Piezoresistive pressure sensor and method for manufacturing such a piezoresistive pressure sensor

Abstract

A piezoresistive pressure sensor for measuring the pressure of a medium in the environment. [Solution] The piezoresistive pressure sensor comprises at least one housing, at least one substrate, and at least one measuring unit. The housing comprises an interior and an opening. The substrate and measuring unit are arranged inside, and the substrate has a blind hole and a diaphragm formed therein, the diaphragm enclosing the blind hole on one side, and the substrate is arranged inside such that the blind hole communicates with the opening. The piezoresistive pressure sensor is designed so that, when exposed to a medium, the medium can penetrate through the opening and the blind hole to the diaphragm. The pressure of the medium that has penetrated the diaphragm causes the diaphragm to flex, generating a change in resistance to the diaphragm's flex, and the change in resistance is proportional to the pressure being measured.

Description

[Technical Field]

[0001] The present invention relates to a piezoresistive pressure sensor by a preamble of an independent claim and to a method for manufacturing such a piezoresistive pressure sensor. [Background technology]

[0002] Pressure sensors are used to measure the pressure of liquid or gaseous media. Pressure measurements can be performed as absolute pressure measurements with reference to a reference pressure, or as relative pressure measurements without such reference. Pressure measurements can be performed statically over long periods of time, such as measuring the pressure inside a car tire, over periods of several months, or dynamically, such as during an explosion in a car's combustion engine, over periods of a fraction of a second. In recent years, a wide variety of pressure measurement principles have been developed, which is why they are distinguished as piezoelectric, piezoresistive, optical, capacitive pressure sensors, and so on.

[0003] Furthermore, the present invention also relates to a piezoresistive pressure sensor as known from German Patent Application Publication No. 202009013919U1. The piezoresistive pressure sensor comprises a silicon or glass substrate with a blind hole introduced on one side. In the region of the blind hole, the substrate forms a diaphragm. A medium guided through the blind hole to the diaphragm applies pressure to the diaphragm, causing it to flex. On the side of the diaphragm opposite the blind hole, a measuring unit is positioned, comprising a resistive element made of a piezoresistive material. The measuring unit detects the flexure of the diaphragm as a change in resistance. A circuit unit, also located on the substrate, converts the change in resistance into a measuring signal.

[0004] By positioning the measuring unit and circuit unit on the diaphragm side opposite the blind hole, the measuring unit and circuit unit are not directly exposed to the medium. As a result, the piezoresistive pressure sensor is also suitable for measuring the pressure of chemically aggressive mediums such as fuel for combustion engines, where the fuel cannot corrode the measuring unit and circuit unit, thus not undesirably impairing the usability of the piezoresistive pressure sensor.

[0005] To protect the measuring unit and circuit unit from harmful environmental influences such as moisture, dust, and contact, and to mount the piezoresistive pressure sensor at the measurement point, the piezoresistive pressure sensor is provided with a housing. The housing of German Patent Application Publication No. 202009013919U1 has a hollow cylindrical shape and is made of metal. The base on which the measuring unit and circuit unit are arranged is fixed inside the housing via a carrier, which is also made of metal. Thus, the base is fixed to the carrier via glass solder or adhesive connections, and the carrier is then hermetically welded to the internal housing. The base is positioned inside so that the medium can reach the blind holes in the base only through the opening on the front side of the housing and the through holes in the carrier. The piezoresistive pressure sensor can be mounted to the measurement point via male threads on the housing side.

[0006] The object of the present invention is to improve upon the piezoresistive pressure sensor described in German Patent Application Publication No. 202009013919U1. The present invention also aims to disclose a method for manufacturing a piezoresistive pressure sensor that is improved compared to the method for manufacturing a piezoresistive pressure sensor described in German Patent Application Publication No. 202009013919U1.

[0007] However, there is still room for improvement.

[0008] The circuit unit described in German Patent Application Publication No. 202009013919U1 comprises integrated circuits and electronic components that are often designed only for continuous operating temperatures within the range of -55°C to 125°C. Therefore, for continuous operating temperatures of piezoresistive pressure sensors exceeding 200°C, special designs of integrated circuits and electronic components are required. Such special designs of integrated circuits and electronic components are manufactured in small quantities, making their acquisition complex and expensive.

[0009] Furthermore, the integrated circuit and measuring unit described in German Patent Application Publication No. 202009013919U1 are manufactured on a silicon carrier. Silicon is a semiconductor and exhibits high leakage current at continuous operating temperatures of piezoresistive pressure sensors exceeding 200°C, which can distort the measurement signal and thus significantly impair the accuracy of pressure measurement.

[0010] The circuit unit and measuring unit are also cast with a casting compound on the side of the diaphragm opposite the blind hole described in German Patent Application Publication No. 202009013919U1, to protect the integrated circuit, electronic components, and electrical connections to the measuring unit from mechanical shock and vibration. The casting compound is typically made of plastic materials such as polyurethane, epoxy resin, or silicone, and begins to decompose at the continuous operating temperature of piezoresistive pressure sensors above 200°C. The missing protective compound can no longer provide protection against mechanical shock and vibration, which undesirably shortens the lifespan of the piezoresistive pressure sensor. The decomposed casting compound can undesirably reduce the functionality of the piezoresistive pressure sensor.

[0011] In addition, in the piezoresistive pressure sensor described in German Patent Application Publication No. 202009013919U1, the silicon or glass substrate, glass solder joint, and metal carrier exhibit different coefficients of thermal expansion. At continuous operating temperatures of piezoresistive pressure sensors exceeding 200°C, mechanical stress can occur, which can lead to cracking or breakage of the substrate or glass solder joint, increasing the likelihood of failure of the piezoresistive pressure sensor.

[0012] Finally, at continuous operating temperatures above 200 °C, the adhesive bond of German Patent Application Publication No. 202009013919U1 may start to creep and even break. As a result, this may impair the fastening of the substrate within the housing and cause premature failure of the piezoresistive pressure sensor.

Summary of the Invention

[0013] These objects are solved by the features of the independent claims.

[0014] The present invention relates to a piezoresistive pressure sensor for measuring the pressure of a medium in an environment. The piezoresistive pressure sensor comprises at least one housing, at least one substrate, and at least one measuring unit. The housing comprises an interior and an opening. The substrate and the measuring unit are arranged inside. The substrate has a blind hole and a diaphragm formed thereon. The diaphragm closes the blind hole on one side. The substrate is arranged inside such that the blind hole communicates with the opening. The piezoresistive pressure sensor is designed such that when exposed to the medium, the medium can penetrate through the opening and the blind hole to the diaphragm. The diaphragm deflects due to the pressure of the medium penetrating the diaphragm. The measuring unit is arranged on the side of the diaphragm opposite to the blind hole and generates a change in resistance with respect to the deflection of the diaphragm. The change in resistance is proportional to the measured pressure. The piezoresistive pressure sensor comprises at least one material bonding connection part, which directly connects the substrate to the housing in a mechanically tight manner, and the material bonding connection part exhibits a melting temperature of 250 °C or higher.

