CN113739901A

CN113739901A - Four-electrode integrated sensitive electrode of MEMS (micro electro mechanical System) electrochemical vibration sensor and manufacturing method thereof

Info

Publication number: CN113739901A
Application number: CN202111045732.9A
Authority: CN
Inventors: 王军波; 段语默; 陈德勇; 许超; 齐文杰
Original assignee: Aerospace Information Research Institute of CAS
Current assignee: Aerospace Information Research Institute of CAS
Priority date: 2021-09-07
Filing date: 2021-09-07
Publication date: 2021-12-03
Anticipated expiration: 2041-09-07
Also published as: CN113739901B

Abstract

The invention discloses a four-electrode integrated sensitive electrode of an MEMS (micro-electromechanical system) electrochemical vibration sensor and a manufacturing method thereof, wherein the four-electrode integrated sensitive electrode comprises a substrate, a first insulating layer formed on the front surface of the substrate, a second insulating layer formed on the back surface of the substrate, a plurality of through holes penetrating through the first insulating layer, the substrate and the second insulating layer, and a through hole side wall insulating layer formed on the inner side wall of each through hole; the first insulating layer is provided with a first anode electrode and a first cathode electrode which is symmetrical to the first anode electrode, and the first cathode electrode is formed on the second part of the first insulating layer and on the inner side wall of the through hole of the second part; the second insulating layer is provided with a second anode electrode and a second cathode electrode which is symmetrical with the second anode electrode, and the second cathode electrode is formed on the third part of the second insulating layer and the inner side wall of the through hole of the third part. Compared with the existing four-electrode integration scheme, the cathode-anode electrode pair design improves the effective utilization rate of the cathode area, and the cathode is manufactured on the inner wall of the flow channel, so that the sensitivity is greatly improved.

Description

Four-electrode integrated sensitive electrode of MEMS (micro electro mechanical System) electrochemical vibration sensor and manufacturing method thereof

Technical Field

The invention relates to the technical field of vibration sensors and MEMS (Micro-Electro-Mechanical-System), in particular to a four-electrode integrated sensitive electrode of an MEMS electrochemical vibration sensor and a manufacturing method thereof.

Background

The vibration sensor is a sensor which converts an external vibration signal into an electric signal for analysis, and has various types and different principles. Mainly, the capacitance type, electromagnetic type, optical type, piezoelectric type, electrochemical type, and the like are available.

The electrochemical vibration sensor adopts a liquid mass block mainly based on iodine-potassium iodide electrolyte to replace the traditional mass block, and the core of the electrochemical vibration sensor is a sensitive electrode core consisting of two pairs of cathodes and anodes and a flow channel. When the accelerometer works, bias voltage is applied to the two pairs of the cathode and the anode. When the external acceleration is zero, the concentration of electrolyte ions is symmetrically distributed, and the differential output of the two pairs of electrodes is zero; when acceleration exists outside, the electrolyte flows through the flow channel, the ion concentration distribution is changed, the two pairs of electrodes generate differential output, and the magnitude of differential output current reflects the magnitude of the acceleration. Compared with other types of detectors, the electrochemical accelerometer has the following outstanding advantages: firstly, electrolyte coupled with an elastic membrane is used as an inertial mass, position and center adjustment is not needed, and the working inclination angle is large; secondly, the interior of the sensor is not provided with precise mechanical parts and moving mechanical parts, so that the sensor is fundamentally ensured to have the advantages of simple operation, impact resistance and the like; when the active ions move in the flow channel under low frequency seismic vibrations, they have sufficient time to diffuse to the electrode surface, resulting in a good response.

The early electrochemical accelerometer is manufactured by adopting a traditional method that a platinum wire mesh is adopted to manufacture an electrode, a ceramic sheet or a polymer is used to manufacture an insulating layer, and then a ceramic sintering process is utilized to assemble the electrode, so that the defects of poor consistency, complex process, higher cost and the like exist. Subsequently MEMS processes were introduced to fabricate the sensitive electrodes to ameliorate the above problems. There is a proposal (patent publication No. CN105158493A) to integrate a pair of cathode and anode into a single silicon chip when manufacturing MEMS electrode structure, which reduces the required chips to two pieces, but still requires manual alignment and installation, and reduces the uniformity of the device. Based on this, some solutions have been proposed to solve the problem of four-electrode monolithic integration.

