Open Cavity Semiconductor Package with Dam and Passivation
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Solution Overview
Problem
The miniaturization of MEMS chips is hindered by the sensitivity of active regions to pressure and contamination during packaging, as well as the cost inefficiency of shrinking molding tools, which complicates the exposure of active regions for sensing functions while avoiding stress and water contact.
Innovation Solution
An open cavity semiconductor package structure with a dam surrounding the active region, where a passivation layer is patterned to protect the region before forming the dam, and then removed via directional etching to expose the region, allowing the dam's retracted top surface to prevent molding compound entry without applying excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the active region is exposed for sensing functions, then sensing capability is improved, but the active region becomes sensitive to pressure and contamination
Solution Approach 1:
A passivation layer is formed over the active region before packaging to protect it from pressure and contamination. The passivation layer is then selectively removed after the package structure is established, allowing the active region to be exposed for sensing while maintaining protection during manufacturing
Solution Approach 2:
The package structure implements different protection levels in different regions: the active region is exposed for sensing functionality while surrounding areas remain encapsulated for protection. This localized differentiation allows the active region to perform sensing functions while minimizing exposure to harmful factors
2Volume of moving object
If molding tools are shrunk to accommodate miniaturization, then device size is reduced, but manufacturing cost increases and tool complexity increases
Solution Approach 1:
The package structure is divided into distinct functional regions: an exposed region for sensing and an encapsulated region for protection. This segmentation allows the use of standard molding tools while achieving miniaturization through optimized spatial arrangement rather than requiring proportionally smaller tools
Solution Approach 2:
The package structure utilizes vertical dimensionality with the dam structure extending upward from the substrate plane. This three-dimensional approach allows compact footprint on the substrate while maintaining adequate working clearances for standard molding tools in the vertical dimension
3Object-affected harmful factors
If a dam structure is formed to prevent molding compound entry, then protection is improved, but stress may be applied to the active region
Solution Approach 1:
A passivation layer is introduced as an intermediary between the dam structure and the active region. This intermediate layer acts as a stress buffer that protects the active region from stress concentrated by the dam structure while allowing the dam to effectively prevent molding compound entry
Solution Approach 2:
The mechanical properties of the passivation layer are optimized to balance protection and stress distribution. By controlling the thickness and material properties of the passivation layer, the structure provides adequate protection against molding compound while minimizing stress transmission to the active region
Data Source
AI summary
A semiconductor package structure includes an electronic device having an exposed region adjacent to a first surface, a dam surrounding the exposed region of the semiconductor die and disposed on the first surface, the dam having a top surface away from the first surface, an encapsulant encapsulating the first surface of the electronic device, exposing the exposed region of the electronic device. A surface of the dam is retracted from a top surface of the encapsulant. A method for manufacturing the semiconductor package structure is also provided.