CN114427930B - Pressure sensor and method for producing the same - Google Patents
Pressure sensor and method for producing the same Download PDFInfo
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- CN114427930B CN114427930B CN202210103055.XA CN202210103055A CN114427930B CN 114427930 B CN114427930 B CN 114427930B CN 202210103055 A CN202210103055 A CN 202210103055A CN 114427930 B CN114427930 B CN 114427930B
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- 238000005530 etching Methods 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 25
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 23
- 229910052710 silicon Inorganic materials 0.000 claims description 23
- 239000010703 silicon Substances 0.000 claims description 23
- 230000005012 migration Effects 0.000 claims description 14
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- 238000000137 annealing Methods 0.000 claims description 9
- 239000000463 material Substances 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 abstract description 8
- 230000035945 sensitivity Effects 0.000 description 19
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- 239000012670 alkaline solution Substances 0.000 description 4
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- 230000007797 corrosion Effects 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
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- 229910052796 boron Inorganic materials 0.000 description 2
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
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- 230000015572 biosynthetic process Effects 0.000 description 1
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- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L7/00—Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements
- G01L7/02—Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements in the form of elastically-deformable gauges
- G01L7/08—Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements in the form of elastically-deformable gauges of the flexible-diaphragm type
- G01L7/082—Measuring the steady or quasi-steady pressure of a fluid or a fluent solid material by mechanical or fluid pressure-sensitive elements in the form of elastically-deformable gauges of the flexible-diaphragm type construction or mounting of diaphragms
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Pressure Sensors (AREA)
- Measuring Fluid Pressure (AREA)
Abstract
The invention provides a pressure sensor and a preparation method thereof, wherein the pressure comprises a substrate layer; a first epitaxial layer disposed over the substrate layer; the inner cavity is arranged above the substrate layer, and the top end of the inner cavity is not higher than the top end of the first epitaxial layer; a second epitaxial layer disposed over the interior chamber; island-like structures disposed in an inner central region of the substrate layer and independent of the substrate layer; the communication deep groove is arranged between the island structure and the substrate layer and is used for enabling the inner cavity to be in communication with external air.
Description
Technical Field
The invention relates to the technical field of micro-electromechanical systems, in particular to a pressure sensor and a preparation method thereof.
Background
Pressure sensors are one of the earliest products of microelectromechanical systems, and are classified according to principles into piezoresistive, capacitive, piezoelectric, etc. The piezoresistive pressure sensor has the advantages of high sensitivity, simple subsequent processing, suitability for mass production and the like, and is widely applied to the fields of consumer electronics, medical treatment, automobile, industrial control and the like.
An important indicator of pressure sensors is sensitivity, which is closely related to the consistency of the thickness of the sensitive membrane. At present, two typical processing methods exist, one is to utilize alkaline solution to corrode from the back of a silicon wafer, and the thickness of the piezoresistive film is controlled by controlling the corrosion time, but the shortcoming is that the consistency of the thickness of the piezoresistive film cannot be ensured and the size is large; the other is to process with silicon on an insulating substrate (i.e. silicon on insulator, SOI), and the thickness of the sensitive film is the thickness of the device layer on the SOI, but the cost is high.
Accordingly, there is a need for a novel pressure sensor and a method for manufacturing the same that solves the above-mentioned problems of the prior art.
Disclosure of Invention
The invention aims to provide a pressure sensor and a preparation method thereof, which can effectively improve the sensitivity consistency and linearity of the pressure sensor and improve the performance of the pressure sensor.
To achieve the above object, the present invention provides a pressure sensor comprising:
a substrate layer;
a first epitaxial layer disposed over the substrate layer;
the inner cavity is arranged above the substrate layer, and the top end of the inner cavity is not higher than the top end of the first epitaxial layer;
a second epitaxial layer disposed over the interior chamber;
island-like structures disposed in an inner central region of the substrate layer and independent of the substrate layer;
and the communication deep groove is arranged between the island-shaped structure and the substrate layer and is used for connecting the inner cavity with external air.
The pressure sensor has the beneficial effects that: in the pressure sensor, the back cavity is connected with the inner cavity in a conducting way through the communicating deep groove, and the inner cavity is positioned on the lower surface of the second epitaxial layer, so that the thickness of the second epitaxial layer determines the thickness of a sensitive film of the pressure sensor, the pressure sensor can obtain better sensitivity by controlling the thickness of the second epitaxial layer, when external air pressure enters the pressure sensor through the back cavity, the pressure effect is respectively generated on the epitaxial layer and the island structure, the island structure deforms, and the island structure has a buffer effect on the entering air, so that the pressure sensor generates more linear signal output, and the sensitivity and accuracy of the whole pressure sensor are effectively improved.
