阅读说明：本技术 一种传感器集成芯片及其制备 (Sensor integrated chip and preparation thereof ) 是由 胡训博 傅邱云 于 2020-04-17 设计创作，主要内容包括：本发明属于电化学传感器领域,公开了一种传感器集成芯片及其制备,该电化学传感器集成芯片,包括位于晶圆级半导体基底上的参考电极和对电极,在参考电极和对电极上各设置有绝缘层,外延硅层则外延沉积在绝缘层上；该外延硅层的一端位于参考电极的上方,另一端位于对电极的上方；半导体基底与外延硅层包围形成内部中空结构,该中空结构用于作为电解液腔容纳电解液；外延硅层上还开设有孔洞,在该外延硅层的表面及孔内壁上自内向外均依次沉积有工作电极绝缘层、工作电极层和隔膜层；孔洞与电解液腔相连通。本发明通过采用Surface MEMS(表面微机械)工艺在半导体基底(如硅基晶圆)上实现规模制备电流型电化学传感器,降低传感器成本,提高普及率。(The invention belongs to the field of electrochemical sensors, and discloses a sensor integrated chip and a preparation method thereof, wherein the electrochemical sensor integrated chip comprises a reference electrode and a counter electrode which are positioned on a wafer-level semiconductor substrate, insulating layers are respectively arranged on the reference electrode and the counter electrode, and an epitaxial silicon layer is epitaxially deposited on the insulating layers; one end of the epitaxial silicon layer is positioned above the reference electrode, and the other end of the epitaxial silicon layer is positioned above the counter electrode; the semiconductor substrate and the epitaxial silicon layer are surrounded to form an internal hollow structure, and the hollow structure is used as an electrolyte cavity to contain electrolyte; the epitaxial silicon layer is also provided with a hole, and a working electrode insulating layer, a working electrode layer and a diaphragm layer are sequentially deposited on the surface of the epitaxial silicon layer and the inner wall of the hole from inside to outside; the hole is communicated with the electrolyte cavity. The invention realizes the scale preparation of the current type electrochemical sensor on a semiconductor substrate (such as a silicon-based wafer) by adopting the Surface MEMS (Surface micro-mechanical system) process, reduces the cost of the sensor and improves the popularization rate.)

1. A semiconductor wafer-level electrochemical sensor integrated chip based on Surface MEMS technology for markers of nitrogen-containing diseases in human exhaled breath is characterized by comprising a reference electrode and a counter electrode which are positioned on a wafer-level semiconductor substrate and are arranged oppositely, wherein insulating layers are respectively arranged on the reference electrode and the counter electrode, and an epitaxial silicon layer is epitaxially deposited on the insulating layers; one end of the epitaxial silicon layer is positioned above the reference electrode and is in contact with the insulating layer positioned on the reference electrode, and the other end of the epitaxial silicon layer is positioned above the counter electrode and is in contact with the insulating layer positioned on the counter electrode; the semiconductor substrate and the epitaxial silicon layer are surrounded to form an internal hollow structure, and the hollow structure is used as an electrolyte cavity to contain electrolyte;

the epitaxial silicon layer is also provided with a hole, and a working electrode insulating layer, a working electrode layer and a diaphragm layer are sequentially deposited on the surface of the epitaxial silicon layer and the inner wall of the hole from inside to outside; the hole is communicated with the electrolyte cavity.

2. The electrochemical sensor integrated chip of claim 1, wherein the wafer-level semiconductor substrate is a silicon wafer substrate;

the supporting layer of the working electrode is prepared from the epitaxial silicon layer, and the thickness of the epitaxial silicon layer is 10-100 microns.

3. The electrochemical sensor integrated chip of claim 1, wherein the epitaxial silicon layer is a polycrystalline silicon epitaxial layer or a monocrystalline silicon epitaxial layer.

4. The electrochemical sensor integrated chip of claim 1, wherein the projected size of the electrochemical sensor on the plane of the surface of the wafer-level semiconductor substrate is 25-400 mm²。

5. The electrochemical sensor integrated chip according to claim 1, wherein the overall height of the electrochemical sensor is 300 to 800 μm.

6. The electrochemical sensor integrated chip of claim 1, wherein the electrolyte chamber is fabricated by etching a sacrificial layer in a Surface MEMS process.

7. The electrochemical sensor integrated chip of claim 1, wherein the electrochemical sensor is capable of real-time detection of exhaled breath nitric oxide, FeNO, gas by selection of the corresponding working electrode, electrolyte and selective membrane.

