The Mo/Si multilayer mirrors used for extreme ultraviolet (EUV) lithography can become contaminated during exposure in the presence of some hydrocarbons [1][2][3]. Because this leads to a loss in the reflectivity of the optics and throughput of the exposure tools, it needs to be avoided. Since photoresists are known to outgas during exposure to EUV radiation in a vacuum environment, the careful choice of materials is important to preserving the EUV optics. Work therefore has been performed to measure the species and quantities of molecules that outgas from EUV resists when exposed to EUV radiation [4][5][6][7].

The development of resists that meet the requirements for resolution, line edge roughness and sensitivity remains one of the challenges for extreme ultraviolet (EUV) lithography. Two important processes that contribute to the lithographic performance of EUV resists involve the efficient decomposition of a photoacid generator (PAG) to yield a catalytic acid and the subsequent deprotection of the polymer in the resist film. We investigate these processes by monitoring the trends produced by specific masses outgassing from resists following EUV exposure and present our initial results. The resists tested are based on ESCAP polymer and either bis(4-tert-butylphenyl)iodonium perfluoro-1-butanesulfonate or bis(4-tert-butylphenyl)iodonium triflate. The components originating from the PAG were monitored at various EUV exposure doses while the deprotection of the polymer was monitored by baking the resist in vacuum and detecting the cleaved by-product from the polymer with an Extrel quadruple mass spectrometer.

A method to evaluate the sensitivity of photoresists used for extreme ultraviolet (EUV) lithography has been developed. EUV sources produce out-of-band radiation and the reflective optics used in EUV tools reflect some of this out-of-band light on the wafer plane. The effect of exposing these photoresists to this unwanted light can reduce the image contrast on the wafer, and thereby reduce the image quality of the printed images. To examine the wavelengths of light that may have an adverse effect on these resists, a deuterium light source mounted with a monochromator has been designed to determine how sensitive these photoresists are to light at selected wavelengths in the range 190-650 nm.

No abstract

The impact of carbon contamination on extreme ultraviolet (EUV) masks is significant due to throughput loss and potential effects on imaging performance. Current carbon contamination research primarily focuses on the lifetime of the multilayer surfaces, determined by reflectivity loss and reduced throughput in EUV exposure tools. However, contamination on patterned EUV masks can cause additional effects on absorbing features and the printed images, as well as impacting the efficiency of cleaning process. In this work, several different techniques were used to determine possible contamination topography. Lithographic simulations were also performed and the results compared with the experimental data.