DE102015210659A1 - Method of making a solid electrolyte sensing element - Google Patents

Abstract

A method for producing at least one solid electrolyte sensor element (110) is proposed. The method comprises the following steps:
a) providing at least one semiconductor substrate (112);
b) forming at least one cavern (114) in at least one surface (116) of the semiconductor substrate (112);
c) at least partially filling the cavern (114) with at least one sacrificial layer material (120);
d) applying at least one layer structure (122) of the solid electrolyte sensor element (110) to the sacrificial layer material (120), wherein the layer structure (122) comprises at least one layer (124) of an electrically conductive electrode material and at least one solid electrolyte layer (126),
e) at least partially removing the sacrificial layer material (120), wherein the cavern (114) is at least partially exposed again so that the cavern (114) is at least partially covered by the layer structure (122).

Description

State of the art

The invention relates to a method for producing a solid electrolyte sensor element. Such solid electrolyte sensor elements can be used for example in the field of exhaust gas sensors and in on-board diagnostic systems. Other applications are conceivable in principle.

Solid state electrolyte sensor elements are known in the art, for example as a lambda probe. A measurement of a residual oxygen content in an exhaust gas of an internal combustion engine and a feedback of the measured value with an engine control may be desirable for a minimization of pollutants, in particular of nitrogen oxides. The lambda probes may in particular comprise ceramic materials, in particular zirconium oxide. In principle, thick-film techniques can be used as the production method. This is for example off T. Baunach, K. Schänzlin, L. Diehl, Clean Exhaust Gas by Ceramic Sensors, Physik Journal, Vol. 5, 2006 known.

For example, a lambda probe designed as a Nernst probe can measure a voltage between two electrodes connected via a solid electrolyte, it being possible, for example, to use yttrium- or scandium-stabilized zirconium dioxide as a membrane. In this case, for example, a property of zirconium dioxide is used, which consists in that at a high temperature, usually at 650 ° C, oxygen ions can be transported electrolytically.

DE 199 41 051 A1 discloses a gas sensor formed as a broadband lambda probe having a ceramic solid electrolyte base and a plurality of electrodes deposited in chambers and on the outside of the solid state electrolyte.

DE 10 2012 201 304 A1 discloses a micro-mechanical solid electrolyte sensor device and a corresponding manufacturing method. The micro-mechanical solid electrolyte sensor device has a micro-mechanical support substrate having a front side and a back side; a first porous electrode and a second porous electrode; and a solid electrolyte embedded between the first porous electrode and the second porous electrode.

However, known manufacturing methods have a number of technical challenges. In principle, thick-film techniques can only permit relatively large minimum dimensions, both with regard to the structure widths, which are typically greater than 30 μm, and also with regard to the layer thicknesses, which are usually greater than 10 μm. Furthermore, the solid-state electrolyte sensor elements can basically be exposed to high loads, in particular high mechanical loads, in known production methods. The stresses can lead to damage of the solid electrolyte sensor element, in particular of the membrane of the solid electrolyte sensor element.

Disclosure of the invention

Therefore, a method is proposed for producing at least one solid electrolyte sensor element which addresses the above-mentioned challenges of known methods.

In the context of the present invention, a solid electrolyte is to be understood as meaning a solid having electrolytic properties, ie having ion-conducting properties. In particular, it may be a ceramic solid electrolyte.

The method according to the invention can comprise the method steps which are described below. The method steps can be carried out, for example, in the predetermined order. However, another order is also conceivable. Furthermore, one or even more process steps can be performed simultaneously or overlapping in time. Furthermore, one, several or all of the method steps can be carried out simply or repeatedly. The method may additionally comprise further method steps.

• a) Bereitstellen mindestens eines Halbleitersubstrats;
• b) Ausbilden mindestens einer Kaverne in mindestens einer Oberfläche des Halbleitersubstrats;
• c) zumindest teilweises Auffüllen der Kaverne mit mindestens einem Opferschichtmaterial;
• d) Aufbringen mindestens eines Schichtaufbaus des Festkörperelektrolyt-Sensorelements auf das Opferschichtmaterial, wobei der Schichtaufbau mindestens eine Schicht eines elektrisch leitfähigen Elektrodenmaterials und mindestens eine Festkörperelektrolytschicht umfasst;
• e) zumindest teilweises Entfernen des Opferschichtmaterials, wobei die Kaverne zumindest teilweise wieder freigelegt wird, so dass die Kaverne zumindest teilweise von dem Schichtaufbau abgedeckt ist.

