In-situ Laser Decapsulation for IC Defect Localization
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Solution Overview
Problem
Current electrical fault localization techniques require removal of surface material from packaged ICs, which is time-consuming and can damage the sample, and existing methods like lock-in thermography face challenges in achieving high spatial resolution due to thermal signature spreading from thick packaging materials.
Innovation Solution
An integrated system using an IR camera and ablative laser for in-situ decapsulation, where the laser ablates encapsulation material around the optical axis, with depth estimation from phase information to determine ablation time, allowing precise removal of a limited area without moving the sample, and a controller operates the system to improve defect localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If surface material is removed using conventional methods (FIB, plasma FIB, chemical etching, mechanical polishing), then defect localization can be achieved, but the process requires vacuum environment or tightly controlled environmental chamber, increasing system complexity and time consumption
Solution Approach 1:
The patent extracts the laser decapsulation function from a dedicated stand-alone system and integrates it into the electrical failure analysis system. This allows the removal of encapsulation material to be performed in-situ within the existing analysis chamber, eliminating the need for separate vacuum or controlled environment chambers while maintaining measurement precision.
Solution Approach 2:
The patent merges the laser decapsulation capability with the electrical failure analysis system by integrating a laser source, optics, and controller into the existing apparatus. This combination enables both defect localization and encapsulation removal to be performed in the same chamber, reducing system complexity and eliminating the need for separate environmental control systems.
2Ease of operation
If lock-in thermography is used to detect hot spots through packaged IC surface, then defect location can be identified without removing surface material, but thick packaging material causes thermal signature to spread out, reducing spatial resolution
Solution Approach 1:
The patent applies preliminary laser decapsulation to remove a portion of the encapsulation material before performing electrical failure analysis. This preliminary action exposes the defect location more directly, allowing subsequent thermography or other analysis methods to achieve higher spatial resolution by reducing thermal signature spreading through thick packaging material.
3Productivity
If stand-alone laser decapsulation system is used to remove large volume of package material, then encapsulation can be removed efficiently, but it requires a dedicated chamber as a single use system, increasing loss of time and reducing productivity
Solution Approach 1:
The patent merges the laser decapsulation system with the electrical failure analysis system into a single integrated apparatus. This allows encapsulation removal and subsequent defect analysis to be performed sequentially in the same chamber without transferring the sample between different systems, eliminating transfer time and improving overall productivity while maintaining efficient material removal capability.
4Loss of information
If conventional electrical failure analysis system with laser marking is used, then physical marks can be left on package surface, but it cannot remove encapsulation material, requiring separate decapsulation process
Solution Approach 1:
The patent implements a multi-functional system where the laser source can perform multiple functions: marking the package surface with physical marks and removing encapsulation material through ablation. This universal laser capability eliminates the need for separate decapsulation equipment while preserving the marking function, reducing device complexity and the number of process steps.
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
This method significantly reduces the time required for defect localization, prevents damage to internal IC components, and maintains thermal conduction, enabling accurate and high-resolution defect identification with improved signal-to-noise ratio.
Implementation Method 1
An integrated system using an IR camera and ablative laser for in-situ decapsulation, where the laser ablates encapsulation material around the optical axis
Implementation Method 2
An IR camera is used to image an IC to identify hot spots
Implementation Method 3
lock-in thermography which allows detection of hot spot at the surface of a packaged IC, indicating the x, y, z origin of the electrical defect location
Data Source
AI summary
An IR camera is used to image an IC to identify hot spots. The objective of the IR camera is removed and laser optics are inserted into the optical axis of the system. A laser is then used to ablate the encapsulation in a defined area around the optical axis. The IR camera operates in a lock-in mode to obtain phase information of the IR signal from the IC. The phase information is used to obtain a depth estimate of the defect. Predetermined etch rates are then used in conjunction with the depth estimate to generate a timed end-point for the laser ablation.