CN108152340A - A kind of MEMS gas sensors and preparation method thereof - Google Patents
A kind of MEMS gas sensors and preparation method thereof Download PDFInfo
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Abstract
The invention belongs to gas sensor technical fields, are related to a kind of MEMS gas sensors and preparation method thereof.The MEMS gas sensors of the present invention include substrate, micro girder construction and gas sensing layer successively, and the gas sensing layer is made of few layer of atom doped black phosphorus material of Li.The gas sensor of the present invention can be used for the detection of CO gases, have higher stability and sensitivity.
Description
Technical field
The invention belongs to gas sensor technical fields, are related to a kind of MEMS gas sensors and preparation method thereof.
Background technology
As pollution sources typical in atmosphere pollution, a growing part of carbon monoxide CO is derived from natural cause, and one
Part is originated from human factor.With the industrialized continuous development of society, the continuous increase of urban traffic pressure, from human factor
CO pollution source ranges it is increasing, greatly to chemical industry, communications and transportation is small to kitchen fume, fireworks and firecrackers etc., therefore CO exists
Shared ratio is higher and higher in air.As the toxic gas in other atmosphere pollutions, CO also has very high toxicity,
It when the gas enters in human body, is easily combined with the hemoglobin in blood, greatly exceeds the knot of oxygen and hemoglobin
Sum velocity so that the oxygen carrying capacity of hemoglobin is greatly reduced.CO will be made one at much lower concentrations by anoxic injury.
The lighter has a headache in poisoning patient, weakness of limbs, expiratory dyspnea.Severe one nausea, stupor even can be because of arrhythmia cordis and breathing fiber crops
Numbness and it is dead.Therefore particularly important is just become to the accuracy and promptness of CO detections.And CO is colourless, and it is odorless, do not pass through profession
The detection device of property is difficult to realize its presence.
MEMS micro-gas sensors are than the volume smaller of traditional gas sensor, and weight is lighter, and cost and power consumption are also opposite
It is relatively low, realizing the integrated and intelligentized production for being conducive to mass in the process.With common metal oxide at present and having
Machine high molecular polymer is compared, and novel two-dimensional material black phosphorus is because have unique atomic structure, outstanding semiconductor property,
Anisotropy of height etc., therefore have advantageous advantage in terms of electronic device, it is increasingly becoming semi-conducting material research
Hot spot, be also considered as to substitute the new era material of graphene.Micro- gas using black phosphorus as gas sensitive material passes
Sensor can be improved according to existing semiconductor preparing process, greatly reduce the complexity in terms of preparation, and with biography
Gas sensitive such as metal oxide, graphene etc. of system hetero-junctions are compared, and same class substance does gas sensitive and avoids that lattice occurs
Mismatch simplifies preparation process flow.Most importantly black phosphorus due to having higher surface area-to-volume ratio, inhale by gas
Attached amount bigger.Different metal doping black phosphorus generated change of properties after adsorbed gas also improves the choosing of micro-gas sensors
Selecting property and sensitivity.
Using with temperature control device solid electrolyte CO gas sensors, having made by traditional handicraft, volume is big, material
The shortcomings of material consumption is more, consistency is poor, power consumption is big, and these shortcomings can be overcome by carrying out micromation using MEMS technology, be solid
The inexorable trend of electrolyte gas sensor development.As Chinese patent application (201010218524.X) discloses a kind of micro-cantilever
Beam gas sensor and preparation method thereof using the gas-sensitive property and piezoresistive characteristic of organic/inorganic nano laminated film, will have
Machine/inorganic nano combined film gas sensing layer and varistor as micro-cantilever gas sensor simultaneously, but it is in stabilization
It need to be improved in property and accuracy.
Invention content
The purpose of the present invention is in view of the above-mentioned problems existing in the prior art, it is proposed that a kind of to CO stability and sensitivity
High MEMS gas sensors.
The purpose of the present invention can be realized by following technical proposal：
A kind of MEMS gas sensors, the MEMS gas sensors include substrate, micro girder construction and gas sensing layer, institute successively
Gas sensing layer is stated to be made of few layer of atom doped black phosphorus material of Li.
Preferably, the substrate includes silicon-based substrate, SiO successively2Protective layer, SiNxPolysilicon layer and it is formed in SiNx
Micro girder construction contact zone and capacitive region on polysilicon layer.
Preferably, the silicon-based substrate is the N-type silicon chip that crystal orientation is (100), thickness is 170-230 μm.
