DE102008041254B4 - Acceleration sensor and method for manufacturing an acceleration sensor - Google Patents

Abstract

Acceleration sensor (101, 102, 103, 104) with a substrate comprising a carrier substrate (110), a first oxide level (120), a conductor track level (130), a second oxide level (140) and an epitaxial functional level (150), a movable element (160, 165, 260, 265), which comprises a seismic mass (161, 166, 261) and is movably connected to the substrate by a spring element (170, 270, 275), and a lower counter-electrode (200, 210 , 300, 310), wherein the spring element (170, 270, 275) in the interconnect level (130), the seismic mass (161, 166, 261) in the epitaxial functional level (150) and the lower counter-electrode (200, 210, 300, 310) is provided in the carrier substrate (110).

Description

The invention relates to an acceleration sensor and a method for producing an acceleration sensor.

State of the art

Micromechanical acceleration sensors for the capacitive detection of acceleration acting perpendicular to a wafer plane (z-direction) of the acceleration sensor are known in the prior art. Such acceleration sensors are based on a spring-mass principle. The acceleration sensor has a seismic mass that is movably suspended via springs. The seismic mass forms a plate capacitor with one or more counter-electrodes fixed on the substrate of the acceleration sensor. An acceleration acting on the seismic mass causes a deflection or tilting of the seismic mass, which changes the distance between the seismic mass and the counter electrodes fixed on the substrate, which leads to a measurable change in the capacitance of the plate capacitor formed by the seismic mass and the counter electrodes leads.

It is known to produce the seismic mass and the springs of an acceleration sensor from an epitaxially grown silicon layer and to produce the counter-electrodes in a buried polysilicon conductor track level lying underneath in the z-direction. Because the springs and seismic mass of these accelerometers are made from the same layer, they have the same thickness. Because of spring and seismic mass lateral extension limitations, it is difficult to combine soft springs with a large seismic mass. This limits the sensitivity of these acceleration sensors. In addition, the deflection or tilting of the seismic mass is only detected via counter-electrodes provided in the printed conductor plane arranged below the seismic mass, while no detection means are provided above the spring-mass system.

Disclosure of Invention

The object of the invention is to provide an improved acceleration sensor. This object is achieved by an acceleration sensor having the features of claim 1 and by a method having the features of claim 15.

According to the invention, an acceleration sensor has a substrate that includes a carrier substrate, a first oxide level, a conductor track level, a second oxide level and an epitaxial functional level. The acceleration sensor also has a movable element, which includes a seismic mass and is movably connected to the substrate by a spring element. In addition, the acceleration sensor has a lower counter-electrode. The spring element is provided in the interconnect level, the seismic mass in the epitaxial functional level and the lower counter-electrode in the carrier substrate.

This accelerometer makes it possible to combine a thin spring element with a thick seismic mass. This allows the realization of a highly sensitive acceleration sensor on a small area.

In one embodiment, the lower counter-electrode is formed by an n-doped area of the carrier substrate, which is enclosed by a p-doped area of the carrier substrate, which in turn is enclosed by an n-doped area of the carrier substrate.

In another embodiment, the lower counter-electrode is formed by a p-doped region of the carrier substrate, which is surrounded by an n-doped region of the carrier substrate, which in turn is surrounded by a p-doped region of the carrier substrate.

In a further embodiment, the lower counter-electrode is formed by a section of the carrier substrate which is insulated from the rest of the carrier substrate by one or more isolation trenches.

In this case, contact is preferably made with the lower counter-electrode via a plated-through hole on the rear side of the carrier substrate.

In a further embodiment of the invention, contact is made with the lower counter-electrode via a contact to the conductor track level.

In a development of the invention, an upper counter-electrode is provided in the epitaxial functional level. As a result, for a given lateral extent of the acceleration sensor, greater capacitances of the capacitors formed by the movable element and the counter-electrodes are made possible, which increases the sensitivity of the acceleration sensor.

The lower counter-electrode and the upper counter-electrode are preferably connected to evaluation electronics in such a way that a differential detection of a deflection of the movable Ele ment is made possible. This increases the accuracy of the acceleration sensor.

In a further development, several upper counter-electrodes are provided. In another development, several lower counter-electrodes are provided.

According to one embodiment of the acceleration sensor, the spring element is a bending spring that can be stretched in a direction perpendicular to the carrier substrate and that enables a translatory deflection of the movable element.

