FIB Delayering Endpoint Detection via RGA Sputtered Byproduct Monitoring
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Solution Overview
Problem
Existing techniques for endpointing milling processes in electronic structures, such as silicon wafers, lack precision in detecting transitions between different material layers, leading to inefficiencies in failure analysis and device validation.
Innovation Solution
The use of a residual gas analyzer (RGA) to monitor by-products of the milling process, specifically analyzing the output signal to detect transitions between layers, allowing for precise endpointing of the milling process by identifying changes in partial pressures of atoms and molecules, with options for time-of-flight or quadrupole RGA units depending on the need for simultaneous or sequential mass analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional milling endpoint detection techniques are used, then the milling process can be stopped, but the detection precision of layer transitions is insufficient
Solution Approach 1:
The patent introduces a residual gas analyzer (RGA) as an intermediary detection device that monitors the milling process indirectly by analyzing gas phase by-products. The RGA detects changes in partial pressures of sputtered atoms and molecules, which serve as intermediate indicators of layer transitions, thereby improving detection precision without directly interfering with the milling process
Solution Approach 2:
The system implements real-time feedback by continuously monitoring RGA signals during milling and using this information to control the milling endpoint. The feedback loop compares detected partial pressure changes against expected layer transition signatures, enabling precise and reliable endpoint detection that adapts to actual process conditions
2Adaptability or versatility
If a time-of-flight RGA unit is used to monitor multiple elements simultaneously, then adaptability improves, but analysis speed decreases compared to quadrupole RGA
Solution Approach 1:
The patent dynamically selects between TOF and quadrupole RGA modes based on the specific detection requirements. TOF mode is activated when broad elemental coverage and adaptability are needed, while quadrupole mode is used when rapid sequential analysis of known targets is required, optimizing the balance between versatility and speed for each detection scenario
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 accurate and efficient endpointing of milling processes, ensuring that specific layers are reached during material analysis, improving the precision of failure analysis and device validation in electronic structures.
Implementation Method 1
milling a region of the sample by scanning a focused ion beam over the region a plurality of iterations in which, for each iteration, the focused ion beam removes material from the sample generating byproducts from the milled region
Implementation Method 2
A TOF RGA unit can monitor and detect atomic masses of multiple different elements simultaneously
Implementation Method 3
A quadrupole RGA unit detects atomic masses sequentially, one mass at a time, which in some instances can provide a faster mass analysis signal than a TOF RGA
Data Source
AI summary
A method of milling a sample that includes a first layer formed over a second layer, where the first and second layers are different materials, the method comprising: milling the region of the sample by scanning a focused ion beam over the region a plurality of iterations in which, for each iteration, the focused ion beam removes material from the sample generating byproducts from the milled region; detecting, during the milling, the partial pressures of one or more byproducts with a residual gas analyzer positioned to have a direct line of sight to the milled region; generating, in real-time, an output detection signal from the residual gas analyzer indicative of an amount of the one or more byproducts detected; and stopping the milling based on the output signal.