Highly selective array MOS sensor and preparation method thereof

Abstract

A highly selective array MOS sensor and a method for preparing the same, the highly selective array MOS sensor comprising: a substrate; a plurality of sensitive units formed on the substrate, the plurality of sensitive units forming an array structure; a heater formed on the substrate, the periphery of the sensitive units; an electrode layer formed on the substrate, the electrode layer being electrically connected to the sensitive units and the heater; wherein the electrode layer comprises a plurality of lead terminals for monitoring the terminal potentials of different combinations of sensitive units. The present invention can achieve highly sensitive responses to different gases by using a plurality of sensitive units in an array structure and a plurality of lead terminals of the electrode layer to form a connection circuit for different combinations of sensitive units.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor sensors, and in particular to a high-selectivity array MOS sensor and a preparation method thereof. Background Art

[0002] With the development of industry and urban transportation, a large number of toxic and harmful gases released from industrial parks, industrial boilers, automobile exhaust, furniture and building materials have filled our living environment with a large number of toxic gases (mainly CO, CO2, SO2, NO2, H2S, formaldehyde, etc.). How to effectively control them? The first key issue is to solve the high-precision, high-sensitivity and rapid detection of their pollution sources. Therefore, a large number of high-sensitivity and high-precision sensors are urgently needed to realize on-site analysis or online monitoring.

[0003] The metal oxide detector is a very important and widely used detector. It is widely used because of its low price and wide range of gas detection (the corresponding sensitive film can be selected according to the gas composition to achieve multiple gas detection).

[0004] However, the existing metal oxide semiconductor (MOS) sensor has poor specificity due to the limitations of design concepts and sensitive materials. In addition to its highly sensitive response to a certain gas for which it is designed, it can also respond to some other gas components. This can easily cause detection errors or even mistakes, and thus it cannot effectively reflect the true situation of the gas in the environment. Summary of the invention

[0005] In view of this, the present invention provides a high-selectivity array MOS sensor and a method for preparing the same, in order to at least partially solve at least one of the above-mentioned technical problems.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] As one aspect of the present invention, a high selectivity array MOS sensor is provided, comprising:

[0008] substrate;

[0009] A plurality of sensitive units are formed on the substrate, and the plurality of sensitive units form an array structure;

[0010] A heater formed on the substrate and outside the sensitive unit;

[0011] An electrode layer, formed on the substrate, the electrode layer being electrically connected to the sensitive unit and the heater;

[0012] Wherein, the electrode layer includes a plurality of lead-out terminals for monitoring the terminal potentials of different sensitive unit combinations.

[0013] As another aspect of the present invention, there is also provided a method for preparing the above-mentioned highly selective array MOS sensor, comprising the following steps:

[0014] forming a heater on a substrate;

[0015] forming an electrode layer on a substrate;

[0016] Coating a photoresist on the substrate to obtain a photoresist mask exposing a sensitive area; wherein the sensitive area includes a portion of the electrode layer area and the substrate area;

[0017] Spray sensitive materials onto sensitive areas;

[0018] Reactive ion etching technology is used to remove the photoresist mask;

[0019] After aging in a nitrogen flow environment, a highly selective array MOS sensor was obtained.

[0020] Based on the above technical solution, compared with the prior art, the present invention has at least one or part of the following beneficial effects:

[0021] (1) The sensitive unit of the present invention adopts a unique array structure design, which has multiple sensitive units, and the electrode layer includes multiple lead-out terminals. Through the connection mode of different combinations of the sensitive units led out by the multiple lead-out terminals, high-precision detection of multiple gases can be achieved;

[0022] (2) At the bottom of the sensitive area, the silicon substrate is hollowed out to leave only 5 to 10 microns of the base as a support beam. This structure can reduce the heat loss of the base;

[0023] (3) A dual-heater structure design is adopted, which makes the heat distribution in the sensitive area more balanced, ensuring that the highly selective array MOS sensor operates at an ideal operating temperature;

