Next-gen, nanoscale transistors for integrated electronics

Electron beam (e-beam) lithography enables researchers to write very small patterns on large substrates with a high level of precision. E-beam writers are used in a variety of applications, from writing patterns on silicon and compound semiconductor chips for electronic device and materials research to genome sequencing platforms.

The Nano3 cleanroom facility at the Qualcomm Institute in the US now houses a new electron beam writer. But what’s unique about this writer is its ability to write patterns on a large scale - with minimum feature size of less than 8 nanometres on wafers with diameters that can be as large as 8 inches.

The writer is important for electrical engineering professor Shadi Dayeh’s two major areas of research. He is developing next-generation, nanoscale transistors for integrated electronics; and neural probes that have the capacity to extract electrical signals from individual brain cells and transmit the information to a prosthetic device or computer. Achieving this level of signal extraction or manipulation requires tiny sensors spaced very closely together for the highest resolution and signal acquisition.

Before the facility opened earlier this year, the closest comparable e-beam writer was in Los Angeles. In an e-beam writer, unique patterns are ‘written’ on a silicon wafer coated with a polymer resist layer that is sensitive to electron irradiation. The machine directs a narrowly focused electron beam onto the surface marking the pattern, making parts of the resist coating insoluble and others soluble. The soluble area is later washed away, revealing the pattern which can have sub-10 nanometre feature dimensions.

Bioengineering professor Todd Coleman will use the new e-beam writer as one essential step in the building of his epidermal, or tattoo, electronic devices. The devices are designed to acquire brain signals for a variety of medical applications, from monitoring infants for seizures in neonatal intensive care to studying the cognitive impairment associated with Alzheimer’s disease or dementia, and soldiers struggling with post-traumatic stress syndrome.

Electrical engineering PhD candidate Andrew Grieco is using the machine to develop a new type of optical waveguide that promises to improve efficiency and reduce power consumption. Grieco works in the laboratory of Shaya Fainman, professor and chair, Department of Electrical and Computer Engineering. Developing on-chip optical networking devices such as waveguides, switches and amplifiers is a critical step in the development of optical chips. Although information systems rely primarily on fibre-optic networks to connect and share data around the world, the underlying computer technology is still based on electronic chips, causing data traffic jams.

Dayeh said technologies enabled by the e-beam writer will be important in local efforts to conduct research under President Obama’s BRAIN Initiative, which will require developing much smaller sensing and stimulating elements with higher resolution on chips the size of a few millimetres.

Electron beam facility is open for business

UC San Diego’s new Vistec Lithography EBPG5200 electron beam writer is available for use by campus researchers, as well as industry and research partners. The e-beam writer, used for nano- and microfabrication is a new addition to the Qualcomm Institute’s Nano3 facility, which provides a synergistic environment for fundamental research and development efforts at the nanoscale with a focus on nanoscience, nanoengineering and nanomedicine. In addition to providing essential nanofabrication capabilities for research on electronic and photonic materials and devices, Nano3 facilitates the pursuit of research in emerging, interdisciplinary and rapidly growing fields such as biomedical and biochemical devices, monolithic and heterogeneous integrated electronic and photonic devices and circuits, and sensor technology.