Optionally, the island structure is located at a side of the first epitaxial layer opposite to the substrate layer, and a projection shape of the island structure on a plane where the first epitaxial layer is located includes at least one of a circle, an ellipse, and a polygon.
Optionally, the island structure is made of the same material as the substrate layer.
Optionally, a plurality of trenches are formed in the first epitaxial layer, one end of each trench is connected with one surface of the second epitaxial layer, which is opposite to the first epitaxial layer, and the other end of each trench is connected with the internal cavity in a conducting manner.
Optionally, the projection shape of the trench on the plane of the first epitaxial layer includes at least one of a circle, an ellipse, and a polygon.
Optionally, a silicon migration layer is disposed above the inner chamber, and the silicon migration layer is located below the second epitaxial layer.
Optionally, a circuit device is arranged on the second epitaxial layer, the circuit device comprises a piezoresistor, a wire and a bonding pad, and the wire is electrically connected with the piezoresistor and the bonding pad.
Optionally, the piezoresistor and the wire are disposed inside the second epitaxial layer, and the bonding pad is disposed on the surface of the second epitaxial layer.
Optionally, the substrate layer is provided with a back cavity, and the back cavity is used for being connected with the internal cavity in a conducting manner through the communication deep groove.
Optionally, the projection of the island structure and the communication deep groove on the plane where the first epitaxial layer is located in the projection of the back cavity on the plane where the first epitaxial layer is located.
The invention also discloses a preparation method of the pressure sensor, which comprises the following steps:
providing a substrate material as a substrate layer;
etching a communication deep groove on the substrate layer, and forming a first epitaxial layer, an internal cavity and a second epitaxial layer above the substrate layer, wherein the internal cavity is positioned below the second epitaxial layer, and the first epitaxial layer is positioned below the second epitaxial layer;
etching the substrate layer to form an island structure below the first epitaxial layer so that the communication deep groove is in conductive connection with the inner cavity.
The preparation method of the pressure sensor has the beneficial effects that: according to the pressure sensor prepared by the method, the back cavity is communicated with the inner cavity through the communicating deep groove, and the inner cavity is positioned on the lower surface of the second epitaxial layer, so that the thickness of the sensitive film of the pressure sensor is determined by the thickness of the second epitaxial layer, the pressure sensor can obtain better sensitivity by controlling the thickness of the second epitaxial layer, and after external air pressure enters the pressure sensor through the back cavity, the pressure effect and deformation are respectively generated on the epitaxial layer and the island structure, and the island structure has a buffer effect on air entering the back cavity, so that the pressure sensor generates more linear signal output, and the sensitivity and accuracy of the whole pressure sensor are effectively improved.
Optionally, the forming a first epitaxial layer, an internal cavity, and a second epitaxial layer over the substrate layer includes:
etching the first epitaxial layer through the mask layer, forming a plurality of grooves on the surface of the first epitaxial layer, and forming a second protruding part and a plurality of first protruding parts on the surface of the first epitaxial layer;
and etching the substrate layer through the groove to form an inner cavity connected with the communication deep groove in a conducting mode in the substrate layer, and extending a second epitaxial layer on the surface of the first epitaxial layer.
Optionally, the etching the substrate layer through the trench to form an internal cavity connected with the communication deep groove in a conducting manner on the upper surface of the substrate layer and the lower surface of the first epitaxial layer includes:
and removing the mask layer, and etching the first epitaxial layer along the groove in an anisotropic etching and isotropic etching mode to form the inner cavity connected with the communication deep groove in a conducting manner in the substrate layer.
Optionally, forming the first epitaxial layer, the internal chamber, and the second epitaxial layer over the substrate layer includes:
forming a second epitaxial layer on the surface of the first epitaxial layer in an epitaxial manner;
and performing rapid annealing treatment on the second epitaxial layer to form a migration layer on the lower surface of the second epitaxial layer and form an inner cavity communicated with the communication deep groove.
Optionally, a piezoresistor, a wire and a bonding pad are sequentially formed on the upper surface of the second epitaxial layer, wherein the piezoresistor is connected with the bonding pad through the wire.
