MEMS Anti-Stiction Mesa With Hardness-Graded Buffer Layers
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Solution Overview
Problem
The increasing complexity of manufacturing semiconductive devices, particularly MEMS devices, leads to issues such as high yield loss, warpage, and low signal-to-noise ratio due to stiction problems during the mechanical movement of movable membranes, which complicates the processing and manufacturing of these devices.
Innovation Solution
An anti-stiction structure is introduced in MEMS devices, featuring multiple stacked layers with mixed hardness arrangements, including mesas protruded from the substrate surface to prevent direct contact between the membrane and the substrate, thereby reducing stiction by distributing the striking force through buffer layers with different hardnesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the membrane directly contacts the substrate during mechanical movement, then the structural simplicity is maintained, but stiction occurs causing low signal-to-noise ratio and high yield loss
Solution Approach 1:
The patent introduces an anti-stiction structure as an intermediary element between the movable membrane and the substrate. This structure includes a first portion that contacts the membrane and a second portion extending to the substrate, with buffer layers having different hardness values. The intermediary structure prevents direct contact between the membrane and substrate, thereby reducing stiction and improving signal-to-noise ratio while maintaining reasonable structural complexity.
2Reliability
If multiple stacked layers with mixed hardness are introduced to reduce stiction, then the reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by creating buffer layers with different hardness values at specific locations within the anti-stiction structure. The first buffer layer has a first hardness value and the second buffer layer has a second hardness value, allowing each layer to perform its specific function in force distribution. This localized differentiation improves reliability by reducing stiction while keeping the overall manufacturing process manageable through targeted material selection.
3Manufacturing precision
If the membrane is designed to move freely without constraints, then the operational simplicity is maintained, but warpage and stiction defects occur
Solution Approach 1:
The patent implements beforehand cushioning by designing the anti-stiction structure with buffer layers that provide cushioning support before the membrane can contact the substrate. The buffer layers with different hardness values are positioned in advance to absorb and distribute striking forces, preventing warpage and stiction defects before they occur. This allows the membrane to move with sufficient freedom while being protected from harmful contact.
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 anti-stiction structure effectively reduces stiction and enhances the sustainability of the MEMS device by evenly distributing the striking force, thereby improving manufacturing yield and reducing defects like warpage and low signal-to-noise ratios.
Implementation Method 1
The mesa includes a material proximal to the membrane; a first buffer layer between the substrate and the material, and at least partially covered by the material; and a second buffer layer between the substrate and the first buffer layer, wherein the material contacts the second buffer layer, and the second buffer layer includes a hardness greater than a hardness of the first buffer layer.
Data Source
AI summary
A semiconductor device includes a substrate and a movable membrane proximal to the substrate. The semiconductor device further includes a mesa over the substrate and protruded from a surface of the substrate toward the movable membrane. The mesa includes a strike hitting portion configured to receive a striking force from the membrane and a hybrid stress buffer under the strike hitting portion, wherein the hybrid stress buffer includes at least two layers which are distinguishable by a difference in hardness.