CN106841314B - A low-power micro-nano gas sensor based on nano-TiO2 and its preparation method - Google Patents

Abstract

The invention discloses a low-power micro-nano gas sensor based on nano-TiO ₂ and a preparation method thereof. The sensor includes a SiO ₂ -Si ₃ N ₄ masking layer, a silicon substrate, and a SiO ₂ -Si ₃ N ₄ from bottom to top. ‑SiO ₂ ‑Si ₃ N ₄ composite insulation layer, electrode layer, sensitive material layer. By arranging temperature-measuring electrodes, the core temperature of the chip is measured in real time. Under the Si substrate, most of the Si is removed by wet etching to form a SiO ₂ ‑Si ₃ N ₄ ‑SiO ₂ ‑Si ₃ N ₄ composite suspension film structure. On the suspension film are centrally symmetrical and spirally arranged heating electrodes and sensitive electrode. The sensitive material is located on the sensitive electrode, and the _TiO2 film and the Ti film are sequentially sputtered in the sensitive material area, where the _TiO2 film is used to define the growth area of the subsequent nanorods, and the Ti source is oxidized into _TiO2 nanorods by hot hydrochloric acid vapor method Prepare the sensitive layer by growing _TiO2 nanorods on the _TiO2 film. The nanorods of the invention are bridged and connected, have a very high specific surface area and better gas response characteristics; the mechanical properties of the suspension film are optimized, heat transfer is reduced, and the temperature is precisely and controllable. The process is simplified and the generation of parasitic electric field is avoided.

Description

A low-power micro-nano gas sensor based on nano-TiO2 and its preparation method

technical field

The invention relates to a structure and a preparation method of a low-power consumption micro-nano gas sensor based on nano- _TiO2 .

Background technique

Many areas of national production and life have a wide range of requirements for the detection of gas types and concentrations. For example, the air quality in confined spaces such as homes, offices, and carriages directly affects people's comfort. If toxic and harmful gases are not detected in time, an alarm will be triggered, and even human life will be threatened. In the field of industrial production, such as petrochemical, pharmaceutical, rubber, leather, etc., especially in workplaces that produce toxic, flammable or odorous gases, it is necessary to detect, monitor and alarm various toxic gases in production. And in the field of agriculture, the level of oxygen or carbon dioxide will directly affect the growth of crops.

Gas sensors are an effective means of gas detection, which can realize real-time monitoring of specific gases and analysis of gas components, etc., and have great application potential in the fields of national production and life. Since the advent of semiconductor metal oxide ceramic gas sensors in 1962, semiconductor gas sensors have become the most widely used and most practical type of gas sensors. Semiconductor gas sensors are components made of metal oxide semiconductor materials. At a certain temperature, surface adsorption or reaction occurs when interacting with gas, causing conductivity or volt-ampere characteristics or surface potential changes characterized by carrier movement. . Therefore, metal oxide gas sensors are generally composed of metal oxide sensitive elements and heating elements.

Among them, the sensitive element has changed from the initial bulk form to the thick film form based on screen printing technology, and now to the thin film form based on MEMS technology, so that the specific surface area of the sensitive material is continuously increased, and the gas response characteristics are gradually enhanced. In particular, various forms of metal oxide nanomaterials studied in recent years, such as nanorods, nanospheres, nanowires, etc., and thin film materials bridged by countless nanometer monomers have extremely high gas-sensing properties.

The heating element is also developing towards the direction of continuous reduction in volume and high integration of each structure. The heating element and sensitive element are integrated on a micron-level device to realize functions such as fast heating and fast resistance measurement, and are formed by releasing the heat insulation groove Compared with ordinary sensors, it is easier to meet the requirements of portable and low-power gas sensors in various industries today. However, the micro-heater composed of various layers of thin films is prone to rupture due to the complexity of the process and the stress of the thin film, which reduces the yield of the device.

In addition, the integration of nano-film materials and low-power micro-heating plates is a difficult point in the preparation of micro-nano gas sensors. How to integrate the nano-film material with high sensitivity and the process of preparing low-power micro-heating plate is a research hotspot.

Contents of the invention

The technical problem to be solved by the invention is to overcome the incompatibility between the preparation of nanometer materials and the traditional MEMS technology, so that the nanometer sensitive materials can be positioned and grown uniformly under the premise of maintaining high sensitivity. At the same time, the mechanical properties of the gas sensor suspension film are improved, and the temperature control electrode is set, thereby providing a metal oxide gas sensor and its preparation method, simplifying the sensor integration process, and preparing a low-power consumption sensor with precise temperature control that can be mass-produced gas sensor.