According to another embodiment of the acceleration sensor, the spring element is a torsion spring, which allows the movable element to tilt.

Two lower counter-electrodes and two upper counter-electrodes are expediently provided, with each lower counter-electrode being electrically connected to each upper counter-electrode. This leads to high capacitances in the capacitors formed by the movable element and the counter-electrodes, which increases the sensitivity of the acceleration sensor and enables differential detection of a tilting of the movable element.

In an alternative configuration, the torsion spring element is provided in the conductor track level and in the epitaxial functional level. This increases the flexural rigidity of the spring element and leads to a lower susceptibility to failure of the acceleration sensor.

According to the invention, a method for producing an acceleration sensor comprises steps for providing a carrier substrate, for producing a lower counter-electrode in the carrier substrate, for depositing a first oxide level on the carrier substrate, for depositing a conductor track level on the first oxide level, for structuring the conductor track level to form a spring element and a lower bulk portion, depositing a second oxide level on the trace level, patterning the second oxide level to partially expose the lower bulk portion, depositing an epitaxial functional level on the second oxide level, patterning the epitaxial functional level to create vertical trenches and partially Bleaching the first oxide level and the second oxide level to create a lower cavity between the support substrate and the lower bulk portion and an upper cavity between the lower bulk portion and the epitaxial functional level n.

A further development of the method provides for carrying out a further method step for structuring the first oxide level after the deposition of the first oxide level in order to partially uncover the lower counter-electrode.

Another development of the method provides that, in order to produce the lower counter-electrode in the carrier substrate, an n-doped region surrounded by a p-doped region is produced in the carrier substrate.

An alternative development of the method provides that a p-doped region surrounded by an n-doped region is produced in the carrier substrate in order to produce the lower counter-electrode in the carrier substrate.

A further alternative embodiment of the method provides that, in order to produce the lower counter-electrode in the carrier substrate, a region of the carrier substrate is electrically insulated from a remaining region of the carrier substrate by one or more isolation trenches.

In this case, after the production of the lower counter-electrode, a plated-through hole is preferably produced on the rear side of the carrier substrate.

character list

• 1 shows a schematic representation of a first embodiment of an acceleration sensor;
• 2 shows a schematic representation of a second embodiment of an acceleration sensor;
• 3 shows a schematic representation of a third embodiment of an acceleration sensor;
• 4 shows a schematic representation of a fourth embodiment of an acceleration sensor;
• 5a shows a schematic representation of a movable element in a first embodiment;
• 5b shows a schematic representation of a movable element in a second embodiment;
• 6 shows a schematic representation of a third embodiment of a movable element;
• 7a until 7k show a schematic representation of different process steps of a method for producing an acceleration sensor.

Embodiments of the invention

1 shows a schematic representation of a section through an acceleration sensor 101 according to a first embodiment of the invention.

Acceleration sensor 101 is made of a substrate, which includes a carrier substrate 110, a first oxide level 120, a conductor track level 130, a second oxide level 140 and an epitaxial functional level 150 in succession in a z-direction. The carrier substrate 110 can be a silicon substrate, for example. The first oxide level 120 can be composed of, for example, a silicon oxide or another material that can be selectively etched out. The first oxide level 120 may have been deposited epitaxially on the carrier substrate 110, for example. The conductor track level 130 consists of a conductive material, for example polycrystalline silicon (polysilicon). The interconnect level 130 may have been epitaxially deposited on the first oxide level 120, for example. The second oxide level 140 can consist of, for example, a silicon oxide or another material that can be selectively leached out. The second oxide level 140 may have been deposited epitaxially on the interconnect level 130, for example. The second oxide level 140 may be the same material as the first oxide level 120 or may be a different material. The first oxide level 120 and the second oxide level 140 can have a comparable thickness in the z-direction. The epitaxial functional level 150 can consist of silicon, for example. The epitaxial functional level 150 may have been epitaxially deposited on the second oxide level 140, for example. The interconnect level 130 can have a smaller thickness than the epitaxial functional level 150 in the z-direction.

The acceleration sensor 101 of 1 comprises a movable element 160. The movable element 160 can also be referred to as a trampoline and can be moved in the z-direction. In the lateral direction, ie perpendicular to the z-direction, the movable element 160 can have a rectangular or round basic shape, for example.