[0024] (4) The highly selective array MOS sensor is externally connected to a power supply module that can adjust the voltage of the fourth lead-out terminal of T4, and can intelligently select a corresponding sensitive unit from multiple sensitive units to be in an ideal working state according to different components to be measured, thereby achieving high sensitivity response to different gases;

[0025] (5) Each sensitive unit is modified with a highly specific sensitive material. Graphene quantum dots are used as the basic material, and transition metals such as Co, Mn, Cu, Au, and Ag are selectively doped to increase the hole concentration of graphene quantum dots and promote charge electron transfer. Then, they are compounded with SnO2, ZnO, In2O3, TiO2, and WO3, and molecular imprinting or template molecule technology is used to achieve high selectivity of gas components.

[0026] (6) In the modification and fixation of nano-sensitive materials, precise masking and large-area spraying methods are adopted to achieve high-precision and uniform coating of sensitive materials. The sensitive units prepared by this technology have good uniformity and the thickness of the sensitive units can be precisely controlled, which is impossible to achieve with the spot coating technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of the structure of a highly selective array MOS sensor according to an embodiment of the present invention;

[0028] Figure 2 This is a highly selective array MOS sensor bridge circuit diagram of an embodiment of the present invention;

[0029] Figure 3 yes Figure 1 Schematic diagram of the middle AA section;

[0030] Figure 4 Schematic diagram of the spraying operation of the highly selective array MOS sensor according to an embodiment of the present invention;

[0031] Figure 5 Schematic diagram of the parallel plate electrode structure of the motor layer according to an embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of the interdigitated electrode structure of the electrode layer in an embodiment of the present invention.

[0033] In the above drawings, the meanings of the reference numerals are as follows:

[0034] 1-electrode layer; 2-heater; 3-sensitive unit; 4-base; 41-silicon substrate; 42-silicon nitride layer; 5-photoresist mask; T1-first lead-out terminal; T2-second lead-out terminal; T3-third lead-out terminal; T4-fourth lead-out terminal. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0036] As one aspect of the present invention, Figure 1As shown, a highly selective array MOS sensor is provided, comprising: a substrate 4, a plurality of sensitive units 3, a heater 2 and an electrode layer 1; wherein the plurality of sensitive units 3 are formed on the substrate 4, and the plurality of sensitive units 3 form an array structure; the heater 2 is formed on the substrate 4, and the heater 2 is located at the periphery of the sensitive units 3; the electrode layer 1 is formed on the substrate 4, and the electrode layer 1 is electrically connected to the sensitive units 3 and the heater 2, wherein the electrode layer 1 comprises a plurality of lead terminals for monitoring the terminal potentials of different combinations of sensitive units 3.

[0037] The working principle of the highly selective array MOS sensor is that the gas is adsorbed on the sensitive unit 3, causing the resistance value of the resistor of the sensitive unit 3 to change, and the voltage value at both ends of the electrical connection will also change accordingly, thereby changing the potential of the output end of the electrode layer 1.

[0038] In the embodiment of the present invention, one of the multiple lead-out terminals is used for grounding, another lead-out terminal is used for connecting an adjustable potential, and the remaining lead-out terminals are potential detection terminals. An adjustable voltage power supply module is externally connected to the lead-out terminal connected to the high potential of the high-selectivity array MOS sensor, and a corresponding sensitive unit 3 among the multiple sensitive units 3 can be intelligently selected to be in an ideal working state according to different components to be measured.

[0039] In a preferred embodiment of the present invention, three rectangular sensitive units 3 (S1, S2, S3) form a rectangular array structure, such as Figure 1 and Figure 2 As shown, the electrode layer 1 includes four lead terminals, which are respectively defined as the first lead terminal T1, the second lead terminal T2, the third lead terminal T3 and the fourth lead terminal T4; the first lead terminal T1 and the fourth lead terminal T4 are diagonally arranged, and the second lead terminal T2 and the third lead terminal T3 are diagonally arranged; wherein, the first lead terminal T1 is used for grounding; the fourth lead terminal T4 is used for connecting the adjustable potential; the second lead terminal T2 and the third lead terminal T3 are potential detection terminals. In addition, the heater 2 includes two, which are symmetrically formed on the periphery of the three sensitive units 3.

