CN106404237B - Pressure sensor chip, preparation method thereof and absolute pressure sensor chip - Google Patents
Pressure sensor chip, preparation method thereof and absolute pressure sensor chip Download PDFInfo
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- CN106404237B CN106404237B CN201510456679.XA CN201510456679A CN106404237B CN 106404237 B CN106404237 B CN 106404237B CN 201510456679 A CN201510456679 A CN 201510456679A CN 106404237 B CN106404237 B CN 106404237B
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Abstract
The embodiment of the invention discloses a pressure sensor chip, a preparation method thereof and an absolute pressure sensor chip. The pressure sensor chip comprises a glass base, a silicon base and a silicon diaphragm which are arranged in sequence. The upper surface of the silicon base is provided with a first concave cavity and a second concave cavity, and a through cavity communicated with the second concave cavity and the lower surface of the silicon base is arranged below the second concave cavity. The inner ring of the through cavity is positioned on the periphery of the inner ring of the second concave cavity, and the distance between the inner ring and the outer ring of the through cavity is smaller than the distance between the inner ring and the outer ring of the second concave cavity. The silicon diaphragm is fixed on the upper surface of the silicon base. And the edge of the area of the surface of the silicon membrane corresponding to the first concave cavity is provided with an absolute pressure piezoresistor and a first Wheatstone bridge for outputting an absolute pressure signal. And a differential pressure piezoresistor and a second Wheatstone bridge for outputting a differential pressure signal are arranged at the edge of the area of the surface of the silicon diaphragm corresponding to the second concave cavity. The glass base is provided with a vent hole which is communicated with the through cavity and the outside of the glass base. The measuring range of the pressure difference measuring device is wide, and synchronous measurement of the pressure difference and the absolute pressure can be achieved.
Description
Technical Field
The invention relates to the field of microelectronic machining, in particular to a pressure sensor chip and a preparation method thereof.
Background
The pressure sensor has wide application in the fields of aviation, aerospace, navigation, petrochemical industry, automobile manufacturing and the like. The pressure sensor belongs to a micro-electromechanical piezoresistive sensor, namely a sensor chip manufactured by using piezoresistive effect of monocrystalline silicon through micro-electromechanical processing technology. Existing pressure sensor chips are divided into differential pressure sensor chips and absolute pressure sensor chips, wherein the differential pressure sensor chips are used for measuring the difference between two pressures. The absolute pressure sensor chip is used for sensing absolute pressure and outputting the absolute pressure value. If the measurement of differential pressure and absolute pressure is to be realized, the measurement must be realized one by the combined detection of one differential pressure sensor chip and one absolute pressure sensor chip.
In addition, the output signal of the existing wide-range pressure sensor chip is low when the existing wide-range pressure sensor chip is used for measuring the micro pressure, and the detection requirement cannot be met, while the small-range pressure sensor chip can meet the detection requirement of the micro pressure but cannot be applied to the measurement of the high pressure, namely, the traditional pressure sensor chip always has the technical difficulty of small measurement range.
Disclosure of Invention
The invention aims to provide a pressure sensor chip which can realize synchronous detection of differential pressure and absolute pressure and has a larger measurement range so as to solve the technical problem of the pressure sensor chip in the prior art.
According to an embodiment of the present invention, there is provided a pressure sensor chip including a glass base, a silicon base, and a silicon diaphragm, which are sequentially disposed, wherein,
the upper surface of the silicon base is provided with a first concave cavity, the periphery of the first concave cavity and the first concave cavity are provided with annular second concave cavities at intervals, and an annular through cavity communicated with the second concave cavity and the lower surface of the silicon base is arranged below the second concave cavity; the inner ring of the through cavity is positioned on the periphery of the inner ring of the second concave cavity, and the distance between the inner ring and the outer ring of the through cavity is smaller than the distance between the inner ring and the outer ring of the second concave cavity;
the silicon diaphragm is fixed on the upper surface of the silicon base and covers the first concave cavity and the second concave cavity;
the edge of the area, corresponding to the first concave cavity, of the surface of the silicon diaphragm is provided with an absolute pressure piezoresistor and a first Wheatstone bridge for outputting absolute pressure signals; the edge of the area of the surface of the silicon diaphragm, which corresponds to the second concave cavity, is provided with a differential pressure piezoresistor and a second Wheatstone bridge for outputting a differential pressure signal;
the glass base is provided with a vent hole which is communicated with the through cavity and the outside of the glass base.
Furthermore, a third concave cavity is arranged between the through cavity and the vent hole, the third concave cavity is downwards sunken from the upper surface of the glass base, and the opening area of the third concave cavity is larger than the cross-sectional area of the outer ring of the through cavity.
Preferably, the centers of the first cavity, the second cavity, the through cavity and the third cavity coincide.
Further preferably, the centers of the glass base, the silicon base and the silicon membrane coincide, and the center of the silicon base coincides with or is parallel to the center of the first cavity.