[0015] The present invention also relates to a method for manufacturing a piezoresistive pressure sensor for measuring the pressure of a medium in an environment, the piezoresistive pressure sensor comprising at least one housing, at least one substrate, and at least one measuring unit, the housing comprising an interior and an opening, the substrate and the measuring unit being arranged inside, the substrate having a blind hole and a diaphragm formed therein, the diaphragm closing off the blind hole on one side, the substrate being arranged inside such that the blind hole communicates with the opening, the piezoresistive pressure sensor being designed such that when exposed to the medium, the medium can penetrate through the opening and the blind hole up to the diaphragm, the diaphragm being deflected by the pressure of the medium penetrating therethrough, the measuring unit being arranged on the side of the diaphragm opposite the blind hole and generating a change in resistance with respect to the deflection of the diaphragm, the change in resistance being proportional to the measured pressure. In a first step of the method, the housing and the substrate are provided. In a further step of the method, the substrate is directly connected to the housing in a mechanically tight manner via at least one material bonding connection, the material bonding connection exhibiting a melting temperature of 250 °C or higher.

[0016] As a first difference from the piezoresistive pressure sensor of German Patent Application Publication No. 202009013919U1, the piezoresistive pressure sensor according to the present invention does not require a metallic carrier. Instead, the substrate is directly connected to the housing in a material bonding manner. The omission of the metallic carrier simplifies and improves the design of the piezoresistive pressure sensor in an economical way.

[0017] As a further difference from the piezoresistive pressure sensor of German Patent Application Publication No. 202009013919U1, the present invention provides a material bonding connection having a melting temperature of 250 °C or higher for mechanically tightly connecting the substrate to the housing. Thereby, creep or breakage of the glass solder or adhesive connection of German Patent Application Publication No. 202009013919U1 is prevented, and the likelihood of failure of the piezoresistive pressure sensor is reduced.

[0018] Preferred embodiments of the present invention are protected by the dependent claims.

[0019] Therefore, a piezoresistive pressure sensor comprises at least one conductor, which taps the change in resistance as a voltage and discharges it to the environment.

[0020] Therefore, in a further step of the method, at least one conductor is provided, and in a further step of the method, the conductor is electrically connected to a measuring unit, and the conductor taps the change in resistance as a voltage and discharges it to the environment.

[0021] Another difference from the piezoresistive pressure sensor described in German Patent Application Publication No. 202009013919U1 is that the piezoresistive pressure sensor according to the present invention does not have a circuit unit within the housing that converts resistance changes into measurement signals. Instead, resistance changes are conducted to the environment as a voltage through a conductor. The absence of a circuit unit within the housing simplifies the design of the piezoresistive pressure sensor. Furthermore, since the electronic components of integrated circuits and circuit units are often designed only for continuous operating temperatures up to 125°C, and large leakage currents occur in integrated circuits with silicon carriers, enabling continuous operating temperatures above 200°C improves the operating range of the piezoresistive pressure sensor.

[0022] A further difference from the piezoresistive pressure sensor described in German Patent Application Publication No. 202009013919U1 is that the piezoresistive pressure sensor according to the present invention does not contain a cast compound for protecting the electronic components of the integrated circuit and circuit unit, as well as for protecting the measuring unit. The cast compound decomposes at the continuous operating temperature of the piezoresistive pressure sensor, which exceeds 200°C, and therefore can no longer fulfill its protective function. On the other hand, the decomposed cast compound may impair the function of the piezoresistive pressure sensor. Illustrative embodiments of the present invention will be described in more detail below with reference to the drawings. [Brief explanation of the drawing]

[0023] [Figure 1] This is a partial longitudinal cross-sectional view of a first embodiment of a piezoresistive pressure sensor 10 having a housing 1 as a single component. [Figure 2] This is a partial longitudinal cross-sectional view of a second embodiment of a piezoresistive pressure sensor 10 having a housing 1 with multiple components. [Figure 3] This is a partial cross-sectional view of the piezoresistive pressure sensor 10 along the cross-sectional path AA, as shown in Figure 1 or Figure 2. [Figure 4] This is a flowchart including steps MI to MVI of the manufacturing method of a piezoresistive pressure sensor 10 according to Figure 1 or Figure 2, which is a modified example using the material bonding connection part 4 in the solder joint embodiment. [Figure 5] This is a flowchart including steps MI to MVI of the method for manufacturing a piezoresistive pressure sensor 10 according to Figure 1 or Figure 2, in a modified example using a material bonding connection 4 in the form of glass solder. [Modes for carrying out the invention]

[0024] In the diagram, the same symbol indicates the same object.

[0025] Figures 1 and 2 show a partial longitudinal section of the piezoresistive pressure sensor 10 along the vertical axis Z. Figure 3 shows the piezoresistive pressure sensor 10 along the cross-sectional path AA in a horizontal plane XY cross-section spanning the horizontal axis X and the vertical axis Y. The three axes X, Y, and Z are perpendicular to each other.

[0026] The piezoresistive pressure sensor 10 is designed for continuous operation at temperatures up to 450°C.

[0027] This piezoresistive pressure sensor 10 comprises at least one housing 1, at least one base 2, and at least one measuring unit 3.

[0028] Housing 1 On the one hand, the housing 1 has the function of protecting the measuring unit 3 from harmful environmental influences such as moisture, dust, and contact. On the other hand, the housing 1 has the function of enabling the piezoresistive pressure sensor 10 to be attached to the measurement point.

[0029] Housing 1 comprises at least one front 1.1, at least one side 1.2, and an interior 1.3. The front 1.1 and side 1.2 completely enclose the interior 1.3. The front 1.1 and side 1.2 confine Housing 1 to the environment E, which is located outside Housing 1. Housing 1 isolates the interior 1.3 from the environment E. The measuring unit 3 is located inside the interior 1.3. Harmful environmental influences from the environment E cannot enter the interior 1.3 through Housing 1.

[0030] The medium M is located within the environment E. The medium M can be any liquid or gaseous medium. The medium M exhibits a pressure P in the range of 1 bar to 250 bar.

[0031] The front surface 1.1 is provided with at least one opening 1.4, which extends from the environment E to the interior 1.3. The function of the opening 1.4 is to guide the medium M to the measuring unit 3 in the desired manner.

[0032] According to Figure 1, the opening 1.4 extends along the vertical axis Z. In a plane perpendicular to the vertical axis Z, the opening 1.4 has a diameter. The minimum diameter of the opening 1.4 is 1000 μm or less, preferably 500 μm or less.

[0033] On the side of the housing 1 facing the interior 1.3 opposite to the front surface 1.1, the housing 1 forms an end face 1.6 in the area of ​​the opening 1.4. According to Figure 1, the end face 1.6 extends in a plane perpendicular to the vertical axis Z around the opening 1.4. The end face 1.6 completely encloses the opening 1.4.

[0034] At least one mounting means 1.5 is attached to the side 1.2. Preferably, the mounting means 1.5 is a male thread. The piezoresistive pressure sensor 10 can be attached to a measurement point in the environment E via the male thread. For this purpose, the measurement point is provided with a female thread that matches the male thread. The measurement point and female thread are not shown.

[0035] Housing 1 can be manufactured from one or more components. For this purpose, housing 1 comprises at least one housing body 1.0, 1.0', 1.0''.

[0036] In the embodiment shown in Figure 1, the housing 1 is manufactured from a single component and comprises a single housing body 1.0. Preferably, the housing body 1.0 has a hollow cylindrical shape and comprises a front surface 1.1 and side surfaces 1.2.

