GETTER DEVICE FOR A MICROMECHANICAL COMPONENT

Abstract

A getter device for a micromechanical component, having a metallic getter structure that is situated in a cavity of the micromechanical component. The getter structure is heatable using a defined electric current. It is possible to evaporate the material of the getter structure in a defined manner.

Claims

1. A getter device for a micromechanical component, comprising: a metallic getter structure situated in a cavity of the micromechanical component; the getter structure being heatable using a defined electric current, material of the getter structure being evaporable in a defined manner.

2. The getter device as recited in claim 1, wherein the getter structure is disposed in the cavity of the micromechanical component in a self-supporting manner.

3. The getter device as recited in claim 1, wherein the getter structure is disposed in the cavity of the micromechanical component on a supporting structure.

4. The getter device as recited in claim 3, wherein the supporting structure of the micromechanical component is an Si structure.

5. The getter device as recited in claim 1, wherein the getter structure is thermally insulated.

6. The getter device as recited in claim 1, wherein the getter structure is disposed in the region of a sensor wafer or in the region of a cap wafer of the micromechanical component.

7. The getter device as recited in claim 1, wherein the material of the getter structure is at least one of the following: aluminum, barium, calcium, cerium, magnesium, niobium, phosphor, strontium, tantalum, terbium, thorium, titanium, and zirconium.

8. A method for manufacturing a getter device for a micromechanical component, comprising: providing a metallic getter structure that is controllable using a defined electric current, the getter structure being evaporable by the control using the defined electric current; and disposing the metallic getter structure in a cavity of the micromechanical component.

9. The method as recited in claim 8, wherein the getter structure is disposed in a cavity of the micromechanical component in a self-supporting manner.

10. The method as recited in claim 8, wherein the getter structure is disposed in the cavity of the micromechanical component on a supporting structure.

11. The method as recited in claim 8, wherein the getter structure is disposed in the region of a sensor wafer or in the region of a cap wafer of the micromechanical component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 shows a specific embodiment of a getter device for a micromechanical component.

[0024] FIG. 2 shows a basic sequence of a specific embodiment of a method for manufacturing a getter device for a micromechanical component.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0025] FIG. 1 shows a top view of a micromechanical component 100 with a first specific embodiment of a getter device 30 for micromechanical component 100. The micromechanical component 100 is developed in this instance as an inertial sensor having a rotation-rate sensor 10 and an acceleration sensor 20. A bonding frame separates cavities of rotation-rate sensor 10 and acceleration sensor 20 from one another. Getter device 30 is developed as a self-supporting or free-standing metallic getter structure in a cavity of the rotation-rate sensor 10, which is heated using an electric control current i and which thereby evaporates getter material in the cavity of the rotation-rate sensor in a defined manner. The electric control current i is supplied via electric terminals 40 of micromechanical component 100. Due to the flow of current through the metallic getter material of the getter structure, the latter is heated, evaporates in the further course and is able to spread evenly in the cavity. As a result, the getter layer of the getter structure absorbs the residual gas in the sensor and reduces in this manner the internal pressure in the cavity. This makes it possible to set an internal pressure in the cavity of rotation-rate sensor 10 in a suitable manner.

[0026] In order to achieve a high temperature in the range of an evaporating point (approx. 1000 C.) of the getter material, the latter is preferably built up in a manner that is thermally insulated as much as possible. This may be achieved by the following design:

[0027] The getter material is applied on a free-standing silicon structure (for example a U-shaped conductor track).

[0028] The getter material is structured in a free-standing manner in the sensor area. This may be done, e.g., by application on an oxide and subsequent removal of the oxide, whereby a free-standing getter structure is produced. This is able to improve a mechanical stability of the getter structure. Using conventional micromechanical structuring processes, it is possible to produce the mentioned supporting structure, e.g., from an Si material in a simple manner.

[0029] The mentioned thermal insulation of the getter structure vis-a-vis the surroundings advantageously promotes the result that less electric energy is required for heating getter device 30 and that the heating process may thus be carried out more quickly. Furthermore, this also advantageously results in less thermal energy being given off to micromechanical component 100 and that the latter therefore is able to maintain a lower operating temperature.

[0030] The getter structure may be disposed both in the region of the sensor wafer as well as in the region of the cap wafer.

[0031] The getter structure is preferably developed from a metal, suitable metallic materials for the getter structure being for example at least one of the following: aluminum (Al), barium (Ba), calcium (Ca), cerium (Ce), magnesium (Mg), niobium (Nb), phosphor (P), strontium (Sr), tantalum (Ta), terbium (Tb), thorium (Th), titanium (Ti), zirconium (Zr). It is also conceivable to provide alloys of the mentioned materials as a material for the getter structure.

[0032] For carrying out the getter process, an electric current having a defined signal form (e.g., current pulse, alternating signal, direct-current signal) is driven through the getter structure. A signal form of the electric current and a duration of the electric current flow are suitably dimensioned in order to achieve a desired getter effect.

[0033] It is advantageously possible for example to drive an electric current pulse via an ASIC in the finished micromechanical component 100 or through micromechanical component 100 already at the wafer stage so that the introduction of the defined internal pressure in the cavity may be performed at different stages of the manufacture of micromechanical component 100. This advantageously optimizes production processes.

[0034] Advantageously, getter device 30 makes it possible to perform the getter process once or, if needed, multiple times, for example at the beginning or also in the interim during the operational life of the micromechanical sensor device. In this manner, it is advantageously possible to perform a follow-up gettering as needed. This may occur for example in that a detection of the internal pressure of a sensor cavity is provided (not shown), which may be used as a feedback loop for controlling gettering device 30. In the event that the internal pressure is too low, gettering is performed.

[0035] In this manner it is possible to compensate for possible changes of the internal pressure over a service life of the sensor even subsequently by a renewed distribution or evaporation of the getter material.

[0036] Advantageously, the getter device 30 according to the present invention makes it possible to perform a separate setting of different pressures in a cavity of a rotation-rate sensor and in a cavity of an acceleration sensor on a chip.

[0037] It is regarded as particularly advantageous that in contrast to conventional methods, a more precise setting of the internal pressure and thus a reduction of the quality fluctuation of the micromechanical sensor is achievable via the wafer. This may be explained by the fact that the conventional method is a chemical, thermally activated getter method using a pasty getter material that is performed once, whereas the provided method provides for a specific conduction of the control current i through the getter structure and in this manner allows for a fine adjustment of the internal pressure in the cavity.

[0038] FIG. 2 shows a basic flow chart of a specific embodiment of the method of the present invention for manufacturing a getter device for a micromechanical component.

[0039] In a step 200, a metallic getter structure is provided, which is controllable using a defined electric current, it being possible to evaporate the getter structure in a defined manner by the control process using the defined electric current.

[0040] In a step 210, the metallic getter structure is disposed in a cavity of the micromechanical component 100.

[0041] In summary, the present invention provides a getter device or a getter pump for a micromechanical component and a method for its manufacture, which advantageously allows for a fine setting of an internal pressure in a cavity of a micromechanical sensor of an inertial sensor. Because the process is controlled by an electric current, a getter process may be performed with a defined frequency, which advantageously makes it possible to increase a quality or sensing quality of the micromechanical component over the operational life.

[0042] Although the present invention is described herein in connection with micromechanical inertial sensors, it is of course also applicable to other micromechanical components. One skilled in the art will thus also implement specific embodiments that are not expressly described, or only partially described, above, without deviating from the core of the present invention.