The absolute voltage piezoresistor in the first Wheatstone bridge outputs the absolute voltage signal through the first heavily doped contact area and the first metal lead;
the differential pressure piezoresistor in the second Wheatstone bridge outputs the differential pressure signal through the second heavily doped contact region and the second metal lead.
According to another aspect of the present invention, there is provided a method of manufacturing the above pressure sensor chip, comprising:
a double-sided polished silicon wafer is used as a silicon base;
manufacturing a first concave cavity and a second concave cavity on the upper surface of the silicon base, wherein the second concave cavity surrounds the periphery of the first concave cavity and is away from the first concave cavity by a set length;
preparing a silicon dioxide layer on the surface of the SOI silicon chip; the device layer of the SOI silicon chip is doped in an N type mode, and the surface where the device layer of the SOI silicon chip is marked is the lower surface of the SOI silicon chip;
bonding the lower surface of the SOI silicon chip and the upper surface of the silicon base in a high-temperature hot melting bonding mode; the SOI silicon chip covers the first concave cavity and the second concave cavity, and the first concave cavity and the lower surface of the SOI silicon chip form a vacuum cavity;
thinning the middle upper part of the SOI silicon chip until an oxide layer in the middle of the SOI silicon chip is exposed;
manufacturing a first Wheatstone bridge comprising an absolute pressure piezoresistor and a second Wheatstone bridge comprising a differential pressure piezoresistor on the thinned surface of the SOI silicon chip;
an annular through cavity communicated with the second cavity is manufactured on the lower surface of the silicon base, an inner ring of the through cavity is positioned on the periphery of an inner ring of the second cavity, and the distance between the inner ring and the outer ring of the through cavity is smaller than the distance between the inner ring and the outer ring of the second cavity; the silicon base in the through cavity forms a silicon island;
preparing a vent hole which is communicated with the upper surface and the lower surface of the glass base on the glass base; and communicating the vent hole with the through cavity, and carrying out anodic bonding on the silicon base and the glass base under the environment that the temperature is 350-400 ℃, the pressure is 500-1200N and the voltage is 800-1200V.
Further, after the vent hole communicating the upper surface and the lower surface of the glass base is prepared on the glass base, before the vent hole is communicated with the through cavity, the method further comprises the following steps:
and etching the upper surface of the glass base by adopting HF acid to prepare a third concave cavity, wherein the opening area of the third concave cavity is larger than the cross sectional area of the outer ring of the through cavity, and the third concave cavity is positioned between the through cavity and the vent hole.
Preferably, the method for manufacturing the pressure sensor chip includes at least one of the following technical solutions:
in the step of forming the first cavity and the second cavity on the upper surface of the silicon base: manufacturing a first concave cavity and a second concave cavity by using a wet etching or dry etching mode;
in the step of preparing the silicon dioxide layer on the surface of the SOI silicon wafer, preparing the silicon dioxide layer by adopting a high-temperature thermal oxidation mode;
in the step of manufacturing the annular through cavity communicated with the second concave cavity on the lower surface of the silicon base, deep etching is carried out by adopting a deep silicon etching technology of DRIE to form the through cavity;
in the step of preparing the vent hole communicating the upper surface and the lower surface of the glass base on the glass base, preparing the vent hole on the glass base by adopting a laser or sand blasting mode;
the step of manufacturing a first Wheatstone bridge comprising absolute pressure piezoresistors and a second Wheatstone bridge comprising differential pressure piezoresistors on the upper surface of the oxide layer of the SOI silicon wafer comprises the following steps:
synchronously preparing an absolute pressure piezoresistor and a differential pressure piezoresistor on the thinned surface of the SOI silicon chip and at the edges above the first concave cavity and the second concave cavity in a boron ion injection mode; and after preparing the absolute pressure piezoresistor and the differential pressure piezoresistor, continuously preparing a first heavily doped contact region and a second heavily doped contact region at the edge positions above the first cavity and the second cavity in a second boron ion injection mode, synchronously activating impurity ions injected twice in a high-temperature annealing mode, photoetching and etching a lead hole, padding metal and finishing the patterning of the metal to form a first metal lead, a second metal lead and a lead hole.
According to another aspect of the invention, the invention further provides an absolute pressure sensor chip, which comprises a glass base, a silicon base and a silicon diaphragm, wherein the glass base, the silicon base and the silicon diaphragm are sequentially arranged, a first concave cavity is arranged on the upper surface of the silicon base, an annular second concave cavity is arranged on the periphery of the first concave cavity and at a distance from the first concave cavity, and an annular through cavity communicated with the second concave cavity and the lower surface of the silicon base is arranged below the second concave cavity; the inner ring of the through cavity is positioned on the periphery of the inner ring of the second concave cavity, and the distance between the inner ring and the outer ring of the through cavity is smaller than the distance between the inner ring and the outer ring of the second concave cavity;
the silicon diaphragm is fixed on the upper surface of the silicon base and covers the first concave cavity and the second concave cavity;
a first voltage insulation piezoresistor and a first Wheatstone bridge for outputting an absolute voltage signal are arranged at the edge of the area of the surface of the silicon membrane corresponding to the first cavity; and a second piezoresistor and a second Wheatstone bridge for outputting absolute pressure signals are arranged at the edge of the area of the surface of the silicon membrane corresponding to the second cavity.