[0037] In the embodiment shown in Figure 2, the housing 1 is manufactured from multiple components and comprises a first housing body 1.0' and at least one second housing body 1.0''. Preferably, the first housing body 1.0' has a hollow cylindrical shape and generates a side surface 1.2. Preferably, the second housing body 1.0'' is disc-shaped and forms a front surface 1.1. The first housing body 1.0' and the second housing body 1.0'' are connected to each other via a material bonding connection 1.7. Preferably, the material bonding connection 1.7 is an annular welded connection extending around the entire circumference 360° of the front surface 1.1. The material bonding connection 1.7 is pressure-tight, meaning that a medium M located in the environment E cannot enter the interior 1.3 through the material bonding connection 1.7, even at a maximum pressure of 250 bar.

[0038] The housing bodies 1.0, 1.0', and 1.0'' are made of mechanically resistant materials such as metal or ceramic. Preferably, the housing body 1.0 or the second housing body 1.0'' is rated for temperatures in the range of 20°C to 450°C. -6 K -1It is made of Material 1.3981 having the following coefficient of thermal expansion. Preferably, the first housing body 1.0’ has 13.0×10 -6 K -1 It is made of Material 1.4548 having the following coefficient of thermal expansion. Preferably, the housing body 1.0 or the second housing body 1.0’’ has 7.0×10 -6 K -1 It is made of aluminum oxide (Al2O3), zirconium silicate, aluminum nitride (AlN), silicon nitride (Si3N4), etc. having the following coefficient of thermal expansion. Those skilled in the art can also use, based on the knowledge of the present invention, for the housing body 1.0 or the second housing body 1.0’’, 7×10 -6 K -1 Another mechanical resistance material having the following coefficient of thermal expansion may be used.

[0039] Substrate 2 Substrate 2 is disposed inside 1.3. Substrate 2 has the function of receiving the pressure P of the medium M to be measured.

[0040] Substrate 2 contains at least one of silicon, silicon oxide, borosilicate glass, or silicon carbide, which are electrically insulating materials. A single crystal made of silicon shows a specific electrical resistance of 10 7 Ωm or more at 20°C. Silicon has a coefficient of thermal expansion of 2.6×10 -6 K -1 at 20°C and rises to 4.2×10 -6 K -1 at​​​​​​​​​​​​​​​​-6 K -1 + / -0.3 10 -6 K -1 This shows the coefficient of thermal expansion. Silicon carbide is 10 at 20°C 6 It exhibits electrical resistivity of Ωm or greater. Silicon carbide has a resistivity of 4.5 10 in the range of 20°C to 450°C. -6 K -1 This shows the coefficient of thermal expansion. Those skilled in the art have also used the knowledge of the present invention to describe silicon nitride and other materials in the range of 20°C to 450°C. 7 Electrical resistance of Ωm or more and 4.5 10 -7 K -1 ~4.5 10 -6 K -1 Different electrical insulating materials with different coefficients of thermal expansion may be used.

[0041] The base body 2 is rectangular. In a specific region, the base body 2 includes a blind hole 2.4 and a diaphragm 2.5. The blind hole 2.4 is located on the rear side of the base body 2 opposite to the horizontal plane XY. The diaphragm 2.5 is located on the front side of the base body 2 facing the horizontal plane XY.

[0042] Preferably, the substrate 2 is constructed using silicon-on-insulator (SOI) technology and includes the following functional layers: The support layer 2.1 is made of one of the following electrically insulating materials: silicon, borosilicate glass, or silicon carbide. The support layer 2.1 has a thickness in the range of 200 to 1200 μm, preferably 500 μm, along the vertical axis Z. Preferably, the support layer 2.1 is made of borosilicate glass or a silicon single crystal. The support layer 2.1 supports the measuring unit 3 and has the function of mechanically separating the measuring unit 3 from the housing 1. The support layer 2.1 is rectangular and has a first support front 2.11 and a second support front 2.12. The two support fronts 2.11 and 2.12 extend perpendicular to the vertical axis Z. A blind hole 2.4 is formed in the support layer 2.1 as a through hole 2.13. The through hole 2.13 extends along the vertical axis Z from the first support front 2.11 to the second support front 2.12. Therefore, the support layer 2.1 has a through hole 2.13 in the region of the first support front surface 2.11. The support layer 2.1 also has a through hole 2.13 in the region of the second support front surface 2.12. Along the vertical axis Z, the opening 1.4 communicates with the through hole 2.13. The molded layer 2.2 is made of silicon and has a thickness in the range of 40 μm to 1000 μm along the vertical axis Z, preferably in the range of 300 μm to 400 μm. The molded layer 2.2 has the function of forming a diaphragm 2.5 in a specific region. The molded layer 2.2 is a rectangle having a first molded front surface 2.21 and a second molded front surface 2.22. The two molded front surfaces 2.21 and 2.22 extend perpendicular to the vertical axis Z. In the molded layer 2.2, a blind hole 2.4 is formed as a trough-shaped recess 2.23. The trough-shaped recess 2.23 includes an inclined wall with respect to the vertical axis Z. The region of the molded layer 2.2 along the vertical axis Z between the trough-shaped recess 2.23 and the second molded front surface 2.22 forms a diaphragm 2.5. The second support surface 2.12 and the first molded surface 2.21 are in direct contact in a plane perpendicular to the vertical axis Z. Preferably, the support layer 2.1 and the molded layer 2.2 are mechanically tightly connected within this contact surface via a connector 2.6. The connector 2.6 can be an electrochemical connection such as an anodic junction, or a chemical connection such as direct bonding. In the context of the present invention, the term “mechanically tight” means that the connection remains functionally stable for the entire service life of the piezoresistive pressure sensor 10, which is at least 10 years. The oxide layer 2.3 is made of silicon oxide. The oxide layer 2.3 has the function of electrically insulating the measuring unit 3, which is arranged in the horizontal plane XY, from the substrate 2. The oxide layer 2.3 is located on the second molded surface 2.22. The oxide layer 2.3 has a thickness of 5 μm or less along the vertical axis Z. The oxide layer 2.3 is 10 at 20°C 12 It has an electrical resistivity of Ωm or more. The oxide layer 2.3 confines the substrate 2 within the horizontal plane XY.

[0043] The support layer 2.1 is connected to the housing 1 via a material bonding connection 4 in a mechanically tight manner. In the case of a single-component housing 1 comprising a housing body 1.0, or a multi-component housing 1 comprising a second housing body 1.0'', the support layer 2.1 is mechanically tightly connected to the housing body 1.0 or the second housing body 1.0'' via the material bonding connection 4. In the case of a housing body 1.0 or the second housing body 1.0'' made of material 1.3981, and a support layer 2.1 made of one of the electrically insulating materials, silicon, borosilicate glass, or silicon carbide, the difference in thermal expansion coefficients between the housing body 1.0 or the second housing body 1.0'' and the support layer 2.1 is 3.0 in the range of 200°C to 450°C. -6 K -1 The following is preferably 2.0 10 -6 K -1 The material bonding joint 4 is formed when the following conditions are met. As a result, because this difference in thermal expansion coefficients is very small, only slight mechanical stress occurs that could lead to cracking or failure of the support layer 2.1 or the material bonding joint 4. Advantageously, this small difference in thermal expansion coefficients also reduces the transmission of mechanical stress to the measuring unit 3.

[0044] Therefore, according to Figure 1, the blind hole 2.4 extends along the vertical axis Z through the through hole 2.13 of the support layer 2.1 and the recess of the molded layer 2.2, reaching the diaphragm 2.5. In a plane perpendicular to the vertical axis Z, the blind hole 2.4 has a diameter. The diameter of the blind hole 2.4 is 1000 μm or less, preferably 500 μm or less.

