is the upper electrode of the reference unit; 2 is the lead wire of the upper electrode of the reference unit; 3 is the pad of the upper electrode of the reference unit; 4 is the pad of the upper electrode of the detection unit; Electrode leads; 6 is the upper electrode of the detection unit; 7 is the biological probe molecule; 8 is the silicon cup; 9 is the silicon nitride film or metal aluminum film; 10Handle layer; 14 is a piezoelectric layer; 15 is a silicon nitride film used as an electrode lead and a pad isolation layer on the diaphragm.

Fig. 3 Schematic diagram of first-order flexible vibration of flexible vibration piezoelectric diaphragm;

Fig. 4 is a schematic diagram of the resonant peak and the detection principle of the sensor of the present invention.

detailed description

This kind of series flexible vibration piezoelectric diaphragm type biosensor of the present invention comprises SOI silicon chip, wherein on the Device layer 12 surface of SOI silicon chip, be provided with bottom electrode adhesion layer 13, piezoelectric layer 14 successively; On piezoelectric layer 14 There are two adjacent flexible vibrating piezoelectric diaphragms: diaphragm one and diaphragm two; the upper and lower electrodes of the flexible vibrating piezoelectric diaphragm are respectively arranged on the upper and lower surfaces of the piezoelectric layer 14; on the surface of the Handle layer 10 of the SOI silicon wafer A layer of silicon nitride film layer 9 is attached, wherein the Handle layer 10 of the SOI silicon chip and the silicon nitride film layer 9 are provided with a silicon cup 8 at the position corresponding to the diaphragm one and diaphragm two; the diaphragm one is used as a detection unit, and the diaphragm The first upper electrode 6 is provided with biological probe molecules 7; the second diaphragm is used as a reference unit. The upper electrode of the flexible vibrating piezoelectric diaphragm is connected to an upper electrode pad through an upper electrode lead wire. The piezoelectric layer 14 is a lead zirconate titanate film, strontium barium titanate film or bismuth sodium titanate film prepared by sol-gel method, magnetron sputtering or pulsed laser deposition process. The lower electrode of the flexible vibrating piezoelectric diaphragm is a platinum, aluminum or nickel metal thin film adhered to the bottom electrode adhesion layer 13. Between the upper electrode leads 2 of the reference unit; the upper electrode pad 3 of the reference unit and the piezoelectric layer 14, there is a silicon nitride film 15 used as an isolation layer for the upper electrode leads of the diaphragm and the pad.

The shape of the flexible vibrating piezoelectric membrane of the present invention can be square or circular, as shown in FIG. 1 and FIG. 2 .

On the upper electrode pads of two adjacent diaphragms, an AC excitation voltage is applied. Since the entire bottom electrode layer is connected, a series diaphragm structure is naturally formed, and flexible vibrations are excited in the two diaphragms due to the piezoelectric effect. When the frequency of the AC excitation voltage coincides with the resonant frequency of the diaphragm, piezoelectric resonance peaks will be generated in the two diaphragms which can be detected by the measuring circuit.

Several specific embodiments of the preparation method of the serial flexible vibration piezoelectric diaphragm type biosensor of the present invention are given below in conjunction with the accompanying drawings:

Example 1

The structural schematic diagram of the series flexible vibration piezoelectric diaphragm biosensor of this embodiment is shown in FIG. 1 . The diaphragm contained in each sensor in this embodiment is a square with a side length of 200 μm.

The specific manufacturing process includes the following steps:

1) The SOI silicon substrate is used, and the front and back are specified for later description. The surface on the Device side is the front, and the surface on the Handle side is the back. The thickness of the Device layer 12 of the SOI silicon substrate is 1 μm, the orientation is (100), the thickness of the buried layer SiO ₂ is 0.1 μm, the thickness of the Handle layer 10 is 400 μm, and the orientation is (100).

2) On the front side, a titanium dioxide (TiO ₂ ) film is deposited as the bottom electrode adhesion layer 13 by radio frequency magnetron sputtering, and a metal platinum (Pt) film is deposited as the bottom electrode (ie, the bottom electrode of the flexible vibrating piezoelectric diaphragm). Both the bottom electrode adhesion layer 13 and the bottom electrode of the flexible vibrating piezoelectric diaphragm are deposited in a radio frequency magnetron sputtering apparatus, the thickness of the TiO ₂ film is 10nm, and the thickness of the Pt film is 100nm.