Furthermore, a third concave cavity is formed in the upper surface of the glass base, and the opening area of the third concave cavity is larger than the cross-sectional area of the outer ring of the through cavity.
According to the technical scheme, the pressure sensor chip can realize synchronous measurement of differential pressure and absolute pressure, and the measuring range of the pressure sensor chip is greatly increased.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a front view of a pressure sensor die shown in accordance with a preferred embodiment;
FIG. 2 is a cross-sectional view taken along line A-B of FIG. 1;
FIGS. 3(a) -3(j) are schematic cross-sectional views of the main process of a pressure sensor chip according to a preferred embodiment;
fig. 4 is a center sectional view of an absolute pressure sensor chip according to a preferred embodiment.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to solve the defect that differential pressure and absolute pressure can not be synchronously measured in the prior art, the inventor of the application integrates a differential pressure sensor chip and an absolute pressure sensor chip into one pressure sensor chip, optimizes the internal structure of the chip and increases the measuring range of the pressure sensor chip, so that the pressure sensor chip in the application is wide in measuring pressure range, strong in overload resistance, capable of realizing synchronous detection of differential pressure and absolute pressure and the like compared with the traditional pressure sensor chip.
The structure and the operation principle of the pressure sensor chip in the present application will be described in detail below.
FIG. 1 is a front view of a pressure sensor die shown in accordance with a preferred embodiment. Fig. 2 is a sectional view taken along line a-B in fig. 1.
As shown in fig. 1 and 2, the pressure sensor chip includes a glass base 1, a silicon base 2, and a silicon diaphragm 3, which are sequentially disposed. Preferably, the centers of the glass base 1, the silicon base 2 and the silicon membrane 3 coincide.
The upper surface of the silicon base 2 is provided with a first cavity 4. And an annular second cavity 5 is arranged at the periphery of the first cavity 4 at intervals of the first cavity 4. In the present embodiment, the second cavity 5 includes, but is not limited to, a circular ring or a regular polygonal ring. An annular through cavity 6 which is communicated with the second cavity 5 and the lower surface of the silicon base 2 is arranged below the second cavity 5. The inner ring of the through cavity 6 is positioned at the periphery of the inner ring of the second cavity 5, and the distance between the inner ring and the outer ring of the through cavity 6 is smaller than the distance between the inner ring and the outer ring of the second cavity 5. The silicon base 2 in the middle of the second cavity 5 and the silicon base 2 in the middle of the through cavity 6 constitute a silicon island 13. Preferably, the shape of the through cavity 6 in the present embodiment includes, but is not limited to, a circular ring or a regular polygonal ring. As a preferred embodiment of the embodiments, the shape of the second cavity 5 is the same as the shape of the through cavity 6 in the present application, that is, when the shape of the second cavity 5 is a circular ring, the shape of the through cavity 6 is also a circular ring; when the second cavity 5 is a regular polygonal ring, the through cavity 6 is also a regular polygonal ring.
As a preferred embodiment among the embodiments, the first cavity 4, the second cavity 5 and the through cavity 6 have their centers coincident, and the center of the first cavity 4 coincides with or is parallel to the center of the silicon base 2.
The silicon membrane 3 is fixed on the upper surface of the silicon base 2 and covers the first cavity 4 and the second cavity 5. The upper and lower surfaces of the silicon membrane 3 are provided with silicon dioxide layers 14, respectively. In the application, the silicon membrane 3 and the silicon base 2 can be bonded in a high-temperature hot-melt bonding mode to further realize fixed connection. When the silicon membrane 3 is fixed on the upper surface of the silicon base 2, the first cavity 4 and the silicon membrane 3 thereon form a vacuum cavity. At this time, the silicon membrane above the vacuum chamber region is the first strained film 30, and the silicon membrane above the second cavity 5 region is the second strained film 31.
At the edge of the first strained film 30, i.e. the edge of the area of the surface of the silicon membrane 3 corresponding to the first cavity 4, absolute piezoresistors Ra1, Ra2, Ra3 and Ra4, a first heavily doped contact region 7 and a first metal lead 8 are arranged. The absolute voltage piezoresistors Ra1, Ra2, Ra3 and Ra4 form a first wheatstone bridge. The absolute voltage piezoresistor in the first Wheatstone bridge outputs an absolute voltage signal through the first heavily doped contact area 7 and the first metal lead 8.
At the edge of the second strained film 31, i.e. the edge of the area of the surface of the silicon membrane 3 corresponding to the second cavity 5, there are provided differential pressure piezoresistors Rd1, Rd2, Rd3 and Rd4, a second heavily doped contact region 9 and a second metal lead 10. The differential pressure piezoresistors Rd1, Rd2, Rd3 and Rd4 form a second wheatstone bridge. The differential pressure piezoresistor in the second wheatstone bridge outputs a differential pressure signal through the second heavily doped contact region 9 and the second metal lead 10.