In some schemes (Hai H, Caranded B, Rui T, et al. micro discrete measured on molecular electronics technology for planar amplification [ J ]. Applied Physics Letters,2013,102(19):4524-4546.), a platinum electrode and a silicon nitride insulating layer are deposited on a silicon substrate, and a focused ion beam technique is used to etch a through hole as a flow channel hole.

In another scheme (Sun Z, Chen D, Jian C, et al. AMEMS based electrochemical semiconductor meter with a novel integrated sensing unit [ C ]//2016IEEE 29th International Conference on Micro Electro Mechanical Systems (MEMS). IEEE,2016.), the integration is realized by first making patterned platinum electrode structures on both sides of a silicon wafer as cathodes, etching the channel holes, then depositing an SU-8 film as an insulating layer, and then depositing a platinum electrode as an anode. However, the solution also has the problems of small contact area between the electrolyte and the electrode, extremely low yield and poor repeatability.

In another scheme (patent publication No. CN110568518A), a pair of cathode and anode are integrated on a substrate, flow channels are formed by etching flow holes, and then two sensing electrodes and a rubber ring are assembled to form a four-electrode sensing core. This scheme has utilized the discharge orifice lateral wall, has increased the cathode area, has promoted output sensitivity, but the integrated level is lower, compares in monolithic integrated structure flow resistance great, and needs the manual work to aim at the installation, influences the uniformity of device.

In another scheme (patent publication No. CN110426532A), patterned planar electrode cathode and anode pairs are respectively made on two sides of a silicon wafer, and then etching flow holes are communicated. The scheme has good repeatability, but because the inner wall of the flow channel has no cathode area, and most of cathodes in the middle of the chip are difficult to utilize, the sensitivity is low, and the low-frequency performance is very poor.

Disclosure of Invention

Aiming at the problems, the invention provides a four-electrode integrated sensitive electrode of an MEMS electrochemical vibration sensor and a manufacturing method thereof. The four-electrode integrated sensitive electrode is a novel four-electrode integrated sensitive electrode, simplifies the manufacturing process on the basis of a pure silicon structure, reduces the flow resistance through monolithic integration, improves the sensitivity of the device by fully utilizing the surface and the area of the electrode on the inner wall of a flow channel, and simultaneously ensures the consistency of the device.

In order to avoid manual alignment, fully utilize the area of a chip electrode, simplify the process, improve the consistency and keep high sensitivity, the invention provides a four-electrode integrated sensitive electrode and a manufacturing method thereof.

The invention adopts the following technical scheme:

a four-electrode integrated sensitive electrode of an MEMS (micro-electromechanical system) electrochemical vibration sensor comprises a substrate, an insulating layer, a plurality of through holes, a first anode electrode, a first cathode electrode, a second anode electrode and a second cathode electrode; wherein the content of the first and second substances,

the substrate comprises a first surface and a second surface opposite to each other;

the insulating layer comprises a first insulating layer, a second insulating layer and a through hole side wall insulating layer, wherein the first insulating layer is formed on the first surface of the substrate, the second insulating layer is formed on the second surface of the substrate, and the through hole side wall insulating layer is formed on the inner side wall of the through hole;

the first insulating layer comprises a first portion, a second portion, and an insulating tape between the first portion and the second portion, and the second insulating layer comprises a third portion, a fourth portion, and an insulating tape between the third portion and the fourth portion; the first part is provided with a plurality of through holes penetrating to the third part, the second part is provided with a plurality of through holes penetrating to the fourth part, and the through holes penetrate through the first insulating layer, the substrate and the second insulating layer;

a first anode electrode formed on a region of the first portion of the first insulating layer except for the through-hole outer circumferential insulating ring;

a first cathode electrode formed on the second portion of the first insulating layer and the inner sidewall of the through hole of the second portion;

a second cathode electrode formed on the third portion of the second insulating layer and the inner sidewall of the through hole of the third portion;

and the second anode electrode is formed on the fourth part of the second insulating layer except for the insulating ring at the periphery of the through hole.