[0040] For example, Figure 2 As shown, when monitoring U TIT3 , U T1T2 , U T2T4 , each voltage value change includes at least one change in the potential of sensitive unit 3, such as U T1T2 YesR S1 and R S2 The sum of the potential changes, U T2T4 YesR s3 After measuring the changes in potential at these endpoints, the concentration of each component in the mixed gas can be obtained through the neural network algorithm.

[0041] Here, different terminal potentials include resistance changes caused by different sensitive materials, so each terminal potential includes at least one response generated by a gas. The present invention combines the voltages of these test terminals and obtains the accurate concentration of each measured gas component through a neural network algorithm.

[0042] Among them, the neural network algorithm is a mature algorithm, and its principle is equivalent to combining several equations containing unknowns and solving them to obtain the quantities of each unknown. The function of obtaining the concentration of the measured gas component using the neural network algorithm can be realized based on conventional hardware such as single-chip microcomputers and conventional software programming, so the present invention does not involve improvements in procedures and algorithms.

[0043] The number of sensitive units 3 and the number of lead terminals are not limited to the above-mentioned preferred embodiment, i.e., three sensitive units 3 and four lead terminals. The corresponding number and the corresponding circuit connection method can also be designed according to the actual needs of the high-selectivity array MOS sensor to meet the actual monitoring needs of the gas components being measured.

[0044] On the one hand, the present invention improves the selectivity and sensitivity of gas detection by designing an array structure of sensitive units and detecting different terminal potentials formed by multiple lead ends; on the other hand, the present invention also improves the selectivity of detection by selecting sensitive materials of the sensitive unit 3.

[0045] In an embodiment of the present invention, the sensitive unit 3 includes a sensitive material composited with graphene quantum dots, transition metals and metal oxides.

[0046] Each sensitive unit 3 of the present invention is modified with a highly specific sensitive material. According to different selections of sensitive materials of each sensitive unit 3, such as all the same, all different, or some of them are the same (such as two are the same), high-precision detection of one or more gas components can be achieved. For example, multiple sensitive units 3 include one or more of a sensitive material specifically responding to formaldehyde, a sensitive material responding to H2S, and a sensitive material responding to NH3.

[0047] In an embodiment of the present invention, the sensitive material is nano-sized particles; the transition metal includes one or more of Co, Mn, Cu, Au, and Ag; and the metal oxide includes one or more of SnO2, ZnO, In2O3, TiO2, and WO3.

[0048] More specifically, the sensitive material of the embodiment of the present invention uses graphene quantum dots (GQDs) as the basic material, and selectively dopes transition metals such as Co, Mn, Cu, Au, Ag, etc. with different gases to increase the hole concentration of graphene quantum dots and promote charge electron transfer; then metal oxide materials such as SnO2, ZnO, In2O3, TiO2, WO3 are selected to compound with it to form a nano-sensitive material.

[0049] In the embodiment of the present invention, the sensitive material can be but is not limited to Au-graphene quantum dots / In2O3 and C o -Graphene quantum dots / SnO2, etc.

[0050] In an embodiment of the present invention, Figure 1 As shown, the heater adopts a double heater structure design, which is symmetrically formed around the sensitive unit 3; this structure makes the heat distribution in the sensitive area more balanced, so that the sensitive unit 3 is heated evenly, which can ensure that the high-selectivity array MOS sensor works at an ideal operating temperature.

[0051] In an embodiment of the present invention, Figure 5 As shown, the electrode layer 1 is a parallel plate electrode structure, but is not limited thereto. Figure 6 As shown, the electrode layer 1 may also be an interdigitated electrode structure.

[0052] In an embodiment of the present invention, Figure 3 and Figure 4 As shown, the base 4 includes a silicon substrate 41 and a silicon nitride layer 42 from bottom to top;

[0053] A back cavity is formed at the back of the silicon substrate 41, and the back cavity corresponds to the sensitive area position of the sensitive unit 3, and the substrate at the corresponding position of the back cavity forms a support beam.