The movable element 160 comprises a lower mass part 162, a connecting piece 163 and a seismic mass 161. The lower mass part 162 is arranged in the z-direction in the conductor plane 130 and consists of the same material as the conductor plane 130. The connecting piece 163 is in z -direction in the plane of the second oxide level 140 and consists of the same material as the epitaxial functional level 150. The seismic mass 161 is arranged in the z-direction in the plane of the epitaxial functional level 150 and consists of the same material as the epitaxial functional level 150 .

In the z-direction below the lower mass portion 162 of the movable element 160, a portion of the first oxide level 120 has been removed such that a lower cavity 240 is formed. In the lateral direction next to the lower mass part 162, a part of the interconnect plane 130 has been removed in order to produce the lower mass part 162 and two spring elements 170. The lower mass part 162 is only connected to the remaining area of the conductor track level 130 via the two spring elements 170 . However, more than two spring elements 170 can also be provided. The spring elements 170 are designed as bending springs lying in the plane of the conductor track plane 130, which can be stretched in the z-direction but are stiff in the lateral direction. The spring elements 170 can consist, for example, of bars running in the plane of the conductor track level 130 and made of the same material as the conductor track level 130 .

Laterally adjacent to the connector 163, a portion of the second oxide level 140 has been removed to form an upper cavity 241. FIG. The upper cavity 241 surrounds the connecting piece 163. The seismic mass 161 is separated from the surrounding epitaxial functional level 150 by one or more vertical trenches 242 running through the epitaxial functional level 150 in the z-direction. Movable element 160 is separated from the surrounding substrate of acceleration sensor 101 by lower cavity 240 , upper cavity 241 and vertical trenches 242 and is only connected to the surrounding substrate of acceleration sensor 101 via spring elements 170 .

A counter-electrode 200 is provided in the carrier substrate 110 below the movable element 160 in the z-direction. The counter-electrode 200 is in the form of a pn trough. Below the surface of the carrier substrate 110 facing the lower cavity 240, the carrier substrate 110 is heavily n-doped and forms an n-doped region 182. In the z-direction downwards and in the lateral direction to the side, the n-doped region 182 is one p-doped region 181 of the carrier substrate 110 surrounded. The p-doped region 181 is in turn surrounded downwards in the z-direction and to the side in the lateral direction by an n-doped region 180 of the carrier substrate 110 . Overall, the p-doped region 181 forms a well surrounded by the n-doped region 180 in the carrier substrate 110. The n-doped region 182 forms a well surrounded by the p-doped region 181 in the carrier substrate 110 and is adjacent to the lower cavity 240 . The n-doped region 180 forms the conductive counter-electrode 200. In an alternative embodiment, the area 180 can be implemented as a p-doped area, the area 181 as an n-doped area and the area 182 as a p-doped area.

A contact 190 is provided in the lateral direction next to the movable element 160 and the lower cavity 240 and produces an electrical connection between the conductor track plane 130 and the counter-electrode 200 . The contact 190 consists of the same material as the conductor track level 130 and extends from the conductor track level 130 through the first 0-oxide level 120 to the counter-electrode 200 in the carrier substrate 110. The counter-electrode 200 is electrically connected via the contact 190 to a conductor track level 130 conductor connected.

The movable element 160 and the counter-electrode 200 form a capacitor whose capacitance depends on the distance between the movable element 160 and the counter-electrode 200 . An acceleration acting on the acceleration sensor 101 in the z-direction leads to a force acting on the seismic mass 161 in the z-direction. As a result, the spring elements 170 are stretched in the z-direction and the movable element 160 is deflected in the z-direction. This changes the distance between the movable element 160 and the counter-electrode 200, as a result of which the capacitance of the capacitor formed by the movable element 160 and the counter-electrode 200 changes. This change in capacitance is all the greater, the greater the acceleration acting on acceleration sensor 101 . The change in capacitance can be detected with evaluation electronics connected to the acceleration sensor 101 .

2 shows a schematic representation of a section through an acceleration sensor 102 according to a second embodiment of the invention. Acceleration sensor 102 has, in contrast to 1 Acceleration sensor 101 shown has no counter electrode 200. Instead, a counter-electrode 210 is provided in carrier substrate 110 of acceleration sensor 102 . The counter-electrode 210 is formed by a section of the carrier substrate 110 which is electrically insulated from the remaining area of the carrier substrate 110 via one or more isolation trenches 220 .