8. The method for preparing the integrated chip of the electrochemical sensor according to any one of claims 1 to 7, wherein the integrated chip of the electrochemical sensor is prepared by a Surface MEMS process fully compatible with a planar semiconductor process, the process comprises the steps of preparing patterns of a reference electrode and a counter electrode on a wafer-level semiconductor substrate, preparing corresponding patterns of an insulating layer for protecting the reference electrode and the counter electrode, depositing and preparing patterns of a sacrificial layer, epitaxially growing and depositing a silicon epitaxial layer, preparing holes on the silicon epitaxial layer by deep ion etching, preparing an insulating layer of a working electrode and a working electrode by utilizing atomic layer deposition, preparing a diaphragm layer, and finally corroding the sacrificial layer through the holes to release an electrolyte cavity, so that the integrated chip of the semiconductor wafer-level electrochemical sensor of the marker of nitrogen-containing diseases exhaled by human body can be obtained.

Technical Field

The invention belongs to the field of electrochemical sensors, and particularly relates to a sensor integrated chip and preparation thereof, in particular to a silicon-based wafer-level electrochemical sensor for nitrogen-containing disease markers of human exhaled breath, which can sense the human exhaled breath.

Background

Some trace gases with the concentration from millimole per liter to picomole per liter in the exhaled gas of the human body are products of the metabolism of the human body, and the difference of the types and the concentrations of the trace gases can reflect the metabolism level of different individuals and the difference of the functions of the human body, so the health condition of the human body can be reflected. For example, nitric oxide NO is produced in the airways and is considered as a marker of airway inflammation, and the levels of feno (fractionated oxygenated nitrile oxide) have been shown to be closely related to asthma, allergy, chronic cough, tuberculosis, and the like. In 2006, gina (global Initiative for assay) incorporated the detection of fenoo (fractionated exogenous nitric oxide) into the asthma management program. In 2008, the respiratory disease society of the Chinese medical society also listed exhaled nitric oxide in the guidelines for prevention and treatment of bronchial asthma, and the nitric oxide in exhaled air is officially taken as a clinical routine detection project in China. The us thoracic association/european respiratory disease society in 2009 clarified the clinical application value, application range and detection method of FeNO. At present, under the frequent conditions of various Respiratory diseases such as SARS (severe Acute Respiratory syndrome), new coronary pneumonia and the like, the clinical detection of FeNO has more requirements and significance.

An ideal sensor for the analysis of the trace gases generated in the breath, FeNO, must have a very high performance: extremely low detection limits (ppb levels) are required; accurate quantitative detection is required; fast response (less than 10 seconds); the device can work under the condition of variable humidity without being interfered by expired gases such as oxygen, has good repeatability and the like. Methods that can be used to detect exhaled nitric oxide are mainly chemiluminescence, laser technology and electrochemical methods. Chemiluminescence analyzers are very sensitive, have fast response times, but are bulky, expensive, and can be used to calibrate other instruments. The laser-based optical sensor method has good selectivity, reliable accuracy and precision and short response time, but the whole detection system needs to be placed in a liquid nitrogen cryostat, and is not suitable for detection in places other than a laboratory. Only the electrochemical sensor can be embedded into a handheld device, the whole weight is less than 1Kg, and the portable device has the advantage of portability. The current clinical measurement system for nitric oxide based on electrochemical sensor technology is mainly NIOX MINO of Aerocrine in Sweden and NObreak of Bedfount in UK, but still has the problems of large volume and expensive detection service charge, and the popularization rate is not high. In order to reduce the cost, a fast-response high-performance small-sized FeNO sensor chip which can be produced in a large scale is urgently needed, so that a low-cost detector which is more miniaturized and can be independently used by each patient is prepared, the popularization rate is improved, and the disease control is facilitated. Semiconductor thin film sensors such as metal oxide gas sensors and the like are considered to be inexpensive sensors that are small in size and easy to mass-produce, however, their slow response, poor selectivity and high power consumption during operation limit their use.

In 2015, Swedish researchers provided a small-sized electrochemical NO sensor based on a Bulk MEMS (Micro-Electro-Mechanical System) process for preparing a microporous electrode, wherein the sensitivity of the microporous electrode is greatly improved to 4 muA/ppm/cm²The lower detection limit is as low as 0.3 ppb. Meanwhile, the response time and the recovery time are reduced to 6 seconds due to the reduction of the size of the sensor. However, such micro-hole electrodes need to be combined with a counter electrode on a PCB to form a complete sensor, and are still bulky and not suitable for being manufactured by an integrated process. Subsequently, they have further structural improvement, and a micropore sensitive electrode is prepared on an SOI (silicon-on-insulator) wafer by adopting a Bulk MEMS process, a counter electrode and a reference electrode are prepared on glass, and then an electrolyte chamber is formed by using a bonding mode. This approach further reduces the volume of the sensor chip, but the process is still too complex.