According to the preparation method of the pressure sensor, the second epitaxial layer is prepared by adopting a silicon epitaxial process, and the thickness of the second epitaxial layer determines the thickness of the sensitive film, so that the sensitivity of the prepared pressure sensor is determined, in actual operation, the thickness of the second epitaxial layer can be controlled to be +/-0.5 micrometers, and compared with the thickness of the sensitive film controlled by corrosion of a non-alkaline solution, the pressure sensor prepared by the method is high in sensitivity, and the size of the prepared epitaxial layer is smaller; on the other hand, the non-SOI silicon chip is adopted as a substrate and directly works on the silicon substrate, so that the process is simple and the cost is lower, in addition, the island structure is formed while the back cavity is formed, and the input gas is buffered through the island structure, so that the linearity of the output signal of the pressure sensor can be effectively improved.
Drawings
FIG. 1 is a schematic diagram of a pressure sensor according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of another structure of a pressure sensor according to an embodiment of the present invention;
FIG. 3 is a schematic cross-sectional structure of a substrate layer when a cross-section of a groove of a pressure sensor according to an embodiment of the present invention is elongated;
FIG. 4 is a schematic cross-sectional structure of a substrate layer when a cross-section of a groove of a pressure sensor according to an embodiment of the present invention is circular;
FIG. 5 is a schematic cross-sectional structure of a substrate layer when a cross-section of a groove of a pressure sensor according to an embodiment of the present invention is polygonal;
FIG. 6 is a flow chart of a method of manufacturing a pressure sensor according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a structure of a substrate layer etched to form a deep communication groove according to a method for manufacturing a pressure sensor according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a top view structure of a substrate layer after etching to form a communicating deep groove according to a method for manufacturing a pressure sensor according to an embodiment of the present invention;
FIG. 9 is a schematic structural diagram of a method for fabricating a pressure sensor according to an embodiment of the present invention after a first epitaxial layer is epitaxially formed on the basis of FIG. 8;
FIG. 10 is a schematic diagram of a structure obtained after forming an internal cavity by anisotropic etching and isotropic etching according to the method for manufacturing a pressure sensor according to an embodiment of the present invention;
FIG. 11 is a schematic structural diagram of a method for fabricating a pressure sensor according to an embodiment of the present invention after a second epitaxial layer is epitaxially formed on the basis of FIG. 10;
FIG. 12 is a schematic diagram of a structure of a pressure sensor according to an embodiment of the present invention after a second epitaxial layer is formed on the basis of FIG. 9;
FIG. 13 is a schematic diagram of a method for manufacturing a pressure sensor according to an embodiment of the present invention after forming an internal chamber by rapid annealing based on FIG. 12;
fig. 14 is a schematic view of the flow of the internal gas circuit when the pressure sensor is the structure of fig. 1 according to the embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. Unless otherwise defined, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. As used herein, the word "comprising" and the like means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof without precluding other elements or items.
In view of the problems existing in the prior art, an embodiment of the present invention provides a pressure sensor, as shown in fig. 1, including:
a substrate layer 1;
a first epitaxial layer 2 disposed above the substrate layer 1;
an internal chamber 5 disposed above the substrate layer 1 and having a top end at a height not higher than that of the top end of the first epitaxial layer 2;
a second epitaxial layer 3 disposed over the first epitaxial layer 2;
island structures 6 provided in an inner central region of the substrate layer 1 and independent of the substrate layer;
and a deep communicating groove 7 arranged between the island-shaped structures 6 and the substrate layer 1 and used for communicating the internal cavity 5 with external air.
Through the pressure sensor composed of the above structures, when the outside air flow enters the interior chamber 5 through the communicating deep groove 7, the whole air circuit can respectively generate pressure action on the island-shaped structure 6 and the second epitaxial layer 3, the second epitaxial layer 3 can deform through the pressure action, the second epitaxial layer 3 can deform through the pressure applied to the island-shaped structure 6, so that the circuit device arranged on the pressure sensor generates electric signal output, and the epitaxial process is adopted, so that the uniformity of the epitaxial film is good, the sensitivity uniformity of the pressure sensor is high, and meanwhile, the linearity of the whole pressure sensor is effectively improved through the island-shaped structure 6 in the pressure sensor, so that the performance of the pressure sensor is effectively improved.