3) On the front side, a barium strontium titanate (BST) piezoelectric film with a thickness of 1 μm is prepared as the piezoelectric layer 14 by using a pulsed laser deposition process.

4) On the front side, a silicon nitride (Si ₃ N ₄ ) film layer is deposited by LPCVD method, and the thickness of the silicon nitride film is 100nm.

5) On the front side, the silicon nitride film is patterned using photolithography and dry etching processes to expose the piezoelectric layer 14 that performs the flexible vibration diaphragm. The exposed piezoelectric layer 14 is the same size and shape as the diaphragm, It is also a square with a side length of 200 μm. During photolithography, care should be taken to align the crystal orientation so that the side of the exposed square area of the piezoelectric layer is parallel to the notch side of the substrate indicating the (100) orientation.

6) On the front side, the titanium/gold (Ti/Au) upper electrode (that is, the upper electrode 6 of the detection unit), the upper electrode lead 5 and the upper electrode pad 4 of the detection unit are prepared by photolithography and radio frequency magnetron sputtering combined with the lift-off process . The thickness of the titanium layer is 10nm, and the thickness of the gold layer is 100nm. The upper electrode 6 of the detection unit is also square and aligned with the exposed square area of the piezoelectric layer 14 with sides parallel to each other. The side length of the upper electrode 6 of the detection unit is 160 μm, the width of the lead wire is 50 μm, and the side length of the welding pad is 150 μm. In the same manner, the upper electrode 1 of the reference unit, the lead wire 2 of the upper electrode of the reference unit and the pad 3 of the upper electrode of the reference unit are prepared beside the upper electrode 6 of the detection unit.

7) On the reverse side, a silicon nitride (Si ₃ N ₄ ) film 9 is deposited by LPCVD, and the thickness of the silicon nitride film 9 is 100 nm;

8) On the reverse side, the silicon nitride film 9 is patterned by double-side alignment photolithography and dry etching process, exposing the silicon etching window of the Handle layer 10 corresponding to the upper electrode. The window is square and centered with the upper electrode (including the upper electrode 6 of the detection unit and the upper electrode 1 of the reference unit), the sides are parallel to each other, and the side length of the window is 760 μm.

9) On the reverse side, use an anisotropic silicon wet etching process to remove the silicon in the silicon etching window area of the Handle layer 10 to form a silicon cup 8 and release the flexible vibration diaphragm. The etching solution is 30% potassium hydroxide (KOH) solution, and the etching temperature is 80°C. The etch stop layer is a buried silicon dioxide (SiO ₂ ) 11 between the Device layer 12 and the Handle layer 10 of the SOI substrate.

10) On the front side, the silicon nitride film on the surface is removed by dry etching.

11) Two adjacent diaphragms constitute a series flexible vibrating piezoelectric diaphragm sensor.

12) Thermally polarize the piezoelectric layer 14 in the diaphragm area of the sensor; then functionalize the surface of the diaphragm used as the detection unit in the series diaphragm, immobilize the bioprobe molecule 7 as protein A, and the immobilization method is physical adsorption , the blocking agent is casein in TBS (tris-buffered saline) buffer. Goat IgG can be detected using this sensor.

Example 2

Fig. 1 shows a schematic three views of the structure of a series flexible vibrating piezoelectric diaphragm biosensor. In this example, the diaphragm contained in each sensor is a square with a side length of 200 μm. The specific manufacturing process includes the following steps:

1) The SOI silicon substrate is used, and the front and back are specified for later description. The surface on the Device side is the front, and the surface on the Handle side is the back. The thickness of the Device layer of the SOI silicon substrate is 1 μm, the orientation is (100), the thickness of the buried layer SiO ₂ is 0.1 μm, the thickness of the Handle layer is 400 μm, and the orientation is (100).

2) On the front side, a titanium dioxide (TiO ₂ ) film is deposited as an adhesion layer by radio frequency magnetron sputtering, and a metal platinum (Pt) film is deposited as a bottom electrode. Both the adhesion layer and the bottom electrode are deposited in a radio frequency magnetron sputtering apparatus, the thickness of the TiO ₂ film is 10nm, and the thickness of the Pt film is 100nm.

