DE102008043171A1 - Pressure sensor, in particular pressure sensor technology - Google Patents

Abstract

A pressure sensor 20 comprises a base body, a measuring diaphragm 7, and a transducer, wherein the measuring diaphragm 7 comprises a semiconductor material, wherein the measuring diaphragm 7 is fastened to the base body including a pressure chamber 6, wherein the measuring diaphragm can be acted upon by at least one pressure and elastically dependent on pressure deformable, wherein the transducer provides an electrical signal dependent on the deformation of the measuring diaphragm, the base body having a diaphragm bed against which the measuring diaphragm rests in the event of an overload in order to support the measuring diaphragm, the diaphragm bed having a glass layer 2 whose surface 3 the measuring membrane faces, and forms a wall of the pressure chamber, and wherein the surface of the glass layer is provided with a contour 3, which is adapted to support the measuring diaphragm in the event of an overload.

Description

The The present invention relates to a pressure sensor, in particular a Differential pressure sensor.

pressure sensors comprise a main body, a measuring membrane and a Transducer, wherein the measuring diaphragm attached to the base body is, wherein the measuring membrane acted upon by at least one pressure is and has a pressure-dependent elastic deformation, and wherein the transducer is dependent on the deformation of the measuring diaphragm provides electrical signal, wherein the main body further comprises a membrane bed, on which the measuring membrane in the case an overload is applied to support the measuring diaphragm.

there it is advantageous if the membrane bed approximates a contour the natural pressure-dependent deformation, the so-called bending line has. The difficulty, however, exists therein, such a membrane bed reproducible and inexpensive manufacture.

The Design of the bed and its production depend on it which material is the membrane bed and the substrate which the Membrane bed wears, has, and what a Connection technology of the main body or the membrane bed with the membrane is selected.

For the measurement of differential pressures, z. B. in level or flow measurements, Si base body are preferred because they withstand static pressure well. For the connection of two silicon wafers, there are various methods, such as. B. eutectic blanks or silicon direct bonding. In view of the requirements for a hermetically sealed, solid and yet low-backlash chip-substrate connection, these prior art bonding methods still provide insufficient yield and reproducibility. In addition, the production of, for example, spherical concave beds after US7360431 B2 of YAMATAKE in silicon is not readily possible. Currently, either the non-established methods of grayscale lithography or a direct grinding / polishing of the silicon are known, which leads to difficult to reproducible results.

The The object of the invention is a pressure sensor, in particular to provide a differential pressure sensor and a method for its manufacture, that with improved yield and improved reproducibility can be carried out inexpensively.

The The object is achieved by the pressure sensor according to the independent claim 1, and the method according to the independent Claim 12.

Of the Pressure sensor according to the invention comprises at least a main body, at least one measuring membrane, and a Converter, wherein the measuring membrane comprises a semiconductor material, wherein the measuring diaphragm including a pressure chamber on the Main body is attached, the measuring diaphragm with at least a pressure can be acted upon and pressure-dependent elastic deformable, the transducer being one of the deformation of the measuring diaphragm provides dependent electrical signal, wherein the Base body has a membrane bed, on which the measuring membrane in case of overload, to support the diaphragm, according to the invention, the membrane bed a glass layer has, whose surface faces the measuring membrane, and forms a wall of the pressure chamber.

In a development of the invention comprises the main body a substrate on which the material of the membrane bed in the form of a Glass layer is applied, the surface of the glass layer provided with a contour which is suitable, the measuring diaphragm in case of overload.

The Surface of the glass layer can according to a Be further developed micromechanical development of the invention.

In a presently preferred embodiment of the invention, the Glass layer on a surface contour, by means of hot stamping is prepared.

The Substrate may for example comprise a semiconductor material, in particular Si.

In A development of the invention is the glass layer by means of anodic Bonding connected to the measuring membrane and / or the substrate.

The Glass layer has according to a development of Invention a thickness of not more than 10 microns, preferably not more than 7 μm, and more preferably not more than 5 μm.

The Glass layer has according to a development of Invention a material thickness of not less than 2 microns on.

In a presently preferred embodiment of the invention includes Semiconductor material Si, wherein the glass of the membrane bed comprises a borosilicate glass, which is adapted to the coefficient of expansion of Si to the thermomechanical stress induced during the bonding process is so small as possible. Particularly suitable glasses are for example Pyrex 7740, TEMPAX or Hoya SD-2.

Farther it is presently preferred if the membrane bed has a surface contour which approximates the bending line of the measuring diaphragm is or corresponds to this.

Of the Pressure sensor according to the invention can be an absolute pressure sensor which measures a pressure against vacuum, or a relative pressure sensor be, which measures a pressure against the atmospheric pressure.