In some embodiments, the island-like structure 6 is located on a side of the first epitaxial layer 2 opposite to the substrate layer 1, and a projection shape of the island-like structure 6 on a plane of the first epitaxial layer 2 includes at least one of a circle, an ellipse, and a polygon.
Specifically, the deep communication grooves 7 are provided around the island 6 so as to enter the deep communication grooves 7 after the air flow is blocked by the island 6.
It should be noted that, the shape of the island-shaped structure 6 includes any one of a circle, an ellipse, and a polygon, which is not limited in this aspect, and will not be described here again.
The island-shaped structures 6 and the substrate layer 1 are the same in material, and the island-shaped structures 6 may be etched by the substrate layer 1 or grown on the substrate layer 1, which is not described herein.
In other embodiments, a back cavity 8 is provided on the substrate layer, and the cavity 8 is used for conducting connection with the inner cavity 5 through the deep communicating groove 7, so as to facilitate external air flow to be sequentially transmitted into the deep communicating groove 7 and the inner cavity 5 through the back cavity 8.
Specifically, the back cavity 8 is disposed inside the substrate layer 1 and penetrates through the lower surface of the substrate layer 1, and the back cavity 8 is respectively in conductive connection with the deep communication groove 7 and the internal cavity 5, and the back cavity is etched by ICP deep silicon, so that the chip size can be reduced compared with a back cavity formed by etching with a conventional alkaline solution.
In this embodiment, the substrate layer 1 is a silicon substrate of a non-SOI silicon wafer, which has low cost and simple manufacturing process.
In some embodiments, a plurality of trenches 503 are disposed inside the first epitaxial layer 2, one end of the trench 503 is connected to a surface of the second epitaxial layer 3 opposite to the first epitaxial layer 2, and the other end is connected to the internal chamber 5 in a conductive manner,
specifically, the inner chamber 5 is partially on the lower surface of the first epitaxial layer 2, another portion is disposed on the upper surface of the substrate layer 1, the inner chamber 5 includes a conductive cavity 501, a plurality of first protruding members 502 are connected to the upper surface of the conductive cavity 501, the top ends of the first protruding members 502 penetrate through the first epitaxial layer 2 and are in contact connection with the second epitaxial layer 3, a groove 503 is disposed between adjacent first protruding members 502, the bottom of the groove 503 is connected with the conductive cavity 501, and the top of the groove 503 is opposite to the second epitaxial layer 3.
In this embodiment, since the top ends of the grooves 503 between the adjacent first protruding parts 502 are in contact with the second epitaxial layer 3, and the bottom ends of the grooves 503 are in conductive connection with the conductive cavity 501, after the external air path enters the back cavity 8 inside the pressure sensor, the air path enters the conductive cavity 501 along the deep communicating groove 7 after the pressure action is generated on the island structure 6, and the pressure action is generated on the second epitaxial layer 3 through the grooves 503 on the conductive cavity 501, so that the second epitaxial layer 3 can deform as a sensitive film, thereby improving the sensitivity consistency of the pressure sensor.
In some embodiments, a second protruding part 504 is disposed at the center of the first epitaxial layer 2, the top end of the second protruding part 504 is connected with the second epitaxial layer 3, the bottom end of the second protruding part 504 is connected with the island structure 6, and the island structure 6 is connected together through the second protruding part 504, so that the island structure 6 can deform according to air pressure while the second epitaxial layer 3 on the top end of the second protruding part 504 can be driven to deform, and the sensitivity consistency of the whole pressure sensor is further improved.
In some embodiments, fig. 2 is a schematic diagram of another structure of the internal chamber according to the embodiment of the present invention, referring to fig. 2, a silicon migration layer 505 is disposed on the upper surface of the internal chamber 5, and the upper surface of the silicon migration layer 505 is in contact with the second epitaxial layer 3.
In this embodiment, since the upper surface of the inner chamber 5 is provided with the silicon migration layer 505, and the top end of the silicon migration layer 505 is in contact with the second epitaxial layer 3, after the gas path passes through the back cavity 8 and enters the inner chamber 5 from the deep communication groove 7, the gas pressure of the gas path can squeeze the second epitaxial layer 3 through the silicon migration layer 505, so that the second epitaxial layer 3 can be guaranteed to deform rapidly, and the sensitivity consistency of the whole pressure sensor is improved.
