NPGS

By JC Nabity Lithography Systems

NPGS is the lowest cost high performance lithography system for SEM/STEM/FIB microscopes that is available. An SEM lithography system is a tool which can be used in a wide variety of applications. The basic lithography process allows patterns to be defined on a flat surface. The subsequent processing, such as metal evaporation or etching, will determine the final structure. NPGS is unique in that it provides a very flexible system which is ideally suited to the wide range of activities in basic research and R&D activities. Examples of some of the structures made with NPGS include: single electron devices, quantum chaos devices, quantum dots, tunnel junctions, one and two dimensional metal wires/films, linear/circular gratings, surface acoustic wave (SAW) devices, split gate devices, as well as "larger" structures such as micromechanical devices, waveguides, and bonding pads. Since NPGS is so versatile, it is well suited for use in almost any application that can be done with e-beam lithography. The primary exceptions are structures covering large areas which require the capabilities of a multi-million dollar beam writer. However, in some cases, the many advanced features of NPGS allow it to be used to fabricate structures that are more difficult to make on an expensive beam writer. NPGS can also be used for lithography with a Focused Ion Beam (FIB) system. In fact, a single NPGS installation can be configured with a dual mode to control either the electron beam or the ion beam on dual FIB/SEM systems, including the Nova Nanolab and Helios models from FEI and the Crossbeam and Auriga models from Zeiss. The NPGS License agreement gives the original buyer full rights to use the "Microscope Installation" of the NPGS software without any time limitations, as long as it is only installed on a single PC. The PC with the "Microscope Installation" (which contains the NPGS hardware) may be moved between different microscopes (which may require different sets of cables/connections) or may be connected simultaneously to two microscopes if they are near each other (with the NPGS Output Relay Box, which allows use of one microscope or the other for lithography). Having simultaneous connections is especially useful for dual beam ion/electron microscopes. The NPGS License agreement allows unlimited "Office Installations" of the NPGS software which may be used within the university or organization where NPGS is installed. The "Office Installation" allows full pattern and run file design/edit/simulation capabilities, but has no pattern writing capabilities, since no NPGS hardware is used. NPGS also ships with a site license of QCAD Professional which is used for pattern design within NPGS. For universities, the QCAD site license allows unlimited installations. For other organizations, it allows 20 installations. Having multiple "Office Installations" of NPGS and QCAD make it easy for each NPGS user to do pattern design away from the microscope. The ultimate writing resolution depends on the SEM in use, the resist, and the operator's skill at optimizing the SEM. With NPGS, features of 20 nm and less are routinely written when using a thermal FE SEM, 30 nm and less when using a 40 kV conventional SEM, and even smaller when using a high voltage STEM. NPGS uses a true vector writing mode which gives the user the maximum control over the beam. For example, the beam will move along sloped lines and tangent to arcs and circles. Also, when filling arbitrary polygons, the beam will sweep parallel to one side of the polygon as specified by the user. This approach enhances the exposure quality over systems using a simple xy raster method or one that breaks each arbitrary polygon into trapezoids with different scan directions. In addition to the vector writing mode, NPGS also provides a raster mode for writing bitmaps which can be useful for FIB milling. NPGS only runs on a PC running the Windows operating system, however, pattern files can be created on other systems and transferred to NPGS to be written.