MEMS Device Bonding Layer Protection via Cavity Nesting
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Solution Overview
Problem
The existing manufacturing processes for MEMS devices often damage or partially remove bonding regions during the definition of structures and removal of etch-stop layers, limiting the choice of materials and imposing design constraints.
Innovation Solution
The bonding layer is accommodated within a cavity on one of the wafers, compressed during bonding, and completely housed inside the cavity, which acts as a seal, protecting it from chemical substances used in subsequent steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the bonding layer is exposed during structure definition and etch-stop layer removal, then the manufacturing process can proceed, but the bonding layer is damaged or partially removed
Solution Approach 1:
The bonding layer is nested within a cavity formed in one of the wafers, placing it inside a protective enclosure. This nesting approach allows the bonding layer to remain exposed for manufacturing processes while being physically contained and protected from damage during etching and structure definition steps.
Solution Approach 2:
The cavity is formed in advance before the bonding layer is deposited or positioned. This preliminary action creates a protective structure that will safeguard the bonding layer during subsequent manufacturing steps, preventing damage before it can occur.
2Manufacturing precision
If chemical substances are used for wet etching and vapor etching, then structure definition and cleaning are achieved, but the bonding regions are damaged or contaminated
Solution Approach 1:
By nesting the bonding layer within a cavity, the invention creates a physical barrier that protects the bonding region from chemical substances used in wet etching and vapor etching processes. The cavity enclosure prevents direct contact between chemicals and the bonding layer while still allowing manufacturing processes to proceed.
Solution Approach 2:
The cavity acts as an intermediary structure between the bonding layer and the chemical substances. It mediates the interaction by allowing manufacturing access while blocking harmful chemical contact, thus protecting the bonding layer from contamination and damage.
3Reliability
If the bonding layer is made thicker to ensure complete housing in the cavity, then protection is improved, but the bonding process complexity increases
Solution Approach 1:
The invention specifies that the bonding layer thickness should be slightly greater than the cavity depth, creating an optimal parameter relationship. This parameter change ensures complete housing and protection of the bonding layer while maintaining a simple bonding process, as the thickness requirement is straightforward and does not complicate the bonding procedure.
Data Source
AI summary
A microelectromechanical device having a first substrate of semiconductor material and a second substrate of semiconductor material having a bonding recess delimited by projecting portions, monolithic therewith. The bonding recess forms a closed cavity with the first substrate. A bonding structure is arranged within the closed cavity and is bonded to the first and second substrates. A microelectromechanical structure is formed in a substrate chosen between the first and second substrates. The device is manufactured by forming the bonding recess in a first wafer; depositing a bonding mass in the bonding recess, the bonding mass having a greater depth than the bonding recess; and bonding the two wafers.