Wafer-Level Cap-Substrate Electrical Connection via Conductive Ground Structure
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Solution Overview
Problem
Traditional methods for electrically connecting a semiconductor substrate and a top cap are time-consuming, expensive, and prone to defects, as they require secondary operations like wire bonding or groove cutting to establish conductivity, which insulates the substrate and cap, leading to static electrical potential issues.
Innovation Solution
An electrical connection is formed at the wafer level by creating an electrically conductive ground structure on the substrate and bonding an electrically conductive top cap to it, using conductive paths and pads to ensure direct conductivity and reduce static electricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bonding methods are used to secure the cap to the MEMS device, then the cap is enclosed and protected, but electrical insulation occurs between substrate and cap requiring secondary operations
Solution Approach 1:
The patent applies preliminary action by forming conductive paths and ground structures in the substrate before bonding the cap. This includes creating conductive vias, filling them with conductive material, and establishing ground connections prior to cap attachment, thereby eliminating the need for secondary wire bonding operations.
Solution Approach 2:
The patent merges the mechanical bonding function with the electrical connection function into a single integrated process. The cap is designed with embedded conductive elements that directly contact the pre-formed conductive paths in the substrate during bonding, combining structure formation and electrical connection into one step.
2Reliability
If wire bonding is performed to establish electrical conductivity, then electrical connection is achieved, but manufacturing time and cost increase
Solution Approach 1:
The conductive paths are formed in the substrate before cap bonding, including etching vias, depositing conductive layers, and establishing ground structures. This preliminary preparation eliminates the need for time-consuming wire bonding operations after assembly.
Solution Approach 2:
The patent extracts the wire bonding step from the manufacturing process by integrating electrical connectivity into the bonding structure itself. The conductive elements are built into the substrate and cap designs, removing the separate wire bonding operation entirely.
3Reliability
If deep grooves are cut through the cap and substrate to form metal surfaces, then electrical conductivity is achieved, but manufacturing complexity and defect risk increase
Solution Approach 1:
The conductive paths are formed in advance within the substrate using standard semiconductor fabrication techniques such as via etching and conductive material deposition. This eliminates the need for deep groove cutting through the assembled cap-structure.
Solution Approach 2:
The patent replaces the mechanical groove-cutting and metal-surfacing process with a semiconductor fabrication approach using deposited conductive layers and filled vias. This substitution uses thin-film deposition and electroplating instead of mechanical machining.
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 reduces manufacturing costs, minimizes secondary operations, and decreases the likelihood of defects by establishing a reliable electrical path between the substrate and top cap, enhancing the durability and efficiency of the semiconductor device.
Implementation Method 1
The top cap is bonded to the substrate so that the electrically conductive surface of the top cap is electrically coupled to the path to the ground structure
Data Source
AI summary
A cap and substrate having an electrical connection at a wafer level includes providing a substrate and forming an electrically conductive ground structure in the substrate and electrically coupled to the substrate. An electrically conductive path to the ground structure is formed in the substrate. A top cap is then provided, wherein the top cap includes an electrically conductive surface. The top cap is bonded to the substrate so that the electrically conductive surface of the top cap is electrically coupled to the path to the ground structure.