The counter-electrode 210 can be contacted via a via 211 on the rear side of the carrier substrate 110 facing away from the lower cavity 240 . A possible structure of the via 211 is known to the person skilled in the art, for example from FIG DE 10 2004 038 187 A1 common. The counter-electrode 210 can additionally be conductively connected via the contact 190 to a conductor track provided in the conductor track plane 130 . The via 211 or the contact 190 can optionally also be omitted, so that only the respective other conductive connection to the counter-electrode 210 is available.

The rest of the structure of the acceleration sensor 102 from 2 corresponds to that of the acceleration sensor 101 1 .

3 shows a schematic representation of a section through an acceleration sensor 103 according to a third embodiment of the invention. Compared to the acceleration sensor 102 of 2 For example, in the acceleration sensor 103, the movable element 160 is replaced by a movable element 165. In addition, the acceleration sensor 103 has an additional upper counter-electrode 230 .

The movable element 165 comprises a lower mass part 162, which is arranged in the z-direction in the plane of the conductor track level 130, consists of the same material as the conductor track level 130 and is connected to the surrounding areas of the conductor track level 130 via the spring elements 170. Above the lower mass part 162 in the z-direction, the movable element 165 has a connecting piece 167 which is arranged in the plane of the second oxide level 140 in the z-direction and consists of the same material as the functional epitaxial level 150 . The connecting piece 167 has a smaller extent than the lower mass part 162 in the lateral direction. Above the connecting piece 167 in the z-direction, the movable element 165 has a seismic mass 166 which is arranged in the plane of the epitaxial functional level 150 in the z-direction and consists of the same material as the epitaxial functional level 150 .

The seismic mass 166 is surrounded by one or more upper counter-electrodes 230 in the lateral direction. The upper counter-electrodes 230 are arranged in the z-direction in the plane of the epitaxial functional level 150 and consist of the same material as the epitaxial functional level 150. The one or more upper counter-electrodes 230 are arranged in the z-direction above a protruding area of the lower mass part 162 and separated therefrom by upper cavity 241. The one or more upper counter-electrodes 230 can be contacted, for example, by one or more contacts on the surface of the epitaxial functional level 150 facing away from the upper cavity 241 .

The one or more upper counter-electrodes 230 together with the lower mass part 162 of the movable element 165 form a first capacitor, the capacitance of which depends on the distance between the lower mass part 162 and the upper counter-electrodes 230 . The counter-electrode 210 arranged in the carrier substrate 110 together with the lower mass part 162 of the movable element 165 forms a second capacitor whose capacitance depends on the distance of the lower mass part 162 from the counter-electrode 210 . In the event of a deflection of the movable element 165 in the z-direction caused by an acceleration acting in the z-direction, the capacitances of the first and second capacitors change with opposite signs. If the movable element 165 moves away from the carrier substrate 110, for example, then the capacitance of the first capacitor increases and that of the second capacitor decreases. The changes in capacitance are greater, the greater the deflection of the movable element 165 is. The changes in capacitance can be evaluated differentially by means of evaluation electronics connected to the acceleration sensor 103 . The differential evaluation enables zero point deviations to be suppressed and thus increases the accuracy of acceleration sensor 103.

The lower counter electrode 210 of the in 3 The acceleration sensor 103 shown could also be formed by a pn-well formed by a counter-electrode 200 as in the acceleration sensor 101 of 1 be replaced.

4 shows a schematic representation of a section through an acceleration sensor 104 according to a fourth specific embodiment. Like the acceleration sensors 101, 102, 103 of 1 until 3 Acceleration sensor 104 is made from a starting material that includes carrier substrate 110, first oxide level 120, interconnect level 130, second oxide level 140 and epitaxial functional level 150 in succession in the z-direction.

The acceleration sensor 104 has a movable element 260 . 5a 12 shows a perspective view of the movable element 260. The movable element 260 comprises a lower mass part 262 which is arranged in the plane of the conductive track layer 130 and consists of the same material as the conductive track layer 130. FIG. The lower mass part 262 has a central beam on which a T-shaped wing is attached on each side. The central bar of each T-shaped wing is perpendicular to the central bar of the lower mass part 262. A spring element 270 is arranged above the central bar of the lower mass part 262, which extends in the z-direction in the plane of the second oxide layer 140 and the epitaxial function layer 150 and is made of the same material as the epitaxial functional level 150. Both ends of the central beam of the lower mass part 262 are connected to the first oxide plane 120 and the support substrate 110 via attachment points 271 . The spring element 270 forms a torsion spring that enables the movable element 260 to rotate about a torsion axis 280 . The torsion axis 280 is disposed within the spring member 270 and is oriented parallel to the center beam of the lower mass portion 262 . The movable element 260 can therefore also be referred to as a rocker.