In some embodiments, referring to fig. 1, a circuit device 4 is disposed on the second epitaxial layer, where the circuit device 4 includes a varistor 401, a wire 402, and a pad 403, and the wire 402 electrically connects the varistor 401 and the pad 403.
Specifically, the piezoresistor 401 and the wire 402 are disposed inside the second epitaxial layer 3, the bonding pad 403 is disposed on the surface of the second epitaxial layer 3, and the piezoresistor 401 is electrically connected with the bonding pad 403 through the wire 402, so that when the second epitaxial layer 3 of the pressure sensor is deformed as a sensitive film through the circuit structure, the piezoresistor 401 is ensured to generate a signal according to external pressure change, and the detection sensitivity of the whole pressure sensor is improved.
In some embodiments, the projection of the island structure 6 and the deep communicating groove 7 on the plane of the first epitaxial layer 2 is located in the projection of the back cavity 8 on the plane of the first epitaxial layer 2, so that the external air passage is easier to enter the deep communicating groove 7 after entering the back cavity 8.
Specifically, the width of back cavity 8 in the horizontal direction exceeds the width of intercommunication deep groove 7 in the horizontal direction, through setting up the width of back cavity 8 beyond the width of intercommunication deep groove 7 for outside gas circuit enters into back cavity 8 after, enters into intercommunication deep groove 7 inside more easily, thereby makes the gas circuit that enters into intercommunication deep groove 7 inside can make pressure sensor produce deformation more easily, in order to further improve pressure sensor's sensitivity.
In some embodiments, referring to fig. 1, the outer side surface of the deep communicating groove 7 is in contact with the inner surface of the substrate layer 1, and the inner side surface of the deep communicating groove 7 is in contact with the outer surface of the island structure 6, so that when the external gas path enters the deep communicating groove 7, a part of gas directly applies pressure to the island structure 6 to make the island structure 6 drive the second epitaxial layer 3 to deform, and meanwhile, the gas pressure also directly applies pressure to the second epitaxial layer 3 to deform the second epitaxial layer 3, thereby further improving the sensitivity of the pressure sensor.
In other embodiments, the projection shape of the trench 503 on the plane where the first epitaxial layer is located includes at least one of a circle, an ellipse, and a polygon, which may be selected according to a specific manufacturing process, and the shape of the trench 503 is not limited in this scheme and will not be described herein.
Specifically, the cross section of the trench 503 along the plane parallel to the plane of the lower surface of the first epitaxial layer 2 is circular, elliptical or polygonal.
In this embodiment, since the number of the grooves 503 is plural, the shapes of the grooves 503 may be the same or different, and the description thereof is omitted.
Specifically, fig. 3 is a schematic cross-sectional view of a substrate layer when the horizontal cross-section of the groove 503 is in a long strip shape, referring to fig. 3, the groove 503 is in a long strip shape, and the first protruding parts 502 are structures between the grooves 503.
Specifically, fig. 4 is a schematic cross-sectional view of a substrate layer when the cross-section of the groove is a horizontal circle, and referring to fig. 4, the groove 503 is a circle, and the first protruding member 502 is a structure between the grooves 503.
Specifically, fig. 5 is a schematic cross-sectional view of a substrate layer when the cross-section of the groove is polygonal, referring to fig. 5, the groove 503 is polygonal, and the first protruding member 502 is a structure between the grooves 503.
The invention also provides a preparation method of the pressure sensor, referring to fig. 6, comprising the following steps:
s601, providing a substrate material as a substrate layer.
In this embodiment, the substrate layer 1 is a silicon substrate of a non-SOI silicon wafer, which has low cost and simple manufacturing process.
S602, forming a communicating deep groove on the substrate layer by etching, and forming a first epitaxial layer, an internal cavity and a second epitaxial layer above the substrate layer, wherein the internal cavity is positioned below the second epitaxial layer, and the first epitaxial layer is positioned below the second epitaxial layer.
Specifically, fig. 7 is a schematic structural diagram of the substrate layer of the present invention after etching to form the communication deep groove, and fig. 8 is a schematic structural diagram of the substrate layer of the present invention in a top view after etching to form the communication deep groove, and referring to fig. 7 and 8, after etching the substrate layer 1, a square communication deep groove 7 is formed inside the substrate layer 1.