To achieve the above object, the present invention is achieved by taking the following technical solutions:

A kind of preparation method based on nano TiO ₂ low-power micro-nano gas sensor, comprises the steps:

(1) SiO ₂ -Si ₃ N ₄ double-layer composite films were prepared by thermal oxidation and low-pressure chemical vapor deposition on the front and back of the Si substrate, respectively;

(2) On the front SiO ₂ -Si ₃ N ₄ double-layer composite film, use plasma enhanced chemical vapor deposition to deposit SiO ₂ and Si ₃ N ₄ in sequence, and anneal at a certain temperature;

(3) On the front insulating layer, the patterns of the sensitive electrode and the lead plate, the heating electrode and the lead plate, the temperature measuring electrode and the lead plate are obtained through a uniform photolithography process;

(4) Sputtering a Cr bonding layer on the heating electrode and the lead pad, the sensitive electrode and the lead pad, the temperature measuring electrode and the lead pad pattern, and then sputtering the Au layer on the bonding layer;

(5) Obtain the sensitive electrode and the lead plate, the heating electrode and the lead plate, the temperature measuring electrode and the lead plate through the stripping process, and perform annealing treatment;

(6) On the rectangular area surrounded by the sensitive electrode, the sensitive layer pattern is obtained through a photolithography process;

(7) sputter _TiO2 thin film on the sensitive layer pattern, define the subsequent nanorod growth position; sputter Ti thin film on _TiO2 thin film, provide titanium source;

(8) Utilize hot hydrochloric acid vapor method to prepare _TiO Nanorod;

(9) Adopting the same photolithography process as in step (3) to obtain the insulating groove on the back of the Si substrate, that is, to complete the fabrication of the low-power micro-nano gas sensor.

Further scheme in above-mentioned technology also is:

In the step (1), the thickness of the SiO ₂ film in the SiO ₂ -Si ₃ N ₄ double-layer composite film is 500 nm, and the thickness of the Si ₃ N ₄ film is 150 nm.

In the step (2), sequentially deposit SiO ₂ with a thickness of 500nm and Si ₃ N ₄ with a thickness of 150nm, and anneal at 500°C-600°C for 5-7h.

In the step (4), the sputtered Cr adhesive layer has a thickness of 50 nm, and the sputtered Au layer has a thickness of 250 nm.

In the step (5), the annealing is performed at 260°C-300°C for 10-30min.

In the step (7), the thickness of the sputtered _TiO2 film is 30nm; the thickness of the sputtered Ti film is 300nm.

In described step (8), prepare _TiO The method for nanorod is as follows:

8a) Place the chip sputtered with _TiO2 thin film and Ti film on a small platform in a high-pressure hydrothermal reactor, mix hydrochloric acid and deionized water at a volume ratio of 1:10 and add it to the reactor, and heat it at 150°C Keep warm for 3.5 hours;

8b) After cooling, take out the chip, wash with ethanol and deionized water in order to remove impurities on the chip surface, and dry at 100°C for 0.5h to obtain a TiO ₂ nanorod film.

In the step (9), preparing the insulating groove on the back side of the Si substrate includes the following steps:

9a) Through the photolithography process, the photoresist is used as a mask layer, and the Si ₃ N ₄ -SiO ₂ layer at the window of the groove is removed by deep dry etching, and the photoresist is removed by the lift-off process to obtain the silicon substrate. Insulation tank graphics;

9b) Spin-coat photoresist on the front of the chip, after drying at 90°C, drop PDMS onto the front of the chip until the front is completely covered, dry at 70°C for 1 hour, stick the front of the chip on a glass sheet, and place the back of the chip Apply a circle of PDMS to make the chip stick firmly on the glass;

9c) Put the chip together with the glass sheet into a 25% tetramethylammonium hydroxide TMAH solution, corrode at 85°C for 16 hours to form an insulating groove; gently tear off the PDMS, soak in acetone, remove the photoresist and The residual PDMS was dried at 100°C for 1 hour to obtain the sensor.

