Semiconductor MEMS Cap Structure With Anti-Stiction Dimples
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Solution Overview
Problem
MEMS devices face issues with stiction, where movable elements adhere to the cap structure during movement, potentially damaging the device due to lack of surface roughness, leading to reduced reliability and increased manufacturing costs.
Innovation Solution
Formation of anti-stiction dimples on the movable elements using a eutectic material during the bond ring process, which increases surface roughness and reduces the likelihood of adhesion, combined with a single process step to form both the bond ring and dimples, simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the movable element has a smooth surface, then the manufacturing process is simpler, but the movable element adheres to the cap structure causing stiction and device damage
Solution Approach 1:
The anti-stiction dimples are formed on the movable element surface before the bonding process. This preliminary action of creating surface roughness features prevents stiction from occurring during device operation, thereby improving reliability without requiring additional steps after bonding
Solution Approach 2:
The formation of the bond ring and the anti-stiction dimples are combined into a single etching process step. The same etch process that creates the bond ring structure also forms the dimples on the movable element surface, eliminating the need for separate processing steps and reducing manufacturing complexity
2Reliability
If anti-stiction dimples are formed on the movable element, then adhesion is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The bond ring formation and anti-stiction dimple formation are merged into a single etching process. The etch process simultaneously creates the bond ring structure and the dimples on the movable element surface, reducing process complexity while maintaining the anti-stiction functionality
Solution Approach 2:
The etching process serves multiple functions: it creates the bond ring structure, forms the anti-stiction dimples, and defines the bonding interface. This multi-functionality reduces the overall process complexity while achieving multiple objectives
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 dimples effectively prevent movable elements from adhering to the cap structure, enhancing device reliability and reducing manufacturing complexity and costs while maintaining high throughput.
Implementation Method 1
an etch process for forming the bond ring is controlled so that eutectic material redeposits on the upper surfaces of the movable elements to form the dimples
Data Source
AI summary
In some embodiments, a semiconductor device is provided. The semiconductor device includes a semiconductor layer, a micro-electromechanical systems (MEMS) structure defined in the semiconductor layer, a bond ring over the semiconductor layer, and a cap structure over the MEMS structure and bonded to the bond ring. The MEMS structure has an upper surface and the cap structure has a lower surface facing the upper surface of the MEMS structure. Dimples of eutectic material are on the upper surface of the MEMS structure.