The glass base 1 is provided with a vent hole 11 which communicates the through cavity 6 with the outside of the glass base 1.
The operation of the pressure sensor chip in the above-described embodiment will be explained in detail.
As shown in fig. 2, the first cavity 4 in the chip, the first strain film 30, the first wheatstone bridge, the first heavily doped contact region 7 and the first metal lead 8 constitute a pressure sensor I, i.e. an absolute pressure sensor. The second cavity 5, the through cavity 6, the vent hole 11, the second strain film 31, the second Wheatstone bridge, the second heavily doped contact region 9 and the second metal lead 10 in the chip form a pressure sensor II, namely a differential pressure sensor.
For the pressure sensor I, the vacuum chamber is sealed by the first strain gauge 30 and the first cavity 4. When pressure exists at the upper end of the first strain film 30, the first strain film 30 can generate bending deformation, and stress generated by the bending deformation is converted into a voltage signal to be output by absolute pressure piezoresistors Ra1, Ra2, Ra3 and Ra4 and a first Wheatstone bridge consisting of the piezoresistors. Since the lower end of the first strain film 30 is vacuum zero pressure, the pressure sensor I can realize the measurement of absolute pressure.
For the pressure sensor II, the lower end of the second strain film 31 is communicated with the external environment through the second cavity, the through cavity 6 and the vent hole 11 on the glass base 1, when there is a pressure difference in the area where the upper end of the second strain film 31 is connected to the vent hole 11, the second strain film 31 will be completely deformed under the action of the pressure difference, the stress generated by the deformation is converted into a voltage signal by the differential pressure piezoresistors Rd1, Rd2, Rd3 and Rd4 and the second wheatstone bridge formed by the differential pressure piezoresistors, and is output, so the pressure sensor II can measure the differential pressure.
Through pressure sensor I and pressure sensor II's combination, the pressure sensor chip in this application can realize the synchronous measurement of absolute pressure and differential pressure.
When pressure is applied to the upper surface of the second strained film 31, the second strained film 31 is deformed by bending downward, and the glass base provides support for the silicon island to offset a portion of the pressure on the second strained film 31. If the second cavity 5 is not provided above the through cavity 6, the second strain film 31 is in contact with the opening of the through cavity 6, and since the contact area between the opening of the through cavity 6 and the second strain film 31 is small, when the pressure on the second strain film 31 gradually increases, the pressure to which the second strain film 31 is subjected is limited, and when the pressure exceeds a certain limit, the second strain film 31 is broken. Therefore, the second cavity 5 is arranged above the through cavity 6 of the pressure sensor chip, the distance between the inner ring and the outer ring of the through cavity 6 is smaller than the distance between the inner ring and the outer ring of the second cavity 5, namely the stress area of the second cavity 5 is larger than the stress area of the through cavity. Since the contact area of the second strain film 31 is greatly increased, the pressure limit borne by the second strain film 31 is increased, and the second strain film 31 cannot be easily broken. Meanwhile, the stressed area of the second concave cavity 5 is larger than that of the through cavity, so that the second strain film 31 has a larger deformation space, and the measuring range of the differential pressure sensor is greatly increased.
It should be noted that in the present application, the larger the difference between the distance between the inner ring and the outer ring of the through cavity 6 and the distance between the inner ring and the outer ring of the second cavity 5, the larger the range of the differential pressure sensor. In the present application, the proportional relationship between the two is not specifically limited, and those skilled in the art can determine the proportional relationship between the two according to the range of the measuring range required in the actual production process.
It should be noted that when the wide range differential pressure sensor in the chip works normally, the pressure borne by the first strain film 30 of the absolute pressure sensor is already much larger than the working range of the wide range differential pressure sensor, i.e. the small range absolute pressure sensor chip needs to bear extremely high overload pressure. In order to avoid the failure of the small-range absolute pressure sensor and ensure the large-range of the pressure sensor chip in the present application, it is further preferable that a third cavity 12 is provided between the through cavity 6 and the vent hole 11. The third concave cavity 12 is recessed downwards from the upper surface of the glass base 1, and the opening area of the third concave cavity 12 is larger than the cross-sectional area of the outer ring of the through cavity 6. Preferably, the center of the third cavity 12 coincides with the centers of the first cavity 4, the second cavity 5 and the through cavity 6, and coincides with or is parallel to the center of the silicon base 2.
The third concave cavity 12 is arranged on the upper surface of the glass base 1, when the pressure borne by the first strain film 30 is increased continuously, the first strain film 30 is bent and deformed downwards, and the silicon island below the first strain film 30 gradually approaches to the third concave cavity 12 on the glass base. Since the third cavity 12 allows the first strain film 30 to have a large deformation space, the measurement range of the absolute pressure sensor is greatly increased. The depth of the third cavity 12 determines the range of span of the first strained membrane 30. The depth of the third cavity 12 is not limited in this application, and those skilled in the art can determine the depth of the third cavity 12 according to the range of the scale required in the actual production process. After the silicon island contacts the bottom of the third cavity 12, the glass pedestal provides support for the silicon island and counteracts a portion of the pressure on the first strained membrane 30, thereby also reducing the possibility of the first strained membrane 30 breaking under overload pressure (pressure much greater than the normal operating range of the first strained membrane is referred to as overload pressure).
