Nanofabrication and diffractive optics for high-resolution x-ray applications

Short wavelength x-ray radiation microscopy is well suited for a number of material and life science studies. The x-ray microscope (XM1) at the Advanc ed Light Source Synchrotron in Berkeley, California uses two diffractive Fr esnel zone plate lenses. The first is a large condenser lens, which collect s soft x-ray radiation from a bending magnet, focuses it, and serves as a l inear monochromator. The second is the objective zone plate lens, which mag nifies the image of the specimen onto a high-efficiency charge coupled devi ce detector. The objective lens determines the numerical aperture and ultim ate resolution. New objective lens zone plates with a minimum linewidth of 25 nm and excellent linewidth control have been fabricated using Berkeley L ab's 100 keV Nanowriter electron beam lithography tool, a calixarene high-r esolution negative resist, and gold electroplating. Although the condenser zone plate is less critical to the resolution of the instrument, its effici ency determines the flux on the sample and ultimately the exposure time. A new condenser zone plate was fabricated and has a 9 mm diameter, 44 000 zon es, and a minimum zone width of 54 nm (optimally the condenser and objectiv e should have the same zone width). It is also fabricated with the Nanowrit er at 100 keV using poly(methylmethacrylate) resist and nickel electroplati ng. The phase shift through the nickel absorber material enhances the diffr action efficiency over an amplitude only zone plate. To evaluate the micros cope's performance transmission test patterns have been made and imaged. Li neout data show modulation for 30 nm lines and 60 (1:2) spaces to be almost 100%. These new diffractive optical elements represent a significant advan cement in the field of high-resolution soft x-ray microscopy. Diffractive o ptical elements have been used to measure the wave front error of an extrem e ultraviolet projection optical system. The reference wave is generated by the spherical wave generated by diffraction from a small freestanding pinh ole. (C) 2000 American Vacuum Society. [S0734-211X(00)11106-0].