In still other embodiments, a first epitaxial layer 2 is first formed on the upper surface of the substrate layer 1, and the resulting structure is shown in fig. 9, and the subsequent processing includes:
growing a mask layer on the surface of the first epitaxial layer;
etching the first epitaxial layer through the mask layer, forming a plurality of grooves on the surface of the first epitaxial layer, and forming a second protruding part and a plurality of first protruding parts on the surface of the first epitaxial layer;
and etching the substrate layer through the groove to form an inner cavity connected with the communication deep groove in a conducting manner on the upper surface of the substrate layer and the lower surface of the first epitaxial layer.
After a mask layer 201 is formed on the upper surface of the first epitaxial layer 2, the first epitaxial layer 2 is etched through the shape of the mask layer 201, so that a plurality of grooves 503 are formed on the surface of the first epitaxial layer 2, and a second protruding part 504 and a plurality of first protruding parts 502 are formed between the adjacent grooves 503, and meanwhile, an internal cavity 5 is etched inside the substrate layer 1.
In some embodiments, the process of etching the substrate layer through the trench to form an internal chamber in conductive connection with the communication deep trench on the upper surface of the substrate layer and the lower surface of the first epitaxial layer includes:
and removing the mask layer 201, and etching the first epitaxial layer 2 along the trench 503 by adopting an anisotropic etching mode and an isotropic etching mode to form the internal cavity 5 which is in conductive connection with the deep communication groove 7 on the upper surface of the substrate layer 1 and the lower surface of the first epitaxial layer 2.
Referring to fig. 10, since the first epitaxial layer 2 is etched along the trench 503 by anisotropic etching and isotropic etching, the trench 503 and the first protruding member 502 become shorter, and the internal chamber 5 is formed inside the substrate layer 1 until the formed internal chamber 5 is in communication with the communication deep groove 7, thereby completing the etching process, and the internal chamber 5 in communication with the communication deep groove 7 is formed inside the substrate layer 1.
Further, a second epitaxial layer 3 is epitaxially formed on the above-obtained structure, the obtained structure being shown in fig. 11.
In some embodiments, forming a first epitaxial layer, an interior chamber, and a second epitaxial layer over the substrate layer, comprises:
forming a second epitaxial layer 3 on the surface of the first epitaxial layer 2 in an epitaxial manner;
and performing rapid annealing treatment on the second epitaxial layer 3 to form a migration layer 505 on the lower surface of the second epitaxial layer 3 and form an internal cavity 5 communicated with the communication deep groove 7.
After removing the mask layer 201, a second epitaxial layer 3 is epitaxially formed on the upper surface of the first epitaxial layer 2, the resulting structure is shown in fig. 12, then, the second epitaxial layer 3 is subjected to a rapid annealing treatment, under the action of high temperature, a migration layer 505 with a certain thickness is formed on the lower surface of the second epitaxial layer 3 due to the migration effect of silicon, and an internal cavity 5 which is in conduction with the communicating deep groove 7 is formed, so that the treatment process is completed, and the resulting structure after the treatment is shown in fig. 13.
In some alternative embodiments, the rapid annealing process for the second epitaxial layer 3 includes a rapid annealing process at a temperature of 1100-1200 c and under hydrogen. Alternatively, the rapid annealing process is performed at 1150 ℃.
In some embodiments, a circuit device is formed on the upper surface of the second epitaxial layer, the process comprising:
a piezoresistor 401 and a wire 402 are arranged in the second epitaxial layer 3, a bonding pad 403 is arranged on the surface of the second epitaxial layer 3, and the piezoresistor 401 is connected with the bonding pad 403 through the wire 402.
In some embodiments, the varistor 401 is formed by lightly doping with boron ions, the lead 402 is formed by heavily doping with boron ions, the metal material of the pad 403 is any one of aluminum, gold, and platinum, and other metal materials that can be suitable for the present solution are also included, and the forming process of the circuit device 4 is the content of the prior art and will not be described herein.
Optionally, a dielectric layer (not shown) is further formed on the outer surface of the second epitaxial layer 3 for protection, where the dielectric layer includes silicon oxide, silicon nitride, or a combination of the two.
And S603, etching the substrate layer to form an island-shaped structure below the first epitaxial layer so that the communication deep groove is in conductive connection with the inner cavity.
By etching the lower surface of the substrate layer 1, a back cavity 8 is formed on the lower surface of the substrate layer 1 until the back cavity 8 is communicated with the deep communication groove 7, and then the island-shaped structures 6 connected with the second protruding parts 504 are formed inside the substrate layer 1, so that the pressure sensor with a final structure is obtained.