The method for producing at least one solid electrolyte sensor element comprises the following steps:

• a) providing at least one semiconductor substrate;
• b) forming at least one cavern in at least one surface of the semiconductor substrate;
• c) at least partially filling the cavern with at least one sacrificial layer material;
• d) applying at least one layer structure of the solid electrolyte sensor element to the sacrificial layer material, the layer structure comprising at least one layer of an electrically conductive electrode material and at least one solid electrolyte layer;
• e) at least partially removing the sacrificial layer material, wherein the cavern is at least partially exposed again, so that the cavern is at least partially covered by the layer structure.

In the context of the present invention, a "semiconductor substrate" is basically an arbitrarily shaped semiconductor, which is subjected to one or more processing or coating steps in the further course of the process. For example, the semiconductor substrate may be a disk-shaped or plate-shaped semiconductor substrate. The semiconductor substrate may be formed in particular as a chip. For example, the semiconductor substrate may be wholly or partly made of silicon. Other semiconductor materials such as silicon carbide, in particular temperature-stable silicon carbide, or gallium nitride are conceivable in principle.

The term "cavern" in the context of the present invention refers to a free and / or open cavity. Preferably, it can be a cavity projecting into the base element. The cavern may, for example, have a cuboidal basic shape or also a truncated pyramidal basic shape. Other basic forms are conceivable in principle.

The formation of the cavern can be done, for example, by an etching process. The etching process may comprise, for example, at least one wet-chemical and / or at least one dry-chemical etching process. The etching process may include, for example, reactive ion etching. The term "reactive ion etching" in the context of the present invention basically refers to an ion-assisted reactive etching process in which reactive ions are used to remove material from the semiconductor substrate or from another material. The etching process can be done primarily physically in this method, and there may be some preferential direction in the etching attack. Accordingly, the etching process for forming the cavern in step b) can in particular be designed wholly or partly as an anisotropic etching process. Shaping of the structures may be assisted by masking, in particular by masking produced by photolithography. It is also conceivable to use further etching processes.

At least one etch stop layer may be introduced between the semiconductor substrate and the sacrificial layer material. The etch stop layer may comprise at least one material selected from the group consisting of: silicon dioxide, silicon nitride, aluminum oxide or aluminum nitride. The material of the etch stop layer may be chemically different than the sacrificial layer material, and may preferably have a significantly lower etch rate in the used etch process than the sacrificial layer material. The etch stop layer may preferably be applied to the semiconductor substrate in a separate process. The etch stop layer may in particular be designed as a barrier during the formation of the cavern. In particular, a depth of the cavern can be adjusted via the position of the etching stop layer.

The method may further include forming at least one etch channel. The cavern and an environment of the semiconductor substrate may be interconnected via the etch channel. The term "etch channel" basically refers to any cavity on the surface of the semiconductor substrate. In particular, it may be an elongated cavity. In particular, the etching channel can be set up such that in step e) the sacrificial layer material can be removed from the cavern through the etching channel. Step d) can be carried out such that the layer structure covers the sacrificial layer material only incompletely and the etching channel comprises at least one uncovered region of the sacrificial layer material.

In the context of the present invention, a "sacrificial layer material" basically refers to any material which is initially applied or introduced during the process for the purpose of structuring the component to be produced and to which, for example, one or more further layers or components are applied but then completely and partially removed before and after completion of the device. The sacrificial layer material thus serves, for example, as a temporary support for subsequent layers or components of the component, in this case the solid electrolyte sensor element, and is later removed completely or partially.

The sacrificial layer material may comprise at least one material selected from the group consisting of: an oxide, in particular a silicon oxide; a semi-finished material, in particular a mixed semiconductor material, in particular silicon germanium; a nitride, in particular silicon nitride. The sacrificial layer material may have a significantly higher etching rate in the etching process than the material of the semiconductor substrate. Alternatively or additionally, when introducing the etching stop layer, the sacrificial layer material may have a significantly higher etching rate in the etching process than the etching stop material. Also other materials are conceivable. The sacrificial layer material may in particular be designed to cover parts of the semiconductor substrate, in particular the cavern. Furthermore, in a later method, the sacrificial layer material can be completely or partially removed from the semiconductor substrate again.

The cavern can be completely or partially filled with the sacrificial layer material. The sacrificial layer material may be further parts of the surface Cover the semiconductor substrate in whole or in part. The sacrificial layer material may in principle be applied by any suitable deposition method, for example by chemical vapor deposition, sputtering, electron beam evaporation, pulsed laser deposition or atomic layer deposition.

The method may further include removing excess sacrificial layer material prior to performing step d) such that the semiconductor substrate and the sacrificial layer material located in the cavity form a common planar surface to which the layer structure is applied. The removal of the excess sacrificial layer material may include at least one process selected from the group consisting of: a chemical mechanical polishing process, a wet chemical etching process, a dry chemical etching process, an ion etching.