[0045] The base body 2 is positioned inside 1.3 such that a blind hole 2.4 communicates with an opening 1.4, and a medium M from the environment E enters the blind hole 2.4 through the opening 1.4 and then passes through to the diaphragm 2.5. Preferably, the blind hole 2.4 and the opening 1.4 are aligned with each other along the vertical axis Z. The pressure P to be measured is applied to the diaphragm 2.5. The pressure P to be measured is schematically shown by the black arrow in Figure 1.

[0046] The diaphragm 2.5 is designed to absorb the pressure P being measured. The diaphragm 2.5 comprises a first surface and a second surface. The first surface faces the blind hole 2.4 and encloses the blind hole 2.4 on one side. The second surface faces away from the blind hole 2.4 and is covered with an oxide layer 2.3. The diaphragm 2.5 absorbs the pressure P being measured through the first surface. Under the influence of pressure P, the diaphragm 2.5 can flex along the vertical axis Z.

[0047] Along the vertical axis Z, the thickness of the diaphragm 2.5 is 400 μm or less, preferably 100 μm or less, and preferably 40 μm or less. In the horizontal plane XY, the diameter of the diaphragm 2.5 is 1500 μm or less, preferably 1000 μm or less.

[0048] Measurement unit 3 The measurement unit 3 has the function of generating a resistance change ΔR with respect to the deflection of the diaphragm 2.5.

[0049] The measuring unit 3 is positioned in the horizontal plane XY. Preferably, the measuring unit 3 is positioned on the oxide layer 2.3 on the second surface of the diaphragm 2.5. As a result, the measuring unit 3 is not directly exposed to the medium M. Therefore, the medium M may be chemically aggressive, such as fuel for an internal combustion engine, which would corrode the measuring unit 3 if the medium M were directly exposed to the fuel, undesirably shortening the service life of the piezoresistive pressure sensor 10. Furthermore, the measuring unit 3 is electrically insulated from the substrate 2 by its position on the oxide layer 2.3. Thus, the oxide layer 2.3 prevents leakage current from the measuring unit 3 to the support layer 2.1, allowing the piezoresistive pressure sensor 10 to be used at continuous operating temperatures up to 450°C.

[0050] The measurement unit 3 comprises multiple resistive elements made of a piezoresistive material such as boron-doped silicon. The resistive elements are applied on an oxide layer 2.3 and electrically insulated from each other by the oxide layer 2.3. The resistive elements are structured in terms of height, length, and width. The resistive elements are connected by conductive elements to form a Wheatstone bridge circuit. The conductive elements are also applied on the oxide layer 2.3. The conductive elements are made of conductive materials such as highly doped silicon, aluminum, titanium, and tungsten. For connection to the Wheatstone bridge circuit, the conductive elements are structured in terms of height, length, and width. The measurement unit 3 is schematically shown in Figure 2 as a full bridge having four resistive elements. The resistive and conductive elements are applied and structured on the oxide layer 2.3 by chemical vapor deposition, physical vapor deposition, epitaxy, lithography, etching, etc. Preferably, each resistive element has a height of 200 μm or less, a length of 500 μm or less, and a width of 50 μm or less. The deflection of the 2.5 diaphragm generates a resistance change ΔR. This resistance change ΔR is proportional to the measured pressure P.

[0051] Conductor 5 The piezoresistive pressure sensor 10 comprises at least one conductor 5. The conductor 5 has the function of applying a current I to the measuring unit 3 and tapping the voltage U from the measuring unit 3 to discharge to the environment E.

[0052] The conductor 5 comprises several conductive paths 5.1, 5.1', ​​5.1'', 5.1''' and several contact points 5.2, 5.2', 5.2'', 5.2''''. The conductive paths 5.1, 5.1', ​​5.1'', 5.1'''' and the contact points 5.2, 5.2', 5.2'', 5.2''' are arranged on an oxide layer 2.3. The conductive paths 5.1, 5.1', ​​5.1'', 5.1''' and the contact points 5.2, 5.2', 5.2'', 5.2''' are made of conductive materials such as highly doped silicon, aluminum, titanium, tungsten, platinum, or gold. Preferably, the conductive paths 5.1, 5.1', ​​5.1'', 5.1''' have a height of 10 μm or less along the vertical axis Z and a width of 100 μm or less in the horizontal plane. Preferably, the contact points 5.2, 5.2', 5.2'', and 5.2'''' are at a height of 10 μm or less along the vertical axis Z and 1 mm within the horizontal plane XY. 2 It has the following area:

[0053] Preferably, the conductor 5 comprises four conductor paths 5.1, 5.1', ​​5.1'', 5.1''' and four contact points 5.2, 5.2', 5.2'', 5.2''''. Each of the four conductor paths 5.1, 5.1', ​​5.1'', 5.1'''' has a first end and a second end. Each of the four conductor paths 5.1, 5.1', ​​5.1'', 5.1'''' contacts the measuring unit 3 at its first end. Each of the four conductor paths 5.1, 5.1', ​​5.1'', 5.1'''' contacts another location between two adjacent resistive elements of the measuring unit 3 at its first end. Each of the four conductor paths 5.1, 5.1', ​​5.1'', 5.1'''' contacts the contact points 5.2, 5.2', 5.2'', 5.2'''' at its second end. Each of the four conductive paths 5.1, 5.1', ​​5.1'', and 5.1'''' contacts another of the four contact points 5.2, 5.2', 5.2'', and 5.2'''' at its second end. The contacts are electrical contacts.

[0054] The four conductor paths 5.1, 5.1', ​​5.1'', and 5.1'''' include two first conductor paths 5.1 and 5.1' and two second conductor paths 5.1'' and 5.1''''. The four contact points 5.2, 5.2', 5.2'', and 5.2'''' include two first contact points 5.2 and 5.2' and two second contact points 5.2'' and 5.2''''. The first conductor paths 5.1 and 5.1' and the second conductor paths 5.1'' and 5.1'''' alternately contact the measuring unit 3. A current I is applied to the measuring unit 3 through the two first conductor paths 5.1 and 5.1' and the two first contact points 5.2 and 5.2'. Preferably, the current I is constant at 1 mA. According to Ohm's law, the resistance change ΔR of the measuring unit 3 and the applied current I result in a voltage U. The voltage U is tapped through two second conductor paths 5.1'', 5.1''' and two second contact points 5.2'', 5.2'''.

[0055] Preferably, at least one passivation layer 2.3' is also applied to the measurement unit 3, the conductor paths 5.1, 5.1', ​​5.1'', 5.1'''', and in some areas to the oxide layer 2.3. The passivation layer 2.3' is suitable for protecting the measurement unit 3 and the conductor paths 5.1, 5.1', ​​5.1'', 5.1'''' from mechanical shocks, the effects of chemically reactive environments such as oxygen, and for forming a mechanical connection with the cover 6 described later. The passivation layer 2.3' is preferably made of an electrically insulating material such as silicon oxide or silicon nitride. The thickness of the passivation layer 2.3' is 5 μm or less along the vertical axis Z. The passivation layer 2.3' is also applied to the measurement unit 3, the conductor paths 5.1, 5.1', ​​5.1'', 5.1'''', and the oxide layer 2.3 by chemical vapor deposition, physical vapor deposition, or the like.

[0056] The conductor 5 comprises several conductive wires 5.3, 5.3', 5.3'', and 5.3''''. The conductive wires 5.3, 5.3', 5.3'', and 5.3'''' are made of conductive materials such as aluminum and gold. The diameters of the conductive wires 5.3, 5.3', 5.3'', and 5.3'''' are in the range of 15 to 200 μm.