Preferably, the micro girder construction includes cantilever beam or clamped beam.
Preferably, the micro girder construction is by SiNxLayer is formed.The micro girder construction has anchoring area.
Preferably, the thickness of the gas sensing layer is 10-20 atomic layer level thickness.
Preferably, the Li atoms adulterated in the gas sensing layer proportion in black phosphorus structure is up to 22.2%.
Another object of the present invention is to provide a kind of preparation method of MEMS gas sensors, the preparation method packet
Include following steps,
The preparation of S1, substrate：Silicon-based substrate is pre-processed, grows SiO in silicon-based substrate2Protective layer, in SiO2Protection
SiN is deposited by LPCVD methods on layerxPolysilicon layer, in SiNxOn polysilicon layer by photoetching process be made micro girder construction contact zone and
Capacitive region；
The preparation of S2, micro- beam layer：In SiNxPhosphorosilicate glass (PSG) sacrificial layer is deposited by LPCVD methods on polysilicon layer,
Micro- beam anchoring area is made by photoetching process on PSG sacrificial layers, SiN is deposited by LPCVD methods on PSG sacrificial layers after etchingxIt is micro-
Beam layer, to SiNxMicro- beam layer carries out wet etching to control the width of micro girder construction；
The preparation of S3, gas sensing layer：It is made by laser molecular beam epitaxy on few layer of black phosphorus surface into the deposition of row metal Li
Few layer of atom doped black phosphorus material of Li obtained is placed on micro- beam layer, shape by the few layer black phosphorus material atom doped into Li
Into gas sensing layer；
S4, by PSG sacrifice layer corrosions, form micro girder construction.
Preferably, the process pre-processed in the step S1 is：Successively silicon substrate is cleaned with propyl alcohol, ethyl alcohol and deionized water
Substrate is cleaned using acidic cleaning solution after drying, is then impregnated again with diluted hydrofluoric acid；
Preferably, the acidic cleaning solution is mass ratio 1:2:8 HCl:H2O2:H2The mixing cleaning solution of O.
The present invention cleans the organic matter that can be effectively removed in silicon-based substrate with propyl alcohol, ethyl alcohol and deionized water successively, adopts
The metal spot in silicon-based substrate can effectively be removed with acidic cleaning solution, and dilute HF acid soaks can effectively remove silicon-based substrate
The silica SiO on surface2。
Preferably, the thickness of PSG sacrificial layers is 2.2-2.8 μm in the step S2, SiNxThe thickness of micro- beam layer is
0.4-0.6μm。
Preferably, also there are annealing steps after PSG sacrificial layers are deposited in the step S2, specially in 1000-1100
The lower annealing 0.8-1.2h of degree.Annealing steps can reduce membrane stress, enhance the integrality of film.
Preferably, the preparation process of micro- beam anchoring area described in the step S2 is, in the condition of 220nm ultraviolet wavelengths
It is lower that mask plate is made by KOH developments, mask plate is placed on PSG sacrificial layers, in SF6、CHF3Pass through plasma dry under atmosphere
Etching method (RIE) performs etching PSG sacrificial layers, then develops at a temperature of 120 DEG C by KOH, after distilled water cleaning 20min
Drying obtains micro- beam anchoring area.
Preferably, laser molecular beam epitaxy prepares the mistake of few layer of atom doped black phosphorus material of Li in the step S3
Cheng Zhong, vacuum degree are 0.8 × 10-6-1.2×10-6Pa, temperature are 880-920 DEG C, laser pulse frequency 1-3Hz, and wavelength is
220-280nm。
Preferably, laser molecular beam epitaxy is gone back after preparing few layer of atom doped black phosphorus material of Li in the step S3
With high-temperature annealing step.
High annealing being capable of releasable material stress, it is ensured that the integrality and ductility of material.
Preferably, the preparation method of few layer black phosphorus is in the step S3：
White phosphorus or red phosphorus at a temperature of 1100-1300Pa pressure, 185-210 DEG C are converted and form sheet black phosphorus crystal；It is logical
Crossing mechanical stripping method will separate in the dilute black phosphorus crystal from sheet of blocky black phosphorus, then by plasma method from blocky black phosphorus
Dilute few layer black phosphorus of middle stripping is dilute；It is immersed in few layer of black phosphorus is dilute in cumyl hydroperoxide CHP solution, after carrying out ultrasonication
Centrifugation obtains few layer black phosphorus.
Preferably, using HF acid by PSG sacrifice layer corrosions in the step S3, then gas is passed using deionized water
Sensor is cleaned, and is dried under infrared lamp.
