Pulsed Laser Cross-Sectioning for Large Semiconductor Package Analysis

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Solution Overview

Problem

Advanced semiconductor packages pose challenges in failure analysis due to their large size and complex structure, as traditional techniques like FIB and Argon Beam tools are limited in cross-sectional capabilities, often causing delamination and cracks during analysis.

Innovation Solution

A pulsed laser sample ablation system is used to create cross-sectional views of advanced packages, employing a focused pulsed laser with variable power and pulse length, combined with confocal sensing for precise depth control and imaging, allowing for deeper and more accurate analysis without causing damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If traditional FIB or Argon Beam tools are used for cross sectioning, then some depth analysis is possible, but the analysis depth is limited to a few hundred microns or less than 2mm, and the process is extremely slow

Engineering Contradiction:

Improvecross-section depthVSAvoidcross-sectioning speed

Core Design Contradiction:

Length of stationary objectVSProductivity

Solution Approach 1:

The patent replaces mechanical cross-sectioning methods (sawing, FIB, Argon Beam) with laser ablation technology. The laser beam removes material through vaporization rather than mechanical cutting, enabling deep cross-sectioning (up to 6mm) at high speeds while minimizing mechanical stress and damage to the package structure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs variable pulse width laser parameters (from femtoseconds to nanoseconds) to optimize ablation depth and quality. By adjusting laser wavelength, pulse duration, and power, the system achieves controlled material removal at different depths while maintaining package integrity, overcoming the depth limitations of traditional methods.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If slow speed low damage saw is used for cross sectioning, then minimal damage is caused, but the process is extremely slow and often still produces delamination and cracks

Engineering Contradiction:

Improvedelamination and cracksVSAvoidcross-sectioning speed

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The patent replaces mechanical sawing with laser ablation, eliminating mechanical contact that causes delamination and cracks. The laser vaporizes material without physical pressure or friction, achieving damage-free cross-sectioning at high speeds.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces laser energy as an intermediary between the cross-sectioning tool and the package. The laser beam transfers energy to vaporize material without mechanical contact, acting as a non-contact mediator that eliminates the harmful mechanical stresses causing delamination and cracking.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If point cross sectioning is performed to identify root cause, then failure mode analysis is possible, but traditional techniques cannot handle packages as large as 50mm×50mm and 6mm thick

Engineering Contradiction:

Improvefailure analysis precisionVSAvoidpackage size

Core Design Contradiction:

Measurement precisionVSLength of stationary object

Solution Approach 1:

The patent segments the large package into manageable cross-sectional views at different depths using laser ablation. By removing material layer by layer and creating sequential cross-sections, the system enables precise failure analysis in large 6mm-thick packages that exceed the capabilities of traditional point cross-sectioning methods.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces traditional mechanical cross-sectioning equipment with laser ablation technology, enabling the analysis of ultra-large packages (50mm×50mm×6mm). The laser's non-contact nature and high precision allow accurate cross-sectioning of packages too large for conventional FIB or mechanical sawing equipment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 efficient and damage-free cross-sectional analysis of large advanced semiconductor packages, identifying root causes of failure modes such as interconnect failures and stress-induced delamination, improving diagnostic capabilities beyond existing methods.

Implementation Method 1

pulsed laser sample ablation system is used to create cross-sectional views of advanced packages

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

employing a focused pulsed laser with variable power and pulse length, combined with confocal sensing for precise depth control and imaging

Methodology Applied

Scientific EffectConfocal sensing:

Data Source

PatentUS20230373028A1Apparatus and method for semiconductor package failure analysis

Publication Date: 2023.11.23 GATAN INC

AI summary

A pulsed laser apparatus for milling a sample is described. The apparatus includes a pulsed laser, a scan head for scanning a beam from the pulsed laser across the sample an F-theta lens for focusing the scanned beam onto the sample and a confocal detector for detection of ablation depth. Methods of pulsed laser milling are also described.