Pressure sensor and method for manufacturing the same

Abstract

The present invention relates to a pressure sensor and a manufacturing method thereof, the method comprising: providing a substrate; forming a plurality of first holes arranged at intervals on the surface of the substrate; performing a first heat treatment so that the plurality of first holes are combined into a suspended first vacuum cavity; forming a groove connected to the first vacuum cavity and a sensing body surrounded by the groove. The method simplifies the manufacturing process of the pressure sensor. The pressure sensing film of the pressure sensor prepared at the same time is less affected by external stress.

Description

Technical Field

[0001] The present invention relates to the field of micro-electromechanical systems, and in particular to a pressure sensor and a manufacturing method thereof. Background Art

[0002] With the continuous development of micro-electromechanical system technology, the cost of pressure sensors is gradually decreasing, and the application of pressure sensors has also entered many fields such as medical, automotive, weather detection, height measurement, consumer electronics, etc. Commonly used pressure sensors are capacitive, piezoelectric, and piezoresistive. Among them, the piezoresistive pressure sensor has a relatively simple process and is suitable for mass production. It is the mainstream direction of pressure sensor development.

[0003] The pressure-sensitive film of the piezoresistive pressure sensor is the most critical structure. Currently, there are several methods commonly used to prepare piezoresistive pressure-sensitive films. One is to use an alkaline solution to anisotropically etch the back of the silicon wafer. This method obtains a back cavity and a certain thickness of the pressure-sensitive film by time control, but this method cannot guarantee the uniformity of the etching of the entire wafer, so it is difficult to obtain a pressure-sensitive film with high flatness. The second is electrochemical etching, which requires an expensive constant potential instrument and has a high production cost. The third is: using the C-SOI process, first etch a groove of the pressure cavity shape on the front of a Si wafer (called wafer 1); then, deposit silicon oxide on both sides of another Si wafer (called wafer 2), and bond the front of wafer 1 to any side of wafer 2 by Si-SiO2; thin wafer 2 to a certain thickness, and then obtain a suspended film and a closed pressure cavity; if used to prepare a gauge pressure sensor, the back of wafer 1 is etched by deep reactive ion etching to connect the pressure cavity to the outside world. The film obtained by this method is relatively thick, and the production cost is high when used to prepare small-range pressure sensors.

[0004] For piezoresistive pressure sensors, the pressure-sensitive film is very sensitive to stress introduced by external factors such as packaging, which can lead to insufficient stability in the output of the pressure sensor.

[0005] Therefore, how to obtain a pressure sensor with low manufacturing cost and good output stability has become a technical problem that needs to be solved urgently in the field. Summary of the invention

[0006] The technical problem to be solved by the present invention is to reduce the manufacturing cost of the pressure sensor, while reducing the influence of external stress on the pressure-sensitive film of the pressure sensor and improving the stability of the output of the pressure sensor.

[0007] In order to solve the above problems, the present invention provides a method for manufacturing a pressure sensor, which includes: providing a substrate; forming a plurality of first holes arranged at intervals on the surface of the substrate; performing a first heat treatment so that the plurality of first holes are merged into a suspended first vacuum cavity; forming a groove connected to the first vacuum cavity and a sensing body surrounded by the groove.

[0008] Optionally, the first heat treatment is rapid thermal annealing.

[0009] Optionally, the temperature of the first heat treatment is not less than 1100 degrees Celsius.

[0010] Optionally, the method further includes: forming a device layer covering the substrate by an epitaxial process.

[0011] Optionally, the method further includes: forming a plurality of second holes arranged at intervals on the surface of the device layer; and performing a second heat treatment so that the plurality of second holes are combined into a suspended second vacuum cavity, wherein the second vacuum cavity is located in the sensing body.

[0012] Optionally, the second heat treatment is rapid thermal annealing.

[0013] Optionally, the temperature of the second heat treatment is not less than 1100 degrees Celsius.

[0014] Optionally, the diameter of the second hole is 0.5 microns to 1.5 microns, and the diameter of the first hole is 0.5 microns to 1.5 microns.

[0015] Optionally, the second vacuum chamber is located directly above the first vacuum chamber.