One of the outboard T-shaped wings of the lower mass portion 262 is connected to a seismic mass 261 . The seismic mass is located in the z-direction in the plane of the second oxide level 140 and the epitaxial functional plane 150 and is made of the same material as the epitaxial functional plane 150. The seismic mass 261 is located over the transom of the T-shaped wing. The lower mass part 262 and the seismic mass 261 together form the movable element 260 which is fixed via the fixing points 271 . The seismic mass 261 causes an unequal distribution of the mass of the movable element 260 with respect to the torsional axis 280.

In the carrier substrate 110 of the acceleration sensor 104 of 4 a first lower counter-electrode 300 and a second lower counter-electrode 310 are arranged. The first lower counter-electrode 300 and the second lower counter-electrode 310 can, like the counter-electrode 200 in 1 as a pn-well or as the counter-electrode 210 of 2 be embodied as regions of the carrier substrate 110 that are insulated from the rest of the carrier substrate 110 by isolation trenches 220 . The first lower counter-electrode 300 and the second lower counter-electrode 310 are located on different sides of an imaginary plane running through the torsion axis 280 in the z-direction. The first lower counter-electrode 300 is located in the z-direction below the side of the movable element 260 that has a lower mass. The second lower counter-electrode 310 is located in the z-direction below the side of the movable element 260 which has a higher mass because of the seismic mass 261 .

A first upper counter-electrode 320 and a second upper counter-electrode 330 are arranged in the epitaxial functional level 150 and are electrically isolated from the surrounding areas of the epitaxial functional level 150 . The first upper counter-electrode 320 and the second upper counter-electrode 330 are one on both sides imaginary plane running through the torsion axis 280 in the z-direction. The first upper counter-electrode 320 is arranged above the part of the movable element 260 with the lower mass and is thus in the z-direction above the first lower counter-electrode 300. The second upper counter-electrode 330 is arranged above the part of the movable element 260 with the greater mass and is therefore above the second lower counter-electrode 310 in the z-direction.

The lower mass part 262 of the movable element 260 forms capacitors with the first lower counter-electrode 300, the second lower counter-electrode 310, the first upper counter-electrode 320 and the second upper counter-electrode 330, the capacitance of which depends on the distance between the lower mass part 262 and the respective counter-electrode 300, 310, 320, 330 depends. An acceleration acting on the acceleration sensor 104 in the z-direction causes a force acting on the seismic mass 261 in the z-direction, which force generates a torque about the torsion axis 280 . Since the spring element 270 can be twisted about the torsion axis 280, the torque causes the movable element 260 to tilt about the torsion axis 280. This changes the distances between the lower mass part 262 of the movable element 260 and the four counter-electrodes 300, 310, 320, 330 As a result, the capacitances of the capacitors formed by these counter electrodes and the lower mass part 262 change, which represents a measure of the magnitude of the acceleration acting on the acceleration sensor 104 .

The first lower counter-electrode 300 and the second upper counter-electrode 330 can be electrically connected to each other so that the first lower counter-electrode 300 and the second upper counter-electrode 330 together form a first capacitor with the lower mass part 262 . The second lower counter-electrode 310 and the first upper counter-electrode 320 can be electrically connected to each other so that the second lower counter-electrode 310 and the first upper counter-electrode 320 together with the lower mass part 262 form a second capacitor. When the movable element 260 tilts about the torsion axis 280, the capacitances of the first and second capacitors change with the opposite sign. This enables a differential evaluation of the changes in capacitance, which cancels out zero point errors and increases the accuracy of the acceleration sensor 104 .

5b FIG. 12 schematically shows a perspective view of a movable element 263 used in place of the movable element 260 in an acceleration sensor such as the acceleration sensor 104 of FIG 4 can be used. In contrast to the movable element 260 of 5a are at the movable element 263 of 5b the two wings of the lower mass part 262 are C-shaped. The two C-shaped wings are perpendicularly attached to the central beam of the lower mass portion 262 such that each of the C-shaped wings forms a ring with the central beam of the lower mass portion 262 . In the embodiment of 5b For example, the central beam of the lower mass part 262 is connected to the first oxide level 120 and the carrier substrate 110 via a centrally arranged attachment point 271 . The rest of the structure and the operation of the movable element 263 correspond to that of the movable element 260 of FIG 5a .