It should be noted that, since two different manufacturing processes may be selected for the inner chamber 5 during the formation of the pressure sensor, the structure of the final pressure sensor is also different, specifically, after the inner chamber 5 is formed by using the isotropic etching method in fig. 10, the structure of the final pressure sensor is shown in fig. 1; and after forming the inner chamber 5 by rapid annealing in fig. 13, the structure of the resulting pressure sensor is shown in fig. 2.
In the preparation process, the thickness of the second epitaxial layer 3 determines the thickness of the sensitive film, so that the sensitivity of the whole pressure sensor is determined, the thickness of the epitaxial layer can be accurately controlled to be +/-0.5 microns by the epitaxial process, and compared with the film thickness controlled by non-alkaline solution corrosion, the thickness of the pressure sensor is high in sensitivity and small in size, and a non-SOI silicon wafer is adopted as a substrate layer to directly operate on a silicon substrate, so that the cost is low and the process is simple.
The back cavity 8 is connected with the inner cavity 5 positioned on the lower surface of the second epitaxial layer 3 in a conducting manner through the deep communicating groove 7, and taking the structure of the pressure sensor in fig. 1 as an example, referring to fig. 14, after the external gas path enters the pressure sensor through the back cavity 8 along the arrow direction in the drawing, the external gas path enters the inner cavity 5 through the deep communicating groove 7, so that the whole gas path can respectively exert pressure effects on the island structure 6 and the second epitaxial layer 3, the second epitaxial layer 3 can be deformed directly due to the pressure effect, meanwhile, the second epitaxial layer 3 can be further promoted to deform due to the pressure exerted on the island structure 6, so that the sensitivity of the whole pressure sensor is improved, meanwhile, the island structure 6 in the pressure sensor buffers the input gas pressure, the linearity of the output signal of the whole pressure sensor is effectively improved, and the performance of the pressure sensor is effectively improved.
While embodiments of the present invention have been described in detail hereinabove, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. It is to be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the following claims. Moreover, the invention described herein is capable of other embodiments and of being practiced or of being carried out in various ways.
Claims (14)
1. A pressure sensor, comprising:
a substrate layer;
the first epitaxial layer is arranged above the substrate layer, a plurality of grooves are formed in the first epitaxial layer, a plurality of first protruding parts are arranged between every two adjacent grooves, and a second protruding part is arranged at the center of the first epitaxial layer;
the inner cavity is arranged above the substrate layer, and the top end of the inner cavity is not higher than the top end of the first epitaxial layer;
the second epitaxial layer is arranged above the inner cavity, one end of the groove is connected with one surface of the second epitaxial layer opposite to the first epitaxial layer, and the other end of the groove is connected with the inner cavity in a conducting way;
island-like structures disposed in an inner central region of the substrate layer and independent of the substrate layer; the island-shaped structure is surrounded by the inner cavity, and the island-shaped structure is connected with the second epitaxial layer through the second protruding part of the first epitaxial layer, so that the second epitaxial layer can be driven to deform;
and the communication deep groove is arranged between the island-shaped structure and the substrate layer and is used for conducting the internal cavity with external gas.
2. A pressure sensor, comprising:
a substrate layer;
the first epitaxial layer is arranged above the substrate layer, and a second protruding part is arranged at the center of the first epitaxial layer;
the inner cavity is arranged above the substrate layer, and the top end of the inner cavity is not higher than the top end of the first epitaxial layer;
a second epitaxial layer disposed over the interior chamber;
island-like structures disposed in an inner central region of the substrate layer and independent of the substrate layer; the island-shaped structure is surrounded by the inner cavity, and the island-shaped structure is connected with the second epitaxial layer through the second protruding part of the first epitaxial layer, so that the second epitaxial layer can be driven to deform;
the communication deep groove is arranged between the island-shaped structure and the substrate layer and is used for conducting the internal cavity with external gas;
and a silicon migration layer is arranged above the inner cavity, and the silicon migration layer is positioned on the lower surface of the second epitaxial layer.
3. The pressure sensor of claim 1 or 2, wherein the island structure is located on a side of the first epitaxial layer opposite to the substrate layer, and a projected shape of the island structure on a plane of the first epitaxial layer includes at least one of a circle, an ellipse, and a polygon.
4. A pressure sensor according to claim 1 or 2, wherein the island structure is of the same material as the substrate layer.