[0057] Conductor wires 5.3, 5.3', 5.3'', and 5.3'''' are connected to contact points 5.2, 5.2', 5.2'', and 5.2'''' by thermosonic ball wedge bonding, ultrasonic wedge bonding, etc.

[0058] Preferably, the conductor 5 comprises four conductor wires 5.3, 5.3', 5.3'', 5.3'''. The four conductor wires 5.3, 5.3', 5.3'', 5.3'' include two first conductor wires 5.3, 5.3' and two second conductor wires 5.3'', 5.3''''. Current I is supplied from the environment E via the two first conductor wires 5.3, 5.3'. Voltage U is discharged into the environment E via the two second conductor wires 5.3'', 5.3'''. The conductor wires 5.3, 5.3', 5.3'', 5.3'''' exit from the interior 1.3 of the housing 1 via an electrical feedthrough of the housing 1 (not shown).

[0059] Cover 6 The piezoresistive pressure sensor 10 includes at least one cover 6. The cover 6 has the function of forming the reference pressure P' of the measuring unit 3.

[0060] The cover 6 is positioned within the horizontal plane XY. The cover 6 is positioned on the oxide layer 2.3. Preferably, the cover 6 is also positioned in areas on the conductive paths 5.1, 5.1', ​​5.1'', 5.1'''. If the measuring unit 3, conductive paths 5.1, 5.1', ​​5.1'', 5.1''', and a passivation layer 2.3' are present, the cover 6 is positioned in areas on the passivation layer 2.3'.

[0061] The cover 6 is made of borosilicate glass or silicon. Preferably, the cover 6 is rectangular in shape and has side lengths. Preferably, the cover 6 has a height of 100 to 800 μm along the vertical axis Z, preferably 500 μm, and side lengths of 2000 μm or less, preferably 1200 μm or less in the horizontal plane XY.

[0062] Those skilled in the art can also use the knowledge of the present invention to measure 10 in the range of 20°C to 450°C. 7 Electrical resistance of Ωm or more and 2.6 10 -6 K -1 ~4.2 10 -6 K -1 Covers 6 made of different electrical insulating materials with different coefficients of thermal expansion can be used.

[0063] Preferably, the cover 6 is pot-shaped and includes a cavity 6.2 surrounded by an edge region 6.1 radially spaced from the vertical axis Z. A cover 6 placed on an oxide layer 2.3 or passivation layer 2.3' is designed to completely house the measuring unit 3 within the cavity 6.2. For this purpose, the height and diameter of the cavity 6.2 are greater than the height and diameter of the measuring unit 3. The reference pressure P' spreads within the cavity 6.2 of the cover 6. A cover 6 placed on an oxide layer 2.3 or passivation layer 2.3' is designed to maintain a constant reference pressure P' within the cavity 6.2 over time. For this purpose, a cover 6 placed on an oxide layer 2.3 or passivation layer 2.3' is in direct contact with the oxide layer 2.3 or passivation layer 2.3' in the horizontal plane XY via the edge region 6.1. Preferably, the cover 6 and the oxide layer 2.3 or passivation layer 2.3' are mechanically tightly connected to each other at this contact surface via a further connection 2.7. The further connection 2.7 can be an electrochemical connection such as an anodic junction, or a chemical connection such as direct bonding. The further connection 2.7 is airtight so that the reference pressure P' in the cavity remains constant for at least 10 years, the average service life of the piezoresistive pressure sensor 10.

[0064] Preferably, the contact surfaces between the cover 6 and the oxide layer 2.3 or passivation layer 2.3' are located within contact points 5.2, 5.2', 5.2'', and 5.2'''' in the radial direction with respect to the vertical axis Z. Thus, contact points 5.2, 5.2', 5.2'', and 5.2'''' are located outside the cavity 6.2. This means that electrical contact between the conductor wires 5.3, 5.3', 5.3'', and 5.3'''' is not restricted by the cover 6.

[0065] Preferably, the contact surface between the cover 6 and the oxide layer 2.3 or passivation layer 2.3' is located radially outside the diaphragm 2.5 with respect to the vertical axis Z. As a result, the mechanical connection of the cover 6 to the oxide layer 2.3 or passivation layer 2.3' does not affect the deflection of the diaphragm 2.5 under the influence of pressure P, and the measured pressure P is not affected by the cover 6.

[0066] The reference pressure P' is 10 -3 It is less than a bar. Therefore, the reference pressure is more than three orders of magnitude smaller than the pressure P being measured. The reference pressure P' serves as the reference for measuring pressure P. Using this reference, the piezoresistive pressure sensor 10 measures the pressure in absolute terms.

[0067] Material bonding connection part 4 The piezoresistive pressure sensor 10 includes at least one material bonding connection 4. The material bonding connection 4 plays the role of mechanically connecting the housing 1 to the base 2 in a tight and airtight manner.

[0068] The material bonding connection 4 includes at least two materials M1 and M2. The two materials M1 and M2 include a first material M1 and a second material M2.

[0069] Solder joint In the first embodiment, the material bonding joint 4 is a solder joint that includes a first material M1 having a higher melting point than the second material M2. The first material M1 is one of the following metals: silver with a melting point of 962°C, gold with a melting point of 1064°C, copper with a melting point of 1085°C, or nickel with a melting point of 1455°C. The second material M2 is one of the following metals: indium with a melting point of 157°C, or tin with a melting point of 232°C.

[0070] Preferably, the first material M1 is gold and the second material M2 is indium. In the material bonding connection 4 made of gold and indium, the mass fraction of gold, which is the first material M1, is 46% or more. Because the mass fraction of gold, which is the first material M1, is 46% or more, the melting temperature TM of the material bonding connection 4 is 250°C or higher, preferably 450°C or higher.

[0071] Preferably, the first material M1 is gold and the second material M2 is tin. In this case, the material bonding connection 4 made of gold and tin has a mass fraction of gold, which is the first material M1, of 80% or more, preferably 89% or more, and preferably 93% or more. Since the mass fraction of gold, which is the first material M1, is 80% or more, the melting temperature TM of the material bonding connection 4 is 250°C or more, preferably 278°C or more. When the mass fraction of gold, which is the first material M1, is 93% or more, the melting temperature TM of the material bonding connection 4 is 522°C or more.

[0072] In the second embodiment, the material bonding joint 4 is a solder joint comprising a first material M1 which is a conductor and a second material M2 which is an electrical semiconductor. The first material M1 is one of the following conductors, namely silver with a melting temperature of 962°C or gold with a melting temperature of 1064°C. The second material M2 is one of the following electrical semiconductors, namely germanium with a melting temperature of 938°C or silicon with a melting temperature of 1410°C.

[0073] Preferably, the first material M1 is gold and the second material M2 is germanium. In the material bonding connection 4 made of gold and germanium, the mass fraction of gold, which is the first material M1, is 88% or more. Because the mass fraction of gold, which is the first material M1, is 88% or more, the melting temperature TM of the material bonding connection 4 is 250°C or higher, preferably 356°C or higher.

[0074] Preferably, the first material M1 is gold and the second material M2 is silicon. In the material bonding connection portion 4 made of gold and silicon, the mass fraction of gold, which is the first material M1, is 96% or more. Because the mass fraction of gold, which is the first material M1, is 96% or more, the melting temperature TM of the material bonding connection portion 4 is 250°C or higher, preferably 363°C or higher.