The through hole is a flow hole and is a flow channel of the electrolyte.

In one embodiment of the invention, the first anode electrode on the first portion and the first cathode electrode on the second portion are symmetrical along a substrate center line, or the first anode electrode on the first portion and the first cathode electrode on the second portion are in an interdigitated design, on the first insulating layer.

In one embodiment of the invention, on the second insulating layer, the second cathode electrode on the third portion and the second anode electrode on the fourth portion are symmetrical along the substrate center line, or the second cathode electrode on the third portion and the second anode electrode on the fourth portion are in an interdigitated design.

In one embodiment of the present invention, the patterns of the first insulating layer and the second insulating layer are centrosymmetric.

In one embodiment of the invention, the substrate is a silicon wafer. Preferably, the silicon wafer has a thickness of 200 microns.

In one embodiment of the present invention, the insulating layer is a silicon oxide insulating layer or a silicon nitride insulating layer. Preferably, the thickness of the insulating layer is 5000-. Preferably, the thickness of the insulating layer is 1 micron.

In one embodiment of the present invention, the anode and cathode materials are Pt, 2000-3000 angstroms thick, respectively.

In one embodiment of the invention, the electrode surface flow holes are in the shape of single circular holes or other patterns, preferably with a pore size of 80-150 microns.

In one embodiment of the invention, the width of the insulating ring is 10 to 20 microns and the width of the insulating tape is 60 to 100 microns. The insulating ring is a silicon dioxide insulating ring or a silicon nitride insulating ring. The insulating tape is a silicon dioxide insulating tape or a silicon nitride insulating tape.

A method of manufacturing an integrated sensor electrode according to any preceding claim, comprising:

step (a): photoetching, coating photoresist on the first surface of the substrate, and photoetching to pattern the surface of the substrate;

step (b): etching the substrate and removing the photoresist, etching the substrate by using Deep Reactive Ion Etching (DRIE) to manufacture a through hole, and removing the residual photoresist on the surface;

step (c): thermal oxidation, namely performing thermal oxidation on the etched substrate to form a first insulating layer, a second insulating layer and a through hole side wall insulating layer so as to insulate the substrate;

step (d): photoetching, namely attaching a layer of dry film on one surface of the substrate and photoetching to manufacture photoresist patterns of a surface electrode, an insulating ring and an insulating tape;

a step (e): sputtering metal and stripping, sputtering transition layer metal titanium and electrode layer metal, then stripping, and simultaneously manufacturing an anode electrode of the surface, a cathode electrode in the surface and the hole, an insulating ring and an insulating tape between the cathode and the anode;

step (f): and (e) repeating the steps (d) to (e) on the other surface to finish the manufacture of the anode electrode and the cathode electrode on the other side.

Further, in the step (e), the anode electrode of the face and the cathode electrode of the face and the hole are insulated from each other.

Further, in step (f), the anode electrode of the face and the cathode electrode of the face and the hole are insulated from each other.

In one embodiment of the invention, the transition layer metal is titanium, preferably having a transition layer thickness of 300 angstroms; the electrode layer metal is platinum, and the thickness of the electrode layer is preferably 2000-3000 angstroms.

The invention has the beneficial effects that:

(1) the four electrodes and the insulating layer of the sensitive core are integrated on one silicon chip, manual alignment is not needed, the process is simplified, and the consistency and the repeatability of the device are improved.

(2) The MEMS technology is simple to operate and high in efficiency, so that the yield is high, and the future production is facilitated.

(3) Parameters influencing the electrode performance, such as the aperture of a flow channel, the distance between a cathode and an anode and the like can be conveniently adjusted, and the optimization and the exploration of the device performance are facilitated.

Compare in existing four electrode integration schemes, this scheme is when reducing the flow resistance, and the effective utilization ratio of negative pole area has been promoted in the design of negative and positive electrode pair, and the runner inner wall has also made the negative pole, has promoted sensitivity by a wide margin.

Drawings

FIG. 1 is a schematic diagram of a four-electrode integrated sensing electrode; FIG. 1(a) is a cross-sectional view of a four-electrode integrated sensing electrode, and FIG. 1(b) is a schematic top view of the four-electrode integrated sensing electrode;

FIG. 2 is a schematic diagram of a manufacturing process of a four-electrode integrated sensitive electrode.