In particular, the term "chemical mechanical polishing method" refers to a method which comprises polishing the semiconductor substrate by a polishing cloth having a defined pressure. In particular, the polishing cloth can be made of a polyurethane foam. Furthermore, during the polishing process, a preferably colloidal polishing agent may be added.

A "dry-chemical etching process" is basically a process in which the removal of material takes place by means of accelerated particles, in particular by argon ions, or by means of plasma-activated gases. In this case, physical effects and / or chemical effects, in particular chemical reactions between accelerated particles and the surface of the substrate, can be exploited.

The term "ion etching" basically refers to a process in which the semiconductor substrate is bombarded with ions. For example, it may be reactive ion etching.

Under a "layer structure" in the context of the present invention is basically any sequence of one or more layers to understand. For example, the layers can be arranged one above the other. The layers can be completely or partially covered. For example, the layers may be arranged next to one another. The layer structure may further comprise layers of different materials. The layer structure may comprise several layers of the same material. Other embodiments are conceivable in principle.

In the context of the present invention, a "porosity" is to be understood as meaning a ratio of void volume to total volume of a substance or mixture of substances as a dimensionless measured variable. This measure can be specified in particular in percent. For example, the porous, electrically conductive electrode material may have a porosity of at least 20%, preferably of at least 30% and particularly preferably of at least 40%. In the case of a setting of the porosity, it may be desirable for there to be at least partial continuous conductivity of the first layer and / or the second layer of at least one porous, electrically conductive material and formation of isolated islands at least substantially reduced. The porous, electrically conductive electrode material may comprise at least one ceramic metal compound, in particular composite materials of ceramic materials with a metallic matrix. The porous electrically conductive electrode material may comprise at least one metal selected from the group consisting of: platinum; Palladium; an alloy. Furthermore, nitrogen-doped graphene can be used. In particular, nitrogen-doped graphene can be used due to a catalytic effect. Other materials are also conceivable. The porous electrically conductive electrode material may further comprise at least one ceramic material selected from the group consisting of: alumina, zirconia. Other materials are basically usable.

The layer structure may in particular form at least one sensor cell, which has at least one first layer of at least one porous, electrically conductive electrode material, and furthermore at least one second layer of at least one porous, electrically conductive electrode material. The layer structure may further comprise at least one solid electrolyte layer. The first layer of the at least one porous, electrically conductive electrode material and the second layer of the at least one porous electrically conductive electrode material can be connected to one another via the solid electrolyte layer. The first layer may be arranged on a side of the layer structure facing the cavern. The solid electrolyte layer may be disposed between the first layer and the second layer. The solid state electrolyte layer may comprise at least one material selected from the group consisting of: yttria-stabilized zirconia; Scandium-doped zirconia.

The designations "first" and "second" layer are to be regarded as pure designations without indicating an order or ranking and, for example, without precluding the possibility that several types of first layers and several types of second layers or in each case exactly one type may be provided. Farther For example, additional layers, for example one or more third layers, may be present in the layer structure.

• d1) Aufbringen mindestens einer ersten Schicht eines porösen, elektrisch leitfähigen Elektrodenmaterials auf der Oberfläche des Halbleitersubstrats, wobei die erste Schicht die Kaverne ganz oder teilweise bedeckt;
• d2) Aufbringen mindestens einer Festkörperelektrolytschicht auf der ersten Schicht, wobei die Festkörperelektrolytschicht die erste Schicht zumindest teilweise bedeckt;
• d3) Aufbringen mindestens einer zweiten Schicht eines porösen, elektrisch leitfähigen Elektrodenmaterials auf der Festkörperelektrolytschicht, wobei die zweite Schicht die Festkörperelektrolytschicht zumindest teilweise bedeckt.

Step d) can comprise the following substeps:

• d1) depositing at least a first layer of a porous, electrically conductive electrode material on the surface of the semiconductor substrate, wherein the first layer completely or partially covers the cavern;
• d2) applying at least one solid electrolyte layer on the first layer, wherein the solid electrolyte layer at least partially covers the first layer;
• d3) applying at least one second layer of a porous, electrically conductive electrode material on the solid electrolyte layer, wherein the second layer at least partially covers the solid electrolyte layer.

At least one layer of the layer structure can take place by a structured deposition. For example, the structured deposition may include at least one shadow mask process. Alternatively or additionally, at least one layer of the layer structure can be structured after application, in particular by means of at least one lithographic process.

Step d) may further comprise applying at least one heating element. In particular, step d) may comprise applying at least one heater insulation layer. The heater insulation layer may at least partially cover another layer of the layer structure. The heater insulation layer may be made of silicon nitride, silicon oxide or aluminum oxide. Other materials are conceivable.

