FEI's Magellan SEM provides higher resolutions at lower energy levels to create undistorted images of the next generation of semiconductor devices.
FEI's Magellan SEM provides sub-nm resolution for inspecting the complex 3-D surfaces in a semiconductor. Image: STMicroelectronics, Malta/Grenoble.
Microscope manufacturers continue to push the limits of their instruments with new technologies. Developers at FEI Co., Hillsboro, Ore., Eindhoven, The Netherlands, and Bruno, Czech Republic, have created a new scanning electron microscope (SEM) with extremely high resolution and the ability to produce images at very low beam energies. The low beam energies avoid the distortions that are traditionally created with higher energy SEMs that penetrate the material below the sample surfaces.
FEI's Magellan XHR SEM (extreme high resolution SEM) family of microscopes allows researchers to see 3-D surface images at many different angles at sub-nm resolutions. Two Magellan models are available-the 400, optimized for scientific research, and the 400L, optimized for use in semiconductor device applications.
The Magellan's sub-nm resolution is obtainable at beam energies of less than 1 keV up to 30 keV. This level of resolution allows semiconductor manufacturers to examine the details of complex 3-D structures in 32-nm feature size devices with unprecedented clarity and contrast. Existing systems that are capable of providing this same level of resolution had to be optimized at beam currents greater than 5 keV and often up to 10 keV. The images produced from these higher beam currents also have less surface detail (than is available on Magellan). The higher beam current systems also have stringent sample preparation requirements.
The Magellan 400L system includes a large sample chamber with an automated load lock system. Lab engineers can load as many as 40 cleaved samples onto the system's five-axis piezo-ceramic 100-mm stage and begin imaging in less than 100 sec. The automated load lock can easily handle larger samples-up to 100-mm dia. The high-precision stage can also be tilted and rotated. The automated load lock reduces chamber pump down times to maximize sample throughput.
The 400L also is equipped with 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 the site requirements and facility preparation costs.
Numerous improvements
To obtain the Magellan's performance characteristics, FEI developers redesigned or modified many areas of the SEM:
• New gun technology for optimized imaging.
• A beam deceleration capability was added for operating in the low voltage regime to improve the system's surface imaging and contrast capabilities.
• The use of a Schottky emitter gun with hot-swap capabilities gives the system the highest stability emission and high beam current modes.
• A two-mode final lens was designed (including the immersion lens) to allow for secondary electron collection in samples in flat and tilted positions and at larger working distances.
• Constant power lenses give the best beam stability during operation.
• The electrostatic scanning speed response times were made more linear than traditional magnetic scanning systems.
Providing higher resolution
The Magellan combines a number of technologies to provide the extreme high resolution capabilities. Its patented Unicolore (UC) technology, beam deceleration capabilities, and a new solid-state backscatter detector work together to maximize the system's resolution, sample surface details, and contrast at the low operating voltages. Newly designed constant power lenses optimize the beam stability during operation, and electrostatic scanning improves the system's response times.
The most innovative aspect of the Magellan's electron focusing column is its UC technology. In UC mode, the electron beam is focused through a small aperture that eliminates the most extreme components of the energy distribution. This results in a beam with an energy spread of less than 0.2 eV. In addition to providing reductions in the resultant spot size, UC mode also reduces the intensity of the electron beam "tails", further enhancing contrast and image quality.
The large current delivered by the Magellan's Schottky emitter and the efficient design of the electron gun ensure ample current in the UC mode for the Magellan's high-resolution applications. -Tim Studt