Disclosure of Invention

Aiming at the defects or improvement requirements in the prior art, the invention aims to provide a sensor integrated chip and preparation thereof, and by taking a silicon wafer substrate as an example, the silicon wafer level electrochemical sensor integrated chip for the nitrogen-containing disease marker in human exhaled air can be correspondingly obtained; meanwhile, due to the reduction of the size of the sensor, the response time and the recovery time can be further reduced, and the real-time detection of the FeNO can be realized.

In order to achieve the above object, according to one aspect of the present invention, there is provided a semiconductor wafer-level electrochemical sensor integrated chip based on Surface MEMS technology, including a reference electrode and a counter electrode on a wafer-level semiconductor substrate and disposed opposite to each other, wherein an insulating layer is disposed on each of the reference electrode and the counter electrode, and an epitaxial silicon layer is epitaxially deposited on the insulating layer; one end of the epitaxial silicon layer is positioned above the reference electrode and is in contact with the insulating layer positioned on the reference electrode, and the other end of the epitaxial silicon layer is positioned above the counter electrode and is in contact with the insulating layer positioned on the counter electrode; the semiconductor substrate and the epitaxial silicon layer are surrounded to form an internal hollow structure, and the hollow structure is used as an electrolyte cavity to contain electrolyte;

the epitaxial silicon layer is also provided with a hole, and a working electrode insulating layer, a working electrode layer and a diaphragm layer are sequentially deposited on the surface of the epitaxial silicon layer and the inner wall of the hole from inside to outside; the hole is communicated with the electrolyte cavity.

As a further preferred aspect of the present invention, the wafer-level semiconductor substrate is a silicon wafer substrate;

the supporting layer of the working electrode is prepared from the epitaxial silicon layer, and the thickness of the epitaxial silicon layer is 10-100 microns.

In a further preferred embodiment of the present invention, the epitaxial silicon layer is a polycrystalline silicon epitaxial layer or a monocrystalline silicon epitaxial layer.

In a further preferred embodiment of the present invention, the projection size of the entire electrochemical sensor on the plane of the surface of the wafer-level semiconductor substrate is 25 to 400mm²。

In a further preferred embodiment of the present invention, the electrochemical sensor has an overall height of 300 to 800 μm.

As a further preferred aspect of the present invention, the electrolyte chamber is prepared by a method of etching a sacrificial layer in a Surface MEMS process.

As a further preferred aspect of the present invention, the electrochemical sensor can be used for real-time detection of exhaled breath nitric oxide, FeNO, gas by selecting the corresponding working electrode, electrolyte and selective membrane.

According to another aspect of the invention, the invention provides a method for preparing the above electrochemical sensor integrated chip, which is characterized in that the sensor chip is prepared by adopting a Surface MEMS process fully compatible with a planar semiconductor process, the process comprises the steps of preparing patterns of a reference electrode and a counter electrode on a wafer-level semiconductor substrate, then preparing corresponding patterns of an insulating layer to protect the reference electrode and the counter electrode, then depositing and preparing patterns of a sacrificial layer, then epitaxially growing and depositing a silicon epitaxial layer, preparing holes on the silicon epitaxial layer by deep ion etching, then preparing an insulating layer of a working electrode and a working electrode by utilizing atomic layer deposition, then preparing a diaphragm layer, and finally corroding the sacrificial layer through the holes to release an electrolyte cavity, thereby obtaining the semiconductor wafer-level electrochemical sensor integrated chip with the markers of nitrogen-containing diseases in exhaled air of a human body.

Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides a method for preparing an electrolyte cavity by etching a sacrificial layer, which can replace a complex traditional method to realize the preparation of the electrolyte cavity on a substrate in a planar process mode.

(2) In order to ensure enough three-phase interface area of the sensitive electrode, electrolyte and gas, the invention provides a ppb level sensor which adopts polycrystalline silicon (or monocrystalline silicon) with thicker epitaxial growth (the thickness can be 10-100 mu m) as a support structure layer of the sensitive electrode, prepares a micropore electrode structure to improve the sensitivity and can meet the real-time detection requirement of nitrogen-containing disease markers FeNO in human exhaled air.

(3) The proposal provided by the invention can realize the preparation of the electrochemical sensor by adopting the Surface MEMS process compatible with the semiconductor planar process, and can realize the scale preparation on the silicon-based wafer (or other wafer-level semiconductor substrates), thereby reducing the cost of the sensor and improving the popularization rate of the sensor.

Taking a wafer-level semiconductor substrate as a silicon-based wafer as an example, a Surface MEMS (micro electro mechanical System) process is adopted to realize scale preparation of the current-type FeNO electrochemical sensor on the silicon-based wafer, and as the process is more planar, the area of a three-phase interface of a sensitive electrode, electrolyte and gas is greatly reduced, and the largest influence is the detection lower limit of the sensor. The commercially available ppb level sensitive element of the current NO electrochemical gas sensor detector generally can meet the requirements of users when the detection lower limit is about 5 ppb. The detection lower limit of the FeNO electrochemical sensor prepared by the Surface MEMS process can be about 3 ppb.

