Wafer Level Packaging Microbolometer Vacuum Hermeticity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wafer level packaging (WLP) methods for microbolometer vacuum package assemblies (VPAs) face challenges in achieving high-volume, cost-effective, and reliable production due to differing packaging requirements compared to conventional semiconductor and MEMS devices, particularly in maintaining high vacuum and hermeticity for infrared detectors.
Innovation Solution
The implementation of a specialized WLP system that includes a continuous vacuum environment, independent heating and cooling of wafers, and a process that involves prebaking, clamping wafers together before bonding, and using getters to maintain low pressures, ensuring high vacuum and hermeticity through ultra-high vacuum (UHV) processing and metal seals, while minimizing gas adsorption by the getter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional WLP methods are used for microbolometer VPAs, then manufacturing simplicity is maintained, but vacuum quality and hermeticity deteriorate
Solution Approach 1:
The packaging process is divided into separate stages: pre-baking chamber for degassing, bonding chamber for hermetic sealing, and post-baking chamber for final vacuum treatment. Each chamber is optimized for its specific function, allowing independent control of temperature, vacuum level, and processing time to achieve superior vacuum quality without compromising process manageability
Solution Approach 2:
Wafers undergo pre-baking treatment in a dedicated chamber before bonding to remove adsorbed gases and moisture. This preliminary degassing action reduces the gas load in the final package, enabling better vacuum quality and reducing the complexity of post-bonding vacuum treatment
2Reliability
If high temperature baking is applied to achieve good vacuum, then outgassing is reduced, but bolometer structure integrity deteriorates
Solution Approach 1:
The bolometer wafer is pre-baked at elevated temperature in a separate chamber before bonding to remove adsorbed gases and reduce outgassing potential. This preliminary treatment achieves vacuum improvement without requiring high-temperature processing after the bolometer structure is assembled, preserving structural integrity
Solution Approach 2:
Different temperature profiles are applied at different stages: high temperature (e.g., 150-200°C) during pre-baking for effective degassing, then lower temperature during and after bonding to protect the bolometer structure. This parameter variation allows vacuum quality improvement while maintaining structural integrity
3Reliability
If wafer bonding is performed in atmospheric conditions, then process simplicity is maintained, but contaminant adsorption increases
Solution Approach 1:
Wafer bonding is performed in a controlled vacuum environment within the packaging system, eliminating atmospheric contaminants. The vacuum chamber maintains a clean environment throughout the bonding process, ensuring low contaminant adsorption while keeping the process integrated and simple
Solution Approach 2:
The bonding process is merged with the vacuum packaging process, occurring within the same chamber that provides vacuum and contaminant protection. This integration eliminates the need for separate atmospheric bonding steps while maintaining manufacturing simplicity through a unified process flow
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 approach enables the production of microbolometer VPAs with high responsivity and extended vacuum maintenance, achieving 100% bolometer responsivity and reducing the size and cost of the package, while maintaining robustness and process flexibility.
Implementation Method 1
The bolometer wafer is baked at a first temperature using the bolometer chuck, and the lid wafer is baked at a second temperature using the lid wafer chuck
Implementation Method 2
the respective temperatures of the bolometer wafer and the lid wafer are then raised to a common bonding temperature using the bolometer and lid wafer chucks
Implementation Method 3
using getters to maintain low pressures
Data Source
AI summary
An apparatus for the wafer level packaging (WLP) of micro-bolometer vacuum package assemblies (VPAs), in one embodiment, includes a wafer alignment and bonding chamber, a bolometer wafer chuck and a lid wafer chuck disposed within the chamber in vertically facing opposition to each other, means for creating a first ultra-high vacuum (UHV) environment within the chamber, means for heating and cooling the bolometer wafer chuck and the lid wafer chuck independently of each other, means for moving the lid wafer chuck in the vertical direction and relative to the bolometer wafer chuck, means for moving the bolometer wafer chuck translationally in two orthogonal directions in a horizontal plane and rotationally about a vertical axis normal to the horizontal plane, and means for aligning a fiducial on a bolometer wafer held by the bolometer wafer chuck with a fiducial on a lid wafer held by the lid wafer chuck.