According to the technical scheme, the pressure sensor chip can realize synchronous measurement of differential pressure and absolute pressure, and the measuring range of the pressure sensor chip is greatly increased.
Fig. 3(a) -3(b) are schematic cross-sectional views illustrating main processes of the pressure sensor chip according to a preferred embodiment.
In FIG. 3(a), a silicon wafer polished on both sides is used as the silicon base 2.
In fig. 3(b), the first cavity 4 and the second cavity 5 are formed on the upper surface of the silicon base 2 by wet etching or dry etching. Wherein, the second cavity 5 surrounds the periphery of the first cavity 4 and is set to be a certain length away from the first cavity 4.
In FIG. 3(c), an SOI silicon wafer is prepared. An SOI silicon wafer with an N-type doped device layer is selected as a spare wafer, a silicon dioxide layer 14 is prepared on the surface of the SOI silicon wafer in a high-temperature thermal oxidation mode, and the surface where the device layer (corresponding to the silicon diaphragm 3 of the sensor) in the marked SOI silicon wafer is the lower surface of the SOI silicon wafer.
In fig. 3(d), the lower surface of the SOI wafer and the upper surface of the silicon base 2 are bonded by high temperature thermal fusion bonding. The SOI silicon wafer covers the first cavity 4 and the second cavity 5, and the first cavity 4 and the lower surface of the SOI silicon wafer form a vacuum cavity.
In fig. 3(e), the middle-upper portion of the SOI wafer is thinned until the oxide layer in the SOI wafer is exposed.
In fig. 3(f), a first wheatstone bridge including an absolute pressure varistor and a second wheatstone bridge including a differential pressure varistor are formed on the thinned surface of the SOI silicon wafer.
Specifically, the manufacturing of the first wheatstone bridge comprising the absolute voltage piezoresistor on the thinned surface of the SOI silicon wafer comprises the following steps:
and (3) synchronously preparing an absolute pressure piezoresistor and a differential pressure piezoresistor on the thinned surface of the SOI silicon chip and at the edges above the first cavity 4 and the second cavity 5 in a boron ion implantation mode. After the absolute pressure-sensitive resistor and the differential pressure-sensitive resistor are prepared, a first heavily doped contact region 7 and a second heavily doped contact region 9 are continuously prepared at the edge positions above the first cavity and the second cavity in a second boron ion injection mode, impurity ions injected twice are synchronously activated in a high-temperature annealing mode, a lead hole is etched through photoetching, metal is filled, and patterning of the metal is completed to form a first metal lead 8, a second metal lead 10 and the lead hole.
In fig. 3(g), the lower surface of the silicon base 2 is etched back by the deep silicon etching technique of DRIE to form an annular through cavity 6 communicating with the second cavity 5, the inner ring of the through cavity 6 is located at the periphery of the inner ring of the second cavity 5, and the distance between the inner ring and the outer ring of the through cavity 6 is smaller than the distance between the inner ring and the outer ring of the second cavity 5; a silicon island is formed through the silicon base 2 in the cavity 6.
In fig. 3(h), the upper surface of the glass base is etched with HF acid to prepare a third cavity 12, and the opening area of the third cavity 12 is larger than the cross-sectional area of the outer ring of the through cavity 6;
in fig. 3(i), a vent hole 11 communicating the upper surface and the lower surface of the glass base is prepared on the glass base by means of laser or sand blasting; the vent hole 11 is made to communicate with the third cavity 12.
In FIG. 3(j), the silicon substrate 2 and the glass substrate are anodically bonded in an environment of 350 to 400 ℃ temperature, 500 to 1200N pressure and 800 to 1200V voltage.
According to still another aspect of the present invention, there is also provided a wide-range absolute pressure sensor chip. Fig. 4 is a center sectional view of an absolute pressure sensor chip according to a preferred embodiment. As shown in fig. 4, the absolute pressure sensor chip includes a glass base 1, a silicon base 2 and a silicon membrane 3, which are sequentially arranged and overlapped at the center. The upper surface of the silicon base 2 is provided with a first concave cavity 4, an annular second concave cavity 5 is arranged on the periphery of the first concave cavity 4 and spaced from the first concave cavity 4, and an annular through cavity 6 communicated with the second concave cavity 5 and the lower surface of the silicon base 2 is arranged below the second concave cavity 5. The inner ring of the through cavity 6 is positioned at the periphery of the inner ring of the second cavity 5, and the distance between the inner ring and the outer ring of the through cavity 6 is smaller than the distance between the inner ring and the outer ring of the second cavity 5. The silicon base 2 in the middle of the second cavity 5 and the silicon base 2 in the middle of the through cavity 6 constitute a silicon island 13.
