Volume 33, Issue 6, November 2015
Index of content:
- 59th International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication
- EIPBN Invited Articles
Direct fabrication of high aspect-ratio metal oxide nanopatterns via sequential infiltration synthesis in lithographically defined SU-8 templates33(2015); http://dx.doi.org/10.1116/1.4929508View Description Hide Description
Nanopatterning high aspect-ratio metal oxide structures remains challenging for conventional nanofabrication methods based on reactive ion etching due to marginal etch selectivity between target oxides and typical mask materials. Here, the authors report the application of sequential infiltration synthesis (SIS) on lithographically defined SU-8 polymer templates for patterning arbitrarily designed, high aspect-ratio metal oxide nanostructures with sub-50 nm linewidths, smooth vertical profiles, and three-dimensional (3D) morphologies difficult to achieve by the conventional fabrication methods. As examples, various AlOx nanostructures with ∼40 nm linewidths and up to 16 aspect ratios were demonstrated, along with TiOx in-plane nanowire arrays of controlled positional registrations. Detailed scanning and transmission electron microscopy studies revealed nanocrystalline and amorphous internal structures of respective AlOx and TiOx, as well as the swelling and contraction behaviors of polymer templates during the SIS process, which allowed the facile fabrication of high aspect-ratio, sub-50 nm-featured oxide nanopatterns with 3D morphologies. These results confirm the potential of vapor-phase material infiltration in directly nanopatterning complexly structured metal oxides.
- Beam Induced Deposition and Etching
Enhancement of XeF2-assisted gallium ion beam etching of silicon layer and endpoint detection from backside in circuit editing33(2015); http://dx.doi.org/10.1116/1.4928744View Description Hide Description
Within the semiconductor industry, backside circuit editing is the process of modifying individual nanometer-scale devices after they have been fabricated by conventional mass production techniques. The technique includes the removal of bulk silicon, to reach the devices, followed by the removal of small and precisely defined volumes of silicon and other materials. It also includes the ability to deposit precise patterns of conductors or insulators to modify the devices in question. Essential to the circuit edit processes are the focused ion beam (FIB) instruments, usually providing a gallium ion beam, to sputter away the volumes which need to be removed. When used in conjunction with specific “precursor” gases, the FIB instrument can deposit metals and insulators in arbitrary patterns to achieve the desired circuit repair or modification. Other gases, such as xenon difluoride (XeF2), can work in conjunction with the FIB to improve the effectiveness and the rate of material removal. Our experimental investigation found that the removal rate of backside silicon by a gallium FIB could be enhanced by 100 times when used in conjunction with the XeF2 gas. The XeF2 also reduced the redeposition of the removed silicon material, making the removal more effective. And importantly, the production of secondary electrons was found to offer a viable endpoint signal to indicate the transition to a new material.
Charging suppression in focused-ion beam fabrication of visible subwavelength dielectric grating reflector using electron conducting polymer33(2015); http://dx.doi.org/10.1116/1.4929152View Description Hide Description
Nanoscale periodic patterning on insulating materials using focused-ion beam (FIB) is challenging because of charging effect, which causes pattern distortion and resolution degradation. In this paper, the authors used a charging suppression scheme using electron conducting polymer for the implementation of FIB patterned dielectric subwavelength grating (SWG) reflector. Prior to the FIB patterning, the authors numerically designed the optimal structure and the fabrication tolerance for all grating parameters (period, grating thickness, fill-factor, and low refractive index layer thickness) using the rigorous-coupled wave analysis computation. Then, the authors performed the FIB patterning on the dielectric SWG reflector spin-coated with electron conducting polymer for the anticharging purpose. They also performed similar patterning using thin conductive film anticharging scheme (30 nm Cr coating) for comparison. Their results show that the electron conducting polymer anticharging scheme effectively suppressing the charging effect during the FIB patterning of dielectric SWG reflector. The fabricated grating exhibited nanoscale precision, high uniformity and contrast, constant patterning, and complied with fabrication tolerance for all grating parameters across the entire patterned area. Utilization of electron conducting polymer leads to a simpler anticharging scheme with high precision and uniformity for FIB patterning on insulator materials.
- Electron Beam Lithography
33(2015); http://dx.doi.org/10.1116/1.4927639View Description Hide Description
Electron-beam direct-write lithography systems must in the future transmit terabits of information per second to be viable for commercial semiconductor manufacturing. Lossless layout image compression algorithms with high decoding throughputs and modest decoding resources are tools to address the data transfer portion of the throughput problem. The earlier lossless layout image compression algorithm Corner2 is designed for binary layout images on raster-scanning systems. The authors propose variations of Corner2 collectively called Corner2-EPC and Paeth-EPC which apply to electron-beam proximity corrected layout images and offer interesting trade-offs between compression ratios and decoding speeds. Most of our algorithms achieve better overall compression performance than portable network graphics, Block C4, and LineDiffEntropy while having low decoding times and resources.
- Optical and Extreme UV (EUV) Lithography
33(2015); http://dx.doi.org/10.1116/1.4929509View Description Hide Description
The Semiconductor High-Numerical-aperture (NA) Actinic Reticle Review Project (SHARP) is an extreme ultraviolet (EUV)-wavelength, synchrotron-based microscope dedicated to advanced EUV photomask research. The instrument is designed to emulate current and future generations of EUV lithography (EUVL). The performance of the SHARP microscope has been well characterized for its low-NA lenses, emulating imaging in 0.25 and 0.33 NA lithography scanners. Evaluating the resolution of its higher-NA lenses, intended to emulate future generations of EUV lithography, requires a photomask with features down to 22-nm half pitch. The authors fabricated a sample with features down to 20-nm half pitch, exposing a wafer with a standard multilayer coating in the Berkeley microfield exposure tool, and used it to demonstrate real-space imaging down to 22-nm half pitch on the SHARP microscope. The demonstrated performance of SHARP's high-NA zoneplates, together with the extended capabilities of the tool, provide a platform that is available today, suited for research targeted at upcoming generations of EUVL many years into the future.