Temporary-Anchor Wafer Bonding for Precise MEMS Alignment
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Solution Overview
Problem
Existing methods for forming fixed and mobile parts in MEMS devices face challenges with thermal or mechanical stress, leading to misalignment and improper functioning of electrical transducers, particularly when using epitaxially deposited two-device layers which are slow and inefficient.
Innovation Solution
A method involving bonding a first device wafer to a second device wafer using temporary anchors, allowing for efficient and reliable formation and alignment of fixed and mobile parts in two layers, with the use of temporary anchor structures to protect microstructures during transfer and etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If epitaxially deposited two-device layers are used to form fixed and mobile parts, then alignment precision is improved, but manufacturing time increases significantly
Solution Approach 1:
The device is divided into two separate device wafers (first device wafer and second device wafer) that are processed independently and then bonded together. This segmentation allows parallel processing of both wafers, significantly reducing manufacturing time while maintaining alignment precision through the bonding interface and temporary anchor structures.
Solution Approach 2:
Temporary anchor structures are formed on both wafers before bonding, and these anchors are used to maintain precise alignment during the bonding process and subsequent microstructure release. This preliminary action ensures that alignment is established early and maintained throughout manufacturing, eliminating the need for slow epitaxial deposition while preserving precision.
2Strength
If device wafers are attached to handle wafers and capping wafers, then structural support is improved, but misalignment of electrical transducers occurs due to thermal and mechanical stress
Solution Approach 1:
Temporary anchor structures serve as intermediary elements between the first and second device wafers during bonding and processing. These anchors maintain precise alignment of electrical transducers across the wafer stack, compensating for thermal and mechanical stress that would otherwise cause misalignment. The anchors are later removed after serving their alignment function.
Solution Approach 2:
The patent employs controlled thermal processing parameters during bonding and annealing steps to minimize thermal stress-induced misalignment. By carefully managing temperature profiles and bonding conditions, the structural support needed for strength is achieved while preventing the thermal expansion and contraction that would cause transducer misalignment.
3Manufacturing precision
If fixed electrodes are formed in two device layers, then alignment precision is improved, but the manufacturing process becomes excessively slow
Solution Approach 1:
Fixed electrodes are formed on separate device wafers that are then bonded together using temporary anchor structures. This segmentation allows the electrode formation processes to occur in parallel on independent wafers using standard semiconductor fabrication techniques, achieving the alignment precision of multi-layer structures without the time penalty of sequential epitaxial deposition.
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
Ensures precise alignment and protection of microstructures from deformation, maintaining functional integrity of electrical transducers despite thermal or mechanical stress, and enabling efficient manufacturing processes.
Implementation Method 1
bonding a first wafer to a second wafer... bonding the first surface of the first wafer to the second wafer so that the at least one first temporary anchor region on the first wafer is attached to the at least one second temporary anchor region on the second wafer
Data Source
Figure 1~2a
Figure 2b~2d
Figure 2e~2g
AI summary
This disclosure describes a method for bonding a first wafer to a second wafer and to a third wafer. The method comprises bonding the first surface of the first wafer to the second wafer so that a first temporary anchor region on the first wafer is attached to a second temporary anchor region on the second wafer. At least one first microstructure in the first wafer is then released from the second wafer by etching through the at least one second temporary anchor region on the second wafer.