In the figure, 100-four electrodes are integrated into a sensitive electrode; 101-a silicon wafer substrate; 102-an insulating layer; 103-anodic platinum electrode; 104-cathode platinum electrode; 105-through holes.

Detailed Description

The invention is described in detail below with reference to the figures and the embodiments. The following examples are only for explaining the present invention, the scope of the present invention shall include the full contents of the claims, and the full contents of the claims of the present invention can be fully realized by those skilled in the art through the following examples.

Fig. 1 is a schematic structural diagram of an integrated sensitive electrode of the MEMS electrochemical accelerometer of the present invention. As shown in fig. 1(a) a cross-sectional view of a sensing electrode, the present invention provides a four-electrode integrated sensing electrode 100 based on MEMS technology. The structure comprises a silicon chip substrate 101, silicon dioxide insulating layers 102 wrapping the front side and the back side of the silicon chip substrate 101 and the upper side and the lower side of the side wall of a runner, anode platinum electrodes 103 and cathode platinum electrodes 104 which are arranged on the insulating layers 102 and are bilaterally symmetrical along the central line of the silicon chip, and a plurality of through holes 105 penetrating through the silicon chip substrate 101 and the insulating layers 102.

The anode platinum electrode 103 includes a first anode electrode and a second anode electrode. The cathode platinum electrode 104 includes a first cathode electrode and a second cathode electrode.

The insulating layer 102 on the front side of the silicon wafer substrate comprises a first part, a second part and an insulating tape between the first part and the second part, wherein the insulating tape separates the first part from the second part and realizes insulation between the first part and the second part, and the width of the insulating tape is preferably 60-100 microns.

The insulating layer 102 on the back side of the silicon wafer substrate 101 comprises a third part, a fourth part and an insulating tape between the third part and the fourth part, wherein the insulating tape separates the third part and the fourth part to realize insulation between the third part and the fourth part, and preferably the width of the insulating tape is 60-100 micrometers.

The first part has a plurality of through holes 105 extending through to the third part and the second part has a plurality of through holes 105 extending through to the fourth part.

And a first anode electrode formed on the first part of the silicon substrate front surface insulating layer 102 except the region of the insulating ring at the periphery of the through hole. Preferably the radial width of the insulating ring is 10-20 microns.

And the first cathode electrode is formed on the second part of the silicon substrate front side insulating layer 102 and the inner side wall of the through hole of the second part.

And the second cathode electrode is formed on the third part of the silicon substrate back surface insulating layer 102 and the inner side wall of the through hole of the third part.

And the second anode electrode is formed on the fourth part of the silicon substrate back surface insulating layer 102 except for the insulating ring at the periphery of the through hole. Preferably the radial width of the insulating ring is 10-20 microns.

The anode platinum electrode 103 and the cathode platinum electrode 104 are electrodes required for redox reaction of the electrolyte, and the through-hole 105 serves as a flow channel of the electrolyte. The through-hole 105 is shaped as a single circular hole or other pattern, and preferably the aperture of the through-hole 105 is 80-150 μm. To facilitate the fabrication of the via 105, and to facilitate the etching process to fabricate the via 105, a silicon wafer thickness of 200 microns is preferred. FIG. 1(b) is a schematic top view of the sensing electrode, wherein the front and back patterns are symmetrical about the center.

The invention relates to an MEMS process manufacturing flow chart of an MEMS electrochemical accelerometer integrated sensitive electrode. As shown in fig. 2, the present invention further provides a manufacturing flow chart of the integrated sensing electrode 100, which includes:

step (a): and (6) photoetching. A layer of positive photoresist AZ4620 is spin-coated on one side of the silicon wafer substrate 101 and is subjected to photolithography to pattern the surface thereof.

Step (b): and etching the silicon substrate and removing the photoresist. And etching the silicon substrate by Deep Reactive Ion Etching (DRIE) to manufacture a flow channel, and removing the residual photoresist on the surface.