[0054] like Figure 3 As shown, the thickness H of the support beam is 5 to 10 microns;

[0055] The highly selective array MOS sensor uses a silicon substrate 41 to hollow out only 5 to 10 microns of the base 4 at the bottom of the sensitive area as a support beam. This structure can reduce the heat loss of the base 4.

[0056] The thickness of the silicon nitride layer 42 ranges from 0.2 to 1 micrometer. The design of the silicon nitride layer 42 can ensure that the support beam has a certain strength and is not easily affected by airflow.

[0057] As a preferred embodiment, the thickness of the silicon nitride layer 42 is 1 micron.

[0058] As another aspect of the present invention, there is also provided a method for preparing the above-mentioned highly selective array MOS sensor, comprising the following steps:

[0059] The surface of the silicon nitride layer 42 is photolithographically processed to obtain the structure of the heater 2 , and then a layer of Pt / Cr is sputtered with a thickness of 100 to 300 nm, preferably 120 nm, and then peeled off to obtain the heater 2 .

[0060] The surface of the silicon nitride layer 42 is photolithographically processed to obtain the structure of the electrode layer 1 , and then a layer of Au / Cr is sputtered with a thickness of 100 to 300 nm, preferably 200 nm, and then peeled off to obtain the electrode layer 1 .

[0061] It is worth mentioning that the order of the steps of forming the heater 2 and the electrode layer 1 on the substrate 4 is not limited, as long as the heater 2 is electrically connected to the electrode layer 1 .

[0062] like Figure 4 As shown, a layer of photoresist with a thickness of 2 to 3 microns is coated on the silicon nitride layer 42 to obtain a photoresist mask 5 exposing the sensitive area; wherein the sensitive area includes a part of the electrode layer area and the substrate area;

[0063] More specifically, the sensitive area is exposed, and the photoresist in the non-sensitive area is retained, forming a protective mask for the non-sensitive area when the sensitive material is sprayed.

[0064] In an embodiment of the present invention, the sensitive material is sprayed on the sensitive area; Figure 4 As shown, the prepared sensitive material is evenly sprayed on a predetermined sensitive area using a spraying technique, and the thickness is determined according to the characteristics of the sensitive material.

[0065] Among them, before spraying, molecular imprinting technology or template molecule technology is used to make the sensitive material form a selective recognition structure for the gas to be tested, that is, to obtain an adsorption and analysis structure with a characteristic shape containing a certain gas, thereby achieving high selectivity.

[0066] In the embodiment of the present invention, the spot coating technology can be selected for the modification of sensitive materials, but in the preferred embodiment of the present invention, such as Figure 4 As shown, by using a photoresist mask 5 and combining it with a large-area spraying technology, a good consistency effect of the sensitive unit 3 can be achieved, and the thickness of the sensitive unit 3 can be accurately controlled according to the spraying rate and time.

[0067] The photoresist mask 5 is removed by using reactive ion etching technology to expose the lead-out end of the electrode layer 1 .

[0068] The thermistor is aged in a nitrogen flow environment, that is, aged at high temperature, to obtain a high-selectivity array MOS sensor.

[0069] In the embodiment of the present invention, the specific conditions of aging include: a temperature of 400 to 600° C. and a time of 4 to 8 hours.

[0070] As a preferred embodiment, the aging temperature may be selected to be 350°C.

[0071] In an embodiment of the present invention, before the step of obtaining the photoresist mask 5 for exposing the sensitive area, the preparation method further comprises the following steps: using an etching technique to remove a portion of the substrate 4 corresponding to the position of the sensitive area to form a back cavity.

[0072] In an embodiment of the present invention, before the step of forming the electrode layer 1 on the substrate 4 , the preparation method further comprises: cleaning the silicon substrate 41 , and then growing a silicon nitride layer 42 on the surface of the silicon substrate 41 .