Step e) may comprise at least one etching process. The etching process may in particular comprise an isotropic etching process. The etching process may comprise at least one process selected from the group consisting of: a wet chemical etching process, a dry chemical etching process, and in particular a reactive ion etching.

Alternatively, or in addition to step e), the method may include selectively removing the semiconductor substrate. By selectively removing the semiconductor substrate, a cavity can be created under the layer structure. The selective removal may in particular comprise a selective etching process, in particular in a chlorofluoride gas and / or in a xenon fluoride gas.

• I. mindestens ein Halbleitersubstrat;
• II. mindestens eine in mindestens einer Oberfläche des Halbleitersubstrats ausgebildete Kaverne;
• III. mindestens einen Schichtaufbau, wobei der Schichtaufbau mindestens eine Schicht eines elektrisch leitfähigen Elektrodenmaterials und mindestens eine Festkörperelektrolytschicht umfasst, wobei der Schichtaufbau die Kaverne zumindest teilweise abdeckt.

In another aspect of the present invention, a solid state electrolyte sensing element is disclosed, comprising:

• I. at least one semiconductor substrate;
• II. At least one cavern formed in at least one surface of the semiconductor substrate;
• III. at least one layer structure, wherein the layer structure comprises at least one layer of an electrically conductive electrode material and at least one solid electrolyte layer, wherein the layer structure at least partially covers the cavern.

The solid electrolyte sensor element can be produced by the method as already described above or described below.

The solid electrolyte layer may in particular form a membrane. Under a membrane according to the present invention is basically an element with an arbitrary surface area and a defined thickness to understand, the thickness is preferably between 100 nm and 5 microns, or more preferably between 300 nm and 1 micron. The membrane may, for example, be permeable to at least one or more substances in one direction. For example, the membrane may be permeable to at least one or more substances in both directions. Other embodiments are possible in principle. On the semiconductor substrate, a plurality of solid electrolyte layers may be formed as membranes. The solid electrolyte layers may preferably be arranged parallel to one another on the semiconductor substrate.

The etching channels can be set up to display a pressure compensation channel for the reference volume, in particular a pumped O reference volume, for the solid electrolyte sensor element.

The second layer of the porous, electrically conductive electrode material may be configured in particular to provide a heater structure and a sensor contact.

The proposed method has numerous advantages over known methods. Average dimensions of the solid electrolyte sensor element can be basically reduced. For example, average dimensions of a thick-film sensor element may be in the range of 5 mm × 5 mm × 2 mm. By the method according to the invention, the average dimensions of the solid electrolyte sensor element, for example, at 1mm × 2mm × 1 mm lie. This can in particular lead to a reduced installation space, a faster operational readiness, in particular of less than 3 seconds and a lower required heating power, for example of 100 mW. By using the sacrificial layer material in the method for producing the solid electrolyte sensor element, in principle, several or all steps of the method can be carried out on a solid material before the solid electrolyte layer is released. In this way, in particular premature membrane rupture can be prevented by mechanical loads during the production process. In addition, it may be advantageous to divide the surface of the solid electrolyte sensor element into a plurality of parallel connected and small-area membranes. In particular, a pressure resistance in a sensor operation can be significantly increased. In particular, with an identical membrane thickness, the compressive strength can be increased eightfold with a fourfold reduction in a membrane area.

In principle, the solid-state electrolyte sensor element can be produced as follows: The substrate can in particular comprise silicon, since a wealth of structuring and deposition processes are available for this material, which are advantageous for producing the layer structure. Furthermore, silicon generally has a high temperature stability (softening temperature 1200 ° C.), which are usually required for use in the area of the exhaust gas sensor system. In the surface of the substrate, the cavern can then be structured, which has a depression in a region of the later active sensor surface, and depending on the requirement, the etching channels, which provide access for the sacrificial layer material and the later required pressure equalization channel for the pumped O reference volume. The cavern can then be filled with the sacrificial layer material, for example via a deposition process. Silica, but alternatively also silicon germanium or silicon nitride may be considered as sacrificial layer material. These materials can be removed basically wet-chemically and / or dry-chemically. The sacrificial layer material can follow a topological course of the cavern. Therefore, a chemical mechanical polishing process may then be performed in which the sacrificial layer material is polished back to a level of the original surface of the substrate. On the polished surface, the application of the first layer of the porous, electrically conductive electrode material, in particular a gas-permeable, porous platinum layer, the solid electrolyte layer and the second layer of the porous, electrically conductive electrode material, take place. The layers can already be deposited in a structured manner, for example via a shadow mask process. The layers can be subsequently structured by lithographic processes and subsequent etching processes, in particular ion beam etching. The structuring can be carried out such that a small part of the projecting etching channels as well as a part of the first layer of the porous, electrically conductive electrode material are exposed for a better subsequent contacting. The second layer of the porous, electrically conductive electrode material may be patterned to provide the heater structure and the sensor contact.

