Wafer-Level Testing of MEMS Magnetic Switches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a lack of wafer-level test systems or methods for testing magnetically operated micro-electromechanical system (MEMS) devices, including switches, prior to packaging, which hinders the detection and rejection of non-compliant devices at an early stage of manufacturing.
Innovation Solution
A testing mechanism and method involving a fixture with a rotatable electromagnetic field generator and a probe card for measuring various parameters of magnetically operated MEMS devices on a semiconductor wafer, allowing for the adjustment of magnetic field orientation and contact with test pads to assess parameters like open and closed circuit resistances, response time, and critical angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If magnetic switches are tested at the wafer level before singulation and packaging, then manufacturing efficiency is improved by detecting faults early, but the complexity of the testing system increases due to the need for specialized wafer-level test equipment
Solution Approach 1:
The patent implements wafer-level testing before singulation and packaging, performing the testing action in advance while the devices are still on the wafer. This preliminary testing allows early detection of non-compliant switches, enabling their rejection before further processing and improving overall manufacturing efficiency by preventing defective devices from advancing through the production line
Solution Approach 2:
The testing system is designed to handle multiple functions within a single wafer-level test platform, including applying magnetic fields, measuring electrical parameters, and characterizing switch performance. This multi-functional approach consolidates what would otherwise require multiple separate testing operations into one integrated system, managing the complexity through consolidation rather than proliferation of separate devices
2Measurement precision
If a rotatable electromagnetic field generator is used to adjust magnetic field orientation, then measurement precision is improved by testing at various angles, but the device complexity increases due to the rotatable mechanism
Solution Approach 1:
The electromagnetic field generator is designed with a rotatable mechanism that allows dynamic adjustment of the magnetic field orientation relative to the wafer. This dynamic capability enables the system to test switches at various angles, including critical angles, by physically rotating the field generator to different positions. The dynamic adjustment provides precise angular measurement capability while consolidating the rotation function into a single controllable mechanism rather than requiring multiple fixed-position generators
3Loss of time
If wafer-level testing is implemented, then loss of time is reduced by rejecting non-compliant switches early, but the use of energy increases due to the testing process
Solution Approach 1:
Testing is performed at the wafer level before singulation and packaging, executing the detection action in advance while devices are still on the wafer. This preliminary testing enables early identification of non-compliant switches, allowing them to be rejected before further processing steps. The time savings from avoiding rework and retesting of defective devices through subsequent packaging and assembly stages outweighs the energy consumption of the wafer-level testing process itself
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
Enables the rejection of non-compliant switches at the wafer level before singulation and packaging, improving manufacturing efficiency by detecting faults early and allowing for potential re-rating of switches that do not meet initial specifications.
Implementation Method 1
The mechanism includes an fixture configured to be supported in a probe ring of a wafer prober. The fixture supports an electromagnetic field generator that can be rotated, relative to the probe ring, to permit adjustment of orientation of a generated magnetic field relative to the MEMS devices of a subject wafer.
Implementation Method 2
When the magnet 112 and the switch 100 are brought into close proximity, the ferromagnetic material of the first and second contact plates 102, 104 is exposed to the magnetic force, which induces a magnetic polarity in the first and second contact plates 102, 104 that is opposite the polarity of the magnet 112.
Implementation Method 3
Under the influence of the magnet 112, the end 108 of the first contact plate 102 is polarized as a south pole, while the end 110 of the second contact plate 104 is polarized as a north pole. Accordingly, as the first and second contact plates 102, 104 flex slightly, the ends 108, 110 of the first and second contact plates are drawn together by magnetic attraction, thereby closing the switch 100.
Implementation Method 4
The magnetic repulsion between the ends 128, 130 causes the first and second contact plates to flex away from each other, opening the switch 120.
Data Source
AI summary
A testing mechanism for testing magnetically operated microelectromechanical system (MEMS) switches at a wafer level stage of manufacture includes an electromagnetic fixture configured to be received in a standard probe ring. The electromagnetic fixture is rotatable, relative to the probe ring, to permit adjustment of orientation of a generated magnetic field relative to the MEMS devices of a subject wafer. The testing mechanism also includes a probe card with probes positioned to contact test pads on the subject wafer. During operation, the probe card is positioned over the wafer to be tested, with the test probes in electrical contact with respective contact pads of the wafer, and the electromagnetic fixture is positioned above the probe card. An electrical potential is applied across the switches on the subject wafer, and the electromagnetic fixture is energized at selected levels of power and duration. Current flow across each switch is measured to determine one or more of: open circuit contact resistance, closed circuit contact resistance, response time, response to switching magnetic field, frequency response, current capacity, critical dimensions, critical angles of magnetic field orientation, etc. Wafer level testing enables rejection of non-compliant switches before the cutting and packaging levels of manufacture.