3) On the front side, a barium strontium titanate (BST) piezoelectric film with a thickness of 1 μm was prepared by a pulsed laser deposition process.

4) A silicon nitride (Si ₃ N ₄ ) film layer is deposited by LPCVD method, and the thickness of the silicon nitride film is 100 nm.

5) On the front side, the silicon nitride film is patterned using photolithography and dry etching processes to expose the piezoelectric layer that performs the flexible vibration diaphragm. The exposed piezoelectric layer is the same size and shape as the diaphragm and is also the side A square with a length of 200 μm. During photolithography, care should be taken to align the crystal orientation so that the side of the exposed square area of the piezoelectric layer is parallel to the notch side of the substrate indicating the (100) orientation.

6) On the front side, the titanium/gold (Ti/Au) upper electrode and its leads and pads are prepared using photolithography and radio frequency magnetron sputtering combined with a lift-off process. The thickness of the titanium layer is 10nm, and the thickness of the gold layer is 100nm. The upper electrode is also square and centered on the exposed square area of the piezoelectric layer with sides parallel to each other. The side length of the upper electrode is 160 μm, the width of the lead wire is 50 μm, and the side length of the pad is 150 μm.

7) A silicon nitride (Si ₃ N ₄ ) film is deposited by LPCVD method, and the thickness of the silicon nitride film is 100 nm.

8) On the reverse side, use double-sided alignment photolithography and dry etching to pattern the silicon nitride film, exposing the silicon etching window of the Handle layer corresponding to the upper electrode. The window is square and centered with the upper electrode, the sides are parallel to each other, and the side length of the window is 760 μm.

9) On the reverse side, use the silicon anisotropic wet etching process to remove the silicon in the silicon etching window area of the Handle layer to form a silicon cup and release the flexible vibration diaphragm. The etching solution is 30% potassium hydroxide (KOH) solution, and the etching temperature is 80°C. The etch stop layer is the SiO ₂ buried layer between the Device layer and the Handle layer of the SOI substrate.

10) On the front side, the silicon nitride film on the surface is removed by dry etching.

11) Two adjacent diaphragms constitute a series flexible vibrating piezoelectric diaphragm sensor.

12) Thermally polarize the piezoelectric layer in the diaphragm area of the sensor; then functionalize the surface of the diaphragm used as the detection unit in the series diaphragm, the immobilized bioprobe molecule is protein A, and the immobilization method is physical adsorption method, blocking The agent is casein in TBS (tris-buffered saline). Goat IgG can be detected using this sensor.

Example 3

Fig. 2 shows another schematic three views of the structure of another series flexible vibrating piezoelectric diaphragm biosensor. The diaphragm contained in each sensor in this example is a circle with a diameter of 300 μm. The specific manufacturing process includes the following steps:

1) The SOI silicon substrate is used, and the front and back are specified for later description. The surface on the Device side is the front, and the surface on the Handle side 10 is the back. The thickness of the Device layer 12 of the SOI silicon substrate is 2 μm, the orientation is (111), the thickness of the buried layer SiO ₂ is 0.5 μm, the thickness of the Handle layer is 400 μm, and the orientation is (111).

2) On the front side, deposit a titanium dioxide (TiO ₂ ) film as the bottom electrode adhesion layer 13 by radio frequency magnetron sputtering, and then deposit a platinum (Pt) film as the bottom electrode. Both the bottom electrode adhesion layer 13 and the bottom electrode are deposited in a radio frequency magnetron sputtering apparatus, the thickness of the TiO ₂ film is 10 nm, and the thickness of the Pt film is 100 nm.

3) On the front side, a zinc oxide (ZnO) piezoelectric film with a thickness of 2 μm is deposited and prepared as the piezoelectric layer 14 by radio frequency magnetron sputtering.

4) Deposit a silicon nitride (Si ₃ N ₄ ) thin film layer on the front surface by LPCVD method, and the thickness of the silicon nitride thin film is 100nm.

5) On the front side, the silicon nitride film is patterned using photolithography and dry etching processes to expose the piezoelectric layer 14 that performs the flexible vibration diaphragm. The exposed piezoelectric layer 14 is the same size and shape as the diaphragm, It is also a circle with a side length of 300 μm.

