MEMS Packaging With Integrated Metal Cap Shielding
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Solution Overview
Problem
Current wafer level packaging methods for MEMS devices fail to integrate electromagnetic shielding while maintaining a small form factor, necessitating additional processes and offsetting the MEMS device position due to vertical release vias.
Innovation Solution
A method involving a metal cap partially anchored to a wafer with an unanchored portion, extending over the MEMS device, and a sealing layer to encapsulate it, where the electrical contact pad and metal cap share the same composition, allowing for integrated electromagnetic shielding and reduced process steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If wafer level capping is used to package MEMS devices, then the package form factor is reduced to 200-250 um, but additional processes are required to form separate EM shields and the device position must be offset due to vertical release vias
Solution Approach 1:
The patent combines the electromagnetic shielding function with the redistribution layer by forming both structures from the same metal layer in a single deposition process. The metal layer serves dual purposes: as the redistribution layer for electrical connections and as the electromagnetic shield for EM interference protection, eliminating the need for separate EM shield formation processes
Solution Approach 2:
The metal layer is designed to perform multiple functions simultaneously: electrical redistribution, electromagnetic shielding, and structural support. This multi-functional approach reduces the number of process steps and integrates EM shielding capabilities into the standard wafer level packaging flow without requiring additional specialized processes
2Object-affected harmful factors
If separate EM shield structures are added to provide electromagnetic shielding, then EM interference protection is improved, but the package thickness increases and manufacturing complexity increases
Solution Approach 1:
The electromagnetic shielding function is merged with the redistribution layer function. Both structures are formed from the same metal layer deposited in a single process step, eliminating the need for additional EM shield layers and reducing overall package thickness while maintaining EM interference protection
3Volume of stationary object
If vertical release vias are used to form cavities, then cavity formation is achieved, but device position must be offset and additional process steps are required
Solution Approach 1:
The patent transitions from vertical release vias (vertical dimension) to lateral release vias (horizontal dimension). This dimensional change allows cavity formation without offsetting the device position, as the lateral vias are formed at the side of the device structure rather than through the bottom, eliminating the need for positional compensation
Data Source
AI summary
A method for packaging a MEMS device includes the following steps. A metal cap is provided that is partially anchored to a wafer comprising the MEMS device where at least one point between the cap and the wafer is unanchored, the metal cap arranged to at least substantially extend over the MEMS device. An electrical contact pad is electrically coupled to the MEMS device. A sealing layer is provided over the metal cap and the wafer such that the sealing layer seals a gap between an unanchored portion of the metal cap and the wafer to encapsulate the MEMS device, where the electrical contact pad and the metal cap include the same composition.