AND TABAT Theory and Experimental Results of a New Diamond Surface-Emission Cathode nikolay n. efremow, jr. is an assistant staff member in the Submicrometer Technology group, where he fabricates and characterizes diamond emitters for flat-panel displays.

■ A new electron-emission mechanism combines the enhanced electric field of a triple junction at the intersection of metal and diamond interfaces in vacuum with the negative electron affinity (NEA) of the diamond surface. This new surface-emission mechanism is compared to two common cathode mechanisms—geometric electric-field enhancement and Schottky-diode electricfield enhancement with an NEA semiconductor. Unlike these two mechanisms, in which electrons tunnel from metal into vacuum or into the conduction band of an NEA semiconductor, in our mechanism electrons tunnel from metal into surface states at the interface of an NEA semiconductor and a vacuum. Once in these states, the electrons are accelerated to sufficient energies to be emitted from the surface into vacuum. New cathodes designed to maximize the surface-emission mechanism exhibit improved consistency and reduced operating voltage when compared to cathodes that use other mechanisms. Gated surface-emission cathodes emit measurable current densities greater than 10 –6 A m –2 at gate voltages of 3 to 4 V

• ROTHSCHILD ET AL. Recent Trends in Optical Lithography Recent Trends in Optical Lithography

■ The fast-paced evolution of optical lithography has been a key enabler in the dramatic size reduction of semiconductor devices and circuits over the last three decades. Various methods have been devised to pattern at dimensions smaller than the wavelength used in the process. In addition, the patterning wavelength itself has been reduced and will continue to decrease in the future. As a result, it is expected that optical lithography will remain the technology of choice in lithography for at least another decade. Lincoln Laboratory has played a seminal role in the progress of optical lithography; it pioneered 193-nm lithography, which is used in advanced production, and 157-nm lithography, which is under active development. Lincoln Laboratory also initiated exploration of liquidimmersion lithography and studied the feasibility of 121-nm lithography. Many of the challenges related to practical implementation of short-wavelength optical lithography are materials-related, including engineering of new materials, improving on existing materials, and optimizing their photochemistry. This article examines the technical issues facing optical lithography and Lincoln Laboratory’s contributions toward their resolution. Optical lithography, the technology of patterning, has enabled semiconductor devices to progressively shrink since the inception of integrated circuits more than three decades ago. Throughout the 1980s and 1990s, the trend of miniaturization continued unabated and even accelerated. Current semiconductor devices are being mass produced with 130-nm dense features; by 2007 these devices will have 65-nm dense features. Optical lithography has been, and will remain for the foreseeable future, the critical technology that makes this trend possible. (To learn the fundamentals of optical lithography, see the sidebar entitled “Optical Lithograph