Preferably, the shape of the through cavity 6 in the present embodiment includes, but is not limited to, a circular ring or a regular polygonal ring. As a preferred embodiment of the embodiments, the shape of the second cavity 5 is the same as the shape of the through cavity 6 in the present application, that is, when the shape of the second cavity 5 is a circular ring, the shape of the through cavity 6 is also a circular ring; when the second cavity 5 is a regular polygonal ring, the through cavity 6 is also a regular polygonal ring. As a preferred embodiment among the embodiments, the first cavity 4, the second cavity 5 and the through cavity 6 have their centers coincident, and the center of the first cavity 4 coincides with or is parallel to the center of the silicon base 2.
Furthermore, the upper surface of the glass base 1 is provided with a third concave cavity 12, and the opening area of the third concave cavity 12 is larger than the cross-sectional area of the outer ring of the through cavity 6.
The silicon diaphragm 3 is fixed on the upper surface of the silicon base 2 and covers the first cavity 4 and the second cavity 5, the first cavity 4 is covered to form a first vacuum cavity, and the second cavity 5, the through cavity 6 and the third cavity 12 form a second vacuum cavity. The silicon membrane 3 above the first vacuum chamber is a first strain film 30, and the silicon membrane 3 above the second vacuum chamber is a second strain film 31.
At the edge of the region of the first vacuum chamber, i.e. the edge of the region of the surface of the silicon membrane 3 corresponding to the first cavity 4, there are provided first insulation piezoresistors Ra1, Ra2, Ra3 and Ra4, a first heavily doped contact region 7 and a first metal lead 8. The absolute voltage piezoresistors Ra1, Ra2, Ra3 and Ra4 form a first wheatstone bridge. The absolute voltage piezoresistor in the first Wheatstone bridge outputs an absolute voltage signal through the first heavily doped contact area 7 and the first metal lead 8. At the edge of the region of the second vacuum chamber, i.e. at the edge of the region of the surface of the silicon membrane 3 corresponding to the second cavity 5, there are provided second piezoresistors Rd1, Rd2, Rd3 and Rd4, a second heavily doped contact region 9 and a second metal lead 10. The absolute voltage piezoresistors Rd1, Rd2, Rd3 and Rd4 form a second wheatstone bridge. The absolute voltage piezoresistor in the second wheatstone bridge outputs an absolute voltage signal through the second heavily doped contact region 9 and the second metal lead 10.
The first vacuum cavity, the first strain film and the first Wheatstone bridge form a wide-range absolute pressure sensor I, and the second vacuum cavity, the second strain film and the second Wheatstone bridge form a small-range absolute pressure sensor II. In contrast to the pressure sensor chip structure in fig. 1, the glass base 1 in the present embodiment is not provided with a vent hole. The second cavity 5, the through cavity 6 and the third cavity 12 constitute a vacuum seal. The first strain film 30 above the wide-range absolute pressure sensor I and the second strain film 31 above the small-range absolute pressure sensor II have the same thickness but different cross-sectional areas, and the cross-sectional area of the second strain film above the small-range absolute pressure sensor II is larger, so that the second strain film has a large deformation amount during pressure measurement, and the sensor sensitivity is high, so that the second strain film can be applied to manufacturing absolute pressure sensors with small measurement ranges. The sectional area of the first strain film is small, the deformation of the first strain film is small under the same pressure, and the sensitivity of the sensor is low, so that the first strain film can be suitable for manufacturing absolute pressure sensors with small measuring ranges. The measurement range of the absolute pressure sensor chip can be expanded in multiples through the combination of the two absolute pressure sensors.
Therefore, the absolute pressure sensor chip in the above embodiment can measure absolute pressure in a small-range and can also measure absolute pressure in a large-range, and the measurement range is greatly enlarged and wider in application range compared with a single small-range absolute pressure sensor and a single large-range absolute pressure sensor.
It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. A method for manufacturing a pressure sensor chip, comprising:
a double-sided polished silicon wafer is used as a silicon base (2);
manufacturing a first concave cavity (4) and a second concave cavity (5) on the upper surface of the silicon base (2), wherein the second concave cavity (5) surrounds the periphery of the first concave cavity (4) and is set to be away from the first concave cavity (4) in length;
preparing a silicon dioxide layer on the surface of the SOI silicon chip; the device layer of the SOI silicon chip is doped in an N type mode, and the surface where the device layer of the SOI silicon chip is marked is the lower surface of the SOI silicon chip;
bonding the lower surface of the SOI silicon chip and the upper surface of the silicon base (2) by a high-temperature hot melt bonding mode; the SOI silicon chip covers the first concave cavity (4) and the second concave cavity (5), and the first concave cavity (4) and the lower surface of the SOI silicon chip form a vacuum cavity;
thinning the middle upper part of the SOI silicon chip until an oxide layer in the middle of the SOI silicon chip is exposed;
manufacturing a first Wheatstone bridge comprising an absolute pressure piezoresistor and a second Wheatstone bridge comprising a differential pressure piezoresistor on the thinned surface of the SOI silicon chip;
an annular through cavity (6) communicated with the second cavity (5) is manufactured on the lower surface of the silicon base (2), an inner ring of the through cavity (6) is positioned on the periphery of an inner ring of the second cavity (5), and the distance between the inner ring and the outer ring of the through cavity (6) is smaller than the distance between the inner ring and the outer ring of the second cavity (5); the silicon base (2) in the through cavity (6) forms a silicon island;
preparing a vent hole (11) which communicates the upper surface and the lower surface of the glass base on the glass base; and communicating the vent hole (11) with the through cavity (6), and carrying out anodic bonding on the silicon base (2) and the glass base under the environment that the temperature is 350-400 ℃, the pressure is 500-1200N and the voltage is 800-1200V.
