MEMS Sensor Package with Cavity and Conductive Bumps
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Solution Overview
Problem
Current methods for fabricating electronics packages, particularly for micro electro-mechanical systems (MEMS) like pressure sensors, face challenges in efficiently integrating sensor chips with conductive electrodes and forming structures that allow for accurate pressure detection while minimizing package size and preventing stress on the sensing film.
Innovation Solution
A wafer level packaging process involving a wafer with cavities sealed by a carrier substrate, a covering plate with an opening structure, and a spacer to create a cavity for the sensor film, along with conductive bumps for electrical connection, which allows for precise sensing and reduced package size by using conductive layers instead of bond wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional packaging method with bond wires is used, then electrical connection is achieved, but package size is increased and stress on sensing film is not minimized
Solution Approach 1:
The patent extracts and eliminates the bond wire connection method, replacing it with direct conductive electrode integration on the sensor chip. This removal of unnecessary components (bond wires) reduces package size and eliminates the stress and potential failure points associated with wire bonding, while maintaining electrical connectivity through planar conductive structures.
Solution Approach 2:
The patent replaces the mechanical bond wire system with a planar conductive electrode system integrated directly on the sensor chip surface. This substitution eliminates the need for physical wire connections that introduce mechanical stress, replacing them with electrically conductive pathways that are mechanically integrated into the chip structure, thereby reducing stress on the sensing film.
2Ease of manufacture
If the covering plate is formed before the opening structure, then manufacturing simplicity is maintained, but fluid communication with the sensing film is blocked
Solution Approach 1:
The patent applies preliminary action by forming the opening structure in the covering plate before final assembly with the sensor chip. This ensures that the fluid communication pathway is pre-established and aligned, allowing for efficient fluid access to the sensing film while maintaining a relatively simple overall manufacturing process through sequential but optimized fabrication steps.
3Volume of moving object
If the sensor chip is packaged without a cavity, then package size is reduced, but stress on the sensing film increases and pressure detection accuracy decreases
Solution Approach 1:
The patent applies local quality by creating a localized cavity structure directly over the sensing film area, while maintaining compact packaging elsewhere. The cavity is positioned specifically where pressure detection occurs, providing the necessary space for accurate pressure measurement and stress relief locally, while the overall package remains compact through efficient spatial arrangement of other components.
Solution Approach 2:
The patent implements nesting by integrating the cavity structure within the compact package volume, where the covering plate with opening structure is positioned over the sensor chip to create the cavity space. This nested arrangement allows the cavity to exist within the overall package footprint without significantly increasing external dimensions, maintaining both compact size and pressure detection functionality.
4Reliability
If conductive bumps are formed after the passivation layer, then electrical connection is achieved, but the process complexity increases
Solution Approach 1:
The patent merges the conductive electrode formation with the passivation layer processing steps. The conductive electrodes are patterned and formed as part of the same fabrication sequence as the passivation layer, combining multiple functions (electrical connection and protective coating) into an integrated structure that reduces the number of separate fabrication steps while ensuring reliable electrical connectivity.
Data Source
AI summary
The invention provides an electronic device package and fabrication method thereof. The electronic device package includes a sensor chip. An upper surface of the sensor chip comprises a sensing film. A covering plate having an opening structure covers the upper surface of the sensor chip. A cavity is between the covering plate and the sensor chip, corresponding to a position of the sensing film, where the cavity communicates with the opening structure. A spacer is between the covering plate and the sensor chip, surrounding the cavity. A pressure releasing region is between the spacer and the sensing film.