The present invention further provides a low-power micro-nano gas sensor based on nano- _TiO2 made according to the above-mentioned process method, including a Si substrate, the back side of the Si substrate is provided with a thermal insulation groove, and the back side of the Si substrate is followed by a _SiO2 masking layer and Si ₃ N ₄ masking layer, the front side is an insulating layer composed of SiO ₂ -Si ₃ N ₄ -SiO ₂ -Si ₃ N ₄ four-layer film, and a pair of sensitive electrodes and their lead pads, two For the heating electrode and its lead plate, two pairs of temperature measuring electrodes and their lead plate, each electrode is located on the same plane, and is prepared by the same material and the same process. The sensitive material is located above the sensitive electrode in the center, and the sensitive layer is composed of thin film and nanorod structure.

Further scheme in above-mentioned structure also is:

The sensitive material is arranged in a rectangular shape at the center of the sensor. A pair of symmetrically distributed spiral-shaped electrode wires lead out from the sensitive electrode and connect to the electrode lead plate; the sensitive electrode has an interdigital structure and is in full contact with the sensitive layer. There are two pairs of symmetrically distributed heating wires in a double helix structure leading out from the sensitive electrode side, and connected to the lead plate of the heating element; surrounding the sensitive electrode, the temperature measuring resistors are respectively arranged on both sides, and each electrode has an independent lead plate, which is distributed on both sides. On the side, all electrodes and lead pads of the sensor are symmetrically arranged in the center.

The sensitive layer is composed of TiO ₂ film and TiO ₂ nanorods, the insulating layer is composed of SiO ₂ -Si ₃ N ₄ -SiO ₂ -Si ₃ N ₄ four-layer film, and the masking layer is composed of SiO ₂ -Si ₃ N ₄ double-layer film composite. Sensitive electrodes, heating electrodes, temperature measuring resistors and lead plates are made of Cr-Au film.

Compared with the prior art, the present invention has the following advantages:

1. Prepare a sensitive layer by sputtering TiO ₂ thin film and Ti thin film, and oxidizing the Ti source to TiO ₂ nanorods by hot hydrochloric acid vapor method, so that TiO ₂ nanorods grow on the TiO ₂ thin film. Compared with simple sputtering films, the specific surface area of sensitive materials is increased, so that it has better gas response characteristics; compared with simply growing TiO ₂ nanorods on electrodes, on an extremely thin layer of TiO ₂ film The growth positions the growth position of the TiO ₂ nanorods better, so that the nanorods are concentrated in the positioning area, which makes it controllable, and can maintain consistency for mass production.

2. The insulating layer is composed of SiO ₂ -Si ₃ N ₄ -SiO ₂ -Si ₃ N ₄ four-layer film from bottom to top, and becomes a suspension film after wet etching the heat insulation groove. Prepare the first layer of SiO ₂ by thermal oxidation method to reduce the intrinsic stress caused by direct bonding, as a buffer layer between Si and Si ₃ N ₄ , and then use PECVD to deposit SiO ₂ and Si ₃ N ₄ layers. On the one hand, use The PECVD method has the advantages of high mechanical strength of the deposited film, which increases the strength of the suspended film. On the other hand, the four-layer interlaced film suppresses the generation of stress between the four-layer films, and uses annealing to greatly eliminate the residual stress between the four-layer films. This approach optimizes the mechanical properties of the suspension.

3. A centrally symmetrical temperature measuring element is set, and the temperature of the sensitive area is determined by measuring the resistance of the temperature measuring resistor, so as to obtain accurate temperature control when the sensor is working.

4. The heating element, sensitive element, and temperature measuring element are arranged on the same layer, and the same material is sputtered onto each pattern at one time, which simplifies the process and avoids the generation of parasitic electric field.

5. The size of the gas sensor of the present invention is only 2×2mm. The heat transfer is reduced through the wet etching heat insulation groove on the back of the Si substrate, and the extremely low power can be achieved when the electrode is heated by itself, which meets the current market demand for low power consumption sensors. .

Description of drawings

FIG. 1 is a cross-sectional view of the structure of the low-power micro-nano gas sensor of the present invention.

Figure 2(a) and Figure 2(b) respectively show the planar structures of the heating electrode, sensitive electrode and temperature measuring electrode of the low power consumption micro-nano gas sensor of the present invention.

Fig. 3(a) and Fig. 3(b) are schematic diagrams of growth of nanorods, the sensitive material of the low-power micro-nano gas sensor of the present invention, on a well-defined TiO ₂ film.

Fig. 4(a)-Fig. 4(m) are the process flow diagram of the preparation process of the low power consumption micro-nano gas sensor of the present invention.