2. The manufacturing method according to claim 1, wherein after the manufacturing of the vent hole (11) communicating the upper surface and the lower surface of the glass base on the glass base, before the communicating the vent hole (11) with the through cavity (6), further comprising:
and etching the upper surface of the glass base by adopting HF acid to prepare a third concave cavity (12), wherein the opening area of the third concave cavity (12) is larger than the cross sectional area of the outer ring of the through cavity (6), and the third concave cavity (12) is positioned between the through cavity (6) and the vent hole (11).
3. The preparation method according to claim 1, characterized by comprising at least one of the following technical solutions:
in the step of making a first cavity (4) and a second cavity (5) on the upper surface of the silicon base (2): manufacturing a first concave cavity (4) and a second concave cavity (5) by using a wet etching or dry etching mode;
in the step of preparing the silicon dioxide layer on the surface of the SOI silicon wafer, preparing the silicon dioxide layer by adopting a high-temperature thermal oxidation mode;
in the step of manufacturing an annular through cavity (6) communicated with the second cavity (5) on the lower surface of the silicon base (2), deep etching is carried out by adopting a deep silicon etching technology of DRIE to form the through cavity (6);
in the step of preparing the vent hole (11) which communicates the upper surface and the lower surface of the glass base on the glass base, preparing the vent hole (11) on the glass base by adopting a laser or sand blasting mode;
the steps of manufacturing a first Wheatstone bridge comprising an absolute pressure piezoresistor and a second Wheatstone bridge comprising a differential pressure piezoresistor on the surface of the thinned SOI silicon wafer comprise:
synchronously preparing an absolute pressure piezoresistor and a differential pressure piezoresistor on the thinned surface of the SOI silicon chip and at the edges above the first concave cavity and the second concave cavity in a boron ion injection mode; and after the absolute pressure-sensitive resistor and the differential pressure-sensitive resistor are prepared, a first heavily doped contact region (7) and a second heavily doped contact region (9) are continuously prepared at the edge positions above the first cavity and the second cavity in a second boron ion injection mode, impurity ions injected twice are synchronously activated in a high-temperature annealing mode, a lead hole is etched by photoetching, metal is filled, and the patterning of the metal is completed to form a first metal lead (8), a second metal lead (10) and the lead hole.
4. The pressure sensor chip prepared by the preparation method of claim 1, which comprises a glass base (1), a silicon base (2) and a silicon diaphragm (3) which are arranged in sequence,
a first concave cavity (4) is formed in the upper surface of the silicon base (2), an annular second concave cavity (5) is formed in the periphery of the first concave cavity (4) at a distance from the first concave cavity (4), and an annular through cavity (6) which is communicated with the second concave cavity (5) and the lower surface of the silicon base (2) is formed below the second concave cavity (5); the inner ring of the through cavity (6) is positioned at the periphery of the inner ring of the second cavity (5), and the distance between the inner ring and the outer ring of the through cavity (6) is smaller than the distance between the inner ring and the outer ring of the second cavity (5);
the silicon membrane (3) is fixed on the upper surface of the silicon base (2) and covers the first concave cavity (4) and the second concave cavity (5);
the edge of the area, corresponding to the first cavity (4), on the surface of the silicon membrane (3) is provided with an absolute pressure piezoresistor and a first Wheatstone bridge for outputting absolute pressure signals; the edge of the area, corresponding to the second cavity (5), on the surface of the silicon diaphragm (3) is provided with a differential pressure piezoresistor and a second Wheatstone bridge for outputting a differential pressure signal;
the glass base (1) is provided with a vent hole (11) which is communicated with the through cavity (6) and the outside of the glass base (1).
5. The pressure sensor chip according to claim 4, wherein a third cavity (12) is provided between the through cavity (6) and the vent hole (11), the third cavity (12) is recessed downward from the upper surface of the glass base (1), and the opening area of the third cavity (12) is larger than the cross-sectional area of the outer ring of the through cavity (6).
6. Pressure sensor chip according to claim 5, characterized in that the centers of the first cavity (4), the second cavity (5), the through cavity (6) and the third cavity (12) coincide.
7. Pressure sensor chip according to claim 6, characterized in that the centers of the glass base (1), the silicon base (2) and the silicon membrane (3) coincide, and the center of the silicon base (2) coincides with or is parallel to the center of the first cavity (4).
8. Pressure sensor chip according to claim 7, characterized in that the absolute voltage piezo-resistor in a first Wheatstone bridge outputs the absolute voltage signal through a first heavily doped contact region (7) and a first metal lead (8);
the differential pressure piezoresistor in the second Wheatstone bridge outputs the differential pressure signal through a second heavily doped contact area (9) and a second metal lead (10).