Step (c): and (4) carrying out thermal oxidation. After the etched silicon wafer substrate 101 is cleaned, thermal oxidation is performed, and a 1-micron silicon dioxide layer 102 is grown to insulate the substrate.

Step (d): and (6) photoetching. And attaching a Dry Film (Dry Film) on one surface of the silicon substrate and photoetching to manufacture a photoresist pattern of the surface electrode, the insulating ring and the insulating tape.

A step (e): sputtering platinum and stripping. Sputtering transition layer titanium and electrode layer platinum, and peeling off to simultaneously manufacture the anode platinum electrode 103 on the surface, the cathode platinum electrode 104 in the surface and the hole, the insulating ring and the insulating tape. The insulating ring around the flow hole and the insulating tape in the middle of the chip ensure the mutual insulation between the cathode and the anode. The stripped metal area is an electrode, the uncovered metal area is an insulating area, and the insulating ring and the insulating tape are stripped after photoetching patterning and are formed together with the electrode.

Step (f): and (e) repeating the steps (d) to (e) on the other surface to complete the manufacture of the anode platinum electrode 103 and the cathode platinum electrode 104 on the other side.

In some embodiments of the present invention, the silicon dioxide insulating layer may be replaced with other materials such as silicon nitride.

In some embodiments of the present invention, the electrode surface pattern is not limited to a single circular hole, and other patterns may be made.

In some embodiments of the present invention, the single-sided cathode and anode may not be limited to a left-right symmetrical form along the center line, and may be modified by designing an insertion finger shape, etc.

The invention has not been described in detail and is part of the common general knowledge of a person skilled in the art. The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and the preferred embodiments are not exhaustive and do not limit the invention to the precise embodiments described. Various modifications and improvements of the technical solution of the present invention may be made by those skilled in the art without departing from the spirit of the present invention, and the technical solution of the present invention is to be covered by the protection scope defined by the claims.

Claims

1. A four-electrode integrated sensitive electrode of an MEMS (micro-electromechanical system) electrochemical vibration sensor is characterized by comprising a substrate, an insulating layer, a plurality of through holes, a first anode electrode, a first cathode electrode, a second anode electrode and a second cathode electrode; wherein the content of the first and second substances,

2. The integrated sensor electrode of claim 1, wherein the first anode electrode on the first portion and the first cathode electrode on the second portion are symmetrical along a substrate centerline, or the first anode electrode on the first portion and the first cathode electrode on the second portion are interdigitated in design, on the first insulating layer.

3. The integrated sensor electrode of claim 1, wherein the second cathode electrode on the third portion and the second anode electrode on the fourth portion are symmetrical along the substrate centerline, or the second cathode electrode on the third portion and the second anode electrode on the fourth portion are interdigitated.

4. The integrated sensor electrode of claim 1, wherein the first and second insulating layers are patterned to be centrosymmetric.

5. The integrated sensor electrode of claim 1, wherein the substrate is a silicon wafer.

6. The integrated sensor electrode of claim 1, wherein the insulating layer is a silicon dioxide insulating layer or a silicon nitride insulating layer.

7. The integrated sensitive electrode according to claim 1, wherein the electrode surface flow holes are in the shape of single circular holes or other patterns, and preferably the flow hole diameter is 80-150 μm.

8. The integrated sensor electrode of claim 1, wherein the insulating ring has a radial width of 10-20 microns and the insulating tape has a width of 60-100 microns.

9. A method of manufacturing an integrated sensor electrode according to any of claims 1 to 8, comprising:

step (b): etching the substrate and removing photoresist, etching the etched substrate by using deep reactive ions to manufacture a through hole, and removing the residual photoresist on the surface;

step (c): performing thermal oxidation, namely performing thermal oxidation on the etched substrate to form a first insulating layer, a second insulating layer and a through hole side wall insulating layer so as to insulate the substrate;

step (f): and (e) repeating the steps (d) to (e) on the other surface to finish the manufacture of the anode electrode, the cathode electrode, the insulating ring and the insulating tape on the other side.

10. The method of claim 9, wherein the transition layer metal is titanium, preferably having a transition layer thickness of 300 angstroms; the electrode layer metal is platinum, and the thickness of the electrode layer is preferably 2000-3000 angstroms.