Protection Layer Stack for Crack-Free FIB Failure Analysis
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Solution Overview
Problem
Conventional methods for preparing semiconductor device samples for failure analysis, such as chemical etching and FIB thinning, often result in damage to the surface layer due to over-etching or charge accumulation, leading to unsuitable samples for TEM analysis.
Innovation Solution
A protection layer comprising a first thin film, a buffer thin film, and a second thin film made of metal oxides, sulfides, selenides, or nitrides is applied to the semiconductor device surface, preventing cracks and distortion during FIB thinning and enhancing stress resistance for microLED and VCSEL elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical etching solution and abrasive cloth are used for surface layer removing process, then the surface layer can be removed, but material layers under the surface layer are damaged due to over etching or over polishing
Solution Approach 1:
The patent introduces a protection layer as an intermediary substance applied to the surface of the malfunction device before FIB thinning. This protection layer serves as a mediator that prevents direct harmful interaction between the FIB process and the device surface, eliminating the need for chemical etching and abrasive polishing that cause underlying layer damage.
Solution Approach 2:
The protection layer is applied in advance before the FIB thinning process to prevent damage proactively. By performing this preliminary protective action, the patent avoids the need for subsequent damage repair and ensures the integrity of underlying material layers throughout the sample preparation process.
2Reliability
If Pt passivation layer is coated on the malfunction device surface before FIB thinning, then charge accumulation during thinning is cancelled, but mass interference occurs between the Pt passivation layer and the surface layer leading to cracks or breaks
Solution Approach 1:
The patent changes the material parameters of the protection layer, selecting materials with appropriate atomic mass and density characteristics that prevent mass interference with the surface layer. By carefully selecting materials with suitable physical and chemical properties, the protection layer provides charge cancellation without causing the cracking and breaking issues associated with Pt passivation layers.
3Manufacturing precision
If FIB instrument is used to execute thinning process on device with polymer surface layer, then thinning is achieved, but the polymer surface layer is peeled off from the malfunction device
Solution Approach 1:
The protection layer acts as an intermediary barrier between the FIB process and the polymer surface layer. This intermediate layer protects the polymer from direct FIB bombardment that would otherwise cause peeling, while still allowing the FIB process to achieve the necessary thinning of the underlying device structure.
4Manufacturing precision
If conventional thinning methods are applied to prepare FA sample, then sample thinning is achieved, but cracks, distortion and collapse occur on the surface layer due to over etching, stress effect or charge accumulation
Solution Approach 1:
The protection layer is applied in advance to prevent morphological damage before it occurs. This preliminary protective measure prevents cracks, distortion, and collapse during the thinning process, preserving the surface layer morphology for accurate failure analysis.
Solution Approach 2:
The protection layer provides beforehand cushioning against the harmful effects of FIB thinning, chemical etching, and mechanical polishing. This cushioning effect absorbs and distributes stresses that would otherwise cause surface layer damage, maintaining morphological integrity throughout the sample preparation process.
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 protection layer ensures successful FIB thinning without cracks or distortion, enabling effective failure analysis and improving the yield of mass transfer processes for microLED and VCSEL devices by providing a stable surface for analysis.
Implementation Method 1
A protection layer comprising a first thin film, a buffer thin film, and a second thin film made of metal oxides, sulfides, selenides, or nitrides is applied to the semiconductor device surface, preventing cracks and distortion during FIB thinning
Implementation Method 2
a malfunction device is arranged to receive a thinning process by using a FIB instrument
Data Source
AI summary
A protection layer for use in fabrication of failure analysis (FA) sample is disclosed, which principally comprises a first thin film, a buffer thin film and a second thin film By forming the protection layer on a surface of a malfunction device die, a FA sample of the malfunction device die is obtained. As a result, in the case of treating the sample with a FIB thinning process, there are no cracks, distortion, and/or collapse resulted from inter-elemental isobaric interferences, stress effect or charge accumulation occurring on the surface layer of the malfunction device die because of the protection of the protection layer. On the other hand, this protection layer can also be applied to a microLED element or a VCSEL element, so as to make microLED element and the VCSEL element possess excellent stress withstanding capability.