In particular, it may be advantageous if, in the layer structure, the second layer of the at least one porous, electrically conductive electrode material in a lateral extent does not extend beyond a lateral extent of the cavity. In the sensor operation, in particular in a pumped sensor operation, an overlap between the second layer and the semiconductor substrate may cause the sensor element to be pumped and pumped to an interface between the first layer of the at least one porous, electrically conductive electrode material and the semiconductor substrate a flaking of the layer structure leads.

It may also be advantageous to first pattern the first layer of the porous, electrically conductive electrode material and then to deposit the solid electrolyte layer and the second layer of the porous, electrically conductive electrode material. As a result, the solid-state electrolyte layer can extend beyond the cavern, in particular, and increase mechanical stability of the solid-state electrolyte layer. The sacrificial layer material can be removed through the etch channel and form a cavity below the layer structure. The etching channel may be formed, for example, in the semiconductor substrate at the interface with the first layer of the porous, electrically conductive electrode material. Alternatively or additionally, the etching channel may constitute a hole in the layer structure. In particular, in order to meet a requirement for the compressive strength of the solid electrolyte layer, contacts on the solid electrolyte layers may be interconnected in a topmost plane of the porous, electrically conductive electrode material.

In one embodiment, the second layer of the porous, electrically conductive electrode material may be used to contact the sensor element. Subsequently, separated by an insulating layer, a further layer of a porous, electrically conductive electrode material for a heater structure can be applied. One advantage may be that for the contacting of the sensor element and for the heating structure each good morphological and / or electrical properties of the layers of the porous, electrically conductive material can be achieved and used.

Brief description of the figures

Further optional details and features of the invention will become apparent from the following description of preferred embodiments, which are shown schematically in the figures.

Show it:

1.1.1 to 1.7.2 2 is a representation of method steps of a first exemplary embodiment of a method according to the invention, wherein the semiconductor substrate is shown in a sectional view (FIG. 1.1.1 . 1.2.1 . 1.3.1 . 1.4.1 . 1.5.1 . 1.6.1 . 1.7.1 ) and in plan view ( 1.1.2 . 1.2.2 . 1.3.2 . 1.4.2 . 1.5.2 . 1.6.2 . 1.7.2 ) is shown;

2.1 to 2.8 a representation of method steps of a second embodiment of a method according to the invention, wherein the semiconductor substrate is shown in sectional view;

3.1 to 3.10 a representation of method steps of a third embodiment of a method according to the invention, wherein the semiconductor substrate is shown in sectional view;

4.1 to 4.2 a representation of substeps of another embodiment of a method according to the invention, wherein the semiconductor substrate is shown in sectional view;

5 Representation of a substep of a further embodiment of a method according to the invention, wherein the semiconductor substrate is shown in sectional view;

6.1 to 6.2 Partial steps of a further embodiment of a method according to the invention, wherein the semiconductor substrate is shown in sectional view; and

7a and 7b Representations of two embodiments of a solid state electrolyte sensor element according to the invention in plan view.

Embodiments of the invention

Various exemplary embodiments of methods according to the invention are shown below. These exemplary embodiments can be implemented separately from one another, but, as the person skilled in the art will recognize, they can also be combined with one another in whole or in part.

The 1.1.1 to 1.7.2 show an exemplary first embodiment of a method according to the invention for producing at least one solid electrolyte sensor element 110 , The sub-steps of the method are each illustrated so that the respective product or intermediate product containing a semiconductor substrate 112 , in each case in sectional representation ( 1.1.1 . 1.2.1 . 1.3.1 . 1.4.1 . 1.5.1 . 1.6.1 . 1.7.1 ) and in plan view ( 1.1.2 . 1.2.2 . 1.3.2 . 1.4.2 . 1.5.2 . 1.6.2 . 1.7.2 ) is shown.

In a step a), first at least the semiconductor substrate 112 provided. This is in the 1.1.1 and 1.1.2 shown. The semiconductor substrate 112 may in particular consist entirely or partially of silicon. The semiconductor substrate 112 may for example have a cuboid, disc-shaped or plate-shaped basic shape. Other embodiments are conceivable in principle.