Compared with prior art, the invention has the advantages that：
1. increasing the degree of absorption of CO using the atom doped few layer black phosphorus of Li as gas sensitive, the suction of CO molecules is promoted
It receives, improves the stability of gas sensor；
2. the gas sensitive of the present invention has significant deformation after CO absorption, be conducive to the application in micro girder construction beam；
Deformation caused by 3.CO absorption can improve gas detection method by electric signal measurements such as capacitance variations
The sensitivity of diversity and sensor so that the time of semiconductor response is less than 10s, and measurement range can cover 0-1000ppm,
Capacitance voltage maximum can reach 15% variation in the environment of 1000ppm；
4. the present invention has better choice compared with traditional gas sensitive, the heterojunction structure of semi-conducting material avoids
The lattice mismatch of gas sensitive and cantilever beam, simplifies preparation process flow, reduces the complexity of preparation.
Description of the drawings
Fig. 1 is deposits SiO in silicon-based substrate2Protective layer and SiNxThe cross-sectional view of polysilicon layer；
Fig. 2 is in SiNxThe cross-sectional view of cantilever beam contact zone and capacitive region is etched on polysilicon layer；
Fig. 3 is in SiNxThe cross-sectional view of PSG sacrificial layers is deposited on polysilicon layer；
Fig. 4 is the cross-sectional view that cantilever beam anchoring area is etched on PSG sacrificial layers；
Fig. 5 is to deposit SiN on PSG sacrificial layers after etchingxThe cross-sectional view of cantilever beam；
Fig. 6 is in SiNxThe cross-sectional view of gas sensitive is covered on cantilever beam；
Fig. 7 is the cross-sectional view of gas sensor after releasing sacrificial layer；
Fig. 8 is structure change comparison of the few layer of black phosphorus of doped metallic elements Li before and after CO absorption gas.
Specific embodiment
The following is specific embodiments of the present invention, and technical scheme of the present invention is further described, but the present invention is simultaneously
It is not limited to these embodiments.
Embodiment 1
The present embodiment illustrates the MEMS gas sensors in the present invention by taking cantilever beam as an example, the MEMS in the present embodiment
Gas sensor is made of following steps：
(1) select thickness be 200 μm, crystal orientation be for (100) N-type silicon chip as silicon-based substrate 1, silicon-based substrate 1 is successively
It is cleaned with acidic cleaning solution after being cleaned, dried up with propyl alcohol, ethyl alcohol and deionized water, is then soaked again with diluted hydrofluoric acid
Bubble, acidic cleaning solution are mass ratio 1:2:8 HCl:H2O2:H2The mixing cleaning solution of O；
(2) as depicted in figs. 1 and 2, SiO is grown in silicon-based substrate2Protective layer 2, then in SiO2Pass through on protective layer 2
LPCVD methods deposit SiNxPolysilicon layer 3, in SiNxCantilever beam contact zone 4 and capacitive region are made by photoetching process on polysilicon layer 3
5；
(3) as shown in figure 3, in SiNxBy LPCVD methods deposition thickness it is 2.5 μm of PSG sacrificial layers 6 on polysilicon layer 3,
Then anneal 1h under 1050 degree；
(4) as shown in figure 4, mask plate is made by KOH developments under conditions of 220nm ultraviolet wavelengths, by mask plate
It is overlying on PSG sacrificial layers 6, in SF6, CHF3PSG sacrificial layers are performed etching by dry plasma etch method (RIE) under atmosphere,
Then by KOH develops, drying obtains cantilever beam anchoring area 7 after distilled water cleaning 20min at a temperature of 120 DEG C；
(5) as shown in figure 5, depositing the SiN of 0.5 μ m-thick on PSG sacrificial layers 6 after etching by LPCVD methodsxCantilever beam
Layer 8, then in SiNxSpin coating positive photoresist on cantilever beam layer 8 develops after alignment exposure, finally removes photoresist by wet etching
To figure, to control the width of cantilever beam structure；
(6) white phosphorus or red phosphorus at a temperature of 1200Pa pressure, 200 DEG C are converted and forms sheet black phosphorus crystal, pass through machinery
Stripping method will be separated in the dilute black phosphorus crystal from sheet of blocky black phosphorus, then by plasma method from the dilute middle stripping of blocky black phosphorus
From few layer black phosphorus is dilute；It is immersed in few layer of black phosphorus is dilute in cumyl hydroperoxide CHP solution, carries out ultrasonication after ten minutes
Centrifugation obtains few layer black phosphorus；
(7) using few layer of black phosphorus as substrate, by laser molecular beam epitaxy on few layer of black phosphorus surface into the heavy of row metal Li
Few layer of black phosphorus is put into the vacuum chamber by product, and setting vacuum degree is 1 × 10-6Pa, temperature are 900 DEG C, and laser pulse frequency is
1Hz, wavelength 250nm are made few layer of atom doped black phosphorus material of Li, then carry out high annealing, it is atom doped that Li is made
Few layer of black phosphorus material in Li atoms in black phosphorus structure proportion be 22.2%；
(8) as shown in fig. 6, few layer of atom doped black phosphorus material of Li obtained is placed on SiN with probexCantilever beam layer
On 8, gas sensing layer 9 is formed, the thickness of gas sensing layer 9 is 16 atomic layer level thickness.