9. An absolute pressure sensor chip comprises a glass base (1), a silicon base (2) and a silicon diaphragm (3) which are sequentially arranged, and is characterized in that a first cavity (4) is formed in the upper surface of the silicon base (2), annular second cavities (5) are formed in the periphery of the first cavity (4) and spaced from the first cavity (4), and an annular through cavity (6) communicated with the second cavity (5) and the lower surface of the silicon base (2) is formed below the second cavity (5); the inner ring of the through cavity (6) is positioned at the periphery of the inner ring of the second cavity (5), and the distance between the inner ring and the outer ring of the through cavity (6) is smaller than the distance between the inner ring and the outer ring of the second cavity (5);
the silicon membrane (3) is fixed on the upper surface of the silicon base (2) and covers the first concave cavity (4) and the second concave cavity (5);
the edge of the area, corresponding to the first cavity (4), on the surface of the silicon membrane (3) is provided with an absolute pressure piezoresistor and a first Wheatstone bridge for outputting absolute pressure signals; a second piezoresistor and a second Wheatstone bridge for outputting absolute pressure signals are arranged at the edge of the area, corresponding to the second cavity (5), on the surface of the silicon membrane (3);
the preparation method of the absolute pressure sensor chip comprises the following steps:
a double-sided polished silicon wafer is used as a silicon base (2);
manufacturing a first concave cavity (4) and a second concave cavity (5) on the upper surface of the silicon base (2), wherein the second concave cavity (5) surrounds the periphery of the first concave cavity (4) and is set to be away from the first concave cavity (4) in length;
preparing a silicon dioxide layer on the surface of the SOI silicon chip; the device layer of the SOI silicon chip is doped in an N type mode, and the surface where the device layer of the SOI silicon chip is marked is the lower surface of the SOI silicon chip;
bonding the lower surface of the SOI silicon chip and the upper surface of the silicon base (2) by a high-temperature hot melt bonding mode; the SOI silicon chip covers the first concave cavity (4) and the second concave cavity (5), and the first concave cavity (4) and the lower surface of the SOI silicon chip form a vacuum cavity;
thinning the middle upper part of the SOI silicon chip until an oxide layer in the middle of the SOI silicon chip is exposed;
manufacturing a first Wheatstone bridge comprising an absolute pressure piezoresistor and a second Wheatstone bridge comprising a differential pressure piezoresistor on the thinned surface of the SOI silicon chip;
an annular through cavity (6) communicated with the second cavity (5) is manufactured on the lower surface of the silicon base (2), an inner ring of the through cavity (6) is positioned on the periphery of an inner ring of the second cavity (5), and the distance between the inner ring and the outer ring of the through cavity (6) is smaller than the distance between the inner ring and the outer ring of the second cavity (5); and the silicon base (2) in the through cavity (6) forms a silicon island.
10. The absolute pressure sensor chip of claim 9, wherein the upper surface of the glass base (1) is provided with a third cavity (12), and the opening area of the third cavity (12) is larger than the cross-sectional area of the outer ring of the through cavity (6).
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| CN108803910B (en) * | 2017-04-28 | 2021-08-06 | 京东方科技集团股份有限公司 | Touch substrate, manufacturing method thereof and touch display device |
| CN107478378A (en) * | 2017-09-26 | 2017-12-15 | 航天南洋（浙江）科技有限公司 | A kind of small two-way signal output pressure sensor structure |
| CN107941407B (en) * | 2017-11-19 | 2019-05-21 | 东北大学 | A kind of micro-voltage high-overload sensor chip |
| CN108332898B (en) * | 2018-04-17 | 2023-05-09 | 南京信息工程大学 | Composite range air pressure sensor and high-precision air pressure detecting and measuring device |
| CN109000830A (en) * | 2018-06-26 | 2018-12-14 | 常州元晶电子科技有限公司 | A kind of double Wheatstone bridge temperature-compensating differential pressure pressure sensors and preparation method thereof |
| JP2020016619A (en) * | 2018-07-27 | 2020-01-30 | アズビル株式会社 | Pressure sensor |
| CN109342836B (en) * | 2018-10-24 | 2021-03-26 | 清华大学 | Production process based on piezoelectric piezoresistive broadband high-field-intensity miniature electric field sensor |
| JP7401248B2 (en) * | 2019-10-09 | 2023-12-19 | アズビル株式会社 | pressure sensor |
| CN111166335A (en) * | 2019-12-31 | 2020-05-19 | 深圳大学 | Absolute pressure sensor assembly and air bag type respiration measuring device |
| CN116659731A (en) * | 2023-04-03 | 2023-08-29 | 北京智芯传感科技有限公司 | MEMS gauge pressure sensor and preparation method thereof |
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| JPH10142086A (en) * | 1996-11-07 | 1998-05-29 | Hitachi Ltd | Semiconductor pressure sensor, its manufacturing method, and differential pressure transmitter using the same |
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