Wafer-Level MEMS Packaging with B-Stage RDL Protection
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Solution Overview
Problem
There is a need for a simple and effective method to produce packaged MEMS assemblies with a redistribution layer (RDL) at the wafer level, particularly for sensitive MEMS structures like pressure sensors and sound transducers, where existing methods may damage or expose these components to adverse chemical influences during RDL application.
Innovation Solution
The method involves applying a b-stage material layer on a semiconductor substrate with cutouts containing MEMS components, allowing vertically projecting contact elements to penetrate through the layer, which is then cured and thinned to expose contact pads for connecting an RDL structure, thereby protecting the MEMS components and enabling standard RDL processes on the entire wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard RDL processes are applied directly on MEMS structures, then manufacturing simplicity is improved, but sensitive MEMS components are damaged or exposed to adverse chemical influences
Solution Approach 1:
A b-stage material layer is introduced as an intermediary protective layer between the MEMS components and the RDL processing environment. This material is applied in a semi-cured state, allowing through-contact elements to be inserted, then fully cured to provide chemical protection during subsequent RDL fabrication steps, enabling standard processes without direct exposure of sensitive MEMS structures
Solution Approach 2:
The b-stage material layer is applied and cured before the RDL structure is formed. This preliminary action creates a protective environment in advance, allowing the MEMS components to be shielded from adverse chemical influences during the subsequent RDL fabrication process, thereby enabling standard manufacturing procedures without compromising component integrity
2Ease of operation
If MEMS components are exposed on the wafer surface, then accessibility for connection is improved, but vulnerability to ambient influences increases
Solution Approach 1:
The b-stage material layer serves as a protective intermediary that covers the exposed MEMS components while allowing through-contact elements to pass through it. This material shields the MEMS structures from ambient influences during RDL processing while maintaining electrical connectivity through the contact elements, thus resolving the contradiction between accessibility and protection
3Object-affected harmful factors
If a protective layer is applied over MEMS structures, then protection from chemical influences is improved, but complexity of the production process increases
Solution Approach 1:
The b-stage material is applied in a semi-cured state with specific physical properties that allow through-contact elements to be inserted, then is fully cured to provide protection. By controlling the curing parameter progression (partial cure → full cure), the process achieves protection functionality while using a single material layer that can be integrated into existing production workflows, minimizing overall process complexity
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 allows for the application of standard RDL processes without damaging sensitive MEMS structures, providing a robust and protective environment for MEMS components during RDL formation, enabling efficient electrical connections while safeguarding against ambient influences.
Implementation Method 1
applying a b-stage material layer cured in an intermediate stage on the wiring layer stack, such that the cutouts in the wiring layer stack are covered by the b-stage material layer
Data Source
AI summary
A production method includes providing a semiconductor substrate with a wiring layer stack having cutouts on a first main surface region of the semiconductor substrate at which MEMS components are arranged in an exposed manner in the cutouts and projecting through contact elements are arranged at metallization regions of the wiring layer stack; applying a b-stage material layer cured in an intermediate stage on the wiring layer stack, such that the cutouts are covered by the b-stage material layer and the vertically projecting through contact elements are introduced into the b-stage material layer; curing the b-stage material layer to obtain a cured b-stage material layer; thinning the cured b-stage material layer; and applying a redistribution layer (RDL) structure on the thinned, cured b-stage material layer to obtain an electrical connection between the wiring layer stack and the RDL structure via the through contact elements.