In the figure: 1. Si ₃ N ₄ masking layer; 2. SiO ₂ masking layer; 3. Si substrate; 4. SiO ₂ insulating layer Ⅰ; 5. Si ₃ N ₄ insulating layer Ⅰ; 6. SiO ₂ insulating layer Ⅱ; 7. Si ₃ N ₄ insulating layer II; 8. Cr-Au heating electrode; 9. TiO ₂ nano film; 10. TiO ₂ nano rod; 11. Cr-Au sensitive electrode; 12. Lead plate; 13. Thermal insulation tank; 14. Temperature measuring electrodes; 15. Sensitive materials.

Detailed ways

The invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it is not used as a basis for any limitation on the invention.

As shown in Fig. 1 and Fig. 2 (a), (b), the present invention is based on nano-TiO ₂ low power consumption micro-nano gas sensor, comprises Si substrate 3, and the back side of Si substrate 3 has thermal insulation groove 13, on Si substrate 3. The back is SiO ₂ masking layer 2 and Si ₃ N ₄ masking layer 1 in turn, and the front is four layers consisting of SiO ₂ insulating layer Ⅰ4-Si ₃ N ₄ insulating layer Ⅰ5-SiO ₂ insulating layer Ⅱ6-Si ₃ N ₄ insulating layer Ⅱ7 Insulating layer composed of thin films, a pair of Cr-Au sensitive electrodes 11 and their lead plates 12, two pairs of Cr-Au heating electrodes 8 and their lead plates 12, two pairs of temperature measuring electrodes 14 and their lead plates are arranged on the insulating layer 12. Each electrode is located on the same plane, and is prepared by the same material and the same process. The sensitive material 15 is located above the sensitive electrode at the center, and the sensitive layer is composed of TiO ₂ nano-film 9 and TiO ₂ nano-rod 10 structure.

As shown in Figure 2(a) and (b), the sensitive material 15 is arranged in a rectangular shape at the center of the sensor, and a pair of symmetrically distributed helical electrode wires lead out from the Cr-Au sensitive electrode 11 and lead to the electrode lead plate; The Cr-Au sensitive electrode 11 has an interdigital structure and is fully in contact with the sensitive layer. The Cr-Au heating electrode 8 leads out from the side of the Cr-Au sensitive electrode 11 with two pairs of symmetrically distributed heating wires in a double helix structure, and leads to the heating element lead Disc: Surrounding the Cr-Au sensitive electrode 11, the temperature measuring electrodes 14 are arranged on both sides respectively, and each electrode has an independent lead disc, which is distributed on both sides, and all electrodes and lead discs of the sensor are symmetrically arranged in the center.

The sensitive layer is composed of TiO ₂ thin film 9 and TiO ₂ nanorod 10. The insulating layer and masking layer are composed of SiO ₂ -Si ₃ N ₄ double-layer thin film; sensitive electrodes, heating electrodes, temperature measuring resistors and lead plates Made of Cr-Au film.

Referring to Fig. 2(a), the heating wire and the sensitive electrode are arranged symmetrically and spirally, the sensitive electrode is surrounded by the heating wire, and the sensitive material is above the sensitive electrode. Referring to Fig. 2(b), the inner circle of a pair of Cr-Au heating wires measures 145 μm×240 μm, the width of the heating wires is 12 μm, and the gap is 40 μm. The Cr-Au sensitive electrode has an electrode width of 15 μm and a gap of 10 μm. As shown in Figure 2(b), the sensitive material is located in the area of the wire frame 14, above the sensitive electrode, and the size is 100 μm×100 μm.

As shown in Figure 3(a) and (b), the nanorods grow on the well-defined TiO ₂ film, and the nanorods are bridged and connected to form a nanorod film with a very high specific surface area.

Referring to Fig. 4, the preparation method of the low power consumption metal oxide gas sensor of the present invention is as follows:

Example 1

(1) As shown in Figure 4(a), SiO ₂ -Si ₃ N ₄ double-layer composite films were prepared by thermal oxidation and low-pressure chemical vapor deposition on the front and back sides of the Si substrate; thermal oxidation of 500nm SiO on both sides of the silicon wafer ₂ -layer, double-sided LPCVD (low pressure chemical vapor deposition) deposition of 150nm Si ₃ N ₄ .

