DE10140322B4 - Microstructured three-dimensional sensor or actuator, and method for its production - Google Patents

Abstract

microstructured three-dimensional sensor or actuator with at least one rotatable part, being for the use of the sensor or actuator in a chemically aggressive environment, the corresponding media-touched surfaces provided on all sides with a chemically resistant surface coating (50) are.

Description

The The invention relates to a microstructured three-dimensional sensor or an actuator, and a process for its preparation, according to claims 1 and 9th

The Microsystem technology learns wider and wider applications, also in industrial products such as sensors and actuators. In the practical use of such sensors and actuators in real industrial process environments must be on it be respected that the sensitive microstructured functional parts do not pass through the adverse environmental conditions are impaired. Such typical Ambient conditions are: corrosive gases and liquids, moisture, abrasion by particles or accumulation of particles.

The Today practically used industrial microsensors draw For this reason, they are either completely hermetic, are gas-tight and watertight encapsulated, such. Acceleration sensors, or the functional parts are only planar (flat) can, in order to be able to cover them by flat protective layers, e.g. Protection of planar Pressure sensor membranes.

From the DE 44 15 84 A1 a pressure sensor semiconductor unit is known, which has on the pressure medium side cavities, which are coated with a corrosion-resistant coating. From the DE 33 37 792 C2 is also known a pressure sensor, which is also just a static structure.

In many cases would it be but beneficial, functional sensor parts also as three-dimensional structures train them and expose them directly to the environment. Only then could the advantages of microstructuring in microsensors and actuators unlimited be used.

A concrete three-dimensional arrangement of this kind is one of silicon produced micro dumbbell as a core component of a sensor for measuring the Oxygen content in process gases, and a microflow sensor made in CMOS technology.

disadvantage the hermetically sealed design of micro sensors and micro actuators is the limitation the functionality, because the process variables thereby usually only indirectly can be determined.

disadvantage The three-dimensional microsensor known today is that in direct media contact with process gases or liquids take damage by corrosion within a short time. So, for example the microstructured flow sensor the Contact point of the hot wire, so the metal-semiconductor junction, attacked by sulphurous gases corrosive. On the micro-hot-wire itself can Particles deposit and affect its functionality. At the micro dumbbell is also the contact point and the applied on the dumbbell Metallic trace corrosive attacked, as well as the vertical Wall of the dumbbell whose optically smooth characteristics are lost can.

Of the The invention is therefore based on the object, three-dimensional microsensors or microactuators that produce unrestrictedly corrosive and harsh environmental conditions can be exposed in industrial conditions.

The Asked task is in terms of a sensor or Aktoranordung according to the invention solved, that all wetted Parts of the microstructured three-dimensional sensor or actuator all sides with a thin one Protective layer are provided.

In advantageous embodiment is specified that the protective layer made of corrosion-resistant material.

In Another advantageous embodiment is specified that the protective layer each consists of a material which is against the respective Measuring medium is resistant.

Farther is stated that the protective layer is formed pinholefrei. She is so skinny that she is the one operability of the sensor or actuator element is not affected. That it limits at thermal Sensors do not heat transfer to the environment, with mechanical sensors, it produces none additional inertia of the element etc.

In Further advantageous embodiment, the coating is made a thin one Teflon layer.

Regarding a method for producing a sensor or actuator of the inventive type, the core of the invention is that the corrosion resistant coating takes place in that the entire three-dimensional structure after pre-assembly with a through Plasma Support coated Teflon layer is covered.

The preparation of plasma-assisted thin Teflon layers is known, but so far only for the production of planar layers such as membranes in fuel cells or chemical sensors used. It has now surprisingly been found that such protective layers can also be applied to three-dimensional structures with great success and, in particular, to form pinhole-free, dense films on arbitrarily shaped three-dimensional surface geometries with which the object according to the invention can be achieved.

In an alternative coating method consists of the coating a diamond-like carbon structure. These are called DLC layers (Diamond-Like-Carbon)

A additional coating option consists of plasma-deposited silicon nitride. These Passivation is significantly resistant.

The Production of DLC layers is known, but so far only for the preparation of planar protective layers e.g. in chemical Sensors used. It has now surprisingly been found that such Protective layers are also very successful on three-dimensional Apply structures and in particular to arbitrarily shaped three-dimensional surface geometries pinhole-free, form dense films with which the object of the invention are achieved can.

The The invention is illustrated in the drawing, and described in more detail below.

It showed:

1 : The coating of a paramagnetic oxygen sensor.

2 : The bondpad connection.

1 shows the three-dimensional construction of a micro-dumbbell for use in a paramagnetic oxygen sensor. A paragmagnetic oxygen sensor consists of a dumbbell which is rotatably mounted in a magnetic field, in particular in an inhomogeneous magnetic field, or is rotatably mounted.

Critical points in the coating are optically smooth vertical surfaces 4 the dumbbell, tracks 3 on ceramic carrier material as well as conductor tracks 1 on the dumbbell.