However, the present invention is especially relevant for differential pressure sensors which detect the difference between a first pressure and a second pressure. Because especially with differential pressure sensors, the risk of large static unilateral overloads is given because the pressure difference to be measured is usually considerably smaller than the first or second pressure whose difference is to be detected. Therefore, in a currently preferred embodiment, the pressure sensor according to the invention is a differential pressure sensor which has a measuring diaphragm, a first main body and a second main body,
wherein the measuring diaphragm is arranged between the first base body and the second base body and connected to each of the two base bodies including a first pressure chamber and a second pressure chamber, wherein the first pressure chamber and the second pressure chamber each have at least one channel through the first and second base body , wherein the measuring membrane can be acted upon by the channels with a first and a second pressure. The deflection of the membrane then depends on the difference between the first pressure and the second pressure.

The Principle of anodic bonding may be related to the process modified according to the present invention Be used. For this purpose, first the substrate wafer made of silicon over the entire surface with a thin layer made of glass. The production of the membrane beds is carried out with hot stamping or impression of the glass with a high-precision stamping tool harder material. Then follows the anodic Round blanks of the stack with the layer sequence silicon, glass and silicon for an absolute pressure or relative pressure sensor as well as silicon, Glass, silicon, glass and silicon for a differential pressure sensor.

The achieved connection is tight and cohesively without interlayer between glass and silicon. The bonding temperature is between 300 and 500 ° C, and is therefore good for a metallization system suitable.

The bonding mechanism is based on the chemical bonding of O ^- ions with silicon atoms, which leads to corresponding SiO2 bonds between glass and silicon.

There it is a compound of a glass layer between two silicon wafers There are various compromises to be made, on the one hand because of the difference in the moduli of elasticity of silicon (about 170 GPa) and glass (about 70 GPa), and on the other hand because of residual mismatch in the thermal expansion coefficient. Because the bonding process at the mentioned high temperatures can in Use of the pressure sensor lead to residual tension. The resulting potential influences on the sensor performance To minimize, the layer thickness should be as low as possible be. The for a reliable anodic connection required layer thicknesses are for example about 2-5 microns.

The Glass layer thickness becomes dependent on the membrane geometry selected. Because wafers with identical material properties can be used and the required intermediate glass thicknesses very are thin, resulting in only low residual stresses in the Sensor chip. This allows a homogeneous, clean bonding process if the glass layer, in particular in the form of a glass thin film, in particular the lowest possible defect density, a spatially homogeneous composition and a largely homogeneous Have layer stress.

Dependent of the shape of the membrane (polygonal, especially hexagonal, rectangular, square or elliptical or circular) can Bed made with appropriately shaped embossing tool become.

The inventive method for producing a Pressure sensor, in particular according to one of the preceding claims, comprises the steps of: (a) providing a semiconductor wafer, in particular a Si wafer; (b) applying a glass layer; (c) Dissecting the shape of membrane beds by means of hot stamping in the glass layer, wherein the shape of the membrane beds in particular the bending line of the measuring membranes in case of overload approaches; (d) preparing pressure channels the substrate and the glass layer; and (e) connecting the second one Wafers and the glass layer by means of anodic bonding.

In a development of the invention comprises the method (f) thinning of the second wafer, in particular by means of an etching process.

In a presently preferred embodiment of the invention, the method relates to that of differential pressure sensors, wherein it further comprises the following steps: (g) applying a pre-fabricated according to steps (a) to (d) assembly with a further glass layer, which hot-stamped Having membrane bed contours, and a further substrate layer, wherein the prefabricated assembly through the further glass layer and the further substrate layer has continuous pressure channels, and connecting the layer of the measuring membranes with the further glass layer by means of anodic bonding.

Provided a plurality of sensors are manufactured in parallel in the wafer composite, Finally, a separation of the sensors follows, for example by Saws.

The Invention will now be described with reference to an illustrated in the drawings Embodiment explained.

It shows:

1 : Section views of layer sequences for the production of differential pressure sensors according to the invention in various stages of production.

In the 1 The illustrated sequence of manufacturing steps begins in step (a) with a Si wafer 1 For example, in the 4-inch format on the in step (b) a glass layer 2 with a thickness of a few microns is applied, the thickness of the glass layer 2 depends on the desired measuring range and the selected geometry of the measuring diaphragm. In a third step (c) is by hot stamping the shape of the membrane beds 3 introduced into the glass layer, which form should approximate the bending line of the measuring membranes in the case of a one-sided overload. In a subsequent process step (d), the pressure channels 4 through the substrate 1 and the glass layer 2 prepared, for example with ultrasonic drills. Now, in step (e), a layer sequence comprising the above-described layers and a second Si wafer 5 that covers the glass layer 2 is connected by anodic bonding. Subsequently, the second wafer 5 in step (f) thinned so far in an etching process until a measuring membrane 7 desired strength stops, which is a pressure chamber 6 in the interior of the layer sequence, wherein the pressure chamber via the bore 4 communicates with the environment and can be acted upon by a pressure.