(2) As shown in Figure 4(b), on the front side SiO ₂ -Si ₃ N ₄ double-layer composite film, 500nm SiO ₂ and 150nm Si ₃ N ₄ were sequentially deposited on the front side by PECVD, and annealed at 500°C for 7h.

(3) As shown in Figure 4(c), on the front insulating layer, the patterns of sensitive electrodes and lead pads, heating electrodes and lead pads, temperature measuring electrodes and lead pads are obtained through uniform photolithography, and the photoresist is made of Positive glue EPG535.

(4) As shown in Figure 4(d), sputter a Cr adhesive layer on the heating electrode, lead pad, sensitive electrode, and lead pad pattern, and then sputter an Au layer on the adhesive layer; use a sputtering machine to sputter in turn Radiation 50nm Cr, 250nm Au.

(5) As shown in Figure 4(e), the photoresist is removed by a lift-off (stripping) process to obtain electrodes and lead pads, which are annealed at 300° C. for 10 minutes.

(6) As shown in Fig. 4(f), on the rectangular area surrounded by the sensitive electrodes, adopt the same photolithography process as step (3) to obtain the sensitive material pattern.

(7) Sputter TiO ₂ thin film on the sensitive layer pattern to define the growth position of subsequent nanorods; sputter Ti thin film on TiO ₂ thin film to provide titanium source; use sputtering machine to sputter 30nm TiO ₂ and 300nm Ti sequentially, such as Figure 4(g) shows.

(8) TiO ₂ nanorods were prepared by the hot hydrochloric acid vapor method; the photoresist was removed by the lift-off process, and the sensitive material pattern was obtained as shown in Figure 4(h).

Place the chips sputtered with _TiO2 thin films and Ti films on the small platform in the high-pressure hydrothermal reactor, mix hydrochloric acid and deionized water at a volume ratio of 1:10, add them to the reactor, and put them in a drying oven. Keep warm at 150°C for 3.5h. After cooling, take out the reactor from the drying oven, then take out the chip, clean the surface impurities with ethanol and deionized water, and dry at 100°C for 0.5h to obtain a TiO ₂ nanorod film. As shown in Figure 4(i).

(9) Adopt the same lithography process as in step (3) to obtain the groove window pattern on the back, as shown in Fig. 4 (j).

(9a) The photoresist is used as a mask layer, and the Si ₃ N ₄ -SiO ₂ layer at the window of the groove is removed by deep dry etching, and the etching time is 13 minutes. The photoresist is removed by the lift-off process, and the window is obtained as shown in Figure 4(k).

(9b) Spin-coat photoresist on the front of the chip, and after drying at 90°C, drop PDMS onto the front of the chip until the front is completely covered, and dry at 70°C for 1 hour, as shown in Figure 4(l). The front side is attached to the glass sheet, and the back of the chip is coated with PDMS to make the chip firmly attached to the glass sheet.

(9c) Put the chip and the glass piece together into a TMAH (25% tetramethylammonium hydroxide) solution, and corrode for 16 hours at 85° C. to form an insulating groove. Gently tear off the PDMS, soak it in acetone, remove the photoresist and residual PDMS, and dry it at 100°C for 1 hour to obtain the sensor as shown in Figure 4(m).

Example 2

(1) SiO ₂ -Si ₃ N ₄ double-layer composite films were prepared by thermal oxidation and low-pressure chemical vapor deposition on the front and back of the Si substrate respectively; 500nm SiO ₂ layers were thermally oxidized on both sides of the silicon wafer, and double-sided LPCVD (low pressure chemical vapor deposition) Vapor deposition) deposited 150nm Si ₃ N ₄ .

(2) On the front side SiO ₂ -Si ₃ N ₄ double-layer composite film, deposit 500nm SiO ₂ and 150nm Si ₃ N ₄ sequentially by PECVD on the front side, and anneal at 600°C for 5h.

(3) On the front insulating layer, the patterns of the sensitive electrode and the lead plate, the heating electrode and the lead plate, the temperature measuring electrode and the lead plate are obtained through the uniform photolithography process, and the photoresist is positive resist EPG535.

(4) Sputter a Cr adhesive layer on the heating electrode, lead pad, sensitive electrode, and lead pad pattern, and then sputter an Au layer on the adhesive layer; use a sputtering machine to sputter 50nm Cr and 250nm Au in sequence.

(5) The photoresist is removed by a lift-off (stripping) process to obtain the electrodes and lead pads, which are annealed at 260° C. for 30 min.