6 FIG. 12 schematically shows a perspective view of a movable element 265 that can be used in place of the movable elements 260 or 263 in an acceleration sensor such as the acceleration sensor 104 of FIG 4 can be used. Like the movable element 260 of 5a the movable element 265 comprises a lower mass part 262 which is arranged in the plane of the conductive track plane 130 and consists of the same material as the conductive track plane 130 . The movable element 265 also has a central beam on which a T-shaped wing is attached on each side. The central beam of each T-shaped wing is perpendicular to the central beam of the lower mass part 262. As with the movable element 260, the movable element 265 has the transom of one of the T-shaped wings of the lower mass part 262 connected to a seismic mass 261 which is arranged in the level of the second oxide level 140 and the epitaxial functional level 150 and consists of the same material as the epitaxial functional level 150.

The central beam of the lower mass part 262 of the movable element 265 represents a spring element 275 which is connected via a rear attachment point 276 to an area of the conductor track plane 130 surrounding the movable element 265 . The spring element 275 can be twisted about the torsion axis 280 lying within the spring element 275 . In contrast to the movable element 260 of 5a is at the movable element 265 of the 6 the spring element 275 is merely formed by a part of the lower mass part 262 lying in the conductor track plane 130 . This has the consequence that the spring element 275 of 6 softer than the spring element 270 of 5 is, so a lower restoring force generated. This allows the construction of more sensitive acceleration sensors, which, however, can also have an increased susceptibility to failure.

7a until 7k show different process steps of a method according to the invention for producing an acceleration sensor. An example is the manufacture of the in 3 acceleration sensor 103 shown.

As in 7a shown, the starting point of the processing is the carrier substrate 110. The carrier substrate 110 can, for example, be a silicon substrate, for example a silicon wafer. First, the carrier substrate 110 is provided with one or more counter-electrodes 200 . For this purpose, a pn trough is produced on the surface of the carrier substrate 110, as can be seen from FIG 1 was described. Methods for producing such pn wells are known to the person skilled in the art from the prior art and are not described below. Instead of a counter-electrode 200 designed as a pn trough, the carrier substrate 110 can also be provided with a counter-electrode 210, which consists of an area of the carrier substrate 110 that is separated from the rest of the carrier substrate 110 by isolation trenches 220 and is already based on FIG 2 was described. In this case, a via 211 for contacting the counter-electrode 210 can also be provided on the rear side of the carrier substrate 110 . 7b shows the carrier substrate 110 provided with a counter-electrode 200.

In the next method step, the first oxide level 120 is applied to the carrier substrate 110 . The first oxide level 120 can consist of silicon oxide, for example, and can be deposited on the carrier substrate 110 by thermal oxidation or with another deposition method. The result of this processing step is in 7c shown.

Next, the first oxide level 120 is patterned. The first oxide level 120 is locally removed in lateral areas on which a contact 190 for contacting the counter-electrode 200 is to be located later. Various options, for example etching techniques, are familiar to the person skilled in the art for this purpose. As 7d 12, first oxide level 120 has an opening to counter electrode 200 after processing.

In the following processing step, the interconnect level 130 is applied to the first oxide level 120 . The conductor track level 130 can consist, for example, of polycrystalline silicon (polysilicon) or of another conductive material. The first interconnect level 130 is applied to the first oxide level 120 using one of the common deposition methods. In lateral sections in which the first oxide level 120 was removed in the previous process step, an electrical contact 190 is created between the counter-electrode 200 and the interconnect level 130. This is shown schematically in FIG 7e shown.

In the next work step, the conductor track level 130 is structured. The structuring can be done, for example, by lithographic techniques and etching. In this case, parts of the conductor track level 130 are removed in order to produce the lower mass part 162, the spring elements 170 and any desired conductor tracks. The lower mass part 162 can have a rectangular or round basic shape, for example. The lower mass part 162 is so completely separated from the remaining areas of the conductor track level 130 in the lateral direction that it is only in contact with the remaining areas of the conductor track level 130 via the spring elements 170 . The result of the processing is shown schematically in 7f shown.

The second oxide level 140 is then applied to the interconnect level 130 . The second oxide level 140 may be the same material as the first oxide level 120 or may be a different material. In lateral areas where the conductor track level 130 has been selectively removed, the second oxide level 140 is in direct contact with the first oxide level 130. The second oxide level 140 can be planarized after the deposition. The result of this process step is shown schematically in 7g shown.

