Getter Recesses in Micromechanical Sensor Cavity
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Solution Overview
Problem
Existing micromechanical sensor devices face challenges in manufacturing due to the imprecision of getter layer application on CMOS wafers, which can lead to increased sensor size and adhesive bonding issues during mechanical shocks, especially when trying to achieve different pressure levels for acceleration and rotation rate sensors.
Innovation Solution
A getter layer is applied to a CMOS system using a lift-off method with isotropic etching to create recesses that prevent contact with movable structures, allowing for precise and robust getter surface formation, enabling compact, cost-effective production of integrated sensors without adhesive risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a getter layer is applied on the CMOS wafer surface, then different pressure levels can be achieved for acceleration and rotation rate sensors, but the application becomes imprecise and increases the risk of adhesive bonding during mechanical shocks
Solution Approach 1:
The getter layer application is segmented into separate recesses for acceleration sensors and rotation rate sensors on the CMOS wafer. Each recess is independently structured to contain a getter layer that achieves the required pressure level for that specific sensor type, preventing imprecise placement and adhesive bonding risks.
Solution Approach 2:
A recess structure acts as an intermediary between the CMOS wafer surface and the getter layer. This recess provides a defined containment space that precisely positions the getter layer, eliminating placement imprecision and preventing direct contact between the getter layer and movable sensor structures during mechanical shocks.
2Ease of manufacture
If the getter layer is applied directly on the CMOS wafer, then the manufacturing process is simplified, but the movable structures may contact the getter layer during mechanical shocks causing adhesive bonding
Solution Approach 1:
The recess structure serves as a pre-established protective barrier that cushions and isolates the getter layer from potential contact with movable sensor structures during mechanical shocks. This beforehand protection prevents adhesive bonding and maintains sensor reliability under stress conditions.
Solution Approach 2:
The recess acts as an intermediary protective structure between the getter layer and movable sensor components. This intermediate containment prevents direct contact during mechanical shocks while maintaining the simplified manufacturing advantage of direct getter layer application on the CMOS wafer.
3Volume of moving object
If the sensor device size is reduced for compact integration, then manufacturing cost decreases, but the getter layer application becomes more imprecise increasing adhesive bonding risk
Solution Approach 1:
The solution transitions from a two-dimensional surface application problem to a three-dimensional recess containment structure. By creating vertical recesses in the CMOS wafer, the getter layer is precisely positioned in depth rather than relying solely on horizontal placement precision, enabling compact sensor integration without sacrificing placement accuracy.
Solution Approach 2:
The compact CMOS wafer is segmented into multiple recesses, each precisely containing a getter layer for specific sensor elements. This segmentation maintains high placement precision within the compact form factor by providing dedicated containment spaces rather than relying on large-area surface application.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for the manufacture of small, precisely defined getter surfaces that maintain sensor functionality after mechanical shocks, ensuring accurate pressure control and preventing adhesive bonding, thus enhancing the reliability and efficiency of micromechanical sensor devices.
Implementation Method 1
A getter layer is applied to a CMOS system using a lift-off method with isotropic etching to create recesses
Implementation Method 2
The getter pumps (getters) the volume of cavern KV2 of rotation rate sensor device S2 to a low pressure
Data Source
AI summary
A micromechanical sensor device and a corresponding manufacturing method are described. The micromechanical sensor device includes a CMOS wafer having a front side and a rear side, a rewiring device formed on the front side of the CMOS wafer including a plurality of stacked printed conductor levels and insulation layers, an MEMS wafer having a front side and a rear side, a micromechanical sensor device formed across the front side of the MEMS wafer, a bond connection between the MEMS wafer and the CMOS wafer, a cavern between the MEMS wafer and the CMOS wafer, in which the sensor device is hermetically enclosed, and an exposed getter layer area applied to at least one of the plurality of stacked printed conductor levels and insulation layers.