(9) as shown in fig. 7, using HF acid by PSG sacrifice layer corrosions, cantilever beam structure is formed, then using deionized water
Gas sensor is cleaned, and is dried under infrared lamp, obtains MEMS gas sensors.
Embodiment 2
The present embodiment illustrates the MEMS gas sensors in the present invention by taking cantilever beam as an example, the MEMS in the present embodiment
Gas sensor is made of following steps：
(1) select thickness be 170 μm, crystal orientation be for (100) N-type silicon chip as silicon-based substrate 1, silicon-based substrate 1 is successively
It is cleaned with acidic cleaning solution after being cleaned, dried up with propyl alcohol, ethyl alcohol and deionized water, is then soaked again with diluted hydrofluoric acid
Bubble, acidic cleaning solution are mass ratio 1:2:8 HCl:H2O2:H2The mixing cleaning solution of O；
(2) as depicted in figs. 1 and 2, SiO is grown in silicon-based substrate2Protective layer 2, then in SiO2Pass through on protective layer 2
LPCVD methods deposit SiNxPolysilicon layer 3, in SiNxCantilever beam contact zone 4 and capacitive region are made by photoetching process on polysilicon layer 3
5；
(3) as shown in figure 3, in SiNxBy LPCVD methods deposition thickness it is 2.2 μm of PSG sacrificial layers 6 on polysilicon layer 3,
Then anneal 1.2h under 1000 degree；
(4) as shown in figure 4, mask plate is made by KOH developments under conditions of 220nm ultraviolet wavelengths, by mask plate
It is overlying on PSG sacrificial layers 6, in SF6, CHF3PSG sacrificial layers are performed etching by dry plasma etch method (RIE) under atmosphere,
Then by KOH develops, drying obtains cantilever beam anchoring area 7 after distilled water cleaning 20min at a temperature of 120 DEG C；
(5) as shown in figure 5, depositing the SiN of 0.4 μ m-thick on PSG sacrificial layers 6 after etching by LPCVD methodsxCantilever beam
Layer 8, then in SiNxSpin coating positive photoresist on cantilever beam layer 8 develops after alignment exposure, finally removes photoresist by wet etching
To figure, to control the width of cantilever beam structure；
(6) white phosphorus or red phosphorus at a temperature of 1100Pa pressure, 210 DEG C are converted and forms sheet black phosphorus crystal, pass through machinery
Stripping method will be separated in the dilute black phosphorus crystal from sheet of blocky black phosphorus, then by plasma method from the dilute middle stripping of blocky black phosphorus
From few layer black phosphorus is dilute；It is immersed in few layer of black phosphorus is dilute in cumyl hydroperoxide CHP solution, carries out ultrasonication after ten minutes
Centrifugation obtains few layer black phosphorus；
(7) using few layer of black phosphorus as substrate, by laser molecular beam epitaxy on few layer of black phosphorus surface into the heavy of row metal Li
Few layer of black phosphorus is put into the vacuum chamber by product, and setting vacuum degree is 0.8 × 10-6Pa, temperature are 920 DEG C, and laser pulse frequency is
1Hz, wavelength 230nm are made few layer of atom doped black phosphorus material of Li, then carry out high annealing, it is atom doped that Li is made
Few layer of black phosphorus material in Li atoms in black phosphorus structure proportion be 18.3%；
(8) as shown in fig. 6, few layer of atom doped black phosphorus material of Li obtained is placed on SiN with probexCantilever beam layer
On 8, gas sensing layer 9 is formed, the thickness of gas sensing layer 9 is 10 atomic layer level thickness.
(9) as shown in fig. 7, using HF acid by PSG sacrifice layer corrosions, cantilever beam structure is formed, then using deionized water
Gas sensor is cleaned, and is dried under infrared lamp, obtains MEMS gas sensors.
Embodiment 3
The present embodiment illustrates the MEMS gas sensors in the present invention by taking cantilever beam as an example, the MEMS in the present embodiment
Gas sensor is made of following steps：
(1) select thickness be 180 μm, crystal orientation be for (100) N-type silicon chip as silicon-based substrate 1, silicon-based substrate 1 is successively
It is cleaned with acidic cleaning solution after being cleaned, dried up with propyl alcohol, ethyl alcohol and deionized water, is then soaked again with diluted hydrofluoric acid
Bubble, acidic cleaning solution are mass ratio 1:2:8 HCl:H2O2:H2The mixing cleaning solution of O；
(2) as depicted in figs. 1 and 2, SiO is grown in silicon-based substrate2Protective layer 2, then in SiO2Pass through on protective layer 2
LPCVD methods deposit SiNxPolysilicon layer 3, in SiNxCantilever beam contact zone 4 and capacitive region are made by photoetching process on polysilicon layer 3
5；
(3) as shown in figure 3, in SiNxBy LPCVD methods deposition thickness it is 2.5 μm of PSG sacrificial layers 6 on polysilicon layer 3,
Then anneal 1h under 1030 degree；
(4) as shown in figure 4, mask plate is made by KOH developments under conditions of 220nm ultraviolet wavelengths, by mask plate
It is overlying on PSG sacrificial layers 6, in SF6, CHF3PSG sacrificial layers are performed etching by dry plasma etch method (RIE) under atmosphere,
Then by KOH develops, drying obtains cantilever beam anchoring area 7 after distilled water cleaning 20min at a temperature of 120 DEG C；
(5) as shown in figure 5, depositing the SiN of 0.5 μ m-thick on PSG sacrificial layers 6 after etching by LPCVD methodsxCantilever beam
Layer 8, then in SiNxSpin coating positive photoresist on cantilever beam layer 8 develops after alignment exposure, finally removes photoresist by wet etching
To figure, to control the width of cantilever beam structure；
(6) white phosphorus or red phosphorus at a temperature of 1180Pa pressure, 190 DEG C are converted and forms sheet black phosphorus crystal, pass through machinery
Stripping method will be separated in the dilute black phosphorus crystal from sheet of blocky black phosphorus, then by plasma method from the dilute middle stripping of blocky black phosphorus
From few layer black phosphorus is dilute；It is immersed in few layer of black phosphorus is dilute in cumyl hydroperoxide CHP solution, carries out ultrasonication after ten minutes
Centrifugation obtains few layer black phosphorus；
(7) using few layer of black phosphorus as substrate, by laser molecular beam epitaxy on few layer of black phosphorus surface into the heavy of row metal Li
Few layer of black phosphorus is put into the vacuum chamber by product, and setting vacuum degree is 0.9 × 10-6Pa, temperature are 890 DEG C, and laser pulse frequency is
2Hz, wavelength 260nm are made few layer of atom doped black phosphorus material of Li, then carry out high annealing, it is atom doped that Li is made
Few layer of black phosphorus material in Li atoms proportion in black phosphorus structure be up to 15.6%；
(8) as shown in fig. 6, few layer of atom doped black phosphorus material of Li obtained is placed on SiN with probexCantilever beam layer
On 8, gas sensing layer 9 is formed, the thickness of gas sensing layer 9 is 13 atomic layer level thickness.
(9) as shown in fig. 7, using HF acid by PSG sacrifice layer corrosions, cantilever beam structure is formed, then using deionized water
Gas sensor is cleaned, and is dried under infrared lamp, obtains MEMS gas sensors.
Embodiment 4
The present embodiment illustrates the MEMS gas sensors in the present invention by taking cantilever beam as an example, the MEMS in the present embodiment
Gas sensor is made of following steps：
(1) select thickness be 210 μm, crystal orientation be for (100) N-type silicon chip as silicon-based substrate 1, silicon-based substrate 1 is successively
It is cleaned with acidic cleaning solution after being cleaned, dried up with propyl alcohol, ethyl alcohol and deionized water, is then soaked again with diluted hydrofluoric acid
Bubble, acidic cleaning solution are mass ratio 1:2:8 HCl:H2O2:H2The mixing cleaning solution of O；
(2) as depicted in figs. 1 and 2, SiO is grown in silicon-based substrate2Protective layer 2, then in SiO2Pass through on protective layer 2
LPCVD methods deposit SiNxPolysilicon layer 3, in SiNxCantilever beam contact zone 4 and capacitive region are made by photoetching process on polysilicon layer 3
5；
(3) as shown in figure 3, in SiNxBy LPCVD methods deposition thickness it is 27 μm of PSG sacrificial layers 6 on polysilicon layer 3,
Then anneal 0.9h under 1080 degree；
(4) as shown in figure 4, mask plate is made by KOH developments under conditions of 220nm ultraviolet wavelengths, by mask plate
It is overlying on PSG sacrificial layers 6, in SF6, CHF3PSG sacrificial layers are performed etching by dry plasma etch method (RIE) under atmosphere,
Then by KOH develops, drying obtains cantilever beam anchoring area 7 after distilled water cleaning 20min at a temperature of 120 DEG C；
(5) as shown in figure 5, depositing the SiN of 0.5 μ m-thick on PSG sacrificial layers 6 after etching by LPCVD methodsxCantilever beam
Layer 8, then in SiNxSpin coating positive photoresist on cantilever beam layer 8 develops after alignment exposure, finally removes photoresist by wet etching
To figure, to control the width of cantilever beam structure；
(6) white phosphorus or red phosphorus at a temperature of 1250Pa pressure, 190 DEG C are converted and forms sheet black phosphorus crystal, pass through machinery
Stripping method will be separated in the dilute black phosphorus crystal from sheet of blocky black phosphorus, then by plasma method from the dilute middle stripping of blocky black phosphorus
From few layer black phosphorus is dilute；It is immersed in few layer of black phosphorus is dilute in cumyl hydroperoxide CHP solution, carries out ultrasonication after ten minutes
Centrifugation obtains few layer black phosphorus；
(7) using few layer of black phosphorus as substrate, by laser molecular beam epitaxy on few layer of black phosphorus surface into the heavy of row metal Li
Few layer of black phosphorus is put into the vacuum chamber by product, and setting vacuum degree is 1.1 × 10-6Pa, temperature are 910 DEG C, and laser pulse frequency is
3Hz, wavelength 270nm are made few layer of atom doped black phosphorus material of Li, then carry out high annealing, it is atom doped that Li is made
Few layer of black phosphorus material in Li atoms proportion in black phosphorus structure be up to 13.5%；
(8) as shown in fig. 6, few layer of atom doped black phosphorus material of Li obtained is placed on SiN with probexCantilever beam layer
On 8, gas sensing layer 9 is formed, the thickness of gas sensing layer 9 is 10-20 atomic layer level thickness.
(9) as shown in fig. 7, using HF acid by PSG sacrifice layer corrosions, cantilever beam structure is formed, then using deionized water
Gas sensor is cleaned, and is dried under infrared lamp, obtains MEMS gas sensors.
Embodiment 5
The present embodiment illustrates the MEMS gas sensors in the present invention by taking cantilever beam as an example, the MEMS in the present embodiment
Gas sensor is made of following steps：
(1) select thickness be 230 μm, crystal orientation be for (100) N-type silicon chip as silicon-based substrate 1, silicon-based substrate 1 is successively
It is cleaned with acidic cleaning solution after being cleaned, dried up with propyl alcohol, ethyl alcohol and deionized water, is then soaked again with diluted hydrofluoric acid
Bubble, acidic cleaning solution are mass ratio 1:2:8 HCl:H2O2:H2The mixing cleaning solution of O；
(2) as depicted in figs. 1 and 2, SiO is grown in silicon-based substrate2Protective layer 2, then in SiO2Pass through on protective layer 2
LPCVD methods deposit SiNxPolysilicon layer 3, in SiNxCantilever beam contact zone 4 and capacitive region are made by photoetching process on polysilicon layer 3
5；
(3) as shown in figure 3, in SiNxBy LPCVD methods deposition thickness it is 2.8 μm of PSG sacrificial layers 6 on polysilicon layer 3,
Then anneal 0.8h under 1000 degree；
(4) as shown in figure 4, mask plate is made by KOH developments under conditions of 220nm ultraviolet wavelengths, by mask plate
It is overlying on PSG sacrificial layers 6, in SF6, CHF3PSG sacrificial layers are performed etching by dry plasma etch method (RIE) under atmosphere,
Then by KOH develops, drying obtains cantilever beam anchoring area 7 after distilled water cleaning 20min at a temperature of 120 DEG C；
(5) as shown in figure 5, depositing the SiN of 0.6 μ m-thick on PSG sacrificial layers 6 after etching by LPCVD methodsxCantilever beam
Layer 8, then in SiNxSpin coating positive photoresist on cantilever beam layer 8 develops after alignment exposure, finally removes photoresist by wet etching
To figure, to control the width of cantilever beam structure；
(6) white phosphorus or red phosphorus at a temperature of 1300Pa pressure, 185 DEG C are converted and forms sheet black phosphorus crystal, pass through machinery
Stripping method will be separated in the dilute black phosphorus crystal from sheet of blocky black phosphorus, then by plasma method from the dilute middle stripping of blocky black phosphorus
From few layer black phosphorus is dilute；It is immersed in few layer of black phosphorus is dilute in cumyl hydroperoxide CHP solution, carries out ultrasonication after ten minutes
Centrifugation obtains few layer black phosphorus；
(7) using few layer of black phosphorus as substrate, by laser molecular beam epitaxy on few layer of black phosphorus surface into the heavy of row metal Li
Few layer of black phosphorus is put into the vacuum chamber by product, and setting vacuum degree is 1.2 × 10-6Pa, temperature are 880 DEG C, and laser pulse frequency is
1Hz, wavelength 280nm are made few layer of atom doped black phosphorus material of Li, then carry out high annealing, it is atom doped that Li is made
Few layer of black phosphorus material in Li atoms in black phosphorus structure proportion be 8.6%；
(8) as shown in fig. 6, few layer of atom doped black phosphorus material of Li obtained is placed on SiN with probexCantilever beam layer
On 8, gas sensing layer 9 is formed, the thickness of gas sensing layer 9 is 10-20 atomic layer level thickness.
(9) as shown in fig. 7, using HF acid by PSG sacrifice layer corrosions, cantilever beam structure is formed, then using deionized water
Gas sensor is cleaned, and is dried under infrared lamp, obtains MEMS gas sensors.
As shown in figure 8, largely shape can occur after CO absorption for few layer of black phosphorus of Li atoms obtained in the present invention
Become, cantilever beam generation can be promoted largely to change by tension, the suction of detectable CO gases is measured by tension variation
Attached situation, and electric signal is converted to, so as to obtain the detection information of CO.
Other micro girder constructions, such as fixed beam structure may be used in cantilever beam in above-described embodiment, by measuring CO gases
Caused by absorption beam shake resonant frequency come detect the presence of CO gases and calculate CO adsorbance sizes.
Comparative example 1
The preparation of MEMS gas sensors is carried out using few layer black phosphorus obtained as gas sensitive, other are same as Example 1.
The sensitivity and sound of MEMS gas sensors obtained under different CO concentration in testing example 1 and comparative example 1
Between seasonable, the results are shown in Table 1.
Table 1：The test result of MEMS gas sensors obtained under different CO concentration in embodiment 1 and comparative example 1
In testing example 1-5 and comparative example 1 sensitivity of the MEMS gas sensors obtained under same CO concentration and
Response time, the results are shown in Table 2.
Table 2：Test result of the MEMS gas sensors obtained under same CO concentration in embodiment 1-5 and comparative example 1
In conclusion the MEMS gas sensors of the present invention lack layer black phosphorus by using Li atom pairs and are doped as gas
Largely deformation can occur after CO absorption, and be combined with micro girder construction for quick material, and this deformation is converted into micro- beam
The tension variation of structure or vibrations are effectively obtained by the tension variation to micro girder construction or the resonant frequency of vibrations and CO are determined
Property and quantitative detection.
Specific embodiment described herein is only an example for the spirit of the invention.Technology belonging to the present invention is led
The technical staff in domain can do various modifications or additions to described specific embodiment or replace in a similar way
In generation, however, it does not deviate from the spirit of the invention or beyond the scope of the appended claims.
Claims (10)
1. a kind of MEMS gas sensors, which is characterized in that the MEMS gas sensors successively include substrate, micro girder construction and
Gas sensing layer, the gas sensing layer are made of few layer of atom doped black phosphorus material of Li.
2. MEMS gas sensors according to claim 1, which is characterized in that the substrate successively include silicon-based substrate,
SiO2Protective layer, SiNxPolysilicon layer and it is formed in SiNxMicro girder construction contact zone and capacitive region on polysilicon layer.
3. MEMS gas sensors according to claim 2, which is characterized in that the silicon-based substrate is that crystal orientation is (100)
N-type silicon chip, thickness be 170-230 μm.
