Magnetic Shielded Probe Card for Wafer Testing
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Solution Overview
Problem
Conventional methods for testing magnetically sensitive semiconductor devices require expensive large-scale magnetic shields and result in low test throughput due to manual assembly and loss of wafer location information, making it difficult to correlate test results with wafer processing effects.
Innovation Solution
Integration of a magnetic material, such as MuMETAL, into the design of probe cards as both inner and outer magnetic shields to attenuate ambient magnetic fields, with the inner shield positioned close to the probe tips to minimize external interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional large-scale magnetic shields are used for testing magnetically sensitive semiconductor devices, then magnetic field shielding is achieved, but cost increases and test throughput decreases
Solution Approach 1:
The magnetic shielding function is segmented and integrated directly into the probe card structure itself, rather than using a separate large-scale shield. The probe card is divided into a body portion and a magnetic shield portion, with the shield being a thin layer (0.002-0.006 inches) positioned adjacent to the probe tips. This segmentation allows the shielding function to be localized and incorporated into the testing apparatus without requiring a large external shield, thereby maintaining test throughput while providing effective magnetic field attenuation for magnetically sensitive devices.
Solution Approach 2:
The magnetic shield is nested within the probe card structure, with the shield portion positioned between the probe tips and the magnetically sensitive device under test. This nesting approach integrates the shielding function directly into the testing pathway, allowing the shield to be in close proximity to the device without interfering with the probing operation. The nested configuration enables effective magnetic field blocking while maintaining compact test setup and high test throughput.
2Adaptability or versatility
If manual assembly methods are used for probe card assembly, then flexibility is maintained, but test throughput decreases and wafer location information is lost
Solution Approach 1:
Wafer location information is captured and recorded during the probing operation itself, before the wafer is removed or repositioned. The system automatically records the precise location where each probe tip contacts the wafer, storing this information in association with the test results. This preliminary capture of location data eliminates the need for manual tracking or re-location procedures, thereby increasing test throughput while maintaining the flexibility to test different wafer configurations.
Solution Approach 2:
The probe card system automatically performs the function of tracking and recording wafer location information without requiring manual intervention. The probing apparatus itself generates and stores the location data as part of the normal testing process, enabling the system to serve its own information management needs. This self-service capability eliminates the bottlenecks associated with manual assembly and data recording, significantly improving test throughput while preserving adaptability.
3Productivity
If thin magnetic shield layers are integrated into probe cards, then cost decreases and test throughput increases, but shielding effectiveness may be reduced
Solution Approach 1:
The magnetic shield is positioned locally adjacent to the probe tips, specifically between the probes and the magnetically sensitive device under test. Rather than using a thick shield over the entire probe card, the thin magnetic shield layer (0.002-0.006 inches) is strategically placed only where it is most needed - in the immediate vicinity of the device being tested. This local quality approach provides effective magnetic field attenuation for the critical region while keeping the overall shield thickness minimal, thereby maintaining both shielding effectiveness and high test throughput.
Solution Approach 2:
The probe card is constructed as a composite structure combining a non-magnetic body portion with a magnetic shield portion made of specific magnetic materials. The magnetic shield layer is integrated into this composite structure, allowing the thin layer to provide effective magnetic field blocking when positioned correctly. The composite material approach enables the thin shield to achieve the necessary shielding effectiveness for magnetically sensitive devices while maintaining cost-effectiveness and high test throughput.
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 shielded probe cards significantly reduce external magnetic fields, enabling efficient testing of sensitive components at the wafer level with improved throughput and correlation of device metrics to wafer processes, while being cost-effective and adaptable to various probe systems.
Implementation Method 1
at least one magnetic shield includes a magnetic material that at least substantially surrounds a projected volume projected 90 degrees above an area that encloses the probe tips
Data Source
AI summary
A probe card includes a mechanical support fixture having an inner aperture with a plurality of probes secured to the fixture that includes probe tips that extend into the inner aperture for contacting probe pads on die of a wafer to be probed. At least one magnetic shield includes a magnetic material that at least substantially surrounds a projected volume over an area that encloses the probe tips. The magnetic material has a relative magnetic permeability of at least 800.