MEMS–ASIC Bond Structures for Reliable Eutectic Electrical Contacts
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Solution Overview
Problem
Existing MEMS sensors face challenges in creating a reliable electrical connection between components due to mechanical stress from external influences, such as bending and thermal expansion, which can lead to issues like electrical short-circuits and mechanical instability.
Innovation Solution
A MEMS element with a punch structure and an ASIC element with a trough structure are designed for eutectic bonding, using a diffusion-blocking layer to prevent germanium penetration and ensure a stable, reliable electrical connection through a punch element that plunges into the trough, with a spacer structure to contain the eutectic material and prevent leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional chip-to-chip contact is used without specialized structures, then the manufacturing process is simpler, but the electrical connection reliability deteriorates due to mechanical stress from external influences
Solution Approach 1:
The contact structure is segmented into distinct functional components: a punch element on the MEMS side, a trough structure on the ASIC side, a diffusion-blocking layer, and a spacer element. This segmentation allows each component to address specific issues - the punch and trough provide mechanical interlocking, the diffusion-blocking layer prevents contamination, and the spacer maintains separation, collectively improving reliability while managing complexity through functional specialization.
Solution Approach 2:
The diffusion-blocking layer acts as an intermediary between the punch element and the eutectic material, preventing germanium penetration while allowing the bonding process to proceed. The spacer element serves as an intermediary that maintains defined separation between components. These intermediary structures enable reliable electrical connections by mediating the interaction between different materials and components, preventing harmful effects while facilitating the bonding process.
2Reliability
If eutectic bonding is used to connect metal layers, then electrical connectivity is improved, but eutectic material outflow occurs causing manufacturing defects
Solution Approach 1:
The trough structure is nested within the passivation layer of the ASIC element, creating a contained space that receives and holds the eutectic material during bonding. The spacer element is positioned within this trough structure, further nesting functional elements within each other to create a hierarchical containment system that prevents material outflow while enabling the bonding process.
Solution Approach 2:
The spacer element acts as an intermediary that defines the boundaries of the eutectic material containment space. It prevents the eutectic material from flowing outward during the bonding process while still allowing the necessary thermal and mechanical contact for reliable electrical connectivity. The spacer mediiates between the bonding process requirements and the containment requirements.
3Stability of the object's composition
If the punch element plunges into the trough structure, then mechanical stability is improved, but precise positioning becomes more difficult
Solution Approach 1:
The punch element and trough structure are designed with predetermined dimensions and positions before bonding. The punch element on the MEMS side and the corresponding trough on the ASIC side are prepared in advance with complementary geometries that guide their relative positioning during bonding. This preliminary structuring ensures that when the punch plunges into the trough, the components automatically align to achieve both mechanical stability and positioning accuracy.
Solution Approach 2:
The diffusion-blocking layer serves as an intermediary that facilitates precise positioning during the bonding process. It provides a stable, controllable interface between the punch element and the eutectic material, allowing the punch to plunge into the trough with controlled precision. The intermediary layer mediates the mechanical interaction, enabling reliable positioning while maintaining the stability benefits of the plunge design.
4Reliability
If germanium is used for bonding, then electrical conductivity is improved, but germanium penetration into metal layers causes electrical short-circuits
Solution Approach 1:
The diffusion-blocking layer is positioned as an intermediary between the punch element and the metal layer, specifically blocking the penetration of germanium into the metal layer while still allowing the eutectic bonding process to proceed. This intermediary structure enables the beneficial electrical conductivity of germanium-based eutectic materials to be achieved at the bonding interface without the harmful effect of germanium penetrating into and short-circuiting the metal layers.
Solution Approach 2:
The harmful function of germanium penetration is extracted and blocked by the diffusion-blocking layer, while the beneficial function of germanium for electrical conductivity is preserved in the eutectic bonding interface. The diffusion-blocking layer selectively removes or blocks the harmful diffusion pathway without interfering with the beneficial bonding process, allowing germanium to fulfill its导电 function while preventing it from causing short-circuits.
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 provides a stable, reliable electrical connection between MEMS and ASIC elements, enhancing mechanical stability and preventing electrical short-circuits while maintaining a defined separation, suitable for various micromechanical sensors.
Implementation Method 1
a first bonding element arranged on the punch element... a bonding element being able to be plunged into the trough element in a eutectic bonding process
Implementation Method 2
an electrically conductive diffusion-blocking layer being arranged on the punch element and on the second passivation layer... preventing germanium penetration
Data Source
AI summary
A MEMS element is provided. The MEMS element includes: a substrate; a first passivation layer arranged on the substrate; a metal layer arranged on the first passivation layer; a second passivation layer arranged on the metal layer and on the first passivation layer; and a punch element, an electrically conductive diffusion-blocking layer being arranged on the punch element and on the second passivation layer, a first bonding element being arranged on the punch element.