Subsequently, in a step b) at least one cavern 114 in at least one surface 116 of the semiconductor substrate 112 educated. This is in the 1.2.1 and 1.2.2 shown. The cavern 114 may have a cuboid basic shape and in the semiconductor substrate 112 protrude. The formation can be carried out by an etching process, for example by reactive ion etching. The method may further include forming at least one etch channel 118 include. The etching channel 118 may have an elongated shape and on the surface 116 of the semiconductor substrate 112 be educated. The cavern 114 and an environment of the semiconductor substrate 112 can over the etching channel 118 be connected to each other.

Subsequently, in a step c), the cavern 114 at least partially with at least one sacrificial layer material 120 refilled. This is in the 1.3.1 and 1.3.2 shown. The sacrificial layer material 120 may comprise at least one material selected from the group consisting of: an oxide, in particular a silicon oxide; a semiconductor material, in particular a mixed semiconductor material, in particular silicon germanium; a nitride, in particular silicon nitride. The sacrificial layer material 120 may be arranged to parts of the semiconductor substrate 112 , especially the cavern 114 to cover.

1.4.1 to 1.7.2 show a step d) of the method according to the invention, in which at least one layer structure 122 of the solid electrolyte sensor element 110 as in the 1.7.1 and 1.7.2 shown on the sacrificial layer material 120 is applied. The step d) can be carried out such that the layer structure 122 the sacrificial layer material 120 only incompletely covered and the etching channel 118 at least one uncovered area of the sacrificial layer material 120 includes. The layer structure 122 comprises at least one layer of an electrically conductive electrode material 124 and at least one solid electrolyte layer 126 , At least one layer of the layer structure 122 can be done by a structured deposition. For example, the structured deposition may include at least one shadow mask process. Alternatively or additionally, at least one layer of the layer structure 122 be structured after application. The patterning may include, for example, at least one lithographic process. Other methods are conceivable in principle.

In step d), the method may comprise the following substeps. In a first partial step d1), a first layer 128 of the porous, electrically conductive electrode material on the surface 116 of the semiconductor substrate 112 be applied. This is in the 1.4.1 and 1.4.2 shown. The first shift 128 can the cavern 114 cover in whole or in part. The first shift 128 can on one of the cavern 114 facing side of the layer structure 122 be arranged.

The porous, electrically conductive electrode material may comprise at least one ceramic metal compound, in particular composite materials of ceramic materials with a metallic matrix. The porous electrically conductive electrode material may comprise at least one metal selected from the group consisting of: platinum; Palladium; an alloy. The porous, electrically conductive electrode material can furthermore in particular comprise at least one ceramic material selected from the group consisting of: aluminum oxide, zirconium dioxide.

In a second partial step d2), the solid electrolyte layer 126 on the first layer 128 be applied. This is in the 1.5.1 and 1.5.2 shown. The solid electrolyte layer 126 can be the first layer 128 at least partially cover. The solid state electrolyte layer may comprise at least one material selected from the group consisting of: yttria-stabilized zirconia; Scandium-doped zirconia.

In a third sub-step d3), a second layer 130 of the porous, electrically conductive electrode material on the solid electrolyte layer 126 be applied. This is in the 1.6.1 and 1.6.2 shown. The second layer 130 can the solid electrolyte layer 126 at least partially cover. The solid electrolyte layer 126 can be between the first layer 128 and the second layer 130 be arranged.

In the 1.7.1 and 1.7.2 a next step e) is shown, in which the sacrificial layer material 120 at least partially removed. The cavern 114 is at least partially re-exposed, so that the cavern 114 at least partially of the layer structure 122 is covered. In this embodiment, the sacrificial layer material 120 through the etching channel 118 through the cavern 114 be removed. Step e) may comprise, for example, at least one etching process. The etching process may in particular comprise an isotropic etching process. The etching process may include at least one process selected from the group consisting of: a wet chemical etching process, a dry chemical etching process, a reactive ion etching.

The 2.1 to 2.8 show sub-steps of a second exemplary embodiment of a method according to the invention. The method corresponds in many parts to the method according to the 1.1.1 to 1.7.2 , so largely on the description of the 1.1.1 to 1.7.2 can be referred to above. The semiconductor substrate 112 is in each case shown in a sectional view, on a plan view has been omitted.

The illustrated sub-steps in the 2.1 to 2.3 comprise the sub-steps a), b) and c) and correspond to the 1.1.1 to 1.3.2 , so in particular to the description of the 1.1.1 to 1.3.2 can be referred to above.

The method may include removing excess sacrificial layer material prior to performing step d). This is in 2.4 shown. The removal can take place such that the semiconductor substrate 112 and that in the cavern 114 and / or in the etch channel 118 located sacrificial layer material 120 a common flat surface 116 form, on which the layer structure 122 can be applied. The removal of the excess sacrificial layer material 120 may comprise at least one process selected from the group consisting of: a chemical mechanical polishing process, a wet chemical etching process, a dry chemical etching process, an ion etching. Other methods are conceivable in principle.