6) On the front side, the titanium/gold (Ti/Au) upper electrodes of the reference unit and the detection unit and their leads and pads are prepared by using photolithography and radio frequency magnetron sputtering combined with the lift-off process. The thickness of the titanium layer is 10nm, and the thickness of the gold layer is 100nm. The top electrode is also circular and is centered on the exposed circular area of the piezoelectric layer. The diameter of the upper electrode is 240 μm, the width of the lead wire is 50 μm, and the side length of the pad is 150 μm.

7) On the reverse side, an aluminum (Al) thin film layer (namely the metal aluminum thin film 9 ) is deposited by radio frequency magnetron sputtering, and the thickness of the aluminum thin film is 200 nm.

8) On the reverse side, the aluminum thin film is patterned by double-side alignment photolithography and lift-off process, exposing the silicon etching window of the Handle layer 10 corresponding to the upper electrode. The window is circular and centered with the upper electrodes of each unit, and the diameter of the window is 300 μm.

9) On the reverse side, the silicon in the silicon etching window area of the Handle layer 10 is removed by a silicon dry etching process to form a silicon cup 8 to release the flexible vibration diaphragm. The corrosive gas is SF ₆ /C ₄ F ₈ . The etch stop layer is the buried silicon dioxide 11 between the Device layer 12 and the Handle layer 10 of the SOI substrate.

10) On the front side, the silicon nitride film on the surface is removed by dry etching. The silicon nitride film 15 used as an isolation layer for electrode leads and pads on the diaphragm remains.

11) Two adjacent diaphragms form a series flexible vibration piezoelectric diaphragm sensor.

12) Thermally polarize the piezoelectric layer in the diaphragm area of the sensor; then functionalize the surface of the diaphragm used as the detection unit in the series diaphragm, the immobilized bioprobe molecule 7 is protein A, and the immobilization method is physical adsorption method, The blocking agent was casein in TBS (tris-buffered saline). Goat IgG can be detected using this sensor.

During detection, as shown in Figure 3, the bioprobe molecules on the functionalized detection unit will capture the target biomolecules. This capture is reflected in the change of the additional mass on the surface of the sensor, which in turn leads to a change in its resonance frequency. Through By comparing the movement of the resonance peaks of the detection unit and the reference unit, the target biomolecules can be detected.

Fig. 4 is a schematic diagram of the resonant peak and detection principle of the present invention. Among them, f ₁ and f ₂ are the first-order resonance peaks of the detection unit and the reference unit before the sensor detects, and f' ₁ and f' ₂ are the first-order resonance peaks of the detection unit and the reference unit after the sensor detects, respectively. Then the frequency shift caused by capturing the target molecule is Δf=(f ₁ -f′ ₁ )-(f ₂ −f′ ₂ )=(22040-21170)-(24350-24180)=700Hz.

To sum up, the sensor of the present invention skillfully avoids the costly and poorly effective piezoelectric layer patterning process in terms of principle and structural design, and at the same time, the existence of the reference unit greatly improves the detection accuracy of the sensor. In addition, compared with the QCM biosensor, the sensor of the present invention is more sensitive, has a high quality factor when used for liquid phase in-situ detection, and is convenient for miniaturization and batch manufacturing; compared with the flexible vibrating cantilever beam sensor, The sensor of the invention has firm structure and high quality factor when used for liquid phase in-situ detection.

Claims (2)