[0016] Optionally, the groove is annular with a notch; the number of the grooves is two, namely the first and second grooves, the first groove surrounds the outside of the second groove, and the notch of the first groove and the notch of the second groove are arranged at a 180-degree interval.

[0017] In addition, the present invention also provides a pressure sensor, which includes: a semiconductor substrate; a suspended first vacuum cavity located in the semiconductor substrate, the first vacuum cavity being formed by merging a plurality of first grooves arranged at intervals through a first heat treatment; a groove located in the semiconductor substrate, the groove passing through a portion of the semiconductor substrate until it is connected to the first vacuum cavity, the groove and the first vacuum cavity forming a sensing body.

[0018] Optionally, the semiconductor substrate includes a substrate and a device layer located on the substrate, and the device layer is an epitaxial layer.

[0019] Optionally, a suspended second vacuum cavity is provided in the device layer, the second vacuum cavity is located in the sensing body, and is formed by merging a plurality of second grooves arranged at intervals through a second heat treatment.

[0020] Optionally, the second vacuum chamber is located directly above the first vacuum chamber.

[0021] Optionally, the second heat treatment is rapid thermal annealing.

[0022] Optionally, the groove is annular with a notch; the number of the grooves is two, namely the first and second grooves, the first groove surrounds the outside of the second groove, and the notch of the first groove and the notch of the second groove are arranged at a 180-degree interval.

[0023] Optionally, the first heat treatment is rapid thermal annealing.

[0024] The present invention first forms a plurality of first holes arranged at intervals on the surface of the substrate, and then performs a first heat treatment on the substrate, so that the plurality of first holes are combined into a suspended first vacuum cavity and the parts between the first holes are combined together to form a pressure-sensitive film (also called a suspended film), thereby simplifying the manufacturing process of the pressure-sensitive film. At the same time, the pressure-sensitive film formed by this heat treatment process has high flatness and a relatively thin thickness, which can be as thin as 1 micron. Furthermore, the side wall of the first vacuum cavity formed by the heat treatment process is relatively smooth, and the corners are all rounded, so that the pressure-sensitive film is basically stress-free.

[0025] Furthermore, after the first heat treatment, a device layer can be formed on the substrate by an epitaxial process. The material of the device layer is the same as that of the pressure-sensitive film and can be used as a part of the pressure-sensitive film. Since the thickness of the device layer is easy to control, the overall thickness of the pressure-sensitive film of the pressure sensor can be adjusted within a wide range. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figures 1 to 15 is a cross-sectional view of a pressure sensor at different manufacturing stages according to an embodiment of the present invention;

[0027] Fig.16 is a plan view of a pressure sensor in one embodiment of the present invention. DETAILED DESCRIPTION

[0028] The specific implementation of the pressure sensor manufacturing method provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0029] like Figure 1 As shown, a substrate 1 is provided, and the substrate 1 includes an upper surface 11 and a lower surface 12. In this embodiment, the substrate 1 is a single crystal silicon substrate. Of course, in other embodiments, the substrate 1 can also be made of other suitable semiconductor materials.

[0030] like Figure 2 As shown, a protective layer 13 having a plurality of patterns 14 (i.e., windows) is formed on the upper surface of the substrate 1. The manufacturing method of the protective layer 13 includes: forming a protective material layer (not shown) on the upper surface of the substrate 1 by low-pressure chemical vapor deposition, plasma chemical vapor deposition, or thermal oxidation, and then removing part of the protective material layer by photolithography and wet etching, or photolithography and dry etching, to form a protective layer 13 having patterns 14. In this specific embodiment, the material of the protective layer 13 is silicon oxide. In other specific embodiments of the present invention, the material of the protective layer 13 may also be dielectric materials such as silicon nitride, silicon carbide, and silicon oxynitride, and may be a single-layer or multi-layer composite structure.

[0031] like Figure 3 As shown, the substrate 1 is etched with the protective layer 13 as a mask to form a plurality of first holes 15 in the substrate 1. Since the first holes 15 are located on the surface of the substrate 1, they can also be referred to as first grooves. In this specific embodiment, an anisotropic etching process, such as a deep reactive ion silicon etching (DRIE) process, is used to etch the substrate 1 to obtain a plurality of first holes 15, and the portion between two adjacent first holes 15 is defined as a pattern 15a. In this embodiment, a plurality of first holes 15 are arranged in an array, and the first holes 15 are circular holes, the depth of the circular holes is several microns, the diameter is about 0.5 microns to 1.5 microns, for example, it can be 1 micron, and the interval between each circular hole is about 0.5 microns. Of course, in other embodiments, the first holes 15 can also be set as holes of other shapes, which can be rectangular, circular, pentagonal, hexagonal or other polygonal shapes, and the size and interval of the first holes can be adjusted accordingly according to the lithography capability of the lithography machine.

[0032] like Figure 4 As shown, the protective layer 13 is removed. In a specific embodiment, the protective layer 13 is removed by using a dry etching process or a wet etching process, such as using buffered hydrofluoric acid (BOE).

[0033] like Figure 5 As shown, the substrate 1 is subjected to a first heat treatment so that a plurality of first holes 15 (reference Figure 4 ) are combined into a suspended first vacuum chamber 16. The so-called suspended means that the first vacuum chamber 16 is located inside the substrate 1 and is spaced a certain distance from the upper surface 11 of the substrate 1. The portion of the substrate 1 between the upper surface 11 and the first vacuum chamber 16 is defined as a first suspended membrane 17.

[0034] Combination Figures 4 to 5As shown, under the action of the first heat treatment, the first hole 15 will expand in the horizontal direction, so that the various first holes 15 are interconnected, and thus merged into a complete large hole, namely the first vacuum chamber 16. At the same time, under the action of the first heat treatment, the upper surface energy of the substrate 1 is reduced, so that the upper surface of the substrate 1 migrates, and the ends of each graphic 15a are combined with each other as a whole, thereby forming a first suspended film 17 above the first vacuum chamber 16. The first suspended film 17 formed by the first heat treatment process is very flat and thin, and can be as thin as 1 micron. In a specific embodiment, the first vacuum chamber 16 is located in the upper center of the substrate 1. Moreover, the side walls of the first vacuum chamber 16 formed by the first heat treatment process are relatively smooth, and as shown in FIG. Figure 5 As shown, the corners of the first vacuum chamber 16 are all rounded, so that there is basically no stress in the first suspended membrane 17. Since the vacuum chamber and the suspended membrane are formed by heat treatment process, a series of adverse effects caused by traditional bulk silicon etching, sacrificial layer etching, and wafer bonding are avoided.

[0035] Specifically, the first heat treatment is performed in an oxygen-free, low-pressure (lower than atmospheric pressure) environment to prevent the substrate 1 from being oxidized. In one embodiment, the oxygen-free environment is a pure hydrogen environment. Of course, in other embodiments, the oxygen-free environment may also be an inert gas environment. The environmental pressure of the first heat treatment may be less than 1 atmosphere, so that the pressure in the first vacuum chamber 16 formed is less than 1 atmosphere.

[0036] In this embodiment, the temperature of the first heat treatment is 1100 degrees Celsius. Of course, in other embodiments, the temperature of the first heat treatment may also be higher than 1100 degrees Celsius. Further, in this embodiment, the first heat treatment is rapid thermal annealing.

[0037] like Figure 6 As shown, a device layer 18 covering the substrate 1 is formed by an epitaxial process. Since the epitaxial process is adopted, the material of the device layer 18 is the same as that of the substrate 1. In this embodiment, the material of the device layer 18 is single crystal silicon.

[0038] like Figure 7As shown, a protective layer 19 having a plurality of patterns 20 (i.e., windows) is formed on the device layer 18. The manufacturing method of the protective layer 19 includes: forming a protective material layer (not shown) on the upper surface of the device layer 18 by low-pressure chemical vapor deposition, plasma chemical vapor deposition, or thermal oxidation, and then removing part of the protective material layer by photolithography and wet etching, or photolithography and dry etching, to form a protective layer 19 having the patterns 20. In this specific embodiment, the material of the protective layer 19 is silicon oxide. In other specific embodiments of the present invention, the material of the protective layer 19 may also be dielectric materials such as silicon nitride, silicon carbide, and silicon oxynitride, and may be a single-layer or multi-layer composite structure.

[0039] like Figure 8 As shown, the substrate 1 with the device layer 18 is etched with the protective layer 19 as a mask to form a plurality of second holes 21 in the substrate 1. Since the second holes 21 are located on the surface of the device layer 18, the second holes 21 can also be referred to as second grooves. In this specific embodiment, an anisotropic etching process, such as a deep reactive ion silicon etching (DRIE) process, is used to etch the substrate 1 to obtain a plurality of second holes 21, and the portion between two adjacent second holes 21 is defined as a pattern 21a. In this embodiment, the plurality of second holes 21 are arranged in an array, and the second holes 21 are circular holes, the depth of the circular holes is several microns, the diameter can be 0.5 microns to 1.5 microns, for example, 1 micron, and the interval between each circular hole is about 0.5 microns. Of course, in other embodiments, the second holes 21 can also be set as holes of other shapes, which can be rectangular, circular, pentagonal, hexagonal or other polygonal. Further, in this embodiment, the plurality of second holes 21 are all located directly above the first vacuum chamber 16.

[0040] like Fig. 9 As shown, the protective layer 19 is removed. In a specific embodiment, the protective layer 19 is removed by using a dry etching process or a wet etching process, such as using buffered hydrofluoric acid (BOE).

[0041] like Fig.10 As shown, the substrate 1 is subjected to a first heat treatment so that a plurality of second holes 21 (reference Fig. 9 ) are combined into a suspended second vacuum chamber 7. The so-called suspended means that the second vacuum chamber 7 is located inside the substrate 1 with the device layer 18, and there is a certain distance from the upper surface of the device layer 18. The portion between the upper surface 11 of the device layer 18 and the second vacuum chamber 7 is defined as a second suspended film 8 (also called a pressure-sensitive film). In this embodiment, the second vacuum chamber 7 is located directly above the first vacuum chamber 16, and the width (horizontal dimension) of the second vacuum chamber 7 is smaller than the width of the first vacuum chamber 16.

[0042] Combination Figures 9 and 10As shown, under the effect of the second heat treatment, the second hole 21 will expand in the horizontal direction, so that the second holes 21 are interconnected, and thus merge into a complete large hole, namely the second vacuum chamber 7. At the same time, under the effect of the second heat treatment, the upper surface energy of the device layer 18 is reduced, so that the upper surface of the device layer 18 migrates, and the ends of each graphic 21a are combined into a whole, thereby forming a second suspended membrane 8 above the second vacuum chamber 7. The second suspended membrane 8 formed by the second heat treatment process is very flat and thin, and can be as thin as 1 micron. Moreover, the side wall of the second vacuum chamber 7 formed by the first heat treatment process is relatively smooth, and as shown in FIG. Fig.10 As shown, the corners of the second vacuum chamber 7 are all rounded, and the second suspended membrane 8 is substantially stress-free.

[0043] Specifically, the second heat treatment is performed in an oxygen-free, low-pressure (lower than atmospheric pressure) environment to prevent the substrate 1 from being oxidized. In one embodiment, the oxygen-free environment is a pure hydrogen environment. Of course, in other embodiments, the oxygen-free environment may also be an inert gas environment. The environmental pressure of the second heat treatment may be less than 1 atmosphere, so that the pressure in the formed second vacuum chamber 7 is less than 1 atmosphere.

[0044] In this embodiment, the temperature of the second heat treatment is 1100 degrees Celsius. Of course, in other embodiments, the temperature of the second heat treatment may also be higher than 1100 degrees Celsius. Furthermore, in this embodiment, the second heat treatment is rapid thermal annealing.

[0045] like Fig.11 As shown, a first dielectric layer 23 is formed on the device layer 18 as a barrier layer. The material may be silicon oxide, silicon nitride, silicon oxynitride, etc. The formation process may be low pressure chemical vapor deposition, plasma chemical vapor deposition or thermal oxidation.

[0046] Continue to refer Fig.11 As shown, a plurality of piezoresistors 10 are formed, and the piezoresistors 10 are located directly above the second vacuum chamber 7. In this embodiment, the piezoresistors 10 are formed by ion implantation, that is, the piezoresistors 10 are obtained by implanting ions into a specific area of ​​the surface of the device layer 18.

[0047] Continue to refer Fig.11 As shown, a second dielectric layer 22 is formed covering the first dielectric layer 23. The material of the second dielectric layer 22 can be silicon oxide, silicon nitride, silicon oxynitride, etc., and the formation process can be low pressure chemical vapor deposition, plasma chemical vapor deposition or thermal oxidation.

[0048] like Fig.12As shown, a portion of the second dielectric layer 22 and the first dielectric layer 23 are removed to form a plurality of windows 24, each of which exposes a corresponding portion of the piezoresistor 10. The windows 24 are formed by photolithography followed by reactive ion etching.

[0049] like Fig.13 As shown, a plurality of metal electrodes 9 are formed on the second dielectric layer 22, and a portion of the metal electrode 9 is filled into the window 24 and forms an ohmic contact with the piezoresistor 10. In this embodiment, the method for forming the metal electrode 9 includes: forming a metal material layer covering the second dielectric layer 22, a portion of the metal material layer is filled into the window 24, and forms an ohmic contact with the piezoresistor 10 below; the metal material layer may be formed by deposition or electroplating; a patterned mask layer is formed above the metal material layer, and the metal material layer is etched using the patterned mask layer as a mask to form the metal electrode 9, the etching process may be dry etching or wet etching, and the patterned mask layer may be a photoresist layer.

[0050] like Fig.14 As shown, a protection layer 26 having a pattern 27 is formed on the metal electrode 9 , the protection layer 26 covers the second dielectric layer 22 , and the pattern 27 is located at the periphery of the metal electrode 9 .

[0051] The manufacturing method of the protective layer 26 includes: after forming a protective material layer (not shown) on the upper surface of the second dielectric layer 22 and the metal electrode 9 by low pressure chemical vapor deposition, plasma chemical vapor deposition or thermal oxidation, a photolithography and wet etching process, or a photolithography and dry etching process is used to remove part of the protective material layer to form a protective layer 26 having a pattern 27. In this specific embodiment, the material of the protective layer 26 is silicon oxide. In other specific embodiments of the present invention, the material of the protective layer 26 can also be a dielectric material such as silicon nitride, silicon carbide, silicon oxynitride, etc., and can be a single layer or a multi-layer composite structure.

[0052] like Fig.15 As shown, the second dielectric layer 22 and the first dielectric layer 23 are etched to the substrate 1 using the protective layer 26 as a mask to form a groove 25 and a sensing body 6 surrounded by the groove 25. The groove 25 is connected to the first vacuum chamber 16 to form a receiving chamber (not marked). In this embodiment, the etching process is dry etching, specifically a deep reactive ion silicon etching (DRIE) process.

[0053] Specifically, the second vacuum chamber 7 is located in the sensing body 6, and the piezoresistance 10 and the metal electrode 9 are both located in the sensing body 6. The sensing body 6 is surrounded by the groove 25 and the first vacuum chamber 16, and can move in a direction perpendicular to the substrate 1, so as to deform when subjected to an external force, thereby detecting pressure according to the change in the resistance value of the piezoresistance 10.

[0054] Combination Fig.15 and Fig.16 As shown, in this embodiment, the groove 25 is in the shape of a ring with a notch (not marked), and the number of grooves 25 is two, namely an outer groove and an inner groove, wherein the notch of the outer groove and the notch of the inner groove are arranged at an interval of 180 degrees. More specifically, the groove 25 is rectangular, and one side is provided with a notch. The portion of the substrate 1 located between the outer groove and the inner groove constitutes a support beam 5, and the portion of the substrate 1 located in the notch of the groove 25 also constitutes another support beam, and the two support beams are connected to the sensing body 6, so that the sensing body 6 can be suspended.

[0055] It should be noted that the reference Fig.15 As shown, in the embodiment of the present invention, the number of grooves 25 is not limited to two, and the number can be set arbitrarily, for example, there can be only one groove 25. The number of notches in each groove 25 can be set arbitrarily, for example, it can be two. In addition, the shape of the groove 25 is not limited to a rectangle, and can also be set to a polygon such as a circle, a pentagon, or a hexagon.

[0056] In addition, the number of the first vacuum chambers 16 should not be limited to one, and can also be two. The two first vacuum chambers 16 are arranged at intervals in the horizontal direction, and the second vacuum chamber 7 is located between the two first vacuum chambers 16. Each first vacuum chamber is connected to the vertically extending groove. In this case, all the first vacuum chambers and all the grooves form a sensing body.

[0057] Furthermore, in a variation of the present embodiment, after forming the first vacuum chamber 16, the steps of forming the device layer and the second vacuum chamber can be omitted, and the steps of forming the piezoresistors, the metal electrodes, and the grooves can be directly performed. There is no second suspended film in the sensing body formed according to the variation method, and the first suspended film formed according to the first heat treatment step is the pressure-sensitive film.

[0058] The specific implementation of the pressure sensor provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0059] like Fig.15 As shown, the pressure sensor includes a substrate 1. In this embodiment, the substrate 1 is a single crystal silicon substrate. Of course, in other embodiments, the substrate 1 may also be made of other suitable semiconductor materials.

[0060] A suspended first vacuum chamber 16 is formed in the substrate 1. The so-called suspended means that the first vacuum chamber 16 is located inside the substrate 1 and is spaced a certain distance from the upper surface (not marked) of the substrate 1. The first vacuum chamber 16 is formed by merging a plurality of first grooves arranged at intervals through a first heat treatment, and the first grooves are located on the surface of the substrate 1. In other words, by first forming a plurality of first grooves arranged at intervals on the surface of the substrate 1 and then performing a first heat treatment, the first grooves can be merged into a suspended first vacuum chamber 16.

[0061] Under the action of the first heat treatment, the first groove will expand in the horizontal direction, so that the first grooves are interconnected, and thus merged into a complete large hole, that is, the first vacuum chamber 16. At the same time, under the action of the first heat treatment, the upper surface energy of the substrate 1 is reduced, so that the upper surface of the substrate 1 migrates, and the ends of the parts between the first grooves are combined into a whole, thereby forming a first suspended film (not marked) above the first vacuum chamber 16. The first suspended film formed by the first heat treatment process is very flat and thin, and can be as thin as 1 micron. In a specific embodiment, the first vacuum chamber 16 is located in the upper center of the substrate 1.

[0062] Specifically, the first heat treatment is performed in an oxygen-free, low-pressure (lower than atmospheric pressure) environment to prevent the substrate 1 from being oxidized. In one embodiment, the oxygen-free environment is a pure hydrogen environment. Of course, in other embodiments, the oxygen-free environment may also be an inert gas environment. The environmental pressure of the first heat treatment may be less than 1 atmosphere, so that the pressure in the first vacuum chamber 16 formed is less than 1 atmosphere.

[0063] In this embodiment, the temperature of the first heat treatment is 1100 degrees Celsius. Of course, in other embodiments, the temperature of the first heat treatment may also be higher than 1100 degrees Celsius. Further, in this embodiment, the first heat treatment is rapid thermal annealing.

[0064] In this embodiment, a device layer 18 is formed on the substrate 1. The device layer 18 is formed by epitaxial growth, that is, it is an epitaxial layer and has the same material as the substrate 1. The substrate 1 and the device layer 18 constitute a semiconductor substrate (not marked).

[0065] A first dielectric layer 23 is formed on the device layer 18 as a barrier layer. The material may be silicon oxide, silicon nitride, silicon oxynitride, etc. The formation process may be low pressure chemical vapor deposition, plasma chemical vapor deposition or thermal oxidation.

[0066] The second dielectric layer 22 is formed on the first dielectric layer 23. The second dielectric layer 22 may be made of silicon oxide, silicon nitride, silicon oxynitride, etc., and may be formed by low pressure chemical vapor deposition, plasma chemical vapor deposition, or thermal oxidation.

[0067] The groove 25 passes through the semiconductor substrate, the first dielectric layer 23 and the second dielectric layer 22 above the first vacuum chamber 16 and communicates with the first vacuum chamber 16. The groove 25 and the first vacuum chamber 16 form a sensing body 6.

[0068] Combination Fig.15 and Fig.16 As shown, in this embodiment, the groove 25 is in the shape of a ring with a notch (not marked), and the number of grooves 25 is two, namely an outer groove and an inner groove, wherein the notch of the outer groove and the notch of the inner groove are arranged at an interval of 180 degrees. More specifically, the groove 25 is rectangular, and one side is provided with a notch. The portion of the substrate 1 located between the outer groove and the inner groove constitutes a support beam 5, and the portion of the substrate 1 located in the notch of the groove 25 also constitutes another support beam, and the two support beams are connected to the sensing body 6, so that the sensing body 6 can be suspended.

[0069] It should be noted that the reference Fig.15 As shown, in the embodiment of the present invention, the number of grooves 25 is not limited to two, and the number can be set arbitrarily, for example, there can be only one groove 25. The number of notches in each groove 25 can be set arbitrarily, for example, it can be two. In addition, the shape of the groove 25 is not limited to a rectangle, and can also be set to a polygon such as a circle, a pentagon, or a hexagon.

[0070] In this embodiment, a suspended second vacuum chamber 7 is formed in the device layer 18. The so-called suspended means that the second vacuum chamber 7 is located inside the device layer 18 and is spaced a certain distance from the upper surface (not marked) of the device layer 18. The second vacuum chamber 7 is located in the sensing body 6 and directly above the first vacuum chamber 16.

[0071] The second vacuum chamber 7 is formed by merging a plurality of second grooves arranged at intervals through a second heat treatment, and the second grooves are located on the surface of the device layer 18. In other words, by first forming a plurality of second grooves arranged at intervals on the surface of the device layer 18 and then performing a second heat treatment, the second grooves can be merged into a suspended second vacuum chamber 7.

[0072] Under the effect of the second heat treatment, the second groove will expand in the horizontal direction, so that each second groove is interconnected, thereby merging into a complete large hole, that is, the second vacuum chamber 7. At the same time, under the effect of the second heat treatment, the upper surface energy of the device layer 18 is reduced, so that the upper surface of the device layer 18 migrates, and the ends of the parts between each second groove are combined into a whole, thereby forming a second suspended membrane (not marked) above the second vacuum chamber 7. The second suspended membrane formed by the second heat treatment process is very flat and thin, and can be as thin as 1 micron. In a specific embodiment, the second vacuum chamber 7 is located in the upper center of the device layer 18.

[0073] Specifically, the second heat treatment is performed in an oxygen-free, low-pressure (lower than atmospheric pressure) environment to prevent the device layer 18 and the substrate 1 from being oxidized. In one embodiment, the oxygen-free environment is a pure hydrogen environment. Of course, in other embodiments, the oxygen-free environment may also be an inert gas environment. The ambient pressure of the second heat treatment may be less than 1 atmosphere, so that the pressure in the formed second vacuum chamber 7 is less than 1 atmosphere.

[0074] In this embodiment, the temperature of the second heat treatment is 1100 degrees Celsius. Of course, in other embodiments, the temperature of the second heat treatment may also be higher than 1100 degrees Celsius. Furthermore, in this embodiment, the second heat treatment is rapid thermal annealing.

[0075] It should be noted that the number of the first vacuum chambers 16 is not limited to one, and can also be two. The two first vacuum chambers 16 are arranged at intervals in the horizontal direction, and the second vacuum chamber 7 is located between the two first vacuum chambers 16. Each first vacuum chamber is connected to the vertically extending groove. In this case, all the first vacuum chambers and all the grooves form a sensing body.

[0076] In a variation of the present invention, there is no second vacuum cavity in the pressure sensor, nor is there a device layer 18 (so that the semiconductor substrate is composed of only a simple substrate), the first dielectric layer 23 directly covers the surface of the substrate 1, and the piezoresistor 10 is directly formed on the surface of the substrate 1.

[0077] A plurality of piezoresistors 10 are formed on the surface of the device layer 18, and the piezoresistors 10 are located directly above the second vacuum chamber 7. In this embodiment, the piezoresistors 10 are formed by ion implantation, that is, ion implantation is performed on a specific area of ​​the surface of the device layer 18 to obtain the piezoresistors 10. The metal electrode 9 is located above the second dielectric layer 22, and one end thereof passes through the second dielectric layer 22 and the first dielectric layer 23 to form an ohmic contact with the piezoresistors 10 below.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for manufacturing a pressure sensor, characterized in that: include: providing a substrate; forming a plurality of first holes arranged at intervals on the surface of the substrate; Performing a first heat treatment so that a plurality of the first holes are combined into a suspended first vacuum cavity, and the corners of the first vacuum cavity are all rounded; A groove connected to the first vacuum chamber and a sensing body surrounded by the groove are formed, wherein the groove is annular with a notch, and there are two grooves, namely the first and second grooves, the first groove surrounds the outer side of the second groove, and the notch of the first groove and the notch of the second groove are arranged at an interval of 180 degrees, a portion of the substrate located between the first groove and the second groove constitutes a support beam, and a portion of the substrate located in the notch of the groove constitutes another support beam, and both support beams are connected to the sensing body, so that the sensing body is suspended.

2. The manufacturing method according to claim 1, characterized in that: The first heat treatment is rapid thermal annealing.

3. The manufacturing method according to claim 1, characterized in that: The temperature of the first heat treatment is not less than 1100 degrees Celsius.

4. The manufacturing method according to claim 1, characterized in that: Also includes: A device layer covering the substrate is formed by an epitaxial process.

5. The manufacturing method according to claim 4, characterized in that: Also includes: forming a plurality of second holes arranged at intervals on the surface of the device layer; A second heat treatment is performed to merge a plurality of the second holes into a suspended second vacuum cavity, wherein the second vacuum cavity is located in the sensing body.

6. The manufacturing method according to claim 5, characterized in that: The second heat treatment is rapid thermal annealing.

7. The manufacturing method according to claim 5, characterized in that: The temperature of the second heat treatment is not less than 1100 degrees Celsius.

8. The manufacturing method according to claim 5, characterized in that: The diameter of the second hole is 0.5 micrometers to 1.5 micrometers, and the diameter of the first hole is 0.5 micrometers to 1.5 micrometers.

9. The manufacturing method according to claim 5, characterized in that: The second vacuum chamber is located directly above the first vacuum chamber.

10. A pressure sensor, characterized in that: include: Semiconductor substrate; A suspended first vacuum chamber located in the semiconductor substrate, wherein the first vacuum chamber is formed by merging a plurality of first grooves arranged at intervals through a first heat treatment, and the corners of the first vacuum chamber are all rounded; A groove located in the semiconductor substrate, the groove passes through a portion of the semiconductor substrate until it is connected to the first vacuum chamber, the groove and the first vacuum chamber form a sensing body, and the groove is a ring with a gap; the number of the grooves is two, namely the first and second grooves, the first groove surrounds the outside of the second groove, and the gap of the first groove and the gap of the second groove are arranged at an interval of 180 degrees, the part of the substrate located between the first groove and the second groove constitutes a support beam, and the part of the substrate located in the gap of the groove constitutes another support beam, and the two support beams are connected to the sensing body, so that the sensing body is suspended.

11. The pressure sensor according to claim 10, characterized in that The semiconductor substrate comprises a substrate and a device layer located on the substrate, and the device layer is an epitaxial layer.

12. The pressure sensor according to claim 11, characterized in that: The device layer has a suspended second vacuum cavity, which is located in the sensing body and is formed by merging a plurality of second grooves arranged at intervals through a second heat treatment.

13. The pressure sensor according to claim 12, characterized in that: The second vacuum chamber is located directly above the first vacuum chamber.

14. The pressure sensor according to claim 12, characterized in that: The second heat treatment is rapid thermal annealing.

15. The pressure sensor according to any one of claims 10 to 14, characterized in that: The first heat treatment is rapid thermal annealing.

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