Micromechanical Sensor Wafer Packaging With Glass Fluid Access
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Micromechanical sensor apparatuses, such as silicon-based pressure sensors, are susceptible to environmental factors like temperature and moisture due to the use of materials with different thermal expansion and moisture absorption capacities, and existing integration methods require additional process effort to electrically insulate conductive contacts from silicon.
Innovation Solution
The use of packaging wafers made of glass or glass ceramic materials for micromechanical sensor apparatuses, with pre-structuring and backthinning to create fluid access, allows for stable double-sided packaging and exposure of electrical contacts without the need for further packaging, using anodic bonding at low temperatures to avoid disruptive influences on MEMS and ASIC wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional packaging methods with cap and gel are used, then the sensor apparatus is protected from environmental factors, but the susceptibility to temperature and moisture increases due to different coefficients of thermal expansion and moisture absorption capacities
Solution Approach 1:
The patent uses a glass packaging wafer that is bonded directly to the silicon sensor wafer, creating a homogeneous integrated structure. The glass material is selected to have thermal expansion properties compatible with silicon, eliminating the differential thermal expansion issues that arise from using dissimilar materials like plastic caps and gel encapsulants.
Solution Approach 2:
The patent employs a composite structure consisting of a glass packaging wafer bonded to a silicon sensor wafer. This composite material approach allows optimization of both mechanical protection and thermal compatibility, as glass provides both protective encapsulation and favorable thermal expansion characteristics when matched with silicon.
2Stability of the object's composition
If vertical integration methods with wafer bonding are used, then integration stability is improved, but additional process effort is required for electrical insulation of conductive vertical contacts
Solution Approach 1:
The patent removes the need for additional electrical insulation layers by designing the vertical integration process to inherently provide electrical isolation. The glass packaging wafer itself serves as the insulating medium, and the bonding process is configured to maintain electrical isolation without requiring separate insulation steps.
Solution Approach 2:
The glass packaging wafer performs multiple functions simultaneously: it provides mechanical protection, thermal compatibility, and electrical insulation. This multi-functional approach eliminates the need for separate insulation layers, as the same glass material that protects the sensor also provides electrical isolation for the vertical contacts.
3Reliability
If further packaging components are added, then protection is improved, but production costs increase and robustness decreases
Solution Approach 1:
The patent merges the packaging function directly into the wafer-level fabrication process. The glass packaging wafer is bonded to the silicon sensor wafer in the same manufacturing line, eliminating the need for separate packaging components and assembly steps. This integration reduces both the number of parts and the manufacturing complexity.
Solution Approach 2:
The patent transitions from traditional three-dimensional packaging with multiple discrete components to a planar wafer-level integration approach. By performing packaging operations at the wafer level before dicing, the process achieves protection without requiring additional vertical packaging layers or components.
4Ease of manufacture
If wafer-level production is implemented, then production costs decrease and robustness increases, but fluid access to the environment becomes more complex
Solution Approach 1:
The patent incorporates fluid access features directly into the wafer structure during the preliminary wafer-level fabrication process. Access channels and openings are formed in the glass packaging wafer before bonding, allowing fluid communication with the sensor cavity without requiring post-packaging modifications or complex assembly steps.
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 reduces production costs, increases robustness, and enables further miniaturization while simplifying electrical contacting and fluid access, providing a stable and cost-effective packaging solution.
Implementation Method 1
utilizing anodic bonding at low temperatures to connect the wafers
Data Source
AI summary
A production method for a micromechanical sensor apparatus. The method includes: providing a bonded wafer stack comprising an ASIC wafer and a MEMS wafer, the ASIC wafer including ASIC switching devices and the MEMS wafer including MEMS sensor devices, an ASIC switching device and a corresponding MEMS sensor device are arranged one above the other such that they form a respective micromechanical sensor apparatus in the bonded wafer stack; providing a first packaging wafer having first front and rear faces; in the first rear face, the first packaging wafer has blind holes assigned to corresponding sensor detection regions of a respective MEMS sensor device; bonding the first rear face to the wafer stack such that the blind holes are each in fluid connection with the corresponding sensor detection region; backthinning, on the first front face, the first packaging wafer bonded to the wafer stack to expose the blind holes.