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SEM Enables Rapid Subnanometer 3-D Surface Imaging
July 6, 2008
As critical dimensions shrink and new materials are introduced, traditional SEMs are running out of steam, making increasingly smaller features more difficult to image, especially as material contrast becomes more challenging. Dedicated ultra-high-resolution SEMs on the market can solve some of these problems, but can be complicated to operate and might have stringent sample preparation requirements. Also, some are optimized for high-resolution imaging at beam currents greater than 10 kV and, when dealing with these kinds of features, lower electron-beam energies are preferable to minimize sample damage, charging, and sample penetration.
FEI Company, (Hillsboro, Oregon), has introduced a new class of instruments—their Magellan family—which it describes as extreme high-resolution scanning electron microscopes (XHR SEMs). The Magellan XHR SEM enables scientists and engineers to quickly see things they could not see before, such as 3-D surface images at different angles and at resolutions below 1 nm. An important feature of the system is that it images samples at very low beam energies, avoiding distortions otherwise caused by a higher-energy beam penetrating into the material.
The Magellan XHR SEM. Source: FEI Company.
According to the company, the Magellan XHR SEM is the only family of instruments to make sub-nanometer resolution accessible in a practical way to non-experts, without restriction on samples. These constraints have previously limited the utility and acceptance of other systems. Sub-nanometer resolution is of critical value in scientific research and industrial R&D, and in the advanced semiconductor manufacturing sector is an absolute requirement in process development, monitoring and control applications. The new systems extend this capability to applications that were previously impossible or impractical with conventional SEM, TEM, or FIB platforms.
Process development labs need better imaging to test and analyze new materials and processes for future nodes, while logic manufacturers need high-resolution 3-D surface imaging at 32 nm and below. Sub-nanometer resolution on large samples, such as cross sections, in an analytical chamber simplifies fast sample transfer and high throughput. As they design new 3-D gate structures, logic manufacturers need to quickly look at material interfaces and profiles. Lower beam energies allow top surface imaging of devices and damage-free imaging of sensitive resist and dielectrics. Manufacturing support labs need better imaging at higher throughput to support faster ramp-to-volume for new devices. Memory manufactures require high resolution and high contrast imaging. UHR SEMs cannot see these fine structures at less than 5 kV; an XHR SEM can see them at 1 kV and below.
XHR SEM image showing a deprocessed sample stripped back to the polysilicon
level. The image is 1 kV at 300,000x. Source: STMicroelectronics, Malta/Grenoble.
The capability to provide sub-nanometer resolution over a broad range of beam energies, from ~1 kV to 30 kV, allows semiconductor manufacturers to see critical detail on complex 3-D structures at the 32-nm node and below, with exceptional clarity and contrast. Researchers working in materials science will now have the ability to generate high-resolution, surface-sensitive images of carbon nanotubes, nanowires and catalysts without the image distortions that can result from electrical charging from higher energy electron beams. Across the board, the Magellan family extends the range of nanoscale imaging and analysis, with the speed and simplicity of traditional SEMs.
The platforms are a result of the integration of new electron optical elements, proprietary electron-gun technology, a very accurate five-axis tilting/rotating piezo-ceramic stage to keep the area of interest in view, and a high-stability platform with a fully configurable analytical chamber. The stage accommodates large samples or multiple smaller samples, while providing fast, accurate navigation and stability.
The Magellan family comes in two models: the 400 is optimized for scientific research while the 400L is configured for semiconductor labs. The semiconductor lab model comes with a load-lock feature that speeds up sample throughput, and includes a retractable solid-state backscatter electron detector and S2 compliance kit. Both models have an optional full environmental enclosure to isolate the instrument from thermal and acoustic interferences, ensuring peak performance while relaxing site requirements and facility preparation costs.
Posted by Alexander E. Braun on July 6, 2008 | Comments (0)