(6) On the rectangular area surrounded by the sensitive electrodes, adopt the same photolithography process as step (3) to obtain the sensitive material pattern.

(7) Sputter TiO ₂ thin film on the sensitive layer pattern to define the growth position of subsequent nanorods; sputter Ti thin film on TiO ₂ thin film to provide titanium source; use sputtering machine to sputter 30nm TiO ₂ and 300nm Ti sequentially.

(8) TiO ₂ nanorods were prepared by hot hydrochloric acid vapor method; photoresist was removed by lift-off process to obtain patterns of sensitive materials.

Place the chips sputtered with _TiO2 thin films and Ti films on the small platform in the high-pressure hydrothermal reactor, mix hydrochloric acid and deionized water at a volume ratio of 1:10, add them to the reactor, and put them in a drying oven. Keep warm at 150°C for 3.5h. After cooling, take out the reactor from the drying oven, then take out the chip, clean the surface impurities with ethanol and deionized water, and dry at 100°C for 0.5h to obtain a TiO ₂ nanorod film.

(9) Obtain the groove window pattern on the back by adopting the same photolithography process as in step (3).

(9a) The photoresist is used as a mask layer, and the Si ₃ N ₄ -SiO ₂ layer at the window of the groove is removed by deep dry etching, and the etching time is 13 minutes. The photoresist is removed by a lift-off process to obtain a window.

(9b) Spin-coat photoresist on the front of the chip, and after drying at 90°C, drop PDMS onto the front of the chip until the front is completely covered, dry at 70°C for 1 hour, stick the front of the chip on a glass sheet, and place the chip A circle of PDMS is coated on the back to make the chip firmly adhere to the glass slide.

(9c) Put the chip and the glass piece together into a TMAH (25% tetramethylammonium hydroxide) solution, and corrode for 16 hours at 85° C. to form an insulating groove. Gently tear off the PDMS, soak it in acetone, remove the photoresist and residual PDMS, and dry it at 100°C for 1 hour to obtain the sensor.

The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solutions disclosed in the present invention, those skilled in the art can make some replacements and modifications to some of the technical features without creative work according to the disclosed technical content. Deformation, these replacements and deformations are all within the protection scope of the present invention.

Claims (8)

1. one kind is based on nano-TiO₂Low-power consumption micro-nano gas sensor preparation method, which is characterized in that including following steps It is rapid:

(1) at Si substrate front surface and the back side, thermal oxide and Low Pressure Chemical Vapor Deposition preparation SiO is respectively adopted₂-Si₃N₄It is double-deck Laminated film constitutes masking layer；

(2) in positive SiO₂-Si₃N₄On double-layer compound film, it is sequentially depositing using plasma reinforced chemical vapour deposition method SiO₂And Si₃N₄, form SiO₂-Si₃N₄-SiO₂-Si₃N₄Four layers of laminated film constitute insulating layer, and move back at a certain temperature Fire；

(3) on the insulating layer of front, by spin coating photoetching process, sensitive electrode and lead wire tray, heating electrode and lead wire tray are obtained With the figure of thermometric electrode and lead wire tray；

(4) the sputtering Cr bonding on heating electrode and lead wire tray, sensitive electrode and lead wire tray and thermometric electrode and lead wire tray figure Then layer sputters Au layers on adhesive layer；

(5) by stripping technology, sensitive electrode and lead wire tray, heating electrode and lead wire tray and thermometric electrode and lead wire tray are obtained, And it is made annealing treatment；

(6) on the rectangular area that sensitive electrode surrounds, sensitive layer pattern is obtained by photoetching process；

(7) TiO is sputtered on sensitive layer pattern₂Film defines subsequent nanorod growth position；In TiO₂It is thin that Ti is sputtered on film Film provides titanium source；

(8) TiO is prepared using hot hydrochloric acid vapour method₂Nanometer rods constitute sensitive layer；

(9) the identical spin coating photoetching process with step (3) is taken to obtain Si backside of substrate insulation tank, i.e. completion low-power consumption micro-nano gas The production of body sensor；

In the step (1), SiO₂-Si₃N₄The middle SiO of double-layer compound film₂Film thickness is 500nm, Si₃N₄Film thickness is 150nm；

In the step (2), it is sequentially depositing SiO₂With a thickness of 500nm and Si₃N₄With a thickness of 150nm, and at 500 DEG C -600 DEG C Anneal 5-7h；

In the step (5), anneal 10-30min at a temperature of 260 DEG C-300 DEG C.

