Barrier Ring for CMOS MEMS vHF Etching Protection
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Solution Overview
Problem
During the fabrication of CMOS MEMS systems, vapor phase hydrofluoric acid (vHF) etching can cause undesired etching of inter-metal dielectrics, leading to reliability and performance issues due to its corrosive nature, necessitating a reliable barrier layer to prevent damage.
Innovation Solution
A semiconductor structure incorporating a barrier ring disposed over the sidewall of conductive structures to protect dielectric materials, with the barrier ring being resistant to vHF etching, ensuring minimal damage and maintaining system reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If vapor phase hydrofluoric acid (vHF) etching is used to remove sacrificial layers, then the sacrificial layer can be effectively removed, but undesired etching of inter-metal dielectrics occurs leading to reliability and performance issues
Solution Approach 1:
A barrier ring made of etchant-resistant material (such as silicon nitride or silicon oxide) is introduced as an intermediary protective layer between the vHF etchant and the inter-metal dielectric materials. This barrier ring is selectively formed around conductive structures and selectively removed after protecting the dielectric materials, thereby enabling effective sacrificial layer removal while preventing undesired etching of the dielectric materials.
2Reliability
If a barrier layer is introduced to protect dielectric materials from vHF etching, then dielectric material integrity is maintained, but process complexity increases
Solution Approach 1:
The barrier ring is formed locally only in specific regions where protection is needed, such as around conductive structures and trenches, rather than applying a universal barrier layer across the entire substrate. This localized approach is achieved through selective deposition and targeted removal processes, reducing overall process complexity while maintaining dielectric material integrity in critical areas.
3Reliability
If the barrier ring is made highly resistant to vHF etching, then protection effectiveness is maximized, but the barrier ring itself becomes difficult to remove
Solution Approach 1:
The barrier ring is formed with specific material parameters and thickness characteristics that provide high resistance to vHF etching during the sacrificial layer removal process. The thickness and material composition are carefully controlled to ensure adequate protection while maintaining removability through selective etching processes that target the barrier ring's specific properties after the dielectric materials are protected.
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 barrier ring effectively mitigates undesired etching of dielectric materials, enhancing the reliability and performance of semiconductor structures by providing a protective layer that withstands vHF exposure with an etching rate less than approximately 1 nm/min.
Implementation Method 1
the barrier ring being resistant to vHF etching, ensuring minimal damage and maintaining system reliability
Data Source
AI summary
A method for forming a semiconductor structure includes following operations. A first substrate including a first side, a second side opposite to the first side, and a metallic pad disposed over the first side is received. A dielectric structure including a first trench directly above the metallic pad is formed. A second trench is formed in the dielectric structure and a portion of the first substrate. A sacrificial layer is formed to fill the first trench and the second trench. A third trench is formed directly above the metallic pad. A barrier ring and a bonding structure are formed in the third trench. A bonding layer is disposed to bond the first substrate to a second substrate. A portion of the second side of the first substrate is removed to expose the sacrificial layer. The sacrificial layer is removed by an etchant.