Fixed-Column FIB Milling with Rotating Stage for TEM Lamellae
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Solution Overview
Problem
Current methods for preparing thin samples for transmission electron microscopy (TEM) are labor-intensive and time-consuming, especially for semiconductor manufacturing, where features below 30 nm require ultra-thin lamellae, and are prone to defects like curtaining and tapering, which reduce the quality of analysis.
Innovation Solution
A method and apparatus that use a focused ion beam system with a fixed FIB column and a sample stage that can rotate about a single axis, allowing for angled milling without tilting the sample, and employing dual FIB columns to create flat-sided cuts and reduce curtaining effects by adjusting the milling angle and rotation angle to maintain a constant curtaining angle throughout the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional FIB milling methods are used to prepare thin samples for TEM, then material can be removed from the substrate, but the sample preparation is labor-intensive and time-consuming
Solution Approach 1:
The invention introduces a rotatable sample stage that enables dynamic adjustment of the substrate orientation during FIB milling. By rotating the sample stage, the system can mill multiple surfaces without requiring manual intervention or complex repositioning, thereby automating the sample preparation process and significantly reducing preparation time while maintaining high quality thin sample production
2Manufacturing precision
If conventional FIB milling is used to create thin lamellae, then samples can be thinned for TEM analysis, but defects like curtaining and tapering occur that reduce analysis quality
Solution Approach 1:
The invention employs asymmetric milling angles by directing the FIB beam at the substrate at angles other than perpendicular to the surface. This asymmetric approach prevents the formation of curtaining effects and tapering that occur with conventional normal-incidence milling, resulting in uniform thin lamellae without surface defects that would compromise TEM analysis quality
Solution Approach 2:
The invention adds the dimension of sample stage rotation to the conventional FIB milling setup. By rotating the sample stage around the beam axis, the system can mill different surfaces of the substrate sequentially, creating uniform thin samples from multiple orientations. This dimensional addition enables precise control over the milling process and eliminates defects caused by single-angle milling
3Manufacturing precision
If the FIB column is tilted to mill at angles, then curtaining effects can be reduced, but the device complexity increases with multiple tilting axes
Solution Approach 1:
Instead of tilting the FIB column to achieve angled milling, the invention inverts the approach by keeping the column fixed and normal to the substrate and instead rotating the sample stage. This reversal maintains device simplicity while achieving the same angled milling effect, as the relative angle between beam and surface is what matters for reducing curtaining
Solution Approach 2:
The sample stage serves multiple functions: it positions the substrate, orients it for milling, and rotates it to present different surfaces to the fixed FIB beam. This multi-functionality eliminates the need for complex column tilting mechanisms while achieving versatile angled milling capabilities across multiple surfaces
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 approach reduces the time and complexity of sample preparation, minimizes defects like curtaining, and improves the quality of TEM samples by maintaining a consistent milling angle and reducing redeposition of material, enabling more efficient analysis of small semiconductor features.
Implementation Method 1
a first particle source for emitting particles to mill features in a substrate; a first focusing column for forming the particles emitted from the first particle source into a first beam and directing the first beam to impinge upon the substrate
Data Source
AI summary
A system for creating a substantially planar face in a substrate, the system including directing one or more beams at a first surface of a substrate to remove material from a first location, the beam being offset from a normal to the first surface by a curtaining angle; sweeping the one or more beams in a plane that is perpendicular to the first surface to mill one or more initial cuts, the initial cuts exposing a second surface that is substantially perpendicular to the first surface; rotating the substrate about an axis other than an axis normal to the first beam or parallel to the first beam; directing the first beam at the second surface to remove additional material from the substrate without changing the curtaining angle; and scanning the one or more beams in across the second surface to mill one or more finishing cuts.