The illustrated sub-steps in the 2.5 to 2.8 include sub-steps d), in particular d1), d2) and d3), and e) and correspond to the representations in the 1.4.1 to 1.4.2 , so that in particular to the description of the 1.4.1 to 1.7.2 can be referred to above.

3.1 to 3.2 show partial steps of a further embodiment of a method according to the invention. The process largely corresponds to the process according to the 2.1 to 2.8 , so largely on the description of the 2.1 to 2.8 can be referred to above.

The illustrated sub-steps in the 3.1 to 3.7 include first the sub-steps a), b) and c) and after performing the sub-step c) the removal of the oversensitive sacrificial layer material. The 3.1 , to 3.7 therefore correspond to the 2.1 to 2.7 , so in particular to the description of the 2.1 to 2.7 can be referred to above.

Step d) may further include applying at least one heating element 132 include. This is in 3.8 shown. In particular, step d) may include applying at least one heater insulation layer 134 include. The heater insulation layer 134 may at least partially another layer of the layer structure 122 cover. The heater insulation layer 134 may in particular be made of silicon nitride. Other materials are conceivable.

The heater insulation layer 134 can be done by a structured deposition, for example by a shadow mask process. Alternatively or additionally, the heater insulation layer 134 after application, for example by at least one lithographic process.

On the heater insulation layer 134 can a third layer 135 a porous, electrically conductive electrode material can be applied. This is in 3.9 shown.

In 3.10 the removal of the excess sacrificial layer material is shown. 3.10 corresponds in many parts of the 2.8 , so largely on the description of the 2.8 can be referred to above.

4.1 and 4.2 show a representation of substeps of a further embodiment of a method according to the invention. The semiconductor substrate 112 is shown in section. The sub-steps can be additional sub-steps of the inventive method according to the 1.1.1 to 1.7.2 . 2.1 to 2.8 or 3.1 to 3.10 represent or instead of illustrated sub-steps of 1.1.1 to 1.7.2 . 2.1 to 2.8 or 3.1 to 3.10 to step.

In 4.1 becomes a semiconductor substrate 112 provided. Between the semiconductor substrate 112 may be at least one etch stop layer 136 be introduced. The etch stop layer 136 For example, it may comprise silicon dioxide. In particular, the material may be chemically different from the sacrificial layer material 120 be. The etch stop layer 136 may preferably be in a separate process on the semiconductor substrate 112 be applied. The etch stop layer 136 in particular as a barrier during the formation of the cavern 114 be furnished. This is in 4.2 shown. In particular, the etch stop layer 136 a depth of the cavern 114 Taxes.

In 5 is a partial step of a further embodiment of a method according to the invention shown. The semiconductor substrate 112 is shown in section. The sub-step may be an additional sub-step of the inventive method according to the 1.1.1 to 1.7.2 . 2.1 to 2.8 or 3.1 to 3.10 represent or instead of illustrated sub-steps of 1.1.1 to 1.7.2 . 2.1 to 2.8 or 3.1 to 3.10 to step.

Sub-step b) can be the formation of several caverns 114 include. The caverns 114 can through the etch stop layer 136 be limited. In addition, the caverns 114 within the semiconductor substrate 112 lead.

6.1 to 6.2 show partial steps of a further embodiment of the method according to the invention. The sub-steps can be additional sub-steps of the inventive method according to the 1.1.1 to 1.7.2 . 2.1 to 2.8 or 3.1 to 3.10 or instead of illustrated sub-steps of 1.1.1 to 1.7.2 . 2.1 to 2.8 or 3.1 to 3.10 to step.

Alternatively, or in addition to step e), the method may include selectively removing the half-substrate 112 include. By selectively removing the semiconductor substrate 112 may be a cavity, in particular a cavern 114 under the layer structure 122 be generated. The selective removal may in particular comprise a selective etching process, in particular in a chlorofluoride gas and / or in a xenon fluoride gas.

7a and 7b show exemplary embodiments of a solid electrolyte sensor element according to the invention 110 in plan view.

The solid electrolyte sensor element 110 comprises at least one semiconductor substrate 112 , at least one in at least one surface 116 of Semiconductor substrate 112 trained cavern 114 , at least one in the surface 116 of the semiconductor substrate 112 trained etching channel 118 and at least one layer structure 122 , The layer structure 122 includes at least one layer 124 an electrically conductive electrode material and at least one solid electrolyte layer 126 , The layer structure 122 covers the cavern 114 at least partially off.

The solid electrolyte sensor element 110 in 7a can have two layer structures. The layer structures 122 can be connected to each other. For example, the layer structures 122 over the second layer 130 of the porous, electrically conductive electrode material to be interconnected.

