Dabrina D. Dutcher

Experimental Investigations on Particle Contamination of Masks Without Protective Pellicles During Vibration or Shipping of Mask Carriers

Extreme ultraviolet lithography (EUVL) is considered the next generation lithography to produce 32-nm feature-size or smaller. The challenge is that conventional pellicles are unavailable for protecting the EUVL masks against contaminant particles, because the EUV beam is easily absorbed by most solid materials. The masks are usually transported or stored in mask carriers. Without the protective pellicles, particles generated inside the mask carrier may deposit on the critical surface of the mask. It is therefore important to identify where the particles are generated inside the mask carrier during shipping. In this paper, two shipping carrier models of different mask holder designs were used. The mask carriers with quartz mask blanks inside were shaken manually, vibrated with a computer-controlled vibration table, or shipped via air freight. In order to simulate the EUVL mask shipping, no pellicles were used. Several online and offline particle detection techniques were employed to investigate particle generation inside the mask carrier during vibration or shipping. It was shown that particles were mostly generated at the contact points between the mask surface and the carrier element. The design of the mask-holding element in the mask carrier played an important role in reducing particle generation.

Fine-particle emissions from solid biofuel combustion studied with single-particle mass spectrometry: Identification of markers for organics, soot, and ash components: CHEMISTRY OF BIOMASS COMBUSTION AEROSOLS

An increased use of biofuels in residential heating is desired to decrease net emissions of green house gases, such as CO2 to the atmosphere. This includes conventional woody biofuels, as well as novel crop fuels such as corn. It is well established that the particle emissions during less optimised combustion in small scale wood combustion are most often dominated by products of incomplete combustion, i.e. organic and elemental carbon (OC/EC), McDonald et al. (2006). In contrast during optimised combustion in modern domestic pellet combustion systems, the aerosol can be dominated by ash compounds, especially KCl and K2SO4 formed via heterogeneous reactions in the gas-phase. However, little research has focused on the variations in physical and chemical particle properties over the combustion cycle This is partly due to the lack of experimental methods with sufficient time resolution to follow the inherently transient nature of batch wise wood log combustion. Further, little information is available on emissions from novel fuels such as corn. For example, corn has higher ash content than conventional wood fuels. In this work we used an Aerosol Time-ofFlight Mass Spectrometer (TSI Inc., Shoreview, MN, USA) to study chemical signatures of single particles from three wood log fuels (oak, pine and birch) and corn. The instrument was equipped with an aerodynamic focusing lens inlet. The wood fuels were combusted in a conventional wood stove, while the corn was combusted in a commercially available corn stove, which operates similarly to modern wood pellets stoves. Each wood-combustion experiment involved start-up from a cold stove with a full load of fuel. Fuel was then added once and experiments were conducted until only glowing embers remained. Particles were sampled and diluted with particle free air using a three stage dilution system which allowed dilution ratios between 1:10 and 1:10000. In a few experiments a Differential Mobility Analyzer was used upstream of the ATOFMS to determine the particles effective density. A Scanning Mobility Particle Sizer was used to determine the particle size distribution (20-800 nm). A gas analyzer (TSI CA-6215) was used to determine the flue gas composition (O2, NOx, CO). Preliminary results show clear differences in the particle composition between: