CN112924515A - Gas sensor and preparation method thereof - Google Patents
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- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- 230000004888 barrier function Effects 0.000 claims abstract description 68
- 239000004065 semiconductor Substances 0.000 claims abstract description 65
- 239000000758 substrate Substances 0.000 claims abstract description 61
- 238000002161 passivation Methods 0.000 claims description 33
- 239000000463 material Substances 0.000 claims description 30
- 229910002601 GaN Inorganic materials 0.000 claims description 20
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 claims description 19
- 238000001514 detection method Methods 0.000 claims description 11
- 229910000449 hafnium oxide Inorganic materials 0.000 claims description 9
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 claims description 9
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 7
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 7
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 6
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 6
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 6
- 230000006698 induction Effects 0.000 claims description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 239000010703 silicon Substances 0.000 claims description 5
- 229910002704 AlGaN Inorganic materials 0.000 claims description 4
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims description 4
- 229910052594 sapphire Inorganic materials 0.000 claims description 4
- 239000010980 sapphire Substances 0.000 claims description 4
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 4
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 4
- 238000012360 testing method Methods 0.000 abstract description 14
- 238000000034 method Methods 0.000 description 22
- 238000004519 manufacturing process Methods 0.000 description 15
- 238000002955 isolation Methods 0.000 description 12
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000001451 molecular beam epitaxy Methods 0.000 description 4
- 230000005533 two-dimensional electron gas Effects 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 238000005530 etching Methods 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 229910052697 platinum Inorganic materials 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005229 chemical vapour deposition Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 230000002269 spontaneous effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052721 tungsten Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
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- 239000000203 mixture Substances 0.000 description 1
- 238000001020 plasma etching Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
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Abstract
The embodiment of the invention discloses a gas sensor and a preparation method thereof, wherein the gas sensor comprises: the semiconductor substrate, the buffer layer, the barrier layer, the cap layer, the source electrode and the drain electrode are sequentially stacked, and the source electrode and the drain electrode are positioned on one side, away from the channel layer, of the barrier layer; the temperature-resistant insulating layer is arranged on one side of the source electrode and one side of the drain electrode, which are far away from the barrier layer; the temperature-resistant insulating layer covers the side walls of the barrier layer and the channel layer along the thickness direction of the sensor, and covers the region of the barrier layer where the source electrode and the drain electrode are not arranged; the grid is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in the sensing area between the source electrode and the drain electrode. The technical scheme provided by the embodiment of the invention improves the temperature resistance of the gas sensor, enlarges the range of testing temperature and increases the range of detecting gas.
Description
Technical Field
The embodiment of the invention relates to the technical field of sensors, in particular to a gas sensor and a preparation method thereof.
Background
There are many types of gas sensors, and a typical semiconductor-type gas sensor is widely used in various fields due to its low cost.
However, the use of semiconductor-type gas sensors is limited by temperature. At present, the optimal test temperature of a semiconductor gas sensor of a silicon substrate cannot exceed 180 ℃, the optimal test temperature of a gas sensor of a conventional gallium nitride structure is about 240 ℃, a device becomes unstable along with the rise of the test environment temperature, the carrier concentration is reduced, the possibility that the detection result is influenced by noise is increased, the detection accuracy of the device at high temperature is reduced, and the detection accuracy, the sensitivity and the effective range of the semiconductor gas sensor to gas are specifically shown to be reduced.
Disclosure of Invention
The embodiment of the invention provides a gas sensor and a preparation method thereof, which are used for improving the temperature resistance and expanding the test temperature range.
In a first aspect, an embodiment of the present invention provides a gas sensor, including:
the semiconductor device comprises a semiconductor substrate, a buffer layer, a barrier layer, a cap layer, a source electrode and a drain electrode, wherein the semiconductor substrate, the buffer layer, the barrier layer and the cap layer are sequentially stacked, and the source electrode and the drain electrode are positioned on one side, away from the barrier layer, of the cap layer;
the source electrode and the drain electrode are arranged on the side, away from the cap layer, of the source electrode and the drain electrode; the temperature-resistant insulating layer covers the side walls of the cap layer, the barrier layer and the buffer layer along the thickness direction of the sensor, and covers the region of the cap layer where the source electrode and the drain electrode are not arranged;
the grid is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in the sensing area between the source electrode and the drain electrode.
Optionally, the thickness of the temperature-resistant insulating layer is not less than 10 nm.
The material of the temperature-resistant insulating layer comprises at least one of aluminum oxide, hafnium oxide, silicon nitride and silicon oxide.
The semiconductor substrate is made of silicon, silicon carbide, sapphire or gallium nitride, the buffer layer is made of aluminum nitride and gallium nitride, the barrier layer is made of AlGaN, and the cap layer is made of gallium nitride.
Optionally, the material of the gate includes Pt and La2O3Or SnO2The grid is used for reacting with the gas to be detected to generate a detection signalNumber (n).
Optionally, the temperature-resistant insulating layer includes a first opening and a second opening, the first opening exposes the source electrode, and the second opening exposes the drain electrode;
the sensor further comprises a first polar plate and a second polar plate, wherein the first polar plate is contacted with the source electrode through the first opening, and the second polar plate is contacted with the drain electrode through the second opening.
Optionally, the sensor further includes a passivation layer, the passivation layer is located on a side of the temperature-resistant insulating layer away from the semiconductor substrate, and a projection of at least a part of the passivation layer on the semiconductor substrate covers a projection of the temperature-resistant insulating layer on the semiconductor substrate, the projection being located outside the sensing region.
In a second aspect, an embodiment of the present invention provides a method for manufacturing a gallium nitride high-temperature gas sensor, including:
sequentially forming a semiconductor substrate, a buffer layer, a barrier layer and a cap layer;
forming a source electrode, a drain electrode and a temperature-resistant insulating layer; the source electrode and the drain electrode are positioned on one side of the cap layer far away from the barrier layer, and the temperature-resistant insulating layer is arranged on one side of the source electrode and the drain electrode far away from the cap layer; the temperature-resistant insulating layer covers the side walls of the cap layer, the barrier layer and the buffer layer along the thickness direction of the sensor, and covers the region of the cap layer where the source electrode and the drain electrode are not arranged;
and forming a grid electrode, wherein the grid electrode is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in an induction area between the source electrode and the drain electrode.
And forming a passivation layer, wherein the passivation layer is positioned on one side of the temperature-resistant insulating layer far away from the semiconductor substrate, and the projection of at least part of the passivation layer on the semiconductor substrate covers the projection of the temperature-resistant insulating layer outside the sensing area on the semiconductor substrate.
Optionally, the thickness of the temperature-resistant insulating layer is not less than 10 nm; the material of the temperature-resistant insulating layer comprises at least one of aluminum oxide, hafnium oxide, silicon nitride and silicon oxide.
The embodiment of the invention provides a gas sensor and a preparation method thereof, wherein the gas sensor comprises: the semiconductor substrate, the buffer layer, the barrier layer, the cap layer, the source electrode and the drain electrode are sequentially stacked, and the source electrode and the drain electrode are positioned on one side, far away from the barrier layer, of the cap layer; the temperature-resistant insulating layer is arranged on one side of the source electrode and the drain electrode, which is far away from the cap layer; the temperature-resistant insulating layer covers the side walls of the cap layer and the barrier layer along the thickness direction of the sensor, and covers the region of the cap layer where the source electrode and the drain electrode are not arranged; the grid is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in the induction area between the source electrode and the drain electrode. According to the technical scheme provided by the embodiment of the invention, the temperature-resistant insulating layer is arranged between the functional film layer grid and the barrier layer, so that the temperature resistance of the gas sensor is improved, the temperature testing range is expanded, and the range of gas detection is enlarged.
Drawings
Fig. 1 is a schematic structural diagram of a gas sensor according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of another gas sensor provided in the first embodiment of the present invention;
FIG. 3 is a flow chart of a method for manufacturing a gas sensor according to a second embodiment of the present invention;
fig. 4 to 5 are cross-sectional views illustrating the structure of the gas sensor formed in step S10 according to the method for manufacturing a gas sensor provided in the second embodiment of the present invention;
fig. 6 to 7 are cross-sectional views illustrating the structure of the gas sensor formed in step S20 according to the method for manufacturing a gas sensor provided in the second embodiment of the present invention;
fig. 8 is a cross-sectional view of the structure of the gas sensor formed in step S20 according to another method for manufacturing a gas sensor provided in the second embodiment of the present invention;
fig. 9 to fig. 11 are cross-sectional views illustrating the structure of the gas sensor formed in step S30 according to the method for manufacturing a gas sensor provided in the second embodiment of the present invention;
fig. 12 to 13 are cross-sectional views of structures of the gas sensor formed in step S30 according to another method for manufacturing a gas sensor provided in the second embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
Example one
An embodiment of the present invention provides a gas sensor, fig. 1 is a schematic structural diagram of a gas sensor provided in an embodiment of the present invention, and referring to fig. 1, the gas sensor includes:
the semiconductor substrate 10, the buffer layer 20, the barrier layer 30, the cap layer 40, and the source electrode 50 and the drain electrode 60 which are positioned on one side of the cap layer 40 far away from the barrier layer 30 are sequentially stacked;
the semiconductor structure further comprises a temperature-resistant insulating layer 70, wherein the temperature-resistant insulating layer 70 is arranged on one side of the source electrode 50 and the drain electrode 60 away from the cap layer 40; the temperature-resistant insulating layer 70 covers the side walls of the cap layer 40, the barrier layer 30 and the buffer layer 20 in the thickness direction of the sensor, and covers the regions of the cap layer 40 where the source electrode 50 and the drain electrode 60 are not arranged;
the semiconductor device further comprises a gate 80, wherein the gate 80 is positioned on one side of the temperature-resistant insulating layer 70 far away from the semiconductor substrate 10 and is positioned in the sensing region A between the source electrode 50 and the drain electrode 60.
Specifically, the material of the semiconductor substrate 10 of the gas sensor includes any one of silicon, silicon carbide, sapphire, gallium nitride, and the like. The buffer layer 20, the barrier layer 30, the cap layer 40, and the source electrode 50 and the drain electrode 60 on the side of the cap layer 40 away from the barrier layer 30 are epitaxially grown on the semiconductor substrate using MBE (Molecular Beam Epitaxy) technology or MOCVD (Metal-organic Chemical Vapor Deposition) technology. The buffer layer 20 is used to reduce stress between the barrier layer 30 and the semiconductor substrate 10, reduce defect density, and electrically insulate; the buffer layer 20 may include a general buffer layer 21 and a space isolation layer 22, the material of the general buffer layer 21 includes gan, the general buffer layer 21 is disposed near the semiconductor substrate 10, the material of the space isolation layer 22 includes aln, and the disposition of the space isolation layer 22 may further reduce the stress between the channel layer 30 and the substrate, reduce the defect density, and enhance the electrical insulation. The thickness of the general buffer layer 21 is greater than that of the space isolation layer 22, the thickness of the general buffer layer 21 is on the micrometer scale and can be set to be 3 μm exemplarily, and the thickness of the space isolation layer 22 is on the nanometer scale and can be set to be 0.7nm to 1 nm. The cap layer 40 serves to reduce contact resistance of the source and drain electrodes 50 and 60 with the barrier layer 30. The cap layer 40 is made of gallium nitride material and has a thickness of nanometer level, and may be set to a thickness of 1nm to 2nm, for example.
The barrier layer 30 may include AlGaN with a thickness of not less than 15nm, and the cap layer 40 may include gallium nitride with a thickness of 0.7nm to 2 nm. In addition, the composition of Al element in AlGaN which is a material of the barrier layer 30 is adjustable, and the barrier layer may be made of Al, for example0.2And GaN. A heterojunction is formed at a contact position between the buffer layer 20 and the barrier layer 30 to generate a Two-dimensional electron gas (2 DEG), which is an electron gas that can freely move in a Two-dimensional direction and is confined in a third-dimensional direction. Piezoelectric and spontaneous polarization effects are generated at the interface of the buffer layer 20 and the barrier layer 30, which are two materials with different energy bands and lattice constants, and the carrier electron concentration of the conductive pipe is increased accordingly. The metal material of the source electrode 50 and the drain electrode 60 on the side of the cap layer 40 away from the barrier layer 30 includes at least three of Ti, Al, Mo, Au, Ni, Pt, or W, and is typically an alloy formed by annealing a metal at a high temperature.
The cap layer 40 and the barrier layer 30 at two ends of the gas sensor are etched until part of the buffer layer 20 is exposed, the gas sensor is in a shape of a Chinese character 'tu', and at the moment, the temperature-resistant insulating layer 70 covers the cap layer 40, the barrier layer 30, the side wall of the exposed buffer layer 20 along the thickness direction of the sensor and the surface of the exposed buffer layer 20, and covers the region of the cap layer 40 where the source electrode 50 and the drain electrode 60 are not arranged. The temperature-resistant insulating layer 70 can prevent the device from contacting with gas or liquid, reduce the leakage of the source electrode 50 and the drain electrode 60 and influence the accuracy of the gas sensor; the temperature-resistant insulating layer 70 can slow down the diffusion phenomenon of the gas detection area in a high-temperature environment, and influence the stability of the gas sensor. The gate is located in a sensing region a between the source electrode 50 and the drain electrode 60 on a side of the temperature-resistant insulating layer 70 away from the semiconductor substrate 10. The sensing region a is a gas detection region of the sensor, and is generally a set region between the source electrode 50 and the drain electrode 60, and the size of the sensing region a is not particularly limited in this embodiment. The gas sensor mainly utilizes the reaction of the grid 80 and the gas to be detected to influence the concentration of two-dimensional electron gas generated by the heterojunction of the buffer layer 20 and the barrier layer 30, thereby converting chemical signals into electrical signals and achieving the purpose of detection. The temperature-resistant insulating layer 70 is arranged between the grid 80 and the cap layer 40, and the temperature-resistant insulating layer 70 is made of a temperature-resistant material, so that the influence of high temperature on the performance of a device can be reduced, the temperature resistance of the gas sensor is improved, and the temperature range of detected gas is enlarged.
Optionally, the thickness of the temperature-resistant insulating layer 70 is greater than or equal to 10nm, and the material of the temperature-resistant insulating layer 70 includes common insulating film materials such as aluminum oxide, hafnium oxide, and silicon oxide. Illustratively, alumina is a high hardness compound having a melting point of 2054 ℃ and a boiling point of 2980 ℃; the melting point of the hafnium oxide is 2758 ℃, the boiling point of the hafnium oxide is 5400 ℃, and both the aluminum oxide and the hafnium oxide have better temperature resistance, so that the influence of high temperature on the performance of the device can be better reduced. Temperature-resistant insulating layers 70 with different thicknesses are arranged, so that the bearing temperature of the gas sensor can be adjusted. In order to better improve the optimal temperature resistance of the gas sensor, the thickness of the temperature-resistant insulating layer 70 arranged between the cap layer 40 and the gate 80 is greater than or equal to 10 nm. Illustratively, when the thickness of the temperature-resistant insulating layer 70 is 10nm, the optimum temperature to which the gas sensor is subjected may be increased to 300 degrees celsius.
Optionally, the material of the gate 80 includes Pt and La2O3Or SnO2The grid 80 is used to react with the gas to be detected to generate a detection signal. Illustratively, a gate 80 of material Pt may be used to test for H2、NH3And NO2Isogas, material is La2O3Can be used to test CO2Gas, material SnO2May be used to test for ozone.
Optionally, with continued reference to fig. 1, the temperature-resistant insulating layer 70 includes a first opening B1 and a second opening B2, the first opening B1 exposes the source 50, and the second opening B2 exposes the drain 60;
the sensor further includes a first plate 51 and a second plate 52, the first plate 51 contacting the source electrode 50 through the first opening B1, and the second plate 52 contacting the drain electrode 60 through the second opening B2.
Specifically, the first electrode plate 51 and the second electrode plate 61 are made of a metal material, including Ti, Al, Mo, Au, Ni, Pt, W, or the like. The first polar plate 51 and the second polar plate 61 are connected with the source electrode 50 and the drain electrode 60 in a one-to-one correspondence manner, and the height of the first polar plate 51 and the second polar plate 61 is higher than that of the temperature-resistant insulating layer 70 at the edge of the opening so as to realize the extraction of the source electrode 50 and the drain electrode 60.
Optionally, with continued reference to fig. 1, the sensor further includes a passivation layer 90, where the passivation layer 90 is located on a side of the temperature-resistant insulating layer 70 away from the semiconductor substrate 10, and a projection of at least a portion of the passivation layer 90 on the semiconductor substrate 10 covers a projection of the temperature-resistant insulating layer 70 on the semiconductor substrate 10 outside the sensing region. The passivation layer 90 may be made of a silicon nitride material, and is used to protect each film layer in the gas sensor, thereby further ensuring the working performance and reliability of the gas sensor.
Note that the temperature-resistant insulating layer 70 may cover the edge regions of the source electrode 50 and the drain electrode 60, and in this case, the gate electrode 80 may completely cover the temperature-resistant insulating layer 70 between the source electrode 50 and the drain electrode 60, as shown in fig. 1. Fig. 2 is a schematic structural diagram of another gas sensor according to an embodiment of the present invention, and referring to fig. 2, the temperature-resistant insulating layer 70 does not cover the edge regions of the source electrode 50 and the drain electrode 60, and at this time, the gate electrode 80 covers a portion of the temperature-resistant insulating layer 70 located between the source electrode 50 and the drain electrode 60, and the passivation layer 90 covers the edge regions of the source electrode 50 and the drain electrode 60 to insulate the gate electrode 80 from the source electrode 50 and the drain electrode 60. In addition, the passivation layer 90 is located on a side of the temperature-resistant insulating layer 70 far away from the semiconductor substrate 10, and a projection of at least a part of the passivation layer 90 on the semiconductor substrate 10 covers a projection of the temperature-resistant insulating layer 70 on the semiconductor substrate 10 outside the sensing region. The passivation layer 90 may cover the first and second electrode plates 51 and 61 (see fig. 1) and may also expose the first and second electrode plates 51 and 61 (see fig. 2). The passivation layer 90 and the temperature-resistant insulating layer 70 may be specifically configured according to actual needs, and are not limited herein.
The present embodiment provides a gas sensor including: the semiconductor substrate, the buffer layer, the barrier layer, the cap layer, the source electrode and the drain electrode are sequentially stacked, and the source electrode and the drain electrode are positioned on one side, away from the channel layer, of the barrier layer; the temperature-resistant insulating layer is arranged on one side of the source electrode and one side of the drain electrode, which are far away from the barrier layer; the temperature-resistant insulating layer covers the side walls of the barrier layer and the cap layer along the thickness direction of the sensor, and covers the region of the barrier layer where the source electrode and the drain electrode are not arranged; the grid is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in the induction area between the source electrode and the drain electrode. According to the technical scheme provided by the embodiment, the temperature-resistant insulating layer is arranged between the functional film layer grid and the barrier layer, so that the temperature resistance of the gas sensor is improved, and the temperature range of the detected gas is enlarged.
Example two
An embodiment of the present invention provides a method for manufacturing a gas sensor, and fig. 3 is a flowchart of a method for manufacturing a gas sensor provided in a second embodiment of the present invention, and with reference to fig. 3, the method includes:
and S10, sequentially forming the semiconductor substrate, the buffer layer, the barrier layer and the cap layer.
Specifically, fig. 4 to 5 are cross-sectional views of the structure of the gas sensor formed in step S10 according to the method for manufacturing a gas sensor provided in the second embodiment of the present invention, and referring to fig. 4 to 5, the buffer layer 20, the barrier layer 30, and the cap layer 40 are epitaxially grown on the semiconductor substrate 10 by using MBE (Molecular Beam Epitaxy) technique or MOCVD (Metal-organic Chemical Vapor Deposition) technique. After the semiconductor substrate, the buffer layer, the barrier layer and the cap layer are formed in sequence, the method further comprises the following steps: an isolation region is formed. The cap layer 40 and the barrier layer 30 at two ends of the gas sensor can be etched by adopting a plasma etching method until part of the buffer layer 20 is exposed, and the gas sensor is in a shape of a Chinese character 'tu' to form an isolation region, so that the isolation between devices is realized. Wherein the material of the semiconductor substrate 10 of the gas sensor includes any one of silicon, silicon carbide, sapphire, gallium nitride, and the like. The buffer layer 20 includes a general buffer layer 21 and a space isolation layer 22, the material of the general buffer layer 21 includes aluminum nitride and gallium nitride, the general buffer layer 21 is disposed near the semiconductor substrate 10, the material of the space isolation layer 22 includes aluminum nitride, the thickness of the general buffer layer 21 is greater than that of the space isolation layer 22, the thickness of the general buffer layer 21 is on a micrometer scale, which can be set to 3 μm exemplarily, and the thickness of the space isolation layer 22 is on a nanometer scale, which can be set to 0.7nm to 1 nm. The buffer layer 20 and the barrier layer 30 have piezoelectric and spontaneous polarization effects at the interface of two materials with different energy bands and lattice constants, and form a two-dimensional electron gas plane at the interface, which has extremely high carrier concentration.
S20, forming a source electrode, a drain electrode and a temperature-resistant insulating layer; the source electrode and the drain electrode are positioned on one side of the cap layer far away from the barrier layer, and the temperature-resistant insulating layer is arranged on one side of the source electrode and the drain electrode far away from the cap layer; the temperature-resistant insulating layer covers the side walls of the cap layer, the barrier layer and the buffer layer in the thickness direction of the sensor, and covers the region of the cap layer where the source electrode and the drain electrode are not arranged.
Specifically, fig. 6 to 7 are cross-sectional views of the structure of the gas sensor formed in step S20 according to the method for manufacturing a gas sensor provided in the second embodiment of the present invention, and referring to fig. 6 to 7, the cap layer 40 and the barrier layer 30 at two ends of the gas sensor are etched away until a portion of the buffer layer 20 is exposed, and after the gas sensor is in a shape of "convex", the source electrode 50, the drain electrode 60, and the temperature-resistant insulating layer 70 are formed. The source electrode 50 and the drain electrode 60 are located on the side of the cap layer 40 away from the barrier layer 30, and the temperature-resistant insulating layer 70 is arranged on the side of the source electrode 50 and the drain electrode 60 away from the cap layer 40; the temperature-resistant insulating layer 70 covers the cap layer 40, the barrier layer 30, and the exposed side walls of the buffer layer 20 in the sensor thickness direction and the surface of the exposed buffer layer 20, and covers the cap layer 40 in the region where the source electrode 50 and the drain electrode 60 are not disposed. The temperature-resistant insulating layer 70 can prevent the device from contacting with gas or liquid, reduce the leakage of the source and drain, and affect the accuracy of the gas sensor. Optionally, the thickness of the temperature-resistant insulating layer is greater than or equal to 10 nm; the material of the temperature-resistant insulating layer comprises at least one of common insulating layers such as aluminum oxide, hafnium oxide, silicon oxide and the like; the metal material of the source and drain electrodes 50 and 60 may include Ti, Al, Mo, Au, Ni, Pt, W, and the like.
The source electrode 50 and the drain electrode 60 may be formed first, and then the temperature-resistant insulating layer 70 may be formed. The source electrode 50 and the drain electrode 60 may be formed after the temperature-resistant insulating layer 70 is formed. Referring to fig. 6-7, when the source electrode 50 and the drain electrode 60 are formed first and then the temperature-resistant insulating layer 70 is formed, a metal layer is deposited on the side of the cap layer away from the barrier layer to form the source electrode 50 and the drain electrode 60, and the temperature-resistant insulating layer 70 is formed on the side of the source electrode 50 and the drain electrode 60 away from the cap layer 40. A first opening B1 and a second opening B2 may be formed on the temperature-resistant insulating layer 70 by etching, wherein the first opening B1 exposes the source 50, and the second opening B2 exposes the drain 60. Finally, the formed temperature-resistant insulating layer 70 covers the cap layer 40, the barrier layer 30, the exposed side walls of the buffer layer 20 in the thickness direction of the sensor, and the exposed surface of the buffer layer 20, covers the regions of the cap layer 40 where the source electrode 50 and the drain electrode 60 are not disposed, and covers at least the edge regions of the source electrode 50 and the drain electrode 60. Fig. 8 is a cross-sectional view of the gas sensor structure formed in step S20 according to another method for manufacturing a gas sensor provided in the second embodiment of the present invention, and referring to fig. 8, when the temperature-resistant insulating layer 70 is formed first and then the source electrode 50 and the drain electrode 60 are formed, the temperature-resistant insulating layer 70 is formed on the side of the cap layer away from the barrier layer, an opening may be formed in the source electrode and the drain electrode by etching, and a portion of the cap layer 40 is exposed. A metal layer is deposited on the positions where the cap layer 40 is exposed to form the source electrode 50 and the drain electrode 60. The process sequence for forming the source electrode 50, the drain electrode 60 and the temperature-resistant insulating layer 70 can be adjusted according to actual needs.
And S30, forming a gate, wherein the gate is positioned on one side of the temperature-resistant insulating layer far away from the semiconductor substrate and is positioned in the sensing area between the source and the drain.
Specifically, fig. 9 to 11 are cross-sectional views of the structure of the gas sensor formed in step S30 according to the method for manufacturing a gas sensor provided in the second embodiment of the present invention, and referring to fig. 9 to 11, the gate 80 is exemplarily formed on the basis of the cross-sectional view of the structure provided in fig. 7. The gate 80 is located on the side of the temperature-resistant insulating layer 70 away from the semiconductor substrate 10 and is located in the sensing region a between the source 50 and the drain 60. The gas sensor mainly utilizes the grid 80 andthe reaction of the detected gas affects the concentration of the two-dimensional electron gas generated by the heterojunction between the buffer layer 20 and the barrier layer 30, so that the chemical signal is converted into an electrical signal, and the purpose of detection is achieved. Illustratively, the material of the gate 80 includes Pt and La2O3Or SnO2The gate 80 of Pt material can be used for testing H2、NH3And NO2Isogas, material is La2O3Can be used to test CO2Gas, material SnO2May be used to test for ozone. That is, the gate 80 is a functional film layer, and the temperature-resistant insulating layer 70 is disposed between the gate 80 and the barrier layer 40, so that the temperature resistance of the gas sensor is improved, the range of the test temperature is expanded, and the range of the detected gas is increased.
Optionally, the method further comprises: forming a passivation layer, wherein the passivation layer is positioned on one side of the temperature-resistant insulating layer far away from the semiconductor substrate, and the projection of at least part of the passivation layer on the semiconductor substrate covers the projection of the temperature-resistant insulating layer outside the sensing area on the semiconductor substrate; and forming a polar plate, wherein the polar plate is positioned on one side of the source electrode and the drain electrode, which is far away from the semiconductor substrate.
Specifically, a first plate 51 and a second plate 52 are formed, the first plate 51 is in contact with the source electrode 50 through the first opening B1, and the second plate 52 is in contact with the drain electrode 60 through the second opening B2. And manufacturing a passivation layer 90, wherein the passivation layer 90 covers the temperature-resistant insulating layer 70, the edge area of the grid electrode, the first electrode plate 51 and the second electrode plate 61, and exposes a part of the grid electrode 80 to form a sensing area A. The passivation layer 90 may be made of a silicon nitride material, and is used to protect each film layer in the gas sensor, thereby further ensuring the working performance of the gas sensor.
In another embodiment of the present invention, the passivation layer 90 may be formed first, and then the first and second electrode plates 51 and 52 may be formed. Fig. 12 to 13 are cross-sectional views of the gas sensor structure formed in step S30 according to another method for manufacturing a gas sensor according to the second embodiment of the present invention, and referring to fig. 12 to 13, a gate 80 is exemplarily formed on the cross-sectional view of the structure provided in fig. 8, the gate 80 is located on a side of the temperature-resistant insulating layer 70 away from the semiconductor substrate 10, and the gate 80 covers a portion of the temperature-resistant insulating layer 70 located between the source 50 and the drain 60. A passivation layer 90 is formed on the source electrode 50 and the drain electrode 60 at a side away from the cap layer 40, and the passivation layer 90 covers the temperature-resistant insulating layer 70 and the source electrode 50 and the drain electrode 60. Openings may be formed in the passivation layer 90 on the source and drain electrodes 50 and 60 by etching to expose the source and drain electrodes 50 and 60. A first plate 51 and a second plate 61 are formed on the exposed source electrode 50 and drain electrode 60, wherein the source electrode 50 contacts the first plate 51 through the opening, and the drain electrode 60 contacts the second plate 61 through the opening. The process cycle sequence for forming the first plate 51, the second plate 52 and the passivation layer 90 can be adjusted according to actual needs.
The embodiment of the invention provides a preparation method of a gas sensor, which comprises the following steps: sequentially forming a semiconductor substrate, a buffer layer, a barrier layer and a cap layer; forming a source electrode, a drain electrode and a temperature-resistant insulating layer, wherein the source electrode and the drain electrode are positioned on one side of the cap layer far away from the barrier layer, and the temperature-resistant insulating layer is arranged on one side of the source electrode and the drain electrode far away from the barrier layer; the temperature-resistant insulating layer covers the side walls of the cap layer, the barrier layer and the channel layer along the thickness direction of the sensor, and covers the region of the barrier layer where the source electrode and the drain electrode are not arranged; forming a grid electrode, wherein the grid electrode is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in an induction area between the source electrode and the drain electrode; and forming a passivation layer and an electrode plate, wherein the passivation layer is positioned on one side of the temperature-resistant insulating layer far away from the semiconductor substrate, and the electrode plate is positioned on one side of the source electrode and the drain electrode far away from the semiconductor substrate. According to the technical scheme provided by the embodiment of the invention, the temperature-resistant insulating layer is arranged between the functional film layer grid and the cap layer, so that the temperature resistance of the gas sensor is improved, the range of the test temperature is expanded, and the range of the detected gas is enlarged.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A gas sensor, comprising:
the semiconductor device comprises a semiconductor substrate, a buffer layer, a barrier layer, a cap layer, a source electrode and a drain electrode, wherein the semiconductor substrate, the buffer layer, the barrier layer and the cap layer are sequentially stacked, and the source electrode and the drain electrode are positioned on one side, away from the barrier layer, of the cap layer;
the source electrode and the drain electrode are arranged on the side, away from the cap layer, of the source electrode and the drain electrode; the temperature-resistant insulating layer covers the side walls of the cap layer, the barrier layer and the buffer layer along the thickness direction of the sensor, and covers the region of the cap layer where the source electrode and the drain electrode are not arranged;
the grid is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in the sensing area between the source electrode and the drain electrode.
2. A gallium nitride high-temperature gas sensor according to claim 1, wherein the thickness of the temperature-resistant insulating layer is not less than 10 nm.
3. The gallium nitride high-temperature gas sensor according to claim 1, wherein the material of the temperature-resistant insulating layer comprises at least one of aluminum oxide, hafnium oxide, silicon nitride, and silicon oxide.
4. The gallium nitride high-temperature gas sensor according to claim 1, wherein the semiconductor substrate comprises silicon, silicon carbide, sapphire or gallium nitride, the buffer layer comprises aluminum nitride and gallium nitride, the barrier layer comprises AlGaN, and the cap layer comprises gallium nitride.
5. A gallium nitride high-temperature gas sensor according to claim 1, wherein the gate is used to react with the gas to be detected to generate the detection signal, and the gate material comprises Pt and La2O3Or SnO2。
6. The gallium nitride high-temperature gas sensor according to claim 1, wherein the temperature-resistant insulating layer comprises a first opening and a second opening, the first opening exposes the source electrode, and the second opening exposes the drain electrode;
the sensor further comprises a first polar plate and a second polar plate, wherein the first polar plate is contacted with the source electrode through the first opening, and the second polar plate is contacted with the drain electrode through the second opening.
7. The GaN high-temperature gas sensor according to claim 6, further comprising a passivation layer located on a side of the temperature-resistant insulating layer away from the semiconductor substrate, wherein a projection of at least a portion of the passivation layer on the semiconductor substrate covers a projection of the temperature-resistant insulating layer on the semiconductor substrate outside the sensing region.
8. A preparation method of a gallium nitride high-temperature gas sensor is characterized by comprising the following steps:
sequentially forming a buffer layer, a barrier layer and a cap layer on a semiconductor substrate;
forming a source electrode, a drain electrode and a temperature-resistant insulating layer; the source electrode and the drain electrode are positioned on one side of the cap layer far away from the barrier layer, and the temperature-resistant insulating layer is arranged on one side of the source electrode and the drain electrode far away from the barrier layer; the temperature-resistant insulating layer covers the side walls of the cap layer, the barrier layer and the buffer layer along the thickness direction of the sensor, and covers the region of the cap layer where the source electrode and the drain electrode are not arranged;
and forming a grid electrode, wherein the grid electrode is positioned on one side of the temperature-resistant insulating layer, which is far away from the semiconductor substrate, and is positioned in an induction area between the source electrode and the drain electrode.
9. The preparation method according to claim 8, characterized in that a passivation layer is formed, the passivation layer is positioned on the side of the temperature-resistant insulating layer far away from the semiconductor substrate, and the projection of at least part of the passivation layer on the semiconductor substrate covers the projection of the temperature-resistant insulating layer on the semiconductor substrate, which is positioned outside the sensing region.
10. The preparation method according to claim 8, wherein the thickness of the temperature-resistant insulating layer is not less than 10 nm; the material of the temperature-resistant insulating layer comprises at least one of aluminum oxide, hafnium oxide, silicon nitride and silicon oxide.
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