Then the second oxide level 140 is patterned. For this purpose, part of the second oxide level 140 is selectively removed in order to produce an opening in the second oxide level 140 in the z-direction above the lower mass part 162 in the interconnect level 130 . The structuring of the second oxide level 140 can take place using one of the common methods. 7h shows the result of the processing.

In the next process step, the epitaxial functional level 150 is deposited on the second oxide level 140 . The epitaxial functional level 150 can consist of silicon, for example. The epitaxial function level 150 can be grown epitaxially on the second oxide level 140, for example. In lateral areas in which the second oxide level 140 was removed in the previous processing step, the epitaxial functional level 150 is deposited directly on the interconnect level 130 . The connecting piece 163 is formed in the opening above the lower mass part 162. After the deposition, the epitaxial functional level 150 can still be planarized. The result of this process step is in 7i shown schematically.

The epitaxial functional level 150 is now structured. For this purpose, one or more vertical trenches 242 in the epitaxial function level 150 generated that separate different lateral sections of the epitaxial functional level 150 from each other. The vertical trenches 242 can be generated by an anisotropic etching process, for example. In the z-direction above the lower mass part 162, a region of the epitaxial functional plane 150 is uncovered, which represents the seismic mass 166 of the movable element 165. One or more upper counter-electrodes 230 are generated in the lateral direction next to the seismic mass 166 . 7y provides a schematic representation of the processing status that has now been reached.

In the following processing step, parts of the first oxide level 120 and the second oxide level 140 are selectively removed. The partial removal of the first oxide level 120 and the second oxide level 140 can be carried out, for example, by etching with a gaseous etching medium, the etching medium attacking the second oxide level 140 and the first oxide level 120 through the vertical trenches 242 . The removal of the first oxide level 120 creates a lower cavity 240 between the counter electrode 200 in the supporting substrate 110 and the lower mass part 162 in the conductor track level 130. The partial removal of the second oxide level 140 creates an upper cavity 241 that exposes the movable element 165. The movable element 165 is now only connected to the surrounding substrate via the spring elements 170 . The result of this processing step is shown schematically in 7k shown and corresponds to the already explained acceleration sensor 103 of FIG 3 .

reference list

101

accelerometer

102

accelerometer

103

accelerometer

104

accelerometer

110

carrier substrate

120

first oxide level

130

trace level

140

second oxide level

150

epitaxial functional level

160

moving element (trampoline; wide)

161

seismic mass (EP; trampoline; wide)

162

lower mass part (trampoline)

163

connector

165

moving element (trampoline; narrow)

166

seismic mass (EP; trampoline; narrow)

167

connector

170

spring element (bending spring)

180

n-doped area

181

p-doped region

182

n ⁺ -doped region

190

Contact

200

counter electrode (tub model)

210

Counter electrode (trench model)

211

via

220

isolation trench

230

Upper counter electrode

240

lower cavity

241

upper cavity

242

vertical trench

260

moving element (rocker; thick spring; lateral suspension)

261

seismic mass (EP; seesaw)

262

lower mass part (rocker)

263

moving element (rocker; thick spring; central suspension)

265

moving element (rocker; thin spring)

270

Spring element (torsion spring; VP+EP)

271

attachment point

275

Spring element (torsion spring; only VP)

276

attachment point

280

torsion axis

300

1. lower counter electrode

310

2. lower counter electrode

320

1. upper counter electrode

330

2. upper counter electrode

Claims (20)

