Advanced laser signal injection microscopy for precise IC fault localization — front side and backside.
The Most Advanced LSIM Technique Available
XIVA™ LSIM (Laser Signal Injection Microscopy) is a powerful technique for locating shorts, junction defects, problematic VIAs, and a wide range of other integrated circuit faults. By scanning a focused laser beam over a device under test (DUT) while continuously monitoring its I/V response, XIVA™ detects the precise location where the laser induces a measurable change — pinpointing defects with high spatial accuracy.
How XIVA™ LSIM Works
The effect produced by the laser depends on its wavelength, giving XIVA™ the flexibility to target different classes of defects. In all three modes, the laser directly impacts device impedance — typically resistance — and the resulting change is captured as a shift in the I/V curve. Both frontside and backside IC investigations are fully supported.
The XIVA™ Filter: Better Signal, Lower Noise
A key innovation in the XIVA™ system is the XIVA™ filter, inserted between the bias supply and the DUT. This filter serves two important functions simultaneously.
- At low frequencies, the filter is transparent — the constant voltage bias reaches the DUT unaffected, exactly as designed.
- When the rapidly scanning laser encounters a defect and causes a sudden impedance change, the filter supplies the required delta current over that brief interval, momentarily maintaining constant current and capturing the event.
- As a coincidental benefit, the filter also removes external pickup noise from the measurement path — yielding significantly greater sensitivity than earlier LSIM methods.
Constant Voltage Biasing Simplifies Multi-Technique Workflows
Most semiconductor circuits are designed to operate under constant voltage. Because XIVA™ uses the same biasing approach, set-up is straightforward when using multiple analytical techniques on the same DUT within a QuantumScope™ system — contributing to consistency of data across techniques.
The XIVA™ Technique Development
Several laser-based fault localization techniques have emerged since OBIC pioneered the field in 1988 — including LIVA, TIVA, IR-OBIRCH, and SEI. Each generates photo-carriers or localized heating to reveal defect locations, but they differ in how the circuit under test is biased and how the measurement signal is captured.
QFI’s patented XIVA™ technique (eXternally Induced Voltage Alteration) was developed around two core design principles that set it apart: constant voltage biasing — simple, practical, and aligned with how most semiconductor circuits are designed to operate — and constant current sensing, delivering superior signal-to-noise performance compared to earlier methods. QFI’s technique encompasses and extends all prior LSIM methods — OBIC, LIVA, SEI, OBIRCH, and TIVA — making XIVA™ the most advanced and comprehensive LSIM technique available for detecting and locating IC faults.
| Technique | Primary Use |
|---|---|
| OBIC (1988) | Pioneer technique — optical beam-induced current for photo-carrier generation |
| LIVA | Light-induced voltage alteration — constant current biasing |
| TIVA | Thermally-induced voltage alteration — thermal laser mode |
| IR-OBIRCH | Infrared optical beam-induced resistance change |
| SEI | Seebeck effect imaging — thermoelectric signal detection |
| XIVA™ LSIM | Encompasses and extends all prior techniques — constant voltage biasing, constant current sensing, broadest defect coverage |
Beyond Basic XIVA™: Full Laser Signal Injection Microscopy
Through product development and close collaboration with partners, QFI extended XIVA™ capabilities well beyond its original scope. This broader capability is captured under the LSIM (Laser Signal Injection Microscopy) designation.
XIVA™ LSIM can accommodate any electrical measurement of the IC, including dynamic measurements such as pass/fail response in a tester loop. A BNC user-input to the A/D card in the system computer allows any signal to be plotted as a function of laser position, in place of the standard XIVA™ image — giving engineers significant flexibility in how they interrogate their devices.
Optional Lock-In Amplifier for Demanding Applications
XIVA™ LSIM is offered with an optional lock-in amplifier for applications where standard sensitivity is insufficient. QFI estimates that 90% of LSIM-detectable defects can be located using the standard XIVA™ electronics alone. For the remaining cases — particularly weak signals in electrically noisy devices — the lock-in amplifier provides a significant improvement in sensitivity.
Lock-In Amplifier: Key Trade-off
Lock-in improves sensitivity for weak or noisy signals, but increases data acquisition time. For most standard applications, the base XIVA™ electronics will be sufficient.
Class 1 Laser Product Safety
QFI’s XIVA™ systems incorporate comprehensive safety mechanisms and interlocks that earn them Class 1 laser product status — the safest classification available for laser equipment. These design features ensure safe operation in laboratory and production environments without compromising analytical performance.
Part of the QuantumScope™ Failure Analysis Platform
XIVA™ LSIM is one of three complementary techniques on the QuantumScope™ system — giving failure analysis engineers complete coverage across electrical, thermal, and optical defect types on a single platform.
Photoemission Microscopy
emmi™
Detect and localize photon-emitting defects — gate leakage, oxide pinholes, forward-biased junctions — with industry-leading sensor sensitivity.
Get More Information About XIVA™
Whether you’re evaluating XIVA™ for your lab, comparing laser configurations, or ready to discuss your specific application, our team is here to help.