In 7b can be part of the etching channels 118 and part of the first layer 124 of the porous, electrically conductive electrode material of the solid electrolyte sensor element 110 exposed. The second layer 1230 of the porous, electrically conductive electrode material may be configured to provide a heater structure and a sensor contact.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19941051 A1 [0004]
• DE 102012201304 A1 [0005]

Cited non-patent literature

• T. Baunach, K. Schänzlin, L. Diehl, Clean Exhaust Gas by Ceramic Sensors, Physik Journal, Vol. 5, 2006 [0002]

Claims (11)

Method for producing at least one solid electrolyte sensor element ( 110 ), the method comprising the following steps: a) providing at least one semiconductor substrate ( 112 ); b) forming at least one cavern ( 114 ) in at least one surface ( 116 ) of the semiconductor substrate ( 112 ); c) at least partial filling of the cavern ( 114 ) with at least one sacrificial layer material ( 120 ); d) applying at least one layer structure ( 122 ) of the solid electrolyte sensor element ( 110 ) on the sacrificial layer material ( 120 ), the layer structure ( 122 ) at least one layer ( 124 ) of an electrically conductive electrode material and at least one solid electrolyte layer ( 126 e) at least partially removing the sacrificial layer material ( 120 ), whereby the cavern ( 114 ) is at least partially exposed again, so that the cavern ( 114 ) at least partially of the layer structure ( 122 ) is covered. Method according to the preceding claim, wherein the method further comprises forming at least one etching channel ( 118 ), the cavern ( 114 ) and an environment of the semiconductor substrate ( 112 ) over the etch channel ( 118 ) are interconnected. Method according to the preceding claim, wherein in step e) the sacrificial layer material ( 120 ) through the etching channel ( 118 ) through the cavern ( 114 ) Will get removed. Method according to one of the two preceding claims, wherein step d) is carried out such that the layer structure ( 122 ) the sacrificial layer material ( 120 ) is incompletely covered, the etch channel ( 118 ) at least one uncovered area of the sacrificial layer material ( 120 ).  Method according to one of the preceding claims, wherein step e) comprises at least one etching process. Method according to the preceding claim, wherein the etching process comprises an isotropic etching process. Method according to one of the preceding claims, wherein the layer structure ( 122 ) forms at least one sensor cell, wherein the sensor cell at least a first layer ( 128 ) of at least one porous, electrically conductive material, wherein the sensor cell further comprises at least one second layer ( 130 ) comprises at least one porous, electrically conductive material, wherein the layer structure ( 122 ) at least one solid electrolyte layer ( 126 ), wherein the first layer ( 128 ) of the at least one porous, electrically conductive material and the second layer ( 130 ) of the at least one porous, electrically conductive material via the solid electrolyte layer ( 126 ) are interconnected. Method according to one of the preceding claims, wherein step d) comprises the following substeps: d1) applying at least one first layer ( 128 ) of a porous, electrically conductive material on the surface ( 116 ) of the semiconductor substrate ( 112 ), the first layer ( 128 ) the cavern ( 114 ) completely or partially covered; d2) applying at least one solid electrolyte layer ( 126 ) on the first layer ( 128 ), wherein the solid electrolyte layer ( 126 ) the first layer ( 128 ) at least partially covered; d3) applying at least one second layer ( 130 ) of a porous, electrically conductive material on the solid electrolyte layer ( 126 ), the second layer ( 130 ) the solid electrolyte layer ( 126 ) at least partially covered. Method according to one of the preceding claims, wherein the method prior to performing step d) removal of excess sacrificial layer material ( 120 ), such that the semiconductor substrate ( 112 ) and in the cavern ( 114 ) sacrificial layer material ( 120 ) a common planar surface ( 116 ) to which the layer structure ( 122 ) is applied. Method according to one of the preceding claims, wherein step d) comprises applying at least one heating element ( 132 ). Method according to one of the preceding claims, wherein between the semiconductor substrate ( 112 ) and the sacrificial layer material ( 120 ) at least one etch stop layer ( 136 ) is introduced. Solid electrolyte sensor element ( 110 ), comprising: I. at least one semiconductor substrate ( 112 ); II. At least one in at least one surface ( 116 ) of the semiconductor substrate ( 112 ) trained cavern ( 114 ); III. at least one layer structure ( 122 ), the layer structure ( 122 ) at least one layer ( 124 ) of an electrically conductive electrode material and at least one solid electrolyte layer ( 126 ), the layer structure ( 122 ) the cavern ( 114 ) at least partially covers; wherein the solid electrolyte sensor element ( 110 ) can be produced by the method according to any one of the preceding claims.

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