[0075] In the first and second embodiments of the material bonding connection 4 as a solder joint, a high mass fraction of gold, which is the first material M1 in the material bonding connection 4, imparts high plastic deformation capacity. Gold exhibits significantly greater plastic deformation capacity than tin or germanium, which is the second material M2. Compared to tin or germanium, gold is significantly more ductile under tensile stress.

[0076] The high plastic deformation capacity of the material bonding connection 4 as a solder joint is important. This is because mechanical stress is generated at the high continuous operating temperature range of the piezoresistive pressure sensor 10, which is 200°C to 450°C, due to the difference in thermal expansion coefficients between the housing 1 and the support layer 2.1. This difference in thermal expansion coefficients can be reduced by the selection of materials for the housing 1 and the electrical insulating material for the support layer 2.1, and as a result the magnitude of the mechanical stress is also reduced. However, the high plastic deformation capacity of the material bonding connection 4 further actively reduces these mechanical stresses. Due to its high plastic deformation capacity, the material bonding connection 4 compensates for the different expansions of the housing 1 and the support layer 2.1. Active reduction of mechanical stress reduces the possibility of failure of the piezoresistive pressure sensor 10 due to cracks or breakage in the support layer 2.1 or the material bonding connection 4. On the other hand, the active reduction of mechanical stress improves the accuracy of pressure P measurement because mechanical stress also affects the measuring unit 3, causing changes in resistance there that are not caused by the pressure P being measured, and thus distorting the measurement signal.

[0077] In the first and second embodiments of the material bonding connection 4 as a solder joint, it is applicable that a high mass fraction of gold, which is the first material M1 in the material bonding connection 4, provides high corrosion resistance. As a result, the piezoresistive pressure sensor 10 can be used with chemically aggressive media M, such as fuel for internal combustion engines, without impairing the usability of the material bonding connection 4 and therefore the piezoresistive pressure sensor 10.

[0078] glass solder In the third embodiment, the material bonding connection 4 is glass solder having a first material M1 that has a higher melting point than the second material M2.

[0079] Preferably, the first material M1 is bismuth(III) oxide with a melting temperature of 817°C, and the second material M2 is boron trioxide with a melting temperature of 475°C. In the material bonding connection portion 4 between bismuth(III) oxide and boron trioxide, the mass fraction of bismuth(III) oxide, which is the first material M1, is 79% to 88%, and the mass fraction of boron trioxide, which is the second material M2, is 5% to 10%. Since the mass fraction of bismuth(III) oxide, which is the first material M1, is 79% to 88%, the melting temperature TM of the material bonding connection portion 4 is 350°C or higher.

[0080] Preferably, the first material M1 is lead(II) oxide with a melting temperature of 888°C, and the second material M2 is boron trioxide with a melting temperature of 475°C. In this case, preferably, the material bonding connection portion 4 exhibits a melting temperature TM of 350°C or higher.

[0081] Manufacturing method for a piezoresistive pressure sensor Figures 4 and 5 show steps MI to MVI in a method for manufacturing a piezoresistive pressure sensor 10. Figures 4 and 5 show two method modifications. Figure 4 shows a first method modification using a material bonding connection 4 in a solder joint embodiment, and Figure 5 shows a second method modification using a material bonding connection 4 in a glass solder embodiment.

[0082] Steps MI to MVI include the first step MI, the further first steps MIa to MIc, and the further steps MII to MVI, which are also referred to below as the further second step MII, the further third step MIII, the further fourth step MIV, the further fifth step MV, and the further sixth step MVI.

[0083] In both modified methods shown in Figures 4 and 5, the first step MI is performed. In the first step MI, the housing 1 and the base 2 are provided. The base 2 is made of an electrically insulating material. The base includes a support layer 2.1.

[0084] In the modified example of the first method shown in Figure 4, the substrate S1 having the first material M1 is provided in a further first step MIa.

[0085] In the modified version of the first method shown in Figure 4, the first material M1 is deposited from the substrate S1 onto the end face 1.6 of the housing 1 in a further first step MIb, forming the first connecting layer L1. The deposition of the first material M1 onto the end face 1.6 of the housing 1 is carried out by chemical vapor deposition, physical vapor deposition, electroplating, etc. Along the vertical axis Z, the first connecting layer L1 has a thickness of 20 μm or less, preferably 10 μm or less.

[0086] Furthermore, only in the modified version of the first method shown in Figure 4, in an additional further first step Mic, the first material M1 is deposited from the substrate S1 onto the first support front surface 2.11 to form a second connecting layer L2. The deposition of the first material M1 onto the first support front surface 2.11 is carried out by chemical vapor deposition, physical vapor deposition, electroplating, etc. Along the vertical axis Z, the second connecting layer L2 has a thickness of 20 μm or less, preferably 10 μm or less.

[0087] In both modified methods shown in Figures 4 and 5, a further second step MII is performed.

[0088] In the modified version of the first method shown in Figure 4, in a further second step MII, alloy A12 is provided from the first material M1 and the second material M2, or the second material M2 is provided alone. Alloy A12 is a macroscopically homogeneous metallic material.

[0089] In the modified version of the second method shown in Figure 5, a mixture M12 of the first material M1 and the second material M2 is provided in a further second step MII.

[0090] Alloy A12 or the second material M2 alone, or mixture M12, can be provided in various ways. For example, alloy A12 or the second material M2 alone, or mixture M12, can be provided as a powder, as a complete part, or as a molded part.

[0091] In both modified versions of the method shown in Figures 4 and 5, a further third step MIII is performed.

[0092] In the modified version of the first method shown in Figure 4, in a further third step MIII, alloy A12 or the second material M2 is placed alone between the first connecting layer L1 and the second connecting layer L2. Alloy A12 or the second material M2 can be placed between the first connecting layer L1 and the second connecting layer L2 by depositing powder or the whole using chemical vapor deposition, physical vapor deposition, electroplating, etc., or this can be achieved by positioning a molded part between the first connecting layer L1 and the second connecting layer L2.

[0093] In the modified version of the second method shown in Figure 5, in a further third step MIII, the mixture M12 is placed between the housing 1 and the substrate 2. The mixture M12 can be placed between the housing 1 and the substrate 2 by depositing it as a powder or in whole using chemical vapor deposition, physical vapor deposition, partitioning, screen printing, electroplating, etc., or by positioning a molded part between the housing 1 and the substrate 2.

[0094] Along the vertical axis Z, the thickness of alloy A12 or the second material M2 alone or mixture M12 is 100 μm or less, preferably 50 μm or less, and preferably 13 μm or less.

[0095] In both modified methods shown in Figures 4 and 5, a further fourth step, MIV, is performed.

[0096] In the modified version of the first method shown in Figure 4, in a further fourth step MIV, the alloy A12 or second material M2 placed between the first and second connecting layers L1 and L2 fuses only with the first and second connecting layers L1 and L2. The melting temperature of alloy A12 or second material M2 alone is lower than the melting temperature TM of the material bonding joint 4. During the fusion process, the first material M1 diffuses from the two connecting layers L1 and L2 into alloy A12 or second material M2, and the second material M2 diffuses into the two connecting layers L1 and L2. By the fusion of alloy A12 or second material M2 alone with the first and second connecting layers L1 and L2, the material bonding joint 4 is formed in the solder joint embodiment.