4. MEMS gas sensors according to claim 1, which is characterized in that the micro girder construction includes cantilever beam or solid
Strutbeam.
5. MEMS gas sensors according to claim 1, which is characterized in that the thickness of the gas sensing layer is 10-20
Atomic layer level thickness.
6. MEMS gas sensors according to claim 1, which is characterized in that the Li atoms adulterated in the gas sensing layer exist
Proportion is up to 22.2% in black phosphorus structure.
7. a kind of preparation method of MEMS gas sensors, which is characterized in that the preparation method includes the following steps,
The preparation of S1, substrate：Silicon-based substrate is pre-processed, grows SiO in silicon-based substrate2Protective layer, in SiO2On protective layer
SiN is deposited by LPCVD methodsxPolysilicon layer, in SiNxMicro girder construction contact zone and capacitance are made by photoetching process on polysilicon layer
Area；
The preparation of S2, micro- beam layer：In SiNxPSG sacrificial layers are deposited by LPCVD methods on polysilicon layer, are passed through on PSG sacrificial layers
Micro- beam anchoring area is made in photoetching process, and SiN is deposited by LPCVD methods on PSG sacrificial layers after etchingxMicro- beam layer, to SiNxMicro- beam layer
Wet etching is carried out to control the width of micro girder construction；
The preparation of S3, gas sensing layer：Few layer of atom doped black phosphorus material of Li is prepared by laser molecular beam epitaxy, by made from
Few layer of atom doped Li black phosphorus material is arranged on micro- beam layer, forms gas sensing layer；
S4, by PSG sacrifice layer corrosions, form micro girder construction.
8. preparation method according to claim 7, which is characterized in that the process pre-processed in the step S1 is：Successively
Silicon-based substrate is cleaned with propyl alcohol, ethyl alcohol and deionized water, is cleaned after drying using acidic cleaning solution, then uses diluted hydrofluoric acid
It impregnates.
9. preparation method according to claim 7, which is characterized in that in the step S3 prepared by laser molecular beam epitaxy
During few layer of atom doped Li black phosphorus material, vacuum degree is 0.8 × 10-6-1.2×10-6Pa, temperature 880-920
DEG C, laser pulse frequency 1-3Hz, wavelength 220-280nm.
10. preparation method according to claim 7, which is characterized in that the preparation method of few layer black phosphorus in the step S3
For：
White phosphorus or red phosphorus at a temperature of 1100-1300Pa pressure, 185-210 DEG C are converted and form sheet black phosphorus crystal；Pass through machine
Tool stripping method will be separated in the dilute black phosphorus crystal from sheet of blocky black phosphorus, then by plasma method from blocky black phosphorus is dilute
The few layer black phosphorus of stripping is dilute；Be immersed in few layer of black phosphorus is dilute in CHP solution, after carrying out ultrasonication centrifugation obtain few layer black phosphorus.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110455875A (en) * | 2019-09-17 | 2019-11-15 | 重庆大学 | A kind of gas sensitive and gas sensor and preparation method thereof |
| CN111380918A (en) * | 2020-04-07 | 2020-07-07 | 合肥微纳传感技术有限公司 | Cantilever beam gas sensor with multiple detection electrodes |
| CN111610233A (en) * | 2020-06-16 | 2020-09-01 | 黑龙江省网络空间研究中心 | Preparation method of MEMS catalytic combustion type gas sensor |
| CN117571795A (en) * | 2024-01-16 | 2024-02-20 | 北京市计量检测科学研究院 | Performance test method of gas sensor in oil smoke interference environment |
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2017
- 2017-12-06 CN CN201711277190.1A patent/CN108152340A/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110455875A (en) * | 2019-09-17 | 2019-11-15 | 重庆大学 | A kind of gas sensitive and gas sensor and preparation method thereof |
| CN111380918A (en) * | 2020-04-07 | 2020-07-07 | 合肥微纳传感技术有限公司 | Cantilever beam gas sensor with multiple detection electrodes |
| CN111610233A (en) * | 2020-06-16 | 2020-09-01 | 黑龙江省网络空间研究中心 | Preparation method of MEMS catalytic combustion type gas sensor |
| CN117571795A (en) * | 2024-01-16 | 2024-02-20 | 北京市计量检测科学研究院 | Performance test method of gas sensor in oil smoke interference environment |
| CN117571795B (en) * | 2024-01-16 | 2024-03-19 | 北京市计量检测科学研究院 | Performance test method of gas sensor in oil smoke interference environment |
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