Scanning Electron Beam Lithography (SEBL) Facility

In 2004, the Nanostructures Lab converted its scanning-electron-beam-lithography (SEBL) facility in Room 38-165 into an Institute-wide service facility under the Research Laboratory of Electronics (RLE). This facility provides MIT and outside users with easily accessible e-beam lithography, coupled with resident expertise and advise. The facility is managed by Mark Mondol who provides training on the e-beam tools, direct patterning service, and advise on optimal nanofabrication techniques and strategies. The Microsystems Technology Laboratories (MTL) has service facilities for spin coating of resists, resist development and other forms of processing.

Projects that made use of the SEBL facility during the past year included: graphene Josephson junctions; single-photon detectors; origami 3D folding membranes; quantum dots; III-V Mosfets; patterned nanotube growth;acoustic-wave resonators; relief templates for self assembly of block copolymers; point-contact devices; 1-D, 2-D and 3D photonic crystals; ring-resonator add/drop filters; optical-polarization splitter-rotator devices; magnetic-logic devices;; templates for nanoimprint lithography; photomasks for interferometric-spatial-phase-imaging alignment and gapping; 4-point contacts for measurements on nanotubes and nanowires; III-V compound T-gate HEMTs and arrays of Fresnel zone plates. Research in lithographic processing included salty development of HSQ (Hydrogen silsesquioxane) which demonstrated improved resolution and contrast. Use of the facility, by the MIT community, was widespread, there were: 45 Principal Investigators, 7 Departments, 8 Labs or Centers, 2 non-MIT entities and 65 distinct trained users over the last year.

In previous years, two SEBL tools were available: a Raith 150 and the VS-26, which was donated in the mid 1990’s by IBM. This year we were forced to decommission the VS 26 due to nonavailability of replacement parts. The laboratory is pursuing means of replacing the VS26 with a commercial system. The electron-optical column in the Raith 150 system is essentially identical to that of a Zeiss Gemini SEM, and provides a beam diameter as fine as 2 nm. Nested L patterns of 11 nm pitch, with linewidths ~ 5 nm have been written with the system. The Raith 150 includes a pattern generator and laser-interferometercontrolled stage with an integrated software package. Version 4.0 software now allows users to do automated field alignment to approximately ± 25nm. The system can operate from 1 to 30keV. Wafers up to 150 mm can be loaded into the system. Typically, users are trained for 4 to 10 hours and then allowed to operate the tool on their own. The tool is available, for most users, 24 hours a day, 7 days a week.

The Raith 150 is used in a program to develop spatial-phase-locked e-beam lithography, described elsewhere. The objectives of that program are to achieve sub-1 nm pattern-placement accuracy, and to reduce the cost and complexity of SEBL. In a conventional SEBL system costing several million dollars, pattern placement accuracy is typically much worse than 10 nm. The SEBL facility encourages users with a variety of experience levels and requirements. Experienced users are able to carry out complex, multilevel aligned exposures on the Raith-150 tool. Less experienced users get hands-on instructions from facility staff, and guidance during the learning and initial fabrication stages.