[0097] In alloy A12 or the second material M2 alone, the mass fraction of the first material M1 is smaller than that of the resulting material bonding joint 4. Because the mass fraction of the first material M1 is higher, the melting temperature TM of the material bonding joint 4 is higher than that of alloy A12 or the second material M2. As a result, the temperature load on the measuring unit 3 placed on the substrate 2 during fusion is significantly lower compared to other equivalent methods, which improves the measurement characteristics of the piezoresistive pressure sensor 10 and reduces the possibility of the measuring unit 3 failing during manufacturing.

[0098] In the modified second method shown in Figure 5, in a further fourth step MIV, the mixture M12 placed between the housing 1 and the substrate 2 fuses with the housing 1 and the substrate 2. When the mixture M12 fuses with the housing 1 and the substrate 2, no diffusion of materials M1 and M2 occurs. The fusion of the mixture M12 with the housing 1 and the substrate 2 forms a material bonding connection 4 in the glass solder embodiment.

[0099] In both modified methods shown in Figures 4 and 5, the conductor 5 is provided in a further fifth step MV.

[0100] In the modified versions of both methods shown in Figures 4 and 5, in a further sixth step MVI, the conductor 5 is electrically connected to the measurement unit 3, and the conductor 5 taps a resistance change ΔR as a voltage U and discharges it to the environment E. [Explanation of symbols]

[0101] 10. Piezoresistive pressure sensor 1 Housing 1.0-1.0'' Housing body 1.1 Front 1.2 Side view 1.3 Internal 1.4 Opening 1.5 Mounting Methods 1.6 End face 1.7 Material bonding connections 2 Base 2.1 Support layer 2.11 First support front 2.12 Second support front 2.13 Through hole 2.2 Molding layer 2.21 First molded front 2.22 Second molding front 2.23 Trough-shaped recess 2.3 Oxide layer 2.3' Passivation Layer 2.4 Blind Hole 2.5 Diaphragm 2.6 Connection 2.7 Further connection points 3. Measurement Unit 4. Material bonding connection 5. Conductors 5.1-5.1''' Conductor Path 5.2-5.2''' Contact point 5.3, 5.3' Conductor wire 6 Covers 6.1 Edge area 6.2 Cavity AA section path A12 alloy E Environment I current L1, L2 connection layers M medium M1, M2 material M12 mixture MI-MVI Method Steps P pressure P' Reference pressure ΔR Resistance Change S1 board TM melting temperature U Voltage X horizontal axis XY horizontal plane Y vertical axis Z vertical axis

Claims

1. A piezoresistive pressure sensor (10) for measuring the pressure (P) of a medium (M) in an environment (E), comprising at least one housing (1), at least one base (2), and at least one measuring unit (3), wherein the housing (1) comprises an interior (1.3) and an opening (1.4), the base (2) and the measuring unit (3) are disposed in the interior (1.3), and the base (2) has a blind hole ( 2.4) and a diaphragm (2.5) are formed, and the diaphragm (2.5) encloses the blind hole (2.4) on one side, and the base (2) is positioned inside (1.3) such that the blind hole (2.4) communicates with the opening (1.4), and when the piezoresistive pressure sensor (10) is exposed to the medium (M), the medium (M) passes through the opening (1.4) and the blind hole (2.4) to the die A piezoresistive pressure sensor (10) is designed to allow penetration to a diaphragm (2.5), the diaphragm (2.5) being deflected by the pressure of the medium (M) that has penetrated the diaphragm (2.5), the measuring unit (3) is positioned on the side of the diaphragm (2.5) opposite to the blind hole (2.4) and generates a change in resistance (ΔR) with respect to the deflection of the diaphragm (2.5), the change in resistance (ΔR) being proportional to the pressure (P) to be measured, wherein the piezoresistive pressure sensor (10) comprises at least one material bonding connection (4), the material bonding connection (4) directly connects the substrate (2) to the housing (1) in a mechanically tight manner, and the material bonding connection (4) exhibits a melting temperature (TM) of 250°C or higher.

2. The piezoresistive pressure sensor (10) according to claim 1, wherein the piezoresistive pressure sensor (10) comprises at least one conductor (5), and the conductor (5) taps the resistance change (ΔR) as a voltage (U) and discharges it to the environment (E).

3. The piezoresistive pressure sensor (10) according to claim 1 or 2, characterized in that the material bonding connection (4) is a solder joint of at least two materials (M1, M2), the materials (M1, M2) include a first material (M1) and a second material (M2), the first material (M1) has a higher melting point than the second material (M2), the first material (M1) is one of the following metals, namely silver, gold, copper, or nickel, and the second material (M2) is one of the following metals, namely indium or tin.

4. The piezoresistive pressure sensor (10) according to claim 3, characterized in that the first material (M1) is gold, the second material (M2) is indium, the mass fraction of the gold in the first material (M1) is 46% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 450°C or more.

5. The piezoresistive pressure sensor (10) according to claim 3, characterized in that the first material (M1) is gold, the second material (M2) is tin, the mass fraction of the gold in the first material (M1) is 80% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 278°C or higher.

6. The piezoresistive pressure sensor (10) according to claim 3, characterized in that the first material (M1) is gold, the second material (M2) is tin, the mass fraction of the gold in the first material (M1) is 93% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 522°C or higher.

7. The piezoresistive pressure sensor (10) according to claim 1 or 2, characterized in that the material bonding connection portion (4) is a solder joint made of at least two materials (M1, M2), the materials (M1, M2) include a first material (M1) and a second material (M2), the first material (M1) is a conductor and the second material (M2) is an electrical semiconductor, the first material (M1) is one of the following metals, i.e., silver or gold, and the second material (M2) is one of the following semiconductors, i.e., germanium or silicon.

8. The piezoresistive pressure sensor (10) according to claim 7, characterized in that the first material (M1) is gold, the second material (M2) is germanium, the mass fraction of the gold in the first material (M1) is 88% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 356°C or higher.

9. The piezoresistive pressure sensor (10) according to claim 7, characterized in that the first material (M1) is gold, the second material (M2) is silicon, the mass fraction of the gold in the first material (M1) is 96% or more, and the melting temperature (TM) of the material bonding connection portion (4) is 363°C or higher.

10. The piezoresistive pressure sensor (10) according to claim 1 or 2, characterized in that the material bonding connection portion (4) is a glass solder comprising at least two materials (M1, M2), wherein the materials (M1, M2) comprise a first material (M1) and a second material (M2), the first material (M1) exhibits a higher melting point than the second material (M2), the first material (M1) is bismuth(III) oxide or lead(II) oxide, the second material (M2) is boron trioxide, and the material bonding connection portion (4) exhibits a melting temperature (TM) of 350°C or higher.

11. The piezoresistive pressure sensor (10) according to any one of claims 1 to 10, characterized in that the housing (1) has an end face (1.6) facing the interior (1.3) within the region of the opening (1.4), the base body (2) comprises a support layer (2.1) and the blind hole (2.5) is formed as a through hole (2.13) in the support layer (2.1), the support layer (2.1) comprises a first support front surface (2.11) within the region of the through hole (2.13), the first support front surface (2.11) is mechanically tightly connected to the end face (1.6) via the material bonding connection portion (4), and the base body (2) is arranged in the interior (1.3) such that the opening (1.4) communicates with the through hole (2.13) along the vertical axis (Z).

12. The piezoresistive pressure sensor (10) according to claim 11, characterized in that the substrate (2) comprises a molded layer (2.2), the blind hole (2.5) in the molded layer (2.2) is formed as a trough-shaped recess (2.23), the molded layer (2.2) comprises a first molded front surface (2.21) and a second molded front surface (2.22), and the region of the molded layer (2.2) along the vertical axis (Z) between the trough-shaped recess (2.23) and the second molded front surface (2.22) forms the diaphragm (2.5).