Acceleration sensor (101, 102, 103, 104) with a substrate comprising a carrier substrate (110), a first oxide level (120), a conductor track level (130), a second oxide level (140) and an epitaxial functional level (150), a movable element (160, 165, 260, 265), which comprises a seismic mass (161, 166, 261) and is movably connected to the substrate by a spring element (170, 270, 275), and a lower counter-electrode (200, 210 , 300, 310), with the spring element (170, 270, 275) in the conductor track level (130), the seismic mass (161, 166, 261) in the epitaxial functional level (150) and the lower counter-electrode (200, 210, 300, 310) is provided in the carrier substrate (110). Acceleration sensor (101, 104) after claim 1 , The lower counter-electrode (200, 300, 310) being formed by an n-doped region (182) of the carrier substrate (110), which is surrounded by a p-doped region (181) of the carrier substrate (110), which in turn is surrounded by an n-doped region (180) of the carrier substrate (110) is enclosed. Acceleration sensor (101, 104) after claim 1 , wherein the lower counter-electrode (200, 300, 310) is formed by a p-doped region of the carrier substrate (110), which is enclosed by an n-doped region of the carrier substrate (110), which in turn is surrounded by a p-doped region of the Support substrate (110) is enclosed. Acceleration sensor (102, 103, 104) according to claim 1 , The lower counter-electrode (210, 300, 310) being formed by a section of the carrier substrate (110) which is insulated from the rest of the carrier substrate (110) by one or more isolation trenches (220). Acceleration sensor (102, 103, 104) according to claim 4 , wherein the lower counter-electrode (210, 300, 310) is contacted via a via (211) on the back of the carrier substrate (110). Acceleration sensor (101, 102, 103, 104) according to one of the preceding claims, wherein the lower counter-electrode (200, 210, 300, 310) is contacted via a contact (190) to the conductor track level (130). Acceleration sensor (103, 104) according to one of the preceding claims, wherein an upper counter-electrode (230, 320, 330) is provided in the epitaxial functional level (150). Acceleration sensor (103, 104) after claim 7 , wherein the lower counter-electrode (200, 210, 300, 310) and the upper counter-electrode (230, 320, 330) are connected to evaluation electronics in such a way that a differential detection of a deflection of the movable element (160, 165, 260, 265) is made possible. Acceleration sensor (103, 104) after claim 7 or 8th , wherein a plurality of upper counter-electrodes (230, 320, 330) are provided. Acceleration sensor (101, 102, 103, 104) according to one of the preceding claims, wherein a plurality of lower counter-electrodes (200, 210, 300, 310) are provided. Acceleration sensor (101, 102, 103) according to one of the preceding claims, wherein the spring element (170) is a bending spring which can be stretched in a direction perpendicular to the carrier substrate (110) and which enables a translational deflection of the movable element (160, 165). Acceleration sensor (104) according to one of Claims 1 until 10 , wherein the spring element (270, 275) is a torsion spring which allows the movable element (260, 265) to tilt. Acceleration sensor (104) after claim 12 , wherein two lower counter-electrodes (300, 310) and two upper counter-electrodes (320, 330) are provided, each lower counter-electrode (300, 310) being electrically connected to a respective upper counter-electrode (330, 320). Acceleration sensor (104) according to one of Claims 12 or 13 , The spring element (270) being provided in the conductor track level (130) and in the epitaxial functional level (150). Method for producing an acceleration sensor (101, 102, 103, 104), comprising the following steps: - providing a carrier substrate (110); - Generating a lower counter-electrode (200, 210, 300, 310) in the carrier substrate (110); - Depositing a first oxide level (120) on the carrier substrate (110); - Depositing a conductor track level (130) on the first oxide level (120); - Structuring of the conductor track level (130) in order to define a spring element (170, 270, 275) and a lower mass part (162, 262); - Depositing a second oxide level (140) on the interconnect level (130); - patterning the second oxide level (140) to partially expose the lower bulk portion (162, 262); - depositing an epitaxial functional level (150) on the second oxide level (140); - patterning the epitaxial functional level (150) to produce vertical trenches (242); - Partial leaching of the first oxide level (120) and the second oxide level (140) to form a lower cavity (240) between the supporting substrate (110) and the lower mass part (162, 262) and an upper cavity (241) between the to produce the lower mass part (162, 262) and the epitaxial functional level (150). procedure after claim 15 , wherein after the first oxide level (120) has been deposited, the following further method step is carried out: - structuring of the first oxide level (120) in order to partially uncover the lower counter-electrode (200, 210, 300, 310). Procedure according to one of Claims 15 or 16 , An n-doped region (182) surrounded by a p-doped region (181) being produced in the carrier substrate (110) to produce the lower counter-electrode (200, 300, 310) in the carrier substrate (110). Procedure according to one of Claims 15 or 16 , A p-doped region (182) surrounded by an n-doped region being produced in the carrier substrate (110) in order to produce the lower counter-electrode (200, 300, 310) in the carrier substrate (110). Procedure according to one of Claims 15 or 16 , wherein in order to produce the lower counter-electrode (210, 300, 310) in the carrier substrate (110), a region of the carrier substrate (110) is electrically insulated from a remaining region of the carrier substrate (110) by one or more isolation trenches (220). procedure after claim 19 , wherein after the production of the lower counter-electrode (210, 300, 310) a via (211) on the back of the carrier substrate (110) is produced.

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