A Dual-Magnetron Deposition System (DMDS) is built up at the Plasma Material Interaction (PMI) group at University of Illinois at Urbana-Champaign (UIUC). The system uses two 2″-diameter DC magnetrons (DCMs) to deposit up to two sputtering materials simultaneously. DMDS includes a ultra high vacuum (UHV) chamber, two mass flow controllers (MFCs) to control the operation gas flow rate, a quartz crystal microbalance (QCM) to monitor the film deposition thickness, a residual gas analyzer (RGA) to monitor the partial pressures, two DC power supplies to provide up to 1 kV and 200 mA of current to DCMs, a DC power supply to bias the substrate holder and films on it for a high quality film fabrication, a stepper motor to rotate the samples during deposition for better film uniformity, an array with two 300 W halogen lamps sitting behind the substrate holder to bake and heat the system, some shields and shutters placed for the purpose of preventing the over heating, protecting the unexpected deposition or pre-sputtering the targets.

A critical issue for EUV lithography (EUVL) (refer to XCEED project) and high volume manufacturing (HVM) is the minimization of collector or thin film degradation from intense plasma erosion and debris dep

osition. Collector optic reflectivity and lifetime will be heavily dependent on surface chemistry interactions between fuels and various mirror materials, such as silicon, in addition to high-energy ion and neutral particle erosion effects. The criterion of a mirror film used for EUV collector optic is strictly limited at high quality. The key requirements are low surface roughness, dense structure, less columnar grains, and oxygen-free. Of course, a thin, smooth and uniform film is desired. DMDS has been developed to fabricate the commercial-level collector mirrors, high quality thin films and to study the detailed effects that high energy debris for the plasma EUV source on them. The appropriate fabricating equipment and corresponding solutions to the above challenges will be investigated by the extensive DMDS experiments.

To reduce the oxygen and other impurity contents, we maintain DMDS at UHV of a base pressure of low 10-9 Torr. The colu

mnar structure or fiber texture could be minimized by heating and biasing the sample during deposition. High energy ions will be induced by this negative bias to bombard the surface during the deposition to break up the columnar structures and suppress local epitaxial growth. The high pre-heated substrate temperature will increase the mobility of the implanted ions to reduce trapping and induced stresses in the film, as well as to prevent H2O layer and improve the film quality according to Thornton diagram. The sputtering target will be cleaned at higher power levels through at least 15-minute pre-sputtering with a closed shutter to remove the surface oxide and contamination layer. The samples held on the substrate holder will be rotated by programming stepper motor to uniform the deposition from dual magnetrons. The pressure of the ultra high purity (UHP) operation gas is controlled below 2 mTorr.

The fabricated and exposed samples will be experimentally analyzed using a variety of surface characterization techniques at the Center for Microanalysis of Materials. Film thickness was measured by looking at a high resolution cross section of the film with Scanning Electron Microscopy (SEM). Film composition was measured by a surface sensitive technique, Auger Electron Spectroscopy (AES). Depth profiling can be obtained to trace the changes of film compositions and their atomic concentrations. Surface roughness can limit reflectivity of surfaces, particularly in the case of a grazing incidence collector. Atomic Force Microscopy (AFM) is used to measure surface height variations over several different lateral length scales.