13. The piezoresistive pressure sensor (10) according to claim 12, characterized in that the second support front surface (2.12) and the first molded front surface (2.21) are in direct contact to form a contact surface, and the support layer (2.1) and the molded layer (2.2) are connected to each other via a connecting portion (2.6) in a mechanically tight manner at the contact surface.

14. A piezoresistive pressure sensor (10) according to any one of claims 11 or 12, characterized in that the substrate (2) comprises an oxide layer (2.3), the oxide layer (2.3) is disposed on the second molded surface (2.22), and the measuring unit (3) is disposed on the oxide layer (2.3), and the measuring unit (3) comprises a plurality of resistive elements made of a piezoresistive material.

15. The piezoresistive pressure sensor (10) comprises at least one cover (6), the cover (6) being pot-shaped and having a cavity (6.2) surrounded by an edge region (6.1), and the cover (6), which is placed on the oxide layer (2.3) having the edge region (6.1), is designed to completely house the measuring unit (3) within the cavity (6.2) and to maintain a constant reference pressure (P') within the cavity (6.2) over time, thereby enabling the piezoresistive pressure sensor (10) to measure the pressure (P) absolutely with respect to the reference pressure (P'). The piezoresistive pressure sensor (10) according to claim 14, wherein, when the passivation layer (2.3') is applied to the oxide layer (2.3), the cover (6) installed on the passivation layer (2.3') having the edge region (6.1) is designed to completely house the measuring unit (3) within the cavity (6.2) and to maintain a reference pressure (P') constant over time within the cavity (6.2), thereby enabling the piezoresistive pressure sensor (10) to measure the pressure (P) absolutely with respect to the reference pressure (P').

16. The housing (1) is a single component having a housing body (1.0), or the housing (1) is a plurality of components having a first housing body (1.0') and at least one second housing body (1.0''), the support layer (2.1) is mechanically tightly connected to the housing body (1.0) or the second housing body (1.0'') via the material bonding connection portion (4), and the housing body (1.0) or the second housing body (1.0'') is rated for temperatures in the range of 20°C to 450°C. －６ K －１ It shall be made of a mechanically resistant material exhibiting the following coefficients of thermal expansion, and the support layer (2.1) shall be 4.5 10 in the range of 20°C to 450°C. －６ K －１ It shall be made of an electrical insulating material exhibiting the following coefficients of thermal expansion, and in the material bonding connection portion (4), the difference in the coefficients of thermal expansion between the housing body (1.0) or the second housing body (1.0'') and the support layer (2.1) shall be 3.0 within the range of 20°C to 450°C. －６ K －１ The following is preferably 2.0 10 －６ K －１ A piezoresistive pressure sensor (10) according to any one of claims 11 to 15, characterized in that it is as follows:

17. A method for manufacturing a piezoresistive pressure sensor (10) for measuring the pressure (P) of a medium (M) in an environment (E), wherein the piezoresistive pressure sensor (10) comprises at least one housing (1), at least one substrate (2), and at least one measuring unit (3), wherein the housing (1) comprises an interior (1.3) and an opening (1.4), and the substrate (2) and the measuring unit (3) are arranged in the interior (1.3). The base (2) is positioned such that a blind hole (2.4) and a diaphragm (2.5) are formed therein, the diaphragm (2.5) encloses the blind hole (2.4) to one side, and the base (2) is positioned inside (1.3) such that the blind hole (2.4) communicates with the opening (1.4), and when the piezoresistive pressure sensor (10) is exposed to the medium (M), the medium (M) communicates with the opening (1.4) and the blind hole (2.4) A method comprising: being designed to allow a medium (M) to penetrate through to the diaphragm (2.5), the pressure of the medium (M) penetrating the diaphragm (2.5) causing the diaphragm (2.5) to flex, the measuring unit (3) being positioned on the side of the diaphragm (2.5) opposite to the blind hole (2.4) to generate a change in resistance (ΔR) to the flexing of the diaphragm (2.5), the change in resistance (ΔR) being proportional to the pressure (P) to be measured, wherein in a first step (MI) of the method, the housing (1) and the substrate (2) are provided, and in further steps (MIa to MIV) of the method, the substrate (2) is directly connected to the housing (1) in a mechanically tight manner via at least one material bonding connection (4), the material bonding connection (4) exhibiting a melting temperature (TM) of 250°C or higher.

18. The method according to claim 17, characterized in that, in a further fifth step (MV) of the method, at least one conductor (5) is provided, and in a further sixth step (MVI) of the method, the conductor (5) is electrically connected to the measuring unit (3), and the conductor (5) taps the resistance change (ΔR) as a voltage (U) and discharges it to the environment (E).

19. The method according to any one of claims 17 or 18, characterized in that, in a further first step (MIa) of the method, a substrate (S1) comprising a first material (M1) is provided, the housing (1) forms an end face (1.6) toward the interior (1.3) in the region of the opening (1.4), and in yet another first step (MIb) of the method, the first material (M1) is deposited from the substrate (S1) onto the end face (1.6) to form a first connecting layer (L1), the thickness of the first connecting layer (L1) is 20 μm or less, preferably 10 μm or less.

20. The method according to claim 19, characterized in that the substrate (2) comprises a support layer (2.1), the blind hole (2.5) is formed in the support layer (2.1) as a through hole (2.13), the support layer (2.1) comprises a first support front surface (2.11) within the region of the through hole (2.13), and in an additional further first step (Mic) of the method, the first material (M1) is deposited from the substrate (S1) onto the first support front surface (2.11) to form a second connecting layer (L2), the thickness of the second connecting layer (L2) being 20 μm or less, preferably 10 μm or less.

21. The method according to claim 20, characterized in that, in a further second step (MII) of the method, an alloy (A12) made of the first material (M1) and the second material (M2) or the second material (M2) alone is provided, and the thickness of the alloy (A12) or the second material (M2) alone is 100 μm or less, preferably 50 μm or less, preferably 13 μm or less; in a further third step (MIII) of the method, the alloy (A12) or the second material (M2) alone is placed between the first connecting layer (L1) and the second connecting layer (L2); and in a further fourth step (MIV) of the method, the alloy (A12) or the second material (M2) alone placed between the first connecting layer (L1) and the second connecting layer (L2) is fused with the first connecting layer (L1) and the second connecting layer (L2).

22. The method according to claim 21, characterized in that the material bonding joint (4) is formed by fusing the alloy (A12) or the second material (M2) alone with the first connecting layer (L1) and the second connecting layer (L2), and the material bonding joint (4) is a solder joint having a melting temperature (TM) higher than the melting temperature of the alloy (A12) or the second material (M2) alone.

23. The method according to any one of claims 17 or 18, characterized in that, in a further second step (MII) of the method, a mixture (M12) of the first material (M1) and the second material (M2) is provided, the thickness of the mixture (M12) is 100 μm or less, preferably 50 μm or less, preferably 13 μm or less; in a further third step (MIII) of the method, the mixture (M12) is placed between the housing (1) and the substrate (2); in a further fourth step (MIV) of the method, the mixture (M12) placed between the housing (1) and the substrate (2) is fused to the housing (1) and the substrate (2); and the fusion of the mixture (M12) to the housing (1) and the substrate (2) forms a material bonding connection (4), the material bonding connection (4) is glass solder.

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