5. The pressure sensor of claim 1, wherein the projected shape of the trench in the plane of the first epitaxial layer comprises at least one of a circle, an ellipse, and a polygon.
6. A pressure sensor according to claim 1 or 2, wherein a circuit device is provided on the second epitaxial layer, the circuit device comprising a varistor, a wire and a bonding pad, the wire electrically connecting the varistor and the bonding pad.
7. The pressure sensor of claim 6, wherein the piezoresistor and the wire are disposed inside the second epitaxial layer, and the bonding pad is disposed on a surface of the second epitaxial layer.
8. Pressure sensor according to claim 1 or 2, characterized in that the substrate layer is provided with a back cavity for conductive connection with the inner chamber through the communication deep groove.
9. The pressure sensor of claim 8, wherein a projection of the island and the communication deep groove on a plane of the first epitaxial layer is located within a projection of the back cavity on the plane of the first epitaxial layer.
10. A method of manufacturing a pressure sensor, comprising:
providing a substrate material as a substrate layer;
etching to form a communicating deep groove on the substrate layer, and forming a first epitaxial layer, an internal cavity and a second epitaxial layer above the substrate layer, wherein the first epitaxial layer is positioned below the second epitaxial layer, the internal cavity is positioned below the second epitaxial layer, and the top end of the internal cavity is not higher than the top end of the first epitaxial layer; a plurality of grooves are formed in the first epitaxial layer, a plurality of first protruding parts are arranged between every two adjacent grooves, one end of each groove is connected with one surface of the second epitaxial layer opposite to the first epitaxial layer, the other end of each groove is connected with the inner cavity in a conducting manner, and a second protruding part is formed at the center of the first epitaxial layer;
etching the substrate layer to form an island structure located below the first epitaxial layer, so that the communication deep groove is in conductive connection with the inner cavity, the island structure is surrounded by the inner cavity, and the island structure is connected with the second epitaxial layer through the second protruding part of the first epitaxial layer, so that the second epitaxial layer can be driven to deform.
11. A method of manufacturing a pressure sensor, comprising:
providing a substrate material as a substrate layer;
etching to form a communicating deep groove on the substrate layer, and forming a first epitaxial layer, an internal cavity and a second epitaxial layer above the substrate layer, wherein the first epitaxial layer is positioned below the second epitaxial layer, the internal cavity is positioned below the second epitaxial layer, and the top end of the internal cavity is not higher than the top end of the first epitaxial layer; forming a second protruding part at the center of the first epitaxial layer, and performing rapid annealing treatment on the second epitaxial layer to form a migration layer on the lower surface of the second epitaxial layer and form an inner cavity communicated with the communication deep groove;
etching the substrate layer to form an island structure located below the first epitaxial layer, so that the communication deep groove is in conductive connection with the inner cavity, the island structure is surrounded by the inner cavity, and the island structure is connected with the second epitaxial layer through the second protruding part of the first epitaxial layer, so that the second epitaxial layer can be driven to deform.
12. The method of manufacturing a pressure sensor of claim 10, wherein forming a first epitaxial layer, an interior chamber, and a second epitaxial layer over the substrate layer comprises:
growing a mask layer on the surface of the first epitaxial layer;
etching the first epitaxial layer through the mask layer, forming a plurality of grooves on the surface of the first epitaxial layer, and forming the second raised parts and a plurality of first raised parts on the surface of the first epitaxial layer;
and etching the substrate layer through the groove to form an inner cavity connected with the communicating deep groove in a conducting way on the upper surface of the substrate layer and the lower surface of the first epitaxial layer, and extending a second epitaxial layer on the surface of the first epitaxial layer.
13. The method of claim 12, wherein etching the substrate layer through the trench to form an internal chamber in conductive connection with the deep communication trench on the upper surface of the substrate layer and the lower surface of the first epitaxial layer, comprises:
and removing the mask layer, and etching the first epitaxial layer along the groove in an anisotropic etching and isotropic etching mode to form the inner cavity connected with the communication deep groove in a conducting manner on the upper surface of the substrate layer and the lower surface of the first epitaxial layer.
14. The method of manufacturing a pressure sensor according to claim 10 or 11, wherein a varistor and a wire are provided inside the second epitaxial layer, and a bonding pad is provided on the surface of the second epitaxial layer, and the varistor is connected to the bonding pad through the wire.
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