Micromechanical Sensor Bonding Pads With Inward-Setback Edges
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Solution Overview
Problem
Existing methods for producing bonding pads in micromechanical sensor elements face challenges in ensuring clean separation during dicing by grinding, leading to potential tearing of metal layers due to lateral protrusions, which can disrupt the singulation process.
Innovation Solution
A method involving the deposition of multiple metal layers with controlled thicknesses and selective etching to form bonding pads with inwardly set-back edges, using a second layer as an etching mask to create a trench and ensure clean separation, followed by a dry ion beam etching process to remove excess metal, thereby preventing lateral protrusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single metal layer is deposited onto the functional layer, then the manufacturing process is simple, but the bonding pad edges protrude laterally causing tearing during dicing by grinding
Solution Approach 1:
The single metal layer is segmented into two distinct layers: a first metal layer deposited over the entire bonding pad region, and a second metal layer deposited only in the border region. This segmentation allows the first layer to provide continuous electrical contact while the second layer prevents lateral protrusion during dicing, resolving the contradiction between manufacturing simplicity and separation reliability.
Solution Approach 2:
The first metal layer is deposited and structured in advance to form the bonding pad region, creating a preparatory structure. Subsequently, the second metal layer is deposited only in the border region to prevent lateral protrusion during dicing. This preliminary action ensures that the bonding pad is ready for electrical contact while preventing tearing during separation.
2Quantity of substance
If the metal layer extends to the peripheral edge of the bonding pad region, then electrical contact area is maximized, but lateral protrusions cause tearing during dicing by grinding
Solution Approach 1:
The first metal layer is deposited over the entire bonding pad region to maximize electrical contact area. The second metal layer is selectively deposited only in the border region to prevent lateral protrusion. This local quality differentiation allows different regions of the metal structure to serve different functions: the first layer provides electrical contact while the second layer prevents tearing during dicing.
3Reliability
If multiple metal layers are deposited with different thicknesses, then lateral protrusions are prevented, but the manufacturing process complexity increases
Solution Approach 1:
The metal structure is segmented into two layers with different thicknesses and deposition patterns. The first metal layer provides the base electrical contact, while the second metal layer with different thickness prevents lateral protrusion. This segmentation, while increasing process steps, ensures reliable prevention of tearing during dicing.
Solution Approach 2:
Different regions of the bonding pad have different metal layer configurations. The first metal layer is deposited over the entire bonding pad region, while the second metal layer is deposited only in the border region with different thickness. This local quality differentiation prevents lateral protrusions while maintaining electrical contact integrity.
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
The method ensures defined, inwardly set-back edges of the bonding pads, preventing tearing during dicing by grinding, facilitating clean separation and reliable electrical contact, thus enhancing the efficiency of the singulation process.
Implementation Method 1
depositing a first metal layer of a first thickness onto a top face of the functional layer, and depositing a second metal layer of a second thickness onto the first metal layer
Implementation Method 2
carrying out an etching process in the exposed portion of the border region starting from the top face of the layered structure, wherein a bonding pad region having the bonding pad is released from a surrounding bonding frame region, wherein the second layer is used as an etching mask
Implementation Method 3
removing the first or second metal layer from the inner portion of the border region using an unmasked etching process
Data Source
AI summary
A method for producing a bonding pad for a micromechanical sensor element. The method includes: depositing a first metal layer onto a top face of the functional layer, and depositing a second metal layer onto the first metal layer, wherein only the first layer or only the second layer is formed in a border region extending around a bonding pad region; covering a protective layer over a top face of the second metal layer in the bonding pad region and over the first or second metal layer in an inner peripheral portion of the border region, which inner peripheral portion adjoins the bonding pad region; etching the first or second layer at least in an outer peripheral portion of the border region down to the top face of the functional layer; removing the protective layer; carrying out an etching process starting from the top face of the layered structure.