Ion Beam Imaging for Cross-Depth Overlay Measurement
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Solution Overview
Problem
Current FIB-SEM systems face challenges in accurately measuring overlay positions of structural objects at different depths within semiconductor devices due to oblique processing surfaces, stage drift, and the need for time-consuming sample preparation, which affects resolution and processing efficiency.
Innovation Solution
An ion beam device that uses a gas field ionization source to switch between hydrogen and neon ion beams for observation and processing, allowing for precise relative positional measurements by comparing pre- and post-processing images, thereby enabling efficient and accurate three-dimensional structure analysis without damaging the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If FIB-SEM is used to obtain three-dimensional structure information, then sample processing capability is improved, but SEM resolution is sacrificed
Solution Approach 1:
The patent divides the imaging task into two separate systems: a FIB system for sample processing and a SIM system for high-resolution imaging. This segmentation allows each system to be optimized independently, with the SIM providing high-resolution images without the resolution compromise inherent in combining FIB and SEM in a single system.
Solution Approach 2:
The patent introduces a SIM (scanning ion microscope) as an intermediary system between the FIB and the final image acquisition. The SIM acts as a mediator that captures high-resolution images of the processed sample without the resolution-degrading effects present in traditional FIB-SEM systems, thereby resolving the contradiction between processing capability and image resolution.
2Measurement precision
If TEM is used to observe thin film samples, then three-dimensional information is obtained, but time-consuming sample preparation is required
Solution Approach 1:
The FIB system performs preliminary sample processing by creating cross-sections and thinning samples in-situ before imaging. This preliminary action prepares the sample in a controlled manner, eliminating the need for time-consuming manual sample preparation required by TEM while still enabling high-quality three-dimensional observation.
Solution Approach 2:
The patent merges the FIB sample preparation capability with the SIM high-resolution imaging capability in a single integrated system. This combination allows samples to be prepared and imaged without removal, eliminating the time-consuming separate sample preparation step required by TEM while maintaining the ability to obtain high-quality three-dimensional information.
3Productivity
If heavy ions are used for sample processing, then processing speed is increased, but sample damage is caused
Solution Approach 1:
The patent changes the ion species parameter dynamically based on the processing stage. Heavy ions (e.g., Ga+, Ar+) are used during initial material removal to achieve high processing speed, while light ions (e.g., He+, Ne+) are used during final precision processing and imaging to minimize sample damage. This parameter change allows the system to optimize for speed when needed and for precision when needed.
Solution Approach 2:
The system dynamically switches between different ion species during the processing sequence. The ion beam characteristics are adjusted in real-time based on the processing requirements, transitioning from aggressive heavy ion removal to gentle light ion refinement. This dynamic adaptation allows the system to achieve both high processing speed and high precision without compromising sample integrity.
4Object-affected harmful factors
If light ions are used for observation, then sample damage is reduced, but processing speed decreases
Solution Approach 1:
The patent segments the overall processing task into two distinct phases: a rough processing phase using heavy ions for high-speed material removal, and a precision processing/imaging phase using light ions for low-damage refinement. This segmentation allows each ion type to be used in the context where it is most effective, achieving both high speed and high precision without compromise.
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 device achieves rapid, low-damage processing and high-resolution three-dimensional structure analysis by stabilizing the ion beam current and preventing bubbling phenomena, allowing for precise positional measurements and improved throughput in semiconductor device inspection.
Implementation Method 1
The GFIS preferably applies a high voltage to a metal emitter tip having a curvature radius of about 100 nm or less at an end, causes an electric field to concentrate at the end, introduces a gas (ionized gas) into the vicinity of the end, ionizes gas molecules, and extracts the ionized gas as an ion beam.
Implementation Method 2
a device that focuses an ion beam through an electrostatic lens, and irradiates the sample with the ion beam to finely process an irradiated position is called a focused ion beam (FIB) device.
Implementation Method 3
extracting ions having a large mass such as neon or argon when it is desired to process the sample surface, damage to the sample at the time of observation can be reduced, and conversely, a processing speed at the time of processing the sample can be increased.
Data Source
AI summary
An object of the invention is to provide an ion beam device that can measure structures existing at different positions in a thickness direction of a sample. The ion beam device according to the invention irradiates a sample with an ion beam obtained by ionizing elements contained in a gas. After obtaining a first observation image of a first shape of a first region using a first ion beam, the ion beam device processes a hole in a second region of the sample using a second ion beam, and uses the first ion beam on the processed hole to obtain a second observation image of a second shape of the second region. By comparing the first observation image and the second observation image, a relative positional relation between the first shape and the second shape is obtained (refer to FIG. 7C).