2. according to claim 1 be based on nano-TiO₂Low-power consumption micro-nano gas sensor preparation method, feature exists In in the step (4), sputtering Cr thickness of adhibited layer is 50nm, sputters Au layers with a thickness of 250nm.

3. according to claim 1 be based on nano-TiO₂Low-power consumption micro-nano gas sensor preparation method, feature exists In, in the step (7), sputtering TiO₂Film thickness is 30nm；Sputtering Ti film thickness is 300nm.

4. according to claim 1 be based on nano-TiO₂Low-power consumption micro-nano gas sensor preparation method, feature exists In, in the step (8), preparation TiO₂The method of nanometer rods is as follows:

Sputtering 8a) there is into TiO₂Film, Ti film chip be placed on the chain-wales in high-pressure hydrothermal reaction kettle, hydrochloric acid and will go It is added in reaction kettle after ionized water 1:10 mixing by volume, keeps the temperature 3.5h at 150 DEG C；

8b) after cooling, chip is taken out, successively cleans removal chip surface sundries, 100 DEG C of drying with ethyl alcohol and deionized water 0.5h obtains TiO₂Nano-rod film.

5. according to claim 1 be based on nano-TiO₂Low-power consumption micro-nano gas sensor preparation method, feature exists In in the step (9), Si backside of substrate is prepared insulation tank and included the following steps:

9a) by photoetching process, photoresist dispels the Si at notch window by deep dry etching as masking layer₃N₄-SiO₂ Layer removes photoresist using lift-off technique, obtains the insulated tank figure below silicon base；

9b) after chip front side spin coating photoresist, 90 DEG C of drying, PDMS is dripped dropwise in chip front side, until front drop is full, Chip back foreign aid on the glass sheet by chip front side patch, and is applied a circle PDMS, chip is made firmly to be attached to glass by 70 DEG C of drying 1h Glass on piece；

It is corruption at a temperature of 85 DEG C in 25% tetramethylammonium hydroxide TMAH solution that chip, which 9c) is put into togerther concentration with sheet glass, It loses 16h and forms insulation tank；PDMS is gently torn, with acetone soak, removes photoresist and remnants PDMS, 100 DEG C of drying 1h are obtained To sensor.

6. a kind of claim 1-5 is described in any item to be based on nano-TiO₂Low-power consumption micro-nano gas sensor, feature exists In, including Si substrate, the back side of Si substrate is provided with insulated tank, is followed successively by SiO in Si backside of substrate₂Masking layer and Si₃N₄Masking Layer, front is by SiO₂-Si₃N₄-SiO₂-Si₃N₄A pair of of sensitive electrical is arranged on insulating layer for the insulating layer that four-level membrane is combined Pole and its lead wire tray, two pairs of heating electrodes and its lead wire tray, two pairs of thermometric electrodes and its lead wire tray, each electrode are located at same flat Face is prepared using the same technique of identical material, and sensitive material is located above the sensitive electrode of centre, and sensitive layer is by film and receives Rice stick structure composition.

7. according to claim 6 a kind of based on nano-TiO₂Low-power consumption micro-nano gas sensor, which is characterized in that institute Stating sensitive material is rectangular arrangement heart position in the sensor, and a pair of symmetrical helically threadiness is led on sensitive electrode Electrode wires, and to contact conductor disk；Sensitive electrode is interdigital structure, is come into full contact with sensitive layer, heats electrode along sensitive electrode It is symmetrical in double-stranded heater strip that side leads to two pairs, and to heating element lead wire tray；Around sensitive electrode, thermometric Resistance is respectively provided at both sides, and each electrode respectively has independent lead wire tray, is distributed in two sides, all electrodes of sensor and lead wire tray It is to be centrosymmetrically arranged.

8. according to claim 6 a kind of based on nano-TiO₂Low-power consumption micro-nano gas sensor, which is characterized in that institute Sensitive layer is stated by TiO₂Film and TiO₂Nanometer rods two parts composition, insulating layer is by SiO₂-Si₃N₄-SiO₂-Si₃N₄Four-level membrane is multiple It closes, masking layer is by SiO₂-Si₃N₄Bilayer film is combined；Sensitive electrode, heating electrode and temperature detecting resistance and each lead Disk is made of Cr-Au film.