1. a series-connection flexible vibration piezoelectric diaphragm type biosensor, it is characterised in that include SOI Silicon chip, wherein Device layer (12) surface at soi wafer be sequentially provided with hearth electrode adhesion layer (13), Piezoelectric layer (14)；Described piezoelectric layer (14) is provided with two adjacent flexible vibration piezoelectricity every Film: barrier film one and barrier film two；The upper/lower electrode of described flexible vibration piezoelectricity barrier film is respectively arranged at piezoelectricity The upper and lower surface of layer (14)；On Handle layer (10) surface of described soi wafer with one layer Silicon nitride film layer (9), wherein the Handle layer (10) of soi wafer and silicon nitride film layer (9) Silicon cup (8) is being offered corresponding to described barrier film one and barrier film two position；Described barrier film one is as detection Unit, is provided with bioprobe molecule (7) on barrier film one on electrode (6)；Described barrier film two is made For reference cell；The upper electrode of described flexible vibration piezoelectricity barrier film is powered on by the connection of upper contact conductor Pole pad, applies ac-excited voltage, with self-assembling formation series connection membrane configuration, and because of piezoelectric effect Flexible vibration is evoked in two barrier films；Described piezoelectric layer (14) is for using sol-gal process, magnetic control PZT thin film, barium strontium titanate or bismuth titanates prepared by sputtering or pulse laser deposition process Sodium thin film；The bottom electrode of described flexible vibration piezoelectricity barrier film is to stick on hearth electrode adhesion layer (13) Platinum, aluminum or thin nickel metal film；On reference cell, contact conductor (2) is powering on of reference cell Have between pole pad (3) and piezoelectric layer (14) as contact conductor on barrier film and pad sealing coat Silicon nitride film (15)；The shape of flexible vibration piezoelectricity barrier film is square or circular.

2. a preparation method for series-connection flexible vibration piezoelectric diaphragm type biosensor, its feature exists In, comprise the following steps:

1) SOI silicon substrate is taken, it is stipulated that the side of its Device layer is front, at Handle layer Side is reverse side；Device layer 12 thickness of SOI silicon substrate is 1 μm, is oriented to (100), buries Layer SiO₂Thickness is 0.1 μm, and Handle layer 10 thickness is 400 μm, is oriented to (100)；

2) in the front of SOI silicon substrate, radio-frequency magnetron sputter method deposition of titanium oxide thin film is used to make For deposition metallic film on hearth electrode adhesion layer (13), then hearth electrode adhesion layer (13) as flexibility The bottom electrode of vibration piezoelectricity barrier film；Thickness as the titanium deoxid film of hearth electrode adhesion layer (13) It is 10～20nm；The bottom electrode thickness of metal film of flexible vibration piezoelectricity barrier film is 100～500nm；Under Electrode is distribution continuous film over the entire substrate；Hearth electrode adhesion layer (13) and flexible vibration pressure The bottom electrode of electric separator is all deposition gained in rf magnetron sputtering instrument；

3) in the front of SOI silicon substrate, deposit on the bottom electrode of described flexible vibration piezoelectricity barrier film Piezoelectric membrane is as piezoelectric layer (14), and the thickness of depositing piezoelectric thin film is 0.1～10 μm；

4) employing LPCVD method at front cvd nitride silicon thin film, the thickness of silicon nitride film is 80～200nm；

5) in front, utilize photoetching and dry etch process that silicon nitride film is patterned, expose Go out to perform the piezoelectric layer (14) of flexible vibration barrier film；

6) in front, utilize photoetching and rf magnetron sputtering and combine stripping technology and prepare Ti/Au and power on Pole and lead-in wire thereof and pad；The Ti/Au wherein contacted with piezoelectric layer (14) is upper electrode, by upper Electrode is connected on the silicon nitride film on side, and the Ti/Au being easy to bonding wire is referred to as lead-in wire and weldering Dish；Wherein Ti layer thickness is 10～20nm, and Au layer thickness is 100～500nm；

7) at reverse side, using LPCVD method cvd nitride silicon thin film, the thickness of silicon nitride film is 80～200nm；

8) at reverse side, utilize photoetching and dry etch process that silicon nitride film is patterned, expose Go out the Handle layer silicon corrosion window corresponding with upper electrode；

9) at reverse side, anisotropic silicon wet etching or dry corrosion process is utilized to remove Handle layer The silicon in silicon corrosion window region, forms silicon cup (8), and release performs flexible vibration barrier film；Corrosive liquid is Potassium hydroxide solution or tetramethyl ammonium hydroxide solution；Etch stop layer is SOI substrate Device layer And the buried regions SiO between Handle layer₂；

10) in front, dry etching is utilized to remove surfaces nitrided silicon thin film；

11) two adjacent barrier films constitute a series-connection flexible vibration piezoelectric diaphragm type biosensor；

12) piezoelectric layer of biosensor diaphragm area is polarized；Then in series connection barrier film The surface of one barrier film carries out functionalization, as probe unit；Another barrier film in series connection barrier film is made For reference cell.