These Areas need Pinholefrei be coated to this three-dimensional structure an all-round conclusive To give coating. Only such a coating is actually chemically resistant.

The Chemical resistance refers to the prevailing one Sample gas. Furthermore, the coating must be made so thin that the respective Sensor and / or actuator area it is unaffected. For this purpose, coatings are suitable Teflon especially if they are applied very thin. Teflon in very thin Layers is advantageously in plasma-assisted polymerization applied.

As well is particularly suitable for frequent use Use of silicon as carrier material of microstructures silicon nitride as a coating. This is chemical very resistant and growing in extremely thin Even approximate layers epitaxially. Silicon nitride is at least in a chemical Subcomponent plasma-assisted deposited. It is also possible, the carrier material a Nitrogen plasma, and thus the silicon substrate superficial to nitride.

As this conductor tracks 3 both on the ceramic carrier and conductor tracks 1 are provided on the dumbbell, but thus have different topographies, but they must be similarly reliable coated under all conditions.

The Thus, overall resulting protective layer is a three-dimensional Layer that follows the topography of the entire microstructure.

2 shows a partial section of a likewise particularly critical area in the coating, namely the area of the bond pads 2 , This provides a solder joint between the conductor or tracks 1 . 3 and a connecting wire 30 dar. The tracks 1 . 3 according to 1 are on a substrate 10 applied. This is preferably made of silicon. The thin tracks 1 and 3 according to 1 are used for electrical contact with connecting wires 30 soldered. This soldering point, ie the bonding pad, is also the process environment 60 exposed, like all other parts. You can be an aggressive process environment 60 consider in this area with a gold bond. Likewise, the interconnects would then also in a consistent manner also, for example, consist of gold or platinum to have a corresponding chemical resistance. However, this is disadvantageous, especially for cost reasons.

For this reason, a coating in accordance with the invention is advantageous because, on the one hand, less noble materials can be used and, on the other hand, the entire microstructure with a uniform passivation 50 including tracks 1 and 3 and bondpads 30 can be coated. Since three-dimensional topographies also result here, the advantage of the three-dimensional subsequent coatability already described above has a particularly advantageous effect.

Further can Tracks and also bond pads also be present whenever the respective microstructure provided with electrical connection means becomes.

Farther can but also electronic elements on the substrate of the microstructure be mitimplementiert.

occasionally is a functional implementation of electronic components of functional metrological advantage. This advantage can be through the inventive Coating still be exploited, because the resulting three-dimensional surface conclusively and in one work step, and above all subsequently passivatable is.

1

conductor path on dumbbell

2

bonding pad

3

conductor path on carrier material

4

optical smooth surfaces

10

substratum

30

Lead wire

40

conductor path

50

surface coating

60

process environment

Claims (12)

Microstructured three-dimensional sensor or actuator with at least one rotatable part, wherein for the use of the sensor or actuator in a chemically aggressive environment, the corresponding media-wetted surfaces on all sides with a chemically resistant surface coating ( 50 ) are provided. Microstructured three-dimensional sensor or Actuator according to claim 1, characterized in that the sensor or Actuator a paramagnetic oxygen sensor with rotatable Dumbbell is. Microstructured three-dimensional sensor or actuator according to claim 1 or 2, characterized in that the surface coating ( 50 ) consists of corrosion-resistant material. Microstructured three-dimensional sensor or actuator according to claim 1 or 2, characterized in that the surface coating ( 50 ) consists of a material which is resistant to the respective measuring medium. Microstructured three-dimensional sensor or actuator according to one of the preceding claims, characterized in that the surface coating ( 50 ) pinholefrei and is designed so thin that the function of the sensor or actuator is not limited. Microstructured three-dimensional sensor or actuator according to one of the preceding claims, characterized in that the surface coating ( 50 ) consists of a thin Teflon layer. Microstructured three-dimensional sensor or Actuator according to one of the preceding claims, characterized that at least one sensor and at least one actuator on a common carrier are arranged together. Microstructure three-dimensional sensor or Actuator according to claim 7, characterized in that the sensor or the sensors with the actuator or the actuators in direct functional or logical connection with each other. Method for producing a microstructured sensor or actuator according to one of claims 1 to 8, characterized in that for the use of the sensor or actuator in a chemically aggressive environment, the corresponding media-contacting surfaces of the three-dimensional structures on all sides with a chemically resistant surface coating ( 50 ) are provided by plasma assisted deposition. Method according to claim 9, characterized that the surface coating Teflon is deposited by polymerizing Teflon polymerized becomes. Method according to claim 9, characterized that the surface coating consists of silicon nitride, by silicon nitride wholly or at least deposited in a chemical sub-component plasma assisted. Process for producing a microstructured Sensor or actuator according to one of claims 1 to 8, characterized that for the use of the sensor or actuator in a chemically aggressive environment, the corresponding wetted surfaces of the three-dimensional structures on all sides with a chemically resistant surface coating be provided, wherein the coating is a diamond-like Has carbon structure and applied as a DLC coating becomes.