In addition, the small-sized electrochemical NO sensor prepared based on the Bulk MEMS process has the advantage that the size of the sensor is smaller than that of the traditional electrochemical NO sensor (the size of the sensor in the invention can be as small as 25 mm)²For example, it may be 25 to 400mm²) The response time and recovery time are reduced to 6 seconds. And if the Surface MEMS technology is adopted, the size of the sensor is further reduced, the response time and the recovery time are further reduced, the feasibility for meeting the requirement of quickly detecting the nitrogen-containing disease marker FeNO in the exhaled air of the human body in real time is realized, and the sensor can be used at room temperature.

Drawings

FIG. 1 is a schematic diagram of a current-mode electrochemical sensor suitable for Surface MEMS process according to the present invention.

Fig. 2(a) and 2(b) are enlarged schematic views of the working electrode and its supporting structure in different regions of the electrochemical sensor shown in fig. 1.

The meanings of the reference symbols in the figures are as follows: 1 is a silicon substrate, 2 is epitaxial silicon, 3 is a reference electrode, 4 is a counter electrode, 5 is an insulating layer, 6 is a working electrode insulating layer, 7 is a working electrode layer, and 8 is a diaphragm layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

By taking a silicon wafer substrate as an example, the invention adopts the Surface MEMS process to realize scale preparation of the current type FeNO electrochemical sensor on the silicon wafer, and because the process is more planar, the thickness of the sensor is reduced to be less than 30 percent of that of the Bulk MEMS process, and the area of a three-phase interface of a sensitive electrode, electrolyte and gas is also greatly reduced, more rigorous requirements are provided for the material, the structure and the process of the sensor. Particularly, the preparation of the electrolyte cavity and the micropore electrode, the invention provides a solution for realizing ppb level electrochemical gas sensors by adopting the method for preparing the electrolyte cavity by etching the sacrificial layer and adopting the epitaxially grown thicker polysilicon as the support structure layer of the sensitive electrode.

Example 1

The device prototype structure of the silicon-based wafer-level electrochemical sensor for the nitrogenous disease marker exhaled by the human body is shown in figure 1, and the silicon-based wafer-level electrochemical sensor comprises a reference electrode and a counter electrode which are positioned on a silicon wafer substrate and are arranged opposite to each other, wherein insulating layers are respectively arranged on the reference electrode and the counter electrode, and an epitaxial silicon layer is epitaxially deposited on the insulating layers; one end of the epitaxial silicon layer is positioned above the reference electrode and is contacted with the insulating layer positioned on the reference electrode, and the other end of the epitaxial silicon layer is positioned above the counter electrode and is contacted with the insulating layer positioned on the counter electrode; the silicon wafer substrate and the epitaxial silicon layer are surrounded to form an internal hollow structure, and the hollow structure is used as an electrolyte cavity to contain electrolyte;

the epitaxial silicon layer is also provided with a hole, and a working electrode insulating layer, a working electrode layer and a diaphragm layer are sequentially deposited on the surface of the epitaxial silicon layer and the inner wall of the hole from inside to outside; the hole is communicated with the electrolyte cavity. The specific materials used for the septum may be directly referred to in the related art, as long as the device is enabled to operate at varying humidity without interference from exhaled gases such as oxygen.

Correspondingly, the structure can be realized by adopting a sacrificial layer method in the Surface MEMS process to prepare an electrolyte cavity and combining an epitaxial growth method to grow thicker silicon as a working electrode supporting structure. Firstly, preparing patterns of a reference electrode and a counter electrode on a silicon substrate through semiconductor processes such as sputtering, photoetching and the like, then preparing corresponding patterns of an insulating layer to protect the reference electrode and the counter electrode, then depositing and preparing patterns of a sacrificial layer, then depositing polycrystalline silicon and growing a thick polycrystalline silicon layer through epitaxy, preparing a microporous structure by deep ion etching, preparing an insulating layer of a working electrode and the working electrode by atomic layer deposition, then preparing a diaphragm layer, corroding the sacrificial layer to release an electrolyte cavity, and finally soaking in electrolyte. By selecting sensitive electrodes (namely working electrodes), electrolyte and diaphragm materials, the sensor can be used for measuring ppb-level trace gas, and is particularly suitable for real-time measurement of FeNO.

The present invention relates to surface MEMS (surface micro-mechanical system) process, which is not described in detail, for example, refer to the instrument book "MEMS materials and process handbook" (author (mei), gades, (mei), lindane, Huang Qing an, etc., press, southeast university press.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.