MEMS Buffer Protection Layer for Etching Damage Prevention
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Solution Overview
Problem
The manufacturing of micro electro mechanical system (MEMS) devices using silicon-on-insulator (SOI) wafers faces challenges in protecting the MEMS membrane from damage during the etching process, particularly when the carrier is removed, leading to reduced product yield and stiffness of the membrane, which affects sound pressure level (SPL) performance.
Innovation Solution
A manufacturing method involving the formation of a buffer protection layer on the semiconductor structure, including the MEMS membrane and wafer, which is located in the slits and on the surface of the membrane, providing support during etching and grinding, and optionally using a temporary bonding layer and carrier, to protect the membrane from external forces and enable the creation of larger cavities and more slits with reduced membrane thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the carrier is removed from the SOI wafer, then the manufacturing process can be completed, but external force easily causes damage to the MEMS membrane
Solution Approach 1:
The buffer protection layer is formed on the MEMS membrane surface before the etching process and carrier removal. This preliminary protective action ensures that when the carrier is later removed, the MEMS membrane is already protected and can withstand external forces without damage.
Solution Approach 2:
The buffer protection layer acts as a cushioning layer that absorbs and distributes external forces applied to the MEMS membrane. This beforehand cushioning prevents direct force transmission to the fragile MEMS membrane structure during carrier removal and subsequent handling.
2Power
If the thickness of the MEMS membrane is reduced to increase deflection, then sound pressure level performance is improved, but the MEMS membrane becomes more susceptible to damage
Solution Approach 1:
The buffer protection layer is applied before any damage can occur to the thin MEMS membrane. This allows the membrane to be made as thin as needed for optimal acoustic performance while the protective layer is already in place to prevent damage during manufacturing and handling.
Solution Approach 2:
The buffer protection layer serves as an intermediary between external forces and the thin MEMS membrane. It mediates the interaction by absorbing mechanical stresses, allowing the membrane to maintain its thin structure for acoustic performance while being protected from damage.
3Power
If the number of slits and cavity length are increased to reduce membrane stiffness, then deflection and sound pressure level performance are improved, but the manufacturing complexity increases
Solution Approach 1:
The buffer protection layer is formed before the complex etching processes that create multiple slits and cavities. This preliminary protection remains in place throughout the complex manufacturing steps, simplifying the process by preventing damage during handling of the increasingly complex structure.
Data Source
AI summary
A manufacturing method of a micro electro mechanical system (MEMS) device includes forming a buffer protection layer on a semiconductor structure, wherein the semiconductor structure includes a wafer, a MEMS membrane, and an isolation layer between the wafer and the MEMS membrane, and the buffer protection layer is located in a slit of the MEMS membrane and on a surface of the MEMS membrane facing away from the isolation layer; etching the wafer to form a cavity such that a portion of the isolation layer is exposed though the cavity; etching the portion of the isolation layer; and removing the buffer protection layer.