Wafer-Level Stacked Accelerometer Magnetometer Die Alignment
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Solution Overview
Problem
Conventional microelectronic package fabrication methods face challenges in achieving precise alignment between the sensing axes of accelerometer and magnetometer dies, leading to increased costs, complexity, and time due to limited rotational alignment tolerances of about 1-2°, necessitating thorough testing and calibration.
Innovation Solution
A wafer-level stacking process is employed to align the sensing axes of accelerometer and magnetometer dies with high precision, allowing rotational alignments within a few hundredths of a degree, and the magnetometer die is bonded directly to the accelerometer die to form a hermetically-sealed cavity, eliminating the need for a separate cap piece and reducing package size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pick-and-place tool is used to position the magnetometer die over the cap piece, then the package can be assembled, but the rotational alignment precision is limited to 1-2° tolerances
Solution Approach 1:
Alignment features (such as protrusions and recesses or registration marks) are pre-formed on the cap piece and magnetometer die during their respective fabrication processes. This preliminary alignment structure ensures that when the magnetometer die is placed on the cap piece, the sensing axes are automatically aligned with high precision (within a few hundredths of a degree), eliminating the need for post-assembly calibration and reducing reliance on pick-and-place tool precision.
2Reliability
If a separate cap piece is used to enclose the accelerometer die, then the MEMS transducer structure is hermetically sealed, but the package size and complexity increase
Solution Approach 1:
The magnetometer die is directly bonded to the accelerometer die in a stacked configuration, eliminating the need for a separate cap piece. The magnetometer die itself serves as the encapsulating element for the MEMS transducer structure, maintaining hermetic sealing while reducing package complexity and size. This integration combines multiple functions into a single component.
3Manufacturing precision
If thorough testing and calibration are performed to achieve precise alignment, then the sensing axes can be accurately aligned, but the manufacturing time and cost increase
Solution Approach 1:
Alignment features are incorporated into the cap piece and magnetometer die during their fabrication processes, ensuring that precise alignment is achieved through the physical geometry of the components themselves. This preliminary design of alignment structures eliminates the need for time-consuming post-assembly testing and calibration, as the alignment is inherently built into the component design.
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 method ensures highly accurate alignment between the sensing axes of the accelerometer and magnetometer dies, reducing or eliminating the need for post-fabrication testing and calibration, improving manufacturing efficiency, and achieving precise alignment beyond conventional methods, while also reducing package size and cost by eliminating the need for a separate cap piece.
Implementation Method 1
a ring of bonding material bonds a singulated magnetometer die to a singulated accelerometer die such that a hermetically-sealed cavity is formed enclosing a MEMS transducer structure provided on the accelerometer die
Data Source
AI summary
Methods for fabricating multi-sensor microelectronic packages and multi-sensor microelectronic packages are provided. In one embodiment, the method includes positioning a magnetometer wafer comprised of an array of non-singulated magnetometer die over an accelerometer wafer comprised of an array of non-singulated accelerometer die. The magnetometer wafer is bonded to the accelerometer wafer to produce a bonded wafer stack. The bonded wafer stack is then singulated to yield a plurality of multi-sensor microelectronic packages each including a singulated magnetometer die bonded to a singulated accelerometer die.