[0073] In summary, in the modification and fixation of nano-sensitive materials, precise masking and large-area spraying methods are adopted to achieve high-precision and uniform coating of sensitive materials. The sensitive unit 3 prepared by this technology has good uniformity and the thickness of the sensitive unit 3 can be precisely controlled, which is impossible to achieve with the spot coating technology.

[0074] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An array MOS sensor, characterized in that: include: A substrate, wherein the substrate comprises a silicon substrate and a silicon nitride layer from bottom to top; a back cavity is formed at the back of the silicon substrate, the back cavity corresponds to the sensitive area position of the sensitive unit, and the substrate at the position corresponding to the back cavity forms a support beam; the thickness of the support beam is 5 to 10 microns; A plurality of sensitive units are formed on the substrate, and the plurality of sensitive units form an array structure; A heater formed on the substrate and outside the sensitive unit; An electrode layer, formed on the substrate, the electrode layer being electrically connected to the sensitive unit and the heater; Wherein, the electrode layer includes a plurality of lead terminals for monitoring the terminal potentials of different sensitive unit combinations; Among them, one of the multiple lead-out terminals is used for grounding, another lead-out terminal is used for connecting an adjustable potential, and the remaining lead-out terminals are potential detection terminals; The sensitive unit includes a sensitive material composited with graphene quantum dots, transition metals and metal oxides; the sensitive material is a nano-sized particle; The transition metal includes one or more of Co, Mn, Cu, Au, and Ag; The metal oxide includes one or more of SnO2, ZnO, In2O3, TiO2, and WO3.

2. The array MOS sensor according to claim 1, characterized in that: The array MOS sensor comprises: Three rectangular sensitive units, the three rectangular sensitive units form a rectangular array structure; Four lead-out terminals are respectively located at four ends of the rectangular array structure, and the four lead-out terminals are respectively defined as a first lead-out terminal, a second lead-out terminal, a third lead-out terminal and a fourth lead-out terminal; wherein the first lead-out terminal is used for grounding; the fourth lead-out terminal is used for connecting an adjustable potential; the second lead-out terminal and the third lead-out terminal are respectively potential detection terminals; Two heaters are symmetrically formed on the periphery of the sensitive unit.

3. The array MOS sensor according to claim 1, characterized in that: in, The electrode layer includes a parallel plate electrode structure or an interdigitated electrode structure; The material of the electrode layer includes Au / Cr, and the thickness of the electrode layer includes 100-300 nm.

4. The array MOS sensor according to claim 3, characterized in that: in, The thickness of the electrode layer is 200 nm.

5. The array MOS sensor according to claim 1, characterized in that: The sensitive materials of the multiple sensitive units are all the same, all different, or partially the same.

6. The array MOS sensor according to claim 1, characterized in that: The material of the heater includes Pt / Cr, and the thickness of the heater includes 100-300 nm.

7. The array MOS sensor according to claim 6, characterized in that: The thickness of the heater is 120 nm.

8. The array MOS sensor according to claim 1, characterized in that: The thickness of the silicon nitride layer is 0.2-1 micrometer.

9. A method for preparing an array MOS sensor according to any one of claims 1 to 8, characterized in that: The steps include: forming a heater on a substrate; forming an electrode layer on a substrate; Coating a photoresist on the substrate to obtain a photoresist mask exposing a sensitive area; wherein the sensitive area includes a portion of the electrode layer area and the substrate area; Spray sensitive materials onto sensitive areas; Reactive ion etching technology is used to remove the photoresist mask; After aging in a nitrogen flow environment, a highly selective array MOS sensor was obtained.

10. The preparation method according to claim 9, characterized in that: Before the step of spraying the sensitive material on the sensitive area, the preparation method further comprises the following step: using molecular imprinting technology or template molecule technology to make the sensitive material form a selective recognition structure for the gas to be detected.

11. The preparation method according to claim 9, characterized in that: Before the step of obtaining a photoresist mask for exposing the sensitive area, the preparation method further comprises the following steps: using an etching technique to remove a portion of the silicon substrate corresponding to the position of the sensitive area to form a back cavity; The specific conditions of the aging include: a temperature of 400-600° C. and a time of 4-8 hours.

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