In this state, the layer sequence for an absolute pressure sensor or a relative pressure sensor would be used, wherein the measuring membrane is typically applied via the pressure channel with a reference pressure, while the measuring pressure to that of the pressure chamber 6 opposite side of the measuring diaphragm 7 acts.

For the production of differential pressure sensors in step (g) still a glass layer 12 and a substrate 11 in the state shown in step d on the layer of the measuring membranes 7 applied and with anodic discs with the layer of measuring membranes 7 connected.

Single differential pressure sensors 20 are separated by dicing along the vertical dashed lines 1g receive.

For the skilled person is of course the one pressure sensor nor a converter for generating a deformation-dependent electrical signal, which, for example, a capacitive or a resistive, in particular a piezoresistive transducer can. The required electrodes or resistive elements are not shown here in detail and can in usual Be prepared.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 7360431 B2 [0005]

Claims (15)

Pressure sensor ( 20 ), comprising: at least one main body, at least one measuring membrane ( 7 ), and a transducer, wherein the measuring membrane ( 7 ) comprises a semiconductor material, wherein the measuring membrane ( 7 ) including a pressure chamber ( 6 ) is attached to the base body, wherein the measuring membrane can be acted upon by at least one pressure and elastically deformable pressure-dependent converter provides a dependent of the deformation of the measuring diaphragm electrical signal, the base body having a diaphragm bed against which the measuring diaphragm in case of overload to support the measuring membrane, characterized in that the membrane bed has a glass layer ( 2 ) whose surface ( 3 ) faces the measuring membrane, and forms a wall of the pressure chamber. Pressure sensor ( 20 ) according to claim 1, wherein the base body is a substrate material ( 1 ), on the glass layer ( 2 ), the surface of the glass layer having a contour ( 3 ), which is suitable for supporting the measuring diaphragm in the event of an overload. Pressure sensor according to claim 1 or 2, wherein the surface of the glass layer ( 2 ) is micromechanically processed. Pressure sensor according to claim 1, 2 or 3, wherein the glass layer ( 2 ) a surface contour ( 3 ), which is prepared by hot stamping. A pressure sensor according to claim 2, 3 or 4, wherein the substrate material ( 1 ) comprises a semiconductor material. Pressure sensor according to one of claims 2 to 5, wherein the glass layer ( 2 ) by means of anodic bonding with the substrate ( 1 ) and the measuring membrane ( 7 ) connected is. Pressure sensor according to one of claims 1 to 6, wherein the glass layer has a thickness of not more than 10 μm, preferably not more than 7 μm, and more preferably not more than 5 μm. Pressure sensor according to one of the preceding claims, wherein the glass layer has a material thickness of not less than 2 microns. Pressure sensor according to claim 2 or one dependent thereof Claim, wherein the substrate material comprises Si, and the glass of the Membranbetts a borosilicate glass having. Pressure sensor according to one of the preceding claims, wherein the membrane bed has a surface contour, which approximates the bending line of the measuring diaphragm or this corresponds. Pressure sensor according to one of claims 1 to 10, in which the pressure sensor is a differential pressure sensor comprising a measuring diaphragm, a first base body and a second base body having, wherein the measuring diaphragm between the first base body and the second base body and arranged with each of the Both basic body along a circumferential joint including a first pressure chamber and a second pressure chamber connected is, wherein the first pressure chamber and the second pressure chamber in each case at least one channel through the first or second base body exhibit, the measuring diaphragm through the channels can be acted upon with a first and a second pressure. Method for producing a pressure sensor, in particular according to one of the preceding claims, comprising the steps: (a) providing a semiconductor wafer, in particular a Si wafer; (b) applying a glass layer; (c) preparing the shape of membrane beds by means of hot stamping into the glass layer, the shape of the membrane beds in particular approximating the bending line of the measuring membranes in the event of an overload; (d) preparing pressure channels through the substrate 1 and the glass layer 2 ; and (e) bonding the wafer and the glass layer by anodic bonding. The method of claim 12, further comprising (f) thinning of the second wafer, in particular by means of an etching process. Method according to one of claims 12 or 13 for the manufacture a differential pressure sensor, in particular according to claim 11, further full: (g) applying one after the steps (a) to (D) prefabricated assembly with a further glass layer, which has hot embossed membrane bed contours, and a further substrate layer, wherein the prefabricated assembly through the further glass layer and the further substrate layer continuous Having pressure channels, and connecting the layer of the measuring membranes with the further glass layer by means of anodic bonding. The method of any one of claims 12 to 15, further comprising: seperate the sensors.