Soft defect localization (SDL) is a dynamic laser fault isolation technique that isolates functional failures caused by resistive defects, damage, or degradation. It is used when a failure cannot be isolated with static techniques such as photon emission microscopy, thermal hotspot detection, or XIVA™.

SDL is also known as thermal DALS (dynamic analysis by laser stimulation) and resistive interconnect localization (RIL), and it belongs to the broader family of dynamic laser stimulation (DLS) techniques.

Failures SDL Localizes

Functional failure modes:

Scan chain failures
Register read and write failures
Race conditions
Shmoo (voltage and frequency marginal) failures
General functional failures

Defect types:

Open or resistive vias and contacts
Stringers
Gate oxide shorts

How SDL Works

The core of an SDL system is the test controller. It steps the laser scanning microscope from pixel to pixel, runs an electrical test on the device under test (DUT) at each position, and reports a pass or fail result to the imaging software. Repeating this across the scan area builds a pass/fail map, with failing pixels plotted in red and passing pixels in green, that highlights the location of the failure mechanism.

SDL uses a 1310 nm laser as a localized heat source. The resistance of a material changes with temperature according to R = R0·[1 + α(T − T0)], where α is the thermal coefficient of resistance, and transistor characteristics also shift with temperature. Because defects typically occupy a small area or volume compared with normal circuit features, local heating at a defect produces a disproportionately large change in device behavior. SDL can be performed from the topside or through the backside of the substrate.

Example: Localizing a Resistive Via

A malformed via or contact creates a high-resistance connection that degrades signal transitions and appears as a functional timing failure. When the SDL laser heats the via, the via expands, increasing the contact area and reducing contact resistance. The output signal improves, and the device shifts from failing to passing at the same clock and supply voltage condition on the shmoo plot. That pass/fail transition pinpoints the via.

SDL vs. LADA

SDL: thermal stimulation at 1310 nm. Most sensitive to resistive defects such as malformed vias, contacts, and stringers.
LADA: photoelectric stimulation at 1080 nm. Most sensitive to timing-critical transistor behavior such as speed paths and threshold voltage shifts.

Turnaround and Deliverables

Typical turnaround for SDL is 3 to 5 days, depending on device complexity, test setup, and the sample preparation required. Results are documented with annotated pass/fail localization images in an engineering report.

Related Services

Frequently Asked Questions

What is soft defect localization (SDL)?

SDL is a dynamic laser fault isolation technique that heats points on a running device with a laser while a test controller checks whether the device passes or fails. The locations where the result changes reveal resistive defects behind marginal functional failures.

Is SDL the same as thermal DALS?

Yes. Thermal DALS and resistive interconnect localization (RIL) describe the same approach: thermal laser stimulation of a device running an electrical test, with the pass/fail result mapped to the laser position.

What is needed to set up an SDL analysis?

The failing device, a test program or test vectors that reproduce the failure, pass/fail criteria, and characterization data such as a shmoo plot showing the failing conditions.

How long does SDL analysis take?

Typical turnaround is 3 to 5 days, depending on device complexity, test setup, and the sample preparation required.

Request SDL Analysis

Watson Analytical is an ISO 9001:2015 certified, ITAR-registered failure analysis laboratory in San Diego, California, serving semiconductor, defense, space, biomedical, and litigation customers. Contact us to discuss your failure and request a quote.

Soft Defect Localization (SDL)